A predator prefers one phenotype to another. Eventually the # in the non prey phenotype will survive to reproduce.
Explanation:
Genetic evolution is the meaning of biologic life, in that it is the why and how of it, as well as the stock of future biological existence. The genes that survive -- and in turn the organisms they make -- are the winners in the existence game. ... We owe our existence to this process, and our future depends on it.
In this example of evolutionary development, we can see a selective advantage.
Developing of new characteristics, in this case, the spots on moth's wings is a part of the process of adaptation of organisms to their environment.
The new characteristics are acquired through mutations and natural selection filters the ones that are the most beneficial for the holder.
For example, a mutation which results in moths having shorter wings is disadvantageous, because it makes the individual who possesses it less likely to survive and reproduce.
On the other hand, developing of spots that resemble eyes can be advantageous, since it enables the holder of the trait to be more successful and more likely to leave offspring.