In a small group of people living in a remote area, there is a high incidence of "blue skin" a condition that results from a variartion in the structure of hemoglobin. All of the "blue-skinned" resident can trace their ancestry to one couple, e who were among the original settlers of this region. The unusually high frequency of "blue skin" in the area is an example of:.
a- genetic drift
b- heterozygote advantage
c- natural selection
d- mutation

(A) Genetic drift

Explanation:

  The genetic drift is one of the process of random sampling in which the existent gene frequency are get changed in the organisms and it is also refers as the allelic effect.

According to the given question, In a small remote area the different types of people are living and in that area the "Blue skin" condition is highly incidence due to the variation in the hemoglobin structure.

So, the high frequency in the Blue skin in that specific area is one of the example of the genetic drift and the main role of the genetic drift is to determining the sampling error from the different generation gene.    

  Therefore, Option (A) is correct answer.  

sheep is a herbivore animal whereas grasshopper belongs to the class chordates but both of them feed on greens.  

if grasshopper and sheep feeding on a pasture land, i do not think both of them will have any impact on each other. however, the number of the species can make difference. since sheep feed on greens, there is a possibility there left no pasture land for the grasshoppers or they may get extinct.