Decay
In this topic you will:
- learn about microorganisms and decay
- investigate how temperature affects the rate of decay
- plan an experiment to test an hypothesis about decay.
Key words
- decay
- decomposer
- mould
- organic matter
- rot
Decomposers and decay
The food chains and food webs that you looked at in the previous topic did not include microorganisms. But microorganisms are everywhere. They live in the air, in the soil, in water, on our skin and inside our bodies.
The apple in the picture has microorganisms growing on its surface. Each spot on the apple is made up of millions of cells of microscopic fungi. This kind of fungus is sometimes called mould. The apple is mouldy.
The microorganisms have changed the apple. They have made it decay. Organisms that make things decay are called decomposers. Many different kinds of microorganisms – including some kinds of bacteria and microscopic fungi – are decomposers.
Apples come from plants, which are living organisms. Any substance that has been made by a living organism (by a plant or animal) is called organic matter. So, apples are organic matter.
Some microorganisms can break down organic matter when they feed on it. This is what has caused the apple to decay. The microscopic fungi have broken down the crisp, fresh apple and made it become brown and soft. They have made the apple rot.
Quick fact: Why does food go bad?
Food goes bad because microorganisms like bacteria and fungi grow on it. These decomposers break down the food’s organic matter, causing it to change color, texture, and smell. This process is called decay.
Common mistake
Some people think decay is caused by the air or temperature alone. In reality, it's microorganisms such as bacteria and fungi that actively break down organic matter and cause decay.
Questions
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Some microorganisms break down dead plants, animals, and waste. These microorganisms are called decomposers because they help return nutrients to the soil.
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Decay can spoil food, making it unsafe to eat. For example, mould growing on an apple makes it inedible.
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Decay recycles nutrients back into the soil, which helps plants grow better.