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
All animals must rest, but do they really sleep as we know it? The answer to this question seems obvious, If an animal regularl
All animals must rest, but do they really sleep as we know it? The answer to this question seems obvious, If an animal regularl
admin
2013-01-15
82
问题
All animals must rest, but do they really sleep as we know it? The answer to this question seems obvious, If an animal regularly stops its activities and stays quiet and unmoving——if it looks as though it is sleeping——then why not simply assume that it is in fact sleeping? But how can observers be sure that an animal is sleeping?
They can watch the animal and notice whether its eyes are open or closed, whether it is active or lying quietly, and whether it responds to light or sound. These factors are important clues, but they often are not enough. Horses and cows, for example, rarely close their eyes, and fish and snakes cannot close them. Yet this does not necessarily mean that they do not sleep. Have you ever seen a cat dozing with an eye partly open? Even humans have occasionally been observed to sleep with one or both eyes partially open. Animals do not necessarily lie down to sleep either. Elephants, for example, often sleep standing up, with their tusks resting in the fork of a tree. Finally, while "sleeping" animals often seem unaware of changes in the sounds and light and other stimuli around them, that does not really prove they are sleeping either.
Observations of animal behavior alone cannot fully answer the question of whether or not animals sleep. The answers come from doing experiments in "sleep laboratories" using a machine called the electroencephalograph (EEC). The machine is connected to animals and measures their brain signals, breathing, heartbeat, and muscle activity. The measurements are different when the animals appear to be sleeping than when they appear to be awake. Using the EEC, scientists have confirmed that all birds and mammals studied in laboratories do sleep. There is some evidence that reptiles, such as snakes and turtles, do not truly sleep, although they do have periods of rest each day, in which they are quiet and unmoving. They also have discovered that some animals, like chimpanzees, cats, and moles (who live underground), are good sleepers while others, like sheep, goats, and donkeys, are poor sleepers. Interestingly, the good sleepers are nearly all hunters with resting places that are safe from their enemies. Nearly all the poor sleepers are animals hunted by other animals: they must always be ’watching for enemies, even when they are resting.
The statement," Horses and cows, for example, rarely close their eyes" aims to show that ______.
选项
A、these animals rarely need any rest
B、they almost always keep alert to danger
C、they often stay awake
D、their eyes are rarely closed even when they are asleep
答案
D
解析
作者在第二段说,马和牛很少闭上眼睛,但这并不能说明它们不睡觉。事实上它们睡觉的时候眼睛经常是睁开的。
转载请注明原文地址:https://kaotiyun.com/show/Yn2O777K
0
考博英语
相关试题推荐
Wearegladtoinformyouthatyourapplicationforapostinourschoolhasbeen______.
______enoughtimeandmoney,theresearcherswouldhavebeenabletodiscovermoreinthisfield.
Thehallwassupportedbysixthick______.
Today’sworkerisnolongerwillingtoworkinanauthoritariananddehumanizingenvironment.Workerswantmeaningintheirwork
Usingextremelydifferentdecoratingschemesinadjoiningroomsmayresultin______andlackofunityinstyle.
Ourshasbecomeasocietyofemployees.AhundredyearsorsoagoonlyoneoutofeveryfiveAmericansatworkwasemployed,i.
Onbehalfofmycompany,Iam______toyouandyourcolleaguesforyourgeneroushelp.
Thecombinationoflensesinacompoundmicroscopemakespossiblegreateramplificationthancanbeachievedwithasinglelens.
AustraliacontinuedthefighttoendJapan’sannualwhalehunts,warningthatitsplantokillhumpbackwhalesinAntarcticacou
MargheritaisaLondongirlandarrivingatCapitalwaslikecominghome."IgrewuplisteningtoCapitalRadio,"shesays."Peo
随机试题
Leadingcadreslaunchrectificationcampaignsatregular______tohearthemasses’views.
A.浆液性囊腺瘤B.卵巢恶性畸胎瘤C.颗粒细胞瘤D.卵巢黄素囊肿E.纤维瘤发生于体腔上皮者
A.设法促进肌张力和主动运动的出现B.降低痉挛,促进分离运动的恢复C.进一步降低肌痉挛,促进更多的分离运动恢复,改善运动速度、精细程度和耐力D.多种训练交替进行,有所侧重,在不引起异常反应和过度疲劳的情况下,逐渐加大活动量E.瘫痪恢复的次序是先躯干
如血气分析标本不能及时测定,需保存在有冰块的水中,其目的是
项目可行性研究的核心内容是( )。
甲公司为增值税一般纳税人,适用的增值税税率为17%,2014年一2017年发生的与固定资产、无形资产和投资性房地产有关业务资料如下:(1)2014年4月1日,甲公司生产车间购入一台需安装的生产线设备,取得增值税专用发票注明的价款为330万元,增值税税额为
下列选项中,属于狭义的执法活动范畴的是()。
若在Shape控件内以Fillstyle属性所指定的图案填充区域,而填充图案的线条的颜色由FillColor属性指定,非线条的区域由Backstyle属性填充,则应______。
Itisastonishinghowlittleisknownabouttheworkingofthemind.Buthoweverlittleormuchisknown,itisfairlycleartha
AttendParents’MeetingwithaGoodImageForthispart,youareallowed30minutestowriteashortessayentitledAttend
最新回复
(
0
)