托福阅读生物类真题.docx

托福阅读生物类真题.docx

《托福阅读生物类真题.docx》由会员分享，可在线阅读，更多相关《托福阅读生物类真题.docx（5页珍藏版）》请在冰豆网上搜索。

托福阅读生物类真题

托福阅读生物类真题

　　小编又带来托福资料了，今天给大家带来的是托福资料之托福阅读生物类真题，文章里面是介绍关于生物方面的问题，大家可以感受一下生物类文章的套路，然后后面有问题提问，并且后面附有答案哦，希望可以帮助大家，下面我们就一起来看看吧。

　　Title：

TheExtinctionoftheDinosaurs

　　GeologistsdefinetheboundarybetweensedimentlayersoftheCretaceousperiod（144.C65millionyearsago）andthePaleoceneperiod（65.C55millionyearsago）inpartbythetypesandamountsofrocksandfossilstheycontainorlack.

　　Beforethelimitof65millionyearsago,marinestrataarerichincalciumcarbonateduetoaccumulationsoffossilsofmicroscopicalgaedepositedontheseafloor.Abovethe65-million-yearlimit,sea-floorsedimentscontainmuchlesscalciumcarbonate,andfossilsofseveralfamiliesofmollusksarenolongerfound.Incontinentalsediments,dinosaurfossils,thoughfrequentbefore65millionyearsago,aretotallyabsent.

　　Bycontrast,newfamiliesofmammalsappear,includinglargemammalsforthefirsttime.Scientistswonderedformanyyearsaboutwhatcouldhavecausedthedinosaurs'rapiddisappearanceattheendoftheCretaceousperiod,comingupwithagreatvarietyoftheoriesandscenarios.Forsome,itcouldhavebeenduetounfavorablegeneticchangestriggeredbyadramaticincreasebyafactorof10,100,1,000incosmic-rayparticlesreachingtheEarthafterasupernovaexplosionsomewhereintheneighborhoodofthesolarsystem.Forthesehigh-energyparticlestoaffectlife,theywouldhavetogetthroughtheprotectivebarrieroftheEarth'smagnetosphere,theregionoftheupperatmospherecontrolledbyEarth'smagneticfield.ThatcouldhavehappenedifthecloudofparticlesfromthesupernovaexplosionreachedtheEarthduringaperiodwhenthemagnetospherewasweakened,somethingthatmayhappenwhentheEarth'smagneticfieldchangesdirection.AndweknowthatthemagneticnorthandsouthpolesoftheEarthswitchontheaveragetwiceeverymillionyears.However,thisisnottheonlypossibleexplanationfordinosaurdestruction.

　　Othertheorieshaveraisedthepossibilityofstrongclimatechangesinthetropics（buttheythenmustbeexplained）.Certainly,ifclimatechanges,thechangeddistributionsoftemperatureandrainfallmodifytheconditionsthatfavoroneecosystemoveranother.Theextinctionofaparticularfamily,genus,orspeciesmayresultfromacomplicatedchainofindirectcausesandeffects.Overthirtyyearsago,scientistCarlSaganquotedonesuggestionthatthedemiseofthedinosaursresultedfromthedisappearanceofaspeciesoffernplantthatwasimportantfordinosaurdigestion.Othertheoriesinvolvedaworldwidecoldwavefollowingthespreadofalayerofcoldbutnotverysaltywaterintheworld'soceans,whichfloatedonthesurfacebecause,withitslowsalinity,thewaterwaslessdense.

　　Proponentsofanothertheorythatremainsunderconsiderationtodaypostulatethattheextinctionofthedinosaurscorrespondstoaperiodofintensevolcanicactivity.It'snotaquestionofjustoneorevenofathousanderuptionscomparabletotheexplosionofKrakatoain1883,oneofthelargestvolcaniceventsinmoderntimes,butratherofaprolongedperiodofactivity.OntheDeccanplateauinIndia,basalt（volcanic）rockscovermorethan500,000squarekilometers（nearly200,000squaremiles）,andcorrespondtomassivelavaoutflowsoccurringpreciselyattheendoftheCretaceous.Thissortofoutflowcouldcorrespondtovolcanicactivitysimilartotheactivitythatdrivessea-floorspreading,withlavaemergingfromelongatedfracturesinthecrustratherthanfromcraters.

　　ThevolcanicconvulsionthatburiedtheDeccanplateauinlavamustalsohavechangedthecompositionoftheatmosphereandseverelyaffectedclimate.Initially,theremusthavebeenstrongsuddencoolingresultingfromtheblockingofsunlightbysulfateaerosolveilsinthestratosphere（partoftheEarth'satmosphere）.Ifstrongcoolinglastedayearaftertheformationoftheaerosols,itwouldhavebeenthedeathoftropicalspeciesunabletoadapttosuchavolcanicwinter.

　　However,alongperiodofstrongvolcanicactivity（again,rememberthousandsofKrakatoas）wouldatthesametimehaveaddedasubstantialamountofcarbondioxidetotheatmosphere,reinforcingthegreenhouseeffect.Thiswouldgraduallywarmthingsup,endingtheextendedcoldsnapandproducingglobalwarmingtogetherwithgeographicshiftsofhumidandarid（dry）zones.Certainlythingswouldchangetoupsetlivingconditions,leadingtotheextinctionofsomespecieswhileotherswouldprofit,ifonlyfromthedisappearanceofpredators.

　　1.Accordingtoparagraph1,whichofthefollowingistrueofPaleocenesediments

　　A.TheylackfossilsfromsomefamiliesofmammalsfoundinCretaceoussediments.

　　B.Theycontainfossilsofdinosaurs.

　　C.TheycontainfossilsofsomeanimalsthatdidnotexistduringtheCretaceous.

　　D.TheycontainfossilsofmorekindsofmollusksthanarefoundinCretaceoussediments.

　　2.Thewordunfavorableinthepassageisclosestinmeaningto

　　A.Unusual

　　B.Disadvantageous

　　C.Sudden

　　D.major

　　3.Thewordtriggeredinthepassageisclosestinmeaningto

　　A.initiated

　　B.intensified

　　C.followed

　　D.aided

　　4.WhydoestheauthorincludetheinformationthatthemagneticnorthandsouthpolesoftheEarthswitchontheaveragetwiceeverymillionyears

　　A.ToprovideevidenceshowingthatEarth'sprotectivebarrierisdifficulttogetthrough

　　B.ToshowthatitisreasonabletothinkthatparticlesfromasupernovaexplosioncouldhavereachedEarth

　　C.Toexplainwhysomescientistsbelieveasupernovaexplosionmayhaveoccurrednearoursolarsystem

　　D.Tohelpexplainwhysomescientistshaverejectedthetheorypresentedinparagraph2

　　5.Accordingtothetheorydiscussedinparagraph2，aweakeningofEarth'smagnetospheremayhave

　　A.causedasupernovatoexplodenearoursolarsystem

　　B.allowedgene-alteringparticlestoreachEarth'ssurface

　　C.forcedEarth'smagneticfieldtochangedirection

　　D.allowedcloudsofprotectiveparticlestoescapefromEarth'supperatmosphere

　　6.AIIofthefollowingarementionedinparagraph3aspossiblecausesfortheextinctionofthedinosaursEXCEPT

　　A.achangeinthedietofdinosaurs

　　B.achangeintheclimateofthetropics

　　C.adecreaseinglobaltemperatures

　　D.adecreaseindeepoceansalinity

　　7.Inparagraph3，whydoestheauthorincludethequotationbyCarlSagan

　　A.Toexplaintheconnectionbetweendinosaurextinctionandtheextinctionofotheranimalspecies

　　B.Tosupporttheclaimaboutspeciesextinctionbeingduetoindirectcausesandeffects

　　C.Toshowthatscientistshaverevisedtheirideasgreatlyinthelastthirtyyears

　　D.Toidentifythedifferencesbetweenthevarioustheoriesfortheextinctionofdinosaurs

　　8.Accordingtoparagraph4，whatwasoneunusualaspectofthevolcanicactivityattheendoftheCretaceous

　　A.SomeexplosionsweremuchlargerthanKrakatoa.

　　B.Eruptionsoccurredoveralongperiodoftime.

　　C.Activevolcanoesweresometimesseparatedbymanykilometers.

　　D.Therewereactivevolcanoesintheseaaswellasonland.

　　9.Whichofthefollowingispresentedinparagraph4asevidencethatintensevolcanicactivityoccurredataboutthetimethatthedinosaursbecameextinct

　　A.ThesizeofthevolcaniccratersontheDeccanplateau

　　B.Anincreaseinsea-floorspreading

　　C.TheformationinIndiaoflargeamountsofatypeofrockassociatedwithvolcanoes

　　D.TheoccurrenceofathousandormorevolcanicexplosionsthesizeofKrakatoa

　　10.Thewordseverelyinthepassageisclosestinmeaningto

　　A.certainly

　　B.consequently

　　C.greatly

　　D.permanently

　　11.Thewordreinforcinginthepassageisclosestinmeaningto

　　A.makingpossible

　　B.spreading

　　C.introducing

　　D.strengthening

　　12.Accordingtoparagraph5，allofthefollowingaretheorizedtohaveoccurredasaresultofvolcanicactivityEXCEPT

　　A.adecreaseintheamountofsunlightreachingEarth'ssurface

　　B.areductioninthenumberofsulfateaerosolveilsinthestratosphere

　　C.increaseddrynessinsomeareasthatwereoncemorehumid

　　D.changesintheatmosphere'scompositionresultinginanincreaseintemperature

　　13.Lookatthefoursquaresthatindicatewherethefollowingsentencecouldbeaddedtothepassage.

　　Thus,ecosystemsfollowingperiodsofextensivevolcanicactivitynecessarilyhaddifferentcombinationsofspeciesthanearlierecosystemsdid.

　　WherewouldthesentencebestfitClickonasquaretoaddthesentencetothepassage.

　　（题目不完整）

　　14.Dragyourchoicestothespaceswheretheybelong.Toreviewthepassage,clickonViewText

　　AnswerChoices

　　A.CosmicraysfromanearbysupernovaexplosionmayhavepenetratedEarth'satmosphere,causinggeneticchangesthatdinosaurpopulationscouldnotsurvive.

　　B.Climatechangesinthetropicsmayhavesetoffachainofindirecteffectsthatnegativelyaffectedtheecosystemsinwhichdinosaurslived.

　　C.ThespreadoflavaoverlargepartsofpreviouslyfavoredhabitatssuchastheDeccanPlateaumayhavemadethesefavoredareasuninhabitableformanyyears.

　　D.Althoughthevolcanicwinterresultingfromtheformationofsulfateaerosolseventuallyended,temperaturesmayhaveremainedbelowlevelsrequiredbydinosaurstosurvive.

　　E.Temperaturechangesandgeographicshiftsinclimatezonesduetotheatmosphericeffectsofvolcanicactivitymayhavebeensignificantenoughtocauseextinction.

　　F.Tobeconvincing，theoriesaboutwhatcauseddinosaurstobecomeextinctmustbeabletoexplainthedisappearanceofotherpredatorsinthefoodchainatthesametime