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1、Unit4ExploringplantsPeriodI单元预习课阶段1导读一话题美文（赏析美文领悟话題］植物是我们牛活中必不可少的一个部分，那么你知道植物的重要性吗?Plantsformthebasicfoodstapleforalllifeforms.Theyarethemajorsourceoffoodandoxygenonearth,sincenoanimalcansupplythesenecessarycomponentswithoutplants.Therearemanydifferenttypesofcashcropstha
2、tproducemoneyforfarmers.Oliveoilcomesfromolives,cornoilcomesfromcorn,andpeanutoilcomesfrompeanuts.Typicalagriculturalproductslikecorn,wheat,rye,andriceareallconsideredcashcrops.Coffeeplantsproducebeansthatareusedtomakecoffee；cocaplantsgiveuschocolate；vanillaplantsgrowlon
3、gthinbeansthatareusedtoproducevanillaflavoring.Plantsarealsousedinagriculturetohelpreducewindspeed.Plantingtreesinarowpreventsthewindfromblowingawaythevaluabletopsoil.Intheforest,treesactasshelterformanyorganisms-Plantsarealsoimportantfortheoverallecologyofanarea.Rootshe
4、lptostabilizesoilandpreventthesoilerosionbywaterrunoff.Plantsarealsoimportantinouratmospherebecausetheyusecarbondioxideandgiveoffoxygenwhiletheyundergophotosynthesis.Plantsarealsousedintheurbansettingtoreducenoise,produceshade,andtobeautifyanarea.Treesaddvaluetohomesandc
5、ommunities.Plantsareessentialtothebalanceofnatureandinpeople'slives.Greenplants,i.e.，thosepossessingchlorophyll（叶绿素）,producetheirownfoodandgiveoffoxygenintheprocesscalledphotosynthesis（光合作用），inwhichwaterandcarbondioxidearecombinedbytheenergyoflight.Plantsaretheultimateso
6、urceoffoodandmetabolicenergyfornearlyallanimals,whichcannotproducetheirownfood.Besidesfoods,plantproductsvitaltohumansincludewoodandwoodproducts,fibers,drugs,oils,latex,pigments,andresins.Coalandpetroleum（石油）arefossilsubstancesofplantorigin.Thusplantsprovidepeoplenotonly
7、sustenancebutshelter,clothing,medicines,fuels,andtherawmaterialsfromwhichinnumerableotherproductsaremade.思考两个诱思问题1•Whatisthepurposeofthesecondparagraph?2.Whyareplantsimportanttoouratmosphere?【答案】l.Givesomeexamplesabouttheuseofplants.2.Becausetheyusecarbondioxideandgiveof
8、foxygenwhiletheyundergophotosynthesis.1必记:核心单词根据词性及英文释义写出单词的正确形式1•adj.farawayinspaceortime2.n.balancefo
