# Introduction

Natural selection acts on phenotypes that vary in survival and reproductive success, and the response to selection is a change in allele frequency resulting in evolution. In this free course, Mosquito resistance to insecticides, you will see how allele frequency can change rapidly in a population in response to selective pressure.

You will consider how alleles that arise and spread through a population because they confer resistance in that environment can have negative fitness consequences in other environments (a situation known as a trade-off). These principles can be illustrated by considering the example of the spread of mutant alleles of a gene called ester in populations of mosquitoes exposed to insecticides.

This OpenLearn course is an adapted extract from the Open University course S317 Biological science: from genes to species.

OpenLearn - Mosquito resistance to insecticides
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