Question

Consider a large population of a finch species, where both small and big beak sizes are advantageous, and an intermediate beak size is maladaptive. Over a period of 10 years, which one of the following evolutionary processes is most likely to operate on the beak size of this finch population?

• A. ( Directional selection )
• B. ( Disruptive selection )
• C. ( Genetic drift )
• D. ( Stabilizing selection )

Hint:

Understanding how different selection pressures affect trait distributions within a population is essential for studying evolutionary biology and ecological dynamics.

Answer 1

The Correct Option is B

Disruptive selection is the process that favors individuals at both extremes of a trait distribution over those with intermediate phenotypes. This form of selection can lead to the presence of two distinct phenotypes within a single population. Analysis of Each Option: (A) Directional selection: Incorrect, as it favors one extreme phenotype over all others, not both extremes. (B) Correct: Disruptive selection accurately describes the scenario where both small and large beak sizes are favored, making the intermediate sizes less common or maladaptive. (C) Genetic drift: Incorrect, genetic drift involves random changes in allele frequencies, which is unlikely to consistently favor both extreme phenotypes, especially in large populations. (D) Stabilizing selection: Incorrect, as it favors intermediate traits over extremes, which is opposite of the described scenario. Conclusion:
Explanation: Given that both extremes of beak size confer advantages, disruptive selection would enhance the frequency of genes contributing to both small and large beak sizes, possibly leading to an increased divergence within the population. This might be an evolutionary response to varied ecological niches or dietary requirements that different beak sizes might fulfill.