托福写作｜TPO10综合阅读+听力文本

在托福写作练习过程中，相信TPO材料中的作文题目都会是大家的首选练习材料小编给考生们带来了托福综合写作TP010,希望可以帮助广大托福考生轻松备考托福TP010ReadingThe sea otter isa smallmammal thatlives inwaters alongthe westerncoast ofNorthAmerica fromCalifornia toAlaska.When someseaotter populations offthe Alaskan coaststarted rapidlydeclining afew yearsago,it causedmuch concernbecause seaottersplay animportant ecologicalrolein the coastal ecosystem.Experts startedinvestigatingthe causeof thedecline andquickly realizedthat there were twopossible explanations:environmental pollutionor attacksby predators.Initially,the pollution hypothesisseemed the more likelyof thetwo.The firstreason whypollution seemedthemorelikely causewas that therewereknownsources ofit alongthe Alaskancoast,such asoil rigsand othersources ofindustrialchemical pollution.Water samplesfrom the area revealedincreased levelsof chemicalsthatcould decreasethe otters，resistance tolife-threatening infectionsand thuscouldindirectly causetheir deaths.Second,other sea mammals such as sealsand sealionsalong theAlaskancoastwere alsodeclining,indicating thatwhatever hadendangeredthe otterswas affectingother seamammals aswell.This factagain pointedtoenvironmental pollution,since itusually affectsthe entireecosystem ratherthan asinglespecies.Only widelyoccurring predators,such asthe orcaa largepredatorywhale,could havethe sameeffect,but orcasprefer to huntmuch largerprey,suchasother whales.Third,scientists believedthatthe pollutionhypothesiscould alsoexplain the unevenpattern ofotter decline:at someAlaskan locationsthe otterpopulations declinedgreatly,while atothers theyremained stable.Some expertsexplained theseobservationsby suggestingthat oceancurrents orother environmentalfactors mayhave createdunevenconcentrations ofpollutants alongthecoast.ListeningProfessor:Well,ongoing investigationshave revealedthat predationis the most likely cause ofseaotter declineafter all.Well,ongoing investigationshave revealedthat predationisthemostlikelycauseof seaotter declineafter all.First,thepollution theory isweakened by the factthat noone canreally findany deadseaothers washingoff onAlaskan beaches.Thats notwhat youwould expectif infectionscausedby pollutionstarted killinga lotof otters.On theother hand,the factthatits sohard tofind deadotters isconsistent withthe predatorhypothesis.If anotteris killedby apredator,its eatenimmediately soit can，t washup onshore.Second,although orcasmay prefertohuntwhales,whales haveessentially disappearedfromtheareabecause ofhuman hunters.That meansthat orcas have hadto changetheirdiet tosurvive andsince onlysmaller seamammals arenow available,orcashaveprobablystarted huntingthose.So itprobably isthe orcasthat arecausing thedecline ofallthe smallerseamammalsmentioned inthepassage-the seals,the sealions andthe seaotters.And third,theunevenpattern ofotter declineis betterexplained bythe orcapredationtheory thanbythepollutiontheory.What happensto ottersseems todepend onwhetherthe locationwhere theylive isaccessible toorcas ornot.In thoselocations thatorcascan accesseasily,the numberof seaotters hasdeclined greatly.However,because orcasareso large,they can，t accessshallow orrocky locations.And shallowand rockylocationsare preciselythe typesof locationswhere seaotterpopulationshave notdeclined.。