These are factors of inanimate nature that directly or indirectly affect the body - light, temperature, humidity, the chemical composition of the air, water and soil environment, etc. (i.e., properties of the environment, the occurrence and impact of which does not directly depend on the activity of living organisms).
Light
(solar radiation) is an environmental factor characterized by the intensity and quality of the radiant energy of the Sun, which is used by photosynthetic green plants to create plant biomass. Sunlight reaching the Earth's surface is the main source of energy for maintaining the thermal balance of the planet, the water metabolism of organisms, the creation and transformation of organic matter by the autotrophic element of the biosphere, which ultimately makes it possible to form an environment capable of satisfying the vital needs of organisms.
The biological effect of sunlight is determined by its spectral composition [show] ,
The spectral composition of sunlight is divided into
- infrared rays (wavelength more than 0.75 microns)
- visible rays (0.40-0.75 µm) and
- ultraviolet rays (less than 0.40 microns)
Different parts of the solar spectrum have unequal biological effects.
Infrared, or thermal, rays carry the bulk of thermal energy. They account for about 49% of the radiant energy that is perceived by living organisms. Thermal radiation is well absorbed by water, the amount of which in organisms is quite large. This leads to heating of the entire body, which is of particular importance for cold-blooded animals (insects, reptiles, etc.). In plants, the most important function of infrared rays is to carry out transpiration, through which excess heat is removed from the leaves by water vapor, as well as to create optimal conditions for the entry of carbon dioxide through the stomata.
Visible spectrum make up about 50% of the radiant energy reaching the Earth. This energy is needed by plants for photosynthesis. However, only 1% of it is used for this, the rest is reflected or dissipated in the form of heat. This part of the spectrum has led to the appearance of many important adaptations in plant and animal organisms. In green plants, in addition to the formation of a light-absorbing pigment complex, with the help of which the process of photosynthesis is carried out, bright colors of flowers have arisen, which helps attract pollinators.
For animals, light mainly plays an informational role and is involved in the regulation of many physiological and biochemical processes. Already the simplest have photosensitive organelles (the light-sensitive ocellus in green euglena), and the reaction to light is expressed in the form of phototaxis - movement towards the highest or lowest illumination. Starting with the coelenterates, almost all animals develop light-sensitive organs of various structures. There are nocturnal and crepuscular animals (owls, bats, etc.), as well as animals that live in constant darkness (mole crickets, roundworms, moles, etc.).
Ultraviolet part characterized by the highest quantum energy and high photochemical activity. With the help of ultraviolet rays with a wavelength of 0.29-0.40 microns, the biosynthesis of vitamin D, retinal pigments, and skin is carried out in the body of animals. These rays are best perceived by the visual organs of many insects; in plants they have a formative effect and contribute to the synthesis of some biologically active compounds (vitamins, pigments). Rays with a wavelength of less than 0.29 microns have a detrimental effect on living things.
Intensity [show] ,
Plants, whose life activity is entirely dependent on light, develop various morphostructural and functional adaptations to the light regime of their habitats. Based on their requirements for lighting conditions, plants are divided into the following environmental groups:
- Light-loving (heliophytes) plants open habitats, growing successfully only in conditions of full sunlight. They are characterized by a high intensity of photosynthesis. These are early spring plants of steppes and semi-deserts (goose onions, tulips), plants of treeless slopes (sage, mint, thyme), cereals, plantain, water lily, acacia, etc.
- Shade-tolerant plants characterized by a wide ecological amplitude to the light factor. They grow best in high light conditions, but are able to adapt to varying levels of shade. These are woody (birch, oak, pine) and herbaceous (wild strawberry, violet, St. John's wort, etc.) plants.
- Shade-loving plants (sciophytes) They do not tolerate strong lighting, they grow only in shaded areas (under the forest canopy), and never grow in open areas. In clearings with strong lighting, their growth slows down and sometimes they die. Such plants include forest grasses - ferns, mosses, wood sorrel, etc. Adaptation to shading is usually combined with the need for a good water supply.
Daily and seasonal frequency [show] .
Daily periodicity determines the processes of growth and development of plants and animals, which depend on the length of daylight hours.
The factor that regulates and controls the rhythm of the daily life of organisms is called photoperiodism. It is the most important signaling factor allowing plants and animals to “measure time” - the ratio between the duration of the period of illumination and darkness during the day, and determine the quantitative parameters of illumination. In other words, photoperiodism is the reaction of organisms to the change of day and night, which manifests itself in fluctuations in the intensity of physiological processes - growth and development. It is the length of day and night that changes very precisely and naturally throughout the year, regardless of random factors, invariably repeating from year to year, therefore organisms in the process of evolution coordinated all stages of their development with the rhythm of these time intervals.
In the temperate zone, the property of photoperiodism serves as a functional climatic factor that determines the life cycle of most species. In plants, the photoperiodic effect manifests itself in the coordination of the period of flowering and fruit ripening with the period of most active photosynthesis, in animals - in the coincidence of the time of reproduction with the period of abundance of food, in insects - in the onset of diapause and exit from it.
Biological phenomena caused by photoperiodism also include seasonal migrations (flights) of birds, the manifestation of their nesting instincts and reproduction, change of fur in mammals, etc.
According to the required length of the photoperiod, plants are divided into
- long-day plants, which require more than 12 hours of light time for normal growth and development (flax, onions, carrots, oats, henbane, dope, young, potatoes, belladonna, etc.);
- short-day plants - they need at least 12 hours of continuous darkness to bloom (dahlias, cabbage, chrysanthemums, amaranth, tobacco, corn, tomatoes, etc.);
- neutral plants in which the development of generative organs occurs both with long and short days (marigolds, grapes, phlox, lilac, buckwheat, peas, knotweed, etc.)
Long-day plants come mainly from northern latitudes, while short-day plants come from southern latitudes. In the tropical zone, where the length of day and night varies little throughout the year, photoperiod cannot serve as a guiding factor for the periodicity of biological processes. It is replaced by alternating dry and wet seasons. Long-day species manage to produce a harvest even in the short northern summer. The formation of a large mass of organic substances occurs in the summer during a fairly long daylight hours, which at the latitude of Moscow can reach 17 hours, and at the latitude of Arkhangelsk - more than 20 hours a day.
The length of the day also significantly affects the behavior of animals. With the onset of spring days, the duration of which progressively increases, birds develop nesting instincts, they return from warm regions (although the air temperature may still be unfavorable), and begin laying eggs; Warm-blooded animals shed.
The reduction in day length in autumn causes opposite seasonal phenomena: birds fly away, some animals hibernate, others grow dense fur, and wintering stages of insects form (despite the still favorable temperature and abundance of food). In this case, a decrease in day length signals living organisms about the imminent onset of the winter period, and they can prepare for it in advance.
In animals, especially arthropods, growth and development also depend on the length of daylight hours. For example, cabbage whites and birch moths develop normally only with long daylight hours, while silkworms, various types of locusts, and moths develop normally only with short daylight hours. Photoperiodism also affects the timing of the onset and termination of the mating season in birds, mammals and other animals; on reproduction, embryonic development of amphibians, reptiles, birds and mammals;
Seasonal and daily changes in illumination are the most accurate clocks, the course of which is clearly regular and has remained virtually unchanged during the last period of evolution.
Thanks to this, it became possible to artificially regulate the development of animals and plants. For example, providing plants in greenhouses, greenhouses or hotbeds with 12-15 hours of daylight allows them to grow vegetables and ornamental plants even in winter, and to accelerate the growth and development of seedlings. Conversely, shading plants in the summer speeds up the appearance of flowers or seeds on late-blooming fall plants.
By extending the day due to artificial lighting in winter, you can increase the egg-laying period of chickens, geese, and ducks, and regulate the reproduction of fur-bearing animals on fur farms. The light factor also plays a huge role in other life processes of animals. First of all, it is a necessary condition for vision, their visual orientation in space as a result of the perception by the organs of vision of direct, scattered or reflected light rays from surrounding objects. Polarized light, the ability to distinguish colors, navigate by astronomical light sources, the autumn and spring migrations of birds, and the navigation abilities of other animals are highly informative for most animals.
Based on photoperiodism, plants and animals in the process of evolution have developed specific annual cycles of periods of growth, reproduction, and preparation for winter, which are called annual or seasonal rhythms. These rhythms manifest themselves in changes in the intensity of the nature of biological processes and are repeated at annual intervals. The coincidence of the periods of the life cycle with the corresponding time of year is of great importance for the existence of the species. Seasonal rhythms provide plants and animals with the most favorable conditions for growth and development.
Moreover, the physiological processes of plants and animals are strictly dependent on the daily rhythm, which is expressed by certain biological rhythms. Consequently, biological rhythms are periodically repeating changes in the intensity and nature of biological processes and phenomena. In plants, biological rhythms are manifested in the daily movement of leaves, petals, changes in photosynthesis, in animals - in temperature fluctuations, changes in the secretion of hormones, the rate of cell division, etc. In humans, daily fluctuations in respiratory rate, pulse, blood pressure, wakefulness and sleep, etc. Biological rhythms are hereditarily fixed reactions, therefore knowledge of their mechanisms is important in organizing human work and rest.
Temperature
One of the most important abiotic factors on which the existence, development and distribution of organisms on Earth largely depends [show] .
The upper temperature limit of life on Earth is probably 50-60°C. At such temperatures, loss of enzyme activity and protein coagulation occurs. However, the general temperature range of active life on the planet is much wider and is limited to the following limits (Table 1)
Table 1. Temperature range of active life on the planet, °C
Among the organisms that can exist at very high temperatures, thermophilic algae are known, which can live in hot springs at 70-80°C. Cruciform lichens, seeds and vegetative organs of desert plants (saxaul, camel thorn, tulips) located in the top layer of hot soil successfully tolerate very high temperatures (65-80°C).
There are many species of animals and plants that can withstand high subzero temperatures. Trees and shrubs in Yakutia do not freeze at minus 68°C. Penguins live in Antarctica at minus 70°C, and polar bears, arctic foxes, and polar owls live in the Arctic. Polar waters with temperatures from 0 to -2°C are inhabited by a variety of flora and fauna - microalgae, invertebrates, fish, whose life cycle constantly occurs in such temperature conditions.
The importance of temperature lies primarily in its direct influence on the speed and nature of metabolic reactions in organisms. Since daily and seasonal temperature fluctuations increase with distance from the equator, plants and animals, adapting to them, exhibit different needs for heat.
Adaptation methods
- Migration is relocation to more favorable conditions. Whales, many species of birds, fish, insects and other animals migrate regularly throughout the year.
- Numbness is a state of complete immobility, a sharp decrease in vital activity, and cessation of nutrition. It is observed in insects, fish, amphibians, and mammals when the environmental temperature decreases in autumn, winter (hibernation) or when it increases in the summer in deserts (summer hibernation).
- Anabiosis is a state of sharp inhibition of life processes, when visible manifestations of life temporarily cease. This phenomenon is reversible. It is observed in microbes, plants, and lower animals. The seeds of some plants can remain in suspended animation for up to 50 years. Microbes in a state of suspended animation form spores, protozoa form cysts.
Many plants and animals, with appropriate preparation, successfully tolerate extremely low temperatures in a state of deep dormancy or suspended animation. In laboratory experiments, seeds, pollen, plant spores, nematodes, rotifers, cysts of protozoa and other organisms, sperm after dehydration or placement in solutions of special protective substances - cryoprotectants - tolerate temperatures close to absolute zero.
Currently, progress has been made in the practical use of substances with cryoprotective properties (glycerin, polyethylene oxide, dimethyl sulfoxide, sucrose, mannitol, etc.) in biology, agriculture, and medicine. Cryoprotectant solutions provide long-term storage of canned blood, sperm for artificial insemination of farm animals, and some organs and tissues for transplantation; protection of plants from winter frosts, early spring frosts, etc. These problems fall within the competence of cryobiology and cryomedicine and are solved by many scientific institutions.
- Thermoregulation. In the process of evolution, plants and animals have developed various mechanisms of thermoregulation:
- in plants
- physiological - the accumulation of sugar in cells, due to which the concentration of cell sap increases and the water content of cells decreases, which contributes to the frost resistance of plants. For example, in dwarf birch and juniper, the upper branches die at excessively low temperatures, while the creeping ones overwinter under the snow and do not die.
- physical
- stomatal transpiration - removing excess heat and preventing burns by removing water (evaporation) from the plant body
- morphological - aimed at preventing overheating: thick pubescence of the leaves to disperse sunlight, a glossy surface to reflect them, reducing the surface absorbing rays - rolling the leaf blade into a tube (feather grass, fescue), placing the leaf edge-on to the sun's rays (eucalyptus), reducing foliage ( saxaul, cactus); aimed at preventing freezing: special forms of growth - dwarfism, the formation of creeping forms (wintering under snow), dark coloring (helps to better absorb heat rays and warm up under the snow)
- in animals
- cold-blooded (poikilothermic, ectothermic) [invertebrates, fish, amphibians and reptiles] - regulation of body temperature is carried out passively by increasing muscle work, the structure and color of the integument, finding places where intense absorption of sunlight is possible, etc., etc. .To. they cannot maintain the temperature regime of metabolic processes and their activity depends mainly on heat coming from outside, and body temperature - on the values of ambient temperature and energy balance (the ratio of absorption and release of radiant energy).
- warm-blooded (homeothermic, endothermic) [birds and mammals] - capable of maintaining a constant body temperature regardless of the temperature of the environment. This property makes it possible for many species of animals to live and reproduce at temperatures below zero (reindeer, polar bear, pinnipeds, penguins). In the process of evolution, they have developed two thermoregulation mechanisms, with the help of which they maintain a constant body temperature: chemical and physical. [show]
.
- The chemical mechanism of thermoregulation is ensured by the speed and intensity of redox reactions and is controlled reflexively by the central nervous system. An important role in increasing the efficiency of the chemical mechanism of thermoregulation was played by such aromorphoses as the appearance of a four-chambered heart and the improvement of the respiratory system in birds and mammals.
- The physical mechanism of thermoregulation is ensured by the appearance of heat-insulating covers (feathers, fur, subcutaneous fat), sweat glands, respiratory organs, as well as the development of nervous mechanisms for regulating blood circulation.
A special case of homeothermy is heterothermy - different levels of body temperature depending on the functional activity of the body. Heterothermy is characteristic of animals that fall into hibernation or temporary torpor during unfavorable periods of the year. At the same time, their high body temperature is noticeably reduced due to slow metabolism (gophers, hedgehogs, bats, swift chicks, etc.).
Endurance limits large values of the temperature factor are different in both poikilothermic and homeothermic organisms.
Eurythermic species are able to tolerate temperature fluctuations over a wide range.
Stenothermic organisms live in conditions of narrow temperature limits, being divided into heat-loving stenothermic species (orchids, tea bush, coffee, corals, jellyfish, etc.) and cold-loving ones (elfin cedar, pre-glacial and tundra vegetation, fish of the polar basins, abyssal animals - the areas of greatest ocean depths, etc.).
For each organism or group of individuals there is an optimal temperature zone within which activity is particularly well expressed. Above this zone is a zone of temporary thermal torpor, and even higher is a zone of prolonged inactivity or summer hibernation, bordering on a zone of high lethal temperature. When the latter decreases below the optimum, there is a zone of cold torpor, hibernation and lethal low temperature.
The distribution of individuals in the population, depending on changes in the temperature factor throughout the territory, generally obeys the same pattern. The optimal temperature zone corresponds to the highest population density, and on both sides of it there is a decrease in density up to the boundary of the range, where it is lowest.
The temperature factor over a large area of the Earth is subject to pronounced daily and seasonal fluctuations, which in turn determines the corresponding rhythm of biological phenomena in nature. Depending on the provision of thermal energy in symmetrical areas of both hemispheres of the globe, starting from the equator, the following climatic zones are distinguished:
- tropical zone. The minimum average annual temperature exceeds 16° C, on the coolest days it does not fall below 0° C. Temperature fluctuations over time are insignificant, the amplitude does not exceed 5° C. Vegetation is year-round.
- Subtropical zone. The average temperature of the coldest month is not lower than 4° C, and the warmest is above 20° C. Sub-zero temperatures are rare. There is no stable snow cover in winter. The growing season lasts 9-11 months.
- Temperate zone. The summer growing season and the winter dormant period of plants are well defined. The main part of the zone has stable snow cover. Frosts are typical in spring and autumn. Sometimes this zone is divided into two: moderately warm and moderately cold, which are characterized by four seasons.
- Cold zone. The average annual temperature is below O° C, frosts are possible even during a short (2-3 months) growing season. The annual temperature fluctuation is very large.
The pattern of vertical distribution of vegetation, soils, and fauna in mountainous areas is also mainly determined by the temperature factor. In the mountains of the Caucasus, India, and Africa, four or five plant belts can be distinguished, the sequence of which from bottom to top corresponds to the sequence of latitudinal zones from the equator to the pole at the same altitude.
Humidity
An environmental factor characterized by the water content in the air, soil, and living organisms. In nature, there is a daily rhythm of humidity: it increases at night and decreases during the day. Together with temperature and light, humidity plays an important role in regulating the activity of living organisms. The source of water for plants and animals is mainly precipitation and groundwater, as well as dew and fog.
Moisture is a necessary condition for the existence of all living organisms on Earth. Life originated in the aquatic environment. Land dwellers are still dependent on water. For many species of animals and plants, water continues to be a habitat. The importance of water in life processes is determined by the fact that it is the main environment in the cell where metabolic processes take place and is the most important initial, intermediate and final product of biochemical transformations. The importance of water is also determined by its quantitative content. Living organisms consist of at least 3/4 water.
In relation to water, higher plants are divided into
- hydrophytes - aquatic plants (water lily, arrowhead, duckweed);
- hygrophytes - inhabitants of excessively moist places (calamus, watch);
- mesophytes - plants with normal humidity conditions (lily of the valley, valerian, lupine);
- xerophytes - plants living in conditions of constant or seasonal moisture deficiency (saxaul, camel thorn, ephedra) and their varieties - succulents (cacti, euphorbia).
Adaptations to living in dehydrated environments and environments with periodic lack of moisture An important feature of the main climatic factors (light, temperature, humidity) is their natural variability during the annual cycle and even daily, as well as depending on geographic zonation. In this regard, adaptations of living organisms also have a regular and seasonal nature. Adaptation of organisms to environmental conditions can be rapid and reversible or quite slow, depending on the depth of exposure to the factor. As a result of their vital activity, organisms are able to change abiotic living conditions. For example, plants of the lower tier find themselves in conditions of less light; the processes of decomposition of organic substances that occur in bodies of water often cause oxygen deficiency for other organisms. Due to the activity of aquatic organisms, temperature and water regimes, the amount of oxygen, carbon dioxide, pH of the environment, the spectral composition of light, etc. change. Air environment and its gas composition
The development of the air environment by organisms began after they reached land. Life in the air required specific adaptations and a high level of organization of plants and animals. Low density and water content, high oxygen content, ease of movement of air masses, sudden changes in temperature, etc. significantly affected the breathing process, water exchange and movement of living beings. The vast majority of terrestrial animals have acquired the ability to fly during evolution (75% of all species of terrestrial animals). Many species are characterized by ansmochoria - dispersal with the help of air currents (spores, seeds, fruits, protozoan cysts, insects, spiders, etc.). Some plants have become wind pollinated. For the successful existence of organisms, not only the physical but also the chemical properties of air and the content of gas components necessary for life are important. Oxygen. For the vast majority of living organisms, oxygen is vital. In an oxygen-free environment, only anaerobic bacteria can grow. Oxygen ensures the implementation of exothermic reactions, during which the energy necessary for the life of organisms is released. It is the final electron acceptor, which is split off from the hydrogen atom in the process of energy exchange. In a chemically bound state, oxygen is part of many very important organic and mineral compounds of living organisms. Its role as an oxidizing agent in the cycle of individual elements of the biosphere is enormous. The only producers of free oxygen on Earth are green plants, which form it during photosynthesis. A certain amount of oxygen is formed as a result of photolysis of water vapor by ultraviolet rays outside the ozone layer. The absorption of oxygen by organisms from the external environment occurs over the entire surface of the body (protozoa, worms) or through special respiratory organs: trachea (insects), gills (fish), lungs (vertebrates).
Oxygen is chemically bound and transported throughout the body by special blood pigments: hemoglobin (vertebrates), hemocyapin (molluscs, crustaceans). Organisms living in conditions of constant lack of oxygen have developed appropriate adaptations: increased oxygen capacity of the blood, more frequent and deeper respiratory movements, large lung volume (in highland dwellers, birds) or a decrease in the use of oxygen by tissues due to an increase in the amount of myoglobin - an oxygen accumulator in the tissues (in inhabitants of the aquatic environment). Due to the high solubility of CO 2 and O 2 in water, their relative content here is higher (2-3 times) than in the air (Fig. 1). This circumstance is very important for hydrobionics, which use either dissolved oxygen for respiration or CO 2 for photosynthesis (aquatic phototrophs). Carbon dioxide. The normal amount of this gas in the air is small - 0.03% (by volume) or 0.57 mg/l. As a result, even small fluctuations in the CO 2 content are significantly reflected in the process of photosynthesis, which directly depends on it. The main sources of CO 2 entering the atmosphere are the respiration of animals and plants, combustion processes, volcanic eruptions, the activity of soil microorganisms and fungi, industrial enterprises and transport. Having the property of absorption in the infrared region of the spectrum, carbon dioxide affects the optical parameters and temperature regime of the atmosphere, causing the well-known “greenhouse effect”. An important environmental aspect is the increase in solubility of oxygen and carbon dioxide in water as its temperature decreases. That is why the fauna of water basins of polar and subpolar latitudes is very abundant and diverse, mainly due to the increased concentration of oxygen in cold water. The dissolution of oxygen in water, like any other gas, obeys Henry's law: it is inversely proportional to temperature and stops when the boiling point is reached. In the warm waters of tropical pools, a reduced concentration of dissolved oxygen limits respiration, and therefore the vital activity and number of aquatic animals. Recently, there has been a noticeable deterioration in the oxygen regime of many water bodies, caused by an increase in the amount of organic pollutants, the destruction of which requires large amounts of oxygen. Zoning of distribution of living organisms
Geographical (latitudinal) zoning In the latitudinal direction from north to south, the following natural zones are successively located on the territory of the Russian Federation: tundra, taiga, deciduous forest, steppe, desert. Among the climate elements that determine the zonality of the distribution and distribution of organisms, the leading role is played by abiotic factors - temperature, humidity, light conditions. The most noticeable zonal changes are manifested in the nature of vegetation - the leading component of the biocenosis. This, in turn, is accompanied by changes in the composition of animals - consumers and destructors of organic residues in food chains. Tundra- a cold, treeless plain of the northern hemisphere. Its climatic conditions are unsuitable for plant growth and decomposition of organic residues (permafrost, relatively low temperatures even in summer, short periods of above-zero temperatures). Here, unique biocenoses, small in species composition (mosses, lichens), were formed. In this regard, the productivity of the tundra biocenosis is low: 5-15 c/ha of organic matter per year. Zone taiga characterized by relatively favorable soil and climatic conditions, especially for coniferous species. Rich and highly productive biocenoses have formed here. The annual formation of organic matter is 15-50 c/ha. Temperate zone conditions led to the formation of complex biocenoses deciduous forests with the highest biological productivity in the Russian Federation (up to 60 c/ha per year). Varieties of deciduous forests are oak forests, beech-maple forests, mixed forests, etc. Such forests are characterized by well-developed shrub and herbaceous undergrowth, which facilitates the placement of fauna of various types and numbers. Steppes- a natural zone of the temperate zone of the Earth’s hemispheres, which is characterized by insufficient water supply, therefore herbaceous, mainly cereal vegetation (feather grass, fescue, etc.) predominates here. The fauna is diverse and rich (fox, hare, hamster, mice, many birds, especially migratory ones). The steppe zone contains the most important areas for grain production, industrial crops, vegetable crops and livestock. The biological productivity of this natural zone is relatively high (up to 50 c/ha per year). Deserts predominate in Central Asia. Due to low precipitation and high temperatures in summer, vegetation occupies less than half of the territory of this zone and has specific adaptations to dry conditions. The fauna is diverse, its biological features have been discussed before. The annual formation of organic matter in the desert zone does not exceed 5 c/ha (Fig. 107). Salinity of the environment Salinity of the aquatic environment characterized by the content of soluble salts in it. Fresh water contains 0.5-1.0 g/l, and sea water contains 10-50 g/l of salts. The salinity of the aquatic environment is important for its inhabitants. There are animals adapted to live only in fresh water (cyprinids) or only in sea water (herrings). In some fish, individual stages of individual development take place at different water salinities, for example, the common eel lives in fresh water bodies and migrates to the Sargasso Sea to spawn. Such aquatic inhabitants require appropriate regulation of the salt balance in the body.
Mechanisms of regulation of the ionic composition of organisms. Land animals are forced to regulate the salt composition of their liquid tissues to maintain the internal environment in a constant or almost constant chemically unchanged ionic state. The main way to maintain salt balance in aquatic organisms and land plants is to avoid habitats with unsuitable salinity. Such mechanisms must work especially intensely and accurately in migratory fish (salmon, chum salmon, pink salmon, eel, sturgeon), which periodically move from sea water to fresh water or vice versa. Osmotic regulation occurs most simply in fresh water. It is known that in the latter the concentration of ions is much lower than in liquid tissues. According to the laws of osmosis, the external environment enters the cells along a concentration gradient through semi-permeable membranes, and a kind of “dilution” of the internal contents occurs. If such a process were not controlled, the body could swell and die. However, freshwater organisms have organs that remove excess water. The preservation of ions necessary for life is facilitated by the fact that the urine of such organisms is quite dilute (Fig. 2, a). The separation of such a dilute solution from the internal fluids probably requires the active chemical work of specialized cells or organs (kidneys) and their consumption of a significant proportion of the total basal metabolic energy. On the contrary, marine animals and fish drink and absorb only sea water, thereby replenishing its constant release from the body into the external environment, which is characterized by a high osmotic potential. In this case, monovalent ions of salt water are actively removed outward by the gills, and divalent ions by the kidneys (Fig. 2, b). Cells spend quite a lot of energy pumping out excess water, so when salinity increases and water in the body decreases, organisms usually switch to an inactive state - salt anabiosis. This is typical for species living in periodically drying pools of sea water, estuaries, and littoral zones (rotifers, amphipods, flagellates, etc.) Salinity of the upper crust is determined by the content of potassium and sodium ions in it, and, like the salinity of the aquatic environment, is important for its inhabitants and, first of all, plants that have appropriate adaptation to it. This factor is not accidental for plants; it accompanies them during the evolutionary process. The so-called saline vegetation (solyanka, licorice, etc.) is confined to soils with a high content of potassium and sodium. The top layer of the earth's crust is soil. In addition to soil salinity, other indicators are distinguished: acidity, hydrothermal regime, soil aeration, etc. Together with the relief, these properties of the earth's surface, called edaphic environmental factors, have an ecological impact on its inhabitants. Edaphic environmental factors Properties of the earth's surface that have an environmental impact on its inhabitants.
Depending on edaphic factors, a number of ecological groups of plants can be distinguished. Based on the reaction to the acidity of the soil solution, they are distinguished:
In relation to the chemical composition of the soil, plants are divided into
In relation to individual batteries
In relation to the mechanical composition
The terrain and the nature of the soil significantly influence the specific movement of animals and the distribution of species whose life activities are temporarily or permanently associated with the soil. The nature of the root system (deep, surface) and the lifestyle of the soil fauna depend on the hydrothermal regime of soils, their aeration, mechanical and chemical composition. The chemical composition of the soil and the diversity of its inhabitants affect its fertility. The most fertile are chernozem soils rich in humus. As an abiotic factor, relief influences the distribution of climatic factors and, thus, the formation of the corresponding flora and fauna. For example, on the southern slopes of hills or mountains there is always a higher temperature, better illumination and, accordingly, less humidity. | |||
Abiotic factors name the entire set of factors in the inorganic environment that influence the life and distribution of animals and plants (V.I. Korobkin, L.V. Peredelsky, 2000).
Chemical factors- these are those that originate from the chemical composition of the environment. They include the chemical composition of the atmosphere, water and soil, etc.
Physical factors- these are those whose source is a physical state or phenomenon (mechanical, wave, etc.). These are temperature, pressure, wind, humidity, radiation regime, etc. The structure of the surface, geological and climatic differences determine a wide variety of abiotic factors.
Among the chemical and physical environmental factors, three groups of factors are distinguished: climatic, soil cover (edaphic) factors and water environment factors.
I. The most important climatic factors:
1. Radiant energy of the Sun.
Infrared rays (wavelength greater than 0.76 microns) are of primary importance for life, accounting for 45% of the total energy of the Sun. In the processes of photosynthesis, the most important role is played by ultraviolet rays (wavelength up to 0.4 microns), constituting 7% of the energy of solar radiation. The rest of the energy is in the visible part of the spectrum with a wavelength of 0.4 - 0.76 microns.
2. Illumination of the earth's surface.
It plays an important role for all living things, and organisms are physiologically adapted to the cycle of day and night. Almost all animals have daily rhythms of activity associated with the change of day and night.
3. Ambient air humidity.
Associated with the saturation of air with water vapor. Up to 50% of all atmospheric moisture is concentrated in the lower layers of the atmosphere (up to 2 km altitude).
The amount of water vapor in the air depends on the air temperature. For a specific temperature, there is a certain limit of air saturation with water vapor, which is called the maximum. The difference between the maximum and given saturation of air with water vapor is called humidity deficit (lack of saturation). Humidity deficiency is an important environmental parameter, as it characterizes two quantities: temperature and humidity.
It is known that an increase in moisture deficiency during certain periods of the growing season promotes increased fruiting of plants, and in some insects leads to outbreaks of reproduction.
4. Precipitation.
Due to condensation and crystallization of water vapor in high layers of the atmosphere, clouds and precipitation form. Dew and fog form in the ground layer.
Moisture is the main factor determining the division of ecosystems into forest, steppe and desert. Annual precipitation below 1000 mm corresponds to the stress zone for many tree species, and the tolerance limit of most of them is about 750 mm/year. At the same time, for most cereals this limit is much lower - approximately 250 mm/year, and cacti and other desert plants are able to grow with 50-100 mm of precipitation per year. Accordingly, in places with precipitation above 750 mm/year, forests usually develop, from 250 to 750 mm/year - cereal steppes, and where there is even less precipitation, the vegetation is represented by drought-resistant crops: cacti, wormwood and tumbleweed species. At intermediate values of annual precipitation, ecosystems of a transitional type develop (forest-steppe, semi-desert, etc.).
Precipitation regime is the most important factor determining the migration of pollutants in the biosphere. Precipitation is one of the links in the water cycle on Earth.
5. Gas composition of the atmosphere.
It is relatively constant and includes mainly nitrogen and oxygen with an admixture of carbon dioxide, argon and other gases. In addition, the upper layers of the atmosphere contain ozone. There are also solid and liquid particles in the atmospheric air.
Nitrogen is involved in the formation of protein structures in organisms; oxygen provides oxidative processes; carbon dioxide is involved in photosynthesis and is a natural damper of the Earth's thermal radiation; Ozone is a screen for ultraviolet radiation. Solid and liquid particles affect the transparency of the atmosphere, preventing the passage of sunlight to the Earth's surface.
6. Temperature on the surface of the globe.
This factor is closely related to solar radiation. The amount of heat falling on a horizontal surface is directly proportional to the sine of the angle of the Sun above the horizon. Therefore, daily and seasonal temperature fluctuations are observed in the same areas. The higher the latitude of the area (north and south of the equator), the greater the angle of inclination of the sun's rays to the Earth's surface and the colder the climate.
Temperature, like precipitation, is very important in determining the nature of an ecosystem, although temperature plays in some sense a secondary role compared to precipitation. Thus, when their quantity is 750 mm/year or more, forest communities develop, and the temperature only determines what type of forest will form in the region. For example, spruce and fir forests are typical for cold regions with heavy snow cover in winter and a short growing season, that is, for the north or high mountains. Deciduous trees are also able to withstand frosty winters, but require a longer growing season, so they predominate at temperate latitudes. Powerful evergreen broadleaf species with rapid growth, unable to withstand even short-term frosts, dominate in the tropics (near the equator). Similarly, any territory with an annual precipitation of less than 250 mm is a desert, but in terms of their biota, deserts in the hot zone differ significantly from those characteristic of cold regions.
7. Movement of air masses (wind).
The cause of wind is unequal heating of the earth's surface associated with pressure changes. The wind flow is directed towards lower pressure, i.e. to where the air is warmer. In the surface layer of air, the movement of air masses affects all parameters: humidity, etc.
Wind is the most important factor in the transfer and distribution of impurities in the atmosphere.
8. Atmospheric pressure.
A normal pressure is 1 kPa, corresponding to 750.1 mm. Hg Art. Within the globe there are constant areas of high and low pressure, and seasonal and daily pressure minimums and maximums are observed at the same points.
II. Abiotic factors of soil cover (edaphic)
Edaphic factors- this is a set of chemical, physical and other properties of soils that affect both the organisms living in them and the root system of plants. Of these, the most important environmental factors are humidity, temperature, structure and porosity, reaction of the soil environment, and salinity.
In the modern understanding, soil is a natural historical formation that arose as a result of changes in the surface layer of the lithosphere by the combined influence of water, air and living organisms (V. Korobkin, L. Peredelsky). The soil is fertile, i.e. gives life to plants and, therefore, food to animals and humans. It consists of solid, liquid and gaseous components; contains living macro- and microorganisms (plant and animal).
The solid component is represented by mineral and organic parts. In the soil there are most of the primary minerals remaining from the parent rock, and less of the secondary minerals formed as a result of the decomposition of the primary ones. These are clay minerals of colloidal sizes, as well as salt minerals: carbonates, sulfates, etc.
The organic part is represented by humus, i.e. complex organic matter formed as a result of the decomposition of dead organic matter. Its content in the soil ranges from tenths to 22%. It plays an important role in soil fertility due to the nutrients it contains.
Soil biota is represented by fauna and flora. Fauna is earthworms, wood lice, etc., flora is mushrooms, bacteria, algae, etc.
The entire liquid component of soils is called soil solution. It may contain chemical compounds: nitrates, bicarbonates, phosphates, etc., as well as water-soluble organic acids, their salts, sugars. The composition and concentration of the soil solution determine the reaction of the environment, the indicator of which is the pH value.
Soil air has a high content of CO2, hydrocarbons and water vapor. All these elements determine the chemical properties of the soil.
All soil properties depend not only on climatic factors, but also on the vital activity of soil organisms, which mechanically mix it and process it chemically, ultimately creating the conditions necessary for themselves. With the participation of organisms in the soil, a constant cycle of substances and migration of energy occurs. The cycle of substances in the soil can be represented as follows (V.A. Radkevich).
Plants synthesize organic matter, and animals perform mechanical and biochemical destruction of it and, as it were, prepare it for humus formation. Microorganisms synthesize soil humus and then decompose it.
Soil provides water supply to plants. The more easily it gives water to plants, the greater the importance of soil in water supply to plants. This depends on the structure of the soil and the degree of swelling of its particles.
Soil structure should be understood as a complex of soil aggregates of various shapes and sizes, formed from the primary mechanical elements of the soil. The following soil structures are distinguished: granular, silty, nutty, lumpy, blocky.
The main function of higher plants in the soil-forming process is the synthesis of organic matter. This organic matter accumulates in the above-ground and underground parts of plants during the process of photosynthesis, and after they die, it passes into the soil and undergoes mineralization. The rate of mineralization of organic matter and the composition of the resulting compounds largely depend on the type of vegetation. The decomposition products of needles, leaves, and grass wood are different both in chemical composition and in their influence on the process of soil formation. In combination with other factors, this leads to the formation of different types of soils.
The main function of animals in the soil-forming process is the consumption and destruction of organic matter, as well as the redistribution of energy reserves. Mobile soil animals play a major role in soil formation processes. They loosen the soil, create conditions for its aeration, and mechanically move organic and inorganic substances in the soil. For example, earthworms throw up to 80–90/ha of material onto the surface, and steppe rodents move hundreds of m3 of soil and organic matter up and down.
The influence of climatic conditions on soil formation processes is undoubtedly great. The amount of precipitation, temperature, and the influx of radiant energy - light and heat - determine the formation of plant mass and the rate of decomposition of plant residues, on which the humus content in the soil depends.
As a result of the movement and transformation of substances, the soil is divided into separate layers, or horizons, the combination of which makes up the soil profile.
The surface horizon, litter or turf, consists mostly of freshly fallen and partially decomposed leaves, branches, animal remains, fungi and other organic matter. Usually painted in a dark color - brown or black. The underlying humus horizon A1 is usually a porous mixture of partially decomposed organic matter (humus), living organisms and some inorganic particles. It is usually darker and looser than the lower horizons. The bulk of soil organic matter and plant roots are concentrated in these two upper horizons.
Its color can tell a lot about soil fertility. For example, a dark brown or black humus horizon is rich in organic matter and nitrogen. Gray, yellow or red soils have little organic matter and require nitrogen fertilizers to increase their yield.
In forest soils, under the A1 horizon lies a low-fertility podzolic horizon A2, which has a light shade and a fragile structure. In chernozem, dark chestnut, chestnut and other types of soils this horizon is absent. Even deeper in many types of soils is the B horizon - the illuvial, or inwash horizon. Mineral and organic substances from the overlying horizons are washed into it and accumulate in it. Most often it is colored brown and has a high density. Even lower lies the parent rock C, on which the soil is formed.
Structure and porosity determine the availability of nutrients to plants and soil animals. Soil particles bound together by molecular forces form the structure of the soil. Between them, voids called pores are formed. The structure and porosity of the soil ensures good aeration. Soil air, like soil water, is located in the pores between soil particles. Porosity increases from clays to loams and sands. Free gas exchange occurs between the soil and the atmosphere, as a result of which the gas composition of both environments is similar. Usually, due to the respiration of the organisms inhabiting it, the soil air contains slightly less oxygen and more carbon dioxide than the atmospheric air. Oxygen is necessary for plant roots, soil animals and decomposer organisms that decompose organic matter into inorganic components. If waterlogging occurs, soil air is displaced by water and conditions become anaerobic. The soil gradually becomes acidic as anaerobic organisms continue to produce carbon dioxide. The soil, if it is not rich in bases, can become extremely acidic, and this, along with the depletion of oxygen reserves, has an adverse effect on soil microorganisms. Prolonged anaerobic conditions lead to plant death.
Temperature soil depends on external temperature, and at a depth of 0.3 m, due to low thermal conductivity, the amplitude of its fluctuations is less than 20C (Yu.V. Novikov, 1979), which is important for soil animals (there is no need to move up and down in search of a more comfortable temperature) . In summer the soil temperature is lower than the air, and in winter it is higher.
Chemical factors include environmental reaction and salinity. Environment reaction very important for many plants and animals. In dry climates, neutral and alkaline soils predominate; in humid areas, acidic soils predominate. Absorbed bases, acids and various salts in the process of their interaction with water create a certain concentration of H+ - and OH- - ions, which determine one or another reaction of the soil. Usually a distinction is made between soils with neutral, acidic and alkaline reactions.
Soil alkalinity is due to the presence of mainly Na+ - ions in the absorbing complex. Such soil, when in contact with water containing CO2, gives a pronounced alkaline reaction, which is associated with the formation of soda.
In cases where the soil absorption complex is saturated with Ca2+ and Mg2+, its reaction is close to neutral. At the same time, it is known that calcium carbonate in pure water and water devoid of CO2 gives strong alkalinity. This is explained by the fact that with an increase in CO2 content in the soil solution, the solubility of calcium (2+) increases with the formation of bicarbonate, which leads to a decrease in pH. But with an average amount of CO2 in the soil, the reaction becomes slightly alkaline.
During the decomposition of plant residues, especially forest litter, organic acids are formed that react with absorbed soil cations. Acidic soils have a number of negative properties, which is why they are infertile. In such an environment, the active beneficial activity of soil microflora is suppressed. To increase soil fertility, the use of lime is widely practiced.
High alkalinity inhibits plant growth, and its water-physical properties sharply deteriorate, destroys the structure, enhances the mobility and removal of colloids. Many cereals give the best harvest on neutral and slightly alkaline soils (barley, wheat), which are usually chernozems.
In areas of insufficient atmospheric moisture, they are common salted soil. Soils with an excess content of water-soluble salts (chlorides, sulfates, carbonates) are called saline. They arise as a result of secondary soil salinization during the evaporation of groundwater, the level of which has risen to the soil horizons. Among saline soils, solonchaks and solonetzes are distinguished. Salt marshes are found in Kazakhstan and Central Asia, along the banks of salty rivers. Soil salinization leads to a drop in crop yields. Earthworms, even with a low degree of soil salinity, cannot survive for a long time.
Plants that live in saline soils are called halophytes. Some of them secrete excess salts through the leaves or accumulate them in their bodies. That is why they are sometimes used to produce soda and potash.
Water occupies the predominant part of the Earth's biosphere (71% of the total area of the earth's surface).
The most important abiotic factors of the aquatic environment are the following:
1. Density and viscosity.
The density of water is 800 times, and the viscosity is approximately 55 times greater than air.
2. Heat capacity.
Water has a high heat capacity, so the ocean is the main receiver and accumulator of solar energy.
3. Mobility.
The constant movement of water masses helps maintain the relative homogeneity of physical and chemical properties.
4. Temperature stratification.
A change in water temperature is observed along the depth of the water body.
5. Periodic (annual, daily, seasonal) temperature changes.
The lowest water temperature is considered to be -20C, the highest + 35-370C. The dynamics of water temperature fluctuations is less than that of air.
6. Water transparency.
Determines the light regime below the surface of the water. The photosynthesis of green bacteria, phytoplankton, higher plants, and, consequently, the accumulation of organic matter depends on transparency (and its inverse characteristic, turbidity).
Turbidity and transparency depend on the content of suspended substances in water, including those entering water bodies along with industrial discharges. In this regard, transparency and suspended solids content are the most important characteristics of natural and waste waters that are subject to control at an industrial enterprise.
7. Salinity of water.
The content of carbonates, sulfates, and chlorides in water is of great importance for living organisms. There are few salts in fresh waters, and carbonates predominate. Ocean waters contain an average of 35 g/l of salts, the Black Sea - 19 g/l, the Caspian - about 14 g/l. Chlorides and sulfates predominate here. Almost all elements of the periodic table are dissolved in sea water.
8. Dissolved oxygen and carbon dioxide.
Excessive consumption of oxygen for the respiration of living organisms and for the oxidation of organic and mineral substances entering the water with industrial discharges leads to the impoverishment of the living population to the point where aerobic organisms cannot live in such water.
9. Hydrogen ion concentration (pH).
All aquatic organisms have adapted to a certain pH level: some prefer an acidic environment, others prefer an alkaline environment, and others prefer a neutral one. A change in these characteristics can lead to the death of aquatic organisms.
10. Flow not only greatly influences the concentration of gases and nutrients, but also directly acts as a limiting factor. Many river plants and animals are morphologically and physiologically specially adapted to maintaining their position in the flow: they have well-defined limits of tolerance to the flow factor.
The main topographic factor is height above sea level. With altitude, average temperatures decrease, daily temperature differences increase, precipitation, wind speed and radiation intensity increase, atmospheric pressure and gas concentrations decrease. All these factors influence plants and animals, causing vertical zonation.
Mountain ranges may serve as climate barriers. Mountains also serve as barriers to the spread and migration of organisms and can play the role of a limiting factor in the processes of speciation.
Another topographic factor is slope exposure. In the northern hemisphere, south-facing slopes receive more sunlight, so the light intensity and temperature here are higher than on valley floors and northern-facing slopes. In the southern hemisphere the opposite situation occurs.
An important relief factor is also slope steepness. Steep slopes are characterized by rapid drainage and soil washing away, so the soils here are thin and drier. If the slope exceeds 35b, soil and vegetation usually do not form, but a scree of loose material is created.
Crown fires have a limiting effect on most organisms - the biotic community has to start all over again with what little is left, and many years must pass before the site becomes productive again. Ground fires, on the contrary, have a selective effect: for some organisms they are a more limiting factor, for others - a less limiting factor and thus contribute to the development of organisms with high tolerance to fires. In addition, small ground fires complement the action of bacteria, decomposing dead plants and accelerating the conversion of mineral nutrients into a form suitable for use by new generations of plants. Plants have developed specialized adaptations to fire, just as they have done to other abiotic factors. In particular, the buds of cereals and pines are hidden from fire in the depths of tufts of leaves or needles. In periodically burned habitats, these plant species benefit because fire promotes their preservation by selectively promoting their flourishing.
Light is one of the main environmental factors. Without light, the photosynthetic activity of plants is impossible, and without the latter, life in general is unthinkable, since green plants have the ability to produce the oxygen necessary for all living beings. In addition, light is the only source of heat on planet Earth. It has a direct effect on the chemical and physical processes occurring in organisms and affects metabolism.
Many morphological and behavioral characteristics of various organisms are associated with their exposure to light. The activity of some internal organs of animals is also closely related to lighting. Animal behavior, such as seasonal migration, egg laying, courtship, and spring rutting, is associated with the length of daylight hours.
In ecology, the term “light” refers to the entire range of solar radiation reaching the earth’s surface. The distribution spectrum of solar radiation energy outside the Earth's atmosphere shows that about half of the solar energy is emitted in the infrared region, 40% in the visible region and 10% in the ultraviolet and x-ray regions.
For living matter, the qualitative characteristics of light are important - wavelength, intensity and duration of exposure. There are near ultraviolet radiation (400-200 nm) and far, or vacuum (200-10 nm). Sources of ultraviolet radiation are high-temperature plasma, accelerated electrons, some lasers, the Sun, stars, etc. The biological effect of ultraviolet radiation is caused by chemical changes in the molecules of living cells that absorb them, mainly molecules of nucleic acids (DNA and RNA) and proteins, and is expressed in division disorders , the occurrence of mutations and cell death.
Some of the sun's rays, having traveled a huge distance, reach the surface of the Earth, illuminate and heat it. It is estimated that our planet receives about one two-billionth of solar energy, and of this amount, only 0.1-0.2% is used by green plants to create organic matter. Each square meter of the planet receives an average of 1.3 kW of solar energy. It would be enough to operate an electric kettle or iron.
Lighting conditions play an exceptional role in the life of plants: their productivity and productivity depend on the intensity of sunlight. However, the light regime on Earth is quite diverse. It is different in the forest than in the meadow. Lighting in deciduous and dark coniferous spruce forests is noticeably different.
Light controls the growth of plants: they grow in the direction of greater light. Their sensitivity to light is so great that the shoots of some plants, kept in darkness during the day, react to a flash of light that lasts only two thousandths of a second.
All plants in relation to light can be divided into three groups: heliophytes, sciophytes, facultative heliophytes.
Heliophytes(from the Greek helios - sun and phyton - plant), or light-loving plants, either do not tolerate or do not tolerate even slight shading. This group includes steppe and meadow grasses, tundra plants, early spring plants, most open ground cultivated plants, and many weeds. Among the species of this group we can find common plantain, fireweed, reed grass, etc.
Sciophytes(from the Greek scia - shadow), or shade plants, do not tolerate strong light and live in constant shade under the forest canopy. These are mainly forest herbs. With a sharp lightening of the forest canopy, they become depressed and often die, but many rebuild their photosynthetic apparatus and adapt to life in new conditions.
Facultative heliophytes, or shade-tolerant plants, are able to develop in both very high and low amounts of light. As an example, we can name some trees - common spruce, Norway maple, common hornbeam; shrubs - hazel, hawthorn; herbs - strawberries, field geranium; many indoor plants.
An important abiotic factor is temperature. Any organism is capable of living within a certain temperature range. The distribution area of living things is mainly limited to the area from just below 0 °C to 50 °C.
The main source of heat, as well as light, is solar radiation. An organism can survive only under conditions to which its metabolism is adapted. If the temperature of a living cell drops below freezing, the cell is usually physically damaged and dies as a result of the formation of ice crystals. If the temperature is too high, protein denaturation occurs. This is exactly what happens when boiling a chicken egg.
Most organisms are able to control their body temperature to some extent through various responses. In the vast majority of living beings, body temperature can vary depending on the ambient temperature. Such organisms are unable to regulate their temperature and are called cold-blooded (poikilothermic). Their activity mainly depends on heat coming from outside. The body temperature of poikilothermic organisms is related to the ambient temperature values. Cold-bloodedness is characteristic of such groups of organisms as plants, microorganisms, invertebrates, fish, reptiles, etc.
A significantly smaller number of living beings are capable of actively regulating body temperature. These are representatives of the two highest classes of vertebrates - birds and mammals. The heat they generate is a product of biochemical reactions and serves as a significant source of increased body temperature. This temperature is maintained at a constant level regardless of the ambient temperature. Organisms that are able to maintain a constant optimal body temperature regardless of the ambient temperature are called warm-blooded (homeothermic). Due to this property, many species of animals can live and reproduce at temperatures below zero (reindeer, polar bear, pinnipeds, penguin). Maintaining a constant body temperature is ensured by good thermal insulation created by fur, dense plumage, subcutaneous air cavities, a thick layer of adipose tissue, etc.
A special case of homeothermy is heterothermy (from the Greek heteros - different). Different levels of body temperature in heterothermic organisms depend on their functional activity. During the period of activity, they have a constant body temperature, and during the period of rest or hibernation, the temperature drops significantly. Heterothermy is characteristic of gophers, marmots, badgers, bats, hedgehogs, bears, hummingbirds, etc.
Humidification conditions play a special role in the life of living organisms.
Water- the basis of living matter. For most living organisms, water is one of the main environmental factors. This is the most important condition for the existence of all life on Earth. All life processes in the cells of living organisms take place in an aquatic environment.
Water is not chemically changed by most of the technical compounds it dissolves. This is very important for living organisms, since the nutrients necessary for their tissues are supplied in aqueous solutions in a relatively little changed form. Under natural conditions, water always contains one or another amount of impurities, not only interacting with solid and liquid substances, but also dissolving gases.
The unique properties of water predetermine its special role in the formation of the physical and chemical environment of our planet, as well as in the emergence and maintenance of an amazing phenomenon - life.
The human embryo consists of 97% water, and in newborns its amount is 77% of body weight. By the age of 50, the amount of water in the human body decreases and already accounts for 60% of its mass. The main part of the water (70%) is concentrated inside the cells, and 30% is intercellular water. Human muscles are 75% water, the liver is 70%, the brain is 79%, and the kidneys are 83%.
The body of an animal, as a rule, contains at least 50% water (for example, an elephant - 70%, a caterpillar eating plant leaves - 85-90%, jellyfish - more than 98%).
The elephant needs the most water (based on daily needs) of any land animal - about 90 liters. Elephants are one of the best “hydrogeologists” among animals and birds: they sense bodies of water at a distance of up to 5 km! Only the bison are further away - 7-8 km. In dry times, elephants use their tusks to dig holes in dry river beds to collect water. Buffaloes, rhinoceroses and other African animals readily use elephant wells.
The distribution of life on Earth is directly related to precipitation. Humidity is not the same in different parts of the world. The most precipitation falls in the equatorial zone, especially in the upper reaches of the Amazon River and on the islands of the Malay Archipelago. Their number in some areas reaches 12,000 mm per year. So, on one of the Hawaiian islands it rains from 335 to 350 days a year. This is the wettest place on Earth. The average annual precipitation here reaches 11,455 mm. By comparison, the tundra and deserts receive less than 250 mm of precipitation per year.
Animals relate to moisture differently. Water as a physical and chemical body has a continuous impact on the life of hydrobionts (aquatic organisms). It not only satisfies the physiological needs of organisms, but also delivers oxygen and food, carries away metabolites, and transports sexual products and aquatic organisms themselves. Thanks to the mobility of water in the hydrosphere, the existence of attached animals is possible, which, as is known, do not exist on land.
Edaphic factors
The entire set of physical and chemical properties of soil that have an ecological impact on living organisms refers to edaphic factors (from the Greek edaphos - base, earth, soil). The main edaphic factors are the mechanical composition of the soil (size of its particles), relative looseness, structure, water permeability, aeration, chemical composition of the soil and substances circulating in it (gases, water).
The nature of the soil granulometric composition may have ecological significance for animals that, at a certain period of life, live in the soil or lead a burrowing lifestyle. Insect larvae generally cannot live in soil that is too rocky; burrowing Hymenoptera, laying eggs in underground passages, many locusts, burying egg cocoons in the ground, need it to be sufficiently loose.
An important characteristic of soil is its acidity. It is known that the acidity of the medium (pH) characterizes the concentration of hydrogen ions in the solution and is numerically equal to the negative decimal logarithm of this concentration: pH = -log. Aqueous solutions can have a pH from 0 to 14. Neutral solutions have a pH of 7, acidic solutions are characterized by pH values less than 7, and alkaline solutions are characterized by pH values greater than 7. Acidity can serve as an indicator of the rate of general metabolism of a community. If the pH of the soil solution is low, this means that the soil contains few nutrients, so its productivity is extremely low.
In relation to soil fertility, the following ecological groups of plants are distinguished:
- oligotrophs (from the Greek olygos - small, insignificant and trophe - food) - plants of poor, infertile soils (Scots pine);
- mesotrophs (from the Greek mesos - average) - plants with a moderate need for nutrients (most forest plants of temperate latitudes);
- eutrophic(from the Greek she - good) - plants that require a large amount of nutrients in the soil (oak, hazel, gooseberry).
Orographic factors
The distribution of organisms on the earth's surface is influenced to a certain extent by factors such as features of relief elements, altitude above sea level, exposure and steepness of slopes. They are combined into a group of orographic factors (from the Greek oros - mountain). Their impact can greatly influence local climate and soil development.
One of the main orographic factors is altitude above sea level. With altitude, average temperatures decrease, daily temperature differences increase, precipitation, wind speed and radiation intensity increase, atmospheric pressure and gas concentrations decrease. All these factors influence plants and animals, causing vertical zonation.
A typical example is vertical zoning in the mountains. Here, with every 100 m rise, the air temperature decreases by an average of 0.55 °C. At the same time, humidity changes and the length of the growing season shortens. As the altitude of the habitat increases, the development of plants and animals changes significantly. At the foot of the mountains there may be tropical seas, and at the top arctic winds blow. On one side of the mountains it can be sunny and warm, on the other it can be damp and cold.
Another orographic factor is slope exposure. On the northern slopes the plants form shadow forms, and on the southern slopes they form light forms. The vegetation here is represented mainly by drought-resistant shrubs. South-facing slopes receive more sunlight, so the light intensity and temperature here are higher than on valley floors and northern-facing slopes. This is associated with significant differences in the heating of air and soil, the rate of snow melting, and soil drying.
An important factor is the steepness of the slope. The influence of this indicator on the living conditions of organisms is reflected mainly through the characteristics of the soil environment, water and temperature regimes. Steep slopes are characterized by rapid drainage and soil washing away, so the soils here are thin and drier. If the slope exceeds 35°, slides of loose material are usually created.
Hydrographic factors
Hydrographic factors include such characteristics of the aquatic environment as water density, the speed of horizontal movements (current), the amount of oxygen dissolved in water, the content of suspended particles, flow, temperature and light regimes of water bodies, etc.
Organisms that live in the aquatic environment are called hydrobionts.
Different organisms have adapted to the density of water and certain depths in their own way. Some species can withstand pressures from several to hundreds of atmospheres. Many fish, cephalopods, crustaceans, and starfish live at great depths at a pressure of about 400-500 atm.
The high density of water ensures the existence of many non-skeletal forms in the aquatic environment. These are small crustaceans, jellyfish, unicellular algae, keeled and pteropod mollusks, etc.
The high specific heat capacity and high thermal conductivity of water determine the more stable temperature regime of water bodies compared to land. The amplitude of annual temperature fluctuations does not exceed 10-15 °C. In continental waters it is 30-35 °C. In the reservoirs themselves, the temperature conditions between the upper and lower layers of water differ significantly. In the deep layers of the water column (in the seas and oceans), the temperature regime is stable and constant (3-4 °C).
An important hydrographic factor is the light regime of water bodies. The amount of light quickly decreases with depth, so in the World Ocean algae live only in the illuminated zone (most often at depths from 20 to 40 m). The density of marine organisms (their number per unit area or volume) naturally decreases with depth.
Chemical factors
The effect of chemical factors manifests itself in the form of penetration into the environment of chemical substances that were not present in it before, which is largely due to modern anthropogenic influence.
A chemical factor such as gas composition is extremely important for organisms living in the aquatic environment. For example, in the waters of the Black Sea there is a lot of hydrogen sulfide, which makes this pool not entirely favorable for the life of some animals in it. The rivers that flow into it carry with them not only pesticides or heavy metals washed off from the fields, but also nitrogen and phosphorus. And this is not only agricultural fertilizer, but also food for marine microorganisms and algae, which, due to an excess of nutrients, begin to develop rapidly (water blooms). When they die, they sink to the bottom and consume a significant amount of oxygen during the process of decay. Over the past 30-40 years, the bloom of the Black Sea has increased significantly. In the lower layer of water, oxygen is replaced by poisonous hydrogen sulfide, so there is practically no life here. The organic world of the sea is relatively poor and monotonous. Its living layer is limited to a narrow surface 150 m thick. As for terrestrial organisms, they are insensitive to the gas composition of the atmosphere, since it is constant.
The group of chemical factors also includes such an indicator as water salinity (the content of soluble salts in natural waters). According to the amount of dissolved salts, natural waters are divided into the following categories: fresh water - up to 0.54 g/l, brackish water - from 1 to 3, slightly salty - from 3 to 10, salty and very salty water - from 10 to 50, brine - more 50 g/l. Thus, in fresh water bodies on land (streams, rivers, lakes) 1 kg of water contains up to 1 g of soluble salts. Sea water is a complex salt solution, the average salinity of which is 35 g/kg of water, i.e. 3.5%.
Living organisms living in an aquatic environment are adapted to a strictly defined salinity of water. Freshwater forms cannot live in the seas, and marine forms cannot tolerate desalination. If the salinity of the water changes, animals move in search of a favorable environment. For example, when the surface layers of the sea are desalinated after heavy rains, some species of sea crustaceans descend to a depth of up to 10 m.
Oyster larvae live in the brackish waters of small bays and estuaries (semi-enclosed coastal bodies of water that freely communicate with the ocean or sea). The larvae grow especially quickly when the water salinity is 1.5-1.8% (somewhere between fresh and salt water). At a higher salt content, their growth is somewhat suppressed. When the salt content decreases, growth is already noticeably suppressed. At a salinity of 0.25%, the growth of larvae stops and they all die.
Pyrogenic factors
These include fire exposure factors, or fires. Currently, fires are considered to be a very significant and one of the natural abiotic environmental factors. When used correctly, fire can be a very valuable environmental tool.
At first glance, fires are a negative factor. But in reality this is not the case. Without fires, the savannah, for example, would quickly disappear and become covered with dense forest. However, this does not happen, since the tender shoots of the trees die in the fire. Because trees grow slowly, few survive fires and grow tall enough. Grass grows quickly and recovers just as quickly after fires.
It should be noted that, unlike other environmental factors, people can regulate fires, and therefore they can become a certain limiting factor in the spread of plants and animals. Human-controlled fires produce ash that is rich in beneficial substances. Mixing with the soil, ash stimulates the growth of plants, the quantity of which determines the life of animals.
In addition, many savanna inhabitants, such as the African stork and the secretary bird, use fires for their own purposes. They visit the boundaries of natural or controlled fires and eat insects and rodents there that escape the fire.
Fires can be caused by both natural factors (lightning strikes) and random and non-random human actions. There are two types of fires. Roof fires are the most difficult to contain and regulate. Most often they are very intense and destroy all vegetation and soil organic matter. Such fires have a limiting effect on many organisms.
Ground fires, on the contrary, have a selective effect: for some organisms they are more destructive, for others - less and, thus, contribute to the development of organisms with high resistance to fires. In addition, small ground fires complement the action of bacteria, decomposing dead plants and accelerating the conversion of mineral nutrients into a form suitable for use by new generations of plants. In habitats with infertile soil, fires contribute to its enrichment with ash elements and nutrients.
When there is sufficient moisture (North American prairies), fires stimulate the growth of grasses at the expense of trees. Fires play a particularly important regulatory role in steppes and savannas. Here, periodic fires reduce the likelihood of desert shrub invasion.
Humans are often the cause of an increase in the frequency of wild fires, although a private individual has no right to intentionally (even accidentally) cause a fire in nature. However, the use of fire by specialists is part of proper land management.
Abiotic factors are factors of inanimate nature that directly or indirectly act on an organism - light, temperature, humidity, the chemical composition of the air, water and soil environment, etc. (i.e., properties of the environment, the occurrence and impact of which does not directly depend on the activities of living organisms ).
Light (solar radiation) is an environmental factor characterized by the intensity and quality of the radiant energy of the Sun, which is used by photosynthetic green plants to create plant biomass. Sunlight reaching the Earth's surface is the main source of energy for maintaining the thermal balance of the planet, the water metabolism of organisms, the creation and transformation of organic matter by the autotrophic element of the biosphere, which ultimately makes it possible to form an environment capable of satisfying vital needs
organisms.
Temperature is one of the most important abiotic factors, on which the existence, development and distribution of organisms on Earth largely depends [show]. The importance of temperature lies primarily in its direct influence on the speed and nature of metabolic reactions in organisms. Since daily and seasonal temperature fluctuations increase with distance from the equator, plants and animals, adapting to them, exhibit different needs for heat.
Humidity is an environmental factor characterized by the water content in the air, soil, and living organisms. In nature, there is a daily rhythm of humidity: it increases at night and decreases during the day. Together with temperature and light, humidity plays an important role in regulating the activity of living organisms. The source of water for plants and animals is mainly precipitation and groundwater, as well as dew and fog.
In the abiotic part of the environment (in inanimate nature), all factors can primarily be divided into physical and chemical. However, to understand the essence of the phenomena and processes under consideration, it is convenient to represent abiotic factors as a set of climatic, topographic, cosmic factors, as well as characteristics of the composition of the environment (aquatic, terrestrial or soil).
The main climatic factors include solar energy, temperature, precipitation and humidity, environmental mobility, pressure, and ionizing radiation.
Environmental factors - properties of the environment that have any effect on the body. Indifferent elements of the environment, for example, inert gases, are not environmental factors.
Environmental factors exhibit significant variability in time and space. For example, temperature varies greatly on the surface of land, but is almost constant at the bottom of the ocean or deep in caves.
Classifications of environmental factors
By the nature of the impact
Direct acting - directly affecting the body, mainly on metabolism
Indirectly acting - influencing indirectly, through changes in directly acting factors (relief, exposure, altitude, etc.)
By origin
Abiotic - factors of inanimate nature:
climatic: annual sum of temperatures, average annual temperature, humidity, air pressure
edaphic (edaphogenic): soil mechanical composition, soil air permeability, soil acidity, soil chemical composition
orographic: relief, height above sea level, steepness and aspect of the slope
chemical: gas composition of air, salt composition of water, concentration, acidity
physical: noise, magnetic fields, thermal conductivity and heat capacity, radioactivity, solar radiation intensity
Biotic - related to the activity of living organisms:
phytogenic - influence of plants
mycogenic - influence of fungi
zoogenic - influence of animals
microbiogenic - influence of microorganisms
Anthropogenic (anthropic):
physical: use of nuclear energy, travel on trains and planes, influence of noise and vibration
chemical: the use of mineral fertilizers and pesticides, pollution of the Earth’s shells with industrial and transport waste
biological: food; organisms for which humans can be a habitat or source of food
social - related to relationships between people and life in society
By spending
Resources - elements of the environment that the body consumes, reducing their supply in the environment (water, CO2, O2, light)
Conditions - environmental elements not consumed by the body (temperature, air movement, soil acidity)
By direction
Vectorized - directionally changing factors: waterlogging, soil salinization
Perennial-cyclical - with alternating multi-year periods of strengthening and weakening of a factor, for example climate change in connection with the 11-year solar cycle
Oscillatory (pulse, fluctuation) - fluctuations in both directions from a certain average value (daily fluctuations in air temperature, changes in the average monthly precipitation throughout the year)
Optimum Rule
In accordance with this rule, for an ecosystem, an organism or a certain stage of its development, there is a range of the most favorable (optimal) factor value. Outside the optimum zone there are zones of oppression, turning into critical points beyond which existence is impossible. The maximum population density is usually confined to the optimum zone. Optimum zones for different organisms are not the same. For some, they have a significant range. Such organisms belong to the group of eurybionts. Organisms with a narrow range of adaptation to factors are called stenobionts.
The range of factor values (between critical points) is called environmental valence. A synonym for the term valence is tolerance, or plasticity (variability). These characteristics depend largely on the environment in which the organisms live. If it is relatively stable in its properties (the amplitudes of fluctuations of individual factors are small), it contains more steno-bionts (for example, in an aquatic environment); if it is dynamic, for example, ground-air, eurybionts have a greater chance of survival in it. The optimum zone and ecological valence are usually wider in warm-blooded organisms than in cold-blooded ones. It should also be borne in mind that the ecological valence for the same species does not remain the same in different conditions (for example, in northern and southern regions during certain periods of life, etc.). Young and senile organisms, as a rule, require more conditioned (homogeneous) conditions. Sometimes these requirements are quite ambiguous. For example, with respect to temperature, insect larvae are usually stenobiont (stenothermic), while pupae and adults may be eurybiont (eurythermic).
Related information.
Introduction
Main abiotic factors and their characteristics
Literature
Introduction
Abiotic environmental factors are components and phenomena of inanimate, inorganic nature that directly or indirectly affect living organisms. Naturally, these factors act simultaneously and this means that all living organisms fall under their influence. The degree of presence or absence of each of them significantly affects the viability of organisms, and varies differently for different species. It should be noted that this greatly affects the entire ecosystem as a whole and its sustainability.
Environmental factors, both individually and in combination, when affecting living organisms, force them to change and adapt to these factors. This ability is called ecological valence or plasticity. The plasticity, or environmental valency, of each species is different and has a different effect on the ability of living organisms to survive under changing environmental factors. If organisms not only adapt to biotic factors, but can also influence them, changing other living organisms, then this is impossible with abiotic environmental factors: the organism can adapt to them, but is not able to have any significant reverse influence on them.
Abiotic environmental factors are conditions that are not directly related to the life activity of organisms. The most important abiotic factors include temperature, light, water, composition of atmospheric gases, soil structure, composition of nutrients in it, terrain, etc. These factors can affect organisms both directly, for example light or heat, and indirectly, for example, terrain, which determines the action of direct factors, light, wind, moisture, etc. More recently, the influence of changes in solar activity on biosphere processes has been discovered.
1. Main abiotic factors and their characteristics
Among the abiotic factors are:
Climatic (the influence of temperature, light and humidity);
Geological (earthquake, volcanic eruption, glacial movement, mudflows and avalanches, etc.);
Orographic (features of the terrain where the studied organisms live).
Let us consider the action of the main direct abiotic factors: light, temperature and the presence of water. Temperature, light and humidity are the most important environmental factors. These factors naturally change both throughout the year and day, and in connection with geographic zoning. Organisms exhibit zonal and seasonal adaptation to these factors.
Light as an environmental factor
Solar radiation is the main source of energy for all processes occurring on Earth. In the spectrum of solar radiation, three regions can be distinguished, different in biological action: ultraviolet, visible and infrared. Ultraviolet rays with a wavelength of less than 0.290 microns are destructive to all living things, but they are retained by the ozone layer of the atmosphere. Only a small portion of longer ultraviolet rays (0.300 - 0.400 microns) reaches the Earth's surface. They make up about 10% of radiant energy. These rays are highly chemically active; at high doses they can damage living organisms. In small quantities, however, they are necessary, for example, for humans: under the influence of these rays, vitamin D is formed in the human body, and insects visually distinguish these rays, i.e. see in ultraviolet light. They can navigate by polarized light.
Visible rays with a wavelength of 0.400 to 0.750 microns (they account for most of the energy - 45% - of solar radiation) reaching the Earth's surface are especially important for organisms. Green plants, due to this radiation, synthesize organic matter (carry out photosynthesis), which is used as food by all other organisms. For most plants and animals, visible light is one of the important environmental factors, although there are also those for which light is not a prerequisite for existence (soil, cave and deep-sea types of adaptation to life in the dark). Most animals are able to distinguish the spectral composition of light - have color vision, and plants have brightly colored flowers to attract pollinating insects.
Infrared rays with a wavelength of more than 0.750 microns are not perceived by the human eye, but they are a source of thermal energy (45% of radiant energy). These rays are absorbed by the tissues of animals and plants, causing the tissues to heat up. Many cold-blooded animals (lizards, snakes, insects) use sunlight to increase their body temperature (some snakes and lizards are ecologically warm-blooded animals). Light conditions associated with the Earth's rotation have distinct daily and seasonal cycles. Almost all physiological processes in plants and animals have a daily rhythm with a maximum and minimum at certain hours: for example, at certain hours of the day, a plant flower opens and closes, and animals have developed adaptations to night and day life. Day length (or photoperiod) is of great importance in the life of plants and animals.
Plants, depending on their living conditions, adapt to the shade - shade-tolerant plants or, on the contrary, to the sun - light-loving plants (for example, cereals). However, strong, bright sun (above optimal brightness) suppresses photosynthesis, making it difficult to produce high yields of protein-rich crops in the tropics. In temperate zones (above and below the equator), the development cycle of plants and animals is confined to the seasons of the year: preparation for changes in temperature conditions is carried out on the basis of a signal - changes in day length, which at a certain time of the year in a given place is always the same. As a result of this signal, physiological processes are turned on, leading to plant growth and flowering in the spring, fruiting in the summer and shedding leaves in the fall; in animals - to molting, fat accumulation, migration, reproduction in birds and mammals, and the onset of the resting stage in insects. Animals perceive changes in day length using their visual organs. And plants - with the help of special pigments located in the leaves of plants. Irritations are perceived through receptors, as a result of which a series of biochemical reactions occur (activation of enzymes or release of hormones), and then physiological or behavioral reactions appear.
The study of photoperiodism in plants and animals has shown that the reaction of organisms to light is based not simply on the amount of light received, but on the alternation of periods of light and darkness of a certain duration during the day. Organisms are able to measure time, i.e. have biological clock - from unicellular organisms to humans. The biological clock - are also governed by seasonal cycles and other biological phenomena. The biological clock determine the daily rhythm of activity of both whole organisms and processes occurring even at the cellular level, in particular cell divisions.
Temperature as an environmental factor
All chemical processes occurring in the body depend on temperature. Changes in thermal conditions, often observed in nature, deeply affect the growth, development and other manifestations of the life of animals and plants. There are organisms with an unstable body temperature - poikilothermic and organisms with a constant body temperature - homeothermic. Poikilothermic animals are entirely dependent on the temperature of the environment, while homeothermic animals are able to maintain a constant body temperature regardless of changes in environmental temperature. The vast majority of terrestrial plants and animals in a state of active life cannot tolerate negative temperatures and die. The upper temperature limit of life is not the same for different species - rarely above 40-45 O C. Some cyanobacteria and bacteria live at temperatures of 70-90 O C, some mollusks (up to 53 O WITH). For most terrestrial animals and plants, the optimum temperature conditions fluctuate within rather narrow limits (15-30 O WITH). The upper threshold of life temperature is determined by the temperature of protein coagulation, since irreversible protein coagulation (disturbance of protein structure) occurs at a temperature of about 60 o WITH.
In the process of evolution, poikilothermic organisms have developed various adaptations to changing temperature conditions of the environment. The main source of thermal energy in poikilothermic animals is external heat. Poikilothermic organisms have developed various adaptations to low temperatures. Some animals, for example, Arctic fish, live constantly at a temperature of -1.8 o C, contain substances (glycoproteins) in tissue fluid that prevent the formation of ice crystals in the body; insects accumulate glycerol for these purposes. Other animals, on the contrary, increase the body's heat production due to active muscle contraction - this way they increase body temperature by several degrees. Still others regulate their heat exchange due to the exchange of heat between the vessels of the circulatory system: the vessels coming from the muscles are in close contact with the vessels coming from the skin and carrying cooled blood (this phenomenon is characteristic of cold-water fish). Adaptive behavior involves many insects, reptiles and amphibians selecting places in the sun to warm themselves or changing different positions to increase the heating surface.
In a number of cold-blooded animals, body temperature can vary depending on the physiological state: for example, in flying insects, the internal body temperature can rise by 10-12 o C or more due to increased muscle work. Social insects, especially bees, have developed an effective way of maintaining temperature through collective thermoregulation (a hive can maintain a temperature of 34-35 o C, necessary for the development of larvae).
Poikilothermic animals are able to adapt to high temperatures. This also occurs in different ways: heat transfer can occur due to the evaporation of moisture from the surface of the body or from the mucous membrane of the upper respiratory tract, as well as due to subcutaneous vascular regulation (for example, in lizards, the speed of blood flow through the vessels of the skin increases with increasing temperature).
The most perfect thermoregulation is observed in birds and mammals - homeothermal animals. In the process of evolution, they acquired the ability to maintain a constant body temperature due to the presence of a four-chambered heart and one aortic arch, which ensured complete separation of arterial and venous blood flow; high metabolism; feathers or hair; regulation of heat transfer; a well-developed nervous system acquired the ability to live actively at different temperatures. Most birds have a body temperature slightly above 40 o C, and in mammals it is slightly lower. Very important for animals is not only the ability to thermoregulate, but also adaptive behavior, the construction of special shelters and nests, the choice of a place with a more favorable temperature, etc. They are also able to adapt to low temperatures in several ways: in addition to feathers or hair, warm-blooded animals use trembling (microcontractions of externally motionless muscles) to reduce heat loss; the oxidation of brown adipose tissue in mammals produces additional energy that supports metabolism.
The adaptation of warm-blooded animals to high temperatures is in many ways similar to similar adaptations of cold-blooded animals - sweating and evaporation of water from the mucous membrane of the mouth and upper respiratory tract; in birds - only the latter method, since they do not have sweat glands; dilation of blood vessels located close to the surface of the skin, which increases heat transfer (in birds, this process occurs in non-feathered areas of the body, for example through the crest). Temperature, as well as the light regime on which it depends, naturally changes throughout the year and in connection with geographic latitude. Therefore, all adaptations are more important for living at low temperatures.
Water as an environmental factor
Water plays an exceptional role in the life of any organism, since it is a structural component of the cell (water accounts for 60-80% of the cell’s mass). The importance of water in the life of a cell is determined by its physicochemical properties. Due to polarity, a water molecule is able to attract any other molecules, forming hydrates, i.e. is a solvent. Many chemical reactions can only occur in the presence of water. Water is present in living systems thermal buffer , absorbing heat during the transition from a liquid to a gaseous state, thereby protecting the unstable structures of the cell from damage during the short-term release of thermal energy. In this regard, it produces a cooling effect when evaporating from the surface and regulates body temperature. The thermal conductivity properties of water determine its leading role as a climate thermoregulator in nature. Water slowly heats up and slowly cools: in summer and during the day, the water of the seas, oceans and lakes heats up, and at night and in winter it also slowly cools. There is a constant exchange of carbon dioxide between water and air. In addition, water performs a transport function, moving soil substances from top to bottom and back. The role of humidity for terrestrial organisms is due to the fact that precipitation is distributed unevenly on the earth's surface throughout the year. In arid areas (steppes, deserts), plants obtain water with the help of a highly developed root system, sometimes very long roots (for camel thorn - up to 16 m), reaching the wet layer. The high osmotic pressure of cell sap (up to 60-80 atm), which increases the suction power of the roots, helps retain water in the tissues. In dry weather, plants reduce water evaporation: in desert plants, the integumentary tissues of the leaves thicken, or a waxy layer or dense pubescence develops on the surface of the leaves. A number of plants achieve a decrease in moisture by reducing the leaf blade (leaves turn into spines, often plants completely lose leaves - saxaul, tamarisk, etc.).
Depending on the requirements for the water regime, the following ecological groups are distinguished among plants:
Hydratophytes are plants that constantly live in water;
Hydrophytes - plants that are only partially immersed in water;
Helophytes - marsh plants;
Hygrophytes are terrestrial plants that live in excessively moist places;
Mesophytes - prefer moderate moisture;
Xerophytes are plants adapted to constant lack of moisture; Among xerophytes there are:
Succulents - accumulating water in the tissues of their body (succulent);
Sclerophytes - lose a significant amount of water.
Many desert animals are able to survive without drinking water; some can run quickly and for a long time, making long migrations to watering places (saiga antelopes, camels, etc.); Some animals obtain water from food (insects, reptiles, rodents). Fat deposits of desert animals can serve as a kind of water reserve in the body: when fats are oxidized, water is formed (fat deposits in the hump of camels or subcutaneous fat deposits in rodents). Low-permeability skin coverings (for example, in reptiles) protect animals from moisture loss. Many animals have switched to a nocturnal lifestyle or hide in burrows, avoiding the drying effects of low humidity and overheating. Under conditions of periodic dryness, a number of plants and animals enter a state of physiological dormancy - plants stop growing and shed their leaves, animals hibernate. These processes are accompanied by reduced metabolism during dry periods.
abiotic nature biosphere solar
Literature
1. http://burenina.narod.ru/3-2.htm
Http://ru-ecology.info/term/76524/
Http://www.ecology-education.ru/index.php?action=full&id=257
Http://bibliofond.ru/view.aspx?id=484744
Tutoring
Need help studying a topic?
Our specialists will advise or provide tutoring services on topics that interest you.
Submit your application indicating the topic right now to find out about the possibility of obtaining a consultation.
