What is Asexual Reproduction, How Many Are Divided, What Are Its Types? In Which Organisms Does Asexual Reproduction Occur?

Asexual reproduction is the reproduction of a new organism from a single organism by inheriting only that organism's genes. There is no ploidy in this breeding method. Except in the case of otomixsis, the organism formed as a result of asexual reproduction is the exact genetic copy of the parent organism. A narrower definition is the term agamogenesis, which means the reproductive method that occurs outside the fusion of gametes. Asexual reproduction is the main reproductive route for single-celled organisms such as archaea, bacteria, and protists. Many plants and fungi also reproduce asexually.

Although all prokaryotes reproduce asexually, horizontal gene transfer mechanisms such as bacterial conjugation, transformation, and transduction are sometimes compared to sexual reproduction in terms of recombination. Completely asexual reproduction is relatively rare in multicellular organisms, especially animals. It is not understood why sexual reproduction is so common in multicellular organisms. Current hypotheses suggest that asexual reproduction may have short-term advantages in rapid population growth and stable environments, but that sexual reproduction has a clear advantage in adapting to changing environments, providing faster genetic variation. Developmental constraints may explain why so few animal species have completely abandoned sexual reproduction throughout their life cycle. One of the constraints in the transition from sexual to asexual reproduction may be that, with the disappearance of meiosis, DNA damage due to meiosis is destroyed in its protective repair by recombination.

Types of Asexual Reproduction

Split in Two
In prokaryotic organisms (archaea and bacteria), it is a type of reproduction in which the mother cell simply divides into two. The two cells formed are genetically identical to each other. In eukaryotes (protists and unicellular fungi) it can occur in a very similar way to mitosis.

Budding
It is seen in single-celled organisms (such as brewer's yeast) and multi-celled organisms (capped mushrooms, celiac, etc.). The mother cell forms a protrusion from itself, forming a smaller cell than itself, like mother and daughter. The bud grows attached to it until it breaks off from the mother.

Spore Reproduction
The production of spores in most multicellular life cycles is called sporogenesis. In animals and some protista, spore formation is not observed as meiosis is immediately followed by fertilization. However, with meiosis seen in plants and most algae, spores with haploid (n) chromosomes are formed rather than gametes. These spores become multicellular individuals without fertilization. These organisms can form new gametes by mitosis. This succession of sexual and asexual reproduction is called metagenesis. Since we define sexual reproduction with fertilization, we do not call it sexual reproduction, no matter how much meiosis occurs and there is a halving in the number of chromosomes. For reproduction in the life cycle of plants, it is necessary to have both spore and sexual reproduction.

Vegetative Reproduction
It is a form of reproduction in plants without seeds, meiosis, spores or fertilization. It is the production of a new plant from plant parts such as steel, tuber, rhizome, creeping stem. Inoculation and tissue culture are also included in this section.

Parthenogenesis
It is the development of the egg cell without fertilization to form a new individual. The unfertilized egg develops by mitosis and forms a male individual.