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1、2019-2020年高考英语二轮复习科普知识阅读理解（1）科普知识（阅读理解）由(xx江苏,C)改编Ifadiversurfacestooquickly,hemaysufferthebends.Nitrogen(氮)dissolved(溶解)inhisbloodissuddenlyliberatedbythereductionofpressure.Theconsequence,ifthebubbles(气泡)accumulateinajoint,issharppainandabentbody—thusthen
2、ame.Ifthebubblesforminhislungsorhisbrain,theconsequencecanbedeath.Otherair-breathinganimalsalsosufferthisdepression(减压)sicknessiftheysurfacetoofast:whales,forexample.Andso,longago,didichthyosaurs.Thattheseancientseaanimalsgotthebendscanbeseenfromtheirbones.
3、Ifbubblesofnitrogenforminsidethebonetheycancutoffitsbloodsupply.Thiskillsthecellsinthebone,andconsequentlyweakensit,sometimestothepointofcollapse.Fossil(化石)bonesthathavecavedinonthemselvesarethusasignthattheanimaloncehadthebends.BruceRothschildoftheUniversi
4、tyofKansasknewallthiswhenhebeganastudyofichthyosaurbonestofindouthowwidespreadtheproblemwasinthepast.Whatheparticularlywantedtoinvestigatewashowichthyosaursadaptedtotheproblemofdepressionoverthe150millionyears.Tothisend,heandhiscolleaguestraveledtheworld’sn
5、atural-historymuseums,lookingathundredsofichthyosaursfromtheTriassicperiodandfromthelaterJurassicandCretaceousperiods.Whenhestarted,heassumedthatsignsofthebendswouldberarerinyoungerfossils,reflectingtheirgradualevolutionofmeasurestodealwithdepression.Instea
6、d,hewasastonishedtodiscovertheopposite.Morethan15%ofJurassicandCretaceousichthyosaurshadsufferedthebendsbeforetheydied,butnotasingleTriassicspecimen(标本)showedevidenceofthatsortofinjury.Ifichthyosaursdidevolveananti-depressionmeans,theyclearlydidsoquickly—an
7、d,moststrangely,theylostitafterwards.ButthatisnotwhatDrRothschildthinkshappened.Hesuspectsitwasevolutioninotheranimalsthatcausedthechange.Whalesthatsufferthebendsoftendosobecausetheyhavesurfacedtoescapeapredator(捕食动物)suchasalargeshark.OneofthefeaturesofJura
8、ssicoceanswasanabundanceoflargesharksandcrocodiles,bothofwhichwerefondofichthyosaurlunches.Triassicoceans,bycontrast,weremercifullyshark-andcrocodile-free.IntheTriassic,then,ichthyosaursweretopofthefoo
