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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.
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 |
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