CHAPTER 4 REVIEW

Year after year, Xavier raises a vegetable garden in the same plot of soil. He observes that the plants grow less abundantly from one year to the next, and they produce fewer vegetables. Which of these measurements could help explain Xavier's observations?

• the rate at which soil bacteria perform photosynthesis

• the rate at which soil bacteria perform denitrification

• the rate at which soil bacteria perform nitrogen fixation

• the rate at which soil bacteria perform chemosynthesis

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Autotrophs can be classified into two groups according to which of these properties?

• energy source, either sunlight or chemicals

• food type, either plant matter or animal matter

• food quality, either living matter or dead matter

• water quality, either fresh water or salt water

Rabbits are members of a community in a meadow. The rabbits eat grasses, clover, as well as roots, seeds, and tree bark. What describes the organisms that share the same trophic level as the rabbits?

• snakes, hawks, and other animals that eat rabbits

• community members that interact with rabbits

• meadow animals that are about the same size as a rabbit

• meadow animals that eat plants and plant products

The diagram shows a model feeding relationship in an ecosystem. What is shown by the arrows that lead to and from the raccoon?

• The raccoon is part of several food chains, but not a food web.

• The raccoon is part of several food chains and several food webs.

• The raccoon is part of one food web, but no food chains.

• The raccoon is part of one food web and several overlapping food chains.

Answer explanation

Remember a food web shows multiple food chains within it.

Laney is asked to research an organism that performs denitrification. Which strategy is the most likely to be successful?

• Look for phytoplankton that perform photosynthesis.

• Look for ocean-dwelling organisms that perform chemosynthesis.

• Look for soil bacteria that convert atmospheric nitrogen to nitrates.

• Look for soil bacteria that convert nitrates to nitrogen gas.

Answer explanation

remember denitrification takes nitrogen from a usable form (nitrates. nitrates) and makes it unusable (nitrogen gas)

Which statement describes all primary producers?

• All harness the energy of sunlight through the process of photosynthesis.

• All take in energy to assemble energy-rich compounds.

• All are small, single-celled organisms, such as bacteria and algae.

• All take in food and break it apart to release energy.

Answer explanation

if you marked "D" watch how the question was worded... ENERGY is never released.

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Karen is classifying a group of organisms that are either primary producers or consumers. What is the direct source of energy for all of the consumers?

• either producers or other consumers

• producers only

• nonliving sources, such as sunlight

• other consumers only

Answer explanation

remember consumers can be herbivores, carnivores, or omnivores

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Which of the following BEST describes the flow of energy through a food chain?

• Energy flows between primary producers and consumers, in either direction.

• Energy flows from consumers to primary producers, in one direction only.

• Energy flows from primary producers to consumers, in one direction only.

• Energy flows between primary producers and consumers, in an endless cycle.

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The diagram shows a model of an ecosystem.

What does the model represent?

• the total biomass in each trophic level

• the total amount of energy in the ecosystem

• the relative amount of energy available at each trophic level

• the conservation of energy as energy transfers between organisms

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A pyramid of biomass is one way to model an ecosystem. How does the amount of biomass generally change from the bottom of the pyramid to the top?

• The amount of biomass decreases.

• The amount of biomass increases.

• The amount of biomass varies only slightly, and may increase or decrease.

• The amount of biomass varies widely, and both increases and decreases.

Answer explanation

It's a triangle (pyramid) for a reason. As the triangle gets narrower, the amount of energy available, biomass, and numbers decrease.

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