If, in one population of pupfish all of the individuals have a blood pigment that is extraordinarily effective at carrying oxygen, but this trait is not seen in any of the other populations, what likely happened?

A) Because oxygen was low where these pupfish lived, a new allele for an effective blood pigment arose.

B) This population was lucky to have an individual with a random mutation for an effective blood pigment, and the frequency of this allele was increased in subsequent generations through natural selection.

C) The ancestral population probably had this type of blood pigment, but it was lost through genetic drift in the other 29 populations.

D) The other populations did not need this pigment, so they did not evolve it.

C) The ancestral population probably had this type of blood pigment, but it was lost through genetic drift in the other 29 populations.

Explanation:

The presence of a blood pigment that is extraordinarily effective at carrying oxygen is a beneficial genetic trait and should be favored by natural selection. According to the given information, the organisms of only a single population of pupfish have this trait while the others do not have it.

This means that the trait was present in the ancestral populations of the pupfish but was lost in the other populations due to some accidental/chance event. Loss or fixing of an allele by a chance event is called genetic drift. It does not include any natural selection but results in a random change in the allele frequencies of a population. Therefore, loss of the trait by genetic trait might have occurred in the other populations.