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11.1: The Science of Ecology

Created by: CK-12

Lesson 11.1: True or False

Name___________________ Class______________ Date________

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

_____ 1. Biotic factors include sunlight, soil, temperature, and water.

_____ 2. Like nutrients and water, energy also recycles through an ecosystem.

_____ 3. An ecosystem consists of all the biotic and abiotic factors in an area and their interactions.

_____ 4. Herbivores are a necessary link between producers and other consumers.

_____ 5. A niche refers to the place an organism lives within its ecosystem.

_____ 6. Dung beetles eat animal feces.

_____ 7. Autotrophs make their own food.

_____ 8. Organisms use 90% of the available energy at each trophic level.

_____ 9. Carnivores include lions, polar bears, hawks, frogs, salmon, and deer.

_____ 10. Biomass increases at the upper levels of a food chain.

_____ 11. Producers occupy the first trophic level.

_____ 12. Scavengers include vultures and raccoons.

_____ 13. In a complex ecosystem, it is likely that two different species will occupy the same niche.

_____ 14. The habitat is the role of a species in its ecosystem.

_____ 15. A food web shows how energy flows through an ecosystem.

Lesson 11.1: Critical Reading

Name___________________ Class______________ Date________

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

Trophic Levels

The feeding positions in a food chain or web are called trophic levels. The different trophic levels are defined in Table below. All food chains and webs have at least two or three trophic levels. Generally, there are a maximum of four trophic levels. Examples are also given in the table.

Trophic Level Where It Gets Food Example
1st Trophic Level: Producer Makes its own food Plants make food
2nd Trophic Level: Primary Consumer Consumes producers Mice eat plant seeds
3rd Trophic Level: Secondary Consumer Consumes primary consumers Snakes eat mice
4th Trophic Level: Tertiary Consumer Consumes secondary consumers Hawks eat snakes

Many consumers feed at more than one trophic level. Humans, for example, are primary consumers when they eat plants such as vegetables. They are secondary consumers when they eat cows. They are tertiary consumers when they eat salmon.

Trophic Levels and Energy

Energy is passed up a food chain or web from lower to higher trophic levels. However, only about 10 percent of the energy at one level is available to the next level. This is represented by the pyramid below. What happens to the other 90 percent of energy? It is used for metabolic processes or given off to the environment as heat. This loss of energy explains why there are rarely more than four trophic levels in a food chain or web. Sometimes there may be a fifth trophic level, but usually there’s not enough energy left to support any additional levels.

Ecological Pyramid. This pyramid shows how energy and biomass decrease from lower to higher trophic levels. Assume that producers in this pyramid have 1,000,000 kilocalories of energy. How much energy is available to primary consumers? (Images of lion and landscape copyright by Eric Isselée, 2010, and image of giraffe copyright Kletr, 2010. Used under licenses from Shutterstock.com. Compilation created by CK-12 Foundation.)

Trophic Levels and Biomass

With less energy at higher trophic levels, there are usually fewer organisms as well. Organisms tend to be larger in size at higher trophic levels, but their smaller numbers result in less biomass. Biomass is the total mass of organisms at a trophic level. The decrease in biomass from lower to higher levels is also represented by the figure above.

Questions

1. What is a trophic level?

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2. Which trophic level includes humans?

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3. What types of organisms are in the first trophic level? Give an example.

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4. Assume that producers in an ecosystem have 1,000,000 kilocalories of energy. How much energy is available to primary consumers?

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5. Which trophic level has the greatest biomass?

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Lesson 11.1: Multiple Choice

Name___________________ Class______________ Date________

Circle the letter of the correct choice.

  1. Examples of biotic factors include
    1. grass, flowers, and sunlight
    2. grass, trees, bees, and ants.
    3. grass, trees, soil, and water.
    4. all of the above
  2. Components of an ecosystem include
    1. soil, sunlight, water, and weather.
    2. grass, trees, bees, and ants.
    3. all the biotic and abiotic factors in an area.
    4. all of the above.
  3. Which describes the possible flow of energy in an ecosystem?
    1. snakes to frogs to caterpillars to trees
    2. trees to frogs to snakes to caterpillars
    3. trees to caterpillars to frogs to snakes
    4. caterpillars to trees to frogs to snakes
  4. The relationship between autotrophs and producers is
    1. that autotrophs make the food the producers eat.
    2. that producers make the food the autotrophs eat.
    3. that autotrophs eat producers.
    4. that they are the same organisms.
  5. Which statement best describes a trophic level?
    1. A trophic level is the feeding position of an organism in a food chain or web.
    2. A trophic level is the position of an organism in an ecosystem.
    3. A trophic level is the niche of an organism in an ecosystem.
    4. A trophic level is the feeding role of an organism in an ecosystem.
  6. Examples of decomposers include
    1. algae and cyanobacteria.
    2. earthworms, dung beetles, and spiders.
    3. vultures and raccoons.
    4. all of the above.
  7. Which organism would usually be in the fourth trophic level?
    1. rats
    2. humans
    3. rabbits
    4. hawks
  8. Which statement best defines ecology?
    1. The study of how living things interact with each other.
    2. The study of how living things interact with each other and with their environment.
    3. The study of how living things interact with their environment.
    4. The study of how living things interact with their habitat.

Lesson 11.1: Vocabulary I

Name___________________ Class______________ Date________

Match the vocabulary word with the proper definition.

Definitions

_____ 1. represents a single pathway through which energy and matter flow

_____ 2. feeding positions in a food chain or web

_____ 3. the living aspects of the environment

_____ 4. the role of a species in its ecosystem

_____ 5. consumes the soft tissues of dead animals

_____ 6. the physical environment in which a species lives

_____ 7. represents multiple pathways through which energy and matter flow

_____ 8. states that two different species cannot occupy the same niche in the same place for very long

_____ 9. the nonliving aspects of the environment

_____ 10. the study of how living things interact with each other and with their environment

_____ 11. the total mass of organisms at a trophic level

_____ 12. break down remains and other wastes, and release simple inorganic molecules back to the environment

_____ 13. consumes both plants and animals

_____ 14. consumes animals

_____ 15. consumes producers

Terms

a. abiotic factor

b. biomass

c. biotic factor

d. carnivore

e. competitive exclusion principle

f. decomposer

g. ecology

h. food chain

i. food web

j. habitat

k. herbivore

l. niche

m. omnivore

n. scavenger

p. trophic level

Lesson 11.1: Vocabulary II

Name___________________ Class______________ Date________

Fill in the blank with the appropriate term.

1. Abiotic factors are the ____________ aspects of the environment.

2. ____________ are organisms that produce food for themselves and other organisms.

3. Scavengers consume the soft tissues of ____________ animals.

4. ____________ levels are the positions in a food chain or food web

5. Ecosystems require constant inputs of ____________ from sunlight or chemicals.

6. Omnivores consume both ____________ and animals.

7. The competitive ____________ principle states that two different species cannot occupy the same niche.

8. Producers are also called ____________.

9. ____________ feed on dead leaves and animal feces, among other debris.

10. Examples of ____________ are lions, polar bears, and hawks.

11. ____________ are organisms that depend on other organisms for food.

12. An ____________ consists of all the biotic and abiotic factors in an area and their interactions.

Lesson 11.1: Critical Writing

Name___________________ Class______________ Date________

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

Describe how energy flows through ecosystems.

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