资源描述：
《2019年高考英语一轮巩固达标练题Unit3Underthesea含解析新人教版选修7 》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、Underthesea***阅读理解。OldFossilsScientistshavefoundwhattheythinkisprobablytheoldestfossilonEarth,aremnantoflifefrom3.7billionyearsagowhenEarth’sskieswereorangeanditsoceansgreen.InanewlymeltedpartofGreenland,Australianscientistsfoundtheleftoverstructurefromamunityofmicrobes（
2、微生物）thatlivedonanancientseafloor.Basedontheiranalysisofthefossils,theresearchersdeterminedthattheyare220millionyearsolderthanthosediscoveredinWesternAustralia,whichwere3.48billionyearsold.Thediscoveryshowslifemayhaveformedquickerandmoreeasilythanoncethought,abouthalfabil
3、lionyearsafterEarthformed.Andthatmayalsogivehopeforlifeformingelsewhere,suchasMars,saidstudyco-authorMartinVanKranendonkoftheUniversityofNewSouthWalesanddirectoroftheAustralianCenterforAstrobiology.＂Itgivesusanideahowourplanetevolvedandhowlifegainedafoothold,＂VanKranendo
4、nksaid.ScientistshadthoughtitwouldtakeatleasthalfabillionyearsforlifetoformafterthemoltenEarthstartedtocoolabit,butthisshowsitcouldhavehappenedquicker,hesaid.That’sbecausethenewlyfoundfossilisfartooplextohavedevelopedsoonaftertheplanet’sfirstlifeforms,hesaid.Inanoutcropo
5、frocksthatusedtobecoveredwithiceandsnowwhichmeltedafteranexceptionallywarmspring,theAustralianteamfoundstromatolites（叠层石）,whicharelayeredstructuresthatareoftenproducedbyamunityofmicrobes.Thestromatoliteswereabout1to4centimetershigh.＂Itislikethehouseleftbehindmadebythemic
6、robes,＂VanKranendonksaid.＂Scientistsusedthelayersofashfromvolcanoesandtinyzircon（锆石）withuraniumandestimatedthattheydatebackto3.7billionyearsago.＂Thedatingseemsaboutright,saidAbigailAllwood,aNASAastrobiologistwhofoundthepreviousoldestfossil,from3.48billionyearsago,inAustr
7、alia.ButAllwoodsaidsheisnotpletelyconvincedthatwhatVanKranendonk’steamfoundoncewasalive.Shesaidtheevidencewasn’tconclusiveenoughthatitwaslifeandnotageologicquirk（地质巧合）.＂Itwouldbenicetohavemoreevidence,butintheserocksthat’salottoask,＂Allwoodsaidinanemail.1.Theunderlinedwo
8、rds＂gainedafoothold＂inParagraph3mean______.A.continuedB.changedC.increasedD.Started2.WecanlearnfromPara
