Understanding Natural Selection

Natural selection is a key mechanism in the process of evolution. It is the process by which certain traits become more common in a population due to the reproductive success of individuals carrying those traits. For example, if a species of bird has variations in beak size, those with beak sizes that are better suited for their environment may find food more easily and, therefore, are more likely to survive and reproduce. Over time, you would expect these advantageous traits to become more prevalent in the population.

Which of the following best defines natural selection?