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1、托福作文写作范文详解ReadingEndothermsareanimalssuchasmodernbirdsandmammalsthatkeeptheirbodytemperaturesconstant.Forinstance,humansareendothermsandmaintainaninternaltemperatureof37oCznomatterwhethertheenvironmentiswarmorcold.Becausedinosaurswerereptiles,andmodernreptilesarenotendothermszitwaslongassumedthatdin
2、osaurswerenotendotherms.However,dinosaursdifferinmanywaysfrommodemreptiles,andthereisnowconsiderableevidencethatdinosaurswerezinfactzendotherms.PolardinosaursOnereasonforbelievingthatdinosaurswereendothermsisthatdinosaurfossilshavebeendiscoveredinpolarregions.Onlyanimalsthatcanmaintainatemperaturewe
3、llabovethatofthesurroundingenvironmentcouldbeactiveinsuchcoldclimates.LegpositionandmovementThereisaconnectionbetweenendothermyandthepositionandmovementofthelegs.Thephysiologyofendothermyallowssustainedphysicalactivity,suchasrunning.Butrunningisefficientonlyifananimalslegsarepositionedunderneathitsb
4、ody,notatthebodyssidezastheyareforcrocodilesandmanylizards.Thelegsofallmodernendothermsareunderneaththebody,andsowerethelegsofdinosaurs.Thisstronglysuggeststhatdinosaurswereendotherms.HaversiancanalsThereisalsoaconnectionbetweenendothermyandbonestructure.Thebonesofendothermsusuallyincludestructuresc
5、alledHaversiancanals.Thesecanalshousenervesandbloodvesselsthatallowthelivinganimaltogrowquicklyzandrapidbodygrowthisinfactacharacteristicofendothermy.ThepresenceofHaversiancanalsinboneisastrongindicatorthattheanimalisanendotherm,andfossilizedbonesofdinosaursareusuallydensewithHaversiancanals.Listeni
6、ngProfessor:Manyscientistshaveproblemswiththeargumentsyoureadinthepassage.Theydontthinkthoseargumentsprovethatdinosaurswereendotherms.Takethepolardinosaurargument.Whendinosaurslived,eventhepolarregions,wheredinosaurfossilshavebeenfound,weremuchwarmerthantoday,warmenoughduringpartoftheyearforanimalst
7、hatwerenotendothermstolive.Andduringthemonthswhenthepolarregionswerecoldztheso-calledpolardinosaurscouldhavemigratedtowarmerareasorhibernatedlikemanymodernreptilesdo.Sothepresenceofdinosaurfossilsinpolarregionsdoesntprovethedinosaurswereendotherms.Wellzwhataboutthefactthatdinosaurshavetheirlegsplace
8、dundertheirbodies,notouttothesidelikecrocodiles.Thatdoesntnecessarilymeandinosaurswerehigh-energyendothermsbuiltforrunning.Thereisanotherexplanationforhavinglegsunderthebody.Thisbodystructuresupportsmoreweightsowiththelegsundertheirbodies,dinosaurscangrowtoaverylargesize.Beinglargehadadvantagesfordi
9、nosaurs,sowedontneedtheideaofendothermyandrunningtoexplainwhydinosaursevolvedtohavetheirlegsundertheirbodies.Okzsohowaboutbonestructure?ManydinosaurbonesdohaveHaversiancanals,thatstrue.Thedinosaurbonesalsohavegrowthrings.Growthringsarethickeningofthebonethatindicatesperiodsoftimewhenthedinosaurswere
10、ntrapidlygrowing.Thesegrowthringsareevidencethatdinosaursstoppedgrowingorgrewmoreslowlyduringcoolerperiods.Thispatternofperiodicgrowth,youknowzrapidgrowthfollowedbynogrowthorslowgrowth,andthenrapidgrowthagainzischaracteristicofanimalsthatarenotendotherms.Animalsthatmaintainaconstantbodytemperatureye
11、ar-roundastrueendothermsdogrowrapidlyevenwhentheenvironmentbecomescool.阅读听力要点概括ReadingPassageMainpoints:Evidencethatdinosaurswereendotherms.Subpoint1:Polardinosaursfound.Subpoint2:Legpositionsuggestsendotherms.Subpoint3:Bonestructureindicatesendothermy.LectureAttitude:Arguments.(Can,tproveendotherms
12、.)SubPoint1:Polarregionswerewarmer.(Migrateorhibernate.)SubPoint2:Legsjustforsupportmoreweight.SubPoint3:Growthrings.（Periodicgrowth.）范文逐段赏析Paragraph1Theprofessoractuallycontradictsthestatementsmadeinthereadingpassage.Sheisoftheviewthatdinosaurswerenotendotherms,orthattheywerenotabletokeeptheirbodyt
13、emperaturesataconstantrate.此段功能：（Listeningpassage后文提到用L代替）（Readingpassage后文用R代替）以L为主，作者开头段写出L反对R做出的观点。她认为恐龙不是暖血动物，或者不能把他们的体温维持恒定。此段结构：作者在开头段立刻表面了逻辑，随后总结了L的观点，准备开始辩论。Paragraph2Theprofessordisputestheissueofdinosaursbeingendotherms.Basedonthelimitedavailabilityoffossilsfromthepolarregions,sheassertsth
14、attheseregionswerenotascoldastheyaretoday,andcouldsustaindinosaurlifeduringwarmerseasons.Duringharshwintersshebelievesthatthereisapossibilitythatthedinosaursactuallymigratedtowarmerregions.此段功能：以L的观点开头，作者说L不认为恐龙是暖血动物，因为当地的极地气候没有现在这么冷，在温暖的时候也许可以让恐龙存活。在冬季的时候恐龙可以迁移到更温暖的地方去。此段结构：此段为总分结构，在第一个极地问题的讨论上，L给了
15、一系列证据支撑她的论点。Paragraph3Theissueoflegpositionandmovementbeingusedasareasontoclassifythedinosaursasendothermsdoesnotsatisfytheprofessoreither.Shesaysthatdinosaurshadlegsundertheirbodiestosupporttheirmassiveweights,andnottoprovideitwithabodystructurelikeotherendothermiccreatures,andonemoresuitedtorunnin
16、g.此段功能：作者继续说L认为大腿位置也不能证明恐龙是暖血动物。L解释恐龙的大腿在1区干下面主要是用于支撑体重或者跑步，不是像其他的暖血动物一样。此段结构：总分结构。作者带出L观点之后详细解释了L的证据。Paragraph4Theprofessoracknowledgesthepresenceofhaversiancanalsbutalsopointsoutthatthatthefossilsshowthepresenceofgrowthrings.Theseringsareduetothethickeningofadevelopingbone.Thethickeningindicatesthatthedinosaurswerenztactuallygrowingcontinuouslybutwereexperiencingperiodsofbothrapidgrowthandnogrowthin
