Original practice · 5 questions · 15 marks · about 17 minutes

Energy Flow and Ecological Pyramids Practice Questions

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These questions test your understanding of how energy flows through ecosystems and how this is represented in ecological pyramids.

1. Question 1

   Paper 4 Extended 4 marks Difficulty 4/5

   Explain why only approximately 10% of energy is transferred from one trophic level to the next.

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   1. Energy is lost through respiration (as heat) at each trophic level.
   2. Not all parts of organisms are eaten (e.g. Bones, fur, roots).
   3. Some energy is lost in waste products (urine, faeces).
   4. Only the energy stored in the body (as biomass) is available to the next level.

2. Question 2

   Paper 4 Both 3 marks Difficulty 3/5

   Explain the difference between a pyramid of numbers and a pyramid of biomass.

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   1. Pyramid of numbers shows the number of organisms at each trophic level.
   2. Pyramid of biomass shows the total mass of organisms at each trophic level.
   3. Pyramids of numbers can be inverted (e.g. One large tree supporting many insects); pyramids of biomass are almost always upright.

3. Question 3

   Paper 4 Extended 3 marks Difficulty 3/5

   Explain why a pyramid of numbers for a food chain starting with one oak tree may look unusual.

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   1. One large oak tree can support thousands of insects (caterpillars).
   2. The base of the pyramid (producer) would be very narrow: just one organism.
   3. The next level (primary consumers) would be much wider: an inverted pyramid.

4. Question 4

   Paper 2 Core 2 marks Difficulty 2/5

   State the original source of energy for almost all food chains.

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   1. The Sun / sunlight.
   2. Green plants capture light energy during photosynthesis.

5. Question 5

   Paper 4 Extended 3 marks Difficulty 4/5

   Explain why eating lower on the food chain (e.g. Eating plants rather than meat) is more energy-efficient for feeding a growing human population.

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   1. Less energy is lost if humans eat plants directly (fewer trophic levels).
   2. Feeding grain to livestock and then eating the livestock wastes about 90% of energy at each step.
   3. The same area of farmland can feed more people with crops than with livestock.