If natural selection favors one extreme variant, causing a shift in the population's average phenotype over time, this is called?

If natural selection favors one extreme variant, causing a shift in the population's average phenotype over time, this is called?

• A. Directional Selection
• B. Stabilizing Selection
• C. Disruptive Selection
• D. Sexual Selection

Answer: (A)

Directional selection occurs when natural selection favors individuals at one end of the phenotypic spectrum, so the average trait value in the population shifts in that direction over generations. Those at the favored extreme have higher fitness and leave more offspring, pulling the distribution of phenotypes toward that end. Over time the population’s mean changes toward the extreme, and genetic variation may decrease as other variants become less common. Classic examples include the shift in peppered moth coloration during industrial pollution or the rise of antibiotic resistance in bacteria. This differs from stabilizing selection, which keeps the mean around a central value and reduces variation without shifting the average, and from disruptive selection, which favors both extremes and can create a bimodal distribution. Sexual selection involves mate choice and can produce its own distinctive patterns, but the described scenario specifically reflects natural selection acting on survival and reproduction to move the mean toward one extreme.

Directional selection occurs when natural selection favors individuals at one end of the phenotypic spectrum, so the average trait value in the population shifts in that direction over generations. Those at the favored extreme have higher fitness and leave more offspring, pulling the distribution of phenotypes toward that end. Over time the population’s mean changes toward the extreme, and genetic variation may decrease as other variants become less common. Classic examples include the shift in peppered moth coloration during industrial pollution or the rise of antibiotic resistance in bacteria. This differs from stabilizing selection, which keeps the mean around a central value and reduces variation without shifting the average, and from disruptive selection, which favors both extremes and can create a bimodal distribution. Sexual selection involves mate choice and can produce its own distinctive patterns, but the described scenario specifically reflects natural selection acting on survival and reproduction to move the mean toward one extreme.