脊椎动物的面部进化历程-凯发k8官网

脊椎动物的面部进化历程
文章来源:未知 文章作者:enread 发布时间:2014-02-13 05:29 字体: [ ] 
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a team of french and swedish researchers have presented new fossil evidence for the origin of one of the most important and emotionally significant parts of our 1(解剖学): the face. using micron resolution x-ray imaging, they show how a series of fossils, with a 410 million year old armoured fish called romundina at its centre, documents the step-by-step assembly of the face during the 2 transition from 3 to 4 vertebrates. the research is published in nature on 12 february 2014.
 
vertebrates, or backboned animals, come in two basic models: jawless and jawed. today, the only jawless vertebrates are lampreys(七鳃类) and hagfishes(八目鳗鱼类), whereas jawed vertebrates number more than fifty thousand species, including ourselves. it is known that jawed vertebrates evolved from jawless ones, a dramatic anatomical(解剖的) 5 that effectively turned the face inside out.
 
in 6 of jawless vertebrates, blocks of tissue grow forward on either side of the brain, meeting in the midline at the front to create a big upper lip surrounding a single midline "7" that lies just in front of the eyes. in jawed vertebrates, this same tissue grows forward in the midline under the brain, pushing between the left and right nasal sacs which open separately to the outside. this is why our face has two 8 rather than a single big hole in the middle. the front part of the brain is also much longer in jawed vertebrates, with the result that our nose is positioned at the front of the face rather than far back between our eyes.
 
until now, very little has been known about the intermediate steps of this strange transformation. the scientists studied the 9 of romundina, an early armoured fish with 10, or placoderm, from arctic canada. the skull is part of a collection of the french national natural history museum in paris.
 
romundina has separate left and right nostrils, but they sit far back, behind an upper lip like that of a jawless vertebrate. "this skull is a mix of 11 and modern features, making it an 12 intermediate fossil between jawless and jawed vertebrates," says vincent dupret of uppsala university, one of two lead authors of the study.
 
by imaging the internal structure of the skull using high-energy x-rays at the european synchrotron (esrf) in grenoble, france, the authors show that the skull housed a brain with a short front end, very similar to that of a jawless vertebrate.
 
"in effect, romundina has the construction of a jawed vertebrate but the proportions of a jawless one," says per ahlberg, of uppsala university and the other lead author of the study. "this shows us that the organization of the major tissue blocks was the first thing to change, and that the shape of the head caught up afterwards," he adds.
 
by placing romundina in a sequence of other fossil fishes, some more primitive and some more advanced, the authors were able to map out all the main steps of the transition.
 
"without the intense x-rays produced at the esrf, we would not have been able to create a virtual representation of the internal structures of the skull" said sophie sanchez from the european synchrotron (esrf) in grenoble.


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1 cwgzh     
n.解剖学,解剖;功能,结构,组织
参考例句:
  • he found out a great deal about the anatomy of animals.在动物解剖学方面,他有过许多发现。
  • the hurricane's anatomy was powerful and complex.对飓风的剖析是一项庞大而复杂的工作。
2 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。
3 e80a5f80af3e56e3685b6223e6701c1a     
参考例句:
4 4cc237811a741e11498ddb8e26425e7d     
adj.有颌的有颚的
参考例句:
  • the color of the big-jawed face was high. 那张下颚宽阔的脸上气色很好。 来自辞典例句
  • she jawed him for making an exhibition of himself, scolding as though he were a ten-year-old. 她连声怪他这样大出洋相,拿他当十岁的孩子似的数落。 来自辞典例句
5 snfwo     
n.变化;改造;转变
参考例句:
  • going to college brought about a dramatic transformation in her outlook.上大学使她的观念发生了巨大的变化。
  • he was struggling to make the transformation from single man to responsible husband.他正在努力使自己由单身汉变为可靠的丈夫。
6 0e62a67414ef42288b74539e591aa30a     
n.晶胚;胚,胚胎( embryo的名词复数 )
参考例句:
  • somatic cells of angiosperms enter a regenerative phase and behave like embryos. 被子植物体细胞进入一个生殖阶段,而且其行为象胚。 来自辞典例句
  • evolution can explain why human embryos look like gilled fishes. 进化论能够解释为什么人类的胚胎看起来象除去了内脏的鱼一样。 来自辞典例句
7 o0iyn     
n.鼻孔
参考例句:
  • the indian princess wore a diamond in her right nostril.印弟安公主在右鼻孔中戴了一颗钻石。
  • all south american monkeys have flat noses with widely spaced nostril.所有南美洲的猴子都有平鼻子和宽大的鼻孔。
8 23a65b62ec4d8a35d85125cdb1b4410e     
鼻孔( nostril的名词复数 )
参考例句:
  • her nostrils flared with anger. 她气得两个鼻孔都鼓了起来。
  • the horse dilated its nostrils. 马张大鼻孔。
9 cetyo     
n.头骨;颅骨
参考例句:
  • the skull bones fuse between the ages of fifteen and twenty-five.头骨在15至25岁之间长合。
  • he fell out of the window and cracked his skull.他从窗子摔了出去,跌裂了颅骨。
10 cq9zzq     
n.口部;嘴
参考例句:
  • the antelope could not escape the crocodile's gaping jaws. 那只羚羊无法从鱷鱼张开的大口中逃脱。
  • the scored jaws of a vise help it bite the work. 台钳上有刻痕的虎钳牙帮助它紧咬住工件。
11 vswz0     
adj.原始的;简单的;n.原(始)人,原始事物
参考例句:
  • it is a primitive instinct to flee a place of danger.逃离危险的地方是一种原始本能。
  • his book describes the march of the civilization of a primitive society.他的著作描述了一个原始社会的开化过程。
12 s4qxe     
adj.无价的,非常宝贵的,极为贵重的
参考例句:
  • a computer would have been invaluable for this job.一台计算机对这个工作的作用会是无法估计的。
  • this information was invaluable to him.这个消息对他来说是非常宝贵的。
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