如果您无法下载资料，请参考说明：
1、部分资料下载需要金币，请确保您的账户上有足够的金币
2、已购买过的文档，再次下载不重复扣费
3、资料包下载后请先用软件解压，在使用对应软件打开
PartIV.ReadingComprehension(30%)Directions:Inthispartofthetesttherearesixpassages.Followingeachpassagetherearefivequestionswithfourchoices.ChoosethebestanswerandmarkyouranswerontheANSWERSHEET.PassageOneCellscannotremainaliveoutsidecertainlimitsoftemperature,andmuchnarrowerlimitsmarktheboundariesofeffectivefunctioning.Enzyme(酶)systemsofmammalsandbirdsaremostefficientonlywithinanarrowrangearound37ºC;adepartureofafewdegreesfromthisvalueseriouslyimpairstheirfunctioning.Eventhoughcellscansurvivewiderfluctuations,theintegratedactionsofbodilysystemsareimpaired.Otheranimalshaveawidertoleranceforchangesofbodilytemperature.Forcenturiesithasbeenrecognizedthatmammalsandbirdsdifferfromotheranimalsinthewaytheyregulatebodytemperatures.Waysofcharacterizingthedifferencehavebecomemoreaccurateandmeaningfulovertime,butpopularterminologystillreflectstheolddivisioninto“warm-blooded’and“cold-blooded”species;warm-bloodedincludedmammalsandbirds,whereasallothercreatureswereconsideredcold-blooded.Asmorespecieswerestudied,itbecameevidentthatthisclassificationwasinadequate.Afencelizardoradesertiguana(鬣蜥)—eachcold-blooded—usuallyhasabodytemperatureonlyadegreeortwobelowthatofhumansandsoisnotcold.Thereforethenextdistinctionwasmadebetweenanimalsthatmaintainaconstantbodytemperature,calledhomotherms（同温动物）,andthosewhosebodytemperaturevarieswiththeirenvironment,calledpoikilotherms(变温动物).Butthisclassificationalsoprovedinadequate,becauseamongmammalstherearemanythatvarytheirbodytemperaturesduringhibernation.Furthermore,manyinvertebrates(无脊椎动物)thatliveinthedepthsoftheoceanneverexperienceachangeinthechillofthedeepwater,andtheirbodytemperaturesremainconstant.Thecurrentdistinctionisbetweenanimalswhosebodytemperatureisregulatedchieflybyinternalmetabolicprocessesandthosewhosetemperatureisregulatedby,andwhogetmostoftheirheatfrom,theenvironment.Theformerarecalledendotherms(恒温动物),andthelatterarecalledectotherms(外温动物).Mostectothermsdoregulatetheirbodytemperature,andtheydosomainlybylocomotingtofavorablesitesor
