Directions and paths of plant evolution. The main paths of plant evolution

Evolution of plants

The first living organisms arose approximately 3.5 billion years ago. They apparently ate food abiogenic origin and were heterotrophs. High speed reproduction led to the emergence of competition for food, and consequently to divergence. Organisms capable of autotrophic nutrition received an advantage - first chemosynthesis, and then photosynthesis. About 1 billion years ago, eukaryotes split into several branches, from some of which multicellular photosynthetic organisms (green, brown and red algae), as well as fungi, arose.

Basic conditions and stages of plant evolution:

• in the Proterozoic era, unicellular aerobic organisms (cyanobacteria and green algae) were widespread;
• formation of soil substrate on land at the end of the Silurian period;
• the emergence of multicellularity, which makes possible the specialization of cells within one organism;
• development of land by psilophytes;
• a whole group arose from psilophytes in the Devonian period land plants- mosses, mosses, horsetails, ferns that reproduce by spores;
• Gymnosperms evolved from seed ferns in the Devonian. The structures that emerged necessary for seed reproduction (for example, a pollen tube) freed the sexual process in plants from dependence on the aquatic environment. Evolution followed the path of reduction of the haploid gametophyte and the predominance of the diploid sporophyte;
• The Carboniferous period of the Paleozoic era is characterized by a wide variety of terrestrial vegetation. Tree ferns spread, forming coal forests;
• During the Permian period, ancient gymnosperms became the dominant group of plants. Due to the emergence of an arid climate, giant ferns and tree mosses disappear;
• V Cretaceous period The heyday of angiosperms begins, continuing to this day.

Main features of evolution flora:

1. transition to the predominance of the diploid generation over the haploid;
2. development of the female shoot on the mother plant;
3. transition from sperm to injection of the male nucleus through the pollen tube;
4. division of the plant body into organs, development of conductive vascular system, supporting and protective fabrics;
5. improvement of reproductive organs and cross-pollination in flowering plants in connection with the evolution of insects;
6. development of the seed to protect the embryo from adverse influences external environment;
7. the emergence of various methods of dispersal of seeds and fruits.

Animal evolution

The oldest traces of animals date back to the Precambrian (over 800 million years). It is assumed that they originated either from the common stem of eukaryotes or from unicellular algae, confirmation of which is the existence of Euglena green and Volvox, capable of both autotrophic and heterotrophic nutrition.

In the Cambrian and Ordovician periods, sponges, coelenterates, worms, echinoderms, trilobites predominated, and mollusks appeared.

In the Ordovician, jawless fish-like organisms appeared, and in the Silurian, fish with jaws appeared. The first gnathostomes gave rise to ray-finned and lobe-finned fish. Lobe-finned animals had supporting elements in their fins, from which the limbs of terrestrial vertebrates later developed. From this group of fish amphibians and then other classes of vertebrates arose.

The most ancient amphibians are Ichthyostegas, who lived in the Devonian. Amphibians flourished in the Carboniferous.

The reptiles that conquered land in the Permian period originated from amphibians, thanks to the appearance of a mechanism for sucking air into the lungs, the refusal of skin respiration, the appearance of horny scales and egg shells covering the body, protecting embryos from drying out and other environmental influences. Among the reptiles, a group of dinosaurs presumably stood out, giving rise to birds.

The first mammals appeared in the Triassic period of the Mesozoic era. Basic progressive biological features mammals - feeding their young with milk, warm-bloodedness, developed cerebral cortex.

Features of the evolution of the animal world:

1. progressive development of multicellularity and, as a consequence, specialization of tissues and all organ systems;
2. a freely mobile lifestyle, which determined the development of various behavioral mechanisms, as well as the relative independence of ontogenesis from fluctuations in environmental factors. The mechanisms of internal self-regulation of the body developed and improved;
3. the appearance of a hard skeleton: external in a number of invertebrates - echinoderms, arthropods; internal in vertebrates. The advantages of the internal skeleton are that it does not limit the increase in body size.

Progressive development nervous system became the basis for the emergence of the system conditioned reflexes and improving behavior.

The evolution of animals led to the development of group adaptive behavior, which became the basis for the emergence of humans.

The main stages and directions of the evolution of the plant world. Until the end of the Silurian period, plants were represented by multicellular algae, which either floated in water or led an attached lifestyle. Multicellular algae were the original branch for terrestrial leafy plants. At the end of the Silurian period of the Paleozoic era, due to intensive mountain-building processes and a reduction in the area of ​​seas, some of the algae, finding themselves in new environmental conditions (in small reservoirs and on land), died. The other part, as a result of multidirectional variability and adaptation to terrestrial environment acquired characteristics that contributed to survival in new conditions. Such signs in the first land plants - rhiniophytes - are the differentiation of tissues into integumentary, mechanical and conductive ones and the presence of a shell in spores. The emergence of plants onto land was prepared by the activity of bacteria and cyanobacteria, which, when interacting with minerals, formed a soil substrate on the land surface.

In the Devonian period, rhyniophytes were replaced by mosses, horsetails and ferns, which also reproduced by spores and preferred a moist environment. Their appearance was accompanied by the emergence of vegetative organs, which increased the efficiency of the functioning of individual parts of plants and ensured their activity as an integral system.

In the Carboniferous period (Carboniferous), the first gymnosperms appeared, arising from ancient seed ferns. The emergence of seed plants was of great importance for the further development of the plant world, since the sexual process became independent of the presence of a droplet-liquid medium. The seed plants that emerged could live in drier climates. During the Permian period, the climate in many areas of the Earth became drier and colder, and tree-like spore plants, which reached their heyday in the Carboniferous, die out. During the same period, the flowering of gymnosperms, which dominated the Mesozoic era, began. The evolution of higher land plants has followed the path of increasing reduction of the haploid generation (gametophyte) and the predominance of the diploid generation (sporophyte).

During the Cretaceous period, the next major step in the evolution of plants took place - the appearance of angiosperms. The first representatives of this group of plants were shrubs or low-growing trees with small leaves. Then, quite quickly, angiosperms achieved a huge variety of forms with significant sizes and large leaves.

The acquisition of various devices for pollinating flowers and distributing fruits and seeds allowed angiosperms to occupy a dominant position in the plant world in the Cenozoic.

Thus, the main features of the evolution of the plant world were:

gradual transition to the dominant position of the sporophyte over the gametophyte in the development cycle;

access to land, differentiation of the body into organs (root, stem, leaf) and differentiation of tissues (conductive, mechanical, integumentary);

transition from external to internal fertilization; the appearance of a flower and double fertilization;

the emergence of seeds containing the smell of nutrients and protected from the effects of unfavorable environmental conditions by the seed integument (and the walls of the pericarp in angiosperms);

improvement of reproductive organs and cross-fertilization in angiosperms in parallel with the evolution of insects;

the emergence of various methods of distribution of fruits and seeds.

The main stages and directions of evolution of the animal world. The history of the evolution of animals has been studied most fully due to the fact that many of them have skeletons and are therefore better preserved in fossilized remains.

Multicellular animals descend from unicellular organisms through colonial forms. The first animals were probably coelenterates. Ancient coelenterates gave rise to flatworms, which are three-layered animals with bilateral symmetry.

From ancient ciliated worms, the first secondary cavities arose - annelids. Ancient marine polychaetes probably served as the basis for the emergence of the types of arthropods, mollusks, and chordates.

The oldest traces of animals date back to the Precambrian (about 700 million years ago). In the Cambrian and Ordovician periods, sponges, coelenterates, worms, echinoderms, trilobites predominated, and mollusks appeared.

In the Late Cambrian, jawless armored fish appeared, and in the Devonian, jawed fish appeared. Most of these animals are characterized by the presence of bilateral symmetry, third germ layer, body cavities, external (arthropods) or internal (walking) solid skeleton, progressive ability for active movement, separation of the anterior end of the body with the oral opening and sensory organs, gradual improvement of the central nervous system.

The first gnathostomes gave rise to ray-finned and lobe-finned fish. Lobe-finned animals had supporting elements in their fins, from which the limbs of terrestrial vertebrates later developed. The most important aromorphoses in this line of evolution are the development of movable jaws from the gill arches (providing active capture of prey), the development from skin folds fins, and then the formation of girdles of paired pectoral and abdominal limbs (increased maneuverability of movements in water). Lungfish and lobe-finned fish could breathe atmospheric oxygen through swim bladders connected to the esophagus and equipped with a system of blood vessels.

The first land animals, stegocephalians, originated from lobe-finned fish. Stegocephalians were divided into several groups of amphibians, which reached their peak in the Carboniferous. The exit of the first vertebrates to land was ensured by the transformation of fins into terrestrial limbs, and air bladders into lungs.

Truly terrestrial animals - reptiles, which conquered land by the end of the Permian period, originated from amphibians. The development of land by reptiles ensured the presence of dry keratinized integuments, internal fertilization, a large amount of yolk in the egg, and protective egg shells that protect embryos from drying out and other environmental influences. Among the reptiles, a group of dinosaurs stood out, which gave rise to mammals. The first mammals appeared in the Triassic period of the Mesozoic era. Later, also from one of the branches of reptiles, toothed birds (Archaeopteryx) evolved, and then modern birds. Birds and mammals are characterized by such features as warm-bloodedness, a four-chambered heart, one aortic arch (creating a complete separation of the large and small circles of blood circulation), intensive metabolism - features that ensured the flourishing of these groups of organisms.

At the end of the Mesozoic, placental mammals appeared, for which the main progressive features were the appearance of the placenta and intrauterine development of the fetus, feeding the young with milk, and a developed cerebral cortex. At first Cenozoic era A detachment of primates separated from insectivores, the evolution of one of the branches of which led to the emergence of humans.

Parallel to the evolution of vertebrates was the development of invertebrate animals. The transition from aquatic to terrestrial habitats took place in arachnids and insects with the development of a perfect solid exoskeleton, articulated limbs, excretory organs, nervous system, sensory organs and behavioral reactions, and the appearance of tracheal and pulmonary respiration. Among mollusks, access to land was observed much less frequently and did not lead to the diversity of species that is observed in insects.

Main features of the evolution of the animal world:

progressive development of multicellularity and, as a consequence, specialization of tissues and all organ systems;

a free way of life, which determined the development of various mechanisms of behavior, as well as the relative independence of ontogenesis from fluctuations in factors environment;

the appearance of a hard skeleton: external in some invertebrates (arthropods) and internal in chordates;

progressive development of the nervous system, which was the basis for the emergence of conditioned reflex activity.

Among the main stages in the evolution of the plant world, one can highlight access to land, the transition from external to internal fertilization, the emergence of seeds and the improvement of methods of their distribution; in the evolution of the animal world - specialization of tissues and organ systems, the emergence of a solid skeleton, progressive development of the nervous system and the ability to lead a free lifestyle

Main directions biological progress are 1) arogenesis(morphological progress), 2) allogenesis, 3) catagenesis(general degradation)

A rogenesis - an evolutionary direction accompanied by the acquisition of major structural changes - aromorphoses. Aromorphosis(from the Greek “airo” - I raise, “morpho” - form, pattern) - this is a qualitative change in which the fitness of a group significantly increases, its vital activity in new living conditions increases, which gives broad advantages to this group and contributes to the expansion of its range . For example, the appearance in flatworms bilateral symmetry body and the third germ layer served as the basis for the complication in subsequent groups of animals of the digestive system, muscles, circulatory and excretory systems, as well as the emergence of the skeleton in vertebrates, etc. In relation to certain groups, for example in mammals, aromorphoses caused the division of the heart into four chambers and the differentiation of two circulation circles with a simultaneous increase in the working capacity of the lungs, the complication of the brain and sensory organs, and hence development of complex behavioral reactions, more flexible adaptation to quick shift situation. In plants, aromorphoses ensured the transition from the aquatic environment to land, from reproduction by spores to reproduction by seeds. Aromorphoses always open up a wide scope for divergent evolution and lead to biological progress.

Allogenesis - evolutionary direction, accompanied by the acquisition idioadaptations. Idiomatic adaptations (from the Greek "idios" - feature, "adaptation" - adaptation) - these are evolutionary adaptations to special conditions environments that occur after aromorphoses. At the same time, there is no general increase in the level of organization and intensity of vital activity of organisms. For example, the emergence of mammals was an evolutionary change at the level of aromorphosis, but later, without fundamental changes in organization, a broad adaptive radiation of this group began, with many new species, genera, families, etc. appearing, which adapted to living in a variety of conditions land, water and air.

The main paths of the evolutionary process (T.A. Kozlova, V.S. Kuchmenko. Biology in tables. M., 2000)

Aromorphosis- the main path of progressive evolution, this is how evolution went from unicellular to multicellular, from two-layered to three-layered
Idiomatic adaptation- evolution expands at one level of organization
Degeneration- transition to the next level

Types of evolutionary changes.

The main types of evolutionary changes include: parallelism, convergence and divergence.

Parallelism is an evolutionary change that results in the formation of similar characteristics in related organisms. For example, among mammals, cetaceans and pinnipeds independently moved to live in aquatic environment and purchased the appropriate devices - fins. Unrelated people have a known common similarity mammals tropical zone, living on different continents, in similar climatic conditions (Fig. 89).

Convergence is a type of evolutionary change, as a result of which unrelated organisms acquire similar characteristics (Fig. 90). Two or more species that are not closely related are becoming more and more similar friend on a friend. This type of evolutionary change is the result of adaptations to similar environmental conditions.

Convergent changes affect only organs directly related to the same environmental factors. Chameleons and climbing agamas that live on tree branches are very similar in appearance, although they belong to different suborders. In marsupials and placental mammals, due to a similar lifestyle, similar structural features arose independently of each other. The European mole and the marsupial mole, the marsupial flyer and the flying squirrel are similar. Convergent similarity is observed even in groups of animals that are very far apart in systematic position. Birds and butterflies have wings, but the origin of these organs is different. In the first case, these are altered limbs, in the second, folds of skin.

Divergence is the most general type evolutionary process, the basis for the formation of new systematic groups.

Divergence (from Latin divergantia - divergence) - divergent evolution. The process of divergence is usually presented in the form of an evolutionary tree with diverging branches (Fig. 91). This is an image of divergent evolution, or radiation: 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 increased adaptation to new living conditions. The class of mammals is divided into numerous orders, the representatives of which differ in structure, lifestyle, and the nature of physiological and behavioral adaptations (insectivores, chiropterans, predators, cetaceans, etc.).

Main directions of evolution.

The development of living nature went from simple to complex and was progressive. Along with this, species adapted to specific living conditions and specialized.

To understand the historical development of the organic world, it is important to determine the main lines of evolution. Major Russian scientists A. N. Severtsov and I. I. Shmalgauzen made a significant contribution to the development of the problem of evolution. They found that the main directions of evolution are aromorphoses, idioadaptations and degenerations (Fig. 92).

Aromorphosis (from the Greek airomorphosis - raising the form) is such a large, large-scale, evolutionary changes, which lead to a general rise in the organization, increase the intensity of life, but are not narrow adaptations to sharply limited conditions of existence. Aromorphoses provide significant advantages in the struggle for existence, making it possible to transition into new environment a habitat.

Aromorphoses in animals include the appearance of viviparity, the ability to maintain a constant body temperature, the emergence of a closed circulatory system, and in plants - the appearance of a flower, a vascular system, and the ability to maintain and regulate gas exchange in the leaves.

Through aromorphosis, large systematic groups of a rank higher than the family arise in the process of evolution. Aromorphoses help increase survival and reduce mortality in populations. The number of organisms increases, their range expands, new ones form populations , the formation of new species is accelerating. All this constitutes the essence of biological progress, or the victory of a species (another systematic unit) in the struggle for existence.

Idioadaptation (from the Greek idios - peculiar and Latin adaptatio - adaptation) is a small evolutionary change that increases the adaptability of organisms to certain environmental conditions. In contrast to aromorphosis, idioadaptation is not accompanied by a change in the basic features of the organization, a general rise in its level and an increase in the intensity of the body’s vital activity.

Examples of idioadaptations are the protective coloring of animals or the adaptation of some fish (flounder, catfish) to life at the bottom - flattening of the body, coloring to match the color of the soil, development of antennae, etc. Another example is adaptations to flight in some mammal species (bats, flying squirrels).

An example of idioadaptation in plants is the variety of adaptations to cross-pollination of a flower by insects or wind, and adaptations to seed dispersal.

Usually small systematic groups - species, genera, families - arise in the process of evolution through idioadaptation. Idioadaptation, like aromorphosis, leads to an increase in the number of species, expansion of the range, acceleration of speciation, i.e., to biological progress.

Many modern species are caught up in biological progress. For example, a hundred years ago, the distribution border of the brown hare in the north reached the line St. Petersburg - Kazan, and in the east - to the Ural River. It has now spread to the north - up to Central Karelia and in the east - to Omsk. Now about 20 of its subspecies are known.

In nature, biological regression is also observed. It is characterized by features opposite to biological progress: a decrease in numbers; narrowing of the area; a decrease in the number of species and populations. As a result, it often leads to the extinction of species.

Of the numerous branches of the most ancient amphibians, only those remained that led to the formation of modern classes of amphibians and reptiles. The ancient ferns and many other groups of plants and animals disappeared.

With the development of human civilization, the causes of biological progress and biological regression are increasingly associated with the changes that humans make to the landscapes of the Earth, disrupting the connections of living beings with the environment that have developed during the process of evolution.

Human activity is a powerful factor in the biological progress of some species, which are often harmful to it, and the biological regression of others, which are necessary and useful to it. Remember the emergence of many species of insects that are resistant to pesticides, pathogenic microbes that are resistant to drugs, and the rapid development of blue-green algae in wastewater. When sowing, humans invade wildlife, destroying large areas of many wild populations, replacing them with a few artificial ones. Intensified extermination by humans of many species leads to their biological regression, which threatens them with extinction. Correlation of evolutionary paths. The evolutionary paths of large systematic groups (for example, phyla and classes) are very complex. Often in the development of these groups there is a consistent replacement of one path of evolution by another. Of all the considered ways to achieve biological progress, the rarest are aromorphoses that raise one or another systematic group to a qualitatively new, higher level of development. Aromorphoses can be considered as turning points in the development of life. For groups that have undergone appropriate morphophysiological transformations, new opportunities open up in mastering the external environment.

Each aromorphosis is followed by many idioadaptations, which provide more full use all available resources and the development of new habitats.

Birds and mammals have taken a dominant position among land animals. The acquisition of a constant body temperature (aromorphosis) allowed them to survive in glaciation conditions and penetrate far into cold countries; then evolution continued through idioadaptations, which led to the emergence of new species that mastered different habitats.

Parallelism. Convergence. Divergence. Aromorphosis. Idioadaptation. General degeneration. Biological progress. Biological regression.

1. Name the main characteristics of biological progress and biological regression. 2. List the main types of evolutionary changes and describe them. 3. What are the main directions of evolution?

Chapter Summary

The evolutionary idea is that living things gradually change over time. Charles Darwin revealed the main driving forces evolutions: heredity, variability and natural selection .

Heredity is the property of all organisms to preserve and transmit the properties of their parents to their offspring.

Variability is the property of organisms to acquire new characteristics. According to Charles Darwin, variability life forms corresponds to changes in environmental conditions in which their lives take place.

The presence of advanced properties allows organisms to become winners in the struggle for existence. By surviving, they have the advantage of passing on advanced properties to their offspring. Darwin called this process natural selection.

Hereditary variability is constantly maintained by the appearance mutations And genetic recombination- a continuous process of gene shuffling during the formation of zygotes.

Scientists define microevolution as directed changes in the gene pool of a population, the characteristics of which are the frequencies of occurrence of certain genes. Factors and mechanisms that control changes in the gene pool are studied by population genetics.

Natural selection eliminates those less fit genotypes , the consequence of which is an increase in the adaptability of populations to environmental conditions. Stabilizing selection is aimed at maintaining the already existing properties of organisms. Driving selection promotes changes in the properties of organisms. Disruptive selection leads to the emergence of polymorphism, which ensures the possibility of existence in a variety of environmental conditions.

Mechanisms of reproductive isolation (isolating mechanisms) lead to metabolic restrictions genetic material between populations. The consolidation of reproductive isolation is maintained by natural selection. A new species may arise as a result of the dismemberment of the range of a population or group of populations by physical barriers. This method of emergence of new species is called allopatric speciation. It is usually observed in the peripheral part of the range of the original species. The second mode of speciation is called sympatric. In this case, isolating mechanisms of one group of living beings from another may arise suddenly, as a result chromosomal rearrangements in the genotype (for example, polyploidy).

The process of formation of larger systematic groups, genera, families, orders, etc. is called macroevolution. Macroevolution occurs over vast periods of time and is therefore inaccessible to direct study.

The same processes operate in macroevolution: the formation of phenotypic changes, the struggle for existence, natural selection, and the extinction of the least adapted forms.

In the process of evolution, the following characteristic types of evolutionary changes are distinguished: parallelism, convergence and divergence. The main lines of evolution are: aromorphosis, idioadaptation, degeneration.

The evolutionary paths of large systematic groups (for example, phyla and classes) are very complex. Often in the development of these groups there is a change from one line of evolution to another.

All living organisms that are found on Earth today have passed a long way evolutionary development, the result of which was the emergence of highly organized life forms. Famous Russian scientists Severtsov A.N. And Shmalhausen I.I. did a great job on theoretical analysis this evolutionary development and identified 3 main directions of the evolutionary process:

1. aromorphosis;
2. idioadaptation;
3. degeneration.

Aromorphosis (morphophysiological progress) are adaptive evolutionary changes: the structure of the body and its functions become more complex, as a result general level its organization and vital activity increases. The appearance of aromorphoses is a very long process, based on hereditary variability And natural selection. With further evolution, aromorphoses are preserved, leading to the emergence of large systematic groups - types and classes.

Idiomatic adaptation – private evolutionary changes of an adaptive nature. They do not affect the general level of the organization. These changes are the result of adaptation to specific environmental conditions. Examples of idioadaptations in animals include protective coloration, the adaptability of amphibians to life on land, different shape wings and beaks in birds, etc.. In plants, these are various adaptations of the flower to pollination, in seeds and fruits - to distribution, and in leaves - to reduce evaporation.

All the directions of evolution described above are closely interconnected. As a rule, aromorphoses occur quite rarely in the process of evolution and always lead to the emergence of new and more highly organized forms that can adapt to other habitats. Then the evolutionary process goes the way idioadaptations. This allows organisms to settle into new ecological niches. But degeneration can occur in the case of deep partial adaptation to certain environmental conditions, i.e. as a result of idioadaptation, but at the same time conditions are created under which new idioadaptations can arise.

Unlike biological progress biological regression can be characterized by a decrease in the level of adaptability to living conditions. As a result, the number of individuals of the species decreases, its range shrinks, and the number and diversity of populations also decreases. As a result, biological regression leads to the extinction of this species. For example, trilobites, crustacean scorpions, dinosaurs, psilophytes, seed ferns, etc. underwent biological regression. Currently, biological regression is occurring in club mosses, horsetails, black cockroaches, black rats, bison, beavers, muskrats, etc., the list goes on. In this process, one of the main factors is now human activity: this includes both direct extermination (Ussuri tiger, bison) and a reduction in the number of species and their habitats as a result economic activity(various steppe plants and animals).