Plant Kingdom

NCERT Solution Part 2

Question 5: Write a note on economic importance of algae and gymnosperms.

Answer: Economic Importance of Algae:

Economic Importance of Gymnosperms:

Question 6: Both gymnosperms and angiosperms bear seeds, then why are they classified separately?

Answer: The seeds of gymnosperm are naked, while those of angiosperms are covered. Hence, they are kept in different groups.

Question 7: What is heterospory? Briefly comment on its significance. Give two examples.

Answer: Some pteriophytes are heterosporous, e.g. Selaginella and Salvinia. In heterospory, the megaspore germinates to produce female gametophyte, while the microspore germinates to produce the male gametophyte. This event is a precursor of the seed habit in higher plants.

Question 8: Explain briefly the following terms with suitable examples:-

(a) Protonema

Answer: A protonema forms the earliest stage of a bryophyte life cycle. It is a thread-like chain of cells. Protonema is formed just after the germination of spores. It subsequently develops into a leafy gametophyte.

(b) Antheridium

Answer: An antheridium is the male sex organ of a plant. It produces the male gametes. It is present in the gametophyte phase of lower plants, but is present in the sporophyte phase of higher plants.

(c) Archegonium

Answer: Archegonium is a structure which is present in the gametophyte phase of some plants. The archegonium produces the female gamete.

(d) Diplontic

Answer: In this case, the diploid sporophyte is the dominant photosynthetic phase of the plant. The gametophyte is represented by the single to few-celled haploid gametophyte. Gymnosperms and angiosperms show this pattern.

(e) Sporophyll

Answer: A leaf or cluste of leaves which bears sporangia is called sporophyll. Sporophylls can produce microspores or megaspores as the case may be.

(f) Isogamy

Answer: In this case, the gametes are similar in size, e.g. Spirogyra. The gametes can be flagellated or non-flagellated.

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