The ground-air environment of life is the most complex in terms of environmental conditions. In the course of evolution, it was mastered much later than aquatic. Life on land required adaptations that became possible only with sufficient high level organization of organisms. The ground-air environment is characterized by low air density, large fluctuations in temperature and humidity, higher intensity of solar radiation in comparison with other environments, and atmospheric mobility.
Low air density and mobility determine its low lifting force and insignificant support. Organisms of the terrestrial environment must have a support system that supports the body: plants - mechanical tissues, animals - a hard or hydrostatic skeleton.
The low lifting force of the air determines the maximum mass and size of terrestrial organisms. The largest land animals are significantly smaller than the giants of the aquatic environment - whales. Animals the size and mass of a modern whale could not live on land, as they would be crushed by their own weight.
Low air density causes low resistance to movement. Therefore, many animals acquired the ability to fly: birds, insects, some mammals and reptiles.
Thanks to the mobility of air, passive flight of some types of organisms, as well as pollen, spores, fruits and seeds of plants, is possible. Dispersal with the help of air currents is called anemochory. Organisms passively transported by air currents are called aeroplankton. They are characterized by very small body sizes, the presence of outgrowths and strong dismemberment, the use of cobwebs, etc. The seeds and fruits of anemochoric plants also have very small sizes (seeds of orchids, fireweed, etc.) or various wing-shaped (maple, ash) and parachute-shaped (dandelion, coltsfoot) appendages.
In many plants, pollen transfer is carried out using the wind, for example, in gymnosperms, beech, birch, elm, cereals, etc. The method of pollinating plants with the help of wind is called anemophilia. Wind-pollinated plants have many adaptations that ensure efficient pollination.
Winds blowing with great force (storms, hurricanes) break trees, often uprooting them. Winds constantly blowing in one direction cause various deformations in tree growth and cause the formation of flags. different forms CZK
In areas where strong winds constantly blow, the species composition of small flying animals is usually poor, since they are not able to resist powerful air currents. Thus, on oceanic islands with permanent strong winds birds and insects that have lost the ability to fly predominate. Wind increases the loss of moisture and heat from organisms, and under its influence desiccation and cooling of organisms occurs faster.
Low air density causes relatively low pressure on land (760 mm Hg). As altitude increases, pressure decreases, which may limit the distribution of species in mountains. A decrease in pressure entails a decrease in oxygen supply and dehydration of animals due to an increase in respiration rate. Therefore, for most vertebrates and higher plants, the upper limit of life is about 6000 m.
Gas composition air in the surface layer of the atmosphere is quite homogeneous. It contains nitrogen - 78.1%, oxygen - 21%, argon - 0.9%, carbon dioxide - 0.03%. In addition to these gases, the atmosphere contains small amounts of neon, krypton, xenon, hydrogen, helium, as well as various aromatic emissions from plants and various impurities: sulfur dioxide, oxides of carbon, nitrogen, and physical impurities. The high oxygen content in the atmosphere contributed to an increase in metabolism in terrestrial organisms and the emergence of warm-blooded (homeothermic) animals. Oxygen deficiency can occur in accumulations of decomposing plant debris, grain reserves, and the root systems of plants on waterlogged or overly compacted soils can experience a lack of oxygen.
The carbon dioxide content can vary in certain areas of the surface layer of air within quite significant limits. In the absence of wind in large cities, its concentration can increase tens of times. There are regular daily and seasonal changes in the carbon dioxide content in the surface layer of air, caused by changes in the intensity of photosynthesis and respiration of organisms. In high concentrations, carbon dioxide is toxic, and in low concentrations it reduces the rate of photosynthesis.
Air nitrogen is an inert gas for most organisms in the terrestrial environment, but many prokaryotic organisms (nodule bacteria, Azotobacter, clostridia, cyanobacteria, etc.) have the ability to bind it and involve it in the biological cycle.
Many contaminants released into the air, mainly as a result of human activities, can significantly affect organisms. For example, sulfur oxide is toxic to plants even in very low concentrations; it causes the destruction of chlorophyll, damages the structure of chloroplasts, and inhibits the processes of photosynthesis and respiration. The damage to plants by toxic gases varies and depends on their anatomical, morphological, physiological, biological and other characteristics. For example, lichens, spruce, pine, oak, and larch are especially sensitive to industrial gases. The most resistant are Canadian poplar, balsam poplar, ash maple, thuja, red elderberry and some others.
Light mode. Solar radiation reaching the Earth's surface is the main source of energy for maintaining the thermal balance of the planet, the water metabolism of organisms, and the creation of organic matter by plants, which ultimately makes it possible to form an environment capable of satisfying the vital needs of organisms. Solar radiation reaching the Earth's surface includes ultraviolet rays with a wavelength of 290–380 nm, visible rays with a wavelength of 380–750 nm, and infrared rays with a wavelength of 750–4000 nm. Ultraviolet rays are highly chemically active and in large doses are harmful to organisms. In moderate doses in the range of 300–380 nm, they stimulate cell division and growth, promote the synthesis of vitamins, antibiotics, pigments (for example, in humans - tanning, in fish and amphibians - dark caviar), and increase plant resistance to diseases. Infrared rays have a thermal effect. Photosynthetic bacteria (green, purple) are able to absorb infrared rays in the range of 800–1100 nm and exist only at their expense. Approximately 50% of solar radiation comes from visible light, which has different ecological significance in the life of autotrophic and heterotrophic organisms. Green plants need light for the process of photosynthesis, the formation of chlorophyll, and the formation of chloroplast structure. It affects gas exchange and transpiration, the structure of organs and tissues, and the growth and development of plants.
For animals, visible light is necessary for orientation in the environment. In some animals, visual perception extends to the ultraviolet and near-infrared parts of the spectrum.
The light regime of any habitat is determined by the intensity of direct and diffuse light, its quantity, spectral composition, as well as the reflectivity of the surface on which the light falls. These elements of the light regime are very variable and depend on the geographic latitude of the area, the height of the sun above the horizon, the length of the day, the state of the atmosphere, the nature of the earth's surface, relief, time of day and season of the year. In this regard, during the long process of evolution, terrestrial organisms have developed various adaptations to the light regime of their habitats.
Plant adaptations. In relation to lighting conditions, three main ecological groups of plants are distinguished: light-loving (heliophytes); shade-loving (sciophytes); shade-tolerant.
Heliophytes– plants of open, well-lit habitats. They do not tolerate shade. Examples of them can be steppe and meadow plants of the upper tier of the community, species of deserts, alpine meadows, etc.
Sciophytes– do not tolerate strong lighting from direct sunlight. These are plants of the lower tiers of shady forests, caves, rock crevices, etc.
Shade-tolerant plants have a wide ecological valency in relation to light. They grow better under high light intensity, but also tolerate shading well, and adapt to changing light conditions more easily than other plants.
Each group of plants considered is characterized by certain anatomical, morphological, physiological and seasonal adaptations to light conditions.
One of the most obvious differences in the appearance of light-loving and shade-loving plants is the unequal size of the leaves. In heliophytes they are usually small or with a dissected leaf blade. This is especially clearly seen when comparing related species growing in different lighting conditions (field violet and forest violets, spreading bell growing in meadows, and forest bell, etc.). The tendency to increase the size of leaves in relation to the entire volume of plants is clearly expressed in herbaceous plants of the spruce forest: wood sorrel, bifolia, crow's eye, etc.
In light-loving plants, in order to reduce the amount of solar radiation, the leaves are arranged vertically or at an acute angle to the horizontal plane. In shade-loving plants, the leaves are arranged predominantly horizontally, which allows them to receive the maximum amount of incident light. The leaf surface of many heliophytes is shiny, facilitating the reflection of rays, covered with a waxy coating, thick cuticle or dense pubescence.
The leaves of shade-loving and light-loving plants also differ in their anatomical structure. Light leaves have more mechanical tissues and the leaf blade is thicker than shadow leaves. The mesophyll cells are small, densely arranged, the chloroplasts in them are small and light-colored, and occupy a wall position. The leaf mesophyll is differentiated into columnar and spongy tissues.
Sciophytes have thinner leaves, the cuticle is absent or poorly developed. Mesophyll is not differentiated into columnar and spongy tissue. There are fewer elements of mechanical tissues and chloroplasts in shade leaves, but they are larger than those of heliophytes. Shoots of light-loving plants often have shortened internodes, are highly branched, and often rosette-shaped.
Physiological adaptations of plants to light are manifested in changes in growth processes, intensity of photosynthesis, respiration, transpiration, composition and quantity of pigments. It is known that in light-loving plants, when there is a lack of light, the stems become elongated. The leaves of shade-loving plants contain more chlorophyll than light-loving ones, so they have a richer dark green color. The intensity of photosynthesis in heliophytes is maximum at high illumination (within 500-1000 lux or more), and in sciophytes - at low amounts of light (50-200 lux).
One of the forms of physiological adaptation of plants to a lack of light is the transition of some species to heterotrophic nutrition. An example of such plants are species of shady spruce forests - creeping goodyera, true nesting plant, and common spruce grass. They live off dead organic matter, i.e. are saprophytes.
Seasonal adaptations of plants to lighting conditions are manifested in habitats where the light regime periodically changes. In this case, plants in different seasons can manifest themselves either as light-loving or shade-tolerant. For example, in the spring in deciduous forests, the leaves of the shoots of the common pine tree have a light structure and are characterized by a high intensity of photosynthesis. The leaves of the summer shoots of the tree, which develop after the leafing of trees and shrubs, have a typical shadow structure. The attitude towards the light regime in plants can change during the process of ontogenesis and as a result of the complex influence of environmental factors. Seedlings and young plants of many meadow and forest species are more shade-tolerant than adult plants. Requirements for the light regime sometimes change in plants when they find themselves in different climatic and edaphic conditions. For example, forest taiga species - blueberry, bileaf - in the forest-tundra and tundra grow well in open habitats.
One of the factors regulating the seasonal development of organisms is the length of the day. The ability of plants and animals to respond to day length is called photoperiodic reaction(FPR), and the range of phenomena regulated by the length of the day is called photoperiodism. Based on the type of photoperiodic reaction, the following main groups of plants are distinguished:
1. Short day plants, which require less than 12 hours of light per day to begin flowering. These, as a rule, come from the southern regions (chrysanthemums, dahlias, asters, tobacco, etc.).
2. Long Day Plants– for flowering they need a day length of 12 hours or more (flax, oats, potatoes, radishes).
3. Neutral to day length plants. For them, the length of the day is indifferent; flowering occurs at any length (dandelion, tomatoes, mustard, etc.).
The length of the day affects not only the passage of the plant’s generative phases, but also its productivity and resistance to infectious diseases. It also plays an important role in the geographical distribution of plants and regulation of their seasonal development. Species common in northern latitudes are predominantly long-day, while in the tropics and subtropics they are mainly short-day or neutral. However, this pattern is not absolute. Thus, long-day species are found in the mountains of the tropical and subtropical zones. Many varieties of wheat, flax, barley and other cultivated plants originating from the southern regions have a long-day FPR. Research has shown that when temperatures drop, long-day plants can develop normally under short-day conditions.
Light in the life of animals. Animals need light for orientation in space; it also affects metabolic processes, behavior, and the life cycle. Completeness of visual perception environment depends on the level of evolutionary development. Many invertebrates have only light-sensitive cells surrounded by pigment, while unicellular organisms have a light-sensitive portion of the cytoplasm. The most perfect eyes of vertebrates are cephalopods and insects. They allow you to perceive the shape and size of objects, color, and determine distance. Three-dimensional vision is typical for humans, primates, and some birds (eagles, falcons, owls). The development of vision and its features also depend on the environmental conditions and lifestyle of specific species. In cave dwellers, the eyes can be completely or partially reduced, as, for example, in the blind beetles, ground beetles, proteas, etc.
Different species of animals are able to withstand lighting of a certain spectral composition, duration and intensity. There are light-loving and shade-loving, euryphotic And stenophotic species. Nocturnal and crepuscular mammals (voles, mice, etc.) tolerate direct sunlight for only 5–30 minutes, and daytime mammals – for several hours. However, in bright sunlight, even desert views lizards cannot withstand irradiation for long, since within 5–10 minutes their body temperature rises to +50–56ºС and the animals die. Illumination of the eggs of many insects accelerates their development, but up to certain limits (different for different species), after which development stops. An adaptation to protection from excessive solar radiation is the pigmented integument of some organs: in reptiles - the abdominal cavity, reproductive organs, etc. Animals avoid excessive radiation by going into shelters, hiding in the shadows, etc.
Daily and seasonal changes in light conditions determine not only changes in activity, but also periods of reproduction, migration, and molting. The appearance of nocturnal insects and the disappearance of daytime insects in the morning or evening occur at a specific lighting brightness for each species. For example, the marbled beetle appears 5–6 minutes after sunset. When songbirds wake up varies from season to season. Depending on the illumination, the hunting areas of birds change. Thus, woodpeckers, tits, and flycatchers hunt in the depths of the forest during the day, and in open places in the morning and evening. Animals navigate using vision during flights and migrations. Birds choose their flight direction with amazing accuracy, guided by the sun and stars. This innate ability is created natural selection as a system of instincts. The ability for such orientation is also characteristic of other animals, for example, bees. Bees that have found nectar transmit information to others about where to fly for a bribe, using the sun as a guide.
Light conditions limit the geographic distribution of some animals. Thus, long days during the summer months in the Arctic and temperate zones attract birds and some mammals there, as it allows them to get the right amount of food (tits, nuthatches, waxwings, etc.), and in the fall they migrate south. The light regime has the opposite effect on the distribution of nocturnal animals. In the north they are rare, and in the south they even predominate over daytime species.
Temperature. The intensity of all chemical reactions components of metabolism. Therefore, the boundaries of the existence of life are the temperatures at which normal functioning of proteins is possible, on average from 0 to +50ºС. However, these thresholds are not the same for different types organisms. Thanks to the presence of specialized enzyme systems, some organisms have adapted to live at temperatures beyond these limits. Species adapted to life in cold conditions belong to the ecological group cryophiles. In the process of evolution, they have developed biochemical adaptations that allow them to maintain cellular metabolism at low temperatures, as well as resist freezing or increase resistance to it. The accumulation of special substances in the cells - antifreeze, which prevent the formation of ice crystals in the body, helps to resist freezing. Such adaptations have been identified in some Arctic fish of the nototheniaceae and cod family, which swim in the waters of the Arctic Ocean, with a body temperature of –1.86ºС.
The extremely low temperature at which cell activity is still possible has been recorded for microorganisms – down to –10–12ºС. Resistance to freezing in some species is associated with the accumulation in their body of organic substances, such as glycerin, mannitol, and sorbitol, which prevent the crystallization of intracellular solutions, which allows them to survive critical frosty periods in an inactive state (torpor, cryptobiosis). Thus, some insects can withstand temperatures down to –47–50ºС in winter in this state. Cryophiles include many bacteria, lichens, fungi, mosses, arthropods, etc.
Species whose optimum life activity is confined to the area of high temperatures are classified as ecological group thermophiles.
Bacteria are the most resistant to high temperatures, many of which can grow and multiply at +60–75ºС. Some bacteria living in hot springs grow at temperatures of +85–90ºС, and one type of archaebacteria has been found to grow and divide at temperatures exceeding +110ºС. Spore-forming bacteria can withstand +200ºС in an inactive state for tens of minutes. Thermophilic species are also found among fungi, protozoa, plants and animals, but their level of resistance to high temperatures is lower than that of bacteria. Higher plants of steppes and deserts can tolerate short-term heating up to +50–60ºС, but their photosynthesis is already inhibited by temperatures exceeding +40ºС. At a body temperature of +42–43ºС, heat death occurs in most animals.
The temperature regime in the terrestrial environment varies widely and depends on many factors: latitude, altitude, proximity of water bodies, time of year and day, state of the atmosphere, vegetation cover, etc. During the evolution of organisms, various adaptations have been developed that make it possible to regulate metabolism when the ambient temperature changes. This is achieved in two ways: 1) biochemical and physiological changes; 2) maintaining body temperature at a more stable level than the ambient temperature. The life activity of most species depends on heat coming from outside, and body temperature depends on the course of external temperatures. Such organisms are called poikilothermic. These include all microorganisms, plants, fungi, invertebrate animals and most chordates. Only birds and mammals are able to maintain a constant body temperature regardless of the ambient temperature. They are called homeothermic.
Adaptation of plants to temperature conditions. The resistance of plants to changes in environmental temperature is different and depends on the specific habitat where their life takes place. Higher plants of moderately warm and moderately cold zones eurytherms. In the active state, they tolerate temperature fluctuations from – 5 to +55ºС. At the same time, there are species that have a very narrow ecological valency in relation to temperature, i.e. are stenothermic. For example, tropical forest plants cannot even tolerate temperatures of +5–+8ºС. Some algae on snow and ice live only at 0ºC. That is, the heat needs of different plant species are not the same and vary over a fairly wide range.
Species living in places with constantly high temperatures, in the process of evolution, acquired anatomical, morphological and physiological adaptations aimed at preventing overheating.
The main anatomical and morphological adaptations include: dense leaf pubescence, shiny leaf surface, which helps reflect sunlight; reduction in leaf area, their vertical position, curling into a tube, etc. Some species are capable of secreting salts, from which crystals are formed on the surface of plants, reflecting the rays of the sun falling on them. In conditions of sufficient moisture effective means from overheating is stomatal transpiration. Among thermophilic species, depending on the degree of their resistance to high temperatures, we can distinguish
1) non-heat resistant plants are damaged already at +30–40ºС;
2) heat-tolerant– tolerate half-hour heating up to +50–60ºС (plants of deserts, steppes, dry subtropics, etc.).
Plants in savannas and dry hardwood forests are regularly affected by fires, where temperatures can rise to hundreds of degrees. Plants that are resistant to fire are called pyrophytes. They have a thick crust on their trunks, impregnated with fire-resistant substances. Their fruits and seeds have thick, often lignified integuments.
The life of many plants passes in conditions of low temperatures. According to the degree of adaptation of plants to conditions of extreme heat deficiency, the following groups can be distinguished:
1) non-cold-resistant plants are severely damaged or killed at temperatures below the freezing point of water. These include plants from tropical areas;
2) non-frost-resistant plants - tolerate low temperatures, but die as soon as ice begins to form in the tissues (some evergreen subtropical plants).
3) frost-resistant plants grow in areas with cold winters.
Resistance to low temperatures is increased by such morphological adaptations of plants as short stature and special forms of growth - creeping, cushion-shaped, which allow them to use the microclimate of the ground layer of air in summer and be protected by snow cover in winter.
More significant for plants are physiological mechanisms adaptations that increase their resistance to cold: leaf fall, dieback aboveground shoots, accumulation of antifreeze in cells, decrease in water content in cells, etc. In frost-resistant plants, in the process of preparing for winter, sugars, proteins, oils accumulate in the organs, the water content in the cytoplasm decreases and its viscosity increases. All these changes reduce the freezing point of tissues.
Many plants are able to remain viable in a frozen state, for example, alpine violet, arctic horseradish, woodlice, daisy, early spring ephemeroids in the forest zone, etc.
Mosses and lichens are able to withstand prolonged freezing in a state of suspended animation. Of great importance in the adaptation of plants to low temperatures is the possibility of maintaining normal life activity by reducing the temperature optimum of physiological processes and the lower temperature limits at which these processes are possible.
In temperate and high latitudes, due to seasonal changes in climatic conditions, plants alternate active and dormant phases in the annual development cycle. Annual plants, after the completion of the growing season, survive the winter in the form of seeds, and perennial plants go into a dormant state. Distinguish deep And compelled peace. Plants in a state of deep dormancy do not respond to favorable thermal conditions. After deep dormancy ends, plants are ready to resume development, but in nature in winter this is impossible due to low temperatures. Therefore, this phase is called forced rest.
Adaptation of animals to temperature conditions. Compared to plants, animals have a greater ability to regulate their body temperature due to their ability to move through space and produce much more of their own internal heat.
The main ways of animal adaptation:
1) chemical thermoregulation– this is a reflex increase in heat production in response to a decrease in environmental temperature, based on a high level of metabolism;
2) physical thermoregulation– is carried out due to the ability to retain heat due to special structural features (presence of hair and feathers, distribution of fat reserves, etc.) and changes in the level of heat transfer;
3) behavioral thermoregulation- this is a search for favorable habitats, a change in posture, the construction of shelters, nests, etc.
For poikilothermic animals, the main way to regulate body temperature is behavioral. In extreme heat, animals hide in the shade and holes. As winter approaches, they seek shelter, build nests, and reduce their activity. Some species are able to maintain optimal body temperature through muscle function. For example, bumblebees warm up their bodies with special muscle contractions, which allows them to feed in cool weather. Some poikilothermic animals avoid overheating by increasing heat loss through evaporation. For example, frogs and lizards in hot weather begin to breathe heavily or keep their mouths open, increasing the evaporation of water through the mucous membranes.
Homeothermic animals are distinguished by very efficient regulation of heat input and output, which allows them to maintain a constant optimal body temperature. Their thermoregulation mechanisms are very diverse. They are characterized chemical thermoregulation, characterized by a high metabolic rate and the production of large amounts of heat. Unlike poikilothermic animals, in warm-blooded animals, when exposed to cold, oxidative processes do not weaken, but intensify. Many animals generate additional heat from muscle and fat tissue. Mammals have specialized brown adipose tissue, in which all the released energy is used to warm the body. It is most developed in animals of cold climates. Maintaining body temperature by increasing heat production requires a large expenditure of energy, so animals, with increased chemical regulation, need a large amount of food or spend a lot of fat reserves. Therefore, the strengthening of chemical regulation has limits determined by the possibility of obtaining food. If there is a lack of food in winter, this method of thermoregulation is environmentally unprofitable.
Physical thermoregulation It is environmentally more beneficial, since adaptation to cold is carried out by retaining heat in the animal’s body. Its factors are skin, thick fur of mammals, feather and down cover of birds, fat deposits, evaporation of water through sweating or through the mucous membranes of the oral cavity and upper respiratory tract, size and shape of the animal’s body. To reduce heat transfer, large body sizes are more advantageous (the larger the body, the smaller its surface per unit mass, and, consequently, heat transfer, and vice versa). For this reason, individuals of closely related species of warm-blooded animals that live in cold conditions are larger in size than those that are common in warm climates. This pattern is called Bergman's rules. Temperature regulation is also carried out through protruding parts of the body - ears, limbs, tails, and olfactory organs. In cold areas, they tend to be smaller in size than in warmer areas ( Allen's rule). For homeothermic organisms, they are also important behavioral methods of thermoregulation, which are very diverse - from changing posture and searching for shelter to constructing complex shelters, nests, and carrying out short and long-distance migrations. Some warm-blooded animals use group behavior. For example, penguins huddle together in a dense heap in severe frost. Inside such a cluster, the temperature is maintained around +37ºС even in the most severe frosts. Camels in the desert also huddle together in extreme heat, but this prevents the surface of the body from becoming too hot.
Combination in various ways chemical, physical and behavioral thermoregulation allows warm-blooded animals to maintain a constant body temperature over a wide range of environmental temperature fluctuations.
Water mode. Normal functioning of the body is possible only with sufficient supply of water. Humidity regimes in the ground-air environment are very diverse - from complete saturation of the air with water vapor in the humid tropics to the almost complete absence of moisture in the air and soil of deserts. For example, in the Sinai Desert the annual rainfall is 10–15 mm, while in the Libyan Desert (in Aswan) there is none at all. The water supply of terrestrial organisms depends on the precipitation regime, the presence of soil moisture reserves, reservoirs, groundwater levels, terrain, atmospheric circulation characteristics, etc. This has led to the development of many adaptations in terrestrial organisms to various moisture regimes of habitats.
Adaptation of plants to water regime. Lower terrestrial plants absorb water from the substrate by parts of the thallus or rhizoids immersed in it, and moisture from the atmosphere by the entire surface of the body.
Among higher plants, mosses absorb water from the soil through rhizoids or the lower part of the stem (sphagnum mosses), while most others absorb water through their roots. The flow of water into the plant depends on the magnitude of the suction force of the root cells, the degree of branching of the root system and the depth of penetration of the roots into the soil. Root systems are very plastic and respond to changing conditions, primarily moisture.
When there is a lack of moisture in the surface horizons of the soil, many plants have root systems that penetrate deep into the soil, but are weakly branched, as, for example, in saxaul, camel thorn, Scots pine, rough cornflower, etc. In many cereals, on the contrary, the root systems are strongly branched and grow in the surface layers of the soil (in rye, wheat, feather grass, etc.). The water entering the plant is carried through the xylem to all organs, where it is spent on life processes. On average, 0.5% goes to photosynthesis, and the rest to replenish losses from evaporation and maintain turgor. The water balance of a plant remains balanced if the absorption of water, its conduction and expenditure are harmoniously coordinated with each other. Depending on their ability to regulate the water balance of their body, land plants are divided into poikihydride and homoyohydride.
Poikihydrid plants are unable to actively regulate their water balance. They do not have devices that help retain water in their tissues. The water content in cells is determined by air humidity and depends on its fluctuations. Poikilohydride plants include terrestrial algae, lichens, some mosses and tropical forest ferns. During the dry period, these plants dry out almost to an air-dry state, but after rain they “come to life” again and turn green.
Homoyohydride plants capable of maintaining the water content in cells at a relatively constant level. These include most higher land plants. Their cells have a large central vacuole, due to which there is always a supply of water. In addition, transpiration is regulated by the stomatal apparatus, and the shoots are covered with an epidermis with a cuticle that is poorly permeable to water.
However, the ability of plants to regulate their water metabolism is not the same. Depending on their adaptability to the moisture conditions of habitats, three main ecological groups are distinguished: hygrophytes, xerophytes and mesophytes.
Hygrophytes- These are plants of wet habitats: swamps, damp meadows and forests, and the banks of reservoirs. They cannot tolerate water deficiency and react to decreased soil and air humidity by rapid wilting or growth inhibition. Their leaf blades are wide and do not have a thick cuticle. Mesophyll cells are loosely arranged, with large intercellular spaces between them. The stomata of hygrophytes are usually wide open and are often located on both sides of the leaf blade. In this regard, their transpiration rate is very high. In some plants in highly humid habitats, excess water is removed through hydathodes (water stomata) located along the edge of the leaf. Excessive soil moisture leads to a decrease in the oxygen content in it, which complicates the breathing and suction function of the roots. Therefore, the roots of hygrophytes are located in the surface horizons of the soil, they are weakly branched, and there are few root hairs on them. The organs of many herbaceous hygrophytes have a well-developed system of intercellular spaces through which atmospheric air enters. Plants that live on heavily waterlogged soils, periodically flooded with water, form special respiratory roots, such as swamp cypress, or support roots, such as mangrove woody plants.
Xerophytes In an active state, they are able to tolerate significant prolonged dryness of air and soil. They are widespread in steppes, deserts, dry subtropics, etc. In the temperate climate zone, they settle on dry sandy and sandy loam soils, on elevated areas of the relief. The ability of xerophytes to tolerate a lack of moisture is due to their anatomical, morphological and physiological characteristics. Based on these characteristics, they are divided into two groups: succulents And sclerophytes.
Succulents- perennial plants with succulent, fleshy leaves or stems, in which water-storing tissue is highly developed. There are leaf succulents - aloe, agaves, sedums, young and stem ones, in which the leaves are reduced, and the ground parts are represented by fleshy stems (cacti, some milkweeds). A distinctive feature of succulents is their ability to store large amounts of water and use it extremely economically. Their transpiration rate is very low, since there are very few stomata, they are often immersed in the tissue of the leaf or stem and are usually closed during the day, which helps them limit water consumption. Closing the stomata during the day impedes the processes of photosynthesis and gas exchange, so succulents have developed a special route of photosynthesis, which partially uses carbon dioxide released during respiration. In this regard, their photosynthesis rate is low, which is associated with slow growth and rather low competitiveness. Succulents are characterized by low osmotic pressure of cell sap, with the exception of those that grow in saline soils. Their root systems are superficial, highly branched and fast growing.
Sclerophytes are hard, dry-looking plants due to the large amount of mechanical tissue and low water content of the leaves and stems. The leaves of many species are small, narrow or reduced to scales and spines; often have dense pubescence (cat's paw, silver cinquefoil, many wormwoods, etc.) or a waxy coating (Russian cornflower, etc.). Their root systems are well developed and often have a total mass many times greater than the above-ground parts of plants. Various physiological adaptations also help sclerophytes successfully withstand the lack of moisture: high osmotic pressure of cell sap, resistance to tissue dehydration, high water-holding capacity of tissues and cells due to the high viscosity of the cytoplasm. Many sclerophytes use the most favorable periods of the year for vegetation, and when drought occurs, they sharply reduce vital processes. All of the listed properties of xerophytes contribute to increasing their drought resistance.
Mesophytes grow in average moisture conditions. They are more demanding of moisture than xerophytes, and less demanding than hygrophytes. Leaf tissues of mesophytes are differentiated into columnar and spongy parenchyma. The integumentary tissues may have some xeromorphic features (sparse pubescence, thickened cuticle layer). But they are less pronounced than in xerophytes. Root systems can penetrate deep into the soil or be located in surface horizons. In terms of their ecological needs, mesophytes are a very diverse group. Thus, among meadow and forest mesophytes there are species with increased love for moisture, which are characterized by a high water content in the tissues and a rather weak water-holding capacity. These are meadow foxtail, swamp bluegrass, soddy meadow grass, Linnaeus holocum and many others.
In habitats with periodic or constant (small) lack of moisture, mesophytes have signs of xeromorphic organization and increased physiological resistance to drought. Examples of such plants are pedunculate oak, mountain clover, middle plantain, crescent alfalfa, etc.
Animal adaptations. In relation to the water regime, animals can be divided into hygrophiles (moisture-loving), xerophiles (dry-loving) and mesophiles (preferring average moisture conditions). Examples of hygrophiles are wood lice, mosquitoes, springtails, dragonflies, etc. All of them cannot tolerate significant water deficits and do not tolerate even short-term drought. Monitor lizards, camels, desert locusts, darkling beetles, etc. are xerophilic. They inhabit the most arid habitats.
Animals obtain water through drinking, food and through the oxidation of organic substances. Many mammals and birds (elephants, lions, hyenas, swallows, swifts, etc.) need drinking water. Desert species such as jerboas, African gerbils, and the American kangaroo rat can survive without drinking water. Clothes moth caterpillars, granary and rice weevils, and many others live exclusively on metabolic water.
Animals have typical ways to regulate water balance: morphological, physiological, behavioral.
TO morphological methods of maintaining water balance include formations that help retain water in the body: shells of land snails, keratinized integuments of reptiles, weak water permeability of insect integuments, etc. It has been shown that the permeability of insect integuments does not depend on the structure of chitin, but is determined by the thinnest waxy layer covering its surface . The destruction of this layer sharply increases evaporation through the covers.
TO physiological adaptations for regulating water metabolism include the ability to form metabolic moisture, saving water during the excretion of urine and feces, tolerance to dehydration, changes in sweating and water release through the mucous membranes. Saving water in the digestive tract is achieved by the absorption of water by the intestines and the formation of practically dehydrated feces. In birds and reptiles, the end product of nitrogen metabolism is uric acid, for the removal of which practically no water is consumed. Active regulation of sweating and evaporation of moisture from the surface of the respiratory tract is widely used by homeothermic animals. For example, in the most extreme cases of moisture deficiency in a camel, sweating stops and evaporation from the respiratory tract is sharply reduced, which leads to water retention in the body. Evaporation, associated with the need for thermoregulation, can cause dehydration of the body, so many small warm-blooded animals in dry and hot climates avoid exposure to heat and save moisture by hiding underground.
In poikilothermic animals, an increase in body temperature following warming of the air allows them to avoid unnecessary water losses, but they cannot completely avoid evaporative losses. Therefore, for cold-blooded animals, the main way to maintain water balance when living in arid conditions is to avoid excessive heat loads. Therefore, in the complex of adaptations to the water regime of the terrestrial environment, they are of great importance behavioral ways regulation of water balance. These include special forms of behavior: digging holes, searching for reservoirs, choosing habitats, etc. This is especially important for herbivores and granivores. For many of them, the presence of bodies of water is a prerequisite for settling in arid areas. For example, the distribution in the desert of such species as the Cape buffalo, waterbuck, and some antelopes completely depends on the availability of watering places. Many reptiles and small mammals live in burrows where relatively low temperatures and high humidity promote water exchange. Birds often use hollows, shady tree crowns, etc.
4.3.1. General characteristics ground-air environment.
4.3.2. Solar radiation and its role in the life of terrestrial organisms.
4.3.3. The influence of temperature on living organisms.
4.3.4. Specifics of heat exchange in plants and animals.
4.3.5. The role of humidity in the life of terrestrial organisms.
4.3.6. adaptation of terrestrial plants and animals to the water regime.
4.3.7. The combined effect of temperature and humidity.
4.3.8. Atmospheric pollution and basic methods for removing impurities from emissions.
4.3.1 General characteristics of the ground-air environment
In the process of evolution of the biosphere, the land-air environment was developed by living organisms much later than the aquatic environment. This is due to the fact that reaching land required a significant restructuring of the organization of plants and animals, their adaptation to life in a gaseous environment with low density, high O2 content, high light intensity and significant fluctuations in temperature and humidity depending on geographical location, season and time of day.
Low density and, as a consequence, insignificant lifting force of air, required the development of mechanical tissues in plants and a solid (less often hydrostatic) skeleton in animals. The low lifting force of the air has led to the fact that terrestrial organisms are inferior in size and weight to aquatic ones. At the same time, the low density of air and its low resistance allowed almost 75% of all terrestrial animals to adapt to active flight or passive movement in moving air masses. The wind is also a kind of shaping factor - it gives the trees a flag-like shape and eliminates bad flyers.
Now the most important ecological features of our planet are determined by the presence and properties of its gas shell of the atmosphere (atmos-vapour). It is believed that it was formed from stage 4 from gases released during the formation of the planet, under the influence of solar radiation, chemical reactions between its components and rocks, and the activity of living organisms. Currently, the atmosphere has a layered spherical structure, which is mainly determined by the peculiarity of the vertical temperature distribution (thermal structure).
Usually the following layers are not distinguished:
Troposphere (tropos - turn), extending to a height of 7-18 km and including about 80% of the total air mass. Here there is a temperature difference from +70 to -;
The stratosphere (stratos-layer), which extends up to 50-55 km and is characterized by an increase in temperature at the upper boundary to +;
The mesosphere, which extends up to 80 km. The temperature varies from plus +10 to -. Noctilucent clouds form here.
The ionosphere, extending up to 800 -1300 km. It is distinguished by high ionization of gases, sharp fluctuations in the magnetic field and aurora; the temperature varies from - 70 to plus.
The exosphere is a sphere of leakage of H2 and He, forming a corona up to 10-20 thousand km around the earth. The temperature here reaches
Each of them is distinguished by a certain combination of physical and chemical factors, including the most solar radiation, temperature, humidity and chemical composition. Their complex impact is most clearly manifested in the troposphere.
4.3.2. Solar radiation and its role in the life of terrestrial organisms.
Solar radiation enters the Earth in the form of elementary particles of different wavelengths, the total energy of which is 2 cal/-min (solar constant). Of the total amount, 42% of radiation is reflected into outer space, 15% is absorbed by the atmosphere and only 43% reaches the earth's surface (including 27% direct and 16% scattered). The most important are:
Electromagnetic waves (Hertz waves) affect the orientation abilities of insects, worms and birds;
X-rays, which in large doses disrupt the functions of the most important life support systems, and in small doses cause mutations in the gene pool;
Ultraviolet rays promote the formation of protective pigments in the skin and provitamin D, and have a bactericidal effect;
Infrared rays affecting the course of oxidative processes and motor reactions;
Visible rays (about 50% of the entire spectrum). Visible rays are of greatest importance for plants, since they affect the formation of chlorophyll, provide photosynthesis, the synthesis of proteins and nucleic acids, influence growth processes, have a formative effect, determine the timing of flowering, fruiting and other phenological phenomena. However, different parts of the visible spectrum have different effects. Thus, plants that absorb red and orange rays are usually located in open areas, and in the forest they occupy the upper tiers; catching green and yellow rays - occupy the lower tiers (in the shade).
Different durations of illumination in different natural zones determined the formation of long-day species (inhabitants of high and temperate latitudes) and short-day species (inhabitants of low latitudes). A number of adaptations have also been developed in relation to the light regime. Based on their totality, plants are distinguished:
Photophilous (heliophytes), inhabiting open places. They are distinguished by their stockiness, strong branching, rosette, leaves with photosynthetic ability;
Shade-loving (sciophytes) are the antipodes of the former;
Shade-tolerant, with intermediate characteristics (these are the majority of plants in our forests).
For animals, light has less, mainly informational value (facilitates the search for food, sexual partners, ensures the avoidance of enemies, orientation in space). However, the completeness of their visual perception is not the same and depends on the evolutionary level of the group and the lifestyle of specific species. In the process of evolution, various animals adapted to lighting of a certain duration (long- and short-day), in conditions of low (night, twilight - photophobes) or strong illumination (daytime - photophiles). The attitude to illumination also affects the distribution of animals. Thus, in high and temperate latitudes there are very few nocturnal species, and in the tropics the number of daytime and nocturnal species is approximately the same. At the same time, nocturnal animals are less fertile in long day conditions. Daily and seasonal changes in illumination and the total amount of light (photoperiodism) also determine the alternation of periods of rest and activity of animals and a number of associated cyclic biological phenomena (reproduction, molting, migrations). The light regime here acts as a signaling factor, a unique mechanism that includes a number of physiological processes and internal biological clocks.
Features of the ground-air habitat. There is enough light and air in the ground-air environment. But air humidity and temperature vary greatly. In swampy areas there is an excessive amount of moisture, in the steppes it is much less. Daily and seasonal temperature fluctuations are also noticeable.
Adaptation of organisms to life in conditions of different temperatures and humidity. A large number of adaptations of organisms in the ground-air environment are associated with air temperature and humidity. Animals of the steppe (scorpions, tarantula and karakurt spiders, gophers, voles) hide from the heat in burrows. Increased evaporation of water from the leaves protects the plant from the hot rays of the sun. In animals, such an adaptation is the secretion of sweat.
With the onset of cold weather, birds fly away to warmer regions in order to return in the spring to the place where they were born and where they will give birth. A feature of the ground-air environment in the southern regions of Ukraine or Crimea is an insufficient amount of moisture.
Check out Fig. 151 with plants that have adapted to similar conditions.
Adaptation of organisms to movement in the ground-air environment. For many animals of the land-air environment, movement on the earth's surface or in the air is important. To do this, they have developed certain adaptations, and their limbs have a different structure. Some have adapted to running (wolf, horse), others to jumping (kangaroo, jerboa, grasshopper), and others to flight (birds, bats, insects) (Fig. 152). Snakes and vipers have no limbs. They move by bending their body.
Significantly fewer organisms have adapted to life high in the mountains, since there is little soil, moisture and air for plants, and animals have difficulty moving. But some animals, for example mouflon mountain goats (Fig. 154), are capable of moving almost vertically up and down if there are at least slight unevenness. Therefore, they can live high in the mountains. Material from the site
Adaptation of organisms to different lighting conditions. One of the adaptations of plants to different lighting is the direction of the leaves towards the light. In the shade, the leaves are arranged horizontally: this way they receive more light rays. Light-loving snowdrops and ryast develop and bloom early spring. During this period, they have enough light, since leaves have not yet appeared on the trees in the forest.
The adaptation of animals to the specified factor of the ground-air habitat is the structure and size of the eyes. Most animals in this environment have well-developed organs of vision. For example, a hawk from the height of its flight sees a mouse running across a field.
Over many centuries of development, organisms of the land-air environment have adapted to the influence of its factors.
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On this page there is material on the following topics:
- report on land-air habitat
- adaptability of the snowy owl to its environment
- essay on the topic of ground-air environment
- land-air habitat animals
- essay description of land-air habitat
Any habitat is a complex system, which is distinguished by its unique set of abiotic and biotic factors, which, in essence, shape this environment. Evolutionarily, the land-air environment arose later than the aquatic environment, which is associated with chemical transformations of the composition atmospheric air. Most of the organisms with a core 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 topsoil ( 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 we 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 temperature and low humidity in eukaryotes, various idioadaptations arise, the purpose of which is to maintain the vital level of water (transformation of plant leaves into needles, accumulation of fat in the humps of a camel).
For terrestrial animals the phenomenon is characteristic photoperiodism, thus most animals are active only during the day or only at night. The terrestrial environment is also characterized by significant fluctuations in temperature, humidity and light intensity. Changes in these factors are associated with geographic location, changing seasons, and time of day. Due to the low density and pressure of the atmosphere, muscle and bone tissue has greatly developed and become more complex.
Vertebrates developed complex limbs adapted to support the body and move on solid substrates in conditions of low atmospheric density. Plants have a progressive root system, which allows them to gain a foothold in the soil and transport substances to a considerable height. Land plants also have developed mechanical, basal tissues, phloem and xylem. Most plants have adaptations that protect them from excess transpiration.
Soil
Although soil is classified as a terrestrial-air habitat, it is very different from the atmosphere in its physical properties:
- High density and pressure.
- Insufficient oxygen.
- Low amplitude of temperature fluctuations.
- Low light intensity.
In this regard, underground inhabitants have their own adaptations that are distinguishable from terrestrial animals.
Aquatic habitat
An environment that includes the entire hydrosphere, both salt and fresh water bodies. This environment is characterized by less diversity of life and its own special conditions. It is inhabited by small invertebrates that form plankton, cartilaginous and bony fish, mollusc worms, and a few species of mammals
Oxygen concentration varies significantly with depth. In places where the atmosphere and hydrosphere meet, 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 body shape of most underwater inhabitants. The amplitude of temperature changes is small, since the heat transfer of water is much less than that of the earth's surface.
Differences between the aquatic and land-air environments
As already mentioned, the main distinctive features different habitats are determined abiotic factors. The land-air environment is characterized by great 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, season and natural climate zone. In the aquatic environment, most of the nutrient organic substances are located in the water column or on its surface, only a small proportion is located at the bottom; in the ground-air environment, all organic substances are located on the surface.
Terrestrial inhabitants are distinguished by better development of sensory systems and nervous system in general, the musculoskeletal, circulatory and respiratory systems have also changed significantly. The skins are very different because they are functionally different. Lower plants (algae) are common under water, which in most cases do not have real organs; for example, rhizoids serve as attachment organs. The distribution of aquatic inhabitants is often associated with warm underwater currents. Along with the differences between these habitats, there are animals that have adapted to live in both. These animals include Amphibians.
WATER ENVIRONMENT
The aquatic environment of life (hydrosphere) occupies 71% of the globe's area. More than 98% of the water is concentrated in the seas and oceans, 1.24% is the ice of the polar regions, 0.45% is the fresh water of rivers, lakes, and swamps.
There are two ecological areas in the world's oceans:
water column - pelagic, and the bottom - benthal.
The aquatic environment is home to approximately 150,000 species of animals, or about 7% of their total number, and 10,000 species of plants – 8%. The following are distinguished: ecological groups of aquatic organisms. Pelagial - inhabited by organisms divided into nekton and plankton.
Nekton (nektos - floating) - This is a collection of pelagic actively moving animals that do not have a direct connection with the bottom. These are mainly large animals capable of traveling long distances and strong water currents. They are characterized by a streamlined body shape and well-developed organs of movement (fish, squid, pinnipeds, whales). In fresh waters, in addition to fish, nekton includes amphibians and actively moving insects.
Plankton (wandering, floating) - This is a set of pelagic organisms that do not have the ability for rapid active movements. They are divided into phyto- and zooplankton (small crustaceans, protozoa - foraminifera, radiolarians; jellyfish, pteropods). Phytoplankton – diatoms and green algae.
Neuston– a set of organisms that inhabit the surface film of water at the border with the air. These are the larvae of decapods, barnacles, copepods, gastropods and bivalves, echinoderms, and fish. Passing through the larval stage, they leave the surface layer, which served them as a refuge, and move to live on the bottom or pelagic zone.
Plaiston – this is a collection of organisms, part of the body of which is above the surface of the water, and the other in the water - duckweed, siphonophores.
Benthos (depth) - a collection of organisms that live at the bottom of water bodies. It is divided into phytobenthos and zoobenthos. Phytobenthos - algae - diatoms, green, brown, red and bacteria; along the coasts there are flowering plants - zoster, ruppia. Zoobenthos – foraminifera, sponges, coelenterates, worms, mollusks, fish.
In the life of aquatic organisms, an important role is played by the vertical movement of water, density, temperature, light, salt, gas (oxygen and carbon dioxide content) regimes, and the concentration of hydrogen ions (pH).
Temperature: It differs in water, firstly, by less heat influx, and secondly, by greater stability than on land. Part of the thermal energy arriving at the surface of the water is reflected, while part is spent on evaporation. The evaporation of water from the surface of reservoirs, which consumes about 2263.8 J/g, prevents overheating of the lower layers, and the formation of ice, which releases the heat of fusion (333.48 J/g), slows down their cooling. Temperature changes in flowing waters follow its changes in the surrounding air, differing in smaller amplitude.
In lakes and ponds of temperate latitudes, the thermal regime is determined by a well-known physical phenomenon - water has a maximum density at 4 o C. The water in them is clearly divided into three layers:
1. epilimnion- the upper layer whose temperature experiences sharp seasonal fluctuations;
2. metalimnion– transitional layer of temperature jump, there is a sharp temperature difference;
3. hypolimnion- a deep-sea layer reaching to the very bottom, where the temperature changes slightly throughout the year.
In summer, the warmest layers of water are located at the surface, and the coldest ones are located at the bottom. This type layer-by-layer distribution of temperatures in a reservoir is called direct stratification. In winter, as the temperature drops, reverse stratification: the surface layer has a temperature close to 0 C, at the bottom the temperature is about 4 C, which corresponds to its maximum density. Thus, the temperature increases with depth. This phenomenon is called temperature dichotomy, observed in most lakes in the temperate zone in summer and winter. As a result of temperature dichotomy, vertical circulation is disrupted - a period of temporary stagnation ensues - stagnation.
In spring, surface water, due to heating to 4C, becomes denser and sinks deeper, and warmer water rises from the depths to take its place. As a result of such vertical circulation, homothermy occurs in the reservoir, i.e. for some time the temperature of the entire water mass equalizes. With a further increase in temperature, the upper layers become less and less dense and no longer sink down - summer stagnation. In autumn, the surface layer cools, becomes denser and sinks deeper, displacing warmer water to the surface. This occurs before the onset of autumn homothermy. When surface waters cool below 4C, they become less dense and again remain on the surface. As a result, water circulation stops and winter stagnation occurs.
Water is characterized by significant density(800 times) superior to air) and viscosity. IN On average, in the water column, for every 10 m of depth, pressure increases by 1 atm. These features affect plants in the fact that their mechanical tissue develops very weakly or not at all, so their stems are very elastic and bend easily. Most aquatic plants are characterized by buoyancy and the ability to be suspended in the water column; in many aquatic animals, the integument is lubricated with mucus, which reduces friction when moving, and the body takes on a streamlined shape. Many inhabitants are relatively stenobatic and confined to certain depths.
Transparency and light mode. This especially affects the distribution of plants: in muddy reservoirs they live only in the surface layer. The light regime is also determined by the natural decrease in light with depth due to the fact that water absorbs sunlight. At the same time, rays with different wavelengths are absorbed differently: red ones are absorbed most quickly, while blue-green ones penetrate to significant depths. The color of the environment changes, gradually moving from greenish to green, blue, indigo, blue-violet, replaced by constant darkness. Accordingly, with depth, green algae are replaced by brown and red ones, the pigments of which are adapted to capture solar rays of different wavelengths. The color of animals also naturally changes with depth. Brightly and variously colored animals live in the surface layers of water, while deep-sea species are devoid of pigments. The twilight habitat is inhabited by animals painted in colors with a reddish tint, which helps them hide from enemies, since the red color in blue-violet rays is perceived as black.
The absorption of light in water is stronger, the lower its transparency. Transparency is characterized by extreme depth, where a specially lowered Secchi disk (a white disk with a diameter of 20 cm) is still visible. Hence, the boundaries of photosynthesis zones vary greatly in different bodies of water. In the cleanest waters, the photosynthetic zone reaches a depth of 200 m.
Salinity of water. Water is an excellent solvent for many mineral compounds. As a result, natural reservoirs have a certain chemical composition. The most important are sulfates, carbonates, and chlorides. The amount of dissolved salts per 1 liter of water in fresh water bodies does not exceed 0.5 g, in seas and oceans - 35 g. Freshwater plants and animals live in a hypotonic environment, i.e. an environment in which the concentration of dissolved substances is lower than in body fluids and tissues. Due to the difference in osmotic pressure outside and inside the body, water constantly penetrates into the body, and freshwater hydrobionts are forced to intensively remove it. In this regard, their osmoregulation processes are well expressed. In protozoa this is achieved by the work of excretory vacuoles, in multicellular organisms - by removing water through the excretory system. Typically marine and typically freshwater species do not tolerate significant changes in water salinity - stenohaline organisms. Eurygalline - freshwater pike perch, bream, pike, from the sea - the mullet family.
Gas mode The main gases in the aquatic environment are oxygen and carbon dioxide.
Oxygen- the most important environmental factor. It enters water from the air and is released by plants during photosynthesis. Its content in water is inversely proportional to temperature; with decreasing temperature, the solubility of oxygen in water (as well as other gases) increases. In layers heavily populated by animals and bacteria, oxygen deficiency may occur due to increased oxygen consumption. Thus, in the world’s oceans, life-rich depths from 50 to 1000 m are characterized by a sharp deterioration in aeration. It is 7-10 times lower than in surface waters inhabited by phytoplankton. Conditions near the bottom of reservoirs can be close to anaerobic.
Carbon dioxide - dissolves in water about 35 times better than oxygen and its concentration in water is 700 times higher than in the atmosphere. Provides photosynthesis of aquatic plants and participates in the formation of calcareous skeletal formations of invertebrate animals.
Hydrogen ion concentration (pH)– freshwater pools with pH = 3.7-4.7 are considered acidic, 6.95-7.3 – neutral, with pH 7.8 – alkaline. In fresh water bodies, pH even experiences daily fluctuations. Sea water is more alkaline and its pH changes much less than fresh water. pH decreases with depth. The concentration of hydrogen ions plays a large role in the distribution of aquatic organisms.
Ground-air habitat
A feature of the land-air environment of life is that the organisms living here are surrounded by a gaseous environment characterized by low humidity, density and pressure, and high oxygen content. Typically, animals in this environment move on the soil (hard substrate) and plants take root in it.
In the ground-air environment, the operating environmental factors have a number of characteristic features: higher light intensity compared to other environments, significant temperature fluctuations, changes in humidity depending on the geographical location, season and time of day. The impact of the factors listed above is inextricably linked with the movement of air masses - wind.
In the process of evolution, living organisms of the land-air environment have developed characteristic anatomical, morphological, and physiological adaptations.
Let us consider the features of the impact of basic environmental factors on plants and animals in the ground-air environment.
Air. Air as an environmental factor is characterized by a constant composition - oxygen in it is usually about 21%, carbon dioxide 0.03%.
Low air density determines its low lifting force and insignificant support. All inhabitants of the air are closely connected with the surface of the earth, which serves them for attachment and support. The density of the air environment does not provide high resistance to organisms when they move along the surface of the earth, but it makes it difficult to move vertically. For most organisms, staying in the air is associated only with settling or searching for prey.
The low lifting force of air determines the maximum mass and size of terrestrial organisms. The largest animals living on the surface of the earth are smaller than the giants of the aquatic environment. Large mammals (the size and mass of a modern whale) could not live on land, as they would be crushed by their own weight.
Low air density creates little resistance to movement. The ecological benefits of this property of the air environment were used by many land animals during evolution, 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.
Thanks to the mobility of air and 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. Many species have developed anemochory - dispersal with the help of air currents. Anemochory is characteristic of spores, seeds and fruits of plants, protozoan cysts, small insects, spiders, etc. Organisms passively transported by air currents are collectively called aeroplankton by analogy with planktonic inhabitants of the aquatic environment.
The main ecological role of horizontal air movements (winds) is indirect in enhancing and weakening the impact on terrestrial organisms of such important environmental factors as temperature and humidity. Winds increase the release of moisture and heat from animals and plants.
Gas composition of air in the ground layer the air is quite homogeneous (oxygen - 20.9%, nitrogen - 78.1%, inert gases - 1%, carbon dioxide - 0.03% by volume) due to its high diffusivity and constant mixing by convection and wind flows. However, various impurities of gaseous, droplet-liquid and solid (dust) particles entering the atmosphere from local sources can have significant environmental significance.
The high oxygen content contributed to an increase in metabolism in terrestrial organisms, and animal homeothermy arose on the basis of the high efficiency of oxidative processes. 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 deficiency created, for example, in accumulations of decomposing plant residues, reserves of grain, flour, etc.
Edaphic 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 called edaphic environmental factors.
The nature of the plant root system 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 shallow depths and spread out wide. Where there is no permafrost, the root systems of these same plants are less widespread and penetrate deeper. In many steppe plants, the roots can reach water from great depths; at the same time, they also have many surface roots in the humus-rich soil horizon, from where the plants absorb elements of mineral nutrition.
The terrain and the nature of the soil affect the specific movement of animals. For example, ungulates, ostriches, and bustards living in open spaces need hard ground to enhance repulsion when running fast. In lizards that live on shifting sands, the toes are fringed with a fringe of horny scales, which increases the surface of support. For terrestrial inhabitants that dig holes, dense soils are unfavorable. The nature of the soil in some cases influences the distribution of terrestrial animals that dig burrows, burrow into the soil to escape heat or predators, or lay eggs in the soil, etc.
Weather and climatic features. Living conditions in the ground-air environment are also complicated by weather changes. Weather is the continuously changing state of the atmosphere at the earth's surface, up to an altitude of approximately 20 km (the boundary of the troposphere). Weather variability is manifested in a constant variation in the combination of environmental factors such 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 of terrestrial organisms. The weather affects the life of aquatic inhabitants to a much lesser extent and only on the population of the surface layers.
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 cycle, deviations from it and their frequency. The climate is determined geographical conditions district.
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 and many other local factors.
For most terrestrial organisms, especially small ones, it is not so much the climate of the area that is important as the conditions of their immediate habitat. Very often, local environmental elements (relief, vegetation, etc.) change the regime of temperature, humidity, light, air movement in a particular area in such a way that it differs significantly from the climatic conditions of the area. Such local climate modifications that develop in the surface layer of air are called microclimate. Each zone has very diverse microclimates. Microclimates of arbitrarily small areas can be identified. For example, a special regime is created in the corollas of flowers, which is used by the inhabitants living there. 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 other ecological roles. Thus, heavy rainfall 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 depth only up to 25 cm; deeper, the temperature remains almost unchanged. With 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 renewal buds and protects green parts of plants from freezing; many species go under the snow without shedding their foliage, for example, hairy grass, Veronica officinalis, etc.
Small land animals also lead an active lifestyle in winter, creating entire galleries of passages under the snow and in its thickness. A number of species that feed on snow-covered vegetation are even characterized by winter reproduction, 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 partridge - burrow in the snow for the night.
Winter snow cover makes it difficult for large animals to obtain food. Many ungulates (reindeer, wild boars, musk oxen) feed exclusively on snow-covered vegetation in winter, and deep snow cover, and especially the hard crust on its surface that occurs during icy conditions, doom them to starvation. Snow depth may limit the geographic distribution of species. For example, real deer do not penetrate north into those areas where the snow thickness in winter is more than 40-50 cm.
Light mode. The amount of radiation reaching the Earth's surface is determined by the geographic latitude of the area, the length of the day, the transparency of the atmosphere and the angle of incidence of the sun's rays. Under different weather conditions, 42-70% of the solar constant reaches the Earth's surface. Illumination on the Earth's surface varies widely. It all depends on the height of the Sun above the horizon or the angle of incidence of the sun's rays, the length of the day and weather conditions, and the transparency of the atmosphere. Light intensity also fluctuates depending on the season and time of day. In certain regions of the Earth, the quality of light is also unequal, for example, the ratio of long-wave (red) and short-wave (blue and ultraviolet) rays. Short-wave rays are known to be absorbed and scattered by the atmosphere more than long-wave rays.
Soil as a habitat
The soil is a loose thin surface layer of land in contact with the air. The soil is not just solid, like most rocks of the lithosphere, but a complex three-phase system in which solid particles are surrounded by air and water. It is permeated with cavities filled with a mixture of gases and aqueous solutions, and therefore it develops extremely diverse conditions favorable for the life of many micro- and macroorganisms. Temperature fluctuations in the soil are smoothed out compared to the surface layer of air, and the presence of groundwater and the penetration of precipitation create moisture reserves and provide a humidity regime intermediate between water and the ground environment. The soil concentrates reserves of organic and minerals supplied by dying vegetation and animal corpses. All this determines the greater saturation of the soil with life.
The heterogeneity of conditions in the soil is most pronounced in the vertical direction. With depth, a number of the most important environmental factors affecting the life of soil inhabitants change dramatically. First of all, this relates to the structure of the soil. It distinguishes three main horizons, differing in morphological and chemical properties: 1) upper humus-accumulative horizon, in which organic matter accumulates and is transformed and from which some of the compounds are carried down by washing waters; 2) the influx horizon, or illuvial, where the substances washed out from above settle and are transformed, and 3) the parent rock, or horizon, the material of which is transformed into soil.
The size of the cavities between soil particles, suitable for animals to live in, usually decreases rapidly with depth. For example, in meadow soils the average diameter of cavities at a depth of 0-1 mm is 3 mm; 1-2 cm 2 mm, and at a depth of 2-3 cm - only 1 mm; deeper the soil pores are even smaller.
Moisture in the soil is present in various states: 1) bound (hygroscopic and film) firmly held by the surface of soil particles; 2) capillary occupies small pores and can move along them in different directions; 3) gravitational fills larger voids and slowly seeps down under the influence of gravity; 4) vaporous is contained in the soil air.
The composition of soil air is variable. With depth, the oxygen content in it decreases greatly and the concentration of carbon dioxide increases. Due to the presence of decomposing organic substances in the soil, the soil air may contain a high concentration of toxic gases such as ammonia, hydrogen sulfide, methane, etc. When the soil is flooded or intensive rotting of plant residues, completely anaerobic conditions may occur in some places.
Fluctuations in cutting temperature only on the soil surface. Here they can be even stronger than in the surface layer of air. However, with every centimeter deeper, daily and seasonal temperature changes become less and less and at a depth of 1-1.5 m they are practically no longer traceable.
All these features lead to the fact that, despite the great heterogeneity of environmental conditions in the soil, it acts as a fairly stable environment, especially for soil organisms. The steep moisture gradient in the soil profile allows soil organisms to provide themselves with a suitable ecological environment through minor movements.
Soil inhabitants, depending on their size and degree of mobility, can be divided into several groups:
1. Microbiota– these are soil microorganisms that make up the main link in the detrital food chain; they represent, as it were, an intermediate link between plant residues and soil animals. These are green and blue-green algae, bacteria, fungi and protozoa. These are aquatic organisms, and the soil for them is a system of micro-reservoirs. They live in soil pores filled with gravitational or capillary moisture, and part of the life can, like microorganisms, be in an adsorbed state on the surface of particles in thin layers of film moisture.
2. Mesobiota is a collection of relatively small, easily removed from the soil, mobile animals (soil nematodes, small insect larvae, mites, etc.). The sizes of soil mesobiota representatives range from tenths to 2-3 mm. For this group of animals, the soil appears as a system of small caves. They have special adaptations for digging. They crawl along the walls of soil cavities using their limbs or wriggling like a worm. Soil air saturated with water vapor allows them to breathe through the integument of the body. Animals usually experience periods of soil flooding with water in air bubbles. Air is retained around their body due to the non-wetting of the integument, which in most of them is equipped with hairs and scales.
Animals of meso- and microbiotypes are able to tolerate winter freezing of the soil, which is especially important, since most of them cannot move down from layers exposed to negative temperatures.
3) Macrobiota– these are large soil animals, with body sizes from 2 to 20 mm (insect larvae, millipedes, earthworms, etc.). They move in the soil, expanding natural wells by moving apart soil particles or digging new passages. Both methods of movement leave an imprint on the external structure of animals. Gas exchange of most species of this group is carried out with the help of specialized respiratory organs, but at the same time it is supplemented by gas exchange through the integument.
Burrowing animals can leave layers where unfavorable conditions arise. By winter and during drought, they concentrate in deeper layers, mostly a few tens of centimeters from the surface.
4) Megabiota- These are large shrews, mainly mammals. Many of them spend their entire lives in the soil (golden moles in Africa, moles in Eurasia, marsupial moles in Australia). They create entire systems of passages and burrows in the soil. Adaptation to a burrowing underground lifestyle is reflected in the appearance and anatomical features of these animals: they have underdeveloped eyes, a compact ridged body with a short neck, short thick fur, strong compact limbs with strong claws.
In addition to the permanent inhabitants of the soil, a separate ecological group is often distinguished among large animals burrow inhabitants(badgers, marmots, gophers, jerboas, etc.). They feed on the surface, but reproduce, hibernate, rest, and escape danger in the soil.