What small animals live in the soil. Soil is a living organism

Soil is a living organism made up of countless microscopic living beings. The number and variety of living microorganisms in the soil is immeasurable. In 1 g of soil there are billions of bacteria, fungi, algae and other organisms, and in addition, a great many earthworms, wood lice, centipedes, snails and other soil organisms, which, as a result of the metabolic process, process dead protein organisms and other organic residues into nutrients available for plant uptake. Thanks to their activity in the soil, humus is formed from the original plant and protein material, from which, as a result of combination with water and oxygen, nutrients for plants are released. Loose soil structure is also achieved largely due to the activity

soil organisms that naturally mix mineral and organic substances, producing a new enriched substance. This greatly increases the fertility of the soil. Soil animals are studied by a special branch of science - soil zoology, which was formed only in our century. After specialists developed methods for recording and fixing animals, which is associated with significant technical difficulties, the eyes of zoologists saw a whole kingdom of creatures, diverse in structure, lifestyle and their significance in the natural processes occurring in the soil. By biodiversity animal world soils can only be compared with coral reefs - a classic example of the richest and most diverse natural communities on our planet.

Among them are large invertebrates such as earthworms, and microorganisms that cannot be seen with the naked eye. In addition to small sizes (up to 1 mm), most soil-dwelling invertebrates also have an inconspicuous body color, whitish or gray, so they can be seen only after special treatment with fixatives, under a magnifying glass or microscope. Microorganisms form the basis of the animal population of the soil, the biomass of which reaches hundreds of centners per hectare. If we talk about the number of earthworms and other large invertebrates, then it is measured in tens and hundreds per square meter, and the number of small and microscopic organisms reaches millions and billions of individuals.

For example, the simplest roundworms(nematodes) with a body size of up to 0.01 mm in their physiology are typically aquatic creatures that can breathe oxygen dissolved in water. The smallest sizes allow them to be content with microscopic droplets of moisture that fill the narrow soil cavities. There the worms move, find food, multiply. When the soil dries out, they are able to long time be in an inactive state, covered on the outside with a dense protective sheath of hardening secretions.

Of the larger soil organisms, one can name soil mites, springtails, small worms - the closest relatives of earthworms. These are real land animals. They breathe atmospheric oxygen, inhabit air intrasoil cavities, root passages, and burrows of larger invertebrates. Small size, flexible

Soil organisms are a vital link in a closed metabolic cycle. Thanks to their vital activity, all products of organic origin decompose, are processed and acquire a mineral form accessible to plants. Minerals dissolved in water come from the soil to the roots of plants, and the cycle begins again

body allow them to exploit even the narrowest gaps between soil particles and penetrate deep horizons of dense loamy soils. For example, shell mites go 1.5-2 m deep. For these small soil inhabitants, the soil is also not a dense mass, but a system of passages and cavities interconnected. Animals live on their walls, like in caves. Waterlogging of the soil is just as unfavorable for its inhabitants as drying out. Soil invertebrates with body sizes larger than 2 mm are clearly distinguishable. Here you can find various groups of worms, terrestrial mollusks, crustaceans (woodlice, amphipods), spiders, harvestmen, false scorpions, millipedes, ants, termites, larvae (beetles, dipterans and hymenoptera insects), butterfly caterpillars. Earthworms and some insect larvae have highly developed muscles. By contracting their muscles, they increase the diameter of their body and push the soil particles apart. The worms swallow the earth, pass it through their intestines and at the same time move forward, as if "eating" through the soil. Behind, they leave their excrement with metabolic products and mucus, abundantly excreted in the intestinal cavity. With these slimy lumps, the worms cover the surface of the passage, strengthening its walls, so such passages remain in the soil for a long time.

And insect larvae have special formations on the limbs, head, sometimes on the back, with which they act like a shovel. For example, in bears, the front legs are turned into strong digging tools - they are expanded, with jagged edges. These scrapers are able to loosen even very dry soil. In the larvae

beetles, digging passages to a considerable depth, use the upper jaws as loosening tools, which look like triangular pyramids with a jagged top and powerful ridges on the sides. The larva hits the soil lump with these jaws, breaks it into small particles and rakes them under itself. Other large inhabitants soils live in existing cavities. They are usually very flexible thin body and can penetrate very narrow and winding passages. digging activity animals has great importance for soil. The system of passages improves its aeration, which favors the growth of roots and the development of aerobic microbial processes associated with humification and mineralization. organic material. No wonder Charles Darwin wrote that long before man invented the plow, earthworms learned how to work the land correctly and well. He dedicated a special book to them, "Formation of the Soil Layer by Earthworms and Observations on the Way of Life of the Last".

Main role soil organisms lies in the ability to quickly process plant residues, manure, household waste, turning them into a high quality natural organic fertilizer biohumus. In many countries, including ours, they learned to breed worms on special farms to obtain organic fertilizers. The following examples will help to evaluate the contribution of the invisible workers of the soil in the formation of its structure. Thus, ants building soil nests throw more than a ton of earth per 1 ha to the surface from deep layers of soil. For 8-10 years, they process almost the entire horizon inhabited by them. And desert wood lice raise from a depth of 50-80 cm to the surface the soil enriched with elements of mineral plant nutrition. Where there are colonies of these woodlice, the vegetation is taller and denser. Earthworms are capable of processing up to 110 tons of land per 1 ha per year.

Moving in the ground and feeding on dead plant residues, animals mix organic and mineral soil particles. Dragging the ground litter into the deep layers, they thereby improve the aeration of these layers, contribute to the activation of microbial processes, which leads to the enrichment of the soil with humus and nutrients. It is the animals that create the humus horizon and soil structure by their activities.

The role of earthworms in biological life soil

Earthworms loosen the soil, penetrating, unlike other soil organisms that can live in only one soil layer, into different soil layers. Through the holes made by the worms, air and water penetrate the roots of the plants.

Earthworms contribute to the enrichment of the soil with oxygen, which prevents the processes of decay of organic material.

: Earthworms absorb organic residues, along with which mineral particles, clay grains, soil algae, bacteria, microorganisms enter the digestive tract. There, this heterogeneous material is mixed and processed, thanks to metabolic processes, it is supplemented with secretions. intestinal microflora worm, acquiring a new state, and then in the form of droppings enters the soil. This qualitatively improves the composition of the soil and gives it a glued, lumpy structure.

Man has learned to cultivate the soil, fertilize it and get high yields. Does it replace the activity of soil organisms? To some extent, yes. But with intensive land use modern methods, when the soil is overloaded with chemicals (mineral fertilizers, pesticides, growth stimulants), with frequent violations of its surface layer and its compaction by agricultural machines, deep violations of natural processes occur, which lead to gradual degradation of the soil, a decrease in its fertility. Excessive amounts of mineral fertilizers poison the earth and kill its biological life. Chemical treatments destroy not only pests in the soil, but also beneficial animals. It takes years to repair this damage. Today, in the period of ecologization of our thinking, it is worth thinking about what criteria to assess the damage caused to the crop. Until now, it was customary to count only losses from pests. But let's also calculate the losses inflicted on the soil itself from the death of soil formers.

To preserve the soil, this unique natural resource The land, capable of self-restoration of its fertility, must first of all preserve its wildlife. Soil organisms, soil formers do what a person with his powerful machinery cannot yet do. They need a stable environment. They need oxygen in the system of passages made and a supply of organic residues, shelters and passages that are not disturbed by humans. Reasonable housekeeping, sparing methods of soil cultivation and the maximum rejection of chemical plant protection products mean the creation of conditions for the preservation of the living bioworld of the soil - the key to its fertility.

Soil nutrients

Plants can obtain all the components necessary for life from the soil only in mineral form. Nutrients that are rich in organic matter, humus and organic fertilizers can be absorbed by plants only after the decomposition process is completed. organic compounds or their mineralization.

The presence of a sufficient amount of nutrients in the soil is one of the main factors for the successful development of plants. Plants build their aboveground part, root system, flowers, fruits and seeds from organic matter: fats, proteins, carbohydrates, acids and other substances produced by the green leaf mass of plants. For the synthesis of organic substances, plants need ten main elements, which are called biogenic. Biogenic chemical elements are constantly included in the composition of organisms and perform certain biological functions that ensure the viability of organisms. Biogenic macronutrients include carbon (C), calcium (Ca), iron (Fe), hydrogen (H), potassium (K), magnesium (Mg), nitrogen (N), oxygen (O), phosphorus (P), sulfur (S). Some of these elements the plant receives from the air, for example, oxygen and carbon, hydrogen is obtained during the decomposition of water in the process of photosynthetic

The process of nutrient metabolism

Nutrients play an important role in the cyclic process of metabolism, ensuring the vital activity of plants. Water dissolves nutrients and trace elements, creating a soil solution that is absorbed by plant roots. solar energy promotes the conversion of nutrients as a result of the process of photosynthesis, which, in turn, depends on the presence in plant tissues of a number of trace elements involved in the formation of the colored substance of chlorophyll

For, the remaining elements come to the plant exclusively from the soil in the form of compounds dissolved in water, the so-called soil solution. If there is a serious deficiency of any of the elements in the soil, the plant weakens and develops only up to a certain stage, until it exhausts its internal biological supply of this element that exists in the tissues of the plant. After this stage, the plant may die. In addition to biogenic macroelements, microelements are necessary for the development of a plant, which are usually contained in very small quantities, but nevertheless play an important role in metabolic processes. Microelements include: aluminum (A1), boron (B), cobalt(Co), copper (Cu), manganese (Mn), molybdenum Mo), sodium (Na), silicon (Si), zinc (Zn). Hei - the balance or excess of trace elements leads to to metabolic disorders, which

behind a lag in the growth and development of the plant, reduced yields and other consequences. Some of the listed trace elements are not vital and are often identified by researchers in the group of so-called "useful elements". Nevertheless, their presence is required for the full development of the plant. All components must be present in the nutrition of the plant in a balanced way, since the absence of at least one of the main elements, such as nitrogen, phosphorus, potassium or calcium, inevitably leads to the insufficiency or inability of the plant to assimilate the remaining three elements, as well as other nutrients. . That is why the presence of all the elements is so important for the full assimilation of the entire nutrient complex by the plant.

The ability of plants to absorb nutrients from the environment is determined by the quality and volume of the root system. Plants absorb nutrients throughout the growing season, but unevenly. The need of plants for nutrients changes in different periods of development. During the period of intensive growth, plants especially need nitrogen, during flowering and fruiting, the need for phosphorus and potassium increases. Assimilated nutrients are selectively fixed in various plant organs.

What animals live in the soil? and got the best answer

Answer from Yatiana[active]
Living organisms - inhabited the soil
Various living organisms live in the soil - bacteria, microscopic fungi, small animals. Life in the soil is associated with a lack of light, difficulties in movement, high humidity or lack of water, a large number of dying plant roots and plant residues on its surface.
Living organisms living in the soil have various adaptations to the soil environment. In a mole, for example, the front legs are short and do not turn down, like in land animals, but to the sides: wide brushes are turned back. Fingers with strong sharp claws are connected by a leathery membrane. With such legs, the mole easily loosens the soil and makes holes in it. The eyes of the mole are underdeveloped and hidden by hair. With them, he distinguishes only light from darkness. In the insect of the bear, the front legs, like those of a mole, are digging, and the eyes are less developed than those of the cockchafer.
Moles and bears constantly live in the soil. They can leave the layers in which unfavorable living conditions are created, to other layers of the soil. In drought and winter, they move to deeper layers. Unlike them, ground squirrels, marmots, badgers, rabbits feed on the surface of the soil, and in the burrows that they make in the soil, they breed from danger and bad weather.
Plants have developed adaptations, including root systems, to the dryness or moisture of the soil. On soils with a lack of moisture, plants form powerful roots that reach groundwater. The camel thorn, growing in deserts, has roots down to a depth of 20 m.
In plants growing in highly humid places, the roots are located close to the surface of the soil, since in the deeper layers, where water displaces all the air, the roots of plants do not have enough air.
Many invertebrates constantly live in the soil - ants, centipedes, worms, ticks, beetles, beetle and fly larvae, slugs, etc. All of them have adapted to life in the soil environment in their own way and play an important role in soil formation processes. Among them, the largest mass is made up of earthworms. The total mass of earthworms on Earth is 10 times the mass of all mankind!

Answer from Yoman Lazarev[active]
moles, for example...

Answer from Johnny[guru]
moles!

Answer from ABRAM[guru]
small, gray, lives 3 meters underground and eats stones

Answer from VladCo[guru]
All animals live in the ground, because they have holes there, but most of them lead a terrestrial lifestyle. Moles, shrews, dormouse are almost constantly underground (3/4 years)

Answer from Olga Perminova[newbie]
well for example: mole, earthworm

Answer from Christina Protopopova[newbie]
Thanks!!! very detailed and clear

Answer from Lika[newbie]
Not only earthworms “work” in the soil, but also their closest relatives - smaller whitish annelids (enchytreids, or potworms), as well as some types of microscopic roundworms (nematodes), small mites, various insects, especially their larvae, and finally woodlice, centipedes and even snails.
Affects the soil and is clean mechanical work many animals living in it. They make passages, mix and loosen the soil, dig holes. All this increases the number of voids in the soil and facilitates the penetration of air and water into its depth. Such “work” involves not only relatively small invertebrates, but also many mammals - moles, marmots, ground squirrels, jerboas, field and forest mice, hamsters, voles, mole rats. The relatively large passages of some of these animals go 1–4 m deep. The passages of large earthworms also go deep: in most of them they reach 1.5–2 m, and in one southern worm even 8 m. in denser soils, plant roots penetrate deeper. In some places, for example in the steppe zone, a large number of dung beetles, bears, crickets, tarantula spiders, ants, and termites in the tropics dig passages and burrows in the soil.

Answer from Yergey Blinov[newbie]
Worms, bears, ants, mole, ant lion ....

Answer from Marina Karpushkina[newbie]
well, for example, a bear, a mole, a dormouse, and a fox

Answer from jura blue[newbie]
moles

Answer from Natalie[newbie]
mole worm spider bugs...
well, I do not know

Answer from Polina Yakovleva[newbie]
centipede, bear, mole, earthworm.

We have known these animals since childhood. They live in the soil, under our feet: lazy earthworms, clumsy larvae, nimble centipedes are born from earthen lumps crumbling under a shovel. Often we squeamishly throw them aside or immediately destroy them as pests of garden plants. How many of these creatures inhabit the soil and who are they - friends or enemies?

Soil animals are studied by a special branch of science - soil zoology, which was formed only in the last century. After specialists developed methods for recording and fixing these animals, which is associated with significant technical difficulties, the eyes of zoologists saw a whole kingdom of creatures, diverse in structure, lifestyle and their significance in natural processes occurring in the soil. In terms of biological diversity, the fauna of the soil can only be compared with coral reefs - a classic example of the richest and most diverse natural communities on our planet.

Here are the Gullivers, like earthworms, and midgets, which cannot be seen with the naked eye. In addition to small sizes (up to 1 mm), most soil-dwelling invertebrates also have an inconspicuous body color, whitish or gray, so they can be seen only after special treatment with fixatives, under a magnifying glass or microscope. Lilliputians form the basis of the animal population of the soil, the biomass of which reaches hundreds of centners per hectare. If we talk about the number of earthworms and other large invertebrates, then it is measured in tens and hundreds per 1 m 2, and small forms - hundreds of thousands and even millions of individuals. For example, here are the simplest roundworms (nematodes), with body sizes up to one hundredth of a millimeter. In their physiology, these are typically aquatic creatures capable of breathing oxygen dissolved in water. The smallest sizes allow such animals to be content with microscopic droplets of moisture filling narrow soil cavities. There they move, find food, multiply. When the soil dries up, these creatures are able to remain in an inactive state for a long time, being covered from the outside with a dense protective shell of hardening secretions.

Of the larger midgets, one can name soil mites, springtails, small worms - the closest relatives of earthworms. These are real land animals. They breathe atmospheric oxygen, inhabit air subsoil cavities, root passages, and burrows of larger invertebrates. Small size, flexible body allows them to use even the narrowest gaps between soil particles and penetrate deep horizons of dense loamy soils. For example, shell mites go 1.5-2 m deep. For these small soil inhabitants, the soil is also not a dense mass, but a system of passages and cavities interconnected. Animals live on their walls, like in caves. Waterlogging of the soil is just as unfavorable for its inhabitants as drying out.

Soil invertebrates with body sizes larger than 2 mm are clearly distinguishable. Here we meet diverse groups worms, terrestrial mollusks, crustaceans (woodlice, amphipods), spiders, haymakers, false scorpions, centipedes, ants, termites, larvae (beetles, diptera and hymenoptera), butterfly caterpillars. Some species of vertebrates living in burrows and feeding on soil invertebrates or plant roots also belong to the inhabitants of the underworld. These are the well-known moles, ground squirrels, etc. For them, the soil passages are too small, so the giants had to acquire special devices for moving in a dense substrate.

Earthworms and some insect larvae have highly developed muscles. By contracting their muscles, they increase the diameter of their body and push the soil particles apart. Worms swallow the earth, pass it through their intestines and move forward, as if eating through the soil. Behind, they leave their excrement with metabolic products and mucus, abundantly excreted in the intestinal cavity. With these slimy lumps, the worms cover the surface of the passage, strengthening its walls, so such passages remain in the soil for a long time.

And insect larvae have special formations on the limbs, head, sometimes on the back, with which they act like a shovel, scraper or pick. For example, the forelegs have been turned into highly specialized digging tools - they are widened, with jagged edges. These scrapers are able to loosen even very dry soil. In the larvae of the beetles, digging passages to a considerable depth, the upper jaws serve as loosening tools, which look like triangular pyramids with a serrated top and powerful ridges on the sides. The larva hits the soil lump with these jaws, breaks it into small particles and rakes them under itself.

Other large inhabitants of the soil live in existing cavities. They are distinguished, as a rule, by a very flexible thin body and can penetrate very narrow and winding passages.

The burrowing activity of animals is of great importance for the soil. The tunnel system improves its aeration, which favors the growth of roots and the development of aerobic microbial processes associated with humification and mineralization of organic material. No wonder Charles Darwin wrote that long before man invented the plow, earthworms learned how to work the land correctly and well. He dedicated a special book to them, "Formation of the Soil Layer by Earthworms and Observations on the Way of Life of the Last".

AT last years there are many publications about these animals that can quickly process plant residues, manure, household waste, turning them into high-quality " biohumus". In many countries, including ours, worms have been bred on special farms to obtain organic fertilizers and as a source of feed protein for fish and poultry.

The following examples will help to assess the contribution of invisible soil organisms to the formation of its structure. Thus, ants building soil nests throw more than a ton of earth per 1 ha to the surface from deep layers of soil. For 8-10 years, they process almost the entire horizon inhabited by them. And the desert woodlice living in Central Asia raise soil enriched with elements of mineral plant nutrition from a depth of 50-80 cm to the surface. Where there are colonies of these woodlice, the vegetation is taller and denser. Earthworms are capable of processing up to 110 tons of land per 1 ha per year. This is on our soddy-podzolic soils near Moscow.

Moving in the ground and feeding on dead plant residues, animals mix organic and mineral soil particles. Dragging the ground litter into the deep layers, they thereby improve the aeration of these layers, contribute to the activation of microbial processes, which leads to the enrichment of the soil with humus and nutrients. It is the animals that create the humus horizon and soil structure by their activities.

Man has learned to fertilize it and get high yields. Does it replace animal activity? To some extent, yes. But with intensive land use by modern methods, when the soil is overloaded with chemicals (mineral fertilizers, pesticides, growth stimulants), with frequent violations of its surface layer and its compaction by agricultural machines, deep violations of natural processes occur, which lead to gradual degradation of the soil, reducing its fertility. Excessive amounts of mineral fertilizers poison the land and degrade the quality of agricultural products.

Chemical treatments destroy not only pests in the soil, but also beneficial animals. It takes years to repair this damage. Today, in the period of ecologization of our economy and our thinking, it is worth thinking about what criteria to assess the damage caused to the crop. Until now, it was customary to count only losses from pests. But let's also calculate the losses inflicted on the soil itself from the death of soil formers.

To save the soil, this unique natural resource of the Earth, capable of self-restoration of its fertility, it is necessary, first of all, to preserve its animal world. Small visible and invisible workers do what a person with his powerful technique cannot yet do. They need to be protected not only in nature reserves and national parks but also on lands used by man. Animals need a stable environment. They need oxygen in the system of passages made and a supply of organic remains, shelters that are not disturbed by man, where animals breed, find shelter from cold and drought. And we diligently remove the remains of roots and stems from the beds, trample the ground around the beds, apply mineral fertilizers, which dramatically change the composition of the soil solution. Reasonable Lead Agriculture, including backyard - it is also the creation of suitable conditions for the conservation of the animal world of the soil - its pledge Seven years ago on its own garden plot, subject to water erosion, I switched to a sod-humus soil maintenance system. The site is located on the Volga slope with a slope of 30-50°...

How animal habitat soil very different from water and air. 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 only solid, 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 minerals supplied by dying vegetation and animal carcasses. All this determines greater saturation of the soil with life.

Every animal to live need to breathe. Conditions for respiration in soil are different than in water or air. Soil is composed of solid particles, water and air. Solid particles in the form of small lumps occupy a little more than half the volume of the soil; the rest of the volume falls on the share of gaps - pores that can be filled with air (in dry soil) or water (in soil saturated with moisture).

Moisture in the soil present in various states:

• bound (hygroscopic and film) is firmly held by the surface of soil particles;
• capillary occupies small pores and can move through them in various directions;
• gravity fills larger voids and slowly seeps down under the influence of gravity;
• vaporous is contained in the soil air.

Compound soil air changeable With depth, the oxygen content decreases sharply and the concentration increases. carbon dioxide. Due to the presence of decomposing organic substances in the soil, the soil air can contain a high concentration of toxic gases such as ammonia, hydrogen sulfide, methane, etc. When the soil is flooded or the plant residues rot intensively, completely anaerobic conditions can occur in places.

Temperature fluctuations cutting only on the surface of the soil. Here they can be even stronger than in the ground layer of air. However, with each centimeter deep, daily and seasonal temperature changes are becoming less and less visible at a depth of 1-1.5 m.

All these features lead to the fact that, despite the large heterogeneity environmental conditions in the soil, it acts as fairly stable environment especially for mobile organisms. It is clear that animals can move relatively quickly in the soil only in natural voids, cracks, or previously dug passages. If there is nothing of this on the way, then the animal can advance only by breaking through the passage and raking the earth back or by swallowing the earth and passing it through the intestines.

Soil dwellers. The heterogeneity of the soil leads to the fact that for organisms of different sizes it acts as a different environment. For microorganisms, the huge total surface of soil particles is of particular importance, since the vast majority of the microbial population is adsorbed on them. Due to this structure of the soil, numerous animals that breathe through their skin. Moreover, hundreds of species of true freshwater animals inhabiting rivers, ponds and swamps. True, these are all microscopic creatures - lower worms and unicellular protozoa. They move, float in a film of water covering soil particles. If the soil dries up, these animals secrete a protective shell and, as it were, fall asleep, fall into a state of suspended animation.

Among soil animals there are also predators and those that feed on parts of living plants, mainly roots. There are in the soil, and consumers of decaying plant and animal residues; it is possible that bacteria also play a significant role in their nutrition. "Peaceful" moles eat great amount earthworms, snails and insect larvae, they even attack frogs, lizards and mice. There are predators among almost all groups of invertebrates living in the soil. Large ciliates feed not only on bacteria, but also on simple animals, such as flagellates. Predators include spiders and related haymakers

Soil animals find their food either in the soil itself or on its surface. The vital activity of many of them is very useful. Earthworms are especially useful. They drag a huge amount of plant debris into their burrows, which contributes to the formation of humus and returns to the soil substances extracted from it by plant roots.

Not only earthworms “work” in the soil, but also their closest relatives:

• whitish annelids (enchytreids, or potworms),
• some types of microscopic roundworms (nematodes),
• small ticks,
• various insects,
• woodlice,
• millipedes,
• snails.

The purely mechanical work of many animals living in it also affects the soil. They make passages, mix and loosen the soil, dig holes. These are moles, marmots, ground squirrels, jerboas, field and forest mice, hamsters, voles, mole rats. The relatively large passages of some of these animals go 1-4 m deep. In some places, for example, in the steppe zone, a large number of passages and burrows are dug in the soil by dung beetles, bears, crickets, tarantulas, ants, and termites in the tropics.

In addition to the permanent inhabitants of the soil, among large animals one can single out a large ecological group of burrow dwellers (ground squirrels, marmots, jerboas, rabbits, badgers, etc.). They feed on the surface, but breed, hibernate, rest, and escape danger in the soil. A number of other animals use their burrows, finding in them a favorable microclimate and shelter from enemies. Norniks have structural features characteristic of terrestrial animals, but have a number of adaptations associated with a burrowing lifestyle. For example, badgers have long claws and strong muscles on the forelimbs, a narrow head, and small auricles. Compared to non-burrowing hares, rabbits have noticeably shortened ears and hind legs, a stronger skull, stronger bones and muscles of the forearms, etc.

The inhabitants of the soil in the process of evolution have developed adaptation to appropriate living conditions:

• features of the shape and structure of the body,
• physiological processes,
• reproduction and development
• ability to endure adverse conditions, behavior.

Earthworms, nematodes, most centipedes, the larvae of many beetles and flies have a highly elongated flexible body that makes it easy to move through winding narrow passages and cracks in the soil. Bristles in rain and others annelids, hairs and claws in arthropods allow them to significantly accelerate their movements in the soil and firmly hold in burrows, clinging to the walls of the passages. How slowly the worm crawls along the surface of the earth and with what speed, in essence, instantly, it hides in its hole. Laying new passages, some soil animals, such as worms, alternately stretch and shorten the body. At the same time, abdominal fluid is periodically pumped into the anterior end of the animal. It swells strongly and pushes the soil particles. Other animals, such as moles, clear their way by digging the ground with their front paws, which have turned into special digging organs.

The color of animals constantly living in the soil is usually pale - grayish, yellowish, whitish. Their eyes, as a rule, are poorly developed or completely absent. But the organs of smell and touch have developed very subtly.

4.3.2. Soil dwellers

The heterogeneity of the soil leads to the fact that for organisms of different sizes it acts as a different environment. For microorganisms, the huge total surface of soil particles is of particular importance, since the vast majority of the microbial population is adsorbed on them. Complexity soil environment creates a wide variety of conditions for a variety of functional groups: aerobes and anaerobes, consumers of organic and mineral compounds. The distribution of microorganisms in the soil is characterized by small foci, since even over a few millimeters different ecological zones can be replaced.

For small soil animals (Fig. 52, 53), which are combined under the name microfauna (protozoa, rotifers, tardigrades, nematodes, etc.), the soil is a system of micro-reservoirs. Essentially, they 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 live in ordinary water bodies. However, soil forms are much smaller than freshwater ones and, in addition, they are distinguished by their ability to stay in an encysted state for a long time, waiting out unfavorable periods. While freshwater amoebas are 50-100 microns in size, soil ones are only 10-15. Representatives of flagellates are especially small, often only 2-5 microns. Soil ciliates also have dwarf sizes and, moreover, can greatly change the shape of the body.

Rice. 52. Testate amoeba feeding on bacteria on decaying forest floor leaves

Rice. 53. Soil microfauna (according to W. Dunger, 1974):

1–4 - flagella; 5–8 - naked amoeba; 9-10 - testate amoeba; 11–13 - ciliates; 14–16 - roundworms; 17–18 - rotifers; 19–20 – tardigrades

For air-breathers of slightly larger animals, the soil appears as a system of shallow caves. Such animals are grouped under the name mesofauna (Fig. 54). The sizes of representatives of the soil mesofauna range from tenths to 2–3 mm. This group includes mainly arthropods: numerous groups of ticks, primary wingless insects (springtails, protura, two-tailed insects), small species of winged insects, centipedes symphyla, etc. They do not have special adaptations for digging. They crawl along the walls of soil cavities with the help of limbs or wriggling like a worm. Soil air saturated with water vapor allows you to breathe through the covers. Many species do not have a tracheal system. Such animals are very sensitive to desiccation. The main means of salvation from fluctuations in air humidity for them is movement inland. But the possibility of migration deep into the soil cavities is limited by the rapid decrease in the diameter of the pores, so only the smallest species can move through the soil wells. More major representatives mesofauna have some adaptations that allow them to endure a temporary decrease in soil air humidity: protective scales on the body, partial impermeability of the integument, a solid thick-walled shell with an epicuticle in combination with a primitive tracheal system that provides breathing.

Rice. 54. Soil mesofauna (no W. Danger, 1974):

1 - false scorion; 2 - Gama new flare; 3–4 shell mites; 5 – centipede pauroioda; 6 – chironomid mosquito larva; 7 - a beetle from the family. Ptiliidae; 8–9 springtails

Representatives of the mesofauna experience periods of flooding of the soil with water in air bubbles. The air is retained around the body of animals due to their non-wetting integuments, which are also equipped with hairs, scales, etc. The air bubble serves as a kind of "physical gill" for a small animal. Breathing is carried out due to oxygen diffusing into the air layer from the surrounding water.

Representatives of micro- and mesofauna are able to tolerate winter freezing of the soil, since most species cannot go down from layers exposed to negative temperatures.

Larger soil animals, with body sizes from 2 to 20 mm, are called representatives macro fauna (Fig. 55). These are insect larvae, centipedes, enchytreids, earthworms, etc. For them, the soil is a dense medium that provides significant mechanical resistance when moving. These relatively large forms move in the soil either by expanding natural wells by pushing apart soil particles, or by digging new passages. Both modes of movement leave an imprint on external structure animals.

Rice. 55. Soil macrofauna (no W. Danger, 1974):

1 - earthworm; 2 – woodlice; 3 – labiopod centipede; 4 – bipedal centipede; 5 - beetle larva; 6 – click beetle larva; 7 – bear; 8 - grub larva

The ability to move along thin holes, almost without resorting to digging, is inherent only in species that have a body with a small cross section that can strongly bend in winding passages (millipedes - drupes and geophiles). Pushing the soil particles apart due to the pressure of the body walls, earthworms, larvae of centipede mosquitoes, etc. move. Having fixed the posterior end, they thin and lengthen the anterior one, penetrating into narrow soil cracks, then fix the anterior part of the body and increase its diameter. At the same time, strong hydraulic pressure of the incompressible intracavitary fluid is created in the expanded area due to the work of the muscles: in worms, the contents of coelomic sacs, and in tipulids, hemolymph. The pressure is transmitted through the walls of the body to the soil, and thus the animal expands the well. At the same time, an open passage remains behind, which threatens to increase evaporation and the pursuit of predators. Many species have developed adaptations to an ecologically more beneficial type of movement in the soil - digging with clogging the passage behind. Digging is carried out by loosening and raking soil particles. For this, the larvae of various insects use the anterior end of the head, mandibles and forelimbs, expanded and reinforced with a thick layer of chitin, spines and outgrowths. At the posterior end of the body, devices for strong fixation develop - retractable supports, teeth, hooks. To close the passage on the last segments, a number of species have a special depressed platform, framed by chitinous sides or teeth, a kind of wheelbarrow. Similar areas are formed on the back of the elytra in bark beetles, which also use them to clog passages with drill flour. Closing the passage behind them, the animals - the inhabitants of the soil are constantly in a closed chamber, saturated with the evaporation of their own body.

Gas exchange of most species of this ecological group is carried out with the help of specialized respiratory organs, but along with this, it is supplemented by gas exchange through the integuments. It is even possible exclusively skin respiration, for example, in earthworms, enchitreid.

Burrowing animals can leave layers where unfavorable conditions arise. In drought and winter, they concentrate in deeper layers, usually a few tens of centimeters from the surface.

Megafauna soils are large excavations, mainly from among mammals. A number of species spend their whole lives in the soil (mole rats, mole voles, zokors, moles of Eurasia, golden moles

Africa, marsupial moles of Australia, etc.). They make whole systems of passages and holes in the soil. Appearance and anatomical features of these animals reflect their adaptability to a burrowing underground lifestyle. They have underdeveloped eyes, a compact, valky body with a short neck, short thick fur, strong digging limbs with strong claws. Mole rats and mole voles loosen the ground with their chisels. Large oligochaetes, especially representatives of the Megascolecidae family living in the tropics and the Southern Hemisphere, should also be included in the soil megafauna. The largest of them is Australian Megascolides australis reaches a length of 2.5 and even 3 m.

In addition to the permanent inhabitants of the soil, a large ecological group can be distinguished among large animals. burrow dwellers (ground squirrels, marmots, jerboas, rabbits, badgers, etc.). They feed on the surface, but breed, hibernate, rest, and escape danger in the soil. A number of other animals use their burrows, finding in them a favorable microclimate and shelter from enemies. Norniks have structural features characteristic of terrestrial animals, but have a number of adaptations associated with a burrowing lifestyle. For example, badgers have long claws and strong muscles on the forelimbs, a narrow head, and small auricles. Compared to non-burrowing hares, rabbits have noticeably shortened ears and hind legs, a stronger skull, stronger bones and muscles of the forearms, etc.

For a range of environmental features soil is an intermediate medium between water and land. FROM aquatic environment the soil is brought closer by its temperature regime, the reduced 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 desiccation in the upper horizons, rather sharp changes temperature regime surface layers.

The intermediate ecological properties of the soil as a habitat for animals suggest that the soil played a special role in the evolution of the animal world. For many groups, in particular arthropods, the soil served as a medium through which initially aquatic life were able to switch to a terrestrial way of life and conquer the land. This path of evolution of arthropods was proved by the works of M. S. Gilyarov (1912–1985).