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AP®Environmental ScienceCollege BoardExam QuestionsUnit 1: The Living World: EcosystemsEnergy Flow & the 10% Rule

Energy Flow & the 10% Rule (College Board AP® Environmental Science): Exam Questions

8 mins8 questions
11 mark

Which of the following would be the correct mathematical routine to determine the amount of energy available to the secondary consumer?

Food web diagram showing a sea turtle, blue crab, periwinkle snails, and marsh grass with energy level labelled as 21,865 kCal.

  • 21,865 kcal x 0.90

  • 21,865 kcal/10

  • 21,865 kcal x 0.10 x 0.10

  • 21,865 kcal x 100%

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21 mark

In a grassland ecosystem, primary producers generate 12,000 joules of energy. The herbivores that consume the plants receive 1,200 joules of energy.  What is the ecological efficiency of this energy transfer?

  • 1%

  • 5%

  •  10%

  • 20%

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31 mark

Which of the following is the source of energy for all terrestrial ecosystems?

  • Solar energy from the sun

  • Radioactive decay of elements in the earth’s core

  • Wind energy converted to mechanical energy

  • Chemical energy from soil nutrients

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41 mark

Researchers studying ecosystem productivity determined that producers were able to convert solar energy into 16,500 kcal of chemical energy stored in organic compounds. Which of the following is the most likely amount of energy available to secondary consumers?

  • 1.7 kcal

  • 165 kcal

  • 1,650 kcal

  • 16,500 kcal

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51 mark

Which of the following statements best describes the first and second laws of thermodynamics?

  • The first law states that energy cannot be created or destroyed, while the second law states that as energy is transformed there is a loss of usable energy.

  • The first law states that energy is always lost in transformations, and the second law indicates that entropy remains constant in an isolated system.

  • The first law implies that heat can be completely converted into work without losses, and the second law states that energy can be recycled indefinitely.

  • The first law states that matter is conserved, and the second law requires that energy must always flow from colder to hotter bodies.

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61 mark

Based on the diagram, which of the following is a tertiary consumer?

Food chain diagram with polar bear on top, followed by ringed seal, Arctic cod, and bottom layer of phytoplankton with 19,250 kcal notation.

  • Arctic cod

  • Phytoplankton

  • Ringed seal

  • Polar bear

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71 mark
Food chain pyramid with polar bear, ringed seal, Arctic cod, and phytoplankton (19,250 kcal), showing energy flow in an Arctic ecosystem.

Based on the laws of thermodynamics, which of the following is the correct mathematical routine used to estimate the biomass of the arctic cod in the pyramid?

  • 19,250 x 10 

  • 19,250/10 x 100%

  • 19,250 x 0.10 x 0.10

  • 19,250 x 0.10

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81 mark

Which of the following best describes the differences between the pyramid of numbers, pyramid of biomass, and pyramid of energy?

Diagram showing ecological pyramids of numbers, biomass, and energy for various ecosystems, including grassland, forest, lake, coral reef, and Silver Springs, Florida.

  • The pyramid of numbers is always upright because the number of organisms at each trophic level can never exceed the number in the level below.

  • The pyramid of energy always decreases at higher trophic levels because energy is lost as heat due to metabolic processes.

  • The pyramid of biomass represents the total energy at each trophic level, which increases at each higher level.

  • All three pyramids always have the same shape, with producers at the bottom and fewer organisms, energy, and biomass at each higher level.

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