Asexual reproduction
Organisms reproduce by two methods. They are asexual reproduction and sexual reproduction and sexual reproduction. In asexual reproduction a new individual is formed without the fusion of male and female gametes. Asexual reproduction is of three types.
- Binary fission
- Budding
- Regeneration.
Binary Fission: The division of a single organism in to two daughter organisms is called binary fission.
We are going to learn an example of Binary fission in paramecium.
Binary fission in Paramecium: Paramecium is a small single celled animal. It divided in to two daughter paramecia. In paramecium the division of the body is transverse through the centre of the cell. It has a small nucleus called as micro-nucleus and a large one known as macronucleus. Before fission, the micro nucleus divided in to two micro nuclei. These move away from one another. Then the macro nucleus elongates length wise and divides transversely in to two macro nuclei. In the mean time, a constriction appears in the middle of the body. This constriction deepens and divides the body in to two daughter paramecia. The daughter paramecia grow in to adults. Binary fission in paramecium is completed in about two hours. It may occur from one to four times in a day.
Budding in Hydra:
Budding: Small buds appear from the body and develop in to new adult organisms. Hydra is a multi cellular organism living in fresh water. The body has a central cavity. It is attached to the plants by the base. At the other end there is thread like structures called tentacles. In hydra reproduction also takes place by budding. During budding, the body wall bulges out. Gradually this bulging increases in size. This bulged structure is called a bud. The bud develops tentacles. It grows in size. Then it separates from the parent Hydra and lives independently.
Regeneration: The process of developing the lost parts of the body is called regeneration.
Regeneration in Earth-worm: By chance an earth worm is cut across in to two bits; the head end is capable of developing the lost part to become a full earth worm. But the tail part of the cut earth worm cannot develop the head portion. So the regeneration of lost parts in earth worm is restricted to head end. Other examples for animals that have great regenerative powers are sponges, hydra and starfish.
Asexual reproduction in animals ensures to give rise to young ones, direct from their bodies.
Like it on Facebook, Tweet it or share this article on other bookmarking websites.