Evolution Outline essays

Evolution Outline essays Geographic distribution of living things Homologous structures of organisms Similarities in early development Darwin proposed that Earth was millions of years old, not thousands. During those millions of years, many different forms of species appeared, lived for a time, and then vanished leaving behind remains, or fossils. One can examine fossils and view the changes of each one; observe the changes in offspring. Each species is slightly different on Island A. Far away, on Island B, the species were also slightly different. The species had changed over time as the populations in different places adapted to local environments. The species had descended with modifications from a mainland ancestor when Island A and Island B were combined as a contiguous land mass. Different species exist on Island C and Island D. Similar structure and behavior were found in different animals which roamed similar environments. As a result, one can conclude that the species now living on different islands had descended from different ancestors. Some species, however, are similar because they were living under similar ecological conditions and thus exposed to similar pressures of natural selection. - Different animals ended up evolving certain striking features in common. Look at mammals, reptiles, and birds; each of those creatures has backbones. There are striking similarities, like limbs. - Some limbs are arms, some are legs; they can also be wings, or even flippers. Each limb has a different form and function, but all are composed of the same basic bones. Each limb had adapted in ways so the organism can survive in different conditions. Despite the different functions, limb bones all developed from the same clumps of cells in growing embryos; these are called homologous structures. - Homologous structures prov...