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Plant Kingdom

NCERT Textual Exercise (Solved)

1. Whatisthebasisofclassificationofalgae? Ans. Classificationofalgaeisbaseduponphotosyntheticpigments. 2. Whenandwheredoesreductiondivisiontakeplaceinthelifecycleofa

liverwort,amoss,afern,agymnospermandanangiosperm? Ans. 1. Liverwort–Sporesareproducedbymeiosisincapsuleofsporangia. 2. Moss–Meiosisoccursincapsuleofsporangium. 3. Fern–Leavesofsporophytebearssporangiainwhichsporesare

producedbymeiosis. 4. Gymnosperm–Inmicrosporophyllsandmegasporophyllsthatbear

microsporangiaandmegasporangia,respectively,reductiondivisionoccurstoproducemicrospores(pollengrains)andmegaspore.

5. Angiosperm–Meiosistakesplaceinstamenandcarpeltoproducepollengrainsandovum,respectively.

3. Namethreegroupsofplantsthatbeararchegonia.Brieflydescribethelifecycleofanyoneofthem.

Ans. 1. Bryophyta, 2. pteridophytaand 3. gymnosperm. Life cycle of gymnosperms:The gymnosperms are heterosporous, they

producehaploidmicrosporesandmegaspores.Thetwokindsofsporesareproducedwithsporangiathatareborneonsporophyllwhicharearrangedspirally along an axis to formor strobili or cones.The strobili bearingmicrosporophyllsandmicrosporongiaarecalledmicrosporongiateormalestrobili.Themicrospores develop into amale gametophytic generationwhichishighlyreduced,andisconfinedtoonlyalimitednumberofcells.Thereducedgametophyteiscalledpollengrain.Thedevelopmentofpollengraintakesplacewithinmicrosporongia.Theconesbearingmegasporophyllswithovulesormegasporangiaarecalledmacrosporangiateorfemalestrobili.Themaleorfemaleconesorstrobilimaybeborneonthesametreeorondifferenttrees.Themegasporemothercellisdifferentiatedfromoneofthecellsofthenucellus.Thenucellusisprotectedbyenvelopsandthecompositestructureiscalledanovule.Theovulesareborneonmegasporophillswhichmaybeclusteredtoformthefemalecones.Thefemalesconesareborneonthemainplantbodyofthesporophyte.Themegasporemothercelldividesmeioticallytoformfourmegaspores.Oneofthemegasporeenclosedwithinthemegasporangiumdevelopsintoamulticellularfemalegametophytethatbearstwoormorearchagoniaorfemalesexorgans.Themulticellularfemalegametophytesarealsoremainedwithinmegasporangium.

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NCERT Textual Exercise (Solved)

4. Mentiontheploidyofthefollowing:protonemalcellsofamoss;primaryendospermnucleusindicot,leafcellofamoss;prothalluscellofafern;gammacellinMarchantia;Meristemcellsofmonocot,ovumofliverwortandzygotofafern.

Ans. Protonemalcellsofamoss–Haploid(n) Primaryendospermnucleusindicot–Triploid(3n) Leafcellofamoss–Haploid(n) Prothalluscellofafern–Haploid(n) GammacellinMarchantia –Haploid(n) Meristemcellsofmonocot–Diploid(2n) Ovumofliverwort–Haploid(n) Zygoteofafern–Diploid(2n) 5. Writeanoteoneconomicimportanceofalgaeandgymnosperms. Ans. AlgaelikeChlorella,Gelidium,Gracilaria(produceagar-agar)areusedas

food.Manyalgaelikediatoms(usedinmanufactureofglass,polishetc.),algin(usedinvulcanisation,artificialfibresetc.),agar-agaretc.,areusedinindustry.Nostoc,Anabaenaetc.,areusefulinincreasingfertilityofsoil.Antibioticchlorellinisextractedfromchlorella.Manyalgaehaveharmfuleffectalso,e.g.microcysts,chrococcus,oscillatoriacausewaterbloomsandcephaleurosspeciesofalgaeareparasiticortealeavesandcauseharmtoteaindustry.

Economic importance of gymnosperms:Gymnospermshelpsincheckingsoilerossion.SeedsofPinus gerardiana, Gietum gnemonandGinko biloba areeaten.ConiferslikePinus longifolia, Cedrus deodara,Picea,Tsugoetc.producesoftwood.BarkofTsugoyields tannins formaking inks, seedsandbarkofCycas are used as poultice forwounds and sores.Ephedra,Gnteumula,Taxusbaccata,Cycles rumphiiareusedformedicinalpurposes.Cedarwoodoil(fromJuniperus,virginia)areusedasimmersionoilinoilimmersionlens.Woodgas,woodtanandwoodalcoholareobtainedfromvariousspeciesofPinus.

6. Bothgymnospermsandangiospermsbearseeds,thenwhyaretheyclassifiedseparately?

Ans. Gymnospermsare‘nackedseeded’plantsbecausetheirseedsarenotenclosedinfruitwallwhereasangiospermare‘enclosedseeds’asseeds(ovules)arefoundenclosedintheovarywall.

7. What is heterospory?Briefly comment on its significance.Give twoexamples.

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NCERT Textual Exercise (Solved)

Ans. Genera likeSelaginellaandSalviniawhichproduce twokindsofsporesmacroandmicrospores,areknownasheterosporous.Themegasporeandmicrospores germinate andgive rise to female andmale gametophytes,respectively.Thefemalegametophytesintheseplantsareretainedontheparent sporophyte for variable periods.Thedevelopment of the zygotesintoyoungembryotakeplacewithinthefemalegametophytes.Thiseventis considered as an important step in evolution leading to seed habit.Significanceofheterosporyisthefirststeptowardsseedhabit.

Example:SelaginellaandMarsilea. 8. Explainbriefly (i) Protonema (ii) Antheridium (iii) Archegonium (iv) Diplontic (v) Sporophyll (vi) Isogamy Ans. (i) Protonema:Thepredominantstageofmossgametophytewhich

directlydevolopfromsporeisknownasprotonema. (ii) Antheridium:Themalesexorgansinbryophytes,pteridophyteand

gymnospermiscalledantheridium.Itbearsmalegamete. (iii) Archegonium: Gymnosperms the female sex organ found in

bryophytes,pteridophytesandgymnosperms.Itbearsfemalegamete. (iv) Diplontic: In the life cycle of plantswhen the diploid stage is

denunantorsurviveforlongtimethenthisiscalleddiplontic. (v) Sporophyll:Thesporophytebearsporongiathataresubtendedby

leaf-likeappendagescalledsporophylls. (vi) Isogamy:Whenthegameteswhichtakespartdominantinsexual

reproductionaremorphologicallysimilarthanthisiscalledisogamy.Thesegametesarephysiologicallydifferent.

9. Differentiatebetweenthefollowing: (i) Redalgaeandbrownalgae (ii) Liverwortsandmoss (iii) Homosporusandheterosporuspteridophyte (iv) Syngamyandtriplefusion Ans. Difference between red algae and brown algae:

Red algae Brown algae1. Thylakoidsinchloroplastsare

notstackedThylakoidsinchloroplastsarestackedingroupsofthree

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NCERT Textual Exercise (Solved)

2. Chlorophyll aandChl.dpresent Chlorophyll aandChl.cpresent3. Resevefoodisflorideanstarch Resevefoodislaminarianstarch4. Nomovementisfound Movementpresent

Difference between liverworts and moss

Liverworts Moss1. Foundinmoistshady

habitatFoundinalmostallconditionsbutabsentinoceans

2. Plantbodyisdorsoventrallyflattened,thalloid

Plantbodyisdifferentiatedintotwostages–protonema stage(nosexorgans)andleafystage (producessexorgans)

3. Asexualreproductionoccursbyformationofgemma

Asexualreproductionoccursbybuddinginthesecondaryprotonema

Difference between homosporus and heterosporus pteridophyte

Homosporus pteridophyte Heterosporus pteridophyte1. Spores are of same type Sporesareofdifferenttype2. Producemonoeciousgametophyte Producedioeciousgametophyte3. E.g., fernslikeAdiantum, Pteris E.g., Selaginella, Marsilea,

Salvinia, Azolla

Difference between syngamy and triple fusion

Syngamy Triple fusion1. One of themale gametes

fuseswiththeegg,resultingintheproductionofdiploidzygote or oospore is calledsyngamy

The secondmale gamete fuseswiththesecondarydiploidnucleus(formedbyfusionoftwohaploidpolarnuclei),producinga tr ip lo id pr imary endosperm nucleus. This is calledtriple fusion

2. Syngamyresultsinformationofdiploidembryo

Triploid primary endosperm nucleusformstriploidendosperm

10. Howwouldyoudistinguishmonocotsfromdicots? Ans. Thedicotyledonsarecharacterisedbyhavingtwocotylendonsintheirseeds

whilemonocotyledonshaveonlyone.

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Plant Kingdom

NCERT Textual Exercise (Solved)

11. Matchthefollowing(columnIwithcolumnII) Column I Column II (a) Chlamydomonas (i) Moss (b) Cycas (ii) Pteridophyta (c) Selaginella (iii) Algae (d) Sphagnum (iv) Gymnosperm Ans. (a)(iii);(b)(iv);(c)(ii);(d)(i) 12. Describetheimportantcharactersticsofgymnosperms. Ans. Gymnosperms:Theseed-formingvascularplantswhichproduceseedsbut

nofruitsarecalledgymnosperms.Generalcharacters: (i) Fertilisationdoesnotrequirewater. (ii) Leavesmaybeoftwokinds–foliageleavesandscaleleave. (iii) Theovulesareorthotropous. (iv) Mostprimitiveseedbearingplants. (v) Mostlysuchplantsareevergreen. (vi) Havenoovarywall,seedsarenaked. (vii) Exhibitpolyembrony. (viii) Sexualreproductionoogamoustype. (ix) Large,tallandwoodytrees.