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6.ALongandHealthyLifeHaveyouwishedforamagicpillormagicformula(方法)thatwouldletyoulivehappilyforever?Ifyouhave,don’tfeelalone!It’saverycommon,naturalwishthathasalonghistory.SpanishexplorersofthesixteenthcenturyeventriedtofindafountainofyouthinwhatisnowthestateofFlorida.Thewaterofthislegendary(传说中的)fountain,whichnoonehasyetfound,wasbelievedtorestoreyouthandgoodhealthtothosewhodrankit.Biologiststodaydon’texpectthatanyonewillfindamagicalfountainofyouth.Growingolderisanaturalpartofthelifecyclethatcan’tbereversed(倒退).Ashumanbeingsgrowolder,organssuchastheheartandlungsmaystopfunctioningproperly.Sightandhearingmaybecomeweak.Andthehumanbodybecomesmorelikelytocomedownwithseriousillnessfromwhichitcannotrecover.Consideredtogether,changesthatbringaboutthedecline(衰退)ofanorganismarecalledaging.Becauseofaging,manybiologistsbelievethattheremaybeamaximum(最大的)agelimittowhicheventhehealthiestorganismscanlive.Forhumanbeings,thismaximumagelimitisabout110years.Perhapsthemostimportantthingthatyoucanlearnfromyourstudyofhumanbiologyisthatyouhavealotofcontrolovertheagingprocessinyourownlife.Infact;withinourcontrolaremanyphysicalandmentalfactorsthathavemuchtodowithaging.Forexample,eachofus,asrecentresearchindicates,candomanythingstohelppreventheartandvessel(血管)disease,whichcauseshalfthedeathseachyearintheUnitedStates.Wecanavoideatingalotoffattymeat.Eatingtoomuchofthesetypesofanimalfatscanleadtotheclogging(阻塞)andhardeningofbloodvessels.Wecancutbackonsmokingandhopefullyofsugarweeat.Wecanexerciseregularlyandstrengthentheheartandotherorgans.Andwecanremembertotaketimeouteachdayforourselves,timejusttorelax.Exercise,recreation(娱乐),andrelaxationallreducestress－innertensionthatishardonallbodyorgans.Onefinalthingwecandoistotrytokeepawareofadvancesmadeinhealtheducation.Informationisoftenavailablefreeofchargefromhealthclinicsorschools.(406words)ComprehensionExercisesⅠ.Choosethebestanswerstothefollowingquestions.1.WhichofthefollowingistheleadingcauseofdeathintheUnitedStates?A.Heartdisease.B.Cancer.C.Alcohol.D.Smoking.2.Whathappensaspeoplegrowolder?A.Theydreamofamagicpilltohelpthemliveahappyandlongtime.B.Theycomedownwithseriousillnesses.C.Theirorgansbecomeweakandmaystopworkingproperly.D.Theirbloodvesselsbecomeclogged.3.Intheopinionofbiologists,＿＿＿.A.theagingprocesscanbereversedB.theagingprocesscanbecontrolledandsloweddownC.theagingprocesscanbegotridofD.theagingprocesscangobeyonditslimit4.Wecanslowdowntheweakeningofallourbodyorgansby＿＿＿.A.noteatinganimalfatB.limitingdrinkingandsmokingC.exercise,recreationandrelaxationtobloodvesselsD.preventingthecloggingandhardeningofbloodvessels5.Besidesphysicalandmentalfactors,whichofthefollowingalsocontributestolivingalongandhealthylifeaccordingtothepassage?A.Healtheducation.B.Traditionalmedicine.C.Artificialorgans.D.Theinventionofmagicpills.Ⅱ.Judgewhetherornotthefollowingstatementsagreewiththeinformationgiveninthepassage,andmarkYforYES,NforNO,orNGifinformationisnotgiveninthepassage.()1.Fewpeoplehavethewishoffindingamagicpillthatwouldbeofhelptolivehappilyforever.()2.Manybiologistsbelievethateachspecieshasanaturalmaximumagelimit.()3.Fromthepassageweknowthatthereismuchwecandotohelppreventmanydiseases.()4.Mentalfactorshavelittletodowithgoodhealth.()5.Doctorsbelievesthatregularexercisereducesthechancesofgettingheartdisease.7.TheEarth'sPastIfthehistoryoftheearthcouldbecompressed（压缩）intothespanofoneyear'stime,thestoryofthehumanracewouldbewrittenasthethelasttwohoursofthefinalday!ThisfactgivesyouanideaofjusthowoldtheEarthisnowrittenrecordtotellustheEarth'sgeologicalpast,theEarthhasleftarecordintheformoffossils.Afossilisthepreservedremainsortracedofanancientlivingthing.Fossilsaremostoftenfoundburiedinrock,buttheymaybones,shells,andwoodyalsobefoundincaves,ancienttar(沥青)beds,andthesolidicethatcoveredtheEarth'spolarregions.Inalltheseplaces,fossilsareprotectedfromdamagingeffectsofweatheringanderosion(侵蚀).Usuallyonlythehardpartsarepreserved.Thehardpartcanincludeones,shells,andwoodytissues.Thesoftparts,likeflesh,eitherdecayorareeatenbyanimalsbeforetheycanbepreserved.Oneexceptioniswhenanorganismissubjectedtoextremecold.Thentheentirebodymaybepreservedinice.Sometimestheremainsofanorganismarepreservedafterafterhavingbeenchangedintoacompletelydifferentform.Forinstance,coaldepositsontheEarthareactuallythefossilremainsofplants.Whenplantsdecompose(腐烂),eventuallyonlydepositsofcarbonremain.Whenthecarbonisunderextremepressureforalongperiodoftime,itisslowlytransformedintocoal.Coaliscalledafossilfuelbecauseofthewayitiscreated.Fossilscanhelpgeologists(地质学家)learnabouthowanimalandplantspecieshavechangedovertime.Sincegeologistscandatetherocksthatthefossilsarein,theycanalsotellduringwhattimeperiodinthepastaspecieslived.Forexample,onthegeologiccalendar,youcanseethatfishfirstappearintheeralabeledPaleozoic(古生代).Thismeansthattheoldestrocksdiscoveredtocontainfishfossilsarebetween225millionand600millionyearsold.Wecanassumethatfishexistedintheworldatleast225millionyearsago.Fossilsarealsousedtostudyextinct(灭绝的)species.Therearenolongeranylivingwoollymammo