Dependence of organisms on environmental factors. Environmental problems associated with the demographic situation. Problems of ecology in large regions. Ecological development strategies.

1. Introduction
2. Resources of the biosphere and modern demographic problems
3. Patterns of dependence of organisms on environmental factors
4. The essence of the concept of environmental risk
5. Features of the ecology of cities and large agricultural areas
6. The concept of a strategy for sustainable environmental development
7. Conclusions and results
8. References

The work contains 1 file

MINISTRY OF EDUCATION AND SCIENCE OF THE RUSSIAN FEDERATION

SAINT PETERSBURG STATE UNIVERSITY OF SERVICE AND ECONOMICS

Department of Ecology

"PATTERNS OF RELATIONSHIPS BETWEEN ORGANISMS AND THE ENVIRONMENT"

The work was done by a 1st year student

Specialty 0608y _____ group

Bogdanovich Anastasia Alexandrovna

The work was checked by __________________

St. Petersburg

2010

1. Introduction
2. Biosphere resources and modern demographic problems
3. Patterns of dependence of organisms on environmental factors
4. The essence of the concept of environmental risk
5. Features of the ecology of cities and large agricultural areas
6. The concept of a sustainable environmental development strategy
7. Conclusions and results
8. Bibliography

Introduction

In my work I will try to describe the problem of human interaction with the environment and vice versa. Consider the dependence of organisms on environmental factors. Describe the environmental problems associated with the demographic situation. Tell about the possibility of environmental risks associated with human economic activity. Raise the issue of environmental problems in large regions. Describe strategies for environmental development.

Resources of the biosphere and modern demographic problems.

Significant demographic changes are characteristic of the 20th and 21st centuries. The population has grown from 1 billion 630 million to almost 6 billion people. Over the three previous centuries (1600 - 1900) the population increased 3 times, and in one (1900 - 2000) - almost 4 times. Significant population growth occurs in all regions of the world, but the population is growing especially rapidly in Asia, Africa, Latin America, India and China. However, in Russia by the beginning of the 21st century. the situation is different, here the population loss (depopulation) is the highest. At the beginning of 2003, 143.1 million people lived in Russia. Demographers' forecasts are disappointing: by 2010 the population in the Russian Federation will be approximately 138-139 million people. Long-term forecasts indicate that if current trends continue, then in 5-6 decades in the second half of the 21st century. , the population of Russia will be reduced by about half.

But in order to increase the standard of living of people with an increase in the population, to maintain a clean environment, a combination of population growth with economic and cultural upsurge is necessary.

The ever-growing population poses the problem of providing people with food for many countries, especially developing ones. About 2 million people die of hunger every year in the world. Along with the solution of the food problem, the problems of providing mankind with water, preserving atmospheric air, and preserving soil fertility are also becoming important. In a number of regions, there are already problems associated with a lack of water, especially fresh water, and environmental pollution. The growing population of the planet must be provided with heat and electricity. According to scientists, classical fuels (coal, oil, natural gas, peat, oil shale) provide humanity with the level of consumption in 1980 for 300-320 years, and with the level of consumption in 2000 - for 140-150 years. In this regard, alternative methods of obtaining energy, in particular, atomic, hydrogen, etc., should come to the fore in use in the national economy. A huge amount of energy can be obtained by man by solving the complex problem of controlling thermonuclear fusion.

Covering the growing needs of man requires the intensive development of productive forces and more and more diverse natural resources, which causes an increase in the influence of noocenosis on the natural environment. Under these conditions, interaction in the system "man - society - nature" should be based on the strict implementation of environmental laws, taking into account the prospects for the development of the biosphere and human society, and not momentary benefits in managing the economy.

Food resources of people and oceans can serve as a significant source of human food. But when using them, it is necessary to develop relationships in the "society - nature" system, based on ecological knowledge, in particular, the laws of minimum, limiting factors and ecological valency, tolerance, optimum, the relationship between man and industrial populations, the law of internal dynamic balance and its consequences.

Patterns of dependence of organisms on environmental factors.

In connection with the activity of the living matter of the planet, the modern chemical composition of the atmosphere and the dissolved substance of the hydrosphere is formed. Since all areas of the biosphere are formed as a result of the activity of living matter, it is natural that biological evolution as an irreversible process determines the irreversibility of the evolution of all shells of the biosphere: the atmosphere, hydrosphere and lithosphere.

Cephalization in the order of primates created the ground for the emergence of intelligence, when all changes in the biosphere must be controlled by consciousness - creative work human brain.

In the evolution of the organized world, the following stages are distinguished:

1) the emergence of a primary biosphere with a biotic cycle;

2) the period of biogenesis - the complication of the structure of multicellular organisms according to purely biological laws;

3) the period of noogenesis - the emergence of human society, the rational activity of which contributes to the transformation of the biosphere into the noosphere.

The period of noogenesis is characterized by the transformation of the biosphere as a result of the purposeful labor activity of mankind.

Living organisms, including humans, inhabit territories with various conditions habitats and experience the effects of a variety of factors. The patterns of relationships between organisms and their environment are studied by a special biological science - ecology.

Ecological patterns are manifested at the level of an individual, a population of individuals, a biocenosis, a biogeocenosis.

The totality of elements that affect a living organism in its habitat is habitat.

Elements of the environment that can have a direct impact on a living organism are called environmental factors, which are divided into biotic and abiotic.

Biotic- these are all possible influences that a living organism experiences from the living beings surrounding it.

Abiotic factors- these are all the elements of inanimate nature that affect the body.

During the period of noogenesis, it became expedient to single out a group of anthropogenic factors that manifest themselves in the active influence of man on nature.

Action environmental factors determined by the rhythm of cosmophysical processes. In accordance with this, environmental factors are divided into primary and secondary, periodic and non-periodic.

to the primary factors. include those that biological objects encountered in the early stages of evolution: temperature, change in the position of the Earth relative to the Sun. Under the influence of these factors, a daily, seasonal, annual periodicity of biological processes has arisen.

Secondary periodic factors are derivatives of the primary ones. For example, humidity levels depend on temperature; where the temperature is lower, the atmosphere contains less water vapor.

Non-periodic factors act on organisms, populations of organisms suddenly, episodically; for example - volcanic eruption, tornadoes, hurricanes, floods; the predator suddenly attacks the prey.

Fluctuations in the intensity of environmental factors are manifested in a change in the number or disappearance of species from certain territories, a change in birth and death rates. Fluctuations in the intensity of environmental factors determine the temporal organization of biosystems. The influence of environmental factors determine biological rhythms in the evolution of living systems.

Biological rhythms are fluctuations in the change and intensity of physiological reactions, which are based on changes in the metabolism of biological systems due to the influence of external and internal factors.

External factors include: changes in illumination (photoperiodism), temperature (thermoperiodism), magnetic field, intensities of cosmic radiations, ebbs and flows, seasonal and solar-lunar influences.

Internal factors are neurohumoral processes occurring at a certain, hereditarily fixed pace and rhythm.

Many physiological processes in the human body undergo periodic fluctuations.

Physiological rhythms are cyclic fluctuations in various body systems. The main characteristics of physiological rhythms are: the period or frequency of oscillations per unit time, amplitude (the value of the maximum deviation from the average), level, phase and form. Physiological rhythms are also classified in relation to periodic changes in the environment.

If the period of rhythms does not coincide with periodic changes in geophysical factors, they are designated as functional (respiratory rate, rhythms of physical activity).

If the period of rhythms coincides with the periods of geophysical cycles, is close or a multiple of them, they are called adaptive or ecological.

In biology, adaptive rhythms are considered from the point of view of the general adaptation of organisms to the environment, and in physiology, from the point of view of identifying internal adaptation mechanisms and studying the dynamics of physiological processes for a long time.

Adaptive physiological rhythms were formed in the process of evolution as a form of adaptation to constantly changing environmental conditions. Most often they are energetically justified. The human body is characterized by an increase in the daytime and a decrease in the nighttime physiological functions that ensure its physiological activity (heart rate, minute blood volume, blood pressure, body temperature, oxygen consumption, lowering blood sugar).

In animals in winter period metabolism, motor activity, body temperature decrease (hibernation, winter sleep, suspended animation); in the spring-summer period - the activity of physiological processes increases.

Accounting for physiological rhythms is necessary when compiling work and rest regimes, since an increase in physiological activity is directly related to an increase in working capacity; accounting for physiological rhythms is important in labor physiology and sports medicine.

Devices that compensate for periodic and aperiodic fluctuations in environmental conditions are very diverse.

In addition to behavioral, physiological, and morphogenetic reactions, these include features of the morphology of organisms that contribute to saving or dissipating energy, diapause, hibernation, the rhythm of daily activity, seasonal migrations, and food storage.

Habitat - this is that part of nature that surrounds a living organism and with which it directly interacts. The components and properties of the environment are diverse and changeable. Any living being lives in a complex, changing world, constantly adapting to it and regulating its life activity in accordance with its changes.

Separate properties or elements of the environment that affect organisms are called environmental factors. Environmental factors are diverse. They may be necessary or, conversely, harmful to living beings, promote or hinder survival and reproduction. Environmental factors have a different nature and specificity of action. Among them are abiotic and biotic, anthropogenic.

Abiotic factors - temperature, light, radioactive radiation, pressure, air humidity, salt composition of water, wind, currents, terrain - these are all properties of inanimate nature that directly or indirectly affect living organisms.

Biotic factors - these are forms of influence of living beings on each other. Each organism constantly experiences the direct or indirect influence of other creatures, enters into contact with representatives of its own species and other species - plants, animals, microorganisms, depends on them and itself has an impact on them. Ambient organic world- an integral part of the environment of every living being.

Mutual connections of organisms are the basis for the existence of biocenoses and populations; consideration of them belongs to the field of syn-ecology.

Anthropogenic factors - these are forms of activity of human society that lead to a change in nature as a habitat for other species or directly affect their lives. In the course of human history, the development of first hunting, and then agriculture, industry, and transport has greatly changed the nature of our planet. The significance of anthropogenic impacts on the entire living world of the Earth continues to grow rapidly.

Although man influences wildlife through a change in abiotic factors and biotic relationships of species, the activities of people on the planet should be singled out as a special force that does not fit into the framework of this classification. At present, practically the fate of the living cover of the Earth, all kinds of organisms, is in the hands of human society, depends on the anthropogenic influence on nature.

The same environmental factor has a different meaning in the life of cohabiting organisms of different species. For example, a strong wind in winter is unfavorable for large, open-dwelling animals, but does not affect smaller ones that take refuge in burrows or under snow. The salt composition of the soil is important for plant nutrition, but is indifferent to most land animals, etc.

Changes in environmental factors over time can be: 1) regularly-periodic, changing the strength of the impact in connection with the time of day, or the season of the year, or the rhythm of the tides in the ocean; 2) irregular, without a clear periodicity, for example, changes in weather conditions in different years, phenomena of a catastrophic nature - storms, showers, landslides, etc .; 3) directed over known, sometimes long, periods of time, for example, during a cooling or warming of the climate, overgrowing of water bodies, constant grazing in the same area, etc.

Among the environmental factors, resources and conditions are distinguished. Resources environment, organisms use, consume, thereby reducing their number. Resources include food, water when it is scarce, shelters, convenient places for breeding, etc. Terms - these are factors to which organisms are forced to adapt, but usually cannot influence them. One and the same environmental factor can be a resource for some and a condition for other species. For example, light is a vital energy resource for plants, and for animals with vision, it is a condition for visual orientation. Water for many organisms can be both a condition of life and a resource.

2.2. Organism adaptations

Organisms' adaptations to their environment are called adaptation. Adaptations are any changes in the structure and functions of organisms that increase their chances of survival.

The ability to adapt is one of the main properties of life in general, as it provides the very possibility of its existence, the ability of organisms to survive and reproduce. Adaptations manifest themselves at different levels: from the biochemistry of cells and the behavior of individual organisms to the structure and functioning of communities and ecological systems. Adaptations arise and develop in the course of the evolution of species.

The main mechanisms of adaptation at the level of the organism: 1) biochemical- manifest themselves in intracellular processes, such as a change in the work of enzymes or a change in their number; 2) physiological– for example, increased sweating with increasing temperature in a number of species; 3) morpho-anatomical- features of the structure and shape of the body associated with lifestyle; four) behavioral- for example, the search for favorable habitats by animals, the creation of burrows, nests, etc.; 5) ontogenetic- acceleration or deceleration of individual development, contributing to survival under changing conditions.

Environmental environmental factors have various effects on living organisms, i.e., they can affect how irritants, causing adaptive changes in physiological and biochemical functions; how limiters, causing the impossibility of existence in these conditions; how modifiers, causing morphological and anatomical changes in organisms; how signals, indicating changes in other environmental factors.

2.3. General laws of the action of environmental factors on organisms

Despite the wide variety of environmental factors, a number of general patterns can be identified in the nature of their impact on organisms and in the responses of living beings.

1. The law of optimum.

Each factor has certain limits. positive impact on organisms (Fig. 1). The result of the action of a variable factor depends primarily on the strength of its manifestation. Both insufficient and excessive action of the factor negatively affects the life of individuals. The beneficial effect is called zone of optimum ecological factor or simply optimum for organisms of this species. The stronger the deviation from the optimum, the more pronounced the inhibitory effect of this factor on organisms. (pessimum zone). The maximum and minimum tolerated values ​​of the factor are critical points per beyond which existence is no longer possible, death occurs. The endurance limits between critical points are called environmental valency living beings in relation to a specific environmental factor.

Rice. one. Scheme of the action of environmental factors on living organisms

Representatives of different species differ greatly from each other both in the position of the optimum and in ecological valency. For example, arctic foxes in the tundra can tolerate fluctuations in air temperature in the range of more than 80 °C (from +30 to -55 °C), while warm-water crustaceans Copilia mirabilis withstand water temperature changes in the range of no more than 6 °C (from up to +29 °C). One and the same force of manifestation of a factor can be optimal for one species, pessimal for another, and go beyond the limits of endurance for the third (Fig. 2).

The wide ecological valency of a species in relation to abiotic environmental factors is indicated by adding the prefix "evry" to the name of the factor. eurythermal species - enduring significant temperature fluctuations, eurybatic– wide pressure range, euryhaline– different degree of salinization of the environment.

Rice. 2. The position of the optimum curves on the temperature scale for different species:

1, 2 - stenothermic species, cryophiles;

3–7 – eurythermal species;

8, 9 - stenothermic species, thermophiles

The inability to endure significant fluctuations in the factor, or narrow ecological valence, is characterized by the prefix "steno" - stenothermal, stenobate, stenohaline species, etc. In a broader sense, species whose existence requires strictly defined environmental conditions are called stenobiont, and those that are able to adapt to different environmental conditions - eurybiontic.

Conditions approaching critical points in one or several factors at once are called extreme.

The position of the optimum and critical points on the factor gradient can be shifted within certain limits by the action of environmental conditions. This occurs regularly in many species as the seasons change. In winter, for example, sparrows withstand severe frosts, and in summer they die from cooling at temperatures just below zero. The phenomenon of shifting the optimum with respect to any factor is called acclimation. With regard to temperature, this is a well-known process of thermal hardening of the body. Temperature acclimation requires a significant period of time. The mechanism is the change in cells of enzymes that catalyze the same reactions, but at different temperatures (the so-called isoenzymes). Each enzyme is encoded by its own gene, therefore, it is necessary to turn off some genes and activate others, transcription, translation, assembly of a sufficient amount of a new protein, etc. The overall process takes an average of about two weeks and is stimulated by changes in the environment. Acclimation, or hardening, is an important adaptation of organisms that occurs under gradually impending adverse conditions or when they enter territories with a different climate. In these cases, it is an integral part of the general process of acclimatization.

2. Ambiguity of the action of the factor on different functions.

Each factor affects different body functions differently (Fig. 3). The optimum for some processes may be the pessimum for others. Thus, the air temperature from +40 to +45 ° C in cold-blooded animals greatly increases the rate of metabolic processes in the body, but inhibits motor activity, and the animals fall into a thermal stupor. For many fish, the water temperature that is optimal for the maturation of reproductive products is unfavorable for spawning, which occurs at a different temperature range.

Rice. 3. Scheme of the dependence of photosynthesis and respiration of a plant on temperature (according to V. Larcher, 1978): t min, t opt, t max– temperature minimum, optimum and maximum for plant growth (shaded area)

The life cycle, in which at certain periods the organism performs predominantly certain functions (nutrition, growth, reproduction, resettlement, etc.), is always consistent with seasonal changes in the complex of environmental factors. Mobile organisms can also change habitats for the successful implementation of all their life functions.

3. Variety of individual reactions to environmental factors. The degree of endurance, critical points, optimal and pessimal zones of individual individuals do not coincide. This variability is determined both by the hereditary qualities of individuals and by sex, age, and physiological differences. For example, in the mill moth butterfly, one of the pests of flour and grain products, the critical minimum temperature for caterpillars is -7 ° C, for adult forms -22 ° C, and for eggs -27 ° C. Frost at -10 °C kills caterpillars, but is not dangerous for adults and eggs of this pest. Consequently, the ecological valence of a species is always wider than the ecological valence of each individual.

4. Relative independence of adaptation of organisms to different factors. The degree of tolerance to any factor does not mean the corresponding ecological valence of the species in relation to other factors. For example, species that tolerate wide temperature changes need not also be adapted to wide fluctuations in humidity or salinity. Eurythermal species can be stenohaline, stenobatic, or vice versa. The ecological valencies of a species in relation to different factors can be very diverse. This creates an extraordinary variety of adaptations in nature. The set of ecological valences in relation to various environmental factors is ecological spectrum of the species.

5. Non-coincidence of the ecological spectra of individual species. Each species is specific in its ecological capabilities. Even among species that are close in terms of ways of adapting to the environment, there are differences in their attitude to any individual factors.

Rice. four. Changes in the participation of certain plant species in meadow grass stands depending on moisture (according to L. G. Ramensky et al., 1956): 1 – meadow clover; 2 - common yarrow; 3 - Delyavina's cellar; 4 – meadow bluegrass; 5 - tipchak; 6 - real bedstraw; 7 – early sedge; 8 - meadowsweet ordinary; 9 - hill geranium; 10 – field barnacle; 11 - short-nosed goat-beard

The rule of ecological individuality of species formulated by the Russian botanist L. G. Ramensky (1924) in relation to plants (Fig. 4), then it was widely confirmed by zoological studies.

6. Interaction of factors. The optimal zone and limits of endurance of organisms in relation to any environmental factor can shift depending on the strength and combination of other factors acting simultaneously (Fig. 5). This pattern has been named interactions of factors. For example, heat is easier to bear in dry rather than moist air. The threat of freezing is much higher in frost with strong winds than in calm weather. Thus, the same factor in combination with others has an unequal environmental impact. On the contrary, the same ecological result can be obtained in different ways. For example, wilting of plants can be stopped by both increasing the amount of moisture in the soil and lowering the air temperature, which reduces evaporation. The effect of partial mutual substitution of factors is created.

Rice. 5. Mortality of eggs of the pine silkworm Dendrolimus pini at different combinations of temperature and humidity

At the same time, the mutual compensation of the action of environmental factors has certain limits, and it is impossible to completely replace one of them with another. The complete absence of water, or even one of the main elements of mineral nutrition, makes the life of the plant impossible, despite the most favorable combination of other conditions. The extreme lack of heat in the polar deserts cannot be made up for either by an abundance of moisture or round-the-clock illumination.

Taking into account the patterns of interaction of environmental factors in agricultural practice, it is possible to skillfully maintain optimal conditions for the vital activity of cultivated plants and domestic animals.

7. The rule of limiting factors. The possibilities of the existence of organisms are primarily limited by those environmental factors that are most distant from the optimum. If at least one of the environmental factors approaches or goes beyond critical values, then, despite the optimal combination of other conditions, individuals are threatened with death. Any factors that strongly deviate from the optimum acquire paramount importance in the life of a species or its individual representatives in specific periods of time.

Environmental limiting factors determine the geographic range of a species. The nature of these factors may be different (Fig. 6). Thus, the movement of a species to the north can be limited by a lack of heat, and to arid regions by a lack of moisture or too high temperatures. Biotic relations, for example, the occupation of a territory by a stronger competitor or the lack of pollinators for plants, can also serve as a factor limiting the distribution. Thus, the pollination of figs depends entirely on a single insect species - the wasp Blastophaga psenes. This tree is native to the Mediterranean. Figs brought to California did not bear fruit until pollinator wasps were brought there. The distribution of legumes in the Arctic is limited by the distribution of bumblebees that pollinate them. On the island of Dixon, where there are no bumblebees, legumes are not found either, although the existence of these plants there is still permissible due to temperature conditions.

Rice. 6. Deep snow cover is a limiting factor in the distribution of deer (according to G. A. Novikov, 1981)

To determine whether a species can exist in a given geographical area, one must first find out whether any environmental factors go beyond its ecological valence, especially in the most vulnerable period of development.

The identification of limiting factors is very important in agricultural practice, since, by directing the main efforts to eliminate them, one can quickly and effectively increase plant yields or animal productivity. So, on highly acidic soils, the wheat yield can be somewhat increased by applying various agronomic effects, but the best effect will be obtained only as a result of liming, which will remove the limiting effects of acidity. Knowing the limiting factors is thus the key to controlling the life of organisms. At different periods of life of individuals, various environmental factors act as limiting factors, therefore, skillful and constant regulation of the living conditions of grown plants and animals is required.

2.4. Principles of ecological classification of organisms

In ecology, the diversity and variety of ways and means of adaptation to the environment create the need for multiple classifications. Using any single criterion, it is impossible to reflect all aspects of the adaptability of organisms to the environment. Ecological classifications reflect the similarities that occur among members of very different groups if they use similar ways of adaptation. For example, if we classify animals according to the methods of movement, then the ecological group of species moving in the water by jet means such animals of different systematic position as jellyfish, cephalopods, some ciliates and flagellates, larvae of a number of dragonflies, etc. (Fig. 7). Ecological classifications can be based on a variety of criteria: methods of nutrition, movement, attitude to temperature, humidity, salinity, pressure etc. The division of all organisms into eurybiont and stenobiont according to the breadth of the range of adaptations to the environment is an example of the simplest ecological classification.

Rice. 7. Representatives of the ecological group of organisms moving in water in a jet way (according to S. A. Zernov, 1949):

1 – flagellar Medusochloris phiale;

2 – ciliate Craspedotella pileosus;

3 – jellyfish Cytaeis vulgaris;

4 – pelagic holothurian Pelagothuria;

5 - a larva of a dragonfly-rocker;

6 – swimming octopus Octopus vulgaris:

a- the direction of the water jet;

b- the direction of movement of the animal

Another example is the division of organisms into groups by the nature of nutrition.Autotrophs- these are organisms that use as a source for building their body not organic compounds. Heterotrophs- all living beings that need food of organic origin. In turn, autotrophs are divided into phototrophs and chemotrophs. The first to synthesize organic molecules use energy sunlight, the second - the energy of chemical bonds. Heterotrophs are divided into saprophytes, using solutions of simple organic compounds, and Holozoic. Holozoans have a complex set of digestive enzymes and can eat complex organic compounds, decomposing them into simpler constituents. Holozoic are divided into saprophages(feed on dead plant matter) phytophages(consumers of living plants), zoophagous(needing living food) and necrophages(carnivorous animals). In turn, each of these groups can be subdivided into smaller ones, which have their own specifics in the nature of nutrition.

Otherwise, you can build a classification by way of getting food. Among animals, for example, such groups as filtrators(small crustaceans, toothless, whale, etc.), grazing forms(ungulates, leaf beetles), collectors(woodpeckers, moles, shrews, chicken), moving prey hunters(wolves, lions, ktyr flies, etc.) and a number of other groups. So, despite the great dissimilarity in organization, the same way of mastering the prey leads in lions and ktyr flies to a number of analogies in their hunting habits and general structural features: leanness of the body, strong development of muscles, the ability to develop high speed for a short time, etc.

Ecological classifications help to identify possible ways in nature to adapt organisms to the environment.

2.5. Active and hidden life

Metabolism is one of the most important properties of life, which determines the close material-energy connection of organisms with the environment. Metabolism shows a strong dependence on the conditions of existence. In nature, we observe two main states of life: active life and rest. With active life, organisms feed, grow, move, develop, multiply, being characterized by an intensive metabolism. Rest can be different in depth and duration, many functions of the body are weakened or not performed at all, since the level of metabolism falls under the influence of external and internal factors.

In a state of deep dormancy, i.e., a reduced material-energy metabolism, organisms become less dependent on the environment, acquire a high degree of stability and are able to endure conditions that they could not withstand during active life. These two states alternate in the life of many species, being an adaptation to habitats with an unstable climate, sharp seasonal changes, which is typical for most of the planet.

With a deep suppression of metabolism, organisms may not show visible signs of life at all. The question of whether it is possible to completely stop metabolism with a subsequent return to active life, that is, a kind of "resurrection from the dead", has been discussed in science for more than two centuries.

First time phenomenon imaginary death was discovered in 1702 by Anthony van Leeuwenhoek, the discoverer of the microscopic world of living beings. The “animalcules” (rotifers) observed by him, when the drops of water dried, wrinkled, looked dead and could remain in this state for a long time (Fig. 8). Placed again in the water, they swelled and moved to an active life. Leeuwenhoek explained this phenomenon by the fact that the shell of the "animalcules" obviously "does not allow the slightest evaporation" and they remain alive in dry conditions. However, a few decades later, natural scientists were already arguing about the possibility that "life can be completely stopped" and restored again "in 20, 40, 100 years or more."

In the 70s of the XVIII century. the phenomenon of "resurrection" after drying was discovered and confirmed by numerous experiments in a number of other small organisms - wheat eels, free-living nematodes and tardigrades. J. Buffon, repeating the experiments of J. Needham with acne, argued that "these organisms can be made to die and come to life as many times as you like in a row." L. Spallanzani first drew attention to the deep dormancy of seeds and spores of plants, regarding it as their preservation in time.

Rice. eight. Rotifer Philidina roseola on different stages drying (according to P. Yu. Schmidt, 1948):

1 – active; 2 - starting to shrink 3 – completely reduced before drying; 4 - in a state of suspended animation

In the middle of the XIX century. it was convincingly established that the resistance of dry rotifers, tardigrades and nematodes to high and low temperatures, lack or absence of oxygen increases in proportion to the degree of their dehydration. However, the question remained open whether there was a complete interruption of life or only its deep oppression. In 1878, Claude Bernal put forward the concept "hidden life" which he characterized by the cessation of metabolism and "a break in the relationship between the being and the environment."

This issue was finally resolved only in the first third of the 20th century with the development of deep vacuum dehydration technology. The experiments of G. Rama, P. Becquerel and other scientists showed the possibility complete reversible cessation of life. In a dry state, when no more than 2% of water remained in the cells in a chemically bound form, such organisms as rotifers, tardigrades, small nematodes, seeds and spores of plants, spores of bacteria and fungi survived in liquid oxygen (-218.4 ° C ), liquid hydrogen (-259.4 °C), liquid helium (-269.0 °C), i.e. temperatures close to absolute zero. At the same time, the contents of the cells harden, there is not even a thermal movement of molecules, and any metabolism, of course, is stopped. Once placed under normal conditions, these organisms continue to develop. In some species, stopping metabolism at ultra-low temperatures is possible even without drying, provided that water freezes not in a crystalline, but in an amorphous state.

The complete temporary suspension of life is called suspended animation. The term was proposed by W. Preyer back in 1891. In a state of suspended animation, organisms become resistant to a wide variety of influences. For example, tardigrades withstood ionizing radiation of up to 570 thousand roentgens for 24 hours in an experiment. Dehydrated larvae of one of the African chironomus mosquitoes - Polypodium vanderplanki - retain the ability to come to life after exposure to a temperature of +102 ° C.

The state of anabiosis greatly expands the boundaries of life preservation, including in time. For example, in the thickness of the glacier of Antarctica, during deep drilling, microorganisms (spores of bacteria, fungi and yeast) were found, which subsequently developed on ordinary nutrient media. The age of the corresponding ice horizons reaches 10–13 thousand years. Spores of some viable bacteria have also been isolated from deeper layers hundreds of thousands of years old.

Anabiosis, however, is a fairly rare occurrence. It is far from possible for all species and is an extreme state of rest in wildlife. His necessary condition- preservation of intact thin intracellular structures (organelles and membranes) during drying or deep cooling of organisms. This condition is not feasible for most species that have a complex organization of cells, tissues and organs.

The ability to anabiosis is found in species that have a simple or simplified structure and live in conditions of sharp fluctuations in humidity (drying shallow water bodies, upper layers of soil, cushions of mosses and lichens, etc.).

Much more widespread in nature are other forms of dormancy associated with a state of reduced vital activity as a result of partial inhibition of metabolism. Any degree of reduction in the level of metabolism increases the resistance of organisms and allows more economical use of energy.

Forms of rest in a state of reduced vital activity are divided into hypobiosis and cryptobiosis, or compelled rest and physiological rest. In hypobiosis, inhibition of activity, or torpor, occurs under the direct pressure of unfavorable conditions and stops almost immediately after these conditions return to normal (Fig. 9). Such suppression of vital processes can occur with a lack of heat, water, oxygen, with an increase in osmotic pressure, etc. In accordance with the leading external factor of forced rest, cryobiosis(at low temperatures), anhydrobiosis(with lack of water), anoxybiosis(under anaerobic conditions), hyperosmobiosis(with a high salt content in water), etc.

Not only in the Arctic and Antarctic, but also in the middle latitudes, some frost-resistant species of arthropods (springtails, a number of flies, ground beetles, etc.) hibernate in a state of torpor, quickly thawing and turning to activity under the rays of the sun, and then again lose their mobility when the temperature drops . Plants sprouting in spring stop and resume growth and development following cooling and warming. After a rainfall, bare soil often turns green due to the rapid reproduction of soil algae, which were in forced rest.

Rice. 9. Pagon - a piece of ice with freshwater inhabitants frozen into it (from S. A. Zernov, 1949)

The depth and duration of suppression of metabolism during hypobiosis depends on the duration and intensity of the inhibitory factor. Forced rest occurs at any stage of ontogeny. The benefits of hypobiosis are the rapid restoration of active life. However, this relatively unstable state of organisms can be damaging for a long time due to the imbalance of metabolic processes, depletion of energy resources, accumulation of underoxidized metabolic products, and other unfavorable physiological changes.

Cryptobiosis is a fundamentally different type of dormancy. It is associated with a complex of endogenous physiological changes that occur in advance, before the onset of adverse seasonal changes, and organisms are ready for them. Cryptobiosis is an adaptation primarily to the seasonal or other periodicity of abiotic environmental factors, their regular cyclicity. It is part of the life cycle of organisms; it does not occur at any, but at a certain stage of individual development, timed to coincide with the experience of critical periods of the year.

The transition to a state of physiological rest takes time. It is preceded by the accumulation of reserve substances, partial dehydration of tissues and organs, a decrease in the intensity oxidative processes and a number of other changes that generally lower tissue metabolism. In the state of cryptobiosis, organisms become many times more resistant to adverse environmental influences (Fig. 10). In this case, the main biochemical rearrangements are in many respects common for plants, animals, and microorganisms (for example, switching of metabolism to a different degree to the path of glycolysis due to reserve carbohydrates, etc.). The way out of cryptobiosis also requires time and energy and cannot be carried out simply by stopping the negative effect of the factor. This requires special conditions that are different for different species (for example, freezing, the presence of drip-liquid water, a certain length of daylight hours, a certain quality of light, mandatory temperature fluctuations, etc.).

Cryptobiosis as a survival strategy in periodically unfavorable conditions for active life is a product of long evolution and natural selection. It is widely distributed in nature. The state of cryptobiosis is typical, for example, for plant seeds, cysts and spores of various microorganisms, fungi, algae. Diapause of arthropods, hibernation of mammals, deep dormancy of plants are also different types of cryptobiosis.

Rice. ten. An earthworm in a state of diapause (according to V. Tishler, 1971)

The states of hypobiosis, cryptobiosis and anabiosis ensure the survival of species in natural conditions different latitudes, often extreme, allow organisms to survive for long unfavorable periods, to settle in space and in many ways push the boundaries of the possibility and spread of life in general.

A living organism under natural conditions is simultaneously exposed to not one, but many environmental factors, and each factor is required by the body in certain quantities or doses.

Plants need significant amounts of moisture, nutrients (nitrogen, phosphorus, potassium), but other substances, such as boron or molybdenum, are required in negligible amounts. Nevertheless, the lack or absence of any substance (both macro- and microelement) negatively affects the state of the body, even if all the others are present in the required quantities.

The law of the limiting (limiting) factor or Liebig's law of the minimum is one of the fundamental laws in ecology, stating that the factor that deviates most from its optimal value is most significant for an organism. 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.

1. Law of Tolerance (Shelford's Law)

However, at the beginning of the 20th century, the American scientist V. Shelford showed that a substance (or any other factor) present not only in a minimum, but also in excess compared to the level required by the body, can lead to undesirable consequences for the body.

For example, even a slight deviation of the content of mercury in the body (in principle, a harmless element) from a certain norm leads to severe functional disorders (the well-known "Minamata disease"). The lack of moisture in the soil makes the nutrients present in it useless for the plant, but excessive moisture leads to similar consequences for reasons, for example, "suffocation" of the roots, acidification of the soil, and the occurrence of anaerobic processes. Many microorganisms, including those used in biological wastewater treatment plants, are very sensitive to the limits of the content of free hydrogen ions, i.e. to the acidity of the medium (pH).

Let us analyze what happens to the organism under the conditions of the dynamics of the regime of one or another environmental factor. If you place any animal or plant in an experimental chamber and change the air temperature in it, then the state (all life processes) of the organism will change. In this case, some best (optimal) level of this factor (Topt) for the organism will be revealed. at which its activity (A) will be maximum (Fig. 2.). But if the regimes of the factor deviate from the optimum in one direction or another (greater or lesser) side, then the activity will decrease. Upon reaching a certain maximum or minimum value, the factor will become incompatible with life processes. Changes will occur in the body that cause its death. These levels will thus be lethal or lethal (Tlet and T'let).

From all of the above follows the law of W. Shelford, or the so-called law of tolerance: any living organism has certain evolutionarily inherited upper and lower limits of resistance (tolerance) to any environmental factor.

1. Tolerance

Theoretically, similar, although not absolutely similar, results can be obtained in experiments with a change in other factors: air humidity, the content of various salts in water, the acidity of the environment, etc. (see Fig. 2, b). The wider the amplitude of the fluctuations of the factor at which the organism can remain viable, the higher its stability, i.e. tolerance to one or another factor (from lat. tolerance- patience).

Tolerance - the endurance of a species in relation to fluctuations in any environmental factor.

The range between the ecological minimum and the maximum of the factor is the limit of tolerance.

Tolerant organisms are organisms that are resistant to adverse environmental changes.

Rice. 2. The impact of the environmental factor on the body

Hence the word "tolerant" is translated as stable, tolerant, and tolerance can be defined as the ability of an organism to withstand deviations of environmental factors from the values ​​that are optimal for its life activity.

Any element of the environment can act as a limiting environmental factor if its level causes irreversible pathological changes in the organism and transfers it (the organism) to an irreversibly pessimal state, from which the organism is not able to exit, even if the level of this factor returns to the optimum.

Any living organism has upper and lower thresholds (limits) of resistance to any environmental factor, beyond which this factor causes irreversible, persistent functional deviations in the body in certain organs and physiological (biochemical) processes, without directly leading to death.

To protect the environment means to ensure the composition and regimes of environmental factors within the limits of the inherited tolerance of a living (primarily human) organism, i.e. manage it in such a way that no factor is limiting in relation to it.

Ecology(from the Greek "oikos" - housing and "logos" - science) - a science that studies the patterns of relationships between organisms and the environment, the way of life of animals and plants, their productivity, changes in numbers, species composition.

Environmental factors

Living environment is part of nature in which organisms live. There are three environments of life - water, air, soil. Water is the primary environment for living beings, since it was in it that life originated. Organisms can live in one environment (fish - in water), in two (terrestrial plants in air and soil) and even in three environments (coastal aquatic plants - in soil, water and air). Some organisms periodically move from one environment to another (insects with aquatic larvae, amphibians). Individual elements of the environment that interact with organisms are called environmental factors.

By their nature, two groups of factors are distinguished:

1. inorganic, or abiotic factors: temperature, light, water, air, wind, salinity and density of the medium, ionizing radiation;
2. biotic factors, associated with cohabitation, the mutual influence of animals and plants on each other.
3. Allocate also anthropogenic factor- human impact on nature. Each of the environmental factors is irreplaceable. So, the lack of heat cannot be replaced by an abundance of light, the mineral elements necessary for plant nutrition cannot be replaced by water.

The intensity of the factor, the most favorable for life, is called optimal or optimum.

The boundaries beyond which the existence of an organism is impossible are called the lower and upper endurance limits.

Abiotic factors

solar radiation serves as the main source of energy for all processes occurring on Earth. The biological effect of light is diverse and is determined by its spectral composition, intensity, and periodicity of illumination.

The spectrum of solar radiation includes ultraviolet, visible and infrared rays.

Ultraviolet rays with a wavelength of 0.29 microns are detrimental to all living things, they are delayed by the ozone layer of the atmosphere. Longer ultraviolet rays (0.3-0.4 microns) have a high chemical activity. In small doses, ultraviolet rays are beneficial.

Visible rays (wavelength 0.4-0.75 microns) are especially great importance for organisms. Green plants synthesize organic matter. For most animals, visible light is one of the important environmental factors.

Infrared rays (wavelength over 0.75 microns) are an important source of thermal energy.

Temperature- an important factor affecting the vital processes of organisms: growth, development, reproduction, respiration, synthesis of organic substances, etc. The optimal temperature depends on the habitat conditions of the species; for most terrestrial animals and plants, it varies within rather narrow limits (15-30°C). Organisms with variable body temperature are called cold-blooded. For them, an increase in temperature causes an acceleration physiological processes. However, these organisms have adaptations from overheating (the presence of stomata in plants, evaporation through the skin in animals).

The most perfect thermoregulation in the process of evolution was acquired by birds and mammals, i.e. warm-blooded animals, due to the formation of a four-chambered heart. This ensured their existence regardless of the temperature conditions of the environment and allowed them to settle throughout the globe.

Water- an indispensable component of living things, an important climatic factor, as it serves as the main means of regulating temperature on the surface of the Earth. Adaptation to experience with a lack of moisture is pronounced in the inhabitants of arid steppes and deserts (modified spiny leaves, a well-developed root system, high osmotic pressure). Some plants (agave, stonecrop, young) have fleshy leaves and stems and are able to retain water for a long time. Other plants (tulips, poppies, goose onions, etc.) have time to grow and bloom in a short spring, when there is still enough moisture in the soil. The ability of these plants to sink into a state of deep physiological dormancy is of great adaptive importance.

Seasonal changes in external conditions are associated with changes in the most important factors of life - temperature, lighting, humidity. The inhabitants of temperate latitudes are characterized by the manifestation of seasonal cycles of development.

In the spring, with an increase in temperature and lighting, an active vital activity of organisms is observed: plants grow and bloom, birds arrive, etc. In summer, plant seeds ripen, most animals give offspring. In autumn, the preparation of organisms for adverse winter conditions begins: nutrients are deposited in plants, molting occurs in animals, etc. In winter, at low temperatures, deep rest sets in. This phenomenon is especially characteristic of plants and some animals.

Each organism has certain adaptations to endure low temperatures. Moreover, the frost resistance of plants and insects increases during the winter. It's called cold hardening. Deep cooling causes a temporary reversible stoppage of life. Such a state is called suspended animation. In birds and mammals, the state of complete suspended animation does not occur, since they are not adapted to hypothermia. They have developed other adaptations for the transfer of the winter season (seasonal migrations, etc.).

In the regulation of seasonal cycles in most plants and animals, the main role belongs to changes in the length of day and night. The response to the length of the light period of the day is called photoperiodism.

photoperiodism- this is a common, important adaptation that regulates seasonal phenomena in the most various organisms. A change in the length of the day is always closely related to the annual course of temperature and precedes its change, following the shortening of the day, the temperature also decreases. During the year, the length of the day changes strictly regularly and is not subject to random fluctuations. Therefore, the length of the day serves as an accurate astronomical harbinger of seasonal changes. Elucidation of the role of day length and the regulation of seasonal phenomena opens up great opportunities for scientific understanding of the development of plants and animals.

Habitat- this is that part of nature that surrounds a living organism and with which it directly interacts. The components and properties of the environment are diverse and changeable. Any living being lives in a complex changing world, constantly adapting to it and regulating its life activity in accordance with its changes.

Organisms' adaptations to their environment are called adaptations. The ability to adapt is one of the main properties of life in general, as it provides the very possibility of its existence, the ability of organisms to survive and reproduce. Adaptations manifest themselves at different levels: from the biochemistry of cells and the behavior of individual organisms to the structure and functioning of communities and ecological systems. Adaptations arise and change during the evolution of species. Separate properties or elements of the environment that affect organisms are called environmental factors. Environmental factors are diverse. They may be necessary or, conversely, harmful to living beings, promote or hinder survival and reproduction. Environmental factors have a different nature and specificity of action. Environmental factors are divided into abiotic and biotic, anthropogenic.

In the complex of action of factors, it is possible to single out some patterns that are largely universal (general) in relation to organisms. These patterns include the rule of optimum, the rule of interaction of factors, the rule of limiting factors, and some others.

Optimum rule. In accordance with this rule, for an organism or a certain stage of its development, there is a range of the most favorable (optimal) value of the factor. The more significant the deviation of the action of the factor from the optimum, the more this factor inhibits the vital activity of the organism. This range is called the zone of oppression. The maximum and minimum tolerated values ​​of the factor are critical points beyond which the existence of an organism is no longer possible.

The maximum population density is usually confined to the optimum zone. Zones of optimum for different organisms are not the same. The wider the amplitude of fluctuations of the factor, at which the organism can remain viable, the higher its stability, i.e. tolerance to this or that factor (from lat. tolerance - patience). Organisms with a wide amplitude of resistance belong to the group of eurybionts (Greek euri - wide, bios - life). Organisms with a narrow range of adaptation to factors are called stenobionts(Greek stenos - narrow). It is important to emphasize that the zones of optimum in relation to various factors differ, and therefore organisms fully show their potential capabilities if they exist under the conditions of the entire spectrum of factors with optimal values.

Rule of interaction of factors. Its essence lies in the fact that some factors can enhance or mitigate the force of other factors. For example, an excess of heat can be somewhat mitigated by low air humidity, a lack of light for plant photosynthesis can be compensated by an increased content of carbon dioxide in the air, etc. It does not, however, follow that the factors can be interchanged. They are not interchangeable.

Rule of limiting factors. The essence of this rule lies in the fact that a factor that is in deficiency or excess (near critical points) negatively affects organisms and, in addition, limits the possibility of manifestation of the strength of other factors, including those that are at the optimum. Limiting factors usually determine the boundaries of the distribution of species, their ranges. The productivity of organisms depends on them.

A person by his activity often violates almost all of the listed patterns of factors. This is especially true for limiting factors (destruction of habitats, disruption of water and mineral nutrition, etc.).