Barn owls eat voles and field mice. Voles and field mice both eat seeds. Four similar plots each started with 20 field mice and equal numbers of seeds. Voles were either left in the plot or removed, and barn owls either had access to the plot or were excluded. The number of field mice was counted after 4 weeks.
| Voles | Barn owls | Number of field mice after 4 weeks |
|---|---|---|
| Present | Excluded | 30 |
| Removed | Excluded | 36 |
| Present | Had access | 22 |
| Removed | Had access | 18 |
Explain, using the results, why the effect of a fall in vole numbers on the field mouse population cannot be predicted from competition alone.
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.