In recent news, interest continues to focus on the plight of the polar bear. Scientists worry that the polar bear, the largest bear, will become extinct. The polar bear evolved from the brown bear. Through this speciation, it became suited to its life in the Artic regions. However, the Arctic regions are shrinking, leading many to be concerned. Regardless, the polar bear provides an interesting look at natural selection, mutation, genetic drift and gene flow.

A polar bear is a species. This means that each polar bear has similar characteristics to every other polar bear. They can also breed and produce fertile offspring. A polar bear and a Giant Panda bear are not the same species. This means they do not breed. In different species, there are a variety of mechanisms that isolate different species from interbreeding. They may live in different areas. They may not be active or fertile during the same seasons. There are also biological reasons why animals cannot breed. The sperm and egg may not fuse correctly. A viable zygote may not be produced. There are examples of hybrids occurring in similar species. Wolf hybrids and grizzly-polar hybrids have occurred. However, hybrids tend to be sterile. Grizzly or Kodiak bears are very similar to polar bears and live in the same regions. Therefore, many of the isolating mechanisms meant to separate these species do not exist. This is the reason for a hybrid to occur.

All the members of a species living in a particular area represent a population. Polar bears are found in the Arctic Circle. Canada has a large population of polar bears. Greenland also has polar bears. These would be two separate populations. The separate populations breed amongst themselves. In this way, a gene pool is formed for each population. Mutations may occur in the genes of parents and be passed on to offspring. These changes in the DNA structure may change the offspring’s relationship with its environment. It may improve its chances of survival or lead to its downfall. Somewhere in the evolutionary chain, the DNA of the polar bear increased its chances of survival in the Arctic Circle. It became a new species, separate from its cousin, the Brown Bear. Its fur became white; it developed strong swimming skills and a thick layer of insulating fat. The development of a new species is called speciation. Likely, those offspring who were not well insulated or good swimmers died off early and did not pass on genes. Those who were well-suited to the Arctic Circle passed on their genes. This created the species over time. There was also a certain amount of luck in this, or random chance. The determination of which genes are passed onto offspring is always random. Genetic drift refers to this random chance of what alleles an offspring inherits from the parents. Weaker offspring die while stronger offspring tend to survive.

Populations may exchange genetic material. This is called gene flow. Polar bears from Canada and polar bears from Greenland may interbreed. This would increase the diversity of genetic material available to both populations.

Natural selection is a nonrandom force of nature. Over time, nature decides what species survive and what species die. It does this through the changing ecosystem and the changing species. If a species is no longer suited to its environment, natural selection allows the species to die off or become extinct. This is the current concern with the polar bears. Polar bears spend most their lives at sea, hunting amidst ice. The Arctic ice is shrinking significantly. The environment of the polar bear is disappearing. Therefore the concern is that the polar bears will also disappear. Current news stories indicate that many polar bears are starving due to the inability to hunt adequately. As the environment changes, species must change or become extinct. Unfortunately, for the polar bears, the environment is changing faster than they can.

What happens to the polar bears is called microevolution. Microevolution focuses on one species or population. However, what is happening to the Arctic Circle is macroevolution. Macroevolution affects numerous species and populations. Macroevolution occurs on a grand scale. The loss of the Arctic habitat is macroevolution. It will affect all of us.