The most significant group of factors at present, intensively changing the environment, is directly related to the many-sided human activity.
Human development on the planet has always been associated with environmental impact, but today this process has accelerated significantly.
Anthropogenic factors include any impact (both direct and indirect) of a person on the environment - organisms, biogeocenoses, landscapes,.
By remaking nature and adapting it to his needs, man changes the habitat of animals and plants, thereby influencing their life. Impact can be direct, indirect and accidental.
Direct impact directed directly at living organisms. For example, unsustainable fishing and hunting have dramatically reduced the number of species. The growing force and the accelerated pace of changes in nature by man make it necessary to protect it.
Indirect impact carried out by changing landscapes, climate, physical condition and the chemistry of the atmosphere and water bodies, the structure of the earth's surface, soils, vegetation and fauna. A person consciously and unconsciously destroys or displaces some types of plants and animals, spreads others or creates favorable conditions for them. For cultivated plants and domestic animals, man has created a largely new environment, multiplying the productivity of the developed lands. But this ruled out the possibility of the existence of many wild species.
In fairness, it should be said that many species of animals and plants disappeared from the face of the Earth even without human intervention. Each species, like a separate organism, has its own youth, flowering, old age and death - a natural process. But in nature this happens slowly, and usually the outgoing species have time to be replaced by new ones, more adapted to the habitat conditions. Man, on the other hand, accelerated the process of extinction to such a rate that evolution gave way to revolutionary, irreversible transformations.
Anthropogenic factors - combination of factors environment caused by accidental or deliberate human activity during the period of its existence.
Types of anthropogenic factors:
· physical - usage atomic energy, movement in trains and airplanes, the influence of noise and vibration, etc .;
· chemical - usage mineral fertilizers and pesticides, pollution of the Earth's shells with industrial and transport waste; smoking, alcohol and drug use, overuse of drugs;
· social - related to relationships between people and life in society.
In recent decades, the effect of anthropogenic factors has increased dramatically, which has led to the emergence of global environmental issues: greenhouse effect, acid rain, destruction of forests and desertification of territories, pollution of the environment with harmful substances, reduction biological diversity planets.
Human habitat. Anthropogenic factors affect the human environment. Since he is a biosocial creature, natural and social environment a habitat.
Natural habitat gives a person health and material for labor activity, is in close interaction with him: a person constantly changes the natural environment in the course of his activities; the transformed natural environment, in turn, affects humans.
A person communicates with other people all the time, entering into interpersonal relationships, which determines social habitat ... Communication can be favorable(contributing to personal development) and unfavorable(leading to psychological overload and breakdowns, to the acquisition of addictions - alcoholism, drug addiction, etc.).
Abiotic environment (environmental factors) - it is a complex of conditions of the inorganic environment that affect the body. (Light, temperature, wind, air, pressure, humidity, etc.)
For example: the accumulation of toxic and chemical elements in the soil, drying up of water bodies during a drought, an increase in the length of daylight hours, intense ultraviolet radiation.
ABIOTIC FACTORS, various factors not related to living organisms.
Light - the most important abiotic factor with which all life on Earth is connected. There are three biologically unequal areas in the spectrum of sunlight; ultraviolet, visible and infrared.
All plants in relation to light can be divided into the following groups:
■ light-loving plants - heliophytes(from the Greek "helios" - the sun and fiton - a plant);
■ shady plants - sciophytes(from the Greek "scia" - a shadow, and "fiton" - a plant);
■ shade-tolerant plants - facultative heliophytes.
Temperature on earth surface depends on the geographical latitude and altitude. In addition, it changes with the seasons of the year. In this regard, animals and plants have different adaptations to temperature conditions. In most organisms, vital processes proceed within the range from -4 ° С to + 40 ... 45 ° С
The most perfect thermoregulation appeared only in higher vertebrates - birds and mammals, providing them with a wide settlement in all climatic zones. They are called homeothermal (Greek. Gom oy about s - equal) organisms.
7. The concept of a population. Structure, system, characteristics and dynamics of populations. Homeostasis of populations.
9. The concept of an ecological niche. The competitive exclusion law of G.F. Gause.
ecological niche- this is the totality of all connections of a species with the habitat, which ensure the existence and reproduction of individuals of a given species in nature.
The term ecological niche was proposed in 1917 by J. Grinnell to characterize the spatial distribution of intraspecific ecological groups.
Initially, the concept of an ecological niche was close to that of a habitat. But in 1927 C. Elton defined the ecological niche as the position of the species in the community, emphasizing the special importance of trophic relations. Domestic ecologist GF Gause expanded this definition: an ecological niche is a place of a species in an ecosystem.
In 1984 S. Spurr and B. Barnes identified three components of a niche: spatial (where), temporal (when) and functional (how). This niche concept emphasizes the importance of both the spatial and temporal components of the niche, including its seasonal and daily changes, taking into account circus and circadian biorhythms.
A figurative definition of an ecological niche is often used: a habitat is the address of a species, and an ecological niche is its profession (Yu. Odum).
Competitive exclusion principle; (= Gause's theorem; = Gause's law)
The Gause exclusion principle - in ecology - is the law according to which two species cannot exist in the same locality if they occupy the same ecological niche.
In connection with this principle, when the possibilities of spatio-temporal separation are limited, one of the species develops a new ecological niche or disappears.
The principle of competitive exclusion contains two general provisions related to sympatric species:
1) if two species occupy the same ecological niche, then almost certainly one of them surpasses the other in this niche and will eventually displace the less adapted species. Or, more succinctly, “coexistence between complete competitors is impossible” (Hardin, 1960 *). The second position follows from the first;
2) if two species coexist in a state of stable equilibrium, then they must be ecologically differentiated so that they can occupy different niches. ,
The principle of competitive exclusion can be viewed in different ways: as an axiom and as an empirical generalization. If we consider it as an axiom, then it is logical, consistent and turns out to be very heuristic. If we consider it as an empirical generalization, it is valid within wide limits, but not universal.
Supplements
Interspecies competition can be observed in mixed laboratory populations or in natural communities. To do this, it is enough to artificially remove one species and see if there will be changes in the abundance of another sympatric species with similar ecological needs. If the number of this other species increases after the removal of the first species, then we can conclude that it was previously suppressed under the influence of interspecific competition.
This result was obtained in mixed laboratory populations of Paramecium aurelia and P. caudatum (Gause, 1934 *) and in natural littoral communities of barnacles (Chthamalus and Balanus) (Connell, 1961 *), as well as in a number of relatively recent studies, for example, on saccular jumpers and lungless salamanders (Lemen, Freeman, 1983; Hairston, 1983 *).
Interspecies competition manifests itself in two broad aspects, which can be called consumption competition and interference competition. The first aspect is the passive use of the same resource by different types.
For example, between different kinds shrubs in the desert community, passive or non-aggressive competition for limited soil moisture resources is highly likely. The species of Geospiza and other ground finches in the Galapagos Islands compete for food, and this competition is important factor, which determines their ecological and geographical distribution over several islands (Lack, 1947; B. R. Grant, P. R. Grant, 1982; P. R. Grant, 1986 *).
The second aspect, often superimposed on the first, is the direct suppression of one species by another competing species.
The leaves of some plant species produce substances that enter the soil and inhibit the germination and growth of neighboring plants (Muller, 1966; 1970; Whittaker and Feeny, 1971 *). In animals, suppression of one species by another can be achieved with the help of aggressive behavior or assertions of superiority based on threats of attack. In the Mojave Desert (California and Nevada), the native bighorn sheep (Ovis sapadensis) and the feral donkey (Equus asinus) compete for water and food. In direct collisions, donkeys dominate the rams: when donkeys approach water sources occupied by rams, the latter give way to them, and sometimes even leave the area altogether (Laycock, 1974; see also Monson, Summer, 1980 *).
Exploitative competition has received a lot of attention in theoretical ecology, but as Hairston (1983 *) points out, interference competition is probably more favorable for any given species.
10. Food chains, food webs, trophic levels. Ecological pyramids.
11. The concept of an ecosystem. Cyclic and directional changes in ecosystems. The structure and biological productivity of ecosystems.
12. Agroecosystems and their features. Stability and instability of ecosystems.
13. Ecosystems and biogeocenoses. V.N.Sukachev's theory of biogeocenology.
14. Dynamics and problems of ecosystem stability. Ecological succession: classification and types.
15. Biosphere as the highest level of organization of living systems. The boundaries of the biosphere.
Biosphere-organized, defined shell crust associated with life. " The basis of the concept of the biosphere is the concept of living matter. More than 90% of all living matter is accounted for by terrestrial vegetation.
The main source of biochemistry. The activity of organisms - solar energy used in the process of photosynthesis is green. Plants and some microorganisms. To create organic a substance that provides food and energy to other organisms. Photosynthesis led to the accumulation of free oxygen in the atmosphere, the formation of the ozone layer, which protects against ultraviolet and cosmic radiation. It maintains the modern gas composition of the atmosphere. Living organisms and their habitat form integral systems-biogeocenoses.
The highest level of organization of life on planet Earth is the biosphere. This term was introduced in 1875. For the first time it was used by the Austrian geologist E. Suess. However, the doctrine of the biosphere as a biological system appeared in the 20s of this century, its author is the Soviet scientist V.I. Vernadsky. The biosphere is the shell of the Earth in which living organisms have existed and exist, and in the formation of which they have played and play a major role. The biosphere has its own boundaries due to the spread of life. V.I. Vernadsky identified three spheres of life in the biosphere:
The atmosphere is the gaseous shell of the Earth. It is not all inhabited by life, its spread is prevented by ultraviolet radiation. The boundary of the biosphere in the atmosphere is located at an altitude of about 25-27 km, where the ozone layer is located, which absorbs about 99% of ultraviolet rays. The most populated is the surface layer of the atmosphere (1-1.5 km, and in the mountains up to 6 km above sea level).
The lithosphere is the solid shell of the Earth. It is also not completely inhabited by living organisms. Distributed
Life here is limited by temperature, which gradually increases with depth and upon reaching 100 ° C causes the transition of water from a liquid to a gaseous state. The maximum depth at which living organisms are found in the lithosphere is 4 - 4.5 km. This is the boundary of the biosphere in the lithosphere.
3. The hydrosphere is the liquid shell of the Earth. It is completely populated with life. Vernadsky drew the boundary of the biosphere in the hydrosphere below the ocean floor, because the bottom is a product of the vital activity of living organisms.
The biosphere is a gigantic biological system that includes a huge variety of constituent components, which are extremely difficult to characterize individually. Vernadsky proposed to combine everything that is part of the biosphere into groups depending on the nature of the origin of the substance. He distinguished seven groups of matter: 1) living matter is the totality of all producers, consumers and decomposers inhabiting the biosphere; 2) inert substance is a set of substances in the formation of which living organisms did not participate, this substance was formed before the appearance of life on Earth (mountains, rocky rocks, volcanic eruptions); 3) a biogenic substance is a set of substances that are formed by the organisms themselves or are products of their vital activity ( coal, oil, limestone, peat and other minerals); 4) bio-inert substance is a substance that is a system of dynamic balance between living and inert substance (soil, weathering crust); 5) a radioactive substance is a collection of all isotopic elements in a state of radioactive decay; 6) the substance of scattered atoms is the totality of all elements that are in an atomic state and are not part of any other substance; 7) cosmic matter is a set of substances that enter the biosphere from space and are of cosmic origin (meteorites, cosmic dust).
Vernadsky believed that living matter plays the main transforming role in the biosphere.
16. The role of man in the evolution of the biosphere. The influence of human activity on modern processes in the biosphere.
17. Living matter biosphere according to V.I. Vernadsky, its characteristics. The concept of the noosphere according to V.I. Vernadsky.
18. Concept, causes and main trends of the modern ecological crisis.
19. Reduction of genetic diversity, loss of the gene pool. Population growth and urbanization.
20. Classification natural resources... Exhaustible and inexhaustible natural resources.
Natural resources are: --- exhaustible - are divided into non-renewable, relatively renewable (soil, forests), renewable (animals). --- inexhaustible - air, solar energy, water, soil
21. Sources and extent of air pollution. Acidic precipitation.
22. Energy resources of the world. Alternative sources energy.
23. Greenhouse effect. The state of the ozone screen.
24. Brief description of the carbon cycle. Cycle stagnation.
25. The nitrogen cycle. Nitrogen fixers. A brief description of.
26. Water cycle in nature. A brief description of.
27. Determination of the biogeochemical cycle. List of main cycles.
28. Energy flow and cycles of biogenic elements in the ecosystem (diagram).
29. The list of the main soil-forming factors (according to Dokuchaev).
30. "Ecological succession". "Climax Community". Definitions. Examples.
31. Basic principles natural arrangement biosphere.
32. International "Red Book". Types of natural areas.
33. The main climatic zones of the globe (short list according to G. Walter).
34. Pollution of ocean waters: scale, composition of pollutants, consequences.
35. Deforestation: scale, consequences.
36. The principle of dividing human ecology into human ecology as an organism and social ecology. Human ecology as an autecology of the organism.
37. Biological pollution of the environment. MPC.
38. Classification of pollutants discharged into water bodies.
39. Environmental factors that cause diseases of the digestive system, circulatory organs, which can cause malignant neoplasms.
40. Rationing: concept, types, maximum permissible concentration. "Smog": concept, reasons for its formation, harm.
41. Population explosion and its danger for the current state of the biosphere. Urbanization and its negative consequences.
42. The concept of "sustainable development". Prospects for the concept of "sustainable development" for the "golden billion" of the population of economically developed countries.
43. Reserves: functions and values. Types of reserves and their number in the Russian Federation, USA, Germany, Canada.
Conditions of existence
Definition 1
Conditions of existence (Conditions of life) are a set of elements necessary for organisms, with which they are inseparably related and without which they cannot exist.
The adaptation of organisms to the environment is called adaptation. The ability to adapt is one of the most important properties of life, which provides the possibilities for its life, reproduction and survival. Adaptations are manifested at various levels - from the biochemistry of the cell and the behavior of an individual organism to the functioning and structure of the community and ecosystem. Adaptation arises and changes during the evolution of species.
Some elements of the environment or properties that affect the body are called environmental factors. There are a large number of environmental factors. They have a different nature and specificity of action. All environmental factors are subdivided into three large groups: biotic, abiotic and anthropogenic
Definition 2
An abiotic factor is a complex of conditions of an inorganic environment that affect a living organism indirectly or directly: light, temperature, radioactive radiation, air humidity, pressure, salt composition of water, etc.
Definition 3
The biotic factor of the environment is a set of influences that other organisms have on plants. any plant does not live in isolation, but in conjunction with other plants, fungi, microorganisms, animals.
Definition 4
The anthropogenic factor is a combination of environmental factors determined by deliberate or accidental human activity and causing a significant impact on the functioning and structure of ecosystems.
Anthropogenic factors
The most important group of factors in our time, which intensively changes the environment, is directly related to the many-sided human activity.
The development and formation of man on the globe have always been associated with environmental impacts, but now this process has accelerated significantly.
The anthropogenic factor includes any impact (both indirect and direct) of humanity on the environment - biogeocenoses, organisms, biosphere, landscapes.
by modifying nature and adapting it to personal needs, people change the habitat of plants and animals, thereby affecting their existence. Impacts can be direct, indirect and incidental.
Direct impacts are directed directly at living organisms. For example, unsustainable hunting and fishing have drastically reduced the number of many species. The accelerated pace and growing force of modification of nature by mankind awakens the need for its protection.
Indirect impacts are carried out by changing the climate, landscapes, chemistry and physical condition of water bodies and the atmosphere, the structure of soil surfaces, flora and fauna. A person unconsciously and consciously displaces or destroys one type of plant or animal, while spreading another or creating favorable conditions for it. For domestic animals and cultivated plants, mankind has created a new environment to a large extent, increasing the productivity of the developed land a hundredfold. But this made the existence of many wild species impossible.
Remark 1
It should be noted that many species of plants and animals disappeared from planet Earth even without anthropogenic human activity. Like an individual organism, each species has its own adolescence, flowering, old age and death - this is a natural process. But in natural conditions, this is done very slowly, and usually the outgoing species has time to be replaced by a new one, more adapted to habitat conditions. Humanity, on the other hand, has accelerated the processes of extinction to such a rate that evolution has given way to irreversible, revolutionary reorganizations of ecosystems.
Anthropogenic factors are human-generated factors that affect the environment.
The whole story scientific and technological progress, in essence, is a combination of human transformation for his own purposes of natural environmental factors and the creation of new ones that did not exist in nature before.
Smelting metals from ores and manufacturing equipment are impossible without creating high temperatures, pressures, and powerful electromagnetic fields. Obtaining and maintaining high yields of agricultural crops requires the production of fertilizers and funds chemical protection plants from pests and pathogens. Modern healthcare is unthinkable without chemo and physiotherapy. These examples can be multiplied.
Achievements of scientific and technological progress began to be used for political and economic purposes, which was manifested in the extreme way in the creation of special environmental factors affecting a person and his property: from firearms to means of mass physical, chemical and biological impact.
On the other hand, in addition to such targeted factors, in the process of exploitation and processing of natural resources, secondary chemical compounds and zones of high levels of physical factors are inevitably formed. In a number of cases, these processes can be abrupt in nature (in the conditions of accidents and disasters) with severe environmental and material consequences. Hence, it was required to create ways and means of protecting a person from dangerous and harmful factors.
In a simplified form, an indicative classification of anthropogenic environmental factors is shown in Fig. 3.
Rice. 3.
Classification of anthropogenic environmental factors
BOV - chemical warfare agents; Mass media - mass media.
Anthropogenic activity significantly affects climatic factors, changing their regimes. So, mass emissions into the atmosphere of solid and liquid particles from industrial enterprises can drastically change the dispersion mode solar radiation in the atmosphere and reduce the arrival of heat to the Earth's surface. Destruction of forests and other vegetation, creation of large artificial reservoirs on former territories land increases the reflection of energy, while dust pollution, such as snow and ice, on the contrary, increases absorption, which leads to their intense melting. Thus, the mesoclimate can change dramatically under the influence of man: it is clear that the climate North Africa in the distant past, when it was a huge oasis, it was significantly different from the current climate of the Sahara Desert.
The global consequences of anthropogenic activities, fraught with environmental disasters, are usually reduced to two hypothetical phenomena: greenhouse effect and nuclear winter.
The essence greenhouse effect is as follows. The sun's rays penetrate through the earth's atmosphere to the surface of the earth. However, the accumulation of carbon dioxide, nitrogen oxides, methane, water vapor, fluorine-chlorine-hydrocarbons (freons) in the atmosphere leads to the fact that the thermal long-wave radiation of the Earth is absorbed by the atmosphere. This leads to the accumulation of excess heat in the surface air layer, i.e., the thermal balance of the planet is disturbed. This effect is similar to what we see in greenhouses covered with glass or foil. As a result, the air temperature near the earth's surface may rise.
Currently, the annual increase in the content of CO 2 is estimated at 1-2 parts per million. Such a situation, as they believe, can lead already in the first half of the XXI century. to catastrophic climate changes, in particular, to the massive melting of glaciers and the rise in the level of the World Ocean. The increasing rates of combustion of fossil fuels lead, on the one hand, to a steady, albeit slow, increase in the content of CO 2 in the atmosphere, and on the other, to the accumulation (albeit still local and scattered) of atmospheric aerosol.
There is a debate among scientists about what consequences will prevail as a result of these processes (warming or cooling). But regardless of points of view, it is necessary to remember that the vital activity of human society is becoming, as V.I. Vernadsky, A.E. Fersman said, a powerful geological and geochemical force capable of significantly changing the ecological situation on a global scale.
Nuclear winter considered a possible consequence of nuclear (including local) wars. As a result nuclear explosions and the inevitable fires after them, the troposphere will be saturated with solid particles of dust and ash. The Earth will be closed (screened) from the sun's rays for many weeks and even months, that is, the so-called "nuclear night" will come. At the same time, as a result of the formation of nitrogen oxides, the ozone layer of the planet will be destroyed.
Shielding the Earth from solar radiation will lead to a strong decrease in temperature with an inevitable decrease in yields, mass death of living organisms, including humans, from cold and hunger. And those organisms that will be able to survive this situation before the atmospheric transparency is restored will be exposed to harsh ultraviolet radiation (due to the destruction of ozone) with an inevitable increase in the frequency of cancer and genetic diseases.
The processes associated with the consequences of a nuclear winter are currently the subject of mathematical and machine modeling by scientists in many countries. But humanity also has a natural model of such phenomena, which makes us take them very seriously.
Man practically does not affect the lithosphere, although the upper horizons of the earth's crust undergo a strong transformation as a result of the exploitation of mineral deposits. There are projects (partly implemented) for burial in the bowels of liquid and solid industrial waste. Such burials, as well as underground nuclear tests can initiate so-called "induced" earthquakes.
It is quite understandable that the temperature stratification of water has a decisive effect on the placement of living organisms in water and on the transfer and dispersion of impurities coming from industrial, agricultural and household enterprises.
The human impact on the environment ultimately manifests itself in a change in the regime of many biotic and abiotic factors... Among anthropogenic factors, there are factors that provide direct influence on organisms (for example, fishing) and factors that indirectly affect organisms through the impact on habitats (for example, environmental pollution, destruction of vegetation cover, construction of dams). The specificity of anthropogenic factors is the difficulty of adapting living organisms to them. Organisms often do not have adaptive reactions to the action of anthropogenic factors due to the fact that these factors did not act during the evolutionary development of the species, or because the action of these factors exceeds the adaptive capabilities of the organism.
Anthropogenic factors - a set of various human influences on inanimate and living nature. Only by their very physical existence, people have a noticeable effect on the environment: in the process of breathing, they annually emit 1 · 10 12 kg of CO 2 into the atmosphere, and with food they consume more than 5-10 15 kcal.
As a result of human impact, the climate, surface relief, chemical composition atmosphere, species and natural ecosystems are disappearing, etc. The most important anthropogenic factor for nature is urbanization.
Anthropogenic activity significantly affects climatic factors, changing their regimes. For example, massive emissions of solid and liquid particles into the atmosphere from industrial enterprises can dramatically change the mode of dispersion of solar radiation in the atmosphere and reduce the arrival of heat to the Earth's surface. The destruction of forests and other vegetation, the creation of large artificial reservoirs on the former land areas increase the reflection of energy, and pollution with dust, for example, snow and ice, on the contrary, increases absorption, which leads to their intense melting.
In much to a greater extent the biosphere is influenced by the production activities of people. As a result of this activity, the relief, the composition of the earth's crust and atmosphere, the climate change, a redistribution of fresh water, natural ecosystems disappear and artificial agro- and technoecosystems are created, cultivated plants, animals are domesticated, etc.
Human impact can be direct or indirect. For example, deforestation and uprooting of a forest have not only a direct effect, but also an indirect one - the conditions for the existence of birds and animals change. It is estimated that since 1600, 162 species of birds, over 100 species of mammals and many other species of plants and animals have been destroyed by man. But, on the other hand, it creates new varieties of plants and breeds of animals, increases their productivity and productivity. Artificial relocation of plants and animals also affects the life of ecosystems. Thus, the rabbits brought to Australia multiplied so much that they caused enormous damage to agriculture.
The most obvious manifestation of anthropogenic influence on the biosphere is environmental pollution. The importance of anthropogenic factors is constantly growing, as man more and more subjugates nature.
Human activity is a combination of human transformation for his own purposes of natural environmental factors and the creation of new ones that did not previously exist in nature. Smelting metals from ores and manufacturing equipment are impossible without creating high temperatures, pressures, and powerful electromagnetic fields. Obtaining and maintaining high yields of agricultural crops requires the production of fertilizers and chemical plant protection from pests and pathogens. Modern healthcare cannot be imagined without chemotherapy and physiotherapy.
Achievements of scientific and technological progress began to be used for political and economic purposes, which was manifested in the extreme way in the creation of special environmental factors affecting a person and his property: from firearms to means of mass physical, chemical and biological impact. In this case, they speak of a combination of anthropotropic (directed at the human body) and anthropocidal factors that cause environmental pollution.
On the other hand, in addition to such targeted factors, in the process of exploitation and processing of natural resources, secondary chemical compounds and zones of high levels of physical factors are inevitably formed. Under the conditions of accidents and catastrophes, these processes can be of a spasmodic nature with severe environmental and material consequences. Hence, it was required to create methods and means of protecting a person from dangerous and harmful factors, which has now been implemented in the above-mentioned system - life safety.
Environmental plasticity. Despite the wide variety of environmental factors, a number of general patterns can be identified in the nature of their impact and in the responses of living organisms.
The effect of the influence of factors depends not only on the nature of their action (quality), but also on the quantitative value perceived by organisms - high or low temperature, degree of illumination, humidity, amount of food, etc. In the process of evolution, the ability of organisms has developed to adapt to environmental factors within certain quantitative limits. A decrease or an increase in the value of a factor outside these limits inhibits vital activity, and when a certain minimum or maximum level is reached, the death of organisms occurs.
The zones of action of the ecological factor and the theoretical dependence of the vital activity of an organism, population or community depend on the quantitative value of the factor. The quantitative range of any environmental factor most favorable for life is called the ecological optimum (lat. ortimus - best). The values of the factor lying in the zone of oppression are called the ecological pessimum (the worst).
The minimum and maximum values of the factor at which death occurs are called respectively ecological minimum and ecological maximum
Any types of organisms, populations or communities are adapted, for example, to exist in a certain temperature range.
The property of organisms to adapt to existence in a particular range of environmental factors is called environmental plasticity.
The wider the range of the ecological factor within which a given organism can live, the greater its ecological plasticity.
According to the degree of plasticity, two types of organisms are distinguished: stenobiont (stenoecs) and eurybiontic (euryecs).
Stenobiontic and eurybiontic organisms differ in the range of environmental factors in which they can live.
Stenobionts(column stenos- narrow, close), or narrowly adapted, species are able to exist only with small deviations
factor from the optimal value.
Eurybiontic(column eirys - wide) are called broadly adapted organisms that can withstand a large amplitude of fluctuations of the ecological factor.
Historically, adapting to environmental factors, animals, plants, microorganisms are distributed in various environments, forming the whole variety of ecosystems that form the biosphere of the Earth.
Limiting factors. The concept of limiting factors is based on two laws of ecology: the law of minimum and the law of tolerance.
Minimum law. In the middle of the last century, the German chemist J. Liebig (1840), while studying the effect of nutrients on plant growth, discovered that the harvest does not depend on those nutrients that are required in large quantities and are present in abundance (for example, CO 2 and H 2 0), and from those that, although the plant needs in smaller quantities, are practically absent in the soil or are inaccessible (for example, phosphorus, zinc, boron).
Liebig formulated this pattern as follows: “The growth of a plant depends on the nutrient that is present in minimum quantity". This finding later became known as Liebig's law of minimum and has been extended to many other environmental factors. Heat, light, water, oxygen, and other factors can limit, or limit, the development of organisms, if their value corresponds to the ecological minimum. For example, tropical angelfish dies if the water temperature drops below 16 ° C. And the development of algae in deep-sea ecosystems is limited by the depth of penetration of sunlight: there are no algae in the bottom layers.
Liebig's law of minimum general view can be formulated as follows: the growth and development of organisms depend, first of all, on those factors of the natural environment, the values of which are approaching the ecological minimum.
Research has shown that the law of minimum has two limitations that should be taken into account in practical application.
The first limitation is that Liebig's law is strictly applicable only under the conditions of a stationary state of the system. For example, in some body of water, the growth of algae is limited to natural conditions lack of phosphates. Nitrogen compounds are present in excess in water. If they start dumping into this body of water wastewater with a high content of mineral phosphorus, the reservoir may "bloom". This process will progress until one of the elements is used up to the limiting minimum. Now it can be nitrogen if the phosphorus continues to flow. At the transitional moment (when there is still enough nitrogen, and there is already enough phosphorus), the effect of the minimum is not observed, that is, none of these elements affects the growth of algae.
The second limitation is related to the interaction of several factors. Sometimes the body is able to replace the deficient element with another chemically similar one. So, in places where there is a lot of strontium, in the shells of mollusks, it can replace calcium with a lack of the latter. Or, for example, the need for zinc in some plants decreases if they grow in the shade. Consequently, a low concentration of zinc will limit plant growth less in shade than in bright light. In these cases, the limiting effect of even an insufficient amount of one or another element may not manifest itself.
The law of tolerance(lat ... tolerantia- patience) was discovered by the English biologist W. Shelford (1913), who drew attention to the fact that not only those ecological factors, the values of which are minimal, but also those that are characterized by an ecological maximum, can limit the development of living organisms. Too much heat, light, water, and even nutrients can be just as damaging as a lack of them. The range of the ecological factor between the minimum and maximum W. Shelford called limit of tolerance.
The tolerance limit describes the amplitude of fluctuations of factors, which ensures the most full-fledged existence of the population. Individuals may have slightly different tolerance ranges.
Later, the limits of tolerance were established for various environmental factors for many plants and animals. The laws of J. Liebig and W. Shelford helped to understand many phenomena and the distribution of organisms in nature. Organisms cannot be distributed everywhere because populations have a certain tolerance limit in relation to fluctuations in environmental factors.
V. Shelford's law of tolerance is formulated as follows: the growth and development of organisms depend primarily on those environmental factors, the values of which are close to the ecological minimum or ecological maximum.
The following was found:
Organisms with a wide range of tolerance to all factors are widespread in nature and are often cosmopolitan, for example, many pathogenic bacteria;
Organisms can have a wide tolerance range for one factor and a narrow range for another. For example, people are more tolerant to lack of food than to lack of water, that is, the limit of tolerance for water is narrower than for food;
If the conditions for one of the environmental factors become suboptimal, then the tolerance limit for other factors may change. For example, with a lack of nitrogen in the soil, cereals require much more water;
The real limits of tolerance observed in nature are less than the potential capabilities of the organism to adapt to this factor. This is due to the fact that in nature the limits of tolerance in relation to the physical conditions of the environment can be narrowed by biotic relations: competition, the absence of pollinators, predators, etc. ). The potential ecological plasticity of an organism, determined in laboratory conditions, is greater than the realized possibilities in natural conditions. Accordingly, a distinction is made between potential and realized ecological niches;
The limits of tolerance in breeding individuals and offspring are less than in adults, that is, females during the breeding season and their offspring are less hardy than adult organisms. Thus, the geographical distribution of game birds is more often determined by the influence of climate on eggs and chicks, and not on adult birds. Caring for offspring and respect for motherhood are dictated by the laws of nature. Unfortunately, sometimes social “achievements” are contrary to these laws;
Extreme (stress) values of one of the factors lead to a decrease in the tolerance limit for other factors. If heated water is dumped into the river, then fish and other organisms spend almost all of their energy to overcome stress. They do not have enough energy to get food, protect themselves from predators, reproduce, which leads to a gradual extinction. Psychological stress can also cause many somatic (gr. soma - body) diseases not only in humans, but also in some animals (for example, in dogs). Under stressful values of the factor, adaptation to it becomes more and more “expensive”.
Many organisms are capable of changing tolerance to certain factors if conditions change gradually. You can, for example, get used to the high temperature of the water in the bath, if you climb into warm water, and then gradually add hot. This adaptation to slow factor changes is a useful protective property. But it can also be dangerous. Sudden, without warning signals, even a small change can be critical. A threshold effect sets in: the “last straw” can be fatal. For example, a thin twig can fracture an already congested camel's back.
If the value of at least one of the environmental factors approaches a minimum or maximum, the existence and prosperity of an organism, population or community becomes dependent precisely on this factor limiting its vital activity.
A limiting factor is any environmental factor that approaches or exceeds the extreme values of the tolerance limits. Such factors deviating from the optimum are of paramount importance in the life of organisms and biological systems. It is they who control the conditions of existence.
The value of the concept of limiting factors is that it allows you to understand the complex relationships in ecosystems.
Fortunately, not all possible environmental factors govern the relationship between the environment, organisms, and humans. Various limiting factors are prioritized in a given period of time. These are the factors that an ecologist must focus on when studying and managing ecosystems. For example, the oxygen content in terrestrial habitats is high and it is so available that it almost never serves as a limiting factor (with the exception of high altitudes and anthropogenic systems). Oxygen is of little interest to terrestrial ecologists. And in water, it is often a factor limiting the development of living organisms ("killing" of fish, for example). Therefore, a hydrobiologist always measures the oxygen content in water, unlike a veterinarian or ornithologist, although oxygen is no less important for terrestrial organisms than for aquatic organisms.
Limiting factors also determine the geographic range of the species. So, the movement of organisms to the south is limited, as a rule, by a lack of heat. Biotic factors also often limit the distribution of certain organisms. For example, figs brought from the Mediterranean to California did not bear fruit there until they guessed to bring there a certain species of wasp - the only pollinator of this plant. Identifying the limiting factors is very important for many types of activities, especially agriculture. By targeted action on limiting conditions, it is possible to quickly and effectively increase plant productivity and animal productivity. So, when cultivating wheat on acidic soils, no agronomic measures will give an effect if liming is not applied, which will reduce the limiting effect of acids. Or, if you grow corn on soils that are very low in phosphorus, then even with enough water, nitrogen, potassium, and other nutrients, it will stop growing. Phosphorus in this case is the limiting factor. And only phosphorus fertilizers can save the harvest. Plants can die from too a large number water or excess fertilizer, which in this case are also limiting factors.
Knowing the limiting factors provides the key to ecosystem management. However, in different periods life of the organism and in different situations various factors act as limiting factors. Therefore, only skillful regulation of the conditions of existence can give effective results management.
Interaction and compensation of factors. In nature, environmental factors do not act independently of each other - they interact. Analysis of the influence of one factor on an organism or a community is not an end in itself, but a way of assessing the comparative significance of various conditions acting together in real ecosystems.
Joint influence of factors can be considered by the example of the dependence of the mortality of crab larvae on temperature, salinity and the presence of cadmium. In the absence of cadmium, the ecological optimum (minimum mortality) is observed in the temperature range from 20 to 28 ° C and salinity - from 24 to 34%. If cadmium, toxic to crustaceans, is added to the water, then the ecological optimum shifts: the temperature lies in the range from 13 to 26 ° C, and the salinity is from 25 to 29%. The limits of tolerance are also changing. The difference between the ecological maximum and minimum for salinity after the addition of cadmium decreases from 11 - 47% to 14 - 40%. The tolerance limit for the temperature factor, on the contrary, expands from 9 - 38 ° С to 0 - 42 ° С.
Temperature and humidity are the most important climatic factors in terrestrial habitats. The interaction of these two factors essentially forms two main types of climate: marine and continental.
Reservoirs soften the land climate, as the water has high specific heat melting and heat capacity. Therefore, the maritime climate is characterized by less sharp fluctuations in temperature and humidity than the continental one.
The effect of temperature and humidity on organisms also depends on the ratio of their absolute values. So, temperature has a more pronounced limiting effect if the humidity is very high or very low. Everyone knows that tall and low temperatures worse when high humidity than with moderate
The relationship between temperature and humidity as the main climatic factors is often depicted in the form of climogram graphs, which make it possible to visually compare different years and regions and predict the production of plants or animals for certain climatic conditions.
Organisms are not slaves to the environment. They adapt to the conditions of existence and change them, that is, they compensate for the negative impact of environmental factors.
Compensation of environmental factors is the desire of organisms to weaken the limiting effect of physical, biotic and anthropogenic influences. Factor compensation is possible at the organism and species level, but is most effective at the community level.
At different temperatures, the same species, which has a wide geographical distribution, can acquire physiological and morphological (column torphe - shape, outline) features adapted to local conditions. For example, in animals, the ears, tails, and paws are shorter, and the body is the more massive, the colder the climate.
This pattern is called Allen's rule (1877), according to which the protruding body parts of warm-blooded animals increase as they move from north to south, which is associated with adaptation to maintaining a constant body temperature in different climatic conditions. So, foxes living in the Sahara have long limbs and huge ears; the European fox is more squat, its ears are much shorter; and the arctic fox, the polar fox, has very small ears and a short muzzle.
In animals with well-developed motor activity, compensation of factors is possible due to adaptive behavior. So, lizards are not afraid of sudden cooling, because during the day they go out into the sun, and at night they hide under heated stones. Changes arising in the process of adaptation are often genetically fixed. At the community level, compensation of factors can be carried out by changing species along the gradient of environmental conditions; for example, with seasonal changes, there is a regular change in plant species.
Organisms also use the natural periodicity of changes in environmental factors to distribute functions over time. They “program” life cycles to make the most of the favorable conditions.
The most striking example is the behavior of organisms depending on the length of the day - photoperiod. The amplitude of the day length increases with latitude, which allows organisms to take into account not only the season, but also the latitude of the area. The photoperiod is a "time relay" or trigger for a sequence of physiological processes. It determines the flowering of plants, molting, migration and reproduction in birds and mammals, etc. The photoperiod is associated with the biological clock and serves as a universal mechanism for regulating functions in time. The biological clock links the rhythms of environmental factors with physiological rhythms, allowing organisms to adapt to the diurnal, seasonal, tidal and other dynamics of factors.
By changing the photoperiod, it is possible to induce changes in body functions. So, flower growers, changing the light regime in greenhouses, get off-season flowering of plants. If after December immediately increase the length of the day, then this can cause the phenomena that occur in spring: flowering plants, molting in animals, etc. In many higher organisms, adaptations to the photoperiod are fixed genetically, that is, The biological clock can work even in the absence of regular daily or seasonal dynamics.
Thus, the point of analyzing environmental conditions is not to compile an immense list of environmental factors, but to discover functionally important limiting factors and to assess the extent to which the composition, structure and functions of ecosystems depend on the interaction of these factors.
Only in this case it is possible to reliably predict the results of changes and disturbances and manage ecosystems.
Anthropogenic limiting factors. It is convenient to consider fires and anthropogenic stress as examples of anthropogenic limiting factors that make it possible to manage natural and man-made ecosystems.
Fires as an anthropogenic factor, they are often assessed only negatively. Research over the past 50 years has shown that natural fires can be part of the climate in many terrestrial habitats. They influence the evolution of flora and fauna. Biotic communities have "learned" to compensate for this factor and adapt to it, as to temperature or humidity. Fire can be viewed and studied as an environmental factor, along with temperature, precipitation and soil. At correct use fire can be a valuable ecological tool. Some tribes burned forests for their needs long before people began to systematically and purposefully change the environment. Fire is a very important factor, also because a person can control it to a greater extent than other limiting factors. It is difficult to find a piece of land, especially in dry season areas, where there has not been a fire at least once in 50 years. The most common cause of fires in nature is a lightning strike.
Fires happen different types and lead to different consequences.
Horseback or "wild" fires are usually very intense and uncontrollable. They destroy the crown of trees and destroy all organic matter in the soil. Fires of this type have a limiting effect on almost all organisms in the community. It will take many years for the site to rebuild.
Grassroots fires are completely different. They have a selective effect: for some organisms they turn out to be more limiting than for others. Thus, ground fires promote the development of organisms with a high tolerance to their consequences. They can be natural or specially organized by man. For example, planned forest burning is undertaken to eliminate competition for the valuable swamp pine species from deciduous trees. Marsh pine, unlike deciduous trees, is resistant to fire, since the apical bud of its seedlings is protected by a bunch of long, poorly burning needles. In the absence of fires, the overgrowth of deciduous trees drowns out pine, as well as cereals and legumes. This leads to the oppression of partridges and small herbivores. Therefore, virgin pine forests with abundant game are ecosystems of the “fire” type, that is, requiring periodic ground fires. In this case, the fire does not lead to the loss of nutrients in the soil, does not harm ants, insects and small mammals.
A small fire is even beneficial for nitrogen-fixing legumes. Burning out is carried out in the evening, so that at night the fire can be extinguished with dew, and the narrow fire front can be easily stepped over. In addition, small ground fires complement the bacteria's action to convert dead residues into mineral nutrients suitable for a new generation of plants. For the same purpose, fallen leaves are often burned in spring and autumn. Planned burning is an example of managing a natural ecosystem using a limiting ecological factor.
The decision as to whether the possibility of fires should be completely ruled out or whether fire should be used as a control factor should depend entirely on what type of community is desired in the area. The American ecologist G. Stoddard (1936) was one of the first to “defend” controlled planned burning to increase the production of valuable timber and game back in the days when, from the point of view of foresters, any fire was considered harmful.
The close relationship of burnout with the composition of herbs plays key role in maintaining an amazing variety of antelopes and their predators in the East African savannas. Fires have a positive effect on many cereals, since their growth points and energy reserves are underground. After the dry aboveground parts are burned out, the nutrients quickly return to the soil and the grasses grow luxuriantly.
The question "to burn or not to burn", of course, can be confusing. Through negligence, a person is often the cause of an increase in the frequency of destructive "wild" fires. Struggle for fire safety in forests and recreation areas - the second side of the problem.
A private person in no case has the right to deliberately or accidentally cause a fire in nature - this is the privilege of specially trained people who are familiar with the rules of land use.
Anthropogenic stress can also be regarded as a kind of limiting factor. Ecosystems are largely able to compensate for anthropogenic stress. It is possible that they are naturally adapted to acute recurrent stresses. And many organisms require occasional disturbances that contribute to their long-term resilience. Large bodies of water often have good self-purification properties and recover from pollution in the same way as many terrestrial ecosystems. However, long-term disruptions can lead to pronounced and lasting negative consequences. In such cases, the evolutionary history of adaptation cannot help organisms - compensation mechanisms are not unlimited. This is especially true of those cases when highly toxic waste is dumped, which is constantly produced by an industrialized society and which were previously absent in the environment. If we cannot isolate this toxic waste from global life support systems, then they will directly threaten our health and become the main limiting factor for humanity.
Anthropogenic stress is conventionally divided into two groups: acute and chronic.
The first is characterized by a sudden onset, a rapid rise in intensity and a short duration. In the second case, violations of low intensity continue for a long time or are repeated. Natural systems often have sufficient capacity to cope with acute stress. For example, the dormant seed strategy allows the forest to recover after being cleared. The consequences of chronic stress can be more severe because the responses to stress are less obvious. It may take years for changes in organisms to be noticed. Thus, the connection between cancer and smoking was identified only a few decades ago, although it existed for a long time.
The threshold effect partly explains why some environmental problems appear unexpectedly. In fact, they have been accumulating over the years. For example, in forests mass death of trees begins after prolonged exposure to air pollutants. We begin to notice the problem only after the death of many forests in Europe and America. By this time, we were 10-20 years late and could not prevent the tragedy.
During the period of adaptation to chronic anthropogenic influences, the tolerance of organisms also decreases to other factors, such as diseases. Chronic stress is often associated with toxic substances, which, although in small concentrations, are constantly released into the environment.
The article "The Poisoning of America" (The Times magazine, September 22, 1980) provides the following data: "Of all human interventions in the natural order of things, not one is growing at such an alarming rate as the creation of new chemical compounds... In the USA alone, cunning "alchemists" create about 1,000 new drugs every year. There are about 50,000 different chemicals on the market. Many of them are undoubtedly of great benefit to humans, but the nearly 35,000 compounds used in the US are definitely or potentially harmful to human health. ”
The danger, possibly catastrophic, is the pollution of groundwater and deep aquifers, which make up a significant proportion of the planet's water resources. Unlike surface waters, groundwater is not subject to natural self-purification processes due to the lack of sunlight, rapid current and biotic components.
The concern is not only caused by harmful substances entering water, soil and food. Millions of tons of hazardous compounds are released into the atmosphere. Only over America in the late 70s. emitted: suspended particles - up to 25 million tons / year, SO 2 - up to 30 million tons / year, NO - up to 23 million tons / year.
We all contribute to air pollution through the use of cars, electricity, manufactured goods, and more. Air pollution is a clear negative feedback signal that can save society from death, as it is easily detected by everyone.
Solid Waste Treatment long time was considered a secondary matter. Until 1980, there were cases when residential quarters were built on former radioactive waste dumps. Now, albeit with some delay, it became clear: the accumulation of waste is limiting the development of industry. Without the creation of technologies and centers for their removal, neutralization and recycling, further progress of the industrial society is impossible. First of all, it is necessary to safely isolate the most toxic substances. The illegal practice of "night discharges" must be replaced reliable insulation... We need to look for substitutes for toxic chemicals. At the right leadership waste disposal and recycling can become a special industry that will create new jobs and contribute to the economy.
The solution to the problem of man-made stress must be based on a holistic concept and requires systems approach... Attempts to deal with every contaminant as independent problem ineffective - they only transfer the problem from one place to another.
If in the next decade it is not possible to contain the process of environmental degradation, then it is likely that not a shortage of natural resources, but the impact harmful substances will become a factor limiting the development of civilization.