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 annals of natural history contain many astonishing examples of the ability of animals to find their way home after making di
The annals of natural history contain many astonishing examples of the ability of animals to find their way home after making di
admin
2016-12-08
35
问题
The annals of natural history contain many astonishing examples of the ability of animals to find their way home after making distant journeys. Salmons, for example, are born in freshwater streams and soon afterward journey down to sea. Several years later, after they have attained maturity, they swim back upstream to spawn and, in many cases, to die. The particular stream that serves as the journey’s end is almost invariably the same one in which they were born. It is chosen out of dozens or hundreds of equally suitable streams. The expression "almost invariably" is used advisedly in this case. In one investigation by Canadian biologists, 469, 326 young sockeye salmon were marked in a tributary of the Fraser River. Several years later almost 11,000 were recovered after they had completed a return journey to the very same stream, but not a single one was ever recovered from other streams nearby. What underwater guideposts can these fish possibly follow? It has been discovered by A. D. Hasler and his associates at the University of Wisconsin that the salmon, like many other fish, have an acute sense of smell and are able tore member slight differences in the chemical composition of water. The most reasonable theory to explain salmon homing is that each individual remembers the distinctive "fragrance" of its native stream. As it moves upstream it makes the correct choice each time a new tributary is encountered, until finally it arrives home.
Long-distance migration is especially common in birds, because many species must make annual journeys between their nesting grounds and prime feeding areas far away. Each year over 100, 000 sooty terns, an attractive tropical sea bird, travel from the waters off the west coast of Africa all the way across the Atlantic to Bush Key, a tiny island near the tip of Florida. Here they build their nests and breed. Once the young can fly, all journey back over the Atlantic. Why do the sooty terns migrate at all? Like many other seabirds, they find protection from cats, foxes, and other predators on isolated islands. It is evidently safer for them to make an entire transoceanic voyage to reach one such haven than it would be to try to nest on the nearby African shores. A somewhat different reason lies behind the north-south migration of birds in the temperate zones. Each spring a legion of migratory forms, from robins, thrushes, and warblers to geese and ducks, makes its way north into the greening countryside, where large quantities of food are becoming freshly available. Working rapidly, they are able to rear one or more broods of young. As winter approaches and the food supply declines, all head south again. Some species proceed all the way to Central and South America. The record annual journey in the Western Hemisphere is made by the golden plover, one group of which travels from northern Canada to southern South America. A second group of the same species migrates from Alaska to Hawaii and the Marquesas Islands. Human beings could never make such journeys unaided by maps and navigational instruments. How do the birds do it? A large part of the answer lies in their ability to use celestial clues. At migration time, caged starlings become unusually restless. If permitted to see the sun, they begin to fly toward the side of the cage that lies in the direction of their normal migration route. However, when the sky is overcast and the sun is obscured from view, their movements persist, but they are non directional. Other migratory birds fly at night and can evidently use the position of the stars to guide them. This surprising fact has been established by several biologists, including S. T. Emlen of Cornell University, who allowed a type of bird called indigo buntings to attempt flights under the artificial night sky of a planetarium. The birds oriented "correctly" with reference to the planetarium sky even when the positions of its constellations did not correspond with the position of the true constellations outside. Thus other outside influences were eliminated, and it could be concluded that the birds were able to orient to what they believed to be the position of the stars.
Question 71 to 75
Complete the summary below with information from the passage, using three words fo fewer for each blank.
Animals are able to get back home after they make long journeys. Salmon, for example, are known to swim back several years later to【R1】______where they were born. What guide these fish upstream? According to scientists at the University of Wisconsin, salmon【R2】______and follow the fragrance of their native stream as they have a sharp【R3】______
Birds also make long distance migration each year. Sooty terns, a type of tropical sea bird, travel across the Atlantic from Africa to an island near Florida, where they breed and can【R4】______from predators. Birds also migrate in order to find food and rear their young. It is discovered that birds are aided by【R5】______to make distant journeys that even human beings cannot make without the assistance of navigational instruments.
【R5】
选项
答案
celestial clues/position of the stars
解析
(文章第二段提到How do the birds do it?A large part of the answer lies in their ability to use celestial clues.因而摘要中可以归纳为celestial clues。)
转载请注明原文地址:https://kaotiyun.com/show/ApAK777K
本试题收录于:
B类竞赛(英语专业本科专科)题库大学生英语竞赛(NECCS)分类
0
B类竞赛(英语专业本科专科)
大学生英语竞赛(NECCS)
相关试题推荐
ThenativepeopleofNorthandSouthAmericaweregiventhename"Indians"bythe【21】ChristopherColumbus.Hethoughthehadrea
Ihearmanyparentscomplainingthattheirteenagechildrenarerebelling.Iwishitwereso.Atyourageyououghttobegrowin
Ontheleftaresomeshapesandcodesthatgowiththem.Youmustdecidehowthecodelettersgowiththeshapes.Whichcodessh
100mphgalescausechaos【76】Strongwinds,whichattimesreachedspeedsof100mph,broughthavoctomanypartsofBritain
Theideaofafishbeingabletogenerateelectricitystrongenoughtolightlampbulbs—oreventorunasmallelectricmotor—is
剑桥大学是具有700多年历史的世界著名学府。(withahistoryof)
Socialdistancemay【66】af______howopenlyemployeesspeakabouttheirwork.Peopleofthesame【67】r______maytalkfranklytoone
他在这个美国城市生活一段时间后,日常生活中同美国人交流没有困难。(havenotroubledoingsth)
连年的战争不仅使人们丧失了对生活的热情,还让他们失去了对未来的希望。(deprive)
中国经济发展潜力大、优势足、空间广,前景光明。【T1】我们有9亿多劳动力,其中1.7亿多受过高等教育或有专业技能。每年大学毕业生700多万,中职毕业生500多万。【T2】科技人员数量世界第一研发投入(R&Dinput)世界第二。(interms
随机试题
我们绝不允许任何人、任何组织、任何政党在任何时候、以任何形式、把任何一块中国领土从中国分裂出去。要贯彻()
男,25岁。反复腹痛、腹泻、便血10个月。近日加重伴发热,体温39℃,1天前因腹痛肌注阿托品治疗6小时后腹胀明显。查体:70/50mmHg,心率120次/分。最可能出现的情况是
国有土地使用权类型一般不包括()。
某风沙治理工程,原来是一片典型的城乡结合部地区,需要进行大规模的绿化隔离建设,原先的居民迁入了楼房,实现3.08km3的绿化,绿化隔离地区总面积为240km2。道路、河流两侧将种上各200m宽的绿化带,其中内侧的20~50m将成为永久绿化带。在其
对工程项目团队成员考核的内容主要有()
甲公司就一项手术刀于2010年6月10日提出实用新型专利申请并于2010年9月29日获授权。乙公司2010年8月15日自行研制出了相同的手术刀,于2010年9月29日前完成了生产制造的准备。未经甲公司许可,乙公司于2010年10月开始制造该手术刀,并通过丙
句子是具有一个句调,能够表达一个_____的语言单位。
设A为m×n矩阵,以下命题正确的是().
设二次型f=xTAx=ax12+2x22一x32+8x1x2+2bx1x3+2cx2x3,矩阵A满足AB=O,其中B=(I)用正交变换化二次型f为标准形;(Ⅱ)判断矩阵A与B是否合同.
用十六位机器码1110001010000000来表示定点整数(最高位为符号位),当它是原码时表示的十进制真值为(1)。当它是补码时表示的十进制真值是(2);当它是反码时表示的十进制真值是(3)。
最新回复
(
0
)