# A food chain in a woodland ecosystem has three trophic levels: oak trees → caterpillars → blue tits. Explain why a pyramid of biomass is considered more useful than a pyramid of numbers for representing this food chain.

> Cambridge International IGCSE Biology (0610) — 19.1 Energy flow · Explain · 4 marks

## Mark scheme (4 marks)

1. A pyramid of numbers does not account for the size or mass of organisms
2. This means the pyramid of numbers may not have a true pyramid shape (e.g. one oak tree supports many caterpillars, so the producer bar would be narrower than the primary consumer bar)
3. A pyramid of biomass measures the total mass of living material at each trophic level
4. A pyramid of biomass gives a true pyramid shape and indicates the amount of energy being passed on at each trophic level, because biomass decreases at each level as energy is lost

## Key terms

- [pyramid of numbers](https://www.gradenine.co.uk/glossary/pyramid-of-numbers)
- [pyramid of biomass](https://www.gradenine.co.uk/glossary/pyramid-of-biomass)
- [trophic level](https://www.gradenine.co.uk/glossary/trophic-level)
- [biomass](https://www.gradenine.co.uk/glossary/biomass)

## Related

- [Revision notes for Cambridge International IGCSE Biology (0610)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-food-chain-in-a-woodland-91f145a1) · Published by Druglandscape Ltd.