《新世纪研究生公共英语教材阅读A》课文Word下载.docx
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FromTheGuardian
1.Thereismoredesertsthansunandsand.Onthesetwopagesyoucanfindouthowplants,animalsandpeoplemanagetosurviveintheseapparentlybarrenplaces.
2.Alldesertsaredry.Thehot,sandyplaceswethinkofwhenwetalkaboutdesertsaresubtropicaldeserts.TheyarefoundneartheTropicsofCancerandCapricornwherethewarmairwhichrisesattheEquatorsinksdownagain,givingaclimateofclearskiesandverylowrainfall.TheSaharaisalmostone-thirdthesizeofAfrica,andisnearlyasbigastheU.S.A.,thefourthlargestcountry.Itwasnotalwaysadesert.Overmillionsofyearsithasbeenconveredinice,sea,forestsandgrasslands.
3.Desertwindsareusuallydry.Somedesertsarein“rainshadow”areaswherethewindshavelostwhatmoisturetheyhadcrossinghighground.Othersareinthemiddleofcontinentswherethewindsblowingoverthemhavelostanymoisturegainedfromdistantoceans.TheGobidesertinMongoliainAsiaisanexampleofsuchaninlanddesert.TheAtacamainnorthernChileisthedriestdesertonEarth.Partsofthedeserthadnorainfor400years,from1570to1971,andinotherparts,rainshadneverbeenrecordedn.OneofthesandiestdesertsistheTaklaMakan.Sandstormscanwhipupthesandashighas3,048m(10.000ft).WindblownsandintheSaharacanbesofiercethatitwillsandblastthepointoffacaroraeroplane.Thetemperatureatnightinahotdesertcandropbelowfreezing,to-4℃(24℉).Duringtheday,thesandcanbeashotas79℃(175℉).
Livinginadesertclimate
4.Desertsaredifficultplacesinwhichtolive.Duringthedaytheyareveryhot.IntheLibyanDesertinNorthAfricathetemperatureon13September1922reached58Cintheshade!
Butdesertnightsareoftencoldbecauseclearskiesallowheattoescapeintotheatmosphere.Thelackofwatercausedbylowrainfallisbadenough,butrainfallisalsohighlyunpredictable.Yearsofdroughtcanendintremendousrainstorms.Manydesertareasarebarerock,orarecoveredwithpebblesandgravel.Sandaccountsforonlyabout15percentoftheearth’sdesertregions.Insomedeserts,thetotalrainfortheyearmightfallinonlytwoorthreestorms.Butthatisenoughforplantseedstosproutandbloom,turningpartsofthedesertintocarpetsofflowersforafewdays.
Howplantssurvive
5.Withinafewhoursofrainfalling,thousandsoffloweringplantswillstarttoappear.Seedsofplantssuchasthedesertdandelionlieinthegroundforyearswaitingfortherain.
6.Theseplantsdieasthedesertdriesoutagain,leavingtheirseedsforthenextrains.Otherplantshaveadaptedtotheharshenvironmentbystoringwaterintheirleaves,stemsorroots.TheAmericansaguarocactuscanhold6to8tonesofwater.Desertplantsoftenhavespreadingrootsystemswhichextracteverydropofmoisturefromtheground.Therootsofthemesquitebushcanbe20mdeep.
7.Plantsgenerallylosewaterthroughporesintheirleaves.Topreventthis,desertplantshavesmallwaxyleavesandfewerpores.Manyclosetheirporesduringthedaysotheydonotlosemoisture.Toprotectthemselvesagainstgrazinganimals,someplantshavethornsoranunpleasanttaste.Cactiareprotectedbytheirsharpspines.CactiarefoundonlyinAmericandeserts.Thetallestaresaguaroswhichcanreach15m(50ft)tall,weigh7tonsandlivefor200years.Waterisstoredinthestemandusedintimesofdrought.
Animallife
8.Althoughdesertsseemempty,fewarewithoutanimals.Mostanimalsshelterfromthedaytimeheatinholesorburrows.Theburrowstrapmoisturearestaycoolerthanthegroundabove.Inthecoolereveningoratdawn,theanimalsemerge.
9.Smallermammalsoftenhavelargeears.Duringtheday,theanimallosesheatthroughitsears.Inthedark,largewarntheanimalofunseendangers.
10.Reptilesventuringoutindaytimetrytoavoidtouchingthehotsand.TheAustralianbeardedlizardsometimesrunsonitshindlegsonly.Theaptlynamedsidewindersnakeonlytouchesthegroundintwoplaces.
11.Alldesertanimalssurviveonlittlewater.Manysmallanimalsliveonthemoistureintheirfood.Largeranimalssuchasthecamelcangowithoutwaterfordays,butdrinkhugeamountswhentheygetthechance.Acamelcandrink10litresofwaterinaminute.
Desertpeoples
12.Overthoughtofyears,peoplehavelearnthowtosurviveinDeserts.TheSanpeopleoftheKalaharidesertinsouthernAfricaandtheAustralianAborigineshuntanimalsandgatherfoodplants.Theylearntraditionalskillsfromolderpeople.
13.Ontheedgesofthedesert,nomadicpeoplesgrazeflocksofsheepandgoats.Theyareconstantlymovingtofresherpastures.NomadssuchastheTuaregoftheSaharainNorthAfricawearloosechothingtoprotectthemsandandheat.Tuareg