高中英語Unit4Exploringplants-section1-2人教版必修9

Unit4Exploringplants-section1PartTwo:TeachingResourcesSection1:DiscoursestudiesofPLANTEXPLORATIONINTHE18THAND19THCENTURIES1.TypeofwritingandsummaryofPLANTEXPLORATIONINTHE18THAND19THCENTURIESTitleoftextPLANTEXPLORATIONINTHE18THAND19THCENTURIESTypeofwritingExposition2.AdiagramofPLANTEXPLORATIONINTHE18THAND19THCENTURIESdatingbacktotheearliesttimesPara1

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2:Background

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4ExploringplantsImportanceofPlantsPlantsformthebasicfoodstapleforalllifeforms.Theyarethemajorsourceoffoodandoxygenonearth,sincenoanimalcansupplythesenecessarycomponentswithoutplants.Thecattleweeatasbeef,feedongrassesandthefishweeat,consumealgaeandarethereforedependentonplantsforwellbeing.Otherimportantusesofplantsinclude,providingshelterforanimals,providingmaterialsforclothing(cottonfibers),paperproducts,medicinesandotherchemicals,producingcoalfromoncelivingplantmaterial,reducingwindspeedandnoiselevels,andreducingsoilerosionandwaterrunoff.Therearemanydifferenttypesofcashcropsthatproducemoneyforfarmers.Oliveoilcomesfromolives,cornoilcomesfromcorn,andpeanutoilcomesfrompeanuts.Typicalagriculturalproductslikecorn,wheat,rye,andriceareallconsideredcashcrops.Coffeeplantsproducebeansthatareusedtomakecoffee;cocaplantsgiveuschocolate;vanillaplantsgrowlongthinbeansthatareusedtoproducevanillaflavoring.Manydrinksandbeverages,likecolaandtea,comefromplants.Rubberfromtreesisalsoacashcrop,asislumber,fruit,vegetables,andcotton.Plantsarealsousedinagriculturetohelpreducewindspeed.Plantingtreesinarowpreventsthewindfromblowingawaythevaluabletopsoil.Intheforest,treesactasshelterformanyorganisms.Plantsarealsoimportantfortheoverallecologyofanarea.Rootshelptostabilizesoilandpreventerosionbywaterrunoff(soilconservation).Plantsarealsoimportantinouratmospherebecausetheyusecarbondioxideandgiveoffoxygenwhiletheyundergophotosynthesis.Plantsarealsousedintheurbansettingtoreducenoise,produceshade,andtobeautifyanarea.Treesaddvaluetohomesandcommunities.Plantsareessentialtothebalanceofnatureandinpeople'slives.Greenplants,i.e.,thosepossessingchlorophyll,manufacturetheirownfoodandgiveoffoxygenintheprocesscalledphotosynthesis,inwhichwaterandcarbondioxidearecombinedbytheenergyoflight.Plantsaretheultimatesourceoffoodandmetabolicenergyfornearlyallanimals,whichcannotmanufacturetheirownfood.Besidesfoods(e.g.,grains,fruits,andvegetables),plantproductsvitaltohumansincludewoodandwoodproducts,fibers,drugs,oils,latex,pigments,andresins.Coalandpetroleumarefossilsubstancesofplantorigin.Thusplantsprovidepeoplenotonlysustenancebutshelter,clothing,medicines,fuels,andtherawmaterialsfromwhichinnumerableotherproductsaremade.2.ThelifecycleofaplantThelifecycleofaplantvariesdependingontheindividualspecies.Thereare,however,certainrequirementsforlifethatmostplantsneed.Thegrowthofaplantisdependentuponlight,water,oxygen,carbondioxide,mineralsinthesoil,temperatureandmicrobesinthesoil.Light,water,andcarbondioxideareneededforphotosynthesiswhichproducesfoodfortheplant.Oxygenisneededwhenitisdark,becausetheplantthenneedsoxygentomaintainitself.Thecorrecttemperature,soil,andmineralsareallneededwhentheplantfirstgerminatesandsubsequentlysoilincludeanumberthatarebeneficialtoplants.Microbialactivityhelpsbringaboutthedecayoforganicmaterial(deadplantmaterialandanimals)necessaryfortheproductionofsoil.Temperatureorlightintensityvariesforeachtypeofplant,andthishelpsexplainglobalplantdistribution;lightintensityortemperaturealsoeffectstherateofphotosynthesisinplants;thetimeatwhichaplantflowersandtherateatwhichwaterlossoccursinaplant(transpiration.)Whentheserequirementsarestaticforaseed,itwillbegintogroworgerminate.Sufficientfoodandmineralsarestoredinalmostallseeds,sothatthesefactorsdonotlimitgermination.Aswaterisabsorbedbyaseed,theinnertissueswellsmorerapidlythantheseedcoat.Thepenetrationofwaterallowsthetissuestobecomehydratedandenzymeactivityincreases.Thefoodthatisstoredinthecotyledonsortheendospermsarenowdigestedandused.3.ThegrowthrequirementsofplantsAllplantsneedlight,water,air,moderatetemperaturesandmostneedsoil.Someplants,suchasmistletoeandduckweed,donotrequiresoilforgrowthandlifebuttheydonotconstitutethemajorityofplants.Therearewidevariationsintheamountoflightandwaterthatplantsrequire.AmatureJoshuatree,forexamplecanstoreenoughwatertolastthreeyearsoruntilanotherrainyseason.Mostplants,however,needwateronamoreregularschedule.Someplantsrequireafullday'shotsun,andotherscannotbetakenoutofdeepshade.Temperaturetolerancealsovariestremendously.TundraandlichenscansurviveneartheArctic,butmanytropicalplantscannotsurvivebeingcarriedfromthestoretoacarwhenitisnearfreezing.4.GrowingplantsfromcuttingsManyplantscanreproduceeithersexually(seeds)orvegetatively(asexual),utilizingotherplantparts.Wholeplantscanbegrownfromstems,leavesorroots,iftherightplantischosen.Thefollowingaresomesuggestionsthatcanbeusedtoillustratevegetativereproduction.Stems:Ivy,potatotubers,bambooandirisrhizome,bulbsofvariouskinds(bulbsareactuallymodifiedshoots),crocusorgladiolus,corn,Philodendron,Monstera(split-leafphilodendron),strawberryandspiderplantoffsets.(Manyotherswillgrow,evenhardwoods,buttheytakealotoftimeandeffort.)Roots:Japaneseanemone,Orientalpoppy,trumpetc