【Native Speaker每日综合训练—45系列】【45-03】科技 Polar Bear

Going

内容：古月小破烂 编辑：Going

Stay tuned to our latest post! Follow us here ---> http://weibo.com/u/3476904471

这次是关于Polar Bear的~~

Part I: Speaker

Santa in Danger: Polar Meltdown
The ice is melting across the Arctic—and Antarctica is starting to thaw, too. David Biello reports
December 11, 2008

The North Pole is melting, and there's very little Santa can do about it. No matter how green his elves are.

It's worse for the Inuit people, polar bears, walruses, and a host of less charismatic residents of the far north. Inuit leaders repeatedly deliver warnings about dwindling caribou herds, ground collapsing from beneath villages and ice too thin to hunt on. This disappearing ice is the very reason polar bears are now listed as an endangered species.

Thin ice also allowed the first commercial ship, the MV Camilla Desgagnes to traverse the fabled Northwest Passage between the Atlantic and Pacific Oceans in September, delivering cargo to Inuit villages. It is a feat, long sought after (and died over) by European Arctic explorers—but it's not good news for Arctic residents.

The South Pole isn't faring much better. The Antarctic Peninsula is among the fastest warming locations in the world and, according to the European Space Agency, the enormous Wilkins Ice Shelf is in imminent danger of collapse, much like the Larsen ice shelf fragmented a few years back. That's bad news for global sea levels as well as would-be ice dwellers.

In future, Santa's reindeers may need water wings.

Source: Scientific America
http://www.scientificamerican.com/podcast/episode/santas-meltdown-08-12-11/

[Rephrase 1, 1:25]

Going

Part II: Speed

Polar Bear Numbers Plummeting in Alaska, Canada—What About the Rest?
Polar bears (pictured, an animal in Manitoba, Canada) as a species are considered vulnerable to extinction.
by Linda Qiu  |  19 Nov 2014

A large population of polar bears in Alaska and Canada has decreased by 40 percent since the start of the new millennium, new research shows.

[Time 2]
The number of the large predators living in the southern Beaufort Sea (map) plummeted from 1,500 animals in 2001 to just 900 in 2010, according to the study, published on November 17 in the journal Ecological Applications.

But there's a lot we don't know about the 18 other known polar bear populations, which are scattered throughout the U.S., Canada, Russia, Greenland, Norway, and Denmark, experts say.

For instance, nine groups, which live in places like northern Siberia, are little studied due to the remoteness of their locations and lack of funding.

Of the most studied populations, four—including the southern Beaufort group—are declining, five are stable, and one, in north-central Canada's M'Clintock Channel (map), is actually increasing, scientists say.

The species as a whole is decreasing in number, and is listed as vulnerable by the International Union for the Conservation of Nature.

The reason for the variability in numbers is location, location, location.

"If you're in the high Arctic, there's a greater possibility of population stability [because] there is more ice pack and prey availability," said David Koons, a National Geographic grantee who studies animal populations at Utah State University, in Logan.

On Thin Ice

The southern parts of the polar bear's range, such as the southern Beaufort Sea, are warming faster than the northern regions and are thus more susceptible to melting sea ice.

As the ocean heats up due to global warming, Arctic sea ice has been locked in a downward spiral. Since the late 1970s, the ice has retreated by 12 percent per decade, and the decline has worsened since 2007, according to NASA.

It's not surprising that the southern Beaufort Sea and its bears are feeling the effects first and more dramatically than those in more northern areas, said Ian Stirling, a biologist at the University of Alberta, in Edmonton, who is studying climate change's impact on polar bears.
[351 words]

[Time 3]
Polar bears in this region are declining because they use sea ice as hunting platforms to catch their primary prey, seals. But "when that ice is there, it's really jumbled up [due to freezing and refreezing events]," said study leader Jeff Bromaghin, a U.S. Geological Survey statistician who studies wildlife population dynamics.

"The seals may be there, but [the polar bears] can't get to them."

In 2007, the U.S. Geological Survey estimated that the global polar bear population will shrink to a third of its current size by 2050, due to loss of habitat and less access to prey. From the Beaufort numbers, it looks like things are right on track, or perhaps even speeding up, according to Bromaghin.

"Nothing in this study contradicts the 2007 estimates," said Bromaghin.

"Actually, observed loss of sea ice in the Arctic has been greater than earlier climate models. We're losing ice faster than forecasted."

Can Polar Bears Cope?

Faced with a less icy Arctic, some polar bears appear to be coping on land, in part by adding snow goose eggs and caribou to their diet.

For a species that needs fat-rich, energy-dense foods, though, a diverse palate might not be enough, according to Bromaghin.

"Sure, they're starting to use land when food sources are limited. They'll eat whatever they can catch. But it's not enough to sustain them in the long run," he said.

"Every scrap of evidence suggests that polar bears are linked to sea ice. There's no evidence they can live on land."

The fate of the species also remains unclear because so little is known about the understudied populations in the high Arctic, Utah State's Koons noted.

Those bears may be in similarly dire straits, but it's just undocumented, the University of Alberta's Stirling pointed out.

"The fundamental concept is simple," he said. "As we continue to lose ice, particularly during key feeding periods, numbers of polar bears will decline."
[320 words]

Source: National geography
http://news.nationalgeographic.com/news/2014/11/141119-polar-bears-arctic-warming-animals-science-alaska/

As Sea Ice Shrinks, Can Polar Bears Survive on Land?
The predators can stay alive on goose eggs and caribou, scientist argues.
by Emma Marris  |  17 July 2014

Here's one possible summer menu for polar bears being forced to stay on land due to a lack of reliable sea ice: 60 snow goose egg clutches, 53 goslings, 63 adult geese, 3 caribou calves, and 3 adult caribou. Garnish with berries.

[Time 4]
Linda J. Gormezano, an ecologist at the American Museum of Natural History in New York City, isn't a polar bear chef. But she has been figuring out what polar bears might have to eat to survive increasingly long ice-free seasons in the western part of Canada's Hudson Bay area

Her calculations, presented this week at the North America Congress for Conservation Biology in Missoula, Montana, suggest that the predators may be able to survive for six months on land-based foods, and, because of climate change, they may have to.

Other scientists have warned that a lack of sea ice due to warming temperatures in the Arctic—and declining seal prey populations—could drive this population extinct by 2020.

There are fewer than a thousand bears in the western Hudson Bay, out of a total global population of up to 25,000, but these bears are among the most visible.

They stay on the sea ice as long as it lasts, eating seals. When the sea ice breaks up, they come on land. During the land season, tourists travel to Churchill, Manitoba, to go out among the bears in special "tundra buggies."

The conventional wisdom has been that polar bears don't eat on land or do much at all except snooze and conserve their energy before the bay refreezes.

But as the climate warms, the sea ice doesn't last as long. Already the bears are showing up on land, on average, three weeks earlier than in the 1980s, according to Gormezano. And by the late 2060s, the western Hudson Bay could be ice free for up to six months.
[267 words]

[Time 5]
Turf, Not Surf

In 2010 an analysis of the bears' energy needs by ecologist Peter Molnar—now at Princeton University—and his colleagues suggested that six months without food would kill 28 to 48 percent of adult male polar bears. At that rate, the population would likely crash.

But this analysis assumed that bears don't eat anything on land. Gormezano said this isn't true.

Her analysis of polar bear poop and observations of behavior suggest that the bears eat lots of land food, including lesser snow geese and their eggs, as well as caribou. So as part of her Ph.D. work under polar bear field biologist Robert F. Rockwell, she repeated Molnar's analysis but added varying levels of these foods.

Bears that come ashore fat and sleek in May in the 2060s, she predicts, will be able to keep their energy reserves topped up with the goose eggs that become available a few weeks later and by the odd caribou calf.

An adult male in bad condition would need the full menu of tundra foods listed above to make it through the ice-free months. Gormezano's analysis considered adult males, as did Molnar's, because the math is more straightforward without factoring in the demands of growth or reproduction.

But her observations show that typically females and cubs chase geese and gnaw on caribou.

Polar Bear Decline

An unanswered question is whether the energetic cost of chasing after a goose or a caribou is worth the calories the food supplies. If so, there are lots and lots of geese and, these days at least, plenty of caribou in the Hudson Bay area, Gormezano said.

"There is potential for this to prevent starvation under the scenarios that Molnar put out there," she said. "However, it does depend on how much energy they spend getting this food."

Molnar hasn't looked at the analysis in depth, but he's skeptical, given trends in this population of polar bears

"The population has declined quite substantially between 1995 and 2005," he said.

"We know that their body conditions are getting worse. They are getting thinner. The real question is not, Can you put land-based feeding into the models or not? The real question is, Why aren't the bears eating enough to prevent declines?"
[375 words]

Source: National Geography
http://news.nationalgeographic.com/news/2014/07/140717-polar-bears-goose-eggs-global-warming-arctic-environment/

How do polar bears stay warm? Research finds an answer in their genes

By Charlotte Hsu | 10 Feb 2014

In the winter, brown and black bears go into hibernation to conserve energy and keep warm. But things are different for their Arctic relative, the polar bear. Within this high-latitude species, only pregnant females den up for the colder months. So how do the rest survive the extreme Arctic winters?

[Time 6]

New research points to one potential answer: genetic adaptations related to the production of nitric oxide, a compound that cells use to help convert nutrients from food into energy or heat.

In a new study, a team led by the University at Buffalo reports that genes controlling nitric oxide production in the polar bear genome contain genetic differences from comparable genes in brown and black bears.

"With all the changes in the global climate, it becomes more relevant to look into what sorts of adaptations exist in organisms that live in these high-latitude environments," said lead researcher Charlotte Lindqvist, PhD, UB assistant professor of biological sciences.

"This study provides one little window into some of these adaptations," she said. "Gene functions that had to do with nitric oxide production seemed to be more enriched in the polar bear than in the brown bears and black bears. There were more unique variants in polar bear genes than in those of the other species."

The paper, titled "Polar Bears Exhibit Genome-Wide Signatures of Bioenergetic Adaptation to Life in the Arctic Environment," appeared Feb. 6 in the journal Genome Biology and Evolution. Co-authors include scientists from UB, Penn State University, the U.S.G.S. Alaska Science Center, Durham University and the University of California, Santa Cruz.

The genetic adaptations the research team saw are important because of the crucial role that nitric oxide plays in energy metabolism.

Typically, cells transform nutrients into energy. However, there is a phenomenon called adaptive or non-shivering thermogenesis, where the cells will produce heat instead of energy in response to a particular diet or environmental conditions.

Levels of nitric oxide production may be a key switch triggering how much heat or energy is produced as cells metabolize nutrients, or how much of the nutrients is stored as fat, Lindqvist said.

"At high levels, nitric oxide may inhibit energy production," said Durham University's Andreanna Welch, PhD, first author and a former postdoctoral researcher at UB with Lindqvist. "At more moderate levels, however, it may be more of a tinkering, where nitric oxide is involved in determining whether -- and when -- energy or heat is produced."

[355 words]

[the rest]

The research is part of a larger research program devoted to understanding how the polar bear has adapted to the harsh Arctic environment, Lindqvist said.

In 2012, she and colleagues reported sequencing the genomes of multiple brown bears, black bears and polar bears.

In a paper in the Proceedings of the National Academy of Sciences, the team said comparative studies between the DNA of the three species uncovered some distinctive polar bear traits, such as genetic differences that may affect the function of proteins involved in the metabolism of fat -- a process that's very important for insulation.

In the new study, the scientists looked at the mitochondrial and nuclear genomes of 23 polar bears, three brown bears and a black bear.

[122 words]

Source: Science Daily

http://www.sciencedaily.com/releases/2014/02/140210135826.htm

Going

Part III: Obstacle

How Old Is the Endangered Polar Bear?
A new genetic analysis suggests the polar bear may have survived past climate changes
By David Biello | 23 July 2012

[Paraphrase 7]
Polar bears may have trod the planet for millions of years, according to a new genetic analysis. That suggests the white-coated, massive bears have weathered previous natural climate changes, and may predate the Arctic ice that is their preferred—and only—habitat today, which is why the species future remains uncertain presently.

"There's no guarantee that they'll survive this time," says geneticist Webb Miller of Pennsylvania State University, an author of the study published July 23 in Proceedings of the National Academy of Sciences. After all, Miller notes, the species currently lacks much genetic diversity to help it adapt to changing conditions as well as facing unprecedented threats such as heavy metal pollution accumulating in the Arctic. By better understanding how old the species is, the scientists hope to better understand what might be done to allow the polar bear to cope with onrushing climate change and other existential challenges.

By analyzing the genomes of 28 bears—polar bears, including a roughly 120,000-year-old specimen from Norway's Svalbard archipelago, as well as modern brown bears and black bears—the scientists in effect read back in time to a common ancestor at least four million years ago. That finding conflicts with a genetic analysis published inScience earlier this year that suggested the species was only 600,000 years old or so, which the team behind the new research suggests may result from misreading past interbreeding events with closely related brown bears.

In fact, the key problem here may be that technically the polar bear may not be aspecies at all. "If one defines that two species separate as when they cannot produce viable offspring, then perhaps brown bears and polar bears aren't yet separate species," Miller admits.
What makes a polar bear a polar bear? There's the white coat and black skin as well as less visible differences like a thicker layer of subcutaneous fat layers and richer milk. These and other unique features of adaptation to the harsh conditions of Arctic life have convinced biologists that the polar bears represent a unique type of animal—a species of its own. After all, the brown bear that is its closest living relative lacks all of these adaptations, looks different, eats different food and would not fare well in the harsh conditions out on the Arctic ice.

Yet, brown bears and polar bears, when they meet, can mate, as evidenced both by the genetic record and observations in the wild. Because polar bears have been spending more time off the ice in recent years, they appear to have begun to interbreed with adjacent brown bear populations, and some of these hybrids are into their second generations. If the basic definition of a species is a group of organisms capable of mating and producing fertile offspring only within their own group, the polar bear and brown bear fail to qualify.

Such interbreeding between bear species makes genetic analysis that much more difficult. After all, if the species interbreed even once, that single event can appear to determine the point at which the two species diverged if a scientist happens to analyze only the portion of the genome influenced by that mating event. And the mixing of genetic material has been going on for a long time between polar and brown bears, making disentangling their genetic history that much harder.

In the case of the polar bear, the differing estimates also rely, on the one hand, on fossil information about when the panda bear became an independent species and, on the other, the mutation rate of primates, including humans. By calibrating what scientists call the molecular clock—the hypothesis that mutation occurs at a predictable rate—to the panda separation 12 million years ago, one group of researchers suggests the polar bear's appearance as a species is a relatively recent phenomenon. By suggesting that bears undergo mutation at roughly the same rate as humans, who also may have interbred with closely related hominins like the Neandertals, the other group finds a much older lineage. "One can already suspect that the mutation rate of carnivores, especially bears, will be most likely different from that of primates," argues bioinformaticist Axel Janke of the Biodiversity and Climate Research Center in Germany, one of the researchers behind the study published inScience.
Regardless of how old the polar bear is as a species, or whether it's a species at all, the purpose of such studies is to gain a better understanding of the great white bear's ability to survive in the Arctic, which is now rapidly transforming as a result of accelerated global warming. Understanding how the bears weathered past climate changes or sea ice–free conditions might help identify what could be done to help the unique animal survive.

The new analysis suggests that the key may be refuges with suitable environmental conditions. For example, the polar bear specimen from roughly 120,000 years ago survived in Svalbard during a warm interglacial period because that Arctic archipelago remained more frozen than other areas. "It is possible that Svalbard may have provided one such important refuge during warming periods, in which small polar bear populations survived and from which founder populations expanded during cooler periods," argues biologist Charlotte Lundqvist of the University at Buffalo, The State University of New York, who is a co-author of the new study. That could also explain modern polar bear's relative lack of genetic diversity, which appears to have been declining for 500,000 years. The new genetic analysis found less difference between polar bears living on opposite sides of the Arctic than between Asians and Europeans.

But places like the ancient icy oasis of Svalbard, should they endure relatively unchanged through human-induced global warming, may not be enough to save the polar bear this time. After all, the bear faces the impacts of human pollution, hunting and increased activity in the Arctic, such as shipping and oil drilling as well as the changes in its sea ice habitat. "There is no species that deserves careful study at this time more than the polar bear," Miller says. "I want my great-grandchildren to be able to see them."
[1019 words]

Source: Scientific America
http://www.scientificamerican.com/article/genetic-analysis-sets-the-clock-back-on-emergence-of-polar-bears/

cesievan

居然赶上沙发了！！！谢谢整理～
11.25[obstacle] 6:53
questions and study about polar bear: why they can survive in such a cold weather with also the significant change in Arctic
key point: bears interbreed: brown bear and polar polar
polar bears’ genes are less diversity
the key to suitable the environment is refuges

carrieli0805

感谢@古月小破烂 @Going
time2: 2:30
the population of polar bear has been declining since 2001. there are some unstudied groups because they live in remoteness area. From the studied group, there are five decreasing, four stable, and only one surprisingly increase. However, the overall in number declined. Location is most important factor to this variability. because of the globe warming, the ice pack is melting and become thinner.
time 3: 2:50
the ice pack is a platform for polar bears to prey, and the melting speed is far faster than what the scientists imagined.  Because of lack of solid place on the ocean, the bears start to find some food on land, but those plants are not enough for them to sustain their energy. they still need a plenty of fat fish. A forecast shows that the population of polar bear will be one third of current number in 2050
time 4: 2:30
can polar bear survive on the land? scientist said that the bear can live on land for less then 6 month and eat some goose eggs or geese. they are standing in the melting icing to find seals. In the past, they used to live on land only for snooze or keep their energy, but now because of the climate change, they have to live on land more than 6 month during the ice free period.
time 5: 3:50
if the free ice time is more than 6 month, how can bear survive? one scientist said that they can find a lot of food on land such as the goose eggs, geese or caribous. But the question is whether the energy that the bear get from those preys is more than that they spend on chasing them since the adult and productive bears' consuming amount will be larger than younger. However, another scientist said that the real problem is not about the energy, it is whether the bears will still strong enough at that time, since lack of sea food bears are becoming weak.
time 6: 3:12
some genes are different between polar bears and black or brown bears. The polar bears' gene included some oxide that can help them to keep warm without eating and spend less energy to transfer to heat.

HaiqingYU

Thanks for sharing!!!!
02:07-> The number of whole polar bear is decreasing , especially in the southern part.
02:13-> The loss of habitat and less access to prey make life difficult for polar bear, some start to prey inland.
01:44-> Loss of ice forces the polar bear to prey inland earlier than in the 1980s.
02:24-> A study and observation: The tendency for polar bear to eat Inland animal
02:36-> The special gene that polar bear have enable it to resist the cold temperature.
06:22-> Comparison of gene of polar bear and  brown bear, panda bear is to trace the time that the polar bear has exist on earth.
            The lack of genetic variety of this species and it face the worsening living environment.

lz721

thanks！
1:55
2:21
1:47
2:43
2:42
0:53

joannahope

time 2 3'17 the species as a whole is decreasing in unmber. the habitats of the polar bears  the southern part of the polar bears range become smaller because the ocean heats up to the global warming and the Actic sea ice melted dramatically than the northern sea area.In the mean time,the sea ice in the southern sea part has been meilted ,helping the polar bears hunting  the preys.
time33'30 the reason for why the sea ice as the hunting platform and the expert get some prediction of the numbers of the polar bears  which will decline 1/3 of right now in 2050.the number of the polar bears will decline due to the melted sea ice.but luckily,the resechers find that the polar bears are changing their habits .they eat other things for survivor.
time 4 2'20 bears may change theri habit to hunt land-based food
time54'50  6months no food they wll die 28-48 percent bears.so they eat land based food such as the goose eggs,But the whether they could survival is the problems ,it depends on how much they spend the energy on food
time 64'20 the genetic adaption procedure .the polar bears product a genetic adaption production of nitrice oxide which can inhibit the energy production and decided whether and when to product the energy.

Phoebedyf2

time2: 1'55'' (184wpm)
Polar bears as a whole is decreasing in number, but some species of them are actually stable, even increasing. The number is depend on the location. Since ices in northern areas are thicker and larger, and temperature is higher than northern areas, it is more likely for polar bears to live in northern areas.

time3: 2'03'' (160wpm)
Polar bears cannot hunt on such thin and small picies of ice, so the food for them is limited. There is few possibilties that they can survive on land. Therefore,if we have fewer ice, then we will have fewer polar bears.

tiem4: 1'45'' (152wpm)
Although polar bears are hard to eat or hunt on lands, they have to move to land for some months because the warmer climate melt the ices they live on.

time5: 2'24'' (156wpm)
Though polar bears don't eat nothing on land, but what matters is that wheather the energy comsumes while hunting can be maked up by the energy provided by the animals the bears hunt for.

time6: 2'04'' (177wpm)
The genetic adpation is the cruical reason for providing energy to the polar bears, because the nitric oxide can control the matabolize level.

Obstacle: 6'40''(154wpm)
It is harder to determine wheather the polar bears survive the harsh climates in the past and how old the polar bears are, because they mate to the brown bears and produce offsprings with more complicated genes.
The key to sustain the populations of polar bears may be refuges with suitable environmental conditions.

sumy217

1. The number of polar bears is declining as a whole species.

2.Losing of ice makes polar bears have less sapce to live and prey.

3.The polar bears can only survive about 6 months on land if there is no ice for them to live.

4.Polar bears can eat food on land to survive.

5.There is a kind of cell in certain species of polar bears named nitric oxide traht can help convert nutrients in food into energy or heat.