pratclif.comVariation of DNA (nucleic acids) can be found in different mechanisms of genetic change: mutations, recombinations, copying errors, ... In order to find a metasystem transition, we need a mechanism that controls or constrains such changes in a non-random way. Although geneticists are still learning a lot about the underlying molecular processes, there is one mechanism which is clearly not the effect of random noise, sexuality. It can be defined as the constrained variation of DNA sequences by recombination with a second sequence from another organism of the same genus.
Each opposite sex brings to the offspring half of its chromosomes. These are produced by breaking up the pairs of chromosomes and randomly constituting a half set of the whole. The process is called meiosis. See Utah university animation on the subject.
Sexuality makes it possible to increase genetic variety without the dangers of random mutation: since both sequences have proven their viability, it unlikely that their recombination would be unviable. Higher variety (or "diversity" in biological terminology) of offspring implies a lower probability that all of them would be eliminated by natural selection, and a high probability that at least one of them would be more fit than the parents. Mutations, on the other hand, are most likely deleterious. The effectiveness of recombination mechanisms for exploring large fitness spaces has been demonstrated in computer applications by genetic algorithms.
The metasystem that emerges from this metasystem transition is the species, which is defined as the set of all organisms that are capable to recombine their genes in the way mentioned. In sexual organisms, no individual organism really reproduces, since the offspring is always genetically different from the parent. The only system that can really be said to maintain and reproduce is the species as a whole, characterized by a more or less stable "gene pool", i.e. the collection of genes available for recombination. See Darwin's "origin of species".
Mis à jour le 01/04/2016 pratclif.com