Warfarin is a poison used to kill rats. Some rats have a variant of a gene that makes them resistant to warfarin. Warfarin was used in one area for many years. What happened to the population of rats in this area?
All of the rats in the population died out over time.
The rats became resistant by eating small amounts of it.
The rats made antibodies against warfarin in their blood.
The percentage of resistant rats in the population increased.
122 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.