Insects resistant to a pesticide reproduce more slowly than non-resistant insects when the pesticide is absent. After pesticide use stops, which prediction is most reasonable?
Resistance must increase because resistant insects always survive better.
Resistance may decrease because non-resistant insects leave more offspring.
Resistance must disappear because all resistance alleles immediately mutate.
Resistance may decrease because all insects lose inherited characteristics.
44 exam-style questions on Edexcel GCSE Biology 4.1 Evolution and natural selection, covering 4.1.1 Work of Darwin and Wallace and 4.1.2 Resistant organisms and evolution. Each one has a worked solution and a mark scheme showing where the marks go.