Plant habitat conditions. Habitat and conditions of existence of organisms. Environmental factors Untouched human habitat for many plants and animals

Plants in the places where they grow are exposed to a wide variety of environmental components. Any components or properties of the environment that influence organisms are called environmental factors.

Classification of environmental factors. Environmental factors, or environmental factors, are extremely diverse, have different natures and specific actions. The following groups of environmental factors are distinguished:

1. Abiotic factors - it is a set of direct or indirect effects of inorganic or nonliving nature. they, in turn, are divided into:

a) climatic - lighting conditions, water supply, temperature conditions, etc.;

b) food properties - include the type of soil and the totality of its physical, chemical and mechanical properties;

c) orographic - relief, slope exposure.

2. Biotic factors- cover all forms of influence of living organisms on each other. These are the relationships of plants with each other, with animals, etc.

3. Anthropogenic factors- these are all forms of human activity. They cause changes in the structure of the earth's surface, the circulation of substances in the biosphere, the thermal balance of the territory, cause a decrease in biodiversity, and the like. Plants can be exposed to both direct anthropogenic impacts and the resulting consequences of general changes in the environment.

A more detailed classification scheme for environmental factors is shown in Fig. 1.2.

Environmental factors are also classified according to frequency, direction of action and depending on the degree of adaptation of organisms to them. From this perspective, the following factors are distinguished:

1. Such, operating periodically (changes in time of day, seasons of the year, tidal phenomena, etc.).

Rice. 1.2.

2. Those that do not act periodically, but are repeated from time to time. This includes some weather phenomena - floods, hurricanes, earthquakes and the like.

3. Directional factors. They usually change in one direction (warming or cooling of the climate, successional processes in vegetation, swamping of territories, etc.).

4. Factors of uncertain action. These include anthropogenic factors that are the most dangerous for organisms and their communities, as well as random factors of various natures.

Like any classification schemes in biology, the classification of plant habitat factors is not absolute. In fact, the factors interact with each other, and the plants themselves change them. Therefore, it is important to understand that the plant reacts with physiological and biochemical processes not to a single factor as such, but to a specific combination of all factors.

Taking into account the characteristics of plant life, all environmental factors that influence the physiological processes of plants are divided into two main groups.

Resources - these are environmental factors that are directly consumed and consumed by plants. These include, for example, reserves of biogenic minerals in the soil, carbon dioxide in the air, water, etc. These environmental factors are sometimes called “divisible” in the sense that plants that grow together are forced to share them among themselves.

Conditions - these are environmental factors that are not consumed by plants, but affect their life. Conditions include, but are not limited to, temperature, soil acidity, etc.

Topic Autecology

Autecology, which studies the relationship of organisms to environmental conditions, is the oldest section of general ecology. Essentially, E. Haeckel understood ecology as autecology. Charles Darwin, the author of the theory of adaptation of organisms to environmental conditions through natural selection, was also an autecologist.

This section of ecology includes characteristics of environmental factors (factorial ecology) and methods of adaptation (adaptation) of organisms to its various conditions. In the 20th century autecology has been replenished with new sections on the functional role of organisms in the ecosystem and their life strategies.

Autecology studies the relationships of organisms to environmental conditions at the species level, which is necessary both for the study of populations (this allows us to “out of brackets” those characteristics that are characteristic of all populations of the same species) and for the study of ecosystems, the elements of which are species.

Environment is one of the basic environmental concepts; it means a complex of natural bodies and phenomena with which the organism is in direct or indirect relationships. The term external environment is widely used , defined as the totality of forces and phenomena of nature, its substance and space, any human activity that is outside the object or subject in question and not necessarily in direct contact with it. The concept of environment is identical to the previous one, but implies direct contact with objects or subjects.

There are also natural environment -(a set of natural and modified by human activity factors of living and inanimate nature that exhibit an effect on organisms), abiotic environment -(all forces and natural phenomena, the origin of which is not directly related to the life activity of living organisms) and biotic environment -(forces and natural phenomena that owe their origin to the vital activity of living organisms).

Aquatic living environment. This is the most ancient environment in which life arose and evolved for a long time even before the first organisms appeared on land. According to the composition of the aquatic environment of life, there are two main variants: freshwater and marine environments.

More than 70% of the planet's surface is covered with water. However, due to the comparative uniformity of the conditions of this environment (“water is always wet”), the diversity of organisms in the aquatic environment is much less than on land. Only every tenth species of the plant kingdom is associated with the aquatic environment; the diversity of aquatic animals is somewhat higher. The overall ratio of the number of land/water species is about 1:5.

The density of water is 800 times higher than the density of air. And the pressure on the organisms inhabiting it is also much higher than in terrestrial conditions: for every 10 m of depth it increases by 1 atm. One of the main directions of adaptation of organisms to life in an aquatic environment is increasing buoyancy by increasing the surface of the body and the formation of tissues and organs containing air. Organisms can float in water (like representatives of plankton - algae, protozoa, bacteria) or actively move, like fish that form nekton. A significant portion of organisms are attached to the bottom surface or move along it. As already noted, an important factor in the aquatic environment is current.

The basis of production of most aquatic ecosystems are autotrophs, which use sunlight breaking through the water column. The possibility of “breaking through” this thickness is determined by the transparency of the water. In clear ocean water, depending on the angle of incidence of sunlight, autotrophic life is possible down to a depth of 200 m in the tropics and 50 m in high latitudes (for example, in the seas of the Arctic Ocean). In highly agitated freshwater bodies, a layer populated by autotrophs (it is called photic), may be only a few tens of centimeters.

The red part of the light spectrum is most actively absorbed by water, therefore, as noted, the deep seas are inhabited by red algae, capable of absorbing green light due to additional pigments. The transparency of water is determined by a simple device - a Secchi disk, which is a white-painted circle with a diameter of 20 cm. The degree of water transparency is judged by the depth at which the disk becomes indistinguishable.

The most important characteristic of water is its chemical composition - the content of salts (including nutrients), gases, hydrogen ions (pH). Based on the concentration of nutrients, especially phosphorus and nitrogen, water bodies are divided into oligotrophic, mesotrophic and eutrophic. When the content of nutrients increases, say, when a reservoir is polluted by runoff, the process of eutrophication of aquatic ecosystems occurs.

The oxygen content in water is approximately 20 times lower than in the atmosphere and amounts to 6-8 ml/l. It decreases with increasing temperature, as well as in stagnant bodies of water in winter, when the water is isolated from the atmosphere by a layer of ice. A decrease in oxygen concentration can cause the death of many inhabitants of aquatic ecosystems, excluding species that are particularly resistant to oxygen deficiency, such as crucian carp or tench, which can live even when the oxygen content decreases to 0.5 ml/l. The carbon dioxide content in water, on the contrary, is higher than in the atmosphere. Sea water can contain up to 40-50 ml/l, which is approximately 150 times higher than in the atmosphere. The consumption of carbon dioxide by phytoplankton during intensive photosynthesis does not exceed 0.5 ml/l per day.

The concentration of hydrogen ions in water (pH) can vary between 3.7-7.8. Waters with a pH from 6.45 to 7.3 are considered neutral. As already noted, with a decrease in pH, the biodiversity of organisms inhabiting the aquatic environment quickly decreases. Crayfish and many species of mollusks die at a pH below 6, perch and pike can withstand a pH of up to 5, eel and char survive when the pH drops to 5-4.4. In more acidic waters, only some species of zooplankton and phytoplankton survive. Acid rain, associated with the release of large quantities of sulfur and nitrogen oxides into the atmosphere by industrial enterprises, has caused acidification of the waters of lakes in Europe and the USA and a sharp depletion of their biological diversity.

Ground-air environment of life. Air has a significantly lower density compared to water. For this reason, the development of the air environment, which occurred much later than the origin of life and its development in the aquatic environment, was accompanied by increased development of mechanical tissues, which allowed organisms to resist the action of the law of gravity and wind (skeleton in vertebrates, chitinous shells in insects, sclerenchyma in plants). In an air-only environment, no organism can live permanently, and therefore even the best “flyers” (birds and insects) must periodically fall to the ground. The movement of organisms through the air is possible due to special devices - wings in birds, insects, some species of mammals and even fish, parachutes and wings in seeds, air sacs in coniferous pollen, etc.

Air is a poor conductor of heat, and therefore it was in the air environment on land that endothermic (warm-blooded) animals arose, which are easier to retain heat than ectothermic inhabitants of the aquatic environment. For warm-blooded aquatic animals, including giant whales, the aquatic environment is secondary; the ancestors of these animals once lived on land.

Life in the air required more complex reproductive mechanisms that would eliminate the risk of drying of germ cells (multicellular antheridia and archegonia, and then ovules and ovaries in plants, internal fertilization in animals, eggs with a dense shell in birds, reptiles, amphibians, etc. ).

In general, there are many more opportunities for the formation of various combinations of factors in the ground-air environment than in the water environment. It is in this environment that climate differences between different regions (and at different altitudes above sea level within the same region) are especially pronounced. Therefore, the diversity of terrestrial organisms is much higher than that of aquatic ones.

Soil living environment. Most of the land is covered with a thin layer (compared to the thickness of the earth's crust) of soil, called V.I. Vernadsky bioinert body. The soil is a complex multilayer “pie” of horizons with different properties, and the composition and thickness of the “pie” are different in different zones. The zonal (from podzols and gray forest soils to chernozems, chestnut and brown soils) and hydrogenic (from wet meadow to bog-peaty) series of soils are well known. In the southern regions, soils can also be saline on the surface (saline soils and solonchaks) or in the depths (solonetzes).

Any soil is a multiphase system, which includes:

1) mineral particles - from the finest silt to sand and gravel;

2) organic matter - from the bodies of just dead animals and dead plant roots to humus, in which this organic matter has undergone complex chemical processing;

3) gas (air) phase, the nature of which is largely determined by the physical properties of the soil - its structure and, accordingly, density and porosity. The gas phase of the soil is always enriched in carbon dioxide and water vapor and can be depleted in oxygen, which brings the living conditions in the soil closer to the conditions of the aquatic environment;

4) aqueous phase. Water in the soil can also be contained in different quantities (from excess to extreme deficiency) and in different qualities, it can be gravitational - freely moving through capillaries and most accessible to the roots of plants and animal organisms, hygroscopic, which is part of colloidal particles, and gas, i.e. . e. in the form of steam.

This multiphase nature of soils makes their environment the most saturated with life. The main biomass of animals, bacteria, fungi is concentrated in soils; it contains the roots of plants that live in the ground-air environment, but extract water with nutrients from the soil and supply organic matter accumulated during photosynthesis in the light to the “dark world” of the soil. The soil is the main “processing shop” of organic matter, and up to 90% of the carbon returned to the atmosphere flows through it.

The gigantic diversity of life in the soil includes not only those organisms that live in it constantly - vertebrates (moles), arthropods, bacteria, algae, earthworms, etc., but also those organisms that are associated with it only at the beginning of their “biography.” (locusts, many beetles, etc.).

Adaptation of plants to some variants of extreme soil conditions (drought, salinity) will be discussed in the next lecture.

Tick-borne encephalitis is a disease that affects the human central nervous system. It is caused by a virus, the carriers and keepers of the virus are ixodid ticks. The favorite habitats of ticks are the southern part of taiga forests throughout the European and Asian parts of Russia.

Modern taxonomy of living organisms is based on the degree of relatedness of organisms. Ecological classifications can be based on a wide variety of criteria: methods of nutrition, movement, relationships to temperature, humidity, free oxygen, etc. The diversity of adaptation to the environment creates the need for multiple classifications.

Among the adaptations of living organisms to the environment, morphological adaptations play a special role. Changes most affect organs that are in direct contact with the external environment. As a result, there is convergence (bringing closer together) of morphological (external) characters in different species, while anatomical and other characters change to a lesser extent, reflecting the relationship and origin of the species.

The morphological (morphophysiological) type of adaptation of an animal or plant to certain living conditions and a certain way of life is called life form of an organism. There are a large number of classifications of life forms of plants and animals, based on different characteristics. The first classifications were based on the appearance of plants, which determined the landscape of the area. Below is one such classification.

- Trees - perennial plants with woody aerial parts, a pronounced one trunk, not less than 2 m in height.

- Shrubs- perennial plants with woody above-ground parts. Unlike trees, they do not have a clearly defined single trunk; branching begins from the ground itself, so several equal trunks are formed.

- Shrubs similar to shrubs, but low-growing, no higher than 50 cm.

Subshrubs They differ from shrubs in that only the lower parts of their shoots become woody, while the upper parts often die off.

- Creepers - plants with climbing, clinging and twining stems.

- Succulents- perennial plants with succulent stems and leaves containing a supply of water.

- Herbal plants- perennial and annual plants in which the above-ground parts die off during the winter (perennials, biennials) or the entire plant dies off (annuals).

Later classifications were based on the adaptive characteristics of plants to living conditions. Among botanists, the classification by K. Raunkier (1905) is popular according to the position of the buds or shoot tips during unfavorable seasons in relation to the surface of the soil and snow cover (Fig. 1). This feature has a deep biological meaning: the protection of meristems intended for continued growth ensures the continuous existence of the individual in a rapidly changing environment. According to this system, plants are divided into five groups:

Phanerophytes (P)- trees, shrubs, vines, epiphytic plants, buds, the renewal of which is located high above the soil surface (not lower than 30 cm) and, thanks to scales and resinous secretions, are well protected from freezing and winter drying out;

Chamephytes (Ch) - low plants - shrubs and subshrubs; their renewal buds on wintering shoots are located at a height of 20-30 cm above the soil level, which ensures their wintering under the protection of snow cover. These include lingonberry (Vaccinium vitisidaea), blueberry (Vaccinium myrtillus), periwinkle (Vinca minor);

Rice. 1 - Life forms of plants according to Raunkier:

1 - 3 - phanerophytes, 4,5 - chamephytes, 6,7 - hemicryptophytes, 8 - 11 - cryptophytes, 12 - therophyte, 13 - seed with embryo.

Hemicryptophytes (H)- herbaceous perennials, in which the main part of the above-ground organs dies, covering the renewal buds located at the soil level. These are stinging nettle (Urtica dioica), dandelion (Taraxacum officinale), etc.

Cryptophytes(K) - a large group of plants in which renewal buds and the tips of modified shoots are located underground or in another substrate. The group is divided into three subgroups:

A) geophytes, in which overwintering buds are located on underground organs (bulbs, rhizomes, roots);

b) helophytes- plants of coastal and marshy habitats, the overwintering buds of which are located below the bottom of the reservoir. These include: arrowhead (Saggitaria saggitifolia), chastukha (Alisma plantagoaquatica), umbrella leaf (Butonus umbellatus);

V) hydrophytes- aquatic plants with floating or submerged leaves. Their renewal buds overwinter at the bottom of the reservoir on perennial rhizomes, as, for example, in the white water lily (Nymphaea alba) or in the form of specialized buds - turions, as is observed in duckweed (Lemna minor), pondweed (Potamogeton perfoliatus).

Therophytes(Th) - annual plants that survive dry or cold periods in the form of seeds or spores, equipped with morphological and physiological adaptations to effectively counteract unfavorable conditions.

The distribution of the listed groups of plants by climatic zones (in percentage terms) forms their biological spectrum:

Zone P Ch H K Th

Tropical 69(8)* 6 12 5 16

Desert 4 8 1 5 82

Mediterranean 12 6 29 11 42

Moderate 8 6 52 25 9

Arctic 1 22 60 15 2

* The number in brackets shows the distribution of epiphytic plants.

D.N. Kashkarov (1945) classified the life forms of animals according to the nature of movement in different environments.

I. Floating forms.

1 Purely aquatic:

a) nekton;

b) plankton;

c) benthos.

2 Semi-aquatic:

a) diving;

b) non-diving;

c) only those that extract food from water.

II. Burrowing forms.

1 Absolute diggers (spending their entire lives underground).

2 Relative excavators (coming to the surface).

III. Ground forms.

1 Those who do not make holes:

a) running;

b) jumping;

c) crawling.

2 Making holes:

a) running;

b) jumping;

c) crawling.

3 Animals of the rocks.

IV. Wood climbing forms:

a) not coming down from trees;

b) only those who climb trees.

V. Air forms:

a) foraging for food in the air;

b) looking for food from the air.

Biological rhythms- these are periodically repeating changes in the intensity and nature of biological processes and phenomena. They are inherent in all living organisms in one form or another and are observed at all levels of organization: from intracellular processes to biosphere ones. Biological rhythms are hereditarily fixed and are a consequence of natural selection and adaptation of organisms. Rhythms can be intraday, daily, seasonal, annual, perennial and centuries-old.

Examples of biological rhythms are: rhythmicity in cell division, DNA and RNA synthesis, hormone secretion, daily movement of leaves and petals towards the Sun, autumn leaf fall, seasonal lignification of wintering shoots, seasonal migrations of birds and mammals, etc. Biological rhythms are divided into exogenous and endogenous.

Exogenous (external) rhythms arise as a reaction to periodic changes in the environment (change of day and night, seasons, solar activity).

Endogenous (internal) rhythms are generated by the body itself. The processes of DNA, RNA and protein synthesis, the work of enzymes, cell division, heartbeat, breathing, etc. have rhythm. External influences can shift the phases of these rhythms and change their amplitude. Among endogenous rhythms, physiological and environmental rhythms are distinguished.

Physiological rhythms(heartbeat, breathing, work of endocrine glands, etc.) support the continuous functioning of organisms.

Ecological rhythms(diurnal, annual, tidal, lunar, etc.) arose as an adaptation of living beings to periodic changes in the environment.

Physiological rhythms vary significantly depending on the state of the body, environmental rhythms are more stable and correspond to external rhythms.

Ecological rhythms are able to adapt to changes in the cyclicity of external conditions, but only within certain limits. This adjustment is possible due to the fact that during each period there are certain time intervals (potential readiness time) when the body is ready to perceive a signal from the outside, for example, bright light or darkness. If the signal is slightly delayed or arrives prematurely, the rhythm phase shifts accordingly. Under experimental conditions at constant light and temperature, the same mechanism ensures a regular phase shift during each period. Therefore, the rhythm period under these conditions usually does not correspond to the natural cycle and gradually diverges from phase with local time.

The endogenous component of rhythm gives the body the ability to navigate in time and prepare in advance for upcoming environmental changes. This is the so-called biological clock of the body. Many living organisms are characterized by circadian and circan rhythms. Circadian (circadian) rhythms - repeating changes in the intensity and nature of biological processes and phenomena with a period of 20 to 28 hours. Circan (annual) rhythms - repeated changes in the intensity and nature of biological processes and phenomena with a period of 10 to 13 months. Circadian and circan rhythms are recorded under experimental conditions at constant temperature, illumination, etc.

The physical and psychological states of a person have a rhythmic character. Disruption of established rhythms of life can reduce performance and have an adverse effect on human health. The study of biorhythms is of great importance in organizing human work and rest, especially in extreme conditions (in polar conditions, in space, when quickly moving to other time zones, etc.).

Time discrepancies between natural and anthropogenic events often lead to the destruction of natural systems. For example, when carrying out too frequent logging.

CONCLUSIONS

1. Thus, the habitat is the immediate environment of the organism, which includes a set of abiotic and biotic factors of an individual organism or the biocenosis as a whole, influencing their growth and development, i.e. it is a part of nature that directly surrounds these living organisms, all that what they live among.

2. In the process of evolution, organisms mastered 4 habitats: aquatic, soil, ground-air, organismal, and also developed certain adaptations (adaptations) to each habitat.

3. Among the adaptations of living organisms to the environment, morphological adaptations play a special role. Changes most affect organs that are in direct contact with the external environment. The morphological type of adaptation of an animal or plant to certain living conditions and a certain way of life is called life form of an organism.

4. Periodically repeated changes in the intensity and nature of biological processes and phenomena are biological rhythms. They are inherent in all living organisms in one form or another and are observed at all levels of organization: from intracellular processes to biosphere ones. Biological rhythms are hereditarily fixed and are a consequence of natural selection and adaptation of organisms. Rhythms are intradiurnal, diurnal, seasonal, annual, perennial and centuries-old.

The life of a plant, like any other living organism, is a complex set of interrelated processes; The most significant of them, as is known, is the exchange of substances with the environment. The environment is the source from which the plant draws food materials, then processes them in its body, creating the same substances as those that make up the plant’s body - the assimilation of substances drawn from the environment takes place, their assimilation. Simultaneously with this process, the destruction of the constituent parts of the body occurs in the body; breaking them down into simpler ones. This opposite process is called dissimilation. Assimilation, dissimilation, the inextricably linked supply of substances from the environment and the release into the environment of unnecessary, waste substances - all this is metabolism. Consequently, metabolic phenomena closely connect the plant organism with the environment. This connection is twofold. Firstly, the plant turns out to be dependent on the environment. The environment must contain all the materials necessary for plant life. A shortage, especially the absence of one or another category of food materials, should lead to a slowdown or even cessation of life phenomena, to death. Secondly, by absorbing nutrients from the environment and releasing products of its vital activity into the environment (for example, in the form of falling leaves, dead surface layers of bark, etc.), the plant changes its environment. Consequently, not only does the plant depend on the environment, but the environment always depends to some extent on the plants.

Changes in the environment by plants are associated not only with the introduction of metabolic products into it, but also with the physical work performed by the plant. When the roots of a plant penetrate the soil, they perform mechanical work of destruction or local compaction of the substrate. The work performed by the plant is not limited to mechanical action on the substrate. In essence, all physiological functions of a plant represent certain forms of work. This leads to the idea of ​​connections between plants and the environment in another way: all work involves the expenditure of energy. But energy, as we know, “does not disappear and is not created again.” Therefore, if a plant expends energy, then, obviously, it must receive it from somewhere.

The source of energy for plants containing chlorophyll is the radiant energy of light, due to which the plant builds organic matter containing, as it were, conserved energy. In plants that do not have chlorophyll, for example mushrooms, the source of energy is organic food, that is, either the organic substance itself created by the green plant, or the same, but in a form already modified by other organisms.

Energy, in one form or another, entering plants undergoes complex changes, ultimately being released into the environment. We can say that the connection between the plant and the environment is not limited to the exchange and transformation of substances - in parallel with this, energy exchange also takes place.

The living environment of a plant is heterogeneous; it contains many components that are closely related to each other. Each element of the environment that affects the body is called an environmental factor. The variety of environmental factors can be grouped into two categories: biotic factors and abiotic factors.

Habitat (ecological niche)- a set of specific abiotic and biotic conditions in which a given individual, population or species lives, a part of nature that surrounds living organisms and has a direct or indirect impact on them. Habitat (ecological niche), often overlaps with the term "area" - the geographical distribution of a biological species. For example, a brown bear. Habitat (ecological niche) - forests. The habitat is wherever there are such forests (Europe, Asia, North America). From the environment, organisms receive everything they need for life and release metabolic products into it. The term is often considered a synonym environment. The environment of each organism is composed of many elements of inorganic and organic nature and elements introduced by man and his production activities. Moreover, some elements may be partially or completely indifferent to the body, others are necessary, and others have a negative effect.

There are natural and artificial (man-made) habitats. Natural habitats are mainly divided into ground-air, soil, water and intraorganismal. Individual properties and elements of the environment that affect organisms are called environmental factors. All environmental factors can be divided into three large groups:

It is also possible to distinguish the following components of the habitat: natural bodies of the habitat, hydroenvironment, air space of the environment, anthropogenic bodies, radiation and gravitational fields of the environment.

Encyclopedic YouTube

• 1 / 3

  Views:

The soil is a loose thin surface layer of land in contact with the air. Its most important property is fertility, those. the ability to ensure the growth and development of plants. Soil is not just a solid body, but a complex three-phase system in which solid particles are surrounded by air and water. It is permeated with cavities filled with a mixture of gases and aqueous solutions, and therefore extremely diverse conditions develop in it, favorable for the life of many micro- and macroorganisms. Temperature fluctuations in the soil are smoothed out compared to the surface layer of air, and the presence of groundwater and the penetration of precipitation create moisture reserves and provide a moisture regime intermediate between the aquatic and terrestrial environments. Reserves of organic and mineral substances supplied by dying vegetation and animal corpses are concentrated in the soil (Fig. 1.3).

Rice. 1.3.

The soil is heterogeneous in its structure and physical and chemical properties. The heterogeneity of soil conditions is most pronounced in the vertical direction. With depth, a number of the most important environmental factors affecting the life of soil inhabitants change dramatically. First of all, this relates to the structure of the soil. It contains three main horizons, differing in morphological and chemical properties (Fig. 1.4): 1) upper humus-accumulative horizon A, in which organic matter accumulates and is transformed and from which some of the compounds are carried down by leaching waters; 2) the inwash horizon, or illuvial B, where the substances washed out from above settle and are transformed, and 3) the parent rock, or horizon C, the material of which is transformed into soil.

Fluctuations in cutting temperature only on the soil surface. Here they can be even stronger than in the surface layer of air. However, with every centimeter deeper, daily and seasonal temperature changes become less and less and at a depth of 1-1.5 m they are practically no longer traceable.

Rice. 1.4.

All these features lead to the fact that, despite the great heterogeneity of environmental conditions in the soil, it acts as a fairly stable environment, especially for mobile organisms. All this determines the greater saturation of the soil with life.

The root systems of land plants are concentrated in the soil. In order for plants to survive, the soil as a habitat must satisfy their need for mineral nutrients, water and oxygen, while pH values ​​(relative acidity and salinity (salt concentration) are important).

1. Mineral nutrients and the ability of the soil to retain them. The following mineral nutrients are necessary for plant nutrition: (biogens), like nitrates (N0 3), phosphates ( P0 3 4),

potassium ( TO+) and calcium ( Ca 2+). With the exception of nitrogen compounds that are formed from atmospheric N 2 during the cycle of this element, all mineral biogens are initially included in the chemical composition of rocks along with “non-nutrient” elements such as silicon, aluminum and oxygen. However, these nutrients are inaccessible to plants while they are fixed in the rock structure. In order for nutrient ions to move into a less bound state or into an aqueous solution, the rock must be destroyed. The breed called maternal, destroyed during the process of natural weathering. When nutrient ions are released, they become available to plants. Being the initial source of nutrients, weathering is still too slow a process to ensure normal plant development. In natural ecosystems, the main source of nutrients is decomposing detritus and metabolic waste of animals, i.e. nutrient cycle.

In agroecosystems, nutrients are inevitably removed from the harvested crop, since they are part of the plant material. Their stock is regularly replenished by adding fertilizers

• 2. Water and water holding capacity. Moisture in the soil is present in various states:
• 1) bound (hygroscopic and film) is firmly held by the surface of soil particles;
• 2) capillary occupies small pores and can move along them in different directions;
• 3) gravitational fills larger voids and slowly seeps down under the influence of gravity;
• 4) vaporous is contained in the soil air.

If there is too much gravitational moisture, then the soil regime is close to the regime of reservoirs. In dry soil, only bound water remains and conditions approach those of land. However, even in the driest soils, the air is moister than the ground air, so the inhabitants of the soil are much less susceptible to the threat of drying out than on the surface.

There are thin pores in the leaves of plants through which carbon dioxide (CO2) is absorbed and oxygen (02) is released during photosynthesis. However, they also allow water vapor from the wet cells inside the leaf to pass out. To compensate for this loss of water vapor from leaves, called transpiration, at least 99% of all water absorbed by the plant is necessary; Less than 1% is spent on photosynthesis. If there is not enough water to replenish losses due to transpiration, the plant withers.

Obviously, if rainwater flows over the surface of the soil and is not absorbed, it will not be useful. Therefore it is very important infiltration, those. absorption of water from the soil surface. Since the roots of most plants do not penetrate very deeply, water that penetrates deeper than a few centimeters (and for small plants, to a much shallower depth) becomes inaccessible. Therefore, during the period between rains, plants depend on the supply of water held by the surface layer of soil, like a sponge. The amount of this reserve is called water holding capacity of the soil. Even with infrequent rainfall, soils with good water-holding capacity can store enough moisture to support plant life over a fairly long dry period.

Finally, the water supply in the soil is reduced not only as a result of its use by plants, but also due to evaporation from the soil surface.

So, the ideal soil would be one with good infiltration and water-holding capacity and a cover that reduces water loss through evaporation.

3. Oxygen and aeration. To grow and absorb nutrients, roots need energy generated by the oxidation of glucose during cellular respiration. This consumes oxygen and produces carbon dioxide as a waste product. Consequently, ensuring the diffusion (passive movement) of oxygen from the atmosphere into the soil and the reverse movement of carbon dioxide is another important feature of the soil environment. He is called aeration. Typically, aeration is hampered by two circumstances that lead to slower growth or death of plants: soil compaction and saturation with water. Seal called the approach of soil particles to each other, in which the air space between them becomes too limited for diffusion to occur. Water saturation - the result of waterlogging.

The loss of water by the plant during transpiration must be compensated by reserves of capillary water in the soil. This reserve depends not only on the abundance and frequency of precipitation, but also on the ability of the soil to absorb and retain water, as well as on direct evaporation from its surface when the entire space between soil particles is filled with water. This can be called "flooding" the plants.

Respiration of plant roots is the absorption of oxygen from the environment and the release of carbon dioxide into it. In turn, these gases must be able to diffuse between soil particles

• 4. Relative acidity (pH). Most plants and animals require a near-neutral pH of 7.0; in most natural habitats such conditions are met.
• 5. Salt and osmotic pressure. For normal functioning, the cells of a living organism must contain a certain amount of water, i.e. require water balance. However, they themselves are not able to actively pump or pump out water. Their water balance is regulated by the ratio - the concentration of salts on the outer and inner sides of the cell membrane. Water molecules are attracted to salt ions. The cell membrane prevents the passage of ions, and water quickly moves through it in the direction of greater concentration. This phenomenon is called osmosis.

Cells control their water balance by regulating internal salt concentrations, and water moves in and out by osmosis. If the salt concentration outside the cell is too high, water cannot be absorbed. Moreover, under the influence of osmosis it will be drawn out of the cell, which will lead to dehydration and death of the plant. Highly saline soils are practically lifeless deserts.

Inhabitants of the soil. The heterogeneity of the soil leads to the fact that for organisms of different sizes it acts as a different environment.

For small soil animals, which are grouped under the name microfauna(protozoa, rotifers, tardigrades, nematodes, etc.), soil is a system of micro-reservoirs. Essentially, these are aquatic organisms. They live in soil pores filled with gravitational or capillary water, and part of life can, like microorganisms, be in an adsorbed state on the surface of particles in thin layers of film moisture. Many of these species also live in ordinary bodies of water. However, soil forms are much smaller than freshwater ones, and, in addition, when exposed to unfavorable environmental conditions, they secrete a dense shell on the surface of their body - cyst(Latin cista - box), protecting them from drying out, exposure to harmful substances, etc. At the same time, physiological processes slow down, animals become motionless, take on a rounded shape, stop feeding, and the body falls into a state of hidden life (encysted state). If the encysted individual again finds itself in favorable conditions, excystation occurs; the animal leaves the cyst, turns into a vegetative form and resumes active life.

To slightly larger air-breathing animals, the soil appears as a system of small caves. Such animals are grouped under the name mesofauna. The sizes of soil mesofauna representatives range from tenths to 2-3 mm. This group includes mainly arthropods: numerous groups of mites, primary wingless insects (for example, two-tailed insects), small species of winged insects, symphila centipedes, etc.

Larger soil animals, with body sizes from 2 to 20 mm, are called representatives macrofauna. These are insect larvae, centipedes, enchytraeids, earthworms, etc. For them, the soil is a dense medium that provides significant mechanical resistance when moving.

Megafauna soils are large shrews, mainly mammals. A number of species spend their entire lives in the soil (mole rats, mole rats, marsupial moles of Australia, etc.). They create entire systems of passages and burrows in the soil. The appearance and anatomical features of these animals reflect their adaptability to a burrowing underground lifestyle. They have underdeveloped eyes, a compact, ridged body with a short neck, short thick fur, strong digging limbs with strong claws.

In addition to the permanent inhabitants of the soil, a large ecological group can be distinguished among large animals burrow inhabitants(gophers, marmots, jerboas, rabbits, badgers, etc.). They feed on the surface, but reproduce, hibernate, rest, and escape danger in the soil.

For a number of ecological features, soil is a medium intermediate between aquatic and terrestrial. The soil is similar to the aquatic environment due to its temperature regime, low oxygen content in the soil air, its saturation with water vapor and the presence of water in other forms, the presence of salts and organic substances in soil solutions, and the ability to move in three dimensions.

The soil is brought closer to the air environment by the presence of soil air, the threat of drying out in the upper horizons, and rather sharp changes in the temperature regime of the surface layers.

The intermediate ecological properties of soil as a habitat for animals suggest that soil played a special role in the evolution of the animal world. For many groups, in particular arthropods, soil served as a medium through which initially aquatic inhabitants were able to transition to a terrestrial lifestyle and conquer land. This path of arthropod evolution has been proven by the works of M.S. Gilyarov (1912-1985).

Table 1.1 provides a comparative description of abiotic environments and the adaptation of living organisms to them.

Characteristics of abiotic environments and adaptation of living organisms to them

Table 1.1

Wednesday	Characteristic	Adaptation of the body to the environment
	The most ancient. Illumination decreases with depth. When diving, for every 10 m, the pressure increases by one atmosphere. Oxygen deficiency. The degree of salinity increases from fresh water to sea and ocean water. Relatively uniform (homogeneous) in space and stable in time	Streamlined body shape, buoyancy, mucous membranes, development of air cavities, osmoregulation
Soil	Created by living organisms. She mastered the ground-air environment simultaneously. Deficiency or complete absence of light. High density. Four-phase (phases: solid, liquid, gaseous, living organisms). Inhomogeneous (heterogeneous) in space. Over time, conditions are more constant than in the terrestrial-air habitat, but more dynamic than in the aquatic and organismal environment. The richest habitat for living organisms	The body shape is valval (smooth, round, cylindrical or spindle-shaped), mucous membranes or a smooth surface, some have a digging apparatus and developed muscles. Many groups are characterized by microscopic or small sizes as an adaptation to life in film water or in air-bearing pores
Ground-based	Sparse. Abundance of light and oxygen. Heterogeneous in space. Very dynamic over time	Development of the supporting skeleton, mechanisms for regulating the hydrothermal regime. Freeing the sexual process from the liquid medium

Questions and tasks for self-control

• 1. List the structural elements of soil.
• 2. What characteristic features of soil as a habitat do you know?
• 3. What elements and compounds are classified as biogens?
• 4. Conduct a comparative analysis of aquatic, soil and ground-air habitats.