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1、.....环球新托福考试院入学英语水平测试题ReadingExtinctionoftheDinosaursPaleontologistshavearguedforalongtimethatthedemiseofthedinosaurswascausedbyclimaticalterationsassociatedwithslowchangesinthepositionsofcontinentsandseasresultingfromplatetectonics.OffandonthroughouttheCreta
2、ceous(thelastperiodoftheMesozoicera,duringwhichdinosaursflourished),largeshallowseascoveredextensiveareasofthecontinents.Datafromdiversesources,includinggeochemicalevidencepreservedinseafloorsediments,indicatethattheLateCretaceousclimatewasmilderthantoday’s.T
3、hedayswerenottoohot,northenightstoocold.Thesummerswerenottoowarm,northewinterstoofrigid.Theshallowseasonthecontinentsprobablybufferedthetemperatureofthenearbyair,keepingitrelativelyconstant.AttheendoftheCretaceous,thegeologicalrecordshowsthattheseseawaysretre
4、atedfromthecontinentsbackintothemajoroceanbasins.Nooneknowswhy.Overaperiodofabout100,000years,whiletheseaspulledback,climatesaroundtheworldbecamedramaticallymoreextreme:warmerdays,coolernights;hottersummers,colderwinters.Perhapsdinosaurscouldnottoleratethesee
5、xtremetemperaturechangesandbecameextinct.Iftrue,though,whydidcold-bloodedanimalssuchassnakes,lizards,turtles,andcrocodilessurvive学习参考.....thefreezingwintersandtorridsummers?Theseanimalsareatthemercyoftheclimatetomaintainalivablebodytemperature.It’shardtounder
6、standwhytheywouldnotbeaffected,whereasdinosaurswerelefttoocrippledtocope,especiallyif,assomescientistsbelieve,dinosaurswerewarm-blooded.CriticsalsopointoutthattheshallowseawayshadretreatedfromandadvancedonthecontinentsnumeroustimesduringtheMesozoic,sowhydidth
7、edinosaurssurvivetheclimaticchangesassociatedwiththeearlierfluctuationsbutnotwiththisone?Althoughinitiallyappealing,thehypothesisofasimpleclimaticchangerelatedtosealevelsisinsufficienttoexplainallthedata.Dissatisfactionwithconventionalexplanationsfordinosaure
8、xtinctionsledtoasurprisingobservationthat,inturn,hassuggestedanewhypothesis.ManyplantsandanimalsdisappearabruptlyfromthefossilrecordasonemovesfromlayersofrockdocumentingtheendoftheCretace
