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时间:2019-11-16
《2019年高考英语一轮总复习 Unit 2 The United Kingdom课时作业 新人教版必修5》由会员上传分享,免费在线阅读,更多相关内容在教育资源-天天文库。
1、2019年高考英语一轮总复习Unit2TheUnitedKingdom课时作业新人教版必修5Ⅰ.阅读理解A(xx·江苏卷)Ifadiversurfacestooquickly,hemaysufferthebends.Nitrogen(氮)dissolved(溶解)inhisbloodissuddenlyliberatedbythereductionofpressure.Theconsequence,ifthebubbles(气泡)accumulateinajoint,issharppainandabentbody—thusthename.Ifthebubblesforminh
2、islungsorhisbrain,theconsequencecanbedeath.Otherair-breathinganimalsalsosufferthisdepression(减压)sicknessiftheysurfacetoofast:whales,forexample.Andsolongago,didichthyosaurs.Thattheseancientseaanimalsgotthebendscanbeseenfromtheirbones.Ifbubblesofnitrogenforminsidethebonetheycancutoffitsbloods
3、upply.Thiskillsthecellsinthebone,andconsequentlyweakensit,sometimestothepointofcollapse.Fossil(化石)bonesthathavecavedinonthemselvesarethusasignthattheanimaloncehadthebends.BruceRothschildoftheUniversityofKansasknewallthiswhenhebeganastudyofichthyosaurbonestofindouthowwidespreadtheproblemwasi
4、nthepast.Whatheparticularlywantedtoinvestigatewashowichthyosaursadaptedtotheproblemofdepressionoverthe150millionyears.Tothisend,heandhiscolleaguestraveledtheworld'snaturalhistorymuseums,lookingathundredsofichthyosaursfromtheTriassicperiodandfromthelaterJurassicandCretaceousperiods.Whenhesta
5、rted,heassumedthatsignsofthebendswouldberarerinyoungerfossils,reflectingtheirgradualevolutionofmeasurestodealwithdepression.Instead,hewasastonishedtodiscovertheopposite.Morethan15%ofJurassicandCretaceousichthyosaurshadsufferedthebendsbeforetheydied,butnotasingleTriassicspecimen(标本)showedevi
6、denceofthatsortofinjury.Ifichthyosaursdidevolveananti-depressionmeans,theyclearlydidsoquickly—and,moststrangely,theylostitafterwards.ButthatisnotwhatDrRothschildthinkshappened.Hesuspectsitwasevolutioninotheranimalsthatcausedthechange.Whalesthatsufferthebendsoftendosobecausetheyhavesurfacedt
7、oescapeapredator(捕食动物)suchasalargeshark.OneofthefeaturesofJurassicoceanswasanabundanceoflargesharksandcrocodiles,bothofwhichwerefondofichthyosaurlunches.Triassicoceans,bycontrast,weremercifullyshark-andcrocodile-free.IntheTriassic,then,ichthyosaurswereto
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