Darwin’s Finches: an example of Adaptive Radiation Read the following article and on a separate piece of paper write 10 points that you did not know before. You will hand this in! When members of a population undergo evolutionary divergence, new species can develop from a common ancestor. For this to occur, members of the population must be reproductively isolated from each other and each group must be exposed to different pressures. Therefore, different groups of the population adapt to different pressures, their gene pools diverge (become different) and new species may be produced, each unable to reproduce successfully with the other. One example of this that we have already talked about is the Resident & Transient Orcas. The most well known example of this can be seen in the Galapagos Finches first described by Charles Darwin. Fourteen species of finches are found on the Galapagos Islands, all have similar plumage, nest building behaviors and calls, but the different species can be easily distinguished by the size and shape of their beaks. Five of these species are shown on the next page. Among the animals Darwin studied were 13 species of finches found nowhere else on earth. Adaptive radiation suggests that an ancestral mainland finch populated the islands very soon after they were formed. With no other species of bird to compete with, finches soon occupied all island niches. Since ecology varied from island to island, finch populations evolved slightly different adaptive patterns. In order to reduce competition for food, finches adapted different feeding habits and evolved different beak structures to match their food source. Darwin's finches are an elegant example of 2 important aspects of the evolutionary process: geographic isolation (isolating mechanism) and adaptive radiation. Over an extended period of time, geographic isolation allows natural selection to produce new species. The evolution of distinctive structural adaptations and behavior patterns in a group of closely related descendant species is called adaptive radiation and is a means by which organisms respond to competition for resources. Natural selection favors those individuals whose characteristics are most suited for survival and reproduction for a particular way of life. The process described above can occur over and over. In the case of Darwin's finches, it must have been repeated a number of times forming new species that gradually divided the available habitats between them. The formation of a number of diverse species from a single ancestral one is called an adaptive radiation.
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