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
Some of the senses that we and other terrestrial mammals take for granted are either reduced or absent in cetaceans or fail to f
Some of the senses that we and other terrestrial mammals take for granted are either reduced or absent in cetaceans or fail to f
admin
2011-02-05
54
问题
Some of the senses that we and other terrestrial mammals take for granted are either reduced or absent in cetaceans or fail to function well in water. For example, it appears from their brain structure that toothed species are unable to smell. Baleen species, on the other hand, appear to have some related brain structures but it is not known whether these are functional. It has been speculated that, as the blowholes evolved and migrated to the top of the head, the neural pathways serving sense of smell may have been nearly all sacrificed. Similarly, although at least some cetaceans have taste buds, the nerves serving these have degenerated or are rudimentary.
The sense of touch has sometimes been described as weak too, but this view is probably mistaken. Trainers of captive dolphins and small whales often remark on their animals’ responsiveness to being touched or rubbed, and both captive and free-ranging cetacean individuals of all species (particularly adults and calves, or members of the same subgroup) appear to make frequent contact. This contact may help to maintain order within a group, and stroking or touching are part of the courtship ritual in most species. The area around the blowhole is also particularly sensitive and captive animals often object strongly to being touched there.
The sense of vision is developed to different degrees in different species. Baleen species studied at close quarters underwater—specifically a grey whale calf in captivity for a year, and free-ranging right whales and humpback whales studied and filmed off Argentina and Hawaii—have obviously tracked objects with vision underwater, and they can apparently see moderately well both in water and in air. However, the position of the eyes so restricts the field of vision in baleen whales that they probably do not have stereoscopic vision.
On the other hand, the position of the eyes in most dolphins and porpoises suggests that they have stereoscopic vision forward and downward. Eye position in freshwater dolphins, which often swim on their side or upside down while feeding, suggests that what vision they have is stereoscopic forward and upward. By comparison, the bottlenose dolphin has extremely keen vision in water. Judging from the way it watches and tracks airborne flying fish, it can apparently see fairly well through the air-water interface as well. And although preliminary experimental evidence suggests that their in-air vision is poor, the accuracy with which dolphins leap high to take small fish out of a trainer’s hand provides anecdotal evidence to the contrary.
Such variation can no doubt be explained with reference to the habitats in which individual species have developed. For example, vision is obviously more useful to species inhabiting clear open waters than to those living in turbid rivers and flooded plains. The South American boutu and Chinese beiji, for instance, appear to have very limited vision, and the Indian sinus are blind, their eyes reduced to slits that probably allow them to sense only the direction and intensity of light.
Although the senses of taste and smell appear to have deteriorated, and vision in water appears to be uncertain, such weaknesses are more than compensated for by cetaceans’ well-developed acoustic sense. Most species are highly vocal, although they vary in the range of sounds they produce, and many forage for food using echolocation. Large baleen whales primarily use the lower frequencies and are often limited in their repertoire. Notable exceptions are the nearly song-like choruses of bowhead whales in summer and the complex, haunting utterances of the humpback whales. Toothed species in general employ more of the frequency spectrum, and produce a wider variety of sounds, than baleen species (though the sperm whale apparently produces a monotonous series of high-energy clicks and little else). Some of the more complicated sounds are clearly communicative, although what role they may play in the social life and ’culture’ of cetaceans has been more the subject of wild speculation than of solid science.
Which type of habitat is related to good visual ability?
选项
答案
clear open waters
解析
(文章倒数第二段的提到vision is obviously more useful to species inhabiting clear open waters than to those living in turbid rivers and flooded plains. “相比那些生活在脏河和洪水泛滥的平原上的种群,视觉对于那些生活在清澈的水里的种群明显更有用。”)
转载请注明原文地址:https://kaotiyun.com/show/RXAK777K
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
Thesedays,collegelecturehallsintheUnitedStatesarebeingfilledmoreandmorewithfemaleratherthanmalestudents.Wom
OxfordStreet,inEngland’scapitalcity,isnotknownforculturalevents.Butfortendaysinearly2001,itwastheaddressf
SummaryListentothepassage.Forquestions26-30,completethenotesusingnomorethanthreewordsforeachblank.The
Ontheafternoonof6thFebruary1958,eightmembersoftheManchesterUnitedfootballteamdiedinaplanecrashinMunich.The
ThecityofLondon,________repeatedlybetween1940and1941,lostmanyofitsfamouschurches.
Centuriesago,mandiscoveredthatremovingmoisturefromfoodhelpstopreserveit,andthattheeasiestwaytodothisistoe
1.AssessingDepartmentItisresponsibleforaccurately【21】______thevalueofallrealandpersonalpropertylocatedwithi
Thegamewascancelledbecausemostoftheteammembers______amatchwithoutastandardcourt.
有些人的成功常常让周围的人大惑不解,因为他们似乎从来都不工作,或者没有长时间地工作。【T1】他们的成功秘诀在于他们专注的能力,因而能够凭借最小的明显努力获得最大的成果。(liein)爱默生说:“无论是在政治、战争、商业,还是在一切人类事务的处理中,专注都
Receptionist:Goodmorning.HopkinsDentalSurgery.Charles:Goodmorning______.Receptionist:Isee.CanyoucomeonThursday
随机试题
法律设置规则调整复保险的目的在于:(1)防止超额保险;(2)避免不当得利;(3)控制道德危险;(4)增强安全保障。关于以上的四种说法
A.1.02B.1.04C.1.06D.1.20E.1.40煎煮完的解表剂药液相对密度应不低于
患者,女性,25岁。因春游赏花,出现咳嗽、咳痰伴喘息,呼气性呼吸困难。查体:喘息貌,口唇发绀,在肺部可闻及广泛哮鸣音。医疗诊断为支气管哮喘。下面哪种是控制症状的首选药
人民检察院没有抗诉但被告人不服一审判决提出上诉的案件,经第二审人民法院审理后,认为原判决认定事实没有错误,但适用法律有错误或者量刑不当的,如何处理?()
在工程竣工验收前,对工程质量进行等级核定的单位是()。
自动化仪表的管线施工应与()配合。
长春市某进出口公司A,购买韩国产新闻纸一批。货物进口时由大连口岸转关至长春海关办理该批货物的报关纳税手续。承担该批货物境内转关运输的是大连某运输公司B。在运输途中,因汽车驾驶员工某吸烟,不慎引发火灾,致使该批新闻纸全部失火。在这种情况下,关于该批货物的纳税
不收取销售服务费的,对持续持有期长于3个月但少于6个月的投资人收取不低于0.5%的赎回费,并将不低于赎回费总额的()计入基金财产。
小高平时安静沉稳,喜欢沉思,考虑问题全面,情绪不易外露,善于忍耐与克制自己,但反应缓慢,对新环境的适应能力较差,小高的气质类型最可能是()。
TVLinkedtoLowerMarksA)Theeffectoftelevisiononchildrenhasbeendebatedeversincethefirstsetswereturnedon.Nowt
最新回复
(
0
)