Sexual vs Asexual Reproduction
The ability to reproduce, that is to produce a new generation of the same species, is one of the fundamental characteristics of living organisms. It involves the transmission of the genetic material from the parental generation to the next generation, ensuring the characteristics of the species and parental organisms are perpetuated. Before a new individual reaches its own reproductive stage, it normally has to go through a period of growth and development. Some members of the species will die before they reach reproductive age due to predation, disease and accidental death, so that a species will only survive if each generation produces more offspring than the parental generation. There are two basic types of reproduction, asexual and sexual.
What is Asexual Reproduction?
Prokaryote like bacteria and unicellular organisms reproduce asexually by cell division or binary fission of the parent cell. This is a type of reproduction done by a single organism without production of gametes. It usually results in the production of identical offspring, the only genetic variation arising as a result of random mutation among the individuals. There are three common modes of asexual reproduction: fission, budding and fragmentation in animals. Lower animal phyla such as prokaryotes, eukaryotes, cnidarians and platyhelminths use this type of reproduction.
What is Sexual Reproduction?
Sexual reproduction is a type of reproduction in which two parents are involved, each capable of producing gametes. It is essentially cellular in nature which involves the fertilization of one haploid gamete with another, producing a new diploid cell called the zygote. The union of structurally similar physiologically different gametes is called isogamy. This is found only in lower forms such as Protozoa. Heterogamy is the fusion of two clearly different kinds of gametes, distinguished as ovum and sperm. Pre-fertilization events include gametogenesis and gamete transfer while post-fertilization events include formation of zygote and embryo. Genetic diversity, which is material for natural selection, is produced by sexual reproduction. Although this is advantageous for a species in the long run, sexual reproduction is costly.
What is the difference between Asexual and Sexual Reproduction?
• Both sexual and asexual reproductions are modes for the propagation of the current generation into the future. All living things depend on it for the survival of their species.
• But, asexual reproduction requires only one parent, whereas sexual reproduction generally requires two.
• Asexual reproduction requires only a single divisible cell to produce a new organism, whereas sexual reproduction requires two gametes, their formation and fusion. Sexual reproduction requires the formation of sexual organs and asexual reproduction generally occurs without them.
• Asexual reproduction does not involve meiosis or fertilization. However, in sexual reproduction meiosis is essential for gametogenesis and fertilization for zygote formation.
• The produced off spring during asexual reproduction are genetically similar to each other and their parent. Genetic variation occurs in the sexual reproduction and can form offspring dissimilar to that of parents and to each other.
• Asexual reproduction is a quick method of reproduction while sexual reproduction is time consuming.
The asexual reproduction preserves the finest traits of the parental generations for the next generation but leave little room for change. This may be a cause for extinction, if faced with a lethal condition. Genetic variation is essential for organisms because offspring showing most adaptations to the environment will have a competitive advantage over the other members of a species and pass on their genes to the next generation, paving the path to evolution. This variation is enabled by sexual reproduction.