Ecologists investigated chemical runoff in two different coastal estuaries, Blackwood Estuary and Greycliffe Sound. They surveyed the macroinvertebrate communities, recording the number of species that were tolerant to organophosphate pesticides and the number of species that were sensitive to (killed by) these pesticides. Their findings are summarised in the table below:
| Blackwood Estuary | Greycliffe Sound | |
|---|---|---|
| Pesticide-tolerant species | 78 | 24 |
| Pesticide-sensitive species | 12 | 56 |
Determine which estuary is likely to be exposed to the highest levels of organophosphate pesticide runoff. Explain your reasoning in terms of natural selection.
38 exam-style questions on OCR GCSE Biology 5.2 Natural selection and evolution, covering 5.2.1 Genetic variation within a population, 5.2.2 Developments in classification systems, 5.2.3 How evolution occurs through natural selection, 5.2.4 Evolution as change over time, 5.2.5 Evidence for evolution, and 5.2.6 Darwin and Wallace. Each one has a worked solution and a mark scheme showing where the marks go.