EcologyTopic Summary
Knowledge Organiser: Biodiversity and Human Impacts
Part of Biodiversity and Human Impacts · GCSE GCSE Biology revision
This topic summary covers Knowledge Organiser: Biodiversity and Human Impacts within Biodiversity and Human Impacts for GCSE Biology. Topic 5: Biodiversity and Human Impacts on Ecosystems It is section 16 of 16 in this topic. Use this topic summary to connect the idea to the wider topic before moving on to questions and flashcards.
Topic position
Section 16 of 16
Practice
20 questions
Recall
19 flashcards
Knowledge Organiser: Biodiversity and Human Impacts
Key Terms
- Biodiversity: Variety of all different species on Earth or in an ecosystem
- Deforestation: Large-scale removal of forest for land use
- Peat bog: Wetland where dead plant matter accumulates; major carbon store
- Eutrophication: Excess nutrients → algae bloom → oxygen depletion → aquatic death
- Greenhouse effect: CO₂ and methane trap infrared radiation, raising temperatures
- Seed bank: Frozen store of plant seeds as extinction insurance
Human Impacts on Biodiversity
- Waste/pollution: water, land, air — destroys species directly
- Land use change: building, quarrying, farming — destroys habitats
- Deforestation: removes habitat + releases CO₂ (combustion + decomposition)
- Peat destruction: releases ancient CO₂ + destroys specialist habitat
- Global warming: sea level rise, species migration, food chain disruption
Conservation Methods
- Breeding programmes — captive breeding of endangered species
- Habitat protection — SSSIs, national parks, nature reserves
- Reforestation — planting trees to restore forest habitats
- Seed banks — frozen seed collections (e.g. Svalbard Global Seed Vault)
- Hedgerow restoration and field margin schemes
- Government conservation schemes
- Recycling — reduces landfill pollution
Must-Know Facts
- Deforestation reasons: timber, biofuel, rice paddies, cattle ranching
- Peat: waterlogged + anaerobic → slow decomposition → carbon stored for centuries
- Drain peat → aerobic decomposers active → CO₂ released → global warming
- Greenhouse gases: CO₂ (fossil fuels, deforestation) and methane (cattle, rice, landfill)
- Global warming effects: sea level rise, habitat loss, species migration, altered food production
- Positive impacts: reforestation, conservation, recycling programmes
Common Mistakes
- Over-complicating the biodiversity definition: AQA defines biodiversity as "the variety of all different species of organisms on Earth, or within an ecosystem." You do not need to mention genetic variation within species at GCSE — a clear definition naming the variety of different species will score full marks. Adding extra detail about genetics can confuse your answer.
- Giving only one reason why deforestation increases CO₂: Deforestation raises atmospheric CO₂ for two reasons — (1) the trees that previously removed CO₂ via photosynthesis are gone, so less CO₂ is absorbed; and (2) burning or decomposing the felled trees releases the carbon that was stored in them. Both reasons are needed for full marks on a 2-mark question.
- Confusing the greenhouse effect with ozone depletion: The greenhouse effect is caused by CO₂ and methane trapping infrared radiation in the atmosphere, leading to global warming. Ozone depletion is a completely separate issue caused by CFCs (chlorofluorocarbons) destroying the ozone layer. These are two different problems — do not mix them up.
- Forgetting methane as a greenhouse gas: CO₂ is not the only greenhouse gas examiners expect you to name. Methane (CH₄) is also required. Sources of methane: livestock (cattle digestion), rice paddies, and decomposition in landfill sites. Questions asking for "two greenhouse gases" expect CO₂ and methane — water vapour is also a greenhouse gas but is less commonly tested at GCSE.
- Grade 7+ separator — eutrophication chain: A Grade 7 answer for eutrophication must include the full chain: fertiliser run-off → nitrates/phosphates in water → algae bloom → algae block light to plants below → plants die → decomposers break down dead plants → decomposers use up oxygen in aerobic respiration → fish and other aquatic organisms die from lack of oxygen. Missing any step in this chain caps the answer at Grade 5.