IGCSE Biology glossary
Decomposer
Biology editorial review is supported by the named review panel. Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.
Definition
An organism that gets its energy from dead or waste organic material, breaking it down and returning nutrients to the environment.
What to include in an exam answer
The paying point is that decomposers feed on dead or waste organic matter, and bacteria and fungi are the named examples to give. Examiners reward linking them to nutrient cycling, for example releasing nitrogen or carbon dioxide back into the ecosystem. Students lose marks calling them 'consumers' or omitting that the material is dead or waste. Appears in Paper 4 food web, carbon cycle and nitrogen cycle questions.
Example in context
Describing their role: 'Decomposers such as bacteria and fungi feed on dead organic material, breaking it down and returning mineral nutrients to the soil for plants to absorb.'
Related syllabus topic
Organisms & their environment