In a very large population, a quantitative trait has the following distribution pattern. If there is no gene flow, the curve shifts to the left or to the right, and the population size consequently increases over successive generations, which of the following is most likely occurring?
A) immigration or emigration
B) directional selection
C) disruptive selection
D) genetic drift

Question

In a very large population, a quantitative trait has the following distribution pattern. If there is no gene flow, the curve shifts to the left or to the right, and the population size consequently increases over successive generations, which of the following is most likely occurring?
A) immigration or emigration 
B) directional selection 
C) disruptive selection 
D) genetic drift

Quizplus · Accepted Answer

If the curve is shifting to the left or right and the population size is increasing over time, it suggests that there is a selective pressure favoring one end of the distribution over the other. This is consistent with directional selection, which causes a shift in the mean of the trait towards one end of the distribution. The other options (immigration or emigration, disruptive selection, and genetic drift) do not necessarily cause a shift in the distribution towards one end, and would not necessarily result in an increase in population size over time.

In a Very Large Population, a Quantitative Trait Has the Following