【考研类试卷】北京师范大学考博英语-试卷3及答案解析.doc
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1、北京师范大学考博英语-试卷 3 及答案解析(总分:98.00,做题时间:90 分钟)一、Reading Comprehensio(总题数:7,分数:90.00)Birds evolved during the great reptilian radiation of the Mesozoic era. Amniotic eggs and scales on the legs are just two of the reptilian features we see in birds. But modern birds look quite different from modern repti
2、les because of their feathers and other distinctive flight equipment. Characteristics of Birds Almost every part of a typical birds anatomy is modified in some way that enhances flight. The bones have an internal structure that is honeycombed, making them strong but light. The skeleton of a frigate
3、bird, for instance, has a wingspan of more than 2 meters but weighs only about 113 grams. Another adaptation reducing the weight of birds is the absence of some organs. Females, for instance, have only one ovary. Also, modern birds are toothless, an adaptation that trims the weight of the head. Food
4、 is not chewed in the mouth but ground in the gizzard, a digestive organ near the stomach.(Crocodiles also have gizzards, as did some dinosaurs.)The birds beak, made of keratin, has proven to be very adaptable during avian evolution, taking on a great variety of shapes suitable for different diets.
5、Flying requires a great expenditure of energy from an active metabolism. Birds are endothermic: they use their own metabolic heat to maintain a warm, constant body temperature. Feathers and, in some species, layers of fat provide insulation that enables birds to retain their metabolically generated
6、heat. An efficient respiratory system and a circulatory system with a four-chambered heart keep tissues well supplied with oxygen and nutrients, supporting a high rate of heat and reduce the density of the body metabolism. The lungs have tiny tubes leading to and from elastic air sacs that help diss
7、ipate. For safe flight, senses, especially vision, must be acute. Birds have excellent eyes, perhaps the best of all the vertebrates. The visual areas of the brains are well developed, as are the motor areas: flight also requires excellent coordination. With brains proportionately larger than those
8、of reptiles and amphibians, birds generally display very complex behavior. Avian behavior is particularly intricate during breeding season, when birds engage in elaborate rituals of courtship. Because eggs are shelled when laid, fertilization must be internal. Copulation involves contact between the
9、 mates vents, the openings to their cloacas. After eggs are laid, the avian embryo must be kept warm through brooding by the mother, father, or both, depending on the species. A birds most obvious adaptation for flight is its wings. Bird wings are airfoils that illustrate the same principles of aero
10、dynamics as the wings of an airplane. Providing power for flight, birds flap their wings by contractions of large pectoral(breast)muscles anchored to a keel on the sternum(breast-bone). Some birds, such as eagles and hawks, have wings adapted for soaring on air currents and flap their wings only occ
11、asionally, other birds, including hummingbirds, must flap continuously to stay aloft. In either case, it is the shape and arrangement of the feathers that form the wings into an airfoil. The fastest birds are the appropriately named swifts, which can fly 170 km/hr. In being both extremely light and
12、strong, feathers are among the most remarkable of vertebrate adaptations. Feathers are made of keratin, the same protein that forms our hair and fingernails and the scales of reptiles. Feathers may have functioned first as insulation during the evolution of endotherm, only later being so-opted as fl
13、ight equipment. Analyses of fossilized skeletons support the hypothesis that the closest reptilian relatives of birds were the theropods, a group of relatively small, bipedal carnivorous dinosaurs. Most researchers agree that the ancestor of birds was a feathered theropod. However, some scientists p
14、lace the origin of birds much earlier, from an ancestor common to both birds and dinosaur. The intense current interest in the origin of birds will undoubtedly bring us closer to understanding how these masters of the sky evolved from non-flying reptiles(分数:14.00)(1).According to paragraph 2, how di
15、d birds adapt to efficient flight?(分数:2.00)A.They developed a skeleton with fewer bones.B.Their organs became smaller overtime.C.Most of their weight was distributed in their heads.D.Teeth were replaced by a beak made of keratin.(2).The word “modified“ in the passage is closest in meaning to_.(分数:2.
16、00)A.made differentB.made betterC.made smallerD.made modern(3).The word “ their“ in the passage refers to_.(分数:2.00)A.feathersB.speciesC.layersD.birds(4).According to paragraph 6, which of the following is true about the wings of birds?(分数:2.00)A.All birds flap their wings constantly by using breast
17、 muscles.B.Eagles and hawks have wings that propel them at 170 km/hr.C.The airfoils of birds function like the wings on airplanes.D.Wings are attached to airfoils in the birds skeletal structure.(5).According to the passage, which characteristic do birds share with reptiles?(分数:2.00)A.They defend th
18、emselves with claws.B.They reproduce by laying eggs.C.They have a similar skeletal structure.D.They utilize a two-chambered heart.(6).Which of the sentences below best expresses the information in the highlighted statement in the passage?(分数:2.00)A.Very early birds appeared after the dinosaurs.B.Bir
19、ds and dinosaurs may share the same ancestor.C.Birds and dinosaurs were probably very common.D.The origin of birds and dinosaurs is very early.(7).All of the following are mentioned as adaptations to the birds anatomy to accommodate flight EXCEPT_.(分数:2.00)A.a covering of feathersB.relatively large
20、brainsC.very sharp eyesD.small legs and feetWhen one animal attacks another, it engages in the most obvious example of aggressive behavior. Psychologists have adopted several approaches to understanding aggressive behavior in people. The Biological Approach. Numerous biological structures and chemic
21、als appear to be involved in aggression. One is the hypothalamus, a region of the brain. In response to certain stimuli, many animals show instinctive aggressive reactions. The hypothalamus appears to be involved in this inborn reaction pattern; electrical stimulation of part of the hypothalamus tri
22、ggers stereotypical aggressive behaviors in many animals. In people, however, whose brains are more complex, other brain structures apparently moderate possible instincts. An offshoot of the biological approach called sociobiology suggests that aggression is natural and even desirable for people. So
23、ciobiology views much social behavior, including aggressive behavior, as genetically determined. Consider Darwins theory of evolution. Darwin held that many more individuals are produced than can find food and survive into adulthood. A struggle for survival follows. Those individuals who possess cha
24、racteristics that provide them with an advantage in the struggle for existence are more likely to survive and contribute their genes to the next generation. In many species, such characteristics include aggressiveness. Because aggressive individuals are more likely to survive and reproduce, whatever
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