Some individuals of a particular species of sea bird underwent a genetic mutation that resulted in larger beaks. the larger size of beaks these birds to break open clams and other mollusks for food. it also them defend themselves against predators. after many generations, almost all of the birds in the population had big beaks. for which two reasons did this phenomenon occur? natural selection mechanical isolation prezygotic barriers to reproduction high genetic variation in the species

Natural Selection and High genetic variation in the specie

Explanation:

According to Darwin, mutations in populations will help indivuduals have a higher or lower adaptation to their environment. The process by which the tend to adapt or not is called Natural Selection, in which only the fittest will survive. Gene flow is any movement of genes from one population to another and is an important source of genetic variation.

In this particular example of the sea birds, the mutation of the beak was possitive in terms of adaptation  for them to defend themselves  and eat better. The high genetic variation of the specie, gave the possibility for the individuals of the specie through out several generations, to acquire this characteristic which led to a stronger and better adapted population in its environment.

b.have there own function.

i think the answer would be d