The process of evolution of different species in a given geographical area starting from a point and literally radiating to other areas of geography (habitats) is called adaptive radiation. When because of the competition for food and living space, a single ancestral species evolves into different species/forms which occupy different habitats (areas), it is called the adaptive radiation.
Adaptive radiation is exemplified by the following examples:
DARWIN’s FINCHES:
Darwin studied the flora and fauna of the Galapagos Islands, a chain of islands on the west coast of South America. There he found an amazing range of creatures existing. He found that there were many varieties of small blackbirds in these islands which differed mainly in the shape of beaks and feeding habits. These varieties of small blackbirds were later called Darwin’s Finches.
After analyzing them, he realized that all of these varieties evolved on the same island itself and were not from separate areas. He conjectured that these varieties evolved from the original seed-eating ancestor bird which was present in South America. Some of them flew to these islands and according to the needs of different environments, they developed different shapes of beaks and feeding habits. Some became insect-eating, some fruit-eating, some cactus eating, etc.
AUSTRALIAN MARSUPIALS:
The wide range of Australian marsupials also supports the phenomenon of adaptive radiation. The figure shows that a number of marsupials, each different from the other, like Koala, Kangaroo, Wombat, etc. originated from an ancestral marsupial, but all within the same island Australia. All these varieties differ from each other in morphology and other features and these differences are due to the adaptations to different environments.
