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NCERT Solutions for Class 11 Biology Chapter 3 - Plant Kingdom

iacst-2022

Chapter 3 "Plant Kingdom" is a continuation of the previous chapter in detail. Previously, we had learned about the wide classification of the living organisms in the form of Five Kingdoms Classification, namely Monera, Fungi, Protista, Plantae, and Animalia, which was put forward by Whittaker (1969).

In this chapter, the students will explore in-depth the further classification in the plant kingdom or the 'Kingdom Plantae.' The meaning and concepts on Algae, Pteridophytes, Angiosperms, Bryophytes, Gymnosperms, Alternation of Generations, and Plant Life Cycles are few other topics discussed here. The topics introduced under the chapter Plant Kingdom are as follows:

  • Algae
  • Bryophytes
  • Pteridophytes
  • Gymnosperms
  • Angiosperms
  • Concepts of Life Cycles of Plant and Changes of Generations

All the species named above are a part of the plant kingdom, and each of them has been explained extensively under chapter 3, providing information about their life cycle, habitat, etc. The proper meaning of algae and how it is classified into different types have been explained generously. The concept of reductional division has also been discussed, explaining its involvement and importance in the life cycle of moss, liverwort, angiosperms, ferns, and gymnosperms.

The above sub-topics also throw light on the significance of the different uses of algae and gymnosperms for the survival of humanity. The three groups of plants that bear archegonia have been talked about, and they are Bryophytes, Gymnosperms, and Pteridophytes. Descriptions on a series of cells, different types of cell divisions, heterospory, and its importance have also been given under this chapter.

 

Q1. What is the basis of classification of algae?

Answer:

Algae are chlorophyll-containing thallus-bearing plants characterised by the absence of embryo stage. A variety of algae are found in a variety of habitats. The various types of algae are classified on the basis of their pigments, flagellation and the reserve food material. Based on these criteria, algae are of three types i.e. red algae, brown algae and green algae.

 

 

Feature

 

Chlorophyceae

 

Phaeophyceae

 

Rhodophyceae

 

Pigment

 

Chlorophyll a and b

 

Chlorophyll a, c and fucoxanthin

 

Chlorophyll a, b and phycoerythrin

 

Reserve food material

 

Starch

 

Mannitol and laminarin

 

Floridean starch

 

Cell wall composition

 

Cellulose

 

Cellulose and algin

 

Cellulose and pectin

 

Flagella

 

2-8, equal and apical

 

2, unequal and lateral

 

Absent



 

Q2. When and where does reduction division take place in the life cycle of a liverwort, a moss, a fern, a gymnosperm and an angiosperm?

Answer:

In the life cycle of a liverwort reduction division takes place in the capsule for the formation of haploid spores that will grow into gametophytic thallus after germination. In mosses, the gametes fertilise and a zygote is formed. The zygote develops into the sporophyte. In the capsule of the sporophyte, reduction division takes place and haploid spores are formed which on germination give rise to gametophytic thallus. In ferns, reduction division takes place in the sporangia present on leaves for the production of spores. Gymnosperms, which have sporophytic plant bodies show reduction division in their microsporangia and megasporangia for the formation of microspores and megaspores. In the case of angiosperms, the main plant body is diploid and reduction division occurs for the formation of gametes. Therefore, in the life cycle of an angiosperm, reduction division takes place in the anther and ovary at the time of microspore and megaspore formation respectively.

 

Q4. Mention the ploidy of the following: protonemal cell of a moss; primary endosperm nucleus in dicot, leaf cell of a moss; prothallus cell of a ferm; gemma cell in Marchantia; meristem cell of monocot, ovum of a liverwort, and zygote of a fern.

Answer:

 

Tissue

 

Ploidy

 

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


 

Q5. Write a note on the economic importance of algae and gymnosperms.

Answer:

Economic importance of algae

  1. Green algae such as Ulva, Caulerpa, Enteromorpha, Chlorella etc are used as food rich in lipid, protein, vitamins, minerals etc.
  2.  Chlorella and Caulerpa are used to obtain antibiotics also.
  3. A number of green algae such as Chlamydomonas, Chlorella, Scenedesmus etc are used in sewage oxidation tanks.

Economic importance of Gymnosperms

  1. The seeds of Pinus gerardiana are roasted and eaten.
  2. The softwood of gymnosperms is used in the construction of furniture, plywood, packing cases, match sticks, railway sleepers etc.
  3.  The wood from Picea, Pinus, Larix and Abies is used in the manufacture of paper.
  4.  Pine needles are used to make fibre boards.
  5. Resins containing terpenes, resin acids and esters can be obtained from gymnosperms. Resins are used in waterproofing, sealing joints etc.
  6. A drug called ephedrine is extracted from Ephedra which is a gymnosperm. This drug is useful in respiratory ailments such as asthma.

 

Q6. Both gymnosperms and angiosperms bear seeds, then why are they classified separately?

Answer:

Both gymnosperms and angiosperms come under the group spermatophyta or seed- bearing plants. However, angiosperms and gymnosperms are classified separately in spermatophyta because gymnosperms possess naked seeds i.e. their seeds are not enclosed in the ovary whereas angiosperms possess seeds that are enclosed in the ovary.

 

Q7. What is heterospory? Briefly comment on its significance. Give two examples.


Answer:

Heterospory- It refers to the existence of two types of meiospores i.e. microspores and megaspores in a single plant. These microspores and megaspores are formed respectively within microsporangia and megasporangia which in turn are borne on two distinct sporophylls called microsporophylls and megasporophylls respectively. The microspores and megaspores upon germination give rise to male and female gametophyte respectively. The megaspore is retained in megasporangia and it ensures proper development of the zygote. which is formed after the fusion of microgametes with the megagametes. The zygote is retained on the plant and it is considered to be a precursor of seed habit.

Significance of heterospory- Heterospory is considered to be an important step in evolution as it is a precursor of seed habit which is seen in higher plants. Heterospory was first observed in pteridophyte Selaginella and Salvinia .
 

Q8. Explain briefly the following terms with suitable examples:-

  1. protonema

Answer:

Protonema- It refers to the creeping, green, branched, often filamentous structure which is formed directly after the germination of moss spore. It represents the first stage in the life cycle of moss. Protonema is short-lived and it grows prostrate on the surface. Protonema bears rhizoids for the absorption of materials.


 

  1. antheridium

Answer:

Antheridium- It is the male sex organ found in bryophytes, pteridophytes and some algae. Antheridium encloses a mass of cells that give rise to male gametes. Generally, antheridium remains enclosed by a jacket of sterile cells.

 

  1. archegonium

Answer:

Archegonium- It is female sex organ found in bryophytes, pteridophytes and gymnosperms. Based on the presence of archegonium, these three groups are referred to as archegoniate. It generally possesses a swollen venter and a tubular neck. The venter possesses ventral canal cells and neck contains neck canal cells. Archegonium also contains the female gamete which is called egg.

 

  1. diplontic

Answer:

Diplontic- This is a term utilized for depicting the life cycle of angiosperms and gymnosperms. In this type of life cycle, the plant body is represented by a diploid plant, i.e. sporophyte. It bears sex organs that produce male and female gamete. The gametophyte is of reduced type and it is dependent on the sporophyte. The male and female gametes fuse and form zygote which develops on the diploid plant.

 

  1. sporophyll

Answer:

Sporophylls- These refer to leaf-like appendages bearing sporangia in pteridophytes, gymnosperms etc. Sporophylls can be either microsporophylls or megasporophylls and respectively they can form either microsporangia or megasporangia.

 

  1. isogamy

Answer:

Isogamy- It refers to the process of fertilisation of two gametes which are exactly similar to each other in morphology, physiology, anatomy etc. Such gametes are called isogametes.

 

Q9. Differentiate between the following:-
 

(i) red algae and brown algae
 

Answer:

Differences between red algae and brown algae are as follows:

 

Red algae

 

Brown algae

 

Red algae possess chlorophyll a, d and phycoerythrin

 

Brown algae consist of chlorophyll a, c and fucoxanthin

 

They contain floridean starch as reserve food material

 

Brown algae contain laminarin and mannitol as reserve food material

 

Cell walls are composed of cellulose, pectin and phycocolloids

 

The cell wall is composed of cellulose and algin

 

Red algae due to the presence of red pigment phycoerythrin, are grouped under Rhodophyceae

 

Brown algae due to the presence of fucoxanthin a brown pigment is grouped under Phaeophyceae
 

 

(ii) liverworts and moss
 

Answer:

Differences between liverworts and mosses are as follows

 

Liverworts

 

Mosses
 

 

Sporophyte has very little photosynthetic tissue, so it is completely parasitic on the gametophyte

 

Sporophyte contains more photosynthetic tissue

 

Scales often present

 

Scales are mostly absent

 

Gemma cups are present for vegetative reproduction in some liverworts

 

Gemma cups are mostly absent

 

Rhizoids are unicellular

 

Rhizoids are multicellular

 

The gametophyte is thalloid with dichotomous branching

 

The gametophyte is leafy, branching is lateral

 

(iii) homosporous and heterosporous pteridophyte

Answer:

 

Homosporous pteridophytes

 

Heterosporous pteridophytes

 

These pteridophytes produce only a single type of spores, hence are called homosporous pteridophytes

 

These pteridophytes produce two types of spores i.e. microspores and megaspores. Hence, they are called heterosporous pteridophytes

 

The produce only a single gametophyte which is bisexual.

 

They further form two types of gametophytes i.e microgametophytes and megagametophytes.


 

(iv) syngamy and triple fusion


Answer:

The differences between syngamy and triple fusion are as follows:

 

Syngamy

 

Triple fusion

 

It refers to the fusion of male gamete with female gamete i.e egg cell in angiosperms is called syngamy

 

It refers to the fusion of the second male gamete with the 2 polar nuclei of the central cell. Since, in this fusion, 2 polar nuclei and one sperm nuclei fuse, it's called triple fusion

 

The end product is zygote which is a diploid structure

 

The end product is the primary endosperm nuclei which are triploid.
 

 

Q10. How would you distinguish monocots from dicots?


Answer:

Differences between monocots and dicots are as follows:

 

Monocots

 

Dicots

 

Monocots possess seeds with a single cotyledon

 

Dicots bear seeds with two cotyledons

 

Monocots possess isobilateral leaves

 

Dicots possess dorsiventral leaves

 

The flowers of monocots are generally trimerous i.e. the number of sepals, petals, stamens and pistil is in the multiples of three in these plants

 

The flowers of dicots are pentamerous i.e. the number of sepals, petals, stamens and pistils are in the multiples of five in these plants.

 

They have fibrous roots

 

They have tap roots

 

Cambium is absent in these plants

 

Cambium is present in these plants


 

Q11. Match the following (column I with column II)

Column I Column II

  1. Chlamydomonas (i) Moss
  2. Cycas (ii) Pteridophyte
  3. Selaginella (iii) Algae
  4. Sphagnum (iv) Gymnosperm

Answer:

Correct matching is (a)-(iii), (b)-(iv), (c)-(ii), (d)-(i)

Column I Column II

  1. Chlamydomonas (iii) Algae
  2. Cycas (iv) Gymnosperm
  3. Selaginella (ii) Pteridophyte
  4. Sphagnum (i) Moss

 

Q12. Describe the important characteristics of gymnosperms

Answer:

Important characteristics of gymnosperms

  1. Gymnosperms are seed plants in which the seeds remain exposed over the surface of megasporophylls.
  2. Gymnosperms are represented by 900 living species.
  3. Gymnosperms are perennial and woody plants (either trees or bushes). The xylem of gymnosperms does not possess vessels except in Gnetum. Phloem is without companion cells and sieve tubes.
  4. Two types of sporophylls occur in gymnosperms. These are microsporophylls and megasporophylls. The microsporophylls aggregate to form male strobili or cone while megasporophylls aggregate to form female strobili or cone. Microsporangia and megasporangia are borne on microsporophylls and megasporophylls respectively.
  5. Microsporangia give rise to microspores of pollen grains whereas megasporangia forms megaspores. The male and female gametophytes are formed within microspores and megaspores.
  6. Female gametophyte contains archegonia. The male gametophyte produces only two male gametes or sperms.
  7. The pollination is direct and is accomplished by wind i.e. anemophily. A pollen tube is formed in gymnosperms. It is called siphonogamy.
  8. Seeds contain endosperm.

 

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Also See    
NCERT Solutions for Class 11 Biology Chapter 1 - The Living World NCERT Solutions for Class 11 Biology Chapter 2 - Biological Classification NCERT Solutions for Class 11 Biology Chapter 4 - Animal Kingdom
NCERT Solutions for Class 11 Biology Chapter 5 - Morphology of Flowering Plants NCERT Solutions for Class 11 Biology Chapter 6 - Anatomy of Flowering Plants NCERT Solutions for Class 11 Biology Chapter 7 - Structural Organization in Animals
NCERT Solutions for Class 11 Biology Chapter 8 - Cells: The Unit of Life NCERT Solutions for Class 11 Biology Chapter 9 - Biomolecules NCERT Solutions for Class 11 Biology Chapter 10 - Cell Cycle and Division
NCERT Solutions for Class 11 Biology Chapter 11 - Transport in Plants NCERT Solutions for Class 11 Biology Chapter 12 - Mineral Nutrition NCERT Solutions for Class 11 Biology Chapter 13 - Photosynthesis in Higher Plants
NCERT Solutions for Class 11 Biology Chapter 14 - Respiration in Plants NCERT Solutions for Class 11 Biology Chapter 15 - Plant Growth and Development NCERT Solutions for Class 11 Biology Chapter 16 - Digestion and Absorption
NCERT Solutions for Class 11 Biology Chapter 17 - Breathing and Exchange of Gases NCERT Solutions for Class 11 Biology Chapter 18 - Body Fluids and Circulation NCERT Solutions for Class 11 Biology Chapter 19 - Excretory Products and their Elimination
NCERT Solutions for Class 11 Biology Chapter 20 - Locomotion and Movement NCERT Solutions for Class 11 Biology Chapter 21 - Neural Control and Coordination NCERT Solutions for Class 11 Biology Chapter 22 - Chemical Coordination and Integration

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