《新世纪研究生公共英语教材阅读A》课文.docx

《新世纪研究生公共英语教材阅读A》课文.docx

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《新世纪研究生公共英语教材阅读A》课文

《新世纪研究生公共英语教材阅读A》课文

Unit3OceanofSand

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