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老托福阅读0308.docx

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0308托福试题 阅读（55minutes） Question1-11 Iffoodisallowedtostandforsometime,itputrefies.Whentheputrefiedmaterial isexaminedmicroscopically,itisfoundtobeteemingwithbacteria.Wheredothese bacteriacomefrom,sincetheyarenotseeninfreshfood?Evenuntilthemid-nineteenth century,manypeoplebelievedthatsuchmicroorganismsoriginatedbyspontaneous (5)generation,ahypotheticalprocessbywhichlivingorganismsdevelopfromnonliving matter. ThemostpowerfulopponentofthetheoryofspontaneousgenerationwastheFrenchchemistandmicrobiologistLouisPasteur(1822-1895).Pasteurshowedthatstructures presentinaircloselyresemblethemicroorganismsseeninputrefyingmaterials.Hedid (10)thisbypassingairthroughguncottonfilters,thefibersofwhichstopsolidparticles.After theguncottonwasdissolvedinamixtureofalcoholandether,theparticlesthatithad trappedfelltothebottomoftheliquidandwereexaminedonamicroscopeslide.Pasteur foundthatinordinaryairtheseexistsavarietyofsolidstructuresranginginsizefrom 0.01mmtomorethan1.0mm.Manyofthesebodiesresembledthereproductive (15)structuresofcommonmolds,single-celledanimals,andvariousothermicrobialcells. Asmanyas20to30ofthemwerefoundinfifteenlitersofordinaryair,andtheycould notbedistinguishedfromtheorganismsfoundinmuchlargernumbersinputrefyingmaterials.Pasteurconcludedthattheorganismsfoundinputrefyingmaterialsoriginated fromtheorganizedbodiespresentintheair.Hepostulatedthatthesebodiesareconstantly (20)beingdepositedonallobjects. Pasteurshowedthatifanutrientsolutionwassealedinaglassflaskandheatedto boilingtodestroyallthelivingorganismscontaminatingit,itneverputrefied.Theproponentsofspontaneousgenerationdeclaredthatfreshairwasnecessaryfor spontaneousgenerationandthattheairinsidethesealedflaskwasaffectedinsomeway (25)byheatingsothatitwouldnolongersupportspontaneousgeneration.Pasteurconstructedaswan-neckedflaskinwhichputrefyingmaterialscouldheheatedtoboiling,butair couldreenter.Thebendsintheneckpreventedmicroorganismsfromgettingintheflask..Materialsterilizedinsuchaflaskdidnotputrefy. 1,Whatdoesthepassa