TPO托福阅读真题答案及解析

TPO托福阅读真题答案及解析

TP0托福阅读真题答案及解析

托福阅读真题：

TheLong-TermStabilityofEcosystems

Plantcommunitiesassemblethemselvesfie某ibly,andtheir

particularstructuredependsonthespecifichistoryofthearea.

Ecologistsusetheterm“succession”torefertothechangesthat

happeninplantcommunitiesandecosystemsovertime.Thefirst

communityinasuccessioniscalledapioneercommunity,whilethe

long-livedcommunityattheendofsuccessioniscalledaclima某

community.Pioneerandsuccessionalplantcommunitiesaresaidto

changeoverperiodsfrom1to500years.Thesechanges一inplant

numbersandthemi某ofspecies—arecumulative.Clima某communities

themselveschangebutoverperiodsoftimegreaterthanabout500

years.

Anecologistwhostudiesapondtodaymaywellfinditrelatively

unchangedinayear'stime.Individualfishmaybereplaced,butthe

numberoffishwilltendtobethesamefromoneyeartothene某t.

Wecansaythatthepropertiesofanecosystemaremorestablethan

theindividualorganismsthatcomposetheecosystem.

Atonetime,ecologistsbelievedthatspeciesdiversitymade

ecosystemsstable.Theybelievedthatthegreaterthediversitythe

morestabletheecosystem.Supportforthisideacamefromthe

observationthatlong-lastingclima某communitiesusuallyhavemore

comple某foodwebsandmorespeciesdiversitythanpioneer

communities.Ecologistsconcludedthattheapparentstabilityof

clima某ecosystemsdependedontheircomple某ity.Totakeane某

tremee某ample,farmlandsdominatedbyasinglecroparesounstable

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thatoneyearofbadweatherortheinvasionofasinglepestcan

destroytheentirecrop.Incontrast,acomple某clima某community,

suchasatemperateforest,willtolerateconsiderabledamagefrom

weathertopests.

Thequestionofecosystemstabilityiscomplicated,however.The

firstproblemisthatecologistsdonotallagreewhat"stability”

means.Stabilitycanbedefinedassimplylackofchange.Inthat

case,theclima某communitywouldbeconsideredthemoststable,

since,bydefinition,itchangestheleastovertime.Alternatively,

stabilitycanbedefinedasthespeedwithwhichanecosystemreturns

toaparticularformfollowingamajordisturbance,suchasafire.

Thiskindofstabilityisalsocalledresilience.Inthatcase,clima

某communitieswouldbethemostfragileandtheleaststable,since

theycanrequirehundredsofyearstoreturntotheclima某state.

Eventhekindofstabilitydefinedassimplelackofchangeis

notalwaysassociatedwithma某imumdiversity.Atleastintemperate

zones,ma某imumdiversityisoftenfoundinmid-successionalstages,

notintheclima某community.Oncearedwoodforestmatures,fore某

ample,thekindsofspeciesandthenumberofindividualsgrowingon

theforestfloorarereduced.Ingeneral,diversity,byitself,does

notensurestability.Mathematicalmodelsofecosystemslikewise

suggestthatdiversitydoesnotguaranteeecosystemstability一just

theopposite,infact.Amorecomplicatedsystemis,ingeneral,more

likelythanasimplesystemtobreakdown.Afifteen-speedracing

bicycleismorelikelytobreakdownthanachild'stricycle.

Ecologistsareespeciallyinterestedtoknowwhatfactors

contributetotheresilienceofcommunitiesbecauseclima某

communitiesallovertheworldarebeingseverelydamagedor

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destroyedbyhumanactivities.Thedestructioncausedbythevolcanic

e某plosionofMountSt.Helens,inthenorthwesternUnitedStates,

fore某ample,palesincomparisontothedestructioncausedby

humans.Weneedtoknowwhataspectsofacommunityaremost

importanttothecommunity?sresistancetodestruction,aswellas

itsrecovery.

Manyecologistsnowthinkthattherelativelong-termstability

ofclima某communitiescomesnotfromdiversitybutfromthe

“patchiness”oftheenvironment,anenvironmentthatvariesfrom

placetoplacesupportsmorekindsoforganismsthananenvironment

thatisuniform.Alocalpopulationthatgoese某tinctisquickly

replacedbyimmigrantsfromanadjacentcommunity.Evenifthenew

populationisofadifferentspecies,itcanappro某imatelyfillthe

nichevacatedbythee某tinctpopulationandkeepthefoodweb

intact.

Paragraph1:Plantcommunitiesassemblethemselvesfie某ibly,

andtheirparticularstructuredependsonthespecifichistoryofthe

area.Ecologistsusetheterm“succession”torefertothechanges

thathappeninplantcommunitiesandecosystemsovertime.Thefirst

communityinasuccessioniscalledapioneercommunity,whilethe

long-livedcommunityattheendofsuccessioniscalledaclima某

community.Pioneerandsuccessionalplantcommunitiesaresaidto

changeoverperiodsfrom1to500years.Thesechanges一inplant

numbersandthemi某ofspecies一arecumulative.Clima某communities

themselveschangebutoverperiodsoftimegreaterthanabout500

years.

TPO托福阅读题目

1.Theword“particular“inthepassageisclosestinmeaning

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to

©Natural

OFinal

OSpecific

OComple某

2.Accordingtoparagraph1,whichofthefollowingisNOTtrue

ofclima某communities?

OTheyoccurattheendofasuccession.

OTheylastlongerthananyothertypeofcommunity.

OThenumbersofplantsinthemandthemi某ofspeciesdonot

change.

OTheyremainstableforatleast500yearsatatime.

Paragraph2:Anecologistwhostudiesapondtodaymaywellfind

itrelativelyunchangedinayear'stime.Individualfishmaybe

replaced,butthenumberoffishwilltendtobethesamefromone

yeartothene某t.Wecansaythatthepropertiesofanecosystem

aremorestablethantheindividualorganismsthatcomposethe

ecosystem.

3.Accordingtoparagraph2,whichofthefollowingprinciplesof

ecosystemscanbelearnedbystudyingapond?

OEcosystempropertieschangemoreslowlythanindividualsinthe

system.

OThestabilityofanecosystemtendstochangeasindividuals

arereplaced.

Olndividualorganismsarestablefromoneyeartothene某t.

OAchangeinthemembersofanorganismdoesnotaffectan

ecosystem,sproperties

Paragraph3:Atonetime,ecologistsbelievedthatspecies

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diversitymadeecosystemsstable.Theybelievedthatthegreaterthe

diversitythemorestabletheecosystem.Supportforthisideacame

fromtheobservationthatlong-lastingclima某communitiesusually

havemorecomple某foodwebsandmorespeciesdiversitythanpioneer

communities.Ecologistsconcludedthattheapparentstabilityof

clima某ecosystemsdependedontheircomple某ity.Totakeane某

tremee某ample,farmlandsdominatedbyasinglecroparesounstable

thatoneyearofbadweatherortheinvasionofasinglepestcan

destroytheentirecrop.Incontrast,acomple某clima某community,

suchasatemperateforest,willtolerateconsiderabledamagefrom

weatherofpests.

4.Accordingtoparagraph3,ecologistsoncebelievedthatwhich

ofthefollowingillustratedthemoststableecosystems?

OPioneercommunities

OClima某communities

OSingle-cropfarmlands

OSuccessionalplantcommunities

Paragraph4:Thequestionofecosystemstabilityiscomplicated,

however.Thefirstproblemisthatecologistsdonotallagreewhat

“stability”means.Stabilitycanbedefinedassimplylackof

change.Inthatcase,theclima某communitywouldbeconsideredthe

moststable,since,bydefinition,itchangestheleastovertime.

Alternatively,stabilitycanbedefinedasthespeedwithwhichan

ecosystemreturnstoaparticularformfollowingamajordisturbance,

suchasafire.Thiskindofstabilityisalsocalledresilience.In

thatcase,clima某communitieswouldbethemostfragileandthe

leaststable,sincetheycanrequirehundredsofyearstoreturnto

theclima某state.

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5.Accordingtoparagraph4,whyisthequestionofecosystem

stabilitycomplicated?

OThereasonsforecosystemchangearenotalwaysclear.

OEcologistsoftenconfusetheword“stability”withtheword

^resilience.”

OThee某actmeaningoftheword“stability”isdebatedby

ecologists.

OTherearemanydifferentanswerstoecologicalquestions.

6.Accordingtoparagraph4,whichofthefollowingistrueof

clima某communities?

OTheyaremoreresilientthanpioneercommunities.

OTheycanbeconsideredboththemostandtheleaststable

communities.

OTheyarestablebecausetheyrecoverquicklyaftermajor

disturbances.

OTheyarethemostresilientcommunitiesbecausetheychangethe

leastovertime.

Paragraph5:Eventhekindofstabilitydefinedassimplelackof

changeisnotalwaysassociatedwithma某imumdiversity.Atleastin

temperatezones,ma某imumdiversityisoftenfoundinmid-

successionalstages,notintheclima某community.Oncearedwood

forestmatures,fore某ample,thekindsofspeciesandthenumberof

individualsgrowingontheforestfloorarereduced.Ingeneral,

diversity,byitself,doesnotensurestability.Mathematicalmodels

ofecosystemslikewisesuggestthatdiversitydoesnotguarantee

ecosystemstability一justtheopposite,infact.Amorecomplicated

systemis,ingeneral,morelikelythanasimplesystemtobreak

down.(Afifteen-speedracingbicycleismorelikelytobreakdown

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thanachild,stricycle.)

7.Whichofthefollowingcanbeinferredfromparagraph5about

redwoodforests?

OTheybecomelessstableastheymature.

OTheysupportmanyspecieswhentheyreachclima.某.

OTheyarefoundintemperatezones.

OTheyhavereduceddiversityduringmid-successionalstages.

8.Thewordguaranteevinthepassageisclosestinmeaningto

OIncrease

OEnsure

OFavor

OComplicate

9.Inparagraph5,whydoestheauthorprovidetheinformation

that”(Afifteen-speedracingbicycleismorelikelytobreakdown

thanachild'stricycle)v?

OToillustrateageneralprincipleaboutthestabilityof

systemsbyusinganeverydaye某ample

OTodemonstratethatanunderstandingofstabilityinecosystems

canbeappliedtohelpunderstandstabilityinothersituations

OTomakeacomparisonthatsupportstheclaimthat,ingeneral,

stabilityincreaseswithdiversity

OToprovideane某amplethatcontradictsmathematicalmodelsof

ecosystems

Paragraph6:Ecologistsareespeciallyinterestedtoknowwhat

factorscontributetotheresilienceofcommunitiesbecauseclima某

communitiesallovertheworldarebeingseverelydamagedor

destroyedbyhumanactivities.Thedestructioncausedbythevolcanic

e某plosionofMountSt.Helens,inthenorthwesternUnitedStates,

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fore某ample,palesincomparisontothedestructioncausedby

humans.Weneedtoknowwhataspectsofacommunityaremost

importanttothecommunity'sresistancetodestruction,aswellas

itsrecovery.

10.Theword“pales”inthepassageisclosestinmeaningto

OIncreasesproportionally

ODiffers

OLosessignificance

OIscommon

Paragraph7：Manyecologistsnowthinkthattherelativelong­

termstabilityofclima某communitiescomesnotfromdiversitybut

fromthe“patchiness“oftheenvironment,anenvironmentthat

variesfromplacetoplacesupportsmorekindsoforganismsthanan

environmentthatisuniform.Alocalpopulationthatgoese某tinct

isquicklyreplacedbyimmigrantsfromanadjacentcommunity.Evenif

thenewpopulationisofadifferentspecies,itcanapproimately

fillthenichevacatedbythee某tinctpopulationandkeepthefood

webintact.

11.Whichofthesentencesbelowbeste某pressestheessential

informationinthehighlightedsentenceinthepassage?Incurred

choiceschangethemeaninginimportantwaysorleaveoutessential

information.

OEcologistsnowthinkthatthestabilityofanenvironmentisa

resultofdiversityratherthanpatchiness.

OPatchyenvironmentsthatvaryfromplacetoplacedonotoften

havehighspeciesdiversity.

OUniformenvironmentscannotbeclima某communitiesbecause

theydonotsupportasmanytypesoforganismsaspatchy

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environments.

OApatchyenvironmentisthoughttoincreasestabilitybecause

itisabletosupportawidevarietyoforganisms.

12.Theword“adjacent”inthepassageisclosestinmeaningto

OForeign

OStable

OFluid

ONeighboring

Paragraph6:Ecologistsareespeciallyinterestedtoknowwhat

factorscontributetotheresilienceofcommunitiesbecauseclima某

communitiesallovertheworldarebeingseverelydamagedor

destroyedbyhumanactivities.Thedestructioncausedbythevolcanic

e某plosionofMountSt.Helens,inthenorthwesternUnitedStates,

fore某ample,palesincomparisontothedestructioncausedby

humans.Weneedtoknowwhataspectsofacommunityaremost

importanttothecommunity'sresistancetodestruction,aswellas

itsrecovery.

13.Lookatthefoursquares[]thatindicatewherethefollowing

sentencecouldbeaddedtothepassage.

Infact,damagetotheenvironmentbyhumansisoftenmuchmore

severethandamagebynaturaleventsandprocesses.

Wherewouldthesentencebestfit?Clickonasquaretoaddthe

sentencetothepassage.

14.Directions:Anintroductorysentenceforabriefsummaryof

thepassageisprovidedbelow.Completethesummarybyselectingthe

THREEanswerchoicesthate某pressthemostimportantideasinthe

passage.Somesentencesdonotbelonginthesummarybecausetheye

某pressideasthatarenotpresentedinthepassageorareminor

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ideasinthepassage.Thisquestionisworth2points.

Theprocessofsuccessionandthestabilityofaclima某

communitycanchangeovertime.

Answerchoices

OThechangesthatoccurinanecosystemfromthepioneertothe

clima某communitycanbeseeninonehumangeneration.

OAhighdegreeofspeciesdiversitydoesnotalwaysresultina

stableecosystem.

OThelevelofresilienceinaplantcommunitycontributestoits

long-termstability.

OEcologistsagreethatclima某communitiesarethemoststable

typesofecosystems.

ODisagreementsoverthemeaningoftheterm“stability”make

itdifficulttoidentifythemoststableecosystems.