托福作文写作范文详解urin.docx
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1、托福作文写作范文详解ReadingLargenumbersofdinosaurfossilshavebeendiscoveredindepositsonAlaskasNorthSlopezaregionthattodayexperiencesanextremelycoldzarcticclimate.OnehundredmillionyearsagozwhenthosedinosaurswerealiveztheenvironmentoftheNorthSlopewasalreadyinhospitable,especiallyduringthewinterwhenitexperienceds
2、everalmonthsoftotaldarkness.Howdidthedinosaurssurvivethewintertime?PaleontologistshaveproposedthatoneofthemostcommonNorthSlopedinosaurs,theelephant-sizededmontosaur(Edmontosaurus)zsurvivedthewinterbymigratingsouthtomorehospitableregions.Severalargumentssupportthemigrationhypothesis.Firstztheedmontos
3、aur1sdietsupportsthemigrationhypothesis.Edmontosaursfedexclusivelyonplants.SincetherewouldhavebeennoplantsgrowingduringthecoldanddarkNorthslopewinter,itappearsthattheedmontosaurmusthaveleftforatleastpartoftheyearandmigratedtomoretemperatezonestofindfood.Secondzmanyedmontosaurskeletonshavebeenunearth
4、edfromthesamesite.Thissuggeststhatedmontosaurslivedinherd.Manymodern-daymigratoryanimals,suchascaribouandbuffalozliveandmigrateinherdsaswell.Movinginherdshelpsanimalscoordinatetheirmigration.Thefindingthatedmonotsaurslivedinherdsfurthersupportsthemigrationhypothesis.Finally,ednonosaurswerephysically
5、capableofmigratinglongdistances.Toreachmorehospitableregion,theedmontosaurhadtomigrateaboutlz600kilometerssouthward.Tomakesuchajourney,theedmontosaurneededtomoveataboutfivekilometersperhourforseveralweeks,whichiscertainlycoulddo.Theseanimalscouldrunveryfast,reachingspeedsupto45kilometersperhour.Itco
6、uldhaveeasilyuseditslocomotivepowertomovetowarmerclimateduringtheharsharcticwinters.ListeningThehypothesesthattheEdmontosaurmigratedeverywinterisnotConvincing.FirstztheEdmontosaurdidnothavetomigratetofindfood.OnehundredmillionyearsagozthesummertemperaturesintheNorthSlopeareawerewarmerthantheyaretoda
7、y.Andremember,inarcticregionsliketheNorthSlope,thesunshines24hoursadayatthepeakofthesummer.Thewarmtemperaturesandextensivedaylightcreatedincrediblygoodgrowingconditionsforplants,somuchvegetationwasproducedduringthesummerthatwhenthevegetationdiedasthewintercame,therewasalotofnutritiousdeadvegetationa
8、roundinthewinter.TheEdmontosaurcouldhaveeasilylivedonthedeadplantmatterduringthewinter.SecondJustbecauseofEdmontosaurlivedinherdsdoesntmeantheymigrated.Animalsliveinherdsformanyotherreasons.Livinginherds,forexample,providesanimalswithextraprotectionfrompredators.Havingextraprotectionisusefulevenfort
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