托福閱讀真題第12套

1、154第 12 套primitive andadvancedtermite speciesparagraph1：termites are insectsthat collect vegetation, chew it up, and leave thechemical breakdown to other organisms.there aretwo strategies.the most primitivetermites swallow the chewedvegetationandpassit to a fermentation chamberin theirbodies.there,a

2、naerobicbacteriabreak down the cellulose,an organiccompoundthatforms about 33 percent of all plant matter. the termites are nourished by theever-growing population of microorganisms in their guts that turn the grass,leaves,and twigs the insectsingest into glucose. cattle do much the samething: they

3、allowbacteria to ferment the cellulose in an airtight rumen (digestive chamber), and thendigest thebacteria.1.according to paragraph1, in what way arethemost primitive termites like cattlethey havetwo waysof breakingdown thecellulose in vegetation.they getno nutritional benefit from eatingvegetation

4、.their digestivechambersarenot airtight.they rely on bacteriato processthe vegetationthey ingest.paragraph2：termite evolution has severalobvious trends, from primitive species,which live in small hidden colonies, to groups millions strong, the builders ofenormous mounds that allow for heat and gas e

5、xchange.the less advancedgroupsdigest microorganisms, which do the real work of breaking food down. the culture(colony) of cellulose digesters is passedalong through a special exchange.youngtermites feed on a special liquid secretion provided by adults, rich in the groupsdigestive heritage. when rep

6、roductive termites those destined to produce offspringleave the nest, they carry in their stomachs the microorganisms essential for thedigestive successof their offspring. treat acolony of thesetermites with an antibioticsolution, andthey will slowly starveto death.2.thephrasespecialexchangein thepa

7、ssagereferstothetransfer of cellulose digestersfrom onecolony of termites to anotherthedevelopmentof small coloniesinto muchlarger onesthetransfer of liquid secretionsfrom adult termitesto young termitesthedepartureof certain reproductivetermitesandthe arrival of others3.why doesthe author include t

8、he statementtreat a colony of thesetermites with anantibiotic solution, andthey will slowly starveto deathto suggestone reasonwhy termitessometimesleavea colonyto emphasizehow dependentthe termitesareonbacteriato accountfor theelimination of certain termite lineagesto help explain why termitesprotec

9、t essentialmicroorganismsby carrying them intheir stomachs155paragraph3： more advancedspecieshave a different feeding strategy.the energysource is still cellulose, but it is digestedoutside the termites body. not having tocarry around large chambers of slowly fermenting cellulose solution makes thes

10、especies more nimble and efficient. foragersbring twigs and leaves back to specialareasand chew them. they then transplantbits of fungus growing on other piecesofnearby vegetation onto the gnawededges,where the fungi break down the cellulose.fungi is the only kingdom of organisms able to digest cell

11、ulose in air, though theyneed warmth and humidity to do the job efficiently. this is just what the termitesprovide. moreover, thesesocial insects carefully tend the fungus-coveredvegetationby treating it with antibiotics they secreteto keep bacterial growth to a minimum.when it is time for the fungu

12、s to reproduce, pieces are carried into the open tocomplete the life cycle. some speciesof fungi arefound only in termite mounds of aparticular species;without their caretakers,thesefungi would die. needlessto say,thetermites eat the fungi; neither can live without the other. reproductive termites e

13、vencarry a chunk of fungi whenthey leaveon mating flights.4.thephraseneedlessto sayin thepassageis closestin meaningtoon the otherhandmost importantlyobviouslybesides5.according to paragraph3, each of the following is true about the fungi found intermite nestsexcept:the fungi candigestcellulose in t

14、he presenceof air.the fungi secreteantibiotics to keepbacterial growth to aminimum.the fungi reproducein the openwith thehelp of termites.the fungi needawarm, humid environmentto function effectively.paragraph4： the evolutionary trend in termites is to forsakeexcavatednestsin soil orwood, like those

15、 of most ants, for carton nestsconstructed inside excavations or ontrees.(when referring to termites, carton means,broadly, nesting material consistingof a mix of adhesivesaliva or feceswith earth or pulp, andeven sand,to createcells,floors, walls, graceful arches,tiered roofs, chimney stacks,and bu

16、ttressedtowers upto twenty feet high.) primitive termites do not store food; they live from hand tomouth, inside a rotting tree,for instance.advanced termites havespecial carton areasfor food they hold in reserve;thesesuppliesconsist of nonperishablematerial such asgrassclippings, analogousto the ha

17、y andstrawfed to cattle in thewinter, and arekeptin a dry carton loft. primitive speciesneed wet cellulose, suchas damp wood; moreadvancedspeciescanalsoprocessdry material.6.theword adhesivein the passageis closestin meaningtosticky156wetordinaryreleased7.which of the sentencesbelow best expressesth

18、e essential information in thehighlighted sentence in the passageincorrect choices change the meaning inimportant waysor leaveout essentialinformation.in winter, when fresh grassis not available, termites must rely on nonperishablefood sourcessuchashay andstraw.advanced termites store different food

19、s in different chambers,reserving the leastperishablematerial for winter.advanced termites have special chambers where they store nonperishable foodsupplies.advanced termitessuppliesof grassclippings arelike hay andstraw fed to cattle inwinter.8.paragraph 4 suggeststhat for primitive termites, a maj

20、or advantage of nestinginside arotting tree is thata rotting treeis a very easysiteto excavateprovidesa readysourceof wet celluloseprovidesa lot of raw material for making cartonhelpspreservestoredfoodparagraph5：to expandtheir niche in this way, dry-diet termites require a sourceofwater. in arid hab

21、itats,they excavatevertical tunnelsdown to the water table,asmuchas 150 feet below, which fan out at the baseto increasethe areaof contact and thusmaximize the rate of subsurfacewater accumulation. finally, less advancedtermitesremain their entire lives in tunnels and cells excavated in or near wood

22、. morecomplex species,on the other hand, searchfor food away from a central nest. toensurethat they can work in safety,they burrow shallowly through the earth or buildmud-covered tunnels on the surface of the ground or treesand around the food theywish to harvest.9.theword ensurein thepassage is clo

23、sestin meaningtoshowprovesuggestguarantee10.according to paragraph5, which of the following is true aboutthe vertical tunnelsconstructedby dry-diet termitesthey allow water from the surfaceto accumulateunderground.they aregenerally wider at thetop thanat thebottom.they provide extra spacesothat dry-

24、diet termite populations canexpand.157they areconstructedto provide direct accessto water.11.according to paragraph 5, why do termites build mud-covered tunnels on thesurfaceof the groundto makeharvestingfood lessdangerousto createasafeplaceto liveto avoid contactwith surfacewaterto avoid competitio

25、n with speciesthatcreatedeepundergroundtunnels12.look at the four squaresthat indicate where the following sentencecould beaddedto the passage.this remarkableadaptation,however,is not uniqueto termites.where would the sentencebest fitclick on a squareto add the sentenceto thepassage.termites are ins

26、ects that collect vegetation, chew it up, and leave the chemicalbreakdown to other organisms. 【a 】 there are two strategies.the most primitivetermites swallow the chewedvegetationandpassit to a fermentation chamberin theirbodies. 【b】there,anaerobicbacteriabreakdown thecellulose,an organiccompoundtha

27、t forms about 33 percent of all plant matter. the termites are nourished by theever-growing population of microorganisms in their guts that turn the grass,leaves,and twigs the insectsingestinto glucose. 【c】cattle do much the samething: theyallow bacteriato ferment the cellulose in an airtight rumen

28、(digestive chamber), andthen digestthe bacteria.【d】13.drag your choicesto thespaceswherethey belong.to review the passage,click onview text.answer choices(左邊選兩個(gè)，右邊選三個(gè)，判斷各個(gè)行為符合哪種)primitive termitesadvancedtermitesanswer choicesa. grow fungi on chewedvegetationb. do not chewvegetationc. must remain cl

29、oseto or insidewoodd. are ableto digestcellulosein aire. canconsumedry vegetationf.takecareof fungi that breakdown celluloseg. have abody chamberspecifically for breaking down celluloseelementsof life158paragraph1：the creation of life requiresa setof chemical elementsfor making thecomponents of cell

30、s. life on earth uses about 25 of the 92 naturally occurringchemical elements,although just 4 of theseelementsoxygen, carbon, hydrogen, andnitrogen make up about 96 percent of the mass of living organisms. thus, a firstrequirementfor life might be thepresenceof most or all of the elementsusedby life

31、.1.theword componentsin the passage is closestin meaningtopartsbodiescombinationscharacteristicsparagraph2： interestingly, this requirementcanprobably bemet by almostany world.scientists have determined that all chemical elements in the universe besideshydrogen and helium (and a trace amount of lith

32、ium) were produced by stars.theseare known as heavy elements becausethey are heavier than hydrogen and helium.although all of theseheavyelementsarequite rarecomparedto hydrogenandhelium,they arefound just about everywhere.2.according to paragraphs1 and2, living cells containwhich of the followingall

33、 chemical elementsin theuniverseexceptlithiumabout 25 different elementsabout 96 percentof all known elementsninety-two naturally occurring elementsparagraph 3 ： heavy elements are continually being manufactured by stars andreleasedinto spaceby stellar deaths, so their amount compared to hydrogen an

34、dhelium gradually rises with time. heavy elements make up about 2 percent of thechemical content (by mass)of our solar system;the other 98 percentis hydrogen andhelium. in some very old star systems,which formed before many heavy elementswere produced,the heavy-elementsharemay be lessthan 0.1 percen

35、t. nevertheless,every star system studied has at least some amount of all the elementsused by life.moreover, when planetesimals-small,solid objects formed in the early solar systemthat may accumulateto becomeplanetscondensewithin a forming star system,theyare inevitably madefrom heavy elementsbecaus

36、ethe more common hydrogen andhelium remain gaseous.thus, planetesimalseverywhere should contain the elementsneededfor life, which means that objects built from planetesimalsplanets, moons,asteroids, and comets also contain these elements. the nature of solar-systemformation explains why earth contai

37、nsall the elementsneededfor life, and it is whywe expect theseelementsto be presenton other worlds throughout our solar system,galaxy,and universe.3.why doesthe author provide the information that heavy elementsarecontinuallybeing manufacturedby starsand releasedinto spaceby stellardeaths159to expla

38、in how it is thatthe elementsrequired for life canbe found everywhereto provide evidencethat our solarsystemis relatively youngto arguethat somesolarsystemsaremore likely to supportlife thanothersto explain why heavyelementshavegreatermassthan hydrogenandhelium4.paragraph3 suggeststhat which of the

39、following may bea difference betweenveryold starsystemsandnewer starsystemsolder star systemsare likely to have fewer planets, moons, asteroids,and cometsthan newerstar systems.newer star systems probably contain more hydrogen and helium than older starsystems.newer starsystemsprobably containmore h

40、eavyelementsthanolder starsystems.the processof solar-systemformation may have been fundamentally different inolder starsystemsthanin newerstar systems.5.the word neverthelessin the passageis closestin meaningtoadditionallyhoweverin particularon the contrary6.the word inevitably in the passage is cl

41、osestin meaningtotypicallyunsurprisinglynecessarilynaturally7.which of the sentencesbelow best expressesthe essential information in thehighlighted sentence in the passageincorrect choices change the meaning inimportant waysor leaveout essentialinformation.planetesimalsmay remain in star systemswhen

42、 hydrogenand helium combine withlesscommon heavierelements.planetesimalsare composedof heavy elementsbecausehydrogen and helium stayin theform of gases.planetesimalsare small, solid objects that condensewithin a forming star systemand maybecomeplanets.when planetesimalsaccumulateto form planets,they

43、 inevitably contain gaseousaswell asheavy elements.paragraph4：note that this argumentdoesnot change,evenif we allow for life verydifferent from life on earth.life on earth is carbonbased,and most biologists believethat lifeelsewhere is likelyto be carbon based as well. however, we cannotabsolutely r

44、ule out the possibility of life with anotherchemical basis,such assiliconor nitrogen. the set of elements(or their relative proportions) usedby life basedon160someother elementmight besomewhatdifferent from that usedby carbon-basedlifeon earth. but the elements are still products of stars and would

45、still be present inplanetesimalseverywhere. no matter what kinds of life we are looking for, we arelikely to find the necessaryelements on almost every planet, moon, asteroid, andcomet in the universe.8.according to paragraph4, which of the following is true about possible life onother planetsit can

46、notbebasedon silicon or nitrogen.it could not survive on earth.it probably would not bemadeof elementsproducedby stars.it is likely to havecarbonasits chemicalbasis.paragraph5：a somewhatstricter requirementis the presenceof theseelementsinmolecules that can be usedas ready-madebuilding blocks for li

47、fe, just asearly earthprobably had an organic soup of amino acids and other complex molecules. earthsorganic molecules likely came from some combination of three sources: chemicalreactionsin the atmosphere,chemical reactionsneardeep-seaventsin the oceans,andmolecules carried to earth by asteroidsand

48、 comets. the first two sourcescan occuronly on worlds with atmospheresor oceans,respectively.but the third sourceshouldhavebrought similar moleculesto nearly all worlds in our solar system.9.according to paragraph5, all of the following aretrue of theorganic moleculesonearly earthexcept:someof themw

49、ere probably brought to earth by asteroidsor comets.someof themprobably formed in theatmosphereandoceans.they were probably significantly different from the organic molecules present onother planetsin thesolar system.they included complex molecules.paragraph6：studies of meteorites and comets suggest

50、that organic molecules arewidespreadamong both asteroidsand comets.becauseeachbody in the solar systemwas repeatedlystruck by asteroidsand comets during the period known asthe heavybombardment (about 4 billion years ago), each body should have received at leastsome organic molecules. however, these

51、molecules tend to be destroyed by solarradiation on surfacesunprotected by atmospheres.moreover, while these moleculesmight stay intact beneaththe surface(as they evidently do on asteroidsand comets),they probably cannot react with each other unless some kind of liquid or gas isavailableto move them

52、about.thus, if we limit our searchto worlds on which organicmolecules are likely to be involved in chemical reactions,we can probably rule outany world that lacks both an atmosphereand a surfaceor subsurfaceliquid medium,suchaswater.10.thephrasewidespreadamongis closestin meaningto161frequently pres

53、entinwidely separatedinasignificant part offound throughout thebodiesof11.theword intact in thepassageis closestin meaningtoburiedwholeconfinedactive12.according to paragraph6, why is life unlikely to befound on any planetthat lacksboth anatmosphereanda surfaceor subsurfaceliquid mediumorganic molec

54、ules must be protected from solar radiation by a surface layer ofliquid.planets that lack both of thesefeaturesare probably too small to have beenhit bymany asteroidsor cometscarrying organicmatter.organic molecules needa liquid or gaseousenvironment to bring them togethersothey caninteract.an atmos

55、phereis neededto protect organic molecules from being destroyedbyasteroidsandcomets.13.look at the four squares that indicate where the following sentencecould beaddedto the passage.to answerthe question “ could life exist on other planets”,we must first look at thenecessarypreconditionsfor life.whe

56、re would the sentencebest fitclick on a squareto add the sentenceto thepassage.paragraph1： 【a】the creationof life requiresa setof chemical elementsfor makingthecomponentsof cells. 【b】 life on earthusesabout25 of the92 naturally occurringchemical elements,although just 4 of theseelementsoxygen, carbo

57、n, hydrogen, andnitrogen makeup about96 percentof the massof living organisms. 【c】thus, afirstrequirementfor life might bethe presenceof most or all of the elementsusedby life.【d】14.drag your choices to the spaceswhere they belong. to review the passage,clickon view text.answer choicessomewherebetwe

58、en 4 and 25 naturally occurring elementsare necessaryfor life,dependingon the complexity of theorganism.the most common elementsused by life oxygen, carbon, hydrogen, and nitrogenarealsosomeof the mostwidely distributed elementsin the universe.life is most likely to be found in the oldest star syste

59、ms,where heavy elements162havebeencontinually producedsincethosesystemswereformed.planets,moons,asteroids,and cometsare all composedof heavy elements,whichmeansthey contain thebasisfor any life form, carbonbasedor otherwise.life is most likely to exist on those bodies that were not heavily bombarded

60、withasteroidsandcometsduring the formation of thesolar system. organic molecules are widely available, but chemical reactions among thesemoleculesprobably require eitheran atmosphereor aliquid medium.agriculture in thelate ottomanempireparagraph1： throughout its history, agriculture was the economic