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

> Pearson Edexcel A-Level Biology A (9BI0) — 3.2 Energy flow and ecosystems · Explain · 5 marks

> Oak trees are the producers in the woodland food chain. The food chain is: oak tree → caterpillar → blue tit → sparrowhawk.

## Mark scheme (5 marks)

1. Energy is lost at each trophic level / between each organism in 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. Less energy is available to sparrowhawks than to caterpillars because energy has been lost at multiple trophic levels before reaching the sparrowhawk
5. Therefore less biomass / fewer organisms can be supported at the level of the sparrowhawk compared to the caterpillar

## Key terms

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

## Related

- [Revision notes for Pearson Edexcel A-Level Biology A (9BI0)](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)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/a-woodland-ecosystem-contains-oak-trees-635c8ebf) · Published by Druglandscape Ltd.