The driving forces of evolution are ... The main factors and driving forces of evolution
In nature there is always a lot of events,which affect the gene pool of any population of organisms. And they all belong to the driving forces of evolution. In their capacity, Charles Darwin singled out natural selection and struggle for existence.
Modern biologists to the driving forcesevolution includes the drift of genes, population waves and the frequency of mutations. Updates and additions to the theory of evolution became possible after the development of molecular biology and the decoding of genomes. What factors are attributed to the driving forces of evolution, according to modern synthetic theory, we consider in this article.
Heredity: nuclear and cytoplasmic
The property of all living organisms to transmitsigns from generation to generation (heredity) knowingly refer to the driving forces of evolution. It is heredity that ensures continuity and fixation of valuable adaptations for the survival, reproduction and discreteness (individuality and diversity) of species. The whole of the chromosomes (genotype) in the nucleus of the body cell acts as the material of evolution. In addition, some cell organelles have their own ring-shaped DNAs, which are inherited independently of the mother to the offspring (plastids in plants and mitochondria in all living organisms).
Variability is the pledge of a variety of species
The driving forces of evolution include the propertydescendants acquire signs that were not in the parental forms. But not every variability leads to the fixation of new features in the genotype. Phenotypic variability, as a factor of adaptability to the environment, does not affect the gene apparatus, but is a form of manifestation of the genotype in the phenotype and is within the limits of the norms of the response of the trait. It is not considered to be the driving forces of evolution. Interest in the context of our article is variability of the genotypic (mutational and combinative), with changes in the genotype.
This type of variability is directly related to sexualprocess and is expressed in the independent discrepancy between chromosomes and crossing-over processes (exchange of sites between homologous chromosomes) as a result of meiosis with the formation of gametes. It is precisely the various combinations of genes and their alleles in the gamete genome and the appearance in sexual reproduction that accelerated the evolutionary processes on the planet and became a significant acquisition in facilitating adaptability to environmental conditions for panmictic (sexually reproducing) organisms.
Mutations of the genomic level
The largest type of mutational process, which changes the entire genome (a set of genes), without affecting the structure of chromosomes.
- Polyploidy is an increase in the number of chromosomes of the organism, which is a multiple of the haploid (n) set (3n, 4n, 5n, 6n, 7n, and so on). This type of mutation is inherent in many plants and protozoa.
- Aneuploidity - the appearance of excess or losschromosomes as a result of disorders in the passage of meiosis. As a result, monosomia (2n-1), trisomy (2n + 1) or nullisomia (2n-2) appear in an organism with a complete set of chromosomes (2n). Most often such individuals are not viable or carry heavy genetic diseases (Down syndrome in humans is associated with the presence of a third chromosome in 21 pairs).
Chromosomes and their mutations
In this case, as a result of violations inthe passage of gametogenesis (formation of gametes), there are changes in the structure of the chromosomes themselves. Such mutations change the functioning of combinations of genes, less often individual genes, but do not affect the change in the number of chromosomes. There are a lot of mutations of this level. We will only name duplications (doubling) and deletions (losses) of the chromosome region.
Mutations of the gene level
This is a small-scale mutation - a pointchange of one gene. It is this type of mutation that is most often attributed to the driving forces of evolution, since they contribute to an increase in the number of new alleles in the genotype and diversity within the species. The changes in one gene lead to a change in one or more (with multiple effects) signs, increasing the variability of the phenotypes. With the accumulation of such mutations in the population, they become a factor in evolution.
Waves of strength
A sharp increase in the number of individuals orThe catastrophic contraction is called the waves of life or population waves. Changes in numbers can occur as a result of many factors (fires, volcanoes, epidemics, the disappearance of natural enemies). But all of them are random and lead to changes in the gene pool of the whole population, when outsiders can be in the forefront and vice versa.
Isolation as a factor and driving force of biological evolution
Isolation as a factor limiting freecrosses between populations of a single species of panmictic organisms - a vivid acceptance of this factor of evolution. Most species on the planet appeared due to the emergence of reproductive isolation of populations. There are the following types:
- Spatial (geographic, anthropogenic).
- Biological (ecological, morphological, ethological, genetic).
In any case, when a barrier of free crossing arises between populations, one can speak about the beginning of the process of speciation.
The struggle for existence as an instrument of natural selection
The instrument of natural selection is the strugglefor existence, when it survives and leaves the fertile offspring only an organism more adapted to the given conditions. Their struggle for existence is:
- Inside, the most cruel and uncompromising. The competition of representatives of one species for food resources, territory, better living conditions and the ability to leave offspring does not leave any chance for weak and unadapted individuals.
- Between representatives of different species, but occupyingone ecological niche. As an example - the competition for plant food giraffe and zebras led to the evolution of the physiological characteristics, reducing competition to a minimum.
Fight organisms with adverse conditions. Example: the fatty humps of a camel and the fleshy leaves of succulents as adaptive mechanisms of life in the desert. Or glowing organs of deep-sea fish.