Scheme of a regular change in the paths of evolution. Main types of evolutionary changes

The evolutionary form of groups of living organisms is divided into divergence, convergence, parallelism.

1. Divergence- divergence of characters within the species, which leads to the formation of new groupings of individuals. The more living organisms differ in structure, mode of existence, the more they diverge into more diverse spaces. Usually one area or area is occupied by animals with the same need for quality and food supply. After a certain time, when the food supply runs out, the animals are forced to change their habitat, move to new places. If animals with different needs for environmental conditions live in the same territory, then competition between them weakens. So, C. Darwin determined that in nature on a plot of 1 m2 there are up to 20 plant species belonging to 18 genera and 8 families. In the process of divergence, branches of a tree of several forms diverge from the nascent population. For example, we can name seven species of deer that formed as a result of divergence: sika deer, deer, reindeer, elk, roe deer, fallow deer, musk deer (Fig. 37).

Rice. 37. Variety of deer species resulting from divergence: 1 - sika deer; 2 - deer; 3 - fallow deer; 4 - reindeer; 5 - elk; 6" - roe deer; 7 - musk deer

Under the influence of natural selection in an endless series of generations, some forms survive, others die out. The processes of extinction and divergence are closely related. The most divergent forms have greater opportunities to leave fertile offspring and survive in the process of natural selection, since they compete less with each other than intermediate ones, which gradually thin out and die out.

As a result of divergence, a population of one species is subdivided into subspecies. A subspecies formed under the influence of natural selection, according to the signs of hereditary change, turns into a species.

2. Convergence- the acquisition of similar traits in different, unrelated groups. For example, sharks (class of fish), ichthyosaurs (class of reptiles), dolphins (class of mammals) have similar body shapes. This is due to the fact that they have the same habitat (water) and living conditions. Chameleon and climbing agama, belonging to different suborders, are outwardly very similar. The similarity of various systematic groups is due to life in a similar habitat. Airborne organisms have wings. The wings of a bird and a bat are modified forelimbs, and the wings of a butterfly are outgrowths of the body. The phenomenon of convergence is widespread in the animal kingdom.

3. Parallelism(Greek parallelos - "walking side by side") - the evolutionary development of genetically close groups, which consists in the independent acquisition of similar structural features by them on the basis of features inherited from common ancestors. Parallelism is widespread among various groups of organisms in the course of their historical development (phylogenesis).

For example, adaptation to an aquatic lifestyle in the evolution of pinnipeds developed in three directions. In cetaceans and pinnipeds (walruses, eared and real seals), as a result of the transition to an aquatic lifestyle, independently of each other, an adaptation to water appeared - flippers. The transformation of the front wings in many groups of winged insects into elytra, the development of signs of amphibians in lobe-finned fish, the appearance of signs of mammals in animal-toothed lizards, etc. The similarity in parallelism indicates the unity of the origin of organisms and the presence of similar conditions of existence.

Evolution is an irreversible process. In every organism adapted to new conditions, the altered organ disappears. Returning to its former habitat, the disappeared organ is not restored. Even Ch. Darwin wrote about the irreversibility of evolution: "Even if the habitat is completely repeated, then the species can never return to its previous state." For example, dolphins, whales never become fish. During the transition of terrestrial animals into the aquatic environment, the limbs change convergently - while convergence is involved only in changing the external structure of organs.

In the internal structure of the fins of a dolphin, a whale, signs of a five-fingered limb of mammals are preserved. Since the mutation leads to the renewal of the gene pool of the population, it never repeats the gene pool of the previous generation. So, if at some stage reptiles arose from primitive amphibians, then reptiles cannot again give rise to amphibians.

On the stem of an evergreen shrub - needles there are shiny thick leaves. In fact, these are modified branches. True scaly leaves are located in the central part of these modified stems. In early spring, flowers appear from the sinus of scales, from which fruits develop later.

The leaves of the butcher's needle disappeared in antiquity, in the process of adapting to drought. Then, when they returned to the aquatic environment, instead of leaves, they had branches that looked like leaves.

Heterogeneity of evolution. For hundreds of millions of years on Earth, they exist in an unchanged form. sabertail, lobe-finned fish, tuatara. They are called "living fossils". However, some plants and animals change rapidly. For example, in the Philippines and Australia, several new genera of rodents appeared over 800 thousand years. In approximately 20 million years, 240 species of crayfish belonging to 34 new genera arose in Baikal. The pace of evolution is not determined by astronomical time. The emergence of a new species is determined by the required number of generations and fitness.

The rate of evolution decreases and slows down in the same stable environmental conditions (deep oceans, cave waters). On islands where there are few predators, natural selection is very slow. Conversely, where there is intense selection, evolution also proceeds faster. For example, in the 1930s a poisonous drug (DDT) was used against pests. Within a few years, drug-resistant forms appeared and quickly spread on Earth. The widespread use of antibiotics - penicillin, streptomycin, gramicidin - in the 40-50s of the XX century. led to the emergence of resistant forms of microorganisms.

Divergence. Convergence. Parallelism. irreversible process. "Living Fossils".

1. Evolutionary forms of groups of living organisms: divergence, convergence, parallelism.

2. Evolution is an irreversible process, that is, an extinct species or organ can never return to its previous state.

3. The pace of evolution is changing.

1. Explain the process of divergence with an example.

2. Describe the convergence, analyze it with an example.

1. Explain the irreversibility of evolution on the examples of plants.

2. What is the reason for the disappearance of some forms acquired during the divergence?

1. Prove the heterogeneity of evolution using an example.

2. Analyze divergence, convergence, parallelism using a diagram or table.

The main laws of the evolutionary process include divergence, convergence and parallelism.

Darwin also formulated the PRINCIPLE OF DIFFERENCE OF SIGNS.

DIFFERENCE OF SIGNS IN RELATED FORMS IS CALLED DIVERGENCE. In the process of divergence, a number of forms originate from one initial population, forming, as it were, branches of a single tree. In an endless series of generations, some branches die off, others develop. Forms that are most divergent in their requirements for environmental conditions are more likely to survive in the course of natural selection, since they compete less with each other than ancestral or intermediate groups. As a result of divergence, subspecies are formed, and then species.

Another phenomenon is also observed in evolution - CONVERGENCE - THE PROCESS OF INDEPENDENT ACQUISITION OF SIMILAR FEATURES BY UNRELATED GROUPS OF ORGANISMS. For example, the body shape of fish and dolphins. This similarity is due to the common habitat (sea) and lifestyle.

In addition to divergence and convergence, there is PARALLELISM in nature, IN WHICH INDEPENDENT ACQUISITION OF SIMILAR FEATURES BY RELATED ORGANISMS IS OBSERVED. In this case, we are talking about a common origin and adaptations to the same habitat. For example, fur seal, walrus, seal. The observed differences formed at the beginning of the speciation process.

What are the general features of the evolutionary process? FIRST OF ALL, THIS IS THE APPEARANCE OF THE "PURPOSE" OF ORGANISMS, I.E. THEIR SUITABILITY TO HABITAT AND THEIR CAPABILITY TO CHANGE AS THESE CONDITIONS CHANGE. SECONDLY, THIS IS A SPECIFICATION PROCESS. THIRD, CONSTANT COMPLICATION OF LIFE FROM PRIMITIVE PRE-CELLULAR FORMS TO HUMANS.

In the entire history of the existence of life on Earth, about 500 million species lived. Today there are about 2 million of them. This shows that the perfection of modern forms is the result of

evolution, during which hundreds of millions of species perished. Evolutionary transformations are irreversible, any simplification or deviation in the organization leads ultimately to regression and extinction.

In a world threatened by human destruction, it is important to understand as quickly as possible how species interact with each other and how they respond to the changes we create, because this is the only way to avoid irreversible ecological changes.

Summing up, we can say about the RULES OF EVOLUTION. There are three of them.

RULE OF IRREVERSIBILITY OF EVOLUTION. Evolution is an irreversible process. A group of organisms cannot return to the previous state already realized in the series of their ancestors. Since in the evolution of vertebrates at some stage reptiles arose from primitive amphibians, they will never give rise to amphibians. Back in the ocean, reptiles (ichthyosaurs) and mammals (whales) did not become fish.

Even a reverse mutation that leads to the reappearance of a given gene for a specific trait does not lead to a repetition of the entire genotype as a whole.

RULE OF PROGRESSIVE SPECIALIZATION. A group that has embarked on the path of specialization, as a rule, will continue to follow the path of ALL DEEPER ADJUSTMENT TO THE NARROW CONDITIONS OF EXISTENCE. If in the process of evolution one of the groups of vertebrates acquired adaptations to flight, then at the subsequent stage of evolution this direction is preserved and strengthened. An organism of a certain structure cannot live in any environment. In choosing an adaptive zone or part of it, the group is limited by the features of its structure.

RULE OF ALTERNATION OF THE MAIN DIRECTIONS OF EVOLUTION. When considering the main directions in the evolution of groups of aromorphoses and idioadaptations, the regular alternation of these types of development in evolution was emphasized.

THEREFORE, EVOLUTION IS A CONTINUOUS PROCESS OF THE ORIGIN AND DEVELOPMENT OF NEW ADAPTATIONS. ONE OF THE NEVER EMERGING ADAPTATIONS TURN OUT TO BE VERY SPECIAL AND THEIR SIGNIFICANCE DOES NOT GO BEYOND NARROW CONDITIONS. OTHER GIVE AN OPPORTUNITY FOR A GROUP TO ENTER A NEW ENVIRONMENT AND NEEDLY LEAD TO A FASTER EVOLUTIONARY DEVELOPMENT OF GROUPS IN A NEW DIRECTION, TO A HIGHER ORGANIZATION.

In addition, there are five basic patterns of evolution recognized by almost all scientists:

1. Evolution occurs at different rates in different periods. At present, it is proceeding rapidly, which is expressed in the appearance of many new forms and the extinction of many old ones.

2. The evolution of organisms of different types occurs at different rates. At one extreme are the brachiopods: some of their species have not changed at all for at least the last 500 million years - the shells of fossil brachiopods found in ancient rocks are completely identical to the shells of modern species. The other pole is occupied by man: over the past few hundred thousand years, several species of hominids have appeared and died out. In general, evolution proceeds faster at the first appearance of a new species, and then, as the group stabilizes, it gradually slows down.

3. New species are formed not from the most highly developed and specialized forms, but, on the contrary, from relatively simple, non-specialized forms. Thus, for example, mammals did not originate from large specialized dinosaurs, but from a group of relatively small non-specialized reptiles.

5. Evolution affects populations, not individuals, and occurs as a result of the processes of mutation, differential reproduction, natural selection and genetic drift.

From this lesson, you will learn how macroevolution differs from microevolution, get acquainted with the phenomenon of parallelism, find out what divergence and convergence are, which organs are called similar and which are homologous. What do a man's hand, a bat's wing, a walrus' flippers, and a horse's hoof have in common? How are the eyes of mollusks and insects different from our eyes? What is phylogenesis and how is it related to our individual development - otnogenesis? Is evolution reversible? Why are shark, tuna, ichthyosaur, dolphin and swimming penguin body shapes so similar?

The largest regularities that are observed within the framework of macroevolution were studied and described in the 19th and 20th centuries.

Elements of macroevolution:

1. feature convergence
2. Feature Divergence
3. Parallelism

Divergence- this is the accumulation of differences in the structure and functions of an organ in the process of evolution. As a result of divergence from one organ, several different organs are formed, connected by a common origin.

For example, the upper limbs of vertebrates evolved into the paws and wings of reptiles, the wings of bats and birds, the fins of dolphins, the legs of ungulates, and the arms of primates.

All these organs perform different functions, but have the same origin.

Rice. 1. Homological organs of vertebrates

The organs formed as a result of divergence are called homologous(Fig. 1). They are formed from similar embryonic rudiments.

Divergence ensures the morphological diversity of living beings.

Convergence is a process inverse to divergence. This is the formation of organs that are similar in function and structure, but differ in origin.

Rice. 2. Similar organs: bird and butterfly wings

But, in fact, they developed quite independently from various ancestral forms. The requirement of the environment and the influence of natural selection determined their external similarity.

Organs that perform the same functions but have different origins are called similar(Fig. 3).

A typical example of similar organs is the eyes of cephalopods and vertebrates. These organs formed independently over hundreds of millions of years, and in the end they turned out to be almost the same, differing only in details.

Rice. 3. Similar organs: the eyes of a mollusk (octopus or squid) and humans

The third element in the transformation process is a cross between divergence and convergence, parallelism- such a process when an organ, as a result of divergence, turns into many homologous organs. But then, in the course of evolution, these homologous organs again begin to perform a common function.

For example, the body and shoulder girdle in vertebrates have given rise to many homologous variants. Ungulates, birds, fish, reptiles were formed from the same elements of the skeleton, but then, in the process of evolution, some of them again acquired the same features (Fig. 4).

Rice. 4. An example of parallelism in the evolution of body shape in cartilaginous fish (shark), reptiles (ichthyosaur) and a mammal (dolphin)

For example, the bodies of an ichthyosaur, a shark and a dolphin (and even a penguin swimming in the water) are very similar and formed from the same skeletal elements, but in completely different evolutionary ways.

The ancestors of ichthyosaurs were lizards, the ancestors of dolphins were herbivorous land mammals, the penguins were birds, and the ancestors of sharks were ancient cartilaginous fish.

Evolution follows three main paths: by divergence, by convergence and by parallelism.

The process of historical development of a species is called phylogenesis.

An important step in understanding evolution was the formulation of " basic phylogenetic law» Ernest Haeckel.

"Ontogeny is an accelerated repetition of phylogenesis" E.G. Haeckel.

Haeckel clearly demonstrated that organisms in the process of embryonic development repeat all the stages that the species went through in the process of evolutionary development (see video). It is important to understand that we are talking about the repetition of the germinal stages of ancestral forms.

In the human embryo at different stages of development of ontogenesis, one can see gills, a heart tube and other signs of embryos of our distant ancestors.

Another important law of phylogeny is "the law of irreversibility of evolution". Despite the presence of convergence, the similarities of different species are never complete.

The evolutionary process, due to the extreme complexity of living organisms, cannot create an exact copy of either an existing species or an extinct one. Each type of living organism is unique.

So, we have learned that as a result of evolution, homologous organs can be formed by divergence, and similar organs can be formed by convergence. Found out that ontogenesis repeats the stages of phylogenesis and that each species of living organisms is unique.

Bibliography

1. A.A. Kamensky, E.A. Kriksunov, V.V. Beekeeper. General biology, grades 10-11. - M.: Bustard, 2005. Download the textbook from the link: ( )
2. D.K. Belyaev. Biology 10-11 class. General biology. A basic level of. - 11th edition, stereotypical. - M.: Education, 2012. - 304 p. ()
3. V.B. Zakharov, S.G. Mamontov, N.I. Sonin, E.T. Zakharov. Biology grade 11. General biology. profile level. - 5th edition, stereotypical. - M.: Bustard, 2010. - 388 p. ()
4. IN AND. Sivoglazov, I.B. Agafonova, E.T. Zakharov. Biology 10-11 class. General biology. A basic level of. - 6th edition, updated. - M.: Bustard, 2010. - 384 p. ()

Homework

1. What is evolution? How is macroevolution different from microevolution?
2. What consequences of macroevolution do you know?
3. What organs are called homologous? Give examples.
4. What organs are called similar? Give examples.
5. What is parallelism?
6. Using the example of the human body, discuss with friends and family the phenomena of homology, analogy, and parallelism.

1. Biological dictionary ().
2. All biology ().
3. Internet portal Bio.fizteh.ru ().
4. Biology ().
5. Internet portal Sochineniya-referati.ru ().

Question 1. What are the main types of evolutionary changes.

Scientists distinguish the following types of evolutionary changes: parallelism, convergence and divergence.

Question 2. What are parallel changes, convergent, divergent?

Parallel changes (parallelism) are the evolutionary development of related species, often having a common ancestor, caused by adaptation to similar habitat conditions.

With convergent changes (convergence), two or more species that are not closely related become more and more similar to each other. This type of evolutionary change is the result of adaptations to similar environmental conditions.

Divergent changes (divergence) are usually presented as an evolutionary tree with divergent branches: a common ancestor gave rise to two or more forms, which, in turn, became the ancestors of many species and genera. Divergence almost always reflects the expansion of adaptation to new living conditions.

Question 3. What is the difference between homologous structures and similar ones?

With parallel and convergent evolution, the similarity of the external structure can be the result of homology - origin from a common ancestor (an example is the limbs of different groups of vertebrates) or analogy - the independent evolution of those organ systems that perform similar functions (for example, wings in birds and insects).

Homologous structures already in the embryonic period develop according to the same genetic programs. Similar structures perform the same functions, but do not have a common genetic basis.

Question 4. What are the main lines of evolution?

There are three main lines of evolution. material from the site

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When constructing phylogenetic series, evolutionary biologists, in addition to paleontological data, widely use the comparative method, with the help of which they establish similarities in the structure of organisms, their biochemical reactions, reproduction characteristics, or other properties that can be used to judge the developmental paths of a group from a common ancestor.

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