Polar Bear And Climate Change Essay

Climate Change and Species Range

Introduction

The title of “Climate Change and Species Range”, gave me the opportunity to explore a vast array of information. It takes into account the broad and controversial topic of climate change; in general terms, the fluctuations of climatic statistical properties over a period ranging from decades to millions of years, no matter the cause (http://nsidc.org/arcticmet/glossary/climate_change.htm, n.d.). Furthermore the specific effect of the ever changing climate on the range of every known species. The area in which a species may be found during its lifetime is defined as its range (Rutledge,K et al., n.d.). Species with a range stretching most of the earth are said to be of cosmopolitan distribution,

The world population of polar bears is currently dwindling and is currently 20,000-25,000 and is split between 19 sub-populations (Effects of climate change on polar bears, 2010). Brown bears are found in Russia, Scandinavia, Europe, North America and Asia. Americans use the term “grizzly” to refer to the smaller lighter coloured bear in the interior parts of North America, whereas “brown bear”, are generally thought off as the larger, darker variation living close to the coast and feeding on salmon (http://www.nwf.org/Wildlife/Wildlife-Library/Mammals/Grizzly-Bear.aspx, n.d.). Brown bears and polar bears are different species and therefore according to the biological species concept should not be able to produce viable fertile offspring. Polar bears have evolved from brown bears between 100,000 and 200,000 years ago (Reece,J, 2010), and can to some extent be looked upon as a white brown bear (Höflinger,L, 2012). Figure 1.2 shows a photograph of what is believed to be a hybrid offspring of U. maritimus and U. arctos. Studies of the remains of a grolar bear killed by hunters show it was a second generation hybrid, indicating the viability and fertility of the grolar bear as a hybrid (Höflinger,L, 2012). Campbell Biology 9th edition defines a according to the biological species concept, “A species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring- but do not produce viable, fertile offspring with members of other such groups.” As the polar and brown bear are considered different species, it raises the question how has the viable, fertile grolar bear come about? There are obviously limitations to this concept and different species concepts are helpful in particular cases. It goes on further to state the lack of gene flow designates species. However gene