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The process of evolution of different species starting from a point in an geographical area and finally radiating to other areas of geography is called adaptive radiation.
Examples of adaptive radiation are:
1. Darwin’s Finches:
Darwin observed an amazing diversity of creature in Galapagos Islands. They represented one of the best examples of adaptive radiation. Of all the varieties of finches, which were observed in the same island, he found that all of them had evolved from original seed-eating finches.
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He explained that after originating from a common ancestral seed-eating stock, the finches must have radiated to different geographical areas and undergone adaptive changes, especially in the type of beaks. Therefore, due to the alternation in beaks gradually, some became insectivorous and some vegetarian. Living in isolation for long, the new kinds of finches emerged that could function and survive in the new habitat.
2. Marsupials of Australia:
These are another examples of adaptive radiation. A number of marsupials (pouched mammals) each evolved differently from an ancestral stock but all within the Australian continent.
3. Placental Mammals in Australia:
Placental mammals in Australia also exhibit adaptive radiation in evolving into varieties of such placental mammals each of which appears to be ‘similar’ to a corresponding marsupial. For example, placental wolf and Tasmanian wolf.
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When more than one adaptive radiation appear to have occurred in an isolated geographical area (representing different habitats) and two or more groups of unrelated animals come to resemble each other for similar mode of life or habitat, it is called convergent evolution.
