Polar bear evolution
One of the earliest ancestors of the modern day polar bear, was a now extinct species named Ursus maritimus tyrannus. This species was a subspecies of brown bear, with mainly brown bear features, but much larger, and is the first emergence of the modern species. Ursus maritimus tyrannus was over twelve feet in length and six feet tall. This subspecies became the modern polar bear after going through several evolutionary cycles to achieve the traits best suited for their extreme environment. Although polar bears and common brown bears branched off of one another earlier on in their evolution, there is proof of the species coming back into contact, in the form of occasional polar bear genes flowing into brown bear populations. Originally through the natural selection process, the arctic species was able to transform and begin to maintain their main characteristics. The bear species' most identifiable trait, it's white fur became a constant in the species due to selective pressures favoring those who are able to camouflage in their environments having higher success in hunting. Individuals with traits such as heavy oily coats and a thick layer of body fat were able to survive over those who were less well suited for the arctic, leaving the best individuals to reproduce and carry on their genes.
Other traits permanently embedded in the genome by evolution include: the appearance of white color due to hollow pigment free hairs that scatter and refract light, causing an effect very similar to that of ice and snow under sunlight, allowing for the most accurate camouflage. A thick layer of blubber up to 4.5 inches thick surrounds the body just under the bear's skin, allowing it to survive and stay a constant body temperature when swimming and spending long periods of time in frigid waters, while it's thick fur keeps its temperature constant when on land. Polar bears developed to best suit their environment mainly through natural selection, but the primary cause f separation was due to an event leading to a portion, if not a large group of individuals of the northern brown bear population to venture further north, whether due to a bottlenecking effect, or event based on natural disaster, or due to environmental pressures leading for individuals to relocate in search of food or other necessities. This event, or migration for survival, led to the above mentioned natural selection processes, and the evolution of the modern polar bear.
Other traits permanently embedded in the genome by evolution include: the appearance of white color due to hollow pigment free hairs that scatter and refract light, causing an effect very similar to that of ice and snow under sunlight, allowing for the most accurate camouflage. A thick layer of blubber up to 4.5 inches thick surrounds the body just under the bear's skin, allowing it to survive and stay a constant body temperature when swimming and spending long periods of time in frigid waters, while it's thick fur keeps its temperature constant when on land. Polar bears developed to best suit their environment mainly through natural selection, but the primary cause f separation was due to an event leading to a portion, if not a large group of individuals of the northern brown bear population to venture further north, whether due to a bottlenecking effect, or event based on natural disaster, or due to environmental pressures leading for individuals to relocate in search of food or other necessities. This event, or migration for survival, led to the above mentioned natural selection processes, and the evolution of the modern polar bear.