托福阅读加试机经.docx

托福阅读加试机经.docx

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托福阅读加试机经

托福阅读经典加试题：

达尔文进化论英文原文及答案

ObservingNaturalSelection

WitnessingnaturalselectionwouldnothaveseemedpossibletoDarwinbecauseheassumednaturalselectionwastooslowandgradualforourshort-termmindstoperceive.Yetlaterbiologistshavebeenabletowitnessflashesofevolutionarychange.Inthelate1980s,forexample,biologistDavidReznickbegantousetheguppiesthatswiminthestreamsofTrinidadforestsinnaturalexperiment.Atlowerelevationstheseguppiesfacetheassaultofpredatoryfishes,buttheonesinhigherwatersliveinpeacebecausefewofthepredatorscanmoveupstreampastthewaterfallsandcraggyrocks.

Likeallanimals,guppieshaveatimetablefortheirlives-howlongtheytaketoreachsexualmaturityhowfasttheygrowduringthattime,howlongtheyliveasadults.Theoreticalbiologistshavepredictedthatthelifehistoryofanimalscanevolveifmutationsthatalteritbringtheanimalsmorereproductivesuccess.Reznickputtheirpredictionstothetest.

Inpondswithalotofpredators,guppiesthatgrowfastshouldbemoresuccessfulthanslow-growingones.Withthethreatofdeathhangingoveraguppy,itwillgrowasquicklyaspossiblesothatitcanstartmatingassoonaspossibleandhaveasmanyoffspringaspossible.Ofcourse,thestrategycomeswithaheavyprice.Bygrowingsoquickly,aguppymayshortenitsownnaturallifespan,andbyquicklygivingbirthtobabies,femaleguppycannottaketimetosupportheroffspringwithenergy,whichputthematriskofdyingyoung.ButReznickreasoned,thatthethreat,ofanearlydeathoffsetbyotherrisk..

Toseewhetherthistrade-offwasreal,Reznickrelocatedguppiesthatwerebeingterrorizedinthedownstreambyputtingtheminpoolswithrelativelyfewpredators.Elevenyearsintheseconditionsproducedguppiesthatwere,onaverage,inlessofarush.Theytook10percentlongertomaturethantheirancestorsandwereover10percentheavierbythetimetheywerefullygrown.Theywerealsolayingsmallerbroodsofeggs.buteachofthenewguppiesthathatchedfromthosewasbigger.

nSometimesnaturerunsevolutionaryexperimentsofitsownwithoutanyhelpfromhumanswhatsoever.nIn1973PeterandRosemaryGrant,husband-and-wifebiologists,arrivedontheGalapagosIslandstostudytheeffectsofnaturalselectiononthebirds.MostyearsontheGalapagos,theweatherfollowsastandardpattern.nForthefirstfivemonthsoftheyearsitishotandrainy,followedbyacool,dryperiod.nButin1977thewetseasonnevercame.AperiodicdisturbanceofthePacificoceancalledLaNinaalteredweatherpatternsovertheGalapagos,causingadisastrousdrought.

OnDaphneIsland,wheretheGrantsworked,thedroughtwaslethal.Outofthe1,200mediumgroundfinchesGeospizafortisthatlivedontheIsland,morethat1,000died.ButtheGrantsdiscoveredthatthedecimationwasnotrandom.Gfortislivesmainlyonseeds,whichitcrackswithitsstrongbeak.SmallG.fontiscanbreakonlysmallseeds,butlargerbirdshavebeaksthatarestrongenoughtobreakbigones.Thedroughthadlingeredforafewmonths,thesmallfinchesranoutofsmallseedsandbegandyingoff.Butthebigfinchesmanagedtosurvive,becausetheycouldeatseedsthatthesmalleronescouldn'tgetto.（Inparticular,theydependedonaplantcalledcaltrop,whichgrowsspikedshellstoprotectitseeds）.

Thesurvivorsonthe1977droughtmatedin1978,andtheGrantscouldseeevolution'smarkontheiroffspring.AnewgenerationofG.fortiswasborn,andtheGrants'studentPeterBoagdiscoveredthat,onaverage,theirbeakswere4percentlargerthanthoseofthepreviousgeneration.Thebig-beakedfinches,whichhadfaredbetterduringthedroughthadputtheirtraittotheiroffspring,alteredtheprofileofthepopulation.

Intheyearssincethedroughtthefincheschanged.In1983,forexample,therewasaseasonofheavyrain,abundantseedsfavoredfincheswithsmallerbeaksandGrantsfoundthatby1985theiraveragesizehaddropper5percent.Thefinchescanchangequickly,butitseemsthatareswingingbackandforthlikeapendulum.

中文大意：

关于naturalselection，Darwin认为是长期且渐进的。

后来，科学家却在短时间内目击witness（词汇题）到进化。

接着用两个relativelyshortevolution'sexamples来supportnaturalselection。

1st，人为控制条件。

有一种鱼guppy，在predator多的时候，长得快，但代价是life-span变短。

不过研究人员认为，这代价被其他危险抵销offset（词汇题）了。

然后，再将一部分放入predator少的pool中，offspring发生了很多changes，比如比它们的ancestorsize上要大，下egg少了，等等。

2ed，自然条件变化。

我们需要做的只是observe。

讲的是finch，有关它们beak的大小的。

又举了一个bird的例子。

一对夫妇学者在一个群鸟研究一种雀鸟，有一年岛上发生致命的lethal（词汇题）干旱，他们发现，当干旱（drought）时，鸟的大量死亡decimation（词汇题）并不是随机的。

那些有大而硬的beak的bird往往能生存下来，这样一来这一地区的这种bird很快都有了大而硬的beak。

干旱的时候小种子少，嘴小的鸟死了，嘴长的鸟存活。

存活的鸟和第二年的鸟交配，后代的鸟嘴整体变长。

雨量又充足的时候，又足够小种子，这个时候，新出生的鸟的鸟嘴又变短了。

考题：

（1）Accordingtoparagraph1,comparedtotheviewsofmodernbiologists,Darwin'sviewofnaturalselectionwaslimitedbyhisbeliefthat

答案：

（A）naturalselectiononlyoccurredoveraverylongperiodoftimeIS-naturalselectioncouldonlybewitnessedinsomespecies

（2）Theword"witness"inthepassageisclosestinmeaningto

答案：

（A）observe

（3）Theword"offset"inthepassageinmeaningto

答案：

（D）balanced

（4）Whichofthefollowingreasonismentionedinparagraph3toexplainwhygrowingfastisanadvantageforguppiesthatliveinpondswithmanypredators

答案：

（A）Theywillproductmoreoffspring.

（5）Whatistheauthor'sprimaryinpresentingtheinformationinparagraph3

答案：

（C）ToexplainReznick'sreasoningaboutwhyitwouldbeanadvantageforguppieswithpredatorstomaturequickly

（6）Allofthefollowingarementionedinparagraph4aschangeintheguppypopulationelevenyearsafterguppiesweretransferredtoupstreampondsEXCEPT

答案：

（B）Moreoffspringwereproduced.

（7）Theword"lethal"inthepassageisclosestinmeaningto

答案：

（C）deadly

（8）Theword"decimation"inthepassageisclosestinmeaningto

答案：

（A）destruction

（9）Accordingtoparagraph6,whatdisadvantagedidsmall-beakedfincheshavecomparedtolarge-beakedfiches

答案：

（A）Small-beakedfincheswerenotabletocrackopenthelargeseeds.

（10）Accordingtoparagraph7,thenewgenerationofG.fortisonaveragedifferedfromearlierpopulationin

答案：

（B）thesizeoftheirbeaks

（11）Accordingtoparagraph8,howshort-termchangestotheenvironmentaffectthernaturalelectionoftraitsinG.fortis

答案：

（A）Short-termchangesresultinquickreversalsofthetraitselected.

（12）HowweretheresultsofthenaturalexperimentwiththefinchessimilartotheresultsofReznick'sexperimentwiththeguppies

答案：

（B）Inbothcases,evolutionarychangesoccurredinarelativelyshortperiodoftime.

（13）Lookatthefoursquaresthatindicatewherethefollowingsentencecouldbeaddedtothepassage.Insuchcase,ifbiologistsareluckyenoughtobepresent,theysimplyhavetoobserve.

答案：

（B）第二个方块。

（14）总结题。

Evolutionarychangesresultingfromchangesintheenvironmentcanoccurinrelativelyshortperiodontime.

Guppiestakenfromupstreampoolsandprecedeindownstreampoolsproducedoffspringthathadsignificantlyshorterlifespans.

ThesurvivaloffincheswithbigbeaksduringaseveredroughtinGalapagosresultedinmorebigbeaksfinchesinthenextgeneration.

背景知识补充：

Reznick'sexperiment

Guppiesaresmallfresh-waterfishthatbiologistshavestudiedforlong.

AUCRiverside-ledresearchteamhasfoundthatassomepopulationsofanorganismevolvealongerlifespan,theydosobyincreasingonlythatsegmentofthelifespanthatcontributesto"fitness"–therelativeabilityofanindividualtocontributeoffspringtothenextgeneration.

Focusingonguppies,smallfresh-waterfishbiologistshavestudiedforlong,theresearchersfoundthatguppieslivinginenvironmentswithalargenumberofpredatorshaveadaptedtoreproduceearlierinlifethanguppiesfromlow-predationlocalities.Moreover,whenreproductionceases,guppiesfromhigh-predationlocalitiesarefarolder,onaverage,thanguppiesfromlow-predationlocalities,indicatingthathigh-predationguppiesenjoyalong"reproductiveperiod"–thetimebetweenfirstandlastreproduction.

Thestudysupportsthecontroversialhypothesisthatnaturalselection–theprocessinnaturebywhichonlyorganismsbestadaptedtotheirenvironmenttendtosurviveandpassontheirgeneticcharactersinincreasingnumberstosucceedinggenerations–introduceschangesinonlyaspecificsegmentofanorganism'slifespan.

TheGrants'observation

TheGalapagosfincheshavebeenintenselystudiedbybiologistsPeterandRosemaryGrantsince1973.

TheGrantshavedonenothinglessthanwitnessDarwin'stheoryofevolutionunfoldbeforetheireyes.ThatwouldhavestunnedDarwin,whothoughtnaturalselectionoperatedovervastperiodsoftimeandcouldn'tbeobserved.

Intheirnaturallaboratory,the100-acreislandcalledDaphneMajor,theGrantsandtheirassistantswatchedthestruggleforsurvivalamongindividualsintwospeciesofsmallbirdscalledDarwin'sfinches.Thestruggleismainlyaboutfood－differenttypesofseeds－andtheavailabilityofthatfoodisdramaticallyinfluencedbyyear-to-yearweatherchanges.

TheGrantswantedtofindoutwhethertheycouldseetheforceofnaturalselectionatwork,judgingbywhichbirdssurvivedthechangingenvironment.

Naturalselectionatitsmostpowerfulwinnowedcertainfinchesharshlyduringaseveredroughtin1977.Thatyearthesmall,softseedswerequicklyexhaustedbythebirds,leavingmainlylarge,toughseedsthatthefinchesnormallyignore.Underthesedrasticallychangingconditions,thestruggletosurvivefavoredthelargerbirdswithdeep,strongbeaksforopeningthehardseeds.

Smallerfincheswithless-powerfulbeaksperished.

TheGrantsfoundthattheoffspringofthebirdsthatsurvivedthe