Polar Bear Evolution Is a Continuing Story Essay

The Polar bear lives in the artic and uses the area’s costal waters and ice sheets. They are well equipped to live in this environment because they have a thick coat which serves as an insulator. They mainly prey on seals but have also been known to consume dead whales. They can grow to be 7.25 to 8 feet tall and can weigh around 900 to 1,600 pounds. Polar bears are a keystone species, if their numbers decrease there is a possibility that the seal populations will increase which could be devastating for crustaceans and fish. They help keep populations in balance.

The polar bear possesses a low, flat skull with high-sitting eyes which is best suited to a semi-aquatic life. This also benefits the Polar bear by enabling them to put their heads into puppy dens or breathing holes.

The melting sea ice is also affecting the polar bear's main prey, seals, forcing the bears to turn to alternate, less nutritious food sources. Once sea ice forms in the winter, seals use the ice to create dens to give birth to their pups. In these months, polar bears use sea ice as their hunting grounds to find seal dens. Now that Seasonal Ice is forming later and melting earlier (IPCC, 2013), seals have less time to build dens and give birth. Consequently, polar bears have less time to hunt their preferred prey of seal pups. They must spend more time on land hunting other animals of less nutritional value. Organizations like Sea World Parks have reported male polar bears occasionally eating newly-born polar bear cubs because they cannot find other food to eat. Lack of nutritional food leads to a reduced body size. Polar bears are becoming thinner and weaker from not eating enough (Rode, Amstrup, & Regehr 2010). They have to swim longer distances to find ice to hunt upon, causing many cubs to die because they are not yet strong enough. In the Hudson Bay, the average polar bear weight has decreased by 15% and the population has decreased by 20% (National Wildlife Federation). In the summer when there is no ice, polar bears in the Hudson Bay go onto land to fast until the ice reforms. Now that ice is

The Polar Bear (Ursus maritimus) is a bear native largely within the Arctic Circle encircling the Arctic Ocean, its surrounding seas and land masses. Although it is closely related to the Brown Bear, it has evolved to occupy a narrower ecological forte, with many body characteristics adapted for cold temperatures, for moving across snow, ice, and open water, and for hunting the seals which make up most of its diet. Though there are many theories surrounding evolution, the two stand outstanding hypotheses applying to the modification from Brown Bear to Polar Bear are Lamarck’s theory of Use and Disuse, and Darwin’s theory of Natural Selection. The intention of this paper is to compare these thesis and determine the most appropriate in

"Polar Bears, Ringed Seals, and the Complex Consequences of Climate Change" is an article written by Mary Bates who earned her PhD studying Bat echolocation. She works for an American Association for the Advancement of Science. In this article Mary talks about how Climate change is impacting different species at different rates. Here, she focuses on sea-ice dependent animals such as Polar Bears and Ringed Seals at Arctic. She explains on how these animals are dependent upon the sea-ice for living. The Arctic is warming at a rate three times greater than the global average, and that the sea ice coverage is declining rapidly. She also talks about Hamilton's study on sea-ice dependent animals. Before the melting of sea ice the Polar bears used

Differences include the size of legs, ears, noses, paws, claws, jaws and the colour of the bear's fur. Polar bears generally have larger legs, smaller noses and ears, soft paws, short claws and small jaws with strong teeth. These adaptations have occurred to improve the polar bears wellbeing and chance of survival whilst living in the Arctic. Whereas, Brown bears have larger and more claws and a heavier and larger skull (Difference Between, 2014). This is too to help them survive in the environment.

Canada is home to many species of rich heritage, cultural significance and meaning to the Canadian people. Of the many species, one holds a strong iconic significance that plays a vital role in the very ecosystem it resides in. The polar bear species are undoubtedly the apex predator of its food chain and a culturally significant species to the indigenous people. With both these traits, it makes the polar bear a true Canadian symbol which is further emphasized by its very place on the Canadian two-dollar coin to the strength and endurance represented by this majestic species. However, no matter how strong and enduring the polar bears are to the arctic, such resilience is not as effective against the harsh changes their environment has gone through.

White bears require a variety of physical characteristics to survive in the harsh environment of the Arctic. Large, wide paws with bumps allow them to distribute weight and grip more efficiently. Water resistant fur with a luminescent quality keep the bear warm and dry. Additionally, Sharp and powerful teeth have the ability to penetrate hard flesh. These special features allow not only the ability to thrive in a difficult environment, but also are important for communicating with other species and another bear.

Their feet are made for the ice and snow; they have rough leather pads so they don’t slip on ice, fur between toes and sharp claws as a weapon. They are plantigrade and left handed. Their toes are webbed so they can swim in water. Their fur is a yellowish white; the top lay is long and hollow to absorb heat and can float in the water. The undercoat covers their black skin that has four inches of blubber, which is an extra layer of warmth. This kind of coat makes it uncomfortable for polar bears to be in the heat. A polar bears sense of smell is the best sense they have, they mostly rely on it. It can smell a dead whale 15 miles away, can smell where a seal is hiding in six inches of ice, and can smell a human before they could even see them. Their eyes are small to block out the sun reflecting off the snow and their ears are small, close to their heads to keep warm.

The Polar Bear are found on the icy coasts that surrounds the North Poles and as far south as Hudson Bay. Around 60%of Polar Bears can be found in Canada with the remainings throughout Greenland, Alaska, Svalbard, and Russia where tend to be close to the ocean across the icy fields. The habitats are affected by human encroachment by hunting , and releasing chemical pollutants into the water.The Polar Bear eats Seals, Walrus, and Seabirds. Polar Bears can live up to 20-30 year. Polar Bears have a lot of fur and their fur is clear, white, or yellow. The Polar Bear is 6.5 ft-8.3ft. they can weigh up to 330lbs -1,322lbs and they can swim up to 25mph.

This is where most of their time is spent: either when hunting, mating, denning, or just roaming. Surprisingly, polar bears are extremely resilient swimmers. According to Defender’s of wildlife, polar bears may be seen in open waters as far as 200 miles off shore. ("Basic facts about Polar Bears," n.d.). One of the reasons for such behavior is, like mentioned earlier, polar bears depend on ice. When newly frozen ice is too thin to support a polar bear’s weight, the polar bear finds a different alternative to get across. In most cases, a polar bear will break through the ice and swim until they require oxygen. (Striling, 2011) This comes to show how they both able to survive using both mediums. However, swimming is considered a very high-priced activity for polar bears to do. In other words, swimming requires an immense amount of energy and as a result, you will not commonly see polar bears

The polar bear lives up in the Arctic region where global warming and climate change are melting the ice caps that the bears thrive on. They use the ice as a platform from hunting and rest. The random pocket holes in the ice, where the seals pop up at, is where the polar bear catches its prey. With this reduction of ice, “the abundance of seals, and increases the amount of energy and time needed for hunting, leaving less energy for reproduction” (Endangered Species and Habitats).

 The polar bear has to be able to stay warm in the harsh winter cold. In fact sometimes because they have such thick fur they have to lay down on the snow to cool off so the harsh cold isnt even enough to keep them up to tempreture.

Adaptions for a diet of seal flesh and blubber. Exhibit decreased surface area of the grinding molar teeth, a trait typically more distinct in omnivorous bears, and a flatter, low, slender skull, perfect for thrusting into dens/ breathing holes of seals. The two species (Polar Bears and Brown bears) are similar in cranial size, however Polar Bear skull is of weaker construction. Polar bears had a very speedy evolution of adaptions for their semi water habitat/ lifestyle and the dietary adaptation in Polar Bears made a cranial morphology less appropriate to processing tough omnivorous or herbivorous sustenance. Eyes sit higher up on the

began to adapt to a different life of cold weather and hunting seals. Brown bears originally are generalized and are capable of being able to live in a variety of habitats. Whereas polar bears are specialised to the environment and live on the edge of the Artic sea ice. They have discovered that it is known that polar bears split from brown bears between 300,000 to 400,000 years ago. A chemical analysis was taken place of a 120,000 year old fossil polar bear jawbone, this showed that in that time the species was already very dependent on marine prey which is rather different from a brown bears diet of a vegetarian fare. This then indicates that the genetic changes had only occurred in just a few hundred years. The jaw bone had provided the