1. 英语小说: 小说下载 在线小说 读书推荐
  2. 英语短文: 家庭保健 健康生活 幸福情感
  1. 能力: 英语口语 英语听力 职场英语 商务英语 影视英语 少儿英语 行业英语 双语阅读
  2. 考试: 英语四级 英语六级 笔译口译 英语单词 考研英语 课堂英语 英语考试 新概念

英语听力

听力入门英语演讲VOA慢速英语美文听力教程英语新闻名校课程听力节目影视听力英语视频

猛犸象:古老物种的“基因图”

kira86 于2008-12-09发布 l 已有人浏览
增大字体 减小字体
Mapping the Genes of the Woolly Mammoth (No Living Example Needed)迅雷专用高速下载 VOICE ONE: This is SCIENCE
    小E英语欢迎您,请点击播放按钮开始播放……

Mapping the Genes of the Woolly Mammoth (No Living Example Needed)


迅雷专用高速下载

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 a genetic map for an animal that disappeared long ago. We will tell about an unusual-looking insect from South America. And we will tell about a reported link between animals and health problems in children.

(MUSIC)

VOICE ONE:

Scientists say they have completed most of a genetic map for an ancient creature -- the woolly mammoth. The map is said to be the first to show the genetic structure of an animal that no longer exists.

Biologists at the Pennsylvania State University studied the remains of two woolly mammoths from Siberia. One mammoth lived twenty thousand years ago. The other lived at least sixty thousand years ago.

VOICE TWO:

The woolly mammoth belongs to a species, or group, linked to the modern African elephant. With its thick, long hair, the now extinct mammoth was able to survive in cold weather. Lead researcher Stephan Schuster says the mammoth and African elephant share more than ninety-nine percent of their genetic material.

STEPHAN SCHUSTER:"So this tells you that they are very, very similar. And also, just because the mammoth is extinct does not mean it is an ancient elephant. It is as modern as an Asian or African elephant. But unfortunately, it had the bad luck to go extinct before today."

VOICE TWO:

Mister Schuster and the research team studied genes, or DNA, that were found in long pieces of mammoth hair. They say genes from hair are better to study than those from bones or other remains. That is because the genes from hair are less likely to mix with other kinds of DNA.

VOICE ONE:

The researchers say they were able to uncover about seventy percent of the mammoth's genome, or genetic structure. They also say the study will help scientists better understand how elephants evolved, or developed.

Mister Schuster says the information shows the mammoth evolved from the African elephant six million years ago. Mammoths disappeared about ten thousand years ago.

VOICE TWO:

The researchers hope their work will also increase understanding of how the woolly mammoth evolved and why it died out. Their findings were reported in the publication Nature.

The study also provides some information that would be needed to re-create the mammoth. But scientists say such an animal would not be possible any time soon -- if ever.

(MUSIC)

VOICE ONE:

Some researchers like to study animals that disappeared long ago. But others want to discover new species -- creatures that may have existed for thousands of years, but remain unknown to scientists.

One recent discovery was made in Brazil. This is where a researcher from the United States discovered a new ant species. Christian Rabeling is a graduate student at the University of Texas in Austin. He believes the species could be linked to some of the earliest kinds of ants to have evolved.

VOICE TWO:

The ant has a very unusual appearance. It is extremely light in color and has no eyes. It also has large extensions from its head called mandibles. These are likely used to capture food.

Because of its appearance, the ant was given the scientific name Martialis heureka. The name means "ant from Mars."

The insect is two to three millimeters long. Scientists believe its appearance resulted from changes that took place for the ant to better live under the ground.

VOICE ONE:

Genetic testing shows the ant belongs to a new ant subfamily. There are twenty-one known ant subfamilies. The discovery marks the first time since nineteen twenty-three that a new ant subfamily has been identified. Since then, new subfamilies have only been found from fossilized ant remains.

The genes of the new ant also show that it comes from a species that first evolved from the wasp. Ants developed from these insects more than one hundred twenty million years ago. Some species changed to live in trees or in their leaves.

Scientists believe others like the new species may have evolved to live in the dirt. That would explain the ant's loss of eyes and light color.

VOICE TWO:

Christian Rabeling collected the only example of the new species in two thousand three. It was found among leaves in the Amazon rainforest. Mister Rabeling reported on the discovery in the Proceedings of the National Academy of Sciences. He says finding new ant species could help scientists understand more about the evolution of ants. He believes many other species have yet to be discovered in warm climates.

(MUSIC)

VOICE ONE:

Many families in the United States have at least one pet. The most popular are dogs, cats and fish. Some Americans own exotic, less traditional pets. They care for animals like hedgehogs, monkeys or snakes.

Recently, a report warned that non-traditional pets may cause serious health problems in children. The report appeared in Pediatrics, a publication of the American Academy of Pediatrics. It says families with children less than five years old should not have exotic pets. It says children that age should avoid contact with such animals in petting zoos, schools and other public places.

VOICE TWO:

The report says the number of exotic pets available in the United States has increased since nineteen ninety two. Many people find them easier to care for than other pets. For example, more than four million American homes have reptiles like snakes and turtles as pets.

Another exotic pet, the hedgehog, is native to Europe, Asia and Africa. But hedgehogs can now be found in forty thousand homes. Yet the animal also can spread salmonella infections. The sharp spines on their back also make it easier to spread infections like E. coli. Exotic pets also can cause allergic reactions and sicknesses like rabies.

VOICE ONE:

Larry Pickering was a lead researcher in the study. He says eleven percent of salmonella infections in children are believed to be caused by touching lizards or other reptiles. Salmonella can cause the uncontrolled expulsion of body wastes. It also can cause high body temperatures and stomach problems.

Children can become sick by kissing or touching animals and then putting their fingers in their mouths. Young children are especially at risk because their natural defenses against disease are still developing. Also at risk are other persons with weakened defense systems, older adults and pregnant woman.

VOICE TWO:

The report says parents need to be educated about the health risks caused by exotic pets. And, it says, families with children under the age of five should not own such animals.

It says parents should first talk with their children's doctors and animal experts to see if there is cause for concern. And, it suggests washing hands often to help decrease risks for disease.

(MUSIC)

VOICE ONE:

Bacterial meningitis must be treated with antibiotic drugs as soon as possible or the infection can cause hearing loss and brain damage. It can also kill.

A large area in Africa holds the world record for the most meningitis cases. Known as the meningitis belt, this area extends from Senegal in the west to Ethiopia in the east. More than two hundred fifty thousand people got sick there in nineteen ninety-six and nineteen ninety-seven. Twenty-five thousand of them died from meningitis. The disease still strikes the area from time to time.

VOICE TWO:

Nations along the meningitis belt agreed in September to support a campaign to protect their populations with a new vaccine. The World Health Organization will provide technical aid with the vaccine.

The campaign will also get help from weather experts. One partner in the effort is America's National Center for Atmospheric Research. It will make long-term weather predictions along the meningitis belt. Local health officials can then plan the best times to vaccinate people.

VOICE ONE:

The disease often strikes during dry, dusty weather. One possible reason is that dust can affect the breathing passages and people may be more open to infection. Another theory is that people may stay in their homes more during the dry season, making it easier to catch meningitis from others. The infections usually stop when the rainy season begins.

Weather experts will provide fourteen-day forecasts of atmospheric conditions. The weather program will start in Ghana next year.

(MUSIC)

VOICE TWO:

This SCIENCE IN THE NEW was written by Lawan Davis, Jerilyn Watson and Brianna Blake, who was also our producer. I'm Barbara Klein.

VOICE ONE:

And I'm Bob Doughty. Join us again next week for more news about science in Special English on the Voice of America.

猛犸(měngmǎ)(Mammuthus primigenins),古脊椎动物,哺乳纲,长鼻目,真象科。也称毛象(长毛象)。

猛犸是鞑靼语“地下居住者”的意思,是世界上曾经最大的象。它身高体壮,有粗壮的腿,脚生四趾,头特别大,在其嘴部长出一对弯曲的大门牙。一头成熟的猛犸,身长达5米,体高约3米,门齿长1.5米左右,体重可达4~5吨。它身上披着黑色的细密长毛,皮很厚,具有极厚的脂肪层,厚度可达9厘米。从猛犸的身体结构来看,它具有极强的御寒能力。与现代象不同,它们并非生活在热带或亚热带,而是生活在北方严寒气候的一种古哺乳动物。大小近似现代的象,但头骨比现代的象短而高。体被棕褐色长毛。无下门齿,上门齿很长,向上、向外卷曲。臼齿由许多齿板组成,齿板排列紧密,约有30片,板与板之间是发达的白垩质层。曾生存于亚、欧大陆北部及北美洲北部更新世晚期的寒冷地区。苏联西伯利亚北部及北美的阿拉斯加半岛的冻土层中,都曾发现带有皮肉的完整个体,胃中仍保存有当地生长的冻土带的植物。我国东北、山东长岛、内蒙古、宁夏等地区也曾发现过猛犸的化石。科学家认为,地球上的猛犸是死于突如其来的冰期,使得死亡后的尸体即遭冻结,故未来得及腐烂。又由于千百年来在地穴中受到冰雪的保护掩埋,故能完整地被保存下来。在阿拉斯加和西伯利亚的冻土和冰层里,曾不止一次发现这种动物冷冻的尸体。


 1 2 下一页
分享到
添加到收藏

VOA慢速排行

  1. 1Money Talks 有钱能使鬼推磨 与钱有关的几
  2. 1VOA词汇掌故:It Will Not Wash 行不通;不起作
  3. 1VOA词汇掌故:Circus 与马戏团相关的成语表达
  4. 1VOA词汇掌故:与苹果相关的美国习惯用语
  5. 1VOA健康报道:放风筝能让人感到心情平静和愉
  6. 1VOA词汇掌故:Dime 形容经济形势不好的几个美
  1. 1VOA词汇掌故:Circus 与马戏团相关的成语表达
  2. 1Money Talks 有钱能使鬼推磨 与钱有关的几
  3. 1VOA词汇掌故:All About Names 和人的名字有
  4. 1VOA慢速: 科学家称夏威夷将有大型火山喷发
  5. 1美国专利局商标局发行第1000万份专利
  6. 1VOA慢速:朝美会晤 朝鲜选新加坡作为会面场所
  1. 1智能农场设备可以大大减少化学药品使用
  2. 1与Earth相关的所有地道英语表达
  3. 1VOA慢速:川普签署钢铝关税宣言 加拿大墨西哥
  4. 1VOA词汇掌故:All About Names 和人的名字有
  5. 1VOA慢速:亚马逊CEO贝佐斯成为全球首位千亿富
  6. 1卫冕冠军德国0:2出局!韩国助墨西哥出线

鸿运国际pt客户端

百度360搜索搜狗搜索