Question

which is the best definition of directional selection?
○ a process by which two species can no longer reproduce
○ a process by which one of the extreme variations of a trait is favored
○ a process by which both extreme variations of a trait are favored
○ a process by which average individuals in a population are favored

Explanation:

To determine the best definition of directional selection, we analyze each option:

• The first option describes speciation (reproductive isolation), not directional selection.
• Directional selection favors one extreme variation of a trait, shifting the population's trait distribution in one direction. This matches the second option.
• The third option describes disruptive selection (favoring both extremes).
• The fourth option describes stabilizing selection (favoring average individuals).

Answer:

B. a process by which one of the extreme variations of a trait is favored (assuming the second option is labeled B; if the original options had labels like A, B, C, D, adjust the identifier as per the actual labeling. Here, based on the order, the correct option is the second one which would typically be labeled as, for example, B if the first is A, etc.)