Reproduction: The biological process through which living organisms produce offspring similar to themselves.
Types of Reproduction:
Asexual Reproduction: Without the involvement of sex cells or gametes.
Sexual Reproduction: Involves the fusion of male and female gametes.
Life Span and Life Cycle:
Life Span: From birth to natural death of an organism.
Life Cycle: Sequence of events from the formation of new generation to the production of its own offspring.
Asexual Reproduction:
Binary Fission: Parent cell divides into two (e.g., Amoeba, Paramecium).
Budding: New individual grows from a certain region on the parent body (e.g., Hydra).
Fragmentation: Body breaks into several pieces; each piece grows into a complete organism (e.g., Spirogyra).
Sporulation: Formation of spores in sporangia (e.g., Rhizopus).
Vegetative Propagation: New plants form from parts like roots, stems, or leaves (e.g., Potato, Bryophyllum).
Sexual Reproduction:
Involves two distinct phases:
Juvenile Phase: Period of growth before reproductive maturity.
Reproductive Phase: Varies among organisms. May be seasonal or throughout life.
Stages:
Pre-fertilization: Involves gametogenesis (formation of gametes) and gamete transfer.
Fertilization: Fusion of male and female gametes.
Post-fertilization: Formation of zygote and embryogenesis.
Gametogenesis:
Homogametes (Isogametes): Gametes are of similar shape and size (e.g., Algae).
Heterogametes: Gametes are of different shapes and sizes. Male gamete is smaller and motile (sperm) while the female gamete is larger and non-motile (ovum).
Significance of Reproduction:
Ensures the continuity of species.
Provides for genetic variation in the offspring.