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CognitoBiodiversity and human impact on ecosystems
Key facts & methods
What is biodiversity?
- Biodiversity: the variety of all living organisms in an area — includes species diversity and genetic diversity within species.
- High biodiversity = healthy, stable ecosystem. More species means more resilience to change.
- Measured by: number of different species (species richness) and population sizes.
- Deforestation: major cause of biodiversity loss — destroys habitats, removes food sources.
- Climate change: alters temperatures and rainfall patterns — many species cannot adapt fast enough.
Human impacts on biodiversity
- Agriculture: monocultures reduce biodiversity; pesticides kill non-target species; fertiliser run-off causes eutrophication.
- Eutrophication: excess nitrates → algal bloom → blocks light → aquatic plants die → decomposers use up O₂ → fish and other organisms die.
- Deforestation: reduces CO₂ absorption, destroys habitats, increases soil erosion.
- Global warming: climate change shifts species ranges, causes habitat loss (e.g. coral bleaching, melting ice).
- Invasive species: outcompete native species, reduce local biodiversity.
Conservation methods
- Breeding programmes: captive breeding of endangered species, then reintroduction.
- Seed banks: store seeds of threatened plant species for future use.
- Habitat protection: nature reserves, national parks, protected areas.
- Reintroduction programmes: returning species to habitats where they were previously lost.
- Reducing deforestation: sustainable forestry, legal protections, reforestation.
- International agreements: e.g. CITES (trade in endangered species) and the Paris Agreement (climate).
Why biodiversity matters
- Ecosystem services: pollination, water purification, climate regulation, soil formation.
- Food security: diverse crops more resilient to disease and climate change.
- Medical resources: many drugs derived from organisms (e.g. aspirin from willow bark, antibiotics from fungi).
- Ethical argument: other species have a right to exist independent of human benefit.
Exam questions — 5 questions · 11 marks · AQA 8461 style
⚡ Show all reasoning — the AI marks against the AQA mark scheme. Partial credit for correct biology even if wording differs.
4 marksEutrophicationAQA 8461 P2 style
A farmer applies excess fertiliser to fields near a river. Explain how this leads to a decrease in the number of fish in the river. (4 marks)
Hint: Chain of events: fertiliser → algal bloom → blocks light → plants die → decomposers increase → O₂ used up → fish die.
+40 XP
1 markBiodiversity definitionAQA 8461 style
What is meant by biodiversity?
A The total number of animals in an ecosystem
B The variety of all living organisms in an area, including species diversity and genetic diversity
C The number of individuals in a single species population
D The total biomass of all organisms in an ecosystem
3 marksConservation argumentAQA 8461 style
Give THREE reasons why maintaining biodiversity is important to humans. (3 marks)
Hint: Three separate reasons. For each, explain the benefit TO HUMANS specifically.
+30 XP
1 markEutrophication causeAQA 8461 style
Which of the following directly causes eutrophication in rivers?
A Acid rain from industrial pollution
B Excess nitrates and phosphates from fertiliser run-off causing excessive plant/algal growth
C Thermal pollution from power stations warming the water
D Plastic waste blocking sunlight from reaching the water
1 markConservation methodAQA 8461 style
What is the purpose of a seed bank?
A To grow food crops in remote areas
B To store seeds from threatened plant species so they can be preserved and potentially used in the future
C To allow plants to reproduce asexually
D To cross-breed plants to create disease-resistant varieties
Module complete! 🎉
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