Anthropogenic factors
These are forms of human society activity that change the habitat for a variety of organisms.
Anthropogenic factors usually act indirectly, by changing the action of abiotic and biotic factors.
For example, thinning in coniferous-broad-leaved forests creates favorable conditions for most small passerine birds, but cutting down hollow trees reduces the number of hollow nests (owls, fly flies)
At the same time, great and direct impact of anthropogenic factors: deforestation, poaching.
The influence of environmental factors on a living organism is very diverse. Some factors have a stronger effect, others are less effective; some affect all aspects of life, others - on some separate life process. Nevertheless, in the nature of their effect on organisms and in the responses of living beings, it is possible to reveal a number of general patterns that fit into a certain general scheme of the action of the ecological factor on the vital activity of the organism.
The abscissa shows the intensity of the factor (for example, temperature, illumination, concentration of salts in the soil solution, soil moisture, etc.), and the ordinate shows the reaction of the organism to an ecological factor in its quantitative expression (for example, the intensity of photosynthesis, respiration, growth The size of the organism or its organs, the number of individuals per unit area, etc.). The range of action of the ecological factor is limited by the corresponding extreme threshold values \u200b\u200b(points of minimum and maximum) of this factor, at which the existence of an organism is still possible. The limits between critical points are called the ecological valence of living beings in relation to a specific environmental factor. The values \u200b\u200bof the ecological factor that are most favorable for a given species are called optimal, or just ecological optimum ... The same values \u200b\u200bof the factor that are unfavorable for a given species are called maximum or simply environmental pessimum .
Different types of living organisms differ markedly from each other both in the position of the optimum and in the ecological valence. For example, Arctic foxes in the tundra can tolerate air temperature fluctuations in the range of about 80 0 С (from +30 to -55 0 С), while warm-water crustaceans Corilia mirabilis can withstand water temperature changes in the range of no more than 6 0 С (from 23 to 29 0 С), and filamentous cyanobacterium oscillatoria living on about. Java in water with a temperature of 64 0 С, dies at 68 0 С after 5-10 minutes. Likewise, some meadow grasses prefer soils with a rather narrow range of acidity (for example, common heather, sorrel, sticking out whitebush serve as indicators of acidic soils with a pH of 3.5-4.5), others grow well in a wide range of pH - from strongly acidic to alkaline ( for example, Scots pine). The types of organisms for the existence of which strictly defined, relatively constant environmental conditions are called stenobiontic , and those that have a wide ecological valence in relation to a complex of factors - eurybiontic ... In this case, the species can have a narrow amplitude in relation to one factor and wide - to another (for example, to be confined to a narrow temperature range and a wide salinity range). In addition, the same strength of factor manifestation may be optimal for one species, pessimal for another, and go beyond the limits of endurance for a third.
Organ survival reaches its maximum at average values \u200b\u200bof this environmental factor.
The ability of a species to reproduce individuals, to compete with others will be limited by the factor that deviates most from its optimal value. If the quantitative value of at least one of the factors goes beyond the limits of endurance, then the existence of the species becomes impossible, no matter how favorable the other conditions are.
Such factors that go beyond the boundaries of the maximum or minimum are called limiting. For example, the spread of many animals and plants to the north usually limits the lack of heat, while in the south the limiting factor for the same species may be lack of moisture or necessary food. Environmental limiting factors also determine the geographic range of the species.
Adaptation of organisms to the seasonal rhythm of external conditions.
Climate is one of the main components of the natural environment. For the life of terrestrial plants and animals, the most important components of the climate are light, temperature and humidity. An important feature of these factors is their regular change during the year and day, and in connection with the geographic zoning. Therefore, adaptations to them are of a zonal and seasonal nature.
Seasonal periodicity is one of the most common phenomena in living nature. It is especially pronounced at measured latitudes. At the heart of external simple and well-known to us seasonal phenomena in the world of organs are complex adaptive reactions of a rhythmic nature, which were revealed relatively recently.
As an example, consider the seasonal frequency in the central regions of our country. Here, the annual temperature variation is of leading importance for plants and animals. The favorable period for life lasts about six months.
Signs of spring appear as soon as the snow melts: willow, alder, hazel are blooming, plant sprouts appear, migratory birds arrive. At this time, even small frosts damage plants and cause the death of many insects.
In the middle of summer, despite the temperature and abundance of rainfall, the growth of many plants slows down. Breeding ends in birds.
The second half of summer and early autumn is the period of ripening of fruits and seeds in most plants and the accumulation of nutrients in their tissues. At the same time, signs of preparation for winter are already noticeable. Wintering buds are formed and shoots on trees are lignified; there is an increased outflow of nutrients from the leaves to the stems and roots. Autumn molt begins in birds and mammals, migratory birds huddle in flocks.
Preparation for winter ends with the fall of plant leaves, the departure of many birds, the disappearance of insects that hide and die. Even before the onset of stable frosts, a period of winter dormancy begins in nature.
The state of winter dormancy is especially pronounced among organisms that are not able to maintain a constant body temperature, i.e. in plants, all invertebrates and lower vertebrates.
Winter dormancy is not just an arrest of development caused by low temperatures, but a very complex physiological adaptation. In each species, the state of winter dormancy occurs only at a certain stage of development. So, plants overwinter seeds, aboveground and underground parts with resting buds. At different stages of development, winter dormancy occurs in insects (malaria mosquito, butterfly - urticaria hibernates in the stage of an adult insect, a butterfly - cabbage in the pupal stage, silkworm in the egg stage).
The hibernating stages of plants and animals have many similar physiological characteristics. The intensity of metabolism is significantly reduced. In birds and mammals, the state of complete suspended animation does not occur. They have developed other adaptations for the winter. For example, the moult in mammals gives way to a thicker and longer coat with a plentiful undercoat, while down is formed in birds. This reduces heat dissipation.
However, winter activity is possible only for those animals and birds that can feed during this period.
Animals for which there is not enough food in winter hibernate (bats, many rodents, badgers, bears).
Birds have experienced seasonal migrations (flights).
The main factor in the regulation of seasonal cycles is the change in the length of the day. The body's response to the length of daylight hours - photoperiodism ... Photoperiodism is an important common adaptation that regulates seasonal phenomena in a wide variety of organisms.
Day length is a signal factor that determines the direction of biological processes. The change in the length of the day is always closely related to the course of temperature and precedes its change. During the year, the length of the day changes in a strictly regular way and is not subject to random fluctuations, like other environmental factors. Therefore, the length of the day serves as an accurate astronomical precursor to seasonal changes in temperature and other conditions.
Environmental factors.
The concept of the natural environment includes all conditions of living and inanimate nature in which an organism, population, and natural community exist. The natural environment directly or indirectly affects their condition and properties. The components of the natural environment that affect the state and properties of the organism, population, natural community are called environmental factors. Among them, there are three different in nature groups of factors:
abiotic factors - all components of inanimate nature, among which the most important are light, temperature, humidity and other components of the climate, as well as the composition of the water, air and soil environment;
biotic factors - interactions between different individuals in populations, between populations in natural communities;
limiting factors - environmental factors that go beyond the maximum or minimum of hardiness, limiting the existence of a species.
anthropogenic factor - all the various human activities that lead to a change in nature as the habitat of all living organisms or directly affect their life.
Various environmental factors, such as temperature, humidity, food, affect each individual. In response to this, organisms, through natural selection, develop various adaptations to them. The intensity of the factors most favorable for life is called the optimal or optimum.
The optimal value of one factor or another for each species is different. Depending on the attitude to this or that factor, the species can be warm and cold-loving (elephant and polar bear), moisture-loving and dry-loving (linden and saxaul), adapted to high or low salinity, etc.
Limiting factor
The body is simultaneously influenced by numerous, diverse and multidirectional environmental factors. In nature, the combination of all influences in their optimal, most favorable values \u200b\u200bis practically impossible. Therefore, even in habitats where all (or leading) ecological factors are most favorably combined, each of them most often deviates somewhat from the optimum. To characterize the action of environmental factors on animals and plants, it is essential that in relation to some factors, organisms have a wide range of endurance and withstand significant deviations in the intensity of the factor from the optimal value.
The effective temperature is understood as the difference between the temperature of the environment and the temperature threshold of development. So, the development of trout eggs begins at 0 ° C, which means that this temperature is the threshold for development. At a water temperature of 2 C, the fry emerge from the facial membranes after 205 days, at 5 ° C - after 82 days, and at 10 ° C - after 41 days. In all cases, the product of positive ambient temperatures by the number of days of development remains constant: 410. This will be the sum of effective temperatures.
Thus, for the implementation of the genetic program of development, animals with variable body temperature (and plants) need to receive a certain amount of heat.
Both the development thresholds and the sum of effective temperatures are different for each species. They are due to the historical adaptation of the species to certain living conditions.
The timing of flowering of plants also depends on the sum of temperatures for a certain period of time. For example, a coltsfoot needs 77 to bloom, 453 for a sour cherry, and 500 for strawberries. The sum of effective temperatures that must be reached to complete the life cycle often limits the geographical distribution of a species. Thus, the northern border of woody vegetation coincides with the July isotherms of S ... 12 ° C. To the north, there is no longer enough heat for the development of trees, and the forest zone is replaced by tundra. Likewise, if barley grows well in the temperate zone (its sum of temperatures for the entire period from sowing to harvest is 160 -1900 ° C), then this amount of heat is not enough for rice or cotton (with the required sum of temperatures of 2000-4000 ° C) ).
Many factors become limiting during the breeding season. The limits of hardiness for seeds, eggs, embryos, larvae are usually narrower than for adult plants and animals. For example, many crabs can enter a river far upstream, but their larvae cannot develop in river water. The range of game birds is often determined by the influence of the climate on eggs or chicks, rather than on adults.
Identifying the limiting factors is very important in practical terms. So, wheat grows poorly on acidic soils, and the introduction of lime into the soil can significantly increase yields. ...
Environmental factors always act on organisms in a complex. Moreover, the result is not the sum of the impact of several factors, but there is a complex process of their interaction. At the same time, the viability of the organism changes, specific adaptive properties arise that allow it to survive in certain conditions, to transfer fluctuations in the values \u200b\u200bof 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 ecological factor for the organism is called optimal or optimum.
Deviation from the optimal action of the factor leads to the inhibition of the vital activity of the organism.
The boundary 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 ice desert of Antarctica are beyond the limits of endurance for many organisms.
An environmental factor that goes beyond the body's endurance is called limiting.
It has an upper and lower limit. So, for fish, the limiting factor is water. Outside the aquatic environment, their life is impossible. A drop in water temperature below 0 ° C is the lower limit, and a rise above 45 ° C is an upper endurance limit.
Figure: 94. The scheme of action of the ecological factor on the body
Thus, the optimum reflects the characteristics of the habitat of various species. In accordance with the level of the most favorable factors, organisms are divided into warm 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 endurance limit, the more plastic the organism. Moreover, the endurance limit in relation to various environmental factors in organisms is not the same. For example, moisture-loving plants can tolerate large temperature changes, while the lack of moisture is destructive for them. Narrowly adapted species are less plastic and have a small endurance limit, 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 tolerated temperature range is 4-8 ° C. As the temperature rises (above 10 ° C), they stop moving and fall into a thermal torpor. On the other hand, fish in equatorial and temperate latitudes tolerate temperature fluctuations from 10 to 40 ° C. Warm-blooded animals have a wider range of endurance. For example, Arctic foxes in the tundra can tolerate temperature drops from -50 to 30 ° C.
Plants in temperate latitudes can withstand temperature fluctuations of 60-80 ° C, while tropical plants have a much narrower temperature range: 30-40 ° C.
Interaction of environmental factors lies in the fact that a change in the intensity of one of them can narrow the endurance limit to another factor or, conversely, increase it. For example, the optimal temperature increases the tolerance for lack of moisture and food. Increased humidity significantly reduces the body's resistance to high temperatures. The intensity of the impact of environmental factors is in direct proportion to the duration of this impact. Prolonged exposure to high or low temperatures is detrimental to many plants, while short-term drops are tolerated by plants normally. The limiting factors for plants are the composition of the soil, the presence of nitrogen and other nutrients in it. So, clover grows better on soils poor in nitrogen, and nettle - on the contrary. A decrease in the 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 adaptability of the organism to individual environmental factors is individual and can have both a wide and a narrow range of endurance. But if the quantitative change of at least one of the factors goes beyond the endurance limit, then, despite the fact that other conditions are favorable, the body dies.
The set of environmental factors (abiotic and biotic) that are necessary for the existence of a species are called ecological niche.
The ecological niche characterizes the way of life of the organism, the conditions of its habitation and nutrition. Unlike a niche, the concept of habitat designates the territory where an organism lives, that is, its "address". For example, the herbivorous steppe dwellers, cow and kangaroo, occupy the same ecological niche, but have different habitats. On the contrary, the inhabitants of the forest - squirrel and elk, which are also herbivores, occupy different ecological niches. The ecological niche always determines the distribution of the organism and its role in the community.
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Section 67. Impact on organisms of certain environmental factors§ 69. Basic properties of populations
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Adaptations of organisms to the environment are called adaptations. The ability to adapt is one of the basic properties of life in general, since 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 during the evolution of species.
Individual 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 things, facilitate or hinder survival and reproduction. Environmental factors are of 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 of inanimate nature that directly or indirectly affect living organisms.
Biotic factors are the 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, depends on them and has an effect on them. The surrounding organic world is an integral part of the environment of every living being. The interconnections of organisms are the basis for the existence of biocenoses and populations; their consideration belongs to the field of synecology.
Anthropogenic factors are forms of human society activity that lead to changes in nature as the habitat of other species or directly affect their lives. Although man influences wildlife through changes in abiotic factors and biotic relationships of species, anthropogenic activity should be distinguished as a special force that does not fit into the framework of this classification. The importance of anthropogenic influence on the living world of the planet continues to grow rapidly. One and the same environmental factor has different meanings in the life of co-living 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 take refuge in burrows or under the snow. The salt composition of the soil is important for plant nutrition, but is indifferent for most land animals, etc.
Changes in environmental factors in time can be: 1) regular-periodic, changing the strength of the impact in connection with the time of day or season of the year or the rhythm of the ebb and flow in the ocean; 2) irregular, without a clear periodicity, for example, changes in weather conditions in different years, phenomena of a catastrophic nature - storms, showers, landslides, etc .; 3) directed over certain, sometimes long, periods of time, for example, when the climate is cold or warming, water bodies are overgrown, cattle are constantly grazing in the same area, etc. Environmental factors have various effects on living organisms, i.e. can influence as stimuli causing adaptive changes in physiological and biochemical functions; as constraints that make 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 the 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 vital activity 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 deviation from the optimum, the more pronounced the depressing effect of this factor on organisms (pessimum zone). The maximum and minimum tolerable values \u200b\u200bof 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 valence (range of tolerance) of living things in relation to a specific environmental factor.
Representatives of different species differ greatly from each other both in the position of the optimum and in the ecological valence. For example, Arctic foxes in the tundra can tolerate air temperature fluctuations in the range of about 80 ° С (from + 30 ° to -55 ° С), while warm-water crustaceans Copilia mirabilis can withstand water temperature changes in the range of no more than 6 ° С (from 23 ° to 29 ° C). The emergence of narrow ranges of tolerance in evolution can be viewed as a form of specialization, as a result of which greater efficiency is achieved at the expense of adaptability and diversity in the community increases.
One and the same strength of factor manifestation can be optimal for one species, pessimal for another, and go beyond the limits of endurance for a third.
The wide ecological valence of a species in relation to abiotic environmental factors is indicated by the addition of the prefix "evry" to the name of the factor. Eurythermal species - withstanding significant temperature fluctuations, eurybate - a wide range of pressure, euryhaline - varying degrees of salinity.
The inability to tolerate significant fluctuations of the factor, or narrow ecological valence, is characterized by the prefix "steno" - stenothermic, stenobathic, stenohaline species, etc. In a broader sense of the word, species for which strictly defined ecological conditions are required are called stenobiont, and those which are able to adapt to different environmental conditions - eurybiontic.
2. Ambiguity of the effect of a factor on different functions. Each factor has a different effect on different body functions. An optimum for some processes may be a 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 physical activity, and the animals fall into thermal torpor. For many fish, the water temperature, which is optimal for the maturation of reproductive products, is unfavorable for spawning, which occurs in a different temperature range.
The life cycle, in which at certain periods the body performs mainly certain functions (nutrition, growth, reproduction, dispersal, etc.), is always consistent with seasonal changes in the complex of environmental factors. Mobile organisms can also change their habitat for the successful implementation of all their vital functions. The breeding period is usually critical; during this period, many environmental factors often become limiting. The tolerance limits for breeding individuals, seeds, eggs, embryos, seedlings and larvae are usually narrower than for non-breeding adult plants or animals. Thus, an adult cypress can grow on dry highlands and submerged in water, but it reproduces only where there is moist, but not flooded soil for the development of seedlings. Many marine animals can tolerate brackish or fresh water with high chloride levels, so they often enter rivers upstream. But their larvae cannot live in such waters, so the species cannot reproduce in the river and does not settle here permanently.
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 a moth 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 at 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 wider than the ecological valence of each individual individual.
4. Species adapt to each of the environmental factors in a relatively independent way. The degree of hardiness to any factor does not mean the corresponding ecological valence of the species in relation to other factors. For example, species that tolerate wide variations in temperature need not also be adapted to wide fluctuations in humidity or salt regime. Eurythermal species can be stenohaline, stenobate, or vice versa. The ecological valences 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 different environmental factors constitutes the ecological spectrum of the species.
5. Non-coincidence of ecological spectra of certain species. Each species is specific in its ecological capabilities. Even in species that are similar in ways of adaptation to the environment, there are differences in relation to any 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 how forcefully and in what combination other factors act simultaneously. This pattern is called the interaction of factors. For example, heat is easier to tolerate in dry than humid air. The risk of freezing is much higher in cold weather with strong winds than in calm weather. Thus, the same factor combined with others has a different environmental impact. On the contrary, the same ecological result can be obtained in different ways. For example, wilting of plants can be halted by both increasing the amount of moisture in the soil and lowering the air temperature, which reduces evaporation. The effect of partial substitution of factors is created.
At the same time, mutual compensation for 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 at least one of the basic elements of mineral nutrition makes plant life impossible, despite the most favorable combinations of other conditions. The extreme heat deficit in polar deserts cannot be compensated for by either an abundance of moisture or round-the-clock illumination.
7. The rule of limiting (limiting) factors. Environmental factors that are farthest from the optimum make it especially difficult for the species to exist under these conditions. If at least one of the environmental factors approaches or goes beyond the critical values, then, despite the optimal combination of other conditions, individuals are threatened with death. Such factors deviating from the optimum are of paramount importance in the life of a species or its individual representatives in each specific period of time.
Environmental limiting factors determine the geographic range of the species. The nature of these factors can be different. Thus, the movement of a species to the north may be limited by a lack of heat, to arid regions - by a lack of moisture or too high temperatures. Biotic relationships, for example, the occupation of a territory by a stronger competitor or the lack of pollinators for plants, can also serve as a limiting factor for the spread.
To determine whether a species can exist in a given geographic area, it is first necessary to find out whether any environmental factors go beyond its ecological valence, especially during the most vulnerable period of development.
Organisms with a wide range of tolerance to all factors are usually the most widespread.
8. The rule of conformity of environmental conditions to the genetic predetermination of the organism. A species of organisms can exist as long and insofar as the natural environment surrounding it corresponds to the genetic ability of this species to adapt to its fluctuations and changes. Each type of living thing arose in a certain environment, to one degree or another adapted to it and its further existence is possible only in it or a close environment. 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.
Environmental factors always act on organisms in a complex. Moreover, the result is not the sum of the impact of several factors, but there is a complex process of their interaction. At the same time, the viability of the organism changes, specific adaptive properties arise that allow it to survive in certain conditions, to transfer fluctuations in the values \u200b\u200bof various factors. The influence of environmental factors on the body can be represented as a diagram ().The most favorable intensity of the ecological factor for the organism is called optimal or optimum.Deviation from the optimal action of the factor leads to the inhibition of the vital activity of the organism.
The boundary 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 ice desert of Antarctica are beyond the limits of endurance for many organisms.
An environmental factor that goes beyond the body's endurance is called limiting.It has an upper and lower limit. So, for fish, the limiting factor is water. Outside the aquatic environment, their life is impossible. A drop in water temperature below 0 ° C is the lower limit, and a rise above 45 ° C is an upper endurance limit.
The scheme of action of the ecological factor on the body
Thus, the optimum reflects the characteristics of the habitat of various species. 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 endurance limit, the more plastic the organism. Moreover, the endurance limit in relation to various environmental factors in organisms is not the same. For example, moisture-loving plants can tolerate large temperature changes, while the lack of moisture is destructive for them. Narrowly adapted species are less plastic and have a small endurance limit, 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 tolerated temperature range is 4–8 ° C. As the temperature rises (above 10 ° C), they stop moving and fall into a thermal torpor. On the other hand, fish in equatorial and temperate latitudes tolerate temperature fluctuations from 10 to 40 ° C. Warm-blooded animals have a wider range of endurance. For example, Arctic foxes in the tundra can tolerate temperature drops from -50 to 30 ° C. Plants in temperate latitudes can withstand temperature fluctuations of 60–80 ° C, while tropical plants have a much narrower temperature range: 30–40 ° C. Interaction of environmental factorslies in the fact that a change in the intensity of one of them can narrow the endurance limit to another factor or, conversely, increase it. For example, an optimal temperature increases your tolerance to moisture and food shortages. Increased humidity significantly reduces the body's resistance to high temperatures. The intensity of the impact of environmental factors is in direct proportion to the duration of this impact. Prolonged exposure to high or low temperatures is detrimental to many plants, while short-term drops are tolerated by plants normally. The limiting factors for plants are the composition of the soil, the presence of nitrogen and other nutrients in it. So, clover grows better on soils poor in nitrogen, and nettle - on the contrary. A decrease in the 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 adaptability of the organism to individual environmental factors is individual and can have both a wide and a narrow range of endurance. But if the quantitative change of at least one of the factors goes beyond the endurance limit, 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 are called ecological niche.The ecological niche characterizes the way of life of the organism, the conditions of its habitation and nutrition. Unlike a niche, the concept of habitat designates the territory where an organism lives, that is, its "address". For example, the herbivorous steppe dwellers, cow and kangaroo, occupy the same ecological niche, but have different habitats. On the contrary, the inhabitants of the forest - squirrel and elk, also related to herbivores, occupy different ecological niches. The ecological niche always determines the distribution of the organism and its role in the community.
