Environmental environmental factors. Living conditions. Definition and classification

Introduction

1. Habitat and living conditions

2. Limiting factors

3. Interaction and compensation of factors

4. Anthropogenic limiting factors

Bibliography

Introduction

The word “ecology” was first introduced into scientific terminology by the German scientist Haeckel in 1866 and for a long time had a narrow scope of application - within the framework of biology. It gained its popularity relatively recently - in the middle of the 20th century, or more precisely, in its second half, when the relationship between man and the environment, society and nature became too strained. Ecology is defined as the study of the interaction of living organisms with their natural habitat.

It is impossible not to notice that in all cases the interaction of living organisms (including humans, society) with the natural environment, and not with the environment in general, can be traced. Thus, we should talk about ecology in its literal sense only in cases where we are talking about interaction with the natural environment. It is necessary to observe the laws of the development of nature, ecological patterns, which, of course, are absent in the non-natural environment, where we include the non-productive, everyday sphere (streets, squares, residential areas - everything that surrounds a person besides nature).

This work examines environmental components that are important for the life of an organism—ecological factors. The work also examines the concept of natural resources, factors of natural resources and their involvement in the sphere of interests of society. The purpose of this work is to study environmental factors and how they affect the environment, as well as to study the concept of natural resources. To achieve the goal, it is necessary to solve a number of problems: study environmental factors, as well as types of environmental factors, consider and analyze their impact on the environment, consider the concept of resources and their classification.

The habitat of living organisms is made up of many inorganic and organic components, including those introduced by humans. Moreover, some of them, such as nutrients and energy, are vital for organisms, while others do not play a significant role in their life. For example, a hare, a wolf, a fox and any other animal in the forest are interconnected with a huge number of elements. They cannot do without air, water, food, or a certain temperature. A boulder, a fallen tree trunk, a stump, a hummock, a ditch are elements of the environment to which they are indifferent. Animals enter into temporary relationships with them (shelter, crossing), but not obligatory ones. Different organisms react differently to the same environmental factors; they force them to adapt to different living conditions. Adaptation (lat. adaptatio- adaptation) to existence in various conditions has been developed historically in organisms.

The socio-economic development of mankind in the second half of the twentieth century was accompanied and continues to be accompanied at the beginning of the 3rd millennium by the depletion of natural resources, degradation and pollution of the natural environment, and an increase in the overall mortality and morbidity rate of the population, including children. The difficult environmental situation is generated by a system of irrational, wasteful environmental management and is an important characteristic and component of the socio-economic, political, spiritual and cultural crisis both in our country and in the world as a whole.

The urgency of preventing an environmental crisis, ensuring the environmentally safe development of human civilization, the need to solve global problems in an interconnected world are the objective basis for the emergence of common interests of various countries and peoples in the search for common coordinated solutions and actions.

In conditions when the scale of anthropogenic impact on the environment has reached such proportions that life on the planet is at risk, environmental protection and rational use of natural resources come to the fore.

Habitat and living conditions

Environmental factors can be necessary or harmful to living things, promoting or hindering survival and reproduction.

Environmental factors are components of the environment that are important for the life of an organism. Habitat– this is the entire natural environment of a living organism. Conditions of existence is a set of environmental factors that determine the growth, development, survival and reproduction of organisms.

The whole variety of environmental factors is usually divided into three groups: abiotic, biotic and anthropogenic.

Abiotic factors is a set of properties of inanimate nature that are important for organisms. These factors, in turn, can be divided into chemical (composition of the atmosphere, water, soil) and physical (temperature, pressure, humidity, currents, etc.). The diversity of relief, geological and climatic conditions also gives rise to a huge variety of abiotic factors.

Of primary importance are climatic ones - sunlight, temperature, humidity; geographical - length of day and night, terrain; hydrological (gr. hydor - water) - flow, waves, composition and properties of water; (gr. edaphos - soil) - composition, structure and properties of soils, etc. All factors can influence organisms directly or indirectly. For example, the terrain affects light, humidity, wind and microclimate. Let's look at some basic abiotic environmental factors.

Sunlight has a dual effect on the body. On the one hand, the direct effect of light on protoplasm is fatal to the body, on the other hand, sunlight is the primary source of energy, without which life is impossible. Consequently, light is not only a vital, but at some minimum and maximum level a deadly factor. The visible, i.e., region of the spectrum perceived by the human eye, lies in the range from 390 to 760 nm. Animals and plants respond to different wavelengths of light. The qualitative attributes of light are wavelength (color), intensity (useful energy), and duration of exposure (length of day). Color vision is developed in some species of arthropods, fish, birds, etc. In mammals, it is well developed only in primates.

Individual organisms adapt to different light intensities, i.e. they can be adapted to shade or to direct sunlight. For example, marine phytoplankton are adapted to low intensity and are suppressed by direct sunlight. The maximum of primary production in the ocean occurs not in the surface layer of water, but in the underlying layer, at a depth of 0.5 - 1.0 m.

The temperature in the Universe fluctuates within thousands of degrees. Compared to this range of fluctuations, the temperature limits for the existence of life are very narrow. Certain types of bacteria can exist for some time in the dormant stage at very low temperatures: up to -250°C. Other types of bacteria and algae are able to live in hot springs - about +90°C.

Temperature variability is an important environmental factor. Temperatures that range from 10 to 20°C (average 15°C) affect organisms differently than a constant temperature of 15°C. The vital activity of organisms that are naturally exposed to variable temperatures (in temperate climates) is suppressed when exposed to constant temperatures. This must be taken into account when conducting laboratory experiments that are carried out at a constant temperature.

Humidity is a parameter characterizing the content of water vapor in the air. In nature, there is a daily regime of humidity: it increases at night and decreases during the day.

Along with light and temperature, humidity plays an important role in the life and distribution of organisms. In addition, humidity affects the effect of temperature. Low humidity causes the drying effect of air, especially on terrestrial plants. Animals try to avoid drying out: they move to protected places or lead an active lifestyle at night.

Water is a necessary environmental factor for any ecosystem. The amount of precipitation, humidity, drying properties of air and available reserves of surface water are the main quantities characterizing this environmental factor. The amount of precipitation depends on the nature of the movement of air masses and the terrain. Wet winds blowing from the ocean leave most of the moisture on the mountain slopes facing the ocean, and behind the mountains a “rain shadow” is created, contributing to the formation of deserts.

The distribution of precipitation by season is important. If the total annual rainfall (about 900 mm) falls in one season, plants and animals have to endure long periods of drought. This uneven distribution of precipitation occurs in the tropics and subtropics. In the tropics, this seasonal rhythm of humidity regulates the seasonal activity of organisms (reproduction, etc.) in the same way as the seasonal rhythm of temperature regulates the activity of organisms in the temperate zone. The formation of the type of ecosystem largely depends on the amount of precipitation: up to 250 mm - deserts, from 250 to 750 mm - forest-steppe, from 750 to 1250 mm - dry forests, over 1250 mm - wet forests.

The type of ecosystem depends not only on the amount of precipitation, but also on transpiration, i.e., the loss of water through evaporation by organisms (mainly plants) and, ultimately, is determined by the equilibrium of these processes.

Currents are an important environmental factor in aquatic ecosystems. Currents directly affect living organisms: the concentration of dissolved gases (0 2, C0 2) and nutrients (N, P, etc.) in water depends on them; Currents carry energy subsidies and the structure and productivity of ecosystems depend on them. Thus, differences in the composition of the biocenosis of a stream and a small pond are determined mainly by differences in the flow factor. Plants and animals of flowing waters are morphologically and physiologically adapted to maintaining their position in the flow. In swamp ecosystems, currents play the role of one of the important sources of energy and largely determine their productivity. Thus, the productivity of swampy forests with standing water is about 0.2 kg/m 2 -year, with slowly flowing water - about 0.7 kg/m 2 tod, and with seasonal floods - over 1.0 kg/m 2 tod.

Biotic factors- this is the totality of the impacts of the life activity of some organisms on others. For each organism, all the others are important environmental factors; they have no less effect on it than inanimate nature.

The whole variety of relationships between organisms can be divided into two main types: antagonistic (gr. antagonizsma - struggle) and non-antagonistic.

Predation is a form of relationship between organisms of different trophic levels, in which one type of organism - the predator - lives at the expense of another - the prey, by eating it. This is the most common form of interaction between organisms in food chains. Predators live separately from the prey and can specialize in one species (lynx - hare) or be polyphagous (wolf).

Victims develop a range of defense mechanisms. Some can run or fly fast. Others have a shell. Still others have a protective color or change it, masquerading as the color of greenery, sand, or soil. Still others release chemicals that frighten or poison the predator, etc. Predators also adapt to obtaining food. Some run very fast, like a cheetah. Others hunt in packs: hyenas, lions, wolves. Still others catch sick, wounded and other defective individuals.

In any biocenosis, mechanisms have evolved that regulate the numbers of both predator and prey. Unreasonable destruction of predators often leads to a decrease in the viability and number of their victims and causes damage to nature and humans.

Competition (lat. concurrentia - competition) is a form of relationship in which organisms of the same trophic level fight for scarce resources: food, CO 2, sunlight, living space, places of shelter and other conditions of existence, suppressing each other. Competition is clearly manifested in plants: trees in the forest strive to cover as much space as possible with their roots in order to receive water and nutrients. They also reach in height towards the light, trying to overtake their competitors. Weeds kill other plants.

There are many examples from the life of animals. Intensified competition explains, for example, the incompatibility of broad-clawed and narrow-clawed crayfish in the same reservoir: the more prolific narrow-clawed crayfish usually wins.

The greater the similarity in the requirements of two species for living conditions, the stronger the competition, which can lead to the extinction of one of them. Given the same access to a resource, one of the competing species may have advantages over another due to intensive reproduction, the ability to consume more food or solar energy, the ability to protect itself, and greater tolerance to temperature fluctuations and harmful influences.

Antagonistic relationships are more pronounced in the initial stages of community development. In mature ecosystems, there is a tendency to replace negative interactions with positive ones that enhance the survival of the species.

The type of interactions between species may vary depending on conditions or life cycle stages.

Non-antagonistic relationships can theoretically be expressed in many combinations: neutral, mutually beneficial, one-sided, etc. The main forms of these interactions are as follows: symbiosis, mutualism and commensalism.

Symbiosis (gr. symbiosis- cohabitation) is a mutually beneficial, but optional relationship between different types of organisms. An example of symbiosis is the cohabitation of a hermit crab and an anemone: the anemone moves, attaching itself to the back of the crab, and with the help of the anemone it receives richer food and protection. A similar relationship can be observed between trees and certain types of fungi that grow on their roots: the fungi obtain dissolved nutrients from the roots and themselves help the tree extract water and mineral elements from the soil. Sometimes the term "symbiosis" is used in a broader sense - "living together."

Mutualism (lat. mutuus - mutual) - mutually beneficial and obligatory for the growth and survival of relationships between organisms of different species. Lichens are a good example of the positive relationship between algae and fungi, which cannot exist separately. When insects distribute plant pollen, both species develop specific adaptations: color and smell in plants, proboscis in insects, etc. They also cannot exist one without the other.

Commensalism (lat. commensalis - dining companion) - a relationship in which one of the partners benefits, but the other is indifferent. Commensalism is often observed in the sea: in almost every mollusk shell and sponge body there are “uninvited guests” who use them as shelters. In the ocean, some species of crustaceans live on the jaws of whales. The crustaceans acquire shelter and a stable source of food. Such a neighborhood brings neither benefit nor harm to the whale. Sticky fish, following the sharks, pick up the remains of their food. Birds and animals that feed on the leftover food of predators are examples of commensals.

Despite competition and other types of antagonistic relationships, in nature many species can get along peacefully. In such cases, they say that each species has its own ecological niche (fr. niche - nest). The term was proposed in 1910 by R. Johnson.

Ecological niche implies a complex of all abiotic and biotic environmental environmental factors necessary for organisms to live, grow and reproduce in a given ecosystem.

Some authors use the term “habitat” instead of the term “ecological niche.” The latter includes only the habitat, and the ecological niche, in addition, determines the function performed by the species. P. Agess (1982) defines an ecological niche and habitat as follows: a habitat is the address where an organism lives, and a niche is also its profession, occupation and lifestyle.

Ecological niche – this is a set of territorial and functional characteristics of the habitat that meet the requirements of a given species.

Depending on food sources, territory size, temperature and other physical and chemical factors, ecological niches are divided into specialized and general.

Specialized ecological niches are occupied by plants and animals that can exist only in a narrow range of environmental factors and feed on a limited range of plants or animals. For example, the giant panda living in China feeds 99% of bamboo shoots. The destruction of bamboo in some areas of China has brought this animal to the brink of extinction.

Tropical rainforests have many specialized niches that support a variety of living organisms. Deforestation of these forests will doom millions of species of plants and animals that can only live in these conditions to extinction.

General ecological niches are occupied by organisms that easily adapt to changes in conditions. They can live in a variety of habitats, consume a variety of foods, and withstand a wide range of environmental fluctuations. Therefore, they are less at risk of extinction than species occupying a specialized niche. Common ecological niches are characterized by, for example, flies, cockroaches, rats, and people.

However, closely related organisms that have similar environmental requirements do not, as a rule, live in the same conditions. If they live in the same place, they either use different resources or have other differences in function. For example, different species of woodpeckers feed on insects in the same way and nest in tree hollows, but have seemingly different specializations. The Great Spotted Woodpecker forages for food in tree trunks, the Medium Spotted Woodpecker in large upper branches, the Lesser Spotted Woodpecker in thin twigs, the Green Woodpecker hunts ants on the ground, and the Three-toed Woodpecker looks for dead and burnt tree trunks, i.e., different species of woodpeckers have different ecological niches. Hawks and owls feed on the same animals, but hawks hunt their prey during the day and owls hunt at night.

Observations show that two species coexisting in the same territory cannot have exactly the same requirements for living conditions. Otherwise, one of them will displace the other.

Theoretically, this pattern can be described by the Lotka-Volterra equations, which were proposed independently of each other in 1925 and 1926:

dN1/dt = r1N1 (K1 – N1 – a1N2)/K1;

dN2/dt = r2N2 (K2 – N2 – a2N1)/K2,

where N1 and N2 are the numbers of two competing species 1 and 2; r1 And r2 - their growth rate; K1 and K2 - maximum population densities; a1 is the competition coefficient characterizing the suppressive effect of species 2 on species 1; a2 is the competition coefficient characterizing the impact of type 1 on type 2.

In the absence of refuges or other possibilities for the distribution of functions, the species that is stronger will sooner or later inevitably displace its partner.

This pattern was experimentally confirmed by the Russian scientist G.F. Gause (1934), who conducted experiments with related species of ciliates - Paramecium caudatum and Paramaecium aurelia, placing their cultures together in a food-rich environment, as if in one ecological niche.

Rice. 1. Competition between related species of ciliates (experiments by G. F. Gause)

After 18 days, almost one type of ciliate was found in the environment - Paramaecium ourelia. At the same time, none of the organisms attacked the other and did not release toxic substances. Just Paramaecium aurelia is characterized by a higher growth and reproduction rate and wins the second species. This pattern is called Gause's rule.

Gause's rule is formed as follows: two species living in the same territory cannot have exactly the same ecological niche.

Two closely related species avoid competition in any way: they have differences in daily or seasonal activity, food, etc. Thus, great and crested cormorants feed in the same waters. But the great cormorant gets food at the bottom (flounder and shrimp), and the crested cormorant catches planktonic fish in the upper layers of the water. If lions and leopards live in the same territory, then lions hunt large animals, and leopards hunt small ones.

Closely related species with similar needs often live in different geographic areas. Probably, the action of natural selection in the process of evolution is aimed at preventing confrontation between species with a similar way of life.

Organisms also influence each other indirectly: bacteria form the chemical composition of soils and water; plants influence the microclimate and other physical factors, etc. When some species become extinct, other species dependent on them may cease to exist.

Information about ecological niches allows you to manage domestic and wild species of plants and animals as sources of food and other resources. In addition, it helps to predict the consequences of the removal or introduction of a particular species into ecosystems.

Anthropogenic factors- is a combination of various human impacts on inanimate and living nature. Only by their physical existence do people have a noticeable impact on their environment: in the process of breathing, they annually release 1-10 12 kg of CO 2 into the atmosphere, and consume over 5-10 15 kcal with food. To a much greater extent, the biosphere is influenced by human production activities. As a result, the relief, composition of the earth's crust and atmosphere, climate change, fresh water is redistributed, natural ecosystems disappear and artificial agro- and techno-ecosystems are created, cultivated plants are cultivated, animals are domesticated, etc.

Human impact can be direct and indirect. For example, cutting down and uprooting forests has not only a direct effect, but also an indirect one - the living conditions of birds and animals change. It is estimated that since 1600, humans have destroyed 162 species of birds, over 100 species of mammals, and many other species of plants and animals. But, on the other hand, it creates new varieties of plants and breeds of animals, increases their yield and productivity. The artificial relocation of plants and animals also affects the life of ecosystems. Thus, 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 increasingly subjugates nature. Their impact is so great that it gave birth to a new discipline - “Environmental Protection”, the ecological principles of which are discussed in the second part of the textbook - “Fundamentals of Applied Ecology”.

The above division of environmental factors into three groups is, of course, conditional. It cannot capture the complexity of the relationships of organisms with each other and with the environment.

Other classifications of environmental factors have been proposed. According to A. S. Monchadsky (1962), for example, environmental factors should be divided into two groups: those that change regularly, periodically, and those that change without any patterns.

Limiting factors

The idea of ​​limiting factors is based on two laws of ecology: the law of the minimum and the law of tolerance.

Law of the minimum. In the middle of the last century, the German simicist J. Liebig (1840), studying the effect of nutrients on doct plants, discovered that the yield does not depend on those nutrients that are required in large quantities and are present in abundance (for example, CO 2 and H 2 O ), and from those that, although the plant needs them in smaller quantities, are actually 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 element that is present in minimal quantities.” This conclusion later became known as Liebig's law of the minimum and was extended to many environmental factors. Heat, light, water, oxygen, and other factors can limit or limit the development of organisms, if their movement corresponds to the ecological minimum. For example, the tropical fish 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 in general can be formulated as follows: the growth and development of an organism depends, first of all, on those environmental factors whose values ​​approach the ecological minimum.

Research has shown that the law of the 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 conditions of a stationary state of the system. For example, in a certain body of water, the growth of algae is limited under natural conditions by a lack of phosphates. Nitrogen compounds are found in excess in water. If wastewater with a high content of mineral phosphorus begins to be discharged into this reservoir, the reservoir may “bloom.” This process will progress until one of the elements is used up to the restrictive minimum. Now it may be nitrogen if phosphorus continues to be supplied. At the transition moment (when there is still enough nitrogen and enough phosphorus), the minimum effect is not observed, i.e., none of these elements affects the growth of algae.

The second limitation relates to the interaction of several factors. Sometimes the body is able to replace the deficient element with another, chemically similar one. Thus, in places where there is a lot of strontium, in mollusk shells it can replace calcium when there is a deficiency of the latter. Or, for example, the need for zinc in some plants is reduced if they grow in the shade. Therefore, a low zinc concentration will limit plant growth less in the 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 was discovered by the English biologist W. Shelford (1913), who drew attention to the fact that not only those environmental factors whose values ​​are minimal, but also those that are characterized by an ecological maximum can limit the development of living organisms. Excess heat, light, water and even nutrients can be just as destructive as their lack. V. Shelford called the range of environmental factors between minimum and maximum the limit of tolerance.

The tolerance limit describes the amplitude of factor fluctuations, which ensures the most fulfilling existence of the population. Individuals may have slightly different tolerance ranges. This particular fish may be able to withstand higher or lower temperatures or amounts of toxic substances.

Later, tolerance limits for various environmental factors were established 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 environmental factors.

V. Shelford's law of tolerance is formulated as follows: the growth and development of organisms depend, first of all, on environmental factors, the values ​​of which approach 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 may have a wide range of tolerance for one factor and a narrow range for another. For example, people are more tolerant to the absence of food than to the lack of water, i.e., the tolerance limit for water is narrower than for food;

If conditions for one of the environmental factors become suboptimal, then the tolerance limit for other factors may also change. For example, when there is a lack of nitrogen in the soil, cereals require much more water;

The actual limits of tolerance observed in nature are less than the potential capabilities of the body to adapt to this factor. This is explained by the fact that in nature the limits of tolerance in relation to the physical conditions of the environment can be narrowed by biotic relationships: competition, lack of pollinators, predators, etc. Any person better realizes his potential in favorable conditions (athletes gather for special training before important competitions, for example ). The potential ecological plasticity of the organism, determined in laboratory conditions, is greater than the realized possibilities in natural conditions. Accordingly, potential and realized ecological niches are distinguished;

The limits of tolerance in breeding individuals and offspring are less than in adult individuals, i.e. females during the breeding season and their offspring are less hardy than adult organisms. Thus, the geographic distribution of game birds is more often determined by the influence of climate on eggs and chicks, rather than on adult birds. Caring for offspring and careful attitude towards motherhood are dictated by the laws of nature. Unfortunately, sometimes social “achievements” contradict these laws;

Extreme (stressful) values ​​of one of the factors lead to a decrease in the tolerance limit for other factors. If heated water is released into a river, fish and other organisms spend almost all their energy coping with stress. They lack energy to obtain food, protect themselves from predators, and reproduce, which leads to gradual extinction. Psychological stress can also cause many somatic (gr. soma- body) diseases not only in humans, but also in some animals (for example, dogs). With stressful values ​​of the factor, adaptation to it becomes more and more “expensive”.

Many organisms are capable of changing tolerance to individual factors if conditions change gradually. You can, for example, get used to the high temperature of the water in the bath if you get into warm water and then gradually add hot water. This adaptation to a slow change in factor is a useful protective property. But it can also be dangerous. Unexpectedly, without warning signs, even a small change can be critical. A threshold effect occurs: the last straw could be fatal. For example, a thin twig can cause a camel's already overloaded back to break.

Fortunately, not all possible environmental factors regulate the relationship between the environment, organisms and humans. Various limiting factors turn out to be priority in a given period of time. It is these factors that the ecologist should focus on when studying and managing ecosystems. For example, the oxygen content in terrestrial habitats is high, and it is so accessible that it almost never serves as a limiting factor (except at high altitudes and anthropogenic systems). Oxygen is of little interest to ecologists interested in terrestrial ecosystems. 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 ones.

Limiting factors also determine the geographical range of the species. Thus, the movement of organisms to the north 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 decided to bring there a certain type of wasp - the only pollinator of this plant. Identification of limiting factors is very important for many activities, especially agriculture. With targeted influence on limiting conditions, it is possible to quickly and effectively increase plant yields and animal productivity. Thus, when growing wheat on acidic soils, no agronomic measures will be effective unless liming is used, which will reduce the limiting effect of acids. Or, if you grow corn in soils that are very low in phosphorus, 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 also die from too much water or excess fertilizer, which in this case are also limiting factors.

Knowledge of limiting factors provides the key to ecosystem management. However, at different periods of an organism’s life and in different situations, various factors act as limiting factors. Therefore, only skillful regulation of living conditions can give effective management results.

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PART II

Chapter 3 . ENVIRONMENTAL FACTORS. GENERAL REGULARITIES OF EFFECT ON ORGANISMS

Environment and conditions of existence of organisms. It is necessary to distinguish between concepts such as environment and conditions of existence of organisms.

The environment is everything that surrounds the organism and directly or indirectly affects its condition, development, growth, survival, reproduction, etc. The environment of each organism is made up of many elements of inorganic and organic nature and elements introduced by man and his production activities. Moreover, some elements may be necessary for the body, others are almost or completely indifferent to it, and others have a harmful effect. So, for example, the white hare (Lepus timidus) in the forest enters into certain relationships with food, oxygen, water, and chemical compounds, without which it cannot do. But a boulder, a tree trunk, a stump, a hummock do not have a significant impact on his life: the hare enters into temporary relationships with them (shelter from bad weather, an enemy), but not obligatory ones.

Conditions of existence, or living conditions, are a set of environmental elements necessary for an organism, with which it is in inextricable unity and without which it cannot exist.

Elements of the environment that are necessary for the body or have a negative impact on it are called environmental factors. In nature, these factors do not act in isolation from each other, but in the form of a complex complex. A complex of environmental factors, without which an organism cannot exist, represents the conditions of existence, or the living conditions of a given organism.

Different organisms perceive and react differently to the same factors. In addition, organisms of each species have their own special conditions. Plants and animals of deserts and semi-deserts exist in conditions of high temperature and low humidity. The tundra is home to plants and animals that are sensitive to lack of moisture and can tolerate low temperatures. Residents of salt and fresh waters perceive the concentration of minerals differently. Animals and plants of the tundra, fresh lakes and salt seas are selective about certain factors.

All adaptations of organisms to existence in various conditions have been developed historically. As a result, groupings of plants and animals specific to each geographical zone were formed.

Classification of factors. Analysis of the huge variety of factors allows us to divide them more or less clearly into three main groups: abiotic, biotic and anthropic.

Abiotic factors are a set of conditions in the inorganic environment that affect the organism. They are divided into chemical (chemical composition of the atmosphere, sea and fresh water, soil, bottom sediments) and physical or climatic (temperature, barometric pressure, wind, humidity, radiation regime, etc.) factors. The structure of the surface (relief), geological and climatic differences determine a huge variety of abiotic factors that play a corresponding role in the life of species of animals, plants and microorganisms that have historically adapted to them. The number (biomass) and distribution of organisms within the range depend on limiting factors, that is, on factors necessary for existence, but presented at a minimum. For desert dwellers this is water, for many aquatic organisms it is the amount of oxygen dissolved in water.

Anthropic factors are the totality of the impact of human activity on the organic world. With the historical development of humanity and the emergence of specific patterns inherent only to it, nature has been enriched with qualitatively new phenomena. By the mere fact of their existence, people have a significant impact on their environment. For example, during the process of respiration, 1.1 10 12 kg of carbon dioxide enters the atmosphere annually, and humanity’s annual need for food is estimated at 2.7 10 15 kcal (11.34 10 15 kJ). But to a much greater extent, nature is influenced by human production activities. As a result, the relief and chemical composition of the earth's surface and atmosphere change, fresh water is redistributed, the climate of the planet as a whole changes, certain natural biogeocenoses are eliminated, artificial agrobiogeocenoses are created everywhere, species of plants and animals that are beneficial to humans are exploited and species harmful to humans are destroyed, cultivated plants are cultivated and domesticated animals. The importance of anthropic factors, as man increasingly conquers and subjugates nature, is constantly increasing.

When analyzing environmental factors, one should take into account their necessity, variability, as well as the adaptive reactions of the body. In this regard, hydroedaphic, or water-soil, factors are often classified as a separate group. A. S. Monchadsky divides their entire set into two main groups - those that change regularly and those that change without regular periodicity.

However, this division of factors into four groups is quite artificial. It does not reveal the entire essence of the relationship between the organism and the environment.

Influence of abiotic factors on the body. Abiotic factors can have a direct and indirect (mediated) effect on the body. For example, the temperature of the environment, acting directly on the body of an animal or plant, determines their thermal balance and the course of physiological processes. At the same time, temperature as an abiotic factor can also have an indirect effect. Thus, by providing certain conditions for the development of plants that serve as food for phytophagous animals, it can affect the life activity of the latter.

The effect of environmental factors depends not only on their nature, but also on the dose perceived by the body (high or low temperature, bright light or darkness). In the process of evolution, all organisms have developed adaptations to perceive factors within certain quantitative limits. However, for each organism, be it a plant, an animal or a microorganism, there is a specific number of factors that are most favorable for it. A decrease or increase in this dose relative to the limits of the optimal range reduces the vital activity of the organism, and when the maximum or minimum is reached, the possibility of its existence is completely excluded (Fig. 2).

The more the dose of a factor deviates from the optimal value for a given type (both upward and downward), the more its vital activity is inhibited. The limits beyond which the existence of an organism is impossible are called the lower and upper limits of endurance.

The intensity of the environmental factor that is most favorable for the life of the organism is called the optimum, and the one that gives the worst effect is called the optimum.– pessimum.

Ecological plasticity of organisms. Each organism and the species as a whole has its own optimal conditions. As it turned out, it is not the same not only for different species in different conditions, but also for individual stages of development of one organism. For example, the optimal temperatures for flowering, fruiting, germination, spawning, and reproduction of many species are well known. Depending on what optimum level is most acceptable for species, they are distinguished between heat- and cold-loving, moisture- and dry-loving, adapted to high or low salinity. Each species is characterized by a degree of endurance. For example, plants and animals of the temperate zone can exist in a fairly wide temperature range, but species of the tropical climate cannot withstand significant fluctuations in temperature.

The ability of species to adapt to a particular range of environmental factors is denoted by the concept of ecological plasticity (ecological valence) of a species. The wider the range of fluctuations in the environmental factor within which a given species can exist, the greater its ecological plasticity.

Species that can exist with small deviations of the factor from the optimal value are called highly specialized, and species that can withstand significant changes in the factor are called broadly adapted. The first group includes the majority of sea inhabitants, whose normal life activity is maintained only with a high concentration of salts in the environment. Freshwater organisms, on the contrary, are adapted to low salt content in the environment. Consequently, both marine and freshwater species have low ecological plasticity with respect to salinity. However, the threespined stickleback (Gasterosteus aculeatus), for example, is characterized by great ecological plasticity, since it can live in both fresh and salt waters.

Ecologically non-plastic, i.e., low-hardy species are called stenobiont (stenos - narrow), more hardy - eurybiont (eyros - wide). Stenobiontism and eurybiontism characterize various types of adaptation of organisms to survival. Species that have developed for a long time in relatively stable conditions lose ecological plasticity and develop stenobiontic traits, while species that existed under significant fluctuations in environmental factors acquire increased ecological plasticity and become eurybiontic (Fig. 3). The attitude of organisms to fluctuations of a particular factor is expressed by adding the prefix eury- or steno- to the name of the factor. Thus, in relation to temperature, eury- and stenothermic organisms are distinguished, in relation to salt concentration - eury- and stenohaline, in relation to light - eury- and stenothermic, etc.

In relation to all environmental factors (or at least to many), there are very few eurybiont organisms. Most often, eury- or stenobiontism manifests itself in relation to one factor. For example, marine and freshwater fish will be stenohaline, while the mentioned three-spined stickleback is a typical euryhaline; a plant, being eurythermic, can at the same time be a stenohygrobiont, i.e., be less resistant to fluctuations in humidity.

Eurybiontism usually contributes to the wide distribution of species. As is known, many protozoa and fungi (typical eurybionts) are cosmopolitan and distributed everywhere. Stenobiontity usually limits its range. However, due to their high specialization, stenobionts often occupy vast territories. Thus, the fish-eating bird osprey (Pandion haliaetus), being a typical stenophage, acts as a eurybiont in relation to other factors. It has the ability to move long distances in search of food and occupies a significant range.

Since all environmental factors are interrelated and none of them are absolutely indifferent for any organism, each population and species as a whole reacts to these factors, but perceives them differently. Such selectivity also determines the selective attitude of organisms to populate a particular territory. The distribution of organisms depends on the time and place of their origin, on the factors to which they have historically adapted. As a result, some factor that prevents the spread of some species may be favorable for others. Thus, for plants and animals adapted to fresh water, the high concentration of salts in the seas and oceans is an obstacle to their colonization and, conversely, marine animals and plants are not able to exist in fresh water bodies.

Different types of organisms have different requirements for soil conditions, temperature, humidity, light, etc. Therefore, different plants grow on different soils and in different climatic zones. In turn, unequal conditions for animals are formed in plant associations. Historically adapting to abiotic environmental factors and entering into certain biotic relationships with each other, animals, plants and microorganisms are distributed across various environments and form diverse biogeocenoses, ultimately uniting into the Earth's biosphere.

Thus, individuals and the populations formed from them adapt to each of the environmental factors in a relatively independent way. At the same time, their environmental valency in relation to different factors turns out to be different. That is why each species has a specific ecological spectrum, that is, the sum of environmental valences in relation to environmental factors.

Chapter 4. JOINT ACTION OF ENVIRONMENTAL FACTORS

Limiting factor. All factors in nature affect the body simultaneously. And not in the form of a simple sum, but as a complex interacting relationship. Such a set of factors is called their constellation. Therefore, the optimum and limits of the body’s endurance in relation to any one factor depend on other influences. For example, at an optimal temperature, tolerance to unfavorable humidity and lack of nutrition increases. On the other hand, the abundance of food increases the body's resistance to changes in several climatic factors. However, this so-called “compensation” of factors is limited, and none of them can be completely replaced by the other. That is why, when one or another condition changes, the vital activity of the organism (the ability to compete with other species, reproduction, etc.) is limited by the factor that deviates more strongly from the optimal value for the species. If, in quantitative terms, at least one of the factors goes beyond the endurance of the species, then the existence of the latter becomes impossible, no matter how favorable the other conditions are. A factor whose level in qualitative or quantitative terms (deficiency or excess) turns out to be close to the endurance limits of a given organism is called limiting.

Consider temperature as the limiting factor. Elk are found much further north in Scandinavia than in Siberia, although the latter has a higher average annual temperature. The reason that prevents moose from expanding their range north in Siberia is low winter temperatures. The limiting factor for the spread of beech in Europe is also the low January temperature. Therefore, the northern boundaries of its range correspond to the January isotherm of -2°C. Reef-forming corals live only in the tropics at water temperatures of at least 20 °C.

High temperature can be a similar factor. Thus, the southern border of the range of the cabbage butterfly, widespread in Europe and North-West Africa, is in Palestine, since it is usually too hot there in the summer.

When the environmental situation changes, the ratio of individual factors is also disrupted. That is why in different areas the factors limiting the development of organisms are often different: in the north, for certain species, this may be a lack of heat, and in the south, for the same species, it may be a lack of moisture, food, or high temperature. It should also be noted that the same factor for one organism acts as a limiting factor for some time, and then becomes non-limiting. It depends on the stage of development of a given organism. Almost all animals and plants are more sensitive to unfavorable conditions during the breeding season. For example, the influence of climatic factors during the geographic distribution of many game birds extends only to eggs and chicks, but not to adult individuals.

Ecological series and ecological individuality. An ecological series is a set of plant communities (phytocenoses) arranged according to the increase or decrease of any factor (or group of factors) in the environment. For example, on a slope, the dryest soil is observed in the upper part, and the least dryness in the lower part, so there are differences in vegetation associated with soil moisture. Some species grow only in the upper part of the slope, others in the middle, and others in the lower. As a result, an ecological series of plant species is clearly distinguished either by increasing or decreasing soil moisture - from top to bottom from more to less dry-loving and, conversely, from bottom to top, from more to less moisture-loving. And the ecological series of tree species according to increasing shade tolerance is as follows: larch - birch - pine - aspen - willow - gray alder - linden - oak - ash - maple - alder - elm - hornbeam - spruce - beech - fir.

Similar ecological series are compiled in relation to plants in relation to thermal conditions, the degree of soil salinity, resistance to wind and other factors. Thus, in the floodplains of the rivers of the southern part of the Russian Plain, in the case of elevation of the area, a change in vegetation is observed (from lowering to a hillock) in the following sequence: meadow-swamp, meadow, meadow-steppe and steppe plant associations. This is an ecological series of phytocenoses. Sometimes up to 10 or more associations are identified in such a series. Their boundaries are often very difficult to determine, since combinations of environmental conditions change gradually in space and a transitional, intermediate zone is formed between cenoses, in which the characteristics of neighboring associations are combined. This is explained by the ecological individuality of each species, and therefore their habitats in the community do not coincide. In other words, different species react differently to the same factors.

In general, the ecological individuality of an individual is a set of its specific features, consisting of a peculiar combination of hereditary and acquired properties. It develops during the development of the organism (ontogenesis) and is expressed in the characteristics of the genotype and phenotype of a given individual. In nature, there are no identical, identical individuals, even in a very homogeneous population. In addition to specific characteristics, each individual also has ecological individuality, manifested in a variety of forms.

Among the large number of individuals that make up a population, it is always possible to identify individuals who are the most or least ecologically plastic in relation to one or another factor. Some are very sensitive to low temperatures, others are relatively cold-tolerant, some cannot withstand even slight dryness, and there are others that survive during dry periods. Due to ecological individuality, the population usually contains the most resilient individuals that survive very unfavorable conditions, which determines the conservation of the species.

Preliminary rule. In 1951, V.V. Alekhine established the pre-plant rule for plants. According to this rule, northern moisture-loving plants within the southern boundaries of the range are located on the northern slopes and at the bottom of ravines, and southern ones, as they move north, move to better warmed southern slopes (Fig. 4). This is especially evident on the southern and northern borders of the forest zone. Along the southern slopes, blueberry spruce and oxalis spruce forests penetrate deep into the northern taiga from the middle taiga. In Yakutia, cold-resistant forests of Dahurian larch (Larix dahurica) grow on the northern slopes, while the southern slopes are covered with pine forests. On the southern outskirts of the forest zone, forests are preserved along the northern slopes, and typical steppe vegetation grows on the southern slopes.

Naturally, the anticipation rule is relative. It is less clearly expressed in mountainous areas, since a more complex set of environmental factors is observed there. Nevertheless, it is of great importance when conducting geobotanical research, since it allows one to predict the composition of vegetation in places that have not yet been surveyed and its former appearance where it has been destroyed.

The principle of stage fidelity. A station is usually understood as the habitat of a species. Due to the fact that species and their constituent populations selectively relate to environmental factors, they inhabit strictly defined stations with corresponding environmental conditions. An area of ​​territory occupied by a population of a species and characterized by certain environmental conditions is called a station. The concept of “station” applies only to the species.

Each species has its own set of stations. There are many transitions between the extremes of a species' habitat selectivity. The Asian locust, for example, lives only in swampy areas, while the Italian locust (Calliptamus italicus) is more flexible and inhabits virgin steppe areas, fallow lands, and pastures. Swedish and Hessian flies, wheat tripe are confined to crops of bread or meadow cereals, while the cabbage armyworm (Baraihra brassicae) is found in the fields of not only cabbage, but also beet, pea, sunflower, clover and even tobacco plantations. The set of habitats is so characteristic of each species that it can serve as no less significant distinguishing feature than morphological and other features. This is of practical importance in determining harmful and beneficial species.

The property of species to selectively populate certain stations is designated as the principle of stationary fidelity. This principle is an important ecological pattern.

Rules for changing habitats and layers. The principle of stage fidelity is applicable only in conditions of limited space and time. The natural change of species in their habitats over a wide range of space and time is the rule of habitat change. This rule was established and formulated by G. Ya. Bey-Bienko (1966).

In turn, M. S. Gilyarov deduced rule for changing tiers, showing that in different zones the same species occupy different layers. This is typical for transzonal species, that is, for species that are widespread and found in many natural zones.

In space, the rule of habitat change is expressed in the zonal and vertical change of stations and in the zonal change of tiers, and in time - in the seasonal and annual change of stations.

Zonal change of stations is a naturally directed change in habitats when a species moves from one natural zone to another. Typically, when moving north, species choose dry, well-warmed open habitats with sparse vegetation cover. Spreading to the south, these same species inhabit more moist and shady places with dense vegetation. For example, migratory locusts (Locusta migratoria) in Central Europe settle in sandy areas, and in Central Asia and Kazakhstan - in damp swampy areas with dense grass. In wet meadows, lasia ants (Lasius niger, L. flavus) manifest themselves as hygrophobes and settle on hummocks. In drier habitats, in the steppe, these same ants act as hygrophiles and choose more humid areas. As Bey-Bienko points out, the zonal change of stations serves as an ecological consequence of the law of geographic zonation and is explained by changes in the thermal regime. Externally identical stations in the north and south differ sharply in terms of thermal regime, therefore, when moving from south to north, species choose habitats that are close in heat to those in the south.

The vertical change of stations is similar to the zonal one, but it is typical for mountain conditions. For example, the gray grasshopper (Decticus verrucivorus) in the forests of the Caucasus inhabits hygrophytic and mesophytic stations, and in the alpine zone it becomes a xerophile.

The zonal change of layers consists in the fact that many species, when moving north, move from a higher plant layer to a lower one, and some in relatively dry zones from terrestrial ones become soil inhabitants. Thus, the forest gardening bark beetle (Blastophagus piniperda) in the central regions and in the north lives under the bark of trunks and large branches of pine trees, and in the southeast of the European part of the USSR it goes into the soil and settles on the roots. The larvae of the stag beetle (Lucanus cervus) in the forest zone develop in rotting trunks and stumps, and in the steppe zone - in rotten roots at a depth of up to 100 cm.

Bey-Bienko believes that the zonal change of stations and tiers and the vertical change of stations place the species in dual and contradictory conditions. On the one hand, the species makes certain demands on the environment, resulting from its hereditary physiological properties; on the other hand, upon successful settlement, it is forced to occupy new stations or even change its layer. As a result, its ecology changes, and at the same time its physiology. Consequently, the change of stations becomes one of the leading factors of evolution.

Seasonal changes in stations occur when the microclimate fluctuates within one season. This is most clearly expressed in dry and hot climates and manifests itself in the migration of steppe and desert species during periods of drought to cultivated crops, meadows, and under the forest canopy, where relatively high humidity and green vegetation cover are maintained. Such migrations are typical for many insects and rodents.

An annual change of stations is observed when weather conditions deviate from the average annual norm. For example, migratory locusts in Southern Kazakhstan in dry years concentrate in depressions with moister soil and thick grass cover, and in wet years they colonize elevated areas.

Thus, changing habitats allows species to maintain their ecological standard in constantly changing conditions.

The principle of stage fidelity and its opposite - the rule of changing habitats and tiers - indicates the complexity of the relationship between organisms and the environment. Clarification of the essence of these relationships makes it possible to penetrate more deeply into the ecology of a particular species and develop rational methods for combating harmful organisms and for protecting and attracting beneficial ones.

Principles of ecological classification of organisms. The ecological classification of organisms differs from systematics in that in the latter the main criterion is the phylogenetic proximity of organisms, i.e., systematics at all levels of taxonomy is based on a single criterion - phylogeny. The environmental classification does not have such a criterion, so it has a lot of schemes.

Ecological classification of organisms can be carried out according to their position in the energy or food chain. In relation to organic matter, heterotrophs and autotrophs are distinguished; according to their function in biogeocenosis, they are producers, consumers and decomposers (destructors).

Ecological classification can also be based on habitats.

Aquatic organisms are divided into benthic, planktonic and nektonic. They can also be classified according to the zones they occupy. With this approach, it is important to find out the position of the organism in all three classification systems, and also to keep in mind that many species at different stages of development lead different lifestyles (tadpole and frog, dragonfly larva and adult insect).

The classification of terrestrial animals causes particular difficulties, since they represent a huge variety of forms, which is associated with the characteristics of their habitats. Already among herbivores there are both small and very large. The abundance of insects and other arthropods, as well as birds, is practically impossible to count and ecologically classify. It is even more difficult to classify decomposers. Soil organisms are usually classified by size, and therefore there are micro-, meso-, and macrobiota.

The most common ecological classification of organisms is by life forms, that is, by the type of external morphology that reflects the most important aspects of the lifestyle and the relationship of the species to the environment. Life forms determine the adaptability of organisms to a complex of factors (in contrast to ecological groups, which characterize adaptation to individual factors), to the specifics of the habitat.

Animals have very diverse life forms. First of all, these are groups that have similar ecological and morphological adaptations for living in a similar environment. In this case, the term “life forms” is borrowed from botany. It became established in zoology only in the present century, although animals have long been divided into divers, burrowers, diggers, etc.

There are many different interpretations of the life forms of animals. This is due to the fact that in some cases the classification is based on the characteristics of reproduction, in others - on methods of movement or obtaining food. Often, classification is based on the association of organisms with certain ecological niches, landscapes, and layers. Nevertheless, the analysis of life forms makes it possible to judge the characteristics of the habitat and the ways in which animals develop adaptation to certain conditions. For example, D.N. Kashkarov (1945) classifies the life forms of animals as follows.

I. Floating forms:

1. Purely aquatic: a) nekton, b) plankton, c) benthos;

2. Semi-aquatic: a) diving, b) non-diving, c) extracting only food from the water.

II. Burrowing forms:

1. Absolute diggers (they spend their entire lives underground);

2. Relative diggers (come to the surface of the earth).

III. Ground forms:

1. Those who do not make holes: a) running, b) jumping, c) crawling;

2. Making holes: a) running, b) jumping, c) crawling;

3. Animals of the rocks.

IV. Arboreal, climbing forms: a) not descending from trees, b) only climbing trees.

V. Aerial forms: a) obtaining food in the air, b) looking for it from the air.

As you can see, this classification is based on devices for movement. In relation to air humidity, Kashkarov distinguishes moisture-loving (hygrophilic) and dry-loving (xerophilic) forms; according to nutrition - herbivores, omnivores, carnivores, gravediggers (corpse eaters); according to the place of reproduction - those reproducing underground, on the surface of the earth, in the layer of grasses, in bushes, on trees.

Various categories of life forms of insects relative to their habitat (geobionts, hydrobionts, etc.) are proposed by V.V. Yakhontov. The zonal-landscape category of life forms was developed by ornithologists A.K. Rustamov, G.P. Dementyev, S.M. Uspensky.

Plants are classified based on adaptation to environmental conditions. Among them are hygrophytes, mesophytes, and xerophytes. This classification is based on the physiological properties of plants, and the division of vegetation into trees, shrubs, and grass gives characteristics of the main terrestrial communities. Due to the diversity of conditions on Earth, plants have developed a huge number of life forms. The concept of life forms of plants was first introduced in 1806 by Humboldt. Typically, woody, semi-woody, terrestrial herbaceous and aquatic herbaceous plants are distinguished. Each of these forms can be represented in smaller groups. The most widely used classification of plant life forms was developed in 1905–1907. Danish botanist S. Raunkier. It is based on the location of renewal buds and the presence of devices for surviving unfavorable seasons. The modern classification is based on this classification, which distinguishes 6 life forms of plants (Fig. 5).

1. Epiphytes* are aerial plants that do not have roots in the soil. They settle on the trunks of other larger plants. In forests these are stem lichens, less often mosses. Of higher plants, epiphytes are numerous in tropical rainforests.

2. Phanerophytes – above-ground plants (trees, shrubs, vines, stem succulents, herbaceous-stem plants). Their renewal buds are located on vertical shoots high above the ground.

3. Chamephytes are herbaceous plants with renewal buds located near the ground. In temperate latitudes, the shoots of these plants go under the snow for the winter and do not die off.

4. Hemicryptophytes are turf-forming plants in which renewal buds are located at the soil level or even in it. Aboveground shoots die off by winter. These are a lot of meadow plants.

5. Cryptophytes, or geophytes, are perennial herbs with dying above-ground parts. Renewal buds are located on underground organs (tuberous or rhizomatous plants).

6. Therophytes are annual plants. By winter, both their aboveground and underground parts die off. An unfavorable period (winter) is experienced at the seed stage.

In the given series of life forms, increasing adaptation to unfavorable conditions is clearly manifested. In tropical rainforests, most species belong to phanerophytic epiphytes. In more northern areas, plants with protected renewal buds predominate.

There are other classification schemes for life forms. The classification of cereals according to the method of tillering, developed by V. R. Williams, has received the greatest recognition. G.N. Vysotsky and L.I. Kazakevich based the classification of life forms on the nature of underground organs and the ability of plants for vegetative reproduction. Recently, I. G. Serebryakov proposed a successful classification of angiosperms, focusing on the structure and life span of aboveground skeletal axes. He identifies 4 divisions and 8 types of life forms of these plants (Diagram 3). Each type is in turn subdivided into forms. For example, in type I there are above-ground crown-forming trees with erect trunks; bush-like, single-trunked with low trunks; stlantsy (with recumbent trunks).

Life forms that dominate in a particular community can serve as indicators of living conditions. Thus, the predominance of stolon-forming plants in broad-leaved and dark-coniferous forests indicates low-fertility, loose and excessively moist soil. In hot and arid climates, animals that live in deep burrows predominate, and on highly fertile and loose soils, diggers create a large number of tunnels.

Chapter 5. IMPORTANT ABIOTIC FACTORS AND ADAPTATION OF ORGANISMS TO THEM

There are such concepts as environment and conditions of existence of organisms.
The environment is a part of nature that surrounds living organisms and has a direct or indirect impact on them. From the environment, organisms receive everything they need for life and secrete metabolic products into it. The environment of each organism is composed of many elements of inorganic and organic nature and elements introduced by man and his production activities. Moreover, some elements may be partially or completely indifferent to the body, others are necessary, and others have a negative effect. For example, a mountain hare (Lepus timidus) in the forest enters into certain relationships with food, water, chemical compounds, oxygen, without which it cannot do, while a tree trunk, stump, hummock, boulder does not have a significant impact on its life influence. The hare enters into temporary connections with them (shelter from the enemy, bad weather), but not obligatory connections.
Living conditions, or conditions of existence, are a set of environmental elements necessary for an organism, with which it is in inextricable unity and without which it cannot exist.
Adaptations of organisms to the environment are called adaptation. The ability to adapt is one of the main properties of life in general, ensuring the 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. All adaptations of organisms to existence in various conditions have been developed historically. As a result, groupings of plants and animals specific to each geographical zone were formed.
Individual properties or elements of the environment that affect organisms are called environmental factors (Table 3.1).
The variety of environmental factors is divided into two large groups: abiotic and biotic.
Abiotic factors are a set of conditions in the inorganic environment that affect the organism.
Biotic factors are a set of influences of the life activity of some organisms on others. In some cases, anthropogenic factors are classified as a separate group of factors along with abiotic and biotic ones, thereby emphasizing the extreme effect of the anthropogenic factor. Agreeing with the above, we still consider it more correct to classify it as part of the factors of biotic influence, since the concept of “biotic factors” covers the actions of the entire organic world, to which man belongs.
Table 3.1
Various approaches to classifying environmental factors

ENVIRONMENTAL FACTORS
ABIOTIC		BIOTIC
Light, temperature, moisture, wind, air, pressure, currents, day length, etc. Mechanical composition of the soil, its permeability, moisture capacity Content of nutrients in soil or water, gas composition, water salinity		The influence of plants on other members of the biocenosis The influence of animals on other members of the biocenosis Anthropogenic factors resulting from human activities
BY TIME	BY PERIODICITY			IN ORDER
Evolutionary Historical	Periodic Non-periodic			Primary Secondary
BY ORIGIN			BY WEDNESDAY OF APPEARANCE
Space Abiotic (abiogenic) Biogenic Biotic Biological Natural-anthropogenic Anthropogenic (including man-made, environmental pollution, including concern			Atmospheric Water (humidity) Geomorphological Edaphic Physiological Genetic Population Biocenotic Ecosystem Biosphere

A set of factors of the same kind constitutes the upper level of concepts. The lower level of concepts is associated with the knowledge of individual environmental factors.
The influence of environmental factors is determined primarily by their impact on the metabolism of organisms. Hence, all environmental factors, according to their action, can be divided into direct and indirect. Both can have significant impacts on the lives of individual organisms and the entire community. Environmental factors can act either directly or indirectly. Each environmental factor is characterized by certain quantitative indicators, such as strength and range of action.
For different types of plants and animals, the conditions in which they feel especially good are different. For example, some plants prefer very moist soil, while others prefer relatively dry soil. Some require extreme heat, others tolerate colder environments better, etc.
The intensity of the environmental factor that is most favorable for the vital activity of the organism is called optimum, and the one that gives the worst effect is called pessimum, i.e., conditions under which the vital activity of the organism is maximally inhibited, but it can still exist. Thus, when growing plants at different temperatures, the point at which maximum growth is observed will be the optimum. In most cases, this is a certain temperature range of several degrees, so it is better to talk here about the optimum zone. The entire range of temperatures, from minimum to maximum, at which growth is still possible is called the range of stability (endurance) or tolerance. The points limiting it, i.e., the maximum and minimum temperatures suitable for life, are the limits of stability. Between the optimum zone and the limits of resistance, as it approaches the latter, the plant experiences increasing stress, i.e. we are talking about stress zones or zones of inhibition within the range of resistance (Fig. 3.1). As you move further down and up the scale from the optimum, not only does stress increase, but ultimately, when the limits of the body’s resistance are reached, its death occurs. alt="" />
Rice. 3.1. Dependence of the action of an environmental factor
on its intensity

Similar experiments can be carried out to test the influence of other factors. The results will graphically correspond to a similar type of curve.
The repeatability of the observed trends makes it possible to conclude that we are talking about a fundamental biological principle here. For each plant (animal) species there is an optimum, stress zones and limits of resistance or endurance in relation to each environmental factor.
When the factor is close to the limits of endurance or tolerance, the organism can usually survive only for a short time. In a narrower range of conditions, long-term existence and growth of individuals is possible. In an even narrower range, reproduction occurs, and the species can exist indefinitely. Typically, somewhere in the middle of the resistance range there are conditions that are most favorable for life, growth and reproduction. These conditions are called optimal, in which individuals of a given species turn out to be the most fit, i.e., they leave the greatest number of descendants. In practice, it is difficult to identify such conditions, and usually the optimum is determined for individual vital indicators - growth rate, survival rate, etc.
The ability of species to adapt to a particular range of environmental factors is denoted by the concept of “ecological plasticity” (ecological valency) of a species. The wider the range of fluctuations in the environmental factor within which a given species can exist, the greater its ecological plasticity.
Species that can exist with small deviations from the factor, from the optimal value, are called highly specialized, and those that can withstand significant changes in the factor are called broadly adapted. Highly specialized species include, for example, freshwater organisms, whose normal life is maintained with a low salt content in the environment. For most sea inhabitants, on the contrary, normal life activities are maintained at high concentrations of salts in the environment. Hence, freshwater and marine species have low ecological plasticity with respect to salinity. At the same time, for example, the three-spined stickleback is characterized by high ecological plasticity, since it can live in both fresh and salt waters.
Ecologically hardy species are called eurybiont (eyros - wide); low-hardy species are called stenobiont (stenos - narrow). Eurybiontism and stenobiontism characterize various types of adaptation of organisms to survival. Species that develop for a long time in relatively stable conditions lose ecological plasticity and develop stenobiontic traits, while species that existed under significant fluctuations in environmental factors acquire increased ecological plasticity and become eurybiontic (Fig. 3.2).

Rice. 3.2. Ecological plasticity of species (according to Yu. Odum, 1975)
The attitude of organisms to fluctuations of a particular factor is expressed by adding the prefix “eury-” or “steno-” to the name of the factor. For example, in relation to temperature, eury- and stenothermic organisms are distinguished, in relation to salt concentration - eurysthenohaline, in relation to light - eury- and stenothermic, etc. In relation to all environmental factors, eurybiont organisms are rare. Most often, eury- or stenobiontism manifests itself in relation to one factor. Thus, freshwater and marine fish will be stenohaline, while the previously named three-spined stickleback is a typical euryhaline representative. The plant, being eurythermic, can at the same time be classified as a stenohygrobiont, i.e., be less resistant to fluctuations in humidity.
Eurybiontism, as a rule, contributes to the wide distribution of species. Many protozoa and fungi (typical eurybionts) are cosmopolitan and distributed everywhere. Stenobiontity usually limits its range. At the same time, often due to high specialization, stenobionts own vast territories. For example, the fish-eating bird osprey (Pandion haliaetus) is a typical stenophage, but in relation to other factors it is a eurybiont, has the ability to move long distances in search of food and occupies a significant range.
All environmental factors are interconnected, and none of them are absolutely indifferent to any organism. The population and the species as a whole respond to these factors by perceiving them differently. Such selectivity also determines the selective attitude of organisms to populate a particular territory.
Different types of organisms have different requirements for soil conditions, temperature, humidity, light, etc. Therefore, different plants grow on different soils and in different climatic zones. On the other hand, different conditions for animals are formed in plant associations. By adapting to abiotic environmental factors and entering into certain biotic relationships with each other, plants, animals and microorganisms are distributed across various environments and form diverse ecosystems that unite into the Earth’s biosphere. Consequently, individuals and the populations formed from them adapt to each of the environmental factors in a relatively independent way. Their ecological valency in relation to different factors turns out to be different. Each species has a specific ecological spectrum, that is, the sum of environmental valences in relation to environmental factors.

3.1. environment and conditions of existence of organisms

There are such concepts as environment and conditions of existence of organisms.

The environment is a part of nature that surrounds living organisms and has a direct or indirect impact on them. From the environment, organisms receive everything they need for life and secrete metabolic products into it. The environment of each organism is composed of many elements of inorganic and organic nature and elements introduced by man and his production activities. Moreover, some elements may be partially or completely indifferent to the body, others are necessary, and others have a negative effect. For example, a mountain hare (Lepus timidus) in the forest enters into certain relationships with food, water, chemical compounds, oxygen, without which it cannot do, while a tree trunk, stump, hummock, boulder does not have a significant impact on its life influence. The hare enters into temporary connections with them (shelter from the enemy, bad weather), but not obligatory connections.

Living conditions, or conditions of existence, are a set of environmental elements necessary for an organism, with which it is in inextricable unity and without which it cannot exist.

Adaptations of organisms to the environment are called adaptation. The ability to adapt is one of the main properties of life in general, ensuring the 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. All adaptations of organisms to existence in various conditions have been developed historically. As a result, groupings of plants and animals specific to each geographical zone were formed.

Individual properties or elements of the environment that affect organisms are called environmental factors (Table 3.1).

The variety of environmental factors is divided into two large groups: abiotic and biotic.

Abiotic factors are a set of conditions in the inorganic environment that affect the organism.

Biotic factors are a set of influences of the life activity of some organisms on others. In some cases, anthropogenic factors are classified as a separate group of factors along with abiotic and biotic ones, thereby emphasizing the extreme effect of the anthropogenic factor. Agreeing with the above, we still consider it more correct to classify it as part of the factors of biotic influence, since the concept of “biotic factors” covers the actions of the entire organic world, to which man belongs.

Table 3.1

Various approaches to classifying environmental factors

ENVIRONMENTAL FACTORS
ABIOTIC		BIOTIC
Light, temperature, moisture, wind, air, pressure, currents, day length, etc. Mechanical composition of the soil, its permeability, moisture capacity		The influence of plants on other members of the biocenosis The influence of animals on other members of the biocenosis Anthropogenic factors resulting from human activities
BY TIME	BY PERIODICITY			IN ORDER
Evolutionary Historical	Periodic Non-periodic			Primary Secondary
BY ORIGIN			BY WEDNESDAY OF APPEARANCE
Space Abiotic (abiogenic) Biogenic Biotic Biological Natural-anthropogenic Anthropogenic (including man-made, environmental pollution, including concern			Atmospheric Water (humidity) Geomorphological Edaphic Physiological Genetic Population Biocenotic Ecosystem Biosphere

A set of factors of the same kind constitutes the upper level of concepts. The lower level of concepts is associated with the knowledge of individual environmental factors.

The influence of environmental factors is determined primarily by their impact on the metabolism of organisms. Hence, all environmental factors, according to their action, can be divided into direct and indirect. Both can have significant impacts on the lives of individual organisms and the entire community. Environmental factors can act either directly or indirectly. Each environmental factor is characterized by certain quantitative indicators, such as strength and range of action.

For different types of plants and animals, the conditions in which they feel especially good are different. For example, some plants prefer very moist soil, while others prefer relatively dry soil. Some require extreme heat, others tolerate colder environments better, etc.

The intensity of the environmental factor that is most favorable for the vital activity of the organism is called optimum, and the one that gives the worst effect is called pessimum, i.e., conditions under which the vital activity of the organism is maximally inhibited, but it can still exist. Thus, when growing plants at different temperatures, the point at which maximum growth is observed will be the optimum. In most cases, this is a certain temperature range of several degrees, so it is better to talk here about the optimum zone. The entire range of temperatures, from minimum to maximum, at which growth is still possible is called the range of stability (endurance) or tolerance. The points limiting it, i.e., the maximum and minimum temperatures suitable for life, are the limits of stability. Between the optimum zone and the limits of resistance, as it approaches the latter, the plant experiences increasing stress, i.e. we are talking about stress zones or zones of inhibition within the range of resistance (Fig. 3.1). As you move further down and up the scale from the optimum, not only does stress increase, but ultimately, when the limits of the body’s resistance are reached, its death occurs.

Rice. 3.1. Dependence of the action of an environmental factor

on its intensity

Similar experiments can be carried out to test the influence of other factors. The results will graphically correspond to a similar type of curve.

The repeatability of the observed trends makes it possible to conclude that we are talking about a fundamental biological principle here. For each plant (animal) species there is an optimum, stress zones and limits of resistance or endurance in relation to each environmental factor.

When the factor is close to the limits of endurance or tolerance, the organism can usually survive only for a short time. In a narrower range of conditions, long-term existence and growth of individuals is possible. In an even narrower range, reproduction occurs, and the species can exist indefinitely. Typically, somewhere in the middle of the resistance range there are conditions that are most favorable for life, growth and reproduction. These conditions are called optimal, in which individuals of a given species turn out to be the most fit, i.e., they leave the greatest number of descendants. In practice, it is difficult to identify such conditions, and usually the optimum is determined for individual vital indicators - growth rate, survival rate, etc.

The ability of species to adapt to a particular range of environmental factors is denoted by the concept of “ecological plasticity” (ecological valency) of a species. The wider the range of fluctuations in the environmental factor within which a given species can exist, the greater its ecological plasticity.

Species that can exist with small deviations from the factor, from the optimal value, are called highly specialized, and those that can withstand significant changes in the factor are called broadly adapted. Highly specialized species include, for example, freshwater organisms, whose normal life is maintained with a low salt content in the environment. For most sea inhabitants, on the contrary, normal life activities are maintained at high concentrations of salts in the environment. Hence, freshwater and marine species have low ecological plasticity with respect to salinity. At the same time, for example, the three-spined stickleback is characterized by high ecological plasticity, since it can live in both fresh and salt waters.

Ecologically hardy species are called eurybiont (eyros - wide); low-hardy species are called stenobiont (stenos - narrow). Eurybiontism and stenobiontism characterize various types of adaptation of organisms to survival. Species that develop for a long time in relatively stable conditions lose ecological plasticity and develop stenobiontic traits, while species that existed under significant fluctuations in environmental factors acquire increased ecological plasticity and become eurybiontic (Fig. 3.2).

Rice. 3.2. Ecological plasticity of species (according to Yu. Odum, 1975)

The attitude of organisms to fluctuations of a particular factor is expressed by adding the prefix “eury-” or “steno-” to the name of the factor. For example, in relation to temperature, stenothermic euryea organisms are distinguished, in relation to salt concentration - eurystenohaline, in relation to light - stenophote euryea, etc. In relation to all environmental factors, eurybiont organisms are rare. Most often, eury or stenobiontism manifests itself in relation to one factor. Thus, freshwater and marine fish will be stenohaline, while the previously named three-spined stickleback is a typical euryhaline representative. The plant, being eurythermic, can at the same time be classified as a stenohygrobiont, i.e., be less resistant to fluctuations in humidity.

Eurybiontism, as a rule, contributes to the wide distribution of species. Many protozoa and fungi (typical eurybionts) are cosmopolitan and distributed everywhere. Stenobiontity usually limits its range. At the same time, often due to high specialization, stenobionts own vast territories. For example, the fish-eating bird osprey (Pandion haliaetus) is a typical stenophage, but in relation to other factors it is a eurybiont, has the ability to move long distances in search of food and occupies a significant range.

All environmental factors are interconnected, and none of them are absolutely indifferent to any organism. The population and the species as a whole respond to these factors by perceiving them differently. Such selectivity also determines the selective attitude of organisms to populate a particular territory.

Different types of organisms have different requirements for soil conditions, temperature, humidity, light, etc. Therefore, different plants grow on different soils and in different climatic zones. On the other hand, different conditions for animals are formed in plant associations. By adapting to abiotic environmental factors and entering into certain biotic relationships with each other, plants, animals and microorganisms are distributed across various environments and form diverse ecosystems that unite into the Earth’s biosphere. Consequently, individuals and the populations formed from them adapt to each of the environmental factors in a relatively independent way. Their ecological valency in relation to different factors turns out to be different. Each species has a specific ecological spectrum, that is, the sum of environmental valences in relation to environmental factors.

Every organism, population, species has a habitat - that part of nature that surrounds all living things and has some impact on it, direct or indirect. It is from it that organisms take everything they need to exist, and it is into it that they secrete the products of their vital activity. Environmental conditions are not the same for different organisms. As they say, what is good for one is death for another. It consists of many organic and inorganic elements that influence a particular species.

Habitat and living conditions

Living conditions are those environmental factors that are vital for a certain type of organism. That minimum without which existence is impossible. These include, for example, air, moisture, soil, as well as light and heat. These are the primary conditions. In contrast, there are other factors that are not so vital. For example, wind or atmospheric pressure. Thus, the habitat and the conditions of existence of organisms are different concepts. The first is more general, the second means only those conditions without which a living organism or plant cannot exist.

Environmental factors

These are all those elements of the environment that are capable of influencing - direct or indirect - on These factors cause adaptations of organisms (or adaptive reactions). Abiotic is the influence of inorganic elements of inanimate nature (soil composition, its chemical properties, light, temperature, humidity). Biotic factors are forms of influence of living organisms on each other. Some species are food for others, serve for pollination and dispersal, and have other effects. Anthropogenic - human activities affecting living nature. The selection of this group is due to the fact that today the fate of the entire biosphere of the Earth is practically in the hands of man.

Most of the above factors are environmental conditions. Some are in the process of modification, others are constant. Their change depends on the time of day, for example, on cooling and warming. Many factors (the same environmental conditions) play a primary role in the life of some organisms, while in others they play a secondary role. For example, the soil salt regime is of great importance in the nutrition of plants with minerals, but in animals it is not so important for the same area.

Ecology

This is the name of the science that studies the living conditions of organisms and their relationship with it. The term was first defined by the German biologist Haeckel in 1866. However, science began to actively develop only in the 30s of the last century.

Biosphere and noosphere

The totality of all living organisms on Earth is called the biosphere. It also includes a person. And it not only enters, but also has an active influence on the biosphere itself, especially in recent years. This is how the transition to the noosphere takes place (according to Vernadsky’s terminology). The noosphere involves not only the crude use of natural resources and science, but also universal cooperation aimed at protecting our common home - planet Earth.

Aquatic habitat conditions

Water is considered the cradle of life. Many of the animals that exist on earth had ancestors that lived in this environment. With the formation of land, some species came out of the water and first became amphibians, and then evolved into land animals. Most of our planet is covered with water. Many organisms living in it are hydrophiles, that is, they do not need any adaptation to their environment.

First of all, one of the most important conditions is the chemical composition of the aquatic environment. It is different in different bodies of water. For example, the salt regime of small lakes is 0.001% salts. In large fresh water bodies - up to 0.05%. Marine - 3.5%. In salty continental lakes, the salt level reaches more than 30%. As salinity increases, the fauna becomes poorer. There are known bodies of water where there are no living organisms.

An important role in environmental conditions is played by such a factor as the content of hydrogen sulfide. For example, in (below 200 meters) no one lives at all except hydrogen sulfide bacteria. And all because of the abundance of this gas in the environment.

The physical properties of water are also important: transparency, pressure, current speed. Some animals live only in clear water, while others are suitable for muddy water. Some plants live in stagnant water, while others prefer to travel with the current.

For deep-sea inhabitants, the absence of light and the presence of pressure are the most important conditions for existence.

Plants

The habitat conditions of plants are also determined by many factors: the presence of lighting, temperature fluctuations. If the plant is aquatic - by the conditions of the aquatic environment. Among the vital ones are the presence of nutrients in the soil, natural watering and irrigation (for cultivated plants). Many of the plants are tied to certain climatic zones. In other areas they are not able to survive, much less reproduce and produce offspring. Ornamental plants, accustomed to “greenhouse” conditions, require an artificially created habitat. They can no longer survive in street conditions.

On the ground

For many plants and animals, soil habitat is important. Environmental conditions depend on several factors. These include climatic zones, temperature changes, and the chemical and physical composition of the soil. On land, as on water, one thing is good for some, and another for others. But in general, soil habitats provide shelter for many species of plants and animals that live on the planet.