Unit4Exploringplants-section1PartTwo:TeachingResourcesSection1:DiscoursestudiesofPLANTEXPLORATIONINTHE18THAND19THCENTURIES1.TypeofwritingandsummaryofPLANTEXPLORATIONINTHE18THAND19THCENTURIESTitleoftextPLANTEXPLORATIONINTHE18THAND19THCENTURIESTypeofwritingExposition2.AdiagramofPLANTEXPLORATIONINTHE18THAND19THCENTURIESSection2:BackgroundinformationforUnit4ExploringplantsImportanceofPlantsPlantsformthebasicfoodstapleforalllifeforms.Theyarethemajorsourceoffoodandoxygenonearth,sincenoanimalcansupplythesenecessarycomponentswithoutplants.Thecattleweeatasbeef,feedongrassesandthefishweeat,consumealgaeandarethereforedependentonplantsforwellbeing.Otherimportantusesofplantsinclude,providingshelterforanimals,providingmaterialsforclothing(cottonfibers),paperproducts,medicinesandotherchemicals,producingcoalfromoncelivingplantmaterial,reducingwindspeedandnoiselevels,andreducingsoilerosionandwaterrunoff.Therearemanydifferenttypesofcashcropsthatproducemoneyforfarmers.Oliveoilcomesfromolives,cornoilcomesfromcorn,andpeanutoilcomesfrompeanuts.Typical用心爱心专心116号编辑datingbacktotheearliesttimesPara1notuntiltheeighteenthandnineteenthcenturiesPara2inChinabythemiddleofthe18thcenturyPara3voyagefromEnglandtoOceaniaPara4anenormouschallengePara5ThesecondhalfofthenineteenthcenturyPara8notenoughmaterialforgrowingparticularspeciesPara.9RobertFortunetouseWardiancasesPara7atightlysealedportableglasscontainerPara6agriculturalproductslikecorn,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,becausetheplantthenneedsoxygentomaintaini...
