In the ground-air environment, temperature has a particularly large effect on organisms. Therefore, the inhabitants of the cold and hot regions of the Earth have developed various adaptations to conserve heat or, conversely, to release its excess.

Give some examples.

The temperature of the plant due to heating by the sun's rays may be higher than the temperature of the surrounding air and soil. With strong evaporation, the temperature of the plant becomes lower than the air temperature. Evaporation through stomata is a process regulated by the plant. With an increase in air temperature, it increases if a quick supply of the required amount of water to the leaves is possible. This saves the plant from overheating, lowering its temperature by 4-6, and sometimes by 10-15 ° C.

During muscle contraction, much more thermal energy is released than during the functioning of any other organs and tissues. The more powerful and active the musculature, the more heat the animal can generate. Compared with plants, animals have more diverse possibilities to regulate, permanently or temporarily, their own body temperature.

By changing the posture, the animal can increase or decrease the heating of the body due to solar radiation. For example, the desert locust exposes the wide lateral surface of the body to the sun's rays in the cool morning hours, and the narrow dorsal surface at noon. In extreme heat, animals hide in the shade, hide in burrows. In the desert during the day, for example, some species of lizards and snakes climb the bushes, avoiding contact with the hot surface of the soil. By winter, many animals seek refuge, where the course of temperatures is smoother than in open habitats. The forms of behavior of social insects are even more complex: bees, ants, termites, which build nests with a well-regulated temperature inside them, almost constant during the period of insect activity.

The thick fur of mammals, feathers and especially the down cover of birds make it possible to keep a layer of air around the body with a temperature close to that of the animal's body, and thereby reduce heat radiation to the external environment. Heat transfer is regulated by the slope of the hair and feathers, the seasonal change of fur and plumage. The exceptionally warm winter fur of animals from the Arctic allows them to do without an increase in metabolism in cold weather and reduces the need for food.

Name the inhabitants of the desert known to you.

In the deserts of Central Asia, a small shrub is a saxaul. In America - cacti, in Africa - euphorbia. The animal world is not rich. Reptiles predominate - snakes, monitor lizards. There are scorpions, few mammals (camel).

1. Continue filling out the table "Habitats of living organisms" (see homework for § 42).

LECTURE 4

ENVIRONMENTS OF LIFE AND ADAPTATION OF ORGANISMS TO THEM.

Water environment.

This is the oldest environment in which life originated and evolved for a long time even before the first organisms appeared on land. According to the composition of the aquatic environment of life, two of its main variants are distinguished: freshwater and marine environments.

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

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

Table 1 - Comparative characteristics of habitats and adaptation of living organisms to them

The basis of the production of most aquatic ecosystems are autotrophs, using sunlight that breaks through the water column. The possibility of "piercing" this thickness is determined by the transparency of the water. In the clear water of the ocean, depending on the angle of incidence of sunlight, autotrophic life is possible up to a depth of 200 m in the tropics and 50 m in high latitudes (for example, in the seas of the Arctic Ocean). In strongly disturbed freshwater reservoirs, a layer inhabited by autotrophs (it is called photic), may be only a few tens of centimeters.

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

The most important characteristic of water is its chemical composition - the content of salts (including nutrients), gases, hydrogen ions (pH). According to the concentration of nutrients, especially phosphorus and nitrogen, water bodies are divided into oligotrophic, mesotrophic and eutrophic. With an increase in the content of nutrients, for example, when a reservoir is polluted with wastewater, the process of eutrophication of aquatic ecosystems occurs.

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

The concentration of hydrogen ions in water (pH) can vary within 3.7-7.8. Waters with a pH of 6.45 to 7.3 are considered neutral. As already noted, with a decrease in pH, the biodiversity of organisms inhabiting the aquatic environment rapidly decreases. Crayfish, many types of mollusks die at pH below 6, perch and pike can withstand pH up to 5, eel and char survive when the pH drops to 5-4.4. In more acidic waters, only some species of zooplankton and phytoplankton survive. Acid rains associated with emissions of large amounts of sulfur and nitrogen oxides into the atmosphere by industrial enterprises have become the cause of acidification of the waters of lakes in Europe and the United States and a sharp depletion of their biological diversity. Oxygen is often the limiting factor. Its content usually does not exceed 1% by volume. With an increase in temperature, enrichment with organic matter and weak mixing, the oxygen content in water decreases. The low availability of oxygen for organisms is also associated with its weak diffusion (it is thousands of times less in water than in air). The second limiting factor is light. Illumination decreases rapidly with depth. In perfectly clean waters, light can penetrate to a depth of 50-60 m, in heavily polluted waters - only a few centimeters.

This environment is the most homogeneous among others. It varies little in space, there are no clear boundaries between individual ecosystems. The amplitudes of the factor values ​​are also small. The difference between the maximum and minimum temperatures here usually does not exceed 50°C (while in the ground-air environment it is up to 100°C). The medium has a high density. For oceanic waters it is equal to 1.3 g/cm 3 , for fresh waters it is close to unity. The pressure only changes with depth: each 10-meter layer of water increases the pressure by 1 atmosphere.

There are few warm-blooded animals in the water, or homoiothermic(Greek homa - the same, thermo - heat), organisms. This is the result of two causes: a small temperature fluctuation and a lack of oxygen. The main adaptive mechanism of homoiothermia is resistance to unfavorable temperatures. In water, such temperatures are unlikely, and in the deep layers the temperature is almost constant (+4°C). Maintaining a constant body temperature is necessarily associated with intensive metabolic processes, which is possible only with a good supply of oxygen. There are no such conditions in water. Warm-blooded animals of the aquatic environment (whales, seals, fur seals, etc.) are former inhabitants of the land. Their existence is impossible without periodic communication with the air environment.

Typical inhabitants of the aquatic environment have a variable body temperature and belong to the group poikiothermal(Greek poikios - varied). To some extent, they compensate for the lack of oxygen by increasing the contact of the respiratory organs with water. Many water dwellers (hydrobionts) consume oxygen through all the integuments of the body. Often, breathing is combined with a filtration type of nutrition, in which a large amount of water is passed through the body. Some organisms during periods of acute lack of oxygen are able to drastically slow down their vital activity, up to the state suspended animation(almost complete cessation of metabolism).

Organisms adapt to high water density mainly in two ways. Some use it as a support and are in a state of free soaring. The density (specific gravity) of such organisms usually differs little from the density of water. This is facilitated by the complete or almost complete absence of the skeleton, the presence of outgrowths, droplets of fat in the body or air cavities. Such organisms are grouped plankton(Greek planktos - wandering). There are plant (phyto-) and animal (zoo-) plankton. The size of planktonic organisms is usually small. But they account for the bulk of aquatic life.

Actively moving organisms (swimmers) adapt to overcome the high density of water. They are characterized by an elongated body shape, well-developed muscles, and the presence of friction-reducing structures (mucus, scales). In general, the high density of water results in a decrease in the proportion of the skeleton in the total body mass of hydrobionts compared to terrestrial organisms. In conditions of lack of light or its absence, organisms use sound for orientation. It spreads much faster in water than in air. To detect various obstacles, reflected sound is used by the type of echolocation. Odor phenomena are also used for orientation (odors are felt much better in water than in air). In the depths of the waters, many organisms have the property of self-luminescence (bioluminescence).

Plants that live in the water column use the most deeply penetrating blue, blue and blue-violet rays in the process of photosynthesis. Accordingly, the color of plants changes with depth from green to brown and red.

The following groups of aquatic organisms are distinguished adequately to adaptive mechanisms: plankton- free floating nekton(Greek nektos - floating) - actively moving, benthos(Greek benthos - depth) - inhabitants of the bottom, pelagos(Greek pelagos - open sea) - inhabitants of the water column, neuston- inhabitants of the upper film of water (part of the body can be in the water, part - in the air).

Human impact on the aquatic environment is manifested in a decrease in transparency, a change in the chemical composition (pollution) and temperature (thermal pollution). The consequence of these and other impacts is oxygen depletion, reduced productivity, changes in species composition, and other deviations from the norm.

Ground-air environment.

Air has a much lower density than water. For this reason, the development of the air environment, which took place much later than the origin of life and its development in the aquatic environment, was accompanied by an increase in the development of mechanical tissues, which allowed organisms to resist the action of the law of universal gravitation and wind (the skeleton in vertebrates, chitinous shells in insects, sclerenchyma in plants). Not a single organism can live permanently in the conditions of only an air environment, and therefore even the best "flyers" (birds and insects) must periodically descend to the ground. The movement of organisms through the air is possible due to special adaptations - wings in birds, insects, some species of mammals and even fish, parachutes and wings in seeds, air sacs in coniferous pollen, etc.

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

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

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

This environment is one of the most complex both in terms of properties and diversity in space. It is characterized by low air density, large temperature fluctuations (annual amplitudes up to 100°C), high atmospheric mobility. Limiting factors are most often a lack or excess of heat and moisture. In some cases, for example, under the canopy of the forest, there is a lack of light.

Large fluctuations in temperature over time and its significant variability in space, as well as a good supply of oxygen, were the motives for the appearance of organisms with a constant body temperature (homeothermic). Homeothermy allowed land dwellers to significantly expand their habitat (species ranges), but this is inevitably associated with increased energy expenditure.

For organisms of the ground-air environment, three mechanisms of adaptation to the temperature factor are typical: physical, chemical, behavioral. Physical controlled by heat transfer. Its factors are skin, body fat, water evaporation (sweating in animals, transpiration in plants). This pathway is characteristic of poikyothermic and homeothermic organisms. Chemical adaptations based on maintaining a certain body temperature. It requires an intense metabolism. Such adaptations are characteristic of homoiothermic and only partially poikyothermic organisms. behavioral path it is carried out by means of the choice of preferred positions by organisms (open to the sun or shaded places, various types of shelter, etc.). It is characteristic of both groups of organisms, but poikyothermic to a greater extent. Plants adapt to the temperature factor mainly through physical mechanisms (covers, evaporation of water) and only partially through behavioral ones (rotation of leaf blades relative to the sun's rays, use of the heat of the earth and the warming role of snow cover).

Adaptations to temperature are also carried out through the size and shape of the body of organisms. For heat transfer, large sizes are more advantageous (than the larger the body, the smaller its surface area per unit mass, and hence heat transfer, and vice versa). For this reason, the same species found in colder environments (in the north) tend to be larger than those found in warmer climates. This pattern is called Bergman's rule. Temperature regulation is also carried out through the protruding parts of the body (ears, limbs, olfactory organs). They tend to be smaller in colder regions than in warmer regions. (Allen's rule).

The dependence of heat transfer on body size can be judged by the amount of oxygen consumed during respiration per unit mass by various organisms. It is the larger, the smaller the size of the animals. So, per 1 kg of weight, oxygen consumption (cm 3 / hour) was: horse - 220, rabbit - 480, rat -1800, mouse - 4100.

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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 set 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, mollusks, 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 the land-water boundary zone. 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.

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)

Land animals and plants have developed their own, no less original adaptations to adverse environmental factors: the complex structure of the body and its integuments, 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

Any habitat is a complex system that is distinguished by its unique set of abiotic and biotic factors, which, in fact, form this environment. Evolutionarily, the land-air environment arose later than the water one, which is associated with chemical transformations of the composition of atmospheric air. Most of the organisms that have a nucleus live in the terrestrial environment, which is associated with a wide variety of natural zones, physical, anthropogenic, geographical and other determining factors.

Characteristics of the ground-air environment

This environment consists of the top layers of soil ( up to 2 km deep) and lower atmosphere ( up to 10 km). The environment is characterized by a wide variety of different life forms. Among the invertebrates, one can note: insects, a few species of worms and mollusks, of course, vertebrates predominate. The high oxygen content in the air led to an evolutionary change in the respiratory system and the presence of a more intense metabolism.

The atmosphere has insufficient and often variable humidity, which often limits the spread of living organisms. In regions with high temperatures and low humidity, eukaryotes develop various idioadaptations, the purpose of which is to maintain the vital water level (transformation of plant leaves into needles, accumulation of fat in camel humps).

Terrestrial animals are characterized by the phenomenon photoperiodism thus most animals are only active during the day or only at night. Also, the terrestrial environment is characterized by a significant amplitude of fluctuations in temperature, humidity and light intensity. The change in these factors is associated with geographical location, change of seasons, time of day. Due to the low density and pressure of the atmosphere, muscle and bone tissue has developed and become more complex.

Vertebrates have developed complex limbs adapted to support the body and move along a solid substrate in conditions of low atmospheric density. Plants have a progressive root system, which allows them to fix themselves in the soil and transport substances to a considerable height. Also, terrestrial plants have developed mechanical, basic tissues, phloem and xylem. Most plants have adaptations that protect them from excessive transpiration.

The soil

Although the soil is classified as a terrestrial-air habitat, it is very different from the atmosphere in its physical properties:

• High density and pressure.
• Insufficient amount of oxygen.
• Low amplitude of temperature fluctuations.
• Low light intensity.

In this regard, the underground inhabitants have their own adaptations, distinguishable from terrestrial animals.

aquatic habitat

An environment that includes the entire hydrosphere, both saline and fresh water bodies. This environment is characterized by less variety of life and its own special conditions. It is inhabited by small invertebrates that form plankton, cartilaginous and bony fish, worms, mollusks, and a few species of mammals.

Oxygen concentration is highly dependent on depth. In places where the atmosphere and hydrosphere come into contact, there is much more oxygen and light than at depth. High pressure, which at great depths is 1000 times higher than atmospheric pressure, determines the shape of the body of most underwater inhabitants. The amplitude of temperature change is small, since the heat transfer of water is much lower than that of the earth's surface.

Differences between the water and ground-air environment

As already mentioned, the main distinguishing features of different habitats are determined by abiotic factors. The land-air environment is characterized by high biological diversity, high oxygen concentration, variable temperature and humidity, which are the main limiting factors for the settlement of animals and plants. Biological rhythms depend on the length of daylight hours, the season and the natural-climatic zone. In the aquatic environment, most nutrient organic substances are located in the water column or on its surface, only a small proportion is located at the bottom; in the terrestrial-air environment, all organic substances are located on the surface.

Terrestrial inhabitants are distinguished by the best development of sensory systems and the nervous system as a whole, the musculoskeletal, circulatory and respiratory systems have also changed significantly. The skin covers are very different, because they are functionally different. Under water, lower plants (algae) are common, which in most cases do not have real organs, for example, rhizoids serve as attachment organs. The spread of aquatic inhabitants is often associated with warm undercurrents. Along with the differences between these habitats, there are animals that have adapted to live in both. These animals include Amphibians.

The ground-air environment is the most difficult in terms of environmental conditions. Life on land required such adaptations that were possible only with a sufficiently high level of organization of plants and animals.

4.2.1. Air as an ecological factor for terrestrial organisms

The low density of air determines its low lifting force and negligible disputability. The inhabitants of the air environment must have their own support system that supports the body: plants - a variety of mechanical tissues, animals - a solid or, much less often, a 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 suspension in the air is impossible.

True, many microorganisms and animals, spores, seeds, fruits and pollen of plants are regularly present in the air and are carried by air currents (Fig. 43), many animals are capable of active flight, however, 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.

Rice. 43. Altitude distribution of aerial plankton arthropods (according to Dajot, 1975)

The low density of air causes low resistance to movement. Therefore, many terrestrial animals in the course of evolution used the ecological benefits of this property of the air environment, acquiring the ability to fly. 75% of the species of all terrestrial animals are capable of active flight, mainly insects and birds, but flyers are also found among mammals and reptiles. Land animals fly mainly with the help of muscular effort, but some can also glide due to air currents.

Due to the mobility of air, the vertical and horizontal movements of air masses existing in the lower layers of the atmosphere, passive flight of a number of organisms is possible.

Anemophilia is the oldest way of pollinating plants. All gymnosperms are pollinated by wind, and among angiosperms, anemophilous plants make up approximately 10% of all species.

Anemophily is observed in the families of beech, birch, walnut, elm, hemp, nettle, casuarina, haze, sedge, cereals, palms and many others. Wind pollinated plants have a number of adaptations that improve the aerodynamic properties of their pollen, as well as morphological and biological features that ensure pollination efficiency.

The life of many plants is completely dependent on the wind, and resettlement is carried out with its help. Such a double dependence is observed in spruce, pine, poplar, birch, elm, ash, cotton grass, cattail, saxaul, juzgun, etc.

Many species have developed anemochory- settling with the help of air currents. Anemochory is characteristic of spores, seeds and fruits of plants, protozoan cysts, small insects, spiders, etc. Organisms passively carried by air currents are collectively called aeroplankton by analogy with the planktonic inhabitants of the aquatic environment. Special adaptations for passive flight are very small body sizes, an increase in its area due to outgrowths, strong dissection, a large relative surface of the wings, the use of cobwebs, etc. (Fig. 44). Anemochore seeds and fruits of plants also have either very small sizes (for example, orchid seeds) or various pterygoid and parachute-shaped appendages that increase their ability to plan (Fig. 45).

Rice. 44. Adaptations for airborne transport in insects:

1 – mosquito Cardiocrepis brevirostris;

2 – gall midge Porrycordila sp.;

3 – Hymenoptera Anargus fuscus;

4 – Hermes Dreyfusia nordmannianae;

5 - larva of the gypsy moth Lymantria dispar

Rice. 45. Adaptations for wind transport in fruits and seeds of plants:

1 – linden Tilia intermedia;

2 – Acer monspessulanum maple;

3 – birch Betula pendula;

4 – cotton grass Eriophorum;

5 – dandelion Taraxacum officinale;

6 – cattail Typha scuttbeworhii

In the settlement of microorganisms, animals and plants, the main role is played by vertical convection air currents and weak winds. Strong winds, storms and hurricanes also have significant environmental impacts on terrestrial organisms.

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, since the usual fluctuations in pressure in their environment are fractions of the atmosphere, and even for birds rising to great heights do not exceed 1/3 of the normal one.

Gas composition of air. In addition to the physical properties of the air environment, its chemical features are extremely important for the existence of terrestrial organisms. The gas composition of air in the surface layer of the atmosphere is quite homogeneous in terms of the content of the main components (nitrogen - 78.1%, oxygen - 21.0, argon - 0.9, carbon dioxide - 0.035% by volume) due to the high diffusive ability of gases and constant mixing convection and wind currents. However, various admixtures of gaseous, droplet-liquid and solid (dust) particles entering the atmosphere from local sources can be of significant ecological importance.

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. Regular daily changes in the carbon dioxide content in the surface layers associated with the rhythm of plant photosynthesis. Seasonal are 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. In high concentrations, carbon dioxide is toxic. In nature, such concentrations are rare.

In nature, the main source of carbon dioxide is the so-called soil respiration. Soil microorganisms and animals respire very intensively. Carbon dioxide diffuses from the soil into the atmosphere, especially vigorously during rain. A lot of it is emitted by soils that are moderately moist, well warmed up, rich in organic residues. For example, the soil of a beech forest emits CO 2 from 15 to 22 kg/ha per hour, and unfertilized sandy soil is only 2 kg/ha.

In modern conditions, human activity in the combustion of fossil fuels has become a powerful source of additional amounts of CO 2 entering the atmosphere.

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

Rice. 46. Mountainside with destroyed vegetation due to sulfur dioxide emissions from nearby industries

Local impurities entering the air can also significantly affect living organisms. This is especially true for toxic gaseous substances - methane, sulfur oxide, carbon monoxide, nitrogen oxide, 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 toxic to plants even in concentrations from one fifty-thousandth to one millionth of the volume of air. Around industrial centers that pollute the atmosphere with this gas, almost all vegetation dies (Fig. 46). Some plant species are especially sensitive to SO 2 and serve as a sensitive indicator of its accumulation in the air. For example, many lichens die even with traces of sulfur oxide in the surrounding atmosphere. Their presence in the forests around large cities testifies to the high purity of the air. The resistance of plants to impurities in the air is taken into account when selecting species for landscaping settlements. Sensitive to smoke, for example, spruce and pine, maple, linden, birch. The most resistant are thuja, Canadian poplar, American maple, elder and some others.

4.2.2. Soil and relief. Weather and climatic features of the ground-air environment

Edaphic environmental factors. Soil properties and terrain also affect the living conditions of terrestrial organisms, primarily plants. The properties of the earth's surface that have an ecological impact on its inhabitants are united by the name edaphic environmental factors (from the Greek "edafos" - foundation, soil).

The nature of the root system of plants depends on the hydrothermal regime, aeration, composition, composition and structure of the soil. For example, the root systems of tree species (birch, larch) in areas with permafrost are located at a shallow depth and spread out in breadth. Where there is no permafrost, the root systems of these same plants are less spread out and penetrate deeper. In many steppe plants, the roots can get water from great depths, while at the same time they have many surface roots in the humus soil horizon, from where the plants absorb mineral nutrients. On waterlogged, poorly aerated soil in mangroves, many species have special respiratory roots - pneumatophores.

A number of ecological groups of plants can be distinguished in relation to different soil properties.

So, according to the reaction to the acidity of the soil, they distinguish: 1) acidophilic species - grow on acidic soils with a pH of less than 6.7 (plants of sphagnum bogs, belous); 2) neutrophilic - gravitate towards soils with a pH of 6.7–7.0 (most cultivated plants); 3) basiphilic- grow at a pH of more than 7.0 (mordovnik, forest anemone); 4) indifferent - can grow on soils with different pH values ​​(lily of the valley, sheep fescue).

In relation to the gross composition of the soil, there are: 1) oligotrophic plants content with a small amount of ash elements (scotch pine); 2) eutrophic, those in need of a large number of ash elements (oak, common goatweed, perennial hawk); 3) mesotrophic, requiring a moderate amount of ash elements (spruce).

Nitrophils- plants that prefer soils rich in nitrogen (dioecious nettle).

Plants of saline soils form a group halophytes(soleros, sarsazan, kokpek).

Some plant species are confined to different substrates: petrophytes grow on rocky soils, and psammophytes inhabit loose sands.

The terrain and the nature of the soil affect the specifics of the movement of animals. For example, ungulates, ostriches, bustards living in open spaces need solid ground to enhance repulsion when running fast. In lizards that live on loose sands, the fingers are bordered with a fringe of horny scales, which increases the support surface (Fig. 47). For terrestrial inhabitants digging holes, dense soils are unfavorable. The nature of the soil in some cases affects the distribution of terrestrial animals that dig holes, burrow into the ground to escape heat or predators, or lay eggs in the soil, etc.

Rice. 47. Fan-toed gecko - an inhabitant of the sands of the Sahara: A - fan-toed gecko; B - gecko leg

weather features. Living conditions in the ground-air environment are complicated, in addition, weather changes.Weather - this is a continuously changing state of the atmosphere near the earth's surface up to a height of about 20 km (the boundary of the troposphere). Weather variability is manifested in the constant variation of the combination of such environmental factors as air temperature and humidity, cloudiness, precipitation, wind strength and direction, etc. Weather changes, along with their regular alternation in the annual cycle, are characterized by non-periodic fluctuations, which significantly complicates the conditions for the existence terrestrial organisms. The weather affects the life of aquatic inhabitants to a much lesser extent and only on the population of the surface layers.

The climate of the area. The long-term weather regime characterizes the climate of the area. The concept of climate includes not only the average values ​​of meteorological phenomena, but also their annual and daily course, deviations from it and their frequency. The climate is determined by the geographical conditions of the area.

The zonal diversity of climates is complicated by the action of monsoon winds, the distribution of cyclones and anticyclones, the influence of mountain ranges on the movement of air masses, the degree of distance from the ocean (continentality), and many other local factors. In the mountains, there is a climatic zonality, in many respects similar to the change of zones from low latitudes to high latitudes. All this creates an extraordinary variety of living conditions on land.

For most terrestrial organisms, especially small ones, it is not so much the climate of the area that is important, but the conditions of their immediate habitat. Very often, local elements of the environment (relief, exposure, vegetation, etc.) in a particular area change the regime of temperature, humidity, light, air movement in such a way that it differs significantly from the climatic conditions of the area. Such local climate modifications that take shape in the surface air layer are called microclimate. In each zone, the microclimates are very diverse. It is possible to single out microclimates of arbitrarily small areas. For example, a special mode is created in the corollas of flowers, which are used by insects living there. Differences in temperature, air humidity and wind strength are widely known in open space and in forests, in herbage and over bare soil areas, on the slopes of the northern and southern exposures, etc. A special stable microclimate occurs in burrows, nests, hollows, caves and other closed places.

Precipitation. In addition to providing water and creating moisture reserves, they can play another ecological role. Thus, heavy rain showers or hail sometimes have a mechanical effect on plants or animals.

The ecological role of snow cover is especially diverse. Daily temperature fluctuations penetrate into the snow thickness only up to 25 cm; deeper, the temperature almost does not change. At frosts of -20-30 ° C, under a layer of snow of 30-40 cm, the temperature is only slightly below zero. Deep snow cover protects the buds of renewal, protects the green parts of plants from freezing; many species go under the snow without shedding foliage, for example, hairy sorrel, Veronica officinalis, hoof, etc.

Rice. 48. Scheme of telemetric study of the temperature regime of a hazel grouse located in a snow hole (according to A. V. Andreev, A. V. Krechmar, 1976)

Small terrestrial animals also lead an active lifestyle in winter, laying entire galleries of passages under the snow and in its thickness. For a number of species that feed on snowy vegetation, even winter breeding is characteristic, which is noted, for example, in lemmings, wood and yellow-throated mice, a number of voles, water rats, etc. Grouse birds - hazel grouse, black grouse, tundra partridges - burrow into the snow for the night ( Fig. 48).

Winter snow cover prevents large animals from foraging. Many ungulates (reindeer, wild boars, musk oxen) feed exclusively on snowy vegetation in winter, and deep snow cover, and especially a hard crust on its surface that occurs in ice, doom them to starvation. During nomadic cattle breeding in pre-revolutionary Russia, a huge disaster in the southern regions was jute - mass loss of livestock as a result of sleet, depriving animals of food. Movement on loose deep snow is also difficult for animals. Foxes, for example, in snowy winters prefer areas in the forest under dense fir trees, where the layer of snow is thinner, and almost do not go out into open glades and edges. The depth of snow cover can limit the geographic distribution of species. For example, true deer do not penetrate north into areas where the snow thickness in winter is more than 40–50 cm.

The whiteness of the snow cover unmasks dark animals. Selection for camouflage to match the background color apparently played a large role in the occurrence of seasonal color changes in the white and tundra partridge, mountain hare, ermine, weasel, and arctic fox. On the Commander Islands, along with white foxes, there are many blue foxes. According to the observations of zoologists, the latter keep mainly near dark rocks and non-freezing surf strip, while whites prefer areas with snow cover.