A temporary pool contains a native species of water flea. Mosquito larvae enter the pool. Water fleas and mosquito larvae both feed on microscopic algae.
Scientists added 120 water fleas to each of several tanks. The tanks had the same abiotic conditions and received the same amount of algae. Some tanks also contained mosquito larvae or a new pathogen that infects water fleas.
The table shows the mean number of water fleas surviving after 12 days.
| Mosquito larvae added | Pathogen added | Mean number of water fleas surviving |
|---|---|---|
| No | No | 96 |
| Yes | No | 72 |
| No | Yes | 60 |
| Yes | Yes | 27 |
A student claims that the pathogen has the same proportional effect on water flea survival whether or not mosquito larvae are present.
Evaluate the student's claim. Use calculations from the data.
Explain why fewer water fleas survived when both mosquito larvae and the pathogen were present than when neither was present.
82 exam-style questions on AQA GCSE Biology 7.1 Adaptations, interdependence and competition, covering 7.1.1 Communities, 7.1.2 Abiotic factors, 7.1.3 Biotic factors, and 7.1.4 Adaptations. Each one has a worked solution and a mark scheme showing where the marks go.