A conservation organisation is comparing two freshwater lakes. Lake A contains 12 different species of invertebrate, 4 species of fish, and 3 species of aquatic plant. Lake B contains 2 species of invertebrate, 1 species of fish, and 1 species of aquatic plant. Describe what is meant by biodiversity and explain why Lake A has greater biodiversity than Lake B.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
A conservation organisation is comparing two freshwater lakes. Lake A contains 12 different species of invertebrate, 4 species of fish, and 3 species of aquatic plant. Lake B contains 2 species of invertebrate, 1 species of fish, and 1 species of aquatic plant.
Model answer (4 marks)
Biodiversity is the variety or range of different species that live in a particular area, habitat or ecosystem.
Lake A has a greater total number of different species (12 + 4 + 3 = 19) than Lake B (2 + 1 + 1 = 4).
Lake A also contains a greater variety of species across more than one group of organisms – invertebrates, fish and aquatic plants – whereas Lake B has only one or two species in each group.
Because of this higher biodiversity, Lake A’s ecosystem is likely to be more stable and less vulnerable to change; the loss of a single species will have a smaller impact on the overall system.
Lake A has a greater total number of different species (12 + 4 + 3 = 19) than Lake B (2 + 1 + 1 = 4).
Lake A also contains a greater variety of species across more than one group of organisms – invertebrates, fish and aquatic plants – whereas Lake B has only one or two species in each group.
Because of this higher biodiversity, Lake A’s ecosystem is likely to be more stable and less vulnerable to change; the loss of a single species will have a smaller impact on the overall system.
Examiner tips
- Use the exact definition of biodiversity – variety of species in an area. Show the total species count for each lake. Mention the variety across multiple organism groups. Explain the stability/robustness benefit of higher biodiversity.
Common mistakes
- Confusing biodiversity with species richness only. Failing to calculate the total species count. Omitting the explanation of ecological stability.
Mark scheme (4 marks)
- Biodiversity is the variety / range of different species in an area / habitat / ecosystem
- Lake A has a greater total number of different species than Lake B
- Lake A has greater variety across more than one group of organisms (invertebrates, fish, and plants)
- Greater biodiversity in Lake A means the ecosystem is more stable / less vulnerable to change / loss of a species has less impact
Key terms in this question
Related
- All WJEC GCSE Biology (Wales) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →