How to Revise IGCSE Biology Topic 20: Human Influences on Ecosystems
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Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.
Key point
Know the three types of pollution with specific examples. Explain the enhanced greenhouse effect and its consequences. Understand eutrophication. Know conservation strategies and sustainable development.
Topic 20 covers how humans affect the environment: pollution (air, water, land), the enhanced greenhouse effect and climate change, deforestation, and strategies for conservation and sustainable development. This topic often appears as a discuss or evaluate question.
Priority 1: Pollution
Air pollution: CO₂ (greenhouse effect), SO₂ (acid rain from burning fossil fuels). Water pollution: fertiliser run-off (eutrophication → algal bloom → oxygen depletion → fish die), sewage. Land pollution: non-biodegradable plastics, pesticides accumulating in food chains (bioaccumulation).
Priority 2: Greenhouse effect and climate change
CO₂ and methane are greenhouse gases that trap heat in the atmosphere. The enhanced greenhouse effect (from burning fossil fuels and deforestation) leads to global warming → climate change → rising sea levels, changing weather patterns, habitat loss, species extinction.
Priority 3: Conservation and sustainability
Conservation strategies: protected areas, captive breeding programmes, seed banks, sustainable forestry, fishing quotas. Sustainable development: meeting current needs without compromising the ability of future generations to meet their needs.
Frequently asked questions
What is eutrophication?
Excess fertiliser runs off into waterways → promotes algal bloom → algae block light → aquatic plants die → decomposing bacteria increase → bacteria use up oxygen → aquatic organisms die from lack of oxygen.
Put the guide into practice
Questions and practical resources
Use a fresh question to check whether the idea can be applied without prompts.