Managers introduced different conservation schemes at two lakes. At Lake A, fishing of perch was restricted. At Lake B, shallow planted margins were created. Perch feed on small fish, which feed on aquatic invertebrates. The planted margins provide habitat for aquatic invertebrates.
Surveys estimated the populations and recorded the number of aquatic invertebrate species at each lake before the schemes and four years later.
| Lake and survey time | Perch population | Small fish population | Plant cover (%) | Aquatic invertebrate species recorded |
|---|---|---|---|---|
| Lake A, before | 42 | 310 | 18 | 8 |
| Lake A, four years later | 76 | 205 | 19 | 12 |
| Lake B, before | 39 | 295 | 16 | 8 |
| Lake B, four years later | 41 | 288 | 44 | 10 |
Compare the evidence for changes in aquatic invertebrate biodiversity at the two lakes. Explain how the changes in the food web could account for the difference between the lakes.
109 exam-style questions on OCR GCSE Biology 6.1 Monitoring and maintaining the environment, covering 6.1.1 Field investigation of distribution and abundance, 6.1.2 Human interactions and biodiversity, 6.1.3 Maintaining biodiversity, and 6.1.4 Environmental change and distribution of organisms. Each one has a worked solution and a mark scheme showing where the marks go.