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《ocean animals have been getting bigger 閱讀理解答案》由會(huì)員上傳分享，免費(fèi)在線閱讀，更多相關(guān)內(nèi)容在應(yīng)用文檔-天天文庫。
1、Oceananimalshavebeengettingbigger閱讀理解答案 Oceananimalshavebeengettingbiggeroverthelasthalf-billionyears.Notalittlebigger.Notevenalotbigger.Theyhavemushroomedgigantically,scientistsnowconclude. Theirnewfindinglendssupportforsomethingknownas“Cope’srule.”
2、Itholdsthatanimalstendtoevolveintospeciesthataremuchlargerthantheirdistantancestors.Thishypothesis(假說)takesitsnamefromthe19thcenturypaleontologistEdwardDrinkerCope.Whilestudyingfossils(化石),hewasthefirsttonoticethistrend. NoelHeimisapaleontologistatSta
3、nfordUniversityinPaloAlto,Calif.Healsoisaco-authorofthenewstudy.HisteamcomparedthebodysizeofanimalsbetweentheCambrianPeriodandmoderntimes.Thiswasaspanof542millionyears.Theanimalsstudiedincludedspeciesfrommorethan17,000genera.Theyrangedfromancienttrilob
4、ites,plesiosaurs(extinctreptileswithalongneckandflippers)andmanylessfamiliarcreaturestotoday’swhalesandclams. Oceananimalstodayareanaverageof150timeslargerthantheywereduringtheCambrian,Heim’sgroupreports.Thesmallestanimalsalivetoday—tinycrustaceanscal
5、ledostracods—areonlyaboutone-tenththesizeoftheCambrian’stiniestanimals.Buttoday’slargestoceananimals—whales—aremorethan100,000timesbiggerthanthebiggestintheCambrian. “Classesofanimalsthatwerealreadybig…tendedtolivelonger,”Heimsays.Theyalsotendedtochan
6、gemorethanclassesofanimalsthatweresmalldid. Thesizegainsinoceananimalsaremuchlargerthanwouldbeexpectedbychance,saysJonathanPayne.He’saco-authorwhoalsoworksatStanford. Thescientistsdon’tknowwhatdrivesthetrend.Onepossibilityisanarmsrace(軍備競賽)betweenpre
7、datorsandprey.Theideahereisthatlargeranimalsarelesslikelytobecomesomeotheranimals’meal.Anotherpossibilityhastodowithoxygen.Landanimalsevolvedfromspeciesthatstartedintheocean.Someoftheselandanimalseventuallyreturnedtotheocean.Andtheykepttheabilitytobrea
8、theoxygen-richair.Thatmayhavemadeiteasierforthemtooutgrowanimalsthathadtofilter(過濾)theiroxygenoutofthewater. Whatcurrentanimalsmaybestillustrate“mushroomed”inparagraphone A.Plesiosaurs.B.Ostracods.C.Whales.D.AfricanElephants. 60.What
