Answer :
Answer: B) the bottleneck effect.
Explanation: The bottleneck effect refers to phenomenon where a species loses a great deal of genetic diversity due to a drastic decrease in population size. These decreases the population are usually the result of a drastic environmental effect, which are sometimes known as bottleneck events. Examples of bottleneck events include natural disasters like droughts or fires and man-made events such as habitat loss or excessive hunting. The culling of a population results in the population's genome being drastically reduced in size, resulting in decreased genetic diversity.
Choice A's founder effect also results in decreased genetic diversity, but for different reasons. Instead, the founder effect refers to the decrease in genetic diversity that occurs when a small subset of an original population find a new habitat to live. Since these "founders" are only a small percentage of the original population, their collective genome is much smaller and thus less diverse.
Choice C is incorrect because the directional effect refers to a specific trait becoming more common in a population due to its fitness in helping individuals survive. It does not occur as a result of population loss, but rather due to natural selection simply taking its course. (an example of this would be a giraffe population getting progressively longer necks over generations to better access food.
Choice D is incorrect because the selective effect is simply a synonym for natural selection. It refers to how organisms most suited to their environments are more likely to survive and pass on their traits through reproduction.
