Question 1 Medium
Producers have 1000 kg of biomass and primary consumers have 100 kg. Calculate the percentage efficiency.
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Answer: 10%
- 100 ÷ 1000 × 100.
- The efficiency is 10%.
Food chains, trophic levels and biomass transfer: GCSE Combined Science Biology practice questions
A second set of questions on food chains, trophic levels and biomass transfer. They are different from the ones on the topic page. Try each, then open the answer and compare your working.
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Question 2 Medium
Which process in an animal releases energy and causes biomass to be lost as carbon dioxide?
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Answer: respiration
- Energy is released for movement.
- It is respiration.
Question 3 Medium
In the food chain algae, shrimp, fish, seal, at which trophic level is the seal?
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Answer: 4
- Algae are level 1, shrimp level 2, fish level 3.
- The seal is level 4.
Question 4 Medium
Producers have 3000 kg of biomass and primary consumers have 450 kg. Calculate the percentage efficiency.
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Answer: 15%
- Divide 450 by 3000 to get 0.15.
- Multiply by 100 to get 15%.
Question 5 Hard
Primary consumers have 500 kg of biomass. Secondary consumers have 40 kg. Calculate the percentage efficiency.
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Answer: 8%
- 40 ÷ 500 = 0.08.
- 0.08 × 100 = 8%.
Question 6 Hard
Producers have 8000 kg of biomass and primary consumers have 600 kg. Calculate the percentage efficiency.
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Answer: 7.5%
- 600 ÷ 8000 = 0.075.
- 0.075 × 100 = 7.5%.
Question 7 Hard
Why is dry mass used in a pyramid of biomass? Give the substance that makes fresh mass less reliable.
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Answer: water
- Water content varies.
- So dry mass is used.
Question 8 Hard
What is the name for an animal at the top of a food chain with no natural predators?
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Answer: apex predator
- It has no predators.
- It is an apex predator.
Quick checks
Short questions with options. Choose one before you open the answer.
Check 1
What is a producer?
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An organism that makes its own food by photosynthesis.
Check 2
What is a primary consumer?
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An animal that eats producers.
Check 3
What is a secondary consumer?
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An animal that eats primary consumers.
Check 4
What is a predator?
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An animal that hunts and eats other animals.
Check 5
What is prey?
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An animal that is hunted by predators.
Check 6
What is an apex predator?
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A predator with no natural predators.
Check 7
What is a trophic level?
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A stage in a food chain.
Check 8
What does an arrow in a food chain show?
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The direction of transfer of biomass and energy.
Check 9
What is biomass?
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The mass of living material.
Check 10
What does a pyramid of biomass show?
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The dry mass of organisms at each trophic level.
Check 11
Why do pyramids of biomass get smaller going up?
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Only a small part of the biomass is passed on at each level.
Check 12
Roughly what percentage of biomass is passed to the next level?
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About 10%.
Check 13
Name three ways biomass is lost between levels.
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Respiration, waste such as faeces and urine, and parts not eaten.
Check 14
What is the equation for efficiency of biomass transfer?
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biomass transferred ÷ biomass available × 100.
Check 15
Why are food chains short?
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Too little biomass is passed on to support more levels.
Check 16
Why does keeping animals indoors raise efficiency?
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Less energy is lost through movement and keeping warm.
Check 17
What is a carnivore?
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An animal that eats only other animals.
Check 18
What is a herbivore?
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An animal that eats only plants.
Check 19
What is an omnivore?
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An animal that eats both plants and animals.
Check 20
What is a tertiary consumer?
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An animal that eats secondary consumers.
Check 21
What is a food web?
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Many food chains linked together.
Check 22
Why is dry mass used in a pyramid of biomass?
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Fresh mass includes water, which changes.
Check 23
At which trophic level are the producers?
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Level 1.
Check 24
Why is eating plants more efficient than eating animals?
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Fewer trophic levels are involved, so less biomass is lost.
Check 25
Why do pyramids of biomass narrow towards the top?
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Biomass is lost at each trophic level.
Check 26
Why is the percentage efficiency answer given only with a % sign?
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It is a percentage, so it has no other unit.
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