The geographic isolation of a population can result in the rise of a new species. A. Isolation can result when a geographic barrier forms and splits a population or when a few organisms somehow get carried across an existing geographic barrier and form a new population. B. Speciation is more likely when an isolated population is small because significant genetic changes are more likely to occur in a small population than in a large one. C. Because of the geographic isolation of the Galapagos Islands, the species that now inhabit them have gene pools that have not changed very much since the islands were first populated. D. Fish populations are more easily isolated by geographic barriers than are populations of most other organisms because fish cannot move across areas where there is no water. E. The Galapagos Islands are well situated for speciation because they provide opportunities for population isolation while also making occasional dispersions between islands possible. F. Evidence indicates that the first organisms to reach the Galapagos Islands were probably a small population of finches that,in less than two million years of isolation,evolved into thirteen species.