Natural Selection: Polar Bears

Natural selection is a process the spans across generations within a population of a particular species. It is based on several premises, one of which being that there are certain members of species in a specific location that have certain traits that make them survive longer and consequently, reproduce more offspring (Audesirk et. al., 2008). A majority of these offspring inherit the positive traits of their parents and the cycle continues until only the members of the population with the desired characteristic remain. In this paper, the Ursus maritimus, more commonly referred to as the Polar Bear is selected as the subject of a hypothetical evolutionary process that is put forward to occur because of continued global warming. In response to global warming, it is theorized in this paper that Polar Bears would evolve to have thinner fur.

Population and characteristic
    The population of polar bears considered in this paper is that which currently resides in the Arctic Circle. The Arctic Circle is an extremely cold geographic region, with temperatures falling to as much as -50° Celsius during wintertime (Stirling, 1988). This makes the region habitable only to species that have powerful biological systems for insulation against cold (with the exception of humans who have developed artificial means of insulation). The polar bear is one such species, with 3 layers of protection against extreme cold. These three layers are composed of polar bear blubber, hide, and fur. A polar bear’s fur grows from 5 to 15 cm long, and appears white to tan in color despite actually being transparent (Stirling, 1988).
Hypothesized evolution by natural selection

    Currently, the fur of a polar bear grows from 5 to 15 cm long. The length of growth is directly proportional to the amount of insulation from the cold that the polar bear receives. That is, the longer the fur growth, the better the insulation. However, the polar bear’s strong insulation against cold is a major drawback for its survival in warmer climates. In fact, a polar bear can suffer physically from being subjected to an environment with temperatures that go over 10° Celsius (Stirling, 1988). This detail is significant when considering the climate change that is occurring in the Arctic Circle because of global warming. As reported by the International Polar Foundation (2008), sea ice in the Arctic is expected to decline continuously and the “area of Arctic land covered by snow is expected to decrease by 10 to 20 percent.” However, the change in the environment is expected to be gradual, and there is not clear prediction as to when the Arctic would become too warm for the polar bears to survive. This gives the population of polar bears enough time to evolve. There are domesticated polar bears that typically develop shorter fur than their wild, Arctic counterparts. It is expected that there are some polar bears that have shorter fur than others, and as the climate in the Arctic becomes warmer, it is expected that these polar bears would have greater lifespan. The increased environmental warmth would make physical activity for polar bears in general more difficult, since expending the energy required for hunting their main food source, seals, would increase body heat. Those who have shorter fur would be able to hunt longer and thus persevere over the rest of its species.

    Given the current trends of global warming, polar bears would have to find ways to adapt to warming temperatures of its natural habitat. Natural selection would most likely enter the picture, with polar bears having shorter fur surviving into the future generations.


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