AIIMS 2017 Botany Natural Selection MCQ Question

Option B represents disruptive selection because it describes a population of butterflies that are either all yellow or all blue, indicating that extreme phenotypes are favored over intermediate ones. This scenario leads to a bimodal distribution of traits, characteristic of disruptive selection, where individuals at both extremes have a selective advantage.

In contrast, option I (industrial melanism in peppered moths) exemplifies directional selection, as it shows a shift towards darker coloration due to pollution. Option III describes a population adapting to a cold climate by increasing body fat, which is an example of stabilizing selection as it favors a trait that enhances survival in a specific environment. Lastly, option IV illustrates a response to predation pressure, suggesting a shift towards smaller size, which is also indicative of directional selection rather than disruptive selection.