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To the Student
In today’s world, knowing science is important for thinking critically, solving problems, and
making decisions. But understanding science sometimes can be a challenge.
South Carolina Science Essentials provides an opportunity for you to prepare for the state science assessment. Each lesson is correlated to one or more of the standards on the South Carolina
Science Assessment Framework for Middle School Science.
In each lesson:
• Before You Read sparks your interest in what you’ll learn and relates it to your world.
• Read to Learn describes important science concepts with words and graphics. Next to the
text you can find a variety of study tips and ideas for organizing and learning information:
• The Study Coach offers tips for getting the main ideas out of the text.
• Foldables™ Study Organizers help you divide the information into smaller,
easier-to-remember concepts.
• Reading Checks ask questions about key concepts. The questions are placed so you
know whether you understand the material.
• Think It Over elements help you consider the material in-depth, giving you an
opportunity to use your critical-thinking skills.
• Picture This questions specifically relate to the art and graphics used with the text.
You’ll find questions to get you actively involved in illustrating the concepts you
read about.
• Applying Math reinforces the connection between math and science.
• Use After You Read to review key terms and answer questions about what you have
learned. The Mini Glossary can assist you with science vocabulary. Review questions
focus on the key concepts to help you evaluate your learning.
See for yourself. South Carolina Science Essentials makes science easy to understand and enjoyable.
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States Copyright Act, no part of this publication may be reproduced or distributed in any form or by any
means, or stored in a database or retrieval system, without the prior written permission of the publisher.
Send all inquiries to:
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ISBN-13: 978-0-07-875654-2
ISBN-10: 0-07-875654-5
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Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Table of Contents Grade 6
South Carolina Science Academic Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .vi
Lesson A Living Things (6-2.1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1
Lesson B How are living things classified? (6-2.2) . . . . . . . . . . . . . . . . . . . .5
Lesson C Introduction to Plant Reproduction (6-2.3, 6-2.8) . . . . . . . . . . . .9
Lesson D Seed Reproduction (6-2.4, 6-2.5) . . . . . . . . . . . . . . . . . . . . . . . . .12
Lesson E Plant Responses (6-2.6) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
Lesson F Photosynthesis and Respiration (6-2.7) . . . . . . . . . . . . . . . . . . . .21
Lesson G Infectious Diseases (6-2.9) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
Lesson H What is an animal? (6-3.1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
Lesson I
Sponges, Cnidarians, Flatworms, and Roundworms
(6-3.1, 6-3.2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37
Lesson J
Mollusks and Segmented Worms (6-3.1, 6-3.2) . . . . . . . . . . . . .42
Lesson K Arthropods and Echinoderms (6-3.1, 6-3.2, 6-3.4, 6-3.5, 6-3.6)47
Lesson L Chordate Animals (6-3.1, 6-3.2, 6-3.3, 6-3.4, 6-3.5) . . . . . . . . . .51
Lesson M Amphibians and Reptiles (6-3.1, 6-3.2, 6-3.3, 6-3.4) . . . . . . . . .55
Lesson N Birds (6-3.1, 6-3.2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .59
Lesson O Mammals (6-3.1, 6-3.2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .62
Lesson P Types of Behavior (6-3.7) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67
Lesson Q The Atmosphere (6-4.1, 6-4.2) . . . . . . . . . . . . . . . . . . . . . . . . . . .72
Lesson R Ocean Currents and Climates . . . . . . . . . . . . . . . . . . . . . . . . . . . .77
Lesson S Waves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .82
Lesson T What is weather? (6-4.5) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .86
Lesson U Weather Patterns (6-4.4, 6-4.6) . . . . . . . . . . . . . . . . . . . . . . . . . . .93
Lesson V Weather Forecasts (6-4.6) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .101
Lesson W Earth's Weather (6-4.7, 6-4.8) . . . . . . . . . . . . . . . . . . . . . . . . . . .104
Lesson X Air Movement (6-4.9) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .111
Lesson Y What is energy? (6-5.1, 6-5.2) . . . . . . . . . . . . . . . . . . . . . . . . . . .117
Lesson Z Energy Transformations (6-5.1, 6-5.2) . . . . . . . . . . . . . . . . . . .122
Lesson AA Sources of Energy (6-5.1, 6-5.3, 6-5.4) . . . . . . . . . . . . . . . . . . .127
Lesson BB Electric Charge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .137
Lesson CC Electric Current (6-5.4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .143
Lesson DD Electricity Circuits (6-5.4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .148
Lesson EE What is magnetism? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .155
Lesson FF Heat (6-5.5) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .160
Lesson GG Work and Power (6-5.6) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .166
Lesson HH Using Machines (6-5.6) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .170
Lesson II Simple Machines (6-5.6, 6-5.7, 6-5.8) . . . . . . . . . . . . . . . . . . . .174
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
South Carolina Science Academic Standards Grade 6
Standards
Lesson
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Structures, Processes, and Responses of Plants
Standard 6-2: The student will demonstrate an understanding of structures, processes, and responses of plants that allow them to survive and
reproduce. (Life Science)
6-2.1 Summarize the characteristics that all organisms share (including the obtainment and use of resources for energy,
A
response to stimuli, the ability to reproduce, and process of physical growth and development).
6-2.2 Recognize the hierarchical structure of the classification (taxonomy) of organisms (including the seven major levels or
B
categories of living things—namely, kingdom, phylum, class, order, family, genus, and species).
6-2.3 Compare characteristic structures of various groups of plants (including vascular or nonvascular, seed or spore-producing, C
flowering or cone-bearing, and monocot or dicot).
6-2.4 Summarize the basic functions of the structures of a flowering plant for defense, survival, and reproduction.
D
6-2.5 Summarize each process in the life cycle of flowering plants (including germination, plant development, fertilization,
D
and seed production).
6-2.6 Differentiate between the processes of sexual and asexual reproduction of flowering plants.
E
6-2.7 Summarize the processes required for plant survival (including photosynthesis, respiration, and transpiration).
F
6-2.8 Explain how plants respond to external stimuli (including dormancy and forms of tropism known as phototropism,
C, E
gravitropism, hydrotropism, and thigmotropism).
6-2.9 Explain how disease-causing fungi can affect plants.
G
Structures, Processes, and Responses of Animals
Standard 6-3: The student will demonstrate an understanding of structures, processes, and responses of animals that allow them to survive and
reproduce. (Life Science)
6-3.1 Compare the characteristic structures of invertebrate animals (including sponges, segmented worms, echinoderms,
H, I, J, K, L, M, N, O
mollusks, and arthropods) and vertebrate animals (fish, amphibians, reptiles, birds, and mammals).
6-3.2 Summarize the basic functions of the structures of animals that allow them to defend themselves, to move, and to
I, J, K, L, M, N, O
obtain resources.
6-3.3 Compare the response that a warm-blooded (endothermic) animal makes to a fluctuation in environmental temperature L, M
with the response that a cold-blooded (ectothermic) animal makes to such a fluctuation.
6-3.4 Explain how environmental stimuli cause physical responses in animals (including shedding, blinking, shivering,
K, L, M
sweating, panting, and food gathering).
6-3.5 Illustrate animal behavioral responses (including hibernation, migration, defense, and courtship) to environmental stimuli. L
6-3.6 Summarize how internal stimuli (including hunger, thirst, and sleep) of animals ensure their survival.
K
6-3.7 Compare learned to inherited behaviors in animals.
P
Earth's Atmosphere and Weather
Standard 6-4: The student will demonstrate an understanding of the relationship between Earth's atmospheric properties and processes and its
weather and climate. (Earth Science)
6-4.1 Compare the composition and structure of Earth's atmospheric layers (including the gases and differences in temperature Q
and pressure within the layers).
6-4.2 Summarize the interrelationships among the dynamic processes of the water cycle (including precipitation, evaporation, Q
transpiration, condensation, surface-water flow, and groundwater flow).
6-4.3 Classify shapes and types of clouds according to elevation and their associated weather conditions and patterns.
6-4.4 Summarize the relationship of the movement of air masses high and low pressure systems, and frontal boundaries to
U
storms (including thunderstorms, hurricanes, and tornadoes) and other weather conditions.
6-4.5 Use appropriate instruments and tools to collect weather data (including wind speed and direction, air temperature,
T
humidity, and air pressure).
South Carolina Science Academic Standards
v
Standards
Lesson
6-4.6 Predict weather conditions and patterns based on weather data collected from direct observations and measurements,
U, V
weather maps, satellites, and radar.
6-4.7 Explain how solar energy affects Earth's atmosphere and surface (land and water).
W
6-4.8 Explain how convection affects weather patterns and climate.
W
6-4.9 Explain the influence of global winds and the jet stream on weather and climatic conditions.
X
Conservation of Energy
Standard 6-5: The student will demonstrate an understanding of the law of conservation of energy and the properties of energy and work.
(Physical Science)
6-5.1 Identify the sources and properties of heat, solar, chemical, mechanical, and electrical energy.
Y, Z, AA
6-5.2 Explain how energy can be transformed from one form to another (including the two types of mechanical energy,
Y, Z
potential and kinetic, as well as chemical and electrical energy) in accordance with the law of conservation of energy.
6-5.3 Explain how magnetism and electricity are interrelated by using descriptions, models, and diagrams of electromagnets,
AA
generators, and simple electrical motors.
AA, CC, DD
FF
GG, HH, II
II
II
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
6-5.4 Illustrate energy transformations (including the production of light, sound, heat, and mechanical motion) in
electrical circuits.
6-5.5 Illustrate the directional transfer of heat energy through convection, radiation, and conduction.
6-5.6 Recognize that energy is the ability to do work (force exerted over a distance).
6-5.7 Explain how the design of simple machines (including levers, pulleys, and inclined planes) helps reduce the amount
of force required to do work.
6-5.8 Illustrate ways that simple machines exist in common tools and complex machines.
vi South Carolina Science Academic Standards
Llesson
3
A
Living Things
Standard 6-2.1: Summarize the characteristics that all organisms share (including the obtainment and use of
resources for energy, response to stimuli, the ability to reproduce, and process of physical growth and
development).
Before You Read
List three living things in your environment. What do these
things need to live?
Read to Learn
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What are living things like?
Any living thing is called an organism. Organisms vary in
size from microscopic bacteria to giant trees. They are found
just about everywhere. They have different behaviors and
food needs. However, all organisms have similar traits. These
traits determine what it means to be alive.
What You’ll Learn
the difference between
living and nonliving
things
■ what living things need
to survive
■
Study Coach
Create a Quiz As you study
the information in this lesson,
create questions about the
information you read. Be sure to
answer your questions.
How are living things organized?
Living things are made up of small units called cells. A
cell is the smallest unit of an organism that carries on the
functions of life. Some organisms are made up of just one
cell. Others are made up of many cells. Cells take in materials
from their surroundings. They use the materials in complex
ways. Each cell has an orderly structure and has hereditary
material. The hereditary material has instructions for cell
organization and function. All the things organisms can do
are possible because of what their cells can do.
Explain Make a half sheet
Foldable, as shown below, to list
the traits of living organisms.
Organisms
How do living things respond?
Living things interact with their surroundings. Anything
that causes some change in an organism is a stimulus (plural,
stimuli). The reaction to a stimulus is a response. Often that
response results in movment.
Made of cells
Use energy
Reproduce
Grow
Develop
South Carolina Science Essentials
1
Place
to live
How do living things get energy?
Identify Make a four-tab
book, as shown below. On each
flap identify things organisms
need to live.
Energy
Food
The energy that most organisms use to perform life
activities comes from the Sun. Plants and some other
organisms get energy directly from the Sun. They do this by
combining sunlight with carbon dioxide and water to make
food. People and most other organisms cannot use the energy
of sunlight directly. Instead, they take in and use food as a
source of energy. People get food by eating plants or other
organisms that eat plants. Most organisms, including plants,
must take in oxygen in order to release the energy of foods.
Some organisms, such as bacteria that live at the bottom
of the oceans where sunlight cannot reach, cannot use the
Sun’s energy to make food. These organisms use chemical
compounds and carbon dioxide to make food. They do not
need oxygen to release the energy found in their food.
How do living things grow and develop?
Organisms grow by taking in raw materials. One-celled
organisms grow by increasing in size. Most growth in manycelled organisms is due to an increase in the number of cells.
Organisms change as they grow. All of the changes that
take place during an organism’s life are called development.
Complete development can take a few days for the butterfly
shown below, or several years for a dog. The length of time
an organism is expected to live is its life span. Some
organisms have a short life span. Some have long life spans.
Picture This
1.
2
Circle the animal that
completes its development
cycle in a few days.
Lesson A Living Things
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Water
Response to Stimuli To carry on its daily activity and to
survive, an organism must respond to stimuli. Organisms
respond to external stimuli such as movement and light.
Living things also respond to stimuli that occur inside
them. For example, water or food levels in organisms’ cells
can increase or decrease. The organisms then make internal
changes to keep the right amounts of water and food in
their cells. An organism’s ability to keep the proper
conditions inside no matter what is going on outside the
organism is called homeostasis.
Why do living things reproduce?
Organisms eventually reproduce. They make more of their
own kind. Some bacteria reproduce every 20 minutes. A
pine tree might take two years to produce seeds. Without
reproduction, living things would not exist to replace those
individuals that die.
2.
Explain Why do living
things reproduce?
3.
List three substances
What do living things need?
To survive, all living things need a place to live and raw
materials. The places where they live and the raw materials
they use can vary.
In what places do organisms live?
The environment limits where organisms can live. Not
many organisms can live in extremely hot or extremely cold
environments. Most cannot live at the bottom of the ocean
or on the tops of mountains. All organisms need living
space in their environment. For example, thousands of
penguins build their nests on an island. The island becomes
too crowded for all the penguins. They fight for space and
some may not find space to build nests. An organism’s
surroundings must provide for all its needs.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What raw materials do organisms need?
Water is important for all living things. Most organisms
are made of more than 50 percent water. Humans are made
of 60 to 70 percent water. Plants and animals take in and
give off large amounts of water each day. Organisms use
homeostasis to balance the amount of water taken in
and lost.
Organisms use water for many things. Blood is about
90 percent water. Blood transports food and wastes in
animals. Plants use water to transport materials between
roots and leaves.
Living things are made up of substances such as sugars,
proteins, and fats. Animals get these substances from the
food they eat. Plants and some bacteria make the substances
using raw materials from their surroundings. These
important substances are used over and over again. When
organisms die, substances from their bodies are broken
down and released into the soil or air. The substances can
then be used again by other organisms.
found in living things.
South Carolina Science Essentials
3
After You Read
Mini Glossary
cell: the smallest unit of an organism that carries on the
functions of life
homeostasis: an organism’s ability to regulate internal,
life-maintaining conditions
organism: any living thing
1. Review the terms and their definitions in the Mini Glossary. Write a sentence explaining
how homeostasis works in humans.
Traits of
Living Things
End of
Lesson
4
Lesson A Living Things
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about living things.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
2. Complete the web diagram below by describing traits that tell what living things are like.
Llesson
3
B
How are living things classified?
Standard 6-2.2: Recognize the hierarchical structure of the classification (taxonomy) of organisms (including
the seven major levels or categories of living things—namely, kingdom, phylum, class, order, family, genus,
and species).
Before You Read
List three living things in your environment. What do these
things need to live?
Read to Learn
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Classification
When similar items are placed together, they are being
classified. Organisms also are classified into groups. Early
classifications of organisms included grouping plants that
were used in medicines. Animals were often classified by
human traits. For example, lions were classified as
courageous animals and owls were classified as wise.
More than two thousand years ago, Aristotle, a Greek,
decided that any organism could be classified as either a
plant or an animal. Then he broke these two groups into
smaller groups. For example, his groups included animals
that had hair and animals that did not have hair, and
animals with and without blood.
Who was Carolus Linnaeus?
In the late 1700s, Carolus Linnaeus, a Swedish naturalist,
developed a new system of grouping organisms. His system
was based on organisms with similar structures. For
example, plants that had a similar flower structure were
grouped together. His system was accepted and used by most
other scientists.
What You’ll Learn
how early scientists
classified living things
■ how similarities are
used to classify
organisms
■ the system of binomial
nomenclature
■ how to use a
dichotomous key
■
Study Coach
Ask and Answer
Questions Read each
subhead. Then work with a
partner to write questions about
the information in each
subhead. Take turns asking and
answering the questions.
1.
Describe the system
used by Linnaeus to group
organisms.
South Carolina Science Essentials
5
What classification do modern scientists use?
Modern scientists also use similarities in structure to
classify organisms. They also use similarities in both external
and internal features. For example, scientists use the number
of chromosomes in cells to understand which organisms
may be genetically related to each other.
In addition, scientists study fossils, hereditary information,
and early stages of development. Scientists use the
information to determine an organism’s phylogeny.
Phylogeny (fi LAH juh nee) is the organism’s evolutionary
history. This tells how the organism has changed over time.
It is the basis for the classification of many organisms.
Explain What can you
learn from the phylogeny of
an organism?
How are organisms grouped?
A classification system commonly used today groups
organisms into six kingdoms. A kingdom is the first and
largest category. Kingdoms are divided into smaller groups.
The smallest classification is a species. Organisms in the
same species can mate and produce fertile offspring. The
figure below shows how a bottle-nosed dolphin can be
classified.
Kingdom
Phylum
Picture This
3.
Classify Circle the names
of the kingdom and species
of the bottle-nosed
dolphin.
Animalia
Chordata
Class
Mammalia
Order
Cetacea
Family
Genus
Delphinidae
Tursiops
Species –Tursiops truncatus
Scientific Names
If scientists used only common names of organisms, it
would be confusing. For example, a jellyfish is neither a fish
nor jelly. A sea lion is more closely related to a seal than a
lion. To avoid confusion, scientists use a naming system
developed by Linnaeus when referring to a particular species.
Each species has a unique, two-word scientific name.
6
Lesson B How are living things classified?
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
2.
What is binomial nomenclature?
The two-word naming system used to name organisms is
called binomial nomenclature (bi NOH mee ul ·
NOH mun klay chur). The first word of the two-word name
identifies the genus of the organism. A genus is a group of
similar species. The second word of the name might tell you
something about the organism. It might tell what it looks
like or where it is found.
Why are scientific names used?
4.
Explain What does the
first word in an organism’s
binomial nomenclature
indicate?
Two-word scientific names are used for four reasons.
• They help avoid mistakes.
• Animals with similar evolutionary history are
classified together.
• Scientific names give descriptive information about
the species.
• Scientific names allow information about organisms to
be organized easily and efficiently.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Tools for Identifying Organisms
Tools used to identify organisms include field guides and
dichotomous (di KAH tuh mus) keys. Field guides include
descriptions and pictures of organisms. They give
information about where each organism lives. You can use
a field guide to identify species from around the world.
What are dichotomous keys?
5.
List two tools that can be
used to identify organisms.
A dichotomous key is a detailed list of identifying
characteristics that includes scientific names. The keys are
set up in steps. Each step has two descriptive statements,
such as hair or no hair. You can use a dichotomous key,
such as the one below, to identify and name a species.
1. Tail hair
2. Ear size
3. Tail length
4. Tail coloration
Key to Some Mice of North America
a. no hair on tail; scales show plainly; house mouse, Mus musculus
b. hair on tail, go to 2
a. ears small and nearly hidden in fur, go to 3
b. ears large and not hidden in fur, go to 4
a. less than 25 mm; woodland vole, Microtus pinetorum
b. more than 25 mm; prairie vole, Microtus ochrogaster
a. sharply bicolor, white beneath and dark above; deer mouse,
Peromyscus maniculatus
b. darker above than below but not sharply bicolor; white-footed mouse,
Peromyscus leucopus
Picture This
6.
Identify the mouse that
has a mostly dark, hairy tail
and large ears.
South Carolina Science Essentials
7
After You Read
Mini Glossary
binomial nomenclature (bi NOH mee ul ·
NOH mun klay chur): the two-word naming system
used to name organisms
genus: a group of similar species
kingdom: the first and largest category of organisms
phylogeny (fi LAH juh nee): the evolutionary history of an
organism
1. Review the terms and their definitions in the Mini Glossary. Choose one of the terms
and explain its role in classifying organisms.
2. Complete the diagram below by explaining what binomial nomenclature is and the
reasons for using it.
Binomial Nomenclature
Reasons for Using
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What is it?
End of
Lesson
8
Lesson B How are living things classified?
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about how living
things are classified.
Llesson
3
C
Introduction to Plant Reproduction
Standard 6-2.3: Compare the characteristic structures of various groups of plants (including vascular or
nonvascular, seed or spore-producing, flowering or cone-bearing, and monocot or dicot).
Standard 6-2.8: Explain how plants respond to external stimuli (including dormancy and forms of tropism
known as phototropism, gravitropism, hydrotropism, and thigmotropism).
Before You Read
List four things you need to survive. Then circle the items
on your list that you think plants also need to survive.
Read to Learn
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Types of Reproduction
What do humans and plants have in common? Both need
water, oxygen, energy, and food to grow. Like humans,
plants reproduce and make similar copies of themselves.
Most plants can reproduce in two different ways—by sexual
reproduction and by asexual reproduction.
What You’ll Learn
the differences
between the two types
of plant reproduction
■ the two stages in a
plant’s life cycle
■
Identify Main Ideas
Underline the important ideas in
this lesson. Review these ideas
as you study the lesson.
What happens in asexual plant reproduction?
Asexual reproduction does not require the production of
sex cells. Instead, one organism produces a new organism
that is genetically identical to it. Under the right conditions,
an entire plant can grow from one leaf or part of a stem or
root. When growers use these methods to start new plants,
they must make sure that the plant part has plenty of water
and anything else it needs to survive. The stems of lawn
grasses grow underground and produce new grass plants
asexually along the length of the stem.
What is sexual plant reproduction?
1.
Analyze A cutting from
a plant can be placed in
water and roots grow. Is
this an example of asexual
or sexual reproduction?
Explain your answer.
Sexual reproduction in plants requires the production of
sex cells—usually called sperm and eggs—in reproductive
organs. The organism produced by sexual reproduction is
genetically different from either parent organism.
South Carolina Science Essentials
9
Fertilization An important part of sexual reproduction is
fertilization. Fertilization happens when a sperm and egg
combine to produce the first cell of the new organism, the
zygote. In plants, water, wind, or animals help bring the
sperm and the egg together.
What reproductive organs do plants have?
A plant’s female reproductive organs produce eggs. The
male reproductive organs produce sperm. Some plants have
both reproductive organs. A plant with both reproductive
organs can usually reproduce by itself. Other plants have
either female or male reproductive organs. For fertilization to
happen, the male and female plants must be near each other.
Plant Life Cycles
book, as shown below. Explain
the two stages of the plant life
cycle.
Haploid
Diploid
Gametophyte
Stage
Sporophyte
Stage
A plant has a life cycle with two stages—the gametophyte
(guh MEE tuh fite) stage and the sporophyte (SPOHR uh fite)
stage. The figure below shows the two stages.
Gametophyte Stage When reproductive cells undergo meiosis and produce haploid cells called spores, the gametophyte
stage begins. Spores divide by cell division to form plant
structures or an entire new plant. The cells in these structures
or plants are haploid and have half a set of chromosomes.
Some of these cells undergo cell division and form sex cells.
Sporophyte Stage Fertilization—the joining of haploid sex
cells—begins the sporophyte stage. Cells formed in this stage
are diploid and have the full number of chromosomes. Meiosis
in some of these cells forms spores, and the cycle repeats.
Picture This
2.
Identify Write the name
of the stage that begins
with meiosis below the
word Meiosis. Write the
name of the stage that
begins with fertilization
above the word
Fertilization.
Fertilization
Sex cells
(sperm and eggs)
(n)
Gametophyte
plant structures
(n)
Haploid
Diploid
Spores
(n)
Meiosis
10
Lesson C Introduction to Plant Reproduction
Sporophyte
plant structures
(2n)
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Explain Make a shutterfold
After You Read
Mini Glossary
gametophyte (guh MEE tuh fite) stage: the stage in plant
reproduction when reproductive cells undergo meiosis
spores: haploid cells produced in the gametophyte stage
sporophyte (SPOHR uh fite) stage: the stage in plant
reproduction when fertilization begins
1. Review the terms and their definitions in the Mini Glossary. Write a sentence that
explains the difference between the gametophyte stage and the sporophyte stage.
2. Choose one of the question headings in the Read to Learn section. Write the question in
the space below. Then write your answer to that question on the lines that follow.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Write your question here.
3. Fill in the table below with either “yes” or “no” to compare asexual and sexual
reproduction in plants.
Asexual
Reproduction
Sexual
Reproduction
a. Requires production of sex cells?
b. Produces organism that is genetically
identical to parent?
c. Requires fertilization?
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about the basics
of plant reproduction.
End of
Lesson
South Carolina Science Essentials
11
Llesson
3
D
Seed Reproduction
Standard 6-2.4: Summarize the basic functions of the structures of a flowering plant for defense, survival,
and reproduction. Standard 6-2.5: Summarize each process in the life cycle of flowering plants (including
germination, plant development, fertilization, and seed production).
What You’ll Learn
the life cycles of most
gymnosperms and
angiosperms
■ the structure and
function of the flower
■ the ways seeds are
scattered
■
Study Coach
Before You Read
On the lines below, write the names of three fruits or
vegetables. Next to each name, describe its seed.
Read to Learn
Define Terms Skim the text
The Importance of Pollen and Seeds
All plants described so far have been seedless plants.
However, the fruits and vegetables that you eat come from
seed plants. Oak, maple, and other shade trees also are
produced by seed plants. All flowers are produced by seed
plants. In fact, most plants on Earth are seed plants.
Reproduction that involves pollen and seeds helps explain
why seed plants are so successful.
What is pollen?
1.
Identify one way a pollen
grain reaches the female
part of the plant.
12
Lesson D Seed Reproduction
In seed plants, some spores develop into small structures
called pollen grains. A pollen grain has a waterproof
covering and contains gametophyte parts that can produce
sperm. The waterproof covering of a pollen grain can be
used to identify the plant that the pollen grain came from.
The sperm of seed plants are carried as part of the pollen
grain by gravity, wind, water, or animals. The transfer of
pollen grains to the female part of the plant is called
pollination.
After the pollen grain reaches the female part of the
plant, a pollen tube is produced. The sperm moves through
the pollen tube, then fertilization can happen.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
and write each key term on an
index card. As you read the
lesson, write the definition of
each term on another index
card. Use the cards to match the
terms to their definitions as you
review the important words in
this lesson.
What are the three main parts of a seed?
After fertilization, the female part can develop into a seed.
As shown in the figure below, a seed has three main parts,
an embryo, stored food, and a protective seed coat. The
embryo will grow to become the plant’s stem, leaves, and
roots. The stored food gives the embryo energy when it
begins to grow into a plant. Because a seed contains an
embryo and stored food, a new plant develops faster from
a seed than from a spore.
Picture This
2.
Stored food
Infer Circle the part of the
seed that will become a
plant.
Embryo
Seed coat
Gymnosperms and Angiosperms Gymnosperms
(JIHM nuh spurmz) and angiosperms are the two groups of
seed plants. In gymnosperms, seeds usually develop in
cones. In angioperms, seeds develop in flowers and fruit.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Gymnosperm Reproduction
Cones are the reproductive structures of gymnosperms.
Gymnosperm plants include pines, firs, cedars, cycads, and
ginkgoes. Each kind of gymnosperm has a different cone.
A pine tree is a gymnosperm. The way pines produce
seeds is typical of most gymnosperms. The pine is a
sporophyte plant that produces both male cones and female
cones. Male and female gametophyte structures are produced
in the cones, but they are very small. A mature female cone
is made up of woody scales on a short stem. At the base of
each scale are two ovules. The egg is produced in the ovule.
Pollen grains are produced in the smaller male cones. In the
spring, clouds of pollen are released from the male cones.
How are gymnosperm seeds produced?
Pollen is carried from the male cones to the female cones
by the wind. The pollen must land between the scales of a
female cone to be useful. There it can be trapped in the sticky
fluid given off by the ovule. If the pollen grain and the
female cone are the same species, fertilization can take place.
It can take from two to three years for the seed to develop.
Categorize Make a folded
chart, as shown below. Write facts
in each block to describe the
reproduction of gymnosperms
and angiosperms.
South Carolina Science Essentials
13
Angiosperm Reproduction
Identify the four main
parts of a flower.
Picture This
4.
Stigma
Locate Highlight the
male reproductive
structure. Circle the female
reproductive structure.
Anther
Pistil
Stamen
Filament
Style
Ovary
Ovule
Sepal
Scarlet pimpernel
How is pollen spread?
Insects and other animals eat the flower, its nectar, or
pollen. As insects and other animals move about the flower,
they get pollen on their body parts. These animals spread
the flower’s pollen to other plants they visit. Some flowers
depend on the wind, rain, or gravity to spread their pollen.
Following pollination and fertilization, the ovules of flowers
can develop into seeds.
14
Lesson D Seed Reproduction
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
3.
Most seed plants are angiosperms. All angiosperms have
flowers, which are the reproductive organs. Flowers have
gametophyte structures that produce sperm or eggs for
sexual reproduction.
Most flowers have four main parts—petals, sepals, stamen,
and pistil, as shown in the figure below. The petals usually
are the most colorful parts of the flower. Sepals often are
small, green, leaflike parts. In some flowers, the sepals are as
colorful and as large as the petals.
Inside the flower are the reproductive organs of the plant.
The stamen is the male reproductive organ of the plant.
The stamen has a thin stalk called a filament. On the end of
the filament is an anther. Pollen grains form inside the
anther. Sperm develop in each pollen grain.
The pistil is the female reproductive organ. It consists of
a stigma, a long stalklike style, and an ovary. Pollen grains
land on the stigma and move down the style to the ovary.
The ovary is the swollen base of the pistil where the ovules
are found. Eggs are produced in the ovules. Not all flowers
have both male and female reproductive parts.
How do angiosperm seeds develop?
A flower is pollinated when pollen grains land on a pistil.
A pollen tube grows from the pollen grain. The pollen tube
enters the ovary and reaches an ovule. The sperm then
travels down the pollen tube and fertilizes the egg in the
ovule. A zygote forms and grows into a plant embryo.
Parts of the ovule develop into the stored food and the
seed coat that surround the embryo, and a seed is formed.
The seeds of some plants, like beans and peanuts, store food
in structures called cotyledons. The seeds of other plants,
like corn and wheat, store food in a tissue called endosperm.
5.
Identify Where is the
egg fertilized?
Seed Dispersal
Some plant seeds are spread by gravity. They fall off the
parent plant. Other seeds have attached structures, like
wings or sails, which help the wind carry them.
Some seeds are eaten by animals and spread after the
seeds are digested. Other seeds are stored or buried by
animals. Raindrops can knock seeds out of dry fruit. Some
fruits and seeds float on flowing water or ocean currents.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What is germination?
A series of events that results in the growth of a plant from
a seed is called germination. Seeds will not germinate until
the environmental conditions are right. Conditions that affect
germination include temperature, light, water, and oxygen.
Germination begins when seed tissues absorb water. This
causes the seed to get larger and the seed coat to break open.
As you can see in the figure below, a root eventually
grows from the seed. Then a stem and leaves grow. Once the
plant grows above the soil, photosynthesis begins.
Photosynthesis provides food as the plant continues to grow.
Picture This
First leaf
Cotyledon
Seed coat
Endosperm
Cotyledons
Seed coat
6.
Locate Highlight the
structure in each plant that
stores food.
In beans, the cotyledons rise above the In corn, the stored food in the
soil. As the stored food is used, the
endosperm remains in the soil and is
cotyledons shrivel and fall off.
gradually used as the plant grows.
South Carolina Science Essentials
15
After You Read
Mini Glossary
germination: a series of events that result in the growth of
a plant from a seed
ovary: the swollen base of the pistil where ovules are found
ovule: the place where eggs are produced
pistil: the female reproductive organ in the flower of
an angiosperm
pollen grain: a small structure in seed plants that has a
waterproof covering and that contains gametophyte
parts that can produce sperm
pollination: the transfer of pollen grains to the female part
of the plant
stamen: the male reproductive organ in the flower of
an angiosperm
1. Review the terms and their definitions in the Mini Glossary. Write a sentence that
describes either the male or the female reproductive organs of a flower.
2. Complete the concept web below to identify the ways seeds are spread.
Ways Seeds
Are Spread
c.
End of
Lesson
16
Lesson D Seed Reproduction
d.
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about seed
reproduction in plants.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
b.
a. gravity
Llesson
E3
Plant Responses
Standard 6-2.6: Differentiate between the process of sexual and asexual reproduction of flowering plants.
Before You Read
Have you ever been suddenly surprised? On the lines below,
describe what surprised you and how your body responded
to the surprise.
Read to Learn
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What are plant responses?
A stimulus is anything in the environment that causes a
response in an organism. A stimulus may come from outside
(external) or inside (internal) the organism. An outside
stimulus could be something that startles or surprises you. An
inside stimulus is usually a chemical produced by the organism.
Many of these chemicals are hormones. Hormones are
substances made in one part of an organism for use
somewhere else in the organism. The response to the stimulus
often involves movement toward or away from the stimulus.
All living organisms, including plants, respond to stimuli.
What You’ll Learn
the relationship
between a stimulus and
a tropism in plants
■ about long-day and
short-day plants
■ how plant hormones
and responses are
related
■
Study Coach
Create a Quiz Write a quiz
question for each paragraph.
Answer the question with
information from the paragraph.
Tropisms
Some plant responses to external stimuli are called
tropisms (TROH pih zumz). A tropism can be seen as
movement caused by a change in growth. It can be positive
or negative. A positive tropism would be growth toward a
stimulus. A negative tropism would be growth away from a
stimulus. You may have seen plants responding to touch,
light, and gravity. Plants also can respond to electricity,
temperature, and darkness.
Compare Make a two-tab
Foldable, as shown below, to
compare inside and outside
stimuli.
Inside
Stimuli
Outside
Stimuli
South Carolina Science Essentials
17
Explain Make a two-tab
concept map Foldable, as shown
below, to describe and list
positive and negative tropisms.
Touch If a pea plant touches a solid object, it responds by
growing faster on one side of its stem than on the other
side. As a result, the stem bends and twists around any
object it touches.
Light When a plant responds to light, the cells on the side
of the plant opposite the light get longer than the cells
facing the light. Because of this, the plant bends toward the
light. The leaves turn and can absorb more light. This
positive response to light is called positive phototropism.
Gravity Plants respond to gravity. The downward growth of
plant roots is a positive response to gravity. A stem growing
upward is a negative response to gravity.
Plant Hormones
Plants have hormones that control the changes in growth
that result from tropisms and affect other plant growth.
These hormones include ethylene, auxin, gibberellin,
cytokinin, and abscisic acid.
Many plants produce the hormone ethylene (EH thuh leen)
gas and release it into the air around them. This hormone
helps fruits ripen. Ethylene also causes a layer of cells to
form between a leaf and the stem. The cell layer causes the
leaf to fall from the stem.
What is auxin?
The plant hormone auxin (AWK sun) causes a positive
response to light in stems and leaves. The figure below
shows the effect of auxin.
When light shines on a plant from one side, the auxin
moves to the shaded side of the stem where it causes a
change in growth. Auxin causes plants to grow toward light.
Picture This
1.
Describe Use the figure
to describe to a partner
how auxin affects a plant’s
response to light.
Light
Cells on
shaded side
grow longer.
Lack of
auxin on
lighted
side
Auxin
moves to
shaded side
18
Lesson E Plant Responses
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
How does ethylene affect plants?
How do gibberellins and cytokinins affect
plant growth?
Two other groups of plant hormones also affect a plant’s
growth. Gibberellins (jih buh REH lunz) can be mixed with
water and sprayed on plants and seeds to stimulate plant
stems to grow and seeds to germinate. Cytokinins
(si tuh KI nunz) promote growth by causing faster cell
division. Cytokinins can keep stored vegetables fresh longer.
2.
Explain How does
abscisic acid affect plants?
3.
Infer Why could you
How does abscisic acid affect plant growth?
Abscisic (ab SIH zihk) acid is a plant hormone that keeps
seeds from sprouting and buds from developing during the
winter. This hormone also causes stomata to close in
response to water loss on hot summer days.
Photoperiods
A plant’s response to the number of hours of daylight and
darkness it receives daily is called photoperiodism
(foh toh PIHR ee uh dih zum). Because Earth is tilted about
23.5° from a line perpendicular to its orbit, the hours of
daylight and darkness change with the seasons. These changes
in the length of daylight and darkness affect plant growth.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
How does darkness affect flowers?
Many plants must have a certain length of darkness to
flower. Plants that need less than 10 h to 12 h of darkness
to flower are called long-day plants. These plants include
spinach, lettuce, and beets. Plants that need 12 or more
hours of darkness to flower are called short-day plants.
These plants include poinsettias, strawberries, and ragweed.
If a short-day plant receives less darkness than it needs to
flower, it will produce larger leaves instead of flowers.
What are day-neutral plants?
Plants that do not need a set amount of darkness to
flower are called day-neutral plants. They can flower within
a range of hours of darkness. These plants include
dandelions and roses. Knowing the photoperiods of plants
helps farmers and gardeners know which plants will grow
best in the area where they live.
produce long-day flowering
plants in a greenhouse
during winter months?
South Carolina Science Essentials
19
After You Read
Mini Glossary
auxin (AWK sun): a plant hormone that causes plant stems
and leaves to exhibit positive response to light
day-neutral plant: a plant that does not have a specific
photoperiod to flower
long-day plant: a plant that needs less than 10 h to 12 h of
darkness to flower
photoperiodism (foh toh PIHR ee uh dih zum): a plant’s
response to the number of hours of daylight and darkness
it receives daily
short-day plant: a plant that needs 12 h or more of
darkness to flower
tropism (TROH pih zum): a response of a plant to an
external stimulus
1. Review the terms and their definitions in the Mini Glossary. Write one or two sentences
to explain the differences among the long-day, short-day, and day-neutral plants.
2. Complete the cause-and-effect chart below to show how plant hormones affect plant
growth.
Effect
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Cause
Ethylene
Auxin
Gibberellin
Cytokinin
End of
Lesson
20
Lesson E Plant Responses
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about
plant responses.
Llesson
F3
Photosynthesis and Respiration
Standard 6-2.7: Summarize the processes required for plant survival (including photosynthesis, respiration,
and transpiration).
Before You Read
Name the parts of a plant that you have seen recently. For
one of the parts, describe its function.
What You’ll Learn
how plants take in and
give off gases
■ the differences and
similarities between
photosynthesis and
respiration
■ why photosynthesis
and respiration are
important
■
Read to Learn
Study Coach
Summarize Main Ideas
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Taking in Raw Materials
Plants make their own food using the raw materials water,
carbon dioxide, and inorganic chemicals in the soil. Plants
also produce wastes.
Which plant structures move water into
the plant?
Read the lesson. Recall and write
down the main ideas. Go back
and check the main ideas to
make sure they are accurate.
Then use your notes to
summarize the main ideas
of this lesson.
The figure below shows the plant structures that take in raw
materials. Most of the water used by plants is taken in through
the roots and moves through the plant to where it is used.
Picture This
1.
Identify Circle the raw
materials that a plant
takes in.
South Carolina Science Essentials
21
What is the function of a leaf?
Gas is exchanged in the leaves. Most of the water taken in
by the roots of a plant exits the plant through its leaves.
Carbon dioxide, oxygen, and water vapor enter and exit the
plant through openings in the leaves.
What is the structure of a leaf?
Picture This
2.
Identify Circle the part
of the leaf where most of
the plant’s food is made.
Upper
epidermis
e
Palisade layer
Spongy layer
Lower
epidermis
Why are chloroplasts important?
3.
Describe What happens
in the chloroplasts?
22
Lesson F Photosynthesis and Respiration
Some cells of a leaf contain small green structures called
chloroplasts. Chloroplasts are green because they contain a
green pigment, or coloring, called chlorophyll (KLOR uh fihl).
Chlorophyll is important to plants because the light energy
that it absorbs is used to make food. This food-making
process, photosynthesis (foh toh SIHN thuh suhs), happens
in the chloroplasts.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
A leaf is made up of many different layers. The outer
layer of the leaf is called the epidermis. The epidermis is
nearly transparent and allows sunlight, which is used to
make food, to reach the cells inside the leaf.
The epidermis has many small openings called stomata
(stoh MAH tuh) (singular, stoma). Raw materials such as
carbon dioxide, water vapor, and waste gases enter and exit
the leaf through the stomata. Many plants have stomata on
their stems. Guard cells surround each stoma to control how
much water enters and exits the plant. Stomata close when a
plant is losing too much water.
As you can see in the figure below, the inside of a leaf is
made up of a spongy layer and a palisade layer. Carbon
dioxide and water vapor fill the spaces of the spongy layer.
Most of the plant’s food is made in the palisade layer.
The Food-Making Process
Photosynthesis is the process during which a plant’s chlorophyll traps light energy and sugars are produced. In plants,
photosynthesis occurs only in cells with chloroplasts. For
example, photosynthesis occurs only in a carrot plant’s green
leaves. The carrot’s root cells do not have chlorophyll, so they
cannot perform photosynthesis. But excess sugar produced in
the leaves is stored in the root. The familiar orange carrot you
eat is the root of the carrot plant. When you eat a carrot, you
benefit from the energy stored as sugar in the plant’s root.
Plants need light, carbon dioxide, and water for
photosynthesis. The chemical equation for photosynthesis is
shown below.
Describe Use two quartersheets of notebook paper, as
shown below, to take notes
about photosynthesis.
Light-dependent
reactions
Light-independent
reactions
chlorophyll
6CO2 6H2O light energy
carbon
dioxide
water
→
C6H12O6 6O2
glucose
oxygen
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What are light-dependent reactions?
Chemical reactions that occur during photosynthesis that
need light are called the light-dependent reactions. During
light-dependent reactions, chlorophyll and other pigments
trap light energy that will be stored in sugar molecules.
Light energy causes water molecules, which were taken up
by the roots, to split into oxygen and hydrogen. The oxygen
exits the plant through the stomata. This is the oxygen that
you breathe. The hydrogen produced when water is split is
used in light-independent reactions.
What are light-independent reactions?
Chemical reactions that occur during photosynthesis that
do not need light are called light-independent reactions. The
light energy trapped during the light-dependent reactions is
used to combine carbon dioxide and hydrogen to make
sugars, such as glucose. The chemical bonds that hold
glucose and other sugars together are stored energy.
What happens to the oxygen and glucose that
are made during photosynthesis?
Most of the oxygen produced during photosynthesis is a
waste product and is released through the stomata. Glucose is
the main form of food for plant cells. A plant usually produces
more glucose than it can use. The extra glucose is stored in
plants as other sugars and starches. When you eat carrots or
potatoes, you are eating the stored product of photosynthesis.
4.
List two other foods that
are stored products of
photosynthesis.
South Carolina Science Essentials
23
How does a plant use glucose?
Glucose also is the basis of a plant’s structure. Plants grow
larger by taking in carbon dioxide gas and changing it to
glucose. Cellulose, an important part of plant cell walls, is
made from glucose. Leaves, stems, and roots are made of
cellulose and other materials produced using glucose.
Why is photosynthesis important?
5.
Photosynthesis produces food. Photosynthesis uses carbon
dioxide and releases oxygen. This removes carbon dioxide
from the atmosphere and adds oxygen to it. Most organisms
need oxygen to live. About 90 percent of the oxygen in the
atmosphere today is a result of photosynthesis.
Determine What does
photosynthesis add to
Earth’s atmosphere?
The Breakdown of Food
Respiration is a series of chemical reactions that breaks
down food molecules and releases energy. Respiration that
uses oxygen to break down food chemically is called aerobic
respiration. The overall chemical equation for aerobic
respiration is shown below.
C6H12O6 6O2
glucose
→
oxygen
6CO2 6H2O energy
carbon
dioxide
water
Before aerobic respiration begins, glucose molecules in the
cytoplasm are broken down into two smaller molecules. These
molecules enter a mitochondrion, where aerobic respiration
takes place. Oxygen is used to break down the molecules
into water and carbon dioxide and to release energy. The
figure below shows aerobic respiration in a plant cell.
Picture This
6.
Identify Circle the part
of the cell where aerobic
respiration occurs.
Highlight the waste
products of respiration.
Mitochondrion
Oxygen is used in the
mitochondrion to break
down these two molecules.
O2
In the cytoplasm, each glucose
molecule is broken down into
two smaller molecules.
24
Lesson F Photosynthesis and Respiration
Water and carbon
dioxide are waste
products of respiration.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Where does aerobic respiration occur?
Why is respiration important?
Food contains energy. But it is not in a form that can be
used by cells. Respiration changes food energy into a form
that cells can use. This energy drives the life processes of
almost all organisms on Earth.
Plants use energy produced by respiration to transport
sugars, to open and close stomata, and to produce
chlorophyll. When seeds sprout, they use energy from the
respiration of stored food in the seed. The figure below
shows some uses of energy in plants.
Picture This
Plant structure
and function
7.
List two uses of energy
produced by respiration
in plants.
Production
of chlorophyll
Sprouting
of seeds
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
The waste product carbon dioxide also is important.
Aerobic respiration returns carbon dioxide to the
atmosphere, where plants and some other organisms use it
for photosynthesis.
Comparison of Photosynthesis
and Respiration
Aerobic respiration is almost the reverse of photosynthesis.
Photosynthesis combines carbon dioxide and water by using
light energy. The end products are glucose (food) and
oxygen. Aerobic respiration combines oxygen and food to
release the energy in the chemical bonds of the food. The
end products of aerobic respiration are energy, carbon
dioxide, and water. Look at the table below to compare the
differences between photosynthesis and aerobic respiration.
Comparing Photosynthesis and Aerobic Respiration
Photosynthesis
Aerobic Respiration
Energy
stored
released
Raw materials
water and carbon dioxide glucose and oxygen
End products
glucose and oxygen
water and carbon dioxide
Where
cells with chlorophyll
cells with mitochondria
Picture This
8.
Compare and
Contrast Highlight water
and carbon dioxide for each
process in one color and
glucose and oxygen in
another color.
South Carolina Science Essentials
25
After You Read
Mini Glossary
chlorophyll (KLOR uh fihl): a green pigment found in
chloroplasts
photosynthesis (foh toh SIHN thuh suhs): the process
during which a plant’s chlorophyll traps light energy and
sugars are produced
respiration: a series of chemical reactions that breaks down
food molecules and releases energy
stomata (stoh MAH tah): small openings in the leaf
epidermis, which act as doorways for raw materials to
enter and exit the leaf
1. Review the terms and their definitions in the Mini Glossary. Write one or two sentences
that explain the difference between photosynthesis and respiration.
2. Choose one of the question headings in the Read to Learn section. Write the question in
the space below. Then write your answer to that question on the lines that follow.
3. How did your notes help you summarize what you read in this section?
End of
Lesson
26
Lesson F Photosynthesis and Respiration
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about
photosynthesis and respiration.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Write your question here.
Llesson
3
G
Infectious Diseases
Standard 6-2.9: Explain how disease-causing fungi can affect plants.
Before You Read
How do you think washing hands helps prevent disease?
Read to Learn
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Disease in History
In the past, there were no treatments for diseases such as
the plague, smallpox, and influenza. These diseases killed
millions of people worldwide. Today the causes of these
diseases are known, and treatments can prevent or cure
them. However, some diseases still cannot be cured. Outbreaks
of new diseases that have no known cure also occur.
What You’ll Learn
the work done by
scientists to discover
and prevent disease
■ diseases caused by
viruses and bacteria
■ the causes of sexually
transmitted diseases
■
Study Coach
Read-and-Say Work with
a partner. Read the information
under a heading to yourselves.
Then discuss together what you
learned. Continue until you both
understand the main ideas of
this lesson.
Do microorganisms cause disease?
In the late 1700s, the microscope was invented. Under a
microscope, scientists were able to see microorganisms such
as bacteria, yeast, and mold spores for the first time. By the
late 1800s and early 1900s, scientists understood that
microorganisms could cause diseases and carry them from
one person to another.
What did Louis Pasteur discover?
The French chemist Louis Pasteur discovered that
micro-organisms could spoil wine and milk. He then
realized that microorganisms could attack the human body
in the same way, causing diseases. Pasteur invented
pasteurization (pas chuh ruh ZAY shun), which is the
process of heating liquid to a specific temperature that kills
most bacteria.
1.
Infer What liquids do you
drink that you think have
undergone pasteurization?
South Carolina Science Essentials
27
Which microorganisms cause diseases?
Many diseases are caused by bacteria, viruses, protists
(PROH tihsts), or fungi. Bacteria can slow the normal
growth and activities of body cells and tissues. Some
bacteria produce toxins, or poisons, that kill body cells on
contact. The table below lists some of the diseases caused by
different groups of pathogens.
Picture This
Identify What type of
pathogen causes strep
throat?
Viruses A virus is a tiny piece of genetic material
surrounded by a protein coating that infects host cells and
multiplies inside them. The host cells die when the viruses
break out of them. These new viruses infect other cells.
Viruses destroy tissues or interrupt important body activities.
Other Pathogens Protists can destroy tissues and blood
cells. They also can interfere with normal body functions.
Fungus infections work in a similar way. They can cause
skin infections, such as athlete’s foot and ringworm, nonhealing wounds, and chronic lung disease.
Many fungi also cause plant diseases. Dutch elm disease,
apple scab, smuts, and rusts are plant diseases caused by
different types of fungi. The damage to and loss of plant
crops because of fungal diseases can cost billions of dollars
each year.
What did Joseph Lister discover?
Organize Make a folded
table with three columns and
three rows, as shown below.
Use the Foldable to record facts
about types of diseases.
28
Lesson G Infectious Diseases
Today we know that washing hands kills bacteria and
other organisms that spread disease. But until the late
1800s, people, including doctors, did not know this. Joseph
Lister, an English surgeon, saw that infection and
cleanliness were related. Lister learned that carbolic
(kar BAH lik) acid kills pathogens. He greatly reduced the
number of deaths among his patients by washing their
skin, his hands, and his surgical instruments with carbolic
acid.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
2.
Pathogens
Bacteria
Protists
Fungi
Viruses
Human Diseases and the Pathogens that Cause Them
Diseases Caused
Tetanus, tuberculosis, typhoid fever, strep throat, bacterial pneumonia, plague
Malaria, sleeping sickness
Athlete’s foot, ringworm
Colds, influenza, AIDS, measles, mumps, polio, smallpox
What operating procedures are followed today?
Today special soaps are used to kill pathogens on skin.
Every person who helps perform surgery must wash his or
her hands thoroughly and wear sterile gloves and a covering
gown. The patient’s skin is cleaned around the area of the
body to be operated on and then covered with sterile cloths.
Surgery instruments and all operating equipment are
sterilized. The air in the operating room is filtered to keep
out pathogens.
3.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
How Diseases Are Spread
List two operating
procedures followed today.
An infectious disease is a disease that is spread from an
infected organism or the environment to another organism.
An infectious disease can be caused by a virus, bacterium,
protist, or fungus. Infectious diseases are spread in many
ways. They can be spread by direct contact with the infected
organism, through water and air, on food, or by contact
with contaminated objects. They can also be spread by
disease-carrying organisms called biological vectors. Rats,
birds, and flies are examples of biological vectors.
People also can be carriers of diseases. When you have the
flu and sneeze, you send thousands of virus particles into
the air. These particles can spread the virus to others. Colds
and many other diseases also can be spread by contact.
Everything you touch may have disease-causing bacteria or
viruses on it. Washing your hands regularly is an important
way to avoid disease.
Sexually Transmitted Diseases
Infectious diseases that are passed from person to person
during sexual contact are called sexually transmitted
diseases (STDs). STDs are caused by bacteria or viruses.
What are bacterial STDs?
Explain Use a quarter-sheet
of notebook paper to define, list
the types of, and explain STDs.
STDs
STDs caused by bacteria are gonorrhea (gah nuh REE uh),
chlamydia (kluh MIH dee uh), and syphilis (SIH fuh lus).
The symptoms for gonorrhea and chlamydia may not appear
right away, so a person may not know that he or she is
infected. The symptoms for these STDs are pain when
urinating, genital discharge, and genital sores. Bacterial STDs
can be treated with antibiotics. If left untreated, gonorrhea
and chlamydia can damage the reproductive system, leaving
the person unable to have children.
South Carolina Science Essentials
29
What are the symptoms for syphilis?
4.
Determine At which
stage does syphilis cause
permanent damage?
Syphilis has three stages. In stage 1, a sore that lasts 10 to
14 days appears on the mouth or sex organ. Stage 2 may
involve a rash, fever, and swollen lymph glands. In stage 3,
syphilis may infect the cardiovascular and nervous systems.
Syphilis can be treated with antibiotics in all stages.
However damage to body organs in stage 3 cannot be
reversed and may lead to death.
What is genital herpes?
Genital herpes is a lifelong STD caused by a virus. The
symptoms include painful blisters on the sex organs. Genital
herpes can be passed from one person to another during
sexual contact or from an infected mother to her child during
birth. The herpes virus hides in the body for long periods of
time without causing symptoms and then reappears suddenly.
The symptoms for genital herpes can be treated with
medicine, but there is no cure or vaccine for the disease.
Human immunodeficiency virus (HIV) can exist in
blood and body fluids. This virus can hide in body cells,
sometimes for years. HIV can be passed on by an infected
person through sexual contact. A person can also be infected
by reusing an HIV-contaminated needle for an injection. A
sterile needle, however, cannot pass on HIV. The risk of
getting HIV through blood transfusion is small because all
donated blood is tested for HIV. An HIV-infected pregnant
woman can infect her unborn child. A baby can get HIV
after birth when nursing from an HIV-infected mother.
5.
Identify What are two
ways that a teenager or
adult can get HIV?
30
Lesson G Infectious Diseases
What is AIDS?
An HIV infection can lead to Acquired Immune
Deficiency Syndrome (AIDS). AIDS is a disease that attacks
the body’s immune system.
HIV is different from other viruses. It attacks the helper
T cells in the immune system. HIV enters the T cell and
multiples. When the infected T cell bursts open, it releases
more HIV that infects more T cells. Soon, so many T cells
are destroyed that not enough B cells are formed to produce
antibodies. Once HIV has reached this stage, the infected
person has AIDS. The immune system can no longer fight
HIV or any other pathogen. There is no cure for AIDS, but
several kinds of medicines help treat AIDS in some patients.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
HIV and Your Immune System
Fighting Disease
The first step to preventing infections is to wash small
wounds with soap and water. Cleaning the wound with an
antiseptic and covering it with a bandage also help fight
infection.
Washing your hands and body helps prevent body odor.
Washing also removes and destroys microorganisms on your
skin. Health-care workers, such as the one shown below,
wash their hands between patients. This reduces the spread
of pathogens from one person to another.
Picture This
6.
Identify other types of
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
jobs where workers should
wash their hands often.
Mark Burnett
Microorganisms in your mouth cause mouth odor and
tooth decay. Brushing and flossing your teeth every day keep
these microorganisms under control.
Exercising, eating healthy foods, and getting plenty of rest
help keep you healthy. You are less likely to get a cold or the
flu if you have good health habits. Having checkups every
year and getting the recommended vaccinations also help
you stay healthy.
7.
Apply List two things you
do every day to keep
healthy.
South Carolina Science Essentials
31
After You Read
Mini Glossary
biological vector: a disease-carrying organism
infectious disease: a disease that is caused by a virus,
bacterium, protist, or fungus and is spread by an
organism or the environment to another organism
pasteurization (pas chuh ruh ZAY shun): the process of
heating a liquid to a specific temperature that kills most
bacteria
sexually transmitted disease (STD): an infectious
disease that is passed from person to person during
sexual contact
virus: a small piece of genetic material surrounded by a
protein coating that infects and multiplies in host cells
1. Review the terms and their definitions in the Mini Glossary. Choose one term that identifies a way a person gets a disease. Write a sentence about how the term you selected
causes infection.
2. Complete the table below to identify the causes, symptoms, and treatments of STDs.
Causes (Bacteria or Virus)
Symptoms
Treatment
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Kinds of STDs
Gonorrhea
Chlamydia
Syphilis
Genital herpes
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games, and projects to help you learn more about infectious
diseases.
32
Lesson G Infectious Diseases
End of
Lesson
Llesson
3
H
What is an animal?
Standard 6-3.1: Compare the characteristic structures of invertebrate animals (including sponges,
segmented worms, echinoderms, mollusks, and arthropods) and vertebrate animals (fish, amphibians, reptiles,
birds, and mammals).
Before You Read
What You’ll Learn
the characteristics of
animals
■ the differences
between vertebrates
and invertebrates
■
List the names of five animals on the lines below. Then
write one thing that these animals have in common.
Read to Learn
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Animal Characteristics
If you asked ten people what all animals have in
common, you would get many different answers. Animals
come in many different shapes and sizes. All animals,
however, have five common characteristics.
1. All animals are many-celled organisms that are made
of different kinds of cells.
2. Most animal cells have a nucleus and organelles. The
nucleus and many of the organelles are surrounded by
a membrane. A cell that contains a nucleus and
organelles surrounded by membranes is called a
eukaryotic (yew ker ee AH tihk) cell.
3. Animals cannot make their own food.
4. Animals digest their food.
5. Most animals can move from place to place.
What is symmetry?
As you study different groups of animals, you will look at
their symmetry (SIH muh tree). Symmetry refers to the way
parts of an object are arranged. If the parts are arranged in
a way that allows the object to be divided into similar
halves, it is symmetrical.
Study Coach
Quiz Yourself As you read
the lesson, write a question for
each paragraph. Answer the
question with information from
the paragraph. Use the
questions and answers to study
the lesson.
1.
Analyze Name one
reason animals need to
move from place to place.
South Carolina Science Essentials
33
What kind of symmetry do most animals have?
Explain What two forms
of symmetry do most
animals have?
Sea anemones have radial symmetry.
Picture This
3.
Classify Draw a simple
human figure beside the
type of symmetry that
humans have.
34
Lesson H What is an animal?
Lobsters have bilateral symmetry.
Many sponges are asymmetrical.
What is an asymmetrical animal like?
An animal with an uneven shape is called asymmetrical
(AY suh meh trih kul). Its body cannot be divided into
halves that are similar. Look at the sponge in the figure
above. Notice that you cannot draw a line down the center
of its body to divide it into two halves that are similar. As
you learn more about invertebrates, think about their body
symmetry. Notice how body symmetry affects the way they
gather food and do other things.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
2.
Most animals have either radial symmetry or bilateral
symmetry. An animal with body parts arranged in a circle
around a central point has radial symmetry. As you can see
in the figure below, a sea anemone has radial symmetry. An
animal with radial symmetry can find food and gather
information from all directions. Other animals that have
radial symmetry are jellyfish and sea urchins.
An animal with bilateral symmetry has parts that are
nearly mirror images of each other. You can draw a line
down the center of its body to divide it into two similar
parts. The figure below shows that a lobster has bilateral
symmetry. A human also has bilateral symmetry.
Animal Classification
Applying Math
Animals have many characteristics in common. But when
you think about the variety of animals you can name, you
know that there are many different kinds of animals. Some
animals have legs, others have wings. Some live on land,
others live in water. Scientists use a classification system to
place all animals into related groups.
Scientists separate animals into two groups—vertebrates
(VUR tuh bruts) and invertebrates (ihn VUR tuh bruts).
These two groups are shown in the figure below. Vertebrates
are animals that have a backbone. Invertebrates are animals
that do not have a backbone. About 97 percent of all
animals are invertebrates.
4.
Create a Circle Graph
In the circle below, draw a
circle graph showing the
percent of invertebrates and
the percent of vertebrates.
Animal Kingdom
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Invertebrates
Vertebrates
Scientists further classify the invertebrates into smaller
groups, as shown in the figure below. The animals in each
group share similar characteristics. These characteristics
show that the animals within the group may have had a
common ancestor.
Picture This
Invertebrates
5.
Cnidarians
Sponges
Roundworms
Flatworms
Mollusks
Annelids
Echinoderms
Identify Circle any words
in the diagram that you do
not know. When you have
finished reading this lesson,
review the words you
circled and state a
characteristic of each one.
Arthropods
South Carolina Science Essentials
35
After You Read
Mini Glossary
invertebrates (ihn VUR tuh bruts): animals that do not
have a backbone
symmetry (SIH muh tree): the way parts of an object are
arranged
1. Review the terms and their definitions in the Mini Glossary. Write a sentence that explains
the difference between an animal that has symmetry and one that is asymmetrical.
2. Fill in the table below to describe the common characteristics of all animals.
Common Characteristics of All Animals
1.
3.
4.
5.
3. How did writing and answering quiz questions help you remember what you have read
about animal characteristics and classification?
End of
Lesson
36
Lesson H What is an animal?
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about the
characteristics of animals.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
2.
Llesson
3I
Sponges, Cnidarians, Flatworms,
and Roundworms
Standard 6-3.1: Compare the characteristic structures of invertebrate animals (including sponges,
segmented worms, echinoderms, mollusks, and arthropods) and vertebrate animals (fish, amphibians, reptiles,
birds, and mammals). Standard 6-3.2: Summarize the basic functions of the structures of animals that allow
them to defend themselves, to move, and to obtain resources.
Before You Read
What You’ll Learn
the structures of
sponges and cnidarians
■ how sponges and
cnidarians get food and
reproduce
■ about flatworms and
roundworms
■
On the lines below, list a difference between the way plants
and animals get food.
Read to Learn
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Sponges
Sponges are classified as animals because they cannot
make their own food. A sponge’s body is made of two layers
of cells. Adult sponges remain attached to one place for
their lifetime. There are about 15,000 species of sponges.
Study Coach
Sticky-Note Discussions
As you read the lesson, use
sticky-note paper to mark
paragraphs you find interesting.
Share the interesting
information with a partner.
How does a sponge eat?
All sponges are filter feeders. Sponges filter tiny food
particles from the water that flows through their bodies. The
inner part of a sponge’s body is lined with collar cells. Thin,
whiplike structures, called flagella (flah JEH luh), are
attached to the collar cells. The whiplike movements of the
flagella keep water moving through the sponge. Other cells
digest the food, carry nutrients to all parts of the sponge,
and remove wastes.
Explain Make a four-tab book
Foldable, as shown below. Take
notes on what you read about
each classification of animal.
How does a sponge protect itself?
Many sponges have soft bodies that are supported by
sharp, glass-like structures called spicules (SPIHK yewlz).
Other sponges contain a substance called spongin, which
is like foam rubber. Spongin makes sponges soft and
stretchable. Some sponges have both spicules and spongin
to protect their soft bodies.
Sponges
Cnidarians
Flatworms
Roundworms
South Carolina Science Essentials
37
How do sponges reproduce?
Sponges can reproduce asexually and sexually. A sponge
reproduces asexually when a bud on the side of the parent
sponge develops into a small sponge. The small sponge
breaks off, floats away, and attaches itself to a new surface.
New sponges also can grow from pieces of a sponge.
Most sponges that reproduce sexually are hermaphrodites
(hur MA fruh dites). This means they produce both eggs
and sperm. The figure below shows sexual reproduction in
sponges. Sponges release sperm into the water. The sperm
float until they are drawn into another sponge. The sperm
fertilizes an egg. A larva develops in the sponge. The larva
leaves the sponge and settles to the bottom. It attaches to
the surface on which it lands and grows into a new sponge.
Picture This
1.
Identify Circle the
names of two structures
needed for sexual
reproduction.
Flagella
Larvae
New sponge
Cnidarians
2.
Explain Why does a
cnidarian use stinging cells?
38
Jellyfish, sea anemones, hydra, and corals are cnidarians.
Cnidarians (nih DAR ee unz) are hollowed-bodied animals
with two cell layers that are organized into tissues. Cnidarians
have tentacles surrounding their mouths. The tentacles shoot
out harpoon-like stinging cells to capture prey. Cnidarians
have radial symmetry, so they can locate food that floats by
from any direction. The inner cell layer digests the food.
Nerve cells work together as a nerve net throughout the
whole body.
Lesson I Sponges, Cnidarians, Flatworms, and Roundworms
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Sperm
cells
Egg
cell
What kinds of body forms do cnidarians have?
Cnidarians have two different body forms. The vase-shaped
body form is called a polyp (PAH lup). Sea anemones and
hydras are polyps. Polyps usually remain attached to a
surface. A jellyfish has a free-swimming, bell-shaped body
that is called a medusa (mih DEW suh). Jellyfish are not
strong swimmers. Instead they drift with the ocean currents.
Some cnidarians go through both a polyp stage and a
medusa stage during their life cycles.
3.
Identify the two body
forms of cnidarians.
How do cnidarians reproduce?
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Cnidarians reproduce both sexually and asexually. The
polyp form of a cnidarian reproduces asexually by budding.
The bud falls off the parent and develops into a new polyp.
Some polyps also can reproduce sexually by releasing eggs
or sperm into the water. Eggs that are fertilized by the
sperm develop into new polyps.
The medusa form of a cnidarian has a two-stage life cycle,
as shown in the figure below. A medusa reproduces sexually
to produce polyps. Then each polyp reproduces asexually to
form new medusae.
Picture This
4.
Apply Draw a circle
around the three pictures of
the medusae in the
diagram.
Medusae
Female
Male
Sperm
Egg
Asexual
reproduction
The young medusae
bud off the polyp, and
the cycle begins again.
In the sexual stage, the
free-swimming female medusa
releases eggs and the male medusa
releases sperm.
In the asexual
stage, the polyp
grows and forms
buds that become
tiny medusae.
Sexual
reproduction
A larva develops and
attaches to rocks or
other surfaces.
Larva
Polyp
South Carolina Science Essentials
39
Flatworms
5.
Explain how a tapeworm
attaches to the host’s
intestine.
Unlike sponges and cnidarians, flatworms search for food.
Flatworms are invertebrates with long, flattened bodies and
bilateral symmetry. A flatworm’s body is soft and has three
layers of tissue organized into organs and organ systems.
Some kinds of flatworms can move around and search for
food. These flatworms have a digestive system with one
opening. Most flatworms are parasites that live in or on their
hosts. A parasite gets its food and shelter from its host.
What are tapeworms?
Tapeworms are flatworms that live in the intestines of
their hosts. A tapeworm does not have a digestive system. It
gets its nutrients from digested food in the host’s intestine.
A tapeworm’s head has hooks and suckers that attach to the
host’s intestine. A human can be a host for a tapeworm.
The body of a tapeworm is made up of segments. A
tapeworm grows by adding segments directly behind its head.
Each body section has both male and female reproductive
organs. Eggs and sperm are released inside the segment. After
it is filled with fertilized eggs, the segment breaks off. The
segment passes with wastes out of the host’s body. If it is
eaten by another host, the fertilized egg hatches and develops
into a tapeworm.
Roundworms
6.
Determine What is the
host for a heartworm?
40
Roundworms are the most widespread animal on Earth.
There are thousands of kinds of roundworms. Heartworms,
which can infect the hearts of dogs, are one kind of
roundworm.
A roundworm’s body is a tube inside a tube. Between the
two tubes is a cavity full of fluid. The fluid-filled cavity
separates the digestive tract from the body wall. The digestive
tract of a roundworm has two openings. Food enters the
roundworm through the mouth, is digested in a digestive
tract, and wastes exit through the anus.
Some roundworms are decomposers. Other roundworms
are predators. The heartworm is a roundworm that is an
animal parasite. Some roundworms are plant parasites.
Lesson I Sponges, Cnidarians, Flatworms, and Roundworms
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
How do tapeworms reproduce?
After You Read
Mini Glossary
cnidarian (nih DAR ee un): a hollow-bodied animal with
tentacles for catching food and two cell layers that are
organized into tissues
medusa (mih DEW suh): a free-swimming, bell-shaped
body of a cnidarian
polyp (PAH lup): a vase-shaped body of a cnidarian
1. Review the terms and their definitions in the Mini Glossary. Choose the term that names
an invertebrate. Write a sentence describing the animal.
2. Complete the Venn diagram below to help you compare flatworms and roundworms.
Roundworms
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Flatworms
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about sponges,
cnidarians, flatworms, and roundworms.
End of
Lesson
South Carolina Science Essentials
41
Llesson
3J
Mollusks and Segmented Worms
Standard 6-3.1: Compare the characteristic structures of invertebrate animals (including sponges,
segmented worms, echinoderms, mollusks, and arthropods) and vertebrate animals (fish, amphibians, reptiles,
birds, and mammals). Standard 6-3.2: Summarize the basic functions of the structures of animals that allow
them to defend themselves, to move, and to obtain resources.
Before You Read
What You’ll Learn
On the lines below, describe some characteristics of an
earthworm.
Read to Learn
Identify Main Ideas
Highlight the main idea in each
paragraph. Review the main
ideas after you have finished
reading.
Mollusks
A mollusk is a soft-bodied invertebrate that usually has a
shell. A mollusk also has a mantle and a large, muscular
foot. The mantle is a thin layer of tissue that covers the
mollusk’s soft body. The foot is used for moving or for
holding the animal in one place. Snails, mussels, and
octopuses are mollusks. Mollusks that live in water have
gills. Gills are organs in which carbon dioxide from the
animal is exchanged for oxygen from the water. Mollusks
that live on land have lungs in which carbon dioxide from
the animal is exchanged for oxygen from the air.
What body systems does a mollusk have?
1.
Define What is a radula?
42
A mollusk has a digestive system with two openings.
Many mollusks have a scratchy tonguelike organ called the
radula (RA juh luh). The radula has rows of tiny, sharp
teeth that the mollusk uses to scrape small bits of food off
rocks and other surfaces. Some mollusks have an open
circulatory system, which means they do not have blood
vessels. Instead, the blood washes over the organs, which are
grouped together in a fluid-filled cavity inside the animal’s
body.
Lesson J Mollusks and Segmented Worms
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
the characteristics of
mollusks
■ differences between an
open and a closed
circulatory system
■ the characteristics of
segmented worms
■ the digestive process of
an earthworm
■
Types of Mollusks
Scientists use three characteristics to classify a mollusk.
1. Does the mollusk have a shell?
2. If the mollusk has a shell, what kind of shell is it?
3. What type of foot does the mollusk have?
What are gastropods?
Gastropods are the largest group of mollusks. Most
gastropods have one shell. Snails and conchs are examples of
single-shelled gastropods. A slug is a gastropod that has no
shell. Some gastropods live in water and others live on land.
A gastropod uses its large, muscular foot to move about.
Gastropods secrete mucus, which helps them glide across
surfaces.
Describe Make a six-tab book
Foldable, as shown below. Write
the main ideas as you read
about each type of mollusk or
segmented worm.
s
opod
Gastr
s
Bivalve
What are bivalves?
pods
Cephalo
Bivalves are mollusks with two shell halves joined by a
hinge. Scallops and clams are bivalves. Large, powerful
muscles open and close the shell halves. Bivalves are water
animals. A bivalve filters food from water that enters into
and is filtered through the gills.
ms
Earthwor
Leeches
orms
Marine W
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What are cephalopods?
Squid and octopuses are cephalopods (SE fah lah pawdz).
Most cephalopods have a stiff plate inside their bodies
instead of a shell on the outside. They have a well-developed
head and a “foot” that is made up of tentacles with suckers.
The mouth is at the base of the tentacles. A cephalopod has
a closed circulatory system in which blood is carried
through blood vessels.
Cephalopods can move quickly through the water. The
figure below compares the movement of a squid as it releases
water to the movement of a balloon as it releases air.
Direction of balloon
Picture This
2.
Air in
Explain Use the figure to
explain to a partner how a
squid moves.
Air out
Direction of squid
Water in
Water out
South Carolina Science Essentials
43
How does a cephalopod move?
A muscular envelope, called the mantle, surrounds a
cephalopod’s internal organs. Water enters the space between
the mantle and the body organs. When the mantle closes,
water is squeezed through a funnel-like structure called a
siphon. This squeezing creates a force that causes the animal
to move in the opposite direction of the stream of water.
Segmented Worms
Earthworms, leeches, and marine worms are segmented
worms. Segmented worms are also called annelids (A nul idz).
A segmented worm’s body is made up of repeating rings
that make the worm flexible. Each ring or segment has
nerve cells, blood vessels, part of the digestive tract, and
the coelom (SEE lum). The coelom is a body cavity that
separates the internal organs from the inside of the body
wall. A segmented worm has a closed circulatory system and
a complete digestive system with two body openings.
Describe What
separates the internal
organs of an earthworm
from the body wall?
How does an earthworm move and eat?
An earthworm has more than 100 rings or segments. Each
segment has bristles, or setae (SEE tee), on the outside.
Setae are used to grip the soil while two sets of muscles
move them through the soil. As the earthworm moves, it
takes soil into its mouth. The earthworm gets its food from
the soil. The soil moves from the mouth, to the crop, to the
gizzard. In the gizzard, the food and the soil are ground. In
the intestine, the food is broken down and absorbed by the
blood. Waste materials and undigested soil leave the
earthworm through the anus. All of these structures are
shown in the figure below.
Mouth
Brain
Hearts
Blood vessels
Crop
Picture This
4.
Reproductive
structures
Main nerve
cord
Intestine
Waste removal
tubes
Gizzard
Identify Circle the parts
of an earthworm that are
also found in humans.
44
Lesson J Mollusks and Segmented Worms
Anus
Setae
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
3.
How does an earthworm breathe?
An earthworm does not have lungs or gills. An earthworm
breathes through its mucous-covered skin. Carbon dioxide
moves out of the body and oxygen moves into the body
through the skin. If the mucus covering the skin is removed,
the earthworm may die of suffocation.
How does a leech get its food?
5.
Explain how an
earthworm breathes.
6.
Apply How do marine
worms use setae?
Leeches can be found in freshwater, salt or marine water,
and on land. A leech is a segmented worm with a flat body.
It has suckers on both ends that it uses to attach itself to an
animal to remove blood.
A leech can store large amounts of blood that it slowly
releases into its digestive system when it needs food. Some
leeches can store as much as ten times their own weight in
blood, and the blood can be stored for months. Although
leeches like a diet of blood, most can eat small water
animals.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What are the characteristics of a
marine worm?
There are more than 8,000 kinds of marine worms.
Marine worms are the most varied group of annelids. The
word polychaete means “many bristles.” A marine worm has
bristles, or setae, along the sides of its body. Because of these
bristles, marine worms are sometimes called bristle worms.
Marine worms can use these setae to walk, swim, or dig.
Some marine worms are filter feeders. They either dig
down into the mud or build hollow tubes. Then they use
their bristles to filter food from the water. Others eat plants
or decaying materials. Some marine worms are predators
and some are parasites. The many ways that marine worms
get food explains why they are so varied.
South Carolina Science Essentials
45
After You Read
Mini Glossary
closed circulatory system: a circulatory system in which
blood is carried through blood vessels
gill: an organ in which carbon dioxide from an animal is
exchanged for oxygen from the water
mantle: a thin layer of tissue that covers a mollusk’s soft body
mollusk: a soft-bodied invertebrate that has a mantle and a
large muscular foot; usually has a shell
open circulatory system: a circulatory system without
blood vessels in which blood washes over the organs
radula (RA juh luh): a tonguelike organ in mollusks
1. Review the terms and their definitions in the Mini Glossary. Write two sentences that
explain the difference between an open circulatory system and a closed circulatory system.
2. Fill in the table below to identify the main characteristics of mollusks and segmented
worms.
Main Characteristics
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
1.
2.
Mollusks
3.
4.
5.
6.
1.
Segmented Worms
2.
3.
4.
End of
Lesson
46
Lesson J Mollusks and Segmented Worms
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about mollusks and
segmented worms.
Llesson
3
K
Arthropods and Echinoderms
Standard 6-3.1: Compare the characteristic structures of invertebrate animals (including sponges,
segmented worms, echinoderms, mollusks, and arthropods) and vertebrate animals (fish, amphibians, reptiles,
birds, and mammals). Standard 6-3.2: Summarize the basic functions of the structures of animals that allow
them to defend themselves, to move, and to obtain resources. Standard 6-3.4: Explain how environmental
stimuli cause physical responses in animals (including shedding, blinking, shivering, sweating, panting, and
food gathering). Standard 6.3.5: Illustrate animal behavioral responses (including hibernation, migration,
defense, and courtship) to environmental stimuli. Standard 6-3.6: Summarize how the internal stimuli
(including hunger, thirst, and sleep) of animals ensure their survival.
Before You Read
What You’ll Learn
the features used to
classify arthropods
■ the structure and
function of the
exoskeleton
■ the features of
echinoderms
■
On the lines below, list three kinds of insects. Next to the
name of each insect, write a short description of the insect.
Read to Learn
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Arthropods
An arthropod (AR thruh pahd) is an invertebrate animal
with jointed appendages (uh PEN dih juz). Appendages are
structures such as claws, legs, or antennae that grow from
the body. Arthropods have bilateral symmetry and
segmented bodies.
Study Coach
Summarize As you read
this lesson, stop after every
paragraph and summarize what
you have just read in your own
words.
How does an arthropod protect itself?
Arthropods have hard body coverings called exoskeletons.
The exoskeleton protects and supports the animal’s body
and reduces water loss. As the animal grows, the old
exoskeleton must be shed because it does not grow with the
animal. The process of shedding the exoskeleton is called
molting.
What are the characteristics of insects?
Insects make up the largest group of arthropods.
Scientists have classified more than 700,000 species of
insects. Insects have three body regions—head, thorax, and
abdomen. Insects have an open circulatory system. Many
insects, such as butterflies, completely change their body
form as they grow. This change in body form is called
metamorphosis (met uh MOR fuh sus).
Compare Make a two-tab
book Foldable, as shown below.
Write statements or phrases
about Arthropods and
Echinoderms as you read. Use
the statements to compare
these animals.
Arthropods
Echinoderms
South Carolina Science Essentials
47
What are two kinds of metamorphosis?
There are two kinds of insect metamorphosis—complete
and incomplete. Complete metamorphosis is shown on the
left in the figure below. It has four stages—egg, larva, pupa
(PYEW puh), and adult. Notice that each stage is different
from the others. The three stages of incomplete
metamorphosis—egg, nymph, and adult—are shown on the
right in the figure below. A nymph looks like a small adult.
Complete Metamorphosis
Incomplete Metamorphosis
Nymph
Eggs
Molt
Nymph
Adult
Egg
Picture This
1.
Identify Circle the names
of the stages that are the
same for complete and
incomplete
metamorphosis.
Molt
Pupa
Larva
Adult
Arachnids (uh RAK nudz) are arthropods that have only
two body regions—a cephalothorax (sef uh luh THOR aks)
and an abdomen. The cephalothorax is a body region made
up of a head and a thorax. An arachnid has four pairs of legs
attached to its cephalothorax. Spiders, ticks, mites, and
scorpions are arachnids.
How do spiders catch their food?
Applying Math
2.
Spiders are predators that use a pair of appendages near
their mouths to inject venom, or poison, into their prey.
The venom makes the prey unable to move. After the prey
has been injected with venom, spiders inject another
substance that turns the prey’s body into a liquid, which
spiders drink. Some spiders weave webs to trap their prey.
Other spiders chase and catch their prey.
Calculate Complete the
What are centipedes and millipedes?
following sentence by
filling in the correct
numbers. A centipede with
30 segments has ______
legs. A millipede with 30
segments has ______ legs.
Centipedes and millipedes are long, thin segmented
animals. Centipedes have one pair of jointed legs attached to
each segment. They are predators that use poison to catch
prey. Millipedes have two pairs of jointed legs attached to
each segment. They eat plants.
48
Lesson K Arthropods and Echinoderms
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What is an arachnid?
What are the characteristics of crustaceans?
Crustaceans include some of the largest arthropods, such
as crabs and lobsters. Most crustaceans are small marine
animals called zooplankton. Zooplankton are tiny free-floating
animals that serve as food for other marine animals.
Most crustaceans have two pairs of antennae attached to
the head, three types of chewing appendages, and five pairs
of legs. Many crustaceans that live in water also have
appendages called swimmerets on the abdomen. Swimmerets
help exchange carbon dioxide from the animal for oxygen
in the water.
3.
Determine What is the
purpose of swimmerets?
Echinoderms
Echinoderms (ih KI nuh durmz) are animals that have
radial symmetry. Sea stars and sand dollars are echinoderms.
Echinoderms have spines of different lengths that cover the
outside of their bodies. Most echinoderms have an internal
skeleton made up of bonelike plates that supports and protects
the animal. Echinoderms have a simple nervous system, but
no head or brain. Some echinoderms are predators, some
are filter feeders, and some feed on decaying matter.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What is a water-vascular system?
An echinoderm has a water-vascular system, which is a
network of water-filled canals and thousands of tube feet. The
tube feet work like suction cups to help the animal move and
capture prey. The figure below shows the parts of a sea star.
A sea star eats by pushing its stomach out of its mouth and
into the opened shell of its prey. After the prey’s body is
digested, the sea star pulls in its stomach. Like some other
invertebrates, sea stars can regrow lost or damaged parts.
Picture This
Anus
4.
Ray
Explain Use the diagram
to explain to a partner how
the sea star eats.
Stomach
Mouth
Radial canal
Tube
feet
South Carolina Science Essentials
49
After You Read
Mini Glossary
appendage (uh PEN dihj): a structure such as a claw, leg,
or antennae that grows from the body
arthropod (AR thruh pahd): an invertebrate animal with
jointed appendages and an exoskeleton
exoskeleton: a hard body covering that protects and
supports the body and reduces water loss
metamorphosis (met uh MOR fuh sus): a change in body
form
1. Review the terms and their definitions in the Mini Glossary. Write a sentence that
describes how an arthropod might use an appendage.
2. Complete the concept map below about arthropod classification.
Body Regions
Arachnids
1.
1.
2.
2.
3.
3. Complete the flowcharts to compare complete and incomplete metamorphosis.
Complete Metamorphosis
1.
2.
3.
4.
Incomplete Metamorphosis
1.
2.
End of
Lesson
50
Lesson K Arthropods and Echinoderms
3.
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about arthropods
and echinoderms.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Insects
Llesson
L3
Chordate Animals
Standard 6-3.1: Compare the characteristic structures of invertebrate animals (including sponges,
segmented worms, echinoderms, mollusks, and arthropods) and vertebrate animals (fish, amphibians, reptiles,
birds, and mammals). Standard 6-3.2: Summarize the basic functions of the structures of animals that allow
them to defend themselves, to move, and to obtain resources. Standard 6-3.3: Compare the response that a
warm-blooded (endothermic) animal makes to a fluctuation in environmental temperature with the response
that a cold-blooded (ectothermic) animal makes to such a fluctuation. Standard 6-3.4: Explain how
environmental stimuli cause physical responses in animals (including shedding, blinking, shivering, sweating,
panting, and food gathering). Standard 6.3.5: Illustrate animal behavioral responses (including hibernation,
migration, defense, and courtship) to environmental stimuli.
Before You Read
What You’ll Learn
List three animals on the lines below. Then write one thing
that all these animals have in common with humans.
Read to Learn
Study Coach
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What is a chordate?
Chordates (KOR dayts) are animals that have the following
three characteristics—a notochord (NOH tuh cord), a nerve
cord, and pharyngeal (fur RIN jee uhl) pouches at some
time during their development.
The notochord is a flexible rod that runs the length of the
developing organism. The nerve cord is made of nerve tissue.
In most chordates, one end of the nerve cord develops into
the organism’s brain.
Pharyngeal pouches are slitlike openings between the
inside of the body and the outside of the body. They are
present only in the early stages of the organism’s
development. In some chordates, like the lancelet in the
figure below, the pharyngeal pouches develop into gill slits.
Nerve cord
the characteristics of
chordates
■ the characteristics of all
vertebrates
■ the difference between
ectotherms and
endotherms
■ the three classes of fish
■
Gill slits
Notochord
Movement
of water
Create a Quiz Write a
question about the main idea
under each heading. Exchange
quizzes with another student.
Together discuss the answers to
the quiz questions.
Define Use a quarter sheet
of notebook paper, as shown
below, to define the key words
in this lesson—chordate,
ectotherm, endotherm, and
cartilage.
Chordate
Ectotherm
Endotherm
Cartilage
South Carolina Science Essentials
51
What are the characteristics of vertebrates?
Chordates are classified into several smaller groups. The
largest group of chordates is made up of the vertebrates,
which include humans. All vertebrates have an internal
system of bones called an endoskeleton. The endoskeleton
supports and protects the body’s internal organs. For
example, the skull is the part of the endoskeleton that
surrounds and protects the brain.
How do vertebrates control body temperature?
Identify Make a two-tab
Foldable, as shown below.
Identify the characteristics of
ectotherms and endotherms.
Ectotherms
Endotherms
Vertebrates are either ectotherms or endotherms.
Ectotherms (EK tuh thurmz) are cold-blooded animals.
Their body temperature changes as the temperature of their
surroundings changes. Fish are ectotherms.
Endotherms (EN duh thurmz) are warm-blooded
animals. Their body temperature does not change with the
surrounding temperature. Humans are endotherms. Your
body temperature is usually about 37°C.
1.
Explain the purpose of
fish gills.
Fish are the largest group of vertebrates. All fish are
ectotherms and live in water. Some species of fish are
adapted to live in freshwater and other species are adapted
to live in salt water.
Fish have gills. Gills are fleshy filaments where carbon
dioxide and oxygen are exchanged. Water that contains
oxygen passes over the gills. When blood is pumped into the
gills, the oxygen in the water moves into the blood. At the
same time, carbon dioxide moves out of the blood in the
gills and into the water.
Most fish have pairs of fanlike fins. Fish use fins to steer,
balance, and move. The motion of the tail fin pushes the
fish through the water.
Most fish have scales. Scales are thin structures made of a
bony material that overlap to cover the skin.
Types of Fish
Scientists classify fish into three groups—bony, jawless,
and cartilaginous (kar tuh LA juh nuhs). Bony fish have
endoskeletons made of bone. Jawless fish and cartilaginous
fish have endoskeletons made of cartilage. Cartilage
(KAR tuh lihj) is a tough, flexible tissue that is similar to
bone but is not as hard or as easily broken.
52
Lesson L Chordate Animals
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Fish
What are the characteristics of bony fish?
About 95 percent of all fish species are bony fish. Goldfish,
trout, and marlins are examples. The body structure of a bony
fish is shown in the figure below. Bony fish swim easily in
water because their scales are covered with slimy mucus.
Bony
vertebra
Picture This
Swim
bladder
Brain
2.
Highlight In the
drawing of a bony fish,
color the skeleton of the
fish and label it Skeleton.
3.
Determine How does
external fertilization take
place?
Nostril
Scales
Mouth
Intestine
Stomach
Liver
Gills
Heart
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Most bony fish have a swim bladder. A swim bladder is an
air sac that helps control the depth at which the fish swims.
Gases move between the swim bladder and the fish’s blood.
When gases move into the swim bladder, the fish rises in the
water. When gases leave the swim bladder, the fish sinks
lower in the water.
How do bony fish reproduce?
Most bony fish reproduce using external fertilization
(fur tuh luh ZAY shun). External fertilization takes place
when egg and sperm cells join outside the female’s body.
First, a female releases large numbers of eggs into the water.
Then, a male swims over the eggs, releasing sperm into the
water. Many eggs are fertilized by the sperm.
What are jawless and cartilaginous fish?
Jawless fish have long, tubelike bodies with no scales.
They have round, muscular mouths with no jaw. Their
mouths have sharp toothlike structures. Their endoskeleton
is made of cartilage. Lampreys are jawless fish that attach to
another fish with their strong mouths. Lampreys feed by
removing blood and other body fluids from the host fish.
Cartilaginous fish also have endoskeletons made of
cartilage. They have movable jaws that usually have
well-developed teeth. Their bodies are covered with
sandpaperlike scales. Sharks, skates, and rays are
cartilaginous fish. Most cartilaginous fish are predators.
South Carolina Science Essentials
53
After You Read
Mini Glossary
cartilage (KAR tuh lihj): a tough, flexible tissue that is
similar to bone, but not as hard or as easily broken
chordate (KOR dayt): an animal that has three
characteristics present at some time during its
development—a notochord, nerve cord, and
pharyngeal pouches
ectotherm (EK tuh thurm): a cold-blooded animal whose
body temperature changes as the temperature of its
surroundings changes
endotherm (EN duh thurm): a warm-blooded animal
whose body temperature does not change with the
temperature of its surroundings
1. Review the terms and their definitions in the Mini Glossary. Write a sentence that
explains the difference between an ectotherm and an endotherm.
2. Complete the concept map below to show the three classes of fish.
3. How does working with a partner to ask and answer quiz questions prepare you for a
test that covers the material you have read?
End of
Lesson
54
Lesson L Chordate Animals
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about
chordate animals.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Fish
Llesson
3
M
Amphibians and Reptiles
Standard 6-3.1: Compare the characteristic structures of invertebrate animals (including sponges,
segmented worms, echinoderms, mollusks, and arthropods) and vertebrate animals (fish, amphibians, reptiles,
birds, and mammals). Standard 6-3.2: Summarize the basic functions of the structures of animals that allow
them to defend themselves, to move, and to obtain resources. Standard 6-3.3: Compare the response that a
warm-blooded (endothermic) animal makes to a fluctuation in environmental temperature with the response
that a cold-blooded (ectothermic) animal makes to such a fluctuation. Standard 6-3.4: Explain how
environmental stimuli cause physical responses in animals (including shedding, blinking, shivering, sweating,
panting, and food gathering).
Before You Read
On the lines below, write four characteristics of frogs and
lizards.
Read to Learn
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Amphibians
Amphibians (am FIH bee unz) are animals that spend
part of their lives in water and part on land. They have many
adaptations that allow for life both on land and in the water.
Amphibians include frogs, toads, salamanders, and newts.
How do amphibians adjust when the
temperature changes?
Amphibians are ectotherms. Their body temperature
changes along with changes in the temperature of their
environment. In cold weather, amphibians become inactive.
They bury themselves in mud or leaves until the temperature warms. This time of inactivity during cold weather is
called hibernation. Amphibians that live in hot, dry climates
become inactive and hide in the ground when the temperature becomes too hot. This time of inactivity during hot
temperatures is called estivation (es tuh VAY shun).
What You’ll Learn
how amphibians have
adapted to live in water
and on land
■ what happens during
frog metamorphosis
■ the adaptations that
allow reptiles to live on
land
■
Study Coach
K-W-L Chart Fold a sheet of
paper into three columns. In the
first column, write what you
know about amphibians and
reptiles. In the second column,
write what you want to know
about amphibians and reptiles.
Then read the lesson. In the third
column, write what you learned
about amphibians and reptiles
from reading the lesson.
Define Use a quarter-sheet of
notebook paper, as shown
below, to define the key words
in this lesson—hibernation,
estivation, and amniotic egg.
What is the body structure of amphibians?
Amphibians are vertebrates with a strong endoskeleton
made of bones. The skeleton helps support their body while
on land. Adult frogs and toads have strong hind legs that
they use for swimming and jumping.
Hibernation
Estivation
Amniotic egg
South Carolina Science Essentials
55
How do amphibians live on land?
1.
Adult amphibians use lungs instead of gills to exchange
oxygen and carbon dioxide. Lungs are an important
adaptation for living on land. Amphibians have
three-chambered hearts, in which blood carrying oxygen
mixes with blood carrying carbon dioxide. This mixing
makes less oxygen available to the amphibian. Adult
amphibians also exchange oxygen and carbon dioxide
through their moist skin, which increases their oxygen
supply. Amphibians can live on land, but they must stay
moist for the exchange of oxygen and carbon dioxide to occur.
Amphibian hearing and vision also are adapted to life on
land. Amphibians have tympanums (TIHM puh nuhmz), or
eardrums, that vibrate in response to sound waves. Large eyes
help some amphibians catch their prey. Land environments
provide many insects as food for adult amphibians. They
have long, sticky tongues used to capture the insects.
Describe two
characteristics that allow
amphibians to live on land.
Most amphibians go through a series of body changes
called metamorphosis (me tuh MOR fuh sus). Eggs are most
often laid in water and hatch into larvae. Young larval forms
of amphibians live in water. They have no legs and breathe
through gills. Over time, they develop the body structures
needed for life on land, including legs and lungs. The rate of
metamorphosis depends on the species, the water temperature,
and the amount of available food. The figure below shows
the stages of development for one amphibian—the frog.
Picture This
2.
Compare Circle the
stage of metamorphosis in
which frogs are most like
fish.
Stage 2: Fertilized frog eggs are hatched
into tadpoles. Tadpoles live in water.
They use their gills for gas exchange.
Stage 1: Frog eggs
are laid and fertilized.
56
Lesson M Amphibians and Reptiles
Stage 4: The adult
frog can live and
move about on land.
Stage 3: Tadpoles begin to grow
into adults. They develop legs and lungs.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
How do amphibians develop?
How do amphibians reproduce?
Most amphibians have external fertilization and require
water for reproduction. Most female amphibians lay eggs in a
pond or lake. However, some amphibians reproduce away from
large bodies of water. For example, some tree frogs that live
in the rain forest lay eggs in rainwater that collects in leaves.
Reptiles
Snakes, lizards, turtles, and crocodiles are reptiles. Reptiles
are vertebrates and ectotherms. Most reptiles live their entire
lives on land and do not depend on water for reproduction.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What are some types of reptiles?
Turtles have bodies covered with a hard shell. Most turtles
can bring their heads and legs into the shell for protection.
Alligators and crocodiles are large reptiles that live in or
near water. Alligators and crocodiles are predators that live
in warmer climates.
Lizards and snakes make up the largest group of reptiles.
These reptiles have a highly developed sense of smell. An
organ in the roof of the mouth senses molecules collected
by the tongue. The constant in-and-out motion of the
tongue allows a snake or lizard to smell its surroundings.
Lizards have movable eyelids and external ears. Most lizards
have legs with clawed toes on each foot. Snakes move
without legs. They don’t have eyelids or ears. Snakes feel
vibrations in the ground instead of hearing sounds.
3.
Identify the largest
group of reptiles.
What are some reptile adaptations?
A thick, dry waterproof skin is an adaptation that allows
reptiles to live on land. Reptile skin is covered with scales to
reduce water loss and help prevent injury. Reptiles breathe
with lungs. Reptiles that live in water, like sea turtles, must
come to the surface to breathe.
Two adaptations allow reptiles to reproduce on land—
internal fertilization and laying shell-covered eggs. Sperm
are deposited directly into the female’s body. Female reptiles
lay fertilized eggs that are covered by tough shells. These
eggs are called amniotic (am nee AH tihk) eggs. An
amniotic egg supplies the embryo with everything it needs
to develop. A leathery shell protects the embryo and yolk.
The yolk gives the embryo a food supply. When it hatches, a
reptile is fully developed.
4.
Determine What is the
purpose of the yolk in the
amniotic egg?
South Carolina Science Essentials
57
After You Read
Mini Glossary
amniotic egg: the environment for the development of a
reptile embryo
estivation (es tuh VAY shun): a time of inactivity during
hot temperatures
hibernation: a time of inactivity during cold weather
1. Review the terms and their definitions in the Mini Glossary. Choose one term that
describes an adaptation of an amphibian to its environment. Explain this adaptation in
one or two sentences.
2. Complete the concept web below to show the adaptations of reptiles for life on land.
1.
3.
Adaptations of Reptiles
5.
End of
Lesson
58
Lesson M Amphibians and Reptiles
4.
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about amphibians
and reptiles.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
2.
Llesson
3
N
Birds
Standard 6-3.1: Compare the characteristic structures of invertebrate animals (including sponges,
segmented worms, echinoderms, mollusks, and arthropods) and vertebrate animals (fish, amphibians, reptiles,
birds, and mammals). Standard 6-3.2: Summarize the basic functions of the structures of animals that allow
them to defend themselves, to move, and to obtain resources.
Before You Read
What You’ll Learn
the characteristics of
birds
■ the adaptations birds
have for flight
■ the function of feathers
■
Think of the wide variety of birds. On the lines below, list
three things all birds have in common.
Read to Learn
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Characteristics of Birds
Birds are vertebrates that have two wings, two legs, and a
bill or beak. Birds are covered mostly with feathers. They lay
eggs with hard shells and sit on their eggs to keep them warm
until they hatch. All birds are endotherms. There are more
than 8,600 species of birds. Different species have different
adaptations. For example, ostriches have strong legs for
running. Penguins can’t fly, but they are excellent swimmers.
Wrens have feet that allow them to perch on branches.
Study Coach
Summarize the Main
Ideas Read the lesson. Recall
and write down the main ideas.
Go back and check the main
ideas to make sure they are
accurate.
Adaptations for Flight
The bodies of most birds are designed for flight. They are
streamlined and have light, strong skeletons. The inside of a
bird’s bones is almost hollow. Special structures make the
bones strong, but lightweight. A bird’s tail is designed to
provide the stiffness, strength, and stability needed for flight.
Birds use their tail to steer.
Birds need a lot of energy and oxygen to fly. They eat
high-energy foods like nectar, insects, and meat. They have a
large, efficient heart. A bird’s lungs connect to air sacs that
provide a constant supply of oxygen to the blood and make
the bird more lightweight.
1.
Infer What features do
airplanes have that are
similar to birds?
South Carolina Science Essentials
59
How do birds fly?
Birds beat their wings up and down as well as forward
and backward. As wind passes above and below the wing, it
creates lift. Lift is what allows birds to stay in flight.
Functions of Feathers
notebook paper, as shown
below, to define the key words
in this lesson—contour feathers
and down feathers.
Birds are the only animals with feathers. They have two
main types of feathers—contour feathers and down feathers.
Contour feathers are strong and lightweight. They give adult
birds their streamlined shape and coloring. Contour feathers
have parallel strands, called barbs, that extend from the main
shaft. Outer contour feathers on the wings and tail help a
bird move, steer, and keep from spinning out of control.
Feather color and patterns help attract mates. The color
patterns also protect birds from predators by helping the
birds blend into their surroundings.
Have you ever noticed that the hair on your arm stands
up on a cold day? This response is one way your body works
to trap and keep warm air close to your skin. Birds have
down feathers, such as the one below, that trap and keep
warm air next to their bodies. In adult birds, down feathers
provide a layer of insulation under the contour feathers.
Down feathers cover the bodies of some young birds.
How do birds care for their feathers?
2.
Identify What term is
used to describe birds
cleaning and rearranging
their feathers?
60
Lesson N Birds
Feathers need to be cared for to keep birds dry, warm,
and able to fly. Birds preen, or use their bills, to clean and
rearrange their feathers. During preening, birds also spread
oil over their bodies and feathers. This oil comes from a
gland found on the bird’s back near its tail. The oil keeps
the bird’s skin soft and keeps feathers and scales from
becoming brittle.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Define Use a quarter-sheet of
After You Read
Mini Glossary
contour feathers: strong, lightweight feathers that give
adult birds their stream-lined shape and coloring
down feathers: feathers that trap and keep warm air next
to birds’ bodies
1. Review the terms and their definitions in the Mini Glossary. Write two sentences that
compare and contrast contour feathers and down feathers.
2. Complete the concept web below. List any six adaptations birds have for flight.
2.
3.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
1.
Adaptations
for Flight
6.
4.
5.
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about birds.
End of
Lesson
South Carolina Science Essentials
61
Llesson
3
O
Mammals
Standard 6-3.1: Compare the characteristic structures of invertebrate animals (including sponges,
segmented worms, echinoderms, mollusks, and arthropods) and vertebrate animals (fish, amphibians, reptiles,
birds, and mammals). Standard 6-3.2: Summarize the basic functions of the structures of animals that allow
them to defend themselves, to move, and to obtain resources.
What You’ll Learn
the characteristics of
mammals
■ how mammals are
adapted to different
environments
■ the differences among
monotremes,
marsupials, and
placentals
■
Before You Read
Make a list of five mammals. Describe one feature that they
have in common.
Read to Learn
Define Words Skim the
Define Use two quartersheets of notebook paper, as
shown below, to define the key
words in this lesson—herbivore,
carnivore, omnivore, monotreme,
marsupial, and placental.
62
Herbivore
Monotreme
Carnivore
Marsupial
Omnivore
Placental
Lesson O Mammals
Mammal Characteristics
Moles, dogs, bats, and humans are some examples of
mammals. Mammals are vertebrates and endotherms. They
live in water and in many different climates on land. They
burrow through the ground and fly through the air.
Mammals have mammary glands in their skin.
A mammal’s skin usually is covered with hair that keeps
the body from being too hot or too cold. The hair also
protects mammals from wind and water. Some mammals,
like bears, have thick fur. Other mammals, like humans,
have a few patches of thick hair while the rest of the body
has little hair. Dolphins have little hair. Porcupines have
quills, which are a kind of modified hair.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
lesson before reading it.
Highlight words that you do not
know. As you read the lesson,
underline the portion of the text
that helps you understand the
meaning of these words.
Why do mammals have mammary glands?
In females, the mammary glands produce and release milk
for the young. For the first few weeks or months of life, the
milk provides all the nutrients the young mammal needs.
What kinds of teeth do mammals have?
Plant-eating animals are called herbivores. Animals that
eat meat are called carnivores. Animals that eat plants and
meat are called omnivores.
Mammals have teeth that are specialized for the type of
food they eat. The four types of teeth are incisors, canines,
premolars, and molars. As you can see in the figure below,
you usually can tell from the kind of teeth a mammal has
whether it eats plants, meat, or both.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Mountain lions are carnivores.
They have sharp canines that
are used to rip and tear flesh.
Humans are omnivores. They have incisors
that cut vegetables, premolars that are
sharp enough to chew meat, and molars
that grind food.
Picture This
1.
Identify Circle the teeth
that carnivores use to rip
and tear flesh. Highlight the
teeth that omnivores and
herbivores use to cut
vegetables.
Herbivores, like this beaver,
have incisors that cut
vegetation and large,
flat molars that grind it.
What body systems do mammals have?
Mammals have well-developed lungs. Mammal lungs are
made of millions of small sacs called alveoli. Alveoli allow
the exchange of carbon dioxide and oxygen during
breathing. Mammals also have a complex nervous system
that lets them learn and remember more than many other
animals. Mammals have larger brains than other animals of
similar size.
All mammals have internal fertilization. After an egg is
fertilized, the developing mammal is called an embryo. Most
mammal embryos develop inside the female in an organ
called the uterus.
2.
Apply What kind of
fertilization do all mammals
have in common?
South Carolina Science Essentials
63
Mammal Types
Mammals are divided into three groups based on where
their embryos develop. The three groups of mammals are
monotremes, marsupials, and placentals.
How do monotreme embryos develop?
Unlike other mammals, monotremes lay eggs with tough,
leathery shells instead of having live births. This small group
of mammals includes duck-billed platypuses and spiny
anteaters. The female monotreme sits on the eggs for about
ten days before they hatch. Monotremes also differ from
other mammals because their mammary glands do not have
nipples. The milk seeps through the skin onto their fur. The
young monotremes lick the milk off the fur. Monotremes
live in New Guinea and Australia.
Compare the mammary
glands of monotremes to
other mammals.
How do young marsupials develop?
Most marsupials carry their young in a pouch. A
marsupial embryo develops for only a few weeks within the
uterus. When a marsupial is born, it is not fully formed. It
has no hair and is blind. The young marsupial uses its sense
of smell to find its way to a nipple usually within the
mother’s pouch. It attaches to the nipple to feed and
finishes developing in the pouch. Most marsupials, such as
kangaroos and koalas, live in Australia. The opossum is the
only marsupial native to North America.
How do placental embryos develop?
Most mammals belong to a group called placentals.
Placentals are named for the placenta, which is a saclike
organ that develops from tissues of the embryo and uterus.
An umbilical cord connects the embryo to the placenta. A
human embryo is shown in the figure below.
Picture This
4.
Determine What
connects the embryo to the
placenta?
Human Embryo at Two Months
Placenta
Umbilical
cord
64
Lesson O Mammals
Uterine
wall
Embryo
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
3.
How does the embryo obtain food and oxygen?
In the placenta, food, oxygen, and wastes are exchanged
between the mother’s blood and the embryo’s blood, but
their bloods do not mix. The umbilical cord connects the
embryo to the placenta. Food and oxygen are absorbed from
the mother’s blood. Blood vessels in the umbilical cord
carry food and oxygen to the developing young. The blood
vessels also take away wastes. In the placenta, the mother’s
blood absorbs wastes from the developing young.
The time of development from fertilization to birth is
called the gestation period. Gestation periods vary widely,
from about 21 days in rats to about 616 days in elephants.
Human gestation lasts about 280 days.
Mammals Today
5.
Define What is the
gestation period?
There are more than 4,000 species of mammals on Earth
today. Mammals can be found on every continent, from
cold arctic regions to hot deserts. Each kind of mammal has
adaptations that enable it to live successfully within its
environment.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What roles do mammals have?
Mammals, like all other groups of animals, have an
important role in maintaining a balance in the environment.
Large carnivores, such as wolves, prey on herbivores, such as
deer. This helps prevent overcrowding and overgrazing. Bats
and other small mammals help pollinate flowers. Other
mammals spread seeds that stick to their fur.
What are some mammals in danger?
Some species of mammals are in danger of becoming
extinct because their habitats are being destroyed. They are left
without enough food, shelter, and space to survive because
their habitats are damaged by pollution or developed for
human needs. The grizzly bear of North America and Europe
is a threatened species. A threatened species is one that is
likely to become endangered in the near future. Grizzly bears
were once found all over the western half of the United States.
Today, they are found only in Alaska, Montana, Wyoming,
Idaho, and Washington. Habitat loss due to human settlement
has greatly reduced the grizzly bear population. If the grizzly
bear population continues to decline and becomes endangered,
the species will be in danger of becoming extinct.
6.
Explain Why has the
grizzly bear population in
the United States been
greatly reduced?
South Carolina Science Essentials
65
After You Read
Mini Glossary
carnivore: an animal that eats meat
herbivore: a plant-eating animal
marsupial: a mammal that carries its young in a pouch
where it continues to develop after birth
monotreme: a mammal that lays eggs with tough, leathery
shells
omnivore: an animal that eats plants and meat
placental: a mammal whose embryos depend on the
mother’s placenta for food and oxygen
1. Review the terms and their definitions in the Mini Glossary. Write one or more sentences
to explain how herbivores, carnivores, and omnivores are different.
2. Complete the diagram below to identify the three types of mammals.
3. Complete the table below to list the common characteristics of mammals.
Common Characteristics of Mammals
1.
2.
3.
4.
5.
6.
End of
Lesson
66
Lesson O Mammals
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about mammals.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Mammal Types
Llesson
3
P
Types of Behavior
Standard 6-3.7: Compare learned to inherited behaviors in animals.
Before You Read
On the lines below, explain how you learned a new skill,
such as in-line skating or jumping rope.
What You’ll Learn
the differences
between innate and
learned behavior
■ how organisms use
reflexes and instincts
to survive
■ examples of different
learned behaviors
■
Read to Learn
Identify Main Ideas
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Behavior
Animals are different from one another in their behavior.
Behavior is the way an organism interacts with other
organisms and its environment. Animals are born with
certain behaviors, and they learn other behaviors.
Anything in the environment that causes a reaction is
called a stimulus. A stimulus can be external, such as a male
dog entering the territory of another male dog. A stimulus
can be internal, such as hunger or thirst. The way an animal
reacts to a stimulus is called a response. Getting a drink of
water is a response to the internal stimulus of thirst.
Innate Behavior
A behavior that an organism is born with is called an
innate behavior. These types of behaviors are inherited.
They do not have to be learned.
Innate behavior patterns occur the first time an animal
reacts to an internal or external stimulus. For birds, building
a nest is an innate behavior. Although the first nest a bird
builds may be messy, it is built correctly.
Highlight each question head
in this lesson. Then use a
different color to highlight the
answers to the questions.
Describe Make a two-tab
Foldable, as shown below.
Describe the innate and learned
behaviors of an animal that you
have observed.
Innate
Behaviors
Learned
Behaviors
South Carolina Science Essentials
67
Why are innate behaviors important?
1.
Explain Why do insects
have mostly innate
behavior?
The behavior of animals with short life spans, such as
insects, is mostly innate behavior. An insect cannot learn
from its parents. By the time the insect hatches, its parents
have died or moved on. Innate behavior allows animals to
respond quickly. A quick response often means the
difference between life and death.
Reflex actions are the simplest innate behaviors. A reflex
is an automatic response that does not involve a message
from the brain. When something is thrown at you, you
blink. Blinking is a reflex action. Your body reacts on its
own. You do not think about the behavior.
What is instinctive behavior?
An instinct is a complex pattern of innate behavior.
Instinctive behavior begins when an animal recognizes a
stimulus. It continues until the animal has performed all
parts of the behavior. Spinning a web is an instinctive
spider behavior. A spider knows how to spin a web as
soon as it hatches. Instinctive behaviors take much more
time to complete than reflexes. A spider may spend days
building a web.
2.
Identify Which animal
likely has more learned
behaviors—a spider or a
monkey? Why?
Animals also have learned behaviors. Learned behavior
develops over an animal’s lifetime as a result of experience
or practice. Animals with more complex brains have more
learned behaviors. Fish, reptiles, amphibians, birds, and
mammals all learn.
Learned behavior helps animals respond to changing
situations. In changing environments, an animal that can learn
a new behavior is more likely to survive than an animal that
cannot learn a new behavior. Learned behavior is important
for animals with long life spans. The longer an animal lives,
the more likely it is that its environment will change.
Can instincts change?
Learned behavior can change instincts. Some young birds
instinctively crouch and freeze if they see something moving
above them. They will crouch and keep still even if the
object is only a moving leaf. Older birds have learned that
some things that move above them, such as leaves, are not
harmful. Learned behavior includes imprinting, trial and
error, conditioning, and insight.
68
Lesson P Types of Behavior
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Learned Behavior
How does imprinting occur?
Imprinting occurs when an animal forms a social
attachment to another organism within a short time after
birth or hatching. A gosling follows the first moving object
it sees after hatching. The moving object is usually an adult
female goose. This behavior is important because adult
geese have experience in finding food, protecting themselves,
and getting along in the world. Animals that become
imprinted toward animals of another species have difficulty
recognizing members of their own species.
What is trial-and-error learning?
Behavior that changes with experience is called trial-anderror learning. You learned many skills through trial and
error, such as feeding yourself, tying your shoes, and riding
a bicycle. Once you learn a skill, you can do it without
having to think about it.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
How does conditioning change behavior?
Animals often learn new behaviors by conditioning. In
conditioning, behavior is changed so that a response to one
stimulus becomes linked with a different stimulus.
There are two types of conditioning. One type adds a new
stimulus before the usual stimulus. Russian scientist Ivan
Pavlov performed an experiment to explain how this
conditioning works. He knew that hungry dogs salivate
when they see and smell food. Pavlov added another
stimulus, as seen in the figure below. He rang a bell before
he fed the dogs. The dogs connected the sound of the bell
with food. The dogs were conditioned to salivate at the
sound of a bell even if they were not fed.
Compare Make a three-tab
Foldable, as shown below. Use a
Venn diagram to compare the
two types of conditioning.
New
Stimulus
Before
Both
New
Stimulus
After
Picture This
3.
Explain Working with a
partner, take turns
describing how Pavlov
conditioned dogs to
respond to a bell.
South Carolina Science Essentials
69
4.
Analyze Give an
example of this second kind
of conditioning from your
own experiences.
Another Type of Conditioning In the second kind of
conditioning, a new stimulus is given after a behavior has
happened. Getting an allowance for doing chores is an
example of this type of conditioning. You do the chores
because you want to get your allowance. You have learned,
or been conditioned, to perform activities that you may not
have done if you had not been offered a reward.
How do past experiences help solve problems?
In the problem-solving experiment shown below, bananas
were placed out of a chimpanzee’s reach. Instead of giving
up, the chimpanzee piled up boxes found in the room,
climbed them, and reached the bananas. At some time in
the past, the chimpanzee must have solved a similar
problem. The chimpanzee used past experiences, or insight,
to solve the problem.
Insight is a form of reasoning that allows animals to use
past experiences to solve new problems. When you were a
baby, you learned to solve problems using trial and error. As
you grow older, you use insight more often to solve
problems. Much of adult human learning is based on insight.
5.
Describe Why was the
chimpanzee able to solve
the problem by piling the
boxes to reach the
bananas?
70
Lesson P Types of Behavior
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Picture This
After You Read
Mini Glossary
behavior: the way an organism interacts with other
organisms and its environment
conditioning: a way of changing a learned behavior so that
a response to one stimulus becomes associated with a
different stimulus
imprinting: a learned behavior that happens when an
animal forms a social attachment to another organism
within a short time after birth or hatching
innate behavior: a behavior that an organism is born with
insight: a form of reasoning that uses past experiences to
solve new problems
instinct: a complex pattern of innate behavior, such as
spinning a web
reflex: an automatic response that does not involve a
message from the brain
1. Review the terms and their definitions in the Mini Glossary. Write a sentence that
explains the difference between instinct and insight.
2. Fill in the graphic organizer below with the different types of animal behavior.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Types of Animal Behavior
Innate behavior
3. How did finding answers to the question heads help you learn about types of behavior?
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about the types
of behavior.
End of
Lesson
South Carolina Science Essentials
71
Llesson
3
Q
A
The Atmosphere
Standard 6-4.1: Compare the composition and structure of Earth’s atmospheric layers (including the gases
and differences in temperature and pressure within the layers). Standard 6-4.2: Summarize the
interrelationships among the dynamic processes of the water cycle (including precipitation, evaporation,
transpiration, condensation, surface-water flow, and groundwater flow).
What You’ll Learn
how the atmosphere
supports life on Earth
■ what makes up the
atmosphere
■ about the water cycle
Before You Read
■
Study Coach
Air is everywhere. It’s always there. Without it, Earth would
be unfit for life. Have you ever wondered how air keeps us
alive? Write your ideas below.
Read to Learn
the text, create a quiz question
for each subject. When you have
finished reading, see if you can
answer your own questions
correctly.
Investigating Air
Classify Make the following
Composition of the Atmosphere
Foldable to help you organize
information about the things that
make up Earth’s atmosphere.
72
Lesson Q The Atmosphere
An Italian scientist named Galileo Galilei (1564–1642)
thought that air was more than just empty space. He
weighed a container, injected air into it, and weighed it
again. He observed that the container weighed more after
air had been added. Galileo concluded that air has weight,
so it must contain matter.
Today, scientists know other facts about Earth’s
atmosphere as well. Air stores and releases heat, and it holds
moisture. Because air has weight, it can exert pressure. All of
these properties, when combined with energy from the Sun,
create Earth’s daily weather.
The atmosphere is the layer of gases surrounding Earth.
It provides Earth with the gases that organisms need to live.
The atmosphere protects living things from harmful doses
of ultraviolet radiation and X-ray radiation. It absorbs heat
from the Sun and keeps Earth warm.
The atmosphere is a mixture of gases, water, and tiny
particles of solids and other liquids. Gravity keeps the
atmosphere around Earth and prevents it from moving
into space.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Create-a-Quiz As you read
What gases are in Earth’s atmosphere?
Nitrogen makes up about 78 percent of the atmosphere.
Oxygen, the gas necessary for human life, makes up about
21 percent. The rest is made up of trace gases or gases that
are found in extremely small amounts.
Two of the trace gases have important roles within the
atmosphere. Water vapor (H2O) is critical to weather. It is
responsible for clouds and precipitation. The other
important trace gas, carbon dioxide (CO2), is needed for
plants to make food. It also absorbs heat and helps keep
Earth warm.
Applying Math
1.
Use Percentages
What percentage of Earth’s
atmosphere is made up of
nitrogen and oxygen? What
percentage is made up of
trace gases? Show your
work.
What are aerosols?
Aerosols (AR uh sahlz) in the atmosphere are solids such
as dust, salt, and pollen, and tiny liquid droplets such as
acids. Dust gets into the atmosphere when wind picks tiny
soil particles off the ground or when volcanoes release ash.
Salt enters the atmosphere when wind blows across the
oceans. Pollen is released by plants. Human activities, such
as burning coal, also can release aerosols.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Layers of the Atmosphere
The atmosphere is divided into five layers. These layers
are based on temperature changes that occur with altitude,
or height above Earth’s surface. The lower layers are the
troposphere and the stratosphere. The upper layers are the
mesosphere, the thermosphere, and the exosphere.
What are the lower layers of the atmosphere?
The troposphere (TROH puh sfihr) is the layer of
atmosphere closest to Earth’s surface. It reaches upward to
about 10 km. The troposphere contains about three fourths
of the matter in Earth’s atmosphere. This is also where
nearly all clouds and weather occur. About 50 percent of the
Sun’s energy passes through the troposphere and reaches
Earth’s surface. The rest is reflected back to space.
Above the troposphere is the stratosphere
(STRAH tuh sfihr). The stratosphere is the layer of
atmosphere that exists from about 10 km to about 50 km
above Earth’s surface. Most of the atmosphere’s ozone is in
the stratosphere. The ozone in the stratosphere absorbs
much of the Sun’s ultraviolet radiation. Without the ozone
in this layer, too much radiation would reach Earth’s
surface, causing health problems for plants and animals.
Organize Information
Make a Foldable to record
information about the
troposphere, stratosphere,
and upper layers.
Upper
Layers
Stratosphere
Troposphere
South Carolina Science Essentials
73
What are the upper layers of the atmosphere?
Above the stratosphere is the mesosphere (ME zuh sfihr).
This layer extends from about 50 km to 85 km above Earth’s
surface. It contains little ozone, so much less heat is absorbed.
The thermosphere (THUR muh sfihr) is above the
mesosphere. This layer reaches from about 85 km to 500 km
above Earth’s surface. Temperatures in the thermosphere can
reach more than 1,700°C. This layer helps filter out harmful
rays from the Sun.
Parts of the thermosphere and mesosphere contain
electrically charged particles called ions. This zone is called the
ionosphere (i AH nuh sfihr). The ionosphere can reflect AM
radio waves, making long-distance communication possible.
The outermost layer of the atmosphere is the exosphere. It
contains few atoms. No clear border separates the exosphere
from space.
2.
Convert Percentages
to Fractions Earth’s
surface is about 70 percent
water. What fraction of
Earth’s surface is water?
What fraction is not water?
Show your work.
Earth’s Water
Earth often is called the water planet. This is because
Earth’s surface is about 70 percent water. Water can exist in
three separate states—ice, water, and water vapor. The table
shows where Earth’s water can be found.
Water is found as solid snow or ice in glaciers. In oceans,
lakes, and rivers, water exists as a liquid. In the atmosphere,
it is a gas called water vapor.
Distribution
of Earth’s Water
Location
Oceans
Picture This
3.
Interpret Data
According to the table,
where would you find the
least amount of Earth’s
water?
74
Lesson Q The Atmosphere
Amount of
Water (%)
97.2
Ice caps
and glaciers
2.05
Groundwater
0.62
Rivers and lakes
0.009
Atmosphere
0.001
Total (rounded)
100.00
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Applying Math
What is the water cycle?
Earth’s water is in constant motion. The water cycle is the
never-ending cycle of water between Earth’s surface and the
atmosphere. The Sun’s energy powers the water cycle. The
water in Earth’s oceans, rivers, and streams absorbs the Sun’s
energy and stores it as heat.
4.
Infer Would you expect
more evaporation to occur
on a sunny day or a cloudy
day?
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Evaporation and Condensation When water has enough
heat energy, it changes from liquid water into water vapor.
This process is called evaporation. Water vapor then enters
the atmosphere. Water also is transferred into the atmosphere
from plant leaves. This process is called transpiration.
As water vapor moves up through the atmosphere, it
becomes cooler. The molecules slow down. Eventually, the
water molecules change back into droplets of liquid water.
This process is called condensation.
Precipitation Water droplets get larger when two or more
droplets join together. Eventually, these droplets become large
enough to be seen. They form a cloud. If the water droplets
continue to get larger, they become too large and heavy to
remain in the atmosphere. They fall to Earth as precipitation.
After the water is on the ground, some of it evaporates. Most
water enters streams or soaks into the soil. In the soil, it is
called groundwater. Much of this water makes its way back to
lakes or to the oceans, where more evaporation occurs and the
water cycle continues. The figure below shows the water cycle.
5.
Compare and
Contrast How is
evaporation different from
condensation?
Droplets inside clouds fall as
precipitation, such as rain or snow.
As water vapor
rises into the air,
it cools and forms
liquid water again.
Tiny water droplets
form clouds.
Picture This
Energy for the water cycle
is provided by the Sun.
6.
Interpret Scientific
Illustrations How does
liquid water become part of
the atmosphere?
Water evaporates from oceans, lakes,
and rivers. Plants release water vapor.
Rain runs off
the land into
streams and
rivers. Plants
also take up
some of the
water.
South Carolina Science Essentials
75
After You Read
Mini Glossary
aerosols (AR uh sahlz): solids such as dust, salt, and pollen,
and tiny liquid droplets such as acids in the atmosphere
atmosphere: layer of gases surrounding Earth that protects
living things from harmful doses of ultraviolet radiation
and X-ray radiation and absorbs and distributes warmth
troposphere (TROH puh sfihr): the layer of the
atmosphere that is closest to Earth’s surface; contains
nearly all clouds and weather
water cycle: the never-ending cycle of water between
Earth’s surface and the atmosphere
1. Review the terms and their definitions in the Mini Glossary above. Choose two of the
terms that are related and write a sentence using both terms.
2. Complete the chart to organize information from this lesson.
Earth’s Atmosphere
Layers
_______________________
gases
troposphere
_______________________
_______________________
_______________________
evaporation
transpiration
condensation
precipitation
_______________________
exosphere
3. You created quiz questions as you read this lesson. How many of the questions can
you answer correctly? How did this strategy help you remember information about the
atmosphere?
End of
Lesson
76
Lesson Q The Atmosphere
Visit msscience.com to access your textbook,
interactive games, and projects to help you learn more about
the atmosphere.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Composition
Llesson
3
R
Ocean Currents and Climates
Before You Read
If you filled a bowl with water and gently dropped a scrap of
paper onto the water surface, it would float. If you want to
make the paper move without touching it or tilting the bowl,
how could you do it? What are you creating when you make
the paper move without touching it or tilting the bowl?
Read to Learn
What You’ll Learn
how wind and Earth’s
rotation affect surface
currents
■ how ocean currents
affect weather and
climate
■ the causes and effects
of density currents
■ how upwelling occurs
■
Study Coach
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Main Idea-Detail Notes
Surface Currents
Ocean water never stands still. Currents move the water
from place to place constantly. Ocean currents are like rivers
that move within the ocean. They exist at both the ocean’s
surface and in deeper water.
As you read about different
types of currents, write notes in
two columns. In the left column,
write the type of current. In the
right column, write details about
that current.
What causes surface currents?
Surface currents are powered by wind and usually move
only the upper few hundred meters of seawater. When the
global winds blow on the ocean’s surface, they set ocean water
in motion. Because of Earth’s rotation, the ocean currents that
result do not move in straight lines. Earth’s rotation causes
surface ocean currents in the northern hemisphere to curve to
their right. Surface ocean currents in the southern hemisphere
curve to their left. You can see this on the map on the next
page. The turning of ocean currents is an example of the
Coriolis effect. Recall that the Coriolis effect also is observed
on winds. Winds curve toward their right in the northern
hemisphere and toward their left in the southern hemisphere.
Understand Cause and
Effect Make the following
Foldable to help you understand
the cause-and-effect relationship
of currents.
South Carolina Science Essentials
77
We
ste
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es
Tr
ad
Tr
ad
r en t
s
ind
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ad
Tr
s
ind
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ad
Tr
The Gulf Stream Much of what is known about surface
currents comes from records kept by early sailors. Sailing
ships depended on certain surface currents to carry them
west and other currents to carry them east. One of the most
important currents for sailing east across the North Atlantic
Ocean is the Gulf Stream.
Find the Gulf Stream current on the map above. The
Gulf Stream flows from Florida northeastward toward
North Carolina. There it curves toward the east and
becomes slower and broader.
The Gulf Stream is 100 km wide. It was discovered in
the 1500s by Ponce de Leon. In 1770, Benjamin Franklin
published a map of the Gulf Stream drawn by Captain
Timothy Folger, a Nantucket whaler.
Can currents influence climates?
Since the Gulf Stream begins near the equator, it is a
warm current. It carries heat from the equator to other
parts of the ocean. Surface currents like the Gulf Stream,
on the eastern coasts of continents, tend to be warm.
They bring heat from the equator to other areas of Earth.
Currents on the western coasts are usually cold. This can
influence the climate of regions near these currents.
78
Lesson R Ocean Currents and Climates
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
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follow a current with your
pencil. Which way does
your pencil turn, left or
right? Why?
es
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Explain In the figure,
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Picture This
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Earth’s Global Winds Create Surface Currents
How do surface currents affect the climates
of Iceland and Southern California?
Based on its name, you might expect Iceland to have a cold
climate. However, the warm water of the Gulf Stream helps
keep Iceland’s climate mild. The current’s warm water flows
past Iceland and heats the surrounding air. This warm air
keeps Iceland’s climate mild and its harbors ice-free all year.
Southern California is known for its warmth and
sunshine. Look at the figure of surface currents on the
previous page. Find the California Current. It carries cold
water from polar regions toward the equator. Cold surface
currents affect the climate of coastal cities. For example, San
Francisco has cool summers and many foggy days because
of the California Current.
2.
Describe What affects
the climate of coastal cities?
3.
Sequence of Events
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Density Currents
Wind has no effect on water deeper than a few hundred
meters. However, currents may develop because of
differences in the density of the water. Seawater becomes
more dense as it gets colder or when it becomes more salty.
Gravity causes dense seawater to sink beneath less dense
seawater. As the mass falls, it spreads to less dense waters of
the ocean. This creates a density current. A density current
is a pattern in the ocean that forms when a mass of dense
seawater sinks beneath less dense seawater. Changes in
temperature and salinity work together to create density
currents. A density current moves very slowly.
How does salinity affect density currents?
One important density current begins in the cold water
north of Iceland. When water freezes, dissolved salts are left
behind in the unfrozen water. The very salty water that is
left behind is more dense and sinks. Slowly, it spreads along
the ocean floor toward the equator and the southern
Atlantic Ocean. As the water is sinking near Iceland, the
warm surface water of the Gulf Stream moves up from the
equator to replace it.
Another density current occurs in the Mediterranean Sea.
Warm air in the Mediterranean region causes the seawater
to evaporate. This leaves salt behind and increases the
salinity of the water. The dense, salty water sinks and flows
out to the Atlantic Ocean. At the surface, less dense water
from the Atlantic Ocean flows into the Mediterranean Sea.
Number the events to show
the order in which a density
current forms near Iceland.
saltier water sinks and
flows
warm water replaces
the cold water
ocean water freezes
South Carolina Science Essentials
79
How do density currents affect climate?
4.
Describe What might be
affected if density currents
stopped?
What if the density currents near Iceland stopped forming?
Some scientists hypothesize that this has happened in the
past and could happen again. Pollution and population
growth could lead to large amounts of carbon dioxide in the
atmosphere. The carbon dioxide would trap more of the Sun’s
heat and raise Earth’s temperature. If Earth’s temperature rose
enough, ice couldn’t form easily near the polar regions.
Glaciers on land would melt. The freshwater from the glaciers
would reduce the salinity of the ocean water. The density
currents would weaken or stop. If density currents stopped
flowing southward, warm equatorial surface water would no
longer flow northward. Earth could face drastic climate
changes, including different rainfall patterns and temperatures.
Picture This
5.
Infer Why does upwelling
around Peru make Peru a
rich fishing ground?
An upwelling is a current in the ocean that brings deep,
cold water to the ocean surface. The Coriolis effect pushes
surface water away from some coastal regions. Cold water
from deep in the ocean rises up to replace it. The illustration
shows an upwelling of cold water. The cold water is full of
nutrients from dead, decayed organisms. Tiny marine
organisms thrive in
Surface winds
these nutrient-rich
areas, which, in turn,
attract many fish. As
a result, areas of
Surface
upwelling are imporwater
tant fishing grounds
Cold water
because fish are
attracted to the areas
to eat the organisms.
What happens during El Niño?
During an El Niño (el NEEN yoh) event, the winds
blowing cold water from the coast of Peru slow down. The
Eastern Pacific Ocean becomes warmer, and upwelling is
reduced or stopped. Without nutrients provided by upwelling,
fish and other organisms cannot find food. This disrupts the
rich fishing grounds off Peru’s coast.
80
Lesson R Ocean Currents and Climates
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Upwelling
After You Read
Mini Glossary
density current: current created by the circulation pattern
in the ocean that forms when a mass of dense seawater
sinks beneath less dense seawater
surface current: ocean current that usually moves only the
upper few hundred meters of seawater
upwelling: ocean current that moves cold, deep water to the
ocean surface
1. Review the terms and their definitions in the Mini Glossary above. Choose a term and
write a sentence in which you provide an example of that term.
2. Complete the chart below to organize information from this lesson.
Ocean
Currents
Density Currents
Surface Currents
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
• travel in the ocean at a depth of
• travel in the ocean at a depth of
.
.
• caused by __________ water sinking
• set in motion by global ___________
below less ________ water.
blowing on Earth’s surface.
3. Earlier, you created two-column notes to help you learn about different types of currents.
How did writing notes make learning about currents easier?
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about ocean
currents and climate.
End of
Lesson
South Carolina Science Essentials
81
Llesson
3
S
Waves
What You’ll Learn
how wind can form
ocean waves
■ how water molecules in
a wave move
■ how the Moon and Sun
cause Earth’s tides
■ what forces cause
shoreline erosion
■
Study Coach
Before You Read
Have you ever surfed? Maybe you have seen someone surf.
How does a surfer who is out in the ocean return to shore?
Read to Learn
Authentic Questions
Understand Cause and
Effect Complete the sections
for waves and tides on the
Foldable you made earlier.
82
Lesson S Waves
Waves Caused by Wind
Surfers catch and ride waves all the way back to the
beach. A wave in water is a rhythmic movement that carries
energy through the water. Waves that surfers ride could have
started halfway around the world.
When wind blows across a body of water, friction pushes
the water along with the wind. When wind speed is great
enough, water will pile up into waves. Three things affect
the height of a wave: the wind speed, the length of time the
wind blows, and the distance over which the wind blows. As
wind continues to blow, the waves become higher. When the
wind stops, waves stop forming. But waves that have already
formed will still continue to travel for long distances.
What are the parts of a wave?
Each wave has a crest, its highest point, and a trough,
its lowest part. The wavelength is the horizontal distance
between the crests or troughs of two waves. Wave height is
the vertical distance from the trough of a wave to the crest.
Most waves in the ocean are between 2 m and 5 m high.
Some storms have been known to produce waves taller than
a six-story building.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Before you begin reading, write
down any questions you have
about waves. Look for the
answers as you read.
How do waves move?
When you watch a wave, it looks as if the water is moving
forward. But unless the wave is breaking onto the shore, the
water is not moving forward. Each molecule of water returns
to its original position when a wave passes. The molecule may
be pushed forward by the next wave, but it will return to its
original position when the wave passes. Water molecules
move in circular patterns within a wave.
1.
What are breakers?
A breaker is a collapsing wave. As a wave approaches the
shore, it changes shape. The bottom of a wave hits the
shallow floor of the ocean and causes friction. This friction
slows the bottom of the wave. However, the wave’s crest
keeps moving at the same speed. Eventually, the bottom of
the wave moves too slowly to support the top of the wave.
The crest outruns the trough, and the wave collapses. Water
tumbles over on itself, and the wave breaks onto the shore.
After a wave crashes, gravity pulls the water back to sea. The
figure below shows how waves break.
Describe How does a
wave affect the position of
a water molecule?
Wave Motion
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Breaker
Wave length decreases
Swells
Beach
Wave height increases
Wave direction
Sloping bottom
Picture This
2.
Describe What happens
to wave lengths and wave
heights as waves move
toward the shore?
On coasts that slope gently, waves deposit eroded sediments
on shore, forming beaches. Beaches extend inland as far as
the tides and waves are able to deposit sediments.
Waves usually hit the shore at slight angles. This creates
a longshore current. Longshore currents move sideways,
parallel to the shore. As a result, beach sediments are moved
sideways. Longshore currents carry many metric tons of
loose sediment from one beach to another.
South Carolina Science Essentials
83
Tides
During the day, the water level at the ocean’s edge
changes. This rise and fall in sea level is called a tide. A tide
is a wave that can be thousands of kilometers long but only
1 m to 2 m high in the open ocean. As the crest of this wave
approaches the shore, the sea level rises to form high tide.
Later in the day, the trough of the wave reaches the shore and
the sea level drops to form low tide. The difference between
sea level at high tide and low tide is the tidal range.
3.
Infer Is a tide always as
high as it is long?
How are tides created?
Tides are created by the gravitational attraction of Earth
and the Moon and of Earth and the Sun. Because the Moon
is much closer to Earth, it has a stronger pull. The Moon’s
gravity pulls at Earth, including its bodies of water. This
forms two bulges of water. One is on the side of Earth
closest to the Moon, caused by the water’s attraction to the
Moon’s gravitational pull. The other is on the side farthest
away, created because the Moon is pulling Earth away from
the water. These two places will have high tide. As Earth
rotates, the bulges follow the Moon. This results in high tide
happening around the world at different times.
The Sun’s gravity can increase or decrease the Moon’s
pull. When the Moon, Earth, and Sun line up, spring tides
are created. During spring tides, high tides are higher and
low tides are lower than usual. When the Moon, Earth, and
the Sun form a right angle, high tides are lower and low
tides are higher than usual. These are called neap tides. The
different positions of the Moon, Earth, and the Sun during
spring tides and neap tides are illustrated below.
Picture This
4.
Spring Tide
Draw Conclusions
There are more floods
during a spring tide than
there are during a neap tide.
Why do you think that is?
Neap Tide
84
Lesson S Waves
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What are spring tides and neap tides?
After You Read
Mini Glossary
tide: rhythmic rise and fall in sea level created by the
gravitational attraction of Earth and the Moon, and
Earth and the Sun
wave: in the ocean, the rhythmic movement that carries
energy through water
1. Review the terms and their definitions in the Mini Glossary above. Then write a sentence
using both vocabulary words.
2. Complete the cause-and-effect chart below to describe how the Moon’s gravitational pull
creates high and low tides.
CAUSE
The Moon is closer to Earth
than the Sun.
EFFECT
The gravitational pull of the _____________________________
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
is stronger than the pull of the _____________________ on Earth.
The Moon’s gravity pulls at Earth.
Two __________________________________ form in the ocean.
As Earth rotates, the bulges
follow the Moon.
High ___________________________________ happens around
_____________________________________ at different times.
3. You wrote down any questions you had about waves before you read. Were any of your
questions answered in the text? If not, ask the class your questions.
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about waves
and tides.
End of
Lesson
South Carolina Science Essentials
85
Llesson
3
T
What is weather?
Standard 6-4.5: Use appropriate instruments and tools to collect weather data (including wind speed and
direction, air temperature, humidity, and air pressure).
how pressure, wind,
temperature, and
moisture content of air
affect weather
■ how clouds form and
how they are classified
■ how rain, hail, sleet and
snow develop
■
Study Coach
Think-Pair-Share Work
with a partner. As you read this
lesson, discuss what you already
know about the topic and what
you learn.
Before You Read
Have you ever flown a kite or watched someone else fly one?
On the lines below, describe how the kite moves in the air.
Read to Learn
Weather Factors
Everybody talks about the weather. It may seem like small
talk, but weather is very important to some people. Pilots,
truck drivers, farmers, and other professionals study the
weather because it can affect their jobs.
What is weather?
You can look out the window and see that it’s raining, or
snowing, or windy. But do you really know what weather is?
Weather is the state of the atmosphere at a specific time
and place. Weather describes conditions such as air pressure,
wind, temperature, and moisture content in the air.
How does the Sun affect weather on Earth?
Organize Use four quarter
sheet note cards to record
information about the factors
that determine weather.
86
air
pressure
wind
temperature
moisture
in air
Lesson T What is weather?
The Sun provides almost all of Earth’s energy. Energy
from the Sun evaporates water on Earth. Evaporated water
enters the atmosphere and forms clouds. Later, the water
falls back to Earth as rain or snow.
The Sun also heats Earth. Heat from the Sun is absorbed
by Earth’s surface, which then heats the air above it. Because
of differences in Earth’s surface, some places in Earth’s
atmosphere are warmer and other places are cooler. Air
currents and water currents move the heat to different
places around Earth. Weather is the result of heat and
Earth’s air and water.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What You’ll Learn
What affects temperature?
Air is made up of molecules that are always moving
randomly, or without any set pattern, even when there is
no wind. Temperature is a measure of the average amount
of motion of molecules. When the temperature is high,
air molecules move rapidly and it feels warm. When the
temperature is low, air molecules move more slowly and it
feels cold.
1.
Have you ever flown a kite? What do you need in order
to get the kite off the ground and into the air? Kites fly
because air is moving. Air that moves in one direction is
called wind. The Sun heats Earth unevenly, but wind helps
spread the heat around.
As the Sun warms the air, the air expands and becomes
less dense. Warm, expanding air has low atmospheric
pressure. Cooler air is denser and sinks, which brings high
atmospheric pressure. Wind is the result of air moving from
areas of high pressure to areas of low pressure.
The temperature of air can affect air pressure. When air is
cooler, molecules are closer together, creating high pressure.
When air is heated, it expands and becomes less dense. This
creates lower pressure. Beaches are often windy as a result of
air moving from areas of high pressure to areas of lower
pressure, as shown in the figure below.
Determine When the
temperature is high, how
do air molecules move?
Picture This
2.
Label one side of the
figure high pressure and one
side low pressure.
Molecules in air
Molecules in air
pressure
Pressure
Pressure
Temperature
Wind
Temperature
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What causes wind?
pressure
South Carolina Science Essentials
87
What tools are used to measure wind?
3.
Explain Name one tool
for measuring wind
direction and tell how it
works.
Some instruments measure wind direction and others
measure wind speed. A wind vane, sometimes seen on
houses or barns, has an arrow that points in the direction
from which the wind is blowing. A wind sock, another tool
that shows wind direction, has an open end to catch the
wind. The wind sock fills and points in the direction toward
which the wind is blowing.
An anemometer (a nuh MAH muh tur) is an instrument
that measures wind speed. Anemometers have four open
cups that catch the wind and cause the anemometer to spin.
The faster the wind blows, the faster the anemometer spins.
What is humidity?
Picture This
4.
Determine Circle the
figure that shows droplets
of water forming.
Water
vapor molecules
Water
droplets
At cooler temperatures, the molecules in air move more
slowly. This slower movement allows the water vapor
molecules to stick together. Droplets of liquid water form,
as shown on the right in the figure above. This process of
liquid water forming from water vapor is called condensation.
If enough water is present in the air for condensation to
take place, the air is saturated.
88
Lesson T What is weather?
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Heat evaporates water into the atmosphere. Where does
the water go? Water vapor molecules fit into spaces among
the molecules that make up air. The amount of water vapor
held in the air is called humidity.
Air does not always hold the same amount of water
vapor. More water vapor can be present when the air is
warm than when it its cool. At warm temperatures, the
molecules of water vapor in the air move quickly. As a
result, the molecules do not come together easily, as shown
on the left in the figure below.
What is relative humidity?
Weather forecasters report the amount of moisture in the
air as relative humidity. Relative humidity is a measure of
the amount of moisture held in the air compared with the
amount of moisture the air can hold at a given temperature.
If the weather forecaster says that the relative humidity is 50
percent, this means that the air contains 50 percent of the
water needed for the air to be saturated at that temperature.
Dew Point
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
When the temperature drops, less water vapor can be
present in the air. If temperatures are low enough, water
vapor will condense to a liquid or form ice crystals. The
temperature at which the air is saturated and condensation
forms is the dew point. Dew point changes as the amount
of water vapor in the air changes.
You’ve probably seen water droplets form on the outside
of a can of cold soda. The cold can cooled the air around it
to its dew point. The water vapor in the air condensed,
forming water droplets on the soda can. Something similar
occurs when you see dew. Air near the ground cools to its
dew point, and then water vapor condenses and forms dew. If
temperatures are near 0° C, frost may form.
5.
Identify What is the
temperature at which
condensation forms called?
Forming Clouds
Clouds form as warm air is forced upward, expands, and
then cools, as shown in the figure below. When the air
cools, the water vapor molecules in the air come together
around particles of dust or salt in the air. These tiny water
droplets are not heavy enough to fall to Earth. So, they stay
suspended in the air. Billions of these droplets form a cloud.
Picture This
6.
Interpret Trace the
arrows that show moist
warm air rising.
Moist warm air
Heat
Damp earth
South Carolina Science Essentials
89
Classifying Clouds
Clouds are grouped, or classified, by shape and height.
Some clouds are tall and rise high into the sky. Some clouds
are low and flat. Dense clouds can bring snow or rain. Thin
clouds usually appear on sunny days. Three main factors
determine the shape and height of clouds—temperature,
pressure, and the amount of water vapor in the air.
What are the different types of clouds?
7.
Classify What are the
three main cloud types?
Stratus clouds are layered in smooth, even sheets across the
sky and may be seen on fair, rainy, or snowy days. Usually
stratus clouds form low in the sky. Fog is a stratus cloud that
forms when air is cooled to its dew point near the ground.
Cumulus (KYEW myuh lus) clouds are large, white, puffy
clouds that are often flat on the bottom and sometimes
tower high into the sky. Cumulous clouds can be seen either
in fair weather or in thunderstorms.
Cirrus (SIHR us) clouds are thin, white, feathery clouds.
They form high in the atmosphere and are made of ice
crystals. Although cirrus clouds are linked with fair weather,
they sometimes appear before a storm.
Cloud names are sometimes given prefixes to describe the
height of the cloud base. Three common cloud prefixes are
cirro-, alto- and strato-. Cirro- describes high clouds. Altois used for clouds that form at middle levels. Strato- is used
for clouds that form closer to the ground.
Cirrostratus clouds are made of ice crystals and form
high in the air. Usually cirrostratus clouds are a sign of
fair weather. Sometimes they signal a storm is on the way.
Altostratus clouds form at middle levels. If these clouds are
not too thick, sunlight can filter through them.
What types of clouds produce rain and snow?
8.
Determine When a
cumulus cloud becomes a
thunderstorm, what is it
called?
90
Lesson T What is weather?
Dark clouds that contain rain or snow are called nimbus
clouds. Nimbus is a Latin word meaning “dark rain cloud.”
The water content of nimbus clouds is so high that only a
little sunlight can pass through them.
When a cumulus cloud grows into a thunderstorm, it is
called a cumulonimbus (kyew myuh loh NIHM bus) cloud.
These high clouds can tower almost 18 km. Nimbostratus
clouds are layered clouds that usually bring long, steady rain
or snowfall.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
How is height used to name clouds?
Precipitation
Precipitation is water falling from clouds. Precipitation
occurs when cloud droplets combine and grow large enough
to fall to Earth. The cloud droplets form around tiny
particles like salt and dust in the air.
Why are some raindrops bigger than others?
Compare and contrast
Make a four-tab Foldable as
shown. As you read, take notes
on how the four forms of
precipitation are similar and
different.
You have probably noticed that some raindrops are bigger
than others. One reason for this size difference is the
strength of updrafts in a cloud. If strong updrafts of wind
keep drops in the air longer, they can combine with other
drops. As a result, they grow larger.
Another factor which affects raindrop size is the rate of
evaporation as the drop falls to Earth. If the air is dry, the
raindrop will get smaller as it falls. Sometimes the raindrop
will evaporate completely before it even hits the ground.
Rain
Hail
Sleet
Snow
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
How does temperature affect precipitation?
Air temperature determines what kind of precipitation
will fall—rain, snow, sleet, or hail. How air temperature
affects precipitation is shown in the figures below. When the
air temperature is above freezing, water falls as rain. If the
air temperature is so cold that water vapor changes to a
solid, it snows. Sleet forms if raindrops fall through a layer
of freezing air near Earth’s surface, forming ice pellets.
During thunderstorms, hail forms in cumulonimbus
clouds. Hailstones form when water freezes around tiny
centers of ice. Hailstones get larger as they’re tossed up and
down by rising and falling air. Most hailstones are small, but
sometimes they can get larger than softballs. Of all forms
of precipitation, hail causes the most damage.
Cloud
droplets
Warm
Raindrops
Ice
crystals Cloud
droplets
Cold
Cloud
droplets
Warm
Snowflakes
Ice
Warm
Cold
Rain
Snow
Cold
Sleet
Ice
crystal
Cloud
droplet
Picture This
9.
Identify In the figures,
circle the name of each type
of precipitation.
Partial
melting
Hail
Warm
Hail
South Carolina Science Essentials
91
After You Read
Mini Glossary
dew point: temperature at which air is saturated and
condensation forms
fog: stratus cloud that forms when air near the ground is
cooled to its dew point
humidity: amount of water vapor held in the air
precipitation: water falling from clouds—including rain,
snow, sleet, and hail—whose form is determined by
air temperature
relative humidity: measure of the amount of moisture held
in the air compared with the amount it can hold at a
given temperature
weather: state of the atmosphere at a specific time and
place; determined by air pressure, wind, temperature,
and how much moisture is in the air
1. Review the terms and their definitions in the Mini Glossary. Then write one sentence
describing today’s weather. Use at least two of the terms.
2. Use these words to fill in the blanks and tell about clouds forming and precipitation:
snow, hail, warm moist air, stratus, cumulus, rain, cirrus, sleet, water vapor, clouds
condenses into tiny droplets.
Droplets suspend in the air, forming
Three types of clouds are
,
Four kinds of precipitation come from clouds:
and
.
, and
,
.
,
.
3. You were asked to discuss and study this lesson with a partner. Was this a helpful
strategy for learning the information? Why or why not?
End of
Lesson
92
Lesson T What is weather?
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about weather.
,
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
rises, expands, and cools.
Llesson
3
U
Weather Patterns
Standard 6-4.6: Predict weather conditions and patterns based on weather data collected from direct
observations and measurements, weather maps, satellites, and radar. Standard 6-4.4: Summarize the
relationship of the movement of air masses, high and low pressure systems, and frontal boundaries to storms
(including thunderstorms, hurricanes, and tornadoes) and other weather conditions.
Before You Read
Have you ever gone into a basement or an attic? Describe how
the temperature felt compared to the rest of the building.
What You’ll Learn
how weather is related
to fronts and high and
low pressure areas
■ about different types of
severe weather
■
Read to Learn
Key Terms Highlight the key
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Weather Changes
Sometimes when you leave school in the afternoon, the
weather is different from what it was earlier in the morning.
Weather constantly changes.
terms and their meanings as you
read this lesson.
What are air masses?
An air mass is a large body of air that has the same
temperature and moisture content as the area over which it
formed. For example, an air mass that develops over land is
drier than one that develops over water. An air mass that
develops in the tropics is warmer than one that develops
over northern regions. When weather changes from one day
to the next, it is because of the movement of air masses.
How does air pressure affect the weather?
Pressure in the atmosphere varies over Earth’s surface. You
may have heard a weather forecaster talk about high- and
low-pressure systems. Low-pressure systems are masses of
rising air. When air rises and cools, clouds form. That’s why
areas of low pressure usually have cloudy weather. But
high-pressure air masses have a sinking motion. As a result,
it’s hard for air to rise and for clouds to form. So, high
pressure usually means nice weather.
Classify Make a four-tab
Foldable as shown. As you read,
take notes on the four different
fronts.
warm
fronts
cold
fronts
occluded
fronts
stationary
fronts
South Carolina Science Essentials
93
What are cyclones and anticyclones?
1.
Describe What type of
weather are cyclones
associated with?
Winds blow from areas of high pressure to areas of low
pressure. In the northern hemisphere, when wind blows into
a low-pressure area, Earth’s rotation causes the wind to swirl
in a counterclockwise direction. These large, swirling areas
of low pressure are called cyclones. Cyclones are associated
with stormy weather.
Winds blow away from an area of high pressure. In the
northern hemisphere, Earth’s rotation causes these winds
to swirl in a clockwise direction. High-pressure areas are
associated with fair weather and are called anticyclones.
Fronts
A boundary between two air masses that have different
temperature, density, or moisture is called a front. There are
four main types of fronts, including cold, warm, occluded,
and stationary.
Picture This
2.
Identify Color the arrow
showing cold air movement
in the cold front blue. Color
the arrow showing warm air
movement in the warm
front red.
A cold front occurs when cold air moves toward warm air,
as shown on the left in the figure below. The cold air goes
under the warm air and lifts it. As the warm air is lifted, it
cools and water vapor condenses, forming clouds. If there is
a large difference in temperature between the cold air and
the warm air, thunderstorms and tornadoes may form.
What is a warm front?
Warm fronts form when lighter, warmer air moves over
heavier, colder air, as shown on the right in the figure
below. In a warm front, wet weather may last for days.
Warm air
Cold Front
94
Cold air
Warm air
Cold air
Lesson U Weather Patterns
Warm Front
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What is a cold front?
What is an occluded front?
Most fronts involve two air masses. But occluded fronts
involve three air masses—cold air, cool air, and warm air. An
occluded front, as shown in the figure below, may form when a
cold air mass moves toward cool air with warm air in between.
The cold air forces the warm air up. The warm air is then
closed off from the surface. The term occlusion means “closure.”
Picture This
3.
Warm air
Interpret Color the
arrows red that show where
the warm air is closed off
from the surface in the
occluded front.
Cool air
Cold air
Occluded Front
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What is a stationary front?
A stationary front occurs when a boundary between air
masses stops moving, as shown in the figure below. Stationary
fronts can stay in the same place for several days. Often
there is light wind and precipitation at the stationary front.
Picture This
4.
Identify Circle the area
in the stationary front
where neither the cold air
nor warm air is moving.
Warm air
Cold air
Stationary Front
Severe Weather
You usually can do your daily activities regardless of the
weather. However, some weather conditions, like blizzards,
tornadoes, and hurricanes, can force you to change your plans.
South Carolina Science Essentials
95
What causes thunderstorms?
During thunderstorms, heavy rain falls, lightning flashes,
and thunder rumbles. Hail might fall. What causes these
weather conditions?
Thunderstorms occur in warm, moist air masses and
along fronts. Warm, moist air is forced up. It cools and
condensation begins, forming cumulonimbus clouds. When
rising air cools, water vapor condenses into water droplets
or ice crystals. Smaller droplets collide and form larger
ones. The larger, heavier droplets fall through the cloud
toward Earth’s surface. The falling droplets collide with
more droplets and get bigger. Raindrops cool the air around
them. The cool, dense air sinks. Sinking, rain-cooled air
and strong updrafts of warmer air cause the strong winds
that often come during thunderstorms. Hail may form as
ice crystals fall.
Explain How do water
droplets falling out of a
thundercloud get bigger
as they fall toward Earth’s
surface?
What damage do thunderstorms cause?
Sometimes thunderstorms stall in one area, causing heavy
rains. When streams can no longer hold all the water
running into them, flash floods occur. Because they occur
with little warning, flash floods are dangerous.
Thunderstorms often bring strong winds that can cause
damage. If a thunderstorm has winds over 89 km/h, it is
called a severe thunderstorm. Hail from thunderstorms can
dent cars, break windows, and flatten crops.
What causes lightning?
Inside a storm cloud, warm air is lifted rapidly as cooler
air sinks. This movement of air can cause different parts of
a cloud to have opposite charges. When an electrical current
runs between areas with opposite charges, lightning flashes.
Lightning can occur between two clouds, inside one cloud,
or between a cloud and the ground.
6.
Determine What causes
different parts of a cloud to
have opposite charges?
96
Lesson U Weather Patterns
What causes thunder?
Thunder comes from the rapid heating of air around a
bolt of lightning. Lightning can reach temperatures of about
30,000° C. That’s five times hotter than the surface of the
Sun. This heat causes air around the lightning to expand
rapidly. Then the air cools quickly and shrinks. Because of
the sudden expanding and shrinking, molecules in the air
move more rapidly. The rapid movement of molecules
creates sound waves. Thunder is the sound waves you hear.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
5.
What are tornadoes?
Some severe thunderstorms produce tornadoes. A tornado
is a violently rotating column of air that touches the
ground. Severe thunderstorms produce wind at different
heights which blow at different speeds and in different
directions. This difference in wind speed and direction is
called wind shear. Wind shear creates a rotating column
parallel to the ground. Updrafts in a thunderstorm can tilt
the rotating column upward, creating a funnel cloud. If the
funnel cloud touches the ground, it is called a tornado.
The figure below shows a diagram of a tornado. Notice
the different levels of winds and the rotating updraft. The
strong updraft usually forms at the base of a type of
cumulonimbus cloud called a wall cloud.
7.
Identify What is a
violently rotating column of
air that touches the ground
called?
Upper-level
winds
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Rotating updraft
Mid-level
winds
Wall cloud
Picture This
Dust envelope
Main inflow
8.
Identify Find the updraft
and trace over it with your
pencil.
How much damage can a tornado do?
Winds from tornadoes can rip apart buildings and tear
trees from the ground. If the winds of a tornado blow
through a house, they can lift off the roof and blow out the
walls. It can look as though the building exploded. In the
center of a tornado is a powerful updraft. The updraft can
lift animals, cars, and even houses into the air. Tornados do
not last long, but they are very destructive. In May of 1999,
thunderstorms produced more than 70 tornadoes in Kansas,
Oklahoma, and Texas. These tornadoes caused 40 deaths,
100 injuries, and more than $1.2 billion in damage.
South Carolina Science Essentials
97
How are tornadoes ranked?
As you have read, winds from tornadoes can cause severe
damage. Theodore Fujita, a tornado expert, created a scale
to describe and rank tornadoes. The scale, named the Fujita
Scale after him, is shown below. The Fujita Scale ranks
tornadoes based on how much damage they cause.
Tornadoes range from F0 which cause only light damage to
F5 which cause incredible damage. Luckily, only about one
percent of all tornadoes are in the category of F4 and F5.
Picture This
9.
Determine Circle the
category that describes
severe damage.
The Fujita Scale
Rank
F0
F1
F2
F3
F4
Wind speed (km/h)
<116
116–180
181–253
254–332
333–419
F5
420–512
Damage
Light: broken branches and chimneys
Moderate: roofs damaged, mobile homes upturned
Considerable: roofs torn off homes, large trees uprooted
Severe: trains overturned, roofs and walls torn off
Devastating: houses completely destroyed, cars picked up
and carried elsewhere
Incredible: total demolition
10.
Identify What are two
storms similar to
hurricanes?
The most powerful storm is a hurricane. A hurricane is a
large, low-pressure system that forms over the warm Atlantic
Ocean and has winds of at least 119 km/h. It is like a
machine that turns heat energy from the ocean into wind.
Similar storms are called typhoons in the Pacific Ocean and
cyclones in the Indian Ocean.
Hurricanes are similar to low-pressure systems over
land—only stronger. In the Atlantic and Pacific Oceans,
low-pressure systems sometimes develop near the equator.
In the northern hemisphere, winds around this low pressure
rotate counterclockwise. As the storms move across the
ocean, they gain strength from the heat and moisture of
warm ocean water.
What happens when a hurricane reaches land?
Hurricanes can strike land with great force. The high
winds sometimes produce tornadoes. Heavy rains and high
waves cause large amounts of damage. Sometimes floods
follow the heavy rains and cause additional damage.
Hurricanes can destroy crops, tear down buildings, and kill
humans and animals.
98
Lesson U Weather Patterns
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What is a hurricane?
What happens to the hurricane on land?
As long as the hurricane remains over water, it gets
energy from the warm moist air rising from the ocean. In
the figure below, small rising arrows show the movement of
warm air from the water below. Cool air goes down through
the eye, or center, of the hurricane. The storm needs this
energy from the ocean water. When a hurricane reaches
land, it loses its energy supply and the storm loses its power.
Outflow
Descending air
Warm moist air
Picture This
11.
Identify Highlight
all the arrows moving
counterclockwise.
Eye
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Spiral rain bands
What is a blizzard?
Severe storms also can occur in the winter. If you live in
the northern United States, you may have experienced the
howling wind and blowing snow of a blizzard. A blizzard
is a winter storm with conditions that include very cold
temperatures, high winds, and blowing snow that makes it
difficult to see. A blizzard usually lasts at least three hours.
How can you stay safe during severe storms?
When severe weather approaches, the National Weather
Service issues a watch or a warning. A watch tells you that
even though the weather isn’t dangerous yet, it may become
dangerous soon. During a watch, stay tuned to a radio or
television station that is reporting the weather.
When a warning is given, the weather is already severe.
During a severe thunderstorm or tornado warning, go to a
basement or to a room in the middle of the house away
from windows. When a hurricane or flood watch is given,
be prepared to leave home. During a blizzard, stay indoors.
12.
Explain What does a
weather watch tell you?
South Carolina Science Essentials
99
After You Read
Mini Glossary
air mass: large body of air that has the same characteristics
of temperature and moisture content as the area where
it formed
blizzard: severe winter storm with temperatures below
–12° C, winds of at least 50 km/h, and blowing snow
that causes poor visibility that lasts at least three hours
front: boundary between two air masses with different
temperature, density, or moisture
hurricane: large, severe storm that forms over tropical
oceans and has winds of at least 119 km/h
tornado: violently rotating column of air in contact with
the ground
1. Review the terms and their definitions in the Mini Glossary. Then write a sentence
explaining how hurricanes get and keep their strength.
2. Write the name of the correct weather front above each description.
Cold air goes under warm air.
Warm air is lifted.
3 air masses: cold, cool, warm
Warm air closed off from Earth.
Neither warm nor cold air is moving.
Lighter, warmer air moves over cold air.
3. Did highlighting key terms and their meanings help you learn the information about
weather patterns? Would you use this study strategy again?
End of
Lesson
100
Lesson U Weather Patterns
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about weather
patterns.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
warm front, stationary front, occluded front, cold front
Llesson
3
V
Weather Forecasts
Standard 6-4.6: Predict weather conditions and patterns based on weather data collected from direct
observations and measurements, weather maps, satellites, and radar.
Before You Read
How good are you at predicting the weather? On the lines
below, list things you consider when you’re deciding what
the day’s weather might be like.
Read to Learn
What You’ll Learn
how data are collected
for weather maps and
forecasts
■ what symbols are used
on a weather map
■
Study Coach
Sticky Notes As you read
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Weather Observations
By looking at the thermometer or at clouds in the sky, you
can tell things about the weather. Certain things about weather
you know just from where you live. For example, if you live in
Florida, you know that it will probably be warm and sunny.
this lesson, mark the pages you
find interesting or where you
have a question. Share these
pages with another student or
with the teacher.
What does a meteorologist do?
A meteorologist (mee tee uh RAH luh jist) studies the
weather. A meteorologist gathers information about
temperature, air pressure, wind, humidity and precipitation.
By using tools like computers, Doppler radar, satellites, and
weather balloons, a meteorologist makes weather maps and
forecasts the weather.
Forecasting Weather
Meteorologists gather information and make predictions
about weather in the future. Because storms can be dangerous,
it is important to know if a storm is coming. The National
Weather Service uses two sources to predict the weather.
They collect information, or data, from the upper
atmosphere. They also collect data from Earth’s surface.
Organize Make a Foldable
like the one shown below to
help you learn about weather
forecasts.
Meteorologist
Weather
Symbols
Weather Map
Weather
Instruments
South Carolina Science Essentials
101
Station Models Meteorologists gather data from Earth’s
surface. Then this data is recorded on a map. A station
model shows weather conditions at a specific location using
symbols on a map. Information coming from station models
and from instruments in Earth’s atmosphere is put into computers and helps forecast weather.
Describe What does a
station model show?
Weather maps have lines that connect locations with the
same temperature or the same pressure. An isotherm
(I suh thurm) is a line that connects places with the same
temperature. Iso means “same.” Therm means “temperature.”
You may have seen isotherms on weather maps on TV.
Weather maps, like the one below, also have isobars. An
isobar is a line that connects two places with the same
atmospheric pressure. Isobars show how fast wind is blowing
in an area. When isobars are drawn close together, there is a
big difference in air pressure. This means a strong wind is
blowing. When isobars are drawn farther apart, there is little
difference in pressure. Winds in this area are gentler. Isobars
also show locations of high- and low-pressure areas.
On the weather map below, the pressure areas are drawn
as circles with the word High or Low in the middle of the
circle. Fronts are drawn as lines and symbols. This
information helps meteorologists forecast the weather.
Picture This
Locate Find the low
1000 1008
1008
sss
ss
1000
1008
1016
HIGH
1032
1024
1032
HIGH
LOW
75
130
67
4 Portland
Legend
Cold front
Warm front
Occluded front
Stationary front
Isobar
Precipitation
41 269
Duluth
35 16
1016
1008
1000
s
58
s
Denver 76 183
57 0
1024
HIGH
100
8
LOW
s
s
Springfield
ss
6
101
79 125
64 227 76 20 84 134Columbia
Little Rock
Nashville 5 8
7
0
71 217 54 1
HIGH
sssssssss
sss
s
San Diego 76 194
70
89 1
2
72
HIGH
28 4 Tucson
LOW
074
54 26
1016
ss
s
s
sss
sss
1024
1024
s
s
sss
pressure area by Portland
and trace over the circle.
s
2.
4
102
Dallas 68 6
LOW
101
6
1024
102
LOW
1016
Lesson V Weather Forecasts
Miami
1024
4
85 24
4
75 HIGH
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
How do maps show temperature and pressure?
s
sss
1.
After You Read
Mini Glossary
isobar: line drawn on a weather map that connects two
places with the same atmospheric pressure
isotherm: line drawn on a weather map that connects
locations with the same temperature
meteorologist: person who studies the weather and uses
information from Doppler radar, weather satellites,
computers, and other instruments to make weather
maps and provide forecasts
station model: indicates weather conditions at a specific
location by using symbols on a map
1. Review the terms and their definitions in the Mini Glossary. Then write a sentence
explaining the difference between an isobar and an isotherm.
2. Arrange the following events in order to show how a meteorologist studies weather and
uses information.
A meteorologist:
forecasts weather
gathers data on weather conditions
makes weather maps
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
First
Second
Third
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about
weather forecasts.
End of
Lesson
South Carolina Science Essentials
103
Llesson
3
W
Earth’s Weather
Standard 6-4.7: Explain how solar energy affects Earth’s atmosphere and surface (land and water).
Standard 6-4.8: Explain how convection affects weather patterns and climate.
how clouds form
what causes
precipitation
■ what causes wind
■
■
Study Coach
Mapping Definitions As
you read, make a definition map
to describe and define
vocabulary words. Your map
should include questions about
each word, such as, “What is it?”
and “What are some examples?”
Organize Information
Make the following Foldable to
help you organize information
about Earth’s weather.
104
Lesson W Earth’s Weather
Before You Read
Hot, cold, windy, snowy, sunny, cloudy—these are all ways
to describe weather. What is your favorite kind of weather?
Describe it.
Read to Learn
Weather
A weather bulletin has been issued for your area. Heavy
snow is expected during the night. Will the schools be
closed? Will people be able to get to work? How might this
weather affect your family?
Weather describes the current condition of the
atmosphere, including temperature, cloud cover, wind speed,
wind direction, humidity, and air pressure. A meteorologist
(mee tee uh RAH luh jist) uses this information to forecast,
or predict, the weather.
What is temperature?
Recall that the Sun’s energy powers the water cycle. In
fact, the Sun is the source of almost all of the energy on
Earth. When the Sun’s rays reach Earth, energy is absorbed.
As gas molecules absorb more energy, they move faster and
farther apart. Temperature is a measure of how fast air
molecules are moving. The faster the molecules move, the
higher the temperature. Temperature is measured with a
thermometer. A thermometer has a scale divided into
degrees. The two scales commonly used to measure
temperature are the Celsius and Fahrenheit scales.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What You’ll Learn
How does energy move through
the atmosphere?
Fast-moving molecules transfer energy to slower-moving
molecules when they bump into each other. This transfer of
energy is called conduction. Conduction transfers heat from
Earth’s surface to nearby molecules in the air.
The heated air rises. As it rises, it starts to cool. When the
rising air becomes cooler than the air around it, it sinks
again. The process of warm air rising and cool air sinking is
called convection. Convection is the main way heat is moved
throughout the atmosphere. How conduction and convection
transfer heat on Earth is shown in the illustration below.
Picture This
Cool air pushes warm
air upward, creating a
convection current.
1.
Interpret Scientific
Illustrations Highlight
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
the processes of
conduction and convection
on the diagram.
A few centimeters of air
near the surface are
heated by conduction.
Energy from the Sun
warms the surface.
How is temperature related to air pressure?
The weight of air exerts pressure. Air pressure decreases
as altitude increases. As you go higher, the weight of the
atmosphere above you is less.
Temperature and air pressure are related. When air is
heated, its molecules move faster, and the air expands. This
makes the air less dense so it exerts less pressure on anything
below it. The lighter, warmer air moves upward. Cooled air
becomes more dense and sinks as the molecules slow down
and move closer together. Sinking air produces more pressure.
So, rising air usually means lower pressure and sinking air
means higher pressure. Air pressure varies over Earth’s surface.
2.
Infer Is air pressure likely
to be greater at the top or
the base of a mountain?
Why?
South Carolina Science Essentials
105
What is humidity?
As air warms up, it can cause water that is touching it to
evaporate and form water vapor. Humidity is the amount of
water vapor in the atmosphere. Warm air causes evaporation
to occur more quickly. Warm air also can hold more moisture.
When air is holding as much water vapor as it can, it is said
to be saturated and condensation may occur. The dew point
is the temperature at which air becomes saturated and
condensation can occur.
Describe When is air
saturated?
What is relative humidity?
Suppose a mass of air is chilled. The amount of water
vapor in the air does not change unless condensation
occurs. However, less moisture can be evaporated into the
chilled air. Relative humidity is a measure of the amount of
water vapor in the air compared to the amount that could
be held at that temperature. As air cools, relative humidity
increases if the amount of water vapor in the air doesn’t
change. When the air holds all the water vapor it can hold
at that temperature, the relative humidity is 100 percent.
Local TV weather reports sometimes give the dew point
on summer days. If the dew point is close to the air
temperature, relative humidity is high. If the dew point is
much lower than the air temperature, relative humidity is low.
Clouds
4.
Describe What are
clouds made of?
One of the best signs that Earth’s atmosphere is in
motion is the presence of clouds. A cloud forms when air
rises, cools to its dew point, and becomes saturated. Water
vapor then condenses onto small particles in the air. If the
temperature is warm, the clouds are made up of small drops
of water. If the temperature is cold, the clouds are made up
of small ice crystals.
Clouds are classified according to the height above Earth’s
surface at which they form. The most common classification
method separates clouds into low, middle, or high groups.
What are low clouds?
Clouds in the low-cloud group form at altitudes of 2,000 m
or less. These include puffy cumulus (KYEW myuh lus)
clouds that form when air currents rise, carrying moisture
with them. Sometimes cumulus clouds are signs of fair
weather. Other cumulus clouds can produce thunder,
lightning, and heavy rain.
106
Lesson W Earth’s Weather
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
3.
Stratus and Nimbostratus Clouds Another type of low
cloud is layered stratus (STRA tus) clouds. Stratus clouds
form as dull, gray sheets that can cover the entire sky.
Nimbostratus (nihm boh STRA tus) clouds form low, dark,
thick layers that block the Sun. Stratus and nimbostratus
clouds produce precipitation.
What are middle clouds?
Clouds that form between about 2,000 m and 8,000 m are
known as the middle-cloud group. Most of these clouds are
of the layered variety. Their names often have the prefix
alto- in front of them, such as altocumulus and altostratus.
These clouds can hold enough moisture to produce light
rain or snow. Sometimes they are made up of a mixture of
liquid water and ice crystals.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
How do high clouds form?
Some clouds form so high in the atmosphere that they
are made up entirely of ice crystals. These are known as the
high-cloud group. They include the high, wispy cirrus
(SIHR us) clouds. They also include cirrostratus clouds,
which are high, layered clouds that can cover the entire sky.
Some clouds extend from low levels to high levels
of the atmosphere. These are clouds of vertical
development. The most common type is cumulonimbus
(kyew myuh loh NIHM bus) clouds. The term nimbus
usually means the cloud creates precipitation.
Cumulonimbus clouds produce the heaviest rains of all.
Known as thunderstorm clouds, they start to form at
heights of less than 1,000 m but can build to more than
16,000 m high.
5.
Precipitation
Rain, freezing rain, sleet, snow, and hail are all forms of
precipitation. Precipitation forms when drops of water or
crystals of ice become too large to be suspended in a cloud
and fall to Earth. The type of precipitation that falls
depends on temperature. For example, rain falls when the
air temperature is above freezing. However, if the air at high
altitudes is above freezing while the air near Earth’s surface
is below freezing, the result might be freezing rain.
Draw Conclusions
Which of these clouds
means that a thunderstorm
is on the way?
a.
b.
c.
d.
altocumulus
altostratus
cirrus
cumulonimbus
South Carolina Science Essentials
107
6.
Think Critically Why
do hailstones develop in
cumulonimbus clouds?
Hail is balls of ice that form within a storm cloud. Strong
winds inside the cloud toss ice crystals up and down. As the
ice crystals move, droplets of water freeze around them.
Hailstones keep growing until they are too heavy for the
winds to keep up. Then they fall to the ground.
Ice crystals
Freezing
Hail
Strong winds
7.
Infer If the wind is
blowing from west to east,
where is the area of high air
pressure?
Warmer air is less dense and moves upward. This causes
regions of low air pressure. When cooled, the molecules in
air move closer together. The air becomes more dense and
sinks. This forms regions of high air pressure. Air moves
from areas of high pressure to low pressure. This movement
is called wind. The greater the difference in temperature or
pressure between two areas, the stronger the wind.
How does air circulate?
Picture This
8.
Compare and
Contrast Do areas near
the equator heat up more
or less than other regions?
What about areas near the
poles?
108
Lesson W Earth’s Weather
Look at the figure.
You can see that the
Sun’s rays strike Earth
at a higher angle near
the equator than near
the poles. This is why
tropical areas heat up
more than polar
regions do. Warm air
flows toward the poles
from the tropics. Cold air flows from the poles toward the
equator.
But the moving air doesn’t flow in a straight line. Because
Earth rotates, winds are pushed to their right in the northern
hemisphere and to their left in the southern hemisphere.
This is known as the Coriolis (kor ee OH lus) effect.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Wind
What are surface winds?
Air at the equator is heated by the rays of the Sun. This
air expands, becomes less dense, and gets pushed upward. At
about 30° latitude, the air is somewhat cooler. This air sinks
and then flows toward the equator. As this air flows, it is
turned by the Coriolis effect. The result is steady winds that
blow from east to west. These steady winds are called the
trade winds. Trade winds are also called tropical easterlies.
9.
Infer The tropical
easterlies are called the
trade winds. Why do you
think they were given this
name?
What are westerlies and easterlies?
Between 30° and 60° latitude north and south of the
equator, winds usually blow from the west. These winds
form between the cold air from the poles and warmer air
closer to the equator. These winds are called the prevailing
westerlies. These regions are known for frequent storms.
Similar winds near the poles blow from the east and are
known as the polar easterlies. The figure below shows
Earth’s major surface winds.
Picture This
Wind belts
Sinking air
High
Rising air
Low
Surface winds
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
10.
Polar
easterlies
High
60º N
30º N
Low
0º Equator
30º S
High
60º S
Prevailing
westerlies
Interpret Scientific
Illustrations The city of
Buenos Aires, Argentina is
at about 34° latitude south
of the equator. What type
of winds affect the city’s
weather?
Trade
winds
Trade
winds
Prevailing
westerlies
Polar
easterlies
Low
High
What are jet streams?
Jet streams are bands of strong winds that develop at
higher altitudes within the zone of the prevailing westerlies.
Jet streams are like giant rivers of air. They are important
because weather systems move along their paths.
South Carolina Science Essentials
109
After You Read
Mini Glossary
dew point: the temperature at which air is saturated and
condensation can occur
humidity: the amount of water vapor in the atmosphere
precipitation: occurs when drops of water or crystals of ice
become too large to be suspended in a cloud and fall to
Earth; rain, freezing rain, sleet, snow, or hail
relative humidity: a measure of the amount of water vapor
in the air compared with the amount that could be held
at a specific temperature
weather: the current condition of the atmosphere, including
cloud cover, temperature, wind speed and direction,
humidity, and air pressure
1. Review the terms and their definitions in the Mini Glossary. Choose a term and write a
sentence in which you provide an example of that term.
2. Complete the concept map to show factors that affect Earth’s weather.
_______________________
Earth’s Weather
_______________________
_______________________
wind
3. As you read this lesson, you made definition maps for the vocabulary words you learned.
How did the mapping strategy help you? What is another strategy you could use to help
you learn new vocabulary?
End of
Lesson
110
Lesson W Earth’s Weather
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about Earth’s
weather.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
air pressure
Llesson
3
X
Air Movement
Standard 6-4.9: Explain the influence of global winds and the jet stream on weather and climatic conditions.
Before You Read
When you think of the word wind what comes to mind?
Brainstorm some words and write them on the lines below.
Read to Learn
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Forming Wind
Earth is mostly rock or land. Three-fourths of Earth’s
surface is covered by the oceans. These two areas strongly
affect wind systems all over Earth.
Because the Sun heats Earth unevenly, some areas are
warmer than others. Remember that warmer air expands
and becomes less dense than cold air. As a result, air
pressure is lower in areas where air is heated. Wind is the
movement of air from an area of higher pressure to an area
of lower pressure.
What You’ll Learn
why different altitudes
receive different
amounts of solar energy
■ about Coriolis effect
■ how air is affected by
land and water surfaces
below it
■
Study Coach
State the Main Ideas As
you read this lesson, stop after
each paragraph and put what
you have just read into your own
words.
What is heated air?
Different areas of Earth receive different amounts of
radiation from the Sun. Why? Because Earth’s surface is
curved. The equator receives more radiation than areas north
or south of it. The Sun’s rays hit the equator more directly.
Because air at the equator is warm, it is less dense. So it is
displaced, or moved, by denser, colder air. Remember that
when cooler, denser air sinks while warmer, less dense air
rises, a convection current forms. The cold, dense air comes
from the poles. They receive less radiation from the Sun,
because its rays strike the poles at an angle, spreading out
the energy. The resulting dense, high-pressure air sinks and
moves along Earth’s surface. However, there is more to wind
than dense air sinking and less dense air rising.
Classify Make a three-column
Foldable to help you understand
the main causes of air
movement.
Convection
currents
Polar
jet
stream
Land
breeze
Coriolis
effect
Global
winds
Sea
breeze
South Carolina Science Essentials
111
What is the Coriolis effect?
1.
Determine What causes
moving air and water to
appear to turn one way in
the southern hemisphere
and the opposite way in the
northern hemisphere?
What would happen if you threw a ball to a person sitting
across from you on a moving merry-go-round? By the time
the ball got to the opposite side, the other person would
have moved and the ball would appear to have curved.
Like the merry-go-round, the rotation of Earth causes the
Coriolis (kohr ee OH lus) effect. The Coriolis effect causes
moving air and water to appear to turn to their left in the
southern hemisphere (south of the equator) and to turn to
the right in the northern hemisphere (north of the equator)
due to Earth’s rotation. This effect is illustrated in the figure
below. The flow of air caused by the Coriolis effect and by
differences in the amount of solar radiation received on
Earth’s surface creates wind patterns on Earth’s surface.
These wind patterns influence the weather.
N
Equ
ato
r
Path of wind
without Coriolis
effect
Picture This
2.
Explain Do winds turn to
their left or their right north
of the equator?
S
Earth's rotation
Global Winds
3.
Identify What is the
name of the windless, rainy
zone near the equator?
112
Lesson X Air Movement
How did Christopher Columbus get from Spain to the
Americas? The Nina, the Pinta, and the Santa Maria had
no source of power other than the wind in their sails.
Early sailors used wind patterns to help them navigate the
oceans. Near the equator, there sometimes was little or no
wind to fill the sails of their ships. It also rained nearly every
afternoon. Why? Because air near the equator has been heated
by the Sun. Warm air rises, creating low pressure and little
wind. The rising air then cools and causes rain. This windless,
rainy zone near the equator is called the doldrums.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Actual path of wind
Picture This
Earth’s Winds
60°N
4.
Polar easterlies
Identify Which winds are
located on either side of the
Equatorial doldrums?
Westerlies
30°N
Trade winds
0°
Equatorial doldrums
Trade winds
30°S
Westerlies
60°S
Polar easterlies
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What winds blow near Earth’s surface?
The figure above shows some of the winds that blow near
Earth’s surface. These prevailing winds move heat and
moisture around Earth.
Trade Winds Air descending to Earth’s surface near 30°
north latitude and 30° south latitude creates steady winds.
These winds blow in tropical regions. Early sailors liked
them because they moved their ships along quickly. Sailors
named them trade winds because they relied on these winds
to help them sail to many places to trade goods.
Prevailing westerlies Between 30° latitude and 60° latitude
in the northern and southern hemispheres, winds called the
prevailing westerlies blow. These winds blow in the opposite
direction from the trade winds. Prevailing westerlies cause
much of the movement of weather across North America.
5.
Explain Why would
sailors like trade winds?
Polar easterlies Another surface wind, polar easterlies, are
found near the poles. Near the north pole, easterlies blow
from northeast to southwest. Near the south pole, polar
easterlies blow from the southeast to the northwest.
South Carolina Science Essentials
113
What winds are in the upper troposphere?
6.
Define What are the
narrow bands of strong
winds that blow near the
top of the troposphere?
Jet streams are narrow bands of strong winds that blow
near the top of the troposphere. The polar jet stream
affecting North America forms along a boundary where
colder air lies to the north and warmer air lies to the south.
It moves faster in the winter because there is a greater
difference between cold air and warm air. As the figure below
shows, the polar jet stream moves in a wavy west-to-east
direction. It is usually found between 10 km and 15 km
above Earth’s surface.
N
Cold air
Polar j
et stream
Picture This
Determine Trace with
your pencil the direction of
the polar jet stream. Is it
moving east to west or west
to east?
Warm air
S
What are the effects of the jet stream?
The jet stream helps move storms across the country from
the west to the east. Jet pilots use information about jet
streams to help them fly. When flying to the east, planes
save time and fuel. Going west, planes avoid the jet stream
by flying at a different altitude. Flying from Boston to
Seattle may take 30 minutes longer than flying from Seattle
to Boston.
8.
Infer Why would it take
longer to fly from east to
west than from west to
east?
114
Lesson X Air Movement
Local Wind Systems
Major weather patterns for the entire planet are
determined by global wind systems. Local weather is
affected by smaller wind systems. Those who live near large
bodies of water experience two such wind systems. They are
sea breezes and land breezes.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
7.
Sea Breeze
Picture This
9.
Interpret What is
happening to the warm air
in both figures?
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Land Breeze
What causes sea breezes and land breezes?
Convection currents over areas where the land meets the
sea can cause wind. During the day, the Sun’s heat warms
the land more than it warms the water. A sea breeze is the
movement of air from sea to land during the day. Air over
the land is heated by conduction. This heated air is less
dense and has lower pressure. Cooler, denser air over the
water has higher pressure and flows towards the warmer,
less dense air above the land. A convection current results,
and wind blows from the sea toward the land.
At night, the land and the air above it cools much faster
than ocean water. Cooler, denser air above the land moves
over the water, as the warm air over the water rises. The
movement of air from land to sea is a land breeze.
10.
Identify What causes
wind over areas where the
land and sea meet?
South Carolina Science Essentials
115
After You Read
Mini Glossary
Coriolis (kohr ee OH lus) effect: causes moving air and
water to appear to turn left in the southern hemisphere
and turn right in the northern hemisphere due to Earth’s
rotation
jet streams: narrow bands of strong winds that blow near
the top of the troposphere
land breeze: movement of air from land to sea at night,
created when cooler, denser air from the land forces
warmer air over the sea
sea breeze: movement of air from sea to land during the day
when cooler air above the water moves over the land
forcing the heated, less dense air above the land to rise
wind: the movement of air from an area of higher pressure to
an area of lower pressure
1. Review the terms and definitions in the Mini Glossary. Then choose one of the
definitions and write it in a sentence in your own words.
2. Fill in the boxes with the correct word, cooler or warmer, to show what occurs in a
sea breeze and a land breeze.
water
_________ air
Land Breeze
_________ air
_________ air
land
water
land
_________ air
3. Think of Earth’s shape. How does the shape of Earth affect the amount of heat different
areas receive?
End of
Lesson
116
Lesson X Air Movement
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about air movement.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Sea Breeze
Llesson
3
Y
What is energy?
Standard 6-5.1: Identify the sources and properties of heat, solar, chemical, mechanical, and electrical
energy. Standard 6-5.2: Explain how energy can be transformed from one form to another (including the
two types of mechanical energy, potential and kinetic, as well as chemical, and electrical energy) in accordance
with the law of conservation of energy.
Before You Read
What does the phrase “She has a lot of energy” mean to you?
Read to Learn
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
The Nature of Energy
Energy is the ability to cause change. An object that has
energy can make things happen. Look around you. Changes
are happening. Someone might be walking by. Sunshine
might be warming your desk. Maybe you can see the wind
move the leaves on a tree. What changes are happening?
What You’ll Learn
what energy is
the difference between
kinetic energy and
potential energy
■ the different forms of
energy
■
■
Highlight Forms of
Energy As you read this
lesson, highlight the different
forms of energy. Then write an
example of each type of energy
next to the places you
highlighted.
When is energy noticed?
You have a lot of energy. So does everything around you.
But you only notice this energy when a change takes place.
When a change happens, energy moves from one object to
another. Energy from sunlight moves to the spot on the
desktop and makes it warm. Energy from the wind moves to
leaves. All objects, including desktops and leaves, have energy.
Energy of Motion
Things that move can cause change. Suppose a bowling ball
rolls down the alley and knocks down some bowling pins.
Does this involve energy? A change happens when the pins
fall over. The bowling ball causes this change. Since energy is
the ability to cause change, the bowling ball has energy. The
energy in the movement of the bowling ball makes the pins
fall. The energy an object has because of its motion is kinetic
energy. So as a bowling ball moves, it has kinetic energy. If
an object is not moving, it does not have kinetic energy.
Organize Information
Make the following Foldable to
organize information about the
nature of energy, the energy of
position, and the different forms
of energy.
South Carolina Science Essentials
117
How are kinetic energy and speed related?
What would happen to the bowling pins if the bowling
ball rolls faster? More of the pins might fall down or they
might move farther. A faster bowling ball causes more
change to happen than a slower bowling ball. The faster the
bowling ball goes, the more kinetic energy it has. This is
true for all moving objects. Kinetic energy increases as an
object moves faster.
Apply Does a slowermoving object have more
or less kinetic energy than
a faster-moving object?
Compare and Contrast
Make the following Foldable to
compare and contrast kinetic
energy and potential energy.
Picture This
2.
Determine Which vase
on the shelves has the most
potential energy?
118
Lesson Y What is energy?
How are kinetic energy and mass related?
Suppose you roll a volleyball down the alley at the same
speed as a bowling ball. Will the volleyball move the pins as
far as the bowling ball will? The answer is no. The volleyball
might not knock down any pins.
How are the volleyball and the bowling ball different?
They are moving at the same speed, but the volleyball has
less mass. The volleyball has less kinetic energy than the
bowling ball because it has less mass. Kinetic energy
increases as the mass of an object increases.
Energy of Position
An object can have energy even if
it is not moving. Look at the vase on
top of the bookcase. The vase does not
have any kinetic energy because it is
not moving. What if it accidentally
falls to the floor? Changes happen.
Gravity pulls the vase downward. The
vase has kinetic energy as it falls.
Where did this energy come from?
When the vase was sitting on the
shelf, it had potential (puh TEN chul)
energy. Potential energy is the energy
stored in an object because of its
position. The position of the vase is
its height above the floor. As the vase
falls, the potential energy is
transformed, or changed, from one form to another. It is
transformed into kinetic energy. A vase has more potential
energy if it is higher above the floor. Potential energy also
depends on mass. The more mass an object has, the more
potential energy it has. The objects in the figure have
different amounts of potential energy.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
1.
Forms of Energy
Food, sunlight, and wind have energy. But they have
different kinds of energy. The energy in food and sunlight is
different from the kinetic energy in the wind. The warmth
you feel from sunlight is different from kinetic energy or
potential energy.
What is thermal energy?
When you sit near a sunny window, you get warm. The
feeling of warmth is a sign that you are getting more
thermal energy. Thermal energy is energy of an object that
increases as the object’s temperature increases. All objects
have thermal energy. In the figure below, a cup of hot
chocolate has more thermal energy than a bottle of cold
water. The bottle of cold water has more thermal energy
than a block of ice with the same mass.
Picture This
3.
Identify Circle the object
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
with the greatest thermal
energy. Put a box around
the object with the least
thermal energy.
Your body makes thermal energy all the time. Chemical
reactions that happen inside your cells make thermal energy.
Where does this energy come from? Thermal energy is
released by chemical reactions. Thermal energy comes from
another kind of energy called chemical energy.
What is chemical energy?
Chemical energy is the energy stored in chemical bonds.
Some of this energy is released when chemicals are broken
apart and new chemicals are made.
For example, food has chemical energy that your body
uses to help you think, move, and grow. Food has chemicals,
such as sugar. The chemicals are made of atoms that are
bonded together. Energy is stored in the bonds between
atoms. These chemical bonds can be broken down in your
body to release energy.
Also, the flame of a candle comes from chemical energy
stored in wax. When the wax burns, chemical energy changes
into thermal energy and light energy.
4.
Explain What has stored
chemical energy that your
body uses?
South Carolina Science Essentials
119
What is radiant energy?
5.
Summarize When does
light energy change to
thermal energy?
Light from the candle flame travels very fast through the
air. It moves at a speed of 300,000 km/s. This is fast enough
to circle Earth almost eight times in 1 s. When light hits an
object, three things can happen. The light can be absorbed
by the object, reflected by the object, or be passed through
the object. When an object absorbs light energy, the object
can get warmer. The light energy changes into thermal
energy. You can feel this happening if you wear a black shirt
outside on a sunny day.
The energy carried by light is radiant energy. You can
use electrical energy to make radiant energy. Imagine a
metal heating coil on an electric stovetop. As it is heated,
it becomes red hot. The hotter it gets, the more radiant
energy it gives off. Electrical energy is being used to make
the heating coil warmer.
6.
Compare Which of the
following can carry the
most current?
a.
b.
c.
d.
9-V battery
220-V electrical outlet
12-V battery
110-V electrical outlet
Electrical energy is used in many ways. Electrical energy
is carried by the electric current that comes out of batteries
and electrical outlets. Electrical lighting uses electrical energy.
Look around at all the devices that use electrical energy.
The amount of electrical energy depends on the voltage.
The current out of a 120-V electrical outlet can carry more
energy than the current out of a 1.5-V battery. Large power
plants are needed to make the huge amount of electrical
energy people use every day. About 20 percent of the
electrical energy made in the United States comes from
nuclear power plants.
What is nuclear energy?
Nuclear power plants use the energy stored in the nucleus
of an atom to make electricity. Nuclear energy is the energy
in the nucleus of every atom. Nuclear energy can be
transformed into other kinds of energy. Releasing nuclear
energy is difficult. Complicated power plants are necessary
to produce nuclear energy. Releasing nuclear energy from an
atom is very different from releasing chemical energy from
wood. To do that, all you need is a lighted match.
120
Lesson Y What is energy?
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What is electrical energy?
After You Read
Mini Glossary
chemical energy: the energy stored in chemical bonds
electrical energy: the energy carried by the electric current
that comes out of batteries and electrical outlets
energy: the ability to cause change
kinetic energy: the energy an object has because of
its motion
nuclear energy: the energy in the nucleus of every atom.
potential energy: the energy stored in an object because of
its position
radiant energy: the energy carried by light
thermal energy: the energy of an object that increases as
temperature increases
1. Read the key terms and definitions in the Mini Glossary above. On the lines below,
explain the difference between the terms potential energy and kinetic energy.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
2. Match the forms of energy with the correct examples. Write the letter of each example in
Column 2 on the line in front of the form of energy it matches in Column 1.
Column 1
Column 2
1. potential energy
a. the energy that makes a television work
2. kinetic energy
b. a lamp giving off light
3. electrical energy
c. the energy in food
4. thermal energy
d. a ball rolling
5. chemical energy
e. a book sitting on a shelf
6. nuclear energy
f. the energy in a cup of hot tea
7. radiant energy
g. the energy in an atom’s nucleus
3. You were asked to highlight the different forms of energy in this lesson. What do you
think would be another way to help you remember the different forms of energy?
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about energy.
End of
Lesson
South Carolina Science Essentials
121
Llesson
3
Z
Energy Transformations
Standard 6-5.1: Identify the sources and properties of heat, solar, chemical, mechanical, and electrical
energy. Standard 6-5.2: Explain how energy can be transformed from one form to another (including the
two types of mechanical energy, potential and kinetic, as well as chemical, and electrical energy) in accordance
with the law of conservation of energy.
What You’ll Learn
to apply the law of
conservation of energy
■ energy changes form
■ how electric power
plants make energy
■
Before You Read
Explain how you used one kind of energy today.
Read to Learn
Highlight the main point in each
paragraph as you read this
lesson. Study the main points,
then state each point in your
own words.
Energy can have different forms such as chemical,
thermal, radiant, and electrical. All around you, at all times,
energy is being transformed. This means it is changing from
one form to another. You see some of these transformations
when you notice a change in your environment. Forest fires
are an example of a change involving energy. They can
happen naturally because of lightning strikes. Changes also
happen as a mountain biker pedals up a hill.
How can you track energy transformations?
Describe Make the following
Foldable. Inside, describe the
law of conservation of energy
and give examples.
Law of
Conservation
of Energy
122
Lesson Z Energy Transformations
A mountain biker’s leg muscles transform chemical energy
into kinetic energy as he pedals. The kinetic energy of his
leg muscles is transformed into kinetic energy of the bicycle
as he pedals. As he moves up the hill, some of this energy is
transformed into potential energy.
Some energy also is transformed into thermal energy. His
body is warmer because chemical energy is being released.
The parts of the bicycle are warmer too because of friction.
When energy is transformed, heat energy usually is made.
People exercising, cars running, and living things growing
all produce heat.
The Law of Conservation of Energy
The law of conservation of energy states that energy is
never created or destroyed. The only thing that changes is
the form of the energy.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Changing Forms of Energy
Identify Main Ideas
When the biker is resting at the top of the hill, all of his
original energy is still around. Some of his energy changed
into potential energy. Some changed into thermal energy.
No energy is missing. It can all be accounted for.
Changing Kinetic and Potential Energy
The law of conservation of energy can be used to identify
energy changes in a system. For example, tossing a ball into
the air and catching it is a simple system. As the ball leaves
your hand, most of its energy is kinetic. As it rises, it gets
slower. It loses kinetic energy. The kinetic energy is changed
into potential energy. The amount of kinetic energy that it
loses equals the amount of potential energy that it gains.
The total amount of energy stays the same.
1.
Draw Conclusions
At what point does the ball
have the most potential
energy?
a. when it reaches its
highest point
b. when it leaves your hand
c. just before you catch
the ball
d. halfway up in the air
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Energy Changes Form
Energy changes form all the time all around you. Many
machines transform energy from one kind to another. For
example, an automobile engine transforms the chemical
energy in gasoline into kinetic energy. Some of the chemical
energy also is transformed into thermal energy, making the
engine hot. An engine that converts chemical energy into
more kinetic energy and less thermal energy is a more
efficient engine. New kinds of cars use an electric motor
along with a gasoline engine. These engines are more
efficient so the car can travel farther on a gallon of gas.
How is chemical energy transformed?
Chemical energy can be transformed into kinetic energy
inside your body. This happens in muscle cells. Chemical
reactions take place and cause certain molecules to change
shape. Many of these changes make your muscles contract.
This makes a part of your body move.
Biomass Biomass is the matter in living organisms.
Biomass contains chemical energy. When organisms die,
chemical compounds in their biomass break down. Bacteria,
fungi, and other organisms help change these chemical
compounds into simpler chemicals. These simpler chemicals
are used by other living things.
Thermal energy also is released when these biomass
breaks down. For example, as a compost pile decomposes,
chemical energy is changed into thermal energy. The
temperature of a compost pile can reach 60°C.
2.
Summarize What kind
of energy does bacteria and
fungi help transform?
South Carolina Science Essentials
123
How is electrical energy transformed?
You use electrical energy every day. When you flip a light
switch or turn on a radio, electrical energy is transformed
into other forms of energy. You use electrical energy when
you plug something into an electrical outlet or use a battery.
Hearing Sounds The figure shows how electrical energy is
transformed into other kinds of energy when you listen to a
radio. A loudspeaker in the radio changes electrical energy
into sound waves. The sound waves travel to your ear. This
is energy in motion. The energy carried by the sound waves
makes parts of your ear move too. This energy of motion
is transformed into chemical and electrical energy in nerve
cells. The nerve cells send the energy to your brain. Your
brain figures out that the energy is a voice or music. Where
does the energy go after the brain? It finally is transformed
into thermal energy.
Picture This
Identify What kind of
energy travels through the
air from a radio?
Electrical
energy
of radio
signal
Kinetic
energy
of
speaker
Sound
energy
of air
Kinetic
energy
of eardrum
and fluid
Electrical
energy
of brain and
nerve cells
What changes into thermal energy?
4.
Check Understanding
How can thermal energy be
used to make kinetic energy?
124
Lesson Z Energy Transformations
Different kinds of energy can be transformed into thermal
energy. When something burns, chemical energy changes into
thermal energy. Electrical energy changes into thermal energy
when a wire that is carrying an electrical current gets hot.
Thermal energy can be used to heat buildings and keep
you warm. Thermal energy also can be used to heat water.
If you heat water to its boiling point, it changes to steam.
Steam can be used by steam engines to make kinetic energy.
Steam engines were once used on steam locomotives to pull
trains. Thermal energy also can be transformed into radiant
energy. This happens when you heat a metal bar until it is
so hot that it glows and gives off heat.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
3.
Energy Transformations
How does thermal energy move?
Thermal energy can move from one place to another. A
cup of hot chocolate has thermal energy. Its thermal energy
moves from the cup to the cooler air around it. Thermal
energy only moves from something at a higher temperature
to something at a lower temperature.
5.
Describe Imagine you
are taking a hot pan out
of the oven using an oven
mitt. Describe where
thermal energy moves in
this example.
6.
Define What machine
turns a generator to make
electricity?
Generating Electrical Energy
Where does the electrical energy in an electrical outlet
come from? It must be made all the time by power plants.
In fossil fuel power plants, coal, oil, or natural gas is burned
to boil water. Steam from the boiling water rushes through a
turbine. A turbine is a machine that has a set of fan blades
that are close together. The steam pushes on the blades and
turns the turbine. The turbine rotates a shaft in the
generator A generator is a device that changes kinetic
energy into electrical energy. All power plants work in a
similar way—they use energy to turn a generator.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Are there different kinds of power plants?
Almost 90 percent of the electrical energy in the United
States comes from nuclear and fossil fuel power plants. Other
kinds of power plants are hydroelectric (hi droh ih LEK trihk)
and wind. Hydroelectric power plants use generators to
change the kinetic energy of moving water into electrical
energy. Wind power plants use generators to change the
kinetic energy of wind into electrical energy.
You can diagram the energy transformations in a power
plant using arrows. A power plant that burns coal makes
energy through the following energy transformations.
Nuclear power plants also use energy transformations like
the ones below.
chemical
thermal
kinetic
kinetic
electrical
energy → energy → energy → energy of → energy out
of coal
of water of steam
turbine
of generator
How are hydroelectric power plants different?
Hydroelectric power plants do not change water into
steam. This is because the water hits the turbine. So the first
two steps in the diagram are not needed. The process starts
with the kinetic energy of the water.
South Carolina Science Essentials
125
After You Read
Mini Glossary
generator: a device that transforms kinetic energy into
electrical energy
law of conservation of energy: states that energy is
never created or destroyed
turbine: a set of steam-powered fan blades that spins a
generator at a power plant
1. Review the terms and their definitions in the Mini Glossary. Write a paragraph about
how a turbine and a generator are used to make electrical energy.
2. Fill in the blanks to tell what type of energy is being transformed as a biker rides
a bicycle.
energy.
Energy from the food makes the biker’s muscles contract. So the energy from the food is transformed into
energy in the muscles.
The movement of the biker’s muscles
makes the biker hot. So some of the
energy in the muscles is transformed into
energy.
End of
Lesson
126
Lesson Z Energy Transformations
The biker’s contracting muscles move
the pedals on the bike. So some of the
energy in the muscles is transformed into
energy in the pedals.
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about energy
transformations.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
When a biker eats food, the food is transformed into
Llesson
AA
3
Sources of Energy
Standard 6-5.1: Identify the sources and properties of heat, solar, chemical, mechanical, and electrical
energy. Standard 6-5.3: Explain how magnetism and electricity are interrelated by using descriptions,
models, and diagrams of electromagnets, generators, and simple electrical motors. Standard 6-5.4:
Illustrate energy transformations (including the production of light, sound, heat, and mechanical motion) in
electrical circuits.
Before You Read
What You’ll Learn
You must plug in most appliances before they will work.
Where does the energy in an electrical outlet come from?
Read to Learn
Identify Details As you
Using Energy
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
what renewable,
nonrenewable, and
alternative resources are
■ the advantages and
disadvantages of using
different energy sources
■
Energy is used every day to provide light and heat to
homes, schools, and workplaces. The law of conservation of
energy states that energy cannot be created or destroyed. It
can only change form. If a car or refrigerator cannot create
energy, where does the energy come from?
read this lesson, highlight the
text each time that you read
about an energy source.
Energy Resources
Energy must come from the natural world. The surface of
Earth gets energy from two places. It comes from the Sun
and radioactive atoms in Earth’s interior. Earth gets far more
energy from the Sun than is made in Earth’s interior. Almost
all the energy you use today can be traced to the Sun. Even
the gasoline used to power a car can be traced to the Sun.
Surface
of Earth
Radiant
energy
from
the Sun
Organize Information
Make the following Foldable to
organize information about the
fossil fuels, nuclear energy,
hydroelectric energy, and
alternative sources of energy.
Thermal energy
from radioactive
atoms
South Carolina Science Essentials
127
Fossil Fuels
Picture This
1.
Identify What three
things changed the plant
molecules into coal
molecules?
Fossil fuels are coal, oil, and natural gas. Oil and natural
gas were made from the remains of microscopic organisms.
These organisms lived in Earth’s oceans millions of years
ago. Heat and pressure slowly turned these organisms into
oil and natural gas. Coal was formed in a similar way.
As shown in the figures below, coal was made from the
remains of plants that once lived on land. Through
photosynthesis (foh toh SIHN thuh sus), ancient plants
transformed the radiant energy from sunlight into chemical
energy. The chemical energy is stored in molecules. Over
time, heat and pressure changed these molecules into fossil
fuel. Chemical energy stored in fossil fuels is released when
the fossil fuels are burned.
Time
Heat
Pressure
Coal mine
Can fossil fuels be replaced?
Compare and Contrast
Use three quarter-sheets of
notebook paper to help you
compare and contrast
nonrenewable resources,
renewable resources, and
inexhaustible energy sources.
Nonrenewable
Resources
Renewable
Resources
Inexhaustible
Resources
128
Lesson AA Sources of Energy
Most of the energy you use comes from fossil fuels. It
takes millions of years to replace each drop of gasoline
and each lump of coal that is burned. This means that the
amount of fossil fuels on Earth will keep decreasing as
it is used. Fossil fuels are nonrenewable resources. A
nonrenewable resource is an energy source that is used
up much faster than it can be replaced.
Disadvantages of Fossil Fuels Burning fossil fuels also
makes chemical compounds that cause pollution. Each year
billions of kilograms of air pollutants are made by burning
fossil fuels. These pollutants cause respiratory illnesses and
acid rain. Carbon dioxide gas is made when fossil fuels are
burned. This carbon dioxide gas might cause Earth’s climate
to warm.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Radiant energy
Nuclear Energy
Can you imagine 1 kg of fuel that has almost 3 million
times more energy than 1 L of gas? What could have so
much energy in so little mass? The answer is the nuclei of
uranium atoms. When these nuclei break apart, they release
huge amounts of energy. This energy is used to make
electricity by heating water. The figure shows this process.
The water makes steam that spins an electric generator. The
generator makes electricity.
Picture This
2.
Identify What type of
energy does the steam and
the turbine have in a
nuclear power plant?
Electrical Energy from Nuclear Energy
1. Nuclear energy
of atoms
2. Thermal energy
of water
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
3. Kinetic energy
of steam
4. Kinetic energy
5. Electrical energy
of turbine
Generator
What are the advantages of nuclear energy?
Making electricity by using nuclear energy helps make the
supply of fossil fuels last longer. Nuclear power plants also
produce almost no air pollution. In one year, a typical nuclear
power plant makes enough energy to supply 600,000 homes
with electricity. To do this, it produces only 1 m3 of waste.
What are the disadvantages of nuclear energy?
One disadvantage of nuclear energy is that uranium is a
nonrenewable resource. It comes from Earth’s crust. Another
disadvantage is that nuclear waste is radioactive and can be
dangerous to living things. Some of the materials in nuclear
waste will remain radioactive for many thousands of years.
This means nuclear waste must be carefully stored so no
radioactivity will be released into the environment for a
long time.
3.
Determine What are
two disadvantages of
nuclear energy?
South Carolina Science Essentials
129
How can nuclear waste be stored?
One way to store nuclear waste is to seal it in a ceramic
material that is put in protective containers. Then the containers are buried far underground. The place to bury them
has to be chosen carefully. It cannot be near underground
water supplies. It also has to be safe from earthquakes and
other natural disasters. Earthquakes and other natural
disasters could cause the radioactive material to leak.
Hydroelectricity
Infer Which of the
following is a renewable
resource? Circle your
answer.
a.
b.
c.
d.
water
coal
oil
natural gas
Picture This
5.
Identify What type of
energy does the water have
when it flows through the
dam?
1. Potential energy
of water
The potential energy of water trapped behind a dam can
be transformed into electrical energy. Energy made this way
is called hydroelectricity. This is shown in the figure below.
About 20 percent of the world’s electrical energy comes
from water. Hydroelectricity is the largest renewable source
of energy. A renewable resource is an energy source that is
replaced continually. As long as rivers flow, hydroelectric
power plants can make electricity.
Hydroelectricity makes little pollution. This is an advantage
over some other sources of electricity. However, the production of hydroelectricity does have a major disadvantage. It
upsets the life cycle of some animals that live in the water.
Dams have caused problems for salmon in the Northwest.
Salmon return to the spot where they were hatched to lay
their eggs. Many salmon cannot reach these places because
of dams. There are plans to remove some dams and build
fish ladders to help fish go around other dams.
2. Kinetic energy
of water
3. Kinetic energy
of turbine
130
Lesson AA Sources of Energy
4. Electrical energy
out of generator
Long-distance
power lines
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
4.
Are energy consumption and production equal?
More energy is being consumed, or used, in the United
States than is being produced, or made. You use energy
every day—to get to school, to watch TV, and to heat or
cool your home. The amount of energy used by an average
person has increased. Therefore, more energy must be made.
The graph shows energy consumption and production by
the United States from 1949 to 1999.
Applying Math
Energy (quadrillion Btu)
U.S. Energy Overview, 1949–1999
6.
120
90
Consumed in
the United States
About what year did the
United States start
consuming more energy
than it produced?
Energy imports
60
30
Reading Graphs
Produced in
the United States
0
1949 1954 1959 1964 1969 1974 1979 1984 1989 1994 1999
Year
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Alternative Sources of Energy
There are many ways to make electrical energy. Each has
disadvantages that can affect the environment and humans.
Alternative resources are being researched. Alternative
resources are new sources of energy that are safer and less
harmful to the environment. Alterative resources include
solar energy, wind energy, and geothermal energy.
Solar Energy
The Sun is an inexhaustible resource. An inexhaustible
resource is an energy source that cannot be used up by
humans. The amount of solar energy that hits the United
States in one day is more than the total amount of energy
used by the country in one year. But less than 0.1 percent of
the energy used in the United States comes directly from
solar energy. One reason is that solar energy is more expensive to use than fossil fuels. However, as the supply of fossil
fuels decreases, it might become more expensive to find and
mine fossil fuels. It might also become more expensive to
mine them from Earth. Then, it might be cheaper to use
solar energy or other energy sources to make electricity.
7.
Identify What type of
resource is the Sun?
South Carolina Science Essentials
131
How is the Sun’s energy collected?
Two types of collectors take in the Sun’s rays. Have you
ever seen large rectangular panels on the roofs of houses or
buildings? These are collectors for solar energy.
Thermal Collector If the panels had pipes coming out of
them, they were thermal collectors. A thermal collector uses
a black surface to absorb the Sun’s radiant energy. Black
absorbs more radiant energy than any other color. The
thermal collector uses the Sun’s radiant energy to heat water.
The water can be heated to about 70°C. The hot water can
be pumped through a house to provide heat. It can also be
used for washing and bathing.
8.
Apply Why are thermal
collectors black?
Photovoltaic If the panel has no pipes, it is a photovoltaic
(foh toh vohl TAY ihk) collector. A photovoltaic is a device
that transforms radiant energy directly into electrical
energy. Photovoltaics are used in calculators and satellites.
They also are used on the International Space Station.
Imagine you could go to the center of Earth, about 6,400
km below the surface. As you went deeper and deeper, the
temperature would increase. After going only about 3 km,
the temperature would be warm enough to boil water. At a
depth of 100 km, the temperature could be over 900°C.
The heat made inside Earth is called geothermal energy.
Some geothermal energy is made when unstable radioactive
atoms inside Earth decay. This transforms nuclear energy
into thermal energy. At some places deep within Earth, the
temperature is hot enough to melt rock. Melted, or molten,
rock is called magma. Magma rises up close to the surface
through cracks in Earth’s crust. Magma reaches the surface
when a volcano erupts. In other places, magma gets close to
the surface and heats the rock around it.
What are geothermal reservoirs?
9.
Determine What does
the magma in geothermic
reservoirs turn water into?
132
Lesson AA Sources of Energy
In some places, magma is very close to Earth’s surface.
Rainwater and water from melted snow can seep down to
the magma through the cracks and openings in Earth’s
surface. The magma heats the water and it can become
steam. The hot water and steam can be trapped under high
pressure in cracks and pockets. These are called geothermal
reservoirs. Geothermal reservoirs are sometimes close
enough to the surface to make hot springs and geysers.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Geothermal Energy
How is geothermal power made?
Wells can be drilled to reach geothermal reservoirs in
places where the reservoirs are less than several kilometers
deep. Hot water and steam from geothermal energy is used
by geothermal power plants to make electricity.
Picture This
Geothermal Power Plant
The steam is cooled
in the cooling towers
and condenses into
water.
10.
pumped back down into a
geothermic reservoir from a
geothermic power plant:
steam, hot water, or cool
water?
The water is
pumped back
down into the
geothermal
reservoir.
Hot water from
a geothermal
reservoir forces
its way through
a pipe to the
surface where it
turns to steam.
Interpret an
Illustration Which is
es
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
The steam turns a
turbine that is
connected to an
electric generator.
The figure shows how geothermal reservoirs make
electricity. Geothermal power is an inexhaustible resource.
But geothermal power plants can be built only where
geothermal reservoirs are close to Earth’s surface, like in the
western United States.
How are heat pumps used?
Geothermal heat usually keeps the temperature of the
ground that is several meters deep at 10° to 20°C. This
constant temperature can be used to heat or cool buildings
by using a heat pump.
During the summer, the air is warmer than the ground
below. A heat pump sends warm water from the building
through the cooler ground. The water cools and then is
pumped back to the building to absorb heat. In the winter,
the air is cooler than the ground below. Then, the cool
water absorbs heat from the ground and releases it from the
heat pump into the building.
11.
Explain Why does the
cool water in the building
absorb heat in the summer?
South Carolina Science Essentials
133
Energy from the Oceans
12.
Explain What kind of
resource is the movement
of the ocean?
The ocean is constantly moving. If you have been to the
seashore, you have seen the waves roll in. If you spent the day
at the beach, you may have also seen the level of the ocean
rise and fall. The rise and fall in the ocean level is called a
tide. The movement of the ocean is an inexhaustible source
of mechanical energy. Mechanical energy can be transformed
into electric energy. Several electric power plants that use the
motion in ocean waves, or tidal energy, have been built.
How much change in water level is needed?
A high tide and a low tide each happen about twice a day.
In most places, the level of the ocean changes by only a few
meters. In some places, it changes by much more. In the Bay
of Fundy in Eastern Canada, the ocean level changes by
16 m between high tide and low tide. Almost 14 trillion kg
of water move into or out of the bay between high tide and
low tide. This tidal energy makes enough electricity to
power about 12,000 homes.
Picture This
13.
Highlight Use a
highlighter to trace the flow
of water into and out of the
tidal power plant.
The figures below show how the power plant that has
been built along the Bay of Fundy works. The first figure
shows that as the tide rises, water flows through a turbine.
The turbine causes a generator to spin, which makes
electricity. The water is then trapped behind a dam. The
second figure shows that when the tide goes out, the
trapped water is released. It flows through the turbine
making the generator spin. This makes more electricity.
Electric power is made each day for about 10 hours.
Tidal energy is a clean, inexhaustible resource. But, only a
few places have a large enough difference between high and
low tide to build an electric power plant.
Tidal Power Plant
Ocean
Ocean
Turbine
134
Lesson AA Sources of Energy
Turbine
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
How is tidal energy used to make electricity?
Wind
Wind is another inexhaustible supply of energy. Modern
windmills, like the ones in the figure, transform the kinetic
energy of the wind into electrical energy. Electrical energy
is made when wind spins the propeller. The propeller is
connected to a generator, which makes electricity. These
windmills produce almost no pollution. But windmills do
make a lot of noise. You also need a large area of land to
place a lot of windmills. Also, studies have shown that birds
sometimes are killed by windmills.
Picture This
14.
Infer Why do you think
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
the windmills shown in the
figure are placed on top of
mountains instead of
between hills or
mountains?
Conserving Energy
Fossil fuels are a valuable resource. They are burned to
provide energy. Oil and coal can be used to make plastics
and other materials. To make the supply of fossil fuels last
longer, people need to use less energy. Using less energy is
called conserving energy.
You can save money by conserving energy. You should
turn off appliances like televisions when you are not using
them to conserve energy. Keep doors and windows closed
tightly when it is hot or cold outside. This will keep heat
from leaking out of or into your house. If cars were used
less or were made more efficient, they would use less gas
and oil, and therefore less energy. You also help conserve
energy when you recycle aluminum cans and glass.
15.
Describe What is
another way you can
conserve energy?
South Carolina Science Essentials
135
After You Read
Mini Glossary
alternative resources: new renewable or inexhaustible
energy sources
inexhaustible resource: an energy source that cannot be
used up by humans
nonrenewable resource: an energy source that is used up
much faster than it can be replaced
photovoltaic: a device that transforms radiant energy
directly into electrical energy
renewable resource: an energy source that is replaced
continually
1. Review the terms and their definitions in the Mini Glossary. What is the difference
between a renewable resource and a nonrenewable resource?
2. Write as many examples of renewable, nonrenewable, and inexhaustible resources in the
chart as you can.
Nonrenewable Resources
Inexhaustible Resources
3. You were asked to highlight the text each time you read about an energy source. How
did this help you learn about energy sources?
End of
Lesson
136
Lesson AA Sources of Energy
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about sources
of energy.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Renewable Resources
Llesson
BB
3
Electric Charge
Before You Read
You use electricity every day. What would be different in
your life if you didn’t have electricity?
Read to Learn
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Electricity
To understand electricity, first you must
think small—very
small. Remember that
all solids, liquids, and
gases are made of
tiny particles called
atoms. Atoms are
made of even smaller
particles called
protons, neutrons,
and electrons. Look
at the figure. Protons and neutrons are held together tightly
in the nucleus at the center of an atom. Electrons swarm
around the nucleus in all directions. Protons and electrons
have electric charge. Neutrons have no electric charge.
What You’ll Learn
how objects become
electrically charged
■ about electric charges
■ about conductors and
insulators
■ about electric discharge
■
Find the Main Idea As you
read, highlight the main idea of
each paragraph.
Picture This
1.
Label Use three different
colored highlighters,
crayons, or pencils to mark
the protons, neutrons, and
electrons. Use a different
color for each.
What are positive and negative charges?
There are two kinds of electric charge—positive and
negative. A proton has a positive charge. An electron has
a negative charge. Atoms have an equal number of protons
and electrons. So, atoms are electrically neutral. They have
no overall electric charge.
South Carolina Science Essentials
137
Explain Does an object
that is positively charged
have more electrons than
protons or fewer electrons
than protons?
Compare and Contrast
Use two quarter sheets of
notebook paper to compare and
contrast information about
gaining and losing electrons.
Gain
Electrons
Lose
Electrons
How can electrons move in solids?
Electrons can move from atom to atom. They also can
move from object to object. Rubbing is one way that electrons
can move. Have you ever had clinging clothes when you took
them out of the dryer? If so, you have seen what happens
when electrons move from one object to another.
Imagine rubbing a balloon on your hair. The atoms in
your hair hold their electrons more loosely than the atoms
in the balloon. The electrons from the atoms in your hair
move to the atoms on the surface of the balloon. So, your
hair loses electrons and becomes positively charged. The
balloon gains electrons and becomes negatively charged.
Your hair and the balloon become attracted to one another.
Your hair stands on end because of the static charge.
What is static charge?
Static charge is an imbalance of electric charge on an
object. Static charge happens in solids because electrons
move from one object to the other. Protons cannot easily
move from the nucleus of an atom. So, protons usually do
not move from one object to another.
How do ions move in solutions?
Picture This
3.
Describe Look at the
figure. How would you
describe the chloride and
sodium ions in the water?
Circle your answer.
a.
b.
c.
d.
138
tightly held together
all the ions are negative
spread out evenly
all the ions are positive
Lesson BB Electric Charge
Sometimes, ions move instead of
Chloride ions (Cl–)
electrons. When ions move, the charge
can move. Table salt, or sodium
chloride, is made of sodium ions and
chloride ions that are held in place
and cannot move through the solid.
Ions cannot move through solids, but
Sodium ions (Na+)
they can move through solutions.
Look at the figure. When salt is dissolved in water, the sodium and chloride ions break apart. The
ions spread out evenly in the water and form a solution. In
the solution, the positive and negative ions are free to move.
Solutions that have ions make parts of your body able to communicate with each other. Nerve cells use ions to send signals
to other cells. These signals move throughout your body so
that you can see, touch, taste, smell, move, and even think.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
2.
Ions An atom can gain electrons. When it does, it becomes
negatively charged. An atom also can lose electrons and
become positively charged. A positively or negatively
charged atom is an ion (I ahn).
Electric Forces
Remember that electrons in an atom swarm around the
nucleus. What keeps the electrons close to the nucleus? The
positively charged protons in the nucleus exert an attractive
electric force on the negatively charged electrons. Electric
force is the force between charged objects. All charged
objects exert an electric force on each other. The electric
force can attract or it can repel, or push away.
Look at the figure below. Objects with unlike charges, like
positive protons and negative electrons, attract each other.
Objects with like charges repel each other. Two positive objects
repel each other. Two negative objects repel each other.
+
+
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Like charges repel.
Foldable to show the differences
between like charges and unlike
charges.
Like
Charges
Unlike
Charges
Picture This
–
Unlike charges attract.
+
Contrast Make the following
–
4.
Apply Circle the part of
the figure that shows the
force between two electrons.
5.
Explain What happens
as a positively charged
object comes closer to a
negatively charged object?
–
Like charges repel.
The electric force between two charged objects depends
on the distance between them. Electric force also depends
on the amount of charge on each object. The electric force
between two charges gets stronger as the charges get closer
together. As positive and negative charges come closer
together, the attraction gets stronger. When two like charges
come closer together, they repel each other more strongly. If
the amount of charge on at least one object increases, then
the electric force between the two objects increases.
What are electric fields?
Charged objects don’t have to touch each other to exert
an electric force on each other. Imagine two charged
balloons. They push each other apart even though they do
not touch. Why does this happen?
Every electric charge has a space, or a field, around it. An
electric field is the space in which charges exert a force on
each other. If an object with a positive charge is placed in
the electric field of another positive object, the objects repel
each other. If an object with a negative charge is placed in
the electric field of an object with a positive charge, the
objects attract each other. Also the closer the objects are, the
stronger the electric fields.
South Carolina Science Essentials
139
Insulators and Conductors
Contrast Make the following
Foldable to show the differences
between insulators and
conductors.
Conductors
Insulators
When you rub a balloon on your hair, the electrons from
your hair move to the balloon. But, only the part of the balloon that is rubbed on your hair gains the electrons. Electrons
cannot move easily through rubber. So, the electrons that
move from your hair to the balloon stay in one place on the
balloon. The balloon is an insulator. An insulator is a material
in which electrons cannot move easily from place to place.
Plastic, wood, glass, and rubber are examples of insulators.
A conductor is a material in which electrons can move
easily from place to place. An electric cable is made from a
conductor coated with an insulator, like plastic. The electrons
move easily in the conductor (the wire), but do not move
easily in the insulator (the plastic). The insulator keeps the
electrons in the conductor so that someone touching the
cable won’t get a shock.
6.
Determine Give an
example of each.
Conductor:
Insulator:
The best conductors are metals, like copper, gold, and
aluminum. In a metal atom, some electrons are not
attracted as strongly to the nucleus as others. When metal
atoms form a solid, the atoms cannot move far. But, the
electrons inside the atoms that are not strongly attracted to
each nucleus can move easily in a solid piece of metal.
Insulators are different. In an insulator, the electrons of an
atom are strongly attracted to the nucleus. The electrons in
an insulator cannot move easily.
Induced Charge
7.
Explain How do the extra
electrons get on your hand?
140
Lesson BB Electric Charge
Have you ever walked on carpet and then touched a
doorknob? Maybe you felt an electric shock or saw a spark.
Look at the figure on the next page to see what happened.
As you walk, electrons rub off the carpet onto your shoes.
The electrons spread over the surface of your skin. As your
hand gets near the doorknob, the electric field around the
extra electrons on your hand repels the electrons in the
doorknob. The doorknob is metal, so it is a good conductor.
The electrons on the doorknob move easily away from your
hand. The part of the doorknob closest to your hand
becomes positively charged. This separation of positive and
negative charges because of an electric field is called an
induced charge. The word induce means “to cause”. You
induced, or caused, a positive charge on the doorknob.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What are the best conductors?
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
A As you walk across the floor, you
rub electrons from the carpet onto the
bottom of your shoes. These electrons
then spread out all over your skin,
including your hands.
B As you bring your hand close to
the metal doorknob, electrons on the
doorknob move as far away from your
hand as possible. The part of the
doorknob closest to your hand is left
with a positive charge.
If the electric field between your hand and the doorknob
is strong enough, charge can be pulled quickly from your
hand to the doorknob. The quick movement of extra charge
from one place to another place is an electric discharge.
Lightning is an example of an electric discharge. Imagine a
storm cloud. The movement of air causes the bottom of the
cloud to become negatively charged. The negative charge
induces a positive charge on the ground below the cloud.
Cloud-to-ground lightning strikes when electric charge
moves between the cloud and the ground.
C The attraction between the
electrons on your hand and the
induced positive charge on the
doorknob might be strong enough to
pull electrons from your hand to the
doorknob. You might see a spark or
feel a mild electric shock.
Picture This
8.
Describe Look at the
figure. When do the
electrons on the doorknob
first begin to move away
from your hand? Circle your
answer.
a. when you walk across
the floor
b. when your hand gets
close to the doorknob
c. when you induce a
positive charge
d. when you touch the
doorknob
9.
Determine Is Earth an
insulator or conductor?
Grounding
Lightning is an electric discharge that can cause damage
and hurt people. A lightning bolt releases a large amount of
electric energy. Even electric discharges that release small
amounts of electric energy can cause damage to electrical
objects, like computers. One way to avoid damage caused by
electric discharges is to make the extra charges flow into
Earth’s surface. Earth is a good conductor. Since it is so
large, it can absorb, or take in, a large amount of extra
charge. You may have seen a lightning rod at the top of a
building. The rods are metal and are connected to metal
cables. These cables conduct the electric charge into Earth if
the rod is struck by lightning. So, the extra charge goes to
Earth and the building is protected.
South Carolina Science Essentials
141
After You Read
Mini Glossary
conductor: a material in which electrons can move easily
from place to place
electric discharge: the quick movement of extra charge
from one place to another place
electric field: the field, or space, in which charges exert a
force on each other
electric force: the attraction or repulsion between
charged objects
insulator: a material in which electrons cannot move easily
from place to place.
ion: a positively or negatively charged atom
static charge: an imbalance of electric charge on an object
1. Read the key terms and definitions in the Mini Glossary above. What would cause the
electric force between two objects to increase? Explain.
2. The table below lists the charges of two objects. Use the words attract and repel to
describe the electric force between the objects.
Electric Force
Positive and positive
Positive and negative
Negative and negative
3. You were asked to highlight the main idea of each paragraph. Did this strategy help you
learn about electric charge? Why or why not?
End of
Lesson
142
Lesson BB Electric Charge
Visit msscience.com to access your textbook, interactive games,
and projects to help you learn more about electric charge.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Charges of Two Objects
Llesson
CC
3
Electric Current
Standard 6-5.4: Illustrate energy transformations (including the production of light, sound, heat, and
mechanical motion) in electrical circuits.
Before You Read
You can turn on the light in a room any time you wish.
Where does the electricity come from?
What You’ll Learn
about electric currents
and voltage
■ how batteries make
electric currents
■ what electrical
resistance is
■
Read to Learn
Study Coach
Outline As you read the
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Flow of Charge
Lights, refrigerators, TV’s and other things need a steady
source of electrical energy that can be controlled. Electric
currents are used for steady and controlled electricity. An
electric current is the flow of electric charge. In solids, the
flowing charges are electrons. In liquids, the flowing charges
are ions. Remember that ions can be positive or negative.
Electric currents are measured in amperes (A). A model of
an electric current is flowing water. Water flows downhill
because a gravitational force acts on it. Electrons flow
because an electric force acts on them.
lesson, make an outline using
each heading. Under each
heading, write the main ideas
that you read.
What is a simple circuit?
The flow of water
can create energy.
Higher-energy
water
Look at the figure.
Height
Water that is pumped
high above the ground
Pump
has potential energy
Lower-energy water
because gravity acts
on it. As water falls, it
loses potential energy. When the water falls on a waterwheel
and turns it, the waterwheel gains kinetic energy. The water
flows through a continuous loop. A closed, conducting loop
that electric charges flow continuously through is a circuit.
Picture This
1.
Highlight Use a
highlighter to mark the flow
of water through the
continuous loop.
South Carolina Science Essentials
143
What are electric circuits?
Organize Information
Make the following Foldable to
write down information about
electric circuits.
Electric Circuit
The simplest electric circuit has a source of electric
energy and an electric conductor. In the figure below,
the source of electric energy is the battery. The electric
conductor is the wire. The wires connect the lightbulb to
the battery in a closed path. Electric current flows in the
circuit as long as the wires, including the filament wire in
the lightbulb, stay connected.
e–
Picture This
2.
Identify Circle the
source of electric energy in
the figure.
e–
Battery
Wire
e–
e–
3.
Identify In a circuit (like
the one in the figure
above), what increases the
electrical potential energy
of the electrons?
Think of the example of the waterwheel. The pump
increases the gravitational potential energy of the water by
raising it from a lower level to a higher level. In an electric
circuit, the battery increases the electrical potential energy
of electrons. This electrical potential energy can be changed
into other forms of energy.
The measure of how much electrical potential energy each
electron can gain is the voltage of a battery. Voltage is
measured in volts (V). As voltage increases, more electrical
potential energy is available to be changed into other forms
of energy.
How does a current flow?
The electrons in an electric circuit move slowly. When the
ends of a wire are connected to a battery, the battery makes
an electric field in the wire. The electric field forces electrons
to move toward the positive end of the battery.
144
Lesson CC Electric Current
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What is voltage?
Look at the plus sign on the battery in the figure on the
previous page. As electrons move, they bump into other
electric charges in the wire. Then, they bounce off in different
directions. Electrons start to move again toward the positive
end of the battery. An electron can have more than ten
trillion of these bumps each second. So, it can take several
minutes for an electron to travel even one centimeter.
How do batteries work?
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Battery Terminals Batteries have a negative terminal, or
end, and a positive terminal. You have learned that the
battery in a circuit makes an electric field that forces electrons
to move toward the positive terminal of the battery. When
the positive and negative terminals of a battery are connected
in a circuit, the electric potential energy of electrons in the
circuit increases. As electrons move toward the positive
terminal, the electric potential energy turns into other forms
of energy. This also happens with water. The gravitational
potential energy of the water turns into kinetic energy as
the water turns the waterwheel.
Electrical Potential Energy The battery changes chemical
energy into electric potential energy. In the figure on the
previous page, the battery shown is an alkaline battery.
Between the positive terminal and negative terminal is a
moist paste. Chemical reactions in the moist paste move
electrons from the positive terminal to the negative
terminal. So, the negative terminal becomes negatively
charged and the positive terminal becomes positively
charged. This makes the electric field in the circuit that
causes the electrons to move away from the negative
terminal to the positive terminal. The chemical energy is
now electrical potential energy.
4.
Explain How does the
negative terminal of a
battery become negatively
charged?
How long can batteries last?
Batteries cannot supply energy forever. Do you know what
happens if the lights on a car are left on for a long time?
The car battery runs down and the car won’t start. Why do
batteries run down? Batteries have only a certain amount of
chemicals in them that react to make chemical energy. As
long as the battery is used, these chemical reactions happen.
The chemicals change into other compounds. When the
chemicals are used up, the chemical reactions stop. The
battery is then “dead.”
5.
Explain Why does a
battery “die”?
South Carolina Science Essentials
145
Resistance
Remember that electrons move more easily through
conductors than through insulators. But, even in conductors,
the flow of electrons can be slowed down. The measure of
how difficult it is for electrons to flow through a material is
resistance. The unit of resistance is the ohm (Ω). Insulators
have a higher resistance than conductors.
You learned that, in a circuit, electrons bump into other
electric charges. When this happens some of the electrical
energy in the electrons turns into thermal energy in the
form of heat or light. The amount of electrical energy that
turns into heat and light depends on the resistance of the
materials in the circuit.
Why are copper wires used in buildings?
The amount of electrical energy that turns into thermal
energy increases when the resistance of the wire increases.
Copper is one of the best conductors of electric energy. It
also has a low resistance. So, less heat is made when an
electric current flows through copper wire. Copper wire is
used in houses and other buildings because copper wire
usually will not become hot enough to cause fires.
6.
Recognize Cause
and Effect What
increases when a wire is
made longer or thinner?
A wire can have high or low electric resistance depending
on what the wire is made of. The electric resistance of a
wire also depends on the wire’s length and thickness. The
electric resistance of a wire increases as the wire becomes
longer. The electric resistance also increases as the wire
becomes narrower.
How do lightbulbs work?
7.
Explain Why is tungsten
used for lightbulb filaments?
146
Lesson CC Electric Current
Lightbulbs have a tiny wire inside called a filament. The
filament wire is so narrow that it has a high resistance.
Remember that a material that has high resistance can turn
electric energy into thermal energy in the form of heat or
light. When electric current flows in the filament, the wire
becomes hot enough to make light. Why doesn’t the filament
melt? The filament is made of tungsten metal. Tungsten has
a much higher melting point than most other metals. So,
the tungsten metal filament will not melt at the high temperature needed to make light.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
How are length and thickness of a wire
related to resistance?
After You Read
Mini Glossary
circuit: a closed, conducting loop that electric charges flow
continuously through
electric current: the flow of electric charge
resistance: the measure of how difficult it is for electrons to
flow through a material
voltage: the measure of how much electrical potential
energy each electron can gain.
1. Review the terms and their definitions in the Mini Glossary. Write one or two sentences
to compare resistance in a conductor and an insulator.
2. Complete the graphic organizer to compare and contrast copper wire and tungsten wire
using the information below.
Copper Wire
Tungsten Wire
1. Low Resistance
1. ___________________________
Both
2. ___________________________
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
___________________________
Good
conductor
___________________________
2. ___________________________
___________________________
3. At the beginning of the lesson, you were asked to create an outline of the lesson. How
did the outline help you learn about electric current?
Visit msscience.com to access your textbook, interactive games,
and projects to help you learn more about electric current.
End of
Lesson
South Carolina Science Essentials
147
Llesson
3
DD
Electric Circuits
Standard 6-5.4: Illustrate energy transformations (including the production of light, sound, heat, and
mechanical motion) in electrical circuits.
What You’ll Learn
how voltage, current,
and resistance are
related
■ about series and parallel
circuits
■ how to avoid dangerous
electric shock
■
Before You Read
You use circuits every day. Name some circuits you have used.
Read to Learn
State the Main Ideas As
you read this lesson, stop after
each paragraph and write down
the main idea in your own
words.
Picture This
1.
Infer Circle the bucket
and hose that show greater
resistance.
Controlling the Current
Electric current flows through a circuit when you connect
a conductor, like a wire, between the positive and negative
terminals of a battery. The amount of current depends on the
voltage of the battery and the resistance of the conductor.
Imagine a bucket of water with a hose attached in the
bottom of it. Look at the figure. If you raise the bucket, you
increase the potential energy of the water in the bucket. This
causes the water to
flow out of the hose
faster. This happens
with electric current,
too. If the amount of
voltage increases, the
amount of current
flowing through a
circuit will increase.
How do voltage and resistance affect current?
As the figure shows, the higher the bucket is raised, the
more energy the water has. Increasing the voltage in a
battery is like increasing the height of the water. The electric
current in a circuit increases if the voltage increases. If the
resistance in an electric circuit is greater, less current can
flow through the circuit.
148
Lesson DD Electric Circuits
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Study Coach
What is Ohm’s law?
Applying Math
In the nineteenth century, a German scientist named Georg
Simon Ohm measured how changing the voltage in a circuit
affects the current. He found a relationship among voltage,
current, and resistance in a circuit, know as Ohm’s law. Ohm’s
law states that when voltage in a circuit increases, the current
increases. The equation below shows this relationship.
2.
Calculate An iron is
plugged in a wall socket.
The current in the iron is
5 A. The resistance is 20 Ω.
What is the voltage
provided by the wall
socket? Show your work.
Voltage (in volts) current (in amperes) resistance
(in ohms)
V IR
If the voltage in a circuit stays the same, but the resistance
changes, the current will change, too. If the resistance
increases, the current in the circuit will decrease.
Circuits control the movement of electric current by
providing paths for electrons to follow. In order for a current
to flow, the circuit must be an unbroken path. Imagine a
string of lights with tiny light bulbs. In some strings of
lights, if only one bulb is burned out, the whole string of
lights won’t work. This is an example of a series circuit.
Some strings of lights will stay lit no matter how many
bulbs burn out. This is an example of a parallel circuit.
Organize Information
Use two half-sheets of notebook
paper to write information
about series and parallel circuits.
Parallel Circuits
Series Circuits
What is a series circuit?
A series circuit is a circuit that has only one path for the
electric current to follow. Look at the figure. If the path is
broken, current cannot flow. The bulbs in the circuit will
not light. The path could be broken if a wire comes off or if
a bulb burns out. The filament in the lightbulb is also part
of the circuit. So, if the filament breaks, then the flow of
current stops.
Picture This
3.
Ba
tte
ry
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Series and Parallel Circuits
Predict Look at the
figure. What would happen
if you remove a wire from
one of the lightbulbs?
South Carolina Science Essentials
149
What happens when resistance increases?
In a series circuit, electrical devices are connected along
the same path. So, the current is the same through every
device. But, if a new device is added to the circuit, the
current will decrease throughout the circuit. Why? Each
device has its own electrical resistance. In a series circuit,
the total resistance increases as each new device is added.
Ohm’s law tells us that if resistance increases and the voltage
doesn’t change, the current will decrease.
4.
Recognize Cause and
Effect A series circuit has
2 lightbulbs on it. What
happens to the resistance if
you add another lightbulb
to the circuit?
What is branched wiring?
What would it be like if all the electrical devices in your
house were on a series circuit? You would have to turn on
all the appliances in your house just so you could watch TV.
5.
Predict Look at the
figure. What would happen
to the lightbulb on the right
if you remove the lightbulb
on the left?
Parallel Circuit
Ba
tte
ry
Picture This
In a parallel circuit, the resistance in each branch can be
different. The resistance in a parallel circuit depends on the
devices in the branch. If the resistance in one branch is
low, then more current will flow through it than in other
branches. So, the current in each branch of a parallel circuit
can be different.
150
Lesson DD Electric Circuits
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Parallel Circuits Your house, school, and other buildings
are wired using parallel circuits. A parallel circuit is a
circuit that has more than one path for the electric current
to follow. The figure shows a parallel circuit. The circuit
branches so that the electrons flow through each of the
paths. If one of the paths is broken, electrons will still flow
through the other paths. So, you can add or remove a device
in one branch and the current will still flow.
Protecting Electric Circuits
In a parallel circuit, electric current that flows out of a
battery or electric outlet increases as more devices are added
to the circuit. As the current through the circuit increases,
the wires heat up.
What are fuses and circuit breakers?
If wires get too hot, they can cause a fire. To make sure
that wires don’t get too hot, the circuits in your house and
other buildings have fuses or circuit breakers. Fuses and
circuit breakers limit the amount of current in the wiring.
If the current becomes greater than 15 A or 20 A, a piece of
metal in the fuse melts or a switch in the circuit breaker
opens, stopping the current. The device that caused the
problem can be removed. Then, the fuse can be replaced
or the circuit breaker can be reset.
6.
Electric Power
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
When you use a toaster or a hair dryer, electrical energy
changes into other kinds of energy. The rate, or speed,
at which electrical energy is changed into other kinds of
energy is electric power. In any electric device or electric
circuit, the electric power that is used can be found by using
the equation below.
Explain What do fuses
and circuit breakers do?
Applying Math
7.
Power (in watts) current (in amperes) voltage (in volts)
P IV
Calculate A toaster is
plugged into a wall outlet.
The current in the toaster
is 10 A. The voltage of the
wall outlet is 110 V. How
much power in watts does
the toaster use? Show your
work.
The electric power is equal to voltage provided to the
electrical device multiplied by the current that flows into the
device. The SI unit of power is the watt. The table lists the
electric power used by some common devices.
Power Used by Common Devices
Device
Power (in watts)
Computer
350
Color TV
200
Stereo
250
Refrigerator
450
Microwave
700–1,500
Hair dryer
1,000
Applying Math
8.
Interpret Data How
many more watts does a hair
dryer use than a color TV?
South Carolina Science Essentials
151
How do electric companies measure power?
Power is the amount of energy that is used per second.
When you use a hair dryer, the amount of electrical energy
you use depends on the power of the hair dryer. It also
depends on how long you use it. Suppose you used the hair
dryer for 10 minutes today and 5 minutes yesterday. You
used twice as much energy today than you did yesterday.
How much does electrical energy cost?
Electric companies make electrical energy and sell it in
units of kilowatt-hours. One kilowatt-hour (kWh) is equal
to using one kilowatt of power continuously for one hour.
This is about the amount of energy needed to light ten
100-W lightbulbs for one hour or just one 100-W lightbulb
for 10 hours.
An electric company charges customers for the number of
kilowatt-hours they use every month. An electric meter on
the outside of each building measures the number of
kilowatt-hours used in that building.
Electrical Safety
Picture This
9.
Infer Why should you not
use an electric device near
water?
Preventing Electric Shock
Never use a device with frayed or damaged electric cords.
Unplug appliances before you work on them. For example, if a piece of toast gets stuck in a
toaster, unplug the toaster before you take the toast out.
Never use an electric device near water.
Never touch power lines with anything, including a kite string or ladder.
Always pay attention to warning signs and labels.
How do electric shocks happen?
10.
Identify Is skin a
conductor or an insulator?
152
Lesson DD Electric Circuits
If an electric current enters your body, you feel an electric
shock. Your body is like a piece of insulated wire. The fluids
inside your body are good conductors of electric current.
The electrical resistance of dry skin is much higher than the
fluids in your body. Skin insulates the body in the same way
that plastic insulates a copper wire. Remember that electrons
cannot move easily in an insulator like plastic. Your skin
works in the same way.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Electricity can be very dangerous. In 1997, electric shocks
killed about 490 people in the United States. Here are some
tips that will help prevent electrical accidents.
You actually become part of an electric circuit when
current enters your body. The shock you feel can be mild or
deadly, depending on the amount of current that flows into
your body.
How much is too much?
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
The amount of current that can light a 60-W lightbulb is
about 0.5 A. If this amount of current enters your body, it
could be deadly. Even a current as low as 0.001 A can be
painful. The table shows what you would feel when a certain
amount of electric current flows through your body.
Current’s Effects
Amount of
Current
(in amperes)
What You Feel
0.0005 A
Tingle
0.001 A
Pain
0.01 A
Can’t let go
0.025 A
0.05 A
Difficult to breathe
0.10 A
0.25 A
0.50 A
Heart failure
1.00 A
Picture This
11.
Interpret Data
Describe how you would
feel if you were shocked by
a current of 0.10 A.
How do you keep safe from lightning?
Electricity in lightning can be very dangerous. Lightning
can harm people, plants, and animals. In the United States,
more people are killed every year by lightning than by
hurricanes or tornadoes. Most of these lightning deaths
happened outdoors. If you are outside and can see lightning
or hear thunder, you need to go indoors right away. If you
cannot go indoors, you need to take the following steps:
• Stay away from open fields and high places
• Stay away from tall objects like trees, flagpoles, or light
towers
12.
Explain Why should you
stay away from metal
fences when you see
lightning or hear thunder?
• Stay away from objects that conduct current such as
water, metal fences, picnic shelters, and bleachers.
South Carolina Science Essentials
153
After You Read
Mini Glossary
electric power: the rate, or speed, at which electrical energy
is changed into other kinds of energy
Ohm’s law: the relationship among voltage, current, and
resistance; when the voltage in a circuit increases, the
current increases
parallel circuit: a circuit that has more than one path for the
electric current to follow
series circuit: a circuit that has only one path for the electric
current to follow
1. Review the terms and their definitions in the Mini Glossary. Explain why it is better to
have a parallel circuit in your home than a series circuit.
2. Explain the main ideas of Ohm’s law in the cause-and-effect map below. Write increases
or decreases in the blanks.
Ohm’s Law
Voltage increases
Effect
Electric current
Cause
Resistance increases
Effect
Electric current
3. You were asked to write the main idea of each paragraph as you read this lesson. How
did you decide which is the main idea for each paragraph?
End of
Lesson
154
Lesson DD Electric Circuits
Visit msscience.com to access your textbook, interactive games,
and projects to help you learn more about electric circuits.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Cause
Llesson
EE
3
What is magnetism?
Before You Read
Do you have magnets on your refrigerator? Why do magnets
stick to a refrigerator and other things?
What You’ll Learn
how magnets behave
how the behavior of
magnets and magnetic
fields are related
■ why some materials are
magnetic
■
■
Read to Learn
Study Coach
Create an Outline Use the
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Early Uses
Thousands of years ago, people found that a mineral
called magnetite attracted other pieces of magnetite. It also
attracted bits of iron. When they rubbed small pieces of
iron with magnetite, the iron began to act like magnetite. If
they let the pieces turn freely, one end pointed north. These
might have been the first compasses. Compasses helped
sailors and explorers know which direction they were going.
Before compasses, sailors and explorers had to look at the
Sun and stars to know which direction they were going.
headings to make an outline of
the information in this lesson.
Magnets
A piece of magnetite is a magnet. Magnets attract objects
made of iron or steel, like nails and paper clips. Magnets also
attract or repel other magnets. To repel means “to push
away.” Every magnet has two ends. The two ends are called
poles. One end is called the north pole. The other end is
called the south pole. The figure on the next page shows what
happens when you put two magnetic poles together. Two
north poles will repel each other. Two south poles also repel
each other. But a north pole and a south pole are attracted to
each other.
1.
Determine Do the
north poles of two magnets
attract or repel each other?
South Carolina Science Essentials
155
Picture This
2.
Highlight Use one color
to circle the poles that are
attracted to each other.
Then use another color to
circle the poles that repel
each other.
Poles That Repel or Attract
Two north poles repel
Two south poles repel
Opposite poles attract
Remember that a force is a push or a pull that can make
an object move. Gravitational and electric forces can act on
an object even when objects are not touching. Magnetic force
also can act on objects when they are not touching. Notice
that the magnets in the figure above are not touching and a
magnetic force is acting on them. A magnet can even make
an object move without touching it. The magnetic force gets
weaker when the magnets move farther apart.
A magnetic field is the space around a magnet where the
magnetic force is. Magnetic fields are around all magnets. If
you sprinkle iron fillings near a magnet, the iron filings will
show the magnetic field lines of the magnet. The figure
below shows these curved lines. The lines start on one pole
and end on the other.
Picture This
3.
Highlight Trace the
magnetic field lines as they
leave the magnet. Which
pole of the magnet did you
always start at?
Magnetic field lines begin at a magnet’s north pole and
end at the south pole. The lines are close together where the
field is strong. The lines get farther apart as the field gets
weaker. The magnetic field is strongest close to the magnetic
poles. It gets weaker farther away from the poles. Field lines
that curve toward each other show attraction. Field lines
that curve away from each other show repulsion.
156
Lesson EE What is magnetism?
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What is a magnetic field?
How are magnetic fields made?
A moving electric charge produces a magnetic field. All
atoms have negatively charged particles called electrons.
These electrons spin around the nucleus of an atom. Each
electron produces a magnetic field because of how it moves.
The electrons in atoms that make up magnets are like even
smaller magnets. The magnetic fields of many of the atoms
in iron and other materials point in the same direction. A
group of atoms with their magnetic fields pointing in the
same direction is called a magnetic domain.
4.
Identify Do the
magnetic fields in a
magnetic domain all point
in the same direction or in
different directions?
How can some materials become magnetized?
A material, like iron or steel, that can become magnetized
has many magnetic domains. When the material is not
magnetized, these magnetic domains point in all directions
as shown in the figure below. The material does not act like
a magnet. This is because the magnetic fields made by the
domains cancel each other out.
Picture This
5.
Explain How do you
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
know that the material in
this picture is not
magnetized?
A magnet has a large number of magnetic domains that
are lined up and pointing in the same direction. Suppose
you hold a strong magnet next to a piece of iron. The
magnet causes the magnetic field in many of the magnetic
domains in the iron to line up with the magnet’s field, as in
the figure below. The magnetic fields of the iron’s magnetic
domains are added together. This magnetizes the iron.
Picture This
6.
Label Which pole of the
bar magnet on the right
should be closest to the
figure on the left? Label this
pole of the bar magnet N
for north or S for south.
South Carolina Science Essentials
157
Earth’s Magnetic Field
Bar magnets are not the only objects that have magnetism.
Earth has a magnetic field, too. The space affected by Earth’s
magnetic field is the magnetosphere (mag NEE tuh sfihr). The
magnetosphere repels most of the charged particles from the
Sun. Earth’s magnetic field probably comes from deep within
Earth’s core. Moving melted iron in the outer core might
produce the magnetic field. The shape of Earth’s magnetic
field is like the magnetic field of a huge bar magnet.
7.
Explain How does
Earth’s magnetosphere
protect Earth from charged
particles from the Sun?
What are magnets found in nature?
Some animals, including honeybees, rainbow trout, and
homing pigeons, use magnetism to find their way. They
have tiny pieces of magnetite in their bodies. These pieces
are so small that they might contain only one magnetic
domain. Scientists have shown that some animals use these
natural magnets to find Earth’s magnetic field. They use
Earth’s magnetic field and the position of the Sun or stars
to help them find their way.
Earth’s magnetic poles do not stay in one place. The
magnetic pole in the north today is in a different place than
it was 20 years ago. Sometimes, Earth’s magnetic field also
changes direction. For example, a compass needle that
pointed south 700 thousand years ago would point north
today. During the last 20 million years, Earth’s magnetic field
has changed direction more than 70 times. The magnetism of
old rocks shows these changes in the magnetic field. When
some kinds of molten rock cool, magnetic domains of iron in
the rock line up with Earth’s magnetic field. After the rock
cools, the domains are frozen in place. So, the old rocks show
the direction of Earth’s magnetic field as it was long ago.
What is a compass needle?
8.
Infer If Earth’s magnetic
field is like a bar magnet,
where is the north pole of
the bar magnet?
158
Lesson EE What is magnetism?
A compass needle is a small bar magnet. It has a north and
a south magnetic pole. When a compass is in a magnetic field,
the needle turns until it lines up with the magnetic field line
at its location.
Earth’s magnetic field also makes a compass needle turn.
The north pole of the compass needle points toward Earth’s
magnetic pole that is in the north which is actually a
magnetic south pole. Earth’s magnetic field is like that of a
bar magnet with the south pole near Earth’s north pole.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
How does Earth’s magnetic field change?
After You Read
Mini Glossary
magnetic domain: a group of atoms with their magnetic
fields pointing in the same direction
magnetic field: the space around a magnet where the
magnetic force is
magnetosphere: the space affected by Earth’s
magnetic field
1. Review the terms and their definitions in the Mini Glossary above. Circle two of the
terms. On the lines below, tell how these two terms are related.
2. Complete the flowchart below to describe how the magnetic domains of a paper clip
change as it becomes magnetized.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
A strong
magnet is
Magnetic
domains
Magnetic
domains point in
all directions.
.
Magnetic fields
add together.
.
.
3. You were asked to make an outline of the lesson. How can you use the outline to help
you study for a quiz?
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about magnetism.
End of
Lesson
South Carolina Science Essentials
159
Llesson
3
FF
Heat
Standard 6-5.5: Illustrate the directional transfer of heat energy through convection, radiation, and
conduction.
compare thermal
energy and heat
■ three ways heat moves
■ what insulators and
conductors are
■
Identify Main Ideas As you
read this lesson, highlight the
main ideas about conduction,
radiation, and convection.
Find Main Ideas Add the
label “Heat” to the right column
of Foldable A as shown below.
As you read this lesson, write
down the main ideas about heat.
160
Lesson FF Heat
Before You Read
Write down two things you do to make yourself feel warmer.
Read to Learn
Heat and Thermal Energy
It’s cold, turn up the heat. Heat the oven to 375°F. A heat
wave has hit the Midwest. You’ve often heard the word heat,
but what exactly is it? Heat is thermal energy that moves
from one object to another when the objects are at different
temperatures. Heat moves, or is transferred, when two
objects are in contact with each other. More heat is
transferred when the difference in temperature between
the objects is large. Less heat is transferred when the
temperature difference is small.
For example, no heat moves between two pots of boiling
water that are touching. The water in both pots is the same
temperature. Suppose a pot of boiling water touches a pot
of cold water. Heat is transferred from the hot pot to the
cold pot. The hot water loses heat and the cold water gains
heat. Heat will transfer until both objects are the same
temperature.
How does heat move?
Heat always is transferred from warmer objects to cooler
objects. It never transfers from a cooler object to a warmer
one. The warmer object loses thermal energy. It becomes
cooler. The cooler object gains thermal energy. It becomes
warmer. Heat can be transferred in three ways––by
conduction, radiation, or convection.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What You’ll Learn
Conduction
When you eat something hot, conduction occurs. As the
hot food touches your mouth, heat moves from the food
to your mouth. Conduction is the movement of heat
between objects that are touching.
When you hold an ice cube in your hand, conduction is
occurring. The ice cube starts to melt and your hand starts
to feel cold. The fast-moving molecules in your warm hand
bump into the slow-moving molecules in the cold ice. When
the faster-moving molecules touch the slower-moving
molecules, energy passes from molecule to molecule. As a
result, heat moves from your warm hand to the cold ice.
The slow-moving molecules in the ice start moving faster.
With more energy, the ice warms and its temperature rises.
The ice begins to melt. The fast-moving molecules in your
hand move more slowly. They lose thermal energy and your
hand becomes cooler.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
When does conduction work best?
Conduction works best in solids and liquids. That’s
because the molecules and atoms are closer together in a
solid or a liquid than in a gas. The molecules and atoms
have to move only a short distance before they bump into
each other and transfer energy to another molecule or atom.
So, heat is transferred by conduction faster in liquids and
solids than in gases.
1.
Describe Give an
example of heat being
transferred by conduction.
2.
Explain What transfers
thermal energy when
objects are heated by
radiation?
Radiation
On a beautiful, clear day, you walk outside and notice the
warmth of the Sun. How does the Sun heat Earth? The Sun
transfers thermal energy to Earth, but not by conduction.
The Sun and Earth do not touch. Instead, the Sun transfers
heat to Earth by radiation. Radiation is the transter of
energy by electro-magnetic waves. Electromagnetic waves
can carry energy through empty space, like the space
between Earth and the Sun. These waves can also carry
energy through solids, liquids, and gases.
The Sun is not the only object that transfers heat by
radiation. Sit next to a fire in a fireplace. You feel heat
transferred by radiation from the fire to your skin. All
objects give off electromagnetic radiation. Warm objects
give off more radiation than cool objects.
South Carolina Science Essentials
161
Convection
When you heat a pot of water, heat transfers by conduction
from the stove to the pot. Heat can be transferred in another
way, too. As gas and liquid molecules move, they carry energy
with them. Convection is the transfer of thermal energy
through the movement of molecules from one part of a
material to another.
How is heat transferred by convection?
3.
Explain Why is a warm
fluid less dense than a cool
fluid?
Heat is transferred by convection as a pot of water is
heated. First, thermal energy is transferred to the water
molecules near the bottom of the pot. These water
molecules begin to move faster as their thermal energy
increases. The faster the molecules move, the farther apart
they get. Now the molecules in the warm water are farther
apart than the molecules in the cooler water near the top of
the pot. So, the warm water is less dense than the cool water.
The warm, less dense water rises to the top of the pot. The
cool, more dense water moves down to the bottom of the pot.
As the cool water is heated, it rises to the top. This repeats
until all the water in the pot is the same temperature.
Picture This
4.
Natural convection takes place when a cool, dense fluid,
pushes away a warm, less dense fluid. Think of the shore of
a lake. The water is cooler than the land during the day. The
warm land heats the air above it by conduction. As the air
gets hotter, its particles move faster and farther away from
each other. The hot air is less dense and it rises. The cooler,
denser air from above the lake moves toward the land. You
feel this movement of cool air as wind. The figure shows that
as cool air moves over the land, it pushes the warm, less
dense air up. The land heats the cool air and the cycle repeats.
Describe Using a
Warm air
highlighter, make one long
stroke that follows the
arrows in the figure to show
the path of the air flow.
Describe the movement of
the air.
Cool air
162
Lesson FF Heat
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What is natural convection?
What is forced convection?
Forced convection takes place when an outside force
pushes a fluid to make the fluid move and transfer heat. A
fan is an example of an outside force. Computers use fans
to keep their electronic parts from getting too hot. The fan
blows cool air onto the hot parts.
Heat from the computer parts is transferred to the air
around them by conduction. Warm air is pushed up and
away from the hot parts and cool air moves in. The hot
parts keep transferring heat to the cool air around them.
Make Lists Make a Foldable
like the one below. List materials
that are thermal conductors
and materials that are thermal
insulators.
T
Therm
Conductors
o
Thermal
Insulators
Thermal Conductors
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Why are most cooking pans made of metal? Why does a
metal spoon in a bowl of hot soup feel warm? Metal is a good
conductor of heat. A conductor is any material that transfers
heat easily. Some materials are good conductors because of the
types of atoms or chemical compounds they are made up of.
Remember that an atom has a nucleus surrounded by one
or more electrons. In some materials, like metals, these
electrons are not held tightly in place. They can move
around freely. These electrons can transfer thermal energy
by bumping into other atoms. Metals such as gold and
copper are the best conductors of heat.
Thermal Insulators
When you cook food in a pan, you want the pan to conduct
heat from the hot burner to your food. But you do not want
heat to move easily to the pan’s handle. An insulator is a
material that heat does not flow through easily. Most
cooking pans have handles made from insulators.
Liquids and gases are usually better insulators than solids
are. Air is a good insulator. Many insulating materials have
spaces filled with air. The air prevents heat from moving
through the material by conduction. Metals and other good
conductors of heat are poor insulators. Air and other good
insulators are poor heat conductors.
Houses and other buildings contain insulating materials.
These materials reduce the heat conduction between the
inside and outside. Insulating windows are made of two
layers of glass. There is a layer of air or other gas in between
the layers of glass. The layer of air reduces heat conduction.
It keeps heat from going outside in the winter and from
coming inside in the summer.
5.
Determine Would a
container made of a
conductor or of an insulator
be better for keeping hot
food from getting cold?
South Carolina Science Essentials
163
Heat Absorption
On a hot day, you can walk barefoot across the lawn. But
the pavement of the street is too hot to walk on. Why is the
pavement hotter than the grass? The change in temperature
of an object as it absorbs heat depends on the material it is
made of.
What is specific heat?
6.
Explain Which kind of
material needs more heat
to raise its temperature, one
with a high specific heat or
one with a low specific heat?
The specific heat of a material is the amount of heat
needed to raise 1 kilogram of that material by 1°C. More
heat is needed to change the temperature of a material
with a high specific heat than a material with a low
specific heat.
For example, the sand on a beach has a lower specific
heat than water in a lake. On a hot summer day, the sand
feels warmer than the water. Both are warmed by radiation
from the Sun. But, the sand heats up faster than the water
because it has a lower specific heat than the water. At night,
the sand feels cool and the water feels warmer. They both
lose thermal energy to the cooler night air. However,
the temperature of the sand decreases faster than the
temperature of the water.
Some power plants and factories use water to cool hot
equipment. The cooling water becomes hot. This hot water
may be released into lakes, rivers, or the ocean. The hot
water increases the temperature of the nearby water.
Thermal pollution is the increase in the temperature of a
body of water caused by warmer water being added to it.
Rainwater falling on warm roads and parking lots can also
cause thermal pollution.
7.
Identify Name one
harmful result of thermal
pollution.
164
Lesson FF Heat
Why is thermal pollution harmful?
Warmer water has less dissolved oxygen than cooler water.
Warm water causes fish and other animals to use more
oxygen. Some animals may die because there is not enough
oxygen in the water. Also, in warmer water, parasites and
diseases are a bigger problem for many organisms. Factories
and power plants can reduce thermal pollution by cooling
hot water in cooling towers before it’s released.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Thermal Pollution
After You Read
Mini Glossary
conduction: the movement of heat between objects that
are touching
conductor: any material that transfers heat easily
convection: the transfer of thermal energy through the
movement of molecules from one part of a material
to another
heat: thermal energy that moves from one object to another
when the objects are at different temperatures
radiation: the transfer of energy by electromagnetic waves
specific heat: the amount of heat needed to raise 1 kilogram
of a material by 1°C
thermal pollution: the increase in the temperature of a
body of water caused by adding warmer water
1. Review the terms and definitions in the Mini Glossary. Chose one of the terms that
describes how heat can be moved and use it in a sentence.
2. Fill in the blanks on the web diagram below with examples of the different methods of
heat transfer.
Conduction
Example:
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Convection
Heat Transfer
Example:
Radiation
Example:
3. You were asked to highlight the main ideas about conduction, radiation, and convection.
What would be another way to learn about these three methods of heat movement?
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about heat.
End of
Lesson
South Carolina Science Essentials
165
Llesson
GG
3
Work and Power
Standard 6-5.6: Recognize that energy is the ability to do work (force exerted over a distance).
when work is done
how to calculate how
much work is done
■ how work and power
are related
■
■
Study Coach
Make Flash Cards After
you read each page, write two
quiz questions on flash cards.
Write a question on one side of
each flash card. Write the answer
on the other side. Quiz yourself
until you know the answers.
Before You Read
Describe the work you have done today.
Read to Learn
What is work?
In science, there is a special definition of work. Work is
done when a force makes an object move in the same
direction as the force that is applied. You do work when
you lift your books, turn a doorknob, or write with a pen.
What does motion have to do with work?
Suppose your teacher asks you to move a box of books.
You try, but the box will not move. It is too heavy. You are
tired because you tried to force the box to move. But you
have not done any work. Two things must happen for you
to do work. First, you must apply a force on an object.
Second, the object must move in the same direction as the
force that you applied. Imagine a girl standing still and
holding two bags of groceries. Is she doing work? No, she
is not moving or causing anything to move.
How does the direction of force affect work?
Organize Information
Make the following Foldable to
help you understand work and
power.
What
is work?
166
What
is power?
Lesson GG Work and Power
Your arms apply a force upward when you lift a basket of
clothes. Your arms have done work because the basket
moved in the same direction as the force applied by your
arms. If you walk forward with the basket, your arms are
still applying an upward force on the basket. But you and
the basket are moving forward. The basket is not moving
in the same direction as the upward force applied by your
arms. So, no work is done by your arms.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What You’ll Learn
Does all of a force do work?
Sometimes only part of a force moves an object. Think
about what happens when you push a lawn mower. Look at
the figure. You push at an angle to the ground. Part of the
force is forward. Part of the force is downward. Which part
of the force does work? Only the part of the force that is
forward does work. It is in the same direction as the motion
of the mower.
Picture This
1.
Identify Which force in
the figure does work? Circle
the label and arrow.
Forward force
Total force
Downward
Force
Motion
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Applying Math
2.
Calculate A woman
lifted a box with a force of
50 N. She lifted the box 2 m.
How much work did she
do? Show your work.
3.
Infer Suppose the woman
Calculating Work
Work is done when a force makes an object move. More
work is done if the force is increased or if the object moves
farther. You can calculate how much work is done by using
the work equation below. The SI unit for work is the joule
(JEWL). The joule is named for the nineteenth-century
scientist James Prescott Joule.
work (joules) force (newtons) distance (meters)
W Fd
What distance is used for the
work equation?
Suppose you give a book a push and it slides across a
table. You use the distance an object moves while a force is
acting on it to calculate work, not the total distance the
object moved. So, the distance in the work equation is the
distance the book moved while you were pushing it.
in Problem 2 above lifted
the box only 1 m. What
happens to the amount
of work done?
South Carolina Science Essentials
167
What is power?
What does it mean to be powerful? Imagine two
weightlifters lifting the same amount of weight. They lift the
weight the same distance above the floor. They both do the
same amount of work. But the amount of power they use
depends on how long it took to do the work. Power is how
quickly work is done. The weightlifter who lifted the weight
in less time is more powerful.
How do you calculate power?
You can calculate power by dividing the amount of work
done by the time needed to do the work.
Applying Math
4.
Calculate A teacher does
140 J of work in 20 s. How
much power in watts did he
use? Show your work.
work (joules)
time (seconds)
W
P
t
power (watts) The SI unit of power is the watt. The watt is named for
James Watt, a nineteenth-century British scientist.
Remember that when something moves, it has kinetic
energy. If you push a chair and make it move, you do work
on the chair. You also change the chair’s energy. By making
the chair move, you increase the chair’s kinetic energy.
If you lift an object higher, you also change the energy of
the object. The potential energy of an object increases when it
is higher above Earth’s surface. When you lift an object, you
do work on the object and increase its potential energy.
5.
Summarize When you
do work on an object, what
two kinds of energy can you
increase for the object?
168
Lesson GG Work and Power
How are power and energy related?
You increase the energy of an object when you do work on
it. Energy cannot be created or destroyed. If the object gains
energy, you must lose energy. When you do work on an
object, you move, or transfer, energy to the object and your
energy decreases. The amount of work done is the amount of
energy transferred to the object. So, power is also equal to the
amount of energy transferred in a certain amount of time.
Sometimes energy can be transferred even when no work
is done. This happens when heat flows from a warm object
to a cold one. Energy can be transferred in many ways, even
when no work is done. Power is always the rate, or speed, at
which energy is transferred. The rate is the amount of
energy transferred divided by the time needed to transfer it.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
How can doing work change energy?
After You Read
Mini Glossary
power: how quickly work is done
work: is done when a force makes an object move in the
same direction as the force that is applied
1. Read the key terms and definitions in the Mini Glossary above. Describe work in your
own words.
2. Complete the table.
Action
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Lifting your books from
the bottom of your locker
Was work done
on the book?
In which direction
was work done?
How did the action
change the energy
of the object?
yes
up
The books now
have potential energy.
Carrying your books from
your locker to class
Pushing your book across
your desk for a friend
to see
3. You were asked to make two flash cards for every page of the lesson. How did this help
you learn the material in the lesson?
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about work.
End of
Lesson
South Carolina Science Essentials
169
Llesson
3
HH
Using Machines
Standard 6-5.6: Recognize that energy is the ability to do work (force exerted over a distance).
What You’ll Learn
how a machine makes
work easier
■ about mechanical
advantage and efficiency
■ how friction reduces
efficiency
■
Locate Information Look
at the lesson headings. Highlight
each question head as you read.
Then, use a different color to
highlight the answers to the
questions.
Before You Read
Describe a machine you used today and what it does.
Read to Learn
What is a machine?
Scissors, brooms, and knives are all machines. A machine
is a device that makes doing work easier.
Organize Information
Make the following Foldable to
help you organize information
about machines, mechanical
advantage, and efficiency.
What is a
machine?
What is
mechanical
advantage?
What is
efficiency?
170
Lesson HH Using Machines
Machines change the way you do work. When you use a
machine, you apply a force over a distance. You use force to
move a rake. The force that you apply on a machine is
input force. The work you do on a machine is equal to the
input force times the distance over which your force moves
the machine. The work that you do on the machine is the
input work.
The machine also does work. It applies a force to move an
object over a certain distance. A rake applies a force to move
leaves. Sometimes this force is called the resistance force.
This means the machine must overcome some resistance.
The force that the machine applies is output force. The
work that the machine does is the output work.
The output work can never be greater than the input
work when you use a machine. So why use a machine? A
machine can make work easier in three ways because it can:
• change the amount of force you need to apply.
• change the distance over which the force is applied.
• change the direction in which the force is applied.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Mechanical Advantage
How does changing force make work easier?
Some machines make work easier by reducing the force
you need to apply. You need less force to do the work. This
kind of machine increases the input force so the output
force is greater than the input force. The number of times
that a machine increases the input force is the mechanical
advantage (MA) of the machine. You can calculate mechanical advantage using this equation:
Applying Math
1.
output force (newtons)
input force (newtons)
F
MA out
Fin
mechanical advantage How does changing distance make work easier?
Some machines let you apply force over a shorter distance.
In these machines, the output force is less than the input
force. A rake is an example of this kind of machine. You
move your hands a small distance at the top of the handle.
But, the bottom of the rake moves a greater distance. The
mechanical advantage of this kind of machine is less than 1.
This is because the output force is less than the input force.
Calculate Suppose you
use a machine to move a
large rock. You apply a
force of 100 N to the
machine. The machine
applies a force of 2,000 N
to the rock. What is the
mechanical advantage of
the machine? Circle your
answer.
a. 2
b. 10
c. 20
d. 100
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
How does changing direction make
work easier?
Sometimes it is easier to
apply a force in a certain
direction. Imagine putting
a flag up on a flagpole. It
is easier to pull down on
the rope on the flagpole
than to pull up on it. Some
machines let you change the
direction of the input force.
In these machines, the
distance and the force do
not change. The mechanical
advantage of this kind of
machine is equal to 1. The
output force is equal to the
input force. The figures
show the three ways
machines make doing
work easier.
Input force
Input force
Input force
Increases
force
Increases
distance
Changes
direction
of force
Larger force
applied over
a shorter
distance
Smaller force
applied over
a longer
distance
Force
applied over
same distance
in a different
direction
Picture This
2.
Describe Write the
words that make the
sentence true on the lines
below: When a machine
increases a.
, it is
applied over a shorter
b.
.
a. _______________________
b. _______________________
South Carolina Science Essentials
171
Efficiency
Applying Math
3.
Calculate Workers use a
ramp to load a piano into a
truck. The output work, or
the amount of work needed
to move the piano, is
12,000 J. The workers do
15,000 J of work. What is
the efficiency of the ramp?
Show your work.
A machine does not increase the input work. For a real
machine, the output work done by the machine is always
less than the input work that is done on the machine. There
is friction when parts of the machine move. Friction
changes some of the input work into heat. So, the output
work is less. If friction in the machine decreases, the
efficiency, or amount of effort, of the machine increases.
The efficiency of a machine is the ratio of the output work
to the input work. You can find efficiency by using this
equation:
output work (joules)
100%
input work (joules)
W
eff out 100%
Win
efficiency (in percent) 4.
Identify What causes
friction?
Imagine pushing a heavy box up a ramp. The bottom
surface of the box slides across the top surface of the ramp.
Neither the box nor the ramp is perfectly smooth. Each
surface has high spots and low spots.
As the two surfaces slide past each other, high spots on
the two surfaces touch each other. The places that they
touch are called contact points. At these contact points,
atoms and molecules can bond together. This makes the
contact points stick together. The attractive forces between
all of the bonds added together is the frictional force. The
frictional force tries to keep the two surfaces from sliding
past each other.
To keep the box moving, a force must be applied. The
force has to break the bonds between the contact points.
Even after these bonds are broken and the box moves, new
bonds form as different parts of the two surfaces touch.
How can friction be reduced?
5.
Evaluate Which will
have more friction, two
pieces of sandpaper or two
pieces of notebook paper?
172
Lesson HH Using Machines
One way to reduce friction between two surfaces is to add
oil to the surfaces. Oil can fill the gaps between the surfaces.
Oil keeps many of the high spots from touching each other.
There are fewer contact points between the surfaces. So, the
force of friction is less. This means more of the input work
is changed to output work by the machine.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
How does friction affect a machine?
After You Read
Mini Glossary
efficiency: the ratio of the output work to the input work
input force: the force that you apply on a machine
mechanical advantage: the number of times that a
machine increases the input force
output force: the force that a machine applies
1. Review the terms and their definitions in the Mini Glossary. Describe how the input
force and output force of a machine work together to make work easier.
2. In the figure below, write the way each machine can be useful. Write the terms increases
force, changes direction of force, and increases distance in the correct locations.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
How Machines Make Work Easier
Input force
Force applied over
same distance in a
different direction
Input force
Smaller force
applied over a
longer distance
Input force
Larger force
applied over a
shorter distance
3. How did highlighting the answers to the headings that were questions help you make
sure you understood the material in the lesson?
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about using
machines.
End of
Lesson
South Carolina Science Essentials
173
Simple Machines
Llesson
I3I
Standard 6-5.6: Recognize that energy is the ability to do work (force exerted over a distance).
Standard 6-5.7: Explain how the design of simple machines (including levers, pulleys, and inclined planes)
helps reduce the amount of force required to do work. Standard 6-5.8: Illustrate ways that simple machines
exist in common tools and complex machines.
What You’ll Learn
what the different
simple machines are
■ how to find the
mechanical advantage
of each simple machine
■
Before You Read
Suppose you need to put a heavy box into a truck. Would
you rather push the box up a ramp or lift it straight into
the air? Explain.
Read to Learn
through this lesson, underline
each kind of simple machine.
Compare and Contrast
Make the following Foldable to
help you compare and contrast
simple and compound
machines.
Simple
Machines
Both
Compound
Machines
174
Lesson II Simple Machines
What is a simple machine?
In the last lesson you learned that machines make work
easier. Some machines like cars, elevators, or computers
are very complicated. But machines can be very simple. A
hammer, a shovel, and a ramp are all machines. A simple
machine is a machine that does work with only one
movement. There are six simple machines: an inclined
plane, a lever, a wheel and axle, a screw, a wedge, and a
pulley. A compound machine is a machine made up of
more than one simple machine. A bicycle is a compound
machine.
Inclined Plane
Ramps have been used for thousands of years. Ancient
Egyptians might have used them to build the pyramids.
Archaeologists hypothesize that the Egyptians built huge
ramps to move limestone blocks. The blocks each weighed
more than 1,000 kg. A ramp is a simple machine known as
an inclined plane. An inclined plane is a flat, sloped surface.
You might need a lot of force if you have to lift an object.
An inclined plane lets you use less force to move an object
from one height to another. The longer an inclined plane is,
the less force is needed to move the object.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Identify Simple
Machines As you read
Weight =
1,500 N
Force = 300 N
1m
How are inclined planes used?
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
5m
Force = 1,500 N
Suppose you have to lift a box weighing 1,500 N into the
back of the truck that is 1 m off the ground. Could you do
that? The force (1,500 N) times the distance (1 m) equals
1,500 J of work. Look at the figure. Suppose you use a
5-m-long ramp to lift the box into the truck. The amount
of work you need to do does not change. You still need to
do 1,500 J of work. But, the distance over which you apply
the force is now 5 m. You can find the force you need by
dividing both sides of the work equation by distance.
Picture This
1.
Evaluate Circle the force
needed to push the box up
the ramp. Then, circle the
force needed to lift the box
straight up. How much
more force is needed to lift
the box straight up?
work (joules)
distance (meters)
1,500 J
Force 300 N
5m
Force When you use the ramp, you need to apply a force of
only 300 N. A force of 300 N is much less than a force of
1,500 N. With the ramp, you apply the force over a distance
that is five times longer. So, the force is five times less.
The mechanical advantage of an inclined plane is the
length of the inclined plane divided by its height. In this
example, the ramp has a mechanical advantage of 5.
Applying Math
2.
Calculate You need to
lift a different box into the
truck. The amount of work
it takes is 1,000 J. You use a
2 m ramp. How much force
do you need? Show your
work.
What is a wedge?
A wedge is an inclined plane that moves. A wedge can
have one or two sloping sides. A knife is an example of a
wedge. An axe and certain kinds of doorstops also are
wedges. The mechanical advantage of a wedge increases as
it becomes longer and thinner.
South Carolina Science Essentials
175
Are there wedges in your body?
You have wedges in your body. Think of biting into an
apple. The bite marks on the apple show that your front
teeth are wedge shaped. A wedge changes the direction of
the applied force. The downward force of your bite is
changed into a sideways force. The sideways force pushes
the skin of the apple apart.
What is a screw?
3.
Explain What holds a
screw into an object?
The screw is another form of inclined plane. A screw is
an inclined plane wrapped around a cylinder or post. The
inclined plane on a screw forms the threads of the screw. A
screw changes the direction of the applied force. The applied
force pulls the screw into the material. Friction between the
threads and the material holds the screw tightly in place.
The mechanical advantage of the screw is the length of the
inclined plane wrapped around the screw divided by the
length of the screw. The more tightly wrapped the threads
are, the easier it is to turn the screw.
A lever is any stiff rod or plank that turns around a
point. The point that the lever turns around is called a
fulcrum. You can find the mechanical advantage of a lever
by dividing the distance from the input force to the fulcrum
by the distance from the fulcrum to the output force. This is
shown in the figure.
Picture This
4.
Calculate Use the figure.
Suppose the distance from
the input force to the
fulcrum is 60 cm. The
distance from the fulcrum
to the output force is 20 cm.
What is the mechanical
advantage? Show your
work.
Input
force
Output
force Mechanical 10 cm 1
=
=
advantage 50 cm 5
10 cm
50 cm
Input
force
Output
force Mechanical 50 cm
=
= 5
advantage 10 cm
50 cm
10 cm
The fulcrum of a lever can be in different positions.
When the fulcrum is closer to the output force than the
input force, the mechanical advantage is greater than 1.
Scissors, a wheelbarrow, and a baseball bat are all levers.
176
Lesson II Simple Machines
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Lever
Wheel and Axle
Imagine a doorknob the size of a pencil. Would it be easy
to turn? No, it would be hard to turn. A doorknob is a
simple machine that makes opening a door easier. A
doorknob is a wheel and axle. A wheel and axle is made
up of two round objects of different sizes that are attached
so they turn together. The larger object is the wheel and the
smaller object is the axle. The faucet handle shown in the
figure is a wheel and axle.
Picture This
Wheel
5.
Axle
Analyze Does the wheel
or the axle of the faucet
make the output force?
Input
force
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Output force
How do you find the MA of a wheel and axle?
The MA (mechanical advantage) of a wheel and axle is
usually greater than 1. You find it by dividing the radius of
the wheel by the radius of the axle. Suppose the radius of
the wheel is 12 cm and the radius of the axle is 4 cm. The
mechanical advantage is 3.
Applying Math
6.
Calculate A wheel has a
radius of 15 cm. The axle
has a radius of 3 cm. What is
the mechanical advantage
of the wheel and axle?
Show your work.
How are wheels and axles used?
In some wheels and axles, the input force turns the wheel.
The wheel turns the axle. The turning axle makes the output
force. The mechanical advantage is greater than 1 because
the wheel is bigger than the axle. This means the output force
is greater than the input force. A doorknob, a steering wheel,
and a screwdriver are examples of this kind of wheel and axle.
In other wheels and axles, the input force turns the axle.
The axle turns the wheel. The wheel makes the output force.
The mechanical advantage is less than 1. The output force is
less than the input force. A fan and a Ferris wheel are
examples of this kind of wheel and axle.
South Carolina Science Essentials
177
Pulley
To raise a sail, a sailor pulls down on a rope. The rope
uses a simple machine called a pulley to change the
direction of the force needed. A pulley is a grooved wheel
with a rope or cable wrapped over it.
What is a fixed pulley?
7.
Describe How does a
pulley change the force
you apply?
Think about the pulley on a sail. The pulley is attached to
something above your head. This kind of pulley is called a
fixed pulley. When you pull down on the rope, the sail is
pulled up. Look at the figure of the fixed pulley below. A
fixed pulley does not change the force you apply. It also does
not change the distance over which you apply a force. A fixed
pulley does change the direction in which you apply your
force. The mechanical advantage of a fixed pulley is 1.
Picture This
8.
Explain How does a
movable pulley change the
input force?
A fixed pulley changes
the direction of the
input force.
Fixed pulley
178
Lesson II Simple Machines
You can also attach a pulley to the object you need to lift.
This is called a movable pulley. A movable pulley lets you
apply a smaller force to lift the object. The mechanical
advantage of a movable pulley is always 2. The middle
pulley in the figure below is a movable pulley.
You often will see movable and fixed pulleys used
together. This is called a pulley system. The mechanical
advantage of a pulley system is equal to the number of
sections of rope pulling up on the object. The mechanical
advantage for the pulley system in the figure is 3.
A movable pulley
multiplies the
input force.
Movable pulley
A pulley system uses
more than one pulley to
increase the mechanical
advantage.
Pulley system
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
What is a movable pulley?
After You Read
Mini Glossary
compound machine: a machine made up of more than one
simple machine
inclined plane: a flat, sloped surface
lever: any stiff rod or plank that turns around a point
pulley: a grooved wheel with a rope or cable wrapped over it
screw: an inclined plane wrapped around a cylinder or post
simple machine: a machine that does work with only
one movement
wedge: an inclined plane that moves
wheel and axle: two round objects of different sizes that
are attached so they turn together
1. Review the terms and their definitions in the Mini Glossary. Write a sentence describing
how a screw and a wedge are related.
2. Match each simple machines with the correct example. Write the letter of each simple
machine in Column 2 on the line in front of the example it is or uses in Column 1.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Column 1
Column 2
1. tooth
a. inclined plane
2. doorknob
b. wheel and axle
3. threads of a lightbulb
c. wedge
4. wheelbarrow
d. screw
5. ramp
e. pulley
6. flagpole rope
f. lever
3. What would be a good way to teach an elementary science class about simple machines?
Visit msscience.com to access your textbook, interactive
games, and projects to help you learn more about simple
machines.
End of
Lesson
South Carolina Science Essentials
179