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
2018-10-19
45
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://jikaoti.com/ti/G5AMFFFM
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
剑桥大学是具有700多年历史的世界著名学府。(withahistoryof)
Ontheleftaretwoshapeswithanarrowbetweenthem.Decidedhowthesecondisrelatedtothefirst.Afterthisthereisathi
Sometincanshavelosttheirlabels.3containsoup,4containbeans,and1containspeas.Ifyoupickacanatrandom,inwhic
Thepresident’seducationspeechescontained______thetongueleadingtopublicconfusionovereducationpolicy.
剑桥大学是具有700多年历史的世界著名学府。(withahistoryof)
Peopletypicallyfindunemploymentapainfulexperience.Itmayresultfromtheinabilitytofindafirstjob,layoffs,dismisse
Therecanbe【D1】______anyonewhohasnotheardofyoga,and,whetheryouare16or60,youcanreapthe【D2】______oftakingitup
Therecanbe【D1】______anyonewhohasnotheardofyoga,and,whetheryouare16or60,youcanreapthe【D2】______oftakingitup
Therecanbe【D1】______anyonewhohasnotheardofyoga,and,whetheryouare16or60,youcanreapthe【D2】______oftakingitup
随机试题
癫癎患者服用抗癫癎药的禁忌是
背景资料某机电安装工程公司承担了一机电工程项目的安装任务,合同工期为120d,合同价款为300万元。该安装工程公司项目经理部根据施工合同和自身的技术水平为该工程编制了施工组织设计,该施工组织设计包括施工组织总设计、单位工程施工组织设计和分部
按照波特的价值链理论,分析判断下列企业的各项活动所属的类别。(1)甲书店提供网络在线销售服务;(2)乙家电生产企业利用外包仓库储存其产成品;(3)丙快递公司重整其人力资源管理,提升员工的服务能力;(4)丁制鞋企业设立特定研究中心专门从事人体工程学和
投资中心的投资额为100000元,资本成本率为20%,剩余收益为10000元,则该中心的投资贡献率为()。
laugh,explain,takepartin,notmean,sweepaway,know,miss,invite,discuss,takeplaceIamsorryyou________thelasttrai
【2012年枣庄市】简述个体身心发展的一般规律。
拉动经济增长的三驾马车是()。
A、 B、 C、 D、 B排除法。A项应该排除,因为一定由两个空白面是相对的;C项应该排除,因为两个有黑点的是不能相邻的;D项应该排除,因为当阴影部分在上边时,相邻两面总有一面有黑点。
研究表明,糟糕的空气质量有可能导致疲劳、头痛等不适反应和更严重的各类疾病,而室内空气污染平均高于室外10倍。下列属于造成室内空气质量不佳的因素是:①空调②复印机、静电除尘器③生理代谢④尘螨
AccordingtotheEUsurvey,Britishmenspendmoretimeon______.Accordingtothepassage,whospendmoretimeonTVthanoth
最新回复
(
0
)