An area has been sprayed with an insecticide every year for ten years. Each year, scientists recorded the percentage of mosquitoes that survived a standard dose of the insecticide. Table
| Year | 1 | 4 | 7 | 10 |
|---|---|---|---|---|
| Percentage of mosquitoes surviving | 2 | 10 | 38 | 71 |
| Which statement explains the change in the percentage of mosquitoes surviving? |
The insecticide caused mutations that made more of the mosquitoes resistant.
The mosquitoes built up a tolerance after being exposed to it every year.
The mosquitoes that were killed passed resistance on to their offspring.
Resistant mosquitoes survived to breed and passed on their resistance alleles.
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.