DNA显示马的进化过程
文章来源:未知 文章作者:meng 发布时间:2009-12-11 03:22 字体: [ ]  进入论坛
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Ancient DNA1 retrieved重新取回 from extinct horse species from around the world has challenged one of the textbook examples of evolution – the fossil record of the horse family Equidae over the past 55 million years. The study, published today in the Proceedings3 of the National Academy of Sciences, involved an international team of researchers and the Australian Centre for Ancient DNA (ACAD) based at the University of Adelaide.

Only the modern horse, zebras, wild asses野驴 and donkey survive today, but many other lineages血统,家系 have become extinct over the last 50,000 years.

ACAD Director Professor Alan Cooper says despite an excellent fossil record of the Equidae, there are still many gaps in our evolutionary6 knowledge. "Our results change both the basic picture of recent equid evolution, and ideas about the number and nature of extinct species."

The study used bones from caves to identify new horse species in Eurasia and South America, and reveal that the Cape7 zebra, an extinct giant species from South Africa, were simply large variants8 of the modern Plains zebra. The Cape zebra weighed up to 400 kilograms and stood up to 150 centimetres at the shoulder blades肩胛骨.

"The Plains zebra group once included the famous extinct quagga已绝种的南非小斑马, so our results confirm that this group was highly variable易变的,多变的 in both coat colour and size."

Lead author of the paper, Dr Ludovic Orlando from the University of Lyon, says the group discovered a new species of the distinct, small hippidion horse in South America.

"Previous fossil records suggested this group was part of an ancient lineage from North America but the DNA showed these unusual forms were part of the modern radiation辐射,发光 of equid species," Dr Orlando says.

A new species of ass4 was also detected on the Russian Plains and appears to be related to European fossils dating back more than 1.5 million years. Carbon dates on the bones reveal that this species was alive as recently as 50,000 years ago.

"Overall, the new genetic9 results suggest that we have under-estimated how much a single species can vary over time and space, and mistakenly assumed more diversity among extinct species of megafauna巨型动物," Professor Cooper says.

"This has important implications for our understanding of human evolution, where a large number of species are currently recognised from a relatively10 fragmentary碎片的,不完全的 fossil record.

"It also implies that the loss of species diversity that occurred during the megafaunal extinctions at the end of the last Ice Age may not have been as extensive as previously11 thought.

In contrast, ancient DNA studies have revealed that the loss of genetic diversity in many surviving species appears to have been extremely severe严厉的,苛刻的," Professor Cooper says. "This has serious implications for biodiversity生物多样性 and the future impacts of climate change."



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1 DNA 4u3z1l     
(缩)deoxyribonucleic acid 脱氧核糖核酸
参考例句:
  • DNA is stored in the nucleus of a cell.脱氧核糖核酸储存于细胞的细胞核里。
  • Gene mutations are alterations in the DNA code.基因突变是指DNA密码的改变。
2 retrieved 1f81ff822b0877397035890c32e35843     
v.取回( retrieve的过去式和过去分词 );恢复;寻回;检索(储存的信息)
参考例句:
  • Yesterday I retrieved the bag I left in the train. 昨天我取回了遗留在火车上的包。 来自《简明英汉词典》
  • He reached over and retrieved his jacket from the back seat. 他伸手从后座上取回了自己的夹克。 来自辞典例句
3 proceedings Wk2zvX     
n.进程,过程,议程;诉讼(程序);公报
参考例句:
  • He was released on bail pending committal proceedings. 他交保获释正在候审。
  • to initiate legal proceedings against sb 对某人提起诉讼
4 ass qvyzK     
n.驴;傻瓜,蠢笨的人
参考例句:
  • He is not an ass as they make him.他不象大家猜想的那样笨。
  • An ass endures his burden but not more than his burden.驴能负重但不能超过它能力所负担的。
5 asses asses     
n. 驴,愚蠢的人,臀部 adv. (常用作后置)用于贬损或骂人
参考例句:
  • Sometimes I got to kick asses to make this place run right. 有时我为了把这个地方搞得像个样子,也不得不踢踢别人的屁股。 来自教父部分
  • Those were wild asses maybe, or zebras flying around in herds. 那些也许是野驴或斑马在成群地奔跑。
6 evolutionary Ctqz7m     
adj.进化的;演化的,演变的;[生]进化论的
参考例句:
  • Life has its own evolutionary process.生命有其自身的进化过程。
  • These are fascinating questions to be resolved by the evolutionary studies of plants.这些十分吸引人的问题将在研究植物进化过程中得以解决。
7 cape ITEy6     
n.海角,岬;披肩,短披风
参考例句:
  • I long for a trip to the Cape of Good Hope.我渴望到好望角去旅行。
  • She was wearing a cape over her dress.她在外套上披着一件披肩。
8 variants 796e0e5ff8114b13b2e23cde9d3c6904     
n.变体( variant的名词复数 );变种;变型;(词等的)变体
参考例句:
  • Those variants will be preserved in the'struggle for existence". 这些变异将在“生存竞争”中被保留下来。 来自辞典例句
  • Like organisms, viruses have variants, generally called strains. 与其他生物一样,病毒也有变种,一般称之为株系。 来自辞典例句
9 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。
10 relatively bkqzS3     
adv.比较...地,相对地
参考例句:
  • The rabbit is a relatively recent introduction in Australia.兔子是相对较新引入澳大利亚的物种。
  • The operation was relatively painless.手术相对来说不痛。
11 previously bkzzzC     
adv.以前,先前(地)
参考例句:
  • The bicycle tyre blew out at a previously damaged point.自行车胎在以前损坏过的地方又爆开了。
  • Let me digress for a moment and explain what had happened previously.让我岔开一会儿,解释原先发生了什么。
TAG标签: evolution DNA horse
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