How does genetic variation prevent environmental factors from wiping out a population?

With more genetic variations, the more adaptations will be developed that will help the population survive the changing environment.
For example, if an environment starts to grow lighter fields, a population will start to develop genetic variation that will help camouflage the animal. Like, make the animal start to have lighter skin to camouflage.

The magnets are probably damaged or there not strong enough to attached to the refrigerator