VOA慢速英语 2008 1104b（在线收听）

VOICE ONE:

This is SCIENCE IN THE NEWS in VOA Special English. I'm Bob Doughty.

VOICE TWO:

And I'm Barbara Klein. This week, we will tell about mammal populations in danger of disappearing. We will also tell about one kind of animal that disappeared long ago. And, we will examine some traditional beliefs about the viruses that cause influenza and the common cold.

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VOICE ONE:
　
The Iberian lynx is called critically endangered

A worldwide study has found that almost twenty-five percent of wild mammals are in danger of permanently disappearing. Scientific researchers considered all known mammal populations. The researchers say permanent disappearance threatens at least one thousand one hundred forty-one species or groups of animals. Mammals are the closest relatives to human beings.

The researchers are blaming loss of habitat, or living space, and hunting for threatened land mammals. They say water mammals suffer more from pollution, being hit by ships and caught in fishing nets.

VOICE TWO:

One thousand seven hundred experts worked on the study. They are from one hundred thirty countries. Their findings were reported at the World Conservation Conference of the International Union for Conservation of Nature in Barcelona, Spain.

The report was presented in connection with the Red List of Threatened Species. The World Conservation Conference announces the Red List each year. The list contains almost forty five thousand animals and plants. Of those, almost seventeen thousand, or about thirty eight percent, are threatened with extinction.

Some scientists say the report provides evidence that Earth's wildlife is going through widespread extinction. The last such period may have taken place millions of years ago, when dinosaurs became extinct.

VOICE ONE:

Jan Schipper led the writing of the report. He directs the I.U.C.N.'s program that observes animal populations worldwide.

Mister Schipper says up to thirty six percent of mammals could be facing extinction. He says this is true because not much information exists about some species. At least seventy-six mammals have permanently disappeared since fifteen hundred.

The director general of the I.U.C.N., Julia Marton-Lefevre, says human activity could cause loss of hundreds of species. She says that is a frightening sign of what is happening to habitats. Still, the report said human efforts also could help save some species. Miz Marton-Lefevre is calling for action to make that happen.

VOICE TWO:

For study purposes, the I.U.C.N. divides animals into groups. The scientists call animals that have disappeared, or almost disappeared, extinct or nearly extinct. A frog-like creature called Holdridge's toad was declared extinct. It lived only in Costa Rica.

Other divisions depend on the amount of threat the animals face. The animals in most danger are considered critically endangered.

For example, the Iberian lynx is called critically endangered. As few as eighty-four adult members of the large, cat-like animals remain alive.

The Red List identifies the second most threatened animals as endangered. The scientists named a Southeast Asian animal, the fishing cat, as among the endangered. Part of the fishing cat's wetland habitat no longer exists.

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VOICE ONE:

A new study suggests the last woolly mammoths in Siberia were native to North America. Scientists had believed these mammoths came from Europe or Asia.

The study involved genetic evidence from the remains of the ancient animal. Woolly Mammoths share an ancestor with modern-day elephants. The mammoth is recognizable for its long hair and large tusks.

VOICE TWO:

Woolly mammoths disappeared thousands of years ago, after Earth's most recent ice age. But mammoths were able to survive for thousands of years. During this period, they slowly changed to live in extremely cold climates.

Scientists believe the ancestors of woolly mammoths came from Africa. As the African mammoths moved north to Eurasia, scientists believe, they grew long hair to protect them from the extreme cold of Siberia.

VOICE ONE:

To better understand these animals, an international research team examined genetic material from more than one hundred woolly mammoth remains. The remains were found in North America, Europe and Asia. These fossils came from woolly mammoths that lived between forty-four thousand and eleven thousand years ago.

Hendrik Poinar is a molecular evolutionary geneticist at McMaster University in Ontario, Canada. He and his team examined genetic material from fossilized teeth and pieces of bones from woolly mammoths. They also examined results of earlier woolly mammoth studies.

VOICE TWO:

Until recently, many scientists believed that mammoths came from Europe and Asia because that is where the oldest fossils were found. Earlier studies of the mammoths involved only one continent at a time. The researchers discovered that mammals traveled back and forth several times between Eurasia and Alaska over thousands of years. The animals were able to travel on a land bridge that connected Siberia and Alaska during low sea levels.

VOICE ONE:

The researchers discovered that the mammoths were divided in three major groups. One group lived mainly in Asia. Another group lived mainly in the Americas. And, a third group lived in both places. They believe the American mammoths traveled back across the Bering Strait and in time replaced the other populations of mammoths.

The researchers believe the animals moved the great distances in search of food. A report with their findings was published in Current Biology. Other researchers disputed the findings. They say the study is based on only limited information.

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VOICE TWO:

Autumn and winter are cold and flu season -- when people are most likely to catch the viruses that cause influenza and the common cold.

Is the old advice true that wearing warm clothing will help prevent a cold? Or if you do get sick, should you follow the old saying, "Feed a cold and starve a fever"? And what about that fever? Should you take medication to reduce your temperature, or is it better to let the body treat the infection itself?

Everyone seems to have an answer. But how much value is there in popular wisdom?

VOICE ONE:

Doctor Alvin Nelson El Amin knows a lot about cold and flu season. He is medical director of the immunization program for the Los Angeles County Department of Public Health in California.

Doctor Nelson El Amin says studies may be just starting to provide evidence for long-held beliefs. For example, scientists for years dismissed the idea that getting cold and wet might cause colds or flu.

But recent studies have shown that cold temperatures cause stress on the body. That stress can create conditions more inviting to viruses. So maybe it does make sense to wrap up warmly before leaving home.

VOICE TWO:

And what about the advice to feed a cold and starve a fever? Doctor Nelson El Amin says you should eat if you have a cold and are hungry. But a higher than normal body temperature suggests a more serious problem. He says people are usually not hungry anyway when they have a high fever. Eating might even cause a person to vomit. But drinking plenty of liquids is important. A fever can easily dehydrate the body.

Finally, when should you treat a fever? Doctor Nelson El Amin says a fever should be treated if it stays at forty degrees centigrade or above for a day or more. A temperature that high can damage brain cells. The doctor also believes in treating a fever if it prevents a person from sleeping.

VOICE ONE:

Aspirin, acetaminophen and ibuprofen can all be used to reduce pain and fever. But aspirin should not be given to children because it can cause a rare condition.

One belief that Doctor Nelson El Amin wanted to make clear is wrong is that influenza vaccine can cause the flu. It cannot. Sometimes people get the flu from another person soon after they get vaccinated, so they blame the vaccine, he says.

But, flu vaccines do not protect everyone who gets them. Still, even if a person does get sick, the vaccine can limit the effects of the virus.

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VOICE TWO:

This SCIENCE IN THE NEWS was written by Jerilyn Watson, Caty Weaver and Brianna Blake, who also was our producer. I'm Barbara Klein.

VOICE ONE:

And I'm Bob Doughty. Read and listen to our programs at voaspecialenglish.com. Listen again next week for more news about science, in Special English, on the Voice of America.