Principle #1 genetic variation: The genetic variation is Black and yellow panthers.
Principle #2 overproduction and the struggle for existence: They have 2 to 4 babies and 2 of them survive. The black panther struggles to survive in the day time because it can't camouflage so it can't catch food as easily as other panthers.
Principle #3 Different survival and reproduction: The yellow panthers have a higher fitness. So they survive and are able to reproduce.
Principle #4 Change of gene pool: The yellow panthers had reproduce so they become more common and the black panther becomes less common.