Ecological features of populated areas. The structure of modern ecology

Ecology (from Greek. oikos - house and logo- doctrine) - the science of the laws of interaction of living organisms with their environment.

German biologist is considered the founder of ecology E. Haeckel(1834-1919), who first used the term in 1866 "ecology". He wrote: “By ecology we mean general science about the relationship between the body and environment, where we include all “conditions of existence” in the broad sense of the word. They are partly organic and partly inorganic in nature.”

This science was originally biology, which studies populations of animals and plants in their environment.

Ecology studies systems at a level above the individual organism. The main objects of its study are:

population - a group of organisms belonging to the same or similar species and occupying a certain territory;
, including the biotic community (the totality of populations in the territory under consideration) and habitat;
- area of distribution of life on Earth.

To date, ecology has gone beyond the scope of biology itself and has turned into an interdisciplinary science that studies the most complex problems of human interaction with the environment. Ecology has traveled a difficult and lengthy path to understanding the “man-nature” problem, relying on research in the “organism-environment” system.

The interaction of Man with Nature has its own specifics. Man is endowed with reason, and this gives him the opportunity to realize his place in nature and purpose on Earth. Since the beginning of the development of civilization, Man has been thinking about his role in nature. Being, of course, part of nature, man created a special habitat, which is called human civilization. As it developed, it increasingly came into conflict with nature. Now humanity has already come to the realization that further exploitation of nature may threaten its own existence.

The relevance of this problem caused by the exacerbation environmental situation on a global scale, led to "greening"- To the need to take into account environmental laws and requirements- in all sciences and in all human activity.

Ecology is currently called the science of man’s “own home” - the biosphere, its characteristics, interaction and relationship with man, and man with the entire human society.

Ecology is not only an integrated discipline where physical and biological phenomena are connected, it forms a kind of bridge between natural and social sciences. It is not one of the disciplines with a linear structure, i.e. It does not develop vertically - from simple to complex - it develops horizontally, covering an ever wider range of issues from various disciplines.

No single science is capable of solving all the problems associated with improving the interaction between society and nature, since this interaction has social, economic, technological, geographical and other aspects. Only integrated (generalizing) science, which is what modern ecology is, can solve these problems.

Thus, from a dependent discipline within biology, ecology has turned into a complex interdisciplinary science - modern ecology- with a pronounced ideological component. Modern ecology has gone beyond the boundaries of not only biology, but also in general. Ideas and principles modern ecology have an ideological character, therefore ecology is connected not only with the sciences of man and culture, but also with philosophy. Such serious changes allow us to conclude that, despite more than a century of environmental history, modern ecology is a dynamic science.

Goals and objectives of modern ecology

One of the main goals of modern ecology as a science is the study of basic laws and the development of the theory of rational interaction in the “man - society - nature” system, considering human society as an integral part of the biosphere.

The main goal of modern ecology at this stage of development human society— to lead Humanity out of the global environmental crisis onto the path sustainable development, in which the satisfaction of the vital needs of the present generation will be achieved without depriving future generations of such an opportunity.

To achieve these goals, environmental science will have to solve a number of diverse and complex tasks, including:

develop theories and methods for assessing the sustainability of ecological systems at all levels;
explore the mechanisms of regulation of population numbers and biotic diversity, the role of biota (flora and fauna) as a regulator of the stability of the biosphere;
study and create forecasts of changes in the biosphere under the influence of natural and anthropogenic factors;
evaluate states and dynamics natural resources and the environmental consequences of their consumption;
develop methods for managing environmental quality;
to form an understanding of the problems of the biosphere and the ecological culture of society.

Surrounding us living environment is not a disorderly and random combination of living beings. It is a stable and organized system that developed in the process of evolution of the organic world. Any systems can be modeled, i.e. it is possible to predict how a particular system will react to external influences. Systems approach— the basis for studying environmental problems.

The structure of modern ecology

Currently, ecology divided into a number of scientific branches and disciplines, sometimes far from the original understanding of ecology as a biological science about the relationship of living organisms with the environment. However, all modern trends in ecology are based on fundamental ideas bioecology, which today represents a combination of various scientific directions. So, for example, they distinguish autecology, exploring the individual connections of an individual organism with the environment; population ecology, dealing with the relationships between organisms that belong to the same species and live in the same territory; synecology, which comprehensively studies groups, communities of organisms and their relationships in natural systems(ecosystems).

Modern ecology is a complex of scientific disciplines. Basic is general ecology , studying the basic patterns of relationships between organisms and environmental conditions. Theoretical ecology explores general patterns organization of life, including in connection with anthropogenic impact on natural systems.

Applied ecology studies the mechanisms of destruction of the biosphere by humans and ways to prevent this process, and also develops principles rational use natural resources. Applied ecology is based on a system of laws, rules and principles of theoretical ecology. The following scientific directions are distinguished from applied ecology.

Ecology of the biosphere, studying global changes occurring on our planet as a result of the impact of human economic activity on natural phenomena.

Industrial ecology, studying the impact of enterprise emissions on the environment and the possibilities of reducing this impact by improving technologies and treatment facilities.

Agricultural ecology, which studies ways to produce agricultural products without depleting soil resources while preserving the environment.

Medical ecology, which studies human diseases associated with environmental pollution.

Geoecology, studying the structure and functioning mechanisms of the biosphere, the connection and interrelation of biosphere and geological processes, the role of living matter in the energy and evolution of the biosphere, the participation of geological factors in the emergence and evolution of life on Earth.

Mathematical ecology models environmental processes, i.e. changes in nature that can occur when environmental conditions change.

Economic ecology develops economic mechanisms for rational use of natural resources and environmental protection.

Legal ecology develops a system of laws aimed at protecting nature.

Engineering ecology - a relatively new direction of environmental science, it studies the interactions of technology and nature, the patterns of formation of regional and local natural technical systems and ways to manage them in order to protect the natural environment and ensure environmental safety. It ensures compliance of equipment and technology of industrial facilities with environmental requirements

Social ecology arose quite recently. Only in 1986 did the first conference dedicated to the problems of this science take place in Lvov. The science of “home”, or the habitat of society (person, society), studies the planet Earth, as well as space - as the living environment of society.

Human ecology - part of social ecology, which considers the interaction of man as a biosocial being with the world around him.

- one of the new independent branches of human ecology - the science of quality of life and health.

Synthetic evolutionary ecology- a new scientific discipline, including particular areas of ecology - general, bio-, geo- and social.

A brief historical path to the development of ecology as a science

In the history of the development of ecology as a science, three main stages can be distinguished. First stage - the origin and development of ecology as a science (until the 1960s), when data on the relationship of living organisms with their habitat was accumulated, the first scientific generalizations were made. During the same period, the French biologist Lamarck and the English priest Malthus first warned humanity about possible negative consequences human impact on nature.

Second phase - formalization of ecology into an independent branch of knowledge (after the 1960s to the 1950s). The beginning of the stage was marked by the publication of works by Russian scientists K.F. Roulier, N.A. Severtseva, V.V. Dokuchaev, who first substantiated a number of principles and concepts of ecology. After Charles Darwin's research in the field of evolution of the organic world, the German zoologist E. Haeckel was the first to understand that what Darwin called the “struggle for existence” represents an independent field of biology, and called it ecology(1866).

How independent science ecology finally took shape at the beginning of the 20th century. During this period, the American scientist C. Adams created the first summary on ecology, and other important generalizations were published. The largest Russian scientist of the 20th century. IN AND. Vernadsky creates a fundamental doctrine of the biosphere.

In the 1930-1940s, the English botanist A. Tansley (1935) first put forward concept of "ecosystem", and a little later V. Ya. Sukachev(1940) substantiated a concept close to him about biogeocenosis.

Third stage(1950s - to the present) - the transformation of ecology into a complex science, including the sciences of protecting the human environment. Simultaneously with the development of the theoretical foundations of ecology, applied issues related to ecology were also being resolved.

In our country, in the 1960-1980s, almost every year the government adopted resolutions to strengthen nature protection; Land, water, forest and other codes were published. However, as the practice of their use has shown, they did not give the required results.

Today Russia is experiencing an environmental crisis: about 15% of the territory is actually an environmental disaster zone; 85% of the population breathe air polluted significantly above the MPC. The number of “environmentally caused” diseases is growing. There is degradation and reduction of natural resources.

A similar situation has developed in other countries of the world. The question of what will happen to humanity in the event of degradation of natural ecological systems and the loss of the biosphere’s ability to maintain biochemical cycles is becoming one of the most pressing.

The active role of organisms in their relationships with the environment was noted above. Therefore, it is necessary to consider the ecological characteristics of animals and plants.

Abiotic and biotic factors acting in unity on a living organism in any conditions are characterized by a certain natural manifestation in different environments life. But each species, being a qualitatively defined state of living nature, differs in its requirements. medium. At the same time, groups of species that have ecological similarities in one way or another can be identified.

Ecology of microorganisms. Although microbes essentially belong to plants, in a number of their properties they are so unique that they are usually classified as a special group of organisms, and the science that studies them - microbiology - has long been isolated as an independent biological discipline.

Bacteria are tiny plants, invisible to the naked eye, consisting of one or more cells. Bacteria are not achromatinobionts, “primitive cytodes” in the sense of Haeckel. A peculiar feature of bacteria, as relatively primitive organic beings, is the constant presence of nucleic substances in the cell.

The size of microbes ranges from 100 to 2-5 microns, and for viruses it is calculated in millimicrons (Peterson, 1953). Based on their shape, bacteria are divided into three main groups: rod-shaped - bacilli, spherical - cocci ("chains" - streptococci) and corkscrew-shaped - spirilla ("comma" - vibrios).

Bacteria are found in large numbers in the air, water, soil, on the surface and inside organisms. The number of bacteria in different environments is characterized by the following figures: air 0.01 copies. /cm 3 water 10-20 million /cm 3 soil 100 thousand - 1 billion /cm 3

Bacteria reproduce by division. Under favorable temperature conditions and the presence of food, division can occur every 0.5 hours. As a result of this progression of reproduction, one specimen produces 115,000 billion bacteria every day. Bacteria multiply faster than any other living thing.

Substances produced by bacteria may be harmful (toxins) or useful to a person(enzymes). Bacteriology and immunology develop issues of protecting organisms from bacteria, and a number of industries (food, leather, etc.) and Agriculture use the beneficial activity of bacteria.

The role of bacteria in the cycle of substances that occurs in nature is enormous. Green plants, or producers, are synthesized from mineral salts (soil and water) and carbon dioxide (air, water), with the participation solar energy, complex organic substances - proteins, fats and carbohydrates. Consumers, i.e. various herbivorous and carnivorous animals, convert this primary production into intermediate and final products. After plants and animals die, their corpses undergo a process of rotting and fermentation with the participation of bacteria, or decomposers.

As a result, mineral salts and gases are formed again, which are released during the decomposition of organisms back into inorganic nature. Thus, bacteria are a necessary link in the general cycle of substances, making possible the existence and development of real plant and animal life on Earth. The importance of microorganisms as a factor in plant productivity is known.

Soil fertility depends not only on minerals, but also on microflora, which takes an active part in all the most important processes occurring in the soil and creating favorable conditions for plant nutrition. Microorganisms are involved in preparing food for plants, in creating conditions for its absorption by plants, and, finally, are directly involved in supplying plants with nutrients.

The weight of microbial bodies, mainly bacterial, in the surface layer of 1 hectare of fertile soil is about 5-7 tons, and if we take into account the continuous reproduction and renewal of this population, then during the growing season its weight will reach tens of tons per hectare (Samoilov, 1957).

Bacteria play a large role in the biological productivity of water bodies. This has been established for the fishery-important Northern Caspian Sea (Osnitskaya, 1954; Zhukova, 1955, etc.) and other basins. River flow Volga affects the distribution, abundance and biomass of bacteria in the sea. In the deltaic part of the sea, the number of bacteria reaches 2-2.5 million per 1 ml of water, and as they move into the open sea it drops to 100-300 thousand per 1 ml. Bacterial biomass: in the Volga delta region is 470-600 mg per 1 m 3.

The number of bacteria per 1 g of soil in the Northern Caspian Sea ranges from hundreds of millions to several billion. The biomass of bacteria reached its greatest value in the deltas of the Volga and Ural rivers and immediately after the flood of 1951 it was equal to 50-52 g/m2 of the bottom in a layer 1 cm thick. In silty soil richer in organic matter, the number of bacteria is greater than in sandy soil.

On the question of the type and relationship of microbes with the environment in microbiology, there are two opposing directions: monomorphism and pleomorphism.

The theories of monomorphism and pleomorphism treat issues of speciation and variability of organisms one-sidedly and idealistically. The dominance of conservative ideas in microbiology hampered the development of this science. However, already from the end of the last century, materials on the variability of microbes began to accumulate, making it possible to overcome the one-sidedness of these opposing concepts.

L. Pasteur showed the possibility of targeted changes in the properties of microorganisms and on this basis developed methods for preparing vaccines. N.F. Gamaleya in 1888 discovered significant variability in the Mechnikovsky vibrio he discovered. Paying great attention problem of variability and speciation, Gamaleya was one of the first to prove the possibility of transforming one type of microbe into another. I. I. Mechnikov found out the meaning of microbial associations, their symbiosis and antagonism. In 1909, he wrote: “It was in the field of microbiology that the possibility of changing the nature of bacteria by changing external conditions was proven, and lasting changes that can be inherited can be achieved.” Similar statements are found in the works of S. N. Vinogradsky, L. S. Tsenkovsky, D. I. Ivanovsky, V. L. Omelyansky and other domestic microbiologists, but only after the victory in biology of the views of I. V. Michurin began a genuine restructuring of microbiology into dialectical-materialist basis.

The work carried out by microbiologists recently has made it possible to identify a number of patterns and causes that determine the processes of variability and speciation, and to draw some general conclusions on this problem. Great importance in this regard, the conference on directed variability and selection of microorganisms, held by the Russian Academy of Sciences at the end of 1951, has

A. A. Imshenetsky (1952) convincingly shows that the failure of previous and modern bourgeois microbiology is rooted in underestimation of the importance of the fundamental law of biology. New forms of microbes were studied morphologically, but no attention was paid to their physiology or their requirements for certain living conditions (the latter remained unified in the laboratory).

The heredity and variability of microbes is characterized by a number of features that distinguish them from higher plants. The most important are the following (according to Imshenetsky):

1. In the vast majority of microorganisms, including bacteria and practically important yeast-like and molds, there is no sexual process. Occurs vegetative propagation organisms in which it is possible to change properties using processes close to vegetative hybridization.

2. Heredity in microorganisms is no less stable than in higher plants, and since most bacteria are completely devoid of a nucleus and chromosomes, this fact in itself is an excellent illustration of the inconsistency of the chromosomal theory of heredity.

3. Exceptional speed of reproduction allows repeated exposure

change the external conditions on young cells and makes it possible to obtain a short time a large number of generations (important for selection).

4. There is extremely close contact between the cells of microorganisms and the external environment. Due to the small size of a microbial cell, it is more exposed to the external environment than a multicellular organism. The great adaptability of microorganisms has led to the emergence of forms adapted in nature to a wide variety of external factors.

The greatest evidence of variability has been established in microbes that cause gastrointestinal diseases in humans and animals, since the most research has been carried out on these microbes (Muromtsev, 1952). It has been shown many times that, for example, the properties of typhoid microbes can change so profoundly in tap water that these microbes become indistinguishable from E. coli or an alkali-forming agent; some strains even acquire properties that take them beyond the typhoid group.

From cultures of the plague causative agent, a microbe was obtained that has all the properties of the causative agent of false tuberculosis in rodents. At the same time, plague and pseudotuberculosis microbes are independent species that differ in morphological, cultural and enzymatic properties, and in the relationships between them the phenomena of interspecific competition are observed.

The species variability of dysentery microbes was undeniably demonstrated under experimental conditions by G. P. Kalina, who obtained the paratyphoid microbe.

Many researchers have described the mutual transitions of pneumococci, hemolytic and green streptococci, both in experiments with artificial environments, and in animal experiments.

As V.D. Timakov (1953) points out, when cultivating microorganisms of the enteric typhoid group under conditions where their source of nutrition is the decay products of other related bacteria, it is possible to obtain cultures that almost fully possess the properties of the culture on whose decay products it was grown. The author comes to the conclusion that “in the world of microorganisms, it is possible to purposefully change and create new forms and types of bacteria that are useful for humans.” S. N. Muromtsev (1952) writes: “It is necessary to recognize as unscientific the idea widespread among microbiologists that existing species microorganisms arose only in ancient times and do not arise again under modern conditions. Speciation in microorganisms also occurs in modern conditions.”

As we indicated above, the existence of bacteria is closely related to plants and animals. In nature it is impossible to find places where there would be other organisms, but bacteria would be absent. In any biocenosis, microorganisms are always present as a constituent element. But there may be biotopes in which the existence of animals and plants is impossible, and bacteria are the only representatives of living beings (for example, in the hydrogen sulfide zone of the Black Sea).

An idea of the microbial life of the ocean depths is provided by recent studies of the Kuril-Kamchatka basin of the Pacific Ocean (Kriss and Biryuzova, 1955). Samples were taken to a depth of 9000 m. It turned out that the bulk of heterotrophic microbes are represented by non-spore-bearing rods, then spore-bearing rods and cocci, as well as yeast; actinomycetes are rare. At a depth of 0-250 m, over 10,000 cells per 1 ml were found; in the zone of pronounced photosynthesis - up to 100,000 cells; at a depth of 300-400 m - thousands and hundreds of cells per ml, and in the deepest places - tens of cells. Biomass of microorganisms: 10-80 mg per 1 m 3 of water in a layer of 0-25 m; 1 -10 mg - up to 300 m depth; below 400 m - tenths and hundredths, and in near-bottom areas - thousandths of a milligram. Tens, hundreds and thousands, rarely more than 10,000 cells per 1 g of sludge, were found in the ocean soil. The distribution of the microbial population in the soil does not depend on the depth of the ocean and is obviously associated with the distribution of assimilable organic matter in the thickness of the soil and in the water above it.

The evolution of microbes has gone and continues in different directions and is associated with their occupation of all possible habitats.

Plant ecology. Plants constitute (together with bacteria) one of the two large divisions of living nature. Modern botany divides the entire plant world into two trunks: lower (layered) and higher (leafy) plants.

Representatives of lower plants (bacteria, algae, fungi, lichens) in most basic types remain in the original aquatic environment, where many have retained the features of a primitive organization to this day. In the past, lower plants were first the only, then the predominant representatives of the plant world, but now they occupy a subordinate position compared to the higher ones.

Higher plants (mosses, ferns, horsetails, mosses, gymnosperms, angiosperms) are represented by approximately 300,000 species. Most of them live on land (they use air and soil), a smaller part - in water.

Among the flowering plants there are several hundred secondary aquatic species (in different systematic groups). The aquatic lifestyle causes increased growth compared to land plants, and the replacement of sexual reproduction with vegetative reproduction (elodea, duckweed, telores). In many aquatic plants, the roots lose their importance as nutrient absorption organs, since this process occurs directly through the integument. As a result, wood is underdeveloped in the vascular bundles of aquatic plants. The body's protection from leaching due to excess water occurs due to mucus abundantly covering the underwater parts. Mechanical tissue does not develop in aquatic plants, since water itself, a dense medium, is a good support for the body for them. Few species of aquatic plants are annual, overwintering in the form of seeds (creeper, small naiad, etc.). The majority, due to the preservation of positive temperatures under the ice in winter, overwinter in the form of certain vegetative parts - rhizomes (water lilies, egg capsules), tubers (arrowhead, comb pondweed), overwintering buds (bladderwort, waterweed) or entirely (duckweed, swampweed , some pondweed).

During the evolution of plants, various adaptations to living conditions took place - abiotic and biotic. For example, the evolution from lower plants to higher ones was associated with the transition from an aquatic to an aerial way of life, but then among the higher ones a process of secondary conquest of the hydrosphere was noticed.

Algae are differentiated into solitary and colonial forms (Volvox). In algae, like in mosses, there is a complex alternation of generations, characterized by changing requirements for living conditions at individual stages of individual development.

Many fungi have taken a very unique place in nature, having adapted to a mutually beneficial symbiosis with other organisms. Thanks to “mutual help,” lichens (fungus and algae) are able to live on the most barren soils and bare rocks, where neither fungus nor algae can live separately. The settlement of fungi on the roots of higher plants forms mycorrhiza, which contributes to a more complete absorption of soil nutrients by the plant. In heather growing in sandy areas, the embryo does not even develop without mycorrhiza.

The flourishing of seed plants is associated with their complete conquest of land and gradual liberation from the participation of the aquatic environment in the process of sexual reproduction. The embryo in the seed is abundantly supplied with food material and is able to withstand both dryness and cold for a long time. Therefore, only flowering plants could become true land organisms, while mosses and ferns remained amphibious.

The vital advantage of angiosperms over gymnosperms is the formation of fruits, which more fully ensure the ripening and distribution of seeds (with the participation of animals). Microspores of gymnosperms are adapted to be transported by wind. Most angiosperms have developed adaptations for pollinating flowers with the assistance of insects (bright perianths, secretion of nectar and aroma, sticky pollen). This method of pollination better ensures cross-fertilization, which is biologically useful.

Thus, an important factor in the evolution of angiosperms is their relationship with the animal world, with pollinating insects, and with birds and mammals that facilitate seed dispersal. As we see, as evolution progresses, the connection between plants and animals intensifies. At the same time, they not only mutually serve each other in the process of feeding, but plants, providing shelter for animals, often include them in their development conditions.

As B. A. Keller (1938) rightly notes, plants’ relationships with the environment have unique features, special qualities associated with the mode of nutrition typical of these organisms. Green plants use food that is around them in extremely rarefied form. For example, in the air this food is carbon dioxide, of which there is only 0.03%, in the soil - nutritious mineral salts, usually in a weak solution. In addition, leaves, as a source of energy during nutrition, capture sunlight. In this regard, the evolutionary development of plants, in general, followed the path of strong outward dissection, the development of a very rich external absorbent surface (leaf and root). As a result, plants turn out to be especially closely related to their environment, which determines their increased intraspecific variability.

The role of plants as producers in individual living environments is different. In water, the main mass of autotrophs consists of algae, and on land - higher plants.

The attached way of life of plants determines the vertical layering in their distribution. Only plants exhibit closeness as a consequence of population density (duckweed in a pond, forest, etc.) under favorable conditions.

In combination with climate and soils, vegetation forms characteristic vertical belts in mountainous areas and latitudinal landscape zones within the northern and southern hemispheres (from the equator to the poles), an integral element of which are representatives of the animal world characteristic of them.

The value of the annual increase in aboveground plant mass, according to the research of E.M. Lavrenko, for tundra, steppe and desert regions it ranges from 4 to 56 c/ha. The gross stock (biomass) of above-ground plant mass reaches its greatest values in forest communities (900 centners/ha in the northern taiga, 1300 centners/ha in the middle taiga, 2600 centners/ha in deciduous forests). In the tundra this figure is 6-32 c/ha, in the forest-tundra 73 c/ha. For steppes, the annual increase (production) of plant mass is almost equal to its gross reserve (biomass) due to the annual death of above-ground parts. Desert steppes and semi-shrub communities. deserts provide the smallest amount of gross stock (5-10 c/ha).

We are not talking about the factors necessary in the life of plants: each species, depending on the environment and living conditions, “at each stage of its ontogenesis needs special conditions of existence and development. Manuals on plant ecology contain material relevant to this, although they are far from comprehensive in covering the issue.

Animal ecology. Animals, represented by more than 1.2 million species, are very diverse in the height of their organization and live in all living environments.

As J. Lamarck pointed out, the effect of the environment on animals is much more complex than on plants. If plants directly experience the influence of external conditions, then in highly organized animals this influence is more indirect than direct. The difference here is not in how the environment acts, but in how the body reacts to these actions.

An immobile plant under the influence of a new factor dies or remains; in the latter case, a change occurs, the organism adapts to the corresponding external influence. A mobile animal organism is in a more advantageous position, since it does not face the dilemma of dying or changing. For him, a third response to the corresponding impact is possible - migration, departure to more favorable conditions. In addition, the nervous system is of utmost importance as a condition for the connection of the organism with the environment in animals. As I.P. Pavlov showed, animals have historically developed constant body responses to external influences (unconditioned reflexes, instincts) and temporary connections ( conditioned reactions), which are of great importance in establishing connections with the environment.

Due to the variety of types of nervous systems in animals and general differences in organization and metabolism, animals are very different ecologically. There are differences both in living environments and in systematic groups.

Like plants, in the animal world, the environment determined the direction and course of evolution.

The development of an external chitinous cover in aquatic arthropods, which delayed evaporation, made it possible for some groups of these small animals to leave the aquatic environment on land and fully master the conditions of terrestrial existence.

The numerous species (up to 1 million) and the wide distribution of arthropods in all living environments indicate the prosperity of this group at the present time. As a result of the high development of the nervous system and the associated phenomena of special adaptability to living conditions, the type of arthropods formed one of the two peaks of the entire animal world.

Only higher vertebrates, along with spiders, millipedes and insects, were able to fully master the air environment and acquire similar adaptations for movement on land (legs that bend at the joints) and in the air (wings for flight). Only in higher arthropods and higher vertebrates do we encounter such a far-reaching differentiation of various parts and organs of the body and, finally, in both of them their neuro-cerebral activity (instincts, etc.) turns out to be the most developed.

In the evolution of animals, a fundamentally important stage is associated with the divergence of protostomes and deuterostomes, which gave rise to two large branches of the animal world. The beginning of the divergence of these groups is due to the fact that one followed the line of adaptation to a benthic way of life (protostomes - worms, mollusks, arthropods), and the other gave rise to forms capable of freely swimming in water (deuterostomes - echinoderms and chordates).

In the evolution of lower vertebrates, adaptation to nutrition played an important role, and therefore two lines of development emerged: jawless (which gave rise to armored and cyclostomes) and jawed (a progressive branch that led from true fish to mammals).

The arid conditions that prevailed over vast areas in the Devonian gave life advantages to such freshwater fish, which were able to do without gill breathing and, in the event of water spoilage or temporary drying out of the reservoir, use atmospheric air for breathing. Such “pulmonary fish” belonged to two different groups: lungfishes and lobe-finned fishes. By the end of the Devonian, the ancient lobe-finned amphibians gave rise to the stegocephalians, whose heyday was the Carboniferous, characterized by a humid climate.

The new climate change towards decreased humidity gave a vital advantage to those modified descendants of ancient amphibians who developed horny formations on the skin and did not need bodies of water to reproduce. Thus, with the arid Permian, the development of reptiles began, and in the Jurassic time they reached great diversity and took a leading position on land.

At the end of the Mesozoic, two trunks separated from reptiles - birds and mammals, which independently developed a similar device - the complete separation of arterial and venous blood flows. This anatomical feature, due to the development of a larger respiratory surface in the lungs, provides a more energetic respiratory exchange and creates the opportunity to maintain a constant body temperature.

The development of both groups of “warm-blooded” animals proceeded almost simultaneously and without mutual interference: they diverged into two different ecological niches and each occupied its own special place in nature. Birds moved from a climbing arboreal lifestyle (Jurassic protobirds) to aerial movement and associated methods of obtaining food. In mammals, evolution has moved mainly towards various possibilities of existence and movement on the land surface.

Mammals switched from laying eggs to viviparity, which ensured significantly greater survival of the offspring.

Thus, the evolution of animals, which took place in connection with changes in living conditions, can be understood only through an ecological analysis of the origin of certain adaptations. AND modern process speciation, characterized by certain specificity in separate groups animals, can also be correctly understood only through an ecological analysis of the material.

Let's take a look at some of the ecological features of vertebrates.

IN environmentally fish are quite noticeably different from other vertebrates. As is known, fish constitute the richest (about 20,000 species) class of vertebrates. Fish are characterized by a high degree of intraspecific variability, which required the use of a particularly differentiated system of taxonomic units. In almost every body of water we can find local forms of one or another species of fish.

What are the reasons for this increased variability in fish?

There are several of them, but the main reason is the exceptional dynamism of the aquatic environment and the action in it of a number of factors that terrestrial vertebrates do not experience (large fluctuations in pressure, light and oxygen conditions, the influence of environmental reactions, different mineralization, etc.). The indicated diversity of living conditions in the aquatic environment contributes to the adaptive radiation of fish, determining the existing diversity of species and the intensively ongoing process of formation of local forms.

The isolation factor affects fish (especially aquatic ones) to a much greater extent than land animals. To confirm this, it is enough to recall that the number of lakes differing in regime globe many times the number of islands with different living conditions. It is not difficult to identify two nearby lakes that differ in the conditions of aquatic life, but neighboring islands are usually similar in the nature of terrestrial life. It should be added that terrestrial animals have a much greater variety of means of overcoming mechanical barriers than fish.

The isolation factor has a dual effect - on the reservoir and on the fish. Installs quickly in an isolated pond special treatment life, consisting of the physical and geographical conditions characteristic of a reservoir, its relationship with the surrounding landscape and depending on the complex of hydrobionts that have entered it. On earth's surface it is impossible to find two completely identical bodies of water, even in the same area, next door to each other. Isolation of water bodies leads to the development of a specific regime, which ultimately increases diversity water conditions life.

On the other hand, the isolation of fish (populations) contributes to the preservation of all those deviations (local forms) that have the opportunity to develop in these various bodies of water and which would be leveled out when they communicate with each other. Isolation promotes the preservation of forms that could be destroyed in the interspecific struggle for existence in the open connection of various bodies of water. Finally, long-term isolation leads to deterioration of heredity and degeneration, as a result of the lack of free crossing of individuals that have developed in different conditions.

The increased variability of fish depends, further, on their significant “subordination” to the aquatic environment. The internal environment of terrestrial vertebrates, formed in the past, possibly with the participation of the external aquatic environment, is now sharply different from it (air). On the contrary, the internal environment of fish (liquid) remains similar and even in some cases close to their external environment. The gaseous and liquid environments of life are sharply different in their physical and chemical properties, and this, of course, creates a fundamental difference between fish and terrestrial vertebrates and cannot but affect the characteristics of their variability.

In the process of evolution, certain groups of fish have developed varying degrees of isolation from the external environment, but, nevertheless, in them, due to the similar nature of the external and internal environments, changes in the first should find a greater response in the second, compared with terrestrial animals.

Finally, the variability of fish cannot but be affected by the fact that they, apparently, are the only animals characterized by growth throughout their entire lives. It is known that organisms have significant plasticity precisely during the period of formation and growth. Adult organisms that have reached maximum growth are the most resilient and therefore less susceptible to the transformative effects of living conditions.

Lifetime growth of fish is undoubtedly a factor increasing variability. In growing terrestrial vertebrates, size and age variability can be distinguished, but after they reach definitive (final) sizes, only age variability remains (in addition to sexual and seasonal). As a result, a taxonomist can operate with absolute measurement data for birds and mammals, but for fish he must translate them into comparable relative indices. This circumstance, by the way, is indirect evidence of the need to distinguish between age and size variability in fish.

Depending on living conditions, the growth of fish in individual reservoirs varies extremely greatly.

The ecological features of birds and mammals were first examined in detail by D.N. Kashkarov and V.V. Stanchinsky (1929). In subsequent years, a large amount of factual material has been accumulated in this area. S. I. Ognev’s book “Essays on the Ecology of Mammals” (1951) is of great value, but it is far from a general summary, since whole line The ecological factors that determine the life of mammals are not covered.

D.N. Kashkarov and V.V. Stanchinsky, characterizing the dependence of birds and mammals on environmental conditions, consider climatic, ecotopic and biocenotic factors.

Climatic factors are divided by these authors into heat, light, pressure and humidity. Birds are quite sensitive to all factors. Being warm-blooded animals, birds are able to tolerate different temperature conditions and live wherever there is food. Eurythermic are: crows, jackdaws, tits, etc. that remain with us for the winter; inhabitants of areas with a pronounced continental climate, such as hazel grouse, saji, and mountain turkeys; rising when flying to high altitudes - vultures and eagles.

Stenothermic forms include birds of tropical countries with a flat coastal climate and migratory birds temperate zone. To protect the body from cooling, a cover of feathers and down is used. The role of the cooling apparatus, in the absence of sweat glands, is taken over by the respiratory organs, evaporating water.

In relation to the light factor, birds are divided into day birds (most) and night birds (owls, etc.). In relation to moisture, birds can be divided into three groups: hydrophiles (water-loving - inhabitants of water basins and their shores), hygrophiles (moisture-loving - for example, waders) and xerophiles (dry-loving - inhabitants of deserts).

As for ecotopic factors, the following characteristic habitats can be distinguished in relation to birds: air (for swifts, swallows, terns, etc., feeding exclusively on flying animals in the air), water (petrels, gulls, etc.), swamps (waders , herons, storks, cranes, etc.), open spaces - meadows, steppes, deserts (ostriches), woody vegetation (woodpeckers, nuthatches).

The biocenotic relationships of birds are very diverse, due to the high development of various instincts.

Kashkarov and Stanchineky characterize the ecology of mammals in a similar way; S.I. Ognev approaches this issue differently. According to the last author, there are 360 species of mammals in the fauna of Russia. In ecological terms, they have been studied very unevenly and completely insufficiently, given the large practical significance many types.

S.I. Ognev pays main attention to the consideration of adaptations in mammals to different conditions life - underground and in open spaces (fast running), in trees (climbing, fluttering) and in the air (flying), in water and on mountains. He further describes burrows and nests, hibernation, molting, migration, reproduction, feeding and population fluctuations. Unfortunately, the author does not evaluate natural factors from the point of view of their significance in the life of mammals as conditions of existence and development.

N.I. Kalabukhov (1951) considers temperature, light, thermal and ultraviolet rays, humidity, precipitation, gas composition of the atmosphere and pressure to be the conditions for the existence of terrestrial vertebrates. Thus, this author speaks only about abiotic factors, without touching on biotic ones. There is no doubt that, despite the importance of the former, the existence of animals without food is still completely impossible, and therefore biotic factors play an equally important role.

Thus, we have to admit that the development of general questions of animal ecology from the standpoint of creative Darwinism is extremely lagging behind, although there are a number of good environmental research individual species, due to their practical significance (acclimatization, hunting, extermination). Most ecological works are devoted to the study of adaptations (morphological, physiological, ecological) that are developed in individual species under the influence of specific living conditions.

But now this is no longer enough. Michurin's teaching does not require that the adaptive significance of the mole's paw to the conditions of underground life be demonstrated again and again or that the bat's wing be described as an adaptation to flight. And this is exactly how S.I. Ognev presents ecology. It is required to show what factors are necessary for the existence and development of a mole, bat and other animals and what influence other environmental conditions have on them. With the appropriate knowledge, ecology will become an effective science.

Some scientists, in particular livestock breeders, are trying to find ways of research in this direction. The work on creating the Kostroma cattle breed and others carried out by Soviet livestock specialists based on the achievements of Michurin’s teachings are examples of deeply scientific environmental research. The work of creating a new breed of animal consists of two parts: 1) selection of sires and crossbreeding (one or more) in order to weaken heredity and enhance the desired properties, 2) an appropriate regime of education and feeding. If the first part of the work is genetic, then the second is environmental. Knowledge the best conditions temperature regime, exercise, nutrition, etc., in which young animals should be raised in order to develop new breed qualities, allows for the creation of highly productive breeds of farm animals in a planned manner and in a short time.

But no less important practical importance is accurate knowledge of the ecological characteristics of animals, also when carrying out work on the acclimatization of valuable species or the extermination of harmful ones, on the rational exploitation of stocks in hunting and fishing and other industries.

There are significant differences in the relationships of plants and animals with the environment and in the nature of development of adaptation to living conditions.

Firstly, the life forms of plants are much less diverse compared to the diversity of animal biomorphs. Convergence is quite common in plants. This is explained by the more monotonous way of life of plants (fixed rooting in the soil) and their more similar vital needs (light, carbon dioxide, water, mineral salts of the soil). In the animal world, the life requirements of different species are more diverse and complex; their methods of obtaining food and protecting themselves from enemies are very different; Differences in methods of movement are very strongly reflected in their structure and appearance.

Secondly, in plant organisms, natural selection has developed a very broad morpho-physiological plasticity in response to changes in external conditions, i.e., the hereditary ability to produce changes of an adaptive nature. It is clear that when plant organisms are immobile, such an ability has very important vital significance for them: plants deprived of this plasticity, if external conditions change, would inevitably die, since they do not have the ability of active shelter.

Rice. 1. Dandelion grown in the lowlands.

Animals have plasticity of a similar nature is much less developed, and adaptability to changes in living conditions is achieved in a different way - by developing mobility, increasing the complexity of the nervous system and sensory organs. When external conditions change, the animal responds to it not so much by changing its organization as by quickly changing its behavior and, in a very large number of cases, can adapt to new conditions quite quickly. Natural selection and promotes to the highest levels in the animal world those organisms in which, along with a general increase in the type of organization, there was also a progressive development of their mental activity.

Thus, the interaction of plants and animals with the environment, while having much in common, is at the same time significantly different.

Literature used: Fundamentals of Ecology: Textbook. lit-ra./B. G. Johannsen
Under. ed.: A. V. Kovalenok, -
T.: Printing house No. 1, -58

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Forest as an ecosystem

Also distinguished anthropogenic factors

Abiotic factors.

1. Photophilous

2. Shade-tolerant

3. Shade-loving

1. Moisture-loving

2. Drought resistant

1. Plants little demanding

2. Plants very demanding

3. Plants medium-demanding

Biotic factors.

1. Phytophagous or herbivores

2. Zoophagi

3. Omnivores

saprophages

Questions and tasks

ECOLOGICAL FEATURES OF FORESTS

Forest as an ecosystem

What is a "plant community"?

Name the signs by which plants are united into forest communities

Forest ecosystems in the Vologda region are the predominant type of terrestrial ecosystems. In our region, forests occupy about 80% of the area. They are quite diverse in structure, composition and habitat conditions. Forests contain a variety of plant life forms. Among them, the main role belongs to trees and shrubs. Plants that form forests exist together and influence each other. In addition, forest plants interact with their environment and other organisms (animals, fungi, bacteria). In their unity they form a complex developing ecosystem.

A peculiar combination natural conditions allowed the formation of woody plant forms. For tree growth, the most important factors are temperature and humidity. Thus, low temperature limits the development of trees in the tundra, and insufficient humidity limits the development of trees in the steppes. In our natural area, the height of trees reaches 35–40 meters.

A feature of the forest ecosystem is the clear distribution of plants into tiers. This is due to the fact that plants differ in height and distribution of root systems in soil horizons. The species composition of plants and the number of tiers depend on the physical conditions of the environment.

In a forest community, tiers are distinguished according to life forms: woody, shrub, herbaceous-shrub and moss-lichen. IN various types forests, these tiers are expressed differently. In forests there is also a group of extra-tiered organisms – epiphytes.

The tree layer in the forests of the Vologda region contains 22 species of trees. But some of them can have two life forms: trees and shrubs (bird cherry, willow, rowan).

Depending on the type of forest, the development of the shrub layer varies - from single specimens to closed thickets. Since shrubs are always lower than trees, their thickets are called "undergrowth". There are 32 species of shrubs in our forests. Some of them - willow, raspberries, buckthorn, currants, rose hips - form thickets.

Herbaceous plants and shrubs form their own special layer in the forest. The dominant species of this layer determine the name of the forest community (lingonberry pine forest, blueberry pine forest, etc.). The species composition of herbaceous plants in the forest is diverse. Each forest community corresponds to a specific complex of herbaceous plant species. IN coniferous forests There are about 10-15 species, and in small-leaved trees there are up to 30-50 species. Among them, flowering plants predominate; higher spore plants (horsetails, mosses, ferns) are found in smaller numbers.

The lowest tier of forests is formed by mosses and lichens. From mosses, depending on moisture, green, long-moss or sphagnum mosses develop. Lichens predominate in dry pine forests: various types of Cladonia, Icelandic Cetraria and others. The dominant species of this layer determine the name of the forest community: lichen pine forest (“white moss”), green moss spruce forest, long-moss spruce forest (with the dominance of cuckoo flax), sphagnum spruce forest.

The out-of-tier group (epiphytes) is formed by algae, mosses and lichens growing on trees and dead wood. Epiphytic mosses are more diverse on deciduous trees, and lichens on old spruce and pine trees.

The tiered distribution of plants creates a variety of habitats for animals. Each species of animal occupies the most favorable conditions for it at a certain altitude. But animals, unlike plants, are mobile. They can use different tiers for feeding and breeding. Thus, fieldfare thrushes build nests in trees, in the first half of summer they feed on invertebrates on the ground, and in the second half of summer they eat berries on trees.

Thanks to the tiered arrangement, a larger number of species coexist in the forest community, which allows for fuller use of the habitat. This ensures diversity of forest organisms.

This is also facilitated by the different combination of living conditions in the forest. On the one hand, the life of organisms depends on the climate of the taiga zone, the topography and soils of the territory where the forest community is located. On the other hand, under the forest canopy, each layer creates its own microclimate. The growth of a certain set of plants depends on fluctuations in temperature and humidity. In turn, this creates habitat features for animals where they can feed, reproduce and hide from enemies.

The living conditions of organisms are a combination of environmental factors.

Natural environmental factors are usually divided into two groups: abiotic and biotic.

Abiotic environmental factors– factors of inanimate nature. In forests, the most important factors for organisms are temperature, light, humidity, soil composition, and relief features.

Also distinguished anthropogenic factors – all forms of human influence on nature.

Abiotic factors. They, first of all, affect the life activity of organisms and have different meaning for plants and animals. For example, light is necessary for photosynthesis for plants, and helps most animals navigate in space. Each species makes certain demands on the environment, which, due to certain environmental factors, do not coincide among different species. For example, Scots pine is photophilous and tolerates dry and poor soils. Norway spruce is shade tolerant and needs richer soils, etc.

In relation to light, there are three main groups of plants: light-loving, shade-tolerant and shade-loving.

1. Photophilous The species grows best in full light. Forest light-loving species include: Scots pine, birch, many shrubs (bearberry) and herbaceous plants of pine forests. The greatest diversity of such species can be found in pine forests.

2. Shade-tolerant The species can grow in full light, but develop better in some shade. It's pretty large group forest herbaceous plants living in different types forests and occupying different tiers, for example, lily of the valley, lungwort, rowan, bird cherry.

3. Shade-loving species never grow in full light. This group includes some forest grasses and mosses: wood sorrel, ferns, wintergreens and other species that are characteristic of dark spruce forests.

The temperature factor and sufficient humidity determine the predominance of woody vegetation over other plant communities in our natural area. These factors change throughout the year, leading to well-defined seasons and changes in the state of the flora and fauna. Appearance forest community and the activity of its inhabitants depend on the time of year. Seasonality corresponds to such phenomena as vegetation, flowering, fruiting, leaf fall, bird migration, reproduction and hibernation of animals.

In relation to humidity, forest plants belong to three main ecological groups:

1. Moisture-loving species growing on waterlogged soils and in conditions of high air humidity (some types of sedges, ferns and others). This group is widespread in communities such as black alder forests and willow forests.

2. Drought resistant Plants are inhabitants of dry places; they are able to tolerate significant and prolonged dryness of air and soil. This includes herbaceous plants growing in pine forests (bearberry, creeping thyme, sheep fescue).

3. The intermediate group consists of plants of moderately humid habitats(many deciduous trees and herbaceous plants). This group of plants predominates due to the climate and topography of the region.

Based on their requirements for the content of mineral nutrients in the soil, three ecological groups of species are distinguished:

1. Plants little demanding to the content of nutrients in the soil. They can grow on very poor sandy soils (Scots pine, heather, cat's foot and others). Many of them develop mycorrhiza on the roots. It helps plants absorb water and nutrients from the soil.

2. Plants very demanding to nutrient content. These are herbaceous species that grow in alder forests: stinging nettle, common stinging nettle, common impatiens, etc.

3. Plants medium-demanding to nutrient content. These are the majority of forest species: two-leaved mynika, common sorrel and others. They predominate in forest communities.

Biotic factors. No less an important condition the existence of organisms in forests is the relationship between them. This can be a cooperative relationship that benefits both species. For example, birds eat the fruits of plants and distribute their seeds. Mutually beneficial relationships between fungi and plants are known. In other cases, one species can take advantage of another without causing harm. Thus, in winter, tits can feed on woodpeckers, who leave some of the food uneaten. Species that have similar requirements for living conditions compete with each other. When growing together, spruce gradually displaces light-loving aspen, creating shading as it grows and preventing its regeneration. Among animals, competition between species occurs over territory and food. For example, 5 species of thrushes living in the Vologda region feed on small invertebrates in the lower tiers of the forest in the first half of summer. Then, as the berries ripen, they mainly stay in the upper tiers of the forest. Competition between them is weakened due to the diversity of invertebrates and the abundance of berries.

Food is a very important environmental factor, as it is the energy for the existence of organisms. The food of animals in forests varies. In general, everything that is in the forest is used for food, and animals are found from the tops of trees to the deepest roots.

Based on nutrition, different ecological groups of animals can be distinguished.

1. Phytophagous or herbivores animals are consumers of various parts of plants (foliage, wood, flowers, fruits). The abundance of plant food is associated with a variety of herbivorous animals. The main consumers of vegetative mass in our forests are moose, white hares and various insects (leaf beetles, bark beetles, longhorned beetles and many others). The generative parts of plants (flowers, fruits, seeds) are eaten by birds (crossbill, redpoll, goldfinch, siskin, bullfinch), mammals (squirrel) and insects. Many insects, feeding on nectar and pollen of plants, simultaneously pollinate them. Therefore, they play exclusively important role in plant propagation. Birds that eat berries take part in the spread of plants, since plant seeds are not digested and fall into new places with excrement.

2. Zoophagi– consumers of other animals. Many people in the forest eat invertebrate animals. Spiders feed on insects. Their fellow insects become prey for predatory insects. These include beetles (ground beetles, soft beetles, ladybugs), wasps, grasshoppers and many others. Toads, lizards, and shrews feed on insects, mollusks, and worms. Tits eat insects, and hawks and falcons hunt other birds. Owls, stoats, and weasels eat small mammals. Wolves chase large animals, and lynx hunt from ambush.

3. Omnivores– animals that consume various foods: plants, mushrooms, animals, including carrion. These are the wild boar, bear, badger, raven, hooded crow and others that live in our forests. These animals are characterized by very diverse methods of obtaining food and places where they feed.

4. A group of animals that use dead vegetation ( saprophages). By processing fallen leaves and dead wood, these organisms play an important role in the existence and development of forests. Insects predominate among them. This is how the larvae of various longhorn beetles develop and feed in dead tree trunks. Among soil animals, worms belong to this group.

In temperate forests, the abundance and availability of food varies greatly during different seasons of the year, so many animals feed on both plant and animal foods. For example, hazel grouse, wood grouse, great spotted woodpecker, and even rodents, which are generally considered herbivorous.

Environmental factors act jointly on organisms, determining the distribution and vital activity of plants and animals. For example, the complex action of abiotic and biotic factors led to the formation of sedentary, nomadic and migratory species in birds.

Questions and tasks

Why are plants in forests distributed into tiers?

Give examples of plants of different tiers. What features are characteristic of them?

Why are temperature, humidity and light some of the most important abiotic factors?

Think about what ecological groups of animals can be distinguished in relation to light?

H Give examples of plants of different ecological groups growing in the forests of your area.

Agrocenosis as special type ecosystems

Note 1

Among ecosystems created with human participation, agrocenoses occupy a special place. Along with urban communities and communities of industrial zones, agrocenoses are specially created by humans to meet their needs. Agrocenoses are intended to provide people with food.

Like natural ecosystems, agrocenoses have a certain taxonomic and ecological composition of organisms and can be characterized in terms of certain relationships between organisms and abiotic environmental conditions, as well as their own structure of trophic relationships between organisms. In agrocenoses, food chains are not fundamentally different from those characteristic of natural ecosystems: there are also producers, consumers of various orders and decomposers.

Agrocenoses occupy about a tenth of the total land surface and supply more than 90% of food energy to humanity. Their advantage in this regard over natural ecosystems is their much higher productivity. However, such productivity is possible only with regular, scientifically based human intervention in natural processes.

Definition 1

Agrocenoses are ecosystems formed on agricultural lands used according to the target principle; the basis of these ecosystems is crops or plantings of cultivated plants. Agrocenoses include:

fields,
vegetable gardens,
gardens,
artificial pastures,
flower beds,
etc.

Ecological specificity of agrocenoses

The specificity of agrocenoses is determined by their artificial origin and agricultural purpose - their edifier is a person who forms agrocenoses and ensures their high productivity, in order to collect and use the maximum harvest. When creating agrocenoses, a person uses a number of agricultural techniques to:

tillage,
reclamation,
artificial irrigation,
sowing and planting special varieties of plants, feeding them,
control of weeds, pests and diseases of cultivated plants.

The most important difference between agrocenoses and natural ecosystems is their lack of stability. This is easily explained, since the structure of agrocenoses is close to the initial stages of restorative succession of ecosystems, which are also not sustainable; on the contrary, natural state Such successions are driven by the dynamics of ecosystems. For this reason, without human participation, constantly returning the agrocenosis to the initial stage of succession, communities of grain and vegetable crops are replaced by others the very next year, crops of perennial grasses - after 3-4 years, orchards - after 20-30 years.

Human activity is an important energy factor in agrocenoses. In addition to solar energy, they receive some additional energy expended by humans on the production of agricultural machinery, fertilizers, plant protection products, land reclamation, etc. On the other hand, a significant amount of energy is lost annually with the harvest. Therefore, the circulation of substances in agrocenoses is always open.

The anthropogenic factor in most cases contributes to the reduction of biological diversity. Agrocenoses are no exception. Here, compared to natural communities, the biodiversity of living organisms is sharply reduced. The objects of cultivation are usually one or several plant species (monocultures), which contributes to the depletion of the taxonomic composition of animals, fungi, and bacteria. On the other hand, this contributes to the mass reproduction of some of their consumers, which transfers these organisms from a human point of view to the category of “pests”.

Note 2

An important difference between agrocenoses and natural communities is the combination of natural and artificial selection processes, which creates completely different directions and pressures than in nature. This serves additional factor reduction of biodiversity.

Environmental characteristics

An ecological characteristic is the attitude of an organism to a complex of environmental factors or environmental conditions. Environmental factors themselves can be defined as dynamic elements of the natural, or environmental, environment that influence the activity of living organisms and their livelihoods. In other words, without the presence of any environmental factor, normal life of the organism is impossible, up to fatal outcome; So environmental factors are the living conditions of plants, animals and humans.
The set of environmental factors for plants includes the following groups: cosmic (the Sun was discussed at the beginning of the book), abiotic and biotic factors. Abiotic factors include climatic (light, heat, moisture, air), soil, orographic (determined by relief). Biotic factors are associated with the influence of living organisms on each other: the influence of human activities on plants (mowing in meadows, cutting down forests, treating crops with drugs, etc.), animals on plants (in pastures, the influence of pollinating insects, plant pests, etc.) . It is believed that all environmental factors are equivalent for organisms, including plants. This is fundamentally true, since each factor will determine the possibility of life. If we take into account the time during which an organism can survive without a single factor, then a certain difference in the significance of the factors appears. So, a plant can be without light for several hours a day (at night), but without heat (when frozen) - only a few minutes or even seconds (with a strong drop in temperature); Some plants tolerate water deficit for days (and in deserts - almost throughout the entire growing season), while others tolerate it only for a few hours. Estimates of the importance of factors also differ in the animal world.

For example, they can live without air for only minutes or even seconds, without sufficient heat - hours, and sometimes only seconds (but some animals spend several months in hibernation, having adapted to a special thermal regime), without water and food - for several months. days. In general, a complex of environmental factors is vital for organisms; in particular, cosmic, all climatic and soil factors are extremely important for plants.
It should be noted that environmental factors are indispensable. For example, an additional supply of water cannot compensate for the deficiency of one or another nutrient element in the soil or the lack of heat, etc. At the same time, some improvement in the growing conditions of plants is still observed if, if there is a deficiency of one factor or one factor, others will be provided to the plant in sufficiently full, without shortage. And yet, it is impossible to completely replace one environmental factor with another.
The variety of required levels of environmental factors, their combination, deficit and surplus are reflected in one of the main, generalizing all such indicators, the law of ecology, formulated by the American ecologist V. Shelford in the works of 1911-1915. This law is called Shelford's law, or the law of tolerance. Its essence is this: the absence or impossibility of prosperity of any organism is determined by a deficiency or excess in qualitative and quantitative senses (indicators) of any of the factors, the level of which may be close to the limits of tolerance, that is, to the limits tolerated by a given organism (from the Latin Shegapye - "patience").
The adaptability of organisms to certain conditions in which their life cycle is possible is expressed by the difference between the minimum and maximum indicators for each environmental factor. This range, or zone, between the levels of factors acceptable for life is called the limits of tolerance, that is, the boundaries of the conditions in which the organism goes through the entire development cycle and can survive. Each type of organism (plants, animals, humans) has individual ranges and differs from the ranges of other organisms (although in some species such zones may be similar, in in some cases almost identical).
Note that individual environmental characteristics have not only representatives of different species, but also forms of organisms within the same species, for example, different varieties of a particular plant species (varietal agricultural cultivation techniques are also based on these differences). This can be illustrated by the example of people with different levels of health and fitness: some can tolerate factor deficits and overloads that are very difficult to tolerate ordinary people. Everyone can easily imagine the difference in the tolerance limits of a weak, sick person and a trained, seasoned athlete or astronaut or tester. After earthquakes, weak women and sometimes old people were found surviving under the rubble after many days. But these are individual characteristics of people and the specifics of circumstances.
And another explanation to the basic law: any factor that approaches the level of tolerance limits (it does not matter - to the ecological maximum or minimum) limits the conditions for the normal development of the body and is called a limiting factor. The quantitative indicator of the factor at which the body develops normally and “thrives” is called the optimal level (from the Latin orytt - “best”).
It is very important that there is a range of indicators according to the optimum for each environmental factor, and the wider it is for a particular organism (plant or animal), the more adapted the organism is to changing conditions. So, optimum -g is not a specific point on the scale of indicators, but rather a zone, optimal conditions under which nature provides the body with the opportunity to develop normally. In the absence of a range of optimal conditions, living organisms would die at the slightest deviation of conditions from the optimal level.
The optimal levels of each factor for the same organism can change (“shift of the optimum”). This means a change in the body’s requirements for conditions both in different periods of development (in different phases growth), and depending on competitive relationships with other organisms, but especially on the level of other environmental factors: with a favorable combination of factors (when each of them is close to the optimal level, without deficiency), they are all used by the body most efficiently and economically. This is very important, in particular, for the practice of cultivating plants: by using agronomic techniques, it is possible to achieve the most rational use of environmental conditions by plants in crops, which always leads to increased yields. This is the ecological essence of agronomy: the plant must be provided optimal levels all environmental factors during the entire period of development of a given plant. It is clear that in order to achieve the best results, it is absolutely necessary to know the environmental characteristics of the cultivated plants and their changes throughout the entire development cycle of the plant.
I would also emphasize that the quality of a factor (its qualitative characteristics) is determined not only by the internal essence and characteristics of this factor (composition of light, air, water, soil), but also by the uniformity of its supply: plants require no deficiency during the entire period of active growing season. In this regard, it is essential bad influence vibrations affect plants weather conditions(periods with the return of cold weather, periods with a lack of precipitation, etc.) and uneven supply of nutrients to plants (failure to follow scientific recommendations for the correct use of fertilizers).
To get a clear idea of the law of tolerance, it is convenient to consider a diagram that shows the effect of this law for different organisms.
The diagram shows the main environmental factors for plants in the form of sectors. A short explanation is required here. Due to the presence of mineral compounds in the soil, plants are nourished. Therefore, each of the elements necessary for plants (nitrogen, phosphorus, potassium, calcium, sulfur and a number of others) is an environmental factor, as well as each physical property of the soil (moisture content, air content, density, etc.), since each of these factors influences the living conditions of plants in the soil. So, everything is chemical and physical properties soils are environmental soil factors.
The difference between plants and animals (II) and humans (III) is obvious: these organisms do not receive food from the soil and air, like plants, but use plants and animals (organic substances) as food.
It is appropriate here to give two more ecological terms: ecological niche and food chains. An ecological niche is understood as a complex of environmental factors between the minimum and maximum indicators for a particular organism. In other words, more generally, it is a set of characteristics that shows the position of a species in an ecosystem. It is within the limits of its individual ecological niche any species develops, reproduces and lives.