Biology

Posted: November 28th, 2013

Biology

Name:

Course:

Institution:

Instructor:

Date:

Biology

The Polar bear is the largest predatory carnivore on land, which is found in the Arctic Circle that includes Arctic Ocean, the surrounding sea and landmasses. It is white yellow in color with a body that is elongated, longer nose and skull. It is found in countries like the U. S., Russia, Canada, Denmark and Norway. The average adult male polar bear weighs between three hundred and fifty kilograms and six hundred and eighty kilograms. An adult female weighs between two hundred kilograms and three hundred kilograms although when pregnant the weight can reach five hundred kilograms. Polar bears measure between one point eight meters and two-point four meters (Patent & Muñoz, 2000). The total population of the polar bears in the world is estimated to be between twenty five thousand and forty thousand. The polar bears spend plenty of time on sea though they are born on land.

They feed on seals both ringed and bearded which they hunt when the seals surface through ice hole to breath or lie on the ice to take a rest. Polar bears have large feet that ensure the weight is evenly distributed when the bear walks on thin ice. In addition, the large feet make it easier for the polar bear to swim. They have a thick hide and fur that insulates their bodies from cold and over heat when exposed to temperatures above ten degrees. They mate in April and may; the fertilized egg stays in a suspension state until august or September when the female bears goes into a hibernation mode after creating a den in the sea ice or on land. The cubs are born between November and February weighing less than one kilogram and blind. They remain in the den until between mid February and mid April, and for all those months, the female does not feed. They have been classified as endangered species.

The polar bears have a life expectancy of twenty-five years though the oldest male polar bear recorded in the history died aged thirty-two years. The oldest female died at the age of forty-two years in Assiniboine park zoo. With the global warming and people hunting them, it is feared that they may be extinct in decades to come.

The genetic and environmental changes that are affecting the polar bears include the climatic changes known as global warming. Increasing temperature is threatening the habitat of polar bears by melting away the arctic ice that they depend on to survive. When the ice melts earlier, the polar bear starve because they have not stored enough fat in the body to last them through the scarce period. The increased temperature causes the ice to be thin making it difficult for the bears to hunt seals hence they become poorly nourished. This causes a low reproduction rate and low cub survival rate (Derocher, 2008). The temperature rise also affects the pregnant females’ ability to build dens causing them to swim for long distance to reach the shore and build dens there. Pollution in the sea accumulates in polar bears causing birth defects and deficiency of the immune system.  Oil spillages in the artic may cause the polar bears to die of hypothermia when the oil sticks to their fur reducing the insulation level in the body. In addition, the oil can enter the dens of pregnant females and females with cubs causing them to abandon the leaving the cubs behind. The polar thick fur and hide causes it to experience heat waves when temperature is rise.

I chose to write about the polar bear as the species due to the interest it has generated across the countries it is found. The governments of these countries have come up with policies to protect the polar bear from being hunted down to reduce the extinction of this species that these practices bring. Another reason why the polar bear was chosen is due to its inhabitation of the Arctic Circle that is covered in ice most of the times. The adaptation that the polar bear has to this climate has baffled many including scientists who over time have come up with different theories of explanations. The fact that the polar bear is the largest predator on land, yet it spends most of the time in the sea, is in itself a fascinating phenomenon. In addition, the fact that it hunts down seals that weigh sixty kilograms and three hundred kilograms on ice is astonishing.

References

Derocher, A. E. (May 2008). Polar Bears and Climate Change. Retrieved from http://www.actionbioscience.org/environment/derocher.html

Patent, D. H., & Muñoz, W. (2000). Polar bears. Minneapolis. MN: Carolrhoda Books.