which of the following is an example of directional selection? question 34 options: a) a mouse population that is originally white in color becoming darker in color after several generations b) a flower population that originally ranges from white to red becoming mostly pink over several generations c) a moth population that is originally grey gradually dividing into discrete white and black populations over several generations
The Correct Answer and Explanation is :
The correct answer is:
A) A mouse population that is originally white in color becoming darker in color after several generations.
Explanation:
Directional selection is a type of natural selection where one extreme phenotype is favored over other phenotypes, causing the population to shift in a specific direction over time. This often occurs in response to environmental changes that make certain traits more advantageous for survival and reproduction. As a result, individuals with those advantageous traits tend to survive and reproduce more than others, causing that trait to become more common in the population across generations.
Option A, which describes a mouse population that changes from white to darker color over time, exemplifies directional selection. In this case, there could be an environmental reason why a darker coat color provides better camouflage, thus improving the darker mice’s chances of survival against predators. Over time, these darker-colored mice reproduce more successfully, gradually shifting the entire population’s color towards the darker spectrum.
In contrast, Option B describes a scenario where a population moves toward a medium, or intermediate, phenotype—in this case, pink flowers. This is an example of stabilizing selection, where the intermediate trait is favored over the extremes, which stabilizes the population around that intermediate trait.
Option C describes a situation where a population divides into two extreme phenotypes (white and black), which is an example of disruptive selection. Disruptive selection favors both extremes over the intermediate, potentially leading to the formation of two distinct groups within the population that may eventually become separate species.
In summary, Option A best represents directional selection because it involves a shift toward a single trait extreme (darker color), aligning with how directional selection drives populations toward an advantageous trait in a specific direction.