Answer 1

Evolution of long neck in Giraffe
Darwin explained evolution of long neck of modern giraffe by presuming existence of variability in the length of neck and legs in the ancestral population of giraffe. The longer-necked giraffe with longer forelegs were more successful in reaching the soft leaves of trees for feeding. Therefore, natural selection favoured longernecked progeny generation after generation. Selection of longer neck for innumerable generations resulted in the evolution of present day longer-necked modern Giraffe.