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 a sufficiently high level of 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 anemochorous 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 flag-shaped crowns.
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 constant 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 of 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 fairly 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, tan in humans, dark caviar in fish and amphibians), 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 more saturated 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. The completeness of visual perception of the 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 are the eyes of vertebrates, 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 kinds. 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 species of 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 by 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, a long day during the summer months in the Arctic and temperate zone attracts 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 regime. The intensity of all chemical reactions that make up metabolism depends on temperature conditions. 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 species of 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 glycerol, 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 an 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 species 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, stomatal transpiration is an effective remedy for overheating. 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 adaptation mechanisms that increase their resistance to cold: leaf fall, death of above-ground 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, etc. accumulate in the organs. oil, 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 the 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, the 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, 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.
The combination of various methods of chemical, physical and behavioral thermoregulation allows warm-blooded animals to maintain a constant body temperature in a wide range of fluctuations in environmental temperature conditions.
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 inhibition of growth. 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 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 xerophilous. 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 elimination 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 loss, 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.
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, physiological, behavioral and other adaptations. Let us consider the features of the impact of basic environmental factors on plants and animals in the ground-air environment of life.
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. 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.
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 all species of land animals are capable of active flight.
Due to the mobility of air that exists in the lower layers of the atmosphere, the vertical and horizontal movement of air masses, passive flight of certain types of organisms is possible, anemochory is developed - settlement with the help of air currents. Wind-pollinated plants have a number of adaptations that improve the aerodynamic properties of pollen.
Their floral integument is usually reduced and the anthers are not protected from the wind in any way. Vertical convection air currents and weak winds play a major role in the dispersal of plants, animals and microorganisms. Storms and hurricanes have a significant environmental impact on terrestrial organisms.
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. The wind causes a change in the intensity of transpiration in plants, which is especially pronounced during hot winds that dry out the air, and can lead to the death of plants. The main ecological role of horizontal air movements (winds) is indirect and consists in enhancing or weakening the impact of such important environmental factors on terrestrial organisms. factors such as temperature and humidity.
Walking through a forest or meadow, you hardly think that you are... in ground-air environment. But this is exactly what scientists call the house for living beings, which is formed by the surface of the earth and the air. Swimming in a river, lake or sea, you find yourself in aquatic environment- another richly populated natural home. And when you help adults dig up the soil in the garden, you see the soil environment under your feet. There are also many, many diverse residents here. Yes, there are three wonderful houses around us - three habitat, with which the fate of the majority of organisms inhabiting our planet is inextricably linked.
Life in each environment has its own characteristics. IN ground-air environment there is enough oxygen, but often there is not enough moisture. There is especially little of it in the steppes and deserts. Therefore, plants and animals of arid places have special adaptations for obtaining, storing and economically using water. Just remember a cactus that stores moisture in its body. There are significant temperature changes in the land-air environment, especially in areas with cold winters. In these areas, the entire life of organisms changes noticeably throughout the year. Autumn leaf fall, the departure of migratory birds to warmer regions, the change of fur of animals to thicker and warmer ones - all these are adaptations of living beings to seasonal changes in nature.
For animals living in any environment, movement is an important problem. In the ground-air environment, you can move on the ground and in the air. And animals take advantage of this. The legs of some are adapted for running (ostrich, cheetah, zebra), others - for jumping (kangaroo, jerboa). Of every hundred animal species living in this environment, 75 can fly. These are most insects, birds and some animals (bats).
IN aquatic environment something, and there is always enough water. The temperature here varies less than the air temperature. But oxygen is often not enough. Some organisms, such as trout fish, can only live in oxygen-rich water. Others (carp, crucian carp, tench) can withstand a lack of oxygen. In winter, when many reservoirs are covered with ice, fish may die - mass death from suffocation. To allow oxygen to penetrate the water, holes are cut in the ice.
There is less light in the aquatic environment than in the air-terrestrial environment. In the oceans and seas at a depth below 200 m - the kingdom of twilight, and even lower - eternal darkness. It is clear that aquatic plants are found only where there is enough light. Only animals can live deeper. They feed on the dead remains of various marine inhabitants that “fall” from the upper layers.
The most noticeable feature of many aquatic animals is their swimming adaptations. Fish, dolphins and whales have fins. Walruses and seals have flippers. Beavers, otters, waterfowl, and frogs have membranes between their toes. Swimming beetles have swimming legs that look like oars.
Soil environment- home to many bacteria and protozoa. Mushroom myceliums and plant roots are also located here. The soil was also inhabited by a variety of animals - worms, insects, animals adapted to digging, such as moles. The inhabitants of the soil find in this environment the conditions they need - air, water, mineral salts. True, there is less oxygen and more carbon dioxide here than in the fresh air. And sometimes there is too much water. But the temperature is more even than on the surface. But light does not penetrate deep into the soil. Therefore, the animals inhabiting it usually have very small eyes or no visual organs at all. Their sense of smell and touch help out.
Ground-air environment
Representatives of different habitats “met” in these drawings. In nature, they could not get together, because many of them live far from each other, on different continents, in the seas, in fresh water...
The champion in flight speed among birds is the swift. 120 km per hour is his usual speed.
Hummingbirds flap their wings up to 70 times per second, mosquitoes - up to 600 times per second.
The flight speed of different insects is as follows: for the lacewing - 2 km per hour, for the housefly - 7, for the cockchafer - 11, for the bumblebee - 18, and for the hawk moth - 54 km per hour. Large dragonflies, according to some observations, reach speeds of up to 90 km per hour.
Our bats are small in stature. But their relatives, fruit bats, live in hot countries. They reach a wingspan of 170 cm!
Large kangaroos make jumps of up to 9 and sometimes up to 12 m. (Measure this distance on the floor in the classroom and imagine a kangaroo jump. It’s simply breathtaking!)
The cheetah is the fastest-footed of animals. It reaches speeds of up to 110 km per hour. An ostrich can run at speeds of up to 70 km per hour, taking steps of 4-5 m.
Water environment
Fish and crayfish breathe through gills. These are special organs that extract dissolved oxygen from water. A frog, while underwater, breathes through its skin. But animals that have mastered the aquatic environment breathe with their lungs, rising to the surface of the water to inhale. Aquatic beetles behave in a similar way. Only they, like other insects, do not have lungs, but special breathing tubes - tracheas.
Soil environment
The body structure of the mole, zokor and mole rat suggests that they are all inhabitants of the soil environment. The front legs of the mole and zokor are the main tool for digging. They are flat, like shovels, with very large claws. But the mole rat has ordinary legs; it bites into the soil with its powerful front teeth (to prevent soil from getting into the mouth, the lips close it behind the teeth!). The body of all these animals is oval and compact. With such a body it is convenient to move through underground passages.
Test your knowledge
- List the habitats you were introduced to in class.
- What are the living conditions of organisms in the ground-air environment?
- Describe the living conditions in the aquatic environment.
- What are the characteristics of soil as a habitat?
- Give examples of the adaptation of organisms to life in different environments.
Think!
- Explain what is shown in the picture. In what environments do you think the animals whose body parts are shown in the picture live? Can you name these animals?
- Why do only animals live in the ocean at great depths?
There are ground-air, water and soil habitats. Each organism is adapted to life in a certain environment.
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 in 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 the topic habitat of a living organism, grade 6
- adaptability of the snowy owl to its environment
- terms on the topic of air
- report on land-air habitat
- adaptation of birds of prey to their environment
Throughout evolution, the terrestrial-air habitat was studied much later than the aquatic one. Its distinctive feature is that it is gaseous, so the composition is dominated by a significant oxygen content, as well as low pressure, humidity and density.
Over a long period of such an evolutionary process, the flora and fauna arose the need to form certain behavior and physiology, anatomical and other adaptations, they were able to adapt to changes in the surrounding world.
Characteristic
The environment is characterized by:
- Constant changes in temperature and moisture levels in the air;
- The passage of time of day and seasons;
- High light intensity;
- Dependence of factors of territorial location.
Peculiarities
The peculiarity of the environment is that plants are able to take root in the ground, and animals can move in the vastness of air and soil. All plants have a stomatal apparatus, with the help of which land organisms of the world can take oxygen directly from the air. Low air humidity and the predominant presence of oxygen in it led to the appearance of respiratory organs in animals - the trachea and lungs. A well-developed skeletal structure allows independent movement on the ground and serves as a strong support for the body and organs, given the low density of the environment.
Animals
The main part of animal species live in the ground-air environment: birds, animals, reptiles and insects.
Adaptation and fitness (examples)
Living organisms have developed certain adaptations to the negative factors of the surrounding world: adaptation to changes in temperature and climate, a special body structure, thermoregulation, as well as the change and dynamics of life cycles. For example, some plants change their shoots and root system to maintain their normal state during periods of cold and drought. Root vegetables - beets and carrots, flower leaves - aloe, tulip and leek bulbs retain nutrients and moisture.
To maintain body temperature unchanged in summer and winter, animals have developed a special system of heat exchange and thermoregulation with the outside world. Plants developed pollen and seeds carried by the wind for reproduction. Such plants have unique capabilities to improve the properties of pollen, resulting in effective pollination. Animals gained purposeful mobility to obtain food. An absolute mechanical, functional and resource connection with the earth has been formed.
- A limiting factor for the inhabitants of the environment is the lack of water sources.
- Living organisms can change their body shape due to the low density in the air. For example, the formation of skeletal parts is important for animals; birds require a smooth wing shape and body structure.
- Plants need flexible connective tissues, as well as the presence of a characteristic crown shape and flowers.
- Birds and mammals owe their acquisition of the warm-blooded function to the presence of the properties of air - thermal conductivity, heat capacity.
conclusions
The ground-air habitat is unusual in terms of environmental factors. The presence of animals and plants in it is possible due to the appearance and formation of many adaptations. All inhabitants are inseparable from the surface of the earth for fastening and stable support. In this regard, the soil is inseparable from the aquatic and terrestrial environment, which plays a major role in the evolution of the animal and plant world.
For many individuals, it was a bridge through which organisms from water sources moved to terrestrial living conditions and thereby conquered land. The distribution of flora and fauna throughout the planet depends on the composition of the soil and the terrain, depending on the way of life.
Recently, the land-air environment has been changing due to human activity. People artificially transform natural landscapes, the number and size of reservoirs. In such a situation, many organisms are not able to quickly adapt to new living conditions. It is necessary to remember this and stop the negative interference of people in the ground-air habitat of animals and plants!
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