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.
1. The law of optimum.
Each factor has certain limits. positive impact on organisms (Fig. 1). The result of the action of a variable factor depends primarily on the strength of its manifestation. Both insufficient and excessive action of the factor negatively affects the life of individuals. The beneficial effect is called zone of optimum ecological factor or simply optimum for organisms of this species. The stronger the deviation from the optimum, the more pronounced the inhibitory effect of this factor on organisms. (pessimum zone). The maximum and minimum portable factor values are critical points behind beyond which existence is no longer possible, death occurs. The endurance limits between critical points are called environmental valence living beings in relation to a specific environmental factor.
Rice. one. Scheme of the action of environmental factors on living organisms
Representatives of different species differ greatly from each other both in the position of the optimum and in ecological valency. For example, Arctic foxes in the tundra can tolerate fluctuations in air temperature in the range of more than 80 °C (from +30 to -55 °C), while warm-water crustaceans Copilia mirabilis withstand water temperature changes in the range of no more than 6 °C (from +23 up to +29 °C). One and the same force of manifestation of a factor can be optimal for one species, pessimal for another, and go beyond the limits of endurance for the third (Fig. 2).
The wide ecological valence of the species in relation to a biotic factors environments are denoted by adding the prefix "evry" to the name of the factor. eurythermal species - enduring significant temperature fluctuations, eurybatic- wide pressure range, euryhaline- different degree of salinization of the environment.
Rice. 2. The position of the optimum curves on the temperature scale for different species:
1, 2 - stenothermic species, cryophiles;
3-7 - eurythermal species;
8, 9 - stenothermic species, thermophiles
The inability to tolerate significant fluctuations in the factor, or narrow ecological valence, is characterized by the prefix "steno" - stenothermal, stenobate, stenohaline species, etc. In a broader sense, species whose existence requires strictly defined environmental conditions are called stenobiont, and those that are able to adapt to different environmental conditions - eurybiontic.
Conditions approaching critical points in one or several factors at once are called extreme.
The position of the optimum and critical points on the factor gradient can be shifted within certain limits by the action of environmental conditions. This occurs regularly in many species as the seasons change. In winter, for example, sparrows withstand severe frosts, and in summer they die from cooling at temperatures just below zero. The phenomenon of shifting the optimum in relation to any factor is called acclimation. With regard to temperature, this is a well-known process of thermal hardening of the body. Temperature acclimation requires a significant period of time. The mechanism is the change in cells of enzymes that catalyze the same reactions, but at different temperatures (the so-called isoenzymes). Each enzyme is encoded by its own gene, therefore, it is necessary to turn off some genes and activate others, transcription, translation, assembly of a sufficient amount of a new protein, etc. The overall process takes an average of about two weeks and is stimulated by changes in the environment. Acclimation, or hardening, is an important adaptation of organisms that occurs under gradually impending adverse conditions or when they enter territories with a different climate. She is in these cases integral part overall process acclimatization.
2. Ambiguity of the action of the factor on different functions.
Each factor affects different body functions differently (Fig. 3). The optimum for some processes may be the pessimum for others. Thus, the air temperature from +40 to +45 ° C in cold-blooded animals greatly increases the rate of metabolic processes in the body, but inhibits motor activity, and the animals fall into a thermal stupor. For many fish, the water temperature that is optimal for the maturation of reproductive products is unfavorable for spawning, which occurs at a different temperature range.
Rice. 3. Scheme of the dependence of photosynthesis and respiration of a plant on temperature (according to V. Larcher, 1978): t min, t opt, t max- temperature minimum, optimum and maximum for plant growth (shaded area)
The life cycle, in which at certain periods the organism performs predominantly certain functions (nutrition, growth, reproduction, resettlement, etc.), is always consistent with seasonal changes in the complex of environmental factors. Mobile organisms can also change habitats for the successful implementation of all their life functions.
3. Variety of individual reactions to environmental factors. The degree of endurance, critical points, optimal and pessimal zones of individual individuals do not coincide. This variability is determined both by the hereditary qualities of individuals and by sex, age, and physiological differences. For example, in the mill moth butterfly, 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 at -10 °C kills caterpillars, but is not dangerous for adults and eggs of this pest. Consequently, the ecological valence of a species is always wider than the ecological valence of each individual.
4. Relative independence of adaptation of organisms to different factors. The degree of tolerance to any factor does not mean the corresponding ecological valence of the species in relation to other factors. For example, species that tolerate wide temperature changes need not also be adapted to wide fluctuations in humidity or salinity. Eurythermal species can be stenohaline, stenobatic, or vice versa. The ecological valencies of a species in relation to different factors can be very diverse. This creates an extraordinary variety of adaptations in nature. The set of ecological valences in relation to various environmental factors is ecological spectrum of the species.
5. Non-coincidence of the ecological spectra of individual species. Each species is specific in its ecological capabilities. Even among species close in terms of adaptation to the environment, there are differences in relation to any individual factors.
Rice. 4. Changes in the participation of certain plant species in meadow grass stands depending on moisture (according to L. G. Ramensky et al., 1956): 1 - meadow clover; 2 - common yarrow; 3 - Delyavina's cellar; 4 - bluegrass meadow; 5 - tipchak; 6 - real bedstraw; 7 - early sedge; 8 - meadowsweet ordinary; 9 - hill geranium; 10 - field barnacle; 11 - short-nosed goat-beard
The rule of ecological individuality of species formulated by the Russian botanist L. G. Ramensky (1924) in relation to plants (Fig. 4), then it was widely confirmed by zoological studies.
6. Interaction of factors. The optimal zone and limits of endurance of organisms in relation to any environmental factor may shift depending on the strength and combination of other factors acting simultaneously (Fig. 5). This pattern has been named interactions of factors. For example, heat is easier to bear in dry rather than moist air. The threat of freezing is much higher in frost with strong winds than in calm weather. Thus, the same factor in combination with others has an unequal environmental impact. On the contrary, the same ecological result can be obtained in different ways. For example, wilting of plants can be stopped by both increasing the amount of moisture in the soil and lowering the air temperature, which reduces evaporation. The effect of partial mutual substitution of factors is created.
Rice. 5. Mortality of eggs of the pine silkworm Dendrolimus pini at different combinations of temperature and humidity
At the same time, the mutual compensation of the action of environmental factors has certain limits, and it is impossible to completely replace one of them with another. The complete absence of water, or even one of the main elements of mineral nutrition, makes the life of the plant impossible, despite the most favorable combination of other conditions. The extreme lack of heat in the polar deserts cannot be made up for either by an abundance of moisture or round-the-clock illumination.
Taking into account the patterns of interaction of environmental factors in agricultural practice, it is possible to skillfully maintain optimal conditions for the vital activity of cultivated plants and domestic animals.
7. The rule of limiting factors. The possibilities of the existence of organisms are primarily limited by those environmental factors that are most distant 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, individuals are threatened with death. Any factors that strongly deviate from the optimum acquire paramount importance in the life of a species or its individual representatives in specific periods of time.
Environmental limiting factors determine the geographic range of a species. The nature of these factors may be different (Fig. 6). Thus, the movement of a species to the north can be limited by a lack of heat, and to arid regions by a lack of moisture or too high temperatures. Biotic relations, for example, the occupation of a territory by a stronger competitor or the lack of pollinators for plants, can also serve as a factor limiting the distribution. Thus, the pollination of figs depends entirely on the only kind insects - Blastophaga psenes wasps. This tree is native to the Mediterranean. Introduced figs to California did not bear fruit until pollinators were introduced there. The distribution of legumes in the Arctic is limited by the distribution of bumblebees that pollinate them. On the island of Dixon, where there are no bumblebees, legumes are not found either, although the existence of these plants there is still permissible due to temperature conditions.
Rice. 6. Deep snow cover is a limiting factor in the distribution of deer (according to G. A. Novikov, 1981)
To determine whether a species can exist in a given geographical area, one must first find out whether any environmental factors go beyond its ecological valence, especially in the most vulnerable period of development.
Identification of limiting factors is very important in practice Agriculture, since by directing the main efforts to eliminate them, it is possible to quickly and effectively increase the yield of plants or the productivity of animals. So, on highly acidic soils, the yield of wheat can be somewhat increased by applying various agronomic influences, but the best effect will be obtained only as a result of liming, which will remove the limiting effects of acidity. Knowing the limiting factors is thus the key to controlling the life of organisms. At different periods of life of individuals, various environmental factors act as limiting factors, therefore, skillful and constant regulation of the living conditions of grown plants and animals is required.
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2.2. Organism adaptations2.4. Principles of ecological classification of organisms
Lesson plan
Discipline: Ecology
subject: Habitat and environmental factors. General laws of action of environmental factors on the body.
Lesson Objectives:
Educational:
Give the concept of the environment of life and the habitat of living organisms.
To be able to distinguish between the concepts of aerobionts, hydrobionts, edaphobionts and endobionts.
Stenobionts and eurybionts
General laws of action of environmental factors on the body.
Developing: development:intellectual skills: analyze and compare, generalize and draw conclusions.Developmentsubject skills and abilities:
Educational: formation of a scientific worldview about a single picture of the organic world.instilling teamwork skills
Structure and course of the lessonTeacher activity
Student activities
Organizing time
Learning new material
Consolidation of the material covered
Greets students. Checks for absentees
1. Habitat and environmental factors
The habitat is the space in which the vital activity of living organisms takes place.
There are four types of habitats on the planet: water, land-air, soil and the living organisms themselves.
Living organisms are always in interaction with the natural formations and phenomena surrounding them.
Aggregate natural conditions and phenomena surrounding living organisms with which these organisms are in constant interaction, is called the habitat.
The role of the environment is twofold. First of all, living organisms get food from the environment in which they live. Besides, various environments limit the spread of organisms around the globe.
Organisms can exist in one or more living environments.
Separate properties or elements of the environment that affect organisms are called environmental factors.
Abiotic factors - temperature, light, radiation, pressure, air humidity, salt composition of water, wind, currents, terrain - these are all properties of inanimatenature that directly or indirectly affect living organisms.
Biotic factors are forms of influence of living beings on each other.
Anthropogenic factors are forms of activity human society, which lead to a change in nature as the habitat of other species or directly affect their lives.
2. General laws of the action of environmental factors on the body
In the complex of action of factors, some patterns can be distinguished that are largely universal (common) in relation to organisms. These patterns include the rule of optimum, the rule of interaction of factors, the rule of limiting factors, and some others.
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The habitat is that part of nature that surrounds a living organism and with which it directly interacts. The components and properties of the environment are diverse and changeable. Any living being lives in a complex and changing world, constantly adapting to it and regulating its life activity in accordance with its changes.
Organisms' adaptations to their environment are called adaptations. The ability to adapt is one of the main properties of life in general, as it provides the very possibility of its existence, the ability of organisms to survive and reproduce. Adaptations manifest themselves at different levels: from the biochemistry of cells and the behavior of individual organisms to the structure and functioning of communities and ecological systems. Adaptations arise and change in the course of the evolution of species.
Separate properties or elements of the environment that affect organisms are called environmental factors. Environmental factors are diverse. They may be necessary or, conversely, harmful to living beings, promote or hinder survival and reproduction. Environmental factors have a different nature and specificity of action. Environmental factors are divided into abiotic and biotic, anthropogenic.
Abiotic factors - temperature, light, radioactive radiation, pressure, air humidity, salt composition of water, wind, currents, terrain - these are all properties inanimate nature that directly or indirectly affect living organisms.
Biotic factors are forms of influence of living beings on each other. Each organism constantly experiences the direct or indirect influence of other creatures, enters into contact with representatives of its own species and other species - plants, animals, microorganisms, depends on them and itself has an impact on them. Ambient organic world- an integral part of the environment of every living being.
Mutual connections of organisms are the basis for the existence of biocenoses and populations; consideration of them belongs to the field of synecology.
Anthropogenic factors are forms of activity of human society that lead to a change in nature as a habitat for other species or directly affect their lives. In the course of human history, the development of first hunting, and then agriculture, industry, and transport has greatly changed the nature of our planet. Meaning anthropogenic impacts to the entire living world of the Earth continues to grow rapidly.
Although man influences wildlife through a change in abiotic factors and biotic relationships of species, the activities of people on the planet should be singled out as a special force that does not fit into the framework of this classification. At present, almost the entire fate of the living cover of the Earth and all types of organisms is in the hands of human society and depends on anthropogenic influence on nature.
The same environmental factor has a different meaning in the life of cohabiting organisms of different species. For example, a strong wind in winter is unfavorable for large, open-dwelling animals, but does not affect smaller ones that hide in burrows or under snow. The salt composition of the soil is important for plant nutrition, but is indifferent to most land animals, etc.
Changes in environmental factors over time can be: 1) regularly-periodic, changing the strength of the impact in connection with the time of day or season of the year or the rhythm of the tides in the ocean; 2) irregular, without a clear periodicity, for example, changes in weather conditions in different years, catastrophic phenomena - storms, downpours, landslides, etc.; 3) directed over certain, sometimes long, periods of time, for example, during a cooling or warming of the climate, overgrowing of water bodies, constant grazing in the same area, etc.
Environmental environmental factors have various effects on living organisms, that is, they can act as irritants that cause adaptive changes in physiological and biochemical functions; as limiters, making it impossible to exist in these conditions; as modifiers causing anatomical and morphological changes in organisms; as signals indicating changes in other environmental factors.
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.
1. The law of optimum. Each factor has only certain limits of positive influence on organisms. The result of the action of a variable factor depends primarily on the strength of its manifestation. Both insufficient and excessive action of the factor negatively affects the life of individuals. The favorable force of influence is called the zone of optimum of the ecological factor or simply the optimum for organisms of a given species. The stronger the deviations from the optimum, the more pronounced the inhibitory effect of this factor on organisms (pessimum zone). The maximum and minimum tolerated values of the factor are critical points, beyond which existence is no longer possible, death occurs. The limits of endurance between critical points are called the ecological valency of living beings in relation to a specific environmental factor.
Representatives of different al-dov differ greatly from each other both in the position of the optimum and in ecological valency. For example, polar foxes from the tundra can tolerate fluctuations in air temperature in the range of about 80°С (from +30 to 29C). The same force of manifestation of a factor can be optimal for one species, pessimal for another, and go beyond the limits of endurance for the third.
The wide ecological valency of a species in relation to abiotic environmental factors is indicated by adding the prefix "evry" to the name of the factor. Eurythermal species - enduring significant temperature fluctuations, eurybatic species - a wide range of pressure, euryhaline - varying degrees of salinity.
The inability to tolerate significant fluctuations in the factor, or a narrow ecological valency, is characterized by the prefix "steno" - stenothermic, stenobatic, stenohaline species, etc. In a broader sense, species that require strictly defined environmental conditions for their existence are called stenobiont, and those that which are able to adapt to different environmental conditions - eurybiont.
2. Ambiguity of the action of the factor on different functions. Each factor affects different functions of the body in different ways. The optimum for some processes may be the pessimum for others. Thus, the air temperature from 40 to 45 ° C in cold-blooded animals greatly increases the rate of metabolic processes in the body, but inhibits motor activity, and the animals fall into a thermal stupor. For many fish, the water temperature that is optimal for the maturation of reproductive products is unfavorable for spawning, which occurs at a different temperature range.
The life cycle, in which at certain periods the organism performs predominantly certain functions (nutrition, growth, reproduction, resettlement, etc.), is always consistent with seasonal changes in the complex of environmental factors. Mobile organisms can also change habitats for the successful implementation of all their life functions.
3. Variability, variability and diversity of responses to the action of environmental factors in individual individuals of the species. The degree of endurance, critical points, optimal and pessimal zones of individual individuals do not coincide. This variability is determined both by the hereditary qualities of individuals and by sex, age, and physiological differences. For example, in the mill moth butterfly, 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 at 10 ° C kills caterpillars, but is not dangerous for adults and eggs of this pest. Consequently, the ecological valence of a species is always wider than the ecological valence of each individual.
4. To each of the environmental factors, species adapt in a relatively independent way. 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 temperature changes need not also be adapted to wide fluctuations in humidity or salinity. Eurythermal species can be stenohaline, stenobatic, or vice versa. The ecological valencies of a species in relation to different factors can be very diverse. This creates an extraordinary variety of adaptations in nature. A set of ecological valences in relation to various environmental factors constitutes the ecological spectrum of a species.
5. Non-coincidence of the ecological spectra of individual species. Each species is specific in its ecological capabilities. Even among species that are close in terms of ways of adapting to the environment, there are differences in their attitude to any individual factors.
The rule of ecological individuality of species was formulated by the Russian botanist L. G. Ramensky (1924) in relation to plants, and then it was widely confirmed by zoological studies.
6. Interaction of factors. The optimal zone and limits of endurance of organisms in relation to any environmental factor can be shifted depending on the strength and combination of other factors acting simultaneously. This pattern is called the interaction of factors. For example, heat is easier to bear in dry rather than moist air. The threat of freezing is much higher in frost with strong winds than in calm weather. Thus, the same factor in combination with others has an unequal environmental impact. On the contrary, the same ecological result can be
beamed in different ways. For example, wilting of plants can be stopped by both increasing the amount of moisture in the soil and lowering the air temperature, which reduces evaporation. The effect of partial mutual substitution of factors is created.
At the same time, the mutual compensation of the action of environmental factors has certain limits, and it is impossible to completely replace one of them with another. The complete absence of water, or even one of the main elements of mineral nutrition, makes the life of the plant impossible, despite the most favorable combination of other conditions. The extreme lack of heat in the polar deserts cannot be made up for either by an abundance of moisture or round-the-clock illumination.
Taking into account the patterns of interaction of environmental factors in agricultural practice, it is possible to skillfully maintain optimal conditions for the vital activity of cultivated plants and domestic animals.
7. The rule of limiting factors. Environmental factors that are farthest away from the optimum make it especially difficult for the species to exist under given conditions. If at least one of the environmental factors approaches or goes beyond critical values, then, despite the optimal combination of other conditions, individuals are threatened with death. Such strongly deviating factors become of paramount importance in the life of a species or its individual representatives at any particular time interval.
Environmental limiting factors determine the geographic range of a species. The nature of these factors may be different. Thus, the movement of a species to the north can be limited by a lack of heat, and to arid regions by a lack of moisture or too high temperatures. Biotic relations, for example, the occupation of a territory by a stronger competitor or the lack of pollinators for plants, can also serve as a factor limiting the distribution. So, pollination of figs depends entirely on a single insect species - the wasp Blastophaga psenes. This tree is native to the Mediterranean. Introduced to California, figs did not bear fruit until pollinator wasps were brought there. The distribution of legumes in the Arctic is limited by the distribution of bumblebees that pollinate them. On the island of Dixon, where there are no bumblebees, legumes are not found either, although the existence of these plants there is still permissible due to temperature conditions.
To determine whether a species can exist in a given geographical area, one must first find out whether any environmental factors go beyond its ecological valence, especially in the most vulnerable period of development.
The identification of limiting factors is very important in the practice of agriculture, since, by directing the main efforts to eliminate them, one can quickly and effectively increase crop yields or animal productivity. Thus, on strongly acidic soils, the yield of wheat can be somewhat increased by applying various agronomic influences, but the best effect will be obtained only as a result of liming, which will remove the limiting effects of acidity. Knowing the limiting factors is thus the key to controlling the life of organisms. At different periods of life of individuals, various environmental factors act as limiting factors, therefore, skillful and constant regulation of the living conditions of grown plants and animals is required.
In the complex of action of factors, some patterns can be distinguished that are largely universal (common) in relation to organisms. These patterns include the rule of optimum, the rule of interaction of factors, the rule of limiting factors, and some others.
Optimum rule . In accordance with this rule, for an organism or a certain stage of its development, there is a range of the most favorable (optimal) value of the factor. The more significant the deviation of the action of the factor from the optimum, the more this factor inhibits the vital activity of the organism. 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 the organism is no longer possible.
The maximum population density is usually confined to the optimum zone. Zones of optimum for different organisms are not the same. The wider the amplitude of fluctuations of the factor, at which the organism can remain viable, the higher its stability, i.e. tolerance to one or another factor (from Lat. tolerance- patience). Organisms with a wide amplitude of resistance belong to the group eurybionts (gr. eury- wide, bios- a life). Organisms with a narrow range of adaptation to factors are called stenobionts (gr. stenos- narrow). It is important to emphasize that the zones of optimum in relation to various factors differ, and therefore organisms fully show their potential capabilities if they exist under conditions of the entire spectrum of factors with optimal values.
Rule of interaction of factors . Its essence lies in the fact that some factors can enhance or mitigate the force of other factors. For example, an excess of heat can be somewhat mitigated by low air humidity, a lack of light for plant photosynthesis can be compensated by an increased content of carbon dioxide in the air, and so on. It does not, however, follow that the factors can be interchanged. They are not interchangeable.
Rule of Limiting Factors . The essence of this rule lies in the fact that a factor that is in deficiency or excess (near critical points) negatively affects organisms and, in addition, limits the possibility of manifestation of the strength of other factors, including those at the optimum. Limiting factors usually determine the boundaries of the distribution of species, their ranges. The productivity of organisms depends on them.
A person by his activity often violates almost all of the listed patterns of factors. This is especially true for limiting factors (destruction of habitats, violation of the regime of water and mineral nutrition, etc.).
The habitat of an organism is a set of abiotic and biotic conditions of its life. The properties of the environment are constantly changing, and any creature, in order to survive, adapts to these changes.
The impact of the environment is perceived by organisms through environmental factors called environmental.
Environmental factors- these are certain conditions and elements of the environment that have a specific effect on the body. They are divided into abiotic, biotic and anthropogenic.
Abiotic factorscalled the whole set of factors of the inorganic environment that affect the life and distribution of animals and plants. Among them are physical, chemical and edaphic.
Physical factors - these are the factors, the source of which is the physical state or phenomenon (mechanical, wave, etc.). For example, the temperature, if it is high, will cause a burn, if it is very low, frostbite. Other factors can also affect the effect of temperature: in water - current, on land - wind and humidity, etc.
Chemical Factors are the factors that come from chemical composition environment. For example, if the salinity of the water is high, life in the reservoir may be completely absent (Dead Sea), but at the same time in fresh water most marine organisms cannot live. The life of animals on land and in water depends on the sufficiency of oxygen content, etc.
Edaphic factors , i.e. soil, is a combination of chemical, physical and mechanical properties of soils and rocks that affect both the organisms living in them, i.e. those for which they are the habitat, and on root system plants. The effect of chemical components is well known ( nutrients), temperature, humidity, soil structure, humus content, etc. on the growth and development of plants.
Biotic factors- a set of influences of the vital activity of some organisms on the vital activity of others, as well as on the non-living environment. In the latter case we are talking about the ability of the organisms themselves to a certain extent influence the living conditions. For example, in the forest, under the influence of vegetation cover, a special microclimate or microenvironment is created, where, in comparison with an open habitat, its own temperature and humidity regime is created: in winter it is several degrees warmer, in summer it is cooler and wetter. A special microenvironment is also created in tree hollows, burrows, caves, etc.
Biotic factors include intraspecific competition and interspecific relationships.
Intraspecific competition is the struggle for the same resources between individuals of the same species. This is an important factor in the self-regulation of populations.
Interspecific relationships are much more diverse. Two species living side by side may not influence each other at all, they may influence favorably or unfavorably. Possible types of combinations and reflect different kinds relationship:
Anthropogenic factors- factors generated by man and affecting the environment (pollution, soil erosion, deforestation, etc.).
Among abiotic factors, climatic (temperature, air humidity, wind, etc.) and hydrographic factors of the aquatic environment (water, current, salinity, etc.) are quite often distinguished.
Most factors change qualitatively and quantitatively over time. For example, climatic - during the day, season, by year (temperature, illumination, etc.).
Factors that change regularly over time are called periodic. These include not only climatic, but also some hydrographic - ebbs and flows, some ocean currents. Factors that arise unexpectedly (volcanic eruption, predator attack, etc.) are called non-periodic.
The division of factors into periodic and non-periodic is very important in studying the adaptability of organisms to living conditions.