If a population's environment favors darker fur on dark rocks, which type of selection is acting?

• A. Directional selection toward darker fur
• B. Stabilizing selection toward mid-tones
• C. Disruptive selection toward extremes
• D. Balancing selection

Answer: (A)

Directional selection happens when the environment favors one end of the trait distribution. If the environment—dark rocks—gives darker-colored individuals a camouflage advantage, those with darker fur have higher survival and reproductive success. Over generations, the population’s average fur color shifts toward darker shades as alleles for darkness become more common. That unidirectional shift is what defines directional selection toward the darker extreme.

Stabilizing selection would push toward intermediate mid-tones and reduce variation, which isn’t happening here. Disruptive selection would favor the extremes (very light and very dark) while disfavouring mid-tones. Balancing selection maintains multiple colors over time due to trade-offs or fluctuating conditions.