What is adaptive radiation? Explain it with reference to Australian marsupials. Can this fauna indicate its parallel evolution with placental mammals? How do you explain their geographic distribution?
Adaptive radiation is a process in which organisms diversify rapidly from an ancestral species into a multitude of new forms, particularly when a change in the environment makes new resources available, creates new challenges, or opens new environmental niches. This can be observed These are other examples of adaptive radiation. A number of marsupials (pouched mammals) each evolved differently from an ancestral stock but all within the Australian continent.
These marsupials evolve with the placental mammals. Close to 70% of the 334 extant species occur on the Australian continent (the mainland, Tasmania, New Guinea, and nearby islands). The remaining 100 are found in the Americas — primarily in South America, but thirteen in Central America, and one in North America, north of Mexico.