Read this article to learn about the characteristics, occurrence and types of asexual reproduction in animals! When offspring is produced by a single parent with or without the involvement of gamete formation, the reproduction is called asexual. As a result, the offspring that are produced are not only similar to one another but are also exact copies of their parent.
Such a group of morphologically and genetically similar individuals is called clone. Asexual reproduction occurs usually in unicellular organisms, such as Monerans and Protists, and in plants and certain animals.
It is absent in the higher invertebrates and all vertebrates. This is the division of the parent body into two or more daughter individuals identical to the parent. Fission can occur by binary fission, multiple fission and plasmotomy.
In this process of asexual reproduction, the parent organism divides into two halves, each half forming an independent daughter organism. Binary fission involves mitosis.
The resultant offspring pi. Depending upon the plane of division, binary fission is of the following types.
The plane of division passes along the longitudinal axis of the animal. It occurs in flagellates such as Euglena. The flagellum divides first followed by body. The plane of division runs along the transverse axis of the individual, e. In Paramecium the meganucleus divides by amitosis, while micronucleus divides by mitosis. Under unfavourable conditions, Amoeba, withdraws its pseudopodia and secretes a three layered thick covering— the cyst wall around itself.
This phenomenon is called encystment. On return of favourable conditions the encysted Amoeba divides by multiple fission and produces many minute amoebae called pseudopodiospores. On return of favourable conditions the cyst wall ruptures to release the pseudopodiospores in the surrounding medium to grow up into many amoebae. Sometimes Amoeba produces a number of spores or ensheathed amoebae. Spores take part in both dispersal and perennation living for a long time.
Under favourable conditions each spore gives rise to a small Amoeba. The process of multiple fission in oocyst is termed sporogony and the daughter individuals are known as sporozoites. It is the division of a multinucleate parent into many multinucleate individuals without division of nuclei. Nuclear division occurs later on to maintain normal number of nuclei. Plasmotomy occurs in Opalina and Pelomyxa Giant Amoeba. Both Opalina and Pelomyxa are protozoans.
In budding, Multiple fission asexual reproduction in fungi daughter individual is formed from a small projection, the bud, arising from the parent body. This budding stage in yeast resembles with a genus Torula. Therefore, this condition is called torula stage and the process is known as torulation.
In this type budding an outgrowth or bud grows externally on the surface of the body.
The bud may split away from the parent and take up an independent existence as in Hydra or it may remain attached and become a more or less independent member of the colony as in Sycon. In the fresh water sponges e. During favourable conditions the mass of archaeocytes comes out through micropyle and later on forms new colony.
The repeated formation of similar segments by a process of budding is called strobilation.
The ephyrae break at interval. So one by one the distal ephyrae are pinched off from the parent strobila and swim in the water. The free ephyrae feed, grow and in due course of time change into jelly fishes. About a dozen ephyrae are formed in a single strobilation. The parent body breaks into two or more fragment. Each body fragment develops into an organism. In a starfish, one arm with a part of central disc can develop into a starfish.
Fragmentation is also found in algae e. These are specialised structures which are green, multicellular, asexual buds, which develop in a small receptacles called gemma Multiple fission asexual reproduction in fungi located on the thalli. The gemmae sing, gemma are separated from the parent body and germinate to form new individuals.
The gemmae formed by the male thallus male thalli while those of the female thallus develop into female thalli. Gemmae formation is found in liverworts e. Regeneration is formation of the whole body of an organism from a small fragment morphallaxis or the replacement of the lost part epimorphosis.
The morphallaxis is a type of asexual reproduction. It is found in Amoeba, Sponge, Hydra, Planaria, etc. Severed body parts can be redeveloped or a body part can develop into complete body, therefore, it is a type of asexual reproduction.
Spores are minute, single celled, thin walled propagules. Propagules are dispersive structures released from the parent body.