Describe an environmental factor that could influence natural selection and decrease genetic
diversity. Pick a specific example to illustrate your
point.

A lot of toxins in a coral reef could influence natural selection so it would become like survival of the fittest. Then the fish would develop certain traits to better protect themselves (less prey means predators would takes bigger measures to get food). This would also cause a decrease genetic variation because there wouldn't be as much fish left. Since the coral reef went from unique to dull from toxins.