Diversification of ancestral line into different forms which in turn occupy diverse ecological niche is referred to as adaptive radiation. For example, the ancestral seed-eating stock of Darwin’s finches diversified based on different types of food that were (plants, seeds, insects, cactus etc) available The of beak adapted to that food and got modified accordingly. The geographical isolation led reproductive isolation and thus, the evolution of new species of finches from the parental stock.