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时间:2018-01-22
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1、EnglishforbiologystudentstranslationLesson6-9第六课AHomeforLife:FormationoftheSolarSystemandPlanetEarthThestoryoflife'soriginsbeginswiththeformationoftheearth. Thesequenceofeventsthatgaverisetoourplanetbegan,inturn,withthecosmicexplosionphysicistscalltheBigBang. Thesunatthecenterofoursolarsystem
2、condensedfromacloudofprimordialmatterroughly5billionyearsago;theplanets,includingtheearth,condensedabout4.6billionyearsago. Theearthiscomposedofanumberoflayers:asolidcrust,asemisolidmantle,andalargelymolten(liquid)corethathasasolidcenter. BasicphysicalfeaturesofEarththatmayhavemadetheemergenc
3、eoflifepossibleincludetheplanet'ssize,temperature,composition,anddistancefromthesun. Themajorcurrenthypothesisholdsthatlifearosespontaneouslyontheearlyearthbymeansof chemicalevolutionfromnonlivingsubstances.生命起源于地球的形成。大爆炸是我们行星形成的开始。太阳在50亿年前生成,位于太阳系中心,行星,包括地球,在46亿年前生成。地球由多层组成:坚硬的地壳,半流体的地幔,一个很大
4、的溶解中心中存在一个坚实的中心。地球的基本特征使生命起源成为可能,包括行星的大小,温度,组成以及离太阳的距离。当前主要假设认为,由非生命的化学物质进化过程自发产生了生命。TheEmergenceoflife:OrganicandBiologicalMoleculesonaPrimitivePlanetEvidenceforprelifestagesofchemicalorganizationcomesfromlaboratoryexperimentsthattrytoduplicatethephysicalenvironmentandchemicalresourcesoftheear
5、lyearth. Theseexperiments,includingthepioneeringworkofMillerandUrey,havesuccessfullyproducedorganicmonomersincludingaminoacids,simplesugars,andnucleicacidbases. Theprobablenextsteptowardlifewasthespontaneouslinkingofsuchmonomersintopolymerssuchasproteinoidsandnucleiacids.Currentresearchsugges
6、tsthatlikelysitesforthispolymerizationwereclayorrocksurfaces.通过创造出地球早期的自然条件和化学资源条件,科学家在实验室中已经获得了化学有机体生命前阶段的证据。这些实验包括米勒等早期所做工作,成功地产出了有机单体,包括氨基酸,单糖,核酸碱基。这些单体自发的连接成多聚体,如类蛋白和核酸,使进入生命状态成为可能。这些聚合作用可能发生在泥土或岩石表面。Researchershavefoundthat,whenenergyisavailabletoasystem,theycangeneratethreekindsoforganicm
7、olecularaggregates. TheRussianAleksandrOparinobtainedpolymer-richdroplets,calledcoacervatesfromsolutionsofpolymers. SidneyFoxgeneratedproteinoidmicrospheresfrommixturesofaminoacidsandwater. Athirdlaboratorystructureistheliposom
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