Biology Class 11 NCERT Solutions: Chapter 3 Plant Kingdom Part 1

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Q: 1. What is the basis of classification of algae?

Answer:

Algae are classified into three main classes –

  • Chlorophyceae

  • Phaeophyceae

  • Rhodophyceae

Image shows the classified algae

Image Shows the Classified Algae

Image shows the classified algae

These divisions are based on the following factors:

(A) Major photosynthetic pigments present

(B) Form of stored food

(C) Cell wall composition

(D) Number of flagella and position of insertion

Class I – Chlorophyceae

Q 1 I image of Chlorophyceae

Q 1 I Image of Chlorophyceae

Q 1 I image of Chlorophyceae

Common name - Green algae

Major pigments - Chlorophylls a and b

Stored food - Starch

Cell wall composition - Cellulose

Flagella number and position - 28; equal and apical

Class II - Phaeophyceae

Common name- Brown algae

Major pigments - Chlorophylls a and c, and fucoxanthin

Stored food - Mannitol and laminarin

Cell wall composition - Cellulose and algin

Flagella number and position - 2; unequal and lateral

Class III - Rhodophyceae

Common name - Red algae

Major pigments - Chlorophylls a and b, and phycoerythrin

Stored food - Floridean starch

Cell wall - Cellulose, pectin, and polysulphate esters

Q: 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?

Answer:

Image shows the group of land plants

Image Shows the Group of Land Plants

Image shows the group of land plants

Liverwort - In liverworts, the main plant-body is haploid (gametophytic). It bears the male and female sex organs, which produce gametes. These gametes fuse to form a zygote. The zygote develops on the gametophytic plant-body to form a sporophyte. The sporophyte is differentiated into the foot, seta, and capsule. Many haploid spores are produced as a result of the reduction division taking place inside the capsule.

Moss - In mosses, the primary protonema (developed in the first stage) develops into the secondary protonema. Both these stages are haploid or gametophytic. The secondary protonema bears the sex organs which produce gametes. These gametes fuse to form a zygote. The zygote develops into a sporophyte. Many spores are formed as a result of the reduction division taking place in the capsule of this sporophyte.

Fern - In ferns, the main plant-body is sporophytic. Its leaves are known as sporophylls and these bear the sporangia. Reduction division takes place in these sporangia, thereby producing many spores.

Gymnosperm - In gymnosperms, the main plant-body is sporophytic. They bear two types of leaves -microsporophylls and megasporophylls. Reduction division takes place in the microsporangia present on the microsporophylls (producing pollen grains) and on the megasporangia present on the megasporophylls (producing megaspores).

Angiosperm - In angiosperms, the main plant-body is sporophytic and bears flowers. The male sex organ in the flower is the stamen, while the female sex organ is the pistil. Reduction division takes place in the anthers of the stamen (producing haploid pollen grains) and in the ovary of the pistil (producing eggs).