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
31
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
baleen / the baleen whales
解析
转载请注明原文地址:https://kaotiyun.com/show/CWNO777K
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.Eachofthe15customerswhoarrivedatacustomerservicedeskbetween9A.M.and10
IfT=abcde-(a+b+c+d+e),whereTisaneveninteger,a,b,c,d,earepositiveintegers,whichofthefollowingCANNOTbethen
Ifaandbareoddintegersanda?b,whichofthefollowingequalstothenumberofevenintegersthataregreaterthanaandl
Pointaandbareonthenumberline,thedistancebetweenaandbis7,ifa=7,whatisthepossiblevalueofb?
Questionsarebasedonthefollowingdata.In1998,ifone-halfoftheoccupationalinjuriesinthecombine34-and-underagegr
Althoughhewas______inhiseffortstopersuadeusofthejustnessofhiscause,hispasthistory,......withfailures,preve
A、GovernmentcompensationprogramsforsurplusB、ClimatestudyC、SoilmanagementD、DripirrigationE、Changesinpatternsoffood
Withasmirk,the______historiantakesitasaprofessionalobligationtoparadehumannaturealwaysasanobjectof______.
Inarecentstudy,DavidCressyexaminestwocentralquestionsconcerningEnglishimmigrationtoNewEnglandinthe1630s:what
WhetherthelanguagesoftheancientAmericanpeopleswereusedforexpressingabstractuniversalconceptscanbeclearlyanswer
随机试题
某公司用市场法对一栋大楼进行评估,选择了三个比较案例,其交易价格分别为116万元、125万元和132万元,经综合考虑交易情况、交易日期、区域因素及个别因素后得到三个比较案例的修正系数分别为1.06、1.03和0.97,则该大楼的评估值为()
窦房结能成为心脏正常起搏点的原因是【】
少白细胞悬浮红细胞,其血细胞比容为
以下()等特种作业人员,必须按照国家有关规定经过专门的安全作业培训,并取得特种作业操作资格证书后,方可上岗作业。
设计压力大于1MPa的流体管道阀门需要进行壳体压力试验和密封试验的比例为()。
已知函数.求函数f(x)的单调增区间;
用蒸馏麦芽渣提取的酒精作为汽油的替代品进入市场,使得粮食市场和能源市场发生了前所未有的直接联系。到1995年,谷物作为酒精的价值已经超过了作为粮食的价值。西方国家已经或正在考虑用从谷物提取的酒精来替代一部分进口石油。如果上述断定为真,对于那些已经用从谷物提
下列选项中,属于附条件民事法律行为的有()。
游客乘电梯从底层到顶层观光,电梯于每个整点的5分、25分、55分从底层上行,设一游客早上8点X分到达底层,且X在[0,60]上服从均匀分布,求游客等待时间的数学期望.
可以创建数据访问页的是()。
最新回复
(
0
)