托福阅读生物类真题Word文档下载推荐.docx
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托福阅读生物类真题Word文档下载推荐.docx
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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'
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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