# A grassland ecosystem contains the following organisms: grass, grasshoppers, frogs, and hawks. Only 10% of the energy stored in one trophic level is available to the next trophic level. Explain why energy is lost between trophic levels in this food chain, and describe how this affects the number of organisms that can be supported at each level.

> Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 3.2 Energy flow and ecosystems · Explain · 5 marks

> In a grassland food chain: grass → grasshoppers → frogs → hawks. Grass absorbs light energy and produces biomass through photosynthesis. At each subsequent trophic level, less energy is available.

## Mark scheme (5 marks)

1. Energy is lost because organisms use energy for life processes such as respiration
2. Energy is also lost as heat (to the surroundings) from metabolic processes
3. Not all of the organism's biomass is consumed / some material is not eaten and is lost in faeces or indigestible parts
4. Because only 10% of energy is transferred, fewer organisms can be supported at each successive trophic level
5. This means the food chain cannot support many trophic levels / pyramids of biomass or numbers are wider at the base

## Key terms

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

## Related

- [Revision notes for Edexcel A-Level Biology A: Salters-Nuffield (9BN0)](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/a-grassland-ecosystem-contains-the-following-cd7bf6d2) · Published by Druglandscape Ltd.