Populations have a genetic variation among individuals and that is important to the populations ability to survive in different situations that have an affect on the natural selection. There are different factors which can increase or decrease the genetic diversity, and influencing natural selection. These factors can include an environmental factor, one of the major factors, which can cause changes in the genetic variation of a population and influence the natural selection. A famous and important example of the environmental factors affecting natural selection was made during the industrial revolution when many more gray moths made up the moth population. This was so that they could blend in with the soot from factories to avoid predators.