Differential reproductive success within one sex of any species.

• A. Stabilizing selection
• B. Sexual selection
• C. Genetic drift
• D. Gene flow

Answer: (B)

Differential reproductive success within one sex is driven by sexual selection. In many species, individuals of the same sex vary in how effectively they secure mates, so those with traits that help them win matings end up leaving more offspring. This can come from direct contest and dominance displays (intrasexual selection) or from preferences that the opposite sex has for certain traits (intersexual selection). Over time, these mating advantages shape features that enhance mating success, even if they don’t improve or may even reduce survival.

Stabilizing selection, by comparison, favors average traits and reduces variation without focusing on mating success within a sex. Genetic drift is random change in allele frequencies, not driven by differences in reproductive success related to traits. Gene flow involves movement of genes between populations, affecting allele frequencies across groups rather than differential mating success within a single sex.