Principal #1: Genetic Variation In the rabbit population, There are many different colored rabbits and there are some with a white color and some with a brown color. Both rabbit colors can be passed to there offspring.
Principal#2: Over population & Selective pressures The rabbit that have have the white color mutation are not able to blend in to there environment as well as the brown rabbits. The brown rabbits are able to survive, while the white rabbits start to die off.
Principal#3: Differencial survival & Reproduction The brown rabbits that camouflage to there surroundings are able to live longer. Since they are able to survive they get to reproduce. The offspring they produce keep the brown color mutation in there species.
Principal#4: Changes of the gene pool All generations from then on will have a brown coloration in there species.This will allow them to survive better and longer to reproduce many more like them who have a better fit than others.