What is stabilizing selection?

What is stabilizing selection?

• A. Natural selection that favors intermediate variants by acting against extreme phenotypes
• B. Natural selection that favors one extreme variation
• C. Genetic drift that fixes alleles
• D. Mutation that introduces new traits

Answer: (A)

Stabilizing selection is a pattern of natural selection where individuals with intermediate traits have higher fitness than those at the extremes, so the population’s average trait value is favored and variation around that average is reduced. This happens when the environment is relatively stable and extreme phenotypes carry greater risks or costs, making the average phenotype the best compromise for survival and reproduction. For example, in humans, birth weights that are too small or too large can lead to higher infant mortality or health complications, so babies with intermediate birth weights tend to have higher survival, illustrating this type of selection. This description fits stabilizing selection because it emphasizes favoring intermediate variants and acting against extreme phenotypes. The other ideas point to different processes: one extreme being favored describes directional selection, where the population shifts toward a single extreme; random changes from genetic drift occur by chance and aren’t about intermediate versus extreme fitness; and mutation introduces new traits rather than preferentially preserving intermediates.

Stabilizing selection is a pattern of natural selection where individuals with intermediate traits have higher fitness than those at the extremes, so the population’s average trait value is favored and variation around that average is reduced. This happens when the environment is relatively stable and extreme phenotypes carry greater risks or costs, making the average phenotype the best compromise for survival and reproduction. For example, in humans, birth weights that are too small or too large can lead to higher infant mortality or health complications, so babies with intermediate birth weights tend to have higher survival, illustrating this type of selection.

This description fits stabilizing selection because it emphasizes favoring intermediate variants and acting against extreme phenotypes. The other ideas point to different processes: one extreme being favored describes directional selection, where the population shifts toward a single extreme; random changes from genetic drift occur by chance and aren’t about intermediate versus extreme fitness; and mutation introduces new traits rather than preferentially preserving intermediates.