The polar bear, the largest land carnivore in North America, one of the largest animals in the world and a favorite at zoos worldwide, has, over the years, adapted to its harsh Arctic environment. The appropriately named ‘ursus maritimum’ or sea bear usually lives between 15 and 18 years in the wild and spends most of its life on ice. It is the most recent of the eight bear species. The first polar bear was a brown bear subspecies, with brown bear dimensions and brown bear teeth. The polar bear evolution was rapid due to the small population and extreme pressure to survive. Even today, the polar bear continues to evolve to better adapt to the harsh realities of Arctic life.
Today’s polar bear evolved from the brown bear. The polar bear can reach weights of more than 1000 pounds. They can swim 100 miles without a break. Their body is longer than an ordinary brown bear and they lack a shoulder hump. Evolution has worked well for the polar bear in its efforts to survive a barren and cold life.
In the overall history of evolution, polar bears are a fairly young breed. Over 200,000 years ago, glaciers covered much of the earth. Hungry brown bears, probably isolated in the glaciers near Siberia and looking for something to eat, discovered seals. The first bears probably just ate seal carcasses that washed ashore because that was their hunting capability at the time. Within 75,000 years (a short period in evolutionary time), rapid changes took place so bears could survive on ice, be an aggressive hunter and reproduce in a frigid land. That new species, the early polar bear, arrived during the mid-Pleistocene period. The early polar bear was much larger than today’s polar bear (Evolution of ...
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...lution was and will continue to be the main element of polar bear adaptability for the future.
Drew, Lisa. “Tales of the Great White Bear.” National Wildlife 35.1 (Dec-Jan 1996): 16-25.
Eliot, John. L. “Polar Bears: Stalkers of the High Artic.” National Geographic 193.1 (Jan. 1998): 52-71.
“Evolution of Polar Bears.” University of Maryland, Department of Geology Site. 17 April 2003
“Field Guide: Polar Bear.” Canadian Wildlife 8.4 (Fall 2002): 10.
Milius, Susan. “Giants of the North.” International Wildlife 24.5 (Sep-Oct 1994): 30-35.
Milner, Richard. “Sea Bear.” Natural History 110.1 (Feb. 2001): 84-85.
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