托福阅读加试机经.docx
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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
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