1.c.5 – Sexuality leads to genetic mixing?

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December 28, 2009 — Riccardo Sabellotti - Giacinto Sabellotti


Sexuality leads to genetic mixing?

Sexuality is a strategy that allows to reuse the genes already available through a different association. The result is similar to that of a mutation but, unlike this, regularly occurs in every reproduction act. The advantage may be insignificant for the individual, but is crucial for the species and its future evolution: by mating occurs fertilization of the egg in which the mother genes recombine with those of the father; thus the descendants of an individual will be able to exploit the positive mutations arising in the other parent, bringing the benefits of evolution arising from different sources; with this procedure we obtain something similar to what symbiosis achieved by combining the different capabilities of different species. The new combinations can also be negative and, in order to diffuse only the positive ones, the intervention of natural selection is necessary. Similar considerations were made even talking about the phenomenon of mutations but, unlike this, which is slow because based on rare events, the phenomenon of sexual reproduction creates new combinations at each new birth and then generates a much higher number of variants. The result of this phenomenon is a much greater capacity and speed of adaptation and this is the great advantage of evolutionary sexuality: it is no coincidence that virtually all animals and plants that we see around us use this technique.
The phenomenon of sexuality joins that of specialization and the result is that in reproduction both parents play different roles; since for playing different roles, different characteristics are necessary, the evolution has led to the creation of two types of sex: male and female.
It seems that the protists have been the first beings, with unicellular nucleus and internal organs, to develop sexuality and, since then, the strategy was no more abandoned. From a greater capacity and speed of adaptation has resulted a faster evolution and diversification.
The appearance of the first unicellular beings with sexual reproduction occurred around one billion and a half years ago and this corresponds, as we have seen, to h. 16:00 on our evolutionary day. Before then, only the bacteria had developed, who reproduce themselves by scission, i.e. asexually; evolution, for almost three quarters of history of the Earth, has produced thus only the bacteria, while with the advent of the first protists, in the last quarter or so, all the forms that we know, and those extinct too, have developed. This incredible acceleration is due to the development of sexuality. It is therefore reasonable to assume that evolution has a natural tendency, irregular and tied to random events, both in terms of adaptability that results in the production of individual variations, and in terms of speed of adaptation i.e. the production of new species. 




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