# Explain why energy is lost at each trophic level in a food chain, and describe how this affects the number of organisms that can be supported at higher trophic levels.

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

> In a grassland ecosystem, grass is eaten by rabbits, which are eaten by foxes. Only a small percentage of the energy stored in the grass is eventually available to the foxes.

## Mark scheme (5 marks)

1. Energy is lost through respiration at each trophic level
2. Energy is lost in faeces / undigested material that is not absorbed
3. Only a small percentage / fraction of energy is transferred to the next trophic level
4. Because less energy is available at each successive trophic level, fewer organisms can be supported
5. This results in a pyramid of biomass / numbers, with fewer organisms (or less biomass) at higher trophic levels

## Key terms

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

## 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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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-energy-is-lost-at-f802413f) · Published by Druglandscape Ltd.