The VIDYANKER team has thoughtfully prepared the NCERT Solutions for Class 11 Biology Chapter 3, "Plant Kingdom" These solutions are designed to help you tackle the NCERT textbook questions with ease. We recommend going through the chapter's theory before diving into the solutions for a deeper understanding. Feel free to share these NCERT Solutions for Class 12 Biology with others—learning is always better when shared!
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 mainly classified algae 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 these plants exhibit a life cycle having one gametophytic (n) generation and one sporophytic (2n) generation. The process involving reduction division or meiosis is required in the life cycles of these plants so that a gametophytic generation can be renewed after the development of the sporophytic generation. It occurs in various body structures depending upon the basic body design of these groups. Haploid spores are produced by reduction division of spore mother cell inside capsule, which forms at the end of the sporophytic generation in a liverwort and moss. Dominant gametophytic generation is formed through spores germination. Reduction division takes place at the end of the dominant sporophytic generation inside the sporangium from spore mother cell by reduction division in fern. They can be of the same type (homospory) or of two different types (heterospory).
Ans. All these plants exhibit a life cycle having one gametophytic (n) generation and one sporophytic (2n) generation. The process involving reduction division or meiosis is required in the life cycles of these plants so that a gametophytic generation can be renewed after the development of the sporophytic generation. It occurs in various body structures depending upon the basic body design of these groups. Haploid spores are produced by reduction division of spore mother cell inside capsule, which forms at the end of the sporophytic generation in a liverwort and moss. Dominant gametophytic generation is formed through spores germination. Reduction division takes place at the end of the dominant sporophytic generation inside the sporangium from spore mother cell by reduction division in fern. They can be of the same type (homospory) or of two different types (heterospory).
The reduction division in gymnosperms takes place at the peak of the dominant sporophytic generation. The reduction division of the two diploid megaspore and microspore mother cell within megasporangium and microsporangium produce the megaspores and microspores, respectively. Reduction division in the angiosperms takes place at the culmination of dominant sporophytic generation. The haploid pollen grain or microspore and haploid egg cell are produced by the reduction division of a diploid (microspore) mother cell and diploid megaspore mother cell respectively. Microsporic division occurs inside anther and megasporic division occurs inside gynoecium or 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.
Ans. The three groups of plants that bear archegonia are: Bryophytes, Pteridophytes and Gymnosperms.
A life cycle of a bryophyte is as described below: The principal plant body of bryophyte is gametophytic, n that is independent and might be thallose (no differentiation occurs in root, stem, leaves) e.g., Riccia, or might be foliose containing leafy axis) e.g., Funaria. The dominant phase of the life cycle of Funaria is the gametophyte, that occur in two stages the protonema stage and the erect, leafy gametophytic plant.
The leafy gametophyte has erect, filiform axis (stem-like) bearing leaves spirally arranged. It has multicellular branched rhizoids attached to substratum. Vegetative reproduction occurs 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) fuse and form a zygote. Zygote develops into a sporophyte; which gets differentiated into foot, seta and capsule and spores are produced inside the capsule. On reaching an appropriate substratum spores germinate to give rise to a filamentous juvenile stage known as primary protonema that later gives rise to secondary protonema that forms erect leafy plants.
4.Mentiontheploidyofthefollowingrprotonemal cell of a moss; primary endosperm nucleus in dicot, leaf cell of a moss; prothallus cell of a fern; gemma cell in Marchantia; meristem cell of monocot, ovum of a liverwort, and zygote of a fern.
Ans.
- Protonemal cell of a moss - Haploid
- Primary endosperm nucleus in a dicot - Triploid
- Leaf cell of a moss - Haploid
- Prothallus of a fern - Haploid
- Gemma cell in Marchantia- Haploid
- Meristem cell of a monocot - Diploid
- Ovum of a liverwort - Haploid
- Zygote of a fern - Diploid
5.Write a note on economic importance of algae and gymnosperms.
Ans. Economic importance of algae: Algae are useful to man in a variety of ways. They perform half of the total carbon dioxide-fixation on earth by photosynthesis, acting as the primary producers in aquatic habitats. Many species of marine algae such as Porphyra, Sargassum, and Laminaria are edible. Chlorella and Spirulina are rich in proteins. Thus, they are used as food supplements. Agar is prepared in making jellies and ice-cream. This is extracted from Gelidium and Gracilaria. Carrageenin is an emulsifier used in chocolates, paints, and toothpastes. These are derived from the red algae. Many red algae like Corallina are used for treating worm infections.
Economic importance of gymnosperms : Gymnospermous plants are used as ornamentals on a large scale. Soft wood used in construction and packing are obtained from many conifers like pine, cedar, etc. Medicinal Uses: An anticancer drug Taxol is extracted from Taxus. Many species of Ephedra yields ephedrine, which is employed for the cure of asthma and bronchitis. The seeds of Pinus gerardiana are edible. Resins are commercially employed for the preparation of sealing waxes and water-proof paints. A type of turpentine resin is obtained from a variety of species of Pinus.
6.Both gymnosperms and angiosperms bear seeds, then why are they classified separately?
Ans. Gymnosperms and angiosperms both bear seeds but they are classified separately because the ovules of gymnosperms are freely exposed on open megasporophylls, whereas seeds or ovules of angiosperms get enclosed within ovary which eventually forms the fruit.
Ans. Gymnosperms and angiosperms both bear seeds but they are classified separately because the ovules of gymnosperms are freely exposed on open megasporophylls, whereas seeds or ovules of angiosperms get enclosed within ovary which eventually forms the fruit.
7.What is heterospory? Briefly comment on its significance. Give two examples.
Ans. Heterospory is a feature where a plant possesses two varieties of spores. The size of these spores varies and the smaller one is called microspore and the bigger ones are called megaspore. Microspore produces the male gametophytes whereas megaspores produce the female gametophyte. Therefore this process has been associated with the essential evolutionary process because it progresses towards the seed habit.
This ultimately led to seed development in gymnosperms and angiosperms.
8.Explain briefly thefollowing terms with suitable examples.
(i) Protonema (ii) Antheridium
(iii)Archegonium (iv) Diplontic (v) Sporophyll (vi) Isogamy
Ans. (i) Protonema : The first, normally branched, green and filamentous structure issued by a germinating moss or fern spore. The protonema of mosses carry buds that mature into the gametophyte plant. In fern the protonema becomes the prothallus .
(ii)Antheridium : The male sex organ of cryptogams (algae, fungi, bryophytes and
Antheridium is described as the part of a pteridophyte that produces male gametes or anthero- zoids. It can be unicellular or it may have a wall which is formed of one or several layers around the developing gametes, thereby giving a sterile jacket.
(iii)Archegonium The female sex organ of bryophytes, pteridophytes and many gymnosperms is called archegonium. It is flask-shaped, multicellular and its dialated base known as venter contains the female gamete or egg or oosphere. The cells of the narrow neck of archegonium liquify so that male gametes can swim towards the oosphere.
(iv)Diplontic : In this type of life cycle, the diploid sporophyte is the dominant one, and this diploid phase is photosynthetic. The gametophytic phase is represented either by gametes only, formed through meiosis or by a highly reduced few celled gametophyte. E.g., all seed-bearing plants (gymnosperms and angiosperms).
(v) Sporophyll : It is an ordinary type of leaf which bears sporangium. In ferns, the sporophylls are the usual foliage leaves. However, in other plants, the sporophylls are either highly modified or they arise from some specialized structure such as the strobili of club-moss, gymnosperms and the flower of angiosperms. In all other sporophylls, generally occur in two types, namely microsporophylls and megasporophylls.
(vi)Isogamy: It is a sexual type of reproduction where union takes place between the two gametes of equal size. The gametes are of equal size and shape and they exhibit equal motility in sexual reproduction, e.g., Spirogyra (algae).
9.Differentiate between the following:
(i) Red algae and brown algae
(ii)Homosporous and heterosporous pteridophytes
(iii)Liverworts and moss
(iv)Syngamy and triple fusion.
Ans.
(i) Red Algae vs. Brown Algae
| Characteristic | Red Algae (Rhodophyceae) | Brown Algae (Phaeophyceae) |
|---|---|---|
| Pigments | Contain chlorophyll a, d, and red pigment phycoerythrin | Contain chlorophyll a, c, and brown pigment fucoxanthin |
| Habitat | Mostly found in marine, deeper waters | Primarily marine, found in colder coastal waters |
| Stored Food | Floridean starch | Laminarin and mannitol |
| Thallus Structure | Mostly multicellular and filamentous | Multicellular with complex structures |
(ii) Homosporous vs. Heterosporous Pteridophytes
| Characteristic | Homosporous Pteridophytes | Heterosporous Pteridophytes |
|---|---|---|
| Spore Types | Produce only one type of spore | Produce two types of spores: microspores and megaspores |
| Gametophyte | Gametophyte is typically bisexual (produces both male and female gametes) | Gametophyte is unisexual (separate male and female) |
| Example | Lycopodium | Selaginella, Salvinia |
(iii) Liverworts vs. Moss
| Characteristic | Liverworts | Moss |
|---|---|---|
| Structure | Thalloid or leafy body with rhizoids | Leafy, branched structure with rhizoids |
| Rhizoids | Unicellular rhizoids | Multicellular rhizoids |
| Reproduction | Asexual reproduction by fragmentation and gemmae | Asexual reproduction by fragmentation; sporophyte produces spores |
| Example | Marchantia | Funaria, Polytrichum |
(iv) Syngamy vs. Triple Fusion
| Characteristic | Syngamy | Triple Fusion |
|---|---|---|
| Definition | Fusion of one male gamete with the egg cell to form a zygote (2n) | Fusion of a second male gamete with two polar nuclei to form the endosperm (3n) |
| Process | Results in the formation of the zygote | Results in the formation of the endosperm |
| Occurrence | Part of fertilization in both lower and higher plants | Unique to angiosperms as part of double fertilization |
10.How would you distinguish monocots from dicots?
Ans.
| Characteristic | Monocot | Dicot |
| Morphology | ||
| Roots | Fibrous roots | Tap roots |
| Venation | Generally parallel venation | Generally reticulate venation |
| Flowers | Trimerous flowers | Pentamerous flowers |
| Cotyledons in seeds | One | Two |
| Anatomy | ||
| No. of vascular bundles in stem | Numerous | Generally 2 – 6 |
| Cambium | Absent | Present |
| Leaves | Isobilateral | Dorsiventral |
11.Match the following (Column I with Column II).
Column I Column II
(a)Chlamydomonas (i)Moss
(b)Cycas (ii)Pteridophyte
(c) Selagmella (iii)Algae
(d) Sphagnum (iv)Gymnosperm
Ans. Chlamydomonas – Algae
Cycas – GymnospermSelayinella – Pteridophyte
Sphagnum – Moss
12.Describe the important characteristics of gymnosperms.
Ans. Gymnosperms are a group of seed-producing plants that include conifers, cycads, ginkgo, and gnetophytes. They have several distinctive characteristics:
Naked Seeds: The seeds of gymnosperms are not enclosed within a fruit; instead, they are exposed on scales or other structures, such as cones.
Vascular Tissues: Gymnosperms possess well-developed vascular tissues (xylem and phloem) for transporting water, nutrients, and food. In the xylem, they lack vessels (except in gnetophytes) and have only tracheids for water conduction.
Woody Plants: Most gymnosperms are woody trees or shrubs. They lack herbaceous (non-woody) forms, unlike angiosperms. The plant body consists of roots, stems, and leaves.
Long Life Cycle: Gymnosperms are typically long-lived with a dominant sporophyte phase. The gametophyte phase is reduced and dependent on the sporophyte.
Cones (Strobili): Reproductive structures are typically cones or strobili. Male cones produce pollen, while female cones produce ovules that develop into seeds upon fertilization.
Pollination by Wind: Gymnosperms are usually wind-pollinated, which allows the transfer of pollen grains from male cones to female cones.
Adaptations to Various Climates: Many gymnosperms have needle-like leaves with a thick cuticle, an adaptation to reduce water loss and survive in dry or cold climates (e.g., pine trees).
No Flowers or Fruits: Gymnosperms do not produce flowers or fruits, distinguishing them from angiosperms (flowering plants).
Example Species: Common examples include pine, fir, spruce (conifers), cycads, Ginkgo biloba, and ephedra (gnetophytes).
These features allow gymnosperms to thrive in diverse environments, especially those with limited water availability.
