Laws and rules of evolution. Evolutionary process

Biological evolution implies the natural development of living organisms, which is accompanied by changes in the genetic make-up of populations, as well as an increase in adaptive properties, the appearance of new species and the extinction of old ones. All these factors eventually change both the ecosystem and the biosphere as a whole.

The basic theory

There are several versions explaining the mechanisms on which the evolutionary process is built. Most scientists are now adherents of the synthetic theory of evolution (STE), based on the fusion of population genetics and Darwinism. Synthetic theory explains the relationship between genetic mutations, that is, the material of evolution, and natural selection (the mechanism of evolution). The evolutionary process within the framework of this theory is a process of changing the frequencies of alleles of different genes in species populations over the course of several generations.

Laws and rules of evolution

Evolution is an irreversible process. Any organism that has been able to adapt to new conditions by accumulation of positive mutations will have to undergo an adaptation path once again when returning to the previous environment. Moreover, no biological species can be fully established, Charles Darwin himself wrote that even if the habitat becomes the same as before, the evolved species can not return to its former state. That is, animals will be able to adapt to the return of old conditions, however, not by "old" methods.

This can be easily traced in the example of dolphins. The internal structure of their fins (along with whales) retains the signs of the extremities of mammals. Mutations update the gene pool of the generation, so they never repeat. Despite the fact that dolphins and whales have changed the habitat, and five-toed limbs - to the fins, they still remain mammals. Just as reptiles have evolved from amphibians at a certain stage, but even returning to their former environment, they can not give rise to amphibians.

Another example of this rule of evolution: an evergreen shrub needle. On its stem are shiny, large and thick leaves, which in fact are mutated branches. The true leaves are scaly and located in the center of these "stems." From the sinus of the scales early in the spring appears a flower from which the fetus will later develop. Iglitsa got rid of the leaves in the process of evolution, as a result of which it was able to adapt to the drought, but then again fell into the aquatic environment, but instead of this foliage, modified stems appeared.

Heterogeneity

The rules of evolution say that the process is very heterogeneous and is not determined by astronomical time. For example, there are animals that existed unchanged for hundreds of millions of years. These are cysteper fishes, hatteria and saber-tail are living fossils. But it happens that speciation and modification takes place very quickly. Over the past 800,000 years, new species of rodents have appeared in Australia and the Philippines, and Lake Baikal has been enriched for 240 cancers over the past 20 million years, which are divided into 34 new genus. The appearance or change of a species does not depend on time as such, but is determined by the lack of fitness and the number of generations. That is, the faster the species multiplies, the higher the rate of evolution.

Closed systems

Processes such as evolution, natural selection and mutations can pass much faster. This happens if the environmental conditions are unstable. However, in the deep-sea oceans, cave waters, islands and other isolated areas, evolution, natural selection and speciation occur very slowly. This explains why the brush fisheries have remained unchanged for millions of years.

To trace the dependence of evolution on the speed of natural selection is quite simple on insects. In the thirties of the last century, from pests began to use poisonous drugs, but after a few years there were species that have adapted to the action of the drug. These forms occupied a dominant position and quickly spread across the planet.

To treat many diseases often used strong antibiotics - penicillin, streptomycin, gramicidin. The rules of evolution came into force: already in the forties scientists noted the emergence of microorganisms resistant to these drugs.

Regularities

There are three main directions of evolution: convergence, divergence and parallelism. During divergence, there is a gradual divergence of intraspecific characters, which eventually leads to new groupings of individuals. As the differences in the structure and method of food production become more and more evident, groups begin to disperse in other areas. If one area is occupied by animals that are the same in the needs of food, then eventually, when the food reserve becomes less, they will have to leave the site and adapt to other conditions. If on the same territory there are species with different needs, the competition between them is much less.

A vivid example of how the evolutionary process of divergence takes place is 7 species of deer, related to each other: they are reindeer, maral, moose, spotted deer, fallow deer, musk deer and roe deer.

Species that have a large degree of divergence have the ability to leave large offspring and compete less with each other. When the divergence of characteristics is strengthened, the population is divided into subspecies, which, due to natural selection, can eventually evolve into separate species.

Commonality

Convergence is called the evolution of living systems, as a result of which unrelated species appear common signs. An example of convergence is the similarity of body shape in dolphins (mammals), sharks (fish) and ichthyosaurs (reptiles). This is the result of existence in the same habitat and the same conditions of life. The climbing agama and chameleon are also unrelated, but very similar in appearance. Wings are also an example of convergence. At bats and birds they arose by changing the forelimbs, but in the butterfly it is the growth of the body. Convergences are very common among the species diversity of the planet.

Parallelism

This term originated from the Greek "parallelos", which means "walking alongside", and this translation well explains its meaning. Parallelism refers to the process of independent acquisition of similar structural features among closely related genetic groups, resulting from the presence of features derived from common ancestors. This type of evolution is widespread in nature. An example of it is the appearance of fins as adaptations to the aquatic environment, which in walruses, eared seals and real seals were formed in parallel. Also among many winged insects there was a transition of the front wings to the elytra. Kistepery fish have signs of amphibians, and zverozuby lizards have signs of mammals. The presence of parallelism not only indicates the unity of the origin of species, but also about similar conditions of existence.