《英语文章精粹》word版

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1、环球雅思学术写作中心www.ielts.com.cn/writing最值得背诵的英语文章精粹环球雅思学术写作中心推荐www.ielts.com.cn/writing1CellsandTemperatureCellscannotremainaliveoutsidecertainlimitsoftemperatureandmuchnarrowerlimitsmarktheboundariesofeffectivefunctioning.Enzymesystemsofmammalsandbirdsaremostefficientonly

2、withinanarrowrangearound37C;adepartureofafewdegreesfromthisvalueseriouslyimpairstheirfunctioning.Eventhoughcellscansurvivewiderfluctuationstheintegratedactionsofbodilysystemsareimpaired.Otheranimalshaveawidertoleranceforchangesofbodilytemperature.Forcenturiesithasbeen

3、recognizedthatmammalsandbirdsdifferfromotheranimalsinthewaytheyregulatebodytemperature.Waysofcharacterizingthedifferencehavebecomemoreaccurateandmeaningfulovertime,butpopularterminologystillreflectstheolddivisioninto“warm-blooded”and“cold-blooded”species;warm-bloodedi

4、ncludedmammalsandbirdswhereasallothercreatureswereconsideredcold-blooded.Asmorespecieswerestudied,itbecameevidentthatthisclassificationwasinadequate.Afencelizardoradesertiguana—eachcold-blooded----usuallyhasabodytemperatureonlyadegreeortwobelowthatofhumansandsoisnotco

5、ld.Thereforethenextdistinction64环球雅思学术写作中心www.ielts.com.cn/writingwasmadebetweenanimalsthatmaintainaconstantbodytemperature,calledhome0therms,andthosewhosebodytemperaturevarieswiththeirenvironments,calledpoikilotherms.Butthisclassificationalsoprovedinadequate,becausea

6、mongmammalstherearemanythatvarytheirbodytemperaturesduringhibernation.Furthermore,manyinvertebratesthatliveinthedepthsoftheoceanneverexperiencechangeinthedepthsoftheoceanneverexperiencechangeinthechillofthedeepwater,andtheirbodytemperaturesremainconstant.2SleepSleetis

7、partofaperson’sdailyactivitycycle.Thereareseveraldifferentstagesofsleep,andtheytoooccurincycles.Ifyouareanaveragesleeper,yoursleepcycleisasfollows.Whenyoufistdriftoffintoslumber,youreyeswillrollaboutabit,youtemperaturewilldropslightly,yourmuscleswillrelax,andyourbreat

8、hingwellslowandbecomequiteregular.Yourbrainwavesslowandbecomequiteregular.Yourbrainwavesslowdownabittoo,withthealpharhythmof