# Explain how biomass is lost at each trophic level in a food chain, and state one reason why this limits the number of trophic levels that can be supported in any ecosystem.

> IB DP Biology Standard Level (2023 syllabus) — C4.2 Transfers of energy and matter · Explain · 4 marks

## Mark scheme (4 marks)

1. Not all ingested biomass is assimilated — some is lost in faeces/egesta
2. Energy/biomass is lost through cellular respiration at each trophic level
3. Some assimilated biomass is used for growth/reproduction/excretion and is not consumed by the next trophic level
4. By the highest trophic levels, so little biomass/energy remains that it is insufficient to sustain another population/trophic level

## Key terms

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

## Related

- [Revision notes for IB DP Biology Standard Level (2023 syllabus)](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-how-biomass-is-lost-at-9909ad63) · Published by Druglandscape Ltd.