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4.1: Energy for Life

Difficulty Level: At Grade Created by: CK-12
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Lesson 4.1: True or False

Name___________________ Class______________ Date________

Write true if the statement is true or false if the statement is false.

_____ 1. All life needs energy.

_____ 2. C6H12O6 + 6O2 → 6CO2 + 6H2O is the chemical reaction of photosynthesis.

_____ 3. Glucose is a carbohydrate that stores chemical energy in a concentrated and stable form.

_____ 4. Many scientists consider photosynthesis to be the most important life process on Earth.

_____ 5. Only autotrophs can perform photosynthesis.

_____ 6. Only four types of organisms — plants, algae, fungi and some bacteria — can make food through photosynthesis.

_____ 7. ATP is the “energy currency” of the cell, so it makes sense that a molecule of ATP contains much more chemical energy than a molecule of glucose.

_____ 8. Whereas photosynthesis occurs in only some organisms, cellular respiration occurs in the cells of all living things.

_____ 9. Like matter, energy is also recycled by living organisms.

_____ 10. Heterotrophs cannot make their own food.

_____ 11. Because you are able to cook your own food in the microwave oven, you are a producer.

_____ 12. As mushrooms are fungi, they are heterotrophs.

_____ 13. A food chain shows how energy and matter flow from consumers to producers.

_____ 14. Photosynthetic animals are autotrophs.

_____ 15. Autotrophs are producers.

Lesson 4.1: Critical Reading

Name___________________ Class______________ Date________

Read these passages from the text and answer the questions that follow.


All living things need energy, which is defined as the ability to do work. You can often see energy at work in living things — a bird flies through the air, a firefly glows in the dark, a dog wags its tail. These are obvious ways that living things use energy, but living things constantly use energy in less obvious ways as well.

Why Living Things Need Energy

Inside every cell of all living things, energy is needed to carry out life processes. Energy is required to break down and build up molecules and to transport molecules across plasma membranes. All life’s work needs energy. A lot of energy is also simply lost to the environment as heat. The story of life is a story of energy flow — its capture, its change of form, its use for work, and its loss as heat. Energy, unlike matter, cannot be recycled, so organisms require a constant input of energy. Life runs on chemical energy. Where do living organisms get this chemical energy?

How Organisms Get Energy: Autotrophs and Heterotrophs

The chemical energy that organisms need comes from food. Food consists of organic molecules that store energy in their chemical bonds. In terms of obtaining food for energy, there are two types of organisms: autotrophs and heterotrophs.


Autotrophs are organisms that make their own food. Most autotrophs use the energy in sunlight to make food in a process called photosynthesis. Only three types of organisms — plants, algae, and some bacteria — can make food through photosynthesis.

Autotrophs are also called producers. They produce food not only for themselves but for all other living things as well (which are known as consumers). This is why autotrophs form the basis of food chains.


Heterotrophs are living things that cannot make their own food. Instead, they get their food by consuming other organisms, which is why they are also called consumers. They may consume autotrophs or other heterotrophs. Heterotrophs include all animals and fungi and many single-celled organisms. What do you think would happen to consumers if all producers were to vanish from Earth?


1. What is energy? Give an example of how energy is used in a living organism.

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2. Distinguish between autotrophs and heterotrophs.

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3. Determine if the following are autotrophs or heterotrophs: (a) a giant redwood tree, (b) a spider, (c) a rose bush, (d) a mushroom, (e) a blue whale.

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4. How is energy used in a cell?

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5. Why are autotrophs considered the basis of food chains?

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Lesson 4.1: Multiple Choice

Name___________________ Class______________ Date________

Circle the letter of the correct choice.

  1. Photosynthesis
    1. uses the energy in sunlight to make food.
    2. uses the glucose in sunlight to make food.
    3. uses the energy in sunlight to make ATP.
    4. breaks down glucose to form ATP.
  2. Which of the following autotrophs is also a producer?
    1. a maple tree
    2. the blue-green bacteria known as cyanobacteria
    3. Laurencia, a marine genus of Red Algae from Hawaii.
    4. All of the above are producers.
  3. In the food chain grass → grasshopper → snake → hawk, which organism(s) are the heterotrophs?
    1. the grass
    2. the grass and grasshopper
    3. the hawk
    4. the grasshopper, snake, and hawk
  4. Which of the following statements is true about glucose and ATP? (1) Glucose is made during photosynthesis. (2) The energy in sunlight is temporarily stored in glucose before it is transferred to ATP. (3) ATP is the energy-carrying molecule that cells use for energy. (4) The processes that make ATP and glucose also recycle oxygen in Earth's atmosphere.
    1. statement 1 only
    2. statements 2 and 3 only
    3. statements 1, 2, and 3 only
    4. All 4 statements are correct.
  5. Photosynthesis can be described as the process that
    1. uses carbon dioxide and water, in the presence of sunlight, to produce food (glucose) and oxygen.
    2. uses glucose and oxygen to produce energy for the cell (ATP), releasing carbon dioxide and water.
    3. uses glucose and oxygen, in the presence of sunlight, to make ATP.
    4. uses carbon dioxide and water, in the presence of sunlight, to produce ATP and oxygen.
  6. Which statement best describes the relationship between a consumer and a producer?
    1. A lion eating an antelope.
    2. A caterpillar eating a leaf.
    3. A snake eating a rat.
    4. A flower absorbing sunlight.
  7. Which of the following statements is true?
    1. The products of photosynthesis are the reactants of cellular respiration.
    2. The products of cellular respiration are the reactants of photosynthesis.
    3. Both statements are true.
    4. Neither statement is true.
  8. The correct chemical formula for photosynthesis (in the presence of sunlight) is
    1. 6CO2 + 6O2 → C6H12O6 + 6H2O.
    2. 6CO2 + 6H2O → C6H12O6 + 6O2.
    3. C6H12O6 + 6O2 → 6CO2 + 6H2O
    4. C6H12O6 + 6CO2 → 6O2 + 6H2O

Lesson 4.1: Vocabulary I

Name___________________ Class______________ Date________

Match the vocabulary word with the proper definition.


_____ 1. the process in which glucose is broken down and ATP is made

_____ 2. organism at the end of a food chain

_____ 3. shows how energy and matter flow from producers to consumers

_____ 4. also known as autotrophs

_____ 5. the ability to do work

_____ 6. stores chemical energy in a concentrated, stable form

_____ 7. the energy-carrying molecule that cells use for energy

_____ 8. process that stores energy from sunlight in the chemical bonds of glucose

_____ 9. organisms that make their own food

_____ 10. all animals and fungi and many single-celled organisms

_____ 11. organisms that must eat

_____ 12. organic molecules that store energy in their chemical bonds


a. ATP

b. autotroph

c. cellular respiration

d. consumer

e. decomposer

f. energy

g. food

h. food chain

i. glucose

j. heterotroph

k. photosynthesis

l. producer

Lesson 4.1: Vocabulary II

Name___________________ Class______________ Date________

Fill in the blank with the appropriate term.

1. Heterotrophs are living things that cannot make their own ____________.

2. ____________ and ____________ are the two types of molecules organisms use for chemical energy.

3. Glucose and ____________ are the products of photosynthesis.

4. ____________, water, and energy are the products of cellular respiration.

5. Photosynthesis is the process in which energy from ____________ is transferred to glucose.

6. ____________ is the process in which energy from glucose is transferred to ATP.

7. Without photosynthesis, there would be no ____________ in the atmosphere.

8. All organisms burn glucose to form ____________ during cellular respiration.

9. The chemical formula of glucose is ____________.

10. Photosynthesis occurs in the ____________, and cellular respiration occurs in the ____________.

11. ____________ make their own food, whereas ____________ get food by eating other living things.

12. Living organisms get their ____________ from food.

Lesson 4.1: Critical Writing

Name___________________ Class______________ Date________

Thoroughly answer the question below. Use appropriate academic vocabulary and clear and complete sentences.

Draw a five level food chain, identifying autotrophs, heterotrophs, producers, and consumers.

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