Lesson 3.2 Review

Energy is said to flow in a “one-way” direction through an ecosystem. In your own words, describe what that means.

Answer explanation

Student answers will vary but should explain that energy flows from producers to consumers and to the environment as heat. Energy is not recycled.

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NGSS.MS-LS1-6

NGSS.MS-LS2-3

What are the three types of ecological pyramids? Explain how each type of pyramid models energy and matter in ecosystems.

Answer explanation

Pyramid of energy, pyramid of numbers, and pyramid of biomass. Students should explain that a pyramid of energy models the amount of energy present in each trophic level; a pyramid of biomass models the amount of living tissue in different trophic levels; a pyramid of numbers shows the relative number of organisms in each trophic level.

Tags

NGSS.MS-LS2-3

Suppose there was a sudden decrease in the number of crayfish in the food web shown in Figure 3-4. Construct an explanation to explain how this change may affect the food webs.

Answer explanation

Student answers will vary but students should indicate that the organisms the crayfish eat (such as grass shrimp) might increase in number, whereas the organisms that feed on crayfish (such as raccoons) might decrease in number. They might also explain that the numbers of those organisms that feed on the same foods as the crayfish might increase.Students must provide evidence from

the diagram and text to support their explanations.

Tags

NGSS.MS-LS2-1

NGSS.MS-LS2-2

NGSS.MS-LS2-3

NGSS.MS-LS2-4

Imagine you have a five-step food chain. If 100 percent of the energy is available at the first trophic level, what percentage of energy is available at the highest trophic level?

Answer explanation

0.01 percent

Tags

NGSS.MS-LS1-6

NGSS.MS-LS2-3

Choose one of the food chains shown within the food web in Figure 3-4. Write a paragraph describing the feeding relationships among the organisms in the food chain. Hint: Use the terms producers, consumers, and decomposers in your description.

Answer explanation

Check that students correctly relate the organisms in the food chain and describe the flow of energy from pro-ducers to consumers to decomposers.

Tags

NGSS.MS-LS2-2

NGSS.MS-LS2-3

Why are decomposers and detritivores essential parts of all food webs?

Answer explanation

Detritivores eat detritus, and decompos-ers break down remains and waste. Bothrecycle matter, which allows producersto use it again.

Tags

NGSS.MS-LS2-3