托福TPO阅读45文本Word下载.docx

托福TPO阅读45文本Word下载.docx

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ItisthroughBeringiathatsmallgroupsoflargemammalhunters,slowlyexpandingtheirhuntingterritories,eventuallycolonizedNorthandSouthAmerica.Onthisarchaeologistsgenerallyagree,butthatiswheretheagreementstopsOnebroadareaofdisagreementinexplainingthepeoplingoftheAmericasisthedomainofpaleoecologists,butitiscriticaltounderstandinghumanhistory:

whatwasBeringialike?

TheBeringianlandscapewasverydifferentfromwhatitistoday.■Broad,windsweptvalleys;

glaciatedmountains;

sparsevegetation;

andlessmoisturecreatedaratherforbiddinglandmass.■Thislandmasssupportedherdsofnow-extinctspeciesofmammoth,bison,andhorseandsomewhatmodernversionsofcaribou,muskox,elk,andsaigaantelope.■Thesegrazerssupportedinturnanumberofimpressivecarnivores,includingthegiantshort-facedbear,thesaber-toothcat,andalargespeciesoflion.■

ThepresenceofmammalspeciesthatrequiregrasslandvegetationhasledArcticbiologistDaleGuthrietoarguethatwhilecoldanddry,theremusthavebeenbroadareasofdensevegetationtosupportherdsofmammoth,horse,andbison.Further,nearlyalloftheice-agefaunahadteeththatindicateanadaptationtograssesandsedges;

theycouldnothavebeensupportedbyamodernfloraofmossesandlichens.Guthriehasalsodemonstratedthatthelandscapemusthavebeensubjecttointenseandcontinuouswinds,especiallyinwinter.Hemakesthisargumentbasedontheanatomy

ofhorseandbison,whichdonothavetheabilitytosearchforfoodthroughdeepsnowcover.Theyneedlandscapeswithstrongwindsthatremovethewintersnows,exposingthedrygrassesbeneath.Guthrieappliedtheterm“mammothsteppe"

tocharacterizethislandscape.

Incontrast,PaulColinvauxhasofferedacounterargumentbasedontheanalysisofpolleninlakesedimentsdatingtothelasticeage.HefoundthattheamountofpollenrecoveredinthesesedimentsissolowthattheBeringianlandscapeduringthepeakofthelastglaciationwasmorelikelytohavebeenwhathetermeda"

polardesert,"

withlittleoronlysparsevegetation,innowaywasitpossiblethatthisregioncouldhavesupportedlargeherdsofmammalsandthus,humanhunters.Guthriehasarguedagainstthisviewbypointingoutthatradiocarbonanalysisofmammoth,horse,andbisonbonesfromBeringiandepositsrevealedthatthebonesdatetotheperiodofmostintenseglaciation.

Theargumentseemedtobeatastandstilluntilanumberofrecentstudiesresultedinaspectacularsuiteofnewfinds.Thefirstwasthediscoveryofa1,000-square-kilometerpreservedpatchofBeringianvegetationdatingtojustover17,000yearsago—thepeakofthelasticeageTheplantswerepreservedunderathickashfallfromavolcaniceruption.Investigationsoftheplantsfoundgrasses,sedges,mosses,andmanyothervarietiesinanearlycontinuouscover,aswaspredictedbyGuthrie.Butthisvegetationhadathinrootmatwithnosoilformation,demonstratingthattherewaslittlelong-termstabilityinplantcover,afindingsupportingsomeoftheargumentsofColinvaux.Amixtureofcontinuousbutthinvegetationsupportingherdsoflargemammalsisonethatseemsplausibleandrealisticwiththeavailabledata.

1.Theword"

remnants"

inthepassageisclosestinmeaning

Oremains

Oevidence

Oresults

Oreminders

2.Theword"

domain"

inthepassageisclosestinmeaningto

Ofieldofexpertise

Ochallenge

Ointerest

Oresponsibility

3.Accordingtoparagraph3,allofthefollowingaretrueoftheBeringianlandscapeEXCEPT.

OTherewaslittlevegetation.

OThemammalspeciesthereallsurvivedintomodernversions.

OTheclimatewasdrierthanitistoday.

OThereweremountainswithglaciers.

4.Thepurposeofparagraph3isto

Ocontrasttoday’sBeringianlandscapewithotherlandscapesintheAmericancontinent

OdescribetheBeringianlandscapeduringthelasticeage

OexplainwhysomanyBeringianspeciesbecameextinctduringthelasticeage

O