Explain the role of time in evolution

The concept of immense periods of geological time are necessary to account for the possibility of the small changes resulting slowly into major changes. Thus long periods of time are essential for Darwin's theory of slow uniform biological changes being responsible for the Origin of the Species.

Explanation:

A hawk eats by finding prey on the ground. Better eyesight in a certain individual would increase it's likelihood of finding food. There is already competition among a population for food, which is generally limited. The individuals with better eyesight would be more likely to survive. The frequency of the better eyesight trait would increase, assuming that the individuals with this trait are more likely to reproduce and the offspring were more likely to survive.  If the birds with better eyesight also had weak wing muscles, they likely wouldn't be able to catch food and survive.