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
You should spend about 20 minutes on Questions 15-26 which are based on Reading Passage 2 below. An examination of the function
You should spend about 20 minutes on Questions 15-26 which are based on Reading Passage 2 below. An examination of the function
admin
2014-08-25
23
问题
You should spend about 20 minutes on Questions 15-26 which are based on Reading Passage 2 below.
An examination of the functioning of the senses in cetaceans, the group of mammals comprising whales, dolphins and porpoises
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 bot-tlenose 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 susus 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 echolo-cation1. 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.
1. echolocation: the perception of objects by means of sound wave echoes.
Questions 15-21
Complete the table below.
Choose NO MORE THAN THREE WORDS from Reading Passage 2 for each answer.
Write your answers in boxes 15-21 on your answer sheet.
选项
答案
taste buds
解析
转载请注明原文地址:https://kaotiyun.com/show/3WNO777K
本试题收录于:
雅思阅读题库雅思(IELTS)分类
0
雅思阅读
雅思(IELTS)
相关试题推荐
Questionsarebasedonthefollowingdata.InApril2004thedollaramountoftheHousingexpenseinregionQwaslessthanth
Inaclassof120students,60percentcanspeakFrenchandtherestcanspeakonlyEnglish.If25percentofthoseintheclass
Ancientpeoplefeltmuch______concerningthenotionthattheappearanceofcometswasinauspicious,butneverthelessexhibited
Peopleshouldnottakegoodconstitutionforgranted,forhumangeneticcodeis______thedevelopmentof______.
Withasmirk,the______historiantakesitasaprofessionalobligationtoparadehumannaturealwaysasanobjectof______.
A、summarizethemainpointoftherefutationtotheargumentdiscussedinthepassageB、explainwhythehypothesisundercritici
Hisinitialbroadcastingsuccessasayoungmanwasdueatleastasmuchtohisconsiderableprofessional______asitwastohis
(Thispassagewaswrittenpriorto1950)Wenowknowthatwhatconstitutespracticallyallofmatterisemptyspa
Althoughthescientist’srecommendationsmayhavebeen______,thestudentshadtroublefollowinghis______presentationandw
随机试题
2016年12月1日,张某突发疾病去世,留下房屋一处,由其儿子小张继承。2017年2月1日,小张将房屋过户到自己名下。2017年3月1日,小张将房屋出租给李某,双方口头约定租期1年,月租金2000元.并未签订书面合同。2017年7月,小张见房价上涨,主
计算机绘图可分为被动式和交互式。()
莎士比亚,文艺复兴时期英国杰出的戏剧家、诗人。他的四大悲剧是《哈姆雷特》、《奥赛罗》、________、《李尔王》。
观感质量检查项目有()%及以上评为好的,观感质量综合评价为好。
法可以根据不同的标准进行不同的分类,以下()属于法的分类。
戊戌变法是中国近代史上一次重要的政治改革,也是一次思想启蒙运动,促进了思想解放。()
WeneedtofollowtheleadofBritain’sfamiliesandputinthehardworktorenewthecontractbetweenthegenerations.Youdon
有一种木马程序,其感染机制与U盘病毒的传播机制完全一样,只是感染目标计算机后它会尽量隐藏自己的踪迹,它唯一的动作是扫描系统的文件,发现对其可能有用的敏感文件,就将其悄悄拷贝到U盘,一旦这个U盘插入到连接互联网的计算机,就会将这些敏感文件自动发送到互联网上指
Thetimeisaboutfouro’clock,or,tobe______,itisoneandaquarterpastfour.
Children’sideasabouttherainforestsandtheimplicationforcoursedesignA)Adultsandchildrenarefrequentlyconfrontedwi
最新回复
(
0
)