Question

Consider a flower population that produces different sizes of blooms and depends on bees for reproduction. Large blooms attract larger bees; small blooms attract smaller bees. Describe how changes in the bee population might lead to disruptive, stabilizing, and directional selection in the flowers.

Answer 1

Disruptive selection occurs when extreme phenotypes are favored over intermediates. In the case of the flower population, if there is a decrease in the population of larger bees (which are attracted to large blooms), then small blooms may have a higher chance of being pollinated by smaller bees. This could lead to a higher frequency of small blooms in the population as they are being selected for by the available smaller bees, while large blooms may not be as successful in reproduction.

Stabilizing selection occurs when intermediate phenotypes are favored over extreme phenotypes. If the bee population remains stable with a balanced ratio of smaller and larger bees, then both small and large blooms may have equal chances of being pollinated and reproducing successfully. This could result in the maintenance of variation in bloom sizes within the population as neither extreme is being favored over the other.

Directional selection occurs when one extreme phenotype is favored over the other extreme. If there is an increase in the population of larger bees (which are attracted to large blooms), then large blooms may have a higher chance of being pollinated and reproducing successfully. This could lead to a shift towards larger blooms in the population as they are being selected for by the available larger bees, while small blooms may not be as successful in reproduction and eventually decrease in frequency.