-Natural selection is one of the basic mechanisms of evolution, along with mutation, migration, and genetic drift.Genetic diversity allows the different organisms to have different physiological characteristics. Some of them provides them with genetic resistance, others don’t. The ones which are resistant survive the pesticide, others don’t ; this is known as natural selection.
-Those that are resistant will live longer and have a larger number of offspring (reproductive success). From one generation to another, there will be more and more resistant pests (because of their larger offspring), and less and less pests that are not resistant (because they tend to die young). If the selection process goes on, someday the pesticide will be useless (it will kill no pest).
The pest population is developing genetic resistance to the environmental changes. Pests are evolving resistance to our pesticides at a fast rate. Insects eat our crops so we spray with pesticides. The pesticides kill the majority of pests, but a few survive. These breed with each other and so propagate a version of pest that is resistant to that particular pesticide. We then change our pesticide and the cycle continues. The end result is a "superbug" that is resistant to all currently used pesticides
