RBSE Solutions for Class 11 Biology Chapter 3 Plant Kingdom

Rajasthan Board RBSE Solutions for Class 11 Biology Chapter 3 Plant Kingdom Textbook Exercise Questions and Answers.

RBSE Class 11 Biology Solutions Chapter 3 Plant Kingdom

RBSE Class 11 Biology Plant Kingdom Textbook Questions and Answers

Question 1. 
What is the basis of classification of algae?
Answer:

• Major photo synthetic pigment present.
• Form of stored food.
• Cell wall composition.
• Number of flagella and position of insertion.

Question 2. 
When and where does reduction division takes place in the life cycle of a liverwort, a moss, a fern, a gymnosperm and an angiosperm?
Answer:
1. Liverworts : In liverworts, main plant body is haploid (gametophytic). It bears the male and female sex organs which produce gametes. These garnets fuse to form zygote. The zygote develops into a sporophyte (2x). Spore mother cells of sporophyte produce haploid spores by meiosis.

2. Moss : In mosses like funaria, meiosis takes place in spore mother cells of spore sacs in the capsule of sporogonium.

3. Fern : Fern plants like Dryopteris bear fertile leaves called sporophylls on which sporangia are borne. Meiosis takes place in spore mother cell of sporangium to form haploid spores, which on germination give rise to prothalli on which gametes are borne.

4. Gymnosperm : In gymnosperms like Pinus, meiosis takes place in microsporangia present on microsporophyll. Meiosis occurs in microspore mother cells to form haploid pollen grains which give-rise to the male gametophyte.

5. Angiosperm : Pollen grains are formed in microspore mother cells of pollen sacs in the anther of stamen. Pollengrain lead to the formation of the male gametophyte. Ovules are borne inside the ovary. In the nucellus of the ovule, the megaspore mother cell is present which undergoes meiosis to form haploid megaspores. The megaspore forms the female gametophyte.

 Question 3. 
Name three groups of plants that bear archegonia. Briefly describe the life cycle of any one of them.
Answer:
Bryophytes, pteridophytes and gymnosperms bear distinct archegonia.
Life cycle of Fern (Dryopteris)

• The leaflets of Dryopteris bear sporangia and are known as sporophylls.
• The sporangium bears a large number of homosporous spores. The aggregate is called a sorus.
• Sori are green in the beginning but turn brown at maturity.
• Each sporangium consists of a stalk and capsule.
• The spores are minute, dark brown, uninucleated and have stored food inside them.
• The prothallus is green and heart shaped. On its under surface, male sex organs (antheridia) and female sex organs (called archegonia) are borne.
• The antheridium is small and spherical or oval body and produces antherozoids.
• Archegonium is a small flask-shaped structure and contains an egg and a venter canal cell.
• Antherozoids swim in water by cilia. The venter canal cell and neck cell disintegrate in the archegonium to produce mucilage and malic acid.
• Many sperms pass down into the venter, and one of them fuses with the egg to form a zygote.
• The zygote develops into an embryo which in turn develops into a new sporophyte.

Question 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.
Answer:

Cell	Ploidy
1. Protonemal cell of moss.	Haploid
2. Primary endosperm nucleus.	Triploid
3. Leaf cell of moss.	Haploid
4. Prothallus of fern.	Haploid
5. Gemma cells in Marchantia.	Haploid
6. Meristem cell of monocot.	Diploid
7. Ovum of liverwort.	Haploid
8. Zygote of fern.	Diploid

Question 5. 
Write a note on economic importance of algae and gymnosperms.
Answer:
Economic Importance of Algae :

• At least half of the total carbon dioxide fixation on the earth is carried out by algae through photosynthesis.
• They are primary producers of energy rich compounds which form the basis of the food cycles of all aquatic animals.
• Certain marine brown and red algae produce large amounts of hydrocolloids (water-holding substances), e.g., algin (brown algae) and carrageen (red algae), which are used commercially.
• Agar one of the commercial product obtained from Gelidium and Gracilaria is used to grow microbes and in preparations of ice creams and jellies.
• Chlorella and Spirulina are unicellular algae which are rich in proteins and are used as food supplements even by space travellers.

Economic importance of Gymnosperms

• Gymnospermous plants are widely used as ornamentals. Conifers are often featured, in formal gardens and are used for bonsai.
• Fibres of conifers make up paper pulp and may occasionally be used for creating artificial silk or other textiles.
• Turpentine and resin are derived from conifer resins. A hardened form of resin from a kauri (Agathis australis), called copal, is used in the manufacture of paints and varnisnes.
• Some useful oils are derived from conifers such as juniperns, pines, hemlock, fir, spruces and arborvitae. These oils serve as air freshners, disinfectants and scents in soaps and cosmetics.
• The seeds of some gymnosperms serve as food sources. Pine seeds may be eaten plain or used as a garnish on bakery products.

Question 6. 
Both gymnosperms and angiosperms bear seeds, then why are they classified separately. 
Answer:
Gymnosperms and angiosperms are classified separately because of the following reasons :

• The ovules of gymnosperms are naked, however in angiosperms, they are enclosed inside the ovary.
• In gymnosperms, the wood is non porous, i.e., the vessels are absent. In angiosperm, the wood is porous, i.e., the vessels are present.
• In gymnosperms, the endosperm is haploid and is formed before fertilisation, double fertilisation is absent. In angiosperms, the endosperm is triploid and formed after double fertilisation.

Question 7. 
What is heterospory? Briefly comment on its significance. Give two examples.
Answer:
Certain pteridophytes produce two kinds of spores in same plant. This phenomenon is called heterospory. Significance

1. Heterospory has led to the development of seeds in gymnosperms and angiosperms.
2. It has helped in the differentiation of male and female gametophytes. Example : Selaginella, Salvinia.

Question 8. 
Explain briefly the following terms with suitable examples :
(i) Protonema
(ii) Antheridium
(iii) Archegonium
(iv) Diplontic
(v) Sporophyll
(vi) Isogamy.
Answer:
(i) Protonema : A protonema is a thread like chain of cells which forms the haploid phase of bryophyte life cycle. When a moss or liverwort first grows from the spore, it grows as a protonema which develops into a leafy gametophore. Example : Some mosses and all liverworts.

(ii) Antheridium : An antheridium is a haploid structure which produce male gametes. It is present in bryophytes and pteridophytes, many algae and some fungi (e.g., ascomycetes.and water moulds) also have antheridia during their reproductive stage.

(iii) Archegonium : It is a multicellular jacketed, flask shaped female sex organ in bryophytes, pteridophytes and gymnosperms. It has a neck and swollen venter and produces a single female gamete called egg or ovum.

(iv) Diplontic : It is a type of life cycle in which the dominant free living phase is diploid (2n). It produces haploid gametes. Examples : Fucus, Sargassum.

(v) Sporophyll : Sporophyll is a leaf which bears sporangia. Sporophyll may be microsporophyll or megasporophyll. Sporophylls aggregate to form cones or strobili. Example : Pinus.

(vi) Isogamy : Isogamy refers to a form of sexual reproduction involving gametes of similar morphology and function. Examples : Ulothrix, Ectocarpus. 

Question 9.
Differentiate between the following :
(i) Red algae and brown algae.
(ii) Liverworts and moss.
(iii) Homosporous and heterosporous pteridophyte.
(iv) Syngamy and triple fusion.
Answer:
(i) Red algae and brown algae

Red Algae	Brown Algae
(i) Chlorophyll ‘a’ and ‘d’ are present.	Chlorophyll ‘a’ and ‘c’ are present.
(ii) Phycobilins are present.	Phycobilins are absent.
(iii) Reserve food material is jfloridean starch.	Reserve food material is laminarin.
(iv) Motile and flagellated bodies are absent.	Motile and flagellated bodies are present.

(ii) Liverworts and moss

Liverworts	Moss
(i) In liverwots, there is no protonema stage.	In moss, the life cycle begins with a protonema stage.
(ii) The gametophytic plant body is dorsiventral, leaf like and	The gametophytic plant body of moss is differentiated into

(iii) Homosporous and Heterosporous pteridophytes :
Homosporous pteriodphytes possess only one type of spores, whereas heterosporous pteridophytes possess two morphological distinct types of spores in separate sporangia.

(iv) Syngamy and Triple fusion : Syngamy is the fusion of male gamete with the egg cell, while the fusion of another male gamete with two polar nuclei is called triple fusion.

Question 10. 
How would you distinguish monocots from dicots?
Answer:

Monocots	Dicots
(i) Primary root system is short lived and is replaced by adventitious roots.	Primary root system is long lived. Adventitious roots also occur in some cases.
(ii) Vascular bundles are scattered.	Vascular bundles are arranged in a ring.
(iii) Vascular cambium is absent.	Vascular cambium is present.
(iv) They show parallel venation pattern.	They show reticulate venation pattern.
(v) They have trimerous flowers.	They have tetramerous or pentamerous flowers.
(vi) They have a single cotyledon.	They have two cotyledons.

Question 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

Answer:

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

Question 12. 
Describe the important characteristics of gymnosperms.
Answer:
Introduction : Gymnosperms are primitive seed producing plants of spermatophytes (phanerogams). They are “naked seeded plants”. The term is derived from two greek words “gymnos” = naked and sperma = seeds. They are characterised by naked ovules (i.e., the ovule without the ovary). The ovules of Gymnosperms are borne directly on the surface of the megasporophyls. Unlike Angiosperms, in Gymnosperms the seeds are not enclosed in the fruit. Thus the Gymnosperms are also known as “phanerogams without ovary”.

Occurence : Gymnosperms are a small ancient group of seed plants consisting of 83 genera and 1080 species. They occur in temperate and tropical regions. Gymnosperms were originated in the paleozoic Era (541-252 million years ago). They were the dominant plant of Jurrasic and cretaceous periods of the mesozoic era. Many primitive Gymnosperms were extinct. Examples of extinct Gymnosperms : Cycadofilicales, Bennettitales, cordaitales.
Examples of Present day Gymnosperms : Cycas, Pinus, Gnetum, Zamia, Ephedra, etc.

Morphology : The plant body is sporophytic (diploid) and differentiated into roots, stem and leaves. Present day Gymnosperms are usually evergreen trees or shrubs. They usually show xerophytic characters. The roots show symbiotic association with fungi or cyanobacteria. Fungi forms mycorrhizal association with the roots of Pinus. The mycorrhiza helps in the absorption of minerals. Algae (nostoc) inhabited in the coralloid roots of Cycas help in nitrogen fixation.

The stem is usually erect, branched and woody. Stem is usually unbranched in cycas and it is underground in Zamia. Presence of permanent leaf scar is a characteristic-feature of Gymnosperms. Leaves are usually dimorphic (two types of leaves in the same plant). They are foliage leaves and scale leaves. The foliage leaves are green, simple or needle-shaped or pinnately compound. Scale leaves are minute and deciduous. Cycas show circinate vernation (young leaves curved inward). Presence of circinate vernation in Cycas is a strong evidence for the pteridophytic origin of Gymnosperms. Cycas acts as the connecting link between pteridophytes and Gymnosperms.

Anatomy : The leaves of Gymnosperms have very thick cuticle. Mesophyll is differentiated into palisade and spongy tissues. Mesophyll is undifferentiated in pinus. Leaves do not have lateral veins. Lateral translocation of nutrients takes place through transfusion tissue. Stomata usually sunken type (to reduce the transpiration). Gymnosperms possess well developed vascular system. Vascular bundles are collateral and open. The vascular system consists of xylem and phloem.

Xylem : Xylem consists of tracheids and parenchyma. Vessels are absent in the xylem. Vessels present in the xylem of Gnetum. Presence of vessels in the wood of Gnetum is a strong evidence for the gymnospermic origin of Angiosperms. Gnetum is a connecting link between Gymnosperms and Angiosperms.

Phloem : Phloem consists of sieve tubes and phloem parenchyma. Companion cells are absent in Gymnosperms.
Stem show secondary growth. The wood may be manoxyclic (Cycas) or pycnoxylic (Pinus). Tanniniferous cells present in the cortex. Roots are diarch (two vascular bundles) to polyarch (many vascular bundles).