托福TPO阅读49原文

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1、托福TPO阅读49原文+题目+答案托福TPO阅读49原文（第一篇）-MatingSongsofFrogs　　Thecallingorsingingoffrogsplaysanimportantroleintheirreproduction—specifically,inhelpingindividualsfindandselectmates.Soundhasmanyadvantagesasacommunicationsignal.Whensoundsarebroadcast,theauditoryreceptorsdonotneedtobeinaparticularorientationr

2、elativetothesoundsourceinordertoreceivestimulation.Loudsongs,particularlythosemadebychorusesoffrogscallingtogether,cantravellongdistancesandthusattractdistantfrogs.Soundstravelaroundlargeobstacles.Theseadvantagesarenotfoundinthevisualmodality,wherethereceivermustbeattentiveandhaveitsvisualreceptor

3、orientatedinthecorrectdirection.Further,mostfrogsandtoadsbreedatnight,whenlightlevelsarelowbutsoundscanbeeasilylocalized.Wecanconcludethatauditorysignalsareusedbyfrogsandtoadsbecausetheycanbeeffectiveoverlongdistancesatnight.　　Malefrogsdomostofthecourtshipcalling.Othermalefrogscanrespondbyaddingth

4、eirvoicestoformacallingchorus.Malefrogscanalsovocalizetoeachotheraspartofaggressivedisplays.Aggressivecallscanbedistinctfromtheadvertisementcallsusedtoattractfemales.Femalescanrespondtomalesongsbymovingtowardthesoundsourceorbyselectingcertainmalesasreproductivepartners.Insomespeciesfemalesalsoresp

5、ondtomalesbycalling:receptivepairscanevenperformduets.Predatorsmayalsocueinoncallingfrogsaspotentialprey.Frogsongscontainseveralpotentiallyimportantpiecesofinformationaboutthecallingmale.First,soundamplitudecanindicatethesizeoftheindividualthatisGalling.Sincemanyfrogsexhibitindeterminategrowth(i.e

6、.,theykeepgettingbiggerastheygetolder),sizeisagoodpredictorofrelativeage.Inmanyspecies,callamplitudeisincreasedbyspecializedvocalsacsthatcanenlargeastheanimalgrows;thus,olderfrogsproduceloudercalls.Themale’sagematterstothefemalebecauseolderfrogshavesuccessfullysurvivedtheenvironmentalhazardsthatth

7、eoffspringtheysirewillsoonbefacing.Amplitudecanalsoconveyinformationonhowfarawaythecallingfrogisor,forchoruses,howmanyfrogsarecallingtogether.Anintenselyvocalizingchorusmayindicateaparticularlyfavorablebreedingsi