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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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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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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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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.