What you'll learn
How ecosystems work and why biodiversity matters.
Ecosystems
- An ecosystem is living organisms plus their non-living environment.
- Food chains and food webs show feeding relationships: producers → consumers → decomposers.
- Energy decreases at each trophic level; nutrients are recycled.
Biodiversity
- Biodiversity is the variety of species in an area.
- Importance: ecosystem stability, resources (food, medicines), and ecosystem services.
- Threats: habitat loss, pollution, over-exploitation, climate change and invasive species.
Exam tips
- Explain energy loss up a food chain.
- Give concrete reasons why biodiversity is valuable.
Common mistakes
- Reversing the direction of energy flow.
- Treating biodiversity as just 'lots of animals'.