The main directions of evolution. The evolution of plants and animals

The questions of the origin of life and its development from ancient times have puzzled scientists. People have always sought to approach these secrets, making the world thus more understandable and predictable. For many centuries, the point of view of the divine principle of the Universe and life prevailed. The theory of evolution has won a place of honor of the main and most probable version of the development of all living things on our planet relatively recently. Its main provisions were formulated by Charles Darwin in the middle of the XIX century. The century that followed gave the world a lot of discoveries in the field of genetics and biology, which made it possible to prove the validity of the teachings of Darwin, expand it, combine it with new data. So there was a synthetic theory of evolution. She has incorporated 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 the historical development of organisms based on unique processes of the functioning of genetic information in certain environmental conditions.

The initial stage of all transformations, eventually leading to the emergence of a new species, is microevolution. Such changes over time accumulate and end with the formation of a new higher level of organization of living creatures: genus, family, class. The formation of supraspecific structures is commonly called macroevolution.

Similar processes

Both levels are basically the same. The driving forces of both micro- and macro-changes are natural selection, isolation, heredity, and variability. A significant difference between the two processes is that crossing between different species is practically impossible. 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 the same species.

Convergence and divergence of signs

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

Another form is phyletic evolution, which involves the transformation of a species without isolating individual populations within it. Each new group is a descendant of the previous and ancestor for the next.

A significant contribution to the diversity of life is made by the convergence or “convergence” of signs. In the process of development of unrelated groups of organisms under the influence of the same environmental conditions, similar organs are formed in individuals. They have a similar structure, but of different origin and perform almost the same functions.

Convergence is very close to parallelism - a form of evolution when initially diverging groups develop in a similar way under the influence of the same conditions. A rather fine line separates convergence and parallelism, and it is often difficult to attribute the evolution of a specific group of organisms to one form or another.

Biological progress

The main directions of evolution were first described in the works of A.N. Severtsova. He suggested highlighting the concept of biological progress. The scientist’s work outlines ways to achieve it, as well as the main paths and directions of evolution. The ideas of Severtsov were developed by I.I. Schmalhausen.

The main directions of the evolution of the organic world, identified by scientists, are biological progress, regression and stabilization. From the names it is easy to understand how 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. The regression is expressed in a reduction in the size of the group and its diversity, leading ultimately to extinction. Stabilization entails the consolidation of acquired characteristics and their transmission from generation to generation in relatively constant conditions.

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

There are three main ways to achieve biological progress:

• arogenesis;
• allogenesis;
• catagenesis.

Arogenesis

This process makes it possible to increase the overall level of organization as a result of the formation of aromorphosis. We offer to find out what is meant by this concept. So, aromorphosis is a direction of evolution leading to a qualitative change in living organisms, accompanied by their complication and increase in adaptive properties. As a result of structural changes, the functioning of individuals becomes more intense; they are given the opportunity to use new, previously unused resources. As a result, organisms in a sense become free from environmental conditions. At a higher level of organization, their adaptations are largely universal in nature, giving the ability to develop independently of environmental 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. Plant evolution is characterized by a significant leap forward as a result of the formation of a pollen tube and seed. Aromorphoses lead to the emergence of new taxonomic units: classes, departments, 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”. He identifies 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 advent of the state, typography, and computer technology.

Allogenesis

In the course of biological progress, less global changes are also forming. They are the essence of allogenesis. This direction of evolution (table below) has a significant difference from aromorphosis. It does not lead to an increase in the level of organization. The main consequence of allogenesis is idioadaptation. In fact, it is 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.

A striking example of such a process is the wolf family. Its species are found in various climatic zones. Each has a certain set of adaptations to its environment, while not significantly exceeding any other species in terms of organization.

Scientists distinguish several types of idioadaptations:

• in shape (for example, the streamlined body of waterfowl);
• by coloring (this includes mimicry, preventive and protective coloring) ;
• by reproduction;
• on movement (membranes of waterfowl, air sac of birds);
• adaptation to environmental conditions.

Differences aromorphosis and idioadaptation

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

Severtsov’s followers are inclined to the idea that idioadaptation should be understood as a transformation of the shape of the body, excessive development or reduction of organs. Aromorphoses are significant changes in embryonic development and the formation of new structures.

Catagenesis

Biological evolution can 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 things. The main result of this direction of evolution (a table comparing the three paths is given below) is the appearance of the so-called catamorphoses or primitive traits that replace the lost progressive ones. An example of organisms that have passed the stage of general degeneration can be any parasite. For the most part, they lose the ability to move independently; their nervous and circulatory systems are greatly simplified. But there are various devices for better penetration into the host’s body and fixing on suitable organs.

Ratio

The main directions of evolution are interconnected and in the course of historical development constantly replace each other. After cardinal transformations in the form of aromorphosis or degeneration, a period begins when a new group of organisms begins to stratify as a result of the development of its individual parts of different geographical zones. Evolution begins by idioadaptations. Over time, the accumulated changes lead to a new qualitative leap.

The direction of plant evolution

Modern flora did not appear immediately. Like all organisms, she has come a long way. Plant evolution included the acquisition of several important aromorphoses. The first of these was the emergence of photosynthesis, which allowed primitive organisms to use the energy of sunlight. Gradually, algae arose as a result of morphological and photosynthetic transformations.

The next step was the development of land. For the successful completion of the “mission”, another aromorphosis was required - tissue differentiation. Mosses, spore plants appeared. A further complication of the organization is associated with the transformation of the process and methods of reproduction. Aromorphoses such as ovule, pollen grains and, finally, seed characterize gymnosperms, which are evolutionarily more developed than spore plants .

Further, the paths and directions of plant evolution moved towards their greater adaptation to environmental conditions, increasing resistance to adverse factors. As a result of the appearance of the pestle and the germinal leaf, flowering or angiosperms were formed, which are now in a state of biological progress.

Animal kingdom

The evolution of eukaryotes (a eukaryotic cell contains a formed nucleus) with a heterotrophic type of nutrition (heterotrophs are not able to create organics through chemo- or photosynthesis) was also accompanied by tissue differentiation in the early stages. Intestinal have one of the first significant aromorphoses in the evolution of animals: two layers, the ecto- and endoderm, form in the embryos. In round and flat worms, the structure is already becoming more complicated. They are characterized by a third germinal leaf, mesoderm. This aromorphosis makes possible the 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 departments. Ringworms already have parapodia (a primitive type of limbs), as well as the circulatory and respiratory systems. The transformation of parapodia into jointed limbs and some other changes caused the appearance of the Arthropod type. After they reached land, insects began to actively develop due to the appearance of germinal membranes. Today they are most adapted to life on earth.

Large aromorphoses such as the formation of a chord, neural tube, abdominal aorta, and heart have made possible the emergence of the Chordate type. Thanks to a number of progressive changes, the diversity of living organisms has replenished with fish, amniotes and reptiles. The latter, due to the presence of germinal membranes, ceased to depend on water and entered land.

Further, evolution follows the path of transformation of the circulatory system. Warm-blooded animals arise. Adaptations to flight made the appearance of birds possible. Aromorphoses such as a four-chamber heart and the disappearance of the right aortic arch, an increase in the hemispheres of the forebrain and the development of the cortex, the formation of wool and mammary glands, and a number of changes led to the appearance of mammals. Among them, in the process of evolution, placental animals stood out, and today are in a state of biological progress.

Directions of the evolution of the human race

The question of the origin and evolution of the ancestors of modern people has not yet been thoroughly studied. Thanks to the discoveries of paleontology and comparative genetics, the already existing ideas about our “genealogy” have changed. Just 15 years ago, the prevailing point was that the evolution of hominids went on a linear type, that is, consisted of successively more developed forms: Australopithecus, skilled man, archanthropist, Neanderthal man (paleoanthropus), neoanthropus (modern man). The main directions of human evolution, as in the case of other organisms, led to the formation of new adaptations and an increase in the level of organization.

The data obtained in the last 10-15 years, however, have made serious adjustments to the already existing picture. New findings and more accurate dating indicate that evolution was more complex. The hominin subfamily (belongs to the hominid family) turned out to consist of almost twice as many species than 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 coexisted together. The narrowing of this diversity occurred due to the crowding out of the evolutionarily more developed groups of other, less developed. For example, it is now generally accepted that Neanderthals and people of the modern type lived at the same time. The former were not our ancestors, but represented a parallel branch, which was supplanted by more developed representatives of hominins.

Progressive changes

The main aromorphoses that led to the prosperity of the subfamily remain undoubted. This is upright posture and an increase in the brain. Scientists disagree about the reasons for the formation of the first. For a long time it was believed that this was a necessary 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 in the trees. This ability appeared in them immediately after separation from the chimpanzee line. According to one version, hominins initially moved like modern orangutans, standing with two legs on one branch and holding hands on the other.

Brain growth took place in several stages. It began for the first time with Homo habilis (a skilled man), who learned how to make the simplest tools. The increase in brain volume coincided with an increase in the proportion of meat in the diet of hominins. The habilis were apparently scavengers. The next increase in the brain was also accompanied by an increase in the amount of meat food and the spread of our ancestors beyond the borders of our native African continent.Scientists suggest that the increase in the proportion of meat in the diet is associated with the need to compensate for the energy spent on maintaining the work of an enlarged brain. Presumably, the next stage of this process coincided with the development of fire: cooked food is not only quality but also caloric, in addition, significantly reduces the time required for chewing.

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