The most favorable conditions for the existence of the organism. Influence of natural conditions on human life and health. Habitat and conditions of existence

Habitat and conditions of existence of organisms. Environmental factors

From the concept of ʼʼhabitatʼʼ one should distinguish the concept of ʼʼexistence conditionsʼʼ - a set of vital environmental factors without which living organisms cannot exist (light, heat, moisture, air, soil). Unlike them, other environmental factors, although they have a significant impact on organisms, are not vital for them (for example, wind, natural and artificial ionizing radiation, atmospheric electricity, etc.).

environmental factors. Elements environment that cause adaptive reactions (adaptations) in living organisms and their communities are called environmental factors.

According to the origin and nature of the action, environmental factors are divided into abiotic (elements of inorganic, or inanimate nature), biotic (forms of the impact of living beings on each other) and anthropogenic (all forms of human activity that affect wildlife).

Abiotic factors divided into physical, or climatic (light, air and water temperature, air and soil humidity, wind), edaphic, or soil-ground (mechanical composition of soils, their chemical and physical properties), topographic, or orographic (landscape features), chemical (water salinity, gas composition water and air, soil and water pH, etc.).

Anthropogenic (anthropic) factors are all forms of activity of human society that change nature as the habitat of living organisms or directly affect their life. The allocation of anthropogenic factors into a separate group is due to the fact that at present the fate of the vegetation cover of the Earth and all now existing species organisms is practically in the hands of human society.

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

Environmental factors act on organisms in different ways. Οʜᴎ can act as stimuli causing adaptive changes in physiological functions; as limiters, predetermining the impossibility of the existence of certain organisms in given conditions; as modifiers that determine morphological and anatomical changes in organisms.

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

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

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

Rice. 14.1. Scheme of the effect of the environmental factor on the vital activity of organisms: 1, 2. 3 - points of minimum, optimum and maximum, respectively; I, II, III zones of pessimum, norm and optimum, respectively.

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

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

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

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

Interaction of environmental factors. limiting factor.
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Environmental factors affect a living organism jointly and simultaneously. At the same time, the effect of one factor depends on the strength and combination of other factors acting simultaneously. This pattern is called the interaction of factors. For example, heat or frost is easier to endure when dry, and not when humid air. The rate of water evaporation by plant leaves (transpiration) is much higher if the air temperature is high and the weather is windy.

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

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

The nature of the limiting factors must be different. For example, the oppression of herbaceous plants under the canopy of beech forests, where, at optimal thermal mode, high carbon dioxide content, rich soils, the development of grasses is limited by a lack of light. This result can only be changed by influencing the limiting factor.

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

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

Populations. Structure and properties of populations

Indicators of the structure of populations. As the first necessary biological system, the population has a certain structure and properties. The structure of the population is reflected by such indicators as the number and distribution of individuals in space, the ratio of groups by sex and age, their morphological, behavioral and other features.

Number - the total number of individuals in the population. This value is characterized by a wide range of variability, but it should not be below certain limits. Reducing the number compared to these limits can lead to the extinction of the population. It is believed "that if the population is less than a few hundred individuals, then any random causes (fire, flood, drought, heavy snowfalls, severe frosts, etc.) can reduce it so much that the remaining individuals cannot meet and leave offspring. Fertility will cease to cover the natural loss, and the remaining individuals will die out within a relatively short time.

Density is the number of individuals per unit area or volume. With an increase in the population density, as a rule, increases; it remains the same only in the case of its resettlement and expansion of its range. In some animals, population density is regulated by complex behavioral and physiological mechanisms.

The spatial structure of the population is characterized by the peculiarities of the distribution of individuals in the occupied territory. It is determined by the properties of the habitat and the biological characteristics of the species. Along with random and uniform distribution in nature, group distribution is most common. A group of animals, making joint efforts, can more easily defend themselves from predators, search for and obtain food. Life in families, herds, colonies, harems also leads to group distribution of individuals. The spatial structure can change over time; it depends on the season of the year, on the population size, age and sex structure, etc.

The sexual structure reflects a certain ratio of males and females in a population. The genetic mechanism of sex determination ensures the splitting of offspring by sex in a ratio of 1: 1. Due to the different viability of male and female individuals, this primary sex ratio at fertilization often differs markedly from the secondary one (at birth - in mammals) and even more so from the tertiary, characteristic for mature individuals. For example, in human populations, the secondary sex ratio is 100 girls/106 boys; by the age of 16-18, this ratio levels off and becomes equal to 1:1, by the age of 50 - 100 women / 85 men, and by the age of 80, the sex ratio becomes 2:1 (100 women / 50 men).

The change in the sexual structure of a population is reflected in its role in the ecosystem, since males and females of many species differ from each other in the nature of nutrition, rhythm of life, behavior, etc.
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So, females of some species of mosquitoes, ticks and midges are blood-sucking, while males feed on plant sap or nectar. The predominance of the proportion of females over males ensures a more intensive growth of the population.

The age structure reflects the ratio of different age groups in populations, depending on life expectancy, the time of onset of puberty, the number of offspring in a litter, the number of offspring per season, etc.
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If any age group decreases or increases, this affects the total population. For example, the mass extermination of large sexually mature individuals as a result of fishing leads to a sharp decrease in the population due to its weak replenishment with young individuals. For this reason, the presence in the population of a large number of individuals of younger age groups indicates its well-being. If the population is dominated by old individuals, it can be said with certainty that this population is ending its existence.

ecological structure indicates the attitude of various groups of organisms to environmental conditions. For example, individuals of one plant population differ in a number of characteristics: in size, number of shoots, flowers, fruits, seeds, etc. At the same time, different individuals of the same population bloom at the same time, which contributes to their more complete pollination (with simultaneous and short-term flowering, insects may not have time to pollinate all the flowers). Such a population has a lower risk of being left without seeds, for example, in the case of short-term frosts (only part of the flowers will freeze).

Population dynamics. Theoretically, any population is capable of unlimited growth in numbers, if it is not limited by environmental factors (limited resources, diseases, predators, etc.). In such a hypothetical case, the rate of population growth will depend only on the magnitude of the biotic potential inherent in each particular species. The biotic potential reflects the theoretically possible number of offspring from one pair (or one individual) for a certain period of time, for example, for the entire life cycle or for a year.

At different types the magnitude of the biotic potential differs sharply. For example, in large mammals, even under the most favorable conditions, the number can increase only 1.05-1.1 times per year. In many insects and crustaceans (aphids, daphnia), the number increases by 10 10 -10 30 times per year, and even more in bacteria. Moreover, in these cases, under ideal conditions, the size of any population over a certain time will grow exponentially (Fig. 14.2). An increase in numbers at a constant rate is called exponential growth. The curve that reflects such a population growth on the graph quickly increases the steepness and goes to infinity.

Rice. 14.2. Exponential (theoretical) (a) and logistic (real) (b) population growth curves.

Under natural conditions, exponential population growth is extremely rare. For example, it has been noted in a rabbit population introduced to Australia, where it had unlimited food and space resources without the deterrent effect of predators. This type of growth is also observed during outbreaks of locusts, gypsy moths and other insects. At the same time, periods of exponential growth are usually short-lived.

With an increase in population density, there is usually a slowdown in population growth, as the population is placed in conditions with limited resources. For example, animals at a high population density may not have enough food, and plants begin to shade each other or they lack moisture. The type of population growth with limited resources, characterized by a decrease in speed as population density increases, is commonly called logistic (see Fig. 14.2).

The general changes in population size are determined by such processes as fertility, mortality and migration of individuals.

Fertility characterizes the frequency of the appearance of new individuals in a population. The average birth rate of each species has historically been defined as an adaptation to replenish population decline. Distinguish between absolute and specific fertility.

Absolute fertility - the number of individuals born (hatched, budded, etc.) in a population per unit of time. Specific birth rate - the number of individuals born in a population per unit of time per individual. The specific birth rate makes it possible to compare the birth rate in populations with different sizes.

The higher the birth rate, the greater the proportion of individuals participating in reproduction, the higher the fecundity, the more often reproductive cycles follow each other. Usually, the birth rate in each population is balanced by its characteristic mortality.

The number of populations is also significantly affected by the migration of individuals.

Migrations are the regular movements of animals between significantly different, spatially disparate habitats. Such migrations are caused by a change in the conditions of existence in habitats or a change in the requirements of an animal for these conditions at different stages of development. The mass movement of individuals between populations can change their structure and basic properties (prevent the death of a population that is on the verge of extinction, or, on the contrary, lead it to a sharp reduction). For example, the mass eviction of settled animals (squirrels, nutcrackers, lemmings, etc.) with a sudden deterioration in conditions (droughts, fires, floods, etc.), overpopulation often ends in their mass death.

Migrations (daily, seasonal) allow organisms to use optimal environmental conditions in places where they permanent residence impossible. Οʜᴎ lead to the development of new biotopes, the expansion of the common range of the species, the exchange of individuals between populations, increase the unity and overall stability of the species, and contribute to success in the struggle for existence.

In the absence of migration, the change in the population size depends on the ratio of the birth rate and death rate.

If the birth rate is higher than the death rate, then the population will increase, and, on the contrary, it will decrease if the death rate exceeds the birth rate. Τᴀᴋᴎᴍ ᴏϬᴩᴀᴈᴏᴍ, the number of populations under natural conditions is constantly changing as environmental conditions change. The amplitude and period of these oscillations depend on the degree of environmental variability, as well as on biological features specific type.

Behavioral factors play an important role in the regulation of population abundance and density. For example, in populations of many rodents, an increase in the concentration of the adrenaline hormone in the blood, observed at a high population density, causes aggressiveness, various hormonal disorders (in females, embryo resorption may occur). As a result, the number of rodents is decreasing.

Another form of behavior - the protection of an individual site (territoriality) - is also aimed at regulating the population. Often, almost the entire territory occupied by a population is divided into individual areas, which are designated different ways(the secret of odorous glands, scratches on trees, the singing of male birds, urine, etc.). Marking and protection of sites that do not allow the reproduction of ʼʼalienʼʼ individuals on them leads to rational use territory. In this case, the excess part of the population does not reproduce or is forced to move out of the occupied space.

There are a number of other historically established mechanisms that retard the growth of populations and thus ensure their stability. These include chemical interactions of individuals (for example, tadpoles release substances into the water that retard the growth of other tadpoles); changes in physiology and behavior with increasing density, which leads to the manifestation of mass migration instincts; the spread of diseases (the probability of transmission of infections increases with an increase in population density), etc.

Τᴀᴋᴎᴍ ᴏϬᴩᴀᴈᴏᴍ, due to a variety of mechanisms, the range of all daily, seasonal and annual changes in the number and level of population density, as a rule, is less than theoretically possible, corresponding to the realization of the entire biotic potential. Overpopulation is always unfavorable for any species, as it can lead to a rapid undermining of environmental resources, lack of food, shelters, space, which will inevitably lead to a general weakening of populations.

Habitat and conditions of existence of organisms. Environmental factors - concept and types. Classification and features of the category "Habitat and conditions for the existence of organisms. Environmental factors" 2017, 2018.

Fundamentals of General Ecology

Wednesday- everything that surrounds the body and directly or indirectly affects its vital activity, development, growth, survival, reproduction, etc.

The environment of each organism is composed of many elements of inorganic and organic nature and elements introduced by man and his production activities. At the same time, some elements are necessary for the body, others are indifferent to it, and others have a harmful effect.

Conditions of existence, or living conditions- a set of elements of the environment necessary for the organism, with which it is in inseparable unity and without which it cannot exist.

Environment elements as necessary for the body, and negatively affecting it, are called environmental factors .

Environmental factors are usually divided into three main groups: abiotic, biotic and anthropic.

abiotic factors - a complex of conditions of the inorganic and organic environment that affect the body. Abiotic factors are divided into chemical (chemical composition of air, ocean, soil, etc.) and physical (temperature, pressure, wind, humidity, light, radiation regime, etc.).

Antropical factors - a set of impacts of human activity on the organic world. Already by the fact of his existence, a person has an impact on the environment (due to breathing, approximately 1.1 10 12 kg SO 2, etc.) and immeasurably more by production activity to an ever-increasing degree.

The impact on the body of abiotic factors can be direct and indirect (indirect). So, for example, the temperature of the environment determines the rate of physiological processes in the body and, accordingly, its development (direct influence); at the same time, influencing the development of plants that are food for animals, it has an indirect effect on the latter.

The effect of environmental factors depends not only on their nature, but also on the dose perceived by the body (high or low temperature, bright light or darkness, etc.). All organisms in the process of evolution have developed adaptations to the perception of factors within certain quantitative limits. Moreover, for each organism there is a set of factors that are most favorable for it.

The more the dose of factors deviates from the optimal value for a given type (increase or decrease), the more its vital activity is inhibited. The boundaries beyond which the existence of an organism is impossible are called lower and upper limit of endurance (tolerance).

The intensity of the environmental factor that is most favorable for the organism (its life activity) is called optimum, and giving the worst effect - pessimism.

Organisms can adapt over time to changing factors. The property of species to adapt to changing ranges of environmental factors is called ecological plasticity (ecological valency). The wider the range of fluctuations of the ecological factor within which a given species can exist, the greater its ecological plasticity, the wider the range of its tolerance (endurance).

Ecologically non-plastic (hardy) species are called stenobiont(from Greek. stenos- narrow), more plastic (hardy) - eurybiontic(from Greek. euros- wide). types of organisms long time developed under relatively stable conditions, lose their ecological plasticity and acquire stenobiont features; species that existed under conditions of significant changes in environmental factors become eurybiont.

The attitude of organisms to fluctuations of one or another environmental factor is expressed by adding prefixes steno- and evry- (steno- and eurythermal, steno- and eurythotic, etc.).

Historically adapting to abiotic environmental factors and entering into biotic relationships with each other, plants, animals and microorganisms are distributed over various environments and form diverse biogeocenoses, eventually merging into biosphere Earth.

Biogeocenosis- territorially (spatially) isolated integral elementary unit of the biosphere, all components of which are closely connected with each other.

All environmental factors act on the body simultaneously and in interaction. Such a combination is called constellation. Therefore, the optimum and limits of the organism's endurance in relation to one factor depend on others. Moreover, if the intensity of at least one factor goes beyond the endurance of the species, then the existence of the latter becomes impossible, no matter how favorable other conditions are. This factor is called limiting. special case The principle of limiting factors is the rule of the minimum, formulated by Liebig (German chemist) to characterize the yield of agricultural crops: the substance that is at a minimum (in the soil, in the air) controls the yield and determines the size and stability of the latter.

From the concept of "habitat" should be distinguished the concept of "conditions of existence" - a set of vital environmental factors, without which living organisms cannot exist (light, heat, moisture, air, soil). Unlike them, other environmental factors, although they have a significant impact on organisms, are not vital for them (for example, wind, natural and artificial ionizing radiation, atmospheric electricity, etc.).

environmental factors. Elements of the environment that cause adaptive reactions (adaptations) in living organisms and their communities are called environmental factors.

According to the origin and nature of the action, environmental factors are divided into abiotic (elements of inorganic or inanimate nature), biotic (forms of the impact of living beings on each other) and anthropogenic (all forms of human activity that affect wildlife).

Abiotic factors are divided into physical, or climatic (light, air and water temperature, air and soil humidity, wind), edaphic, or soil-ground (mechanical composition of soils, their chemical and physical properties), topographic, or orographic (landscape features ), chemical (water salinity, gas composition of water and air, soil and water pH, etc.).

Anthropogenic (anthropic) factors are all forms of activity of human society that change nature as the habitat of living organisms or directly affect their life. The allocation of anthropogenic factors into a separate group is due to the fact that at present the fate of the vegetation cover of the Earth and all currently existing species of organisms is practically in the hands of human society.

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

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

The environment is a part of nature that surrounds living organisms and has a direct or indirect effect on them. From the environment, organisms receive everything necessary for life and excrete metabolic products into it. The habitat of each organism is composed of many elements of inorganic and organic nature and elements introduced by man and his production activities. At the same time, some elements may be partially or completely indifferent to the body, others are necessary, and still others have a negative effect. For example, a white hare (Hersh ip[ ...]

The conditions of life, or the conditions of existence, are a set of elements of the environment necessary for the organism, with which it is in inseparable unity and without which it cannot exist.[ ...]

Organisms' adaptations to their environment are called adaptations. The ability to adapt is one of the basic properties of life in general, providing the very possibility of its existence, the ability of organisms to survive and reproduce. Adaptations are manifested 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 developed historically. As a result, groupings of plants and animals specific to each geographical area were formed.[ ...]

Light, temperature, moisture, wind, air, pressure, currents, day length, etc.[ ...]

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

Abiotic factors are a set of conditions of the inorganic environment that affect the body.[ ...]

Biotic factors are a set of influences of the vital activity of some organisms on others. In some cases, anthropogenic factors are singled out as an independent group of factors along with abiotic and biotic ones, thereby emphasizing the extraordinary effect of the anthropogenic factor. While agreeing with this, it is still more correct to classify it as part of the factors of biotic influence, since the concept of "biotic factors" covers the actions of everything organic world, to which the person also belongs.[ ...]

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 life of individual organisms and on the entire community. Environmental factors can act either in the form of a direct one, or in the form of an indirect one. Each environmental factor is characterized by certain quantitative indicators, for example, strength and range of action.[ ...]

For different types of plants and animals, the conditions in which they feel especially good are not the same. For example, some plants prefer very moist soil, while others prefer relatively dry soil. Some require intense heat, others tolerate colder environments better, etc.

Wednesday -- it is a part of nature that surrounds living organisms and has a direct or indirect effect on them. From the environment, organisms receive everything necessary for life and excrete 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. At the same time, some elements may be partially or completely indifferent to the body, others are necessary, and still others have a negative effect.

living conditions, or the conditions of existence, is a set of elements of the environment necessary for the organism, with which it is in inseparable unity and without which it cannot exist.

Organisms' adaptations to their environment are called adaptation. The ability to adapt is one of the main properties of life in general, which ensures 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 developed historically. As a result, groupings of plants and animals specific to each geographical area were formed.

Separate properties or elements of the environment that affect organisms are called environmental factors .

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

Abiotic factors -- This is a complex of conditions of the inorganic environment that affect the body.

Biotic factors -- it is a set of influences of the vital activity of some organisms on others. In some cases, anthropogenic factors are singled out as an independent group of factors along with abiotic and biotic ones, thereby emphasizing the extraordinary effect of the anthropogenic factor.

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 indirectly acting. Both can have significant impacts on the life of individual organisms and on the entire community. Environmental factors can act either in the form of a direct one, or in the form of an indirect one. 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 not the same. For example, some plants prefer very moist soil, while others prefer relatively dry soil. Some require intense heat, others tolerate colder environments better, etc. biosphere organism water substance

The intensity of the environmental factor, the most favorable for the life of the organism, is called the optimum, and giving the worst effect - the pessimum. , i.e., the conditions under which the vital activity of the organism is maximally inhibited, but it can still exist.

Environment? this is everything that surrounds the body and directly or indirectly affects its state and functioning (development, growth, survival, reproduction, etc.). The environment that provides the possibility of the existence of organisms on Earth is very diverse. Four qualitatively different environments of life can be distinguished on our planet: water, land-air, soil and a living organism.

Water environment

Water serves as a habitat for many organisms. From water, they receive all the substances necessary for life: food, water, gases. Therefore, no matter how high the diversity of aquatic organisms, they must all be adapted to the main features of life in the aquatic environment. These features are determined by the physical and chemical properties water.

In the water column there is constantly a large number of small representatives of plants and animals leading life in suspension. Their ability to soar is provided not only physical properties water, which has a buoyant force, but also special adaptations of the organisms themselves. For example, numerous outgrowths and appendages that significantly increase the surface of the body relative to its mass and, therefore, increase friction against the surrounding fluid.

Animals are adapted to movement in the aquatic environment in different ways. Active swimmers (fish, dolphins, etc.) have a characteristic streamlined body shape and limbs in the form of fins. Their fast swimming is also facilitated by the peculiarities of the structure of the outer integument and the presence of a special lubricant? mucus that reduces friction with water.

In some aquatic beetles, the exhaust air released from the spiracles is retained between the body and the elytra due to hairs that are not wetted by water. With the help of such a device, an aquatic insect quickly rises to the surface of the water, where it releases air into the atmosphere. Many protozoa move with the help of oscillating cilia (ciliates) or flagella (euglena).

Water has a very high heat capacity, i.e., the ability to accumulate and retain heat. For this reason, there are no sharp temperature fluctuations in water, which often occur on land. Can the waters of the polar seas be very cold? close to freezing. However, the constancy of temperature allowed the development of a number of adaptations that ensure life even in these conditions.

One of the most important properties of water is the ability to dissolve other substances that can be used by aquatic organisms for respiration and nutrition.

Breathing requires oxygen. Therefore, the saturation of water with it is of great importance.

The amount of oxygen dissolved in water decreases with increasing temperature. Moreover, oxygen dissolves worse in sea water than in fresh water. For this reason, the waters of the open sea of ​​the tropical zone are poor in living organisms. Conversely, in polar waters, where there is more oxygen, is there an abundance of plankton? small crustaceans that feed on representatives of a rich fauna, including fish and large cetaceans.

Respiration of aquatic organisms can be performed by the entire surface of the body or by special organs? gills. For successful breathing, it is necessary that there is a constant renewal of water near the body. This is achieved by various kinds of movements. For many organisms it is necessary to maintain a constant flow of water. This can be provided by the movement of the animal itself or by special devices, such as oscillating cilia or tentacles, which produce a whirlpool near the mouth, driving food particles into it.

The saline composition of water is very important for life, Ca 2+ ions are of particular importance for organisms. Mollusks and crustaceans need calcium to build their shells or shells. The concentration of salts in water can vary greatly. Water is considered fresh if it contains less than 0.5 g per liter of dissolved salts. Sea water differs in constancy of salinity and contains on the average 35 g of salts in one liter.

Ground-air environment

The ground-air environment, mastered later in the course of the evolution of the aquatic environment, is more complex and diverse. She is more high level organization of the living.

The most important factor in the life of organisms living here is the properties and composition of the surrounding air masses. The density of air is much lower than the density of water, so do terrestrial organisms have highly developed supporting tissues? internal and external skeleton. The forms of movement are extremely diverse: running, jumping, crawling, flying, etc. Birds and many insects move through the air. Air currents carry plant seeds, spores, microorganisms.

Air masses are characterized by a huge volume and are constantly in motion. Air temperature can change very quickly and over large spaces. Therefore, organisms living on land have numerous adaptations to withstand or avoid sudden changes in temperature. The most remarkable adaptation is the development of warm-bloodedness, which arose precisely in the ground-air environment.

In general, the air-land environment is more diverse than the water; living conditions here vary greatly in time and space. These changes are noticeable even at a distance of several tens of meters, for example, at the border of a forest and a field, at different heights in the mountains, even on different slopes of small hills. At the same time, pressure drops are less pronounced here, but often there is a lack of moisture. Therefore, terrestrial inhabitants have developed adaptations associated with providing the body with water, especially in arid conditions. In plants, this is a powerful root system, a waterproof layer on the surface of leaves and stems, and the ability to regulate the evaporation of water through stomata. In animals, in addition to the structural features of the external integument, these are also behavioral features that contribute to maintaining the water balance, for example, migration to watering places or avoidance of drying conditions.

Of great importance for the life of terrestrial organisms is the composition of the air (79% nitrogen, 21% oxygen and 0.03% carbon dioxide), which provides the chemical basis of life. Thus, a decrease in the specific amount of oxygen in the air, depending on the elevation of the terrain, determines the upper limit of animal life. Humans, for example, have never formed permanent settlements above 6,000 meters above sea level.

Carbon dioxide (carbon dioxide) is the most important raw material source for photosynthesis. Air nitrogen is necessary for the synthesis of proteins and nucleic acids.

The soil

Soil as a habitat? the top layer of land formed by mineral particles recycled by activity soil inhabitants. This is an important and very complex component of the biosphere, closely related to its other parts. Soil life is extraordinarily rich. Some organisms spend their whole life in the soil, others - part of their life. Soil plays an important role in plant life.

The conditions of life in the soil are largely determined by climatic factors, the most important of which is temperature.

Organism bodies