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Chapter 2
It’s Alive!! Or Is It?
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Section 1 Characteristics of Living Things
Section 2 The Necessities of Life
Concept Mapping
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Chapter 2
Section 1 Characteristics of
Living Things
Bellringer
What are four living and nonliving things that you
interact with every day? How do you know whether
each is living or nonliving? Do you know what the
word inanimate means? If so, write out a definition.
Does nonliving mean the same thing as dead?
Explain your answer.
Write your answers in your science journal.
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Chapter 2
Section 1 Characteristics of
Living Things
Objectives
• Describe the six characteristics of of living things.
• Describe how organisms maintain stable internal
conditions.
• Explain how asexual reproduction differs from sexual
reproduction.
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Chapter 2
Section 1 Characteristics of
Living Things
Living Things Have Cells
• All living things are composed of one or more cells.
• A cell is a membrane-covered structure that
contains all of the materials necessary for life.
• Some organisms are made up of only one cell and
some are made up of trillions of cells. In an organism
with many cells, different kinds of cells perform
specialized functions.
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Chapter 2
Section 1 Characteristics of
Living Things
Living Things Sense and Respond to Change
• A stimulus is anything that causes a reaction or
change in an organism or any part of an organism.
• Homeostasis is the maintenance of a stable
internal environment.
• Responding to External Change Organisms must
respond to change in the external environment in
order to maintain their homeostasis.
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Chapter 2
Section 1 Characteristics of
Living Things
Living Things Reproduce
• Organisms make other organisms similar to
themselves.
• In sexual reproduction, two parents produce
offspring that will share characteristics of both
parents.
• In asexual reproduction, a single parent produces
offspring that are identical to the parent.
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Chapter 2
Section 1 Characteristics of
Living Things
Living Things Have DNA
• The cells of all living things contain the molecule
deoxyribonucleic acid, or DNA.
•DNA controls the structure and function of cells.
•The passing of traits through DNA is called heredity.
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Chapter 2
Section 1 Characteristics of
Living Things
Living Things Use Energy
• Organisms use energy to carry out the activities
of life.
• An organism’s metabolism is the total of all of
the chemical activities that the organism performs.
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Chapter 2
Section 1 Characteristics of
Living Things
Living Things Grow and Develop
• All living things, whether they are made of one cell
or many cells, grow during periods of their lives.
• Living things may develop and change as they grow.
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Chapter 2
Section 2 The Necessities of Life
Bellringer
What do you think your mass would be if there were
no water in your body? What else besides water is
your body composed of? Where do you think you get
the minerals that make up your body mass?
Record your answers in your science journal.
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Chapter 2
Section 2 The Necessities of Life
Objectives
• Explain why organisms need food, water, air, and
living space.
• Describe the chemical building blocks of cells.
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Chapter 2
Section 2 The Necessities of Life
Water
• Your cells and the cells of almost all living organisms
are approximately 70% water. Most of the chemical
reactions involved in metabolism require water.
Air
• Air is a mixture of several different gases, including
oxygen and carbon dioxide. Most living things use
oxygen in the chemical process that releases energy
from food.
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Chapter 2
Section 2 The Necessities of Life
A Place to Live
• All organisms need a place to live that contains all
of the things they need to survive. Space on Earth is
limited, so organisms are often in competition with
each other.
Food
• All living things need food. Food gives organism
energy and the raw material needed to carry on life
processes.
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Chapter 2
Section 2 The Necessities of Life
Food, continued
• Making Food Some organisms, such as plants, are
called producers. Producers can make their own food
by using energy from their surroundings.
• Taking Food Other organisms are called
consumers because they must eat (consume) other
organisms to get food. Decomposers are consumers
that get their food by breaking down the nutrients in
dead organisms or animal wastes.
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Chapter 2
Section 2 The Necessities of Life
Comparing Consumers and Producers
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Visual Concept
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Chapter 2
Section 2 The Necessities of Life
Putting It All Together
• All organisms need to break down that food in order
to use the nutrients in it.
• Nutrients are made up of molecules.
• Molecules found in living things are usually made up
of six elements: carbon, hydrogen, nitrogen, oxygen,
phosphorus, and sulfur.
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Chapter 2
Section 2 The Necessities of Life
Proteins
• Proteins are large molecules made up of amino
acids.
•Making Proteins Organisms break down the
proteins in food to supply their cells with amino acids
that are then linked together to form new proteins.
• Proteins in Action Some proteins form structures
that are easy to see. Other proteins help cells do their
jobs. Proteins called enzymes start or speed up
chemical reactions in cells.
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Chapter 2
Section 2 The Necessities of Life
Carbohydrates
• Molecules made of sugars are called carbohydrates.
•Simple Carbohydrates Simple carbohydrates are
made up of one sugar molecule or a few sugar
molecules linked together.
• Complex Carbohydrates Complex carbohydrates
are made of hundreds of sugar molecules linked
together. Organisms store extra sugar as complex
carbohydrates.
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Chapter 2
Section 2 The Necessities of Life
Lipids
• Lipids are compounds that cannot mix with water.
•Phospholipids are the molecules that form much of
the cell membrane.
• Fats and Oils Fats and oils are lipids that store
energy. When an organism has used up most of its
carbohydrates, it can get energy from these lipids.
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Chapter 2
Section 2 The Necessities of Life
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Chapter 2
Section 2 The Necessities of Life
ATP
• Adenosine triphosphate, or ATP, is the major energycarrying molecule in cells.
• The energy in carbohydrates and lipids must first be
transferred to ATP, which then provides fuel for cellular
activities.
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Chapter 2
Section 2 The Necessities of Life
Nucleic Acids
• Nucleic acids are large molecules made up of
subunits called nucleotides.
• Nucleic acids are sometimes called the blueprints of
life because they have all the information needed for
a cell to make proteins.
• DNA is a nucleic acid.
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Chapter 2
Section 2 The Necessities of Life
Nucleic Acid
Click below to watch the Visual Concept.
Visual Concept
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Chapter 2
It’s Alive!! Or Is It?
Concept Mapping
Use the terms below to complete the concept map on
the next slide.
DNA
sugars
energy
enzymes
living cells
proteins
starches
carbohydrates
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Chapter 2
It’s Alive!! Or Is It?
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Chapter 2
It’s Alive!! Or Is It?
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