The habitat of one species of Martian, the pliggot, is the mountain, Olympus Mons, on the planet, Mars. The mountain is covered in iron oxide giving it a red color. The vast majority of the pliggots in this population are red. A few individual pliggots carry a mutation that prevents the production of the red pigment; as a result these individual pliggots are gray. Pliggots are the favorite food of the galywags, a predatory alien similar to weasel.

A meteor hits Mars and causes a volcanic eruption near Olympus Mons. The volcano erupts periodically for 10 years and each eruption coats the surface of Olympic Mons and the surrounding area with fresh ash and basalt.  As a result, the surface of Olympic Mons turns gray-black.

Using what you have learned about natural selection, explain how this change in environment may have affected the evolution of  this pliggot population (not including possible direct effects volcanic activity on the pliggots). Iclude the following terms in your explanation: allele frequency, selective pressure, differential reproduction, beneficial trait, evolution.