NCERT Solutions For Class 11 Biology Plant Kingdom
NCERT Solutions Class 11 Biology Plant Kingdom
NCERT Solutions For Class 11 Biology Plant Kingdom is designed and prepared by the best teachers across India. All the important topics are covered in the exercises and each answer comes with a detailed explanation to help students understand concepts better. These NCERT solutions play a crucial role in your preparation for all exams conducted by the CBSE, including the JEE.
NCERT TEXTBOOK QUESTIONS SOLVED
1. What is the basis of classification of algae?Ans. Fritsch (1935), has classified algae considering phylogeny, affinities and inter-relationships of various forms. He classified algae mainly on the basis of the characters like structure of plant body, nature of the pigments, reserve food material, number and position of flagella, chemistry of cell wall and methods of reproduction etc. Algae is divided into 11 classes but among them 3 main classes are Chlorophyceae, Phaeophyceae and Rhodophyceae.
2. When and where does reduction division take place in the life cycle of a liverwort, a moss, a fern, a gymnosperm and an angiosperm?Ans. All of these plants show life cycle with one gametophytic (n) generation and one sporophytic (2n) generation. Reduction division or meiosis that produces haploid (n) cells from diploid cells (2n) is necessary in their life cycles to restore gametophyte generation after sporophytic generation. It occurs in different body structures according to the basic body design of these groups. Reduction division in a liverwort and moss takes place at the end of the sporophytic generation, where haploid spores are formed by reduction division of spore mother cell inside capsule. Spores germinate to produce dominant gametophytic generation. Reduction division in fern takes place at the end of the dominant sporophytic generation inside the sporangium from spore mother cell by reduction division. Spores may be of one type (homospory) or of two types (heterospory). Reduction division in gymnosperms takes place at the end of dominant sporophytic generation. Megaspore and microspores are produced by the reduction division of diploid megaspore mother cell and diploid microspore mother cell respectively, inside megasporangium and microsporangium. Reduction division in angiosperms takes place at the end of dominant sporophytic generation. The haploid pollen grain or microspore and the haploid egg cell are produced by the reduction division of diploid (microspore) mother cell and diploid megaspore mother cell respectively. Microsporic division occurs inside anther and megasporic division occurs inside gynoecium (ovary).
3. Name three groups of plants that bear archegonia. Briefly describe the life cycle of any one of them.Ans. The three groups of plants that bear archegonia are bryophytes, pteridophytes and gymnosperms.
Life cycle of a bryophyte is as follows : The main plant body of bryophyte is gametophytic (n), which is independent and may be thallose (no differentiation in root, stem, leaves) e.g., Riccia, or may be foliose (having leafy axis) e.g., Funaria. The dominant phase in the life cycle of Funaria is the gametophyte, which occurs in two stages, the protonema stage and the erect, leafy gametophytic plant.
The leafy gametophyte consists of an upright, slender axis (stem-like) that bears spirally arranged leaves and is attached to the substratum by multicellular, branched rhizoids. Vegetative reproduction takes place
by fragmentation; by the buds formed in secondary protonema etc. The sex organs, antheridia and archegonia are produced in dusters at the apices of the leafy shoots. Antheridia produces antherozoids and archegonia produces egg. Antherozoid (male gamete) and egg (female gamete) fuses and form zygote.Zygote develops into a sporophyte; which is differentiated into foot, seta and capsule and spores are produced in the capsule.
Spores on reaching a suitable substratum germinate to produce a filamentous juvenile stage, .called the primary protonema, which later produces secondary protonema that forms erect leafy plants.
Ans. Protonemal cell of a moss – haploid. Primary endosperm nucleus in dicot – triploid.
Leaf cell of a moss – haploid.
Prothallus cell of a fern – haploid.
Gemma cell in Marchantia – haploid. Meristem cell of monocot – diploid.
Ovum of a liverwort – haploid.
Zygote of a fern – diploid.
Ans. 'Gymnosperms and angiosperms both bear seeds but they are classified separately because gymnosperms are a group of plants in which the ovules are freely exposed on open megasporophylls, whereas in angiosperms the seeds or ovules are enclosed within ovary which later forms the fruit.
Ans. 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 first evolved in pteridophytes. Significance of heterospory
(i) Heterospory is associated with the sexual differentiation of gametophyte .a microspore develops into a male gametophyte whereas a megaspore develops into a female gametophyte.
(ii)In homosporous pteridophytes spores have to germinate on soil thus face more environmental problems. In heterosporous pteridophytes, spores germinate within the sporangium and the gametophytes are retained inside for variable periods of time. Hence, germinating gametophyte has better chances of survival. This lays the foundation of complete retention of gametophytes within sporophytes in angiosperms and gymnosperms.
(iii)Heterospory is the basis of development of seed habit in higher plants.
(i) Protonema (ii) Antheridium
(iii)Archegonium (iv) Diplontic (v) Sporophyll (vi) Isogamy
Ans. (i) Protonema : It is the first, usually branched, green and filamentous structure produced by a germinating moss or fern spore. The protonema of mosses bears buds that develop into the gametophyte plant. In fern the protonema becomes the prothallus.
(ii)Antheridium : The male sex organ of cryptogams (algae, fungi, bryophytes and
pteridophytes) is known as antheridium. It produces the male gametes or anthero- zoids. It may consist of a single cell or it may have a wall that is made up of one or several layers forming a sterile jacket around the developing gametes.
(iii)Archegonium : The multicellular flask shaped female sex organ of bryophytes, pteridophytes and many gymnosperms is known as archegonium. Its dialated base called the venter contains the female gamete or egg or oosphere. The cells of the narrow neck of archegonium liquify to allow the male gametes to swim towards the oosphere.
(iv)Diplontic : It is the kind of life cycle in which the diploid sporophyte is dominant and this diploid phase is photosynthetic. The gametophytic phase is represented either by gametes only, that are formed through meiosis or by a highly reduced few celled gametophyte. E.g., all seed-bearing plants (gymnosperms and angiosperms).
(v) Sporophyll : It is a type of leaf bearing sporangia. In ferns, the sporophylls are the normal foliage leaves, but in other plants the sporophylls are modified and arise in specialised structure such as the strobili of club-moss, gymnosperms and the flower of angiosperms. In most plants sporophylls are of two types – microsporophylls and megasporophylls.
(vi)Isogamy: It is a type of sexual reproduction where fusion takes place between two identical gametes. The gametes are similar in size and structure and they show equal motility during sexual reproduction, e.g., Spirogyra (algae).