Charles darwin

             and best-known research. On these islands, Darwin found an array of animal life .
             and found that related but different species lived on different islands even though .
             all these islands were very similar in geological, climatic, and other physical .
             conditions. He found an array of ground finches with beaks ranging from large .
             and powerful to small or fine. He correlated these differences not with physical .
             conditions on the islands but with birds" feeding habits. Those primarily fed on .
             insects. He stated that each finch was particularly suited to the food that was .
             available it its environment, an example of what later became known as .
             adaptation.
             Along the pacific coast of South America, Darwin observed that closely .
             related species often lived in adjacent geographic areas and that species found .
             on isolated oceanic islands often resembled species found on the nearest .
             continent. Established biological thinking held that all species were unchanging .
             and specially created: however, Darwin found that similar species were always .
             present in adjacent geographic areas. When he found, at a given location, fossils .
             of extinct species that were similar to living species, he began to question why .
             similar species existed in successive geologic time periods.
             Darwin collected many geologic and biologic specimens, studied many fossils, .
             and made observations of the form, numbers, diversity, and living habits of .
             different forms of life. From his research he arrived at the idea that species .
             descend, with modifications, from other species, or that species evolve from .
             other species.
             Also while on the voyage of the HMS Beagle, Darwin challenged a scientist .
             ideas on the formation of coral reefs by volcanic action. Darwin contended that .
             the reefs were part of a process of gradual changes in the earth's crust resulting .
             from the subsidence of some landmasses and corresponding elevations .
             elsewhere. He explained that coral, which only grows in shallow waters, forms a .