Producers, consumers and decomposersSpec B15.2.4, B15.2.5, B15.2.6, B15.2.7, B15.2.8, B15.2.9
In short
A producer is an organism that makes its own organic nutrients, usually using energy from sunlight, through photosynthesis. A consumer gets its energy by feeding on other organisms: herbivores eat plants and carnivores eat other animals. Consumers are primary, secondary, tertiary or quaternary. Decomposers, such as bacteria and fungi, get energy from dead or waste organic material.
- Producer
- An organism that makes its own organic nutrients, usually using energy from sunlight, through photosynthesis.
- Consumer
- An organism that gets its energy by feeding on other organisms.
- Herbivore
- An animal that gets its energy by eating plants.
- Carnivore
- An animal that gets its energy by eating other animals.
- Decomposer
- An organism that gets its energy from dead or waste organic material.
Consumers are classed by their position in a food chain.
| Class | What it eats | Example |
|---|---|---|
| Primary consumer | Producers (so it is a herbivore) | Grasshopper |
| Secondary consumer | Primary consumers (a carnivore) | Frog |
| Tertiary consumer | Secondary consumers (a carnivore) | Snake |
| Quaternary consumer | Tertiary consumers (a carnivore) | Eagle |
Decomposers, such as bacteria and fungi, feed on dead organisms and waste. They get their energy from dead or waste organic material, and they return nutrients to the soil.
Learn the definitions word for word. A producer makes its own organic nutrients, usually by photosynthesis. Do not just say that it 'makes its own food'.
Quick check
State the principal source of energy input to biological systems.
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The Sun.
What does a food chain show?
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The transfer of energy from one organism to the next, beginning with a producer.
What is a food web?
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A network of interconnected food chains.
Define a consumer.
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An organism that gets its energy by feeding on other organisms.
Define a decomposer.
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An organism that gets its energy from dead or waste organic material.
Written and checked against the Cambridge IGCSE Combined Science (0653) specification · Updated October 2026