Source: Cummings, M.R. (1996). Biology: Science and Life. West Publishing Company: St. Paul, MN
Adaptive Radiation- is the development of a variety of species from a single ancestral form. It happens when a burst of speciation takes place when a new habitat or geographical region is made available to populations of an organism.
Perfect Example: Darwin's Finches
Finches in the Galapagos went through an adaptive radiation, Darwin recorded 13 species of finches in the Galapagos, Islands of South America. He found that some finches adapted by natural selection to new environments creating species of finches adapted to ground dwelling and life on the trees. Also, he assumed that this could not have happened if the ancetral organims haven't had originated on the mainland and on, reaching the islands.