Chapter-Reproduction: How Life Continues Science Exploration class 9 in english Medium CBSE Notes

Chapter 11. Reproduction: How Life Continues

This section explains the processes of pollination and fertilisation in flowering plants. It also describes the formation of fruits and seeds after fertilisation, seed germination and the different modes of fertilisation in animals. 

Pollination, Fertilisation and Reproduction in Animals

Pollination

Pollination is the transfer of pollen grains from the anther to the stigma of a flower. It is the first step in the sexual reproduction of flowering plants.

Types of Pollination

1. Self-pollination

• Pollen grains are transferred to the stigma of the same flower or another flower on the same plant.
• Usually occurs in bisexual flowers.
• Produces less genetic variation.

2. Cross-pollination

• Pollen grains are transferred from one plant to the flower of another plant of the same species.
• Produces greater genetic variation.
• Increases adaptability and survival.

Agents of Pollination

Agent	Examples
Wind	Maize, Grass
Water	Hydrilla, Vallisneria
Insects	Bees, Butterflies
Birds	Sunbirds, Hummingbirds

Fertilisation

Fertilisation is the fusion of the male gamete with the female gamete to form a zygote. After pollination, the pollen grain germinates on the stigma and forms a pollen tube that carries the male gamete to the ovule. 

Events After Fertilisation

• The zygote develops into an embryo.
• The ovule develops into a seed.
• The ovary develops into a fruit.
• The other floral parts gradually wither away.

Seed Germination

Seed germination is the process by which a seed develops into a young plant under favourable conditions.

Conditions Required for Germination

• Adequate water.
• Oxygen (air).
• Suitable temperature.

Sexual Reproduction in Animals

Animals reproduce sexually through the fusion of male and female gametes. Depending on where fertilisation takes place, it may be external or internal.

External Fertilisation

• Fertilisation occurs outside the body of the female.
• Common in aquatic animals.
• Examples: Fish and Frogs.

Internal Fertilisation

• Fertilisation occurs inside the body of the female.
• Provides better protection to the developing embryo.
• Examples: Reptiles, Birds and Mammals.

Difference Between External and Internal Fertilisation

External Fertilisation	Internal Fertilisation
Occurs outside the female body.	Occurs inside the female body.
Usually seen in aquatic animals.	Common in terrestrial animals.
Less protection to gametes and embryo.	Greater protection to gametes and embryo.
Examples: Fish, Frog.	Examples: Birds, Reptiles, Mammals.

Importance of Sexual Reproduction

• Produces genetic variation.
• Improves adaptability to changing environments.
• Supports evolution of species.
• Ensures the continuity of life.

ATP Education Concept Builder

Remember the sequence in flowering plants: Pollination → Pollen Tube Formation → Fertilisation → Zygote → Embryo → Seed → Fruit. In animals, fertilisation may occur either outside or inside the body depending on the species. 

ATP Education Exam Booster

• Differentiate between self-pollination and cross-pollination.
• Learn the agents of pollination with examples.
• Remember the changes that occur after fertilisation.
• Know the conditions necessary for seed germination.
• Differentiate between external and internal fertilisation.
• CBSE competency-based questions often ask students to arrange the stages from pollination to seed formation and compare fertilisation in plants and animals.

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