# Explain why biomass tends to decrease at successive trophic levels in most food chains.

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

## Mark scheme (4 marks)

1. Energy/biomass is lost as heat through cellular respiration at each trophic level
2. Not all biomass consumed is assimilated — some is egested as faeces
3. Only a small proportion (typically around 10%) of energy/biomass is transferred to the next trophic level
4. Biomass is also used for growth, reproduction, and other metabolic activities, meaning less is available for the next trophic level / biomass accumulates only in the living tissues that survive to be consumed

## 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 Higher 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-why-biomass-tends-to-decrease-9a02953e) · Published by Druglandscape Ltd.