搜索
2012年雅思考试阅读模拟试题(含答案)Don’twashthosefossils!StandardmuseumpracticecanwashawayDNA.1.Washing,brushingandvarnishingfossils—allstandardconservationtreatmentsusedbymanyfossilhuntersandmuseumcuratorsalike—vastlyreducesthechancesofrecoveringancientDNA.2.Instead,excavatorsshouldbehandlingatleastsomeoftheirbountywithgloves,andfreezingsamplesastheyarefound,dirtandall,concludesapaperintheProceedingsoftheNationalAcademyofSciencestoday.3.AlthoughmanypalaeontologistsknowanecdotallythatthisisthebestwaytouptheoddsofextractinggoodDNA,Eva-MariaGeigloftheJacquesMonodInstituteinParis,France,andhercolleagueshavenowshownjusthowimportantconservationpracticescanbe.Thisinformation,theysay,needstobehammeredhomeamongthepeoplewhoareactuallyoutinthefielddiggingupbones.4.Geiglandhercolleagueslookedat3,200-year-oldfossilbonesbelongingtoasingleindividualofanextinctcattlespecies,calledanaurochs.ThefossilsweredugupatasiteinFranceattwodifferenttimes—eitherin1947,andstoredinamuseumcollection,orin2004,andconservedinsterileconditionsat-20oC.5.Theteam’sattemptstoextractDNAfromthe1947bonesallfailed.Thenewlyexcavatedfossils,however,allyieldedDNA.6.Becausetheboneshadbeenburiedforthesameamountoftime,andinthesameconditions,theconservationmethodhadtobetoblamesaysGeigl.AsmuchDNAwasdegradedinthese57yearsasinthe3,200yearsbefore,shesays.Washin,washout7.Becausemanypalaeontologistsbasetheirworkontheshapeoffossilsalone,theirmethodsofconservationarenotdesignedtopreserveDNA,Geiglexplains.8.Thebiggestproblemishowtheyarecleaned.Fossilsareoftenwashedtogetheron-siteinalargebath,whichcanallowwater—andcontaminantsintheformofcontemporaryDNA—topermeateintotheporousbones.NotonlyistheauthenticDNAgettingwashedout,butcontaminationisgettingwashedin,saysGeigl.9.MostancientDNAspecialistsknowthisalready,saysHendrikPoinar,anevolutionarygeneticistatMcMasterUniversityinOntario,Canada.Butthatdoesn’tmeanthatbestpracticehasbecomewidespreadamongthosewhoactuallyfindthefossils.10.GettingholdoffossilsthathavebeenpreservedwiththeirDNAinmindreliesoncloserelationshipsbetweenlab-basedgeneticistsandtheexcavators,sayspalaeogeneticistSvantePbooftheMaxPlanckInstituteforEvolutionaryAnthropologyinLeipzig,Germany.Andthatonlyoccursinexceptionalcases,hesays.11.Pbo’steam,whichhasbeensequencingNeanderthalDNA,continuallyfacestheseproblems.WhenyouwanttostudyancienthumanandNeanderthalremains,there’sabigissueofcontaminationwithcontemporaryhumanDNA,hesays.12.Thisdoesn’tmeanthatallmuseumspecimensarefatallyflawed,notesPbo.TheNeanderthalfossilsthatwererecentlysequencedinhisownlab,forexample,hadbeenpartofamuseumcollectiontreatedinthetraditionalway.ButPboiskeentoseesamplesoffossilsfromeverymajorfindpreservedinlinewithGeigl’srecommendations—justincase.Warmandwet13.Geiglherselfbelievesthat,withcooperationbetweenbenchandfieldresearchers,preservingfossilsproperlycouldopenupavenuesofdiscoverythathavelongbeenassumedclosed.14.Muchhumanculturaldevelopmenttookplaceintemperateregions.DNAdoesnotsurvivewellinwarmenvironmentsinthefirstplace,andcanvanishwhenfossilsarewashedandtreated.Forthisreason,Geiglsays,mostancientDNAstudieshavebeendoneonpermafrostsamples,suchasthewoollymammoth,oronremainsshelteredfromtheelementsincoldcaves—includingcavebearandNeanderthalfossils.15.Betterconservationmethods,andafocusonfreshfossils,couldboostDNAextractionfrommoredelicatespecimens,saysGeigl.Andthatcouldshedmorelightonthestoryofhumanevolution.(640wordsnature)GlossaryPalaeontologists古生物学家Aurochs欧洲野牛Neanderthal(人类学)尼安德特人，旧石器时代的古人类。Permafrost(地理)永冻层Questions1-6AnswerthefollowingquestionsbyusingNOMORETHANTHREEWORDSforeachanswer.1.Howdidpeopletraditionallytreatfossils?2.WhatsuggestionsdoGeiglandhercolleaguesgiveonwhatshouldbedonewhenfossilsarefound?3.Whatproblemsmaybeposediffossilbonesarewashedon-site?NameONE.4.WhatcharacteristicdofossilboneshavetomakethemsusceptibletobecontaminatedwithcontemporaryDNAwhentheyarewashed?5.Whatcouldbebetterunderstoodwhenconservationtreatmentsareimproved?6.Thepassagementionedseveralanimalspeciesstudiedbyresearchers.Howmanyofthemarementioned?Questions7-11Dothefollowingstatementsagreewiththeinformationgiveninthepassage?PleasewriteTRUEifthestatementagreeswiththewriterFALSEifthestatementdoesnotagreewiththewriterNOTGIVENifthereisnoinformationaboutthisinthepassage7.IntheirpaperpublishedintheProceedingsoftheNationalAcademyofSciences,GeiglandhercolleagueshaveshownwhatconservationpracticesshouldbefollowedtopreserveancientDNA.8.ThefossilbonesthatGeiglandhercolleaguesstudiedareallfromthesameaurochs.9.Geneticistsdon’thavetoworkonsite.10.OnlynewlyexcavatedfossilbonesusingnewconservationmethodssuggestedbyGeiglandhercolleaguescontainancientDNA.11.Paaboisstillworriedaboutthepotentialproblemscausedbytreatmentsoffossilsintraditionalway.Questions12-13CompletethefollowingthestatementsbychoosingletterA-Dforeachanswer.12.“Thisinformation”inparagraph3indicates:[A]ItiscriticaltofollowproperpracticesinpreservingancientDNA.[B]ThebestwayofgettinggoodDNAistohandlefossilswithgloves.[C]Fossilhuntersshouldwearhome-madehammerswhilediggingupbones.[D