What factors are called environmental? Ecological environmental factors

Environmental factors is a complex of environmental conditions affecting living organisms. Distinguish inanimate factors— abiotic (climatic, edaphic, orographic, hydrographic, chemical, pyrogenic), wildlife factors— biotic (phytogenic and zoogenic) and anthropogenic factors (impact human activity). Limiting factors include any factors that limit the growth and development of organisms. The adaptation of an organism to its environment is called adaptation. The external appearance of an organism, reflecting its adaptability to environmental conditions, is called life form.

The concept of environmental environmental factors, their classification

Individual components of the environment that affect living organisms, to which they respond with adaptive reactions (adaptations), are called environmental factors, or environmental factors. In other words, the complex of environmental conditions affecting the life of organisms is called environmental environmental factors.

All environmental factors are divided into groups:

1. include components and phenomena of inanimate nature that directly or indirectly affect living organisms. Among the many abiotic factors, the main role is played by:

• climatic(solar radiation, light and light regime, temperature, humidity, precipitation, wind, atmospheric pressure, etc.);
• edaphic (mechanical structure and chemical composition of the soil, moisture capacity, water, air and thermal regime of the soil, acidity, humidity, gas composition, level groundwater and etc.);
• orographic(relief, slope exposure, slope steepness, elevation difference, altitude above sea level);
• hydrographic(water transparency, fluidity, flow, temperature, acidity, gas composition, content of mineral and organic substances, etc.);
• chemical(gas composition of the atmosphere, salt composition of water);
• pyrogenic(exposure to fire).

2. - the totality of relationships between living organisms, as well as their mutual influences on the habitat. The effect of biotic factors can be not only direct, but also indirect, expressed in the adjustment of abiotic factors (for example, changes in soil composition, microclimate under the forest canopy, etc.). Biotic factors include:

• phytogenic(the influence of plants on each other and on the environment);
• zoogenic(the influence of animals on each other and on the environment).

3. reflect the intense influence of humans (directly) or human activities (indirectly) on the environment and living organisms. Such factors include all forms of human activity and human society that lead to changes in nature as a habitat for other species and directly affect their lives. Every living organism is influenced by inanimate nature, organisms of other species, including humans, and in turn has an impact on each of these components.

The influence of anthropogenic factors in nature can be either conscious, accidental, or unconscious. Man, plowing virgin and fallow lands, creates agricultural land, breeds highly productive and disease-resistant forms, spreads some species and destroys others. These influences (conscious) are often negative, for example, the thoughtless resettlement of many animals, plants, microorganisms, the predatory destruction of a number of species, environmental pollution, etc.

Biotic environmental factors are manifested through the relationships of organisms belonging to the same community. In nature, many species are closely interrelated, their relationships with each other as components environment can be worn extremely complex nature. As for the connections between the community and the surrounding inorganic environment, they are always two-way, reciprocal. Thus, the nature of the forest depends on the corresponding type of soil, but the soil itself is largely formed under the influence of the forest. Similarly, temperature, humidity and light in the forest are determined by vegetation, but the prevailing climatic conditions in turn affect the community of organisms living in the forest.

Impact of environmental factors on the body

The impact of the environment is perceived by organisms through environmental factors called environmental. It should be noted that the environmental factor is only a changing element of the environment, causing in organisms, when it changes again, adaptive ecological and physiological reactions that are hereditarily fixed in the process of evolution. They are divided into abiotic, biotic and anthropogenic (Fig. 1).

They name the entire set of factors in the inorganic environment that influence the life and distribution of animals and plants. Among them there are: physical, chemical and edaphic.

Physical factors - those whose source is a physical state or phenomenon (mechanical, wave, etc.). For example, temperature.

Chemical factors- those that originate from the chemical composition of the environment. For example, water salinity, oxygen content, etc.

Edaphic (or soil) factors are a set of chemical, physical and mechanical properties of soils and rocks that affect both the organisms for which they are a habitat and the root system of plants. For example, the influence of nutrients, humidity, soil structure, humus content, etc. on plant growth and development.

Rice. 1. Scheme of the impact of the habitat (environment) on the body

— human activity factors affecting the natural environment (hydrosphere, soil erosion, forest destruction, etc.).

Limiting (limiting) environmental factors These are factors that limit the development of organisms due to a lack or excess of nutrients compared to the need (optimal content).

Thus, when growing plants at different temperatures, the point at which maximum growth occurs will be optimum. The entire temperature range, from minimum to maximum, at which growth is still possible is called range of stability (endurance), or tolerance. The points limiting it, i.e. the maximum and minimum temperatures suitable for life are the limits of stability. Between the optimum zone and the limits of stability, as it approaches the latter, the plant experiences increasing stress, i.e. we're talking about about stress zones, or zones of oppression, within the stability range (Fig. 2). As you move further down and up the scale from the optimum, not only does stress intensify, but when the limits of the body's resistance are reached, its death occurs.

Rice. 2. Dependence of the action of an environmental factor on its intensity

Thus, for each species of plant or animal there is an optimum, stress zones and limits of stability (or endurance) in relation to each environmental factor. When the factor is close to the limits of endurance, the organism can usually exist only for a short time. In a narrower range of conditions, long-term existence and growth of individuals is possible. In an even narrower range, reproduction occurs, and the species can exist indefinitely. Typically, somewhere in the middle of the resistance range there are conditions that are most favorable for life, growth and reproduction. These conditions are called optimal, in which individuals of a given species are the most fit, i.e. leave the greatest number of descendants. In practice, it is difficult to identify such conditions, so the optimum is usually determined by individual vital signs (growth rate, survival rate, etc.).

Adaptation consists in adapting the body to environmental conditions.

The ability to adapt is one of the main properties of life in general, ensuring the possibility of its existence, the ability of organisms to survive and reproduce. Adaptations manifest themselves at different levels - from the biochemistry of cells and the behavior of individual organisms to the structure and functioning of communities and ecological systems. All adaptations of organisms to existence in various conditions have been developed historically. As a result, groupings of plants and animals specific to each geographical zone were formed.

Adaptations may be morphological, when the structure of an organism changes until a new species is formed, and physiological, when changes occur in the functioning of the body. Closely related to morphological adaptations is the adaptive coloration of animals, the ability to change it depending on the light (flounder, chameleon, etc.).

Widely known examples of physiological adaptation are: hibernation animals, seasonal bird migrations.

Very important for organisms are behavioral adaptations. For example, instinctive behavior determines the action of insects and lower vertebrates: fish, amphibians, reptiles, birds, etc. This behavior is genetically programmed and inherited (innate behavior). This includes: the method of building a nest in birds, mating, raising offspring, etc.

There is also an acquired command, received by an individual in the course of his life. Education(or learning) - the main way of transmitting acquired behavior from one generation to another.

The ability of an individual to manage his cognitive abilities to survive unexpected changes in his environment is intelligence. The role of learning and intelligence in behavior increases with improvement nervous system- enlargement of the cerebral cortex. For humans, this is the defining mechanism of evolution. The ability of species to adapt to a particular range of environmental factors is denoted by the concept ecological mystique of the species.

The combined effect of environmental factors on the body

Environmental factors usually act not one at a time, but in a complex manner. The effect of one factor depends on the strength of the influence of others. Combination various factors has a significant impact on optimal conditions life of the organism (see Fig. 2). The action of one factor does not replace the action of another. However, with the complex influence of the environment, one can often observe a “substitution effect”, which manifests itself in the similarity of the results of the influence of different factors. Thus, light cannot be replaced by excess heat or an abundance of carbon dioxide, but by influencing changes in temperature, it is possible to stop, for example, plant photosynthesis.

In the complex influence of the environment, the impact of various factors on organisms is unequal. They can be divided into main, accompanying and secondary. The leading factors are different for different organisms, even if they live in the same place. The role of a leading factor at different stages of an organism’s life can be played by one or another element of the environment. For example, in the lives of many cultivated plants, such as cereals, during the period of germination the leading factor is temperature, during the period of heading and flowering - soil moisture, during the period of ripening - the amount of nutrients and air humidity. The role of the leading factor may change at different times of the year.

The leading factor may be different for the same species living in different physical and geographical conditions.

The concept of leading factors should not be confused with the concept of. A factor whose level in qualitative or quantitative terms (deficiency or excess) turns out to be close to the limits of endurance of a given organism, called limiting. The effect of the limiting factor will also manifest itself in the case when other environmental factors are favorable or even optimal. Both leading and secondary environmental factors can act as limiting factors.

The concept of limiting factors was introduced in 1840 by the chemist 10. Liebig. Studying the influence of the content of various chemical elements in the soil on plant growth, he formulated the principle: “The substance found in the minimum controls the yield and determines the size and stability of the latter over time.” This principle is known as Liebig's law of the minimum.

The limiting factor can be not only a deficiency, as Liebig pointed out, but also an excess of factors such as, for example, heat, light and water. As noted earlier, organisms are characterized by ecological minimums and maximums. The range between these two values ​​is usually called the limits of stability, or tolerance.

IN general view the entire complexity of the influence of environmental factors on the body is reflected by V. Shelford’s law of tolerance: the absence or impossibility of prosperity is determined by a deficiency or, conversely, an excess of any of a number of factors, the level of which may be close to the limits tolerated by a given organism (1913). These two limits are called tolerance limits.

Numerous studies have been carried out on the “ecology of tolerance”, thanks to which the limits of existence of many plants and animals have become known. Such an example is the effect of air pollutants on the human body (Fig. 3).

Rice. 3. The influence of air pollutants on the human body. Max - maximum vital activity; Additional - permissible vital activity; Opt - optimal (not affecting vital activity) concentration harmful substance; MPC is the maximum permissible concentration of a substance that does not significantly change vital activity; Years - lethal concentration

The concentration of the influencing factor (harmful substance) in Fig. 5.2 is indicated by the symbol C. At concentration values ​​of C = C years, a person will die, but irreversible changes in his body will occur at significantly lower values ​​of C = C MPC. Consequently, the range of tolerance is limited precisely by the value C MPC = C limit. Hence, C MPC must be determined experimentally for each pollutant or any harmful chemical compound and not allow it to exceed Cplc in a specific habitat (living environment).

In protecting the environment, it is important upper limits of body resistance to harmful substances.

Thus, the actual concentration of the pollutant C actual should not exceed C maximum permissible concentration (C fact ≤ C maximum permissible value = C lim).

The value of the concept of limiting factors (Clim) is that it gives the ecologist a starting point when studying difficult situations. If an organism is characterized by a wide range of tolerance to a factor that is relatively constant, and it is present in the environment in moderate quantities, then such a factor is unlikely to be limiting. On the contrary, if it is known that a particular organism has a narrow range of tolerance to some variable factor, then it is this factor that deserves careful study, since it may be limiting.

Competitors, etc. - are characterized by significant variability in time and space. The degree of variability of each of these factors depends on the characteristics of the habitat. For example, temperatures vary greatly at the land surface but are nearly constant at the ocean floor or deep in caves.

The same environmental factor has different significance in the life of co-living organisms. For example, the salt regime of the soil plays a primary role in the mineral nutrition of plants, but is indifferent to most terrestrial animals. The intensity of illumination and the spectral composition of light are extremely important in the life of phototrophic plants, and in the life of heterotrophic organisms (fungi and aquatic animals), light does not have a noticeable effect on their life activity.

Environmental factors affect organisms in different ways. They can act as irritants that cause adaptive changes in physiological functions; as limiters that make it impossible for certain organisms to exist under given conditions; as modifiers that determine morphological and anatomical changes in organisms.

Classification of environmental factors

It is customary to highlight biotic, anthropogenic And abiotic environmental factors.

• Biotic factors- all the many environmental factors associated with the activities of living organisms. These include phytogenic (plants), zoogenic (animals), microbiogenic (microorganisms) factors.
• Anthropogenic factors- all the many factors associated with human activity. These include physical (use of nuclear energy, movement on trains and airplanes, the influence of noise and vibration, etc.), chemical (use mineral fertilizers and toxic chemicals, pollution of the Earth’s shells with industrial and transport waste; biological (food; organisms for which a person can be a habitat or source of nutrition), social (related to relationships between people and life in society) factors.
• Abiotic factors- all the many factors associated with processes in inanimate nature. These include climate ( temperature regime, humidity, pressure), edaphogenic (mechanical composition, air permeability, soil density), orographic (relief, altitude above sea level), chemical (gas composition of air, salt composition of water, concentration, acidity), physical (noise, magnetic fields, thermal conductivity , radioactivity, cosmic radiation)

Frequently encountered classification of environmental factors (environmental factors)

BY TIME: evolutionary, historical, active

BY PERIODICITY: periodic, non-periodic

ORDER OF APPEARANCE: primary, secondary

BY ORIGIN: cosmic, abiotic (also known as abiogenic), biogenic, biological, biotic, natural-anthropogenic, anthropogenic (including man-made, environmental pollution), anthropic (including disturbances)

BY WEDNESDAY OF APPEARANCE: atmospheric, aquatic (aka humidity), geo-morphological, edaphic, physiological, genetic, population, biocenotic, ecosystem, biosphere

THE NATURE: material-energy, physical (geophysical, thermal), biogenic (also biotic), informational, chemical (salinity, acidity), complex (ecological, evolutionary, system-forming, geographical, climatic)

BY OBJECT: individual, group (social, ethological, socio-economic, socio-psychological, species (including human, social life)

ACCORDING TO ENVIRONMENTAL CONDITIONS: density dependent, density independent

BY DEGREE OF IMPACT: lethal, extreme, limiting, disturbing, mutagenic, teratogenic; carcinogenic

BY IMPACT SPECTRUM: selective, general action

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The term “ecology” was introduced into science by the German scientist Ernst Haeckel in 1869. A formal definition is quite easy to give, since the word “ecology” comes from the Greek words “oikos” - dwelling, shelter and “logos” - science. Therefore, ecology is often defined as the science of the relationships between organisms or groups of organisms (populations, species) with their environment. In other words, the subject of ecology is a set of connections between organisms and the conditions of their existence (environment), on which the success of their survival, development, reproduction, distribution, and competitiveness depends.

In botany, the term “ecology” was first used by the Danish botanist E. Warming in 1895.

In a broad sense, the environment (or environment) is understood as a set of material bodies, phenomena and energy, waves and fields that in one way or another influence. However, different environments are far from being perceived equally by a living organism, since their significance for life is different. Among them there are practically indifferent to plants, for example, inert gases contained in the atmosphere. Other elements of the environment, on the contrary, have a noticeable, often significant effect on the plant. They are called environmental factors. These are, for example, light, water in the atmosphere and in the soil, air, salinization of groundwater, natural and artificial radioactivity, etc.). With the deepening of our knowledge, the list of environmental factors is expanding, since in some cases it is discovered that plants are able to respond to elements of the environment that were previously considered indifferent (for example, magnetic field, strong noise exposure, electric fields, etc.).

Classification of environmental factors

Environmental factors can be classified in different conceptual coordinate systems.

There are, for example, resource and non-resource environmental factors. Resource factors are a substance and (or) involved in the biological cycle by the plant community (for example, light, water, the content of mineral nutrition elements in the soil, etc.); Accordingly, non-resource factors do not participate in cycles of transformation of matter and energy and ecosystems (for example, relief).

There are also direct and indirect environmental factors. The former directly affect metabolism, morphogenesis processes, growth and development (light), the latter affect the body through changes in other factors (for example, transabiotic and transbiotic forms of interactions). Since in different environmental situations many factors can act both directly and indirectly, it is better to talk not about the separation of factors, but about their direct or indirect effect on the plant.

The most widely used classification of environmental factors according to their origin and nature of action is:

I. Abiotic factors:

a) climatic - light, heat (its composition and movement), moisture (including precipitation in various forms, air humidity), etc.;

b) edaphic (or soil-soil) - physical (particle-size composition, water permeability) and chemical (soil pH, content of mineral nutrition elements, macro- and microelements, etc.) properties of soils;

c) topographic (or orographic) - relief conditions.

II. Biotic factors:

a) phytogenic - direct and indirect effects of co-inhabiting plants;

b) zoogenic - direct and indirect influence of animals (eating, trampling, digging activities, pollination, distribution of fruits and seeds);

c) prokaryotogenic factors - the influence of bacteria and blue-green algae (negative effects of phytopathogenic bacteria, positive effects of free-living and symbiotically associated nitrogen-fixing bacteria, actinomycetes and cyanides);

Read more about biotic factors you can read the article

Specific forms of human impact on vegetation, their direction, and scale make it possible to identify anthropogenic factors.

III. Anthropogenic factors associated with multilateral forms of human agricultural activity (grazing, haymaking), industrial activities (gas emissions, construction, mining, transport communications and pipelines), space exploration and recreational activities.

This simple classification does not fit everything, but only the main environmental factors. There are other plants that are less essential for life (atmospheric electricity, the Earth’s magnetic field, ionizing radiation, etc.).

Note, however, that the above division is to a certain extent arbitrary, since (and this is important to emphasize both in theoretical and in practical terms) the environment affects the organism as a whole, and the separation of factors and their classification is nothing more than a methodological technique that facilitates the knowledge and study of the patterns of relationships between the plant and the environment.

General patterns of influence of environmental factors

The influence of environmental factors on a living organism is very diverse. Some factors - leading - have a stronger impact, others - secondary - have a weaker effect; Some factors influence all aspects of a plant’s life, others influence any specific life process. Nevertheless, it is possible to imagine a general diagram of the dependence of the body’s reaction under the influence of an environmental factor.

If the intensity of the factor in its physical expression is plotted along the abscissa axis (X) ( , concentration of salts in the soil solution, pH, illumination of the habitat, etc.), and along the ordinate axis (Y) - the reaction of the organism or population to this factor in its quantitative expression (intensity of a particular physiological process - photosynthesis, water absorption by roots, growth, etc.; morphological characteristics - plant height, leaf size, number of seeds produced, etc.; population characteristics - number of individuals per unit area , frequency of occurrence, etc.), we get the following picture.

The range of action of the environmental factor (the area of ​​tolerance of the species) is limited by the minimum and maximum points, which correspond to the extreme values ​​of this factor at which the plant’s existence is possible. The point on the x-axis corresponding to the best performance indicators of the plant means the optimal value of the factor - this is the optimum point. Due to difficulties in precise definition This point is usually spoken of as a certain optimum zone, or comfort zone. The points of optimum, minimum and maximum constitute three cardinal points that determine the possibility of a species’ reaction to a given factor. The extreme sections of the curve, expressing the state of oppression with a sharp deficiency or excess of a factor, are called pessimum areas; they correspond to the pessimal values ​​of the factor. Near the critical points there are sublethal values ​​of the factor, and outside the tolerance zone - lethal values.

Species differ from each other in the position of the optimum within the gradient of the environmental factor. For example, the attitude towards heat in arctic and tropical species. The width of the range of action of the factor (or optimum zone) may also be different. There are species, for example, for which a low level of illumination is optimal (cave bryophytes) or relatively high level illumination (high mountain alpine plants). But there are also species known that grow equally well both in full light and in significant shading (for example, the hedgehog - Dactylis glomerata).

Exactly the same alone meadow grass prefer soils with a certain, rather narrow range of acidity, others grow well in a wide range of pH - from strongly acidic to alkaline. The first case indicates a narrow ecological amplitude of plants (they are stenobiont or stenotopic), the second - a wide ecological amplitude (the plants are eurybiont or eurytopic). Between the categories of eurytopic and stenotopic there are a number of intermediate qualitative categories (hemieurytopic, hemistenotopic).

The breadth of ecological amplitude in relation to different environmental factors is often different. It is possible to be stenotopic with respect to one factor and eurytopic with respect to another: for example, plants can be confined to a narrow range of temperatures and a wide range of salinity.

Interaction of environmental factors

Environmental factors influence the plant jointly and simultaneously, and the effect of one factor largely depends on the “ecological background,” i.e., on the quantitative expression of other factors. This phenomenon of interaction of factors is clearly illustrated by the example of an experiment with the aquatic moss Fontinalis. This experiment clearly shows that illumination has a different effect on the intensity of photosynthesis at different CO 2 contents.

The experiment also shows that a similar biological effect can be obtained by partially replacing the action of one factor with another. Thus, the same intensity of photosynthesis can be achieved either by increasing illumination to 18 thousand lux, or, at lower illumination, by increasing the concentration of CO 2.

Here the partial interchangeability of the action of one environmental factor with another is manifested. At the same time, none of the necessary environmental factors can be replaced by another: a green plant cannot be grown in complete darkness, even with very good mineral nutrition or with distilled water under optimal thermal conditions. In other words, there is a partial replaceability of the main environmental factors and at the same time their complete irreplaceability (in this sense, they are sometimes also said to be of equal importance for the life of a plant). If the value of at least one of the necessary factors goes beyond the tolerance range (below the minimum and above the maximum), then the existence of the organism becomes impossible.

Limiting factors

If any of the factors that make up the conditions of existence has a pessimal value, then it limits the action of the remaining factors (no matter how favorable they may be) and determines the final result of the action of the environment on the plant. This end result can only be changed by influencing the limiting factor. This “limiting factor law” was first formulated in agricultural chemistry by the German agricultural chemist, one of the founders of agricultural chemistry, Justus Liebig in 1840 and is therefore often called Liebig’s law.

He noticed that if there is a deficiency of one of the necessary chemical elements in the soil or nutrient solution, no fertilizers containing other elements have an effect on the plant, and only the addition of “minimum ions” gives an increase in yield. Numerous examples of the action of limiting factors not only in experiment, but also in nature show that this phenomenon has general ecological significance. One example of the “law of the minimum” in nature is oppression herbaceous plants under the canopy of beech forests, where, with optimal thermal conditions, increased carbon dioxide content, sufficiently rich soils and other optimal conditions, the possibilities for the development of grasses are limited by a sharp lack of light.

Identifying “factors at a minimum” (and at a maximum) and eliminating their limiting effect, in other words, optimizing the environment for plants, constitutes an important practical task in rational use vegetation cover.

Autecological and synecological area and optimum

The attitude of plants to environmental factors closely depends on the influence of other plant-inhabitants (primarily on competitive relations with them). Often there is a situation where a species can successfully grow in a wide range of action of some factor (which is determined experimentally), but the presence of a strong competitor forces it to be limited to a narrower zone.

For example, Scots pine (Pinus sylvestris) has a very wide ecological range in relation to soil factors, but in the taiga zone it forms forests mainly on dry, poor sandy soils or on heavily waterlogged peatlands, i.e. where there are no competing tree species. Here, the actual position of optima and tolerance regions is different for plants that do or do not experience biotic influence. In this regard, a distinction is made between the ecological optimum of a species (in the absence of competition) and the phytocenotic optimum, which corresponds to the actual position of the species in the landscape or biome.

In addition to the optimum position, the endurance limits of a species are distinguished: the ecological area (the potential limits of the species' distribution, determined only by its relationship to a given factor) and the actual phytocenotic area.

Often in this context they talk about potential and actual optimum and range. IN foreign literature They also write about the physiological and ecological optimum and habitat. It is better to talk about the autecological and synecological optimum and the range of the species.

U different types the ratio of ecological and phytocenotic areas is different, but the ecological one is always wider than the phytocenotic one. As a result of plant interaction, a narrowing of the range and often a shift in the optimum occurs.

Any properties or components of the external environment that influence organisms are called environmental factors. Light, heat, salt concentration in water or soil, wind, hail, enemies and pathogens - all these are environmental factors, the list of which can be very large.

Among them there are abiotic related to inanimate nature, and biotic related to the influence of organisms on each other.

Environmental factors are extremely diverse, and each species, experiencing their influence, responds to it differently. However, there are some general laws that govern the responses of organisms to any environmental factor.

The main one is law of optimum. It reflects how living organisms tolerate different strengths of environmental factors. The strength of each of them is constantly changing. We live in a world with variable conditions, and only in certain places on the planet the values ​​of some factors are more or less constant (in the depths of caves, at the bottom of the oceans).

The law of optimum is expressed in the fact that any environmental factor has certain limits of positive influence on living organisms.

When deviating from these limits, the sign of the effect changes to the opposite. For example, animals and plants do not tolerate extreme heat and severe frost; Medium temperatures are optimal. Likewise, drought and constant heavy rain are equally unfavorable to the crop. The law of optimum indicates the extent of each factor for the viability of organisms. On the graph it is expressed by a symmetrical curve showing how the vital activity of the species changes with a gradual increase in the influence of the factor (Fig. 13).

Figure 13. Scheme of the action of environmental factors on living organisms. 1,2 - critical points
(to enlarge the image, click on the picture)

In the center under the curve - optimum zone. At optimal values ​​of the factor, organisms actively grow, feed, and reproduce. The more the factor value deviates to the right or to the left, i.e. in the direction of decreasing or increasing the force of action, the less favorable it is for organisms. The curve reflecting vital activity descends sharply on either side of the optimum. There are two pessimum zones. When the curve intersects with horizontal axis there are two critical points. These are the values ​​of the factor that organisms can no longer withstand, beyond which death occurs. The distance between critical points shows the degree of tolerance of organisms to changes in the factor. Conditions close to critical points are especially difficult for survival. Such conditions are called extreme.

If you draw optimum curves for a factor, such as temperature, for different species, they will not coincide. Often what is optimal for one species is pessimistic for another or even lies outside the critical points. Camels and jerboas could not live in the tundra, and reindeer and lemmings could not live in the hot southern deserts.

The ecological diversity of species is also manifested in the position of critical points: for some they are close together, for others they are widely spaced. This means that a number of species can live only in very stable conditions, with minor changes in environmental factors, while others can withstand wide fluctuations. For example, the impatiens plant withers if the air is not saturated with water vapor, and feather grass tolerates changes in humidity well and does not die even in drought.

Thus, the law of optimum shows us that for each type there is its own measure of the influence of each factor. Both a decrease and an increase in exposure beyond this measure leads to the death of organisms.

For understanding the relationship of species with the environment, it is no less important limiting factor law.

In nature, organisms are simultaneously influenced by a whole complex of environmental factors in different combinations and with different strengths. It is not easy to isolate the role of each of them. Which one means more than the others? What we know about the law of optimum allows us to understand that there are no entirely positive or negative, important or secondary factors, but everything depends on the strength of each influence.

The law of the limiting factor states that the most significant factor is the one that deviates the most from the optimal values ​​for the body.

The survival of individuals in this particular period depends on it. At other periods of time, other factors may become limiting, and throughout life, organisms encounter a variety of restrictions on their life activity.

Agricultural practice constantly faces the laws of optimum and limiting factors. For example, the growth and development of wheat, and therefore the harvest, are constantly limited by critical temperatures, either a lack or excess of moisture, or a lack of mineral fertilizers, and sometimes such catastrophic effects as hail and storms. It takes a lot of effort and money to maintain optimal conditions for crops, and at the same time, first of all, compensate or mitigate the effect of limiting factors.

Living conditions various types amazingly varied. Some of them, for example, some small mites or insects, spend their entire lives inside the leaf of a plant, which is the whole world for them, others master vast and varied spaces, such as reindeer, whales in the ocean, migratory birds.

Depending on where representatives of different species live, they are affected by different complexes environmental factors. On our planet there are several basic living environments, very different in terms of living conditions: water, ground-air, soil. Habitats are also the organisms themselves in which others live.

Aquatic living environment. All aquatic inhabitants, despite differences in lifestyle, must be adapted to the main features of their environment. These features are determined, first of all, by the physical properties of water: its density, thermal conductivity, and ability to dissolve salts and gases.

Density water determines its significant buoyant force. This means that the weight of organisms in water is lightened and it becomes possible to lead a permanent life in the water column without sinking to the bottom. Many species, mostly small, incapable of fast active swimming, seem to float in the water, being suspended in it. The collection of such small aquatic inhabitants is called plankton. Plankton includes microscopic algae, small crustaceans, fish eggs and larvae, jellyfish and many other species. Planktonic organisms are carried by currents and are unable to resist them. The presence of plankton in water makes possible the filtration type of nutrition, i.e., straining, using various devices, small organisms and food particles suspended in water. It is developed in both swimming and sessile bottom animals, such as crinoids, mussels, oysters and others. A sedentary lifestyle would be impossible for aquatic inhabitants if there were no plankton, and this, in turn, is possible only in an environment with sufficient density.

The density of water makes active movement in it difficult, so fast-swimming animals, such as fish, dolphins, squids, must have strong muscles and a streamlined body shape. Due to the high density of water, pressure increases greatly with depth. Deep-sea inhabitants are able to withstand pressure that is thousands of times higher than on the land surface.

Light penetrates water only to a shallow depth, so plant organisms can exist only in the upper horizons of the water column. Even in the most clean seas photosynthesis is possible only to depths of 100-200 m. At greater depths there are no plants, and deep-sea animals live in complete darkness.

Temperature in water bodies it is softer than on land. Because of high heat capacity water, temperature fluctuations in it are smoothed out, and aquatic inhabitants do not face the need to adapt to severe frosts or forty-degree heat. Only in hot springs can the water temperature approach the boiling point.

One of the difficulties in the life of aquatic inhabitants is limited amount of oxygen. Its solubility is not very high and, moreover, decreases greatly when the water is polluted or heated. Therefore, in reservoirs there are sometimes freezes- mass death of inhabitants due to lack of oxygen, which occurs for various reasons.

Salt composition The environment is also very important for aquatic organisms. Marine species cannot live in fresh waters, and freshwater - in the seas due to disruption of cell function.

Ground-air environment of life. This environment has a different set of features. It is generally more complex and varied than aquatic. It has a lot of oxygen, a lot of light, sharper temperature changes in time and space, significantly weaker pressure drops and moisture deficiency often occurs. Although many species can fly, and small insects, spiders, microorganisms, seeds and plant spores are carried by air currents, feeding and reproduction of organisms occurs on the surface of the ground or plants. In such a low-density environment as air, organisms need support. Therefore, land plants have developed mechanical fabrics, and in terrestrial animals, the internal or external skeleton is more pronounced than in aquatic animals. The low density of air makes it easier to move around in it.

M. S. Gilyarov (1912-1985), a prominent zoologist, ecologist, academician, founder of extensive research into the world of soil animals, passive flight was mastered by about two-thirds of land inhabitants. Most of them are insects and birds.

Air is a poor conductor of heat. This makes it easier to conserve heat generated inside organisms and maintain a constant temperature in warm-blooded animals. The very development of warm-bloodedness became possible in terrestrial environment. The ancestors of modern aquatic mammals - whales, dolphins, walruses, seals - once lived on land.

Land dwellers have a wide variety of adaptations related to providing themselves with water, especially in dry conditions. In plants it is powerful root system, a waterproof layer on the surface of leaves and stems, the ability to regulate water evaporation through stomata. In animals, these are also different structural features of the body and integument, but, in addition, appropriate behavior also contributes to maintaining water balance. They may, for example, migrate to watering holes or actively avoid particularly dry conditions. Some animals can live their entire lives on dry food, such as jerboas or the well-known clothes moth. In this case, the water needed by the body arises due to the oxidation of food components.

Many other environmental factors also play an important role in the life of terrestrial organisms, such as air composition, winds, and the topography of the earth's surface. Weather and climate are especially important. The inhabitants of the land-air environment must be adapted to the climate of the part of the Earth where they live and tolerate variability in weather conditions.

Soil as a living environment. The soil is thin layer surface of the land, processed by the activity of living beings. Solid particles are permeated in the soil with pores and cavities, filled partly with water and partly with air, so small aquatic organisms can also inhabit the soil. The volume of small cavities in the soil is a very important characteristic of it. In loose soils it can be up to 70%, and in dense soils it can be about 20%. In these pores and cavities or on the surface of solid particles live a huge variety of microscopic creatures: bacteria, fungi, protozoa, roundworms, arthropods. Larger animals make passages in the soil themselves. The entire soil is penetrated by plant roots. Soil depth is determined by the depth of root penetration and the activity of burrowing animals. It is no more than 1.5-2 m.

The air in soil cavities is always saturated with water vapor, and its composition is enriched in carbon dioxide and depleted in oxygen. These living conditions in the soil resemble aquatic environment. On the other hand, the ratio of water and air in soils is constantly changing depending on weather conditions. Temperature fluctuations are very sharp at the surface, but quickly smooth out with depth.

The main feature of the soil environment is the constant supply organic matter mainly due to dying plant roots and falling leaves. It is a valuable source of energy for bacteria, fungi and many animals, so soil is the most vibrant environment. Her hidden world is very rich and diverse.

By the appearance of different species of animals and plants, one can understand not only what environment they live in, but also what kind of life they lead in it.

If we have in front of us a four-legged animal with highly developed muscles of the thighs on the hind legs and much weaker muscles on the front legs, which are also shortened, with a relatively short neck and a long tail, then we can confidently say that this is a ground jumper, capable for fast and maneuverable movements, inhabitant of open spaces. The famous Australian kangaroos, desert Asian jerboas, African jumpers, and many other jumping mammals - representatives of various orders living on different continents - look like this. They live in steppes, prairies, and savannas - where fast movement on the ground is the main means of escape from predators. The long tail serves as a balancer during fast turns, otherwise the animals would lose their balance.

The hips are strongly developed on the hind limbs and in jumping insects - locusts, grasshoppers, fleas, psyllid beetles.

A compact body with a short tail and short limbs, of which the front ones are very powerful and look like a shovel or rake, blind eyes, a short neck and short, as if trimmed, fur tell us that this is an underground animal that digs holes and galleries. . This could be a forest mole, a steppe mole rat, an Australian marsupial mole, and many other mammals leading a similar lifestyle.

Burrowing insects - mole crickets are also distinguished by their compact, stocky body and powerful forelimbs, similar to a reduced bulldozer bucket. In appearance they resemble a small mole.

All flying species have developed wide planes - wings in birds, bats, insects, or straightening folds of skin on the sides of the body, like in gliding flying squirrels or lizards.

Organisms that disperse through passive flight, with air currents, are characterized by small sizes and very diverse shapes. However, they all have one thing in common - strong surface development compared to body weight. This is achieved in different ways: due to long hairs, bristles, various outgrowths of the body, its lengthening or flattening, lightening specific gravity. This is what small insects and flying fruits of plants look like.

External similarity that arises among representatives of different unrelated groups and species as a result of a similar lifestyle is called convergence.

It affects mainly those organs that directly interact with the external environment, and is much less pronounced in the structure internal systems- digestive, excretory, nervous.

The shape of a plant determines the characteristics of its relationship with the external environment, for example, the way it tolerates the cold season. Trees and tall shrubs have the highest branches.

The form of a vine - with a weak trunk entwining other plants, can be found in both woody and herbaceous species. These include grapes, hops, meadow dodder, and tropical vines. Wrapping around the trunks and stems of upright species, liana-like plants bring their leaves and flowers to the light.

In similar climatic conditions on different continents, a similar appearance of vegetation arises, which consists of different, often completely unrelated species.

The external form, reflecting the way it interacts with the environment, is called the life form of the species. Different species may have similar life forms, if they lead a close lifestyle.

The life form is developed during the centuries-long evolution of species. Those species that develop with metamorphosis naturally change their life form during the life cycle. Compare, for example, a caterpillar and an adult butterfly or a frog and its tadpole. Some plants can take on different life forms depending on their growing conditions. For example, linden or bird cherry can be both an upright tree and a bush.

Communities of plants and animals are more stable and more complete if they include representatives of different life forms. This means that such a community makes fuller use of environmental resources and has more diverse internal connections.

The composition of life forms of organisms in communities serves as an indicator of the characteristics of their environment and the changes occurring in it.

Engineers who design aircraft carefully study the different life forms of flying insects. Models of machines with flapping flight have been created, based on the principle of movement in the air of Diptera and Hymenoptera. Modern technology has constructed walking machines, as well as robots with lever and hydraulic methods of movement, like animals of different life forms. Such vehicles are capable of moving on steep slopes and off-road.

Life on Earth developed under conditions of regular day and night and alternating seasons due to the rotation of the planet around its axis and around the Sun. The rhythm of the external environment creates periodicity, i.e., repeatability of conditions in the life of most species. Both critical periods, difficult for survival, and favorable ones are repeated regularly.

Adaptation to periodic changes in the external environment is expressed in living beings not only by a direct reaction to changing factors, but also in hereditarily fixed internal rhythms.

Circadian rhythms. Circadian rhythms adapt organisms to the cycle of day and night. In plants, intensive growth and flower blooming are timed to a certain time of day. Animals change their activity greatly throughout the day. Based on this feature, diurnal and nocturnal species are distinguished.

The daily rhythm of organisms is not only a reflection of changing external conditions. If you place a person, or animals, or plants in a constant, stable environment without a change of day and night, then the rhythm of life processes is maintained, close to the daily rhythm. The body seems to live according to its internal clock, counting down time.

The circadian rhythm can affect many processes in the body. In humans, about 100 physiological characteristics are subject to the daily cycle: heart rate, breathing rhythm, secretion of hormones, secretions of the digestive glands, blood pressure, body temperature and many others. Therefore, when a person is awake instead of sleeping, the body is still tuned to the night state and sleepless nights have a bad effect on health.

However, circadian rhythms do not appear in all species, but only in those in whose lives the change of day and night plays an important ecological role. The inhabitants of caves or deep waters, where there is no such change, live according to different rhythms. And even among land dwellers, not everyone exhibits daily periodicity.

In experiments under strictly constant conditions, Drosophila fruit flies maintain a daily rhythm for tens of generations. This periodicity is inherited in them, as in many other species. So profound are the adaptive reactions associated with the daily cycle of the external environment.

Disturbances in the body's circadian rhythm during night work, space flights, scuba diving, etc. represent a serious medical problem.

Annual rhythms. Annual rhythms adapt organisms to seasonal changes in conditions. In the life of species, periods of growth, reproduction, molting, migration, and deep rest naturally alternate and repeat in such a way that critical time organisms are found in the most stable state. The most vulnerable process - reproduction and rearing of young animals - occurs during the most favorable season. This periodicity of changes in physiological state throughout the year is largely innate, that is, it manifests itself as an internal annual rhythm. If, for example, Australian ostriches or the wild dog dingo are placed in a zoo in the Northern Hemisphere, their breeding season will begin in the fall, when it is spring in Australia. The restructuring of internal annual rhythms occurs with great difficulty, over a number of generations.

Preparation for reproduction or overwintering is a long process that begins in organisms long before the onset of critical periods.

Sharp short-term changes in weather (summer frosts, winter thaws) usually do not disrupt the annual rhythms of plants and animals. The main environmental factor to which organisms respond in their annual cycles is not random changes in weather, but photoperiod- changes in the ratio of day and night.

The length of daylight hours naturally changes throughout the year, and it is these changes that serve as an accurate signal of the approach of spring, summer, autumn or winter.

The ability of organisms to respond to changes in day length is called photoperiodism.

If the day shortens, species begin to prepare for winter; if it lengthens, they begin to actively grow and reproduce. In this case, what is important for the life of organisms is not the change in the length of day and night itself, but its signal value, indicating impending profound changes in nature.

As is known, the length of the day greatly depends on geographical latitude. In the northern hemisphere, summer days are much shorter in the south than in the north. Therefore, southern and northern species react differently to the same amount of day change: southern species begin to reproduce with shorter days than northern ones.

ENVIRONMENTAL FACTORS

Ivanova T.V., Kalinova G.S., Myagkova A.N. "General Biology". Moscow, "Enlightenment", 2000

• Topic 18. "Habitat. Environmental factors." Chapter 1; pp. 10-58
• Topic 19. "Populations. Types of relationships among organisms." chapter 2 §8-14; pp. 60-99; Chapter 5 § 30-33
• Topic 20. "Ecosystems." chapter 2 §15-22; pp. 106-137
• Topic 21. "Biosphere. Cycles of matter." Chapter 6 §34-42; pp. 217-290

These are any environmental factors to which the body responds with adaptive reactions.

Environment is one of the main ecological concepts, which means a complex of environmental conditions that affect the life of organisms. In a broad sense, the environment is understood as the totality of material bodies, phenomena and energy that affect the body. It is also possible to have a more specific, spatial understanding of the environment as the immediate surroundings of an organism - its habitat. The habitat is everything that an organism lives among; it is a part of nature that surrounds living organisms and has a direct or indirect influence on them. Those. elements of the environment that are not indifferent to a given organism or species and in one way or another influence it are factors in relation to it.

The components of the environment are diverse and changeable, therefore living organisms constantly adapt and regulate their life activities in accordance with the occurring variations in the parameters of the external environment. Such adaptations of organisms are called adaptation and allow them to survive and reproduce.

All environmental factors are divided into

• Abiotic factors are factors of inanimate nature that directly or indirectly affect the body - light, temperature, humidity, chemical composition of the air, water and soil environment, etc. (i.e., properties of the environment, the occurrence and impact of which does not directly depend on the activity of living organisms) .
• Biotic factors are all forms of influence on the body from surrounding living beings (microorganisms, the influence of animals on plants and vice versa).
• Anthropogenic factors are various forms of activity of human society that lead to changes in nature as the habitat of other species or directly affect their lives.

Environmental factors affect living organisms

• as irritants causing adaptive changes in physiological and biochemical functions;
• as limitations that make it impossible to exist in given conditions;
• as modifiers that cause structural and functional changes in organisms, and as signals indicating changes in other environmental factors.

In this case, it is possible to establish the general nature of the impact of environmental factors on a living organism.

Any organism has a specific set of adaptations to environmental factors and exists safely only within certain limits of their variability. The most favorable level of the factor for life is called optimal.

At small values ​​or with excessive exposure to the factor, the vital activity of organisms drops sharply (noticeably inhibited). The range of action of an environmental factor (the area of ​​tolerance) is limited by the minimum and maximum points corresponding to the extreme values ​​of this factor at which the existence of the organism is possible.

The upper level of the factor, beyond which the vital activity of organisms becomes impossible, is called the maximum, and the lower level is called the minimum (Fig.). Naturally, each organism is characterized by its own maximums, optimums and minimums of environmental factors. For example, a housefly can withstand temperature fluctuations from 7 to 50 ° C, but the human roundworm lives only at human body temperature.

The optimum, minimum and maximum points make up three cardinal points that determine the body’s ability to react to a given factor. The extreme points of the curve, expressing the state of oppression with a deficiency or excess of a factor, are called pessimum areas; they correspond to the pessimal values ​​of the factor. Near the critical points there are sublethal values ​​of the factor, and outside the tolerance zone there are lethal zones of the factor.

Environmental conditions under which any factor or their combination goes beyond the comfort zone and has a depressing effect are often called extreme, borderline (extreme, difficult) in ecology. They characterize not only environmental situations (temperature, salinity), but also habitats where conditions are close to the limits of existence for plants and animals.

Any living organism is simultaneously affected by a complex of factors, but only one of them is limiting. A factor that sets the framework for the existence of an organism, species or community is called limiting (limiting). For example, the distribution of many animals and plants to the north is limited by a lack of heat, while in the south the limiting factor for the same species may be a lack of moisture or necessary food. However, the limits of the body's endurance in relation to the limiting factor depend on the level of other factors.

The life of some organisms requires conditions limited by narrow limits, that is, the optimum range is not constant for the species. The optimum effect of the factor is different in different species. The span of the curve, i.e., the distance between the threshold points, shows the area of ​​influence of the environmental factor on the body (Fig. 104). In conditions close to the threshold action of the factor, organisms feel depressed; they may exist, but do not reach full development. The plants usually do not bear fruit. In animals, on the contrary, puberty accelerates.

The magnitude of the range of action of the factor and especially the optimum zone makes it possible to judge the endurance of organisms in relation to a given element of the environment and indicates their ecological amplitude. In this regard, organisms that can live in fairly diverse environmental conditions are called zvrybionts (from the Greek “euros” - wide). For example, a brown bear lives in cold and warm climates, in dry and humid areas, and eats a variety of plant and animal foods.

In relation to private environmental factors, a term beginning with the same prefix is ​​used. For example, animals that can live in a wide range of temperatures are called eurythermal, while organisms that can live only in narrow temperature ranges are called stenothermic. By the same principle, an organism can be euryhydrid or stenohydrid, depending on its response to fluctuations in humidity; euryhaline or stenohaline - depending on the ability to tolerate different meanings salinity of the environment, etc.

There are also the concepts of ecological valence, which represents the ability of an organism to inhabit a variety of environments, and ecological amplitude, which reflects the width of the range of a factor or the width of the optimum zone.

The quantitative patterns of the reaction of organisms to the action of an environmental factor differ in accordance with their living conditions. Stenobionticity or eurybionticity does not characterize the specificity of a species in relation to any environmental factor. For example, some animals are confined to a narrow range of temperatures (i.e., stenothermic) and at the same time can exist in a wide range of environmental salinity (euryhaline).

Environmental factors influence a living organism simultaneously and jointly, and the action of one of them depends to a certain extent on the quantitative expression of other factors - light, humidity, temperature, surrounding organisms, etc. This pattern is called the interaction of factors. Sometimes the deficiency of one factor is partially compensated by the increased activity of another; partial substitutability of the effects of environmental factors appears. At the same time, none of the factors necessary for the body can be completely replaced by another. Phototrophic plants cannot grow without light under the most optimal temperature or nutrition conditions. Therefore, if the value of at least one of the necessary factors goes beyond the tolerance range (below the minimum or above the maximum), then the existence of the organism becomes impossible.

Environmental factors that have a pessimal value in specific conditions, i.e., those that are furthest from the optimum, especially complicate the possibility of the species existing in these conditions, despite the optimal combination of other conditions. This dependence is called the law of limiting factors. Such factors deviating from the optimum acquire paramount importance in the life of a species or individual individuals, determining their geographic range.

Identification of limiting factors is very important in agricultural practice to establish ecological valency, especially in the most vulnerable (critical) periods of the ontogenesis of animals and plants.