Evolutionary factor

As a factor of evolution is called in biology processes by which the gene pool - that is the total of all genetic variations in a population - is changed. A definition of the term is due to the population genetics: evolution factors are processes that lead to changes in allele frequencies in the gene pool of a population. After the synthetic theory of evolution, these processes are the cause of all evolutionary changes.

The main factors of evolution are recombination, mutation, selection and genetic drift.

  • Mutations, spontaneous changes of the base sequences of DNA that are perpetually new genetic material. Finding a mutation in a cell instead of later germ cells emerge from the so altered the genetic trait of the fertilized egg is transferred to the offspring, thus changing the gene pool of the population. The new genetic trait leads to characteristic values ​​that did not occur previously in the population. Whether it comes to a lasting change in the gene pool, depends crucially on how the selection to the new characteristic value acts. Hereditary factors that lead to adverse characteristic values ​​disappear from the gene pool or remain rare.
  • By recombination, which occurs through meiosis in germ cell formation and nuclear fusion during fertilization, the genetic traits of the parents are recombined so that offspring with individual ( unique ) combinations of genetic traits arise. In the recombination, the relative frequencies of the genes in a population to remain unchanged, but the (in particular phenotypic ) variability of the individuals in a population will be effectively increased. Recombination does not occur in asexual reproduction and is also not effective between identical twins, which arise from a common fertilized egg.
  • The selection is natural selection by the environment. A requirement for selection is caused by recombination and mutation of variability in a population. In most populations much more offspring are produced than can survive in their habitat. To die many individuals of a generation before they can reproduce, or get fewer offspring than other individuals with advantageous characteristic values ​​. Thus, the individuals make a different contribution to the gene pool of the next generation. The relative frequency of hereditary traits with low characteristic values ​​are increasing in the population, while the relative frequencies of genetic decrease with unfavorable characteristic values ​​.
  • Under genetic drift is defined as a random change in the gene pool. It is effective in small populations than in large ones. For example, when a natural disaster or an epidemic, a group from a specific condition die suddenly. It spreads the surviving fraction of the population with some other genetic composition, the random survival of individuals with adverse genetic spread even this out. Another example of genetic drift is the colonization of a new habitat by a small founder population. The new population has the frequency distribution of the genetic material of the founder population, the random differ from the stock population.

Evolution on the wider determinants are also

  • Migration,
  • Gene flow,
  • Isolation,
  • Horizontal and vertical gene transfer and
  • Hybridization.
Allele frequency Karyogamy Horizontal gene transfer
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