Polar Bears- 500 Word Essay

550 Words3 Pages
Polar bears maintain homeostasis (the tendency of an organism to regulate internal stability when dealing with external changes) by eating and sleeping regularly, hibernating, and their skin and fur. Their fur consists of a dense insulating undercoat with hairs of different lengths. It’s not actually white it just looks that way. Polar bears skin prevents them from suffering heat loss. Polar Bears have Eukaryotic cells because its cells have a nucleus. They also have 74 chromosomes. A polar bear has cells that go through mitosis, because it divides the chromosomes in the nucleus, producing two identical daughter cells during prophase, pro-metaphase, metaphase, anaphase and teleophase. Polar bears reproduce by sexual reproduction, the creation of a new organism by combining the genetic material of two organisms. They also have DNA strands, because they have eukaryotic cells, which have a nucleus. DNA is organized into chromosomes, where as in prokaryotic cells, DNA is just a single loop. Polar bears first appeared 200,000 years ago during the Pleistocene. They were much larger than the ones today. They have evolved over time to withstand the bitter cold of the Artic. Scientists believe polar bears descended from a group of brown bears that became isolated by glaciers in an area near Siberia. They underwent rapid series of changes in order to survive; from the color of their fur and the shape of their body, to keener senses and sharper teeth. Some scientists’ researches have proved that some white standard poodles have descended from polar bears. They both carry the same DNA mutations in a gene IGF1. The simplest explanation is that the mutations arose in a common ancestor. Similar organisms to the polar bear are Panda bears, Koala bears, Grizzly bears, Black bears, Red pandas and Brown bears. From our body systems section, a polar bear has a nervous system,

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