Population after natural selection Original population The image depicts what type of selection? a) Stabilizing selection b) Directional selection c) Disruptive selection d) No selection Previous Page Next Page Page
The Correct Answer and Explanation is:
Correct Answer: b) Directional selection
Explanation:
The image described likely shows a shift in the population’s traits after natural selection, where the average value of a particular trait moves toward one extreme. This pattern is characteristic of directional selection. In this type of selection, individuals with traits at one end of the phenotypic spectrum have higher fitness than those in the middle or at the other end. As a result, the population’s trait distribution gradually shifts in that favored direction over generations.
For example, imagine a population of birds with varying beak sizes. If the environment changes so that larger seeds become the primary food source, birds with larger beaks are more likely to survive and reproduce. Over time, the average beak size in the population increases. This shift in the average trait value without favoring both extremes or the middle is what defines directional selection.
This differs from other types of selection. Stabilizing selection favors the average phenotype and reduces variation by selecting against extremes. An example would be human birth weight, where extremely low or high birth weights are associated with higher mortality. Disruptive selection favors both extremes of a trait over the intermediate forms, potentially leading to two distinct populations. For instance, in some environments, both very light and very dark-colored animals may have a survival advantage over those with medium coloration. No selection would result in no change in the population’s trait distribution over time.
In summary, the population shifting toward one end of the trait spectrum after natural selection clearly represents directional selection. It highlights how environmental pressures can guide evolutionary change by consistently favoring one trait over others in a population.
