2. 职称英语
  3. The fossil remains of the first flying vertebrates, the pterosaurs, have int

The fossil remains of the first flying vertebrates, the pterosaurs, have int

游客2024-01-13  70
问题     The fossil remains of the first flying vertebrates, the pterosaurs, have intrigued paleontologists lor more than two centuries. How such large crea- tures, which weighed in some cases 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 winglike 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 all 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 bats 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 warmblooded because flying implies a high rate of metabolism, which in turn implies a high internal temperature. Hux- ley 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 hairlike 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 crests of waves. Each hypothesis has its difficulties. The first wrongly assumes that the pterosaurs’ hind feet resembled a bat’s and could serve as hooks by which the animal could hang in preparation for flight. The second hypothesis seems un- likely 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. [br] The ideas attributed to T. H. Huxley in the passage suggest that he would most likely agree with which of the following statements?
选项 A、An animal’s brain size has little bearing on its ability to master complex behaviors.
B、An animal’s appearance is often influenced by environmental requirements and physical capabilities.
C、Animals within a given family group are unlikely to change their appearance dramatically over a period of time.
D、The origin of flight in vertebrates was an accidental development rather than the outcome of specialization or adaptation.
E、The pterosaurs should be classified as birds, not reptiles.
答案 B
解析 赫氏的理论表明他最少能同意下列哪个观点?赫氏理论：翼龙飞行一需要高新陈代谢率一需要恒温一需要毛发覆盖体表A．动物神经大小和它是否有复杂行为无关。无。B．动物的外表特点经常受环境要求和身体能力的影响。正确。赫氏理论：毛发是飞行的要求。C．一个科的动物一段时间内不会有大的外形变化。无。D．脊椎动物中飞行的起源与其说是特异性或适应的结果，不如说是偶然结果。未谈飞行起源问题。E．翼龙是鸟，不是爬行动物。赫氏没提翼龙的分类。
转载请注明原文地址:https://tihaiku.com/zcyy/3359372.html
相关试题推荐
随机试题
最新回复(0)