# A woodland ecosystem contains oak trees, caterpillars, blue tits, and sparrowhawks arranged in a food chain. Explain why the number of sparrowhawks that the woodland can support is much smaller than the number of caterpillars.

> Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 3.2 Energy flow and ecosystems · Explain · 5 marks

> Oak trees → Caterpillars → Blue tits → Sparrowhawks

## Mark scheme (5 marks)

1. Energy is lost at each trophic level / as you move along the food chain
2. Energy is lost through heat released during respiration
3. Energy is lost in waste materials such as faeces / urine / undigested food
4. Only approximately 10% of energy is transferred from one trophic level to the next
5. By the time energy reaches the sparrowhawks, so little energy is available that only a small population can be sustained / there is not enough energy to support a large number of sparrowhawks

## Key terms

- [food chain](https://www.gradenine.co.uk/glossary/food-chain)

## Related

- [Revision notes for Edexcel A-Level Biology A: Salters-Nuffield (9BN0)](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-woodland-ecosystem-contains-oak-trees-ef58d9d4) · Published by Druglandscape Ltd.