Scientists place equal numbers of freshwater snails in tanks for 14 days. Each tank starts with 40 snails and has the same volume of water and food. The scientists vary the dissolved oxygen concentration and water temperature. All other conditions are controlled.
| Dissolved oxygen concentration in mg/dm³ | Mean number surviving at 10 °C | Mean number surviving at 20 °C |
|---|---|---|
| 2 | 9 | 3 |
| 6 | 30 | 34 |
| 10 | 31 | 39 |
Which statement correctly describes the effect of temperature across the three dissolved oxygen concentrations?
At 2, 6 and 10 mg/dm³, raising temperature lowers survival, with the greatest decrease at 2 mg/dm³.
At 2, 6 and 10 mg/dm³, raising temperature raises survival, with the greatest increase at 10 mg/dm³.
At 2 mg/dm³, raising temperature lowers survival; at 6 and 10 mg/dm³, it raises survival, with the greatest increase at 10 mg/dm³.
At 2 mg/dm³, raising temperature has no effect; at 6 and 10 mg/dm³, it raises survival by the same amount.
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.