A factor that goes beyond the limits of the body's endurance is called. Environmental factors. General information. Endemic diseases include

Law of Optimum. Environmental environmental factors have quantitative expression. Each factor has certain limits of positive influence on organisms (Fig. 2). Both insufficient and excessive action of the factor negatively affects the life activity of individuals.

In relation to each factor, one can distinguish an optimum zone (zone of normal life activity), a pessimum zone (zone of depression), upper and lower limits of the body's endurance.

Optimum zone, or optimum (from lat. optimum- the noblest, the best), - such an amount of environmental factor at which the intensity of the vital activity of organisms is maximum.

Pessimum zone, or pessimum (from lat. pessimum - cause harm, suffer damage) - such an amount of environmental factor at which the intensity of the vital activity of organisms is suppressed.

Upper Endurance Limit - maximum amount environmental factor under which the existence of an organism is possible.

Rice. 2.

Lower Endurance Limit - the minimum amount of environmental factor at which the existence of an organism is possible.

Beyond the limits of endurance, the existence of an organism is impossible.

The curve can be wide or narrow, symmetrical or asymmetrical. Its form depends on the species of the organism, on the nature of the factor and on which of the body’s reactions is chosen as a response and at what stage of development.

The ability of living organisms to tolerate quantitative fluctuations in the action of an environmental factor to one degree or another is called ecological valency (tolerance, stability, plasticity).

The environmental factor values ​​between the upper and lower endurance limits are called zone of tolerance.

Species with a wide tolerance zone are called eurybiont (from Greek euris - wide), with narrow - stenobiont (from Greek stems - narrow) (Fig. 3 and 4).

Organisms that can tolerate significant temperature fluctuations are called eurythermic , and adapted to a narrow temperature range - stenothermic. In the same way, in relation to pressure, they distinguish eury- and stenobate organisms, in relation to humidity - eury- and stenohydric, in relation to the degree of

Rice. 3.1 - eurybiont: 2 - stenobiont

Rice. 4.

salting environment - eury- and stenohaline, in relation to the oxygen content in water - eury- and stenoxybiont, in relation to writing - eury- and stenophagous, in relation to the habitat - eury- and steno-oic, etc.

Thus, the direction and intensity of the action of an environmental factor depend on the quantities in which it is taken and in combination with what other factors it acts. There are no absolutely beneficial or harmful environmental factors: it’s all a matter of quantity. For example, if the temperature environment too low or too high, that is, beyond the endurance limits of living organisms, this is bad for them. Only optimal values ​​are favorable. At the same time, environmental factors cannot be considered in isolation from each other. For example, if the body experiences a lack of water, then it is more difficult for it to tolerate high temperatures.

The phenomenon of acclimatization. The position of the optimum and endurance limits on the factor gradient can shift within certain limits. For example, a person can more easily tolerate lower ambient temperatures in winter than in summer, and higher temperatures, vice versa. This phenomenon is called acclimatization (or acclimation). Acclimatization occurs when the seasons change or when entering an area with a different climate.

The ambiguity of the factor’s effect on various body functions.

The same amount of factor has different effects on different body functions. The optimum for some processes may be a pessimum for others. For example, in plants, the maximum intensity of photosynthesis is observed at an air temperature of +25...+35 °C, and respiration - +55 °C (Fig. 5). Accordingly, at lower temperatures there will be an increase in plant biomass, and at higher temperatures there will be a loss of biomass. In cold-blooded animals, an increase in temperature to +40 °C or more greatly increases the rate of metabolic processes in the body, but inhibits motor activity, and the animals fall into thermal stupor. In humans, the testes are located outside the pelvis, since spermatogenesis requires lower temperatures. For many fish, the water temperature that is optimal for gamete maturation is unfavorable for spawning, which occurs at a different temperature.

The life cycle, in which during certain periods the organism primarily performs certain functions (nutrition, growth, reproduction, settlement, etc.), is always consistent with seasonal changes in a complex of environmental factors. Mobile organisms can

Rice. 5.t MUH, t onm, t MaKC- temperature minimum, optimum and maximum for plant growth (shaded area)

also change habitats for the successful implementation of all their vital functions.

Ecological valency of the species. The ecological valences of individual individuals do not coincide. They depend on the hereditary and ontogenetic characteristics of individual individuals: gender, age, morphological, physiological, etc. Therefore, the ecological valence of a species is broader than the ecological valence of each individual individual. For example, for the miller moth - one of the pests of flour and grain products - the critical minimum temperature for caterpillars is -7 °C, for adult forms - 22 °C,

and for eggs - 27 °C. Frost of -10 °C kills caterpillars, but is not dangerous for

imago and eggs of this pest.

Ecological spectrum of the species. The set of ecological valences of a species in relation to various environmental factors is ecological spectrum of the species. Ecological spectra different types differ from each other. This allows different species to occupy different habitats. Knowledge of the ecological spectrum of a species allows for the successful introduction of plants and animals.

Interaction of factors. In nature, environmental factors act together, that is, in a complex manner. The combined effect of several environmental factors on the body is called constellation. The optimum zone and limits of endurance of organisms in relation to any environmental factor can shift depending on the strength with which and in what combination other factors act simultaneously. For example, high temperatures are more difficult to tolerate when there is a shortage of water, strong wind increases the effect of cold, heat is easier to tolerate in dry air, etc. Thus, the same factor in combination with others has different environmental impacts (Fig. 6). Accordingly, the same environmental result can be obtained in different ways. For example, compensation for the lack of moisture can be done by watering or lowering the temperature. The effect of partial interchange of factors is created. However, mutual compensation of environmental factors has certain limits, and it is impossible to completely replace one of them with another.

Rice. 6. Mortality of pine silkworm eggs Dendrolimuspini at different combinations of temperature and humidity (according to N.M. Chernova, A.M. Bylova, 2004)

Thus, the absolute absence of any of mandatory conditions It is impossible to replace life with other environmental factors, but the deficiency or excess of some environmental factors can be compensated by the action of other environmental factors. For example, the complete (absolute) absence of water cannot be compensated for by other environmental factors. However, if other environmental factors are at their optimum, then it is easier to tolerate a lack of water than when other factors are in deficiency or excess.

Law of limiting factor. The possibilities for the existence of organisms are primarily limited by those environmental factors that are furthest away from the optimum. An ecological factor, the quantitative value of which goes beyond the endurance of the species, is called limiting (limiting) factor. Such a factor will limit the existence (distribution) of the species even if all other factors are favorable (Fig. 7).

Rice.

Limiting factors determine the geographical range of the species. For example, the advancement of a species to the poles may be limited by a lack of heat, and to arid regions by a lack of moisture or too high temperatures.

Human knowledge of the limiting factors for a particular type of organism allows, by changing environmental conditions, to either suppress or stimulate its development.

Living conditions and living conditions. The complex of factors under the influence of which all the basic life processes of organisms, including normal development and reproduction, are carried out is called living conditions. Conditions in which reproduction does not occur are called conditions of existence.

Despite the wide variety of environmental factors, a number of general patterns can be identified in the nature of their impact on organisms and in the responses of living beings.

Law of tolerance (law of optimum or W. Shelford’s law) – Each factor has certain limits of positive influence on organisms. Both insufficient and excessive action of the factor negatively affects the life activity of individuals (too much “good” is also “not good”).

Environmental factors have quantitative expression. In relation to each factor, one can distinguish optimum zone (zone of normal life activity), pessimum zone (zone of oppression) and endurance limits body. Optimum is the amount of environmental factor at which the intensity of vital activity of organisms is maximum. In the pessimum zone, the vital activity of organisms is suppressed. Beyond the limits of endurance, the existence of an organism is impossible. There are lower and upper limits of endurance.

The ability of living organisms to tolerate quantitative fluctuations in the action of an environmental factor to one degree or another is called ecological valency (tolerance, stability, plasticity).

The environmental factor values ​​between the upper and lower endurance limits are called zone of tolerance. Species with a wide tolerance zone are called eurybiont, with a narrow one - stenobiont . Organisms that can tolerate significant temperature fluctuations are called eurythermic, and adapted to a narrow temperature range – stenothermic. In the same way, in relation to pressure, they distinguish evry- and stenobate organisms, in relation to the degree of salinity of the environment – evry- And stenohaline, in relation to nutrition evry- And stenotrophs(in relation to animals the terms are used evry- And stenophages) etc.

The environmental valences of individuals do not coincide. Therefore, the ecological valence of a species is broader than the ecological valence of each individual individual.

The ecological valence of a species to different environmental factors can differ significantly. The set of environmental valences in relation to various environmental factors is ecological spectrum of the species.

An ecological factor, the quantitative value of which goes beyond the endurance of the species, is called limiting (limiting) factor.

2. Ambiguity of the factor’s effect on different functions – Each factor affects different body functions differently. The optimum for some processes may be a pessimum for others. Thus, for many fish, the water temperature that is optimal for the maturation of reproductive products is unfavorable for spawning.

3. Diversity of individual reactions to environmental factors – the degree of endurance, critical points, optimal and pessimal zones of individual individuals of the same species do not coincide. This variability is determined both by the hereditary qualities of individuals and by gender, age and physiological differences. For example, the mill moth butterfly, one of the pests of flour and grain products, has a critical minimum temperature for caterpillars of -7 °C, for adult forms -22 °C, and for eggs -27 °C. Frost of -10 °C kills caterpillars, but is not dangerous for the adults and eggs of this pest. Consequently, the ecological valence of a species is always broader than the ecological valency of each individual individual.

4. Relative independence of adaptation of organisms to different factors– the degree of tolerance to any factor does not mean the corresponding ecological valency of the species in relation to other factors. For example, species that tolerate wide variations in temperature do not necessarily also need to be able to tolerate wide variations in humidity or salinity. Eurythermal species can be stenohaline, stenobatic, or vice versa.

5. Discrepancy between the ecological spectra of individual species– each species is specific in its ecological capabilities. Even among species that are similar in their methods of adaptation to the environment, there are differences in their attitudes to certain individual factors.

6. Interaction of factors– the optimal zone and limits of endurance of organisms in relation to any environmental factor can shift depending on the strength and in what combination other factors act simultaneously. For example, heat is easier to bear in dry rather than humid air. The risk of freezing is much greater in cold weather with strong winds than in calm weather.

7. The law of the minimum (J. Liebig’s law or the rule of limiting factors) – The possibilities for the existence of organisms are primarily limited by those environmental factors that are furthest from the optimum. If at least one of the environmental factors approaches or goes beyond critical values, then, despite the optimal combination of other conditions, the individuals are threatened with death. Thus, the movement of the species to the north may be limited (limited) by a lack of heat, and into arid regions by a lack of moisture or too high temperatures. Identifying limiting factors is very important in agricultural practice.

8. Hypothesis of the irreplaceability of fundamental factors (V. R. Williamson)– complete absence in the environment complete absence in the environment of fundamental environmental factors (physiologically necessary; for example, light, water, carbon dioxide, nutrients) cannot be compensated (replaced) by other factors. Thus, according to the Guinness Book of Records, a person can live up to 10 minutes without air, 10–15 days without water, and up to 100 days without food.

Environmental factors have quantitative expression. In relation to each factor, one can distinguish optimum zone(zone of normal life activity), pessimum zone(zone of oppression) and endurance limits body. Optimum is the amount of environmental factor at which the intensity of vital activity of organisms is maximum. In the pessimum zone, the vital activity of organisms is suppressed. Beyond the limits of endurance, the existence of an organism is impossible. There are lower and upper limits of endurance.

The ability of living organisms to tolerate quantitative fluctuations in the action of an environmental factor to one degree or another is called ecological valence (tolerance, stability, plasticity). The interval of environmental factor values ​​between the upper and lower limits of endurance is called zone of tolerance. Species with a wide tolerance zone are called eurybiont, with a narrow - stenobiont. Thus, organisms that tolerate significant temperature fluctuations are called eurythermic, while those adapted to a narrow temperature range are called stenothermic. In the same way, in relation to pressure, eury- and stenohaline organisms are distinguished, in relation to the degree of salinity of the environment - eury- and stenohaline, etc.

The environmental valences of individuals do not coincide. Therefore, the ecological valence of a species is broader than the ecological valence of each individual individual.

The ecological valence of a species to different environmental factors can differ significantly. The set of environmental valences in relation to various environmental factors is ecological spectrum of the species.

An ecological factor, the quantitative value of which goes beyond the endurance of the species, is called limiting (limiting) factor. This factor will limit the spread of the species even if all other factors are favorable. Limiting factors determine the geographical range of the species. Human knowledge of the limiting factors for a particular type of organism allows, by changing environmental conditions, to either suppress or stimulate its development.

We can highlight the main patterns of action of environmental factors:

1. law of relativity of environmental factors- the direction and intensity of the action of an environmental factor depend on the quantities in which it is taken and in combination with what other factors it acts. There are no absolutely beneficial or harmful environmental factors: everything depends on their quantity. For example, if the ambient temperature is too low or too high, e.g. goes beyond the endurance of living organisms, this is bad for them. Only optimal values ​​are favorable;
2. law of relative replaceability and absolute irreplaceability of environmental factors- the absolute absence of any of the mandatory conditions of life cannot be replaced by other environmental factors, but the deficiency or excess of some environmental factors can be compensated by the action of other environmental factors. For example, the complete (absolute) absence of water cannot be compensated for by other environmental factors. However, if other environmental factors are at their optimum, then it is easier to tolerate a lack of water than when other factors are in deficiency or excess.

Environmental factors always act on organisms in combination. Moreover, the result is not the sum of the influence of several factors, but is difficult process their interactions. At the same time, the vitality of the organism changes, specific adaptive properties arise that allow it to survive in certain conditions and tolerate fluctuations in the values ​​of various factors.

The influence of environmental factors on the body can be represented in the form of a diagram (Fig. 94).

The most favorable intensity of the environmental factor for the body is called optimal or optimum.

Deviation from the optimal action of the factor leads to inhibition of the body’s vital functions.

The limit beyond which the existence of an organism is impossible is called endurance limit.

These boundaries are different for different species and even for different individuals of the same species. For example, the upper layers of the atmosphere, thermal springs, and the icy desert of Antarctica are beyond the limits of endurance for many organisms.

An environmental factor that goes beyond the limits of the body's endurance is called limiting.

It has upper and lower limits. So, for fish the limiting factor is water. Outside aquatic environment their life is impossible. A decrease in water temperature below 0 °C is the lower limit, and an increase above 45 °C is the upper limit of endurance.

Rice. 94. Scheme of the action of an environmental factor on the body

Thus, the optimum reflects the characteristics of living conditions various types. In accordance with the level of the most favorable factors, organisms are divided into heat- and cold-loving, moisture-loving and drought-resistant, light-loving and shade-tolerant, adapted to life in salt and fresh water, etc. The wider the limit of endurance, the more plastic the organism. Moreover, the limit of endurance in relation to various environmental factors varies among organisms. For example, moisture-loving plants can tolerate large temperature changes, while the lack of moisture is detrimental to them. Narrowly adapted species are less plastic and have a small limit of endurance; widely adapted species are more plastic and have a wide range of fluctuations in environmental factors.

For fish living in the cold seas of Antarctica and the Arctic Ocean, the temperature range is 4–8 °C. As the temperature rises (above 10 °C), they stop moving and fall into thermal stupor. On the other hand, fish from equatorial and temperate latitudes tolerate temperature fluctuations from 10 to 40 °C. Warm-blooded animals have a wider range of endurance. Thus, arctic foxes in the tundra can tolerate temperature changes from -50 to 30 °C.

Temperate plants tolerate temperature fluctuations of 60–80 °C, while tropical plants have a much narrower temperature range: 30–40 °C.

Interaction of environmental factors is that changing the intensity of one of them can narrow the limit of endurance to another factor or, conversely, increase it. For example, optimal temperature increases tolerance to lack of moisture and food. High humidity significantly reduces the body's resistance to high temperatures. The intensity of exposure to environmental factors is directly dependent on the duration of this exposure. Long-term exposure to high or low temperatures is detrimental to many plants, while plants tolerate short-term changes normally. The limiting factors for plants are the composition of the soil, the presence of nitrogen and other nutrients in it. Thus, clover grows better in soils poor in nitrogen, and nettle does the opposite. A decrease in nitrogen content in the soil leads to a decrease in the drought resistance of cereals. Plants grow worse on salty soils; many species do not take root at all. Thus, the organism’s adaptability to individual environmental factors is individual and can have both a wide and narrow range of endurance. But if the quantitative change in at least one of the factors goes beyond the limit of endurance, then, despite the fact that other conditions are favorable, the organism dies.

The set of environmental factors (abiotic and biotic) that are necessary for the existence of a species is called ecological niche.

Ecological niche characterizes the way of life of an organism, its living conditions and nutrition. In contrast to a niche, the concept of habitat denotes the territory where an organism lives, i.e. its “address”. For example, the herbivorous inhabitants of the steppes, cows and kangaroos, occupy the same ecological niche, but have different habitats. On the contrary, the inhabitants of the forest - squirrel and elk, also classified as herbivores, occupy different ecological niches. The ecological niche always determines the distribution of an organism and its role in the community.