Characteristics of the soil environment. Soil habitat (Lecture). The body as a habitat

The soil is a thin layer on the surface of the land, recycled by the activities of living beings. This is a three-phase medium (soil, moisture, air). Air in soil cavities is always saturated with water vapor, and its composition is enriched with carbon dioxide and depleted in oxygen. On the other hand, the ratio of water and air in soils is constantly changing depending on weather conditions. Temperature fluctuations are very sharp near the surface, but quickly smooth out with depth. The main feature of the soil environment is the constant supply of organic matter, mainly due to dying plant roots and falling leaves. It is a valuable source of energy for bacteria, fungi and many animals, so the soil is the most saturated environment with life. Her hidden world is very rich and diverse.

The inhabitants of the soil environment are edaphobionts.

Organism environment.

Organisms inhabiting living beings are endobionts.

Aquatic life environment. All aquatic inhabitants, despite differences in lifestyle, must be adapted to the main features of their environment. These features are determined, first of all, by the physical properties of water: its density, thermal conductivity, and the ability to dissolve salts and gases.

The density of water determines its significant buoyancy force. This means that the weight of organisms is lightened in water and it becomes possible to lead a permanent life in the water column without sinking to the bottom. Many species, mostly small ones, incapable of fast active swimming, seem to hover in the water, being in it in a suspended state. The collection of such small aquatic inhabitants is called plankton. The composition of plankton includes microscopic algae, small crustaceans, fish eggs and larvae, jellyfish and many other species. Planktonic organisms are carried by the currents, unable to resist them. The presence of plankton in the water makes possible the filtration type of nutrition, i.e., straining, with the help of various devices, small organisms and food particles suspended in water. It is developed in both swimming and sedentary bottom animals, such as sea lilies, mussels, oysters and others. A sedentary lifestyle would be impossible for aquatic inhabitants if there were no plankton, and it, in turn, is possible only in an environment with sufficient density.

The density of water makes it difficult to actively move in it, so fast swimming animals, such as fish, dolphins, squids, must have strong muscles and a streamlined body shape. Due to the high density of water, pressure increases strongly with depth. Deep-sea inhabitants are able to endure pressure, which is thousands of times higher than on the land surface.

Light penetrates into the water only to a shallow depth, so plant organisms can exist only in the upper horizons of the water column. Even in the cleanest seas, photosynthesis is possible only to depths of 100-200 m. There are no plants at great depths, and deep-sea animals live in complete darkness.

The temperature regime in water bodies is milder than on land. Due to the high heat capacity of water, temperature fluctuations in it are smoothed out, and aquatic inhabitants do not face the need to adapt to severe frosts or forty-degree heat. Only in hot springs can the water temperature approach the boiling point.

One of the difficulties of the life of aquatic inhabitants is the limited amount of oxygen. Its solubility is not very high and, moreover, it greatly decreases when the water is contaminated or heated. Therefore, in reservoirs there are sometimes freezes - the mass death of inhabitants due to a lack of oxygen, which occurs for various reasons.

The salt composition of the environment is also very important for aquatic organisms. Marine species cannot live in fresh waters, and freshwater species cannot live in the seas due to cell malfunction.

Ground-air environment of life. This environment has a different set of features. It is generally more complex and diverse than water. It has a lot of oxygen, a lot of light, sharper temperature changes in time and space, much weaker pressure drops, and often there is a moisture deficit. Although many species can fly, and small insects, spiders, microorganisms, seeds, and plant spores are carried by air currents, organisms feed and reproduce on the surface of the ground or plants. In such a low-density medium as air, organisms need support. Therefore, mechanical tissues are developed in terrestrial plants, and in terrestrial animals, the internal or external skeleton is more pronounced than in aquatic ones. The low air density makes it easier to move around in it.

Air is a poor conductor of heat. This facilitates the possibility of conserving the heat generated inside the organisms and maintaining a constant temperature in warm-blooded animals. The very development of warm-bloodedness became possible in the terrestrial environment. The ancestors of modern aquatic mammals - whales, dolphins, walruses, seals - once lived on land.

Land dwellers have very diverse adaptations associated with providing themselves with water, especially in arid conditions. In plants, this is a powerful root system, a waterproof layer on the surface of leaves and stems, and the ability to regulate the evaporation of water through stomata. In animals, these are also various features of the structure of the body and integument, but, in addition, the appropriate behavior also contributes to maintaining the water balance. They may, for example, migrate to watering places or actively avoid particularly dry conditions. Some animals can live their entire lives on dry food, such as jerboas or the well-known clothes moth. In this case, the water needed by the body arises due to the oxidation of the constituent parts of food.

In the life of terrestrial organisms, many other environmental factors also play an important role, for example, the composition of the air, winds, and the topography of the earth's surface. Weather and climate are of particular importance. The inhabitants of the ground-air environment must be adapted to the climate of the part of the Earth where they live, and endure the variability of weather conditions.

Soil as a living environment. The soil is a thin layer of the land surface, processed by the activities of living beings. Solid particles are permeated in the soil with pores and cavities filled partly with water and partly with air, so small aquatic organisms can also inhabit the soil. The volume of small cavities in the soil is a very important characteristic of it. In loose soils, it can be up to 70%, and in dense soils - about 20%. In these pores and cavities, or on the surface of solid particles, a huge variety of microscopic creatures live: bacteria, fungi, protozoa, roundworms, arthropods. Larger animals make their own passages in the soil. The entire soil is permeated with plant roots. Soil depth is determined by the depth of root penetration and the activity of burrowing animals. It is no more than 1.5-2 m.

The air in soil cavities is always saturated with water vapor, and its composition is enriched with carbon dioxide and depleted with oxygen. In this way, the conditions of life in the soil resemble an aquatic environment. On the other hand, the ratio of water and air in soils is constantly changing depending on weather conditions. Temperature fluctuations are very sharp near the surface, but quickly smooth out with depth.

The main feature of the soil environment is the constant supply of organic matter, mainly due to dying plant roots and falling leaves. It is a valuable source of energy for bacteria, fungi and many animals, so the soil is the most saturated environment with life. Her hidden world is very rich and diverse.

By the appearance of different species of animals and plants, one can understand not only in what environment they live, but also what kind of life they lead in it.

If we have a four-legged animal with highly developed thigh muscles on the hind limbs and much weaker on the forelimbs, which are also shortened, with a relatively short neck and a long tail, then we can say with confidence that this is a ground jumper capable of to fast and maneuverable movements, an inhabitant of open spaces. This is what the famous Australian kangaroos look like, and the desert Asian jerboas, and African jumpers, and many other jumping mammals - representatives of various orders living on different continents. They live in the steppes, prairies, savannas - where rapid movement on the ground is the main means of escape from predators. The long tail serves as a balancer during fast turns, otherwise the animals would lose their balance.

The hips are strongly developed on the hind limbs and in jumping insects - locusts, grasshoppers, fleas, psyllid beetles.

A compact body with a short tail and short limbs, of which the front ones are very powerful and look like a shovel or rake, blind eyes, a short neck and short, as if trimmed, fur tell us that we have an underground animal digging holes and galleries . This may be a forest mole, and a steppe mole rat, and an Australian marsupial mole, and many other mammals leading a similar lifestyle.

Burrowing insects - bears also have a compact, stocky body and powerful forelimbs, similar to a reduced bulldozer bucket. In appearance, they resemble a small mole.

All flying species have developed wide planes - wings in birds, bats, insects or straightening folds of skin on the sides of the body, like in gliding flying squirrels or lizards.

Organisms settling by passive flight, with air currents, are characterized by small sizes and very diverse shapes. However, they all have one thing in common - a strong development of the surface compared to body weight. This is achieved in different ways: due to long hairs, bristles, various outgrowths of the body, its lengthening or flattening, and lightening the specific gravity. This is how small insects and flying fruits of plants look.

The external similarity that occurs in representatives of different unrelated groups and species as a result of a similar lifestyle is called convergence.

It affects mainly those organs that directly interact with the external environment, and is much less pronounced in the structure of internal systems - the digestive, excretory, and nervous systems.

The shape of a plant determines the characteristics of its relationship with the external environment, for example, the way it endures the cold season. Trees and tall shrubs have the tallest branches.

The form of a creeper - with a weak trunk wrapping around other plants, can be in both woody and herbaceous species. These include grapes, hops, meadow dodder, tropical creepers. Wrapping around the trunks and stems of upright species, liana-like plants carry their leaves and flowers to the light.

In similar climatic conditions on different continents, a similar external appearance of vegetation arises, which consists of various, often completely unrelated species.

The external form, which reflects the way of interaction with the environment, is called the life form of the species. Different species may have a similar life form if they lead a close lifestyle.

The life form is developed during the secular evolution of species. Those species that develop with metamorphosis naturally change their life form during the life cycle. Compare, for example, a caterpillar and an adult butterfly, or a frog and its tadpole. Some plants can take on different life forms depending on growing conditions. For example, linden or bird cherry can be both an upright tree and a bush.

Communities of plants and animals are more stable and complete if they include representatives of different life forms. This means that such a community uses the resources of the environment more fully and has more diverse internal connections.

The composition of the life forms of organisms in communities serves as an indicator of the characteristics of their environment and the changes taking place in it.

Aircraft engineers carefully study the different life forms of flying insects. Models of machines with flapping flight were created, according to the principle of movement in the air of Diptera and Hymenoptera. In modern technology, walking machines have been designed, as well as robots with lever and hydraulic movement, like animals of different life forms. Such machines are able to move on steep slopes and off-road.

Life on Earth developed under conditions of a regular change of day and night and alternation of seasons due to the rotation of the planet around its axis and around the Sun. The rhythm of the external environment creates periodicity, that is, the repetition of conditions in the life of most species. Both critical, difficult to survive periods, and favorable ones are regularly repeated.

Adaptation to periodic changes in the external environment is expressed in living beings not only by a direct reaction to changing factors, but also in hereditarily fixed internal rhythms.

LECTURE PLAN

1. General characteristics of the soil

2. Soil organic matter

3. Humidity and aeration

4. Ecological groups of soil organisms

1. General characteristics of the soil

Soil is the most important component of any terrestrial ecological system, on the basis of which plant communities develop, which in turn form the basis of the food chains of all other organisms that form the ecological systems of the Earth, its biosphere. People are no exception here: the well-being of any human society is determined by the availability and condition of land resources, soil fertility.

Meanwhile, during the historical time on our planet, up to 20 million km 2 of agricultural land has been lost. For every inhabitant of the Earth today there is an average of only 0.35- 0.37 ha , whereas in the 70s this value was 0.45- 0.50 ha . If the current situation does not change, then in a century, at such a rate of loss, the total area of ​​land suitable for agriculture will be reduced from 3.2 to 1 billion hectares.

V.V. Dokuchaev identified 5 main soil-forming factors:

1. climate;

2. parent rock (geological basis);

3. topography (relief);

4. living organisms;

5. time.

Currently, another factor in soil formation can be called human activity.

Soil formation begins with primary succession, which manifests itself in physical and chemical weathering, leading to loosening from the surface of parent rocks, such as basalts, gneisses, granites, limestones, sandstones, and shales. This weathering layer is gradually colonized by microorganisms and lichens, which transform the substrate and enrich it with organic matter. As a result of the activity of lichens, the most important elements of plant nutrition, such as phosphorus, calcium, potassium and others, accumulate in the primary soil. Plants can now settle on this primary soil and form plant communities that determine the face of biogeocenosis.

Gradually, deeper layers of the earth are involved in the process of soil formation. Therefore, most soils have a more or less pronounced layered profile, divided into soil horizons. A complex of soil organisms settles in the soil - edaphone : bacteria, fungi, insects, worms and burrowing animals. Edaphon and plants are involved in the formation of soil detritus, which is passed through their body by detritophages - worms and insect larvae.

For example, earthworms per hectare of land process about 50 tons of soil per year.

During the decomposition of plant detritus, humic substances are formed - weak organic humic and fulvic acids - the basis of soil humus. Its content ensures the structure of the soil and the availability of mineral nutrients to plants. The thickness of the layer rich in humus determines the fertility of the soil.

The composition of the soil includes 4 important structural components:

1. mineral base (50-60% of the total soil composition);

2. organic matter (up to 10%);

3. air (15-20%);

4. water (25-35%).

Mineral base- an inorganic component formed from the parent rock as a result of its weathering. Mineral fragments vary in size (from boulders to grains of sand and the smallest particles of clay). It is the skeletal material of the soil. It is divided into colloidal particles (less than 1 micron), fine soil (less than 2 mm) and large fragments. The mechanical and chemical properties of the soil are determined by small particles.

The structure of the soil is determined by the relative content of sand and clay in it. The soil that contains sand and clay in equal amounts is most favorable for plant growth.

In the soil, as a rule, 3 main horizons are distinguished, differing in mechanical and chemical properties:

1. Upper humus-accumulative horizon (A), in which organic matter is accumulated and transformed, and from which part of the compounds is carried down by washing water.

2. Washout horizon or illuvial (B), where the substances washed from above are deposited and converted.

3. parent rock or horizon (C), the material that is converted into soil.

Within each layer, more fractional horizons are distinguished, differing in their properties.

The main properties of the soil as an ecological environment are its physical structure, mechanical and chemical composition, acidity, redox conditions, organic matter content, aeration, moisture capacity and moisture content. Various combinations of these properties form many varieties of soils. On Earth, five typological groups of soils occupy the leading position in terms of prevalence:

1. soils of humid tropics and subtropics, mainly red soils and zheltozems , characterized by the richness of the mineral composition and high mobility of organic matter;

2. fertile soils of savannas and steppes - black soil, chestnut and brown soils with a powerful humus layer;

3. poor and extremely unstable soils of deserts and semi-deserts belonging to different climatic zones;

4. relatively poor soils of temperate forests - podzolic, sod-podzolic, brown and gray forest soils ;

5. permafrost soils, usually thin, podzolic, marsh , gley , depleted in mineral salts with a poorly developed humus layer.

On the banks of the rivers there are floodplain soils;

Saline soils are a separate group: salt marshes, salt marshes and etc. which account for 25% of soils.

Salt marshes - soils constantly strongly moistened with saline waters up to the surface, for example, around bitter-salty lakes. In summer, the surface of the salt marshes dries up, becoming covered with a crust of salt.

Rice. Saline

Salt licks - the surface is not saline, the upper layer is leached, structureless. The lower horizons are compacted, saturated with sodium ions; when dried, they crack into pillars and blocks. The water regime is unstable - in spring - moisture stagnation, in summer - severe drying.

2. Soil organic matter

Each type of soil corresponds to a certain flora, fauna and a combination of bacteria - edaphon. Dying or dead organisms accumulate on the surface and within the soil, forming soil organic matter called humus . The process of humification begins with the destruction and grinding of the organic mass by vertebrates, and then it is transformed by fungi and bacteria. Such animals include phytophages that feed on the tissues of living plants, saprophages , consuming dead plant matter, necrophages feeding on the carcasses of animals, coprophages destroying animal excrement. All of them make up a complex system called saprofile animal complex .

Humus differs in the type, form and nature of its constituent elements, which are divided into humic and non-humic substances. Non-humic substances are formed from compounds found in plant and animal tissues, such as proteins and carbohydrates. When these substances decompose, carbon dioxide, water, ammonia are released. The energy generated is used soil organisms. In this case, complete mineralization of the nutrients occurs. Humic substances as a result of the vital activity of microorganisms are processed into new, usually high-molecular compounds - humic acids or fulvic acids .

Humus is divided into nutrient, which is easily processed and serves as a source of nutrition for microorganisms, and sustainable, which performs physical and chemical functions, controlling the balance of nutrients, the amount of water and air in the soil. Humus tightly glues the mineral particles of the soil, improving its structure. Soil structure also depends on the amount of calcium compounds. The following soil structures are distinguished:

– mealy,

– powdery,

– grainy

– nutty,

– lumpy

– clayey.

The dark color of humus contributes to better heating of the soil, and its high moisture capacity - to water retention by the soil.

The main property of the soil is its fertility, i.e. the ability to provide plants with water, mineral salts, air. The thickness of the humus layer determines the fertility of the soil.

3. Humidity and aeration

Soil water is divided into:

– gravitational

– hygroscopic,

– capillary

– vaporous

Gravity water - mobile, is the main type of mobile water, fills wide gaps between soil particles, seeps down under the influence of gravity until it reaches groundwater. Plants easily absorb it.

Hygroscopic water in the soil is retained by hydrogen bonds around individual colloidal particles in the form of a thin, strong bonded film. It is released only at a temperature of 105 - 110 o C and is practically inaccessible to plants. The amount of hygroscopic water depends on the content of colloidal particles in the soil. In clay soils it is up to 15%, in sandy soils - 5%.

As the amount of hygroscopic water accumulates, it passes into capillary water, which is held in the soil by surface tension forces. Capillary water easily rises to the surface through pores from groundwater, easily evaporates, and is freely absorbed by plants.

Vaporous moisture occupies all water-free pores.

There is a constant exchange of soil, ground and surface waters, changing its intensity and direction depending on the climate and seasons.

All pores free from moisture are filled with air. On light (sandy) soils, aeration is better than on heavy (clay) soils. The air regime and humidity regime are related to the amount of precipitation.

4. Ecological groups of soil organisms

On average, the soil contains 2-3 kg/m 2 of living plants and animals, or 20-30 t/ha. At the same time, in the temperate zone, plant roots are 15 t / ha, insects 1 t, earthworms - 500 kg, nematodes - 50 kg, crustaceans - 40 kg, snails, slugs - 20 kg, snakes, rodents - 20 gk, bacteria - 3 t, fungi - 3 t, actinomycetes - 1.5t, protozoa - 100kg, algae - 100kg.

The heterogeneity of the soil leads to the fact that for different organisms it acts as a different environment. According to the degree of connection with the soil as a habitat animals grouped into 3 groups:

1. Geobionts – animals permanently living in the soil (earthworms, primary wingless insects).

2. Geophylls – animals, part of the cycle of which necessarily takes place in the soil (most insects: locusts, a number of beetles, centipede mosquitoes).

3. geoxenes – animals that occasionally visit the soil for temporary shelter or refuge (cockroaches, many hemiptera, beetles, rodents and other mammals).

Depending on the size of the soil inhabitants can be divided into the following groups.

1. Microbiotype , microbiota - soil microorganisms, the main link in the detritus chain, an intermediate link between plant residues and soil animals. These are green, blue-green algae, bacteria, fungi, protozoa. The soil for them is a system of micro-reservoirs. They live in soil pores. Able to tolerate freezing soil.

3. Macrobiotype , macrobiota - large soil animals, up to 20 mm in size (insect larvae, centipedes, earthworms, etc.). soil for them is a dense medium that provides strong mechanical resistance when moving. They move in the soil by expanding natural wells by moving apart soil particles or by digging new passages. In this regard, they developed adaptations for digging. Often there are specialized respiratory organs. They also breathe through the integument of the body. For the winter and during the dry period, they move to deep soil layers.

4. Megabiotype , megabiota - large shrews, mostly mammals. Many of them spend their whole lives in the soil (gold moles, mole voles, zokors, moles of Eurasia, marsupial moles of Australia, mole rats, etc.). They lay a system of holes, passages in the soil. They have underdeveloped eyes, a compact, valky body with a short neck, short thick fur, strong compact limbs, burrowing limbs, strong claws.

5. The inhabitants of the holes - badgers, marmots, ground squirrels, jerboas, etc. They feed on the surface, breed, hibernate, rest, sleep, and escape from danger in soil burrows. The structure is typical for terrestrial ones, however, they have adaptations of burrows - strong claws, strong muscles on the forelimbs, a narrow head, small auricles.

6. Psammophiles - sand dwellers. They have peculiar limbs, often in the form of “skis”, covered with long hairs, horny outgrowths (thin-clawed ground squirrel, crested jerboa).

7. Gallophiles - inhabitants of saline soils. They have adaptations to protect against excess salts: dense covers, devices for removing salts from the body (larvae of desert beetles).

8. Plants are divided into groups depending on the requirements for soil fertility.

9. Eutotrophic or eutrophic - grow in fertile soils.

10. Mesotrophic – less demanding soils.

11. Oligotrophic – contented a small amount of nutrients.

12. Depending on the exactingness of plants to individual soil microelements, the following groups are distinguished.

13. Nitrophils - demanding on the presence of nitrogen in the soil, they settle where there are additional sources of nitrogen - clearing plants (raspberries, hops, bindweed), garbage (nettle amaranth, umbrella plants), pasture plants.

14. Calciophiles - demanding on the presence of calcium in the soil, settle on carbonate soils (lady's slipper, Siberian larch, beech, ash).

15. calcium phobes - plants that avoid soils with a high content of calcium (sphagnum mosses, marsh, heather, warty birch, chestnut).

16. Depending on the pH requirements of the soil, all plants are divided into 3 groups.

17. acidophiles - plants that prefer acidic soils (heather, white-bearded, sorrel, small sorrel).

18. Basiphylls - plants that prefer alkaline soils (coltsfoot, field mustard).

19. Neutrophils - plants that prefer neutral soils (meadow foxtail, meadow fescue).

Plants that grow in saline soils are called halophytes ( European soleros, knobby sarsazan), and plants that cannot withstand excessive salinity - glycophytes . Halophytes have a high osmotic pressure, which allows the use of soil solutions, they are able to release excess salts through the leaves or accumulate them in their body.

Plants adapted to loose sands are called psammophytes . They are able to form adventitious roots when they are covered with sand, adventitious buds form on the roots when they are exposed, often have a high growth rate of shoots, flying seeds, strong covers, have air chambers, parachutes, propellers - devices for not falling asleep with sand. Sometimes a whole plant is able to break away from the ground, dry out and, together with the seeds, be carried by the wind to another place. Seedlings germinate quickly, arguing with the dune. There are adaptations for drought tolerance - root covers, root corking, strong development of lateral roots, leafless shoots, xeromorphic foliage.

Plants that grow in peat bogs are called oxylophytes . They are adapted to high soil acidity, strong moisture, anaerobic conditions (ledum, sundew, cranberries).

Plants that live on rocks, rocks, scree belong to the lithophytes. As a rule, these are the first settlers on rocky surfaces: autotrophic algae, scale lichens, leaf lichens, mosses, lithophytes from higher plants. They are called slit plants - chasmophytes . For example, saxifrage, juniper, pine.

The soil environment occupies an intermediate position between the water and ground-air environments. The temperature regime, low oxygen content, moisture saturation, the presence of a significant amount of salts and organic substances bring the soil closer to the aquatic environment. And sharp changes in the temperature regime, desiccation, saturation with air, including oxygen, bring the soil closer to the ground-air environment of life.

Soil is a loose surface layer of land, which is a mixture of mineral substances obtained from the decay of rocks under the influence of physical and chemical agents, and special organic substances resulting from the decomposition of plant and animal remains by biological agents. In the surface layers of the soil, where the freshest dead organic matter enters, many destructive organisms live - bacteria, fungi, worms, the smallest arthropods, etc. Their activity ensures the development of the soil from above, while the physical and chemical destruction of the bedrock contributes to the formation of soil from below.

As a living environment, the soil is distinguished by a number of features: high density, lack of light, reduced amplitude of temperature fluctuations, lack of oxygen, and a relatively high content of carbon dioxide. In addition, the soil is characterized by a loose (porous) structure of the substrate. The existing cavities are filled with a mixture of gases and aqueous solutions, which determines an extremely wide variety of conditions for the life of many organisms. On average, there are more than 100 billion cells of protozoa, millions of rotifers and tardigrades, tens of millions of nematodes, hundreds of thousands of arthropods, tens and hundreds of earthworms, mollusks and other invertebrates, hundreds of millions of bacteria, microscopic fungi (actinomycetes), algae and other microorganisms. The entire population of the soil - edaphobionts (edaphobius, from the Greek edaphos - soil, bios - life) interacts with each other, forming a kind of biocenotic complex, actively participating in the creation of the soil life environment itself and ensuring its fertility. Species inhabiting the soil environment of life are also called pedobionts (from the Greek paidos - a child, i.e., passing through the stage of larvae in their development).

The representatives of edaphobius in the process of evolution developed peculiar anatomical and morphological features. For example, animals have a valky body shape, small size, relatively strong integument, skin respiration, eye reduction, colorless integument, saprophagy (the ability to feed on the remains of other organisms). In addition, along with aerobicity, anaerobicity (the ability to exist in the absence of free oxygen) is widely represented.

An important stage in the development of the biosphere was the emergence of such a part of it as the soil cover. With the formation of a sufficiently developed soil cover, the biosphere becomes an integral complete system, all parts of which are closely interconnected and dependent on each other.

The soil is a loose, thin surface layer of land in contact with the air. Despite its insignificant thickness, this shell of the Earth plays a crucial role in the spread of life. The soil is not just a solid body, like most rocks of the lithosphere, 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 are formed in it, favorable for the life of many micro- and macro-organisms.

In the soil, temperature fluctuations are smoothed 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. The soil concentrates reserves of organic and mineral substances supplied by dying vegetation and animal corpses. All this determines the high saturation of the soil with life.

The root systems of terrestrial plants are concentrated in the soil. On average, there are more than 100 billion cells of protozoa, millions of rotifers and tardigrades, tens of millions of nematodes, tens and hundreds of thousands of ticks and springtails, thousands of other arthropods, tens of thousands of enchitreids, tens and hundreds of earthworms, mollusks and others per 1 m 2 of the soil layer. invertebrates. In addition, 1 cm 2 of soil contains tens and hundreds of millions of bacteria, microscopic fungi, actinomycetes and other microorganisms. In the illuminated surface layers, hundreds of thousands of photosynthetic cells of green, yellow-green, diatoms and blue-green algae live in every gram. Living organisms are as characteristic of the soil as its non-living components. Therefore, V. I. Vernadsky attributed the soil to the bio-inert bodies of nature, emphasizing its saturation with life and inseparable connection with it.

The heterogeneity of conditions in the soil is most pronounced in the vertical direction. With depth, a number of the most important environmental factors that affect the life of the inhabitants of the soil change dramatically. First of all, this refers to the structure of the soil.

The main structural elements of the soil are: the mineral base, organic matter, air and water.

The mineral base (skeleton) (50-60% of the total soil) is an inorganic substance formed as a result of the underlying mountain (parent, soil-forming) rock as a result of its weathering. Sizes of skeletal particles: from boulders and stones to the smallest grains of sand and silt particles. The physicochemical properties of soils are mainly determined by the composition of parent rocks.

The permeability and porosity of the soil, which ensure the circulation of both water and air, depend on the ratio of clay and sand in the soil, the size of the fragments. In temperate climates, it is ideal if the soil is formed by equal amounts of clay and sand, i.e. represents loam. In this case, the soils are not threatened by either waterlogging or drying out. Both are equally detrimental to both plants and animals.

Organic matter - up to 10% of the soil, is formed from dead biomass (plant mass - litter of leaves, branches and roots, dead trunks, grass rags, organisms of dead animals), crushed and processed into soil humus by microorganisms and certain groups of animals and plants. The simpler elements formed as a result of the decomposition of organic matter are again assimilated by plants and are involved in the biological cycle.

Air (15-25%) in the soil is contained in cavities - pores, between organic and mineral particles. In the absence (heavy clay soils) or the filling of pores with water (during flooding, thawing of permafrost), aeration worsens in the soil and anaerobic conditions develop. Under such conditions, the physiological processes of organisms that consume oxygen - aerobes - are inhibited, the decomposition of organic matter is slow. Gradually accumulating, they form peat. Large reserves of peat are characteristic of swamps, swampy forests, and tundra communities. Peat accumulation is especially pronounced in the northern regions, where coldness and waterlogging of soils mutually determine and complement each other.

Water (25-30%) in the soil is represented by 4 types: gravitational, hygroscopic (bound), capillary and vaporous.

Gravitational - moving water, occupy wide gaps between soil particles, seeps down under its own weight to the groundwater level. Easily absorbed by plants.

Hygroscopic, or bound - is adsorbed around the colloidal particles (clay, quartz) of the soil and is retained in the form of a thin film due to hydrogen bonds. It is released from them at high temperature (102-105°C). It is inaccessible to plants, does not evaporate. In clay soils, such water is up to 15%, in sandy soils - 5%.

Capillary - held around soil particles by surface tension. Through narrow pores and channels - capillaries, it rises from the groundwater level or diverges from cavities with gravitational water. Better retained by clay soils, easily evaporates. Plants easily absorb it.

Vaporous - occupies all pores free from water. Evaporates first.

There is a constant exchange of surface soil and groundwater, as a link in the general water cycle in nature, changing speed and direction depending on the season and weather conditions.

Soil structure is heterogeneous both horizontally and vertically. The horizontal heterogeneity of soils reflects the heterogeneity of the distribution of soil-forming rocks, position in the relief, climate features and is consistent with the distribution of vegetation cover over the territory. Each such heterogeneity (soil type) is characterized by its own vertical heterogeneity, or soil profile, which is formed as a result of vertical migration of water, organic and mineral substances. This profile is a collection of layers, or horizons. All processes of soil formation proceed in the profile with the obligatory consideration of its division into horizons.

In nature, there are practically no situations where any single soil with properties that are unchanged in space extends for many kilometers. At the same time, differences in soils are due to differences in the factors of soil formation. The regular spatial distribution of soils in small areas is called the soil cover structure (SCC). The initial unit of SPP is the elementary soil area (EPA) - a soil formation, within which there are no soil-geographical boundaries. ESAs alternating in space and to some extent genetically related form soil combinations.

According to the degree of connection with the environment in edaphone, three groups are distinguished:

Geobionts are permanent inhabitants of the soil (earthworms (Lymbricidae), many primary wingless insects (Apterigota)), from mammals, moles, mole rats.

Geophiles are animals in which part of the development cycle takes place in a different environment, and part in the soil. These are the majority of flying insects (locusts, beetles, centipede mosquitoes, bears, many butterflies). Some go through the larval phase in the soil, while others go through the pupal phase.

Geoxens are animals that occasionally visit the soil as cover or shelter. These include all mammals living in burrows, many insects (cockroaches (Blattodea), hemipterans (Hemiptera), some species of beetles).

A special group is psammophytes and psammophiles (marble beetles, ant lions); adapted to loose sands in deserts. Adaptations to life in a mobile, dry environment in plants (saxaul, sandy acacia, sandy fescue, etc.): adventitious roots, dormant buds on the roots. The former begin to grow when covered with sand, the latter when

sand blowing. They are saved from sand drift by rapid growth, reduction of leaves. Fruits are characterized by volatility, springiness. Sandy covers on the roots, corking of the bark, and strongly developed roots protect against drought. Adaptations to life in a mobile, dry environment in animals (indicated above, where thermal and humid conditions were considered): they mine the sands - they push them apart with their bodies. In burrowing animals, paws-skis - with growths, with hair.

Soil is an intermediate medium between water (temperature conditions, low oxygen content, saturation with water vapor, the presence of water and salts in it) and air (air cavities, sudden changes in humidity and temperature in the upper layers). For many arthropods, soil was the medium through which they were able to move from an aquatic to a terrestrial lifestyle.

The main indicators of soil properties, reflecting its ability to be a habitat for living organisms, are the hydrothermal regime and aeration. Or humidity, temperature and soil structure. All three indicators are closely related. With an increase in humidity, thermal conductivity increases and soil aeration worsens. The higher the temperature, the more evaporation occurs. The concepts of physical and physiological dryness of soils are directly related to these indicators.

Physical dryness is a common occurrence during atmospheric droughts, due to a sharp reduction in water supply due to a long absence of precipitation.

In Primorye, such periods are typical for late spring and are especially pronounced on the slopes of southern exposures. Moreover, with the same position in the relief and other similar growth conditions, the better the vegetation cover is developed, the faster the state of physical dryness sets in.

Physiological dryness is a more complex phenomenon, it is due to adverse environmental conditions. It consists in the physiological inaccessibility of water with a sufficient, and even excessive amount of it in the soil. As a rule, water becomes physiologically inaccessible at low temperatures, high salinity or acidity of soils, the presence of toxic substances, and a lack of oxygen. At the same time, water-soluble nutrients such as phosphorus, sulfur, calcium, potassium, etc., become inaccessible.

Due to the coldness of soils, and the waterlogging and high acidity caused by it, large reserves of water and mineral salts in many ecosystems of the tundra and northern taiga forests are physiologically inaccessible to own-rooted plants. This explains the strong suppression of higher plants in them and the wide distribution of lichens and mosses, especially sphagnum.

One of the important adaptations to the harsh conditions in the edasphere is mycorrhizal nutrition. Almost all trees are associated with mycorrhizal fungi. Each type of tree has its own mycorrhiza-forming type of fungus. Due to mycorrhiza, the active surface of root systems increases, and the secretions of the fungus by the roots of higher plants are easily absorbed.

As V.V. Dokuchaev "... Soil zones are also natural historical zones: here the closest connection between climate, soil, animal and plant organisms is obvious ...". This is clearly seen in the example of soil cover in forest areas in the north and south of the Far East.

A characteristic feature of the soils of the Far East, which are formed under monsoonal, i.e. very humid climate, is a strong leaching of elements from the eluvial horizon. But in the northern and southern regions of the region, this process is not the same due to the different heat supply of habitats. Soil formation in the Far North takes place under conditions of a short growing season (no more than 120 days), and widespread permafrost. The lack of heat is often accompanied by waterlogging of soils, low chemical activity of weathering of soil-forming rocks and slow decomposition of organic matter. The vital activity of soil microorganisms is strongly suppressed, and the assimilation of nutrients by plant roots is inhibited. As a result, the northern cenoses are characterized by low productivity - wood reserves in the main types of larch woodlands do not exceed 150 m 2 /ha. At the same time, the accumulation of dead organic matter prevails over its decomposition, as a result of which powerful peaty and humus horizons are formed, and the humus content is high in the profile. Thus, in northern larch forests, the thickness of the forest litter reaches ?10-12 cm, and the reserves of undifferentiated mass in the soil are up to 53% of the total biomass reserve of the stand. At the same time, elements are carried out of the profile, and when the permafrost is close, they accumulate in the illuvial horizon. In soil formation, as in all cold regions of the northern hemisphere, the leading process is podzol formation. Zonal soils on the northern coast of the Sea of ​​Okhotsk are Al-Fe-humus podzols, and in continental regions - podburs. Peat soils with permafrost in the profile are common in all regions of the Northeast. Zonal soils are characterized by a sharp differentiation of horizons by color.

Your attention is invited to a lesson on the topic "Habitats of organisms. Acquaintance with organisms of habitats. A fascinating story will immerse you in the world of living cells. During the lesson, you will be able to find out what habitats of organisms are on our planet, get acquainted with the representatives of living organisms of these environments.

Subject: Life on Earth.

Lesson: Habitats of Organisms.

Acquaintance with organisms of various habitats

Life takes place on a large expanse of diverse surface of the globe.

Biosphere- this is the shell of the Earth, where living organisms exist.

The biosphere includes:

The lower part of the atmosphere (the air shell of the Earth)

Hydrosphere (water shell of the Earth)

The upper part of the lithosphere (the solid shell of the Earth)

Each of these shells of the Earth has special conditions that create different environments of life. Various conditions of living environments generate a variety of forms of living organisms.

environments of life on earth. Rice. one.

Rice. 1. Life environments on Earth

The following habitats are distinguished on our planet:

Ground-air (Fig. 2)

soil

Organismic.

Rice. 2. Ground-air habitat

Life in every environment has its own characteristics. In the ground-air environment there is enough oxygen and sunlight. But often there is not enough moisture. In this regard, plants and animals of arid habitats have special adaptations for obtaining, storing and economically using water. In the ground-air environment, there are significant temperature changes, especially in areas with cold winters. In these areas, the whole life of the organism noticeably changes during the year. Autumn leaf fall, the flight of birds to warmer climes, the change of wool in animals to a thicker and warmer one - all this is an adaptation of living beings to seasonal changes in nature. For animals living in any environment, an important problem is movement. In the ground-air environment, you can move around the Earth and through the air. And animals take advantage of it. The legs of some are adapted for running: ostrich, cheetah, zebra. Others - for jumping: kangaroo, jerboa. Of every 100 animals living in this environment, 75 can fly. These are most insects, birds and some animals, for example, a bat. (Fig. 3).

Rice. 3. Bat

The champion in flight speed among birds is a swift. 120 km/h is his usual speed. Hummingbirds flap their wings up to 70 times per second. The flight speed of different insects is as follows: for the lacewing - 2 km / h, for the house fly - 7 km / h, for the May beetle - 11 km / h, for the bumblebee - 18 km / h, and for the hawk moth - 54 km / h h. Our bats are small in stature. But their relatives fruit bats reach a wingspan of 170 cm.

Large kangaroos jump up to 9 meters.

Birds are distinguished from all other creatures by their ability to fly. The whole body of a bird is adapted for flight. (Fig. 4). Forelimbs of birds turned into wings. So the birds became bipedal. The feathered wing is much more adapted to flight than the flying membrane of bats. Damaged wing plumage is quickly restored. The lengthening of the wing is achieved by lengthening the feathers, not the bones. The long thin bones of flying vertebrates can break easily.

Rice. 4 Pigeon Skeleton

As an adaptation for flight on the sternum of birds, a bone keel. This is the support for the bone flying muscles. Some modern birds are keelless, but at the same time they have lost the ability to fly. All unnecessary weights in the structure of birds that interfere with flight, nature tried to eliminate. The maximum weight of all large flying birds reaches 15-16 kg. And for non-flying, such as ostriches, it can exceed 150 kg. bird bones in the process of evolution became hollow and light. At the same time, they retained their strength.

The first birds had teeth, but then heavy the dentition is completely gone. The birds have a horny beak. In general, flying is an incomparably faster way of moving than running or swimming in water. But energy costs are about twice as high as running and 50 times higher than swimming. Therefore, birds must absorb quite a lot of food.

Flight may be

waving

Soaring

Soaring flight is perfectly mastered by birds of prey. (Fig. 5). They use warm air currents rising from the heated ground.

Rice. 5. Griffon Vulture

Fish and crustaceans breathe with gills. These are special organs that extract oxygen dissolved in it, which is necessary for breathing.

The frog, being under water, breathes through the skin. Mammals that have mastered the water breathe with their lungs, they need to periodically rise to the surface of the water to inhale.

Water beetles behave in a similar way, only they, like other insects, do not have lungs, but special respiratory tubes - tracheas.

Rice. 6. Trout

Some organisms (trout) can only live in oxygen-rich water. (Fig. 6). Carp, crucian carp, tench withstand a lack of oxygen. In winter, when many reservoirs are ice-bound, fish can die, that is, their mass death from suffocation. So that oxygen enters the water, holes are cut in the ice. There is less light in the aquatic environment than in the land-air environment. In the oceans and seas at a depth of 200 meters - the realm of twilight, and even lower - eternal darkness. Accordingly, aquatic plants are found only where there is enough light. Only animals can live deeper. Deep-sea animals feed on the dead remains of various marine life falling from the upper layers.

A feature of many marine animals is swimming device. In fish, dolphins and whales, these are fins. (Fig. 7), seals and walruses have flippers. (Fig. 8). Beavers, otters, waterfowl have webbed toes. The swimming beetle has paddle-like swimming legs.

Rice. 7. Dolphin

Rice. 8. Walrus

Rice. 9. Soil

In the aquatic environment, there is always enough water. The temperature here changes less than the air temperature, but oxygen is often not enough.

The soil environment is home to a variety of bacteria and protozoa. (Fig. 9). There are also myceliums of mushrooms, roots of plants. A variety of animals also inhabited the soil: worms, insects, animals adapted to digging, for example, moles. The inhabitants of the soil find in it the necessary conditions for them: air, water, food, mineral salts. Soil has less oxygen and more carbon dioxide than outdoors. And there is too much water here. The temperature in the soil environment is more even than on the surface. Light does not penetrate the soil. Therefore, the animals inhabiting it usually have very small eyes or are completely devoid of organs of vision. Rescues their sense of smell and touch.

Soil formation began only with the appearance of living beings on Earth. Since then, for millions of years, there has been a continuous process of its formation. Solid rocks in nature are constantly destroyed. It turns out a loose layer, consisting of small pebbles, sand, clay. It contains almost no nutrients needed by plants. But still unpretentious plants and lichens settle here. Humus is formed from their remains under the influence of bacteria. Now plants can settle in the soil. When they die, they also give humus. So gradually the soil turns into a habitat. Various animals live in the soil. They increase her fertility. So the soil cannot come into existence without living beings. At the same time, both plants and animals need soil. Therefore, everything in nature is interconnected.

1 cm of soil is formed in nature in 250-300 years, 20 cm - in 5-6 thousand years. That is why the destruction and destruction of the soil must not be allowed. Where people have destroyed plants, the soil is washed away by water, a strong wind blows. The soil is afraid of many things, for example, pesticides. If they are added more than the norm, they accumulate in it, polluting it. As a result, worms, microbes, bacteria die, without which the soil loses its fertility. If too much fertilizer is applied to the soil or it is watered too abundantly, an excess of salts accumulates in it. And this is harmful to plants and to all living things. To protect the soil, it is necessary to plant forest strips in the fields, to plow correctly on the slopes, and to carry out snow retention in winter.

Rice. 10. Mole

The mole lives underground from birth to death, it does not see white light. As a digger, he knows no equal. (Fig. 10). Everything he has for digging is adapted in the best possible way. The fur is short and smooth so as not to cling to the ground. The eyes of a mole are tiny, the size of a poppy seed. Their eyelids are tightly closed when necessary, and in some moles the eyes are completely overgrown with skin. The mole's front paws are real shovels. The bones on them are flat, and the brush is turned out so that it is more convenient to dig the earth in front of you and rake it back. During the day he breaks through 20 new moves. Underground labyrinths of moles can stretch for vast distances. There are two types of mole moves:

Nests in which he rests.

Stern, they are located near the surface.

A sensitive sense of smell tells the mole in which direction to dig.

The structure of the body of the mole, zokor and mole rat suggests that they are all inhabitants of the soil environment. The front legs of the mole and zokor are the main digging tool. They are flat, like spades, with very large claws. And the mole rat has normal legs. It bites into the soil with powerful front teeth. The body of all these animals is oval, compact, for more convenient movement through underground passages.

Rice. 11. Ascaris

1. Melchakov L.F., Skatnik M.N. Natural history: textbook. for 3.5 cells. avg. school - 8th ed. - M.: Enlightenment, 1992. - 240 p.: ill.

2. Bakhchieva O.A., Klyuchnikova N.M., Pyatunina S.K. and others. Natural history 5. - M .: Educational literature.

3. Eskov K.Yu. et al. Natural History 5 / Ed. Vakhrusheva A.A. - M.: Balass.

1. Encyclopedia Around the World ().

2. Geographical directory ().

3. Facts about mainland Australia ().

1. List the environments of life on our planet.

2. Name the animals of the soil habitat.

3. How have animals of different habitats adapted to locomotion?

4. * Prepare a short message about the inhabitants of the ground-air environment.