托福TPO听力32文本+答案解析Word格式.docx

托福TPO听力32文本+答案解析Word格式.docx

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　　Icanlook.Butwearestillputtingthelisttogether.Professorshaveto

　　telluswhatbooksthey’lldefinitelyneedagainnextsemester,andthedeadline

　　forthemtoletusknowisn’tforacoupleofdays.SothelistIhavehereis

　　notreallycomplete.Um…whatclasswasthebookfor?

　　Introtoeconomics,withProfessorMurphy.

　　ProfessorMurphy.OK.IcheckedearlierandIknowshehasn’tgottenback

　　tousonthatclassyet.Sowedon’tknowifshe’llusethesamebooknexttime.

　　Usuallyifanupdatededitionofatextbookisavailable,professorswillgofor

　　thatone.

　　Um…soifthisbookdoesn’tenduponthebuybacklist,whatcanIdo?

I

　　spentoverahundreddollarsforit,andIwanttogetsomethingback.

　　Well,ifaprofessordidn’tassignitforaclasshere,wecouldbuyback

　　forawholesellerwhowoulddistributeitforsaleatanotheruniversity

　　bookstore.

　　OK.

　　Anyway…ifProfessorMurphydoesputitonthelist,itisimportantthatyou

　　comeinasearlyaspossiblenextThursday.There’sonlyalimitednumberof

　　bookswewouldbuyback.Oncewegetthenumberofbooksweneedfornext

　　semester,wewouldstopbuyingthem.

　　OK.SohowmuchmoneywillIgetforthebook?

　　Well,ifit’sonthebuybacklist,we’llpayfiftypercentofwhatthenew

　　pricewas.Butthatalsodependsonwhatconditionthebookisin,soitneeds

　　tobecleanedupasmuchaspossible.

　　Cleanedup?

　　Becauseusedbooksshowwearandtear,youknow,waterstains,scruffy

　　covers,yellowhighlighting…Youreallyneedtomakesuretherearenopencil

　　marksonthebook.Thepriceyoucangetforatextdependsontheshapeit’s

　　in.

　　YoumeanIhavetoeraseallthepencilmarks?

　　Ifyouwantthebestpriceforit…

　　Andwhatifyoudecidethebookistoobeat-upanddon’tbuyitback?

　　Thatdoeshappen.Hmm…well,onemorethingyoucantryistoplaceanadin

　　thestudentnewspapertoseeifyoucansellitdirectlytoanotherstudent.

　　Lecture1-Archaeology（Bananas&

AfricanHistory）

　　Listentopartofalectureinanarchaeologyclass.

　　Professor

　　Oneoftheimportantaspectsofthefieldofarchaeology…oneofthethings

　　thatexcitesmeaboutthefield…isthatseeminglyinsignificantthingscan

　　suddenlychangethewaywethinkaboutaculture.Wearealwaysmakingnew

　　discoveriesthathavethepotentialtochallengewidelyheldbeliefs.

　　Takesomethinglikethebanana,forexample.Itturnsoutthatthis

　　ordinaryfruitmaybeforcingscientiststorewritemajorpartsofAfrican

　　history!

WeknowthebananaswereintroducedtoAfricaviaSoutheastAsia.And

　　untilrecently,wethoughtweknewwhentheywereintroduced—about2,000years

　　ago.ButdiscoveriesinUganda,that’sinEasternAfrica,arethrowingthatinto

　　question.Scientistsstudyingsoilsamplestherediscoveredevidenceofbananas

　　insedimentthatwas5,000yearsold!

　　Now,letmeexplainthatit’snoteasytofindtracesofancientbananas.

　　Thefruitissoftanddoesn’thaveanyhardseedsthatmightsurviveoverthe

　　ages.Soafter5,000years,youmightthinktherewouldbenothingleftto

　　study.Well,fortunatelyforarchaeologists,allplantscontainwhatarecalled

　　phytolithsintheirstemsandleaves.Phytolithsaremicroscopicstructuresmade

　　ofsilica,andtheydonotdecay.Whenplantsdieandrotaway,theyleavethese

　　phytolithsbehind.Becausedifferentplantsproducedifferentlyshaped

　　phytoliths,scientistscanidentifythetypeofplantfromancientremains.

　　So,thosescientistsinUganda,dugdowntosedimentsthatwere5,000years

　　old.Andwhatdoyouthinktheyfound?

Bananaphytoliths!

Obviouslythismeant

　　thatwehadtorethinkourpreviousnotionsaboutwhenbananasfirstarrivedin

　　Africa.But,well,thisdiscoveryhadotherimplicationsforhistory.

　　Assoonasbananasappearinthearchaeologicalrecord,weknowwehave

　　contactbetweenAfricaandSoutheastAsia.Itwouldappearnowthatthiscontact

　　occurredmuchearlierthanpreviouslythought.

　　Al…although…nowhere’swheretheuncertaintycomesin…wedon’treallyhave

　　anysolidevidenceoftradebetweenthepeoplesofthesetworegionsthatlong

　　ago.Presumably,ifpeoplewerebringingbananastoAfrica,they’dalsobe

　　bringingotherthingstoo:

pottery,tools…allsortsofobjectsmadefortradeor

　　dailyuse.Butanysuchevidenceismissingfromthearchaeologicalrecord.

　　Theearlyappearanceofbananasalsosuggeststhatagriculturebeganin

　　thispartofAfricaearlierthanscientistsimagined.Yousee,bananas,atleast

　　theediblekind,can’tgrowwithouthumanintervention.Theyhavetobe

　　cultivated.Peopleneedtoplantthemandcareforthem.Soifbananaswere

　　presentinUganda5,000yearsago,wewouldhavetoassume…that…that…that

　　someoneplantedthem.

　　Theabovetextisatranscriptofthislecturepreparedbylady&

bird

　　.

　　But,therearequestionsaboutthistoo.Weknowthatbananascanbea

　　staplefoodthatcansupportlargepopulations,astheydidinUgandainthe

　　morerecentpast.Ifbananasweregrownthousandsofyearsago,whydon’twesee

　　evidenceoflargepopulationsthrivingintheareaearlier?

　　So,weareleftwiththismystery.Wehavewhatappearstobestrong

　　biologicalevidencethatbananaswerebeingcultivatedinUgandaasearlyas

　　5,000yearsago.Butwearemissingotherkindsofevidencethatwould

　　conclusivelyprovethatthisisso.

　　Clearly,moreresearchneedstobedone.Perhapsbysomenewscholarsfrom

　　thisuniversity?

Atleastgiveitsomethought.

　　Lecture2-Biology（PopulationsinanEcosystem）

　　Listentopartofalectureinabiologyclass.

　　Professor,sincewearegoingtotalkaboutchangesinanimalpopulations

　　inthewild,I’dliketoaskaboutsomethingIreadinanarticleonline,about

　　howthepopulationsizeofsomeanimalspeciescanaffectotheranimalspecies,

　　andhowotherenvironmentalfactorscomeintoplaytoo.

　　Right.Relationshipsbetweenanimalspeciesinagivenecosystemcanget

　　prettycomplex.Becauseinadditiontopredator-preyrelationships,thereare

　　othervariablesthataffectpopulationsize.

　　Thearticlementionedthatpopulationsofpredatorsandtheirpreymightgo

　　uprapidlyandthendeclineallofasudden.

　　Oh.Yeah!

Ireadaboutthatinmyecologyclass.Ithappensincycles.I

　　thinkthat’scalledaboom-and-bustcycle.Right?

　　OK.Well,holdonasecond.FirstIwanttogooversomekeyconcepts.

　　Let’ssaytherewasaspeciesthathadaccesstoplentyoffoodandideal

　　conditions.Underthosecircumstances,itspopulationwouldincrease

　　exponentially,meaningitwouldincreaseatanever-acceleratingpace.

　　Wow!

Thatsoundsalittlescary.

　　Well,itdoesn’tusuallyhappen.Likeyousaid,arapidpopulationgrowth

　　isoftenfollowedbyasuddendecline.Butwedooccasionallyseeexponential

　　growthinnonnativespecieswhentheyaretransplantedintoanewenvironment.

　　Um…becausetheyfacelittlecompetitionandhavefavorablegrowing

　　conditions.

　　Butformostspecies,mostofthetime,resourcesarefinite.There’sonly

　　somuchavailable…whichleadsmetomypoint.Everyecosystemhaswhatwecalla

　　carryingcapacity.Thecarryingcapacityisthemaximumpopulationsizeofa

　　speciesthatcanbesustainedbytheresourcesofaparticularecosystem.

　　Resourcesare,ofcourse,food,water,andjustasimportant,space.

　　Althougheveryspecieshasamaximumrateatwhichthepopulationofthat

　　speciescouldincrease,assumingidealconditionsforthespeciesinits

　　environment.Therearealwaysgoingtobeenvironmentalfactorsthatlimit

　　populationgrowth.Thisiscalledenvironmentalresistance.Environmental

　　resistanceisimportantbecauseitstopspopulationsfromgrowingoutofcontrol.

　　Factorssuchfoodsupply,predationanddiseaseaffectpopulationsize,andcan

　　changefromyeartoyearorseasontoseason.

　　OK.IthinkIgetit.

　　Well,let’slookatacasestudy.Thatshouldmakethingsclear.Someyears

　　ago,someofmycolleaguesconductedanexperimentinanoakforestinvolving

　　threedifferentspecies:

white-footedmice,gypsymothsandoaktrees.Theabove

　　textisatranscriptofthislecturepreparedbylady&

bird.

　　OK.Nowletmeexplainwhatthesituationisinthisforest.Oaktrees

　　produceacorns,andacornsareaprimaryfoodsourceforwhite-footedmice.

　　Anotherfoodsourceforthewhite-footedmiceisthegypsymoth.Sothesizeof

　　thegypsymothpopulationiscontrolledbythewhite-footedmice,whichisa

　　goodthingbecausegypsymothcaterpillarsareconsideredpests.Theystripaway

　　theleavesfromtheoaktreeseverytenyearsorso.

　　Sothemiceeatbothacornsfromtheoaktreesandgypsymoths.Andth