Practise 45 exam-style questions on Pyramids of biomass (biology only) for AQA GCSE Biology. Write your answer as you would in the exam and get it marked in seconds against the mark scheme, point by point, with an AI tutor on hand if you get stuck.
45 questions
2–4 marks each
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20 questions, marked as you go
Sample questions with model answers
Here are 4 of the questions in this topic, each with a model answer, an explanation of why it earns the marks and the mark scheme an examiner would use.
Question 1
2 marks
What is meant by 'producer' in a pyramid of biomass? Give one example.
Model answer
Producers are organisms that make organic matter from inorganic materials by photosynthesis (e.g., plants, algae). Example: grass, phytoplankton.
Explanation
Producers convert sunlight into chemical energy, forming the base of a biomass pyramid; examples include terrestrial plants and aquatic algae.
Mark scheme
1 mark
organisms that make organic matter by photosynthesis
1 mark
example e.g., grass, phytoplankton
Question 2
3 marks
Describe how you would construct an accurate pyramid of biomass from field data measured for an ecosystem.
Model answer
Measure dry mass of all organisms at each trophic level per unit area (e.g., g m–2) after drying to constant mass; calculate mean biomass per m2 for each trophic level and draw bars to scale stacked with producers at the base.
Explanation
Dry mass per unit area avoids water content bias. Use mean values and draw accurately scaled bars representing biomass at each trophic level with producers at the base.
Mark scheme
1 mark
measure biomass per unit area (suggest dry mass) for each trophic level
dry mass required to avoid water variance
1 mark
use mean biomass per m2 for levels / standardise per area
1 mark
draw bars to scale stacked with producers at the bottom
Question 3
3 marks
A field survey gives the following dry masses per m2: Moss 30 g, Insect herbivores 6 g, Spiders 0.6 g. Calculate: a) the percentage transfer from moss to insects, b) the percentage transfer from insects to spiders.
Model answer
a) (6/30)×100 = 20% b) (0.6/6)×100 = 10%.
Explanation
Percentage transfer = (higher trophic biomass / lower trophic biomass) × 100 for each step; plug in values to get 20% and 10%.
Mark scheme
1 mark
calculation a shown (6/30)*100
1 mark
answer a = 20%
1 mark
calculation b shown and answer = 10%
Question 4
4 marks
Explain how the concept of biomass transfer efficiency is important when deciding whether to convert pasture to grow crops for direct human consumption or for feeding livestock.
Model answer
Low transfer efficiencies mean much plant biomass/energy is lost when fed to livestock; growing crops for direct human consumption (skipping trophic transfers) yields more food energy per unit land. Thus converting pasture to crops for humans is often more efficient for feeding people.
Explanation
Because energy declines up trophic levels, producing plant food for humans is usually more efficient in food production per hectare than using those plants to feed animals.
Mark scheme
1 mark
transfer efficiency is low so feeding plants to animals loses much energy
1 mark
growing crops for direct human consumption avoids trophic losses
1 mark
more food energy produced per unit land if eaten directly by humans
1 mark
therefore land-use decisions should consider transfer efficiency and food yield
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