Final answer:
Natural selection occurs when individuals with certain traits produce the most offspring. Those individuals with advantageous traits have a better chance of surviving and reproducing, which leads to the prevalence of those traits in the population over time.
Step-by-step explanation:
Natural selection occurs when individuals with certain traits are selected in the sense that they produce the most offspring. This means that individuals who have traits that give them a better chance of surviving and reproducing will pass those traits on to their offspring. For example, if the selective pressure is a predator, individuals who are best able to avoid being eaten will survive and reproduce at a higher rate. The survivors must be able to reproduce in order for their traits to become more prevalent in the population over time.