Asexual Reproduction:
Production of offspring by a single parent without the formation and fusion of gametes is called Asexual Reproduction. Meiosis doesn’t occur in sexual reproduction. All divisions are mitotic. All individuals formed through Asexual reproduction from a parent are generally similar to one another as well as their parents. A morphologically and genetically similar individual is called a clone. Asexual reproduction is common among lower groups of organisms – simple plants and simple animals. It is absent in higher invertebrates and vertebrates.
Characteristics of Asexual Reproduction:
1. A single parent is involved in reproduction.
2. Gametes are not formed in sexual reproduction.
3. Fertilization doesn’t occur.
4. No meiosis, only mitotic cell division takes place.
5. Daughter individuals are generally identical to parents.
6. Multiplication occurs in a rapid manner.
Types of Asexual Reproduction:
Asexual reproduction takes place by –
- Fission
- Budding
- Regeneration
- Fragmentation
- Gemmule Formation
- Sporulation
Fission:
It is a mode of asexual reproduction in which the body of the parent individual divides into two or more equal-sized daughters. It can occur by binary fission, multiple fission, and plasmogamy.
Budding:
In this process, the daughter individuals are formed from the parent as small outgrowth or bud which grows gradually and acquires the form of a parent.
Regeneration:
This type of reproduction is found in Planaria, Hydra and flatworm. If the body of the animal is fragmented by any means into places, each of the fragmented parts develops into a new animal through cell division.
Fragmentation:
In this method, the body of the adult organism breaks apart into two or more pieces, each of which then grows and reforms the deficient parts to reconstitute a complete animal. It is found in sponges, coelenterates, and echinoderms such as Starfish. Fragmentation is also found in algae (Spirogyra), fungi(Rhizopus), Bryophytes (Riccia, Marchantia), Pteridophytes (Selaginella Rupestric), etc.
Gemmule Formation:
The bud-like organ is called a gemmule, which is formed inside the body of some sponge. These gemmules after maturation detach from the mother’s body and develop into new individuals. There are small groups of cells, i.e, archaeocytes enclosed by a protective cost. Archaeocytes come out through micropyle during favorable conditions and later form a new colony. In the case of liverworts, gemmates develops in small receptacles known as gemma cups.
Sporulation:
Spore formation is a common form of asexual reproduction, which is widely distributed among and in certain protozoans (Sporozoa). Spores are minute, single-celled release from the parent body that germinates to form a new individual. Sporulation is common in members of monera, protista, fungi, and algae.
Asexual reproduction takes place by means of spore formation in the life history of most cryptogamic plants like algae, fungi, bryophytes, and pteridophytes. Spores are formed inside the specified organ called sporangium. After liberation from the sporangium, each spore independently germinates into a new plant.