Question

The average speed of a greyhound dog increases gradually in succeeding generations after only the fastest of a brood are allowed to interbreed. What is this variation an example of?



Genetic drift



Stabilizing selection



Directional selection



Disruptive selection

Answer 1

It is C. Directional selection is the removal of undesired phenotype, thus allowing the desired phenotype to appear more often which causes a shift in the distribution of the phenotype of the population. In this case, slower dogs were not bred; only the fastest dogs were allowed to breed, thereby hopefully making the succeeding generations of greyhounds faster than their predecessors.

A. Genetic drift or allelic drift is the change in the frequency of a gene variant (allele) in a population due to random sampling.

B. Stabilising or ambidirectional selection is a type of natural selection in which genetic diversity decreases as the population stabilizes on a particular trait value.

C. Directional selection is a mode of natural selection in which a single phenotype is favored, causing the allele frequency to continuously shift in one direction.

D. Disruptive selection, also called diversifying selection, describes changes in population genetics in which extreme values for a trait are favored over intermediate values.