NCRT Exemplar Class 11 Biology Solutions Plant Kingdom
Multiple Choice Questions
1.Cyanobacteria are classified under (a) Protista (b) Plantae
(c) Monera (d) Algae.
Soln.(c): Cyanobacteria are classified under Kingdom Monera as they are prokaryotes. They are generally photosynthetic in nature and contain pigments, chlorophyll a, and carotenoids, etc. Nostoc and Oscillatoria are examples of this category.
2.Fusion of two motile gametes which are dissimilar in size is termed as
(a) oogamy
(b) isogamy
(c) anisogamy
(d) zoogamy.
Soln.(c): Anisogamy is fusion of two motile gametes dissimilar in size. It is observed in some species of Chlamydomonas. Oogamy is also fusion of two dissimilar sized gametes in which female gamete is larger but non-motile.
3.Holdfast, stipe and frond constitute the plant body in case of
(a) Rhodophyceae
(b) Chlorophyceae
(c) Phaeophyceae
(d) all of these.
Soln.(c): Phaeophyceae (Brown algae) are eukaryotic marine algae. The body consists of branched filamentous structure in lower forms (e.g. Ectocarpus) and parenchymatous structure in higher forms (e.g. Sargassum). The plant body is often differentiated into holdfast, stipe and lamina (frond). Lamina may be simple or divided variously and is photosynthetic.
4.A plant shows thallus level of organisation. It shows rhizoids and is haploid. It needs water to complete its life cycle because the male gametes are motile. It may belong to
(a) pteridophytes (b) gymnosperms (c) monocots (d) bryophytes.
Soln.(d): Bry ophytes are non-vascular terrestrial plants of moist habitat in which a multicellular diploid sporophyte lives as a parasite on an independent multicellular haploid gametophyte that develops multi-cellular jacketed sex organs. True roots are absent, instead rhizoids occur, which may be unicellular or multicellular. An external layer of water is essential for the swimming of male gametes to the archegonia.
5.A prothallus is
(a) a structure in pteridophytes formed before the thallus develops
(b) a sporophytic free living structure formed in pteridophytes
(c) a gametophyte free living structure formed in pteridophytes
(d) a primitive structure formed after fertilisation in pteridophytes.
Soln.(c): Prothallus is a small, flattened multicellular structure that represents the independent gametophyte generation in pteridophytes, e.g., club mosses, horsetails and ferns. In some of the pteridophytes a single prothallus bears both male and female sex organs. In others there are separate male and female prothalli.
6.Plants of this group are diploid and well adapted to extreme conditions. They grow bearing sporophylls in compact structures called cones. The group in reference is
(a) monocots
(b) dicots
(c) pteridophytes
(d) gymnosperms.
Soln.(d): Gymnosperms are those seed plants in which the seeds remain exposed over the surface of the megasporophylls because the latter are not folded to form pistils. Flowers are absent. Two types of sporophylls, microsporophylls and megasporophylls are usually aggregated to form distinct cones or strobili, pollen cones (male cones) and seed cones (female cones) respectively.
7.The embryo sac of an angiosperm is made up of
(a) 8 cells
(b) 7 cells and 8 nuclei
(c) 8 nuclei
(d) 7 cells and 7 nuclei.
Soln.(b) : Female gametophyte or embryo sac of angiosperms develops upto 8-nucleate, 7-celled state prior to fertilisation. There is a three celled apparatus (one egg cell or oosphere and two synergids), three antipodal cells and two polar nuclei. The two polar nuclei fuse to form a diploid secondary nucleus.
8.If the diploid number of a flowering plant is 36, what would be the chromosome number in its endosperm?
(a) 36 (b) 18
(c) 54 (d) 72
Soln.(C) : Endosperm of flowering plants is a triploid structure. As 2n = 36, then n = 18, therefore 3n = 54.
9.Protonema is
(a) haploid and is found in mosses
(b) diploid and is found in liverworts
(c) diploid and is found in pteridophytes
(d) haploid and is found in pteridophytes.
Soln.(a): The predominant stage in the life cycle of a moss (bryophyte) is the gametophyte which consists of two stages. The first stage is the protonema stage, which develops directly from a spore. It is a creeping, green, branched
and frequently filamentous stage. The second stage is the leafy stage, which develops from the secondary protonema as a lateral bud. It consists of upright, slender axes bearing spirally arranged leaves attached to the soil through multicellular and branched rhizoids. This stage bears the sex organs.
10.The giant Redwood tree (Sequoia sempervirens) is a/an
(a) angiosperm (b) free fern
(c) pteridophyte (d) gymnosperm.
Soln.(d): Sequoia sempervirens is a gymno-sperm. It is the sole living species of genus Sequoia. Its common names include coast red wood, California red wood. It is an evergreen, long living monoecious tree.
Short Answer Type Questions
1.Food is stored as floridean starch in Rhodophyceae. Mannitol is the reserve food material of which group of algae?
Soln. Mannitol is the reserve food material found in Class Phaeophyceae of Algae.
2.Give an example of plants with
(a) Haplontic life cycle
(b) Diplontic life cycle
(c) Haplo-diplontic life cycle
Soln. (a) Many algae such as Volvox, Spirogyra Chlamydomonas, Ulothrix, Chara, etc., represent haplontic life cycle pattern.
(b) All seed bearing plants (gymnosperms and angiosperms) such as Cycas, Pinus, Hibiscus rosq sinensis, Mangifera indica represent diplontic life cycle pattern.
(c) Haplodiplontic life cycle pattern is shown by bryophytes and pteridophytes, e.g., Marchantia, Marsilea, Sphagnum, Funaria, Selaginella, Equisetum.
3.The plant body in higher plants is well differentiated and well developed. Roots are the organs used for the purpose of absorption. What is the equivalent of roots in the less developed lower plants?
Soln. In less developed lower plants such as bryophytes, root-like structures called rhizoids are present instead of roots for the purpose of absorption.
4.Most algal genera show haplontic life style. Name an alga which is
(a) Haplo-diplontic (b) Diplontic
Soln.
(a): Algae such as Ectocarpus and Polysiphonia represent haplo-diplontic life cycle’pattern.
(b) Algae such as Fucus and Sargassum represent diplontic life cycle-pattern.
5.In bryophytes male and female sex organs are
called and .
Soln. In bryophytes male and female sex organs are called antheridia and archegonia.
Short Answer Type Questions
1.Why are bryophytes called the amphibians of the Plant Kingdom?
Soln. Bryophytes are non vascular terrestrial plants of moist habitats in which a multicellular diploid sporophyte lives as a parasite on an independent, multicellular, haploid gametophyte that develops multicellular jacketed sex organs. Bryophytes are called as amphibians of Plant Kingdom because they require an external layer of water on the soil surface for their existence. The external layer of water is required for :
(i) Dehiscence of antheridia and archegonia
(ii)Swimming of male gametes to archegonia
(iii)Protection from transpiration and hence dessication
(iv)Protection from transpiration and hence dessication as the plant body is not covered by cuticle
(v)Supply of water to all parts through capillary in the absence of vascular tissues.
2.The male and female reproductive organs of several pteridophytes and gymnosperms are comparable to floral structures of angiosperms. Make an attempt to compare the various reproductive parts of pteridophytes and gymnosperms with reproductive structures of angiosperms.
Soln. Comparison of various reproductive parts of pteridophytes and gymnosperms with reproductive structure of angiosperms is as follows:
3.Heterospory i.e., formation of two types of spores – microspores and megaspores is a characteristic feature in the life cycle of a few members of pteridophytes and all spermatophytes. Do you think heterospory has some evolutionary significance in PlantKingdom?
Soln. The occurrence of two kinds of spores in the same plant is called as heterospory. Among them the smaller spore is called microspore and the larger spore is called megaspore. Heterospory has evolutionary
significance in Plant Kingdom that has been described as follows:
(i) It expresses sex determining capability of the plant. In homosporous species, differentiation of sex takes place at the gametophytic stage whereas in heterosporous species the sex of the gametophyte can be predicted at the spore stage.
(ii) Biological significance of heterospory is that in heterosporous forms development of gametophyte is endosporic and the nutrition for the developing gametophyte is derived from the sporophyte. Hence, the development of gametophyte is not affected by ecological factors.
(iii) An important characteristic of seed habit is that the megaspore is retained by the parent even after fertilisation, which ensures nutrition for the developing embryo.
4.How far does Selaginella one of the few living members of Lycopodiales (Pteridophytes) fall short of seed habit.
Soln.Selaginella is the most common genus of the heterosporous pteridophytes. Most of the species of Selaginella are heterosporous and they have only one functional megaspore mother cell which gives rise to four megaspores after meiosis. Only a single functional megaspore in a sporangium is present in Selaginella rupestris, S. monospora and S. erythropus like spermatophytes. The development of female gametophyte, fertilisation and embryo development takes place within the megasporangium. Thus, evolution of seed habit took place in such species of Selaginella. However, the seeds developed in these species cannot be called true seeds. They fall short of seed habit due to:
(i)Absence of integument like covering around the megasporangium.
(ii)Occurrence of thick wall around the functional megaspore and absence of nucellus like tissue to provide nourish-ment to female gametophyte.
(iii)Absence of resting stage after embryo development.
(iv)Development of embryo accompanied with the development of shoot and rhizophore.
(v)Megasporangium containing the embryo is never shed as seed.
5.Each plant or group of plants has some phylogenetic significance in relation to evolution: Cycas, one of the few living members of gymnosperms is called as the ‘relic of past’. Can you establish a phylogenetic relationship of Cycas with any other group of plants that justifies the above statement?
Soln.Cycas is one of the few living members of gymnosperms and is called as the ‘relic of past’. Cycas has phylogenetic relationship with pteridophytes which justifies the above statement. These are discussed as follows:
(i)Stem when young is underground and subterranean.
(ii)Leaf base scars are like the tree ferns.
(iii)Young leaves exhibit circinate vernation.
(iv)Sporophylls are leaf like structure.
(v)Microsporophylls are aggregated to form male strobilus : Microsporangia are aggregated in definite groups known as sori on the lower or adaxial surface of the microsporophylls.
(vi)Sperms are multiciliated and motile structures.
(vii)Megasporophylls are not organised into cones instead they occur in close spirals in acropetal succession around the stem apex of the female plant.
6.The heterosporous pteridophytes show certain characteristics, which are precursor to the seed habit in gymnosperms. Explain.
Soln. The heterosporous pteridophytes show certain characteristics which are precursor to the seed habit in gymnosperms. These are discussed as follows:
(i) Formation of two types of spores, microspores and megaspores and hence two types of gametophytes, male and female.
(ii)Gametophytes are nutritionally dependent on parent sporophyte.
(iii)Gametophytes show precocious development.
(iv)In some species, a single megaspore mother cell is functional and gives rise to four megaspores. Out of these, one functional megaspore develops into a megasporangium, e.g., S. monospora.
(v)In some species, the megaspore is not shed but develops completely inside partially opened megasporangia, e.g., S. apus, S. rupestris. Microspores reach there and form male gametophyte. Fertilisation and development of embryo also occur there. However, seed formation does not occur.
7.Comment on the life cycle and nature of a fern prothallus.
Soln. In fern the diploid sporophyte is represented by a dominant, independent, photosynthetic, vascular plant body. It alternates with multicellular, saprophytic/ autotropic, independent but short-lived haploid gametophyte. Such a pattern is known as haplo-diplontic life cycle. Prothallus in fem is green thalloid, nonvascular, free living, inconspicuous,small,multicellular,independent gametophyte which is monoecious, i.e., bears both the types of sex organs, male antheridia and female archegonia.
8.How are the male and female gametophytes of pteridophytes and gymnosperms different from each other?
Soln. Male and female gametophytes of pteridophytes and gymnosperms are different from each other, in the following manner.
A.Differences between pteridophytes and gymnosperms with respect to male gameto-phyte are as follows:
(i)In pteridophytes, male gametophytes may not be present whereas in gymnosperms a distinct male gemetophyte is always present.
(ii)Pteridophytes contain an antheridium whereas in gymnosperms antheridium is not formed.
(iii)Male gametes in pteridophytes are flagellate whereas in gymnosperms male gametes may or may not be flagellated.
(iv)In pteridophytes, male gametes reach the female gamete by swimming in a thin film of water whereas in gymnosperms, male gametes reach the female gamete through a pollen tube, water is not required.
B.Differences between pteridophytes and gymnosperms with respect to female gametophyte are as follows:
(i)In pteridophytes, a distinct female gametophyte may or may not be present whereas in gymnosperms, a distinct female gametophyte is always present.
(ii)In pteridophytes, female gametophyte is largely independent whereas in gymnosperms, female gametophyte does not leave the parent plant.
(iii)In pteridophytes, female gametophyte is not enclosed in an ovule whereas in gymnosperms, female gametophyte is enclosed inside an ovule.
9.In which plant will you look for mycorrhiza and corolloid roots? Also explain what these terms mean.
Soln.Coralloid roots are peculiar feature of Cycas plant. These are specialised apogeotropic roots which grow on surface of soil. They are irregular, dichotomously branched coral like roots which do not possess root hairs and root caps. Coralloid roots have a symbiotic association with blue green algae like Nostoc
and Anabaena species. The cortex of these roots possess specific algal zone where colonies
• of these blue-green algae are present. The coralloid roots possess lenticels which help in respiration.
Mycorrhiza is mutually beneficial or symbiotic association of a fungus with the root of higher plant. Mycorrhizal roots often show a wooly covering of fungal hyphae. The shape is different from normal roots. Root cap and root hairs are absent. Mycorrhizal association are present in plants like Pinus, Cedrus, Abies, and Picea.
Long Answer type Questions
1.Gametophyte is a dominant phase in the life cycle of a bryophyte. Explain.
Soln. Bryophytes are a group of the simplest and primitive plants belonging to embryophyta gametophytic and sporophytic phases are present in the life cycle of bryophytes and both these phases are morphologically distinct (heteromorphic). Gametophytic phase in bryophytes is more conspicuous, long lived, independent, green and freely branched whereas, the sporophytic phase is short lived and dependent upon the gametophyte. The main plant body of the bryophyte is haploid and bears sex organs i.e., antheridium and archegonium.
Antheridium produces a number of flagellate male gametes called sperms or antherozoids and archegonium is flask shaped with tubular neck and swollen venter. The gametophytic plant body of bryophytes is thalloid in liverworts whereas foliose in mosses. In liverworts, the thallus is differentiated into a dorsal photosynthetic and ventral storage region. Sex organs antheridia and archegonia are either distributed on the dorsal surface of the thallus or are on distinct receptacles. In mosses, the gametophyte has two growth stages (i) Protonema stage- It is the juvenile stage represented by prostrate, creeping, green and branched filamentous structure; it develops from the spore and is only a transitory vegetative stage and (ii) leafy stage or gametophore – an erect cylindrical shoot with persistent leaves and sex organs.
2.With the help of a schematic diagram describe the haplo-diplontic life cycle pattern of a plant group.
Soln. Haplo-diplontic life cycle pattern, involves sequential recurrence of two well developed somatic phases, gametophytic phase and sporophytic phase.
The sporophyte possesses diploid chromo-some number (2n). Meiosis takes place in it at the time of formation of meiospores. The haploid meiospores germinate to produce haploid gametophytes. The gametophytes produce gametes. The fusion product of gametes is a diploid zygote which develops into the sporophytic thallus of the progeny. There is a clear alternation of generations between a haploid gamete producing gametophyte and a diploid spore producing sporophyte.
In bryophytes, a dominant, independent, photosynthetic, thalloid or erect phase is represented by a haploid gametophyte and it alternates with the short-lived multioelluler sporophyte totally or partially dependent on the gametophyte for its anchorage and nutrition.
In pteridophytes, the diploid sporophyte is represented by a dominant, independent, photosynthetic, vascular plant body. It alternates with multicellular, usually autotrophic, independent but short-lived haploid gametophyte.
While most algal genera are haplontic, some of them such as Ectocarpus, Polysiphonia, kelps are haplo-diplontic.
3.Lichen is usually cited as an example of ‘symbiosis’ in plants where an algal and a fungal species live together for their mutual benefit. Which of the following will happen if algal and fungal partners are separated from each other?
(a).Both will survive and grow normally and independent from each other.
(b).Both will die
(c).Algal component will survive while the fungal component will die.
(d).Fungal component will survive while algal partner will die.
Based on your answer how do you justify this association as symbiosis.
Soln.(a) Lichens are small group of plants which represent symbotic association between fungi and algae. The algal component is known as phycobiont and the fungal component is known as mycobiont. Lichens have a composite thallus of a specific structure which neither resembles algae nor fungi. The algal components of lichens forms carbohydrates by photosynthesis whereas the fungal component is responsible for absorption and retention of water. Lichens cite good example of mutualism, where algae and fungi can survive in adverse conditions, viz high temperature and dry conditions for long time. Both fungal and algal species found in lichens are capable of living independently, although habitat requirements may be greatly different from those of the lichen.
In nature, algal and fungal components of a lichen remain together sharing an obligatory relationship. Algal and fungal partners can be separated only under laboratory conditions. In this case, both will survive and grow normally if provided with suitable growth conditions. However, on a barren rock or dry environment, algal and fungal Components of lichen cannot grow independently, if separated. Therefore they get mutually associated to form lichens for survival and perpetuation in such unfavourable conditions. ,
4.Explain why sexual reproduction in angiosperms is said to take place through double fertilisation and triple fusion. Also draw a labelled diagram of embryo sac to explain the phenomena.
Soln.In sexual reproduction of angiosperms, one male gamete fuses with oosphere or egg cell to form zygote. It is called generative fertilisation or syngamy. The second male gamete fuses with diploid, secondary nucleus to form triploid primary endosperm nucleus (PEN). It represents vegetative fertilisation on triple fusion. Since two types of fusions, syngamy and triple fusion take place in an embryo sac of angiosperms therefore, this phenomenon is termed as double fertilisation. Thus, in angiosperms sexual reproduction is said to take place through double fertilisation.
5.Draw labelled diagrams of
(a) Female and male thallus of a liverwort.
(b) Gametophyte and sporophyte of Funaria.
(c) Alternation of generation in Angiosperm.
Soln.(a): Labelled diagrams of female and male thallus of liverwort are as follow
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