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
37
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
freshwater dolphin(s)/ the freshwater dolphin(s)
解析
转载请注明原文地址:https://kaotiyun.com/show/xWNO777K
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
Thereare10peopleinaroom.Ifeachpersonshakeshandwithexactly4otherpeople,whatisthetotalnumberofhandshakes?
If0≤n≤100,and(n+7)/4isamultipleof2butnotamultipleof3or4,thenwhichofthefollowingcouldbetrue?Indicateall
Pointaandbareonthenumberline,thedistancebetweenaandbis7,ifa=7,whatisthepossiblevalueofb?
X,YareinasetwhichhaspropertyPthatanyrealnumberbetweenX,Yalsobelongstotheset,whichofthefollowingisthe
Thereare30studentsinaclass.12ofthemplaybasketball,15ofthemplayfootball,and19ofthemplaypingpang.If7ofth
AlthoughmostpeoplewhoacquireWestNilehaveno______andthosewhodonormallysufferlittlemorethanflu-likeillness,it
A、GovernmentcompensationprogramsforsurplusB、ClimatestudyC、SoilmanagementD、DripirrigationE、Changesinpatternsoffood
A、suggestarefugefromthelonghistoryofsexistliterarycriticismB、offerasenseofpoliticalpurposethatcanonlybeawak
Althoughthescientist’srecommendationsmayhavebeen(i)______,thestudentshadtroublefollowinghis(ii)______presentation
Inarecentstudy,DavidCressyexaminestwocentralquestionsconcerningEnglishimmigrationtoNewEnglandinthe1630s:what
随机试题
公安机关办理治安案件的期限,自受理之日起不得超过();案情重大、复杂的,经上一级公安机关批准,可以延长()。
琦君的散文《髻》刻画出【】
脊髓是内脏反射活动的初级中枢,但不参与完成的反射是
A.龙胆泻肝汤合涤痰汤B.六味地黄丸合交泰丸C.安神定志丸D.黄连温胆汤E.天王补心丹合朱砂安神丸治疗阴虚火旺心悸的代表方为
按照科斯定理,如果产权是明晰的,只要通过市场交易,而无需政府的直接干预,就可以解决外部性的问题,前提是交易费用为零或者很小。()[2009年真题]
下列各项中,可以成为我国经济法律关系客体的有()。
以下关于考评指标标准的评分方法表述正确的有()。
过去5亿年里,地球高温期一般与大气中二氧化碳浓度较高的时期相吻合,反之亦然。目前,科学家正研究地球历史上的气候变迁,以预测今后大气中二氧化碳浓度上升时地球气候会发生怎样的变化,而不仅仅依靠计算机模型的预测。研究地球历史上的气候变迁可利用各种各样的
下列选项中,不属于C++关键字的是()。
Attheapartment,wefoundanunshaven,grey-hairedmansittinginashabbyrecliner.Hehadan【B1】______grinonhisface.His
最新回复
(
0
)