# A woodland ecosystem contains oak trees, caterpillars, blue tits and sparrowhawks. Explain how interdependence means that a sudden increase in the number of sparrowhawks could affect the populations of both blue tits and oak trees in this woodland ecosystem.

> OCR GCSE Biology A: Gateway Science (J247) — B4.1 Ecosystems · Explain · 4 marks

> Sparrowhawks are predators that feed on blue tits. Blue tits feed almost entirely on caterpillars during spring and summer. Caterpillars feed on the leaves of oak trees.

## Mark scheme (4 marks)

1. More sparrowhawks means more predation of blue tits, so the blue tit population decreases
2. Fewer blue tits means fewer caterpillars are eaten, so the caterpillar population increases
3. More caterpillars eat more oak leaves, so the oak trees are damaged / oak leaf biomass decreases
4. This shows interdependence because a change in one species' population affects other species / the organisms in the ecosystem depend on each other to survive

## Key terms

- [interdependence](https://www.gradenine.co.uk/glossary/interdependence)
- [ecosystem](https://www.gradenine.co.uk/glossary/ecosystem)

## Related

- [Revision notes for OCR GCSE Biology A: Gateway Science (J247)](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-20881306) · Published by Druglandscape Ltd.