In the desert there are two diffrent lizards, one is blue and doesn't blend in and the other is tan and blends right into the sand.
Evolution Step Three: Selection
As you can see there are more tan lizards than blue lizards because the blue lizards are not as fit as the tan lizards to survive in this environment. There are more tan lizards because they are mating with more tan lizards because there is more of them.
As you can see, the tan lizard is not as easy to spot in the sand. The hawk can see the blue lizard very well so, the blue lizard is easier to get.
As you can see in the picture, there are very many tan lizards due to evolution
As the offspring passes, more and more tan lizards appear because of survival of the fittest.
As you can see in the the picture the population is now all tan lizards due to evolution.