高一英语 Unit19《Modern agriculture第一课时》精品教案 旧人教版第一册VIP免费

Unit19ModernagricultureⅠ.TeachingGoals:1.Talkaboutmodernagricultureandtheeffectsithasonpeople'slife.2.Practisegivingadviceandmakingdecisions.3.Use“It”foremphasis.4.Readstatisticalgraphs.5.Writeaplanforavegetablegarden.Ⅱ.TeachingTime:FiveperiodsⅢ.BackgroundInformation:1.AnAmericanSmallFarmLastyear,atharvesttime,wevisitedtheSteenhoekfarm,whichis2200mu,or340acres.Typicalfamilyfarmsarerunentirelybyfamilymembers,witheverymemberplayingavitalpartintheoperation.BothofthesefamiliesaredescendantsofDutchimmigrantswhosettledhereoveracenturyago.TheSteenhoekfarmsupports3generations.ThefamilyofMr.andMrs.Steenhoekincludesthreechildrenand2grandchildren.Aswewillsee,thisfamilyisanexcellentexampleofhardworking,experiencedfarmerswhostayonthelandnotpurelybecauseofprofit,butbecausetheyarelivingalife-stylethatsatisfiesthem.SixtypercentoftheSteenhoek'sacresaredevotedtopastureland,onwhichtheyraise120beefcattle.Therestofthelandisusedforgrowingcorn.Fifteenyearsago,theAmericanfarmeconomywasbooming.Farmerscouldspecialize,raisingonecrop,oronetypeofanimal.Today,withanuncertainfarmeconomy,suchanideaisconsideredfoolhardy,anddiversifyingisonewaythatfarmerscanlessontheirriskofloss.Forexample,ifweatheraffectsthesizeofacrop,thesaleofthelivestockwillmakeupthedifference.Iftheanimalsareplaguedbydisease,atleastthereisgraintotaketomarket.KendallSteenhoek,Simon'seldestson,divideshistimebetweenrunningthismachineshopandfarmingzooacresofcorn.HeattendedacommunitycollegeinIowafortwoyearstostudydieselmechanics.Thenheopenedthisrepairshopforfarmmachinery.Kendallalsoplantsandharvestsover30000bushelsofcorneachyear,butitistheincomefromtherepairshopthathasenabledhimtostaywithinthefarmingcommunity.Theheavyequipmentusedonthefarmstodayisinconstantneedofmaintenance,andrequiresprecisiontoolingforrepairs.Byfar,themostimpressiveandcertainlythemostcostlypieceoffarmequipmentusedonasmallfarmisaharvestingmachinecalledacombine,whichcancostupto$100000.ThistypeofmachineryiswhatmakestheAmericanfarmsoefficient.Withacombine,onemanandhisfamilycanharvestanentirecropofa500acrefarmintwoweeks.Thevalueofthecombineisthatitperformsseveralfunctions.Asitmovesthroughafieldofcorn,thissophisticatedmachinecutsthestalk,pluckstheear,discardsthestalk,shucksthecornkernelsofftheearanddepositesthekernelsinastoragebinintheback.Then,aspinningdeviceintherearofthecombineshredsthehusksandshaftsandscattersthemacrossthefield,toserve用心爱心专心1asmulch,cuttingdownonthepossibilityofsoilerosionfromwinterrains.ThemachineisevenmoreamazingwhenyouthinkthatithasbeeninuseonAmericanfarmsforonlyonegeneration.2.GenesEverylivingcellcontainsgenes.Theyaretoosmalltobeseeninamicroscope,buttheyarevitallyimportant.Eachsetofgenesinthebodycontainsalltheinstructionsneededtomakeahumanbeing.Somegenesdeterminehaircolor.Somedeterminetheshapeofanose.Somegeneshelpdetermineyourheightandevenyourweight.GenesaremadeofachemicalcalledDNA—thelettersstandfordeoxyribonucleicacid(脱氧核糖核酸).Intheearly1950's,twoscientists,FrancisCrickandJamesWatson,figuredouthowthepartsofDNAfittogether.Oncescientistsunderstoodthisstructure,itbecamepossibletotakepiecesofDNAapartandputthemtogetherinnewways.Newkindsofgenescouldbemadeinthismanner.Scientistshavestudiedthegenesofmanyplantsandanimals.Theyhaveworkedoutwhichgenesaffectthecolorofatomatoandthesticknessofitsskin.Workingoutwhichgenesdeterminewhichfeaturesisca...