Lecture 2. HABITATS AND THEIR CHARACTERISTICS

In the process of historical development, living organisms have mastered four habitats. The first is water. Life originated and developed in water for many millions of years. The second - land-air - on land and in the atmosphere, plants and animals arose and rapidly adapted to new conditions. Gradually transforming the upper layer of land - the lithosphere, they created a third habitat - the soil, and themselves became the fourth habitat.

aquatic habitat

Water covers 71% of the earth's area. The bulk of water is concentrated in the seas and oceans - 94-98%, polar ice contains about 1.2% of water and a very small proportion - less than 0.5%, in fresh waters of rivers, lakes and swamps.

About 150,000 species of animals and 10,000 plants live in the aquatic environment, which is respectively only 7 and 8% of the total types of the earth.

In the seas-oceans, as in the mountains, vertical zonality is expressed. The pelagial - the entire water column - and the benthal - the bottom differ especially strongly in ecology. The water column is pelagial, vertically divided into several zones: epipeligial, bathypeligial, abyssopeligial and ultraabyssopeligial(Fig. 2).

Depending on the steepness of the descent and the depth at the bottom, several zones are also distinguished, to which the indicated zones of the pelagial correspond:

Littoral - the edge of the coast, flooded during high tides.

Supralittoral - part of the coast above the upper tidal line, where splashes of surf reach.

Sublittoral - a gradual decrease in land to 200m.

Batial - a steep drop in land (continental slope),

Abyssal - a smooth lowering of the bottom of the ocean bed; the depth of both zones together reaches 3-6 km.

Ultra-abyssal - deep-water depressions from 6 to 10 km.

Ecological groups of hydrobionts. The warmest seas and oceans (40,000 species of animals) are distinguished by the greatest diversity of life in the region of the equator and the tropics; to the north and south, the flora and fauna of the seas are depleted hundreds of times. As for the distribution of organisms directly in the sea, their bulk is concentrated in the surface layers (epipelagial) and in the sublittoral zone. Depending on the method of movement and stay in certain layers, marine life is divided into three ecological groups: nekton, plankton and benthos.

Nekton (nektos - floating) - actively moving large animals that can overcome long distances and strong currents: fish, squid, pinnipeds, whales. In fresh water bodies, nekton also includes amphibians and many insects.

Plankton (planktos - wandering, soaring) - a collection of plants (phytoplankton: diatoms, green and blue-green (fresh water only) algae, plant flagellates, peridine, etc.) and small animal organisms (zooplankton: small crustaceans, from larger ones - pteropods mollusks, jellyfish, ctenophores, some worms), living at different depths, but not capable of active movement and resistance to currents. The composition of plankton also includes larvae of animals, forming special group – neuston . This is a passively floating "temporary" population of the uppermost layer of water, represented by various animals (decapods, barnacles and copepods, echinoderms, polychaetes, fish, molluscs, etc.) in the larval stage. The larvae, growing up, pass into the lower layers of the pelagela. Above the neuston is located pleiston are organisms that top part the body grows above the water, and the lower one grows in the water (duckweed - Lemma, siphonophores, etc.). Plankton plays an important role in the trophic relationships of the biosphere, since is food for many aquatic life, including the main food for baleen whales (Myatcoceti).

Benthos (benthos - depth) - bottom hydrobionts. Represented mainly by attached or slowly moving animals (zoobenthos: foraminephores, fish, sponges, coelenterates, worms, molluscs, ascidians, etc.), more numerous in shallow water. Plants (phytobenthos: diatoms, green, brown, red algae, bacteria) also enter benthos in shallow water. At a depth where there is no light, phytobenthos is absent. The stony areas of the bottom are richest in phytobenthos.

In lakes, zoobenthos is less abundant and diverse than in the sea. It is formed by protozoa (ciliates, daphnia), leeches, mollusks, insect larvae, etc. The phytobenthos of the lakes is formed by free-swimming diatoms, green and blue-green algae; brown and red algae are absent.

The high density of the aquatic environment determines the special composition and nature of the change in life-supporting factors. Some of them are the same as on land - heat, light, others are specific: water pressure (with depth increases by 1 atm for every 10 m), oxygen content, salt composition, acidity. Due to the high density of the medium, heat and light values ​​change much faster with the height gradient than on land.

Thermal regime. The aquatic environment is characterized by a lower heat input, because a significant part of it is reflected, and an equally significant part is spent on evaporation. Consistent with the dynamics of land temperatures, the water temperature has less fluctuations in daily and seasonal temperatures. Moreover, water bodies significantly equalize the course of temperatures in the atmosphere of coastal areas. In the absence of an ice shell, the sea in the cold season has a warming effect on the adjacent land areas, in summer it has a cooling and moisturizing effect.

The range of water temperatures in the World Ocean is 38° (from -2 to +36°C), in fresh water - 26° (from -0.9 to +25°C). The water temperature drops sharply with depth. Up to 50 m, daily temperature fluctuations are observed, up to 400 - seasonal, deeper it becomes constant, dropping to + 1-3 ° С. Since the temperature regime in reservoirs is relatively stable, their inhabitants are characterized by stenothermy.

Due to the different degree of heating of the upper and lower layers during the year, ebbs and flows, currents, storms, there is a constant mixing of the water layers. The role of mixing water for aquatic life is exceptionally great, because. at the same time, the distribution of oxygen and nutrients inside the reservoirs is leveled, providing metabolic processes between organisms and the environment.

In stagnant water bodies (lakes) of temperate latitudes, vertical mixing takes place in spring and autumn, and during these seasons the temperature in the entire water body becomes uniform, i.e. comes homothermy. In summer and winter, as a result of a sharp increase in heating or cooling of the upper layers, the mixing of water stops. This phenomenon is called temperature dichotomy, and the period of temporary stagnation - stagnation(summer or winter). In summer, the lighter warm layers remain on the surface, being located above the heavy cold ones (Fig. 3). In winter, on the contrary, the bottom layer has warmer water, since directly under the ice the surface water temperature is less than +4°C and, due to the physicochemical properties of water, they become lighter than water with a temperature above +4°C.

During periods of stagnation, three layers are clearly distinguished: the upper (epilimnion) with the sharpest seasonal fluctuations in water temperature, the middle (metalimnion or thermocline), in which there is a sharp jump in temperature, and near-bottom ( hypolimnion), in which the temperature varies little during the year. During periods of stagnation, oxygen deficiency is formed in the water column - in the summer in the bottom part, and in the winter in the upper part, as a result of which fish die-offs often occur in winter.

Light mode. The intensity of light in water is greatly attenuated due to its reflection by the surface and absorption by the water itself. This greatly affects the development of photosynthetic plants.

The absorption of light is the stronger, the lower the transparency of water, which depends on the number of particles suspended in it (mineral suspensions, plankton). It decreases with the rapid development of small organisms in summer, and in temperate and northern latitudes it also decreases in winter, after the establishment of an ice cover and covering it with snow from above.

Transparency is characterized by the maximum depth at which a specially lowered white disk with a diameter of about 20 cm (Secchi disk) is still visible. The most transparent waters are in the Sargasso Sea: the disk is visible to a depth of 66.5 m. In the Pacific Ocean, the Secchi disk is visible up to 59 m, in the Indian - up to 50, in shallow seas - up to 5-15 m. The transparency of rivers is on average 1-1.5 m, and in the most muddy rivers it is only a few centimeters.

In the oceans, where the water is very transparent, 1% of light radiation penetrates to a depth of 140 m, and in small lakes at a depth of 2 m, only tenths of a percent penetrate. Rays of different parts of the spectrum are absorbed differently in water, red rays are absorbed first. With depth it becomes darker, and the color of the water becomes green at first, then blue, blue and finally blue-violet, turning into complete darkness. Accordingly, hydrobionts also change color, adapting not only to the composition of light, but also to its lack - chromatic adaptation. In light zones, in shallow waters, green algae (Chlorophyta) predominate, the chlorophyll of which absorbs red rays, with depth they are replaced by brown (Phaephyta) and then red (Rhodophyta). Phytobenthos is absent at great depths.

Plants have adapted to the lack of light by developing large chromatophores and by increasing the area of ​​assimilating organs (leaf surface index). For deep-sea algae, strongly dissected leaves are typical, leaf blades are thin, translucent. For semi-submerged and floating plants, heterophylly is characteristic - the leaves above the water are the same as those of terrestrial plants, they have a whole plate, the stomatal apparatus is developed, and in the water the leaves are very thin, consist of narrow filiform lobes.

Animals, like plants, naturally change their color with depth. In the upper layers they are brightly colored in different colours, in the twilight zone (sea bass, corals, crustaceans) are painted in colors with a red tint - it is more convenient to hide from enemies. Deep-sea species are devoid of pigments. In the dark depths of the ocean, organisms use the light emitted by living beings as a source of visual information. bioluminescence.

high density(1 g/cm3, which is 800 times the density of air) and the viscosity of water ( 55 times higher than that of air) led to the development of special adaptations of hydrobionts :

1) Plants have very poorly developed or completely absent mechanical tissues - they are supported by water itself. Most are characterized by buoyancy, due to air-bearing intercellular cavities. Characterized by active vegetative reproduction, the development of hydrochoria - the removal of flower stalks above the water and the spread of pollen, seeds and spores by surface currents.

2) In animals living in the water column and actively swimming, the body has a streamlined shape and is lubricated with mucus, which reduces friction during movement. Developed devices to increase buoyancy: accumulation of fat in tissues, swim bladders in fish, air cavities in siphonophores. In passively swimming animals, the specific surface of the body increases due to outgrowths, spines, and appendages; the body flattens, reduction of skeletal organs occurs. Different modes of locomotion: bending of the body, with the help of flagella, cilia, jet mode of locomotion (cephalopods).

In benthic animals, the skeleton disappears or is poorly developed, the size of the body increases, the reduction of vision is common, and the development of tactile organs.

currents. A characteristic feature of the aquatic environment is mobility. It is caused by ebbs and flows, sea currents, storms, different levels of elevations of river beds. Adaptations of hydrobionts:

1) In flowing waters, plants are firmly attached to immovable underwater objects. The bottom surface for them is primarily a substrate. These are green and diatom algae, water mosses. Mosses even form a dense cover on fast-flowing rivers. In the tidal zone of the seas, many animals also have devices for attaching to the bottom (gastropods, barnacles), or they hide in crevices.

2) In fish of flowing waters, the body is round in diameter, and in fish that live near the bottom, like in benthic invertebrates, the body is flat. Many on the ventral side have organs of fixation to underwater objects.

Salinity of water.

Natural water bodies have a certain chemical composition. Carbonates, sulfates, and chlorides predominate. In fresh water bodies, the salt concentration is not more than 0.5 ‰ (and about 80% are carbonates), in the seas - from 12 to 35 ‰ (mainly chlorides and sulfates). With a salinity of more than 40 ppm, the reservoir is called hyperhaline or oversalted.

1) In fresh water ( hypotonic environment) processes of osmoregulation are well expressed. Hydrobionts are forced to constantly remove the water penetrating into them, they are homoiosmotic (ciliates “pump” through themselves an amount of water equal to its weight every 2-3 minutes). In salt water (isotonic medium), the concentration of salts in the bodies and tissues of hydrobionts is the same (isotonic) with the concentration of salts dissolved in water - they are poikiloosmotic. Therefore, osmoregulatory functions are not developed among the inhabitants of salt water bodies, and they could not populate fresh water bodies.

2) Aquatic plants are able to absorb water and nutrients from the water - "broth", with the entire surface, therefore, their leaves are strongly dissected and conductive tissues and roots are poorly developed. The roots serve mainly to attach to the underwater substrate. Most freshwater plants have roots.

Typically marine and typically freshwater species are stenohaline and do not tolerate significant changes in water salinity. There are few euryhaline species. They are common in brackish waters (freshwater walleye, pike, bream, mullet, coastal salmon).

Composition of gases in water.

In water, oxygen is the most important environmental factor. In oxygen-saturated water, its content does not exceed 10 ml per 1 liter, which is 21 times lower than in the atmosphere. When water is mixed, especially in flowing water bodies, and when the temperature decreases, the oxygen content increases. Some fish are very sensitive to oxygen deficiency (trout, minnow, grayling) and therefore prefer cold mountain rivers and streams. Other fish (carp, carp, roach) are undemanding to the oxygen content and can live at the bottom of deep water bodies. Many aquatic insects, mosquito larvae, lung molluscs are also tolerant to the oxygen content in the water, because from time to time they rise to the surface and swallow fresh air.

There is enough carbon dioxide in water (40-50 cm 3 / l - almost 150 times more than in air. It is used in plant photosynthesis and goes to the formation of calcareous skeletal formations of animals (shells of mollusks, covers of crustaceans, skeletons of radiolarians, etc.) .

Acidity. In freshwater reservoirs, the acidity of water, or the concentration of hydrogen ions, varies much more than in marine ones - from pH = 3.7-4.7 (acid) to pH = 7.8 (alkaline). The acidity of water is largely determined by the species composition of hydrobiont plants. In the acidic waters of the swamps, sphagnum mosses grow and shell rhizomes live in abundance, but there are no toothless mollusks (Unio), and other mollusks are rare. In an alkaline environment, many types of pondweeds and elodea develop. Most freshwater fish live in the pH range of 5 to 9 and die en masse outside of these values. The most productive waters are pH 6.5-8.5.

The acidity of sea water decreases with depth.

Acidity can serve as an indicator of the overall metabolic rate of a community. Low pH waters contain few nutrients, so productivity is extremely low.

hydrostatic pressure in the ocean has great importance. With immersion in water at 10 m, the pressure increases by 1 atmosphere. In the deepest part of the ocean, the pressure reaches 1000 atmospheres. Many animals are able to tolerate sudden fluctuations in pressure, especially if they do not have free air in their bodies. Otherwise, gas embolism may develop. High pressures, characteristic of great depths, as a rule, inhibit vital processes.

According to the amount of organic matter available to hydrobionts, water bodies can be divided into: - oligotrophic (blue and transparent) - not rich in food, deep, cold; - eutrophic (green) - rich in food, warm; dystrophic (brown) - poor in food, sour due to ingestion a large number soil humic acids.

eutrophication– enrichment of water bodies with organic nutrients under the influence of an anthropogenic factor (eg, wastewater discharge).

Ecological plasticity of hydrobionts. Freshwater plants and animals are ecologically more plastic (eurythermal, euryhaline) than marine ones, inhabitants of coastal zones are more plastic (eurythermal) than deep-sea ones. There are species that have a narrow ecological plasticity in relation to one factor (lotus is a stenothermic species, Artemia crustacean (Artimia solina) is stenogal) and wide in relation to others. Organisms are more plastic in relation to those factors that are more variable. And it is they that are more widely distributed (elodea, rhizomes of Cyphoderia ampulla). Plasticity also depends on the age and phase of development.

Sound travels faster in water than in air. Orientation to sound is generally better developed in hydrobionts than visual. A number of species even pick up very low frequency vibrations (infrasounds) that occur when the rhythm of the waves changes. A number of aquatic organisms look for food and navigate using echolocation - the perception of reflected sound waves(whales). Many perceive reflected electrical impulses, producing discharges of different frequencies when swimming.

The most ancient method of orientation, characteristic of all aquatic animals, is the perception of the chemistry of the environment. The chemoreceptors of many aquatic organisms are extremely sensitive.

Ground-Air Habitat

In the course of evolution, this environment was mastered later than the water. Ecological factors in the terrestrial-air environment differ from other habitats in high light intensity, significant fluctuations in air temperature and humidity, the correlation of all factors with geographical location, the change of seasons of the year and time of day. The environment is gaseous, therefore it is characterized by low humidity, density and pressure, high oxygen content.

Characterization of abiotic environmental factors of light, temperature, humidity - see the previous lecture.

Gas composition of the atmosphere is also an important climatic factor. Approximately 3-3.5 billion years ago, the atmosphere contained nitrogen, ammonia, hydrogen, methane and water vapor, and there was no free oxygen in it. The composition of the atmosphere was largely determined by volcanic gases.

At present, the atmosphere consists mainly of nitrogen, oxygen, and relatively smaller amounts of argon and carbon dioxide. All other gases present in the atmosphere are contained only in trace amounts. Of particular importance for the biota is the relative content of oxygen and carbon dioxide.

The high oxygen content contributed to an increase in the metabolism of terrestrial organisms compared to primary aquatic ones. It was in the terrestrial environment, on the basis of the high efficiency of oxidative processes in the body, that animal homoiothermia arose. Oxygen, due to its constantly high content in the air, is not a factor limiting life in the terrestrial environment. Only in places, under specific conditions, is a temporary deficit created, for example, in accumulations of decaying plant residues, stocks of grain, flour, etc.

The content of carbon dioxide can vary in certain areas of the surface layer of air within fairly significant limits. For example, in the absence of wind in the center of large cities, its concentration increases tenfold. Diurnal changes in the carbon dioxide content in the surface layers are regular, associated with the rhythm of plant photosynthesis, and seasonal, due to changes in the intensity of respiration of living organisms, mainly the microscopic population of soils. Increased air saturation with carbon dioxide occurs in zones of volcanic activity, near thermal springs and other underground outlets of this gas. Low maintenance carbon dioxide inhibits the process of photosynthesis. Under indoor conditions, the rate of photosynthesis can be increased by increasing the concentration of carbon dioxide; this is used in the practice of greenhouses and greenhouses.

Air nitrogen for most inhabitants of the terrestrial environment is an inert gas, but a number of microorganisms (nodule bacteria, Azotobacter, clostridia, blue-green algae, etc.) have the ability to bind it and involve it in the biological cycle.

Local impurities entering the air can also significantly affect living organisms. This is especially true for toxic gaseous substances - methane, sulfur oxide (IV), carbon monoxide (II), nitrogen oxide (IV), hydrogen sulfide, chlorine compounds, as well as particles of dust, soot, etc., polluting the air in industrial areas. The main modern source of chemical and physical pollution of the atmosphere is anthropogenic: the work of various industrial enterprises and transport, soil erosion, etc. Sulfur oxide (SO 2), for example, is poisonous to plants even in concentrations from one fifty-thousandth to one millionth of the volume of air .. Some plant species are particularly sensitive to S0 2 and serve as a sensitive indicator of its accumulation in the air (for example, lichens.

Low air density determines its low lifting force and insignificant bearing capacity. The inhabitants of the air environment must have their own support system supporting the body: plants - with a variety of mechanical tissues, animals - with a solid or, much less often, hydrostatic skeleton. In addition, all the inhabitants of the air environment are closely connected with the surface of the earth, which serves them for attachment and support. Life in a suspended state in the air is impossible. True, many microorganisms and animals, spores, seeds and pollen of plants are regularly present in the air and are carried by air currents (anemochory), many animals are capable of active flight, but in all these species the main function of their life cycle - reproduction - is carried out on the surface of the earth. For most of them, being in the air is associated only with resettlement or the search for prey.

Wind It has a limiting effect on the activity and even distribution of organisms. Wind can even change the appearance of plants, especially in habitats such as alpine zones where other factors are limiting. In open mountain habitats, wind limits plant growth, causing plants to bend on the windward side. In addition, wind increases evapotranspiration in low humidity conditions. Of great importance are storms, although their action is purely local. Hurricanes, as well as ordinary winds, are capable of transporting animals and plants over long distances and thereby changing the composition of communities.

Pressure, apparently, is not a limiting factor of direct action, but it is directly related to weather and climate, which have a direct limiting effect. The low density of air causes a relatively low pressure on land. Normally, it is equal to 760 mm Hg, Art. As altitude increases, pressure decreases. At an altitude of 5800 m, it is only half normal. Low pressure may limit the distribution of species in the mountains. For most vertebrates, the upper limit of life is about 6000 m. A decrease in pressure entails a decrease in oxygen supply and dehydration of animals due to an increase in the respiratory rate. Approximately the same are the limits of advancement to the mountains of higher plants. Somewhat more hardy are arthropods (springtails, mites, spiders) that can be found on glaciers above the vegetation boundary.

In general, all terrestrial organisms are much more stenobatic than aquatic ones.

The inanimate and living nature surrounding plants, animals and humans is called the habitat (living environment, external environment). According to the definition of N.P. Naumov (1963), the environment is “everything that surrounds organisms and directly or indirectly affects their state, development, survival and reproduction.” From the habitat, organisms receive everything necessary for life and release the products of their metabolism into it.

Organisms can live in one or more living environments. For example, man, most birds, mammals, seed plants, lichens are inhabitants only ground-air environment; most fish live only in the aquatic environment; dragonflies spend one phase in the water, and the other - in the air.

Aquatic life environment

The aquatic environment is characterized by a great originality of the physicochemical properties of organisms favorable for life. Among them: transparency, high thermal conductivity, high density (about 800 times the density of air) and viscosity, expansion upon freezing, the ability to dissolve many mineral and organic compounds, high mobility (fluidity), the absence of sharp temperature fluctuations (both daily and seasonal), the ability to equally easily support organisms that differ significantly in mass.

The unfavorable properties of the aquatic environment are: strong pressure drops, poor aeration (the oxygen content in the aquatic environment is at least 20 times lower than in the atmosphere), lack of light (especially little of it in the depths of water bodies), lack of nitrates and phosphates (necessary for the synthesis of living matter ).

Distinguish between fresh and sea water, which differ both in composition and in the amount of dissolved minerals. Sea water is rich in sodium, magnesium, chloride and sulfate ions, while fresh water is dominated by calcium and carbonate ions.

Organisms living in the aquatic environment of life constitute one biological group - hydrobionts.

In reservoirs, two ecologically special habitats (biotopes) are usually distinguished: the water column (pelagial) and the bottom (benthal). The organisms living there are called pelagos and benthos.

Among the pelagos, the following forms of organisms are distinguished: plankton - passively floating small representatives (phytoplankton and zooplankton); nekton - actively swimming large forms (fish, turtles, cephalopods); neuston - microscopic and small inhabitants of the surface film of water. In fresh water bodies (lakes, ponds, rivers, swamps, etc.), such ecological zoning is not very clearly expressed. The lower limit of life in the pelagial is determined by the depth of penetration sun rays, sufficient for photosynthesis and rarely reaches a depth of more than 2000 m.

In Bentali, special ecological zones of life are also distinguished: a zone of a gradual decrease in land (up to a depth of 200-2200 m); steep slope zone, oceanic bed (with an average depth of 2800-6000 m); depressions of the oceanic bed (up to 10,000 m); the edge of the coast, flooded with tides (littoral). The inhabitants of the littoral live in conditions of abundant sunlight at low pressure, with frequent and significant fluctuations in temperature. The inhabitants of the zone of the oceanic bed, on the contrary, exist in complete darkness, at constantly low temperatures, oxygen deficiency and under enormous pressure, reaching almost a thousand atmospheres.

Ground-air environment of life

The land-air environment of life is the most complex in terms of ecological conditions and has a wide variety of habitats. This led to the greatest diversity of land organisms. The vast majority of animals in this environment move on a solid surface - soil, and plants take root on it. The organisms of this living environment are called aerobionts (terrabionts, from Latin terra - earth).

A characteristic feature of the environment under consideration is that the organisms living here significantly influence the living environment and in many respects create it themselves.

Favorable characteristics of this environment for organisms are the abundance of air with a high content of oxygen and sunlight. Unfavorable features include: sharp fluctuations in temperature, humidity and lighting (depending on the season, time of day and geographical location), constant moisture deficiency and its presence in the form of steam or drops, snow or ice, wind, change of seasons, relief features terrain, etc.

All organisms in the terrestrial-air environment of life are characterized by systems of economical use of water, various mechanisms of thermoregulation, high efficiency oxidative processes, special organs for the assimilation of atmospheric oxygen, strong skeletal formations that allow the body to be maintained in conditions of low density of the environment, various adaptations for protection against sudden temperature fluctuations.

The ground-air environment in terms of its physical and chemical characteristics is considered to be quite severe in relation to all living things. But, despite this, life on land has reached a very high level, both in terms of the total mass of organic matter and in the diversity of forms of living matter.

The soil

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.

The body as a living environment

As a living environment, the organism for its inhabitants is characterized by such positive features as: easily digestible food; constancy of temperature, salt and osmotic regimes; no risk of drying out; protection from enemies. Problems for the inhabitants of organisms are created by factors such as: lack of oxygen and light; limited living space; the need to overcome the protective reactions of the host; spread from one host to other hosts. In addition, this environment is always limited in time by the life of the host.

Lecture 3 HABITAT AND THEIR CHARACTERISTICS (2h)

1. Aquatic habitat

2. Ground-air habitat

3. Soil as a habitat

4. The body as a habitat

In the process of historical development, living organisms have mastered four habitats. The first is water. Life originated and developed in water for many millions of years. The second - land-air - on land and in the atmosphere, plants and animals arose and rapidly adapted to new conditions. Gradually transforming the upper layer of land - the lithosphere, they created a third habitat - the soil, and themselves became the fourth habitat.

Aquatic habitat - hydrosphere

Ecological groups of hydrobionts. The warmest seas and oceans (40,000 species of animals) are distinguished by the greatest diversity of life in the region of the equator and the tropics; to the north and south, the flora and fauna of the seas are depleted hundreds of times. As for the distribution of organisms directly in the sea, their bulk is concentrated in the surface layers (epipelagial) and in the sublittoral zone. Depending on the method of movement and stay in certain layers, marine life is divided into three ecological groups: nekton, plankton and benthos.

Nekton(nektos - floating) - actively moving large animals that can overcome long distances and strong currents: fish, squid, pinnipeds, whales. In fresh water bodies, nekton also includes amphibians and many insects.

Plankton(planktos - wandering, soaring) - a collection of plants (phytoplankton: diatoms, green and blue-green (fresh water only) algae, plant flagellates, peridine, etc.) and small animal organisms (zooplankton: small crustaceans, from larger ones - pteropods mollusks, jellyfish, ctenophores, some worms), living at different depths, but not capable of active movement and resistance to currents. The composition of plankton also includes animal larvae, forming a special group - neuston. This is a passively floating "temporary" population of the uppermost layer of water, represented by various animals (decapods, barnacles and copepods, echinoderms, polychaetes, fish, molluscs, etc.) in the larval stage. The larvae, growing up, pass into the lower layers of the pelagela. Above the neuston is the pleuston - these are organisms in which the upper part of the body grows above the water, and the lower part grows in the water (duckweed - Lemma, siphonophores, etc.). Plankton plays an important role in the trophic relationships of the biosphere, since is food for many aquatic life, including the main food for baleen whales (Myatcoceti).

Benthos(benthos - depth) - bottom hydrobionts. Represented mainly by attached or slowly moving animals (zoobenthos: foraminephores, fish, sponges, coelenterates, worms, brachiopods, ascidians, etc.), more numerous in shallow water. Plants (phytobenthos: diatoms, green, brown, red algae, bacteria) also enter benthos in shallow water. At a depth where there is no light, phytobenthos is absent. Along the coasts there are flowering plants of zoster, rupee. The stony areas of the bottom are richest in phytobenthos.

In lakes, zoobenthos is less abundant and diverse than in the sea. It is formed by protozoa (ciliates, daphnia), leeches, mollusks, insect larvae, etc. The phytobenthos of the lakes is formed by free-swimming diatoms, green and blue-green algae; brown and red algae are absent.

Rooting coastal plants in lakes form distinct belts, the species composition and appearance of which are consistent with environmental conditions in border zone"land-water". Hydrophytes grow in the water near the shore - plants semi-submerged in water (arrowhead, calla, reeds, cattail, sedges, trichaetes, reeds). They are replaced by hydatophytes - plants submerged in water, but with floating leaves (lotus, duckweed, egg-pods, chilim, takla) and - further - completely submerged (weeds, elodea, hara). Hydatophytes also include plants floating on the surface (duckweed).

The high density of the aquatic environment determines the special composition and nature of the change in life-supporting factors. Some of them are the same as on land - heat, light, others are specific: water pressure (with depth increases by 1 atm for every 10 m), oxygen content, salt composition, acidity. Due to the high density of the medium, heat and light values ​​change much faster with the height gradient than on land.

Thermal regime. The aquatic environment is characterized by a lower heat input, because a significant part of it is reflected, and an equally significant part is spent on evaporation. Consistent with the dynamics of land temperatures, the water temperature has less fluctuations in daily and seasonal temperatures. Moreover, water bodies significantly equalize the course of temperatures in the atmosphere of coastal areas. In the absence of an ice shell, the sea in the cold season has a warming effect on the adjacent land areas, in summer it has a cooling and moisturizing effect.

The range of water temperatures in the World Ocean is 38° (from -2 to +36°C), in fresh water - 26° (from -0.9 to +25°C). The water temperature drops sharply with depth. Up to 50 m, daily temperature fluctuations are observed, up to 400 - seasonal, deeper it becomes constant, dropping to + 1-3 ° С (in the Arctic it is close to 0 ° С). Since the temperature regime in reservoirs is relatively stable, their inhabitants are characterized by stenothermy. Minor temperature fluctuations in one direction or another are accompanied by significant changes in aquatic ecosystems.

Examples: a “biological explosion” in the Volga delta due to a drop in the level of the Caspian Sea - the growth of lotus thickets (Nelumba kaspium), in southern Primorye - the overgrowth of calla oxbow rivers (Komarovka, Ilistaya, etc.) along the banks of which woody vegetation was cut down and burned.

Due to the different degree of heating of the upper and lower layers during the year, ebbs and flows, currents, storms, there is a constant mixing of the water layers. The role of water mixing for aquatic inhabitants (hydrobionts) is exceptionally great, because at the same time, the distribution of oxygen and nutrients inside the reservoirs is leveled, providing metabolic processes between organisms and the environment.

In stagnant water bodies (lakes) of temperate latitudes, vertical mixing takes place in spring and autumn, and during these seasons the temperature in the entire water body becomes uniform, i.e. comes homothermy. In summer and winter, as a result of a sharp increase in heating or cooling of the upper layers, the mixing of water stops. This phenomenon is called temperature dichotomy, and the period of temporary stagnation is called stagnation (summer or winter). In summer, the lighter warm layers remain on the surface, being located above the heavy cold ones (Fig. 3). In winter, on the contrary, the bottom layer has warmer water, since directly under the ice the surface water temperature is less than +4°C and, due to the physicochemical properties of water, they become lighter than water with a temperature above +4°C. During periods of stagnation, three layers are clearly distinguished: the upper layer (epilimnion) with the sharpest seasonal fluctuations in water temperature, the middle layer (metalimnion or thermocline), in which there is a sharp jump in temperature, and the near-bottom layer (hypolimnion), in which the temperature changes little during the year. During periods of stagnation, oxygen deficiency is formed in the water column - in the summer in the bottom part, and in the winter in the upper part, as a result of which fish die-offs often occur in winter.

Light mode. The intensity of light in water is greatly attenuated due to its reflection by the surface and absorption by the water itself. This greatly affects the development of photosynthetic plants. The less transparent the water, the more light is absorbed. Water transparency is limited by mineral suspensions and plankton. It decreases with the rapid development of small organisms in summer, and in temperate and northern latitudes it also decreases in winter, after the establishment of an ice cover and covering it with snow from above.

In the oceans, where the water is very transparent, 1% of light radiation penetrates to a depth of 140 m, and in small lakes at a depth of 2 m, only tenths of a percent penetrate. Rays of different parts of the spectrum are absorbed differently in water, red rays are absorbed first. With depth it becomes darker, and the color of the water becomes green at first, then blue, blue and finally blue-violet, turning into complete darkness. Accordingly, hydrobionts also change color, adapting not only to the composition of light, but also to its lack - chromatic adaptation. In light zones, in shallow waters, green algae (Chlorophyta) predominate, the chlorophyll of which absorbs red rays, with depth they are replaced by brown (Phaephyta) and then red (Rhodophyta). Phytobenthos is absent at great depths.

Plants have adapted to the lack of light by developing large chromatophores, providing a low photosynthesis compensation point, as well as by increasing the area of ​​assimilating organs (leaf surface index). For deep-sea algae, strongly dissected leaves are typical, leaf blades are thin, translucent. For semi-submerged and floating plants, heterophylly is characteristic - the leaves above the water are the same as those of terrestrial plants, they have a whole plate, the stomatal apparatus is developed, and in the water the leaves are very thin, consist of narrow filiform lobes.

Heterophyllia: capsules, water lilies, arrowhead, chilim (water chestnut).

Animals, like plants, naturally change their color with depth. In the upper layers, they are brightly colored in different colors, in the twilight zone (sea bass, corals, crustaceans) are painted in colors with a red tint - it is more convenient to hide from enemies. Deep-sea species are devoid of pigments.

The characteristic properties of the aquatic environment, different from the land, are high density, mobility, acidity, the ability to dissolve gases and salts. For all these conditions, hydrobionts have historically developed appropriate adaptations.

2. Ground-air habitat

In the course of evolution, this environment was mastered later than the water. Its peculiarity lies in the fact that it is gaseous, therefore it is characterized by low humidity, density and pressure, high oxygen content. In the course of evolution, living organisms have developed the necessary anatomical, morphological, physiological, behavioral and other adaptations.

Animals in the ground-air environment move through the soil or through the air (birds, insects), and plants take root in the soil. In this regard, animals developed lungs and tracheas, while plants developed a stomatal apparatus, i.e. organs by which the land inhabitants of the planet absorb oxygen directly from the air. The skeletal organs, which provide autonomy of movement on land and support the body with all its organs in conditions of low density of the medium, thousands of times less than water, have received a strong development. Ecological factors in the terrestrial-air environment differ from other habitats in high light intensity, significant fluctuations in air temperature and humidity, the correlation of all factors with geographical location, the change of seasons of the year and time of day. Their impact on organisms is inextricably linked with the movement of air and position relative to the seas and oceans and is very different from the impact in the aquatic environment (Table 1).

Living conditions of air and water organisms

(according to D. F. Mordukhai-Boltovsky, 1974)

air environment

aquatic environment

Humidity	Very important (often in short supply)	Does not have (always in excess)
Density	Minor (except for soil)	Large compared to its role for the inhabitants of the air
Pressure	Has almost no	Large (can reach 1000 atmospheres)
Temperature	Significant (fluctuates within very wide limits - from -80 to + 100 ° С and more)	Less than the value for the inhabitants of the air (fluctuates much less, usually from -2 to + 40 ° C)
Oxygen	Minor (mostly in excess)	Essential (often in short supply)
suspended solids	unimportant; not used for food (mainly mineral)	Important (food source, especially organic matter)
Solutes in the environment	To some extent (only relevant in soil solutions)	Important (in a certain amount needed)

Land animals and plants have developed their own, no less original adaptations to adverse environmental factors: the complex structure of the body and its integument, the frequency and rhythm of life cycles, thermoregulation mechanisms, etc. Purposeful animal mobility has developed in search of food, wind-borne spores, seeds and pollen of plants, as well as plants and animals, whose life is entirely connected with the air environment. An exceptionally close functional, resource and mechanical relationship with the soil has been formed.

Many of the adaptations we have discussed above as examples in the characterization of abiotic environmental factors. Therefore, it makes no sense to repeat now, because we will return to them in practical exercises

The layered structure of the Earth's shells and the composition of the atmosphere; light regime as a factor of the ground-air environment; adaptation of organisms to different light regimes; temperature conditions in the ground-air environment, temperature adaptations; air pollution

The ground-air environment is the most difficult in terms of environmental conditions of life. Life on land required such morphological and biochemical adaptations that were possible only with enough high level organization of both plants and animals. In fig. 2 shows a diagram of the shells of the Earth. The outer part can be attributed to the ground-air environment lithosphere and the bottom atmosphere. The atmosphere, in turn, has a fairly pronounced layered structure. The lower layers of the atmosphere are shown in fig. 2. Since the bulk of living beings live in the troposphere, it is this layer of the atmosphere that is included in the concept of the ground-air environment. The troposphere is the lowest part of the atmosphere. Its height in different areas is from 7 to 18 km, it contains the bulk of water vapor, which, condensing, form clouds. In the troposphere, there is a powerful movement of air, and the temperature drops by an average of 0.6 ° C with a rise for every 100 m.

The Earth's atmosphere consists of a mechanical mixture of gases that do not chemically act on each other. All meteorological processes take place in it, the totality of which is called climate. The upper boundary of the atmosphere is conditionally considered to be 2000 km, i.e. its height is V 3 part of the Earth's radius. Various physical processes continuously take place in the atmosphere: temperature, humidity change, water vapor condenses, fogs and clouds appear, the sun's rays heat the atmosphere, ionizing it, etc.

The bulk of the air is concentrated in the 70 km layer. Dry air contains (in%): nitrogen - 78.08; oxygen - 20.95; argon - 0.93; carbon dioxide - 0.03. There are very few other gases. These are hydrogen, neon, helium, krypton, radon, xenon - most of the inert gases.

Atmospheric air is one of the main vital elements of the environment. It reliably protects the planet from harmful cosmic radiation. Under the influence of the atmosphere on Earth, the most important geological processes take place, which ultimately form the landscape.

Atmospheric air belongs to the category of inexhaustible resources, but the intensive development of industry, the growth of cities, the expansion of space exploration increase the negative anthropogenic impact on the atmosphere. Therefore, the issue of protecting atmospheric air is becoming increasingly important.

In addition to air of a certain composition, living organisms inhabiting the ground-air environment are affected by air pressure and humidity, as well as solar radiation and temperature.

Rice. 2.

Light mode, or solar radiation. For the implementation of vital processes, all living organisms need energy coming from outside. Its main source is solar radiation.

The effect of different parts of the spectrum of solar radiation on living organisms is different. It is known that in the spectrum of sunlight emit ultraviolet, visible and infrared area, which, in turn, consist of light waves of different lengths (Fig. 3).

Among the ultraviolet rays (UFL), only long-wave (290-300 nm) reach the Earth's surface, and short-wave (less than 290 nm), destructive to all living things, are almost completely absorbed at a height of about 20-25 km by the ozone screen - a thin layer of the atmosphere containing molecules 0 3 (see Fig. 2).

Rice. 3. The biological effect of different parts of the spectrum of solar radiation: 1 - protein denaturation; 2 - intensity of wheat photosynthesis; 3 - spectral sensitivity of the human eye. The area of ​​ultraviolet radiation that does not penetrate is shaded.

through the atmosphere

Long-wave ultraviolet rays (300-400 nm), which have high photon energy, have high chemical and mutagenic activity. Large doses of them are harmful to organisms.

In the range of 250–300 nm, UV radiation has a powerful bactericidal effect and causes the formation of anti-rickets vitamin D in animals, i.e., in small doses, UV radiation is necessary for humans and animals. At a length of 300-400 nm, UV light causes a tan in humans, which is defensive reaction skin.

Infrared rays (IRL) with a wavelength of more than 750 nm have a thermal effect, are not perceived by the human eye and provide the thermal regime of the planet. These rays are especially important for cold-blooded animals (insects, reptiles), which use them to increase body temperature (butterflies, lizards, snakes) or for hunting (ticks, spiders, snakes).

Currently, many devices have been manufactured that use one or another part of the spectrum: ultraviolet irradiators, household appliances with infrared radiation for quick cooking, etc.

Visible rays with a wavelength of 400-750 nm are of great importance for all living organisms.

Light as a condition for plant life. Light is essential for plants. Green plants use solar energy in this region of the spectrum, capturing it in the process of photosynthesis:

Due to the different need for light energy, plants develop various morphological and physiological adaptations to the light regime of their habitat.

Adaptation is a system for regulating metabolic processes and physiological characteristics that ensures maximum adaptability of organisms to environmental conditions.

In accordance with adaptations to the light regime, plants are divided into the following ecological groups.

• 1. Light-loving- having the following morphological adaptations: strongly branching shoots with shortened internodes, rosette; the leaves are small or with a strongly dissected leaf blade, often with a waxy coating or pubescence, often turned with an edge towards the light (for example, acacia, mimosa, sophora, cornflower, feather grass, pine, tulip).
• 2. Shade-loving- constantly in conditions of strong shading. Their leaves are dark green in color, arranged horizontally. These are plants of the lower tiers of forests (for example, wintergreens, two-leaved mink, ferns, etc.). With a lack of light, deep-sea plants (red and brown algae) live.
• 3. shade-tolerant- can tolerate shading, but grow well in the light (for example, forest grasses and shrubs growing both in shady places and on the edges, as well as oak, beech, hornbeam, spruce).

In relation to the light, plants in the forest are arranged in tiers. In addition, even in the same tree, the leaves capture light differently depending on the tier. As a rule, they constitute sheet mosaic, i.e. arranged in such a way as to increase the leaf surface for better light capture.

The light regime varies depending on the geographical latitude, time of day and season. In connection with the rotation of the Earth, the light regime has a distinct daily and seasonal rhythm. The reaction of the body to a change in lighting mode is called photoperiodism. In connection with photoperiodism in the body, the processes of metabolism, growth and development change.

The phenomenon associated with photoperiodism in plants phototropism- the movement of individual plant organs towards the light. For example, the movement of a sunflower basket during the day following the sun, opening the inflorescences of a dandelion and bindweed in the morning and closing them in the evening, and vice versa - opening flowers of night violet and fragrant tobacco in the evening and closing them in the morning (daily photoperiodism).

Seasonal photoperiodism is observed in latitudes with the change of seasons (temperate and northern latitudes). With the onset of a long day (in spring), active sap flow is observed in plants, the buds swell and open. When autumn comes short day plants shed their leaves and prepare for winter dormancy. It is necessary to distinguish between "short day" plants - they are common in the subtropics (chrysanthemums, perilla, rice, soybeans, cocklebur, hemp); and plants of the "long day" (rudbeckia, cereals, cruciferous, dill) - they are distributed mainly in temperate and subpolar latitudes. "Long day" plants cannot grow in the south (they do not produce seeds), and the same applies to "short day" plants if grown in the north.

Light as a condition for animal life. For animals, light is not a factor of paramount importance, as for green plants, since they exist due to the energy of the sun accumulated by these plants. Nevertheless, animals need light of a certain spectral composition. Basically, they need light for visual orientation in space. True, not all animals have eyes. In primitives, these are simply photosensitive cells or even a place in the cell (for example, the stigma in unicellular organisms or the "light-sensitive eye").

Figurative vision is possible only with a sufficiently complex structure of the eye. For example, spiders can distinguish the contours of moving objects only at a distance of 1-2 cm. The eyes of vertebrates perceive the shape and size of objects, their color and determine the distance to them.

Visible light is a conventional term for different types animals. For a person, these are rays from purple to dark red (recall the colors of the rainbow). Rattlesnakes, for example, perceive the infrared part of the spectrum. Bees, on the other hand, distinguish multicolor ultraviolet rays, but do not perceive red ones. The spectrum of visible light for them is shifted to the ultraviolet region.

The development of the organs of vision largely depends on the ecological situation and environmental conditions of organisms. So, in permanent inhabitants of caves, where sunlight does not penetrate, the eyes can be completely or partially reduced: in blind ground beetles, bats, some amphibians and fish.

Ability to color vision also depends on whether the organisms are diurnal or nocturnal. Dogs, cats, hamsters (which feed by hunting at dusk) all see in black and white. The same vision is in night birds - owls, nightjars. Diurnal birds have well-developed color vision.

Animals and birds also have adaptations for daytime and nocturnal lifestyles. For example, most ungulates, bears, wolves, eagles, larks are active during the day, while tigers, mice, hedgehogs, owls are most active at night. The length of daylight hours affects the onset of the mating season, migrations and flights in birds, hibernation in mammals, etc.

Animals navigate with the help of their organs of vision during long-distance flights and migrations. Birds, for example, choose the direction of flight with amazing accuracy, overcoming many thousands of kilometers from nesting to wintering grounds. It has been proven that during such long-distance flights, birds are at least partially oriented by the Sun and stars, i.e., astronomical light sources. They are capable of navigation, changing orientation in order to get to the desired point on the Earth. If the birds are transported in cages, then they correctly choose the direction for wintering from anywhere in the world. Birds do not fly in continuous fog, as they often go astray during the flight.

Among insects, the ability for this kind of orientation is developed in bees. They use the position (height) of the Sun as a guide.

Temperature regime in the ground-air environment. Temperature adaptations. It is known that life is a way of existence of protein bodies, therefore the boundaries of the existence of life are the temperatures at which the normal structure and functioning of proteins is possible, on average from 0°C to +50°C. However, some organisms have specialized enzyme systems and are adapted to active existence at temperatures outside these limits.

Species that prefer cold (they are called cryophiles), can maintain cell activity down to -8°... -10°C. Bacteria, fungi, lichens, mosses, and arthropods can endure hypothermia. Our trees also do not die at low temperatures. It is only important that during the period of preparation for winter, the water in the plant cells passes into special condition, and did not turn into ice - then the cells die. Plants overcome hypothermia by accumulating substances in their cells and tissues - osmotic protectors: various sugars, amino acids, alcohols, which “pump out” excess water, preventing it from turning into ice.

There is a group of species of organisms whose optimum life is high temperatures, they are called thermophiles. These are various worms, insects, mites that live in deserts and hot semi-deserts, these are bacteria of hot springs. There are springs with a temperature of + 70 ° C, containing living inhabitants - blue-green algae (cyanobacteria), some types of mollusks.

If, however, we take into account latent(long-term dormant) forms of organisms, such as spores of some bacteria, cysts, spores and seeds of plants, they can withstand greatly abnormal temperatures. Bacterial spores can withstand temperatures up to 180°C. Many seeds, plant pollen, cysts, unicellular algae withstand freezing in liquid nitrogen (at -195.8°C) and then long-term storage at -70°C. After thawing and placing in favorable conditions and sufficient nutrient medium, these cells can become active again and begin to multiply.

The temporary suspension of all vital processes of the body is called suspended animation. Anabiosis can occur in animals both with a decrease in the temperature of the environment, and with its increase. For example, in snakes and lizards, when the air temperature rises above 45 ° C, thermal torpor occurs. In amphibians at water temperatures below 4 ° C, vital activity is practically absent. From the state of anabiosis, living beings can return to normal life only if the structure of macromolecules in their cells (primarily DNA and proteins) is not disturbed.

Resistance to temperature fluctuations in terrestrial inhabitants is different.

Temperature adaptations in plants. Plants, being immobile organisms, are forced to adapt to those temperature fluctuations that exist in their habitats. They have specific systems that protect against hypothermia or overheating. transpiration- this is a system for the evaporation of water by plants through the stomatal apparatus, which saves them from overheating. Some plants have even acquired resistance to fires - they are called pyrophytes. Fires often occur in savannahs, bush thickets. Savannah trees have thick bark impregnated with refractory substances. Their fruits and seeds have thick, lignified skins that crack when set on fire, which helps the seeds to fall into the ground.

Temperature adaptations of animals. Animals, compared with plants, have greater ability to adapt to changes in temperature, as they are able to move, have muscles and produce their own internal heat. Depending on the mechanisms of maintaining a constant body temperature, there are poikilothermic(cold-blooded) and homoiothermal(warm-blooded) animals.

Poikilothermic are insects, fish, amphibians, reptiles. Their body temperature changes with the temperature of the environment.

Homeothermic- animals with a constant body temperature, able to maintain it even with strong fluctuations in outside temperature (these are mammals and birds).

The main ways of temperature adaptations:

• 1) chemical thermoregulation- increase in heat production in response to a decrease in ambient temperature;
• 2) physical thermoregulation- the ability to retain heat due to hair and feathers, the distribution of fat reserves, the possibility of evaporative heat transfer, etc.;

3) behavioral thermoregulation- the ability to move from places of extreme temperatures to places of optimum temperatures. This is the main way of thermoregulation in poikilothermic animals. When the temperature rises or falls, they tend to change their posture or hide in the shade, in a hole. Bees, ants, termites build nests with a well-regulated temperature inside them.

In warm-blooded animals, the thermoregulation system has improved significantly (although it is weak in young and chicks).

To illustrate the perfection of thermoregulation in higher animals and humans, we can give the following example. About 200 years ago, Dr. C. Blegden in England set up the following experiment: together with his friends and a dog, he spent 45 minutes in a dry chamber at +126°C without health consequences. Fans of the Finnish bath know that it is possible to spend some time in a sauna with a temperature of more than + 100 ° C (for everyone - their own), and this is good for health. But we also know that if a piece of meat is kept at this temperature, it will cook.

Under the action of cold in warm-blooded animals, oxidative processes are intensified, especially in the muscles. Chemical thermoregulation comes into play. Muscle tremors are noted, leading to the release of additional heat. Lipid metabolism is especially enhanced, since fats contain a significant supply of chemical energy. Therefore, the accumulation of fat reserves provides better thermoregulation.

The increased production of heat production is accompanied by the consumption of a large amount of food. So, birds remaining for the winter need a lot of food, they are not afraid of frost, but starvation. With a good harvest, spruce and pine crossbills, for example, even in winter breed chicks. People - residents of harsh Siberian or northern regions - from generation to generation developed a high-calorie menu - traditional dumplings and other high-calorie foods. Therefore, before following the fashionable Western diets and rejecting the food of the ancestors, one must remember the expediency existing in nature, which underlies the long-term traditions of people.

An effective mechanism for regulating heat transfer in animals, as in plants, is the evaporation of water through sweating or through the mucous membranes of the mouth and upper respiratory tract. This is an example of physical thermoregulation. Man at extreme heat can produce up to 12 liters of sweat per day, while dissipating heat 10 times more than normal. Part of the excreted water must be returned through drinking.

Warm-blooded animals, like cold-blooded animals, are characterized by behavioral thermoregulation. In the burrows of animals living underground, temperature fluctuations are the smaller, the deeper the hole. Skillfully built nests of bees maintain an even, favorable microclimate. Of particular interest is the group behavior of animals. For example, penguins in severe frost and snowstorm form a "turtle" - a dense pile. Those who found themselves on the edge gradually make their way inside, where the temperature is maintained at about +37°C. In the same place, inside, cubs are placed.

Thus, in order to live and reproduce in certain conditions of the ground-air environment, animals and plants in the process of evolution have developed a wide variety of adaptations and systems to correspond to this habitat.

Air pollution. Recently, an increasingly significant external factor that changes the ground-air habitat has become anthropogenic factor.

The atmosphere, like the biosphere, has the property of self-purification, or maintaining balance. However, the volume and speed of modern atmospheric pollution exceed the natural possibilities of their neutralization.

Firstly, it is natural pollution - various dust: mineral (products of weathering and destruction of rocks), organic (aeroplankton - bacteria, viruses, plant pollen) and space (particles entering the atmosphere from space).

Secondly, these are artificial (anthropogenic) pollution - industrial, transport and domestic emissions into the atmosphere (dust of cement plants, soot, various gases, radioactive contamination, pesticides).

According to rough estimates, 1.5 million tons of arsenic have been released into the atmosphere over the past 100 years; 1 million tons of nickel; 1.35 million tons of silicon, 900 thousand tons of cobalt, 600 thousand tons of zinc, the same amount of copper and other metals.

Chemical enterprises emit carbon dioxide, iron oxide, nitrogen oxides, chlorine. Of the pesticides, organophosphorus compounds are especially toxic, from which even more toxic ones are obtained in the atmosphere.

As a result of emissions in cities where ultraviolet radiation is reduced and there is a large crowd of people, the air basin is degraded, one of the manifestations of which is smog.

Smog happens "classical"(a mixture of toxic fogs that occur during slight cloudiness) and " photochemical» (a mixture of caustic gases and aerosols, which is formed without fog as a result of photochemical reactions). The most dangerous is London and Los Angeles smog. It absorbs up to 25% of solar radiation and 80% of ultraviolet rays, the urban population suffers from this.

The ground-air environment is the most difficult for the life of organisms. Physical factors, its components are very diverse: light, temperature. But organisms have adapted over the course of evolution to these changing factors and have developed adaptation systems to ensure extreme adaptability to environmental conditions. Despite the inexhaustibility of air as an environmental resource, its quality is rapidly deteriorating. Air pollution is the most dangerous form of environmental pollution.

Questions and tasks for self-control

• 1. Explain why the ground-air environment is the most difficult for the life of organisms.
• 2. Give examples of adaptations in plants and animals to high and low temperatures.
• 3. Why does temperature have a strong influence on the vital activity of any organisms?
• 4. Analyze how light affects the life of plants and animals.
• 5. Describe what photoperiodism is.
• 6. Prove that different waves of the light spectrum have different effects on living organisms, give examples. List the groups into which living organisms are divided according to the way they use energy, give examples.
• 7. Comment on what seasonal phenomena in nature are connected with and how plants and animals react to them.
• 8. Explain why air pollution poses the greatest danger to living organisms.

By "environment" is meant everything that surrounds the body and in one way or another affects it. In other words, the living environment is characterized by a certain set of environmental factors. Wednesday- living environment - aquatic environment - ground-air environment - soil environment - organism as a living environment - key concepts.

generally accepted definition environments is the definition of Nikolai Pavlovich Naumov: " Wednesday- everything that surrounds organisms directly or indirectly affects their state, development, survival and reproduction. "On Earth, there are four qualitatively different living environments that have a set of specific environmental factors: - land-water (land); - water; - the soil; - other organisms.

ground-air The environment is characterized by a huge variety of living conditions, ecological niches and organisms inhabiting them. Organisms play a primary role in shaping the conditions of the ground-air environment of life, and above all - gas composition atmosphere. Almost all oxygen in the earth's atmosphere is of biogenic origin. The main features of the ground-air environment are

Large changes in environmental factors,

Heterogeneity of the environment,

The action of the forces of gravity

Low air density.

The complex of physical, geographical and climatic factors related to a certain natural zone leads to the adaptation of organisms to life in these conditions, the diversity of life forms. The high oxygen content in the atmosphere (about 21%) determines the possibility of the formation of a high (energy) level of metabolism. Atmospheric air is characterized by low and variable humidity. This circumstance largely limited the possibilities of mastering the ground-air environment.

Atmosphere(from the Greek atmos - steam and sphaira - ball), the gaseous shell of the earth. Accurate upper bound the earth's atmosphere cannot be specified. The atmosphere has a pronounced layered structure. The main layers of the atmosphere:

1)Troposphere- height 8 - 17 km. all water vapor and 4/5 of the mass of the atmosphere are concentrated in it, and all weather phenomena develop.

2)Stratosphere- a layer above the troposphere up to 40 km. It is characterized by almost complete invariability of temperature in height. In the upper part of the stratosphere, the maximum concentration of ozone is observed, which absorbs a large amount of ultraviolet radiation from the sun.

3) Mesosphere- layer between 40 and 80 km; in its lower half, the temperature rises from +20 to +30 degrees, in the upper half it drops to almost -100 degrees.

4) Thermosphere(ionosphere) - a layer between 80 - 1000 km, which has an increased ionization of gas molecules (under the influence of freely penetrating cosmic radiation).

5) Exosphere(scattering sphere) - a layer above 800 - 1000 km, from which gas molecules are scattered into outer space. The atmosphere transmits 3/4 of solar radiation, thereby increasing total heat going to the development of natural processes on the Earth.

Aquatic life environment. Hydrosphere (from hydro ... and sphere), the intermittent water shell of the Earth, located between the atmosphere and solid the earth's crust(lithosphere). Represents the totality of oceans, seas, lakes, rivers, swamps, and groundwater. The hydrosphere covers about 71% of the earth's surface. The chemical composition of the hydrosphere approaches the average composition of sea water.

Quantity fresh water makes up 2.5% of all water on the planet; 85% - sea ​​water. Fresh water reserves are distributed extremely unevenly: 72.2% - ice; 22.4% - groundwater; 0.35% - atmosphere; 5.05% - sustainable flow of rivers and water of lakes. The share of water that we can use accounts for only 10-12% of all fresh water on Earth.

Primary environment life was precisely the aquatic environment. First of all, most organisms are not capable of active life without water entering the body or without maintaining a certain fluid content inside the body. The main feature of the aquatic environment is: daily and seasonal temperature fluctuations. Huge environmental significance, have a high density and viscosity of water. The specific gravity of water is commensurate with that of the body of living organisms. The density of water is about 1000 times that of air. Therefore, aquatic organisms (especially actively moving ones) are faced with greater strength hydrodynamic resistance. The high density of water is the reason that mechanical vibrations (vibrations) propagate well in the aquatic environment. This is very important for the senses, orientation in space and between aquatic inhabitants. The speed of sound in the aquatic environment has a higher frequency of echolocation signals. Larger than in the air, four times. Therefore, there is a whole group aquatic organisms(both plants and animals), existing without obligatory connection with the bottom or other substrate, "floating" in the water column.