Flexible foraging strategies, including prey switching. The polar bear ursus maritimus introduction polar bears. This is any inheritable trait that increases its survival rate so that it can live longer, reproduce longer, and have more offspring that also have that trait. Pdf nuclear genomic sequences reveal that polar bears are an. The usgs alaska science center leads longterm research on polar bears to inform local, state, national and international policy makers regarding conservation of the species and its habitat.
Polar bear evolution is a continuing story essay 1748 words. The native biome of the species is the arctic tundra which is known for its extremely cold climate, low vegetation and cold desert like conditions. Introduction polar bears face an uncertain future as climate change melts the sea ice they need for survival. One small fossil, one giant step for polar bear evolution. The arctic is becoming warmer at a high rate, and contractions in the extent of sea ice are currently changing the habitats of marine toppredators dependent on ice. Polar bears and brown bears are ideal species for such an analysis as they are closely related, yet ecologically distinct. In the united states, polar bears are located in two alaskan populations. Previous estimates of polar bear evolution had placed the split any where from 70,000 years ago to more than one million years ago.
Polar bear evolution is a continuing story essay 1748 words 7 pages polar bear evolution is a continuing story the polar bear, the largest land carnivore in north america, one of the largest animals in the world and a favorite at zoos worldwide, has, over the years, adapted to its harsh arctic environment. Adaptation in the polar bear adaptation in a population of living things happens as a result of an adaptive trait. Previously, it had been suggested that the white bear of the north was a. Polar bears ursus maritimus depend on sea ice for hunting seals. They are the only terrestrial mammals, other than humans, to have adapted so completely to sea ice, a quite different habitat, spatially and temporally, from that occupied by.
Even though the polar bear does fit into the category of being a bear, there is scientific evidence to show it has evolved into a definite species of its own. Icon of the arctic, the polar bear thrives in the remote arctic landscape of ice and snow. A population of brown bears that lived along the coast became specialized for hunting seals, eventually evolving into the polar bear around 700,000 years ago. In polar bears, the most strongly selected genes included several related to lipid processing and to the development of the heart and circulatory system, adaptations that may help polar bears cope with an extremely highfat diet. Matt cronin, in case you didnt know, was the first to pick up the close genetic relationship between polar bears and grizzlies, as a result of research he and colleagues did back in the early 1990s cronin et al. The polar bear management agreement for the southern beaufort sea, between the inupiat hunters of alaska and inuvialuit hunters of canada, was ratified in 1988. As a family, bears are thought to have evolved some 4. In the beginning, the polar bears would have variations of a certain trait. Polar bears ursus maritimus and brown bears ursus arctos have long fascinated naturalists and the public, and bear ecology and evolution.
Polar bears and brown bears are excellent models for exploring the impact of natural selection on cnv, the researchers write, because they inhabit vastly. Evoloution of polar bears lamarck vs darwin essay 1102 words 5 pages the polar bear ursus maritimus is a bear native largely within the arctic circle encircling the arctic ocean, its surrounding seas and land masses. The researchers also show that the polar bear has developed the capabilities to live in the arctic during just a couple of hundred thousand years and this is a very fast evolution. During winter polar bears will migrate along the southern edge of an ice pack. Darwin approved of lamonts hypothesis, and, because lamonts thinking on the subject predated the publication of on the origin of species, he later credited lamont as he did alfred russel wallace. Polar bears and brown bears are ideal species for such an analysis as they are closely related. Just as changes in the genes have led to changes in the fur colour from brown to white, a natural selection has led to changes in the genes that regulate the. Animation describing how brown bears adapted to life in the arctic.
This is believed to be an important step in the evolution of a new subspecies of bear ursus maritimus or the polar bear. Agreement on the conservation of polar bears and their habitat. Brown bears were noted to have evolved 800,000 years ago. Although it is closely related to the brown bear, it has evolved. Polar bear name and evolution polar bears international. Ursidae are placed in the order carnivora but, except for the largely carnivorous polar bear, bears are. There are plenty of questions about the evolution of the polar bear that we simply dont have answers to. The premolars and molars of polar bears are more jagged and sharper than those of other bears, reflecting their rapid evolutionary shift toward carnivory from the flatter grinding teeth of their more omnivorous relatives stirling, 2002. Evoloution of polar bears lamarck vs darwin 1086 words. Mar 01, 2010 they found that the polar bear whose jawbone was sequenced existed very close to the most recent common ancestor of polar bears and brown bears. Estimates of when polar bears started splitting from brown bears continue to change as geneticists learn more about the polar bears genome. How did the polar bear evolve from its grizzly relative. Nature once exerted such extreme pressure on the brown bear. An adult male of a polar bear, also known as boar, weighs approximately 772 to 1,543 pounds.
References by topic updated as i have time, from my 2017 book polar bears. All of these characteristics, unique to the polar bear, have been part of its evolution. But some biologists think that polar bears and brown bears diverged from their common ancestor as early as 600,000 years ago. It is only the arctic limitation that is putting check on the rapid evolution of polar bears. Dna evidence from the fossil records also shows that the polar bears are in the process of evolution. Polar bears ursus maritimus are one of 4 marine mammal species managed by the u. The oldest polar bear fossils found are from svalbard and northern norway and have been dated at 115,000,000 years old, before the beginning of the last ice age. Polar bears split from the brown bear, their closest relative, less than 500,000 years agofar more. Nuclear genomic sequences reveal that polar bears are an. Past estimates for this divergence came from brown bears living on the admiralty, baranof and. White fur helps polar bears blend into the arctic ice and snow so they can hunt more successfully. The pattern of organisms around the globe the absence of some species from environments that would. This is because there are so many differences from them and other forms of bears. Considering pinnipeds and polar bears to be marine mammals, the kodiak bear is the largest of the living landbased mammalian predators.
Using available raw wholegenome dna sequence data, the team of researchers compared differences in gene copy numbers among 17 polar bears, nine brown bears and two black bears. Scientists agree that modern polar bears have lately been derived from ancestors. This provides more time for polar bear evolution and confirms previous suggestions that polar bears carry introgressed brown bear mitochondrial dna due to. Jul 02, 2019 polar bears also have shortened tails and smaller ears to reduce heat loss, specialized front paws for swimming, and greater adipose deposits under the skin for thermal regulation 5. A new study in the proceedings of the national academy of sciences early edition online, is shaking up sciences view of polar bear evolution. Jun 10, 2008 in 2006, a hybrid grizzlypolar bear, which some call a pizzly, was discovered in the canadian arctic, providing researchers proof that polar bears and grizzly bears can interbreed, even in. There are plenty of questions about the evolution of the polar bear. To date, global warming has been most pronounced in the arctic, and this trend is projected to continue. Harington 1966, manning 1971, and wilson 1976 subsequently. Polar bears evolved from brown bears 100,000 to 250,000 years ago. Polar bears are the largest land carnival in the world and are now at the top of their food chain.
The polar bear ursus maritimus polar bears international. Polar bear evolution and adaptation even though the polar bear does fit into the category of being a bear, there is scientific evidence to show it has evolved into a definite species of its own. Polar bears are found throughout the arctic and are the most nomadic of all bear species. Brown and polar bears modern brown bears first appeared in asia during the middle pleistocene epoch and then spread to north america and europe, even reaching northern africa. The polar bear is a member of the ursidae family and shares a common ancestor with the black and brown bear. Rethinking polar bear evolution the global warming policy. The hearing and eyesight of polar bears is quite similar to human beings, however, over the years, the polar bear developed an extraordinary sense of smell.
The female polar bear, also known as a sow, weighs about half the weight of the male. The latest scientific findings show that the polar bear has weathered worse climatic storms in the past. By comparing these dna samples, it made it possible to scientists to create a family tree describing the evolution of polar bears. Polar bears and brown bears also have drastically different diets owing to their differing ecologies. Brown bear to polar bear evolution in 1996 scientists concluded that the brown bears of alexander archipelago were derived from ancestors which gave birth to modern day polar bears. Pregnant polar bears will spend time on coastlines in maternity dens where they stay a few months after they give birth. For these toppredators, longer icefree seasons are hypothesized to force the bears to hunt for alternative terrestrial food, such as eggs from colonial breeding. Polar bear evolution is a continuing story essay 1748.
Climate change and the increasing impact of polar bears on. One small fossil, one giant step for polar bear evolution april 2010. Encouraged by darwins response, lamont elaborated upon walrus and polar bear evolution in his 1861 travelogue, seasons with the seahorses. The spectacled bear tremarctos ornatus is the only member of ursidae in south america. Polar bear evolution is marked by rapid changes in. Recent research suggests up to twothirds of the worlds.
Worldrenowned polar bear scientist ian stirling offers his thoughts on the state of polar bears in the wild, the threats they face today, and insights from his recent book, polar bears. Harington 1966, manning 1971, and wilson 1976 subsequently promoted use of the name ursus maritimus, and it has predominated ever since. All dna evidences prove that the modern polar bears are only derived. Survival of the fittest natural selection polar bears youtube. There are suggestions that before midcentury we could have a nearly icefree arctic in the summer. Polar bears ursus maritimus have 3842 teeth and a dental formula of i33, c1l, p2424, m23. Oct 19, 2015 survival of the fittest natural selection polar bears. This was predicted to have happened when a number of brown bears became stranded on a glacier. Polar bears are intimately associated with arctic sea ice and their distribution is approximated by its winter extent. Evoloution of polar bears lamarck vs darwin evoloution of polar bears lamarck vs darwin essay.
In this essay i will be talking about the evolution of polar bears from brown bears, specifically skin and fur colour, skull and ear shape, and digestion of seal fat ill also talk about the two theorists jeanbaptiste lamark 17441829 and charles darwin 18091882. Polar bears ursus maritimus are among those species most susceptible to the rapidly. Polar bears are an integral part of the arctic ecosystem and the food web for indigenous peoples who have hunted polar bears sustainably for millennia. According to canadian wildlife magazine, polar bears can smell seals at ranges up to 32 kilometers. Today, polar bears are adapted to their harsh northern environment. Hecht in chaline, 1983 describes polar bear evolution. Over the next 20,000 years, body size reduced and the skull elongated. Brown bears and polar bears are found in europe and these 2 species plus the american black bear ursus americanus inhabit north america. Today, we have dna evidence to show differences between early polar bears and those found today. It has no natural predators and knows no fear of humans, making it an extremely dangerous animal.
Polar bear evolution tracked climate change sciencedaily. The ancestors probably had lived in the southeastern alaska during pleistocene period and separated from brown bears. On the mating system of polar bears canadian journal of. Polar bears and brown bears diverged long ago evolution. This dna evidence also supports the theory that the polar bear split from the brown bear about 150,000 years ago. Polar bears ursus maritimus are the poster child for the impacts of climate change on species, and justifiably so. You cannot use traditional methods of pinpointing the timing. As shown in the diagram on the left, the polar bear is also related to the spectacled bear, the sloth bear, the sun bear, the american black bear, the asiatic black bear, and the brown bear. Evoloution of polar bears lamarck vs darwin essay bartleby. This is any inheritable trait that increases its survival rate so that it can live longer, reproduce longer, and have more offspring that also. One that stood out was a gene called apob, which helps transfer fat from blood into cells. Recent findings suggest that polar bears evolved from a common ancestor of the brown bear between 350,0006 million years ago. 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. The evolution of polar bears via fossils is very well documented.
Although not genetically isolated from other bears. Polar bear, great white northern bear found throughout the arctic region. It is believed that about 1 million years ago, the changing conditions on earth and migration caused the species to adapt and form what we now call polar bears. Mar 14, 20 polar bears and brown bears diverged much longer ago than previously thought, new research suggests. The authors of a new paper out in plos genetics cahill et al. Although not genetically isolated from other bears, evidence. Polar bears live in the arctic, but not the antarctic. Estimates of when polar bears started splitting from brown bears continue to change as geneticists learn more about the polar bear s genome. In my opinion, the most important conclusion of this paper is that occasional but widespread hybridization among bears is why it has been so hard to say with confidence when polar bears arose which i addressed years ago, in my polar bear evolution series. Polar bears evolved just 150,000 years ago live science. It was enacted to protect the polar bears traveling between the canadian portion of the beaufort sea region and chukchi sea in the united states.
Exploring the natural history of polar bears national. Recent studies have shown that the polar bear matriline mitochondrial dna evolved from a brown bear lineage since the late pleistocene, potentially indicating rapid speciation and adaption to arctic conditions. Polar bear evolution where do polar bears come from. Polar bears, also known as ursus maritimus, are large carnivorous mammals native to the region lying within the arctic circle, which includes the arctic ocean and its surrounding seas and landmasses. Jun 20, 2012 today, we have dna evidence to show differences between early polar bears and those found today. Polar bear evolution polar bear facts and information. Outstanding survivors of climate change where polar bears live and other basics andersen, m. Evolutionary history of polar and brown bears esa journals wiley.
What they discovered was that the dna from the fossil showed that this ancient polar bear was the halfway point between the evolution of brown bears to polar bears. The ability of polar bears to swim in water can be explained using the theory of natural selection. They travel an average of 5,500 miles a year or 15 miles a day. The evolution of the polar bear from brown bear to arctic wonder. Jul 23, 2012 an analysis of newly sequenced polar bear genomes is providing important clues about the species evolution, suggesting that climate change and genetic exchange with brown bears helped create the. Polar bear evolution was fast and furious science aaas. Apr 19, 2017 polar and brown bears belong to the subfamily ursinae, which comprises six extant, morphological and ecological distinct species 11, but hybridization among some ursine bears is possible.
Climate change likely caused polar bear to evolve quickly. It has been known that polar bears evolved from brown bears, but. Except for one subspecies of grizzly bear, the polar bear is the largest and most powerful carnivore on land. There is a new polar bear genetics paper out in the journal of heredity, by university of alaska fairbanks genetics professor matt cronin and colleagues.
Evolution similar bone structure and size has proved that the polar bear species derives from the brown bear. But, beginning in the 1700s, largescale hunting by european, russian and north american hunters and trappers took place, raising concerns about the future survival of polar bears. Dna from a polar bear jawbone has revealed the arctic species first originated about 150,000 years ago, scientists announced today. The origin and evolution of the polar bear matriline. Rethinking polar bear evolution the global warming. Just so darwin why did the brown bear evolve into the polar bear. The polar bear ursus maritimus is a bear native largely within the arctic circle encircling the arctic ocean, its surrounding seas and land masses. Here, we compare differences in gene copy numbers among 17 polar bear and 9 brown bear individuals to evaluate the impact of copy number variation on polar bear evolution.