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VOA慢速英语 2007 0612b

时间:2007-12-13 06:07:26

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(单词翻译)

VOICE ONE:

This is SCIENCE IN THE NEWS, in VOA Special English.  I'm Barbara Klein.

VOICE TWO:

And I'm Steve Ember.  On our program this week, we will tell about an animal that can reproduce without mating.  We also will tell about a Swedish man who developed a naming system for all living things.  And, we answer a listener's question about weight loss. 

(MUSIC)

VOICE ONE:

 
File photo of a hammerhead shark, the kind involved in the first known case of asexual reproduction in sharks.
The birth of a shark in the United States has been confirmed as the first case of a female shark reproducing without a male shark.  Scientists from Florida, Nebraska and Northern Ireland studied genetic1 material taken from a baby hammerhead shark.  The baby shark was born six years ago at a zoo in Omaha, Nebraska.  At the time, its mother had been living without male sharks for three years.

Another fish was said to have killed the baby shark shortly after it was born.  Recently, tests showed the baby had no genetic material from a male shark.  The findings were reported in the publication Biology Letters.

VOICE TWO:

At the time of the birth, researchers believed that the mother had possibly used reproductive fluid received from a male shark years earlier.  Female sharks are able to store such fluid from male sharks.  However, no shark has been known to do this for several years.

Instead, the scientists found the mother’s own genetic material combined when her egg was produced.  This form of reproduction involving only one animal is called parthenogenesis.  It is also known as asexual reproduction. 

VOICE ONE:

Asexual reproduction has been known to happen in some animals, including snakes and lizards2.  But it has never been confirmed in mammals.  The shark's birth was the first time asexual reproduction had been observed in a shark.  It has yet to be observed in animals that live in the wild. 

Scientists say the discovery may also explain growing numbers of sharks born in captivity3 without males present.  However, genetic material from these sharks must also be tested to confirm asexual reproduction.

VOICE TWO:

Scientists now wonder if animals living in the wild also reproduce in this way.  Many shark populations are decreasing because people are killing4 too many of the animals.  The asexual form of reproduction could help population numbers.  Yet scientists say it could also be harmful for the species itself. 

Biologists say that sharks born asexually with only their mother’s genetic material will have less chance of surviving than other sharks.  Genetic material from a male and female helps living creatures to better deal with disease and other threats.  If sharks in the wild are reproducing asexually, their young will be genetically5 weaker than those produced sexually. 

(MUSIC)

VOICE ONE:

 
Carl Linnaeus
Last month, scientists around the world celebrated6 the birthday of an important man in the history of science.  His name was Carl Linnaeus.  He was born three hundred years ago in Sweden. 

Carl Linnaeus is remembered for developing a system of scientific names for all the living things on Earth.  Experts say his system continues to influence the way people think about the natural world.

VOICE TWO:

Linnaeus was a medical doctor.  He also was very interested in plants.  In seventeen thirty-five, he produced a book that listed all the known plants in the world by their sexual parts.  The book was called "Systema Naturae," or "System of Nature." 

Linnaeus later published two more books.  They proposed a system of dividing and ordering plants by groups.  These publications listed and ordered all the known plants and animals in the world.  That was more than seven thousand kinds of plants and more than four thousand kinds of animals.

Linnaeus continued to make changes in his system and publish books describing them.  The tenth version of "Systema Naturae" was published more than twenty years after the first one.  The naming system he described in that book is the one that has been used ever since by scientists.

VOICE ONE:

The system that Linnaeus used to organize all living things started with the largest group, called a kingdom.  He divided all living things into one of three kingdoms: plant, animal, or mineral.  Members of each kingdom were then placed into increasingly smaller groups.  Linnaeus' system was the first to place human beings in the same group as animals that walk on two legs.

The main part of the system that survives today combines two groups that have biological meaning.  It is the two-word description of an organism based on its physical appearance: the genus name and the descriptor.  A good example is the expression Linnaeus used to describe human beings and that we continue to use -- homo sapiens. 

VOICE TWO:

Scientists have been making changes to his naming system for more than two hundred years.  Today, some experts want to re-organize the system.  They say this is needed because of the scientific progress that has been made since Linnaeus' time.  For example, biology experts want changes because knowledge of genetic material has created much new information. 

Some people are calling for a system that would group organisms with a common history.  But others feel there is no real agreement as to how to place new discoveries in groups.  They say Linneus' system has been used for so long that it would be very difficult to change.

Scientists say the main reason the system survives is because it is simple.  They say its use makes it possible for persons who speak different languages to understand each other, and agree on what they are talking about.  The system also makes it easy for scientists today to identify all the ten million known species of plants and animals.  That is many more living things than were known during Carl Linnaeus' lifetime.          

(MUSIC)

VOICE ONE:                              

Finally, a listener has written from China for advice about how to lose weight.  Michael in Shanghai says he is twenty-six years old and has been severely7 overweight for most of his life.

Doctors say this condition, also known as obesity8, is complex.  A doctor may advise medical interventions9 in addition to changes in behavior.  But experts say the most successful weight-loss plans include a well-balanced diet and exercise.

VOICE TWO:

People who want to avoid weight gain have to balance the number of calories they eat with the number of calories they use.  To lose weight, you can reduce the number of calories you take in, or increase the number you use, or both.

Experts at America's National Institutes of Health say a person wishing to lose weight should have an hour of moderate to intensive physical activity most days of the week.  This could include fast walking, sports or strength training.

You should also follow a nutritious10 eating plan and take in fewer calories than your body uses each day.

VOICE ONE:

A recent study looked at four of the most popular dieting plans in the United States.  Researchers at Stanford University in California studied more than three hundred overweight women.  Most of the women were in their thirties and forties.

Each woman went on one of the four plans: Atkins, The Zone, Ornish or LEARN.  The women attended diet classes and received written information about the food plans.

At the end of a year, the women on the Atkins diet had lost the most -- more than four and one-half kilograms on average.  They also did better on tests including cholesterol11 levels and blood pressure.  The Journal of the American Medical Association published the findings. 

VOICE TWO:

Christopher Gardner led the study.  He says the Atkins diet may be more successful because of its simple message to lower intake12 of sugars.  Also, he says the advice to increase protein in the diet leads to more satisfying meals.

He says there was not enough money to also study men, but that men would probably have similar results.

VOICE ONE:

Another report suggests that only a small minority of people have long-term success with dieting.  Researchers at the University of California, Los Angeles, medical school found that most dieters regained13 their lost weight within five years.  And often they gained back even more.  But those who kept the weight off generally were the ones who exercised.

The report was based on thirty-one studies.  It was published in the journal American Psychologist. 

(MUSIC)

VOICE TWO:

This SCIENCE IN THE NEWS was written by Brianna Blake, Nancy Steinbach and Caty Weaver14.  Our producer was Mario Ritter.  I'm Steve Ember.

VOICE ONE:

And I'm Barbara Klein.  Join us again at this time next week for more news about science in Special English on the Voice of America.


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点击收听单词发音收听单词发音  

1 genetic PgIxp     
adj.遗传的,遗传学的
参考例句:
  • It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
  • Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。
2 lizards 9e3fa64f20794483b9c33d06297dcbfb     
n.蜥蜴( lizard的名词复数 )
参考例句:
  • Nothing lives in Pompeii except crickets and beetles and lizards. 在庞培城里除了蟋蟀、甲壳虫和蜥蜴外,没有别的生物。 来自辞典例句
  • Can lizards reproduce their tails? 蜥蜴的尾巴断了以后能再生吗? 来自辞典例句
3 captivity qrJzv     
n.囚禁;被俘;束缚
参考例句:
  • A zoo is a place where live animals are kept in captivity for the public to see.动物园是圈养动物以供公众观看的场所。
  • He was held in captivity for three years.他被囚禁叁年。
4 killing kpBziQ     
n.巨额利润;突然赚大钱,发大财
参考例句:
  • Investors are set to make a killing from the sell-off.投资者准备清仓以便大赚一笔。
  • Last week my brother made a killing on Wall Street.上个周我兄弟在华尔街赚了一大笔。
5 genetically Lgixo     
adv.遗传上
参考例句:
  • All the bees in the colony are genetically related. 同一群体的蜜蜂都有亲缘关系。
  • Genetically modified foods have already arrived on American dinner tables. 经基因改造加工过的食物已端上了美国人的餐桌。 来自英汉非文学 - 生命科学 - 基因与食物
6 celebrated iwLzpz     
adj.有名的,声誉卓著的
参考例句:
  • He was soon one of the most celebrated young painters in England.不久他就成了英格兰最负盛名的年轻画家之一。
  • The celebrated violinist was mobbed by the audience.观众团团围住了这位著名的小提琴演奏家。
7 severely SiCzmk     
adv.严格地;严厉地;非常恶劣地
参考例句:
  • He was severely criticized and removed from his post.他受到了严厉的批评并且被撤了职。
  • He is severely put down for his careless work.他因工作上的粗心大意而受到了严厉的批评。
8 obesity Dv1ya     
n.肥胖,肥大
参考例句:
  • One effect of overeating may be obesity.吃得过多能导致肥胖。
  • Sugar and fat can more easily lead to obesity than some other foods.糖和脂肪比其他食物更容易导致肥胖。
9 interventions b4e9b73905db5b0213891229ce84fdd3     
n.介入,干涉,干预( intervention的名词复数 )
参考例句:
  • Economic analysis of government interventions deserves detailed discussion. 政府对经济的干预应该给予充分的论述。 来自辞典例句
  • The judge's frequent interventions made a mockery of justice. 法官的屡屡干预是对正义的践踏。 来自互联网
10 nutritious xHzxO     
adj.有营养的,营养价值高的
参考例句:
  • Fresh vegetables are very nutritious.新鲜蔬菜富于营养。
  • Hummingbirds have discovered that nectar and pollen are very nutritious.蜂鸟发现花蜜和花粉是很有营养的。
11 cholesterol qrzzV     
n.(U)胆固醇
参考例句:
  • There is cholesterol in the cell of body.人体细胞里有胆固醇。
  • They are determining the serum-protein and cholesterol levels.他们正在测定血清蛋白和胆固醇的浓度。
12 intake 44cyQ     
n.吸入,纳入;进气口,入口
参考例句:
  • Reduce your salt intake.减少盐的摄入量。
  • There was a horrified intake of breath from every child.所有的孩子都害怕地倒抽了一口凉气。
13 regained 51ada49e953b830c8bd8fddd6bcd03aa     
复得( regain的过去式和过去分词 ); 赢回; 重回; 复至某地
参考例句:
  • The majority of the people in the world have regained their liberty. 世界上大多数人已重获自由。
  • She hesitated briefly but quickly regained her poise. 她犹豫片刻,但很快恢复了镇静。
14 weaver LgWwd     
n.织布工;编织者
参考例句:
  • She was a fast weaver and the cloth was very good.她织布织得很快,而且布的质量很好。
  • The eager weaver did not notice my confusion.热心的纺织工人没有注意到我的狼狈相。

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