The most important abiotic environmental factors. Abiotic environmental factors

Classification of environmental factors.

ENVIRONMENTAL FACTORS

4.1. Classification of environmental factors.

4.2. Abiotic factors

4.3. Biotic factors

4.3. ecological plasticity. The concept of a limiting factor

From an ecological point of view, the environment is natural bodies and phenomena with which the organism is in direct or indirect relations.

The environment surrounding the body is characterized by great diversity, consisting of many elements, phenomena, conditions that are dynamic in time and space, which are considered as factors.

Environmental factor- this is any environmental condition that can have a direct or indirect effect on living organisms, at least during one of the phases of their individual development, or any environmental condition to which the organism adapts. In turn, the organism reacts to the environmental factor with specific adaptive reactions.

Environmental environmental factors are divided into three categories:

1) factors of inanimate nature (abiotic);

2) wildlife factors (biotic);

3) anthropogenic.

Of the many existing classifications of environmental factors, it is advisable to use the following for the tasks of this course (Fig. 1).

Rice. 4.1. Classification of environmental factors

Anthropogenic factors- these 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.

All environmental factors in the general case can be grouped into two large categories: factors of non-living, or inert, nature, otherwise called abiotic or abiogenic, and wildlife factors - biotic or biogenic. But in their origin, both groups can be both natural, and anthropogenic, i.e., associated with human influence. Sometimes they distinguish anthropic And anthropogenic factors. The first include only direct human impacts on nature (pollution, fishing, pest control), and the second - mainly indirect consequences associated with changes in the quality of the environment.

Along with the considered, there are other classifications of environmental factors. Allocate factors dependent And independent of the number and density of organisms. For example, climatic factors do not depend on the number of animals, plants, and mass diseases caused by pathogenic microorganisms (epidemics) in animals or plants are certainly related to their number: epidemics occur with close contact between individuals or with their general weakening due to lack of feed, when rapid transmission of the pathogen from one individual to another is possible, and resistance to the pathogen is lost.

The macroclimate does not depend on the number of animals, and the microclimate can change significantly as a result of their vital activity. If, for example, insects, with their high abundance in the forest, destroy most of the needles or foliage of trees, then the wind regime, illumination, temperature, quality and quantity of food will change here, which will affect the state of subsequent generations of the same or other animals living here. Mass breeding of insects attracts insect predators and insectivorous birds. Yields of fruits and seeds affect the population of murine rodents, the squirrel and its predators, and many seed-eating birds.

We can divide all the factors into regulating (controlling) And adjustable (managed), which is also easy to understand in connection with the examples above.

The original classification of environmental factors was proposed by A.S. Monchadsky. He proceeded from the idea that all adaptive reactions of organisms to certain factors are associated with the degree of constancy of their impact, or, in other words, with their periodicity. In particular, he highlighted:

1. primary periodic factors(those that are characterized by the correct periodicity associated with the rotation of the Earth: change of seasons, daily and seasonal changes in illumination and temperature); these factors are inherent in our planet and the nascent life had to adapt to them immediately;

2. secondary periodic factors(they are derived from the primary ones); these include all physical and many chemical factors, such as humidity, temperature, precipitation, the dynamics of the number of plants and animals, the content of dissolved gases in water, etc.;

3. non-periodic factors, which are not characterized by the correct periodicity (cyclicity); such, for example, are soil-related factors or various kinds of natural phenomena.

Of course, only the body of the soil itself, the soil underlying it, is "non-periodic", while the dynamics of temperature, humidity and many other properties of the soil are also associated with primary periodic factors.

Anthropogenic factors unambiguously refer to non-periodic ones. Among such factors of non-periodic action, first of all, pollutants contained in industrial emissions and discharges. In the process of evolution, living organisms are capable of developing adaptations to natural periodic and non-periodic factors (for example, hibernation, wintering, etc.), and plants and animals, as a rule, cannot acquire and hereditarily fix the corresponding adaptation. True, some invertebrates, for example, plant-eating mites from the class of arachnids, which have dozens of generations a year under closed ground conditions, are capable, with the constant use of the same pesticides against them, to form poison-resistant races by selecting individuals that inherit such resistance.

It must be emphasized that the concept of "factor" should be approached differentially, given that factors can be both direct (immediate) and indirect action. The differences between them are that the direct action factor can be quantified, while the indirect action factors cannot. For example, climate or relief can be designated mainly verbally, but they determine the regimes of direct action factors - humidity, daylight hours, temperature, physical and chemical characteristics of the soil, etc.

Abiotic factors is a set of properties of inanimate nature that are important for organisms.

The abiotic component of the terrestrial environment is a combination of climatic and soil-soil factors that affect both each other and living beings.

Temperature

The range of temperatures existing in the Universe is 1000 degrees, and in comparison with it, the limits in which life can exist are very narrow (about 300 0) from -200 0 С to +100 0 С (in hot springs at the bottom of the Pacific Ocean at the entrance to Bacteria were found in the Gulf of California, for which the optimum temperature is 250 0 C). Most species and most of the activity are confined to an even narrower range of temperatures. The upper temperature limit for hot spring bacteria is about 88 0 C, for blue-green algae about 80 0 C, and for the most resistant fish and insects - about 50 0 C.

The range of temperature fluctuations in water is smaller than on land, and the temperature tolerance range of aquatic organisms is narrower than that of terrestrial animals. Thus, temperature is an important and very often limiting factor. Temperature very often creates zonation and stratification in aquatic and terrestrial habitats. Easily measurable.

Temperature variability is extremely important from an ecological point of view. The vital activity of organisms, which in nature are usually exposed to variable temperatures, is partially or completely suppressed or slowed down when exposed to a constant temperature.

It is known that the amount of heat incident on a horizontal surface is directly proportional to the sine of the angle of the sun above the horizon. Therefore, in the same regions, daily and seasonal fluctuations in temperature are observed, and the entire surface of the globe is divided into a number of belts with conditional boundaries. The higher the latitude of the area, the greater the angle of inclination of the sun's rays to the surface of the earth and the colder the climate.

Radiation, light.

With regard to light, organisms face a dilemma: on the one hand, the direct effect of light on protoplasm is fatal to organisms, on the other hand, light serves as the primary source of energy, without which life is impossible. Therefore, many morphological and behavioral characteristics of organisms are associated with the solution of this problem. The evolution of the biosphere as a whole has been directed mainly to taming the incoming solar radiation, using its useful components and weakening or protecting against harmful ones. Illumination plays a crucial role for all living things, and organisms are physiologically adapted to the change of day and night, to the ratio of the dark and light periods of the day. Almost all animals have circadian rhythms associated with the change of day and night. In relation to light, plants are divided into light-loving and shade-loving.

Radiation is electromagnetic waves of different lengths. Light corresponding to two regions of the spectrum easily passes through the Earth's atmosphere. These are visible light (48%) and adjacent regions (UV - 7%, IR - 45%), as well as radio waves with a length of more than 1 cm. the region of the spectrum perceived by the human eye covers the wavelength range from 390 to 760 nm. Infrared rays are of primary importance for life, and orange-red and ultraviolet rays play the most important role in the processes of photosynthesis. The amount of solar radiation energy passing through the atmosphere to the Earth's surface is practically constant and is estimated at approximately 21 * 10 23 kJ. This value is called the solar constant. But the arrival of solar energy at different points on the Earth's surface is not the same and depends on the length of the day, the angle of incidence of rays, the transparency of atmospheric air, etc. Therefore, more often the solar constant is expressed in the number of joules per 1 cm 2 of the surface per unit time. Its average value is about 0.14 J / cm 2 in 1 s. Radiant energy is associated with the illumination of the earth's surface, which is determined by the duration and intensity of the light flux.

Solar energy is not only absorbed by the earth's surface, but also partly reflected by it. The general mode of temperature and humidity depends on how much of the solar radiation energy the surface absorbs.

Atmospheric air humidity

Associated with its saturation with water vapor. The lower layers of the atmosphere (1.5 - 2.0 km.) are richest in moisture, where about 50% of all moisture is concentrated. The amount of water vapor contained in the air depends on the temperature of the air. The higher the temperature, the more moisture the air contains. However, at a specific air temperature, there is a certain limit of its saturation with water vapor, which is called the maximum. Usually, the saturation of air with water vapor does not reach the maximum, and the difference between the maximum and this saturation is called moisture deficiency. Humidity deficiency is the most important environmental parameter, because It characterizes two quantities at once: temperature and humidity. The higher the moisture deficit, the drier and warmer and vice versa. An increase in moisture deficit in certain segments of the growing season contributes to increased fruiting of plants, and in a number of animals, such as insects, leads to reproduction up to outbreaks.

Precipitation

Precipitation is the result of condensation of water vapor. Due to condensation in the surface layer of air, dews, fogs are formed, and at low temperatures moisture crystallization (hoarfrost) is observed. Due to the condensation and crystallization of water vapor in the higher layers of the atmosphere, clouds and precipitation are formed. Precipitation is one of the links in the water cycle on Earth, and there is a sharp unevenness in their precipitation, and therefore, humid (wet) and arid (dry) zones are distinguished. The maximum amount of precipitation falls in the tropical forest zone (up to 2000 mm per year), while in arid zones - 0.18 mm. per year (in the desert of the tropical zone). Zones with rainfall less than 250mm. per year are considered dry.

Gas composition of the atmosphere

The composition is relatively constant and includes mainly nitrogen and oxygen, with an admixture of CO 2 and Ar (argon). The upper atmosphere contains ozone. There are solid and liquid particles (water, oxides of various substances, dust and fumes). Nitrogen is the most important biogenic element involved in the formation of the protein structures of organisms; oxygen - provides oxidative processes, respiration; ozone - screening role in relation to the UV part of the solar spectrum. Impurities of the smallest particles affect the transparency of the atmosphere, preventing the passage of sunlight to the surface of the Earth.

The movement of air masses (wind).

The reason for the wind is the unequal heating of the earth's surface, associated with pressure drops. The wind flow is directed towards lower pressure, i.e. where the air is warmer. In the surface layer of air, the movement of air masses affects the regime of temperature, humidity, evaporation from the Earth's surface, and plant transpiration. Wind is an important factor in the transfer and distribution of impurities in the atmospheric air.

Atmospheric pressure.

Normal pressure is 1 kPa, corresponding to 750.1 mm. rt. Art. Within the globe, there are constant areas of high and low pressure, and at the same points seasonal and daily minimums and pressure maxima are observed.

The impact of environmental factors on living organisms individually and on the community as a whole is multifaceted. When assessing the influence of one or another environmental factor, it is important to characterize the intensity of its action on living matter: under favorable conditions, they speak of an optimal factor, and with an excess or deficiency, a limiting factor.

Temperature. Most species are adapted to a fairly narrow range of temperatures. Some organisms, especially in the resting stage, are able to exist at very low temperatures. For example, spores of microorganisms can withstand cooling down to -200 °C. Certain types of bacteria and algae can live and multiply in hot springs at temperatures from +80 to -88 °C. The range of temperature fluctuations in water is much smaller than on land, respectively, and the limits of resistance to temperature fluctuations in aquatic organisms are narrower than in terrestrial ones. However, for both aquatic and terrestrial inhabitants, the optimum temperature is in the range from +15 to +30 ° С.

There are organisms with unstable body temperature - poikilothermic (from the Greek. poikilos- different, changeable and therme- heat) and organisms with a constant body temperature - homoiothermic (from the Greek. homoios- similar and therme- warm). The body temperature of poikilothermic organisms depends on the ambient temperature. Its increase causes in them an intensification of vital processes and, within certain limits, an acceleration of development.

Temperature is not constant in nature. Organisms that are normally exposed to the seasonal temperature fluctuations that occur in temperate zones are less able to tolerate constant temperatures. Sharp fluctuations in temperature - severe frosts or heat - are also unfavorable for organisms. There are many devices to deal with cooling or overheating. With the onset of winter, plants and poikilothermic animals fall into a state of winter dormancy. The intensity of metabolism is sharply reduced, a lot of fats and carbohydrates are stored in the tissues. The amount of water in the cells decreases, sugars and glycerin accumulate, preventing freezing. In the hot season, physiological mechanisms are activated that protect against overheating. In plants, the evaporation of water through the stomata increases, which leads to a decrease in leaf temperature. In animals under these conditions, the evaporation of water through the respiratory system and skin integuments also increases. In addition, poikilothermic animals avoid overheating through adaptive behavior: they choose habitats with the most favorable microclimate, hide in burrows or under stones during the hot hours of the day, and are active at certain times of the day, etc.

Thus, ambient temperature is an important and often life-limiting factor.

Homoiothermal animals - birds and mammals - are much less dependent on the temperature conditions of the environment. Aromorphic changes in the structure allowed these two classes to remain active at very sharp temperature drops and master almost all habitats.

The depressing effect of low temperatures on organisms is intensified by strong winds.

Light. Light in the form of solar radiation provides all life processes on Earth (Fig. 25.4). For organisms, the wavelength of the perceived radiation, its intensity and the duration of exposure (length of the day, or photoperiod) are important. Ultraviolet rays with a wavelength of more than 0.3 microns make up approximately 40% of the radiant energy reaching the earth's surface. In small doses, they are necessary for animals and humans. Under their influence, vitamin D is formed in the body. Insects visually distinguish ultraviolet rays and use this to navigate the terrain in cloudy weather. Visible light with a wavelength of 0.4-0.75 microns has the greatest effect on the body. The energy of visible light is about 45% of the total amount of radiant energy incident on the Earth. Visible light is least attenuated when passing through dense clouds and water. Therefore, photosynthesis can take place both in cloudy weather and under a layer of water of a certain thickness. But still, only 0.1 to 1% of the incoming solar energy is spent on biomass synthesis.

Rice. 25.4.

Depending on the habitat conditions, plants adapt to the shade - shade-tolerant plants or, conversely, to the bright sun - light-loving plants. The last group includes cereals.

An extremely important role in the regulation of the activity of living organisms and their development is played by the duration of exposure to light - the photoperiod. In temperate zones, above and below the equator, the cycle of development of plants and animals is timed to the seasons of the year and preparation for changing temperature conditions is carried out on the basis of a day length signal, which, unlike other seasonal factors, is always the same at a certain time of the year in a given place. The photoperiod is, as it were, a trigger mechanism that sequentially turns on physiological processes that lead to growth, flowering of plants in spring, fruiting in summer and shedding leaves in autumn, as well as to molting and fat accumulation, migration and reproduction in birds and mammals, and the onset of a dormant stage in insects. .

In addition to seasonal changes, the change of day and night determines the daily rhythm of activity of both whole organisms and physiological processes. The ability of organisms to sense time, the presence of a “biological clock” in them, is an important adaptation that ensures the survival of an individual in given environmental conditions.

Infrared radiation makes up 45% of the total amount of radiant energy incident on the Earth. Infrared rays increase the temperature of plant and animal tissues, are well absorbed by inanimate objects, including water.

For plant productivity, i.e. formation of organic matter, the most important indicator is the total direct solar radiation received over long periods of time (months, years).

Humidity. Water is a necessary component of the cell, therefore its quantity in certain habitats serves as a limiting factor for plants and animals and determines the nature of the flora and fauna in a given area. Excess water in the soil leads to the development of marsh vegetation. Depending on soil moisture (and annual rainfall), the species composition of plant communities changes. With an annual rainfall of 250 mm or less, a desert landscape develops. The uneven distribution of precipitation over the seasons is also an important limiting factor for organisms. In this case, plants and animals have to endure long droughts. In a short period of high soil moisture, the accumulation of primary production for the community as a whole occurs. He determines the size of the annual supply of food for animals and saprophages (from the Greek. sapros- rotten and phagos- devourer) - organisms that decompose organic residues.

In nature, as a rule, there are daily fluctuations in air humidity, which, along with light and temperature, regulate the activity of organisms. Humidity as an environmental factor is important in that it changes the effect of temperature. Temperature has a more pronounced effect on the body if the humidity is very high or low. In the same way, the role of humidity increases if the temperature is close to the limits of the species' hardiness. Species of plants and animals living in areas with insufficient moisture, in the process of natural selection, have effectively adapted to the adverse conditions of aridity. In such plants, the root system is powerfully developed, the osmotic pressure of cell sap is increased, which contributes to the retention of water in the tissues, the leaf cuticle is thickened, and the leaf blade is greatly reduced or turned into spines. In some plants (saxaul), the leaves are lost, and photosynthesis is carried out by green stems. In the absence of water, the growth of desert plants ceases, while moisture-loving plants wither and die under such conditions. Cacti are able to store a large amount of water in their tissues and use it sparingly. A similar adaptation was found in African desert spurges, which is an example of the parallel evolution of unrelated groups under similar environmental conditions.

Desert animals also have a range of physiological adaptations to tolerate lack of water. Small animals - rodents, reptiles, arthropods - extract water from food. The source of water is also fat, which accumulates in large quantities in some animals (the hump of a camel). In the hot season, many animals (rodents, turtles) hibernate, lasting several months.

Ionizing radiation. Radiation with very high energy, which can lead to the formation of pairs of positive and negative ions, is called ionizing. Its source is radioactive substances contained in rocks; moreover, it comes from outer space.

The intensity of ionizing radiation in the environment has increased significantly as a result of human use of atomic energy. Nuclear weapons testing, nuclear power plants, their fuel generation and waste disposal, medical research and other peaceful uses of nuclear energy create local “hot spots” and generate waste that is often released into the environment during transportation or storage.

Of the three types of ionizing radiation that are of great ecological importance, two are corpuscular radiation (alpha and beta particles), and the third is electromagnetic (gamma radiation and X-ray radiation close to it).

Corpuscular radiation consists of a stream of atomic or subatomic particles that transfer their energy to whatever they collide with. Alpha radiation is helium nuclei, they are huge in comparison with other particles, sizes. The length of their run in the air is only a few centimeters. Beta radiation is fast electrons. Their dimensions are much smaller, the length of the path in the air is several meters, and in the tissues of an animal or plant organism - several centimeters. As for ionizing electromagnetic radiation, it is similar to light, only its wavelength is much shorter. It travels long distances in the air and easily penetrates matter, releasing its energy over a long trail. Gamma radiation, for example, easily penetrates living tissues; this radiation can pass through the body without any effect, or it can cause ionization over a long distance. Biologists often refer to radioactive substances that emit alpha and beta radiation as "internal emitters" because they have the greatest effect when absorbed, ingested, or otherwise placed inside the body. Radioactive substances emitting predominantly gamma radiation are referred to as "external emitters", since this penetrating radiation can have an effect when its source is outside the body.

Cosmic and ionizing radiation emitted by natural radioactive substances contained in water and soil form the so-called background radiation, to which existing animals and plants are adapted. In different parts of the biosphere, the natural background varies by 3-4 times. Its lowest intensity is observed near the sea surface, and the highest at high altitudes in the mountains formed by granite rocks. The intensity of cosmic radiation increases with elevation above sea level, and granite rocks contain more naturally occurring radionuclides than sedimentary rocks.

In general, ionizing radiation has the most destructive effect on more highly developed and complex organisms, and man is particularly sensitive.

Large doses received by the body in a short time (minutes or hours) are called acute doses, as opposed to chronic doses that the body could tolerate throughout its life cycle. The impact of low chronic doses is more difficult to measure, as they may cause long-term genetic and somatic effects. Any increase in the level of radiation in the environment above the background or even a high natural background can increase the frequency of harmful mutations.

In higher plants, sensitivity to ionizing radiation is directly proportional to the size of the cell nucleus. In higher animals, no such simple or direct relationship has been found between sensitivity and cell structure; for them, the sensitivity of individual organ systems is more important. Thus, mammals are very sensitive even to low doses due to the slight damage to rapidly dividing hematopoietic tissue - the bone marrow - by irradiation. The digestive tract is also sensitive, and damage to non-dividing nerve cells is observed only at high levels of radiation.

When released into the environment, radionuclides disperse and dilute, but they can accumulate in living organisms in various ways as they move along the food chain. Radioactive substances can also accumulate in water, soil, sediment or air if the rate of entry exceeds the rate of natural radioactive decay.

contaminants. The conditions of human life and the stability of natural biogeocenoses have been rapidly deteriorating over the past decades due to environmental pollution with substances generated as a result of its production activities. These substances can be divided into two groups: natural compounds that are waste products of technological processes, and artificial compounds that are not found in nature.

The first group includes sulfur dioxide (copper-smelting production), carbon dioxide (thermal power plants), oxides of nitrogen, carbon, hydrocarbons, compounds of copper, zinc and mercury, etc., mineral fertilizers (mainly nitrates and phosphates).

The second group includes artificial substances that have special properties that satisfy human needs: pesticides (from lat. pestis- infection, destruction and cido- kill) used to control animal pests of agricultural crops, antibiotics used in medicine and veterinary medicine for the treatment of infectious diseases. Pesticides include insecticides (from lat. insecta- insects and cido- kill) - means for combating harmful insects and herbicides (from lat. herba- grass, plant and cido- kill) - means for weed control.

All of them have a certain toxicity (poisonousness) to humans. At the same time, they serve as anthropogenic abiotic environmental factors that have a significant impact on the species composition of biogeocenoses. This influence is expressed in a change in soil properties (acidification, transition of toxic elements to a soluble state, structural disturbance, impoverishment of its species composition); changes in water properties (increased mineralization, increased content of nitrates and phosphates, acidification, saturation with surfactants); a change in the ratio of elements in soil and water, which leads to a deterioration in the conditions for the development of plants and animals.

Such changes serve as selection factors, as a result of which new plant and animal communities with a depleted species composition are formed.

Changes in environmental factors in terms of their effect on organisms can be: 1) regularly-periodic, for example, in connection with the time of day, the season of the year, or the rhythm of the tides in the ocean; 2) irregular, for example, changes in weather conditions in different years, disasters (storms, downpours, landslides, etc.); 3) directed: in case of cooling or warming of the climate, overgrowth of reservoirs, etc. Populations of organisms living in a particular environment adapt to this variability through natural selection. They develop certain morphological and physiological features that allow them to exist in these and no other environmental conditions. For each factor influencing the body, there is a favorable force of influence, called the zone of optimum of the ecological factor or simply its optimum. For organisms of this species, the deviation from the optimal intensity of the factor action (decrease or increase) depresses vital activity. The boundaries beyond which the death of the organism occurs are called the upper and lower limits of endurance (Fig. 25.5).

Rice. 25.5. Intensity of action of environmental factors

Anchor points

Most species of organisms are adapted to life in a narrow range of temperatures; the optimum temperature values are from +15 to +30 °С.
Light in the form of solar radiation provides all life processes on Earth.
Cosmic and ionizing radiation emitted by natural radioactive substances form the "background" radiation to which the existing plants and animals are adapted.
Pollutants, having a toxic effect on living organisms, impoverish the species composition of biocenoses.

Questions and tasks for repetition

1. What are abiotic environmental factors?
2. What adaptations do plants and animals have to changes in environmental temperature?
3. Indicate which part of the visible radiation spectrum of the Sun is most actively absorbed by the chlorophyll of green plants?
4. Tell us about the adaptations of living organisms to the lack of water.
5. Describe the effect of various types of ionizing radiation on animal and plant organisms.
6. What is the impact of pollutants on the state of biogeocenoses?

The following groups of abiotic factors (factors of inanimate nature) are distinguished: climatic, edaphogenic (soil), orographic and chemical.

I) Climatic factors: these include solar radiation, temperature, pressure, wind and some other environmental influences.

1) Solar radiation is a powerful environmental factor. It propagates in space in the form of electromagnetic waves, of which 48% is in the visible part of the spectrum, 45% is infrared radiation (with a long wavelength) and about 7% is short-wave ultraviolet radiation. Solar radiation is the primary source of energy, without which life on Earth is impossible. But, on the other hand, direct exposure to sunlight (especially its ultraviolet component) is detrimental to a living cell. The evolution of the biosphere was aimed at reducing the intensity of the ultraviolet part of the spectrum and protecting it from excess solar radiation. This was facilitated by the formation of ozone (the ozone layer) from oxygen released by the first photosynthetic organisms.

The total amount of solar energy reaching Earth is roughly constant. But different points on the earth's surface receive different amounts of energy (due to differences in illumination time, different angles of incidence, degree of reflection, transparency of the atmosphere, etc.)

A close connection between solar activity and the rhythm of biological processes has been revealed. The more solar activity (more spots on the Sun), the more perturbations in the atmosphere, magnetic storms that affect living organisms. An important role is also played by the change in solar activity during the day, which determines the daily rhythms of the body. In humans, more than 100 physiological characteristics are subject to the daily cycle (hormone release, respiratory rate, the work of various glands, etc.)

Solar radiation largely determines other climatic factors.

2) Ambient temperature is related to the intensity of solar radiation, especially the infrared part of the spectrum. The vital activity of most organisms proceeds normally in the temperature range from +5 to 40 0 C. Above +50 0 - +60 0, the irreversible destruction of the protein that is part of living tissues begins. At high pressures, the upper temperature limit can be much higher (up to +150−200 0 C). The lower temperature limit is often less critical. Some living organisms are able to withstand very low temperatures (up to -200 0 C) in a state of suspended animation. Many organisms in the Arctic and Antarctic constantly live at sub-zero temperatures. Some arctic fish have a normal body temperature of -1.7 0 C. At the same time, the water in their narrow capillaries does not freeze.

The dependence of the intensity of vital activity of most living organisms on temperature has the following form:

Fig.12. The dependence of the vital activity of organisms on temperature

As can be seen from the figure, with an increase in temperature, biological processes are accelerated (the rate of reproduction and development, the amount of food consumed). For example, the development of cabbage butterfly caterpillars at +10 0 C requires 100 days, and at +26 0 C - only 10 days. But a further increase in temperature leads to a sharp decrease in the parameters of vital activity and death of the organism.

In water, the range of temperature fluctuations is less than on land. Therefore, aquatic organisms are less adapted to temperature changes than terrestrial ones.

Temperature often determines zoning in terrestrial and aquatic biogeocenoses.

3) Environmental humidity is an important environmental factor. Most living organisms are 70-80% water - a substance necessary for the existence of protoplasm. The humidity of the area is determined by the humidity of the atmospheric air, the amount of precipitation, and the area of water reserves.

Humidity depends on temperature: the higher it is, the more water is usually contained in the air. The lower layers of the atmosphere are richest in moisture. Precipitation is the result of condensation of water vapor. In the temperate zone, the distribution of precipitation over the seasons is more or less uniform, in the tropics and subtropics it is uneven. The available supply of surface water depends on groundwater sources and rainfall.

The interaction of temperature and humidity forms two climates: maritime and continental.

4) Pressure is another climatic factor that is important for all living organisms. There are areas on Earth with constantly high or low pressure. Pressure drops are associated with uneven heating of the earth's surface.

5) Wind - the directed movement of air masses, which is the result of pressure differences. Wind flow is directed from an area of high pressure to an area of lower pressure. It affects temperature, humidity and the movement of impurities in the air.

6) Lunar rhythms determine the ebb and flow to which marine animals are adapted. They use the ebb and flow for many life processes: movement, reproduction, and so on.

II) Edafogenic factors determine various characteristics of the soil. Soil plays an important role in terrestrial ecosystems - the role of the accumulator and reserve of resources. The composition and properties of soils are strongly influenced by climate, vegetation and microorganisms. Steppe soils are more fertile than forest soils, since grasses are short-lived and annually a large amount of organic matter enters the soil, which quickly decomposes. Ecosystems without soils are usually very unstable. The following main characteristics of soils are distinguished: mechanical composition, moisture capacity, density and air permeability.

The mechanical composition of soils is determined by the content of particles of various sizes in it. There are four types of soils, depending on their mechanical composition: sand, sandy loam, loam, clay. The mechanical composition directly affects plants, underground organisms, and through them - on other organisms. The moisture capacity (ability to retain moisture), their density and air permeability of soils depend on the mechanical composition.

III) Orographic factors. These include the height of the terrain above sea level, its relief and location relative to the cardinal points. Orographic factors largely determine the climate of a given area, as well as other biotic and abiotic factors.

IV) Chemical factors. These include the chemical composition of the atmosphere (gas composition of the air), the lithosphere, and the hydrosphere. For living organisms, the content of macro- and microelements in the environment is of great importance.

Macronutrients are elements required by the body in relatively large quantities. For most living organisms, this is phosphorus, nitrogen, potassium, calcium, sulfur, magnesium.

Trace elements are elements that are required by the body in extremely small quantities, but are part of vital enzymes. Trace elements are necessary for the normal functioning of the body. The most common trace elements are metals, silicon, boron, and chlorine.

There is no clear boundary between macroelements and microelements: what is a microelement for some organisms, for another is a macroelement.

Abiotic factors are factors of inanimate nature that directly or indirectly affect the body - light, temperature, humidity, the chemical composition of the air, water and soil environment, etc. (i.e., the properties of the environment, the occurrence and impact of which does not directly depend on the activity of living organisms ).

Light (solar radiation) is an environmental factor characterized by the intensity and quality of the radiant energy of the Sun, which is used by photosynthetic green plants to create plant biomass. Sunlight reaching the Earth's surface is the main source of energy for maintaining the planet's heat balance, water metabolism of organisms, the creation and transformation of organic matter by the autotrophic link of the biosphere, which ultimately makes it possible to form an environment capable of satisfying vital needs.

organisms.

Temperature is one of the most important abiotic factors, on which the existence, development and distribution of organisms on Earth largely depends [show]. The significance of temperature lies primarily in its direct influence on the rate and nature of the course of metabolic reactions in organisms. Since daily and seasonal temperature fluctuations increase with distance from the equator, plants and animals, adapting to them, show different needs for heat.

Humidity is an environmental factor characterized by the water content in the air, soil, and living organisms. In nature, there is a daily rhythm of humidity: it rises at night and falls during the day. Together with temperature and light, humidity plays an important role in regulating the activity of living organisms. The source of water for plants and animals is mainly atmospheric precipitation and groundwater, as well as dew and fog.

In the abiotic part of the habitat (in inanimate nature), all factors can primarily be divided into physical and chemical. However, to understand the essence of the phenomena and processes under consideration, it is convenient to represent abiotic factors as a combination of climatic, topographic, space factors, as well as characteristics of the composition of the environment (aquatic, terrestrial or soil).

The main climatic factors include solar energy, temperature, precipitation and humidity, medium mobility, pressure, ionizing radiation.

Environmental factors - properties of the environment that have any effect on the body. Indifferent elements of the environment, for example, inert gases, are not environmental factors.

Environmental factors are highly variable in time and space. For example, the temperature varies greatly on the surface of the land, but is almost constant at the bottom of the ocean or in the depths of caves.

Classifications of environmental factors

By the nature of the impact

Directly acting - directly affecting the body, mainly on metabolism

Indirectly acting - influencing indirectly, through a change in directly acting factors (relief, exposure, altitude, etc.)

Origin

Abiotic - factors of inanimate nature:

climatic: annual sum of temperatures, average annual temperature, humidity, air pressure

edaphic (edaphogenic): soil mechanical composition, soil air permeability, soil acidity, soil chemical composition

orographic: relief, height above sea level, steepness and exposure of the slope

chemical: gas composition of air, salt composition of water, concentration, acidity

physical: noise, magnetic fields, thermal conductivity and heat capacity, radioactivity, intensity of solar radiation

Biotic - associated with the activities of living organisms:

phytogenic - influence of plants

mycogenic - influence of fungi

zoogenic - influence of animals

microbiogenic - influence of microorganisms

Anthropogenic (anthropic):

physical: the use of nuclear energy, travel in trains and planes, the impact of noise and vibration

chemical: the use of mineral fertilizers and pesticides, pollution of the Earth's shells with industrial and transport waste

biological: food; organisms for which a person can be a habitat or source of food

social - related to people's relationships and life in society

By spending

Resources - elements of the environment that the body consumes, reducing their supply in the environment (water, CO2, O2, light)

Conditions - elements of the environment that are not consumed by the body (temperature, air movement, soil acidity)

By direction

Vectorized - directionally changing factors: waterlogging, soil salinization

Multi-year-cyclic - with alternating multi-year periods of strengthening and weakening of the factor, for example, climate change due to the 11-year solar cycle

Oscillatory (impulse, fluctuation) - fluctuations in both directions from a certain average value (daily fluctuations in air temperature, change in the average monthly precipitation during the year)

Optimum Rule

In accordance with this rule, for an ecosystem, an organism, or a certain stage of its development, there is a range of the most favorable (optimal) value of the factor. Outside the zone of optimum lie zones of oppression, passing into critical points, beyond which existence is impossible. The maximum population density is usually confined to the optimum zone. Zones of optimum for different organisms are not the same. For some, they have a significant range. Such organisms belong to the group of eurybionts. Organisms with a narrow range of adaptation to factors are called stenobionts.

The range of factor values (between critical points) is called ecological valence. A synonym for the term valence is tolerance, or plasticity (variability). These characteristics depend largely on the environment in which the organisms live. If it is relatively stable in its properties (the amplitudes of fluctuations of individual factors are small), there are more stenobionts in it (for example, in the aquatic environment), if it is dynamic, for example, in land-air, eurybionts are more likely to survive in it. The zone of optimum and ecological valence are usually wider in warm-blooded organisms than in cold-blooded ones. It should also be borne in mind that the ecological valency for the same species does not remain the same under different conditions (for example, in the northern and southern regions in certain periods of life, etc.). Young and senile organisms, as a rule, require more conditioned (homogeneous) conditions. Sometimes these requirements are quite ambiguous. For example, in relation to temperature, insect larvae are usually stenobiont (stenothermic), while pupae and adults may be eurybionts (eurythermal).

Similar information.

Abiotic factors they call the whole set of factors of the inorganic environment that affect the life and distribution of animals and plants (V.I. Korobkin, L.V. Peredelsky, 2000).

Chemical Factors are those that come from the chemical composition of the environment. They include the chemical composition of the atmosphere, water and soil, etc.

Physical factors- these are those whose source is a physical state or phenomenon (mechanical, wave, etc.). These are temperature, pressure, wind, humidity, radiation regime, etc. Surface structure, geological and climatic differences cause a wide variety of abiotic factors.

Among the chemical and physical environmental factors, three groups of factors are distinguished: climatic, soil cover (edaphic) and aquatic factors.

I. Essential climatic factors:

1. The radiant energy of the sun.

Infrared rays (wavelength greater than 0.76 microns) are of primary importance for life, which account for 45% of the total energy of the Sun. In the processes of photosynthesis, the most important role is played by ultraviolet rays (wavelength up to 0.4 microns), which make up 7% of the energy of solar radiation. The rest of the energy is in the visible part of the spectrum with a wavelength of 0.4 - 0.76 microns.

2. Illumination of the earth's surface.

It plays an important role for all living things, and organisms are physiologically adapted to the change of day and night. Almost all animals have daily rhythms of activity associated with the change of day and night.

3. Humidity of atmospheric air.

Associated with the saturation of the air with water vapor. Up to 50% of all atmospheric moisture is concentrated in the lower layers of the atmosphere (up to 2 km high).

The amount of water vapor in the air depends on the air temperature. For a specific temperature, there is a certain limit of air saturation with water vapor, which is called the maximum. The difference between the maximum and given saturation of the air with water vapor is called the humidity deficit (lack of saturation). Humidity deficit is an important environmental parameter, as it characterizes two quantities: temperature and humidity.

It is known that an increase in moisture deficit in certain periods of the growing season contributes to increased fruiting of plants, and in some insects leads to outbreaks of reproduction.

4. Precipitation.

Due to the condensation and crystallization of water vapor in the high layers of the atmosphere, clouds and precipitation are formed. Dews and fogs form in the surface layer.

Moisture is the main factor determining the division of ecosystems into forest, steppe and desert. Annual rainfall below 1000 mm corresponds to a stress zone for many tree species, and the limit of resistance for most of them is about 750 mm/year. At the same time, for most cereals, this limit is much lower - about 250 mm / year, and cacti and other desert plants can grow with 50-100 mm of precipitation per year. Accordingly, in places with rainfall above 750 mm / year, forests usually develop, from 250 to 750 mm / year - cereal steppes, and where they fall even less, the vegetation is represented by drought-resistant crops: cacti, wormwood and tumbleweed species - field. At intermediate values of the annual precipitation, ecosystems of a transitional type develop (forest-steppes, semi-deserts, etc.).

The precipitation regime is the most important factor determining the migration of pollutants in the biosphere. Precipitation is one of the links in the water cycle on Earth.

5. Gas composition of the atmosphere.

It is relatively constant and includes mainly nitrogen and oxygen with an admixture of carbon dioxide, argon and other gases. In addition, the upper atmosphere contains ozone. The atmospheric air also contains solid and liquid particles.

Nitrogen is involved in the formation of protein structures of organisms; oxygen provides oxidative processes; carbon dioxide is involved in photosynthesis and is a natural damper of the Earth's thermal radiation; ozone is a screen for ultraviolet radiation. Solid and liquid particles affect the transparency of the atmosphere, preventing the passage of sunlight to the Earth's surface.

6. Temperature on the surface of the earth.

This factor is closely related to solar radiation. The amount of heat incident on a horizontal surface is directly proportional to the sine of the angle of the Sun above the horizon. Therefore, in the same areas, daily and seasonal temperature fluctuations are observed. The higher the latitude of the area (north and south of the equator), the greater the angle of inclination of the sun's rays to the Earth's surface and the colder the climate.

Temperature, as well as precipitation, is very important in determining the nature of an ecosystem, although temperature plays a somewhat secondary role compared to precipitation. So, with their number of 750 mm/year and more, forest communities develop, and the temperature only determines what type of forest will be formed in the region. For example, spruce and fir forests are typical for cold regions with heavy snow cover in winter and a short growing season, i.e. for the north or highlands. Deciduous trees are also able to tolerate frosty winters, but require a longer growing season and therefore predominate in temperate latitudes. Powerful evergreen broad-leaved species with rapid growth, unable to withstand even short-term frosts, dominate in the tropics (near the equator). In the same way, any territory with an annual precipitation of less than 250 mm is a desert, but in terms of their biota, the deserts of the hot zone differ significantly from those characteristic of cold regions.

7. The movement of air masses (wind).

Wind is the most important factor in the transport and distribution of impurities in the atmosphere.

8. Atmospheric pressure.

II. Abiotic soil cover factors (edaphic)

Edaphic factors- this is a combination of chemical, physical and other properties of soils that affect both the organisms living in them and the root system of plants. Of these, the most important environmental factors are humidity, temperature, structure and porosity, reaction of the soil environment, and salinity.

In the modern sense, soil is a natural-historical formation that arose as a result of a change in the surface layer of the lithosphere due to the combined effect of water, air and living organisms (V. Korobkin, L. Peredelsky). The soil is fertile, i.e. gives life to plants and, consequently, food to animals and humans. It consists of solid, liquid and gaseous components; contains live macro- and micro-organisms (vegetable and animal).

The solid component is represented by mineral and organic parts. In the soil, most of the minerals are primary, left over from the parent rock, less - secondary, formed as a result of the decomposition of the primary. These are clay minerals of colloidal sizes, as well as minerals - salts: carbonates, sulfates, etc.

The organic part is represented by humus, i.e. complex organic matter formed as a result of the decomposition of dead organic matter. Its content in the soil ranges from tenths to 22%. It plays an important role in soil fertility due to the nutrients it contains.

Soil biota is represented by fauna and flora. Fauna is earthworms, wood lice, etc., flora is fungi, bacteria, algae, etc.

The entire liquid component of soils is called soil solution. It may contain chemical compounds: nitrates, bicarbonates, phosphates, etc., as well as water-soluble organic acids, their salts, sugars. The composition and concentration of the soil solution determine the reaction of the medium, which is indicated by the pH value.

Soil air has a high content of CO2, hydrocarbons and water vapor. All these elements determine the chemical properties of the soil.

All soil properties depend not only on climatic factors, but also on the vital activity of soil organisms, which mechanically mix it and chemically process it, ultimately creating the conditions necessary for themselves. With the participation of organisms in the soil, there is a constant circulation of substances and the migration of energy. The circulation of substances in the soil can be represented as follows (V.A. Radkevich).

Plants synthesize organic matter, and animals produce mechanical and biochemical destruction of it and, as it were, prepare it for humus formation. Microorganisms synthesize soil humus and then decompose it.

The soil provides water to the plants. The value of the soil in the water supply of plants is the higher, the easier it gives them water. It depends on the structure of the soil and the degree of swelling of its particles.

Under the structure of the soil should be understood as a complex of soil aggregates of various shapes and sizes, formed from the primary mechanical elements of the soil. The following soil structures are distinguished: granular, silty, nutty, lumpy, blocky.

The main function of higher plants in the soil-forming process is the synthesis of organic matter. This organic matter in the process of photosynthesis accumulates in the aboveground and underground parts of plants, and after their death passes into the soil and undergoes mineralization. The rate of organic matter mineralization processes and the composition of the resulting compounds largely depend on the type of vegetation. Decomposition products of needles, leaves, wood of grassy cover are different both in terms of chemistry and influence on the process of soil formation. In combination with other factors, this leads to the formation of various types of soils.

The main function of animals in the soil-forming process is the consumption and destruction of organic matter, as well as the redistribution of energy reserves. An important role in the processes of soil formation is played by mobile soil animals. They loosen the soil, create conditions for its aeration, mechanically move organic and inorganic substances in the soil. For example, earthworms throw up to 80 - 90 / ha of material to the surface, and steppe rodents move up and down hundreds of m3 of soil and organic matter.

The influence of climatic conditions on the processes of soil formation is, of course, great. The amount of precipitation, temperature, the influx of radiant energy - light and heat - determine the formation of plant mass and the rate of decomposition of plant residues, which determine the content of humus in the soil.

As a result of the movement and transformation of substances, the soil is divided into separate layers, or horizons, the combination of which makes up the soil profile.

The surface horizon, litter or sod, consists mostly of freshly fallen and partially decomposed leaves, branches, animal remains, fungi, and other organic matter. It is usually painted in a dark color - brown or black. The underlying A1 humus horizon is usually a porous mixture of partially decomposed organic matter (humus), living organisms, and some inorganic particles. It is usually darker and looser than the lower horizons. The main part of soil organic matter and plant roots are concentrated in these two upper horizons.

Its color can tell a lot about soil fertility. For example, a dark brown or black humus horizon is rich in organic matter and nitrogen. Grey, yellow or red soils have little organic matter and require nitrogen fertilizers to increase their yield.

In forest soils, under the A1 horizon, there is an infertile A2 podzolic horizon, which has a light shade and a fragile structure. In chernozem, dark chestnut, chestnut, and other soil types, this horizon is absent. Even deeper in many types of soils is the B horizon - the illuvial, or intrusion horizon. Mineral and organic substances from overlying horizons are washed into it and accumulate in it. Most often it is colored brown and has a high density. Even lower lies the parent rock C, on which the soil is formed.

Structure and porosity determine the availability of nutrients for plants and soil animals. Soil particles, interconnected by forces of molecular nature, form the structure of the soil. Between them, voids are formed, called pores. The structure and porosity of the soil provide good aeration. Soil air, like soil water, is located in the pores between soil particles. Porosity increases from clays to loams and sands. Free gas exchange occurs between the soil and the atmosphere, as a result of which the gas composition of both environments has a similar composition. Usually in the air of the soil due to the respiration of the organisms inhabiting it, there is somewhat less oxygen and more carbon dioxide than in atmospheric air. Oxygen is necessary for plant roots, soil animals and organisms - decomposers that decompose organic matter into inorganic components. If waterlogging occurs, soil air is displaced by water, and conditions become anaerobic. The soil gradually becomes acidic as the anaerobic organisms continue to produce carbon dioxide. The soil, if it is not rich in bases, can become extremely acidic, and this, along with the depletion of oxygen reserves, adversely affects soil microorganisms. Prolonged anaerobic conditions lead to the death of plants.

Temperature soil depends on the external temperature, and at a depth of 0.3 m, due to low thermal conductivity, its oscillation amplitude is less than 20 ° C (Yu.V. Novikov, 1979), which is important for soil animals (there is no need to move up and down in search of a more comfortable temperature) . In summer, the soil temperature is lower than the air, and in winter it is higher.

Chemical factors include the reaction of the environment and salinity. Environment reaction very important for many plants and animals. In a dry climate, neutral and alkaline soils predominate, in humid areas - acidic. Absorbed bases, acids and various salts in the process of their interaction with water create a certain concentration of H + - and OH - ions, which cause one or another reaction of the soil. Soils are usually distinguished with neutral, acidic and alkaline reactions.

Soil alkalinity is due to the presence of mainly Na + - ions in the absorbing complex. Such soil, when in contact with water containing CO2, gives a pronounced alkaline reaction, which is associated with the formation of soda.

When the soil absorbing complex is saturated with Ca2+ and Mg2+, its reaction is close to neutral. At the same time, it is known that calcium carbonate in pure water and water devoid of CO2 gives a strong alkalinity. This is explained by the fact that with an increase in the content of CO2 in the soil solution, the solubility of calcium (2+) increases with the formation of bicarbonate, which leads to a decrease in pH. But with an average amount of CO2 in the soil, the reaction becomes weakly alkaline.

In the process of decomposition of plant residues, especially forest litter, organic acids are formed, which react with absorbed soil cations. Acidic soils have a number of negative properties, and therefore they are infertile. In such an environment, the active beneficial activity of soil microflora is suppressed. Lime is widely used to improve soil fertility.

High alkalinity inhibits plant growth, and its water-physical properties deteriorate sharply, destroys the structure, enhances the mobility and removal of colloids. Many cereals give the best harvest on neutral and slightly alkaline soils (barley, wheat), which are usually chernozems.

In areas of insufficient atmospheric moisture, salted soil. Saline soils are soils with an excess content of water-soluble salts (chlorides, sulfates, carbonates). They arise as a result of secondary salinization of soils during the evaporation of groundwater, the level of which has risen to the soil horizons. Solonchaks and solonetzes are distinguished among saline soils. There are solonchaks in Kazakhstan and Central Asia, along the banks of salty rivers. Soil salinization leads to a drop in crop yields. Earthworms, even with a low degree of soil salinity, cannot withstand a long time.

Plants that live in saline soils are called halophytes. Some of them excrete excess salts through the leaves or accumulate them in their bodies. That is why they are sometimes used to make soda and potash.

Water occupies the predominant part of the Earth's biosphere (71% of the total area of the earth's surface).

The most important abiotic factors of the aquatic environment are the following:

1. Density and viscosity.

The density of water is 800 times and the viscosity is about 55 times that of air.

2. Heat capacity.

Water has a high heat capacity, so the ocean is the main receiver and accumulator of solar energy.

3. Mobility.

The constant movement of water masses contributes to maintaining the relative homogeneity of physical and chemical properties.

4. temperature stratification.

A change in water temperature is observed along the depth of the water body.

5. Periodic (annual, daily, seasonal) temperature changes.

The lowest water temperature is considered to be -20C, the highest + 35-370C. The dynamics of fluctuations in water temperature is less than that of air.

6. Water transparency.

Determines the light regime under the water surface. The photosynthesis of green bacteria, phytoplankton, higher plants, and, consequently, the accumulation of organic matter, depends on transparency (and its opposite characteristic, turbidity).

Turbidity and transparency depend on the content of substances suspended in water, including those entering water bodies along with industrial discharges. In this regard, the transparency and content of suspended solids are the most important characteristics of natural and waste waters that are subject to control at an industrial enterprise.

7. Salinity of water.

The content of carbonates, sulfates, chlorides in water is of great importance for living organisms. There are few salts in fresh waters, and carbonates predominate. The waters of the ocean contain an average of 35 g / l of salts, the Black Sea - 19 g / l, the Caspian - about 14 g / l. Chlorides and sulfates predominate here. Almost all elements of the periodic table are dissolved in sea water.

8. Dissolved oxygen and carbon dioxide.

The excess consumption of oxygen for the respiration of living organisms and for the oxidation of organic and mineral substances entering the water with industrial discharges leads to the depletion of the living population up to the impossibility of living in such water for aerobic organisms.

9. Hydrogen ion concentration (pH).

All hydrobionts have adapted to a certain pH level: some prefer an acidic environment, others prefer an alkaline environment, and still others prefer a neutral one. Changes in these characteristics can lead to the death of hydrobionts.

10. Flow not only greatly affects the concentration of gases and nutrients, but also directly acts as a limiting factor. Many river plants and animals are morphologically and physiologically adapted in a special way to maintaining their position in the stream: they have well-defined limits of tolerance to the flow factor.

The main topographic factor is height above sea level. With altitude, average temperatures decrease, the daily temperature difference increases, the amount of precipitation, wind speed and radiation intensity increase, atmospheric pressure and gas concentrations decrease. All these factors affect plants and animals, causing vertical zonality.

mountain ranges can serve as climate barriers. Mountains also serve as barriers to the spread and migration of organisms and can play the role of a limiting factor in the processes of speciation.

Another topographical factor is slope exposure. In the northern hemisphere, south-facing slopes receive more sunlight, so the light intensity and temperature are higher here than at the bottom of the valleys and on the slopes of the northern exposure. The situation is reversed in the southern hemisphere.

An important relief factor is also slope steepness. Steep slopes are characterized by rapid drainage and soil erosion, so the soils here are thin and drier. If the slope exceeds 35b, soil and vegetation usually do not form, but screes of loose material are created.

Crown fires have a limiting effect on most organisms - the biotic community has to start all over again with what little is left, and many years must pass before the site becomes productive again. Ground fires, on the contrary, have a selective effect: for some organisms they are more limiting, for others they are a less limiting factor and thus contribute to the development of organisms with high tolerance to fires. In addition, small ground fires supplement the action of bacteria by decomposing dead plants and speeding up the transformation of mineral nutrients into a form suitable for use by new generations of plants. Plants have developed special adaptations to fire, just as they have done to other abiotic factors. In particular, the buds of cereals and pines are hidden from fire in the depths of bunches of leaves or needles. In periodically burnt habitats, these plant species benefit, as fire contributes to their conservation by selectively promoting their prosperity.