Biodiversity is important for the stability of ecosystems. Explain why a reduction in biodiversity can have serious consequences for an ecosystem, including the potential effects on food webs and human welfare.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Tropical rainforests contain millions of species of plants, animals, fungi and microorganisms. Human activities such as deforestation and pollution are causing species to become extinct at an increasing rate, reducing biodiversity in these ecosystems.
Model answer (5 marks)
Biodiversity is the variety of species in an ecosystem. When species are lost, food webs are disrupted – for example, if a prey species disappears, predators lose a food source and may decline or go extinct. The loss of one species can trigger a cascade, causing further species to decline or disappear. Reduced biodiversity also threatens human welfare: fewer plant species mean fewer potential medicines, food varieties and genetic resources. Finally, lower biodiversity makes ecosystems less stable and less able to recover from disturbances such as disease or climate change.
Examiner tips
- Use the word ‘disrupt’ or ‘cascade’ to show understanding of food‑web effects
- Mention both ecological and human impacts
- Show cause–effect links clearly
Common mistakes
- Confusing biodiversity with ecosystem diversity
- Failing to link species loss to human welfare
- Using vague terms like ‘many species’ without explanation
Mark scheme (5 marks)
- Biodiversity refers to the variety/number of different species in an ecosystem
- Loss of a species can disrupt food webs, e.g. removal of a prey species reduces the food available for predators
- Loss of one species can lead to the decline or extinction of other species (knock-on / cascading effects)
- Reduced biodiversity threatens human welfare, e.g. loss of plant species reduces the potential for developing new medicines / food sources
- Reduced biodiversity decreases ecosystem stability, making the ecosystem less able to recover from change / disturbance
Key terms in this question
biodiversity · food web · ecosystem
Related
- All Pearson Edexcel A-Level Biology A (9BI0) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
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