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
67
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.
【R3】
选项
答案
sense of smell
解析
(文中提到like many other fish,have an acute sense of smell“和其他的鱼一样,鲑鱼也有敏锐的嗅觉。”)
转载请注明原文地址:https://kaotiyun.com/show/t68K777K
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
Ontheleftaretwoshapeswithanarrowbetweenthem.Decidedhowthesecondisrelatedtothefirst.Afterthisthereisathi
Peopletypicallyfindunemploymentapainfulexperience.Itmayresultfromtheinabilitytofindafirstjob,layoffs,dismisse
Smith:Comeinplease,Linda.I’vegotsomegreatnewsforyou.Afterreviewingyourrecord,themanagementhasdecidedtosend
Therecanbe【D1】______anyonewhohasnotheardofyoga,and,whetheryouare16or60,youcanreapthe【D2】______oftakingitup
Therecanbe【D1】______anyonewhohasnotheardofyoga,and,whetheryouare16or60,youcanreapthe【D2】______oftakingitup
Goodmannersandetiquette(礼仪)arenotcomplicated.Anyonecan【D1】______courtesyandconsiderationforothers—thestuffofwhich
随机试题
Aprettypotplantmightmakeanunemotionalworkspacefeelmorepersonal.Butnewresearchhasrevealedthatofficeplantsdo
BeforetheUnitedStateswasacountry,itwasagroupofEnglishcolonies.Until1763,Englanddidn’treallybothertheAmerica
签订《土地权属界线协议书》,违约缺席指界的,调查结果以书面形式送达违约方。违约方在()天内未提出异议或未提出重新指界的,按调查结果认定权属界线。
根据《工程造价咨询企业管理办法》的规定,下列属于乙级工程造价咨询企业资质标准的是()。
物业管理计划的表现形式包括()
所谓“言必信”是指发展人际关系所必须遵循的()。
谈谈你对“不听老人言,吃亏在眼前”的理解。
春节期间很多地区都讲究吃年糕,因为年糕又称“年年糕”,与“年年高”谐音,____________人们的工作和生活一年比一年好。所以,年糕____________是一种节日美食,____________代表着美好的寓意和希望。依次填入画横线部分最恰当的一项是
Ofallthelessonstaughtbythefinancialcrisis,themostpersonalhasbeenthatAmericansaren’tsogoodatmoney-management.
A、Theareaisforpassengersonly.B、Themanisaskingthewomantoleave.C、Themanfeelssorryforthewoman.D、Thewomanisa
最新回复
(
0
)