Answer:
According to the given case, one type of beak is well adapted to the available food and other is not. Birds with better beaks will be more successful in feeding hence will be healthy and live long. Whereas birds with the inferior beaks will face challenge while feeding and survival for them will become difficult. So, number of birds with better beaks will increase in population whereas number of birds with inferior beaks will decrease. As a result, frequency of the better allele will increase in gene pool. Eventually, it will surpass the inferior allele.