鸟叫研究英语阅读真题鸟叫研究英语阅读真题新GRE考试非常人性的'一点，对于考题出的很严格，经过多次锤炼之后，能考验出考生们的水平。考生们可以根据题库的题目复习新GRE考试，下面就将新GRE阅读理解真题进行解析，为考生们彻底分析在GRE阅读中出现的真题，帮助考生们复习。17.鸟叫研究Overtheyears,biologistshavesuggestedtwomainpathwaysbywhichsexualselectionmayhaveshapedtheevolutionofmalebirdsong.Inthefirst,malecompetitionandintrasexualselectionproducerelativelyshort,simplesongsusedmainlyinterritorialbehavior.Inthesecond,femalechoiceandintersexualselectionproducelonger,morecomplicatedsongsusedmainlyinmateattraction;likesuchvisualornamentationasthepeacockstail,elaboratevocalcharacteristicsincreasethemaleschancesofbeingchosenasamate,andhethusenjoysmorereproductivesuccessthanhislessostentatiousrivals.Thetwopathwaysarenotmutuallyexclusive,andwecanexpecttofindexamplesthatreflecttheirinteraction.Teasingthemaparthasbeenanimportantchallengetoevolutionarybiologists.Earlyresearchconfirmedtheroleofintrasexualselection.Inavarietyofexperimentsinthefield,malesrespondedaggressivelytorecordedsongsbyexhibitingterritorialbehaviornearthespeakers.Thebreakthroughforresearchintointersexualselectioncameinthedevelopmentofanewtechniqueforinvestigatingfemaleresponseinthelaboratory.Whenfemalecowbirdsraisedinisolationinsound-proofchamberswereexposedtorecordingsofmalesong,theyrespondedbyexhibitingmatingbehavior.Byquantifyingtheresponses,researcherswereabletodeterminewhatparticularfeaturesofthesongweremostimportant.Infurtherexperimentsonsongsparrows,researchersfoundthatwhenexposedtoasinglesongtyperepeatedseveraltimesortoarepertoireofdifferentsongtypes,femalesrespondedmoretothelatter.Thebeautyoftheexperimentaldesignisthatiteffectivelyrulesoutconfoundingvariables;acousticisolationassuresthatthefemalecanrespondonlytothesongstructureitself.Ifintersexualselectionoperatesastheorized,maleswithmorecomplicatedsongsshouldnotonlyattractfemalesmorereadilybutshouldalsoenjoygreaterreproductivesuccess.Atfirst,however,researchersdoingfieldworkwithsongsparrowsfoundnocorrelationbetweenlargerrepertoiresandearlymating,whichhasbeenshowntobeoneindicatorofrep