The term "ecology" was introduced into science by the German scientist Ernst Haeckel (E. Haeckel) in 1869. It is quite easy to give a formal definition, since the word "ecology" comes from the Greek words "oikos" - dwelling, shelter and "logos" - science. Therefore, ecology is often defined as the science of the relationship between organisms or groups of organisms (populations, species) with their environment. In other words, the subject of ecology is a set of relationships between organisms and the conditions of their existence (environment), on which the success of their survival, development, reproduction, distribution, and competitiveness depend.

In botany, the term "ecology" was first used by the Danish botanist E. Warming in 1895.

In a broad sense, the environment (or environment) is understood as the totality of material bodies, phenomena and energy, waves and fields, one way or another affecting. However, different environments are far from equally perceived by a living organism, since their significance for life is different. Among them there are practically indifferent to plants, for example, inert gases contained in the atmosphere. Other elements of the environment, on the contrary, have a noticeable, often significant effect on the plant. They are called environmental factors. These are, for example, light, water in the atmosphere and soil, air, salinization of groundwater, natural and artificial radioactivity, etc.). With the deepening of our knowledge, the list of environmental factors is expanding, since in a number of cases it is found that plants are able to respond to elements of the environment that were previously considered indifferent (for example, a magnetic field, strong noise exposure, electric fields, etc.).

Classification of environmental factors

It is possible to classify environmental factors in different conceptual coordinate systems.

Distinguish, for example, resource and non-resource environmental factors. Resource factors are substances and (or) involved in the biological cycle by the plant community (for example, light, water, the content of mineral nutrients in the soil, etc.); accordingly, non-resource factors do not participate in the cycles of matter and energy transformation and ecosystems (for example, relief).

There are also direct and indirect environmental factors. The former directly affect metabolism, shaping processes, growth and development (light), the latter affect the body through a change in other factors (for example, transabiotic and transbiotic forms of interactions). Since in different ecological situations many factors can act both directly and indirectly, it is better to speak not about the separation of factors, but about their direct or indirect effect on the plant.

The most widely used classification of environmental factors according to their origin and nature of action:

I. Abiotic factors:

a) climatic - light, heat (its composition and movement), moisture (including precipitation in various forms, air humidity), etc .;

b) edaphic (or soil-ground) - physical (granulometric composition, water permeability) and chemical (pH of soils, content of mineral nutrition elements, macro- and microelements, etc.) properties of soils;

c) topographic (or orographic) - relief conditions.

II. Biotic factors:

a) phytogenic - direct and indirect impact of plant cohabitants;

b) zoogenic - direct and indirect influence of animals (eating, trampling, digging activities, pollination, distribution of fruits and seeds);

c) prokaryotic factors - the influence of bacteria and blue-green algae (negative effect of phytopathogenic bacteria, positive effect of free-living and symbiotically associated nitrogen-fixing bacteria, actinomycetes and cyanides);

Read more about biotic factors in the article

The specific forms of human impact on the vegetation cover, their direction, and scale make it possible to single out anthropogenic factors as well.

III. Anthropogenic factors associated with the multilateral forms of human agricultural activity (grazing, haymaking), its industrial activity (gas emissions in, construction, mining, transport communications and pipelines), space exploration and recreational activities.

Far from everything fits into this simplest classification, but only the main environmental factors. There are other plants that are less essential for life (atmospheric electricity, the Earth's magnetic field, ionizing radiation, etc.).

Note, however, that the above division is to a certain extent conditional, since (and this is important to emphasize both in theoretical and practical terms) the environment affects the organism as a whole, and the separation of factors and their classification is nothing more than a methodological technique, facilitating the knowledge and study of the patterns of relationships between the plant and the environment.

General patterns of influence of environmental factors

The influence of environmental factors on a living organism is very diverse. Some factors - leading ones - have a stronger effect, others - secondary ones - act weaker; some factors affect all aspects of plant life, others - on any particular life process. Nevertheless, it is possible to present a general scheme of the dependence of the body's reaction under the influence of an environmental factor.

If the intensity of the factor in its physical expression is plotted along the abscissa (X) axis ( , salt concentration in the soil solution, pH, illumination of the habitat, etc.), and along the ordinate (Y) - the reaction of the organism or population to this factor in its quantitative expression (intensity of one or another physiological process - photosynthesis, water absorption by roots, growth, etc.; morphological characteristic - plant height, leaf size, number of seeds produced, etc.; population characteristics - number of individuals per unit area , frequency of occurrence, etc.), we get the following picture.

The range of the ecological factor (the area of ​​tolerance of the species) is limited by the minimum and maximum points, which correspond to the extreme values ​​of this factor, at which the existence of the plant is possible. The point on the abscissa axis, corresponding to the best indicators of the plant's vital activity, means the optimal value of the factor - this is the optimum point. Due to the difficulties in accurately determining this point, one usually speaks of a certain optimum zone, or a comfort zone. The optimum, minimum, and maximum points make up three cardinal points that determine the possibilities of a species' reaction to a given factor. The extreme sections of the curve, expressing the state of oppression with a sharp lack or excess of the factor, are called areas of pessimum; they correspond to the pessimal values ​​of the factor. Sub-lethal values ​​of the factor lie near the critical points, and lethal values ​​lie outside the tolerance zone.

Species differ from each other by the position of the optimum within the gradient of the ecological factor. For example, the attitude to heat in arctic and tropical species. The width of the range of the factor (or optimum zone) can also be different. There are species, for example, for which a low level of illumination (cave bryophytes) or a relatively high level of illumination (alpine alpine plants) is optimal. But species are also known that grow equally well both in full light and in significant shading (for example, the team hedgehog - Dactylis glomerata).

In the same way, some meadow grasses prefer soils with a certain, rather narrow range of acidity, while others grow well in a wide pH range - from strongly acidic to alkaline. The first case indicates a narrow ecological amplitude of plants (they are stenobiont or stenotopic), the second - a wide ecological amplitude (plants are eurybiont or eurytopic). Between the categories of eurytopicity and stenotopicity lies a number of intermediate qualitative categories (hemieurytopic, gemistenotopic).

The breadth of the ecological amplitude in relation to different environmental factors is often different. It is possible to be stenotopic with respect to one factor and eurytopic with respect to another: for example, plants can be confined to a narrow range of temperatures and a wide range of salinity.

Interaction of environmental factors

Environmental factors act on the plant jointly and simultaneously, and the effect of one factor depends to a large extent on the "ecological background", that is, on the quantitative expression of other factors. This phenomenon of interaction of factors is clearly seen in the experiment with the aquatic moss Fontinalis. This experiment clearly shows that illumination has a different effect on the intensity of photosynthesis at different CO 2 content in .

The experiment also shows that a similar biological effect can be obtained by partially replacing the action of one factor with another. Thus, the same intensity of photosynthesis can be achieved either by increasing the illumination to 18 thousand lux, or, at lower illumination, by increasing the concentration of CO 2 .

Here, the partial interchangeability of the action of one environmental factor with another is manifested. At the same time, none of the necessary environmental factors can be replaced by another: a green plant cannot be grown in complete darkness even with very good mineral nutrition or on distilled water with optimal thermal conditions. In other words, there is a partial substitution of the main ecological factors and, at the same time, their complete indispensability (in this sense, they are sometimes also spoken of as equally important for plant life). If the value of at least one of the necessary factors goes beyond the tolerance range (below the minimum and above the maximum), then the existence of the organism becomes impossible.

Limiting factors

If any of the factors that make up the conditions of existence has a pessimal value, then it limits the action of the remaining factors (no matter how favorable they may be) and determines the final result of the effect of the environment on the plant. This end result can only be changed by acting on the limiting factor. This "law of the limiting factor" was first formulated in agricultural chemistry by the German agricultural chemist, one of the founders of agricultural chemistry, Justus Liebig in 1840 and is therefore often called Liebig's law.

He noticed that with a lack of one of the necessary chemical elements in the soil or nutrient solution, no fertilizers containing other elements have an effect on the plant, and only the addition of “minimum ions” gives an increase in yield. Numerous examples of the action of limiting factors, not only in experiment, but also in nature, show that this phenomenon is of general ecological significance. One example of the operation of the “law of the minimum” in nature is the suppression of herbaceous plants under the canopy of beech forests, where, under optimal thermal conditions, high carbon dioxide content, sufficiently rich soils and other optimal conditions, the possibilities for grass development are limited by a sharp lack of light.

The identification of "factors at a minimum" (and at a maximum) and the elimination of their limiting effect, in other words, the optimization of the environment for plants, constitute an important practical task in the rational use of vegetation cover.

Autecological and synecological range and optimum

The attitude of plants to environmental factors closely depends on the influence of other plant cohabitants (primarily on competitive relations with them). Often there is a situation when a species can successfully grow in a wide range of action of some factor (which is determined experimentally), but the presence of a strong competitor forces it to be limited to a narrower zone.

For example, Scots pine (Pinus sylvestris) has a very wide ecological range in relation to soil factors, but in the taiga zone it forms forests mainly on dry poor sandy soils or on highly waterlogged peatlands, i.e., where there are no competing tree species. Here, the real position of the optima and areas of tolerance is different for plants that experience or do not experience biotic influence. In this regard, a distinction is made between the ecological optimum of a species (in the absence of competition) and the phytocenotic optimum corresponding to the real position of the species in the landscape or biome.

In addition to the position of the optimum, the limits of the endurance of the species are distinguished: the ecological range (the potential limits of the distribution of the species, determined only by its relation to this factor) and the real phytocenotic range.

Often in this context one speaks of a potential and real optimum and area. In foreign literature, they also write about the physiological and ecological optimum and range. It is better to talk about the autecological and synecological optimum and the range of the species.

In different species, the ratio of the ecological and phytocenotic ranges is different, but the ecological range is always wider than the phytocenotic one. As a result of the interaction of plants, the range narrows and often the optimum shifts.

Environmental factors, their impact on organisms

Temperature, physico-chemical, biological elements of the environment that have a constant or periodic, direct or indirect effect on organisms and populations are called environmental factors.

Environmental factors are divided as follows:

Abiotic - temperature and climatic conditions, humidity, chemical composition of the atmosphere, soil, water, illumination, relief features;

Biotic - living organisms and direct products of their vital activity;

Anthropogenic - man and the direct products of his economic and other activities.

Main abiotic factors

1. Solar radiation: ultraviolet rays are detrimental to the body. The visible part of the spectrum provides photosynthesis. Infrared rays increase the temperature of the environment and the body of organisms.

2. Temperature affects the rate of metabolic reactions. Animals with a constant body temperature are called homoiothermic, and with a variable - poikilothermic.

3. Humidity is characterized by the amount of water in the environment and inside the body. Animal adaptations are associated with the acquisition of water, the storage of fat as a source of water during oxidation, with the transition to hibernation in the heat. Plants develop root systems, thicken the cuticle on the leaves, reduce the area of ​​the leaf blade, and reduce the leaves.

4. Climate - a set of factors characterized by seasonal and daily periodicity, due to the rotation of the Earth around the Sun and its own axis. Animal adaptations are expressed in the transition to hibernation in the cold season, in stupor in poikilothermic organisms. In plants, adaptations are associated with the transition to a dormant state (summer or winter). With large losses of water, a number of organisms fall into a state of anabiosis - the maximum slowdown in metabolic processes.

5. Biological rhythms - periodic fluctuations in the intensity of the action of factors. Daily biorhythms determine the external and internal reactions of organisms to the change of day and night

Organisms adapt (adapt) to the influence of certain factors in the process of natural selection. Their adaptive capabilities are determined by the norm of reaction in relation to each of the factors, both constantly acting and fluctuating in their values. For example, the length of daylight hours in a particular region is constant, while temperature and humidity can fluctuate within fairly wide limits.

Environmental factors are characterized by the intensity of the action, the optimal value (optimum), the maximum and minimum values ​​within which the life of a particular organism is possible. These parameters are different for representatives of different species.

Deviation from the optimum of any factor, such as a decrease in the amount of food, can narrow the limits of endurance of birds or mammals in relation to a decrease in air temperature.

The factor, the value of which is currently on the limits of endurance or beyond them, is called limiting.

Organisms that can exist within a wide range of factor fluctuations are called eurybionts. For example, organisms that live in continental climates tolerate wide fluctuations in temperature. Such organisms usually have wide distribution areas.

Factor intensity minimum optimal maximum

Rice. 23. The effect of the environmental factor on living organisms: A - general scheme; B - scheme for warm-blooded and cold-blooded animals

Basic biotic factors

Organisms of one species enter into relationships of various nature both with each other and with representatives of other species. These relationships are respectively subdivided into intraspecific and interspecific.

Intraspecific relationships are manifested in intraspecific competition for food, shelter, a female, as well as in behavioral features, a hierarchy of relations between members of a population.

Interspecies relationships:

Mutualism is a form of mutually beneficial symbiotic relationship between two populations of different species;

Commensalism is a form of symbiosis in which the relationship is beneficial primarily for one of the two species living together (pilot fish and sharks);

Predation is a relationship in which individuals of one species kill and eat individuals of another species.

Anthropogenic factors are associated with human activities, under the influence of which the environment changes and forms. Human activity extends to almost the entire biosphere: mining, the development of water resources, the development of aviation and astronautics affect the state of the biosphere. As a result, destructive processes occur in the biosphere, which include water pollution, the "greenhouse effect" associated with an increase in the concentration of carbon dioxide in the atmosphere, ozone layer disturbances, "acid rains", etc.

Biogeocenosis

Biogeocenosis is a set of populations of different species living together and interacting with each other and with inanimate nature, forming a complex, self-regulating system in relatively homogeneous environmental conditions. The term was introduced by V.N. Sukachev.

The composition of biogeocenosis includes: biotope (non-living part of the environment) and biocenosis (all types of organisms inhabiting the biotope).

The totality of plants living in a given biogeocenosis is commonly called a phytocenosis, the totality of animals is a zoocenosis, the totality of microorganisms is a microbiocenosis.

Characteristics of biogeocenosis:

Biogeocenosis has natural boundaries;

In biogeocenosis, all environmental factors interact;

Each biogeocenosis is characterized by a certain circulation of substances and energy;

Biogeocenosis is relatively stable in time and is capable of self-regulation and self-development in the case of unidirectional changes in the biotope. The change of biocenoses is called succession.

Structure of biogeocenosis:

Producers - plants that produce organic substances in the process of photosynthesis;

Consumers - consumers of finished organic matter;

Decomposers - bacteria, fungi, as well as animals that feed on carrion and manure - destroyers of organic substances, converting them into inorganic ones.

The listed components of biogeocenosis constitute trophic levels associated with the exchange and transfer of nutrients and energy.

Organisms of different trophic levels form food chains in which substances and energy are transferred stepwise from level to level. At each trophic level, 5-10% of the energy of the incoming biomass is used.

Food chains usually consist of 3-5 links, for example: plants-cow-man; plants-ladybug-titmouse-hawk; plants-fly-frog-snake-eagle.

The mass of each subsequent link in the food chain decreases by about 10 times. This rule is called the ecological pyramid rule. Ratios of energy costs can be reflected in the pyramids of numbers, biomass, energy.

Artificial biocenoses created by people involved in agriculture are called agrocenoses. They have great productivity, but do not have the ability to self-regulate and stability, as they depend on the attention of a person to them.

Biosphere

There are two definitions of the biosphere.

1. The biosphere is the inhabited part of the geological shell of the Earth.

2. The biosphere is a part of the geological shell of the Earth, the properties of which are determined by the activity of living organisms.

The second definition covers a wider area: after all, atmospheric oxygen formed as a result of photosynthesis is distributed throughout the atmosphere and is present where there are no living organisms.

The biosphere, according to the first definition, consists of the lithosphere, the hydrosphere and the lower layers of the atmosphere - the troposphere. The limits of the biosphere are limited by the ozone screen, the upper limit of which is at a height of 20 km, and the lower one - at a depth of about 4 km.

The biosphere, according to the second definition, includes the entire atmosphere.

The doctrine of the biosphere and its functions was developed by Academician V.I. Vernadsky.

The biosphere is the area of ​​distribution of life on Earth, including living matter (substance that is part of living organisms). Bioinert substance is a substance that is not part of living organisms, but is formed due to their activity (soil, natural waters, air).

Living matter, which makes up less than 0.001% of the mass of the biosphere, is the most active part of the biosphere.

In the biosphere there is a constant migration of substances of both biogenic and abiogenic origin, in which living organisms play a major role. The circulation of substances determines the stability of the biosphere.

The main source of energy for sustaining life in the biosphere is the Sun. Its energy is converted into the energy of organic compounds as a result of photosynthetic processes occurring in phototrophic organisms. Energy is accumulated in the chemical bonds of organic compounds that serve as food for herbivorous and carnivorous animals. Organic food substances decompose in the process of metabolism and are excreted from the body. The isolated or dead remains, in turn, are decomposed by bacteria, fungi and some other organisms. The resulting chemical compounds and elements are involved in the circulation of substances.

The biosphere needs a constant influx of external energy, since all chemical energy is converted into thermal energy.

Biosphere functions:

Gas - release and absorption of oxygen and carbon dioxide, nitrogen reduction;

Concentration - the accumulation by organisms of chemical elements scattered in the external environment;

Redox - oxidation and reduction of substances during photosynthesis and energy metabolism;

Biochemical - is realized in the process of metabolism.

Energy - associated with the use and transformation of energy.

As a result, biological and geological evolution occur simultaneously and are closely interrelated. Geochemical evolution occurs under the influence of biological evolution.

The mass of all living matter of the biosphere is its biomass, which is approximately 2.4-1012 tons.

Land-dwelling organisms make up 99.87% of the total biomass, ocean biomass - 0.13%. The amount of biomass increases from the poles to the equator. Biomass (B) is characterized by:

a) productivity - the increase in the substance per unit area (P);

b) reproduction rate - the ratio of production to biomass per unit of time (P/B).

The most productive are tropical and subtropical forests.

The part of the biosphere that is under the influence of active human activity is called the noosphere - the sphere of the human mind. The term implies a reasonable influence of man on the biosphere in the modern era of scientific and technological progress. However, most often this influence is detrimental to the biosphere, which in turn is detrimental to humanity.

The circulation of substances and energy in the biosphere is due to the vital activity of organisms and is a necessary condition for their existence. Cycles are not closed, so chemical elements accumulate in the external environment and in organisms.

Carbon is taken up by plants during photosynthesis and released by organisms during respiration. It also accumulates in the environment in the form of fossil fuels, and in organisms in the form of reserves of organic substances.

Nitrogen is converted into ammonium salts and nitrates as a result of the activity of nitrogen-fixing and nitrifying bacteria. Then, after the use of nitrogen compounds by organisms and denitrification by decomposers, nitrogen is returned to the atmosphere. Sulfur is found in the form of sulfides and free sulfur in marine sedimentary rocks and soil. Turning into sulfates as a result of oxidation by sulfur bacteria, it is included in plant tissues, then, together with the remains of their organic compounds, it is exposed to anaerobic decomposers. The hydrogen sulfide formed as a result of their activity is again oxidized by sulfur bacteria.

Phosphorus is found in the composition of rock phosphates, in freshwater and ocean sediments, and in soils. As a result of erosion, phosphates are washed out and in an acidic environment become soluble with the formation of phosphoric acid, which is absorbed by plants. In animal tissues, phosphorus is a part of nucleic acids and bones. As a result of decomposition by decomposers of the remains of organic compounds, it again returns to the soil, and then to the plants.

ENVIRONMENTAL FACTORS

Environmental factors - these are certain conditions and elements of the environment that have a specific effect on a living organism. The body reacts to the action of environmental factors with adaptive reactions. Environmental factors determine the conditions for the existence of organisms.

Classification of environmental factors (by origin)

• 1. Abiotic factors are a set of factors of inanimate nature that affect the life and distribution of living organisms. Among them are distinguished:
• 1.1. Physical factors- such factors, the source of which is a physical state or phenomenon (for example, temperature, pressure, humidity, air movement, etc.).
• 1.2. Chemical Factors- such factors that are due to the chemical composition of the environment (water salinity, oxygen content in the air, etc.).
• 1.3. Edaphic factors(soil) - a set of chemical, physical, mechanical properties of soils and rocks that affect both the organisms for which they are the habitat and the root system of plants (humidity, soil structure, content of nutrients, etc.).
• 2. Biotic factors - a set of influences of the life activity of some organisms on the life activity of others, as well as on the non-living component of the habitat.
• 2.1. Intraspecific interactions characterize the relationships between organisms at the population level. They are based on intraspecific competition.
• 2.2. Interspecies interactions characterize the relationship between different species, which can be favorable, unfavorable and neutral. Accordingly, we denote the nature of the impact as +, - or 0. Then the following types of combinations of interspecies relationships are possible:
• 00 neutralism- both types are independent and have no effect on each other; rarely found in nature (squirrel and elk, butterfly and mosquito);

+0 commensalism- one species benefits, while the other does not have any benefit, harm too; (large mammals (dogs, deer) serve as carriers of fruits and seeds of plants (burdock), without receiving any harm or benefit);

-0 amensalism- one species experiences inhibition of growth and reproduction from another; (light-loving herbs growing under a spruce suffer from shading, and this is indifferent to the tree itself);

++ symbiosis- mutually beneficial relationship:

• ? mutualism- species cannot exist without each other; figs and pollinating bees; lichen;
• ? proto-operation- coexistence is beneficial to both species, but is not a prerequisite for survival; pollination by bees of different meadow plants;
• - - competition- each of the species has an adverse effect on the other; (plants compete with each other for light and moisture, i.e. when they use the same resources, especially if they are insufficient);

Predation - a predatory species feeds on its prey;

• 2.3. Impact on inanimate nature(microclimate). For example, in the forest, under the influence of vegetation cover, a special microclimate or microenvironment is created, where, in comparison with an open habitat, its own temperature and humidity regime is created: in winter it is several degrees warmer, in summer it is cooler and wetter. A special microenvironment is also created in the crown of trees, in burrows, in caves, etc.
• 3. Anthropogenic factors - factors generated by human activity and affecting the natural environment: direct human impact on organisms or impact on organisms through human change in their habitat (environmental pollution, soil erosion, deforestation, desertification, reduction of biological diversity, climate change, etc.). ). The following groups of anthropogenic factors are distinguished:
• 1. change in the structure of the earth's surface;
• 2. change in the composition of the biosphere, the circulation and balance of its constituent substances;
• 3. change in the energy and heat balance of individual sections and regions;
• 4. changes introduced into the biota.

There is another classification of environmental factors. Most factors qualitatively and quantitatively change over time. For example, climatic factors (temperature, illumination, etc.) change during the day, season, and year. Factors that change regularly over time are called periodical . These include not only climatic, but also some hydrographic - ebbs and flows, some ocean currents. Factors that arise unexpectedly (volcanic eruption, predator attack, etc.) are called non-periodic .

The environment that surrounds living beings consists of many elements. They affect the life of organisms in different ways. The latter react differently to various environmental factors. Separate elements of the environment interacting with organisms are called environmental factors. The conditions of existence are a set of vital environmental factors, without which living organisms cannot exist. With regard to organisms, they act as environmental factors.

Classification of environmental factors.

All environmental factors accepted classify(distributed) into the following main groups: abiotic, biotic And anthropic. V Abiotic (abiogenic) factors are physical and chemical factors of inanimate nature. biotic, or biogenic, factors are the direct or indirect influence of living organisms both on each other and on the environment. Antropical (anthropogenic) In recent years, factors have been singled out as an independent group of factors among biotic ones, due to their great importance. These are factors of direct or indirect impact of man and his economic activity on living organisms and the environment.

abiotic factors.

Abiotic factors include elements of inanimate nature that act on a living organism. Types of abiotic factors are presented in Table. 1.2.2.

Table 1.2.2. Main types of abiotic factors

climatic factors.

All abiotic factors manifest themselves and operate within the three geological shells of the Earth: atmosphere, hydrosphere And lithosphere. Factors that manifest themselves (act) in the atmosphere and during the interaction of the latter with the hydrosphere or with the lithosphere are called climatic. their manifestation depends on the physical and chemical properties of the geological shells of the Earth, on the amount and distribution of solar energy that penetrates and enters them.

Solar radiation.

Solar radiation is of the greatest importance among the variety of environmental factors. (solar radiation). This is a continuous flow of elementary particles (velocity 300-1500 km/s) and electromagnetic waves (velocity 300 thousand km/s), which carries a huge amount of energy to the Earth. Solar radiation is the main source of life on our planet. Under the continuous flow of solar radiation, life originated on Earth, has passed a long way of its evolution and continues to exist and depend on solar energy. The main properties of the radiant energy of the Sun as an environmental factor is determined by the wavelength. Waves passing through the atmosphere and reaching the Earth are measured in the range from 0.3 to 10 microns.

According to the nature of the impact on living organisms, this spectrum of solar radiation is divided into three parts: ultraviolet radiation, visible light And infrared radiation.

shortwave ultraviolet rays almost completely absorbed by the atmosphere, namely its ozone layer. A small amount of ultraviolet rays penetrates the earth's surface. The length of their waves lies in the range of 0.3-0.4 microns. They account for 7% of the energy of solar radiation. Shortwave rays have a detrimental effect on living organisms. They can cause changes in hereditary material - mutations. Therefore, in the process of evolution, organisms that are under the influence of solar radiation for a long time have developed adaptations to protect themselves from ultraviolet rays. In many of them, an additional amount of black pigment, melanin, is produced in the integument, which protects against the penetration of unwanted rays. That is why people get tanned by being outdoors for a long time. In many industrial regions there is a so-called industrial melanism- darkening of the color of animals. But this does not happen under the influence of ultraviolet radiation, but due to pollution with soot, environmental dust, the elements of which usually become darker. Against such a dark background, darker forms of organisms survive (well masked).

visible light manifests itself within the wavelength range from 0.4 to 0.7 microns. It accounts for 48% of the energy of solar radiation.

It also adversely affects living cells and their functions in general: it changes the viscosity of the protoplasm, the magnitude of the electrical charge of the cytoplasm, disrupts the permeability of membranes and changes the movement of the cytoplasm. Light affects the state of protein colloids and the flow of energy processes in cells. But despite this, visible light was, is and will continue to be one of the most important sources of energy for all living things. Its energy is used in the process photosynthesis and accumulates in the form of chemical bonds in the products of photosynthesis, and then is transmitted as food to all other living organisms. In general, we can say that all living things in the biosphere, and even humans, depend on solar energy, on photosynthesis.

Light for animals is a necessary condition for the perception of information about the environment and its elements, vision, visual orientation in space. Depending on the conditions of existence, animals have adapted to varying degrees of illumination. Some animal species are diurnal, while others are most active at dusk or at night. Most mammals and birds lead a twilight lifestyle, do not distinguish colors well and see everything in black and white (dogs, cats, hamsters, owls, nightjars, etc.). Life in twilight or in low light often leads to hypertrophy of the eyes. Relatively huge eyes capable of capturing an insignificant fraction of the light characteristic of nocturnal animals or those that live in complete darkness and are guided by the organs of luminescence of other organisms (lemurs, monkeys, owls, deep-sea fish, etc.). If, in conditions of complete darkness (in caves, underground in burrows), there are no other sources of light, then the animals living there, as a rule, lose their organs of vision (European proteus, mole rat, etc.).

Temperature.

The sources of the creation of the temperature factor on Earth are solar radiation and geothermal processes. Although the core of our planet is characterized by an extremely high temperature, its influence on the surface of the planet is insignificant, except for the zones of volcanic activity and the release of geothermal waters (geysers, fumaroles). Consequently, solar radiation, namely, infrared rays, can be considered the main source of heat within the biosphere. Those rays that reach the Earth's surface are absorbed by the lithosphere and hydrosphere. The lithosphere, as a solid body, heats up faster and cools just as quickly. The hydrosphere is more heat-capacious than the lithosphere: it heats up slowly and cools slowly, and therefore retains heat for a long time. The surface layers of the troposphere are heated due to the radiation of heat from the hydrosphere and the surface of the lithosphere. The earth absorbs solar radiation and radiates energy back into the airless space. Nevertheless, the Earth's atmosphere contributes to the retention of heat in the surface layers of the troposphere. Due to its properties, the atmosphere transmits short-wave infrared rays and delays long-wave infrared rays emitted by the heated surface of the Earth. This atmospheric phenomenon is called greenhouse effect. It was thanks to him that life on Earth became possible. The greenhouse effect helps to retain heat in the surface layers of the atmosphere (most organisms are concentrated here) and smooths out temperature fluctuations during the day and night. On the Moon, for example, which is located in almost the same space conditions as the Earth, and on which there is no atmosphere, daily temperature fluctuations at its equator appear in the range from 160 ° C to + 120 ° C.

The range of temperatures available in the environment reaches thousands of degrees (hot volcanic magma and the lowest temperatures of Antarctica). The limits within which life known to us can exist are quite narrow and equal to approximately 300 ° C, from -200 ° C (freezing in liquefied gases) to + 100 ° C (boiling point of water). In fact, most species and much of their activity is tied to an even narrower range of temperatures. The general temperature range of active life on Earth is limited by the following temperatures (Table 1.2.3):

Table 1.2.3 Temperature range of life on Earth

Plants adapt to different temperatures and even extreme ones. Those that tolerate high temperatures are called fertile plants. They are able to tolerate overheating up to 55-65 ° C (some cacti). Species growing at high temperatures tolerate them more easily due to a significant shortening of the size of the leaves, the development of a felt (pubescent) or, conversely, wax coating, etc. Plants without prejudice to their development are able to withstand prolonged exposure to low temperatures (from 0 to -10 ° C) are called cold-resistant.

Although temperature is an important environmental factor affecting living organisms, its effect is highly dependent on the combination with other abiotic factors.

Humidity.

Humidity is an important abiotic factor that is determined by the presence of water or water vapor in the atmosphere or lithosphere. Water itself is a necessary inorganic compound for the life of living organisms.

Water is always present in the atmosphere in the form water couples. The actual mass of water per unit volume of air is called absolute humidity, and the percentage of vapor relative to the maximum amount that air can contain, - relative humidity. Temperature is the main factor affecting the ability of air to hold water vapor. For example, at a temperature of +27°C, the air can contain twice as much moisture as at a temperature of +16°C. This means that the absolute humidity at 27°C is 2 times greater than at 16°C, while the relative humidity in both cases will be 100%.

Water as an ecological factor is extremely necessary for living organisms, because without it metabolism and many other related processes cannot be carried out. The metabolic processes of organisms take place in the presence of water (in aqueous solutions). All living organisms are open systems, so they are constantly losing water and there is always a need to replenish its reserves. For a normal existence, plants and animals must maintain a certain balance between the intake of water in the body and its loss. Large loss of body water (dehydration) lead to a decrease in its vital activity, and in the future - to death. Plants satisfy their water needs through precipitation, air humidity, and animals also through food. The resistance of organisms to the presence or absence of moisture in the environment is different and depends on the adaptability of the species. In this regard, all terrestrial organisms are divided into three groups: hygrophilic(or moisture-loving), mesophilic(or moderately moisture-loving) and xerophilic(or dry-loving). Regarding plants and animals separately, this section will look like this:

1) hygrophilic organisms:

- hygrophytes(plants);

- hygrophiles(animal);

2) mesophilic organisms:

- mesophytes(plants);

- mesophiles(animal);

3) xerophilic organisms:

- xerophytes(plants);

- xerophiles, or hygrophobia(animals).

Need the most moisture hygrophilous organisms. Among plants, these will be those that live on excessively moist soils with high air humidity (hygrophytes). In the conditions of the middle zone, they include among herbaceous plants that grow in shaded forests (sour, ferns, violets, gap-grass, etc.) and in open places (marigold, sundew, etc.).

Hygrophilous animals (hygrophiles) include those ecologically associated with the aquatic environment or with waterlogged areas. They need a constant presence of a large amount of moisture in the environment. These are animals of tropical rainforests, swamps, wet meadows.

mesophilic organisms require moderate amounts of moisture and are usually associated with moderate warm conditions and good mineral nutrition conditions. It can be forest plants and plants of open places. Among them there are trees (linden, birch), shrubs (hazel, buckthorn) and even more herbs (clover, timothy, fescue, lily of the valley, hoof, etc.). In general, mesophytes are a broad ecological group of plants. To mesophilic animals (mesophiles) belongs to the majority of organisms that live in temperate and subarctic conditions or in certain mountainous land regions.

xerophilic organisms - This is a fairly diverse ecological group of plants and animals that have adapted to arid conditions of existence with the help of such means: limiting evaporation, increasing the extraction of water and creating water reserves for a long period of lack of water supply.

Plants living in arid conditions overcome them in different ways. Some do not have structural adaptations to carry the lack of moisture. their existence is possible in arid conditions only due to the fact that at a critical moment they are at rest in the form of seeds (ephemeris) or bulbs, rhizomes, tubers (ephemeroids), they very easily and quickly switch to active life and in a short period of time completely pass annual cycle of development. Efemeri mainly distributed in deserts, semi-deserts and steppes (stonefly, spring ragwort, turnip "box, etc.). Ephemeroids(from Greek. ephemeri And to look like)- these are perennial herbaceous, mainly spring, plants (sedges, grasses, tulips, etc.).

A very peculiar category of plants that have adapted to endure drought conditions is succulents And sclerophytes. Succulents (from the Greek. juicy) are able to accumulate a large amount of water in themselves and gradually use it. For example, some cacti of the North American deserts can contain from 1000 to 3000 liters of water. Water accumulates in leaves (aloe, stonecrop, agave, young) or stems (cacti and cactus-like spurges).

Animals obtain water in three main ways: directly by drinking or absorbing through the integument, along with food and as a result of metabolism.

Many species of animals drink water and in large enough quantities. For example, caterpillars of the Chinese oak silkworm can drink up to 500 ml of water. Some species of animals and birds require regular water consumption. Therefore, they choose certain springs and regularly visit them as watering places. Desert bird species fly daily to the oases, drink water there and bring water to their chicks.

Some animal species do not consume water by direct drinking, but can consume it by absorbing it with the entire surface of the skin. In insects and larvae that live in soil moistened with tree dust, their integuments are permeable to water. The Australian Moloch lizard absorbs rainfall moisture with its skin, which is extremely hygroscopic. Many animals get moisture from succulent food. Such succulent foods can be grass, succulent fruits, berries, bulbs and tubers of plants. The steppe tortoise living in the Central Asian steppes consumes water only from succulent food. In these regions, in places where vegetables are planted or on melons, turtles cause great damage by eating melons, watermelons, and cucumbers. Some predatory animals also get water by eating their prey. This is typical, for example, of the African fennec fox.

Species that feed exclusively on dry food and do not have the opportunity to consume water get it through metabolism, that is, chemically during the digestion of food. Metabolic water can be formed in the body due to the oxidation of fats and starch. This is an important way of obtaining water, especially for animals that inhabit hot deserts. For example, the red-tailed gerbil sometimes feeds only on dry seeds. Experiments are known when, in captivity, the North American deer mouse lived for about three years, eating only dry grains of barley.

food factors.

The surface of the Earth's lithosphere constitutes a separate living environment, which is characterized by its own set of environmental factors. This group of factors is called edaphic(from Greek. edafos- soil). Soils have their own structure, composition and properties.

Soils are characterized by a certain moisture content, mechanical composition, content of organic, inorganic and organo-mineral compounds, a certain acidity. Many properties of the soil itself and the distribution of living organisms in it depend on the indicators.

For example, certain types of plants and animals love soils with a certain acidity, namely: sphagnum mosses, wild currants, alders grow on acidic soils, and green forest mosses grow on neutral ones.

Beetle larvae, terrestrial mollusks and many other organisms also react to a certain acidity of the soil.

The chemical composition of the soil is very important for all living organisms. For plants, the most important are not only those chemical elements that they use in large quantities (nitrogen, phosphorus, potassium and calcium), but also those that are rare (trace elements). Some of the plants selectively accumulate certain rare elements. Cruciferous and umbrella plants, for example, accumulate 5-10 times more sulfur in their body than other plants.

Excess content of certain chemical elements in the soil can negatively (pathologically) affect animals. For example, in one of the valleys of Tuva (Russia), it was noticed that sheep were suffering from some specific disease, which manifested itself in hair loss, deformation of hooves, etc. Later it turned out that in this valley in the soil, water and some plants there was high selenium content. Getting into the body of sheep in excess, this element caused chronic selenium toxicosis.

The soil has its own thermal regime. Together with moisture, it affects soil formation, various processes taking place in the soil (physico-chemical, chemical, biochemical and biological).

Due to their low thermal conductivity, soils are able to smooth out temperature fluctuations with depth. At a depth of just over 1 m, daily temperature fluctuations are almost imperceptible. For example, in the Karakum Desert, which is characterized by a sharply continental climate, in summer, when the soil surface temperature reaches +59°C, in the burrows of gerbil rodents at a distance of 70 cm from the entrance, the temperature was 31°C lower and amounted to +28°C. In winter, during a frosty night, the temperature in the burrows of gerbils was +19°C.

The soil is a unique combination of physical and chemical properties of the surface of the lithosphere and the living organisms that inhabit it. The soil cannot be imagined without living organisms. No wonder the famous geochemist V.I. Vernadsky called the soil bio-inert body.

Orographic factors (relief).

The relief does not refer to such directly acting environmental factors as water, light, heat, soil. However, the nature of the relief in the life of many organisms has an indirect effect.

Depending on the size of the forms, the relief of several orders is rather conventionally distinguished: macrorelief (mountains, lowlands, intermountain depressions), mesorelief (hills, ravines, ridges, etc.) and microrelief (small depressions, irregularities, etc.). Each of them plays a certain role in the formation of a complex of environmental factors for organisms. In particular, relief affects the redistribution of factors such as moisture and heat. So, even slight depressions, a few tens of centimeters, create conditions of high humidity. From elevated areas, water flows into lower areas, where favorable conditions are created for moisture-loving organisms. The northern and southern slopes have different lighting and thermal conditions. In mountainous conditions, significant amplitudes of heights are created in relatively small areas, which leads to the formation of various climatic complexes. In particular, their typical features are low temperatures, strong winds, changes in the humidification regime, the gas composition of the air, etc.

For example, with rise above sea level, the air temperature drops by 6 ° C for every 1000 m. Although this is a characteristic of the troposphere, but due to the relief (highlands, mountains, mountain plateaus, etc.), terrestrial organisms may find themselves in conditions that are not similar to those in neighboring regions. For example, the mountainous volcanic massif of Kilimanjaro in Africa at the foot is surrounded by savannahs, and higher up the slopes are plantations of coffee, bananas, forests and alpine meadows. The peaks of Kilimanjaro are covered with eternal snow and glaciers. If the air temperature at sea level is +30°C, then negative temperatures will already appear at an altitude of 5000 m. In temperate zones, a decrease in temperature for every 6°C corresponds to a movement of 800 km towards high latitudes.

Pressure.

Pressure is manifested in both air and water environments. In atmospheric air, the pressure varies seasonally, depending on the state of the weather and the height above sea level. Of particular interest are the adaptations of organisms that live in conditions of low pressure, rarefied air in the highlands.

The pressure in the aquatic environment varies depending on the depth: it grows by about 1 atm for every 10 m. For many organisms, there are limits to the change in pressure (depth) to which they have adapted. For example, abyssal fish (fish of the deep world) are able to endure great pressure, but they never rise to the surface of the sea, because for them it is fatal. Conversely, not all marine organisms are capable of diving to great depths. The sperm whale, for example, can dive to a depth of 1 km, and seabirds - up to 15-20 m, where they get their food.

Living organisms on land and aquatic environment clearly respond to pressure changes. At one time it was noted that fish can perceive even slight changes in pressure. their behavior changes when atmospheric pressure changes (eg, before a thunderstorm). In Japan, some fish are specially kept in aquariums and the change in their behavior is used to judge possible changes in the weather.

Terrestrial animals, perceiving slight changes in pressure, can predict changes in the state of the weather with their behavior.

Pressure unevenness, which is the result of uneven heating by the Sun and heat distribution both in water and in atmospheric air, creates conditions for mixing water and air masses, i.e. the formation of currents. Under certain conditions, the flow is a powerful environmental factor.

hydrological factors.

Water as an integral part of the atmosphere and lithosphere (including soil) plays an important role in the life of organisms as one of the environmental factors, which is called humidity. At the same time, water in the liquid state can be a factor that forms its own environment - water. Due to its properties, which distinguish water from all other chemical compounds, it in a liquid and free state creates a set of conditions for the aquatic environment, the so-called hydrological factors.

Such characteristics of water as thermal conductivity, fluidity, transparency, salinity manifest themselves in different ways in water bodies and are environmental factors, which in this case are called hydrological. For example, aquatic organisms have adapted differently to varying degrees of water salinity. Distinguish between freshwater and marine organisms. Freshwater organisms do not amaze with their species diversity. Firstly, life on Earth originated in sea waters, and secondly, fresh water bodies occupy a tiny part of the earth's surface.

Marine organisms are more diverse and quantitatively more numerous. Some of them have adapted to low salinity and live in desalinated areas of the sea and other brackish water bodies. In many species of such reservoirs, a decrease in body size is observed. So, for example, the shells of mollusks, edible mussel (Mytilus edulis) and Lamarck's heartworm (Cerastoderma lamarcki), which live in the bays of the Baltic Sea at a salinity of 2-6% o, are 2-4 times smaller than individuals that live in the same sea, only at a salinity of 15% o. The crab Carcinus moenas is small in the Baltic Sea, while it is much larger in desalinated lagoons and estuaries. Sea urchins grow smaller in lagoons than in the sea. The crustacean Artemia (Artemia salina) at a salinity of 122% o has a size of up to 10 mm, but at 20% o it grows to 24-32 mm. Salinity can also affect life expectancy. The same Lamarck's heartworm in the waters of the North Atlantic lives up to 9 years, and in the less saline waters of the Sea of ​​\u200b\u200bAzov - 5.

The temperature of bodies of water is a more constant indicator than the temperature of land. This is due to the physical properties of water (heat capacity, thermal conductivity). The amplitude of annual temperature fluctuations in the upper layers of the ocean does not exceed 10-15 ° C, and in continental waters - 30-35 ° C. What can we say about the deep layers of water, which are characterized by a constant thermal regime.

biotic factors.

The organisms that live on our planet not only need abiotic conditions for their life, they interact with each other and are often very dependent on each other. The totality of factors of the organic world that affect organisms directly or indirectly is called biotic factors.

Biotic factors are very diverse, but despite this, they also have their own classification. According to the simplest classification, biotic factors are divided into three groups, which are caused by plants, animals and microorganisms.

Clements and Shelford (1939) proposed their own classification, which takes into account the most typical forms of interaction between two organisms - co-actions. All coactions are divided into two large groups, depending on whether organisms of the same species or two different ones interact. The types of interactions of organisms belonging to the same species is homotypic reactions. Heterotypic reactions name the forms of interaction between two organisms of different species.

homotypic reactions.

Among the interaction of organisms of the same species, the following coactions (interactions) can be distinguished: group effect, mass effect And intraspecific competition.

group effect.

Many living organisms that can live alone form groups. Often in nature you can observe how some species grow in groups plants. This gives them the opportunity to accelerate their growth. Animals are also grouped together. Under such conditions, they survive better. With a joint lifestyle, it is easier for animals to defend themselves, get food, protect their offspring, and survive adverse environmental factors. Thus, the group effect has a positive effect on all members of the group.

Groups in which animals are combined can be of different sizes. For example, cormorants, which form huge colonies on the coasts of Peru, can exist only if there are at least 10 thousand birds in the colony, and there are three nests per 1 square meter of territory. It is known that for the survival of African elephants, the herd must consist of at least 25 individuals, and the herd of reindeer - from 300-400 animals. A pack of wolves can number up to a dozen individuals.

Simple aggregations (temporary or permanent) can turn into complex groups consisting of specialized individuals that perform their own function in this group (families of bees, ants or termites).

Mass effect.

A mass effect is a phenomenon that occurs when a living space is overpopulated. Naturally, when united in groups, especially large ones, there is also some overpopulation, but there is a big difference between group and mass effects. The first gives advantages to each member of the association, and the other, on the contrary, suppresses the vital activity of all, that is, it has negative consequences. For example, the mass effect is manifested in the accumulation of vertebrates. If large numbers of experimental rats are kept in one cage, then acts of aggressiveness will appear in their behavior. With prolonged keeping of animals in such conditions, embryos dissolve in pregnant females, aggressiveness increases so much that rats gnaw off each other's tails, ears, and limbs.

The mass effect of highly organized organisms leads to a stressful state. In humans, this can cause mental disorders and nervous breakdowns.

Intraspecific competition.

Between individuals of the same species there is always a kind of competition in obtaining the best living conditions. The greater the population density of a particular group of organisms, the more intense the competition. Such competition of organisms of the same species among themselves for certain conditions of existence is called intraspecific competition.

Mass effect and intraspecific competition are not identical concepts. If the first phenomenon occurs for a relatively short time and subsequently ends with a rarefaction of the group (mortality, cannibalism, reduced fertility, etc.), then intraspecific competition exists constantly and ultimately leads to a wider adaptation of the species to environmental conditions. The species becomes more ecologically adapted. As a result of intraspecific competition, the species itself is preserved and does not destroy itself as a result of such a struggle.

Intraspecific competition can manifest itself in anything that organisms of the same species can claim. In plants that grow densely, competition may occur for light, mineral nutrition, etc. For example, an oak tree, when it grows alone, has a spherical crown, it is quite spreading, since the lower side branches receive a sufficient amount of light. In oak plantations in the forest, the lower branches are shaded by the upper ones. Branches that receive insufficient light die off. As the oak grows in height, the lower branches quickly fall off, and the tree takes on a forest shape - a long cylindrical trunk and a crown of branches at the top of the tree.

In animals, competition arises for a certain territory, food, nesting sites, etc. It is easier for mobile animals to avoid tough competition, but it still affects them. As a rule, those that avoid competition often find themselves in unfavorable conditions, they are forced, like plants (or attached animal species), to adapt to the conditions with which they have to be content.

heterotypic reactions.

Table 1.2.4. Forms of interspecies interactions

0 - interaction between species does not benefit and does not harm either side;

Interactions between species produce positive consequences; -interaction between species has negative consequences.

Neutralism.

The most common form of interaction occurs when organisms of different species, occupying the same territory, do not affect each other in any way. A large number of species live in the forest, and many of them maintain neutral relationships. For example, a squirrel and a hedgehog inhabit the same forest, but they have a neutral relationship, like many other organisms. However, these organisms are part of the same ecosystem. They are elements of one whole, and therefore, with a detailed study, one can still find not direct, but indirect, rather subtle and imperceptible connections at first glance.

Eat. Doom, in his Popular Ecology, gives a playful but very apt example of such connections. He writes that in England old single women support the power of the royal guards. And the connection between guardsmen and women is quite simple. Single women, as a rule, breed cats, while cats hunt mice. The more cats, the less mice in the fields. Mice are enemies of bumblebees, because they destroy their holes where they live. The fewer mice, the more bumblebees. Bumblebees are not known to be the only pollinators of clover. More bumblebees in the fields - more clover harvest. Horses graze on clover, and the guardsmen like to eat horse meat. Behind such an example in nature, one can find many hidden connections between various organisms. Although in nature, as can be seen from the example, cats have a neutral relationship with horses or jmels, they are indirectly related to them.

Commensalism.

Many types of organisms enter into relationships that benefit only one side, while the other does not suffer from this and nothing is useful. This form of interaction between organisms is called commensalism. Commensalism often manifests itself in the form of coexistence of various organisms. So, insects often live in the burrows of mammals or in the nests of birds.

Often one can also observe such a joint settlement, when sparrows nest in the nests of large birds of prey or storks. For birds of prey, the neighborhood of sparrows does not interfere, but for the sparrows themselves, this is a reliable protection of their nests.

In nature, there is even a species that is named like that - the commensal crab. This small, graceful crab readily settles in the mantle cavity of oysters. By this, he does not interfere with the mollusk, but he himself receives a shelter, fresh portions of water and nutrient particles that get to him with water.

Protocooperation.

The next step in the joint positive co-action of two organisms of different species is protocooperation, in which both species benefit from interaction. Naturally, these species can exist separately without any losses. This form of interaction is also called primary cooperation, or cooperation.

In the sea, such a mutually beneficial, but not obligatory, form of interaction arises when crabs and intestinales are combined. Anemones, for example, often take up residence on the dorsal side of crabs, camouflaging and protecting them with their stinging tentacles. In turn, the sea anemones receive from the crabs the bits of food left over from their meal, and use the crabs as a vehicle. Both crabs and sea anemones are able to freely and independently exist in the reservoir, but when they are nearby, the crab, even with its claws, transplants the sea anemones onto itself.

The joint nesting of birds of different species in the same colony (herons and cormorants, waders and terns of different species, etc.) is also an example of cooperation in which both parties benefit, for example, in protection from predators.

Mutualism.

Mutualism (or obligate symbiosis) is the next stage of mutually beneficial adaptation of different species to each other. It differs from protocooperation in its dependency. If, under protocooperation, the organisms that enter into a relationship can exist separately and independently of each other, then under mutualism, the existence of these organisms separately is impossible.

This type of coaction often occurs in quite different organisms, systematically remote, with different needs. An example of this would be the relationship between nitrogen-fixing bacteria (bubble bacteria) and legumes. Substances secreted by the root system of legumes stimulate the growth of bubble bacteria, and the waste products of bacteria lead to deformation of the root hairs, which begins the formation of bubbles. Bacteria have the ability to assimilate atmospheric nitrogen, which is deficient in the soil but an essential macronutrient for plants, which in this case is of great benefit to leguminous plants.

In nature, the relationship between fungi and plant roots is quite common, called mycorrhiza. The fungus, interacting with the tissues of the root, forms a kind of organ that helps the plant more effectively absorb minerals from the soil. Mushrooms from this interaction receive the products of photosynthesis of the plant. Many types of trees cannot grow without mycorrhiza, and certain types of fungi form mycorrhiza with the roots of certain types of trees (oak and porcini, birch and boletus, etc.).

A classic example of mutualism is lichens, which combine the symbiotic relationship of fungi and algae. The functional and physiological connections between them are so close that they are considered as a separate group organisms. The fungus in this system provides the algae with water and mineral salts, and the algae, in turn, gives the fungus organic substances that it synthesizes itself.

Amensalism.

In the natural environment, not all organisms positively influence each other. There are many cases when one species harms another in order to ensure its life. This form of coaction, in which one type of organism suppresses the growth and reproduction of an organism of another species without losing anything, is called amensalism (antibiosis). The suppressed species in a pair that interacts is called amensalom, and the one who suppresses - inhibitor.

Amensalism is best studied in plants. In the process of life, plants release chemicals into the environment, which are factors influencing other organisms. Regarding plants, amensalism has its own name - allelopathy. It is known that, due to the excretion of toxic substances by the roots, the Volokhatensky nechuiweter displaces other annual plants and forms continuous single-species thickets over large areas. In fields, wheatgrass and other weeds crowd out or overwhelm crops. Walnut and oak oppress grassy vegetation under their crowns.

Plants can secrete allelopathic substances not only by their roots, but also by the aerial part of their body. Volatile allelopathic substances released by plants into the air are called phytoncides. Basically, they have a destructive effect on microorganisms. Everyone is well aware of the antimicrobial preventive effect of garlic, onion, horseradish. Many phytoncides are produced by coniferous trees. One hectare of common juniper plantations produces more than 30 kg of phytoncides per year. Often conifers are used in settlements to create sanitary protection belts around various industries, which helps to purify the air.

Phytoncides negatively affect not only microorganisms, but also animals. In everyday life, various plants have long been used to fight insects. So, baglitsa and lavender are a good way to fight moths.

Antibiosis is also known in microorganisms. Its first time was opened By. Babesh (1885) and rediscovered by A. Fleming (1929). Penicil fungi have been shown to secrete a substance (penicillin) that inhibits bacterial growth. It is widely known that some lactic acid bacteria acidify their environment so that putrefactive bacteria that need an alkaline or neutral environment cannot exist in it. The allelopathic chemicals of microorganisms are known as antibiotics. Over 4 thousand antibiotics have already been described, but only about 60 of their varieties are widely used in medical practice.

Protection of animals from enemies can also be carried out by isolating substances that have an unpleasant odor (for example, among reptiles - vulture turtles, snakes; birds - hoopoe chicks; mammals - skunks, ferrets).

Predation.

Theft in the broad sense of the word is considered to be a way of obtaining food and feeding animals (sometimes plants), in which they catch, kill and eat other animals. Sometimes this term is understood as any eating of some organisms by others, i.e. relationships between organisms in which one uses the other as food. With this understanding, the hare is a predator in relation to the grass that it consumes. But we will use a narrower understanding of predation, in which one organism feeds on another, which is close to the first in a systematic way (for example, insects that feed on insects; fish that feed on fish; birds that feed on reptiles, birds and mammals; mammals, that feed on birds and mammals). An extreme case of predation, in which a species feeds on organisms of its own species, is called cannibalism.

Sometimes a predator selects a prey in such quantity that it does not negatively affect the size of its population. By this, the predator contributes to a better state of the prey population, which, moreover, has already adapted to the pressure of the predator. The birth rate in the populations of the prey is higher than is required for the usual maintenance of its numbers. Figuratively speaking, the prey population takes into account what the predator must select.

Interspecies competition.

Between organisms of different species, as well as between organisms of the same species, interactions arise due to which they try to get the same resource. Such co-actions between different species are called interspecific competition. In other words, we can say that interspecific competition is any interaction between populations of different species that adversely affects their growth and survival.

The consequences of such competition may be the displacement of one organism by another from a certain ecological system (the principle of competitive exclusion). At the same time, competition promotes the emergence of many adaptations through selection, which leads to the diversity of species that exist in a particular community or region.

Competitive interaction may involve space, food or nutrients, light, and many other factors. Interspecific competition, depending on what it is based on, can lead either to the establishment of an equilibrium between two species, or, with more intense competition, to the replacement of a population of one species by a population of another. Also, the result of competition may be such that one species will displace the other in a different place or force it to move to other resources.

Environmental factor - a condition of the environment that affects the body. The environment includes all bodies and phenomena with which the organism is in direct or indirect relations.

One and the same environmental factor has a different meaning in the life of cohabiting organisms. For example, the salt regime of the soil plays a primary role in the mineral nutrition of plants, but is indifferent to most land animals. The intensity of illumination and the spectral composition of light are extremely important in the life of phototrophic plants, while in the life of heterotrophic organisms (fungi and aquatic animals), light does not have a noticeable effect on their vital activity.

Environmental factors act on organisms in different ways. They can act as stimuli causing adaptive changes in physiological functions; as constraints that make it impossible for certain organisms to exist under given conditions; as modifiers that determine morphological and anatomical changes in organisms.

Classification of environmental factors

It is customary to single out biotic, anthropogenic and abiotic environmental factors.

Biotic factors are the whole set of environmental factors associated with the activity of living organisms. These include phytogenic (plants), zoogenic (animals), microbiogenic (microorganisms) factors.

Anthropogenic factors - the whole set of factors associated with human activity. These include physical (use of atomic energy, travel in trains and planes, the impact of noise and vibration, etc.), chemical (use of mineral fertilizers and pesticides, pollution of the Earth's shells with industrial and transport waste; smoking, alcohol and drug use, excessive use of medicinal funds [source not specified 135 days]), biological (food; organisms for which a person can be a habitat or source of food), social (related to human relations and life in society) factors.

Abiotic factors are the whole set of factors associated with processes in inanimate nature. These include climatic (temperature, humidity, pressure), edaphogenic (mechanical composition, air permeability, soil density), orographic (relief, altitude), chemical (gas composition of air, salt composition of water, concentration, acidity), physical (noise, magnetic fields, thermal conductivity, radioactivity, cosmic radiation)

A common classification of environmental factors (environmental factors)

BY TIME: evolutionary, historical, current

BY PERIODICITY: periodic, non-periodic

IN ORDER OF APPEARANCE: primary, secondary

BY ORIGIN: cosmic, abiotic (aka abiogenic), biogenic, biological, biotic, natural-anthropogenic, anthropogenic (including technogenic, environmental pollution), anthropogenic (including disturbances)

BY THE ENVIRONMENT OF APPEARANCE: atmospheric, water (aka humidity), geo-morphological, edaphic, physiological, genetic, population, biocenotic, ecosystem, biospheric

BY CHARACTER: material-energy, physical (geophysical, thermal), biogenic (aka biotic), informational, chemical (salinity, acidity), complex (environmental, evolutionary, backbone, geographical, climatic)

BY OBJECT: individual, group (social, ethological, socio-economic, socio-psychological, species (including human, society life)

BY MEDIA CONDITIONS: density-dependent, density-independent

BY DEGREE OF IMPACT: lethal, extreme, limiting, disturbing, mutagenic, teratogenic; carcinogenic

ACCORDING TO THE SPECTRUM OF IMPACT: selective, general action

3. Patterns of the action of environmental factors on the body

The reaction of organisms to the influence of abiotic factors. The impact of environmental factors on a living organism is very diverse. Some factors have a stronger influence, others are weaker; some affect all aspects of life, others - on a specific life process. Nevertheless, in the nature of their impact on the body and in the responses of living beings, a number of general patterns can be identified that fit into some general scheme of the action of the environmental factor on the vital activity of the organism (Fig. 14.1).

On fig. 14.1, the intensity (or “dose”) of the factor (for example, temperature, illumination, salt concentration in soil solution, pH or soil moisture, etc.) is plotted along the abscissa axis, and the body’s response to the impact of the environmental factor in its quantitative expression (for example, the intensity of photosynthesis, respiration, growth rate, productivity, number of individuals per unit area, etc.), i.e., the degree of beneficialness of the factor.

The range of action of the ecological factor is limited by the corresponding extreme threshold values ​​(minimum and maximum points), at which the existence of an organism is still possible. These points are called the lower and upper limits of endurance (tolerance) of living beings in relation to a particular environmental factor.

Point 2 on the abscissa axis, corresponding to the best indicators of the vital activity of the organism, means the most favorable value of the influencing factor for the organism - this is the optimum point. For most organisms, it is often difficult to determine the optimal value of the factor with sufficient accuracy, so it is customary to talk about the optimum zone. The extreme sections of the curve, expressing the state of oppression of organisms with a sharp deficiency or excess of the factor, are called areas of pessimum or stress. The sublethal values ​​of the factor lie near the critical points, and the lethal values ​​lie outside the survival zone.

Such a regularity of the reaction of organisms to the impact of environmental factors allows us to consider it as a fundamental biological principle: for each species of plants and animals there is an optimum, a zone of normal life, pessimal zones and limits of endurance in relation to each environmental factor.

Different types of living organisms differ markedly from each other both in the position of the optimum and in the limits of endurance. For example, arctic foxes in the tundra can tolerate fluctuations in air temperature in the range of about 80°С (from +30 to -55°С), some warm-water crustaceans withstand changes in water temperature in the range of no more than 6°С (from 23 to 29°С), the filamentous cyanobacterium oscillatoria, living on the island of Java in water with a temperature of 64 ° C, dies at 68 ° C after 5-10 minutes. In the same way, some meadow grasses prefer soils with a rather narrow range of acidity - at pH = 3.5-4.5 (for example, common heather, white-backed protruding, small sorrel serve as indicators of acidic soils), others grow well in a wide range of pH - from strongly acidic to alkaline (e.g. Scotch pine). In this regard, organisms whose existence requires strictly defined, relatively constant environmental conditions are called stenobiont (Greek stenos - narrow, bion - living), and those that live in a wide range of environmental variability are called eurybiont (Greek eurys - wide). At the same time, organisms of the same species can have a narrow amplitude with respect to one factor and a wide amplitude with respect to another (for example, adaptability to a narrow temperature range and a wide range of water salinity). In addition, the same dose of a factor can be optimal for one species, pessimal for another, and go beyond endurance limits for a third.

The ability of organisms to adapt to a certain range of variability of environmental factors is called ecological plasticity. This feature is one of the most important properties of all living things: by regulating their vital activity in accordance with changes in environmental conditions, organisms acquire the ability to survive and leave offspring. This means that eurybiont organisms are ecologically the most plastic, which ensures their wide distribution, while stenobiont organisms, on the contrary, are characterized by poor ecological plasticity and, as a result, usually have limited distribution areas.

Interaction of environmental factors. limiting factor. Environmental factors affect a living organism jointly and simultaneously. At the same time, the effect of one factor depends on the strength and combination of other factors acting simultaneously. This pattern is called the interaction of factors. For example, heat or frost is easier to bear in dry rather than moist air. The rate of evaporation of water from plant leaves (transpiration) is much higher if the air temperature is high and the weather is windy.

In some cases, the lack of one factor is partially compensated by the strengthening of another. The phenomenon of partial interchangeability of environmental factors is called the compensation effect. For example, the wilting of plants can be stopped both by increasing the amount of moisture in the soil and by lowering the air temperature, which reduces transpiration; in deserts, the lack of precipitation is compensated to a certain extent by increased relative humidity at night; in the Arctic, long daylight hours in summer compensate for the lack of heat.

At the same time, none of the environmental factors necessary for the body can be completely replaced by another. The absence of light makes plant life impossible, despite the most favorable combination of other conditions. Therefore, if the value of at least one of the vital environmental factors approaches a critical value or goes beyond it (below the minimum or above the maximum), then, despite the optimal combination of other conditions, individuals are threatened with death. Such factors are called limiting (limiting).

The nature of the limiting factors may be different. For example, the suppression of herbaceous plants under the canopy of beech forests, where, with optimal thermal conditions, high carbon dioxide content, and rich soils, the possibilities for grass development are limited by a lack of light. This result can only be changed by influencing the limiting factor.

Environmental limiting factors determine the geographic range of a species. Thus, the advancement of the species to the north can be limited by a lack of heat, and to areas of deserts and dry steppes - by a lack of moisture or too high temperatures. Biotic relations can also serve as a factor limiting the distribution of organisms, for example, the occupation of the territory by a stronger competitor or the lack of pollinators for flowering plants.

The identification of limiting factors and the elimination of their action, i.e., the optimization of the habitat of living organisms, is an important practical goal in increasing crop yields and the productivity of domestic animals.

Tolerance limit (lat. tolerantio - patience) - the range of the environmental factor between the minimum and maximum values, within which the survival of the organism is possible.

4. The law of the limiting (limiting) factor or Liebig's law of the minimum is one of the fundamental laws in ecology, which states that the most significant factor for the organism is the one that most of all deviates from its optimal value. Therefore, during the forecasting of environmental conditions or the performance of examinations, it is very important to determine the weak link in the life of organisms.

The survival of the organism depends on this, minimally (or maximally) presented at a given particular moment, the ecological factor. In other periods of time, other factors may be limiting. In the course of their lives, individuals of species meet with a variety of restrictions on their vital activity. So, the factor limiting the distribution of deer is the depth of the snow cover; butterflies of the winter scoop (a pest of vegetables and grain crops) - winter temperature, etc.

This law is taken into account in the practice of agriculture. The German chemist Justus Liebig found that the productivity of cultivated plants primarily depends on the nutrient (mineral element) that is least represented in the soil. For example, if phosphorus in the soil is only 20% of the required rate, and calcium is 50% of the rate, then the limiting factor will be a lack of phosphorus; First of all, it is necessary to introduce phosphorus-containing fertilizers into the soil.

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