Question 1

Cyanobacteria are classified under

Accepted Answer

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

Question 2

Fusion of two motile gametes which are dissimilar in size is termed as

Accepted Answer

Anisogamy Sexual reproduction is lower group of plants like algae exhibit great variation in 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 big oospore female with small male gamete. Isogamy is fusion of similar gametes. Zoogamy is sexual reproduction of animals.

Question 3

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. Identify the group to which it belongs to

Accepted Answer

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

Question 4

A prothallus is

Accepted Answer

Prothallus is usually a gametophytic stage in the life of a Pteridophyte. Spore germinates to form a prothalium, it is short lived inconspicuous heart shaped structure with a number of rhizoids developed beneath and sex organs, archegonium and antheridium.

Question 5

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

Accepted Answer

Gymnosperms include medium sized trees or tall trees and shrubs. Leaves of these plants are well adapted to with stand extremes of temperature, humidity and wind. Reproductive organs are usually in the form of cones or strobili. The male cone are made up of microsporophyll and 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, pteridophytes do not have microsporphylls and are not adapted to the above said conditions.

Question 6

The embryo sac of an angiosperm is made up of

Accepted Answer

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

Question 7

If the diploid number of a flowering plant is 36. What would be the chromosome number in its endosperm?

Accepted Answer

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

Question 8

Protonema is

Accepted Answer

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.

Question 9

The giant redwood tree (Sequoia sempervirens) is a/an

Accepted Answer

(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 is primitive group, no tree is included in this. Ferns are included in Pteridophytes. Angiosperms are different form gymnosperms in seed habit and adaptations.

Question 10

Food is stored as floridean starch in Rhodophyceae. Mannitol is the reserve food material of which group of algae?

Accepted Answer

The members of Phaeophyceae (brown algae) store mannitol as a reserve food material.

Question 11

Give an example of plants with (a) haplontic life cycle (b) diplontic life cycle (c) haplo diplontic life cycle

Accepted Answer

(a) Haplontic life cycle It is exhibited by Volvox, Spirogyra and Chlamydomonas. The dominant photosynthetic phase in these plants is gamotophytic phase which develops from a haploid spores after a mitotic cell division of zygote. (b) Diplontic life cycle is found in gymnosperms and angiosperms. The dominant phase is diploid sporophyte plant develop from zygote.(c) Haplodiplontic life cycle It is an intermediate conditions exhibited by bryophytes and pteridophytes. Here haploid gametophytic stage alternates with diploid sporophytic stage.

Question 12

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?

Accepted Answer

Roots are represented by root like structure called rhizoids in less developed lower plants (bryophytes and pteridophytes). The plant tissue system in these is not differentiated into true leaf, stem and roots as it is found in higher plants (gymnosperm and angiosperm).

Question 13

Most algal genera show haplontic life style. Name an alga which is (a) Haplo diplontic (b) Diplontic

Accepted Answer

Haplo diplontic type of life cycle is exhibited by Ectocarpus, Polysiphonia and Kelps. Here, diploid saprophytic phase alternate with haploid gametophytic phase. In Fucus, the main plant body is saprophytic and it shows diplontic type of life cycle.

Question 14

In bryophytes male and female sex organs are called ......... and ......... .

Accepted Answer

In bryophytes the male sex organ is antheridium and female sex organ is archegonium. The gametophyte (n) in bryophyte bears the primiture sex organs in the form of antheridium (male) which produce flagellate antherozoids which are male gamete and need thin film of water to swim and reach female reproductive organ (archegonium). Archegonia is female part which has single egg cell. Both these reproductive parts are born on male and female, anthridiophore and archegoniophores borne on haploid gametophyte.

Question 15

Why are bryophytes called the amphibians of the plant kingdom?

Accepted Answer

Bryophytes are amphibian of plant kingdom. It is a group of primitive plant having a dominant gametophytic plant body. These plants can live in soil but depend on water for movement of male gametes called antherozoids to reach archegonium (female organ having egg cell) so that fertilisation can take place.

Question 16

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.

Accepted Answer

The structures are as given

Question 17

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 plant kingdom?

Accepted Answer

Heterospory is production of spores of two different sizes and sexes by the sporophytes of land plants. Two types of spores are produced by heterosporic plants. Small spores are microspores which germinate into male gametophyte and large spores are macrospores which develop into female gametophyte. In evolution of plants pteridophytes are intermediate between bryophytes and gymnosperms. All bryophytes are homosporous and all gymnosperms are heterosporous. This condition is advanced as sexual dimorphism result in cross fertilisation. Primitive or earlier pteridophytes are homosporous later pteriodophytes are heterosporous e.g., Dryopteris, Pteris-homosporous Selaginella, Salvinia-heterosporous.

Question 18

How far does Selaginella one of the few living members of Lycopodiales (pteridophytes) fall short of seed habit?

Accepted Answer

Seed habit The differentiation of spores into microspores and megaspores and their dependence on the parent sporophyte for the nutrition, are the certain features in the life cycle of Selaginella, which have been considered as the essential pre-requite for formation of seed, the characteristic of spermatophyte.The evolution of heterospory and seed habits in Selaginella is evident by the following characters(i) Reduction to a single functional megaspore per sporangium.(ii) Retention and germination of megaspore within megasporangium(iii) Development of protective layer and nutritive tissue called tapetum is present.(iv) Development of embryosac with in the sporangium.(v) Modification of distal end of mega sporangium to capture pollen grain.(vi) Pollination and siphonogamy.(vii) Temporary suspension of growth of embryo (dormancy period).

Question 19

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?

Accepted Answer

Cycas as the relic of past Cycas is an evergreen plant which looks like a palm. It has unbranched stem and large compound leaf. It exhibit phylogenetic relationship with pteridophyte. Its evolutionary characters are(i) Slow growth.(ii) Shedding of seed when the embryo is still immature.(iii) Little secondary growth and manoxylic wood.(iv) Leaf like megasporophyllus.(v) Flagellate sperms even when pollen tube is present.(vi) Persistent leaf bases.(vii) Circinate ptysix.(viii) Arrangement of microsporangia is well defined archegonia.

Question 20

The heterosporous pteridophyte show certain characteristics, which are precursor to the seed habit in gymnosperms. Explain.

Accepted Answer

Heterospory, i.e., production of two types of spores smaller microspores and larger megaspore was first reported in Selaginella a pteridophyte. In Selaginella, the smaller microspores are destined to produce male gametophytes and the larger megaspores to female gametophyte. The male gametophyte produces male gametes, whereas the female gametophyte produces archegonia and also provides nourishment to the developing embryo.The phenomenon of heterospory, thus lead to the reduction of gametophyte, in situ germination of spores, retention of megagametophyte in the megasporangia and finally to the seed development. Thus, the heterospory in Selaginella forms the base for seed habit development in gymnosperms.

Chapter 3 : Plant Kingdom