# Decomposer

A microorganism, mostly bacteria and fungi, that breaks down dead plants and animals and returns nutrients to the soil.

Biology (school) · Part 07: Ecosystems and food chains · Card 9 of 11 · Last updated 2026-10-19

## Analogy

The recycling team of nature.

## In practice

Fallen leaves rot into soil because of decomposers. Warm, moist conditions speed this up.

## Practice

### Flashcards

- **Which two groups of organisms act as decomposers?** Bacteria and fungi.

### Interview questions

**Describe how carbon moves through the carbon cycle.**

- Plants take carbon dioxide from the air by photosynthesis
- Carbon passes to animals when they eat
- Respiration and burning return carbon dioxide to the air
- Decomposers release carbon from dead material

## Questions people ask

### Why are decomposers important?

They break down dead organisms and waste, releasing minerals such as nitrates back into the soil, where plants can take them up again. Without decomposers, dead material would pile up and nutrients would run out. They also release carbon dioxide into the air as they respire.

### What conditions help decay?

Decay is fastest when it is warm, moist and has plenty of oxygen, because decomposers respire and multiply well in these conditions. Cold, dry or oxygen-poor conditions slow decay. That is why food keeps longer in a fridge and why bodies can be preserved in cold peat bogs.

## Related concepts

- [Carbon cycle](https://studyvisually.com/learn/science/biology-school/biology-school-part-7/biology-school-part-7-concept-10)
- [Producer](https://studyvisually.com/learn/science/biology-school/biology-school-part-7/biology-school-part-7-concept-5)
- [Water cycle](https://studyvisually.com/learn/science/biology-school/biology-school-part-7/biology-school-part-7-concept-11)

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