gmat如何学？申友权威名师解读gmat阅读解析13

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1、Passage13_by申友Alice老师Whilethemostabundantanddominantspecieswithinaparticularecosystemisoftencrucialinperpetuatingtheecosystem,a"keystone"species,heredefinedasonewhoseeffectsaremuchlargerthanwouldbepredictedfromitsabundance（插入语，解释说明akeystone"species）,canalsoplayavitalrole.//介绍akeystonespecies

2、的意义。Butbecausecomplexspeciesinteractionsmaybeinvolved,identifyingakeystonespeciesbyremovingthespeciesandobservingchangesintheecosystemisproblematic.//通过移动或者观察的方法很难确定akeystonespecies。Itmightseemthatcertaintraitswouldclearlydefineaspeciesasakeystonespecies;forexample,Pisasterochraceusisoftenak

3、eystonepredatorbecauseitconsumesandsuppressesmusselpopulations,whichintheabsenceofthisstarfishcanbeadominantspecies.Butsuchpredationonadominantorpotentiallydominantspeciesoccursinsystemsthatdoaswellasinsystemsthatdonothavespeciesthatplaykeystoneroles.Moreover,whereasP.ochraceusoccupiesanunam

4、biguouskeystoneroleonwave-exposedrockyheadland,inmorewave-shelteredhabitatstheimpactofP.ochraceuspredationisweakornonexistent,andatcertainsitesasandburialisresponsibleforeliminatingmussels.//通过特性来鉴定akeystonespecies，举例Pisasterochraceus消耗抑制蚌数量的特性确定为akeystonespecies；但抑制的作用在没有统治种类的生态系统上也发生，并且受环境

5、中wave-exposed或wave-sheltered的影响。Keystonestatusappearstodependoncontext,whetherofparticulargeographyorofsuchfactorsascommunitydiversity(forexample,areductioninspeciesdiversitymaythrustmoreoftheremainingspeciesintokeystoneroles)andlengthofspeciesinteraction(sincenewlyarrivedspeciesinparticular

6、maydramaticallyaffectecosystems).//提出观点判断keystonestatus的地位依据环境来确定。逻辑简图第一层：介绍akeystonespecies的意义。第二层：通过移动或者观察的方法很难确定akeystonespecies。第三层：通过特性来鉴定akeystonespecies，举例Pisasterochraceus消耗抑制蚌数量的特性确定为akeystonespecies；但抑制的作用在没有统治种类的生态系统上也发生，并且受环境中wave-exposed或wave-sheltered的影响。第四层：提出观点判断keystonestatu

7、s的地位依据环境来确定。1.ThepassagementionswhichofthefollowingasafactorthataffectstheroleofP.ochraceusasakeystonespecieswithindifferenthabitats?（细节题，定位到文章的第三层）(A)Thedegreetowhichthehabitatisshelteredfromwaves（符合原文）(B)Thedegreetowhichotheranimalswithinahabitat