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AP®Environmental ScienceCollege BoardExam QuestionsUnit 1: The Living World: EcosystemsTrophic Levels

Trophic Levels (College Board AP® Environmental Science): Exam Questions

7 mins7 questions
11 mark

Which of the following phenomena explains why it is more efficient to eat at a lower trophic level?

  • Niche partitioning 

  • Ecological tolerance

  • Competitive exclusion

  • Second law of thermodynamics

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21 mark

Which of the following is the best explanation for why there are rarely more than 4 trophic levels in a food chain?

  • Predators at higher trophic levels reproduce too slowly to sustain larger populations.

  • Energy is lost at each trophic level, leaving insufficient energy to support additional levels.

  • There are not enough different species to form more than four trophic levels.

  • Decomposers break down all available energy before it can reach higher trophic levels.

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31 mark

Which of the following organisms in the salt marsh is an herbivore?

Food pyramid with sea turtle, blue crab, periwinkle snails, and marsh grass at the base, showing energy flow of 21,865 kcal.

  • Marsh grass

  • Periwinkle snails

  • Blue crab

  • Sea turtle

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41 mark

Which of the following occupies the lowest trophic level in an arctic food chain?

  • Polar bear

  • Phytoplankton

  • Small fish

  • Seal

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51 mark

In the 1990s, ecologists Deborah Letourneau and Lee Dyer studied a tropical forest shrub called the piper plant and the various species of insects that live on and near the shrub. A species of ant uses the piper plant as a home by hollowing out some of its branches and building colonies inside the hollow branch cores. The ants do not eat the plant’s leaves. Instead, the leaves are consumed mostly by caterpillars. When the ants encounter caterpillars or caterpillar eggs on the plant’s leaves, they either eat them or kick them off. Letourneau and Dyer added beetles that eat ants. The figure shows the results of one of Letourneau and Dyer’s experiments in which they compared the leaf area of piper plants in control plots to that of experimental plots to which they had added beetles that eat ants. 

Line graph showing leaf area per plant over 18 months. Red circles indicate "without beetle" with steady growth; blue triangles show "with beetle" and increasing growth.

Which of the following is a correct interpretation of the data from the experiment?

  • Increasing the number of ants increased the leaf area per plant.

  • Adding beetles increased the leaf area of the plant.

  • Caterpillars play no role in determining plant leaf area.

  • When beetles are absent plant leaf area increases.

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61 mark

In the 1990s, ecologists Deborah Letourneau and Lee Dyer studied a tropical forest shrub called the piper plant and the various species of insects that live on and near the shrub. A species of ant uses the piper plant as a home by hollowing out some of its branches and building colonies inside the hollow branch cores. The ants do not eat the plant’s leaves. Instead, the leaves are consumed mostly by caterpillars. When the ants encounter caterpillars or caterpillar eggs on the plant’s leaves, they either eat them or kick them off. Letourneau and Dyer added beetles that eat ants. The figure shows the results of one of Letourneau and Dyer’s experiments in which they compared the leaf area of piper plants in control plots to that of experimental plots to which they had added beetles that eat ants. 

Line graph showing leaf area per plant over 18 months. Red circles indicate "without beetle" with steady growth; blue triangles show "with beetle" and increasing growth.

What is the difference in mean leaf area between plots with beetles and plots without beetles 18 months after the start of the experiment?

  • 1000 cm2

  • 1400  cm2

  • 1600  cm2

  • 2000  cm2

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71 mark

In the 1990s, ecologists Deborah Letourneau and Lee Dyer studied a tropical forest shrub called the piper plant and the various species of insects that live on and near the shrub. A species of ant uses the piper plant as a home by hollowing out some of its branches and building colonies inside the hollow branch cores. The ants do not eat the plant’s leaves. Instead, the leaves are consumed mostly by caterpillars. When the ants encounter caterpillars or caterpillar eggs on the plant’s leaves, they either eat them or kick them off. Letourneau and Dyer added beetles that eat ants. The figure shows the results of one of Letourneau and Dyer’s experiments in which they compared the leaf area of piper plants in control plots to that of experimental plots to which they had added beetles that eat ants. 

Line graph showing leaf area per plant over 18 months. Red circles indicate "without beetle" with steady growth; blue triangles show "with beetle" and increasing growth.

Which of the following explains the results of the experiment?

  • The ants directly consume piper plant leaves, reducing overall plant growth.

  • The beetles protect the piper plant by preying on caterpillars, leading to less leaf damage.

  • The presence of beetles that eat ants leads to increased caterpillar herbivory, resulting in greater leaf loss in piper plants.

  • The removal of ants has no significant effect on caterpillar populations or leaf consumption.

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