野生蛇中首次发现单性生殖-凯发k8官网

野生蛇中首次发现单性生殖
文章来源:未知 文章作者:enread 发布时间:2012-09-12 08:53 字体: [ ] 
(单词翻译:双击或拖选)
a form of 1 birth has been found in wild vertebrates for the first time.

野生脊椎动物界首次发现单性生殖案例。
a virgin female and her son
a virgin female and her son
 
researchers in the us caught pregnant females from two snake species and 3 analysed the litters.
 
that proved the north american pit 4 reproduced without a male, a phenomenon called facultative parthenogenesis(兼单性生殖) that has 5 been found only in captive species. 
 
scientists say the findings could change our understanding of animal reproduction and vertebrate evolution.
 
it was thought to be extremely rare for a normally sexual species to reproduce asexually.
 
first identified in domestic chickens, such "virgin births" have been reported in recent years in a few snake, shark, 6 and bird species.
 
crucially though, all such virgin births have occurred in 7, to females kept away from males.
 
virgin births in vertebrates in general have been viewed as "8 novelties", said warren booth, from the university of tulsa, oklahoma, us.
 
professor booth is lead author of a paper published in the royal society's biological letters that challenges this label.
 
he and his collaborators investigated virgin births in wild populations of two 9 separated and long-studied species of snake.
 
they captured pregnant copperhead and cottonmouth female pit-vipers from the field, where males were present.
 
the snakes gave birth, allowing the scientists to study the physical and 2 characteristics of the litters.
 
of the 22 copperheads(铜斑蛇), the scientists found one female that must have had a virgin birth. 
 
another single virgin birth occurred within the 37 cottonmouth litters.
 
"i think the frequency is what really shocked us," said prof booth.
 
"that's between 2.5 and 5% of litters produced in these populations may be resulting from parthenogenesis.
 
"that's quite 10 for something that has been considered an evolutionary novelty," he said.


点击收听单词发音收听单词发音  

1 phpwj     
n.处女,未婚女子;adj.未经使用的;未经开发的
参考例句:
  • have you ever been to a virgin forest?你去过原始森林吗?
  • there are vast expanses of virgin land in the remote regions.在边远地区有大片大片未开垦的土地。
2 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。
3 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
4 fb66fba4079dc2cfa4d4fc01b17098f5     
n.蝰蛇( viper的名词复数 );毒蛇;阴险恶毒的人;奸诈者
参考例句:
  • the fangs of pit vipers are long, hollow tubes. 颊窝毒蛇的毒牙是长的空心管子。 来自辞典例句
  • vipers are distinguishable from other snakes by their markings. 根据蛇身上的斑纹就能把┹蛇同其他蛇类区别开来。 来自辞典例句
5 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。
6 p0ex0     
n.蜥蜴,壁虎
参考例句:
  • a chameleon is a kind of lizard.变色龙是一种蜥蜴。
  • the lizard darted out its tongue at the insect.蜥蜴伸出舌头去吃小昆虫。
7 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。
8 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。
9 mg6xa     
adv.地理学上,在地理上,地理方面
参考例句:
  • geographically, the uk is on the periphery of europe. 从地理位置上讲,英国处于欧洲边缘。 来自辞典例句
  • all these events, however geographically remote, urgently affected western financial centers. 所有这些事件,无论发生在地理上如何遥远的地方,都对西方金融中心产生紧迫的影响。 来自名作英译部分
10 8vbx6     
adj.显著的,异常的,非凡的,值得注意的
参考例句:
  • she has made remarkable headway in her writing skills.她在写作技巧方面有了长足进步。
  • these cars are remarkable for the quietness of their engines.这些汽车因发动机没有噪音而不同凡响。
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