# Explain why the efficiency of energy transfer between trophic levels in a food chain is typically only 10%, with reference to the forms in which energy is lost.

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

## Mark scheme (4 marks)

1. A large proportion of energy ingested by organisms at each trophic level is lost as heat through cellular respiration
2. Not all biomass at one trophic level is consumed/ingested by the next — some organisms die and are broken down by decomposers, so that energy does not pass up the food chain
3. Some ingested material cannot be digested and is egested as faeces, so this energy is not assimilated into consumer biomass
4. Because energy losses (heat, egestion, decomposers) are large at each step, only approximately 10% of the energy available at one trophic level is incorporated into the biomass of the next, limiting the length of food chains

## Key terms

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

## 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)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-why-the-efficiency-of-energy-b2c7b538) · Published by Druglandscape Ltd.