Imagine you are studying leaf size in a large population of plants over several years. In one year of your study there is a below-average amount of rainfall, and the following year the average leaf size in the population is smaller than before. However, the amount of variation in leaf size is the same and the population size doesn't change. Other scientists have done experiments showing that small leaves are better adapted to dry conditions than large leaves. What has most likely occurred?

Question

Quizplus · Accepted Answer

The below-average rainfall likely caused a selective pressure for smaller leaves, as small leaves are better adapted to dry conditions. This resulted in directional selection favoring smaller leaves and a decrease in average leaf size in the population. The amount of variation in leaf size remaining the same suggests that stabilizing or disruptive selection did not occur. Genetic drift and the founder effect involve random fluctuations in allele frequencies and do not seem relevant in this scenario.

Imagine You Are Studying Leaf Size in a Large Population