Page 112 - Ripples SCIENCE 7 - TEJPUR Edition 2024 Answer Key

2. How does sexual reproduction take place in flowering plants? Discuss.
Ans. Sexual reproduction in flowering plants involves:

(a) Pollination : Pollen grains from the anther are transferred to the stigma of the
same or another flower.
(b) Fertilization : Pollen travels down the style to reach the ovary, where it fertilises
the ovule.

(c) Seed formation : The fertilised ovule develops into a seed.
(d) Fruit formation : The ovary develops into a fruit, which contains the seeds.
(e) Germination : When conditions are favourable, the seed germinates & grows
into a new plant.
3. Differentiate between self-pollination and cross-pollination.
Ans. Self-pollination: When pollens from the anthers of a flower are transferred to the

stigma of the same flower or another flower of the same plant, it is called self-
pollination.
Cross-pollination: When the pollens from the anthers of a flower are transferred
to the stigma of a flower of another plant of the same species, it is called cross-
pollination.

4. Explain reproduction in plants by spore formation.
Ans. Spore Formation
In this asexual mode of reproduction, organisms, such as fungi, produce hundreds of
tiny microscopic structures called spores. Such organisms bear sac-like reproductive
structures called sporangia (singular sporangium), which produce and bear spores.
Each spore is covered with a hard outer protective covering that enables it to

withstand extreme conditions of temperature and lack of moisture and nutrients.
As soon as they find favourable conditions, they germinate and form new organisms.
Certain fungi like Rhizopus and plants, such as mosses and ferns, reproduce by spore
formation.
5. Discuss the advantages and disadvantages of tissue culture.

Ans. Advantages of tissue culture
• Plant can be grown in a short period of time.
• New plants are more likely to be disease free.
• Its application requires a sterile workplace, nursery and greenhouse, and trained
manpower.
• The process of tissue culture is not dependent on seasons as plants can be

grown throughout the year.
• An important technology for developing countries.
Disadvantages of tissue culture
• The process is very costly.

• Since the propagated plants are grown in controlled environments, they may
become more prone to infections when moved outside.
• Success with the tissue culture is not guaranteed.

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