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Average Score: 56%

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 exemplifies natural selection as it demonstrates how a trait (pesticide resistance) becomes more prevalent in a population due to selective pressure from environmental factors (the pesticide). The bedbugs that survive are more likely to reproduce, passing their resistant traits to the next generation.

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

While this scenario may lead to evolutionary changes over time due to isolation, it primarily illustrates the concept of allopatric speciation rather than natural selection. The birds' isolation does not directly relate to the survival of individuals based on advantageous traits in response to environmental pressures.

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

This choice describes a population's response to a disaster, leading to a reduction in genetic diversity or changes in population size. However, it does not depict natural selection, as there is no indication of advantageous traits being favored for survival within the remaining population.

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

This example illustrates natural selection effectively, as the bedbugs that survive pesticide application are those with genetic mutations that confer resistance. These individuals reproduce, leading to a population that is increasingly resistant to the pesticide, demonstrating the core mechanism of natural selection.

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

This situation highlights a random mortality event rather than a selective process. While it affects population numbers, it does not directly indicate the survival or reproduction of individuals based on advantageous traits, which is central to the concept of natural selection.

Conclusion

Natural selection operates through environmental pressures that favor certain traits, leading to increased prevalence of those traits in future generations. The emergence of pesticide-resistant bedbug populations effectively exemplifies this mechanism, as resistance becomes advantageous in the face of pesticide use. In contrast, the other options either describe random events or processes that do not directly illustrate the selective survival of advantageous traits.

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