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
Humans and nearly all other animals vary their level of activity according to the time of day. Daily rhythms are not simply resp
Humans and nearly all other animals vary their level of activity according to the time of day. Daily rhythms are not simply resp
admin
2009-04-23
21
问题
Humans and nearly all other animals vary their level of activity according to the time of day. Daily rhythms are not simply responses to daylight and darkness or to other signs of the time of day. They are generated by the animals themselves. This is shown by experiments in which animals live in artificial surroundings that do not vary with time of day. They experience no daylight, no darkness, no day-night swings of temperature, and no contact with other animals that "know" the time of day. Under such conditions, the animals continue to exhibit near-daily rhythms of activity and rest. These rhythms must be generated by the animals’ own inner "clock". Such a biological clock is normally reset every day, mainly by the cycle of daylight and darkness. An animal’s activity and rest periods are thereby kept "in step" with the environment and with the activity cycles of other animals.
Daily periods of reduced activity serve at least two purposes. First, they allow the animal to save its resources for the time of day at which it is best suited to compete for food. Second, they make the animal less conspicuous to its enemies. The resting condition is reversible. Animals can become active at unusual times of day if they detect risks or if opportunities for feeding develop at times of shortage.
Whether the resting state of an animal qualifies as "sleep", however, depends on the complexity of its nervous system. Mammals and birds are the animals in which true sleep, of the nature indicated above, has been observed. Other animals exhibit resting periods.
选项
答案
animals have their own inner clock
解析
由题干experiments可定位至首段第四句:在人工环境下,动物仍然表现出平常的作息习惯,第七句做出推断说动物们一定有自己的内部时钟。
转载请注明原文地址:https://kaotiyun.com/show/TLC7777K
0
大学英语四级
相关试题推荐
AUKsupermarkethasbecomethefirstintheworldtoletshopperspayforgroceriesusingjusttheveinsintheirfingertips.
Forthispart,youareallowed30minutestowriteanessaybasedonthepicturebelow.Youshouldstartyouressaywithabrief
A、TheybelievedinMontgomeryWardandRichardSears.B、Theycouldgetthethingstheywantedatalowprice.C、Itwasconvenien
Waffles?Frenchtoast?Bacon?Bigbreakfastsmaybeathingofthepast.AccordingtotheAssociatedPress,moreAmericansarec
E此处需填入动词的过去分词,与have构成完成时态。空格所在的that定语从句修饰theirlonghairandsounds.说明披头士乐队的长发和声音对一代摇滚歌星和青少年的“影响”或“作用”,故选择influenced“影响”。
A、Aphenomenonofagingfacebecauseoffacingcomputerforlong.B、Afeatureofscreen-shapefacebecauseofpeoplefollowingf
A、Becausehermindwentblankundergreatstress.B、Becauseherintelligencewasbelowaverage.C、Becauseshestudiedfortoolo
A、It’satraditionalEuropeanfestival.B、ItfallsonthedaybeforeEaster.C、Thetraditionalcelebrationisdecoratingeggs.D
Forthispart,youareallowed30minutestowriteashortessayonNEET("NEET"means"NotCurrentlyEngagedinEducation,Empl
Predictingthefutureisalwaysrisky.Butit’sprobablysafetosaythatatleastafewhistorianswillonedayspeakofthe20
随机试题
分封制最早出现的朝代是()。
空调所用制冷技术属于()。
公司策划的首要内容是()
A.长吸式呼吸B.喘息样呼吸C.陈—施呼吸D.比奥呼吸在脑桥上、中部之间横断脑干并同时切断双侧颈迷走神经,动物将出现
国家药品不良反应监测中心报告,某省药品生产企业生产的某药品疗效不确,不良反应大,对该药品应当
根据社会保险法律制度的规定,下列情形应当视同为工伤的是()。
下列关于国债的表述正确的是:
【2015河南邓州】父母均为大学教师的小英从小受家庭的影响,很重视学习。初中期间,当她看书学习时,旁边如有人讲话,就特别反感。进入高中后,小英成绩优秀,担任了班长,但同学们都认为她自以为是,什么工作都必须顺着她,一些同学很讨厌她,为此她感到十分苦恼。如果小
计算机为了通过串行,将数据发送出去,必须(26)。
FromChristianityandthebarbariankingdomsofthewestemergedthemedievalversionofpolitics______inturnevolvedthepol
最新回复
(
0
)