Use the concept of natural selection to explain how a population of moths might evolve if only a few members can blend in with their environment.

A great example is the peppered moths evolution. Since the Industrial Revolution the birch trees started to turn black from the soot. This casued all the white moths to be eaten from birds. The ones that were left to mate were black moths which favored the black gene. So overtime black moths became more common. They were naturaly selected based on color to survived and pass down their black colored genes.  

Explanation:

the answer to your question is sperm