natural selection - is the main evolutionary tool.During the existence of the species each another of his offspring exposed to certain mutations.Nature as it searches for new forms and methods for better adaptability of the organism to the ever-changing environment.To this end, all living things produce offspring more than "necessary" than can survive.In a population of organisms incorporated genetic variation, which is expressed by a set of certain genetic traits.As a result, it creates competition between organisms for su
rvival, and then the ability and the right to reproduction.Thus, organisms with heredity, more in keeping with the idea of adapting to this environment have advantages in transferring their genetic characteristics to the next generation. a result of sudden changes in environmental conditions may be that popular are "bad" alleles (forms of a gene).The evolution does not necessarily lead to an increase in the complexity of the organism.
Natural selection operates at all levels of the organization - at the level of genes, cells, organisms, groups of organisms, and finally species.Selection can operate simultaneously on different levels.It should also be borne in mind and interspecific competition for food resources for living space.In this case, evolution may lead to the extinction of poorly adapted species, an example of the dinosaurs.Changed conditions also contribute to the emergence of new species to the newly established conditions.
artificial selection, or selection, carried out by man to obtain higher yielding crops, and more productive breeds of domestic animals.Initially, this selection carried the unconscious, spontaneous.Eventually he got the methodological basis, and the selection of pairs for crossing began to make a definite purpose. a result of artificial selection man also displays fine breeds of domestic animals and plants in their natural environment would be culled immediately and inevitably died.
Today, artificial selection is already at the genetic level and has fantastic prospects.Against the background of the rapid increase in world population and the reduction of land under arable land and pastures, this area becomes an important character is invaluable.