Principle #1 (Genetic Variation): Most deer mice living in the sandy desert of Nebraska are dark grey, but very few are a tan color due to a mutation.
Principle #2 (Overproduction and Struggle for Survival): The mice are constantly reproducing, but the grey-colored mice are more easily seen by predators, such as foxes, hawks, and owls, and they are being eaten more often.
Principle #3 (Differential Survival and Reproduction): The grey mice are rapidly being eaten and are dying, while the tan ones are beginning to survive and reproduce more in their environment.
Principle #4 (Change in the Gene Pool): After many generations have passed, the tan mice are the ones who were able to survive and reproduce, while most of the grey mice were wiped out. However, there is always the chance for there to be few grey mice in the population/.