英语听力英语高级听力材料Wild AfricaDesertsWord下载.docx

英语听力英语高级听力材料Wild AfricaDesertsWord下载.docx

《英语听力英语高级听力材料Wild AfricaDesertsWord下载.docx》由会员分享，可在线阅读，更多相关《英语听力英语高级听力材料Wild AfricaDesertsWord下载.docx（7页珍藏版）》请在冰豆网上搜索。

Beetles,manydifferentspecieshavefoundwaystoharvestthisbounty.Alongwithtermitesandlizards,they'

rethefoundationsforadelicatechainoflifeintheNamib.

Inthisbarrenseaofsand,it'

sharderforlargeranimalstofindenoughtoeat.You'

vegottobearealspecialist,liketheNamibsandsnake.Bysidewinding,itcanswimitswayupthedunes.Butinsuchanopenarena,ambushistricky,it'

sspeedthatcounts.Thewedge-snoutedlizardcanaffordtobeblase.Ithasasecretweapon,rocketpropulsion.Thenit'

sunderthesandasfastasyoucan,thebestplacetoescapepredatorsandthesun.

HereintheNamib,shelterissparse.Whatlittlethereis,isfiercelyprotected.ColoniesofduneantsmonopoliesthetoughNamibgrasses.Thoughaggressivetomostinvaders,theantsdotoleratethepresenceofsmallsap-suckingbugswhichtheygettomilkforprecioussugarywater.Intheirgrassyhome,theantsareshadedfromtheworstofthesun.Butoutonthesurfaceofthesand,thetemperaturecanreachablistering60Celsius.

Spoorspidershaveanextraordinarysurvivalstrategy.Withnowheretohangtheirwebs,theyspintheirsilkontheground,meshingsandgrainstogether.Theresult:

aminiblanketwhichservesasasunscreen.Butthesesandyblanketsdomorethanshelter.Theyarebeautifullycamouflagedstickytraps.

Duneantsgetmostofthefoodtheyneedontheirdoorstep.Buttosupplementtheirdiettheymustalsoventureoutontothesand.Theirlonglegsliftthemabovethebakinggroundtowherethetemperatureisslightlycooler.Buttheymuststilltreadcarefully,it'

saminefieldoutthere.

Pinningtheantstothehotsandsurface,thespidersfirstcookthemtodeathbeforedraggingthemunder.

IntheNamib,eventhetoughestanimalsstrugglewiththeheat.Gemsboktrektothecrestsofthehighestdunestoseekreliefinthebreeze.

Withnocloudcover,solarradiationblastingthedesertisintense.Themid-daysandissohot.It'

slikeabedofburningcoals.TheNamibquickstep.Overmillionsofyears,youlearntokeepyourclawscool.Pushedbythewind,thedunesavalanche.TheNamib'

sresidentscan'

tfightthetide.

Thoughthedunesareunstable,theyprovideahomeforaremarkablecreature.Thetrapdoorspideronlybuildsitsnestonthetopofthesteepestdunes.It'

slearnedtodothisbecauseithasaveryaggressiveenemy,awasp,whichrelentlesslyscoursthesand.

Thoughitseyesightispoor,thewasphasverysensitivehairsonitslegswhichcanpickuptheslightestscentofaspider.Whenitfindsanest,thewaspquicklyworksouthowdeeptheburrowis.Ifit'

sshallow,thewaspstartsdiggingforuptotwohours.It'

shardworkagainsttheslippingsand.

Withthespiderexposed,it'

snowabattlebetweenthewasp'

sparalyzingstingandthespider'

sjaws.Butthewasphasquickreflexes.Cornered,thespidernowplaysitstrumpcard.Hurlingitselfdownthedune,itflipsintoawheel.Travelingatover40turnsasecond,itmakesadizzydashforfreedom.Safe,atlast.

Backupthedune,thewaspisleftstanding,chasingthescentofitsvanishedmeal.

Instincthonedovertime,governsmuchofthelifeintheNamib.Butsomecreaturesalsohavetolearnhowtoconquerthesesands,usingknowledgepasseddownovergenerations.

Africanelephantsaresoresourceful,theycansurviveevenhereintheheartofthedesert.

Elephantshaveremarkablepowersofmemory.Thoughthisdesertismorethan2millionsquarekilometersinsize,100orsoelephantsitsupportsknowpreciselywheretofindenoughtoeatanddrink.Ittakesalotoffood,upto300kilosadaytofeedtheworld'

slargestlandanimal.Andallofthat-fromadesert.

Butthere'

soneplanthere,theNara,whoserootsdrawwaterfromdeepunderground.Eachyearitproducesabumpercropofmelons.Elephantsjustlovethem.

Eachmelonisavaluablepackageofmoistureandseeds.Theplantalsobenefitsfromthisplunderasitsseedsmaybecarriedforfiftykilometersintheelephant'

sstomachbeforebeingdroppedinapileoffertilizingdung.

ButtheNaraneedsmorethanapassingtradewithelephantstospreaditsseeds.Underthecoverofdarkness,thenutritiousmelonsalsopullinthelocals,likeCapeporcupines.Porcupinesmaywanderuptofifteenkilometersanightinsearchofripemelons.Theyrelyonasharpsenseofsmell.

Naramelonshaveatoughoutershell,buttheporcupines'

largeincisorsmakeshortworkofthem.Likeelephants,porcupineshelptheNaratospreaditsseeds.Byopeningupfruits,theyalsocreateopportunitiesforotherdunecreatures.

Hairy-footedgerbilsarehotontheirheels.Inthecoolofthedesertnight,theselittlerodentsburnupenergyquickly,andsomustgatherfoodfast.Thoughplentiful,theNaraseedstakesomeplucking.Thegerbilsprovisionforleanertimesahead,buttheymustalsokeepalert.

CavefoxespatroltheNarabushes,lookingforgerbils.Surprisingly,thefoxesarealsopartialtothethirst-quenchingmelons.Butthereisagreatmysteryhere.ThisisthemostextremeAfricanenvironment;

itmaynotrainfortenyearsatastretch.SohowdoestheNamibsupportsomuchlife?

Oncertainnights,thesecretisrevealed.Warm,dampairmovinginfromthemid-Atlanticistransformedtofogasitcrossesthecoldcoastalcurrent.

Avastblanketofmoisturesteadilyrollsacrossthedesert.

ThisveilofmististhesavinggraceoftheNamib.Justafewpreciousdropsbutenoughtoallowlifetoflourish.Atinybitofmoisture,atinybitoffoodandtensofmillionsofyearsofevolutionarethesecretstosuccessinthisharshestofAfricandeserts.

WhereelsebuttheNamibwouldaningeniouslittlebeetlestaggerupthehighestdunesoncoldmornings,putitsbacktobreeze,andthenstandonitsheadtocollectalife-givingdrink?

ImpressivesanddunesdominatetheNamib,buttothesouthandeastisaverydifferentkindofdesert,anexpanseofrockyscrubknownasthekaroo.

ThisdesertisasoldastheNamib,buthereitismainlyrain,notfogthatdriveslife.Inthekaroo,upto30centimetersofrainmayfallduringwinterandthisextrasprinkleofmoisturemakestheworldofdifference.

Inspring,thedesertundergoesaremarkabletransformation.

Forjustafewweeksayear,theflowersofover3,000differentplantspeciesturnthisdesertintotheGardenofAfrica.

Thisdazzlingvarietyofcolorhasevolvedovertimeforaveryspecialpurpose--forplantstoseducetheirinsectpollinators.

Someextraordinaryrelationshipshavebeenforged.ThebrightpurpleblossomsofLapeirousiaaredesignedpurelytoattracttheflywiththelongesttongueinAfrica.Astheflyprobesforasipofnectarinthelongfloraltubes,pollenisdabbedontoitsforehead.Asmartdesign,butonawindyday,it'

snotsoeasytohitthetarget.

Diasciaflowersusenotnectarbutnutritiousoilssecretedbyglandsatthetipsoftheirfloraltubestotemptpollinators.Flowerandbee,inthiscase,aperfectfitastheinsectdipsitstoesforoil.

Ignitedbytherain,thefloweringoftheKarootouchesthelivesofallitsinhabitants.Brandt'

swhistlingratsarequicktoharvesttheblossomsaroundtheirburrows.

Thesedesertratstimetheirbreedingtothebirthoffreshfood,butwithsnakesaround,motherscan'

triskleavingtheiryoungstersathome.Clingingtohernipples,they'

recarriedalong,asortofmealsonwheels.

Withinamonth,thespringbloomsarefinished.Theplantsnowsettheirseeds,takingadvantageofthewarmsummerwindswhichsweepthedesert.

Forawhile,thekaroojustglows.

Buttroubleisstiring.Triggeredbytherains,anall-devouringarmy--locusts.

Millionsemergefromeggsburiedinthesand,gatheringintocolumnswhichmaystretchfortenkilometers.Atthisstage,theycan'

tfly,onlyhop,butitdoesn'

thindertheirprogress.Thesesweepinghordesdevastateanyfreshgrowthintheirpath.

Afterfiveweeksofsteadymunching,theinfantrybecomesairborne.Thesebreedingswarmscancoverupto80kilometersaday,butonlywhilethefoodandmoisturelast.

SohowdoyoudefineadesertinAfrica?

Theyareplaceswherelessthan50centimetersofrainfallsayear.Neighbouringthekarooisadesertwhichgetsthemaximum,inbrief,butintensesummermonsoons.

It’sthewettestofallAfricandeserts,thegreatKalahari.

ThesandsoftheKalaharicovermoreofsouthernAfricathananyotherdesert.Butthehigherrainfallheregivesitaverydistinctiveappearance.Morelikeasavanna,itssandyridgescarpetedwithgrassesandascatteringoftrees.Inthewetseason,theKalaharisandsareloosenedbytherain,makingthemeasiertoexcavate.

Damaramole-ratswhospendtheirlivesundergroundarenowattheirmostactive,huntingforrootsandbulbs.Butdiggingtakesonethousa