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Name ____________________________ Date ____________________ Class ____________
Living Things
■
Section Summary
Domains and Kingdoms
Guide for Reading
■ What characteristics are used to classify organisms?
How do bacteria and archea differ?
■
What are the kingdoms within the domain Eukarya?
Today, a three-domain system of classification is commonly used. The three
domains are Bacteria, Archaea, and Eukarya. Within the domains are
kingdoms. Organisms are placed into domains and kingdoms based
on their cell type, their ability to make food, and the number of cells
in their bodies.
Members of the domain Bacteria are prokaryotes. Prokaryotes are
organisms whose cells lack a nucleus. A nucleus is a dense area in a cell that
contains nucleic acids—the chemical instructions that direct the cell’s
activities. In prokaryotes, nucleic acids are scattered throughout the cell.
Members of the domain Archaea, whose name comes from the Greek
word for “ancient,” can be found in some of the most extreme environments
on Earth, including hot springs, very salty water, swamps, and the intestines
of cows! Scientists think that the harsh conditions in which archaea live are
similar to those of ancient Earth. Like bacteria, archaea are unicellular
prokaryotypes. And like bacteria, some archaea are autotrophs while others
are heterotrophs. Although bacteria and archaea are similar in some ways,
there are important differences in the structure and chemical makeup of
their cells.
Members of the domain Eukarya are eukaryotes—organisms with cells
that contain nuclei. Scientists classify organisms in the domain Eukarya
into one of four kingdoms: protists, fungi, plants, or animals.
Slime molds are protists. The protist kingdom is sometimes called the
“odds and ends” kingdom because its members are so different from one
another. Protists can be autotrophs or heterotrophs. Although many protists
are unicellular, some, such as seaweeds, are multicellular.
Mushrooms, molds, mildew, and yeast are all fungi. Most fungi are
multicellular eukaryotes. A few, such as yeast, are unicellular eukaryotes.
Fungi are found almost everywhere on land, but only a few live in fresh
water. All fungi are heterotrophs. Most fungi feed by absorbing nutrients
from dead or decaying organisms.
Plants are all multicellular eukaryotes. The plant kingdom includes a
variety of organisms. In general, plants are autotrophs and feed almost all of
the heterotrophs on land.
All animals are multicellular eukaryotes. All animals are heterotrophs.
Animals have different adaptations that allow them to find food, capture it,
eat it, and digest it. Members of the animal kingdom are found in diverse
environments on earth.
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Living Things
■
Name ____________________________ Date ____________________ Class ____________
Ecosystems and Biomes
■
Section Summary
Energy Flow in Ecosystems
Guide for Reading
■ What energy roles do organisms play in an ecosystem?
■
How does energy move through an ecosystem?
■
How much energy is available at each level of an energy pyramid?
An organism’s energy role is determined by how it obtains energy and how it
interacts with the other living things in its ecosystem. Each of the organisms
in an ecosystem fills the energy role of producer, consumer, or decomposer.
Plants, algae, and some bacteria can carry out photosynthesis. In this
process, the organism uses the sun’s energy to turn water and carbon
dioxide into sugar molecules. An organism that can make its own food is a
producer. Producers are the source of all the food in an ecosystem.
Other organisms cannot make their own food. They depend on producers
for food and energy. An organism that obtains energy by feeding on other
organisms is a consumer. Consumers are classified by what they eat.
Consumers that eat only plants are called herbivores. Consumers that eat only
animals are called carnivores. A consumer that eats both plants and animals is
called an omnivore. A scavenger is a carnivore that feeds on the bodies of
dead organisms. An organism may play more than one role in an ecosystem.
Organisms that break down wastes and dead organisms and return the
raw materials to the environment are called decomposers. As decomposers
obtain energy for their own needs, they return simple molecules to the
environment to be used again by other organisms.
The movement of energy through an ecosystem can be shown in
diagrams called food chains and food webs. A food chain is a series of
events in which one organism eats another and obtains energy. The first
organism in a food chain is always a producer. The second organism, called
a first-level consumer, eats the producer. The next consumer, called a secondlevel consumer, eats the first-level consumer. A food chain shows just one
possible path of energy through an ecosystem.
Most producers and consumers are part of many food chains. A more
realistic way to show the flow of energy through an ecosystem is a food web.
A food web consists of the many overlapping food chains in an ecosystem.
When an organism makes its own food or eats other organisms, it obtains
energy. The organism uses most of this energy for its own life processes.
Only some of the energy will be available to the next organism in the food
web. A diagram called an energy pyramid shows the amount of energy that
moves from one feeding level to another in a food web. The most energy is
available at the producer level of the pyramid. As you move up the
pyramid, each level has less available energy than at the level below. In
general, only about 10 percent of the energy at one level of a food web is
transferred to the next higher level. For this reason, most food webs have
only three or four feeding levels, with few organisms at the highest level in
a food web.
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
Name ____________________________ Date ____________________ Class ____________
Introduction to Plants
■
Section Summary
Photosynthesis and Light
Guide for Reading
■ What happens when light strikes a green leaf?
■
How do scientists summarize the process of photosynthesis?
The light that you see is called white light. White light is made up of the
colors of the rainbow—red, orange, yellow, green, blue, and violet. These
colors are called the visible spectrum. Some objects reflect some colors of the
visible spectrum and absorb others. When light strikes a red shirt, the shirt
absorbs most colors and reflects red. The shirt looks red because your eyes
see the reflected color.
Some objects such as glass and other transparent materials allow light to
pass through them. This process is called transmission. When light hits a
shiny surface such as mirror, the light bounces back. This process is called
reflection. When dark objects, such as street pavements, take in light, it is
called absorption.
Like most other objects, plants absorb some colors and reflect others.
When light strikes the green leaves of a plant, most of the green part of the
spectrum is reflected. Most of the other colors of light are absorbed.
Chlorophyll absorbs most of the blue and red light. Accessory pigments,
which include orange and yellow pigments, are also found in leaves and
absorb different colors of light than chlorophyll. Most accessory pigments
are not visible in plants because they are masked by chlorophyll.
Plants use energy from light to power the process of photosynthesis.
Carbon dioxide gas from the air and water from the soil are the raw
materials for photosynthesis. Sugar and oxygen are the products. The
many chemical reactions of photosynthesis can be summarized by this
equation:
light energy
carbon dioxide +
water →
sugar + oxygen
(CO2)
(H2O)
(C6H12O6)
(O2)
This equation reads, “carbon dioxide and water combine in the presence
of light to produce sugar and oxygen.” Photosynthesis takes place in the
parts of a plant that contain chlorophyll.
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
Name ____________________________ Date ____________________ Class ____________
Cell Structure and Function
■
Section Summary
Looking Inside Cells
The cell wall is a rigid layer of nonliving material that surrounds the cells of
plants and some other organisms. A plant’s cell wall helps to protect and
support the cell. The cell wall is made of a strong, flexible material called
cellulose, and many materials can pass through it.
In cells that do not have cell walls, the cell membrane is the outside
boundary that separates the cell from its environment. All cells have cell
membranes. In cells with cell walls, the cell membrane is located just inside
the cell wall. The cell membrane controls what substances come into and
out of a cell.
Inside a cell are tiny structures called organelles, which carry out specific
functions within the cell. The nucleus is a large, oval structure that acts as
the “brain” of the cell. You can think of the nucleus as the cell’s control
center, directing all of the cell’s activities. The nucleus is surrounded by a
protective membrane called the nuclear envelope. Materials pass in and out
of the nucleus through small openings, or pores, in the nuclear envelope.
The cytoplasm is the region between the cell membrane and the nucleus.
Many cell organelles are found in the cytoplasm. The mitochondria are known
as the “powerhouses” of the cell because they convert energy in food
molecules to energy the cell can use to carry out its functions. Passageways
called the endoplasmic reticulum carry proteins and other materials from one
part of the cell to another. Small, grainlike bodies called ribosomes function as
factories to produce proteins. Collections of sacs and tubes called Golgi bodies
receive proteins and other newly formed materials from the endoplasmic
reticulum, package them, and distribute them to other parts of the cell. The
Golgi bodies release materials outside the cell. In plants and some other
organisms, large, green structures called chloroplasts capture energy from
sunlight and use it to produce food for the cell. Large water-filled sacs called
vacuoles are the storage areas of cells. A vacuole stores food and other
materials needed by the cell. Small, round structures called lysosomes contain
chemicals that break down certain materials in the cell.
Plants and animals contain many cells. In a many-celled organism, the cells
are often quite different from each other and are specialized to perform specific
functions. In many-celled organisms, cells are often organized into tissues,
organs, and organ systems. Bacterial cells are smaller and different from plant
and animal cells. While a bacterial cell does have a cell wall and a cell
membrane, it does not contain a nucleus. The bacterial cell’s genetic material,
which looks like a thick, tangled string, is found in the cytoplasm. Bacterial cells
contain ribosomes, but none of the other organelles found in plant or animal cells.
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
Cell Structure
and Function
Guide for Reading
■ What role do the cell wall and cell membrane play in the cell?
■ What are the functions of cell organelles?
■ How are cells organized in many-celled organisms?
■ How do bacterial cells differ from plant and animal cells?
Name ____________________________ Date ____________________ Class ____________
Cell Processes and Energy
■
Section Summary
Cell Division
Guide for Reading
■ What events take place during the three stages of the cell cycle?
■
How does the structure of DNA help account for the way in which DNA
copies itself?
The regular sequence of growth and division that cells undergo is known as
the cell cycle. The cell cycle is divided into three main stages.
The first stage of the cell cycle is called interphase. During interphase, the
cell grows, makes a copy of its DNA, and prepares to divide into two cells.
During the first part of interphase, the cell grows to full size and produces all
the structures it needs. In the next part of interphase, the cell makes an exact
copy of the DNA in its nucleus in a process called replication. At the end of
DNA replication, the cell contains two identical sets of DNA.
Once interphase is complete, the second stage of the cell cycle begins.
Mitosis is the stage during which the cell’s nucleus divides into two new
nuclei. During mitosis, one copy of the DNA is distributed into each of the
two daughter cells. Scientists divide mitosis into four parts, or phases:
prophase, metaphase, anaphase, and telophase. During prophase, the
threadlike chromatin in the cell’s nucleus condenses to form double-rod
structures called chromosomes. Each identical rod in a chromosome is called
a chromatid. The two chromatids are held together by a structure called a
centromere. As the cell progresses through metaphase, anaphase, and
telophase, the chromatids separate from each other and move to opposite
ends of the cell. Then two nuclei form around the chromatids at the two ends
of the cell.
After mitosis, the final stage of the cell cycle, called cytokinesis, completes
the process of cell division. During cytokinesis, the cytoplasm divides,
distributing the organelles into each of the two new cells. Each daughter cell
has the same number of chromosomes as the original parent cell. At the end of
cytokinesis, each cell enters interphase, and the cycle begins again. The length
of each stage and cell cycle varies, depending on the type of cell.
DNA replication ensures that each daughter cell will have all of the
genetic information it needs to carry out its activities. The two sides of the
DNA ladder are made up of alternating sugar and phosphate molecules.
Each rung of the DNA ladder is made up of a pair of molecules called
nitrogen bases. There are four kinds of nitrogen bases: adenine, thymine,
guanine, and cytosine. Adenine only pairs with thymine, and guanine only
pairs with cytosine. DNA replication begins when the two sides of the DNA
molecule unwind and separate. Next, nitrogen bases that are floating in the
nucleus pair up with the bases on each half of the DNA molecule. Because of
the way in which the nitrogen bases pair with one another, the order of the
bases in each new DNA molecule exactly matches the order in the original
DNA molecule. Once the new bases are attached, two new DNA molecules
are formed.
© Pearson Education, Inc., publishing as Pearson Prentice Hall. All rights reserved.
Name ____________________________ Date ____________________ Class ____________
Protists and Fungi
■
Section Summary
Protists
Guide for Reading
■
What are the characteristics of animal-like, funguslike, and plantlike protists?
The protist kingdom is very diverse. All protists are eukaryotes that cannot
be classified as animals, plants, or fungi. All live in moist surroundings. Most
are unicellular, but some are multicellular. Some are heterotrophs, some are
autotrophs, and some are both. Protists can be divided into three categories:
animal-like, funguslike, and plantlike protists.
Like animals, animal-like protists are heterotrophs, and most are able
to move from place to place to obtain food. Animal-like protists are also
called protozoans. Protozoans can be divided into four types: sarcodines,
ciliates, flagellates, and those that are parasites. Sarcodines move and feed
by using pseudopods. Pseudopods are temporary bulges of the cell.
Pseudopods form when cytoplasm flows toward one location and the rest of
the organism follows. Protozoans that live in fresh water, such as amoebas,
have a contractile vacuole, which collects the extra water and expels it from
the cell. Ciliates have structures called cilia, which are hairlike projections
that move with a wavelike motion. Flagellates move using whiplike flagella.
Some flagellates live inside the bodies of other organisms in a state of
symbiosis. Symbiosis is a close relationship between two species where at
least one of the species benefits. Sometimes, flagellates harm their hosts. In
other cases, their relationship is one of mutualism, in which both partners
benefit. Protozoans that are parasites feed on their hosts’ cells and body
fluids.
Plantlike protists are called algae. Like plants, algae are autotrophs.
Algae can exist in a variety of colors because they contain many types of
pigments—chemicals that produce color. Plantlike protists include diatoms,
dinoflagellates, euglenoids, red algae, green algae, and brown algae.
Diatoms have beautiful, glasslike cell walls. Dinoflagellates are covered by
stiff plates and move using two flagella. Euglenoids can be heterotrophs
when sunlight is not available. Red algae and brown algae live in the oceans.
Green algae live in fresh water, salt water, and moist places on land.
Like fungi, funguslike protists are heterotrophs, have cell walls, and
use spores to reproduce. Spores are tiny cells that are able to grow into new
organisms. All funguslike protists are able to move at some point in their
lives. The three types of funguslike protists are slime molds, water molds,
and downy mildews. Slime molds live in moist soil and on decaying plants.
Water molds and downy mildews grow as tiny threads in water or moist
places.
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