高考英语阅读理解解析版汇编（73）含解析

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1、2017高考英语阅读理解解析版汇编(73)阅读下列四篇短文，从每小题后所给的A,B,C或D四个选项屮，选出最佳选项。ArecentstudyofancientandmodernelephantshascomeupwiththeunexpectedconelusionthattheAfricanelephantisdividedintotwodistinet（不同的）species.ThediscoverywasmadebyresearchersatYorkandHarvardUniversitieswhentheywereexami

2、ningthegeneticrelationshipbetweentheancientwoollymammothandmastodontomodernelephants—theAsianelephant,Africanforestelephant,andAfricansavannaelephant.OncetheyobtainedDNAsequences（序歹U）fromtwofossils（化右），mammothsandmastodon®theteamcomparedthemwithDNAfrommodernelephants.T

3、heyfoundtotheiramazementthatmodernforestandsavannaelephantsareasdistinetfromeachotherasAsianelephantsandmammoths.ThescientistsuseddetailedgeneticanalysistoprovethattheAfricansavannaelephantandtheAfricanforestelephanthavebeendistinetspeciesforseveralmillionyears・Thedive

4、rgeneeofthetwospeciestookplacearoundthetimeofthedivergenceofAsianelephantsandwoollymammoths.Thisresultamazedallthescientists.Therehaslongbeendebateinthescientificcommunitythatthetwomightbeseparatespecies,butthisisthemostconvincingscientificevideneesofarthattheyareindee

5、ddifferentspecies.Previously,manynaturalistsbelievedthatAfricansavannaelephantsandAfricanforestelephantsweretwopopulationsofthesamespecies,despitetheelephants"sigrdficantsizedifferences・Thesavannaelephanthasanaverageshoulderheightof3.5metreswhiletheforestelephanthasana

6、verageshoulderheightof2.5metres.Thesavannaelephantweighsbetweensixandseventons,roughlydoubletheweightoftheforestelephant.Butthefactthattheylooksodifferentdoesnotnecessarilymeantheyaredifferentspecies.HowevertheprooflayintheanalysisoftheDNA.AlfredRoca,assistantprofessor

7、intheDepartmentofAnimalSciencesattheUniversityofIllinois,said,"Wenowhavetotreattheforestandsavannaelephantsastwodifferentunitsforconservationpurposes・Since1950,allAfricanelephantshavebeenconservedasonespecies.Nowthatweknowtheforestandsavannaelephantsaretwoverydistincti

8、veanimals,theforestelephantshouldbecomeabiggerpriority（优先）forconservationpurposes/1.Oneofthefossilsstudiedbytheresear