NCERT Exemplar MCQs

Hint

(c) Monera Kingdom-Monera is one group which exclusively includes all forms of bacteria. All bacteria are prokaryotes and do not have a well-defined nucleus and other cell organelles.
The other options Protista, Algae, and Plantae include eukaryotic and unicellular or multicellular organisms.

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(c) Anisogamy Sexual reproduction is lower group of plants like algae that exhibit great variation in the mode of sexual and asexual reproduction. Some algae produce gametes which are not similar in shape, size, and structure, when they fuse, it is called Anisogamy. e.g., Chlamydomonas.
The other options are incorrect because oogamy is the fusion of a big oospore female with a small male gamete. Isogamy is a fusion of similar gametes. Zoogamy is the sexual reproduction of animals.

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(c) Phaeophyceae In the members of class Phaeophyceae, the plant body is usually attached to the substratum by a holdfast and has a stalk called a stipe and a leaf-like photosynthetic organ called a frond.

Note: Phaeophyceae Brownalgae are eukaryotic marine algae. The body consists of branched filamentous structures in lower forms (e.g. Ectocarpus) and parenchymatous structures in higher forms e.g. Sargassum. The plant body is often differentiated into holdfast, stipe, and lamina frond. The lamina may be simple or divided variously and is photosynthetic. 

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(d) Bryophyta is a group of plants that have a gametophytic haploid thalloid body. The motile male gamete is produced in a special male reproductive structure called antheridia.
These gametes need a thin film of water to move and reach the female reproductive organ called archegonia. Whereas, pteridophytes, gymnosperm, and monocots show division of labour and their body shows a higher level of organisation.

Note: A plant shows thallus level of organization. It shows rhizoids and is haploid. It needs water to complete its life cycle because the male gametes are motile. It is bryophytes.

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(c) Prothallus is usually a gametophytic stage in the life of a Pteridophyte. The spore germinates to form a prothallium, it is a short-lived inconspicuous heart-shaped structure with a number of rhizoids developed beneath, and sex organs, archegonium, and antheridium.

Note: The gametophyte in Pteridophytes is known as prothallus. It is a small, inconspicuous, and multicellular structure that is formed from the germination of haploid spores. It is independent and autotrophic. The prothallus is generally monoecious as it bears both male and female sex organs i.e. antheridia and archegonia respectively or it may be dioecious if male and female sex organs are present on different plants.

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(d) Gymnosperms include medium-sized trees or tall trees and shrubs. The leaves of these plants are well adapted to withstand extremes of temperature, humidity, and wind. Reproductive organs are usually in the form of cones or strobili.
The male cone is made up of microsporophyll and the female cones are made up of megasporophyll. The presence of sporophyll (micro and megasporophyll) shows the development of seed habit but seeds develop from naked ovule and are not covered.
Other examples are incorrect because monocots and dicots belong to angiosperms which have well-developed covered seeds. Whereas, whereas pteridophytes do not have microsporphylls and are not adapted to the above-said conditions.

Note: Plants of this group are diploid and well adapted to extreme conditions. They grow bearing sporophylls in a compact structure called cones. The group in reference is gymnosperms.

Hint

(b) Embryo sac in the angiosperm is a female gametophyte. It contains 2 synergids, 1 egg cell, 3 antipodal cells, and one secondary nucleus.

Note: The seven cells are; one egg cell, two synergids, three antipodal cells, and one secondary nucleus. The secondary nucleus contains two nuclei; while the other cells contain one nucleus each.

Hint

(c) Endosperm is a product of triple fusion. One male nuclei \((n=18)\) fuses with diploid secondary nucleus \((2 n=36)\), so it becomes triploid structure \((3 n=54)\). So, ploidy of endosperm is \((3 n)\) and chromosomes will be \(54 .\)

Note: When a flowering plant’s diploid number is 36, the chromosome number in its endosperm is \(\mathbf{5 4}\). In flowering plants, the number of chromosomes will be diploid, i.e. \(2 n\),\(2 n=36\) and \(n=36 / 2=18\) will be found in endosperm. Flowering plant endosperm has a triploid structure. The endosperm is formed by the fusion of 3 haploid nuclei i.e., two polar nuclei of the central cell which belong to the female gametophyte ad the one male gametophyte. As a result, endosperm has \(3 n=18 * 3=54\).

Hint

(a) The germination of haploid spores of mosses produced by sporophyte after reduction division these haploid spores when germinate, form the Protonema. This structure later develops into an independent gametophytic plant.

Note: The predominant stage of 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. So, the correct answer is ‘Haploid and is found in mosses’.

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(d) Sequoia sempervirens is a gymnospermic plant. It is a group of plants having thick, woody, branched stems. These plants also have some xeric adaptations which help them survive in adverse climatic conditions. The other examples are incorrect because pteridophytes are a primitive group, no tree is included in this. Ferns are included in Pteridophytes. Angiosperms are different from gymnosperms in seed habit and adaptations.

Note: The giant redwood tree is a gymnosperm. These are coniferous gymnosperms having naked seeds and they have their green needle-shaped leaves present all year round. They are gymnosperms because they do not possess flowers they are generally present in the mountain areas with the precipitation is more prominent. These are the tallest and the largest trees which belong to the coniferous group and sempervirens species.