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剑桥雅思阅读7(test1)真题解析.docx

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剑桥雅思阅读7(test1)真题解析READINGPASSAGE1Youshouldspendabout20minutesonQuestions1-13,whicharebasedonReadingPassage1below.Let’sGoBatsABatshaveaproblem:howtofindtheirwayaroundinthedark.Theyhuntatnight,andcannotuselighttohelpthemfindpreyandavoidobstacles.Youmightsaythatthisisaproblemoftheirownmaking,onethattheycouldavoidsimplybychangingtheirhabitsandhuntingbyday.Butthedaytimeeconomyisalreadyheavilyexploitedbyothercreaturessuchasbirds.Giventhatthereisalivingtobemadeatnight,andgiventhatalternativedaytimetradesarethoroughlyoccupied,naturalselectionhasfavouredbatsthatmakeagoofthenight-huntingtrade.Itisprobablethatthenocturnaltradesgowaybackintheancestryofallmammals.Inthetimewhenthedinosaursdominatedthedaytimeeconomy,ourmammalianancestorsprobablyonlymanagedtosurviveatallbecausetheyfoundwaysofscrapingalivingatnight.Onlyafterthemysteriousmassextinctionofthedinosaursabout65millionyearsagowereourancestorsabletoemergeintothedaylightinanysubstantialnumbers.BBatshaveanengineeringproblem:howtofindtheirwayandfindtheirpreyintheabsenceoflight.Batsarenottheonlycreaturestofacethisdifficultytoday.Obviouslythenight-flyinginsectsthattheypreyonmustfindtheirwayaboutsomehow.Deep-seafishandwhaleshavelittleornolightbydayorbynight.Fishanddolphinsthatliveinextremelymuddywatercannotseebecause,althoughthereislight,itisobstructedandscatteredbythedirtinthewater.Plentyofothermodernanimalsmaketheirlivinginconditionswhereseeingisdifficultorimpossible.CGiventhequestionsofhowtomanoeuvreinthedark,whatsolutionsmightanengineerconsider?Thefirstonethatmightoccurtohimistomanufacturelight,tousealanternorasearchlight.Firefliesandsomefish(usuallywiththehelpofbacteria)havethepowertomanufacturetheirownlight,buttheprocessseemstoconsumealargeamountofenergy.Firefliesusetheirlightforattractingmates.Thisdoesn’trequireaprohibitiveamountofenergy:amale’stinypinprickoflightcanbeseenbyafemalefromsomedistanceonadarknight,sincehereyesareexposeddirectlytothelightsourceitself.However,usinglighttofindone’sownwayaroundrequiresvastlymoreene