高一英语必修4 Unit 2.ppt

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1、Unit2WorkingthelandTask1:BrainstormingWhatwillyouthinkofwhenyouseetheword“agriculture”?agriculturefarmirrigationfoodcropfieldplantsplainGMFgrainfarmerfertilizerseedprairiecountrysidelandarablelandagriculturewheatcornricesoybeancottonbroomcornpeanutTerraceDroughtIrrigatedlandGreenhouseInthef

2、irstpicture:*Terracedfields.Inthesecondpicture:*Drybarrenfarmland.Inthethirdpicture:*Irrigatedfarmland.Inthefourthpicture:*Greenhouses.Whatarethedifferences?Comparetheoldandthemodernwaysofirrigation.NaturalClimateControlledClimateinbadweather,cropslostclimatecontrolled,lessdamageThelandscap

3、elosesitsnaturalbeauty.Onlyarablelandcangrowcrops.Greenhousescanbebuiltalmosteverywhere.Thelandscapeismorebeautiful.Ifthereisapowerfailure,youmaylosecrops.Whataregenetically-modifiedfoods?ThetermGMfoodsorGMOs(genetically-modifiedorganisms)ismostcommonlyusedtorefertocropplantscreatedforhuman

4、oranimalconsumptionusingthelatestmolecularbiologytechniques.Theseplantshavebeenmodifiedinthelaboratorytoenhancedesiredtraitssuchasincreasedresistancetoherbicidesorimprovednutritionalcontentveryrapidlyandwithgreataccuracy.Forexample,plantgeneticistscanisolateageneresponsiblefordroughttoleran

5、ceandinsertthatgeneintoadifferentplant.Thenewgenetically-modifiedplantwillgaindroughttoleranceaswell.WhataresomeoftheadvantagesofGMfoods?Theworldpopulationhastopped6billionpeopleandispredictedtodoubleinthenext50years.Ensuringanadequatefoodsupplyforthisboomingpopulationisgoingtobeamajorchall

6、engeintheyearstocome.GMfoodspromisetomeetthisneedinanumberofways:1).Pestresistance2).Diseaseresistance3).Coldtolerance4).Droughttolerance/salinitytolerance5).NutritionThirteencountriesgrewgenetically-engineeredcropscommerciallyin2000,andofthese,theU.S.producedthemajority.In2000,68%ofallGMcr

7、opsweregrownbyU.S.farmers.Incomparison,Argentina,CanadaandChinaproducedonly23%,7%and1%,respectively.Soybeansandcornarethetoptwomostwidelygrowncrops(82%ofallGMcropsharvestedin2000)WhataresomeofthecriticismsagainstGMfoods?MostconcernsaboutGMfoodsfallintoth