首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
The fossil remains of the first flying vertebrates, the pterosaurs. have intrigued paleontologists for more than two centuries,
The fossil remains of the first flying vertebrates, the pterosaurs. have intrigued paleontologists for more than two centuries,
admin
2009-03-16
73
问题
The fossil remains of the first flying vertebrates, the pterosaurs. have intrigued paleontologists for more than two centuries, How such large creatures, which weighed in some eases as much as a piloted hang-glider and had wingspans from 8 to 12 meters, solved the problems of powered flight, and exactly what these creatures were — reptiles or birds — are among the questions scientists have puzzled over.
Perhaps the least controversial assertion about the pterosaurs is that they were reptiles. Their skulls, pelvises, and hind feet are reptilian. The anatomy of their wings suggests that they did not evolve into the class of birds. In pterosaurs a greatly elongated fourth finger of each forelimb supported a wing like membrane. The other fingers were short and reptilian, with sharp claws. In birds the second finger is the principal strut of the wing, which consists primarily of feathers. If the pterosaurs walked on ail fours, the three short fingers may have been employed for grasping. When a pterosaur walked or remained stationary, the fourth finger. and with it the wing, could only turn upward in an extended inverted V-shape along each side of the animal’s body.
The pterosaurs resembled both birds and hats in their overall structure and proportions. This is not surprising because the design of any flying vertebrate is subject to aerodynamic constraints. Both the pterosaurs and the birds have hollow bones, a feature that represents a savings in weight. In the birds, however, these bones are reinforced more massively by internal struts.
Although scales typically cover reptiles, the pterosaurs probably had hairy coats. T.H. Huxley reasoned that flying vertebrates must have been warm-blooded because flying implies a high rate of metabolism, which in turn implies a high internal temperature. Huxley speculated that a coat of hair would insulate against loss of body heat and might streamline the body to reduce drag in flight. The recent discovery of a pterosaur specimen covered in long, dense, and relatively thick hair—like fossil material was the first clear evidence that his reasoning was correct.
Efforts to explain how the pterosaurs became airborne have led to suggestions that they launched themselves by jumping from cliffs, by dropping from trees or even by rising into light winds from the surfaces of waves Each hypothesis has its difficulties. The first wrongly assumes that the pterosaurs’ hind feet resembled a hat’s and could serve as hooks by which the animal could hang in preparation for flight. The second hypothesis seems unlikely because large pterosaurs could not have landed in trees without damaging their wings. The third calls for high waves to channel updrafts. The wind that made such waves however, might have been too strong for the pterosaurs to control their flight once airborne.
选项
A、enormous wingspans of the pterosaurs enabled them to fly great distances
B、structure of the skeleton of the pterosaurs suggests a close evolutionary relationship to hats
C、fossil remains of the pterosaurs reveal how they solved the problem of powered flight
D、pterosaurs were reptiles
答案
D
解析
分析推理题。文章第二段第一句指出;Perhaps the least controversial assertion about the pterosurs is that they were reptiles(也许最没有争议的主张就是翼龙属于爬行动物)。既然对这个主张的争议最少,那么说明大家都同意这一论断,因此答案是[D]。
转载请注明原文地址:https://kaotiyun.com/show/dFPd777K
本试题收录于:
公共英语四级笔试题库公共英语(PETS)分类
0
公共英语四级笔试
公共英语(PETS)
相关试题推荐
Accordingtothepassage,AmericanscanaccepteverythingEXCEPTthat______.
Thisbookisaninvitationtosharetheexperiencesofpeople(31)likeyou,learnanewlanguageorcometoliveinacultured
Thisbookisaninvitationtosharetheexperiencesofpeople(31)likeyou,learnanewlanguageorcometoliveinacultured
Whatshouldonedoifhewantstoworkmoreefficientlyathislowpointinthemorning?
"Themoregadgetsthereare,the【C1】______thingsseemtoget."saidHonoreErvin,co-authorofTheEtiquetteGirls:ThingsYou
Whatdoesthemanthinkofthegovernment’spresentproposalaboutbuildingmorepowerstationsinthecountry?
AlthoughsocialchangesintheUnitedStateswerebeingwroughtthroughoutmostofthenineteenthcentury,publicawarenessoft
HenryKissingerwasborninasmalltown,located【C1】______thesouthGermanprovinceofFranconia,onMay27,1923.Hisfatherwa
Everyyeartelevisionstationsreceivehundredsofcomplaintsabouttheloudnessofadvertisements.However,federalrulesforbi
随机试题
已知向量组α1=(1,-1,1)T,α2=(-1,1,1)T,α3=(1,1,-1)T,此向量组的秩为
A、RussianB、racialC、specialD、industrialD画线部分读[ie],其他选项的画线部分读[e]。
产权具有()等多种形态。
在项目投资现金流量表中,以下不属于现金流出的是()。
会计科目是对()具体内容进行分类核算的项目。
在中国境内拥有并且使用车船的外商投资企业和外国企业,均为车船使用税的纳税人。()
《导游人员管理条例》规定,()人员不得颁发导游证。
伪操作“ARRAY DB 50DUP(0,3DUP(1,2),0,3)”中定义了( )字节。
A.comfortableB.preferC.investmentD.academicallyE.workedoutF.overwhelmedG.landH.optI.orientedJ.leading
A、Hefeltuneasyaboutthejob.B、Hedidn’tliketotravelabroad.C、Hewasnotsatisfiedwiththesalary.D、Hefeltthejobwas
最新回复
(
0
)