托福作文写作范文详解elow.docx

托福作文写作范文详解ReadingThecanetoadisalarge(1.8kg)amphibianspeciesnativetoCentralandSouthAmerica.ItwasdeliberatelyintroducedtoAustraliain1935withtheexpectationthatitwouldprotectfarmers'cropsbyeatingharmfulinsects.Unfortunately,thetoadmultipliedrapidlyzandalargecanetoadpopulationnowthreatenssmallnativeanimalsthatarenotpests.SeveralmeasureshavebeenproposedtostopthespreadofthecanetoadinAustralia.Onewaytopreventthespreadofthetoadwouldbetobuildanationalfence.AfencethatblockstheadvanceofthetoadswillpreventthemfrommovingintothosepartsofAustraliathattheyhavenotyetcolonized.Thisapproachhasbeenusedbefore:anationalfencewaserectedintheearlypartofthetwentiethcenturytopreventthespreadofrabbits,anotheranimalspeciesthatwasintroducedinAustraliafromabroadandhadaharmfulimpactonitsnativeecosystems.Second,thetoadscouldbecapturedanddestroyedbyvolunteers.Canetoadscaneasilybecaughtinsimpletrapsandcanevenbecapturedbyhand.Youngtoadsandcanetoadeggsareeveneasiertogatheranddestroy,sincetheyarerestrictedtothewater.IftheAustraliangovernmentweretoorganizeacampaignamongAustraliancitizenstojoinforcestodestroythetoadszthecollectiveeffortmightstopthetoadfromspreading.Third,researchersaredevelopingadisease-causingvirustocontrolthecanetoadpopulations.Thisviruswillbespeciallydesigned:althoughitwillbeabletoinfectanumberofreptileandamphibianspecies,itwillnotharmmostoftheinfectedspecies;itwillspecificallyharmonlythecanetoads.Theviruswillcontrolthepopulationofcanetoadsbypreventingthemfrommaturingandreproducing.ListeningThecanetoadwon'tbeaseasytogetridofasthereadingsuggests.Themeasuresproposedbythereadingarelikelyeithertobeunsuccessfulortocauseunwantedenvironmentaldamage.Firstofall,anationalfenceprobablywon'tstopthespreadofthetoad.Thatsbecauseyoungtoadsandtoadeggsarefoundinriversandstreams.Nomatterwherethefenceislocated,atsomepointtherewillberiversorstreamsflowingfromonesidetotheother.Thesewaterwayswillbeabletocarrytheyoungtoadsandtheireggstotheotherside.Sinceit'sonlynecessaryforafewyoungtoadsoreggstogetthroughthefenceinordertoestablishpopulationontheotherside,thefenceisunlikelytobeeffective.Secondly,amassivegroupofvolunteerscouldhavesuccesstrappinganddestroyingtoads.ButitslikelythattheseuntrainedvolunteerswouldinadvertentlydestroymanyofAustralia'snativefrogs.Someofwhichareendangered.Itsnotalwayseasytotellthecanetoadapartfromnativefrogsespeciallywhenit'syoung.Third,usingthevirusisabadideabecauseitcouldhaveterribleconsequencesforcanetoadsintheiroriginalhabitatinCentralandSouthAmerica.YoumightbewonderinghowcanavirusreleasedinAustraliacauseharmintheAmerica.WellzAustralianreptilesandamphibiansareoftentransportedtoothercontinentsbyresearchersorpetcollectorsforexample.OncetheanimalsinfectedbythevirusreachCentralandSouthAmerica,theviruswillattackthenativecanetoadsanddevastatetheirpopulations.ThatwouldbeandecologicaldisasterbecauseintheAmericacanetoadsareanativespeciesandavitalpartoftheecosystem.Soiftheyareeliminated,thewholeecosystemwillsuffer.一、阅读听力要点概括ReadingPassageMainpoints:SeveralmeasuresareproposedtostopCaneToadspreading.Subpoint1:Buildanationalfence.Subpoint2:Volunteerscandestroytoads.Subpoint3:Viruscancontrolthecanetoadpopulations.LectureAttitude:Unsuccessfulorunwanteddamage.SubPoint1:Fencewon'tstopthespread.(Eggsinriversandstreams,afewcanpassthefence.)SubPoint2:Volunteercandestroynativefrogs.(Untrained,frogsendangered.)SubPoint3:ViruscanbetransferredtoAmerica.(Byreptilesandamphibians,Disasterforecosystem.)二、范文逐段赏析Paragraph1Thelecturerarguesagainstthethreemeasuresmentionedinthereadingpassagethoughttoreducethepopulationofthecanetoad,aspeciesintroducedtotheAustraliancontinent.此段功能：（Listeningpassage后文提到用L代替）（Readingpassage后文用R代替）以L的观点为主要观点，作者说L反对R中提到的三点，并总结了要解决的问题：如何解决澳洲大陆上的蟾蛛数量。此段结构：作者用一句话总结了全文讨论的问题，并告诉大家全文逻辑为相反。极其简练直接，随即展开全文辩论。Paragraph2Thelecturerarguesthatthefirstmeasure,anationalfence,wouldnotpreventtheflowofstreamsorriversandztherefore,wouldallowyoungtoadsortoadeggstotravelthroughthefence.Thereadingpassage,however,arguesthatsuchafencewouldeffectivelycutofftheroutethatanimalsusetoestablishcoloniesandexpandinpopulation.此段功能：以L的观点起头，谈第一种方法，全国栅栏并不能阻止小溪河流，这样小蟾蛛或者蟾嫁卵可以通过栅栏继续传播。所以R中提到的栅栏方法没有用。此段结构：此段为分分结构，从L的辩论开始，列举了栅栏会失效的证据，最后达到说明R中的栅栏是无用的目的。Paragraph3Regardingthesecondmeasure,recruitingalargegroupofvolunteers,thelecturerexplainsthatvolunteersoftenhavedifficultydistinguishingbetweencanetoadsandnativefrogs,whichareanendangeredspecies.Therefore,volunteersmightunintentionallykillmembersofbothspecies.Thereadingpassagegivestheoppositeview:organizingalargegroupofvolunteerstojoinanexterminationcampaigncouldspeedthedestructionofcanetoads.此段功能:继续转入下一方法，志愿者杀蟾蛛方案。L解释到这些志愿者很难分辨蟾蛛和当地的珍贵青蛙，这样会造成无辜的伤害。所以R中提到的这个方法，也是行不通的。此段结构：此段为分分结构，先列出L中举的证据，最后达到说明R的想法不周全的结果。Paragraph4Finallythelecturerobjectstothethirdmeasure:usinganinfectiousvirustokillthepopulationoftoads.ShepointsoutthatavirusintendedtoeliminateAustralia'scanetoadpopulationcouldbetransmittedtoothercontinentswherecanetoadsareanesse