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1、2019-2020年高中英语（人教大纲）第三册：Unit4Greenworld(备课资料)Ⅰ.异域风情PlantsinDesertOnlyspecialplantscansurvivetheterribleclimateofadesert,fortheseareregionswheretheannualrangeofthesoiltemperaturecanbeover75℃.Furthermore,duringthesummertherearefewcloudsintheskytoprotect
2、plantsfromthesun’sray.Anotherproblemisthefactthattherearefrequentlystrongwindswhichdrivesmall,sharpparticlesofsandintotheplants,tearinganddamagingthem.Themostdifficultproblemforallformsofplantlife,however,isthefactthattheentireannualrainfalloccursduring
3、afewdaysorweeksinspring.Grassesandflowersindesertsurvivefromoneyeartothenextbyexistingthroughthelong,hot,dryseasonintheformofseeds.Theseseedsremaininactiveunlesstherightamountofrainfalls.Ifnorainfalls,orifinsufficientrainfalls,theywaituntilthenextyear,
4、orevenstillthenext.Anotherfactorthathelpstheseplantstosurviveisthefactthattheirlifecyclesareshort.Bythetimethatthewaterfromthespringrainsdisappears—justafewweeksafteritfalls—suchplantsnolongerneedany.Theperennialshavespecialfeatureswhichenablethemtosur
5、viveasplantsforseveralyears.Thus,nearlyalldesertperennialshaveextensiverootsystemsbelowgroundandasmallshootsystemaboveground.Thelargerootnetworkenablestheplanttoabsorbasmuchwateraspossibleinashorttime.Thesmallshootsystem,ontheotherhand,considerablylimit
6、swaterlossbyevaporation.Anotherfeatureofmanydesertperennialsisthataftertherainyseasontheylosetheirleavesinpreparationforthelong,dryseason,justastreesinwetterclimateslosetheirsinpreparationforthewinter.Thisreducestheirwaterlossbyevaporationduringthedrys
7、eason.Then,inthenextrainyseason,theyefullyaliveoncemore,andgrownewbranches,leavesandflowers,justasthegrassesandflowersindesertdo.Ⅱ.知识归纳1.accumulate用法归纳(1)积累(vt.)Thescientisthasaccumulatedawealthofexperience.这位科学家已经积累了丰富的经验。(2)堆积，越积越多(vi.）Ifyoudon
8、’tclearawaytherubbishregularly,itwilljustaccumulate.如果你不定时清除垃圾，便会越积越多。Apileofworkaccumulatedonhisdesk.他桌子上有一大堆文件要他处理。2.involve的用法归纳(v.)(1)牵涉，牵连ThiseventinvolvedourinterestsinEurope.这牵涉到我们在欧洲的股份。有时表示“有……参加”。Morethan4milli
