Difficulty: Easy

Average Score: 100%

Which of the following best illustrates the mechanism of natural selection?

Rationale

The appearance of pesticide-resistant populations of bedbugs after prolonged use of a pesticide.

This scenario illustrates natural selection as it demonstrates how certain individuals within a population adapt and survive due to advantageous traits—in this case, resistance to pesticides. The selective pressure of the pesticide leads to the survival and reproduction of resistant bedbugs, thereby increasing the frequency of this trait in subsequent generations.

A (The isolation of a group of mainland birds on an island after a major hurricane) YOUR ANSWER

While the isolation of birds can lead to speciation and evolutionary changes over time, it does not directly illustrate the mechanism of natural selection. Isolation may create opportunities for divergence, but without specific selective pressures acting on traits, it does not demonstrate how advantageous characteristics are favored in a population.

B (The emigration of half of the members of a population of mice after a large fire) YOUR ANSWER

This choice describes a scenario of gene flow or population dynamics rather than natural selection. The emigration itself does not involve the survival of individuals based on advantageous traits; rather, it reflects changes in population size and structure as a response to environmental change without directly illustrating the selection of specific traits.

C (The appearance of pesticide-resistant populations of bedbugs after prolonged use of a pesticide) CORRECT

This option exemplifies natural selection as it shows how certain bedbugs survive due to their resistance to pesticides. Over time, these resistant individuals reproduce and pass on their traits, illustrating how environmental pressures can lead to evolutionary changes within a population.

D (The death of three members of a population of mountain goats in an avalanche) YOUR ANSWER

Although this choice describes a mortality event, it does not illustrate natural selection. The random deaths caused by an avalanche do not provide a selective advantage or disadvantage based on traits; hence, it fails to demonstrate the process of natural selection where traits influence reproductive success.

Conclusion

Natural selection is a process whereby individuals with advantageous traits are more likely to survive and reproduce in specific environments. In this context, the appearance of pesticide-resistant bedbugs effectively demonstrates this concept, as their survival and reproduction in the face of pesticide application lead to an increase in resistance within the population. Other choices describe scenarios that do not directly involve the selection of traits based on environmental pressures.

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