# A farmer grows wheat in a large field. The wheat is eaten by mice, which are eaten by owls. The farmer wants to produce as much food as possible for humans. Explain why humans eating wheat directly is more efficient than humans eating meat from animals that have been fed on wheat.

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

> Ecologists studying food chains measure the amount of energy stored in organisms at each trophic level. In a typical food chain, only around 10% of the energy stored in one trophic level is transferred to the next.

## Mark scheme (5 marks)

1. Only approximately 10% of energy is transferred from one trophic level to the next
2. Energy is lost through heat released during respiration
3. Energy is also lost in waste materials / faeces / urine / indigestible parts
4. Eating wheat directly means only one energy transfer occurs, so less energy is lost overall
5. Therefore more energy is available for humans / a greater proportion of the original energy in the wheat reaches humans

## 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)

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