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
60
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 of the senses is best developed in cetaceans?
选项
答案
acoustic
解析
(文章最后一段提到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.“虽然触觉和嗅觉已经退化,在水中的视觉也不能确定,但鲸高度敏锐的听觉能力足以能弥补这一切。”)
转载请注明原文地址:https://kaotiyun.com/show/xXAK777K
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
OxfordStreet,inEngland’scapitalcity,isnotknownforculturalevents.Butfortendaysinearly2001,itwastheaddressf
Manypeoplecomplainthattheirmemoryisbad,particularlyastheygetolder.Phonenumbers,names,factswestudiedonlyafew
Itisover4,000kilometerslongandcrossestwo-thirdsoftheUSA.Ithasbeencalled"TheMotherRoad"and"TheMainStreeto
Whendifficultpeopleexpressthemselvesorally,theygenerallywantatleasttwothings:they’vebeenheardandthey’vebeenund
Whenyourphoneisinyourpocket,therearetwopossiblestates:itiseithervibrating【D1】________.Meanwhile,youalsoha
Fillinthemissingnumbersinthissequence;15,873x7=111,11115,873x14=222,22215,873x(a)=333,33315(b)x28=(c)4
Choosethewordmostnearlyoppositeinmeaningtothecapitalizedword:GRATUITOUS?
WhyhasMarybeenabsentfromclass?
WhyhasMarybeenabsentfromclass?
Youaretryingtofillabathwithbothtapson,buthaveaccidentallyleftouttheplug.Normallythehotwatertaptakes8min
随机试题
公证行政法律责任
Shepretended______indifferentbutherfacialexpressionbetrayedher.
患者,女,26岁。高热、寒战、腰痛2天,尿呈酱油色,红细胞2.0×1012/L,网织红细胞50%,血Ham试验(+),血红蛋白尿(+)。下列处理方法适宜的是
为加强城乡规划管理监督检查工作,除了要加强和完善城乡规划的法制建设,建立和完善城乡规划管理监督制度,尚需形成一种机制,以强化对城乡规划实施情况的监督工作。这种机制是()。
某单层堆垛储物仓库,耐火等级为二级,占地面积为2500m2,储存物质为用塑料瓶包装的成品罐装饮料,储物高度为4m,已知每瓶饮料总质量为1.5kg,塑料瓶包装质量为0.32kg。仓库内设有自动喷水灭火系统,划分为一个防火分区。根据以上材料,回答下列问
某企业销售产品一批,货款100000元,增值税税额为17000元。款项尚未收到,产品成本为80000元。那么该企业应做的会计处理是()。
北京城最早的基础是唐代的幽州城。在此后的一千年中,北京曾经有过四次大规模的发展,或扩建,或新修,分别为金代的中都、元代的大都、明代早期所修的内城以及中叶以后所建的外城。北京的凸字形城墙就是这样完成的。清代承继了明朝的北京,对城市的整体布局系统未加改动,一直
某银行保险柜被撬,巨额现金和证券失窃。警察局经过侦破,拘捕了三名重大的犯罪嫌疑人:施辛格,赖普顿和安杰士。通过审讯,查明了以下的事实:(1)保险柜是用专门的作案工具撬开的,使用这种工具必须受过专门的训练。(2)只有施辛格作案,安杰士才作案。(3)赖普
下列问题是基于如下叙述:关系模式Student(Sno,Sname,Cno,Cname,Grade,Tname,Taddr)的属性分别表示学号、学生姓名、课程号、课程名、成绩、任课教师名和教师地址。其中,一个学生可以选修若干门课程,一个教师可以讲授若干门课
Thegovernmentistobanpaymentstowitnessesbynewspapersseekingtobuyuppeopleinvolvedinprominenteases【C1】______the
最新回复
(
0
)