Tuesday, May 5, 2020

Evolution of polar bear lamarck and darwins theroy free essay sample

Polar bears have lived in the arctic for many years. Their bodies have adapted and developed in order for their survival in the polar region. Polar bears are able to live in the deep freeze for many reasons. They have thick fur that keeps in their body heat. They have small ears and a small tail which means they lose less heat. Their paws are so big that they act like snowshoes, and the pads on their feet have an anti-slip skin, which would be similar to sandpaper. For thousands of years polar bears have lived a great life in the North. The Inuit (a tribe) people have lived with them, hunting them occasionally for food or clothing. There was never any fear that the Inuit would over hunt the polar bears because it was dangerous and the weapons available to them were creative. In more recent times, the polar bears have been sought out by hunters, just not the Inuit who live in the North. They have been over hunted by people looking for the big trophy. Eventually in the 1970s the over hunting was brought under control by the International Agreement on the conservation of polar bears and their habitat. Polar bear number once again began to grow because of this. Though there are many theories surrounding evolution, the two stand outstanding assumptions applying to the change from Brown Bear to Polar Bear are Lamarck’s theory of Use and Disuse, and Darwin’s theory of Natural Selection. The intention of this paper is to compare this theory and decide the most appropriate in relation this event. Charles Darwin simply brought something new to the old philosophy a plausible mechanism called natural selection. Natural selection acts to preserve and accumulate minor advantageous genetic mutations. Suppose a member of a species developed a functional advantage (it grew wings and learned to fly). Its offspring would inherit that advantage and pass it on to their offspring. The inferior (disadvantaged) members of the same species would gradually die out, leaving only the superior (advantaged) members of the species. Natural selection is the preservation of a functional advantage that enables a species to compete better in the wild. Natural selection is the naturalistic equivalent to domestic breeding. Over the centuries, human breeders have produced dramatic changes in domestic animal populations by selecting individuals to breed. Breeders eliminate undesirable traits gradually over time. Similarly, natural selection eliminates inferior species gradually over time. According to Lamarck’s theory, features can be strengthened or cleared of completely through use or disuse over generations. For example, Jean Baptise Lamarck believed that the giraffes long neck was an acquired characteristic. After a lifetime of straining to reach up to eat leaves, a giraffe’s neck would elongate. Baptise thought that the offspring of these giraffes would then be born with longer necks. Lamarck’s theory has widely been disproved, especially with the discovery of heredity genetics. If the theory were correct, a man who works hard to get large muscles, would father naturally strong children. Though the physical side of the idea may be dismissed, many researchers are studying whether behavioural traits can be passed down from a parent to their young. It is thought that the polar bear evolved from the brown bear. It was likely that 100,000 to 250,000 years ago brown bears (Ursus arctos) became parted by glaciers. Most of the bears probably died on the ice. However some didn’t die because they survived due to the fact that organisms vary (Gould, 1977). This means that every litter of grizzlies has different kinds of coat thickness to keep them warm and coat colour so that they would suit their environment better, which gives them a small benefit to survive compared to some cubs of each litter. Successful individuals in each litter of grizzles repeated this simple process over and over again. This gave a rapid series of evolutionary changes (driven, most likely, by the small population, and intense selection pressure) in order to survive. Note that these new variants were not necessarily better in any exact way, or on any complete bear scale of perfection. They were simply more in keeping with their new environment than their immediate ancestors or their more unfortunate siblings. Today, polar bears are adapted to their harsh northern environment. Hecht (in Chaline, 1983) describes polar bear evolution: the first polar bear, Ursus maritimus tyrannus, was essentially a brown bear subspecies, with brown bear dimensions and brown bear teeth. So if you look at the evolution of the brown bear into a polar specifically skin and fur colour, skull and ears shapes and digestions of seal fat and the theories of Darwin and Lamarck. Darwin using â€Å"natural selection† changing what the polar bear needs to change to let them adopt and survive and Lamarck using the theory of â€Å"use and disuse if you don’t use it you’ll lose it basically. Then look at all the references and evidence and would have to say that Darwin’s theory was the one that made the most sense because you could actually see the polar bear evolving from the brown bear. The polar bear skin became thicker and keeps them warm. Also the polar bears fur colour changed to white so they suited their environments. Another change was the polar bear skull and ear this changed so they could maintain their body temperature. So I am stating that based on evidence that Darwin’s theory will win the scientific debate about the process of evolution of the polar bears from brown bears Chaline, J. 1983. Modalites, Rythmes, Mecanismes de LEvolution Biologique: Gradualisme phyletique ou equilibres ponctues? Editions du Centre National de la Recherche Scientifique, Paris. [Collection of symposium papers, most in French with English abstracts provided some in English. ] †¢ Kurten, B. 1964. The evolution of the polar bear, Ursus maritimus (Phipps). Acta Zoologica Fennica 108:1-26. †¢ GOULD, S. J. (1977). Ever Since Darwin. New York: W. W. Norton. †¢ Kurten, B. 1968. Pleistocene Mammals of Europe. Aldine, Chicago. †¢ Kurten, B. 1976. The Cave Bear Stor

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