托福阅读生物类真题.docx
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托福阅读生物类真题.docx
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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
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