Genetic variation and environmental pressures can lead to a change in the characteristics of a population by the consequential increase of species having a trait that allows them to adjust to the environmental pressures. As an example, before factories were built in England, Peppered Moths had two types, white and black. This was a result of genetic variation. When factories rose, soot and smoke covered the tress and caused the white moths to be easy target to predators. Eventually, the peppered moth population was made up of majority of black moths.
