Describe the process of natural selection

Natural Selection is nxormally seen as a competitive advantage for an organism, for example Rock Pocket Mice have two fur colors, light and dark. This genetic variation is caused by a mutation as most variant genes are, and this in turn can affect an organism's chances of survival depending on the environment. Lighter fur would be much more helpful in a desert like environment, it helps the mice hide from predators while the dark fur mice will be nearly killed off, thus giving the light fur mice an advantage in this situation. Once the dark fur mice are nearly killed off, the light fur mice will reproduce, allowing for the population to regrow, but the lighter fur will be much more common in this generation as the last generation was left only with light fured mice to reproduce with, meaning the trait was passed down, this is called microevolution, it is a smaller change such as change in fur color or size, but keep in mind, natural selection can only occur when the environment changes and a struggle for survival emerges.