Speciation And Adaptive Radiation

Adaptive radiation is the process by which a single ancestral species rapidly diversifies into many new forms, each adapted to a particular ecological niche or way of life. Darwin's finches on the Galapagos Islands descended from a common seed-eating ancestor and evolved a remarkable variety of beak shapes and sizes suited to different diets, from seed-crushing to insect-eating, illustrating this radiation within a confined geographic setting. Convergent evolution is incorrect because it describes unrelated species independently developing similar features due to similar environments, the opposite of one ancestor diversifying. Genetic drift refers to random allele-frequency changes and does not specifically explain the adaptive, niche-based diversification seen in the finches. Industrial melanism is a particular case of natural selection in peppered moths involving colour change due to pollution, unrelated to the radiation of finch beaks. As described in NCERT Class 12, Chapter 7 (Evolution), Darwin's finches are the classic textbook example of adaptive radiation. As a logical check, multiple distinct forms arising from one ancestor to fill different niches precisely matches the definition of adaptive radiation, confirming the answer.