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General patterns of the action of environmental factors on organisms

Total environmental factors, affecting the body or the biocenosis, is huge, some of them are well known and understood, for example, the temperature of water and air, the effect of others, for example, changes in the force of gravity, has only recently begun to be studied. Despite the wide variety of environmental factors, a number of regularities can be distinguished in the nature of their impact on organisms and in the responses of living beings.

The law of optimum (tolerance)

According to this law, first formulated by W. Shelford, for a biocenosis, an organism or a certain stage of its development, there is a range of the most favorable (optimal) value of the factor. Outside the optimum zone, there are zones of oppression, turning into critical points beyond which existence is impossible.

The maximum population density is usually confined to the optimum zone. Optimum zones for various organisms are not the same. For some, they have a significant range. Such organisms belong to the group eurybionts(Greek euri - wide; bios - life).

Organisms with a narrow range of adaptation to factors are called stenobionts(Greek stenos - narrow).

Species that can survive over a wide range of temperatures are called eurythermal, and those that are able to live only in a narrow range of temperature values ​​- stenothermic.

The ability to live in conditions with different salinity of water is called euryhaline, at various depths - eurybacity, in places with different soil moisture - eurygyricity etc. It is important to emphasize that the optimal zones in relation to various factors differ, and therefore organisms fully show their potential capabilities if the entire range of factors has optimal values ​​for them.

The ambiguity of the effect of environmental factors on different functions organism

Each environmental factor affects different functions of the body in different ways. The optimum for some processes may be oppressive for others. For example, air temperature from + 40 to + 45 ° C in cold-blooded animals greatly increases the rate of metabolic processes in the body, but at the same time inhibits motor activity, which ultimately leads to thermal torpor. For many fish, the water temperature, which is optimal for the maturation of reproductive products, is unfavorable for spawning.

The life cycle, in which at certain periods of time the body mainly performs certain functions (nutrition, growth, reproduction, resettlement, etc.), is always consistent with seasonal changes in the totality of environmental factors. At the same time, mobile organisms can change their habitats for the successful implementation of all the needs of their lives.

Variety of individual responses to environmental factors

Endurance capacity, critical points, zones of optimum and normal life activity quite often change throughout the life cycle of individuals. This variability is determined both by hereditary qualities and by age, sex and physiological differences. For example, adults of freshwater cyprinids and perch-like fish species, such as carp, common European pike perch, etc., are quite capable of living in the water of bays of inland seas with a salinity of up to 5-7 g / l, but their spawning grounds are located only in highly desalinated areas, near mouths of rivers, because the eggs of these fish can develop normally when the water salinity is not more than 2 g/l. Crab larvae cannot live in fresh water, but adults are found in the estuarine zone of rivers, where the abundance of organic material carried by the river flow creates a good food base. The mill moth butterfly - one of the dangerous pests of flour and grain products - is critical for life minimum temperature for caterpillars -7 °С, for adult forms -22 °С, and for eggs -27 °С. Lowering the air temperature to -10 ° C is fatal for caterpillars, but not dangerous for adult forms and eggs of this species. Thus, the ecological tolerance inherent in the species as a whole turns out to be wider than the tolerance of each individual at a given stage of its development.

Relative independence of adaptation of organisms to different environmental factors

The degree of endurance of an organism to some particular factor does not mean the presence of a similar tolerance in relation to another factor. Species that can exist in a wide range temperature conditions, may not be able to withstand large fluctuations in water salinity or soil moisture. In other words, eurythermal species can be stenohaline or stenohygric. A set of ecological tolerances (sensitivities) to various environmental factors is called ecological spectrum of the species.

Interaction of environmental factors

The zone of optimum and the limits of endurance in relation to any factor of the environment can shift depending on the strength and combination of other factors acting simultaneously. Some factors can increase or decrease the strength of other factors. For example, excess heat can be softened to some extent by low air humidity. The wilting of the plant can be stopped both by increasing the amount of moisture in the soil and by lowering the air temperature, thereby reducing evaporation. The lack of light for plant photosynthesis can be compensated for by an increased content of carbon dioxide in the air, etc. It does not follow from this, however, that the factors can be interchanged. They are not interchangeable. The complete absence of light will lead to the rapid death of the plant, even if the soil moisture and the amount of all nutrients in it are optimal. The combined action of several factors, in which the effect of their influence is mutually enhanced, is called synergy. Synergy is clearly seen in combinations of heavy metals (copper and zinc, copper and cadmium, nickel and zinc, cadmium and mercury, nickel and chromium), as well as ammonia and copper, synthetic surfactants. With the combined effect of pairs of these substances, their toxic effect increases significantly. As a result, even small concentrations of these substances can be lethal to many organisms. An example of synergy can also be an increased risk of freezing during frost with strong wind than in calm weather.

In contrast to synergy, certain factors can be distinguished, the impact of which reduces the power of the resulting effect of the impact. The toxicity of zinc and lead salts is reduced in the presence of calcium compounds, and hydrocyanic acid in the presence of iron oxide and ferrous oxide. Such a phenomenon is called antagonism. At the same time, knowing which substance has an antagonistic effect on a given pollutant, one can achieve a significant reduction in its negative impact.

The rule of limiting environmental factors and the law of the minimum

The essence of the rule of limiting environmental factors lies in the fact that a factor that is in deficiency or excess negatively affects organisms and, in addition, limits the possibility of manifesting the strength of the action of other factors, including those that are at the optimum. For example, if the soil contains in abundance all but one chemical or physical environmental factor necessary for a plant, then the growth and development of the plant will depend precisely on the magnitude of this factor. Limiting factors usually determine the boundaries of the distribution of species (populations), their ranges. The productivity of organisms and communities depends on them.

The rule of limiting factors of the environment made it possible to come to the justification of the so-called "law of the minimum". It is assumed that for the first time the law of the minimum was formulated by the German agronomist J. Liebig in 1840. According to this law, the result of the impact of a combination of environmental factors on crop yields depends primarily not on those elements of the environment that are usually present in sufficient quantities, but on those for which are characterized by minimal concentrations (boron, copper, iron, magnesium, etc.). For example, a deficit boron sharply reduces the drought resistance of plants.

AT modern interpretation this law sounds in the following way: the endurance of an organism is determined by the weakest link in the chain of its ecological needs. That is, the vital possibilities of an organism are limited by environmental factors, the quantity and quality of which are close to the minimum necessary for a given organism. Further reduction of these factors leads to to the death of the organism.

Adaptive capabilities of organisms

To date, organisms have mastered four main habitats, which differ significantly in physicochemical conditions. This is water, land-air, soil environment, as well as the environment, which are the living organisms themselves. In addition, living organisms have been found in layers of organic and organo-mineral substances located deep underground, in groundwater and artesian waters. Thus, specific bacteria have been found in oil deposited at depths of more than 1 km. Thus, the Sphere of Life includes not only the soil layer, but can, under favorable conditions, spread much deeper into the earth's crust. At the same time, the main factor preventing penetration into the depths of the Earth is apparently the temperature of the environment, which increases with increasing depth from the soil surface. It is believed that at temperatures above 100 ° C, active life is impossible.

The adaptations of organisms to the environmental factors in which they live are called adaptations. Adaptations are any changes in the structure and functions of organisms that increase their chances of survival. The ability to adapt can be considered one of the main properties of life in general, as it provides the ability for organisms to survive and reproduce sustainably. Adaptations appear in different levels: from the biochemistry of cells and the behavior of individual organisms to the structure and functioning of communities and entire ecological systems.

The main types of adaptations at the level of the organism are the following:

· biochemical - they manifest themselves in intracellular processes, may relate to changes in the functioning of enzymes or their total number;

· physiological - for example, increased respiratory rate and heart rate with intense movement, increased sweating with increasing temperature in a number of species;

· morphoanatomical- features of the structure and shape of the body associated with the way and environment of life;

· behavioral - for example, the construction of nests and burrows by some species;

· ontogenetic - acceleration or deceleration of individual development, contributing to survival under changing conditions.

Organisms most easily adapt to those environmental factors that change clearly and steadily.

The history of ecological knowledge goes back many centuries. Already primitive people needed to have certain knowledge about plants and animals, their way of life, relationships with each other and with the environment. As part of the overall development natural sciences there was also an accumulation of knowledge that now belongs to the field of environmental science. As an independent isolated discipline, ecology stood out in the 19th century.

The term Ecology (from the Greek eco - house, logos - teaching) was introduced into science by the German biologist Ernest Haeckel.

In 1866, in his work “The General Morphology of Organisms”, he wrote that this is “... the sum of knowledge related to the economics of nature: the study of the totality of the relationship of an animal with its environment, both organic and inorganic, and above all its friendly or hostile relations with those animals and plants with which it directly or indirectly comes into contact. This definition refers ecology to the biological sciences. At the beginning of the XX century. formation systems approach and the development of the doctrine of the biosphere, which is a vast field of knowledge, which includes many scientific areas of both the natural and humanitarian cycles, including general ecology, led to the spread of ecosystem views in ecology. Ecosystem has become the main object of study in ecology.

An ecosystem is a set of living organisms that interact with each other and with their environment through the exchange of matter, energy and information in such a way that this single system remains stable for a long time.

The ever-increasing impact of man on the environment has required a new expansion of the boundaries of ecological knowledge. In the second half of the XX century. Scientific and technological progress has led to a number of problems that have received the status of global ones, thus, in the field of view of ecology, the issues of a comparative analysis of natural and man-made systems and the search for ways for their harmonious coexistence and development have clearly emerged.

Accordingly, the structure of ecological science was differentiated and complicated. Now it can be represented as four main branches, which are further divided: Bioecology, geoecology, human ecology, applied ecology.

Thus, we can define ecology as a science about the general laws of the functioning of ecosystems of various orders, a set of scientific and practical issues of the relationship between man and nature.

2. Environmental factors, their classification, types of impact on organisms

Any organism in nature experiences the influence of a wide variety of components of the external environment. Any properties or components of the environment that affect organisms are called environmental factors.

Classification of environmental factors. Environmental factors (environmental factors) are diverse, have different nature and specific action. The following groups of environmental factors are distinguished:

1. Abiotic (factors inanimate nature):

a) climatic - lighting conditions, temperature conditions, etc.;

b) edaphic (local) - water supply, soil type, terrain;

c) orographic - air (wind) and water currents.

2. Biotic factors are all forms of influence of living organisms on each other:

Plants Plants. Plants Animals. Plants Mushrooms. Plants Microorganisms. Animals Animals. Animals Mushrooms. Animals Microorganisms. Mushrooms Mushrooms. Mushrooms Microorganisms. Microorganisms Microorganisms.

3. Anthropogenic factors are all forms of activity of human society that lead to a change in the habitat of other species or directly affect their lives. The impact of this group of environmental factors is rapidly increasing from year to year.

Types of impact of environmental factors on organisms. Environmental factors affect living organisms in various ways. They may be:

Irritants that contribute to the appearance of adaptive (adaptive) physiological and biochemical changes (hibernation, photoperiodism);

Limiters that change the geographical distribution of organisms due to the impossibility of existence in these conditions;

Modifiers that cause morphological and anatomical changes in organisms;

Signals indicating changes in other environmental factors.

General patterns of environmental factors:

Due to the extreme diversity of environmental factors, different types of organisms, experiencing their influence, respond to it in different ways, however, a number of general laws (patterns) of the action of environmental factors can be identified. Let's dwell on some of them.

1. The law of optimum

2. Law of ecological individuality of species

3. The law of the limiting (limiting) factor

4. Law of ambiguous action

3. Patterns of the action of environmental factors on organisms

1) The rule of optimum. For an ecosystem, an organism or a certain stage of it

development, there is a range of the most favorable value of the factor. Where

favorable factors population density is maximum. 2) Tolerance.

These characteristics depend on the environment in which the organisms live. If she

stable in its

its-am, it has more chances for the survival of organisms.

3) The rule of interaction of factors. Some factors may increase or

mitigate the effect of other factors.

4) The rule of limiting factors. A factor that is deficient or

excess negatively affects organisms and limits the possibility of manifestation. strength

the action of other factors. 5) Photoperiodism. Under photoperiodism

understand the reaction of the body to the length of the day. response to changing light.

6) Adaptation to the rhythm of natural phenomena. Adaptation to the daily and

seasonal rhythms, tidal phenomena, rhythms of solar activity,

lunar phases and other phenomena that repeat with strict periodicity.

Ek. valency (plasticity) - the ability of org. adapt to the environmental factors. environment.

Patterns of the action of environmental factors on living organisms.

Ecological factors and their classification. All organisms are potentially capable of unlimited reproduction and dispersal: even species that lead an attached lifestyle have at least one developmental phase in which they are capable of active or passive distribution. But at the same time species composition organisms that live in different climatic zones, does not mix: each of them has a certain set of species of animals, plants, fungi. This is due to the limitation of excessive reproduction and settlement of organisms by certain geographical barriers (seas, mountain ranges, deserts, etc.), climatic factors (temperature, humidity, etc.), as well as relationships between individual species.

Depending on the nature and characteristics of the action, environmental factors are divided into abiotic, biotic and anthropogenic (anthropic).

Abiotic factors are components and properties of inanimate nature that directly or indirectly affect individual organisms and their groups (temperature, light, humidity, gas composition of air, pressure, salt composition of water, etc.).

A separate group of environmental factors include various forms human economic activities that change the state of the habitat of various species of living beings, including man himself ( anthropogenic factors). For relatively short period human existence as species, its activities have radically changed the face of our planet and every year this influence on nature is increasing. The intensity of some environmental factors may remain relatively stable over long historical periods of biosphere development (for example, solar radiation, gravity, salt composition of sea water, gas composition of the atmosphere, etc.). Most of them have a variable intensity (temperature, humidity, etc.). The degree of variability of each of the environmental factors depends on the characteristics of the habitat of organisms. For example, the temperature on the soil surface can vary significantly depending on the time of year or day, weather, etc., while in water bodies at depths of more than a few meters there are almost no temperature drops.

Changes in environmental factors can be:

Periodic, depending on the time of day, season, the position of the Moon relative to the Earth, etc.;

Non-periodic, for example, volcanic eruptions, earthquakes, hurricanes, etc.;

Directed over significant historical periods of time, for example, changes in the Earth's climate associated with the redistribution of the ratio of land areas and the oceans.

Each of the living organisms constantly adapts to the whole complex of environmental factors, that is, to the environment, regulating the processes of life in accordance with changes in these factors. Habitat is a set of conditions in which certain individuals, populations, groupings of organisms live.

Patterns of the influence of environmental factors on living organisms. Despite the fact that environmental factors are very diverse and different in nature, some patterns of their influence on living organisms, as well as the reactions of organisms to the action of these factors, are noted. Adaptations of organisms to environmental conditions are called adaptations. They are produced at all levels of the organization of living matter: from molecular to biogeocenotic. Adaptations are not permanent, since they change in the process of the historical development of individual species, depending on changes in the intensity of the action of environmental factors. Each species of organisms is adapted to certain conditions of existence in a special way: there are no two close species that are similar in their adaptations (the rule of ecological individuality). So, the mole (series Insectivores) and the mole rat (series Rodents) are adapted to existence in the soil. But the mole digs passages with the help of its forelimbs, and the mole rat uses its incisors, throwing the soil out with its head.

Good adaptation of organisms to a certain factor does not mean the same adaptation to others (the rule of relative independence of adaptation). For example, lichens, which can settle on substrates poor in organic matter (such as rocks) and withstand dry periods, are very sensitive to air pollution.

There is also the law of optimum: each factor has a positive effect on the body only within certain limits. Favorable for organisms of a certain type, the intensity of the impact of an environmental factor is called the optimum zone. The more the intensity of the action of a certain environmental factor deviates from the optimal one in one direction or another, the more pronounced its depressing effect on organisms (pessimum zone). The value of the intensity of the impact of the environmental factor, according to which the existence of organisms becomes impossible, is called the upper and lower limits of endurance (critical points of maximum and minimum). The distance between the limits of endurance determines the ecological valency of a certain species with respect to one or another factor. Therefore, ecological valence is the range of intensity of the influence of an ecological factor in which the existence of a certain species is possible.

The broad ecological valency of individuals of a certain species with respect to a specific ecological factor is denoted by the prefix "euro-". Thus, arctic foxes are eurythermic animals, since they can withstand significant temperature fluctuations (within 80°C). Some invertebrates (sponges, kilchakiv, echinoderms) are eurybatic organisms, therefore they settle from the coastal zone to great depths, withstanding significant pressure fluctuations. Species that can live in a wide range of fluctuations of various environmental factors are called eurybiontyms. Narrow ecological valency, that is, the inability to withstand significant changes in a certain environmental factor, is denoted by the prefix "steno-" (for example, stenothermic, stenobatni, stenobiontic, etc.).

The optimum and limits of the organism's endurance with respect to a certain factor depend on the intensity of the action of others. For example, in dry, calm weather, it is easier to withstand low temperatures. So, the optimum and limits of endurance of organisms in relation to any environmental factor can shift in a certain direction, depending on the strength and combination of other factors (the phenomenon of the interaction of environmental factors).

But the mutual compensation of vital ecological factors has certain limits and none can be replaced by others: if the intensity of the action of at least one factor goes beyond the limits of endurance, the existence of the species becomes impossible, despite the optimal intensity of the action of others. Thus, the lack of moisture inhibits the process of photosynthesis even with optimal illumination and CO2 concentration in the atmosphere.

The factor, the intensity of which goes beyond the limits of endurance, is called restrictive. Limiting factors determine the area of ​​distribution of the species (range). For example, the spread of many species of animals to the north is hampered by a lack of heat and light, to the south by a lack of moisture.

Thus, the presence and prosperity of a certain species in a given habitat is due to its interaction with a whole range of environmental factors. Insufficient or excessive intensity of the action of any of them is impossible for the prosperity and the very existence of individual species.

Environmental factors are any components of the environment that affect living organisms and their groups; they are divided into abiotic (components of inanimate nature), biotic (various forms of interaction between organisms) and anthropogenic (various forms of human economic activity).

Adaptations of organisms to environmental conditions are called adaptations.

Any environmental factor has only certain limits of positive influence on organisms (the law of optimum). The limits of the intensity of the action of the factor, according to which the existence of organisms becomes impossible, are called the upper and lower limits of endurance.

The optimum and limits of endurance of organisms in relation to any environmental factor may vary in a certain direction, depending on the intensity and combination of other environmental factors (the phenomenon of interaction of environmental factors). But their mutual compensation is limited: no vital factor can be replaced by others. An environmental factor that goes beyond the limits of endurance is called a restrictive one; it determines the range of a certain species.

ecological plasticity of organisms

Ecological plasticity of organisms (ecological valence) - the degree of adaptability of a species to changes in the environmental factor. It is expressed by the range of values ​​of environmental factors within which a given species retains normal vital activity. The wider the range, the greater the ecological plasticity.

Species that can exist with small deviations of the factor from the optimum are called highly specialized, and species that can withstand significant changes in the factor are called widely adapted.

Ecological plasticity can be considered both in relation to a single factor and in relation to a complex of environmental factors. The ability of species to tolerate significant changes in certain factors is denoted by the corresponding term with the prefix "evry":

Eurythermal (plastic to temperature)

Eurygoline (water salinity)

Eurythotic (plastic to light)

Eurygyric (plastic to moisture)

Euryoic (plastic to the habitat)

Euryphagic (plastic to food).

Species adapted to small changes in this factor are designated by the term with the prefix "wall". These prefixes are used to express the relative degree of tolerance (for example, in a stenothermic species, the ecological temperature optimum and pessimum are close).

Species with wide ecological plasticity in relation to a complex of ecological factors are eurybionts; species with low individual adaptability - stenobionts. Eurybiontness and istenobiontness characterize Various types adaptations of organisms for survival. If eurybionts develop for a long time in good conditions, then they can lose their ecological plasticity and develop stenobiont traits. Species that exist with significant fluctuations in the factor acquire increased ecological plasticity and become eurybionts.

For example, there are more stenobionts in the aquatic environment, since it is relatively stable in its properties and the amplitudes of fluctuations of individual factors are small. In a more dynamic air-land environment, eurybionts predominate. Warm-blooded animals have a wider ecological valence than cold-blooded animals. Young and old organisms tend to require more uniform environmental conditions.

Eurybionts are widespread, and stenobiont narrows the ranges; however, in some cases, due to their high specialization, stenobionts own vast territories. For example, the fish-eating osprey is a typical stenophage, but in relation to other environmental factors, it is a eurybiont. In search of the necessary food, the bird is able to cover long distances in flight, therefore it occupies a significant area.

Plasticity - the ability of an organism to exist in a certain range of values ​​of the environmental factor. Plasticity is determined by the reaction rate.

According to the degree of plasticity in relation to individual factors, all types are divided into three groups:

Stenotopes are species that can exist in a narrow range of environmental factor values. For example, most plants of moist equatorial forests.

Eurytopes are wide-plastic species capable of developing various habitats, for example, all cosmopolitan species.

Mesotopes occupy an intermediate position between stenotopes and eurytopes.

It should be remembered that a species can be, for example, a stenotope according to one factor and a eurytope according to another, and vice versa. For example, a person is a eurytope in relation to air temperature, but a stenotope in terms of the oxygen content in it.

inanimate and Live nature, surrounding plants, animals and humans, is called the habitat. The set of individual components of the environment that affect organisms are called environmental factors.

According to the nature of origin, abiotic, biotic and anthropogenic factors are distinguished.

Abiotic factors - These are properties of inanimate nature that directly or indirectly affect living organisms.

Biotic factors - these are all forms of influence of living organisms on each other. Earlier to biotic factors human impact on living organisms was also attributed, but at present a special category of factors generated by humans is distinguished.

Anthropogenic factors - these are all forms of activity of human society that lead to a change in nature as a habitat and other species and directly affect their lives.

Thus, every living organism is influenced by inanimate nature, organisms of other species, including humans, and, in turn, affects each of these components.

Laws of the impact of environmental factors on living organisms

Despite the variety of environmental factors and the different nature of their origin, there are some general rules and patterns of their impact on living organisms.

For the life of organisms, a certain combination of conditions is necessary. If all environmental conditions are favorable, with the exception of one, then it is this condition that becomes decisive for the life of the organism in question. It limits (limits) the development of the organism, therefore it is called limiting factor . Initially, it was found that the development of living organisms is limited by the lack of any component, for example, mineral salts, moisture, light, etc. In the middle of the 19th century, the German organic chemist J. Liebig was the first to experimentally prove that plant growth depends on the nutrient element that is present in a relatively minimal amount. He called this phenomenon the law of the minimum (Liebig's law).

In the modern formulation, the law of the minimum sounds like this: the endurance of an organism is determined by the weakest link in the chain of its ecological needs. However, as it turned out later, not only a deficiency, but also an excess of a factor can be limiting, for example, the death of a crop due to rains, oversaturation of the soil with fertilizers, etc. The concept that, along with a minimum, a maximum can also be a limiting factor was introduced 70 years after Liebig by the American zoologist W. Shelford, who formulated law of tolerance . According to the law of tolerance, the limiting factor for the prosperity of a population (organism) can be both a minimum and a maximum of environmental impact, and the range between them determines the amount of endurance (tolerance limit) or the ecological valency of the organism to this factor.

The favorable range of the environmental factor is called the zone of optimum (normal life). The greater the deviation of the factor from the optimum, the more this factor inhibits the vital activity of the population. This range is called the zone of oppression. The maximum and minimum tolerated values ​​of the factor are critical points beyond which the existence of an organism or population is no longer possible.

The principle of limiting factors is valid for all types of living organisms - plants, animals, microorganisms and applies to both abiotic and biotic factors.

In accordance with the law of tolerance, any excess of matter or energy turns out to be a source of pollution.

The limit of tolerance of an organism changes during the transition from one stage of development to another. Often, young organisms are more vulnerable and more demanding on environmental conditions than adults. The most critical from the point of view of the impact of various factors is the breeding season: during this period, many factors become limiting. The ecological valence for breeding individuals, seeds, embryos, larvae, eggs is usually narrower than for adult non-breeding plants or animals of the same species.

Until now, we have been talking about the limit of tolerance of a living organism in relation to one factor, but in nature all environmental factors act together.

The optimal zone and limits of the body's endurance in relation to any environmental factor may shift depending on the combination of other factors acting simultaneously. This pattern has been named interactions of environmental factors .

However, mutual compensation has certain limits and it is impossible to completely replace one of the factors with another. This implies the conclusion that all environmental conditions necessary to maintain life play an equal role and any factor can limit the possibility of the existence of organisms - this is law of equivalence of all conditions of life .

It is known that each factor differently affects different functions of the body. Conditions that are optimal for some processes, for example, for the growth of an organism, may turn out to be a zone of oppression for others, for example, for reproduction, and go beyond tolerance, that is, lead to death, for others. So life cycle, according to which the body during certain periods mainly performs certain functions - nutrition, growth, reproduction, resettlement - is always consistent with seasonal changes in environmental factors.

Among the laws that determine the interaction of an individual or an individual with its environment, we single out the rule of correspondence between environmental conditions and the organism's genetic predetermination. It argues that a species of organisms can exist as long as and insofar as the natural environment surrounding it corresponds to the genetic possibilities of adapting this species to its fluctuations and changes. Each species of living arose in a certain environment, to one degree or another adapted to it, and the further existence of the species is possible only in this or a environment close to it. A sharp and rapid change in the environment of life can lead to the fact that the genetic capabilities of the species will be insufficient to adapt to new conditions. This, in particular, is the basis of one of the hypotheses of the extinction of large reptiles with a sharp change in abiotic conditions on the planet: large organisms are less variable than small ones, so they need much more time to adapt. In this regard, the fundamental transformations of nature are dangerous for the currently existing species, including for man himself.

LECTURE #5

TOPIC: GENERAL REGULARITIES OF THE ACTION OF ENVIRONMENTAL FACTORS ON ORGANISMS

PLAN:

1. Cumulative impact of environmental factors.

2. Liebig's law of the minimum.

3. Shelford's law of limiting factors.

4. The reaction of organisms to changes in the level of environmental factors.

5. Variability.

6. Adaptation.

7. Ecological niche of the body.

7.1. Concepts and definitions.

7.2. Specialized and General ecological niches.

8. Ecological forms.

Environmental factors are dynamic, changeable in time and space. warm time the year is regularly replaced by cold, fluctuations in temperature and humidity are observed during the day, day follows night, etc. All these are natural (natural) changes in environmental factors, however, a person can interfere with them. Anthropogenic influence on the natural environment is manifested in a change in either the regimes of environmental factors (absolute values ​​or dynamics), or the composition of factors (for example, the development, production and use of plant protection products, mineral fertilizers, etc. that did not previously exist in nature).

1. Cumulative impact of environmental factors

Environmental environmental factors affect the body simultaneously and jointly. The cumulative impact of factors - a constellation, to some extent mutually changes the nature of the impact of each individual factor. The effect of air humidity on the perception of temperature by animals has been well studied. With an increase in humidity, the intensity of evaporation of moisture from the surface of the skin decreases, which makes it difficult for one of the most effective mechanisms of adaptation to high temperature. Low temperatures are also easier to tolerate in a dry atmosphere, which has a lower thermal conductivity (better thermal insulation properties). Thus, the humidity of the environment changes the subjective perception of temperature in warm-blooded animals, including humans.

AT complex action environmental environmental factors the value of individual environmental factors is not equivalent. Among them, there are leading (main) and secondary factors.

Leading are those factors that are necessary for life, secondary - existing or background factors. Usually, different organisms have different leading factors, even if the organisms live in the same place. In addition, a change in the leading factors is observed during the transition of the organism to another period of its life. So, during the flowering period, the leading factor for the plant can be light, and during the period of seed formation, moisture and nutrients.

Sometimes the lack of one factor is partially compensated by the strengthening of another. For example, in the Arctic, long daylight hours compensate for the lack of heat.

2. Law minimum Liebig

Any living organism needs not temperature, humidity, mineral and organic substances, or any other factors in general, but their specific regimen. The reaction of the body depends on the amount (dose) of the factor. In addition, a living organism under natural conditions is exposed to many environmental factors (both abiotic and biotic) simultaneously. Plants need significant amounts of moisture and nutrients (nitrogen, phosphorus, potassium) and at the same time relatively "negligible" amounts of elements such as boron and molybdenum.

Any kind of animal or plant has a clear selectivity for the composition of food: each plant needs certain mineral elements. Any kind of animal in its own way is demanding on the quality of food. In order to exist and develop normally, the body must have the entire set of necessary factors in optimal modes and in sufficient quantities.

The fact that limiting the dose (or absence) of any of the substances necessary for the plant, related to both macro- and microelements, leads to the same result - growth retardation, was discovered and studied by one of the founders of agricultural chemistry German chemist Eustace von Liebig. The rule he formulated in 1840 is called Liebig's law of the minimum: the value of the crop is determined by the amount in the soil of that of the nutrients, the need of the plant for which is least satisfied.

At the same time, J. Liebig drew a barrel with holes, showing that the lower hole in the barrel determines the level of liquid in it. The law of the minimum is valid for both plants and animals, including humans, who in certain situations have to use mineral water or vitamins to compensate for the lack of any elements in the body.

Subsequently, clarifications were made to Liebig's law. An important amendment and addition is law of the ambiguous(selective) action of the factor on various body functions: any environmental factor affects the functions of the body differently, the optimum for some processes, such as respiration, is not the optimum for others, such as digestion, and vice versa.

E. Ryubel in 1930 was installed law (effect) of compensation (interchangeability) of factors: the absence or lack of some environmental factors can be compensated by another close (similar) factor.

For example, a lack of light can be compensated for by an abundance of carbon dioxide for a plant, and when building shells by mollusks, the missing calcium can be replaced by strontium.

However, these possibilities are extremely limited. In 1949 he formulated law of indispensability of fundamental factors: the complete absence of fundamental environmental factors (light, water, nutrients, etc.) in the environment cannot be replaced by other factors.

This group of refinements of Liebig's law includes a somewhat different rule of phase reactions "benefit- harm ": small concentrations of a toxicant act on the body in the direction of strengthening its functions (stimulating them), while higher concentrations depress or even lead to its death.

This toxicological pattern is true for many (for example, medicinal properties small concentrations of snake venom), but not all poisonous substances.

3. Law limiting factors Shelford

The environmental factor is felt by the body not only when it is deficient. Problems also arise with an excess of any of the environmental factors. From experience it is known that with a lack of water in the soil, the assimilation of elements by the plant mineral nutrition difficult, but an excess of water leads to similar consequences: the death of roots is possible, the occurrence of anaerobic processes, acidification of the soil, etc. The vital activity of the organism is also noticeably inhibited at low values ​​and with excessive exposure to such an abiotic factor as temperature.

The environmental factor most effectively affects the organism only at a certain average value, which is optimal for the given organism. The wider the limits of fluctuations of any factor at which the organism can remain viable, the higher the stability, i.e., the tolerance of the given organism to the corresponding factor (from Latin tolerantia - patience). Thus, tolerance- this is the ability of the body to withstand deviations of environmental factors from the optimal values ​​for its life.

The first assumption about limiting (limiting) The influence of the maximum value of the factor on a par with the minimum value was expressed in 1913 by the American zoologist W. Shelford, who established the fundamental biological law of tolerance: any living organism has certain, evolutionarily inherited upper and lower limits of resistance (tolerance) to any environmental factor.

Another formulation of W. Shelford's law explains why the law of tolerance is simultaneously called the law of limiting factors: even a single factor outside the zone of its optimum leads to a stressful state of the organism and, in the limit, to its death.

Therefore, the environmental factor, the level of which approaches any limit of the organism's endurance range or goes beyond this limit, is called the limiting factor. The law of tolerance is supplemented by the provisions of the American ecologist Y. Odum:

Organisms may have a wide range of tolerance for one environmental factor and a low range for another;

Organisms with a wide range of tolerance for all environmental factors are usually the most common;

the range of tolerance can also narrow in relation to other environmental factors, if the conditions for one environmental factor are not optimal for the organism;

Many environmental factors become limiting (limiting) during especially important (critical) periods of the life of organisms, especially during the breeding season.

These provisions are also adjoined by the Mitcherlich-Baule law, called by A. Thienemann law of cumulative action: a combination of factors has the strongest effect on those phases of development of organisms that have the least plasticity - the minimum ability to adapt.

4. Reaction organisms on the level changes environmental

factors

Optimal impact on different organisms the same factor can have different values. So, some plants prefer very moist soil, while others prefer relatively dry soil. Some animals like intense heat, others tolerate it better. moderate temperature environments, etc.

In addition, living organisms are divided into those capable of existing in a wide or narrow range of changes in any environmental factor. Organisms adapt to each environmental factor in a relatively independent way. An organism may be adapted to a narrow range of one factor and a wide range of another. For the organism, not only the amplitude is important, but also the rate of fluctuations of one or another factor.

If the influence of environmental conditions does not reach the limit values, living organisms react to it with certain actions or changes in their state, which ultimately leads to the survival of the species. Overcoming the adverse effects of animals is possible in two ways:

By avoiding them;

By acquiring stamina.

The first method is used by animals that have sufficient mobility, thanks to which they migrate, build shelters, etc.

Demanding and tolerance to environmental factors determines the area of ​​geographical distribution of individuals of the species under consideration, regardless of the degree of constancy of their habitat, i.e., the range of the species.

Plant responses are based on the development of adaptive changes in their structure and life processes. Under rhythmically repeating climatic situations, plants and animals can adapt by developing an appropriate temporal organization of life processes, as a result of which they alternate periods of active functioning of the body with periods of hibernation (a number of animals) or with a state of rest (plants).

5. Variability

Variability- one of the main properties of living things at various levels of its organization. For each species, the variability of its constituent individuals is important. For example, people differ from each other in height, physique, eye and skin color, and show different abilities. Similar intraspecific variability is inherent in all organisms: elephants, flies, oaks, sparrows and others.

Individuals of any species differ from each other in external and internal features. sign- any feature of an organism as in its appearance(size, shape, color, etc.), and in internal structure. Resistance to disease, low or high temperatures, the ability to swim, fly, and so on are all traits, many of which can be changed or developed through training or training. However, their main property is a genetic, i.e. hereditary, basis. Each organism is born with a set of certain characteristics.

Studies have shown that the hereditary basis of the characteristics of any kind is encoded in DNA molecules, that is, in the genes of an organism, the totality of which is called its genotype. The genotype of almost all organisms, including humans, is represented by not one but two sets of genes. Body growth is accompanied by cell division, during which each new cell receives an exact copy of both sets of genes. However, only one set from each of the parents is passed on to the next generation, and therefore new combinations of genes arise in children that are different from the parents. Thus, all descendants, and, consequently, individuals of a species (with the exception of identical twins) differ in their genotypes.

Genetic variability is the basis of hereditary variability of traits. Another source of hereditary variation is DNA mutation affecting any gene or group of genes.

Differences resulting from learning, training, or simply trauma are the development of some innate trait, but do not change its genetic basis.

If hereditary variability in sexual reproduction is inevitable, then in the asexual reproduction of individuals, i.e., during cloning, a different picture is observed. Thus, when cutting plants, a new organism appears as a result of a simple cell division, accompanied by an exact copying of the parental DNA. Therefore, all individuals of the clone (with the exception of mutants) are genetically identical. Gene pool - a set of gene samples of all individuals of a certain group of organisms of the same species. The gene pool of a species is unstable, it can change from generation to generation. If individuals with rare traits do not reproduce, then part of the gene pool is reduced.

In nature, the gene pool of a species is constantly changing through natural selection, which is the basis of the evolutionary process. Each generation is subjected to selection for survival and reproduction, therefore, almost all signs of organisms, to one degree or another, serve the survival and reproduction of the species.

However, the gene pool can be changed purposefully with the help of artificial selection. Modern pet breeds and varieties cultivated plants were taken out of wild ancestors exactly. It is also possible to intervene in the gene pool when crossing closely related species (non-closely related species do not produce offspring). This method is called hybridization, and the offspring are called hybrids.

Recent advances in science are associated with the development of genetic engineering technology, which consists in obtaining specific genes (DNA segments) of one species and introducing them directly to another species without crossing. This allows hybridization of any species, not only closely related ones, and therefore causes serious controversy due to the unpredictability of the final results of such a radical intervention in the gene pools of living beings.

6. Adaptation

Animals and plants are forced to adapt to many factors of constantly changing living conditions. The dynamism of environmental factors in time and space depends on astronomical, helioclimatic, geological processes that play a controlling role in relation to living organisms.

The traits that contribute to the survival of an organism are gradually enhanced by natural selection until the maximum adaptability to existing conditions is reached. Adaptation can occur at the level of cells, tissues, and even the whole organism, affecting the shape, size, ratio of organs, etc. Organisms in the process of evolution and natural selection develop hereditarily fixed features that ensure normal life in changed environmental conditions, i.e., occurs adaptation.

Adaptation- adaptation of organisms (and species) to the environment is a fundamental property of living nature. The habitat of any living being, on the one hand, slowly and steadily changes over the life of many generations of the corresponding biological species, and on the other hand, it imposes on the body a variety of requirements that change in short periods of individual life. Therefore, there are three levels of the adaptation process.

Genetic level. This level ensures the adaptation and preservation of the viability of the species in generations based on the property of genetic variability.

Profound metabolic changes. Adaptation to seasonal and annual natural cycles is carried out with the help of profound changes in metabolism. In animals, neurohumoral mechanisms play a central role in these processes, for example, preparation for the breeding season or for hibernation"switched on" by nerve stimuli, but is carried out due to changes in the hormonal status of the body. In plants, seasonal and other long-term changes are provided by the work of phytohormones and growth factors.

Rapid changes in response to short-term deviations of environmental factors. In animals, they are carried out by a variety of nervous mechanisms leading to a change in behavior and a rapid reversible transformation of metabolism. In plants, reactions to changes in light are an example of rapid change.

Practically all regularities characteristic of living things have an adaptive value. In the course of natural selection, species are transformed and better adapted to their habitats. For example, giraffes have gradually adapted to eating leaves from the tops of trees. With an increase in the adaptability of organisms to a habitat, the rate of their change decreases.

In the case of a predator-prey relationship natural selection affects, first of all, the genes that allow the most effective avoidance of the enemy, and in predators - the genes that increase its hunting abilities. This is true for all biotic interactions. Organisms that for some reason have lost the ability to adapt are doomed to extinction.

So, when the conditions of existence change (deviation of the value of one or more environmental factors beyond the normal fluctuations), some species adapt and transform, while other species die out. It depends on a number of circumstances. The main condition for adaptation is the survival and reproduction of at least a few individuals in new conditions, which is associated with the genetic diversity of the gene pool and the degree of environmental change. With a more diverse gene pool, even in the event of strong environmental changes, some individuals will be able to survive, while with a low diversity of the gene pool, even minor fluctuations in environmental factors can lead to the extinction of the species.

If changes in conditions are subtle or occur gradually, then most species can adapt and survive. The more abrupt the change, the greater the diversity of the gene pool is necessary for survival. In case of catastrophic changes (for example, nuclear war), perhaps no species will survive. The most important ecological principle says that the survival of a species is ensured by its genetic diversity and weak fluctuations in environmental factors.

In addition to genetic diversity and environmental change, another factor can be added - geographical distribution. The more widespread the species (the more range species), the more genetically diverse it is and vice versa. In addition, with an extensive geographic distribution, some parts of the range may be removed or isolated from areas where the conditions of existence were violated. In these areas, the species persists even if it disappears from other places.

If some of the individuals survived in the new conditions, then further adaptation and restoration of numbers depend on the rate of reproduction, since the change in traits occurs only through selection in each generation. For example, a pair of insects has hundreds of offspring that go through a developmental life cycle in a few weeks. Consequently, their reproduction rate is a thousand times higher than that of birds that feed only 2-6 chicks per year, which means that the same level of adaptability to new conditions will develop as many times faster. That is why insects quickly adapt and acquire resistance to all kinds of "plant protection products", while others wild species die from these treatments.

It is important to note that pesticides by themselves do not cause beneficial mutations. Change happens randomly. Adaptive traits develop due to the hereditary diversity already existing in the gene pool of the species. The size of the body also matters. Flies can even exist in a trash can, and large animals need vast territories to survive.

The adaptation has the following features:

Adaptation to one environmental factor, for example, high humidity, does not give the organism the same adaptability to other environmental conditions (temperature, etc.). This pattern is called the law of relative independence of adaptation: high adaptability to one of the environmental factors does not give the same degree of adaptation to other living conditions.

Each species of organisms in the ever-changing environment of life is adapted in its own way. This is expressed by formulated in 1924. ecological identity rule: each species is specific in terms of ecological adaptation possibilities; no two species are identical.

The rule of conformity of environmental conditions with the genetic predestination of an organism reads: a species of organisms can exist as long as and insofar as its environment corresponds to the genetic possibilities of adaptation to its fluctuations and changes.

Selection is the process of changing the gene pool of an already existing species. Neither man nor modern nature they cannot create a new gene pool or a new species from nothing, from scratch. Only what is already there changes.

7. Ecological niche organism

7.1. Concepts and definitions

Any living organism is adapted (adapted) to certain environmental conditions. Changing its parameters, their going beyond certain boundaries suppresses the vital activity of organisms and can cause their death. The requirements of this or that organism to the ecological factors of the environment determine the range (limits of distribution) of the species to which the organism belongs, and within the range - specific habitats.

habitat- a spatially limited set of environmental conditions (abiotic and biotic), providing the entire cycle of development and reproduction of individuals (or groups of individuals) of the same species. These are, for example, a hedge, a pond, a grove, a rocky shore, etc. At the same time, places with special conditions can be distinguished within the habitat (for example, under the bark of a rotting tree trunk in a grove), in some cases called microhabitats.

For the total characterization of the physical space occupied by organisms of a species, their functional role in the biotic habitat, including the mode of nutrition (trophic status), lifestyle and relationships with other species, the American scientist J. Grinnell introduced the term "ecological niche" in 1928. Its modern definition is as follows.

ecological niche is the collection:

All requirements of the body to the conditions of the environment (composition and regimes of environmental factors) and the place where these requirements are met;

Total set biological characteristics and physical parameters of the environment that determine the conditions for the existence of a particular species, its transformation of energy, the exchange of information with the environment and their own kind.

Thus, the ecological niche characterizes the degree of biological specialization of a species. It can be argued that the habitat of an organism is its “address”, while the ecological niche is its “occupation”, or “lifestyle”, or “profession”.

Ecological specificity of species is emphasized axiom of ecological adaptability: each species is adapted to a strictly defined, specific set of conditions for its existence - an ecological niche.

Since the species of organisms are ecologically individual, they also have specific ecological niches.

Thus, there are as many species of living organisms on Earth as there are ecological niches.

Organisms that lead a similar way of life, as a rule, do not live in the same places due to interspecific competition. According to the Soviet biologist (1910-1986) established in 1934 principle of competitive mutual exclusion: two species do not occupy the same ecological niche.

It also works in nature rule of obligation to fill ecological niches: an empty ecological niche will always and certainly be filled.

Folk wisdom formulated these two postulates as follows: “Two bears cannot get along in one lair” and “Nature does not tolerate emptiness.”

These systematic observations are realized in the formation of biotic communities and biocenoses. Ecological niches are always filled, although this sometimes takes a considerable amount of time. The common expression "free ecological niche" means that in a certain place there is little competition for any type of food and there is an underutilized sum of other conditions for a certain species included in similar natural systems, but absent in the considered one.

It is especially important to take into account natural patterns when trying to intervene in an existing (or prevailing in a certain place) situation in order to create more favorable conditions for a person. So, biologists have proved the following: in cities, with an increase in the contamination of the territory with food waste, the number of crows increases. When trying to improve the situation, for example, by physically destroying them, the population may face the fact that the ecological niche in the urban environment, vacated by ravens, will be quickly occupied by a species that has a close ecological niche, namely, rats. Such a result can hardly be considered a victory.

7.2. Specialized and generalenvironmentalniches

Ecological niches of all living organisms are divided into specialized and general. This division depends on the main food sources of the respective species, the size of the habitat, and sensitivity to abiotic environmental factors.

Specialized Niches. Most plant and animal species are adapted to exist only within a narrow range climatic conditions and other characteristics of the environment, feed on a limited set of plants or animals. Such species have a specialized niche that determines their habitat in the natural environment.

So, the giant panda has a highly specialized niche, because it feeds on 99% of leaves and bamboo shoots. The mass destruction of certain types of bamboo in areas of China where the panda lived led this animal to extinction.

The variety of species and forms of flora and fauna that exists in tropical rainforests is associated with the presence of a number of specialized ecological niches in each of the clearly defined tiers of forest vegetation. Therefore, the intensive deforestation of these forests has caused the extinction of millions of specialized plant and animal species.

General Niches. Species with common niches are characterized by easy adaptability to changes in environmental environmental factors. They can successfully exist in a variety of places, eat a variety of foods and withstand sharp fluctuations. natural conditions. Flies, cockroaches, mice, rats, humans, etc. have common ecological niches.

For species that have common ecological niches, there is a significantly lower threat of extinction than for those with specialized niches.

8. Environmental forms

The natural environment forms the phenotype of organisms - a set of morphological, physiological and behavioral characteristics. Species living in similar conditions (with a similar set of environmental factors) have similar fitness for these conditions, even if they belong to different categories in the classification of the animal and flora. Ecology takes this into account by classifying organisms into various ecological (life) forms. At the same time, the life form of a species is called the existing complex of its biological, physiological and morphological properties, which determine a certain reaction to the influence of the environment. There are many classifications of organisms according to life forms. So, for example, geobionts are distinguished - inhabitants of the soil, dendrobionts - associated with woody plants, chortobionts - inhabitants of the grass cover, and much more.

Hydrobionts- inhabitants aquatic environment It is customary to divide into such ecological forms as benthos, periphyton, plankton, nekton, neuston.

Benthos(from Greek benthos - depth) - benthic organisms leading an attached or free lifestyle, including those living in the bottom sediment layer. Mostly these are mollusks, some lower plants, crawling insect larvae.

Periphyton- animals and plants attached to the stems of higher plants and rising above the bottom.

Plankton(from the Greek plagktos - soaring) - floating organisms capable of performing vertical and horizontal movements mainly in accordance with the movement of the masses of the aquatic environment. It is customary to distinguish between phytoplankton, which is a producer, and zooplankton, which is a consumer and feeds on phytoplankton.

Nekton(from Greek nektos - floating) - freely and independently floating organisms - mainly fish, amphibians, large aquatic insects, crustaceans.

Neuston- a set of marine and freshwater organisms that live near the surface of the water; for example, mosquito larvae, water striders, from plants - duckweed, etc.

The ecological form is a reflection of the adaptability of a wide variety of organisms to individual environmental factors that are limiting in the process of evolution. Thus, the division of plants into hygrophytes (moisture-loving), mesophytes (average demands for moisture) and xerophytes (dry-loving) reflects their reaction to a specific environmental factor - moisture. At the same time, xerophyte plants represent a single ecological form with animals and xerobionts, since both of them live in deserts and have specific adaptations that prevent moisture loss (for example, obtaining water from fats).

Control questions and tasks

1. What laws of the general action of environmental factors do you know?

2. How is the law of the minimum formulated? What are the clarifications to it?

3. Formulate the law of tolerance. Who established this pattern?

4. Give examples of the use of the laws of minimum and tolerance in practice.

5. What mechanisms will allow living organisms to compensate for the effect of environmental factors?

6. What is the difference between habitat and ecological niche?

7. What is the life form of organisms? What is the importance of life forms in the adaptation of organisms?

Environmental factors are dynamic, changeable in time and space. The warm season is regularly replaced by cold, fluctuations in temperature and humidity are observed during the day, day follows night, etc. All these are natural (natural) changes in environmental factors. Also, as mentioned above, a person can interfere in them by changing either the regimes of environmental factors (absolute values ​​or dynamics) or their composition (for example, by developing, producing and using plant protection products, mineral fertilizers, etc., which did not previously exist in nature). ).

Despite the variety of environmental factors, the different nature of their origin, their variability in time and space, it is possible to distinguish general patterns their impact on living organisms.

The concept of the optimum. Liebig's Law of the Minimum

Each organism, each ecosystem develops under a certain combination of factors: moisture, light, heat, availability and composition of nutrient resources. All factors act on the body simultaneously. The reaction of the body depends not so much on the factor itself, but on its quantity (dose). For each organism, population, ecosystem, there is a range of environmental conditions - a range of stability within which the life of objects occurs ( Fig.2).

Fig.2.

In the process of evolution, organisms have formed certain requirements for environmental conditions. The doses of factors at which the organism achieves the best development and maximum productivity correspond to the optimum conditions. With a change in this dose in the direction of decreasing or increasing, the organism is inhibited, and the stronger the deviation of the values ​​of the factors from the optimum, the greater the decrease in viability, up to its death. The conditions under which vital activity is maximally depressed, but the organism still exists, are called pessimal. For example, in the south, the limiting factor is moisture availability. Thus, in Southern Primorye, the optimal forest growth conditions are characteristic of the northern slopes of the mountains in their middle part, and the pessimal conditions are characteristic of dry southern slopes with a convex surface.

The fact that limiting the dose (or absence) of any of the substances necessary for the plant, related to both macro and microelements, leads to the same result - a slowdown in growth and development, was discovered and studied by the German chemist Eustace von Liebig. The rule formulated by him in 1840 is called Liebig's law of the minimum: greatest influence plant endurance is affected by those factors that are at a minimum in a given habitat.2 At the same time, J. Liebig, conducting experiments with mineral fertilizers, drew a barrel with holes, showing that the bottom hole in the barrel determines the level of the liquid in it.

The law of the minimum is true for both plants and animals, including man, who certain situations you have to use mineral water or vitamins to compensate for the lack of any elements in the body.

A factor whose level is close to the endurance limits of a particular organism is called limiting (limiting). And it is to this factor that the body adapts (produces adaptations) in the first place. For example, the normal survival of sika deer in Primorye takes place only in oak forests on the southern slopes, because. here the thickness of the snow is insignificant and provides the deer with a sufficient food base for the winter period. The limiting factor for deer is deep snow.

Subsequently, clarifications were made to Liebig's law. An important amendment and addition is the law of the ambiguous (selective) effect of a factor on various functions of the body: any environmental factor affects the functions of the body differently, the optimum for some processes, such as respiration, is not the optimum for others, such as digestion, and vice versa.

In 1930, E. Ryubel established the law (effect) of compensation (interchangeability) of factors: the absence or deficiency of some environmental factors can be compensated by another close (similar) factor.

For example, a lack of light can be compensated for by an abundance of carbon dioxide for a plant, and when building shells by mollusks, the missing calcium can be replaced by strontium. However, the compensatory possibilities of the factors are limited. No factor can be completely replaced by another, and if the value of at least one of them goes beyond the upper or lower limits of the organism's endurance, the existence of the latter becomes impossible, no matter how favorable the other factors are.

In 1949 V.R. Williams formulated the law of indispensability of fundamental factors: the complete absence of fundamental environmental factors (light, water, etc.) in the environment cannot be replaced by other factors.

This group of refinements of Liebig's law includes a rule of "benefit-harm" phase reactions that is somewhat different from others: low concentrations of a toxicant act on the body in the direction of strengthening its functions (stimulating them), while higher concentrations inhibit or even lead to its death.

This toxicological regularity is true for many (for example, the medicinal properties of small concentrations of snake venom are known), but not for all toxic substances.