Chapter 1 bio notes

Class 12 Biology – Chapter 1: Reproduction in Organisms (Quick Revision)

1. Reproduction

• Process by which organisms produce offspring.

• Ensures continuity of a species.

• Not essential for the survival of an individual, but essential for the survival of the species.

2. Lifespan

• Time between birth and natural death.

• Different organisms have different lifespans.

3. Types of Reproduction

Asexual Reproduction

• Involves a single parent.

• No fusion of gametes.

• Offspring are genetically identical (clones).

• Fast and energy-efficient.

Common methods:

• Binary fission

• Budding

• Fragmentation

• Spore formation

• Vegetative propagation

Sexual Reproduction

• Involves formation and fusion of male and female gametes.

• Produces genetically diverse offspring.

• Helps in adaptation and evolution.

4. Clone

• A group of genetically identical individuals produced by asexual reproduction.

5. Vegetative Propagation

Natural methods:

• Rhizome

• Tuber

• Bulb

• Runner

Artificial methods:

• Cutting

• Layering

• Grafting

• Tissue culture

6. Juvenile Phase

• Period before an organism becomes reproductively mature.

7. Reproductive Phase

• Organism becomes capable of producing offspring.

• In flowering plants, this phase is marked by flowering.

8. Senescent Phase

• Ageing stage after the reproductive phase.

• Reproductive ability gradually declines.

9. Events in Sexual Reproduction

• Pre-fertilization events

• Fertilization (syngamy)

• Post-fertilization events

Important NEET Points

• Clones are genetically identical.

• Meiosis occurs during gamete formation.

• Fertilization restores the diploid chromosome number.

• Genetic variation is a major advantage of sexual reproduction.

NCERT Keywords

• Lifespan

• Clone

• Asexual reproduction

• Sexual reproduction

• Vegetative propagation

• Juvenile phase

• Reproductive phase

• Senescence

• Fertilization

• Gamete