The main directions of evolution. Evolution of plants and animals

Questions of the origin of life and its development since ancient times have puzzled scientists. People have always sought to approach these mysteries, making the world, therefore, more understandable and predictable. For many centuries the point of view about the divine beginning of the universe and life dominated. The theory of evolution has won the honorary place of the main and most probable version of the development of all life on our planet relatively recently. The main provisions of it was formulated by Charles Darwin in the middle of the XIX century. The ensuing century gave the world a wealth of discoveries in the field of genetics and biology, which made it possible to prove the validity of Darwin's teaching, expand it, and combine it with new data. So there was a synthetic theory of evolution. It absorbed all the ideas of the famous researcher and the results of scientific research in various fields from genetics to ecology.

From individual to class

Biological evolution is a historical development of organisms, based on unique processes of functioning of genetic information in certain environmental conditions.

The initial stage of all transformations, which eventually leads to the appearance of a new species, is microevolution. Such changes over time are accumulated and result in the formation of a new higher level of organization of living beings: genus, family, class. The formation of supernumerary structures is usually called macroevolution.

Similar processes

Both levels are basically the same. The driving forces of both micro- and macro-changes are natural selection, isolation, heredity, variability. The essential difference between the two processes is that crossing is virtually impossible between different species. As a result, macroevolution is based on interspecific selection. A huge contribution to microevolution is made by the free exchange of genetic information between individuals of one species.

Convergence and divergence of features

The main directions of evolution can take several forms. A powerful source of diversity in life is the divergence of traits. It acts both within a particular species, and at higher levels of the organization. Environmental conditions and natural selection lead to the separation of one group into two or more, which are distinguished by certain characteristics. At the species level, the divergence can be reversible. In this case, the formed populations again merge into one. At higher levels, the process is irreversible.

Another form is phyletic evolution, which assumes the transformation of a species without the isolation of individual populations within it. Each new group is a descendant of the previous one and an ancestor for the subsequent one.

A significant contribution to the diversity of life is made by convergence or "convergence" of features. In the process of development of unrelated groups of organisms under the influence of identical environmental conditions, individuals form similar organs. They have a similar structure, but they have different origins and perform almost identical functions.

Convergence is very close to parallelism - a form of evolution, when initially divergent groups develop in a similar way under the influence of identical conditions. Convergence and parallelism share a rather fine line, and it is often difficult to classify the evolution of a particular group of organisms in one form or another.

Biological progress

The main directions of evolution were first described in the works of A.N. Severtsova. He proposed to distinguish the concept of biological progress. In the works of the scientist, the ways of achieving it are described, as well as the main ways and directions of evolution. Ideas Severtsova developed II. Schmalhausen.

The main directions of the evolution of the organic world, singled out by scientists, are biological progress, regression and stabilization. By names it is easy to understand what these processes differ from each other. Progress leads to the formation of new signs that increase the degree of adaptation of the organism to the environment. Regress is expressed in the reduction in the size of the group and its diversity, resulting in the event of extinction. Stabilization entails securing the acquired features and transferring them from generation to generation in relatively unchanging conditions.

In a narrower sense, denoting the main directions of organic evolution, it means exactly biological progress and its forms.

There are three main ways to achieve biological progress:

• Arogenesis;
• Allogenez;
• Catagenesis.

Arogenesis

This process makes it possible to increase the overall level of organization as a result of the formation of aromorphosis. We suggest to find out what is meant by this concept. Thus, aromorphosis is the direction of evolution leading to a qualitative change in living organisms, accompanied by their complication and an increase in adaptive properties. As a result of the change in the structure, the functioning of individuals becomes more intensive, they are able to use new, previously unused resources. As a consequence, organisms become in some sense free from environmental conditions. At a higher level of organization, their adaptations are largely universal, giving the ability to develop independently of the surrounding conditions.

A good example of aromorphosis is the transformation of the circulatory system of vertebrates: the appearance of four chambers in the heart and the separation of two circles of blood circulation - large and small. The evolution of plants is characterized by a significant leap forward as a result of the formation of the pollen tube and seed. Aromorphosis leads to the emergence of new taxonomic units: classes, divisions, types and kingdoms.

Aromorphosis, according to Severtsov, is a relatively rare evolutionary phenomenon. It marks a morphophysiological progress, which, in turn, initiates general biological progress, accompanied by a significant expansion of the adaptive zone.

Social aromorphosis

Considering the directions of evolution of the human race, some scientists introduce the concept of "social aromorphosis". They denote universal changes in the development of social organisms and their systems, leading to complication, greater fitness and increased mutual influence of societies. Such aromorphoses include, for example, the appearance of the state, printing and computer technologies.

Allogenez

In the course of biological progress, changes of a less global nature are formed. They form the essence of allogenez. In this direction of evolution (the table is shown below) there is a significant difference from aromorphosis. It does not lead to an increase in the level of organization. The main consequence of allogenez is idioadaptation. In fact, it represents a particular change, thanks to which the body is able to adapt to certain conditions. This direction of the evolution of the organic world allows close species to live in very different geographical areas.

An expressive example of such a process is the family of wolves. Its species are found in a variety of climatic zones. Each has a certain set of adaptations to its habitat, while not significantly exceeding any other kind of organization level.

Scientists distinguish several types of idioadaptations:

• By shape (for example, streamlined body of waterfowl);
• In color (this includes mimicry, preventive and patronizing coloration) ;
• On reproduction;
• On movement (membranes of waterfowl, air bag of birds);
• Adaptation to environmental conditions.

Differences in aromorphosis and idioadaptation

Some scientists disagree with Severtsov and do not see sufficient reasons for distinguishing between idioadaptations and aromorphoses. They believe that the degree of progress can only be estimated after a considerable time after the appearance of the change. In fact, it is difficult to realize to what evolutionary processes a new quality or developed ability will lead.

The followers of Severtsov tend to think that under idioadaptation, one should understand the transformation of the body form, the excessive development or reduction of organs. Aromorphosis is a significant change in embryonic development and the formation of new structures.

Catagenesis

Biological evolution can also proceed with the simplification of the structure of organisms. Catagenesis is a general degeneration, a process leading to a decrease in the organization of living beings. The main result of this trend of evolution (the table comparing the three ways, is given below) consists in the appearance of so-called catamorphoses or primitive signs that replace the lost progressive ones. An example of organisms that have undergone a stage of general degeneration can be any parasite. For the most part, they lose the ability to move independently, they greatly simplify the nervous and circulatory system. But there are various adaptations for better introduction into the body of the host and fixation on suitable organs.

Ratio

The main directions of evolution are interrelated and in the course of historical development constantly replace each other. After cardinal changes in the form of aromorphosis or degeneration, a period begins when a new group of organisms begins to separate as a result of the development by separate parts of different geographical zones. The evolution begins with idioadaptations. After a while, the accumulated changes lead to a new qualitative leap.

The direction of the evolution of plants

Modern flora did not appear immediately. Like all organisms, it has passed a long way of becoming. The evolution of plants included the acquisition of several important aromorphoses. The first was the appearance of photosynthesis, which allowed primitive organisms to use the energy of sunlight. Gradually, as a result of morphological changes and photosynthetic properties, algae appeared.

The next stage was the development of land. For the successful passage of the "mission", another aromorphosis was needed - differentiation of tissues. There were mosses, spore plants. Further complication of the organization is associated with the transformation of the process and methods of reproduction. Such aromorphoses as ovules, pollen grains and, finally, seeds, characterize gymnosperms that are evolutionarily more developed than spore plants .

Further, the ways and directions of the evolution of plants moved towards an even greater adaptation of them to environmental conditions, an increase in resistance to unfavorable factors. As a result of the appearance of the pistil and the embryonic leaf, flowered or angiospermous plants were formed, which are now in a state of biological progress.

Animal Kingdom

Evolution of eukaryotes (the eukaryotic cell contains a formed nucleus) with a heterotrophic type of food (heterotrophs are not able to create organic chemo or photosynthesis) also in the first stages was accompanied by differentiation of tissues. The intestines have one of the first significant aromorphoses in the evolution of animals: the embryos form two layers, the ecto- and endoderm. In round and flat worms, the structure is already becoming more complicated. They are characterized by a third embryonic leaf, mesoderm. This aromorphosis makes possible further differentiation of tissues and the appearance of organs.

The next stage is the formation of the secondary cavity of the body and its further division into sections. Ringworms already have parapodia (primitive type of limbs), as well as the circulatory and respiratory systems. The transformation of parapodia into segmented limbs and some other changes has caused the appearance of the type of Arthropods. Already after their release on the dry land, insects began to develop actively due to the appearance of embryonic membranes. Today they are most adapted to life on earth.

Such large aromorphoses as the formation of a chord, a neural tube, an abdominal aorta, and a heart made possible the appearance of the Chordov type. Due to a number of progressive changes, a variety of living organisms has been replenished with fish, amniotes and reptiles. The latter, because of the presence of the embryonic membranes, ceased to depend on the water and left on land.

Further evolution follows the path of transformation of the circulatory system. There are warm-blooded animals. Adaptations to the flight made possible the appearance of birds. Such aromorphoses as a four-chambered heart and the disappearance of the right aortic arch, an increase in the cerebral hemispheres and development of the cortex, the formation of a wool cover and mammary glands, and a number of changes have led to the appearance of mammals. Among them, in the evolutionary process, placental animals were isolated, and today they are in a state of biological progress.

Directions of evolution of the human race

The question of the origin and evolution of the ancestors of modern people has not yet been studied thoroughly. Thanks to the discoveries of paleontology and comparative genetics, the already formed notions of our "genealogy" have changed. 15 years ago the point of view was dominated by the view that the evolution of hominids was linear, that is, consistently replacing each other with more and more developed forms: Australopithecus, man of skill, archanthropist, Neanderthal man (paleanthropic), neanthropus (modern man). The main directions of human evolution, as in the case with other organisms, led to the formation of new adaptations, an increase in the level of organization.

The data obtained in the last 10-15 years, however, made serious adjustments to the already existing picture. New findings and updated dating indicate that evolution was more complex. The subfamily Hominin (belongs to the Hominid family) turned out to consist of almost twice as many species as previously thought. Its evolution was not linear, but contained several simultaneously developing lines or branches, progressive and dead-end. At different times, three or four or more species co-existed together. The narrowing of this diversity was due to the displacement by evolutionarily more developed groups of others, less developed. For example, it is now generally accepted that Neanderthals and people of the modern type lived simultaneously. The first were not our ancestors, but represented a parallel branch, which was replaced by more developed representatives of hominins.

Progressive changes

The basic aromorphoses that led to the prosperity of the subfamily remain undoubted. This is the uprightness and increase of the brain. The reasons for the formation of the first scientists disagree. For a long time it was believed that this was a forced measure necessary for the development of open spaces. However, recent data suggest that the ancestors of people walked on two legs during the period of life on trees. This ability appeared in them immediately after separation from the chimpanzee line. According to one version, the hominins originally moved like modern orangutans, standing with two legs on one branch and holding hands for the other.

The growth of the brain took place in several stages. It first began with Homo habilis (a man of skill) who learned how to make the simplest tools. The growth of the volume of the brain coincided with the increase in the share of meat in the diet of hominins. Khabilisy, apparently, were scavengers. The next increase in the brain was also accompanied by an increase in the number of meat meals and the resettlement of our ancestors outside the native African continent. Scientists suggest that the increase in the share of meat in the diet is associated with the need to replenish the energy costs that go to support the work of the enlarged brain. Presumably, the next stage of this process coincided with the development of fire: cooked food differs not only in quality but also in calorie, in addition, the time required for chewing is significantly reduced.

The main directions of the evolution of the organic world, acting for many centuries, have formed a modern flora and fauna. The movement of the process towards adaptation to the changing environmental conditions has led to a huge variety of life forms. The main directions of evolution are the same at all levels of the organization, as evidenced by the data of biology, ecology and genetics.