These are the deer that lives in this environment and since they are dark they are camouflage so they usually arent eaten by anything at night , which it means that they are nocturnal.
The light dear is not camouflage like the dark dear so they will be eaten by the wolves and the dark ones won't because they are camouflage so the wolves won't be able to see them. The light dear is a result of mutation.
The environment changed so a enviromental change occurred. Which was that the environment changed to daytime.
When the enviroment changed the dark nocturnal deer was no longer camouflage to the wolves and the light deer were , so the dark deer will be eaten instead.
The light dear were better suited for the environment so they survived.
Genes were pass down and more light deer were reproduce because they were the ones to survive.