NCERT Class 11 Biology Chapter 3 Plant Kingdom

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NCERT Class 11 Biology Chapter 3 Plant Kingdom

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Plant Kingdom

Chapter: 3

BIOLOGY

TEXTUAL QUESTIONS ANSWERS

Q.1. What is the basis of classification of algae?

Ans. Algae are classified into Chlorophyce-ae, Phaeophyceae, and Rhodophyceae on the basis of following factors:

(a) Major photosynthetic pigments present.

(b) Form of stored food.

(c) Cell wall composition.

(d) Number and position of flagella.

Q.2. When and where does reduction division take place in the life cycle of a liverwort, amoss, a fern, a gymnosperm and an angiosperm?

Ans. Reduction division take place at the end of sporophytic generation.

Liverwort and Moss – Haploid spores are produced as a result of the reduc- tion division of spore mother cells tak- ing place inside the capsule of sporo-phyte.

Fern-Sporophyte bears the sporan-gia. Reduction division takes place in these sporangia which produces many spores.

Gymnosperm-Sporophyte bears mi-crosporophylls and megasporophylls. Reduction division takes place in the microsporangia present on the micro-sporophylls (producing pollen grains) and on the megasporangia present on the megasporophylls (producing me-gaspores).

Angiosperm – Sporophyte bears flowers. The male sex organ in the flower is the stamen, while the female sex organ is the pistil. Reduction division takes place in the anthers of the sta-men (producing haploid pollen grains) and in the ovary of the pistil (produc-ing eggs).

Q.3. Name three groups of plants that bear archegonia. Briefly describe the life cycle of anyone of them.

Ans. Archegonium is present in the life cycles of bryophytes, pteridophytes, and gymnosperms.

Flow chart of Life cycle of Pteridophytes – Sporophyte (2n) – Sporophylls (2n) – Sporangia (2n) – Spore mother cells (2n) – Spores (n) – Prothallus/Gameto – phyte (n) – Archegonia and Antheridia – Female and Male gametes (n) – Zy – gote (2n) – Sporophyte (2n).

Q.4. Mention the ploidy of the following: protonemal cell of a moss; primary endosperm nucleus in dicot, leaf cell of a moss; prothallus cell of a fern; gemma cell in Marchantia;meristem cell of monocot, ovum of a liverwort, and zygote of a fern.

Ans. (a) Protonemal cell of a moss Haploid.

(b) Primary endosperm nucleus in a dicot – Triploid.

(c) Leaf cell of a moss – Haploid.

(d) Prothallus of a fern – Haploid.

(e) Gemma cell in Marchantia – Haploid.

(f) Meristem cell of a monocot – Diploid.

(g) Ovum of a liverwort – Haploid.

(h) Zygote of a fern – Diploid.

Q.5. Write a note on economic impor-tance of algae and gymnosperms.

Ans. Economic importance of algae:

(i) Algae are primary producer of food in marine or fresh water.

(ii) They are used as food eg – Porphyra Laminaria, Sargassum

(iii) Gelidium and Gracilaria are source of agar.

Economic importance of gymnosperms:

(i) They are sources of soft wood used in construction and packing.

(ii) Source of resins.

(iii) They are grown for ornamental pur-poses.

Q.6. Both gymnosperms and angio-sperms bear seeds, then why are they classified separately?

Ans. Gymnosperms and angiosperms are classified separately because gymno-sperms have naked seeds i.e. ovules lie exposed on open megasporophylls while angiosperms have development of seeds inside the fruits i.e. ovules are enclosed in ovary/fruit.

Q.7. What is heterospory? Briefly comment on its significance. Give two examples.

Ans. Heterospory is a phenomenon in which two kinds of spores [microspore and megaspore] are borne by the same plant. Development of heterospory is a requirement for seeds formation. It is seen in Pteridophytes like Selaginella, Salvinia, Marsilea, all gymnosperms and angiosperms)

Q.8. Explain briefly the following terms with suitable examples:

(i) Protonema.

Ans. Protonema – Mosses have branched filamentous juvenile stage called protonema. Meiospores germinate to form gametophyte [haploid] in Mosses through protonema [n].

(ii) Antheridium.

Ans. Antheridium – It is the multicellular and jacketed male sex organ present in bryophytes and Pteridophytes. Antheridium produces flagellate male gamete called sperm / antherozoids.

(iii) Archegonium.

Ans. Archegonium – It is the multicellular and jacketed female sex organ present in bryophytes, pteridophyte. Archegoni- um is flask shaped with a tubular neck and swollen venter. Venter encloses a sterile cell and a fertile egg or oosphere.

(iv) Diplontic.

Ans. Diplontic life cycle – It has Single So-matic phase or diploid sporophyte. It undergoes meiosis to give haploid gametes.

Gametes fuse to give diploid zygote.

Zygote gives rise to sporophyte.

Alteration of generations is absent. It is seen in Brown algae — Fucus, Sar-gassum.

It is seen in gymnosperms and angio- sperms. Both have independent dom-inant sporophyte phase and gameto-phyte phase is reduced & dependent.

(v) Sporophylls.

Ans. Sporophyll – Leaves bearing sporangia are called sporophylls In Pteridophytes and gymnosperms.

(vi) Isogamy.

Ans. Isogamy – Sexual reproduction in- volves isogamy i.e. gametes are of similar size e.g. Chlamydomonas (flagellated gametes) and Spirogyra (non flagellated gametes).

Q.9. Differentiate between the following:

(i) Red algae and brown algae.

Ans. Red algae and brown algae:

Red algae	Brown algae
1. Stored food: floride an starch	1. Mannitol or laminarin.
2. Photosynthetic pigments: chlorophylls a and d & phycoery-thrin.	2. Chlorophylls a and c & fucoxanthin.
3. Cell walls are composed of Cellulose, pectin, and phycocolloids.	3. Cell walls are composed of Cellulose and algin.
4. Flagella are absent.	4. Two flagella are present.

(ii) Liverworts and moss.

Ans. Liverworts and moss:

Liverworts:

(i) Thallus is dorsoventrally flat, dichotomously branched with unicellular rhizoids and multicellular scales.

(ii) Sporogonium of Marchantia has elaters for spore dispersal.

(iii) Eg Riccia, Marchantia.

Mosses:

(i) Foliose/leafy with radial symmetry, laterally branched with multicellular rhizoids.

(ii) Sporogonium has sterile columella and periostome teeth for spore dispersal.

(iii) It has branched filamentous juvenile stage called protonema.

(iv) E.g. Funaria, Sphagnum.

(iii) Homosporous and heterosporous pteridophyte.

Ans. Homosporous and heterosporous pteri-dophyte:

Spores may be homosporous (similar C spores) eg Pteris, Adiantum, Equise-tum or heterosporous (micro and mega spores) eg Selaginella, Salvinia, Mar-silea.

(iv) Syngamy and triple fusion.

Ans. Syngamy and triple fusion:

Syngamy: One male gamete fuses with oosphere to form diploid zygote (synga-my / generative fertilization) in angio-sperms.

Triple fusion: Second male gamete fus- es to diploid secondary nucleus to form triploid Primary Endosperm Nucleus / PEN (vegetative fertilization / triple fusion) in angiosperms.

Q.10. How would you distinguish monocots from dicots?

Ans. Dicotyledons-

(i) Two cotyledons in seeds.

(ii) Reticulate venation in leaves.

(iii) Stem has concentric open vascular bundles arranged in ring.

(iv) Pentamerous or tetramerous flowers.

(iv) Eg-Pea, Rose, Sunflower, Eucalyptus, Cotton.

Monocotyledons-

(i) One cotyledon in seeds.

(ii) Parallel venation in leaves.

(iii) Stem has scattered closed vascular bundles.

(iv) Trimerous flowers.

(v) Eg – Banana, Cereals, Palms, Lily, Grasses, Orchids.

Q.11. Match the following (column I with column II)

Column I	Column II
(a) Chlamydomonas	(i) Moss
(b) Cycas	(ii) Pteridophyte
(c)  Selaginella	(iii) Algae
(d) Sphagnum	(iv) Gymnosperm

Ans. 

Column I	Column II
(a) Chlamydomonas	(iii) Algae
(b) Cycas	(iv) Gymnosperm
(c)  Selaginella	(ii) Pteridophyte
(d) Sphagnum	(i) Moss

Q.12. Describe the important character-istics of gymnosperms.

Ans. Important characteristics of gymno-sperms:

(a) All gymnosperms are perennial and woody forming either bushes or trees.

Sequoia is the tallest and Zamia is smallest gymnosperm.

(b) Two types of sporophylls (microspo-rophyll and megasporophyll) are aggregated to form distinct cones or strobili – pollen cone (male cone) and seed cone (female cone).

(c) Microsporophyll has flat fertile prox-imal region and bent sterile region or apophysis.

Fertile region has pollen sacs which bears pollen grains.

Before pollination, pollen grains develop three cells: prothallial cell, generative cell, tube cell.

(d) Seeds do not occur inside fruits – na – ked seeds.

(e) Female gametophyte has archegonia.

(f) Male gametophyte produces only two male gamete or sperms.

(g) Pollination is direct because stigma is absent and pollen grains directly reach the ovules.

Pollination is done by wind i.e. anemophily.

(h) Male gametophyte forms a pollen tube for fertilization – siphonogamy.

(i) Seed has food laden tissue or endo-sperm. Endosperm represents fe-male gametophyte.

(j) Leaves are dimorphic:

(i) Foliage leaves – green, simple or compound.

(ii) Scaly leaves.

(k) Xylem has tracheids and xylem pa-renchyma only. Phloem is without companion cells and sieve tubes.

(l) Wood is monoxylic (parenchyma present) eg Cycas or pycnoxylic (pa-renchyma absent) eg Pinus.

(m) Development of embryo is meroblas-tic i.e. it develops only from a part of zygote.

(n) Gymnosperms have soft wood.

(o) Gymnosperms secret resin. Resin is distilled to get turpentine and rosin.

(p) Two important groups are Cycads (Cycas) and Conifers (Pinus).