Q: Assertion : Megaspore mother cell undergoes meiotic division.Reason : All four megaspres form female gametophyte.

\textbf{Correct option:} \textbf{Solution:} \bullet The mass of the cell nucellus has abundant reserve food materials,dense cytoplasm and prominent nucleus . These cells act as megaspore mother cells. \bullet The megaspore mother cell undergoes meiotic division to produce four megaspores,in most of the flowering plants there is one functional megaspore and three degenerates. \bullet The functional megaspore develops into embryo sac or female gametophyte ,this process of development from one megaspore is known as monosporic development. \bullet Assertion is true but Reason is false

Question 1

Assertion : Megaspore mother cell undergoes meiotic division.Reason : All four megaspres form female gametophyte.

Accepted Answer

extbf{Correct option:}   	extbf{Solution:} \bullet  The mass of the cell nucellus has abundant reserve food materials,dense cytoplasm and prominent nucleus . These cells act as megaspore mother cells. \bullet  The megaspore mother cell undergoes meiotic division to produce four megaspores,in most of the flowering plants there is one functional megaspore and three degenerates. \bullet  The functional megaspore develops into embryo sac or female gametophyte ,this process of development from one megaspore is known as monosporic development. \bullet  Assertion is true but Reason is false

Question 2

Question 3

Which of the following correctly represents the type of life cycle patterns from the options given?

Accepted Answer

In the diplontic life cycle, the diploid sporophyte is the dominant photosynthetic independent phase of the plant body. The haploid phase is represented by gametes only. In gametic meiosis, instead of immediately dividing meiotically to produce haploid cells, the zygote divides mitotically to produce a multicellular diploid individual. Cells from the diploid individuals then undergo meiosis to produce haploid cells or gametes. Haploid cells may divide again (by mitosis) to form more haploid cells, as in many yeasts, but the haploid phase is not the predominant life cycle phase. In most diplonts, mitosis occurs only in the diploid phase, i.e., gametes usually form quickly and fuse to produce diploid zygotes. The main plant body is the diploid (sporophyte 2n). Example  All seed-bearing plants, gymnosperms, and angiosperms.In the haplontic life cycle, the haploid phase of the cells is predominant. The zygotic meiosis produces haploid spores. These haplonts will then divide mitotically to produce more haplonts. These haplonts will give rise to male and female gametes. In haplontic life cycle, 2n state of nuclei is present only in the zygote and this state is very short-lived. The organism ends its diploid phase and produces several haploid cells. These cells divide mitotically to form either larger, multicellular individuals, or more haploid cells. Two opposite types of gametes (e.g., male and female) from these individuals or cells fuse to become a zygote. The main vegetative plant body is a haploid.  Example - fungi, green algae, and many protozoa.In the haplodiplontic cycle, both the diploid (2n) and haploid (1n) phases are multicellular. The 2n sporophyte produces sporocytes in a sporangium, each of which goes through meiosis to create four (4) spores. These spores are dispersed and germinate into gametophytes. Gametophytes mature and produce sex cells: male (e.g. sperm) and female (e.g. eggs) in gametangia. Sex cells fuse, during fertilization, to create a young sporophyte or zygote. This cycle is also called the diplo-haplontic life cycle or alternation of generations or sporic meiosis. Examples: All land plants, chytridiomycetes, red algae, some brown algae, and some green algae. Most land plants (except bryophytes) have a dominant sporophyte phase, with a reduced gametophyte. This can make land plants seem like they are diplontic, but they are not. Every land plant group has a multicellular gametophyte (although hidden), which makes them haplo-diplontic.

Question 4

Which one of the following is considered important in the development of seed habit?

Accepted Answer

Correct Option: BExplanation: Seed habit is the ability to form seeds.A. Dependent sporophyte is found in Bryophytes and it is dependent on the gametophyte for nutrition.B. Heterospory is the production of spores of two different sizes and two different development patterns. Small spores are called the male spores or microspores and the larger spores are called female spores or megaspores. Heterospory is an expression of sex determining process of the plants. It is the most important evolutionary development in the vascular plants because it ultimately leads to the seed development.C. Haplontic life cycle is a primitive type of life cycle which is characterized by zygotic meiosis and haploid adults.D. Free living gametophyte is the one that does not depend on sporophyte for its nutrition.Hence, heterospory leads to development of seed habit.So, the correct answer is 'Heterospory'.

Question 5

Consider the following four statements and find out which of them are wrong.
(A) The sporophyte in liverworts is more elaborate than that in mosses.
(B) Salvinia is heterosporous.
(C) The life-cycle of all seed-bearing plants is diplontic.
(D) In pinus, male and female cones are borne on different trees.

Accepted Answer

Liverwort sporophytes have a spore-containing capsule. This capsule is spherical to cylindrical in shape and is blackish when mature. The mature capsules split open to release the spores. Within the capsules of most species, there are elaters as well as spores. Elaters are microscopic, spiral-like structures that usually twist or untwist in response to changes in humidity and often help in spore dispersal. Moss spore capsules don't have elaters.  Also, the spore capsules in almost all moss species open by a definite method, rather than by splitting. Hence sporophyte is more developed in mosses rather than liverwort. The plant body of pinus is sporophyte and the plants are monoecious. The plant body is differentiated into roots, stems, and leaves. Pinus plant is sporophyte (2x), heterosporous (producing two types of spores - microspores and megaspores), monoecious (male and female cones are borne on the same plant), and autoecious (male and female cones are borne on different branches). So, options A and D are not correct.

Question 6

Bryophytes have a life cycle, with alternation of a haploid, sexual generation with a diploid, asexual generation. Unlike vascular plants, in bryophytes, the _______ is usually longer or of similar duration as the _______.

Accepted Answer

Bryophytes have a life cycle, with alternation of a haploid, sexual generation with a diploid, asexual generation. Unlike vascular plants, in bryophytes, the  \underline{gametophytic}  phase is usually longer or of similar duration as the  \underline{sporophytic}  phase.

Question 7

Which of the following remained unchanged for last many million years?

Accepted Answer

Ginkgo biloba, or maidenhair tree, has been described as a living fossil, because it is the sole survivor of an ancient group of trees older than the dinosaurs. The Ginkgo is an oddity in nature because it is a single species with no known living relatives; a living fossil that has been essentially unchanged for more than 200 million years. Ginkgo biloba has been used in Chinese traditional medicine for centuries. The leaves are used in herbal remedies for cognitive complaints, such as alzheimers disease, dementia and vertigo. The phytochemistry and bioactivity of it, have been the subject of extensive research.

Question 8

Which of the following statement is not a difference between monocots and dicots?

Accepted Answer

Monocot Dicot Seeds with a single cotyledon.Seeds with two cotyledons.Pollen with single furrow or pore. Pollen with three furrows or pores. Flower parts in multiples of three. Flower parts in multiples of four or five. Major leaf veins parallel. Major leaf veins reticulated. Stem vascular bundles scattered. Stem vascular bundles in a ring. Roots are adventitious. Roots develop from radicle. Secondary growth absent. Secondary growth often present.Thus, the correct answer is option C.

Question 9

Largest ovules and male gametes are found in:

Accepted Answer

Cycas is the plant that produces largest ovules and pollens. Since it is gymnosperm, largest ovules and male gametes are found in gymnosperms.Hence, option 'D' is correct.

Question 10

Give information about reproduction of gymnosperms?

Accepted Answer

In gymnosperms, sexual reproduction takes place by the formation of male and female cones. The cones are either borne on the same plant as in Pinus or two different plants as in Cycas. The male cone contains microsporophyll, each microsporophyll bears microsporangia. They are sac-like structures that produce pollen grains or microspores. Each microspore is a male gametophyte forming a male gamete. The female cone contains megasporophyll, each megasporophyll bears ovules, the ovules contain the female gametophyte that gives rise to the egg cell.In gymnosperms, pollination is by wind, i.e. Anemophily, the pollen grains are deposited in the pollen chamber of the ovule that contains archegonia.Archegonia contains egg. The fusion of male gamete and egg takes place in the archegonia through siphonogamy to form a diploid zygote. The diploid zygote then develops into an embryo.

Plant Kingdom