Questions of the origin of life and its development have puzzled scientists since ancient times. People have always sought to get closer to these mysteries, thus making the world 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 place of honor as the main and most probable version of the development of all life on our planet relatively recently. Its main provisions were formulated by Charles Darwin in the middle of the 19th 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 Darwin's teachings, to expand it, to combine it with new data. This is how the synthetic theory of evolution appeared. She 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 the historical development of organisms based on the unique processes of the functioning of genetic information incertain environmental conditions.
The initial stage of all transformations, eventually leading to the emergence of a new species, is microevolution. Such changes accumulate over time and end with the formation of a new higher level of organization of living beings: 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, variability. The essential difference between the two processes is that crossing between different species is practically excluded. 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 lines of evolution can take several forms. A powerful source of diversity in life is the divergence of features. It operates both within a particular species and at higher levels of organization. Environmental conditions and natural selection lead to the division of one group into two or more, differing in certain characteristics. At the species level, divergence can be reversible. In this case, the resulting populations again merge into one. At higher levels, the process is irreversible.
Another form is phyletic evolution, which involves the transformation of a species without separating individualpopulations. Each new group is a descendant of the previous one and an ancestor of the next one.
Convergence or “convergence” of signs also makes a significant contribution to the diversity of life. 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 different origins and perform almost the same functions.
Parallelism is very close to convergence - a form of evolution when initially divergent groups develop in a similar way under the influence of the same conditions. There is a fine line between convergence and parallelism, and it is often difficult to attribute the evolution of a particular group of organisms to one form or another.
Biological progress
The main directions of evolution were first described in the works of A. N. Severtsov. He suggested highlighting the concept of biological progress. The works of the scientist outline the ways to achieve it, as well as the main ways and directions of evolution. Severtsov's ideas 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. By name, it is easy to understand how these processes differ from each other. Progress leads to the formation of new features that increase the degree of adaptation of the organism to the environment. Regression is expressed in a reduction in the size of the group and its diversity, eventually leading to extinction. Stabilization entails the consolidation of acquired characteristics and their transmission from generation togeneration under relatively unchanged conditions.
In a narrower sense, denoting the main directions of organic evolution, they mean precisely 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 propose to clarify 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 an increase in adaptive properties. As a result of a change in the structure, the functioning of individuals becomes more intense, they get the opportunity to use new, previously unused resources. As a consequence, organisms become, in a sense, free from environmental conditions. At a higher level of organization, their adaptations are largely universal in nature, giving the ability to develop regardless 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 the pollen tube and the seed. Aromorphoses lead to the emergence of new taxonomic units: classes, departments, types and kingdoms.
Aromorphosis, according to Severtsov, is a relatively rare evolutionaryphenomenon. It marks a morphophysiological progress, which, in turn, initiates a general biological progress, accompanied by a significant expansion of the adaptive zone.
Social aromorphosis
Considering the direction of evolution of the human race, some scientists introduce the concept of "social aromorphosis". It denotes universal changes in the development of social organisms and their systems, leading to complication, greater adaptability and an increase in the mutual influence of societies. Such aromorphoses include, for example, the emergence of the state, printing and computer technology.
Allogenesis
In the course of biological progress, changes of a less global nature are also formed. 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 private change, thanks to which the body is able to adapt to certain conditions. This direction of evolution of the organic world allows closely related species to live in very different geographical areas.
An expressive 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 habitat, while not significantly superior to any other species in terms of organization.
Scientists identify several types of idioadaptations:
- in shape (for example, a streamlined bodywaterfowl);
- by color (this includes mimicry, warning and protective coloration);
- for reproduction;
- for locomotion (waterfowl membranes, air sac of birds);
- adaptation to environmental conditions.
Differences between aromorphosis and idioadaptation
Some scientists do not agree with Severtsov and do not see sufficient reasons to distinguish between idioadaptations and aromorphoses. They believe that the extent of progress can only be assessed after a significant amount of time has passed since the change has occurred. In fact, it is difficult to realize what evolutionary processes a new quality or developed ability will lead to.
Severtsov's followers tend to think that idioadaptation should be understood as a transformation of the body shape, 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 beings. The main result of this line of evolution (a table comparing the three paths is given below) is the appearance of so-called catamorphoses or primitive signs 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 system is greatly simplified.and circulatory systems. But various adaptations appear for better penetration into the host's body and fixation on suitable organs.
| Arogenesis | Allogenesis | Catagenesis | |
| Major change | aromorphosis | idioadaptation | catamorphosis |
| Essence of direction |
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Ratio
The main directions of evolution are interconnected and constantly replace each other in the course of historical development. 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 by its individual parts of different geographical zones. Evolution begins through idioadaptation. After a while, the accumulated changes lead to a new qualitative leap.
Direction of plant evolution
Modern flora did not appear immediately. Like all organisms, it has come a long way of becoming. Plant evolution has included the acquisition of several important aromorphoses. The first of these was the advent of photosynthesis, which allowed primitive organisms to use the energy of sunlight. Gradually, as a result of transformations in morphology and photosynthetic properties, algae arose.
The next step was the development of land. For the successful completion of the “mission”, one more aromorphosis was needed - differentiation of tissues. Mosses and spore plants appeared. Further complication of the organization is associated with the transformation of the process and methods of reproduction. Such aromorphoses as the ovule, pollen grains and, finally, the seed characterize gymnosperms, which are evolutionarily more developed than spores.
Further, the paths and directions of plant evolution moved towards even greater adaptation to environmental conditions, increasing resistance to adverse factors. As a result of the appearance of the pistil and germ layer, flowering orangiosperms that are in a state of biological progress today.
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 organic matter using chemo- or photosynthesis) was also accompanied by tissue differentiation at the first stages. Coelenterates have one of the first significant aromorphoses in the evolution of animals: two layers are formed in the embryos, ecto- and endoderm. In roundworms and flatworms, the structure is already becoming more complex. They have a third germ layer, the mesoderm. This aromorphosis allows further differentiation of tissues and the emergence of organs.
The next stage is the formation of a secondary body cavity and its further division into sections. Annelids already have parapodia (a primitive type of limbs), as well as circulatory and respiratory systems. The transformation of parapodia into jointed limbs and some other changes caused the appearance of the Arthropod type. Already after they landed, insects began to actively develop due to the appearance of embryonic membranes. Today they are most adapted to life on earth.
Such major aromorphoses as the formation of the notochord, neural tube, abdominal aorta and heart made possible the appearance of the Chordata type. Thanks to a series of progressive changes, the diversity of living organisms was replenished with fish, amniotes and reptiles. The latter, due to the presence of embryonic membranes, ceased to depend on water and came to land.
Nextevolution follows the path of transformation of the circulatory system. There are warm-blooded animals. Adaptations to flight made the emergence of birds possible. Such aromorphoses as a four-chambered heart and the disappearance of the right aortic arch, an increase in the forebrain hemispheres and the development of the cortex, the formation of a coat and mammary glands, and a number of other changes led to the appearance of mammals. Among them, in the process of evolution, placental animals stood out, and today they 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 studied thoroughly. Thanks to the discoveries of paleontology and comparative genetics, the already established ideas about our “pedigree” have changed. Even 15 years ago, the point of view prevailed that the evolution of hominids followed a linear type, that is, it consisted of successively replacing each other more and more developed forms: Australopithecus, a skilled man, archanthrope, Neanderthal man (paleoanthropist), neoanthrope (modern man). The main directions of human evolution, as in the case of other organisms, led to the formation of new adaptations, an increase in the level of organization.
Data obtained in the last 10-15 years, however, have made serious adjustments to the already existing picture. New finds and updated dating indicate that evolution was more complex. The Hominina subfamily (belongs to the Hominid family) turned out to consist of almost twice as many species aswas considered earlier. Its evolution was not linear, but contained several simultaneously developing lines or branches, progressive and dead ends. At different times, three or four or more species coexisted together. The narrowing of this diversity occurred due to the displacement by evolutionarily more developed groups of other, less developed ones. For example, it is now generally accepted that Neanderthals and modern humans lived at the same time. The former were not our ancestors, but were a parallel branch that was supplanted by more advanced hominins.
Progressive changes
The main aromorphoses that led to the prosperity of the subfamily remain undoubted. This is bipedalism 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 forced measure necessary for the development of open spaces. However, recent data suggest that the ancestors of people walked on two legs even during their life on trees. This ability appeared in them immediately after the separation from the chimpanzee line. According to one version, hominins originally moved like modern orangutans, standing with both feet on one branch and holding hands on another.
The growth of the brain took place in several stages. It first began with Homo habilis (handy 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 appear to have been scavengers. The next increase in the brain was also accompanied by an increase in the amount of meat food andresettlement of our ancestors outside the native African continent. Scientists suggest that the increase in the proportion of meat in the diet is associated with the need to replenish the energy spent on maintaining 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 content, in addition, the time required for chewing is significantly reduced.
The main directions of the evolution of the organic world, acting over many centuries, formed the modern flora and fauna. The movement of the process towards adaptation to changing environmental conditions has led to a huge variety of life forms. The main directions of evolution operate in the same way at all levels of organization, as evidenced by the data of biology, ecology and genetics.
