---
title: "Decomposers and the Rate of Decay"
description: "Bacteria and fungi break dead material down and return carbon to the air and mineral ions such as nitrates to the soil. Decay speeds up with temperature, water and oxygen, which is what a compost heap"
canonical: https://lightmysky.com/learn/science/decomposers-and-the-rate-of-decay-mt_4152TrzD6A
source: https://lightmysky.com/learn/science/decomposers-and-the-rate-of-decay-mt_4152TrzD6A.md
retrieved: 2026-09-12
---

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# Decomposers and the Rate of Decay

Bacteria and fungi break dead material down and return carbon to the air and mineral ions such as nitrates to the soil. Decay speeds up with temperature, water and oxygen, which is what a compost heap and a fridge each work on.

Subject: Science · Area: Organisms & Life Processes · Ages 15 to 16
Page: https://lightmysky.com/learn/science/decomposers-and-the-rate-of-decay-mt_4152TrzD6A

## Ready when they can

- Names what decomposers return to the soil and what they return to the air.
- Predicts the effect of temperature, water or oxygen on decay rate and explains it through the decomposers' own respiration.
- Explains why a compost heap is turned and why a fridge slows food going off.

## Lesson: Rot that feeds the world

Decomposers are bacteria and fungi that digest dead matter and recycle its nutrients. They return mineral ions such as nitrates to the soil for plants, and carbon to the air as carbon dioxide. Without them, nutrients would lock in corpses and growth would halt.

Decay answers to what decomposers need for respiration: warmth, moisture and oxygen, plus surface area to attack. Warmth quickens their enzymes, water carries them and oxygen fuels them. A fridge slows decay by cooling and drying, while a compost heap is turned to feed oxygen in. Low oxygen slows most decay, but some microbes manage without air, so sealed rot does not always stop.

**Example.** Turn a log to see white fungal threads digesting wood from outside in. In a compost heap all four dials sit high: chopped scraps for surface, water, warmth and regular turning for air. In a fridge the cold slows the decomposers, so milk keeps for days.

**Tip.** Explain every decay claim through the decomposers. Name the dial that changed, say what it does to their respiration, then give the result. Cold slows enzymes, so the fridge slows rot.

**Recap.** Decomposers recycle soil minerals and air carbon, fastest when warm, moist and aired.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [The Carbon Cycle](https://lightmysky.com/learn/science/the-carbon-cycle-mt_Be1A88GUpu)

## Opens up

- [The Nitrogen Cycle and the Microbes That Drive It](https://lightmysky.com/learn/science/the-nitrogen-cycle-and-the-microbes-that-drive-it-mt__K1J47NhWj)
- [Fertilisers, Leaching and Eutrophication](https://lightmysky.com/learn/science/fertilisers-leaching-and-eutrophication-mt_9lTF20DWOZ)
- [Fungi: Hyphae, Spores and Digestion Outside the Body](https://lightmysky.com/learn/science/fungi-hyphae-spores-and-digestion-outside-the-body-mt_qfp2nuk1IH)
- [Productivity, Nutrient Limitation and Ecosystem Stoichiometry](https://lightmysky.com/learn/science/productivity-nutrient-limitation-and-ecosystem-stoichiometry-mt_QWdZj1G9iT)