Organisation of an Ecosystem

This lesson explores how energy flows through ecosystems and how matter is cycled. You will learn about trophic levels, producers and consumers, food chains and food webs, pyramids of biomass, and the role of decomposers in recycling nutrients. These concepts are central to AQA GCSE Biology Topic 7: Ecology.

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Producers, Consumers and Decomposers

Every organism in an ecosystem can be classified by how it obtains its energy:

Role	Definition	Examples
Producer	An organism that makes its own food by photosynthesis (autotroph)	Grass, trees, algae, phytoplankton
Primary consumer	A herbivore that eats producers	Rabbit, caterpillar, zooplankton
Secondary consumer	A carnivore or omnivore that eats primary consumers	Fox, blue tit, frog
Tertiary consumer	A top predator that eats secondary consumers	Eagle, shark, lion
Decomposer	An organism that breaks down dead organic matter and waste, returning nutrients to the soil	Bacteria, fungi, earthworms