CBSE Class 12 Biology
Revision Notes
CHAPTER-01
REPRODUCTION IN ORGANISMS
Reproduction is a biological process of formation of new offsprings from the
pre-existing organism.Reproduction becomes a vital process without which
species cannot survive for long It ensures continuity of species generation
after generations as older individuals undergo senescence and ultimately they
die.
Lifespan- The period from birth to the natural death of an organism
represents its life span. Life span of organisms varies from few days
(Butterfly-1to 2 weeks) to thousands of years (Banyan tree).
Types of Reproduction:
Based on whether there is one or two organisms taking part in the process of
reproduction
•ASEXUAL REPRODUCTON
•SEXUAL REPRODUCTION
When the offspring is produced by single parents with or without the
involvement of gamete formation, the reproduction is called asexual
reproduction.
When two parents (opposite sex) participates in reproduction process and
also involves the fusion of male and female gametes, it is called sexual
reproduction.
Asexual Reproduction
1. Usually followed by organisms with relatively simpler organizations.
2. Off springs produced by single parent.
3. With/without involvement of gamete formation.
4. Off springs produced are genetically and morphologically similar to each
other and to the parent, i.e. they are clones.
, • In Protista and Monera, the parent cells divides into two to give rise to new
individuals. Thus, in these organisms cell division is the mode of reproduction
itself.
• Binary fission- in this method of asexual reproduction, a cell divides into two
halves and rapidly grows into an adult. Ex- amoeba, paramecium.
• Budding- small buds are produced that remain attached initially with parents
and get separated on maturation. Ex. Yeast.
•Fungi and simple plants like algae reproduce through special reproductive
structures likezoospores (motile structure), conidia (penicillium), buds (hydra)
and gemmules (sponges).
• In plants, vegetative reproduction occurs by vegetative propagules like
runner, rhizome, sucker, tuber, offset and bulb.
Revision Notes
CHAPTER-01
REPRODUCTION IN ORGANISMS
Reproduction is a biological process of formation of new offsprings from the
pre-existing organism.Reproduction becomes a vital process without which
species cannot survive for long It ensures continuity of species generation
after generations as older individuals undergo senescence and ultimately they
die.
Lifespan- The period from birth to the natural death of an organism
represents its life span. Life span of organisms varies from few days
(Butterfly-1to 2 weeks) to thousands of years (Banyan tree).
Types of Reproduction:
Based on whether there is one or two organisms taking part in the process of
reproduction
•ASEXUAL REPRODUCTON
•SEXUAL REPRODUCTION
When the offspring is produced by single parents with or without the
involvement of gamete formation, the reproduction is called asexual
reproduction.
When two parents (opposite sex) participates in reproduction process and
also involves the fusion of male and female gametes, it is called sexual
reproduction.
Asexual Reproduction
1. Usually followed by organisms with relatively simpler organizations.
2. Off springs produced by single parent.
3. With/without involvement of gamete formation.
4. Off springs produced are genetically and morphologically similar to each
other and to the parent, i.e. they are clones.
, • In Protista and Monera, the parent cells divides into two to give rise to new
individuals. Thus, in these organisms cell division is the mode of reproduction
itself.
• Binary fission- in this method of asexual reproduction, a cell divides into two
halves and rapidly grows into an adult. Ex- amoeba, paramecium.
• Budding- small buds are produced that remain attached initially with parents
and get separated on maturation. Ex. Yeast.
•Fungi and simple plants like algae reproduce through special reproductive
structures likezoospores (motile structure), conidia (penicillium), buds (hydra)
and gemmules (sponges).
• In plants, vegetative reproduction occurs by vegetative propagules like
runner, rhizome, sucker, tuber, offset and bulb.
