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Fundamentals of General Ecology.
2.1. Environment and conditions for the existence of organisms.
Wednesday- everything that surrounds the body and directly or indirectly affects its life, development, growth, survival, reproduction, etc.The environment of each organism is composed of multitudes of inorganic and organic nature and elements introduced by man and his production activities. At the same time, some elements are necessary for the body, others are indifferent to it, and others have a harmful effect.
Conditions of existence, or living conditions- a set of environmental elements necessary for an organism, with which it is in indissoluble unity and without which it cannot exist.
The elements of the environment, both necessary for the body and negatively affecting it, are called environmental factors.
Environmental factors are usually divided into three main groups: abiotic, biotic and anthropic.
Abiotic factors - a complex of conditions of the inorganic and organic environment that affect the body. Abiotic factors are subdivided into chemical (chemical composition of air, ocean, soil, etc.) and physical (temperature, pressure, wind, humidity, light, radiation regime, etc.).
Anthropic factors - the totality of the effects of human activity on the organic world. Already by the fact of his existence, a person influences the environment (due to respiration, about 1.1 10 12 KgСО 2, etc.) and an immeasurably greater production activity to an ever increasing degree.
The influence of abiotic factors on the body can be direct and indirect (mediated). So, for example, the temperature of the environment determines the speed of physiological processes in the body and, accordingly, its development (direct influence); at the same time, influencing the development of plants that are food for animals, it has an indirect effect on the latter.
The effect of environmental factors depends not only on their nature, but also on the dose perceived by the body (high or low temperature, bright light or darkness, etc.). All organisms in the process of evolution have developed adaptations to the perception of factors within certain quantitative limits. Moreover, for each organism there is a set of factors that are most favorable for it.
The more the dose of factors deviates from the optimal value for a given type (increase or decrease), the more its vital activity is inhibited. The boundaries beyond which the existence of an organism is impossible are called lower and upper endurance limits (tolerance).
The intensity of the ecological factor, the most favorable for the organism (its vital activity), is called optimum, and giving the worst effect - pessimum.
Organisms can adapt over time to changing factors. The property of species to adapt to changing ranges of environmental factors is called environmental plasticity (ecological valence). The wider the range of fluctuations of the ecological factor, within which a given species can exist, the greater its ecological plasticity, the wider the range of its tolerance (endurance).
Ecologically non-plastic (low-tolerant) species are called stenobiontic(from the Greek. stenos- narrow), more plastic (hardy) - eurybiontic(from the Greek. eurys- wide). Species of organisms that have developed for a long time under relatively stable conditions lose their ecological plasticity and acquire the traits of stenobionticity; species that existed under conditions of significant changes in environmental factors become eurybiontic.
The attitude of organisms to fluctuations of a particular environmental factor is expressed by adding the prefixes wall- and evri- (steno- and eurythermal, steno- and eurythemic, etc.).
Historically adapting to the abiotic factor of the environment and entering into biotic connections with each other, plants, animals and microorganisms are distributed in different environments and form diverse biogeocenoses eventually merging into biosphere Earth.
Biogeocenosis- territorially (spatially) isolated integral elementary unit of the biosphere, all components of which are closely related to each other.
All environmental factors act on the body simultaneously and in interaction. Such a set of them is called constellation... Therefore, the optimum and the limits of the body's endurance in relation to any one factor depend on others. Moreover, if the intensity of at least one factor goes beyond the endurance of the species, then the existence of the latter becomes impossible, no matter how favorable the other conditions are. This factor is called limiting... A special case of the principle of limiting factors is the minimum rule formulated by Liebig (German chemist) to characterize the yield of agricultural crops: a substance at a minimum (in the soil, in the air) controls the yield and determines the magnitude and stability of the latter.
2.2. The most important abiotic factors and adaptation of organisms to them.
2.2.1. Light.
Light is one of the most important environmental factors, especially for photosynthesizing green plants. The main source of light for the Earth is the Sun, which emits a huge amount of energy, including electromagnetic. The approximate composition of the last wavelength ( , nm) next: 48 % - infrared ( = 1 · 10 6 ... 760); 50 % - visible ( = 760…360); 2% - ultraviolet ( = 360 ... 10) and ionizing ( Ultraviolet radiation with nm is fatal to life, s = 250…360 n m - stimulates the formation of vitamin in animals D and with = 200…300 nm detrimental to microorganisms.
Electromagnetic radiation with = 380…400 nm possesses high photosynthetic activity.
Infrared radiation is perceived by all organisms as heat.
Of particular importance in the life of all organisms is visible light, due to which chlorophyll is formed and the most important process of photosynthesis in the life of the biosphere is carried out (the formation of organic substances from inorganic ones using solar energy). Photosynthesis provides the planet with organic matter and accumulated solar energy.
In the total energy balance of the Earth, solar is ~ 99.9 % ... If we take the solar energy reaching the Earth as 100 % , then ~ 19 % it is absorbed by the atmosphere, ~ 34 % reflected into space and ~ 47 % reaches the earth's surface in the form of direct and scattered electromagnetic energy. Direct electromagnetic energy is a spectrum of radiation with from 0.1 to 30,000 nm... The ultraviolet part of this spectrum is 1 ... 5 % , visible 16 ... 45 % , infrared 49 ... 84 % ... The amount of scattered electromagnetic energy increases with a decrease in the height of the Sun above the horizon and an increase in atmospheric turbidity. The spectral composition of the electromagnetic radiation of a cloudless sky is characterized by maximum energy with = 400…480 nm.
From the spectrum of ultraviolet radiation, only the long-wavelength part reaches the Earth's surface with = 290…380 nm, and its short-wave component, destructive for all living things, is almost completely absorbed by the ozone of the stratosphere at an altitude of 20 ... 25 km... The long-wavelength part of the spectrum of ultraviolet radiation has a high photon energy, which determines its high photochemical activity. Large doses of this radiation are harmful to organisms, and small doses are necessary for many of them. In the range = 250…300 nm ultraviolet radiation has a powerful bactericidal effect, contributes to the formation of antirachitic vitamin D in animals, and when = 200…380 n m initiates the "tan" of the human skin, which is a protective reaction of the body. Infrared electromagnetic radiation with > 750 nm has a thermal effect on organisms.
Physiologically active electromagnetic energy ( = 300…800 nm), within which the photosynthetically active range is = 380…710 nm... The area of physiologically active electromagnetic energy is usually divided into a number of zones: ultraviolet (UV) - nm; blue-violet (S-F) - = 400…500 nm; yellow-green (F-Z) - = 500…600 nm; orange-red (O-K) - = 600…700 nm and far red (DK) - > 700 nm.
Of the total flux of photosynthetically active electromagnetic energy reaching the earth's surface, about 0.2 % cumulated by plants, due to the unique reaction of photosynthesis according to the scheme
CO 2 + H 2 O + sun. energy chlorophyll CH 2 O + O 2
The rate of photosynthesis depends on the type of plant, light intensity, temperature, concentration CO 2 and other factors. For example, in central Russia, most agricultural (sх) plants have a photosynthesis rate of 20 mg CO 2 on 1 dm 2 sheet surface in hour.
Photosynthesis practically does not occur in the yellow-green part of the visible spectrum.
In general, light affects: the rate of growth and development of plants; the intensity of photosynthesis; animal activity; changes in humidity and temperature of the environment; diurnal and seasonal biocycles caused by the rotation of the Earth around its axis and movement around the Sun.
The vital activity of organisms is also affected by the light regime - the totality of illumination ( OK, W / m 2), the amount of light (the total amount of electromagnetic energy) and the quality of light (spectral composition). The light regime depends on the latitude of the area, relief, turbidity of the atmosphere, underlying surface, cloudiness and other factors.
In relation to light, the following ecological groups of plants are distinguished: light (light-loving), shade-loving (shade-loving), shade-tolerant.
Light views ( heliophytes) live in open places with good illumination and form a sparse and low vegetation cover (for example, sunflower).
Shadow views ( sciophytes) grow under forest canopy in constant shade (for example, forest grasses).
Shade-tolerant species ( facultative heliophytes) can grow both in good light and in shade conditions (most forest plants).
A change in the specificity of the light regime in the first two groups leads to the suppression of their vital activity up to death.
Light is the most important means of orienting animals. In animals, orientation towards light is carried out as a result of phototaxis: positive (moving towards higher illumination) and negative (moving towards lower illumination).
The light regime affects the geographical distribution of animals.
Bioluminescence, the ability of organisms to glow, has a definite role in the life of animals. This happens as a result of the oxidation of organic substances - luciferins in response to irritations from the environment. Bioluminescence has a signal value in the life of animals, for example, to attract individuals of the opposite sex at night and twilight in firefly beetles.
Thus, plants need light mainly for photosynthesis, and animals mainly for obtaining information about their environment.
2.2.2. Heat (temperature).
Heat- a set of various types of internal energy of matter (the energy of vibrational motion of atoms and molecules, the energy of interatomic and intermolecular bonds, etc., with the exception of intra-atomic and nuclear energy).Temperature- a parameter reflecting the average kinetic velocity of the vibrational motion of atoms and molecules in a substance.
The temperature of organisms depends on the temperature of the environment, as well as the rate of chemical reactions that make up the metabolism. Therefore, the boundaries of the existence of life are the temperatures at which the formation and normal functioning of proteins is possible (on average, from 0 to +50 O WITH). However, some organisms, possessing specialized enzyme systems, can exist at body temperatures outside these limits.
Types of organisms that prefer cold form an ecological group cryophiles... They can remain active at cell temperatures up to (-8) ... (-10 O WITH), when the liquid phase of their body is in a hypothermic state (bacteria, fungi, mosses, lichens, etc., living in the Arctic, highlands, etc. places).
The types of organisms that have adapted to living in high temperatures belong to the group thermophiles... They can actively exist at ambient temperatures up to
90…98 O WITH(insect larvae, organisms living on the soil surface and in decaying organic debris, as well as a number of microorganisms).
The temperature limits of the existence of life for many species expand into their latent condition (latent period of life). So, the spores of some bacteria can withstand heating up to +180 for several minutes. O WITH, and dehydrated seeds, pollen and spores of some plants withstood the temperature (-271.16 O WITH) with the subsequent return to life. In this case, all molecules are in a state of almost complete rest and no biochemical reactions are possible. This state of the body (suspension of all life processes) is called anabiosis... From it, the body can return to normal life only in the absence of disturbances in the structure of macromolecules in its cells.
Ambient temperature instability poses a significant environmental problem. So, a decrease in temperature causes the danger of such a slowdown in metabolism, in which the manifestation of basic vital functions is impossible, and an increase in temperature can disrupt the normal life of the body long before the thermal destruction of enzymes and proteins due to a sharp increase in the need for food and oxygen, which are not always satisfied.
In the course of evolution, organisms have developed various mechanisms for regulating metabolism when the ambient temperature changes, the main ones are as follows:
biochemical and physiological restructuring of life support systems (change in the set, concentration and activity of enzymes, dehydration, lowering the freezing point of body solutions, etc.);
maintaining body temperature at a more stable level (compared to the ambient temperature), which ensures an almost constant rate of biochemical reactions. This stability is due to the processes of heat release as a by-product of biochemical reactions and heat transfer to the environment.
Organisms that are able to maintain a constant optimal body temperature regardless of changes in the environment are called homeothermal(from the Greek. gomoios- the same). These are only 2 upper classes of vertebrates - birds and mammals. A special case of homeothermia - heterothermy typical for animals that hibernate or stupor during an unfavorable period of the year, while the metabolism slows down (ground squirrels, marmots, hedgehogs, bats, etc.).
In poikilothermic organisms, after cold oppression, normal metabolism is restored at a temperature called temperature threshold of development and proceeds the more intensively, the higher the ambient temperature, which accelerates the passage of all stages and the entire life cycle of the organism.
Thus, for the implementation of the genetic development program, such organisms need to receive a certain amount of heat from the environment. This heat is measured by the sum of the effective temperatures. Effective temperature- the positive difference between the ambient temperature and the temperature threshold for the development of the body. The effective temperature has upper limits for each species.
The sum of effective temperatures is calculated by the formula
? THIS. = ( t
O.S. - t
P.R.) ּ n
where: ?
THIS. - the sum of effective temperatures, O WITH;
t O.S. - ambient temperature, O WITH;
t NS. - temperature threshold of development, O WITH;
n - number of hours or days since t O.S. > t NS.
The sum of effective temperatures required for the life cycle limits the geographic distribution of species.
Since the terrestrial habitat has a wide range of temperature fluctuations, organisms have developed various adaptive mechanisms of life in it.
So, in plants, the chemical composition of solutions, the rate of biochemical reactions, the ability to absorb or reflect sunlight, and other characteristics change.
Unlike plants, animals with muscles produce much more of their own internal heat, which determines the following main ways of their temperature adaptations:
chemical thermoregulation - an active increase in heat production in response to a decrease in ambient temperature;
physical thermoregulation - a change in the level of heat transfer, the ability to retain heat or, conversely, dissipate its excess. This is due to the peculiarities of the anatomy and physiology of animals (hair and feathers, the distribution of fat reserves, the presence of evaporative heat transfer, etc.);
behavior of organisms - movement in space, change of posture, etc.
An effective thermoregulatory mechanism is the evaporation of water through perspiration through the skin or through moist mucous membranes of the mouth and upper respiratory tract. Since the heat of vaporization of water is high (2.3 10 6 J / kg), in this way a lot of excess heat is removed from the body. So, a person in the heat per day can allocate up to 10 ... 12 l sweat, upon evaporation of which ~ 2.5 10 7 J thermal energy, which corresponds to the consumed power ~ 580 W.
Maintaining the temperature balance of the body of warm-blooded animals also depends on the ratio of the body surface to its volume. So, according to Bergman's rule, of two closely related warm-blooded species, the larger one lives in a cold climate, and the smaller one in a warm climate; and according to Allen's rule, the relative sizes of the limbs and other protruding parts of the body (tails, ears, beaks) increase from high to low latitudes.
The reason for these changes is the dependence of heat production on the body weight, and heat transfer to the environment from the body surface.
Thermoregulation with a general high level of oxidative processes in the body allows homeothermic animals to maintain their thermal balance (almost constant temperature) against the background of a wide range of fluctuations in ambient temperature.
Based on the above, we can conclude that each of the considered 2 groups of organisms in the aspect of the thermal factor has its own environmental benefits.
2.2.3. Water (moisture).
Water is one of the most important environmental factors in the life of terrestrial organisms. It makes up the bulk of the protoplasm of cells, tissues, plant and animal juices. Water with substances dissolved in it determines the osmotic pressure of cellular and tissue fluids, as well as intercellular exchange. The water content in the body ranges from 40 % mass... (tree trunks) up to 98 % mass... (seaweed).In the process of evolution, terrestrial organisms have developed adaptations that regulate water exchange and moisture consumption.
A moisture deficit leads to a decrease in plant growth, a limited number of organisms, their spread across the globe and to other consequences.
Air humidity plays an important role in the life of plants and animals. Distinguish between absolute and relative air humidity.
Absolute humidity reflects the concentration of water vapor in the air and varies in Russia from 1.5 g / m 3 (winter) to 14 g / m 3 (in summer).
Relative humidity characterizes the degree of air saturation with water vapor and is determined by the formula
,
%
where: A
- absolute air humidity under given conditions, g / m 3 ;M - the maximum possible absolute air humidity under the same conditions, g / m 3 .
In ecology, relative humidity is most often taken into account, because it influences to a greater extent the intensity of evaporation processes. A parameter called saturation deficit is widely used, which also characterizes the intensity of evaporation processes.
In relation to the water regime, terrestrial organisms are divided into three main ecological groups: hygrophilic (moisture-loving), xerophilic (dry-loving) and mesophilic(preferring moderate humidity).
Plants are most susceptible to the influence of the water regime, because they cannot move in search of the necessary environment.
In relation to fluctuations in water supply and evaporation, plants are divided into poikilohydric and homoyohydric... In the former, the amount of water in the tissues is variable and depends on the humidity of the environment (mosses, ferns, etc.). The latter are able to maintain a relative constant water content in tissues and are less dependent on environmental conditions (most higher plants).
In terrestrial animals, water supply is carried out in three main ways: through drinking; with juicy food; as a result of metabolism (due to oxidation and breakdown of fats, proteins and carbohydrates).
Water loss in animals occurs through evaporation and excretion of urine, as well as with the remains of undigested food. Excessive loss of water is dangerous for animals and can lead to their death rather than starvation.
Animal species that receive water mainly through drinking gravitate towards water bodies (large mammals, birds).
Many animals can do without drinking water, getting it from the air, soil, food, and other methods (small desert animals).
In the process of evolution, animals have developed the following adaptations to maintain water balance: behavioral (searching for water bodies, digging holes, etc.); morphological (shells of land snails, keratinized covers of reptiles, etc.); physiological (formation of metabolic water, water saving during the excretion of urine and feces, regulation of perspiration, etc.).
Dehydration tolerance is higher in animals exposed to thermal stress. So, for a person, a loss of water exceeding 10 % body weight, fatal, at the same time, camels tolerate water loss up to 27 % , sheep - up to 23 % , dogs - up to 17 % .
Saving water excreted through the kidneys is achieved by restructuring nitrogen metabolism. So, in aquatic organisms, during the breakdown of proteins, ammonia is formed ( NH 3), for the removal of which a lot of water is spent, and in terrestrial mammals - urea (urea) ( CO(NH 2) 2), which is a less toxic product and can accumulate in the body without causing much harm, and, therefore, be excreted in a more concentrated form with less water.
In poikilothermic animals, heating the body as a result of an increase in air temperature avoids unnecessary losses of water, which is spent in homeothermic animals to maintain a constant temperature. This factor is also used by some animals with good thermoregulation. For example, camels are able to “turn off” thermoregulatory vapors for a while. In the summer in the morning, his body temperature is ~ 35 O WITH, and in the daytime in the heat reaches 40.7 O WITH, i.e. almost to the limit of endurance. This allows the animal to save on evaporation up to 5 l water per day.
All aquatic inhabitants, despite differences in lifestyle, must be adapted to the main features of their environment. These features are determined, first of all, by the physical properties of water: its density, thermal conductivity, ability to dissolve salts and gases.
The density of the water determines its significant buoyancy. This means that the weight of organisms is lightened in water and it becomes possible to lead permanent life in the water column, without sinking to the bottom. Many species, mostly small ones, incapable of rapid active swimming, seem to soar in water, being in suspension in it. The collection of such small aquatic inhabitants is called plankton. Plankton includes microscopic algae, small crustaceans, fish eggs and larvae, jellyfish and many other species. Planktonic organisms are carried by currents unable to resist them. The presence of plankton in the water makes possible a filtration type of nutrition, i.e., straining, with the help of various devices, small organisms and food particles suspended in the water. It is developed in both swimming and sedentary benthic animals such as sea lilies, mussels, oysters and others. A sedentary lifestyle would be impossible for aquatic inhabitants if there were no plankton, which, in turn, is possible only in an environment with sufficient density.
The density of the water makes it difficult to actively move in it, therefore, fast-swimming animals, such as fish, dolphins, squids, must have strong muscles and a streamlined body. Due to the high density of water, the pressure increases strongly with depth. Deep sea creatures are able to withstand pressures that are thousands of times higher than on the land surface.
Light penetrates the water only to a shallow depth; therefore, plant organisms can exist only in the upper horizons of the water column. Even in the cleanest seas, photosynthesis is possible only down to depths of 100-200 m. At great depths, there are no plants, and deep-sea animals live in complete darkness.
The temperature regime in water bodies is milder than on land. Due to the high heat capacity of water, temperature fluctuations in it are smoothed out, and aquatic inhabitants do not face the need to adapt to severe frosts or forty-degree heat. Only in hot springs can the water temperature approach the boiling point.
One of the difficulties in aquatic life is the limited amount of oxygen. Its solubility is not very high and, moreover, it greatly decreases with pollution or heating of water. Therefore, there are sometimes deaths in reservoirs - mass death of inhabitants due to a lack of oxygen, which occurs for various reasons.
PART II
Chapter 3 . ENVIRONMENTAL FACTORS. GENERAL REGULARITIES OF EFFECTS ON ORGANISMS
Environment and conditions for the existence of organisms. It is necessary to distinguish between such concepts as the environment and the conditions for the existence of organisms.
The environment is everything that surrounds the organism and directly or indirectly affects its state, development, growth, survival, reproduction, etc. The environment of each organism is composed of many elements of inorganic and organic nature and elements introduced by man, his production activities. In this case, some elements may be necessary for the body, others are almost or completely indifferent to it, and still others have a harmful effect. So, for example, the white hare (Lepus timidus) in the forest enters into a certain relationship with food, oxygen, water, chemical compounds, without which it cannot do. But a boulder, a tree trunk, a stump, a hummock do not have a significant effect on his life: the hare enters with them in temporary (shelter from the weather, the enemy), but not obligatory connections.
The conditions of existence, or the conditions of life, are the totality of the elements of the environment necessary for the organism, with which it is in indissoluble unity and without which it cannot exist.
The elements of the environment that are necessary for the body or have a negative effect on it are called environmental factors. In nature, these factors do not act in isolation from each other, but in the form of a complex complex. The complex of environmental factors, without which an organism cannot exist, represents the conditions of existence, or the conditions of life of a given organism.
Different organisms perceive and react differently to the same factors. In addition, organisms of each species are characterized by their own special conditions. Plants and animals of deserts and semi-deserts exist in conditions of high temperature and low humidity. The tundra is inhabited by plants and animals that are sensitive to lack of moisture and can tolerate low temperatures. Inhabitants of salt and fresh waters perceive the concentration of minerals differently. Animals and plants of the tundra, freshwater lakes and salty seas selectively relate to certain factors.
All adaptations of organisms to existence in different conditions have developed historically. As a result, groupings of plants and animals specific for each geographic zone were formed.
Classification of factors. Analysis of a huge variety of factors allows them to be divided more or less clearly into three main groups: abiotic, biotic and anthropic.
Abiotic factors are a complex of conditions of the inorganic environment that affect the body. They are divided into chemical (chemical composition of the atmosphere, sea and fresh waters, soil, bottom sediments) and physical, or climatic (temperature, barometric pressure, wind, humidity, radiation regime, etc.), factors. The structure of the surface (topography), geological and climatic differences determine a huge variety of abiotic factors that play a corresponding role in the life of species of animals, plants and microorganisms that have historically adapted to them. The number (biomass) and distribution of organisms within the range depend on limiting factors, that is, on factors necessary for existence, but presented at a minimum. For desert dwellers, this is water, for many aquatic organisms - the amount of oxygen dissolved in water.
Anthropic factors - the totality of the impact of human activities on the organic world. With the historical development of mankind and the emergence of specific laws inherent only to him, nature has been enriched with qualitatively new phenomena. By the very fact of their existence, people have a noticeable impact on their environment. For example, in the process of breathing, 1.1 10 12 kg of carbon dioxide enters the atmosphere annually, and the annual human need for food is estimated at 2.7 · 10 15 kcal (11.34 · 10 15 kJ). But to a much greater extent, nature is influenced by the production activities of people. As a result, the relief and chemical composition of the earth's surface and the atmosphere change, fresh water is redistributed, the climate of the planet as a whole is changing, individual natural biogeocenoses are being eliminated, artificial agrobiogeocenoses are being created everywhere, useful and harmful plant and animal species are exploited, cultivated plants are cultivated and domesticated animals. The significance of anthropic factors, as man more and more fully conquers and subjugates nature, is constantly growing.
When analyzing environmental factors, one should take into account their necessity, variability, as well as the adaptive reactions of the organism. In this regard, hydroedaphic, or water-soil, factors are often distinguished into an independent group. A.S. Monchadskiy divides their totality into two main groups - changing regularly and changing without regular periodicity.
However, this division of factors into four groups is rather artificial. It does not reveal the whole essence of the relationship between the organism and the environment.
Influence of abiotic factors on the body. Abiotic factors can have a direct effect on the body and indirect (indirect). For example, the temperature of the environment, acting directly on the organism of an animal or plant, determines their thermal balance, the course of physiological processes. At the same time, temperature as an abiotic factor can also have an indirect effect. So, providing certain conditions for the development of plants that are food for animal phytophages, it can affect the vital activity of the latter.
The effect of exposure to environmental factors depends not only on their nature, but also on the dose perceived by the body (high or low temperature, bright light or darkness). All organisms in the process of evolution have developed adaptations to the perception of factors within certain quantitative limits. However, for each organism, be it a plant, animal or microorganism, there is a specific number of factors that are most favorable for it. A decrease or increase in this dose relative to the limits of the optimal range reduces the vital activity of the organism, and when a maximum or minimum is reached, the possibility of its existence is completely excluded (Fig. 2).
The more the factor dose deviates from the optimal value for a given type (both upward and downward), the more its vital activity is inhibited. The boundaries beyond which the existence of an organism is impossible are called the lower and upper limits of endurance.
The intensity of the ecological factor, which is most favorable for the vital activity of the organism, is called the optimum, and the one that gives the worst effect,– pessimum.
Ecological plasticity of organisms. For each organism and for the species as a whole, there is an optimum of conditions. As it turned out, it is not the same not only for different species in different conditions, but also for individual stages of development of one organism. For example, the optimum temperatures for flowering, fruiting, germination, spawning, and reproduction of many species are well known. Depending on what level of optimum is most acceptable for the species, they are distinguished between warm and cold-loving, moisture-loving and dry-loving, adapted to high or low salinity. For each species, the degree of endurance is also characteristic. For example, plants and animals of the temperate zone can exist in a fairly wide temperature range, while species of a tropical climate do not withstand significant fluctuations in it.
The property of species to adapt to a particular range of environmental factors is denoted by the concept of ecological plasticity (ecological valence) of a species. The wider the range of fluctuations of the ecological factor, within which a given species can exist, the greater its ecological plasticity.
Species that can exist with small deviations of the factor from the optimal value are called highly specialized, and those that withstand significant changes in the factor are widely adapted. The former includes most of the inhabitants of the seas, whose normal life activity is maintained only with a high concentration of salts in the environment. On the other hand, freshwater organisms are adapted to the low salt content in the environment. Consequently, both marine and freshwater species have low ecological plasticity in relation to salinity. However, the three-spined stickleback (Gasterosteus aculeatus), for example, has great ecological plasticity as it can live in both fresh and salty waters.
Ecologically nonplastic, i.e. low-hardy species are called stenobiontic (stenos - narrow), more hardy - eurybiontic (eyros - wide). Stenobionism and eurybionism characterize different types of habitation of organisms for survival. Species that developed for a long time under relatively stable conditions lose their ecological plasticity and develop stenobiontic traits, while species that existed under significant fluctuations in environmental factors acquire increased ecological plasticity and become eurybiontic (Fig. 3). The attitude of organisms to the fluctuations of a particular factor is expressed by adding the prefix eury- or steno- to the name of the factor. So, in relation to temperature, eury- and stenothermal organisms are distinguished, to the concentration of salts - eury- and stenohaline, to light - eury- and stenophotic, etc.
In relation to all environmental factors (or at least to many), there are very few eurybiontic organisms. Most often, eury- or stenobionism manifests itself in relation to one factor. For example, marine and freshwater fish will be stenohaline, while the mentioned three-spined stickleback is a typical euryhaline representative; a plant, being eurythermal, can at the same time belong to stenoigrobionts, i.e., be less resistant to fluctuations in humidity.
Eurybionism usually contributes to the wide distribution of species. As you know, many protozoa, fungi (typical eurybionts) are cosmopolitan and widespread. Stenobionism, on the other hand, usually limits areas. However, often due to the high specialization of stenobionts, vast territories belong. Thus, the fish-eating osprey bird (Pandion haliaetus), being a typical stenophage, acts as a eurybiont in relation to other factors. It has the ability to travel long distances in search of food and occupies a significant area.
Since all environmental factors are interrelated and among them there are no absolutely indifferent for any organism, each population and species as a whole reacts to these factors, but perceive them differently. This electoral nature also determines the selective attitude of organisms to the settlement of a particular territory. The distribution of organisms depends on the time and place of their origin, on the factors to which they have historically adapted. As a result, some factor that prevents the spread of some species may be beneficial for others. So, for plants and animals adapted to fresh water, the high concentration of salts of the seas and oceans is an obstacle to their settlement, and, conversely, marine animals and plants are not able to exist in fresh water bodies.
Different types of organisms have different requirements for soil conditions, temperature, humidity, light, etc. Therefore, different plants grow on different soils, in different climatic zones. In turn, different conditions for animals are formed in plant associations. Historically, adapting to abiotic factors of the environment and entering into certain biotic connections with each other, animals, plants and microorganisms are distributed in different environments and form diverse biogeocenoses, ultimately uniting in the biosphere of the Earth.
Thus, individuals and the populations that form from them adapt to each of the environmental factors in a relatively independent way. Moreover, their ecological valence in relation to different factors turns out to be unequal. That is why each species has a specific ecological spectrum, that is, the sum of ecological valences in relation to environmental factors.
Chapter 4. JOINT ACTION OF ENVIRONMENTAL FACTORS
Limiting factor. All factors in nature affect the body at the same time. And not in the form of a simple sum, but as a complex interacting ratio. This combination of factors is called their constellation. Therefore, the optimum and the limits of the organism's endurance in relation to any one factor depend on other influences. For example, at an optimal temperature, tolerance to unfavorable humidity and nutritional deficiencies increases. On the other hand, an abundance of food increases the body's resistance to changes in several climatic factors. However, this so-called "compensation" of factors is limited, and none of them can be completely replaced by another. That is why, when a particular condition changes, the vital activity of the organism (the ability to compete with other species, reproduction, etc.) is limited by the factor that deviates more from the optimal value for the species. If in quantitative terms at least one of the factors goes beyond the endurance of the species, then the existence of the latter becomes impossible, no matter how favorable the other conditions are. The factor, the level of which in qualitative or quantitative terms (deficiency or excess) is close to the limits of endurance of a given organism, is called limiting.
Consider temperature as a limiting factor. Elk in Scandinavia is found much farther north than in Siberia, although in the latter the average annual temperature is higher. The reason preventing the elk from expanding their range northward in Siberia is the low winter temperatures. The low January temperature is also a limiting factor in the spread of beech in Europe. Therefore, the northern boundaries of its range correspond to the January isotherm of -2 ° C. Reef-forming corals live only in the tropics at a water temperature of at least 20 ° C.
High temperature can be a similar factor. For example, the southern border of the range of the cabbage butterfly, which is widespread in Europe and North-West Africa, is located in Palestine, since it is usually too hot there in summer.
With changes in the ecological situation, the ratio of individual factors is also violated. That is why in different localities the factors limiting the development of organisms are often not the same: in the north, for certain species, this may be a lack of heat, and in the south for the same species - a lack of moisture, food, and high temperatures. It should also be noted that the same factor for one organism acts as a limiting one for some time, and then becomes non-limiting. It depends on the stage of development of a given organism. Almost all animals and plants during the breeding season are more sensitive to adverse conditions. For example, the influence of climatic factors during the geographical distribution of many game birds extends only to eggs and chicks, but not to adults.
Ecological ranks and ecological personality. An ecological series is a set of plant communities (phytocenoses) located in accordance with the increase or decrease of any factor (or group of factors) of the environment. For example, on a slope, the greatest dryness of the soil is observed in the upper part, and the least - in the lower part, therefore, differences in vegetation associated with soil moisture are noted here. Some species grow only in the upper part of the slope, others in the middle, and still others in the lower. As a result, the ecological series of plant species is clearly distinguished either by increasing or decreasing soil moisture - from top to bottom from more to less dry-loving and, conversely, from bottom to top, from more to less moisture-loving. And the ecological range of tree species in terms of increasing shade tolerance is as follows: larch - birch - pine - aspen - willow - gray alder - linden - oak - ash - maple - scooping alder - elm - hornbeam - spruce - beech - fir.
Similar ecological series are compiled for the relation of plants to the thermal regime, to the degree of soil salinity, resistance to wind and other factors. So, in the floodplains of the rivers of the southern part of the Russian Plain, in the case of an elevation of the terrain, a change in vegetation (from a depression to a hillock) is observed in the following sequence: meadow-bog, meadow, meadow-steppe and steppe plant associations. This is an ecological series of phytocenoses. Sometimes in such a series, up to 10 or more associations are distinguished. Their boundaries are often very difficult to determine, since combinations of ecological conditions change in space gradually and between cenoses a transitional, intermediate strip is formed, in which signs of neighboring associations are combined. This is explained by the ecological individuality of each of the species, and therefore their ranges in the community do not coincide. In other words, different species react differently to the same factors.
In general, the ecological individuality of an individual is a set of its specific features, which consist in a peculiar combination of hereditary and acquired properties. It develops during the development of an organism (ontogenesis) and is expressed in the characteristics of the genotype and phenotype of a given individual. In nature, there are no identical, identical, individuals, even in a very homogeneous population. In addition to specific traits, each individual also has an ecological individuality, which manifests itself in a variety of forms.
Among the large number of individuals that make up a population, it is always possible to single out individuals most or least ecologically plastic in relation to one factor or another. Some are very sensitive to a drop in temperature, others are relatively cold-tolerant, some cannot withstand even slight dryness, and there are those that survive in a dry season. Due to ecological individuality, the population usually contains the most viable individuals, experiencing very unfavorable conditions, which determines the preservation of the species.
Preceding rule. In 1951, V.V. Alekhin established the rule of anticipation for plants. According to this rule, northern moisture-loving plants within the southern boundaries of the range are located on northern slopes and at the bottom of ravines, and southern ones, as they move north, move to better warmed southern slopes (Fig. 4). This is especially evident on the southern and northern borders of the forest zone. On the southern slopes, from the middle taiga deep into the northern one, bilberry spruce and oxalis spruce forests penetrate deeply. In Yakutia, on the northern slopes, cold-tolerant forests of Daurian larch (Larix dahurica) grow, and the southern ones are covered with pine forests. Forests remain on the southern outskirts of the forest zone along the northern slopes, and typical steppe vegetation grows on the southern ones.
Naturally, the advance rule is relative. It is less clearly expressed in mountainous areas, since a more complex set of environmental factors is noted there. Nevertheless, it is of great importance in conducting geobotanical studies, since it allows one to predict the composition of vegetation in areas not yet surveyed and its former appearance where it has been destroyed.
The principle of stadial fidelity. The station is usually understood as the habitat of the species. Due to the fact that the species and their constituent populations are selectively related to environmental factors, they inhabit strictly defined stations with appropriate environmental conditions. An area of the territory occupied by a population of a species and characterized by certain ecological conditions is called a station. The term "station" applies only to a species.
Each species has its own set of stations. There are many transitions between the extreme indicators of species selectivity to habitats. The Asian locust, for example, lives only in swampy areas, while the Italian locust (Calliptamus italicus) is more plastic and inhabits virgin steppe areas, fallow lands, and pastures. The Swedish and Hessian flies, the wheat trippe are confined to crops of grain or meadow grains, while the cabbage scoop (Baraihra brassicae) is found in the fields of not only cabbage, but also beet, pea, sunflower, clover, and even tobacco plantations. The set of stations is so characteristic for each species that it can serve as no less significant distinctive feature of it than morphological and other features. This is of practical importance in identifying harmful and beneficial species.
The property of species to selectively populate certain stations is designated as the principle of stationary fidelity. This principle is an important environmental law.
Habitat and line change rules. The principle of stadial fidelity is applicable only in conditions of limited space and time. The natural change by species of their habitats in a wide range of space and time is the rule for changing habitats. This rule was established and formulated by G. Ya. Bei-Bienko (1966).
In turn, M.S.Gilyarov deduced tier change rule, showing that in different zones the same species occupy different tiers. This is typical for transzonal species, that is, for species that are widespread and found in many natural zones.
In space, the habitat change rule is expressed in the zonal and vertical change of stations and in the zonal change of stages, and in time - in the seasonal and annual change of stations.
Zonal change of habitats is a naturally directed change in habitats during the transition of a species from one natural zone to another. Usually, when moving to the north, the species choose dry, well-warmed by the sun, open stations with a sparse vegetation cover. Spreading to the south, these same species inhabit more humid and shady places with dense vegetation. For example, the migratory locust (Locusta migratoria) in Central Europe settles on sandy places, and in Central Asia and Kazakhstan - on damp swampy areas with dense grass. In wet meadows, lasia ants (Lasius niger, L. flavus) manifest themselves as hygrophobes and settle on hummocks. In drier areas, in the steppe, these same ants act as hygrophils and choose more humid stations. As Bei-Bienko points out, the zonal change of habitats is an ecological consequence of the law of geographic zoning and is explained by a change in the thermal regime. Externally, the same stations in the north and south differ sharply precisely in terms of the thermal regime, therefore, when moving from south to north, the species choose habitats that are close to the southern ones in terms of the amount of heat.
The vertical change of stations is similar to the zonal change, but it is typical for mountain conditions. For example, the gray grasshopper (Decticus verrucivorus) in the forests of the Caucasus inhabits hygrophytic and mesophytic stations, and becomes a xerophile in the alpine belt.
The zonal change of tiers consists in the fact that many species move northward from a higher vegetation layer to a lower one, and some, in relatively dry zones, from terrestrial ones become soil inhabitants. So, the forest gardener bark beetle (Blastophagus piniperda) in the central regions and in the north lives under the bark of trunks and large branches of pine, and in the southeast of the European part of the USSR it goes into the soil and settles on the roots. The larvae of the stag beetle (Lucanus cervus) develop in the forest zone in rotting trunks and stumps, and in the steppe - in rotten roots at a depth of up to 100 cm.
Bei-Bienko believes that the zonal change of stations and stages and the vertical change of stations put the species in dual and contradictory conditions. On the one hand, the species makes certain demands on the environment arising from its hereditary physiological properties; on the other hand, in case of successful resettlement, he is forced to occupy new stations or even change the tier. As a result, its ecology changes, and at the same time its physiology. Consequently, the change of stations becomes one of the leading factors of evolution.
Seasonal change of stations occurs when the microclimate fluctuates during one season. This is most clearly expressed in a dry and hot climate and manifests itself in the migration of steppe and desert species during a drought to crops of cultivated plants, to meadows, under the forest canopy, where relatively high humidity and green vegetation cover remain. Such migrations are typical for many insects and rodents.
The annual change of stations is observed when weather conditions deviate from the average annual rate. For example, migratory locusts in southern Kazakhstan in dry years concentrate in depressions with wetter soil and thick grass cover, and in wet years they inhabit high places.
Thus, the change of habitat allows the species to maintain their ecological standard in constantly changing conditions.
The principle of stadial fidelity and its opposite - the rules for changing habitats and layers - testifies to the complexity of the relationship of organisms with the environment. Elucidation of the essence of these relationships makes it possible to penetrate more deeply into the ecology of a particular species and to develop rational methods to combat harmful organisms and to protect and attract useful ones.
Principles of ecological classification of organisms. The ecological classification of organisms differs from taxonomy in that the main criterion in the latter is the phylogenetic proximity of organisms, i.e., the taxonomy at all levels of taxonomy is based on a single criterion - phylogenesis. There is no such criterion in the ecological classification, therefore it has a lot of schemes.
The ecological classification of organisms can be made according to their position in the energy or food chain. In relation to organic matter, heterotrophs and autotrophs are distinguished, according to their function in biogeocenosis - producers, consumers and reducers (destructors).
The ecological classification can also be based on habitats.
In this case, aquatic organisms are subdivided into benthic, planktonic, and nekton. They can be classified according to the zones they occupy. With this approach, it is important to find out the position of the organism in all three classification systems, and also keep in mind that many species at different stages of development lead different lifestyles (tadpole and frog, dragonfly larva and adult insect).
The classification of terrestrial animals causes particular difficulties, since they represent a huge variety of forms, which is associated with the characteristics of their habitats. Already among herbivores there are both small and very large ones. The abundance of insects and other arthropods, as well as birds, practically defies accounting and ecological classification. It is even more difficult to classify decomposers. Soil organisms are usually classified by size, which is why micro-, meso- and macrobiota differ.
The most common ecological classification of organisms according to life forms, that is, according to the type of external morphology, reflecting the most important moments of the way of life, the relation of the species to the environment. Life forms determine the adaptability of organisms to a complex of factors (as opposed to ecological groups that characterize adaptation to individual factors), to the specificity of the habitat.
Life forms in animals are very diverse. First of all, these are groups with similar ecological and morphological adaptations for living in a similar environment. In this case, the term "life forms" is borrowed from botany. It has established itself in zoology only in the present century, although animals have long been subdivided into divers, burrowers, diggers, etc.
There are many different interpretations of the life forms of animals. This is due to the fact that in some cases the characteristics of reproduction are taken as the basis for the classification, in others - the methods of movement or obtaining food. Often, the classification is based on the confinement of organisms to certain ecological niches, landscape, and tier. Nevertheless, the analysis of life forms makes it possible to judge the characteristics of the habitat and the ways in which animals develop adaptation to certain conditions. For example, D. N. Kashkarov (1945) classifies the life forms of animals as follows.
I. Floating forms:
1.Pure water: a) nekton, b) plankton, c) benthos;
2. Semi-aquatic: a) diving, b) diving, c) extracting only food from the water.
II. Burrowing forms:
1. Absolute diggers (spend their whole life underground);
2. Relative diggers (come to the surface of the earth).
III. Terrestrial forms:
1. Not making holes: a) running, b) jumping, c) crawling;
2. Making holes: a) running, b) jumping, c) crawling;
3. Animals of the rocks.
IV. Woody, climbing forms: a) do not descend from trees, b) only climb trees.
V. Air forms: a) getting food in the air, b) looking out for it from the air.
As you can see, this classification is based on devices for movement. In relation to air humidity, Kashkarov distinguishes between hygrophilous (hygrophilic) and dry-loving (xerophilic) forms; on nutrition - herbivorous, omnivorous, carnivorous, gravediggers (corpse eaters); at the place of breeding - those that breed underground, on the surface of the earth, in the layer of grasses, in bushes, on trees.
Various categories of life forms of insects in relation to their habitat (geobionts, hydrobionts, etc.) are proposed by V.V. Yakhontov. The zonal-landscape category of life forms was developed by ornithologists A. K. Rustamov, G. P. Dementyev, S. M. Uspensky.
Plants are classified based on their adaptation to the environment. Among them are hygrophytes, mesophytes, xerophytes. This classification is based on the physiological properties of plants, and the division of vegetation into trees, shrubs, and grass gives the characteristics of the main terrestrial communities. Due to the variety of conditions on Earth, plants have developed a huge number of life forms. The concept of life forms of plants was first introduced in 1806 by Humboldt. Usually, woody, semi-woody, terrestrial herbaceous and aquatic herbaceous plants are distinguished. Each of these forms can be represented by smaller groups. The most widespread classification of life forms of plants, developed in 1905-1907. Danish botanist S. Raunkier. It is based on the location of the buds of renewal and the presence of adaptations for experiencing an unfavorable season. The modern classification is based on this classification, in which 6 life forms of plants are distinguished (Fig. 5).
1. Epiphytes * - aerial plants that do not have roots in the soil. They settle on the trunks of other larger plants. In forests, these are trunk lichens, less often mosses. Among the higher plants, epiphytes are numerous in tropical rainforests.
2. Fanophytes - aboveground plants (trees, shrubs, lianas, stem succulents, herbaceous stem plants). Renewal buds are found on vertically located shoots high above the ground.
3. Khamefits are herbaceous plants with renewal buds located near the ground. In temperate latitudes, the shoots of these plants go under the snow for the winter and do not die off.
4. Hemicryptophytes - sod-forming plants in which the buds of renewal are at the level of the soil or even in it. Aerial shoots die off by winter. These are many meadow plants.
5. Cryptophytes, or geophytes, are perennial grasses with dying aerial parts. Renewal buds are located on underground organs (tuberous or rhizome plants).
6. Therophytes are annual plants. By winter, their aboveground and underground parts die off. An unfavorable period (winter) is experienced at the seed stage.
In the given series of life forms, an increasing adaptation to unfavorable conditions is clearly manifested. In tropical rainforests, most species belong to phanerophytic epiphytes. In more northern regions, plants with protected regeneration buds prevail.
There are other schemes for classifying life forms. The greatest recognition was received by the classification of cereals by the method of tillering, developed by V.R. Williams. G.N. Vysotsky and L.I. Kazakevich based the classification of life forms on the character of underground organs and the ability of plants for vegetative reproduction. Recently, IG Serebryakov proposed a successful classification of angiosperms, focusing on the structure and duration of life of the aboveground skeletal axes. He distinguishes 4 divisions and 8 types of life forms of these plants (Scheme 3). Each type, in turn, is subdivided into forms. For example, in type I, aerial crown-forming trees with erect trunks are distinguished; bushy, single-barreled with low trunks; stanzas (with recumbent trunks).
Life forms that dominate in a particular community can serve as indicators of living conditions. Thus, the predominance of stolon-forming plants in broad-leaved and dark-coniferous forests indicates a marginal, loose and excessively moist soil. In hot and arid climates, animals that live in deep holes predominate, and on highly fertile and loose soils, diggers create a large number of passages.
Chapter 5. THE MOST IMPORTANT ABIOTIC FACTORS AND BODIES 'ADAPTATION TO THEM
Every organism, population, species has a habitat - that part of nature that surrounds all living things and has any effect on it, direct or indirect. It is from it that organisms take everything they need to exist, and they also release the products of their vital activity into it. The living conditions of different organisms are not the same. As they say, what is good for one person, then death for another. It is composed of many organic and inorganic elements that affect a particular species.
Habitat and living conditions
Conditions of existence - those factors of the environment that are vital for a certain type of organisms. That minimum, without which existence is impossible. These include, for example, air, moisture, soil, as well as light and heat. These are the primary conditions. In contrast, there are other factors that are not so vital. For example, wind or atmospheric pressure. Thus, the habitat and conditions for the existence of organisms are different concepts. The first - more general, the second - denotes only those conditions without which a living organism or plant cannot exist.
Environmental factors
These are all those elements of the habitat that are capable of influencing - direct or indirect - on These factors cause adaptations of organisms (or adaptive reactions). Abiotic is the influence of inorganic elements of inanimate nature (soil composition, its chemical properties, light, temperature, humidity). Biotic factors are forms of influence of living organisms on each other. Some species are food for others, serve for pollination and dispersal, and have other effects. Anthropogenic - human activities affecting wildlife. The selection of this group is associated with the fact that today the fate of the entire biosphere of the Earth is practically in the hands of man.
Most of the above factors are environmental conditions. Some are in the process of modification, others are constant. Their change depends on the time of day, for example, from cooling and warming. Many factors (the same environmental conditions) play a primary role in the life of some organisms, while in others they play a secondary role. For example, the soil salt regime is of great importance in the nutrition of plants with minerals, while in animals it is not so important for the same area.
Ecology
This is the name of the science that studies the conditions of the living environment of organisms and their relationship with it. The term was first defined by the German biologist Haeckel in 1866. However, science began to develop actively only by the 30s of the last century.
Biosphere and noosphere
The totality of all living organisms on Earth is called the biosphere. It also includes a person. And not only enters, but also has an active influence on the biosphere itself, especially in recent years. This is how the transition to the noosphere is carried out (in the terminology of Vernadsky). The noosphere presupposes not only the rough use of natural resources and science, but also universal human cooperation aimed at protecting our common home - planet Earth.
Aquatic habitat conditions
Water is considered the cradle of life. Many of the animals that exist on earth had ancestors that lived in this environment. With the formation of land, some species emerged from the water and became at first amphibians, and then evolved into terrestrial ones. Most of our planet is covered with water. Many organisms living in it are hydrophilic, that is, they do not need any adaptation to their environment.
First of all, one of the most important conditions is the chemical composition of the aquatic environment. It is different in different water bodies. For example, the salt regime of small lakes is 0.001% salt. In large fresh water bodies - up to 0.05%. Marine - 3.5%. In salty continental lakes, the salt level reaches over 30%. Fauna becomes poorer with increasing salinity. Water bodies are known where there are no living organisms.
An important role in environmental conditions is played by such a factor as the content of hydrogen sulfide. For example, in (below 200 meters) no one lives at all, except for hydrogen sulfide bacteria. And all because of the abundance of this gas in the environment.
The physical properties of water are also important: transparency, pressure, speed of currents. Some animals live only in clear water, while muddy water is suitable for others. Some plants live in stagnant water, while others prefer to travel with the current.
For deep-sea dwellers, the absence of light and the presence of pressure are the most important conditions for existence.
Plants
The habitat conditions of plants are also determined by many factors: the presence of lighting, temperature fluctuations. If the plant is aquatic - by the conditions of the aquatic environment. Of the vital - the presence of nutrients in the soil, natural watering and irrigation (for cultivated plants). Many of the plants are tied to specific climatic zones. In other areas, they are not able to survive, much less reproduce and give offspring. Ornamental plants, accustomed to "greenhouse" conditions, require an artificially created habitat. In street conditions, they can no longer survive.
On the ground
For many plants and animals, the soil habitat is relevant. Environmental conditions depend on several factors. These include climatic zones, temperature changes, chemical and physical composition of the soil. On land, as well as on water, one thing is good for some, another is good for others. But in general, the soil habitat provides shelter for many species of plants and animals living on the planet.
Fundamentals of General Ecology
Wednesday- everything that surrounds the body and directly or indirectly affects its life, development, growth, survival, reproduction, etc.
The environment of each organism is composed of many elements of inorganic and organic nature and elements introduced by man and his production activities. At the same time, some elements are necessary for the body, others are indifferent to it, and others have a harmful effect.
Conditions of existence, or living conditions- a set of environmental elements necessary for an organism, with which it is in indissoluble unity and without which it cannot exist.
The elements of the environment, both necessary for the body and negatively affecting it, are called environmental factors .
Environmental factors are usually divided into three main groups: abiotic, biotic and anthropic.
Abiotic factors - a complex of conditions of the inorganic and organic environment that affect the body. Abiotic factors are subdivided into chemical (chemical composition of air, ocean, soil, etc.) and physical (temperature, pressure, wind, humidity, light, radiation regime, etc.).
Anthropic factors - the totality of the effects of human activity on the organic world.
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Already by the fact of his existence, a person influences the environment (due to respiration, about 1.1 10 12 Kg CO 2, etc.) and an immeasurably greater production activity to an ever increasing degree.
The influence of abiotic factors on the body should be direct and indirect (mediated). So, for example, the temperature of the environment determines the speed of physiological processes in the body and, accordingly, its development (direct influence); at the same time, influencing the development of plants that are food for animals, it has an indirect effect on the latter.
The effect of environmental factors depends not only on their nature, but also on the dose perceived by the body (high or low temperature, bright light or darkness, etc.). In the course of evolution, all organisms have developed adaptations to the perception of factors within certain quantitative limits. Moreover, for each organism there is a set of factors that are most favorable for it.
The more the dose of factors deviates from the optimal value for a given type (increase or decrease), the more its vital activity is inhibited. The boundaries beyond which the existence of an organism is impossible are called lower and upper endurance limits (tolerance).
The intensity of the ecological factor, the most favorable for the organism (its vital activity), is usually called optimum, and giving the worst effect - pessimum.
Organisms can adapt over time to changing factors. The property of species to adapt to changing ranges of environmental factors is usually called environmental plasticity (ecological valence). The wider the range of fluctuations of the ecological factor, within which a given species can exist, the greater its ecological plasticity, the wider the range of its tolerance (endurance).
Ecologically non-plastic (low-tolerant) species are called stenobiontic(from the Greek. stenos- narrow), more plastic (hardy) - eurybiontic(from the Greek. eurys- wide). Species of organisms that have developed for a long time in relatively stable conditions lose their ecological plasticity and acquire features of stenobionticity; species that existed under conditions of significant changes in environmental factors become eurybiontic.
The attitude of organisms to fluctuations of a particular environmental factor is expressed by adding the prefixes wall- and evri- (steno- and eurythermal, steno- and eurythemic, etc.).
Historically adapting to the abiotic factor of the environment and entering into biotic connections with each other, plants, animals and microorganisms are distributed in different environments and form diverse biogeocenoses eventually merging into biosphere Earth.
Biogeocenosis- territorially (spatially) isolated integral elementary unit of the biosphere, all components of which are closely related to each other.
All environmental factors act on the body simultaneously and in interaction. Such a set of them is usually called constellation... For this reason, the optimum and the limits of the body's endurance in relation to any one factor depend on others. Moreover, if the intensity of at least one factor goes beyond the endurance of the species, then the existence of the latter becomes impossible, no matter how favorable the other conditions are. This factor is usually called limiting... A special case of the principle of limiting factors is the minimum rule formulated by Liebig (German chemist) to characterize the yield of agricultural crops: a substance at a minimum (in the soil, in the air) controls the yield and determines the magnitude and stability of the latter.
Environment and conditions of existence of organisms - concept and types. Classification and features of the category "Environment and conditions for the existence of organisms" 2017, 2018.
