General characteristics. In the course of evolution, the land-air environment was mastered much later than the aquatic environment. Life on land required adaptations that became possible only with a relatively high level of organization in both plants and animals. A feature of the land-air environment of life is that the organisms that live here are surrounded by air and a gaseous environment characterized by low humidity, density and pressure, and high oxygen content. Typically, animals in this environment move on the soil (hard substrate) and plants take root in it.
In ground- air environment operating environmental factors have a number of characteristic features: higher light intensity compared to other environments, significant temperature fluctuations, changes in humidity depending on geographical location, season and time of day (Table 5.3).
The impact of the above factors is inextricably linked with the movement of air masses - wind. In the process of evolution, living organisms of the land-air environment have developed characteristic anatomical, morphological, physiological, behavioral and other adaptations. For example, organs have appeared that provide direct absorption of atmospheric oxygen during respiration (the lungs and trachea of animals, the stomata of plants). Skeletal formations (animal skeleton, mechanical and supporting tissues of plants) have received strong development, which support the body in conditions of low environmental density. Adaptations have been developed to protect against unfavorable factors, such as the periodicity and rhythm of life cycles, the complex structure of the integument, mechanisms of thermoregulation, etc. A close connection with the soil has formed (animal limbs, plant roots), the mobility of animals in search of food has developed, and air currents have appeared. seeds, fruits and pollen of plants, flying animals.
Let us consider the features of the impact of basic environmental factors on plants and animals in the ground-air environment of life.
Low air density determines its low lifting force and insignificant controversy. All inhabitants of the air are closely connected with the surface of the earth, which serves them for attachment and support. The density of the air does not provide high resistance to the body when moving along the surface of the earth, but it makes it difficult to move vertically. For most organisms, staying in the air is associated only with settling or searching for prey.
The low lifting force of air determines the maximum mass and size of terrestrial organisms. The largest animals on the surface of the earth are smaller than the giants of the aquatic environment. Large mammals (the size and mass of a modern whale) could not live on land, as they would be crushed by their own weight. Giant Mesozoic dinosaurs led a semi-aquatic lifestyle. Another example: tall, erect redwood plants (Sequoja sempervirens), reaching 100 m, have powerful supporting wood, while in the thalli of the giant brown algae Macrocystis, growing up to 50 m, the mechanical elements are only very weakly isolated in the core part of the thallus.
Low air density creates little resistance to movement. The ecological benefits of this property of the air environment were used by many land animals during evolution, acquiring the ability to fly. 75% of all species of land animals are capable of active flight. This for the most part insects and birds, but also mammals and reptiles. Land animals fly mainly with the help of muscular efforts. Some animals can glide using air currents.
Due to the mobility of air that exists in the lower layers of the atmosphere, vertical and horizontal movement of air masses, passive flight is possible individual species organisms, developed anemochory - dispersal by air currents. Organisms passively transported by air currents are collectively called aeroplankton, by analogy with planktonic inhabitants of the aquatic environment. For passive flight along N.M. Chernova, A.M. Bylova (1988) organisms have special adaptations - small body size, an increase in its area due to outgrowths, strong dismemberment, a large relative surface of the wings, the use of a web, etc.
Anemochorous seeds and fruits of plants also have very small sizes (for example, fireweed seeds) or various wing-shaped (maple Acer pseudoplatanum) and parachute-shaped (dandelion Taraxacum officinale) appendages
Wind-pollinated plants have a number of adaptations that improve the aerodynamic properties of pollen. Their floral integument is usually reduced and the anthers are not protected from the wind in any way.
In the distribution of plants, animals and microorganisms main role vertical conventional air flows and weak winds play a role. Storms and hurricanes also have a significant environmental impact on terrestrial organisms. Quite often, strong winds, especially blowing in one direction, bend tree branches and trunks to the leeward side and cause the formation of flag-shaped crowns.
In areas where strong winds constantly blow, the species composition of small flying animals is usually poor, since they are not able to resist powerful air currents. Thus, a honey bee flies only when the wind force is up to 7 - 8 m/s, and aphids fly only when the wind is very weak, not exceeding 2.2 m/s. Animals in these places develop dense integuments that protect the body from cooling and loss of moisture. On oceanic islands with constant strong winds, birds and especially insects predominate, having lost the ability to fly, they lack wings, since those who are able to rise into the air are blown out to sea by the wind and die.
The wind causes a change in the intensity of transpiration in plants and is especially pronounced during dry winds, which dry out the air and can lead to the death of plants. The main ecological role of horizontal air movements (winds) is indirect and consists in strengthening or weakening the impact on terrestrial organisms of such important environmental factors as temperature and humidity. Winds increase the release of moisture and heat from animals and plants.
When there is wind, heat is easier to bear and frost is more difficult, and desiccation and cooling of organisms occurs faster.
Terrestrial organisms exist in conditions of relatively low pressure, which is caused by low air density. In general, terrestrial organisms are more stenobatic than aquatic ones, because normal pressure fluctuations in their environment amount to fractions of the atmosphere, and for those that rise to high altitudes, for example, birds, do not exceed 1/3 of normal.
Gas composition of air, as already discussed earlier, in the ground layer of the atmosphere it is quite homogeneous (oxygen - 20.9%, nitrogen - 78.1%, m.g. gases - 1%, carbon dioxide - 0.03% by volume) due to its high diffusion ability and constant mixing by convection and wind currents. At the same time, various impurities of gaseous, droplet-liquid, dust (solid) particles entering the atmosphere from local sources often have significant environmental significance.
Oxygen, due to its constantly high content in the air, is not a factor limiting life in terrestrial environment. High oxygen content contributed to increased metabolism in terrestrial organisms, and based on high efficiency oxidative processes gave rise to animal homeothermy. Only in places, under specific conditions, is a temporary oxygen deficiency created, for example, in decomposing plant debris, grain reserves, flour, etc.
In certain areas of the surface air layer, the carbon dioxide content can vary within fairly significant limits. Thus, in the absence of wind in large industrial centers and cities, its concentration can increase tenfold.
There are regular daily changes in the content of carbon dioxide in the ground layers, determined by the rhythm of plant photosynthesis (Fig. 5.17).
Using the example of daily changes in the vertical profile of CO 2 concentration in forest air, it is shown that during the day, at the level of tree crowns, carbon dioxide is spent on photosynthesis, and in the absence of wind, a zone poor in CO 2 (305 ppm) is formed here, into which CO comes from the atmosphere and soil (soil respiration). At night, a stable air stratification is established with an increased concentration of CO 2 in the soil layer. Seasonal fluctuations in carbon dioxide are associated with changes in the respiration rate of living organisms, mostly soil microorganisms.
In high concentrations, carbon dioxide is toxic, but such concentrations are rare in nature. Low CO 2 content inhibits the process of photosynthesis. To increase the rate of photosynthesis in the practice of greenhouse and greenhouse farming (in closed ground conditions), the concentration of carbon dioxide is often artificially increased.
For most inhabitants of the terrestrial environment, air nitrogen is an inert gas, but microorganisms such as nodule bacteria, azotobacteria, and clostridia have the ability to bind it and involve it in the biological cycle.
The main modern source of physical and chemical pollution of the atmosphere is anthropogenic: industrial and transport enterprises, soil erosion, etc. Thus, sulfur dioxide is toxic to plants in concentrations from one fifty-thousandth to one millionth of the volume of air. Lichens die when there are traces of sulfur dioxide in the environment. Therefore, plants that are particularly sensitive to SO 2 are often used as indicators of its content in the air. Common spruce and pine, maple, linden, and birch are sensitive to smoke.
Light mode. The amount of radiation reaching the Earth's surface is determined by the geographic latitude of the area, the length of the day, the transparency of the atmosphere and the angle of incidence of the sun's rays. Under different weather conditions, 42 - 70% of the solar constant reaches the Earth's surface. Passing through the atmosphere, solar radiation undergoes a number of changes not only in quantity, but also in composition. Short-wave radiation is absorbed by the ozone shield and oxygen in the air. Infrared rays are absorbed in the atmosphere by water vapor and carbon dioxide. The rest reaches the Earth's surface in the form of direct or diffuse radiation.
The combination of direct and diffuse solar radiation makes up from 7 to 7„ of the total radiation, while on cloudy days the diffuse radiation is 100%. At high latitudes, diffuse radiation predominates, while in the tropics, direct radiation predominates. Scattered radiation contains up to 80% of yellow-red rays at noon, direct radiation - from 30 to 40%. On clear sunny days, solar radiation reaching the Earth's surface consists of 45% visible light (380 - 720 nm) and 45% infrared radiation. Only 10% comes from ultraviolet radiation. The radiation regime is significantly influenced by atmospheric dust. Due to its pollution, in some cities the illumination may be 15% or less of the illumination outside the city.
Illumination on the Earth's surface varies widely. It all depends on the height of the Sun above the horizon or the angle of incidence of the sun’s rays, the length of the day and weather conditions, and the transparency of the atmosphere (Fig. 5.18).
Depending on the season and time of day, the light intensity also fluctuates. In certain regions of the Earth, the quality of light is also unequal, for example, the ratio of long-wave (red) and short-wave (blue and ultraviolet) rays. Short-wave rays are known to be absorbed and scattered by the atmosphere more than long-wave rays. In mountainous areas there is therefore always more short-wave solar radiation.
Trees, shrubs, and plant crops shade the area and create a special microclimate, weakening radiation (Fig. 5.19).
Thus, in different habitats, not only the intensity of radiation differs, but also its spectral composition, the duration of illumination of plants, the spatial and temporal distribution of light of different intensities, etc. Accordingly, the adaptations of organisms to life in a terrestrial environment under one or another light regime are also varied. . As we noted earlier, in relation to light there are three main groups of plants: light-loving(heliophytes), shade-loving(sciophy-you) and shade-tolerant. Light-loving and shade-loving plants differ in the position of their ecological optimum.
In light-loving plants it is located in the area of full sunlight. Strong shading has a depressing effect on them. These are plants of open areas of land or well-lit steppe and meadow grasses (the upper tier of the grass stand), rock lichens, early spring herbaceous plants of deciduous forests, most cultivated plants of open ground and weeds, etc. Shade-loving plants have an optimum in the area of low light and cannot tolerate strong light. These are mainly the lower shaded layers of complex plant communities, where shading is the result of the “interception” of light by taller plants and co-inhabitants. This includes many indoor and greenhouse plants. For the most part, these come from the herbaceous cover or epiphyte flora of tropical forests.
The ecological curve of the relationship to light in shade-tolerant plants is somewhat asymmetrical, since they grow and develop better in full light, but adapt well to low light. They are a common and highly flexible group of plants in terrestrial environments.
Plants in the terrestrial-air environment have developed adaptations to various light conditions: anatomical-morphological, physiological, etc.
A clear example anatomical and morphological adaptations is a change in external appearance in different light conditions, for example, the unequal size of leaf blades in plants related by systematic position, but living in different lighting conditions (meadow bell - Campanula patula and forest - C. trachelium, field violet - Viola arvensis, growing in fields, meadows, forest edges, and forest violets - V. mirabilis), fig. 5.20.
Under conditions of excess and lack of light, the spatial arrangement of leaf blades in plants varies significantly. In heliophyte plants, the leaves are oriented to reduce the influx of radiation during the most “dangerous” daytime hours. The leaf blades are located vertically or at a large angle to the horizontal plane, so during the day the leaves receive mostly sliding rays (Fig. 5.21).
This is especially pronounced in many steppe plants. An interesting adaptation to the weakening of the received radiation is in the so-called “compass” plants (wild lettuce - Lactuca serriola, etc.). The leaves of wild lettuce are located in the same plane, oriented from north to south, and at noon the arrival of radiation to the leaf surface is minimal.
In shade-tolerant plants, the leaves are arranged so as to receive the maximum amount of incident radiation.
Often, shade-tolerant plants are capable of protective movements: changing the position of leaf blades when exposed to strong light. Areas of grass cover with folded oxalis leaves coincide relatively precisely with the location of large sun flares. A number of adaptive features can be noted in the structure of the leaf as the main receiver of solar radiation. For example, in many heliophytes, the leaf surface helps to reflect sunlight (shiny - in laurel, covered with a light hairy coating - in cactus, euphorbia) or weaken their effect (thick cuticle, dense pubescence). For internal structure the leaf is characterized by powerful development of palisade tissue, the presence large quantity small and light chloroplasts (Fig. 5.22).
One of the protective reactions of chloroplasts to excess light is their ability to change orientation and move within the cell, which is clearly expressed in light plants.
In bright light, chloroplasts occupy a wall position in the cell and become an “edge” towards the direction of the rays. In low light, they are distributed diffusely in the cell or accumulate in its lower part. Physiological adaptations plants to the light conditions of the ground-air environment cover various vital functions. It has been established that in light-loving plants, growth processes react more sensitively to a lack of light compared to shady plants. As a result, there is an increased elongation of stems, which helps plants break through to the light and into the upper tiers of plant communities.
The main physiological adaptations to light lie in the area of photosynthesis. In general terms, the change in photosynthesis depending on light intensity is expressed by the “photosynthesis light curve.” Its following parameters are of ecological importance (Fig. 5.23).
1. The point of intersection of the curve with the ordinate axis (Fig. 5.23, A) corresponds to the magnitude and direction of gas exchange in plants in complete darkness: photosynthesis is absent, respiration takes place (not absorption, but release of CO 2), therefore point a lies below the x-axis.
2. The point of intersection of the light curve with the abscissa axis (Fig. 5.23, b) characterizes the “compensation point,” i.e., the light intensity at which photosynthesis (CO 2 absorption) balances respiration (CO 2 release).
3. The intensity of photosynthesis with increasing light increases only up to a certain limit, then remains constant - the light curve of photosynthesis reaches a “saturation plateau”.
In Fig. 5.23 the inflection area is conventionally designated by a smooth curve, the break of which corresponds to a point V. The projection of point c onto the x-axis (point d) characterizes the “saturated” light intensity, i.e., the value above which light no longer increases the intensity of photosynthesis. Projection onto the ordinate axis (point d) corresponds to the highest intensity of photosynthesis for a given species in a given ground-air environment.
4. Important characteristic light curve - the angle of inclination (a) to the abscissa, which reflects the degree of increase in photosynthesis with increasing radiation (in the region of relatively low light intensity).
Plants exhibit seasonal dynamics in their response to light. Thus, in the hairy sedge (Carex pilosa), in early spring in the forest, the newly emerged leaves have a plateau of light saturation of photosynthesis at 20 - 25 thousand lux; with summer shading in these same species, the curves of the dependence of photosynthesis on light become corresponding to the “shadow” parameters, t That is, the leaves acquire the ability to use weak light more efficiently, and these same leaves, after overwintering under the canopy of a leafless spring forest, again display the “light” features of photosynthesis.
A unique form of physiological adaptation during a sharp lack of light is the loss of the plant’s ability to photosynthesize and the transition to heterotrophic nutrition with ready-made organic substances. Sometimes such a transition became irreversible due to the loss of chlorophyll by plants, for example, shady orchids spruce forests(Goodyera repens, Weottia nidus avis), whirligig (Monotropa hypopitys). They live off dead organic matter obtained from trees and other plants. This method nutrition is called saprophytic, and plants are called saprophytes.
For the vast majority of terrestrial animals with day and night activity, vision is one of the methods of orientation and is important for searching for prey. Many animal species also have color vision. In this regard, animals, especially victims, developed adaptive features. These include protective, camouflage and warning coloring, protective similarity, mimicry, etc. The appearance of brightly colored flowers of higher plants is also associated with the characteristics of the visual apparatus of pollinators and, ultimately, with the light regime of the environment.
Water mode. Moisture deficiency is one of the most significant features of the land-air environment of life. The evolution of terrestrial organisms took place through adaptation to obtaining and preserving moisture. The humidity regimes of the environment on land are varied - from complete and constant saturation of the air with water vapor, where several thousand millimeters of precipitation falls per year (regions of equatorial and monsoon-tropical climates) to their almost complete absence in the dry air of deserts. Thus, in tropical deserts the average annual precipitation is less than 100 mm per year, and at the same time, rain does not fall every year.
The annual amount of precipitation does not always make it possible to assess the water supply of organisms, since the same amount can characterize a desert climate (in the subtropics) and a very humid one (in the Arctic). An important role is played by the ratio of precipitation and evaporation (total annual evaporation from the free water surface), which also varies in different regions of the globe. Areas where this value exceeds the annual precipitation amount are called arid(dry, arid). Here, for example, plants experience lack of moisture during most of the growing season. Areas in which plants are provided with moisture are called humid, or wet. Transition zones are often identified - semi-arid(semiarid).
The dependence of vegetation on average annual precipitation and temperature is shown in Fig. 5.24.
The water supply of terrestrial organisms depends on the precipitation regime, the presence of reservoirs, soil moisture reserves, the proximity of groundwater, etc. This contributed to the development of many adaptations to terrestrial organisms different modes water supply.
In Fig. Figure 5.25 from left to right shows the transition from lower algae living in water with cells without vacuoles to primary poikilohydric terrestrial algae, the formation of vacuoles in aquatic green and charophytes, the transition from thallophytes with vacuoles to homoyohydric cormophytes (the distribution of mosses - hydrophytes is still limited to habitats with high air humidity; in dry habitats, mosses become secondary poikilohydric); among ferns and angiosperms (but not among gymnosperms) there are also secondary poikilohydric forms. Most leafy plants are homoyohydric due to the presence of cuticular protection against transpiration and strong vacuolization of their cells. It should be noted that xerophilicity of animals and plants is characteristic only of the ground-air environment.
Precipitation (rain, hail, snow), in addition to providing water and creating moisture reserves, often plays another environmental role. For example, during heavy rains, the soil does not have time to absorb moisture, the water quickly flows in strong streams and often carries weakly rooted plants, small animals and fertile soil into lakes and rivers. In floodplains, rain can cause floods and thus have adverse effects on the plants and animals living there. In periodically flooded places, unique floodplain fauna and flora are formed.
Hail also has a negative effect on plants and animals. Agricultural crops in individual fields are sometimes completely destroyed by this natural disaster.
The ecological role of snow cover is diverse. For plants whose renewal buds are located in the soil or near its surface, and for many small animals, snow plays the role of a heat-insulating cover, protecting them from low winter temperatures. When frosts are above -14°C under a 20 cm layer of snow, the soil temperature does not fall below 0.2°C. Deep snow cover protects the green parts of plants from freezing, such as Veronica officinalis, hoofed grass, etc., which go under the snow without shedding their leaves. Small land animals lead an active lifestyle in winter, creating numerous galleries of passages under the snow and in its thickness. In the presence of fortified food, rodents (wood and yellow-throated mice, a number of voles, water rats, etc.) can breed there in snowy winters. During severe frosts, hazel grouse, partridges, and black grouse hide under the snow.
Winter snow cover often prevents large animals from obtaining food and moving, especially when an ice crust forms on the surface. Thus, moose (Alces alces) freely overcome a layer of snow up to 50 cm deep, but this is inaccessible to smaller animals. Often during snowy winters, the death of roe deer and wild boars is observed.
Large amounts of snow also have a negative impact on plants. In addition to mechanical damage in the form of snow chips or snow blowers, a thick layer of snow can lead to damping off of plants, and when the snow melts, especially in a long spring, to soaking of plants.
Plants and animals suffer from low temperatures and strong winds in winters with little snow. Thus, in years when there is little snow, mouse-like rodents, moles and other small animals die. At the same time, in latitudes where precipitation falls in the form of snow in winter, plants and animals have historically adapted to life in snow or on its surface, developing various anatomical, morphological, physiological, behavioral and other characteristics. For example, in some animals the supporting surface of their legs increases in winter by overgrowing them with coarse hair (Fig. 5.26), feathers, and horny scutes.
Others migrate or fall into an inactive state - sleep, hibernation, diapause. A number of animals switch to feeding on certain types of feed.
The whiteness of the snow cover reveals dark animals. The seasonal change in color in the ptarmigan and tundra partridge, ermine (Fig. 5.27), mountain hare, weasel, and arctic fox is undoubtedly associated with selection for camouflage to match the background color.
Precipitation, in addition to its direct impact on organisms, determines one or another air humidity, which, as already noted, plays an important role in the life of plants and animals, as it affects the intensity of their water metabolism. Evaporation from the surface of the body of animals and transpiration in plants are more intense, the less the air is saturated with water vapor.
In plants in highly humid terrestrial habitats, there is often a need to remove excess moisture. As a rule, this happens when the soil is well warmed up and the roots actively absorb water, and there is no transpiration (in the morning or during fog, when the air humidity is 100%).
Excess moisture is removed by guttation - this is the release of water through special excretory cells located along the edge or at the tip of the leaf (Fig. 5.28).
Not only hygrophytes, but also many mesophytes are capable of guttation. For example, in the Ukrainian steppes, guttation was found in more than half of all plant species. Many meadow grasses humidify so much that they wet the soil surface. This is how animals and plants adapt to the seasonal distribution of precipitation, its quantity and nature. This determines the composition of plants and animals, the timing of certain phases in their development cycle.
Humidity is also affected by the condensation of water vapor, which often occurs in the surface layer of air when the temperature changes. Dew appears when the temperature drops in the evening. Often dew falls in such quantities that it abundantly wets plants, flows into the soil, increases air humidity and creates favorable conditions for living organisms, especially when there is little other precipitation. Plants contribute to the deposition of dew. Cooling at night, they condense water vapor on themselves. The humidity regime is significantly affected by fogs, thick clouds and other natural phenomena.
When quantitatively characterizing the plant habitat based on the water factor, indicators are used that reflect the content and distribution of moisture not only in the air, but also in the soil. Soil water, or soil moisture, is one of the main sources of moisture for plants. Water in the soil is in a fragmented state, interspersed with pores of different sizes and shapes, has a large interface with the soil, and contains a number of cations and anions. Hence, soil moisture is heterogeneous in physical and chemical properties. Not all the water contained in the soil can be used by plants. By physical condition, mobility, availability and importance for plants, soil water is divided into gravitational, hygroscopic and capillary.
The soil also contains vaporous moisture, which occupies all water-free pores. This is almost always (except in desert soils) saturated water vapor. When the temperature drops below 0°C, soil moisture turns into ice (initially free water, and with further cooling - part of the bound water).
The total amount of water that can be held by soil (determined by adding excess water and then waiting until it stops dripping out) is called field moisture capacity.
Consequently, the total amount of water in the soil cannot characterize the degree of moisture supply to plants. To determine it, it is necessary to subtract the wilting coefficient from the total amount of water. However, physically accessible soil water is not always physiologically available to plants due to low soil temperature, lack of oxygen in soil water and soil air, soil acidity, and high concentration of mineral salts dissolved in soil water. The discrepancy between the absorption of water by the roots and its release by the leaves leads to wilting of plants. The development of not only the above-ground parts, but also the root system of plants depends on the amount of physiologically available water. In plants growing on dry soils, root system, as a rule, more branched, more powerful than in wet conditions (Fig. 5.29).
One of the sources of soil moisture is groundwater. When their level is low, capillary water does not reach the soil and does not affect its water regime. Moistening the soil due to precipitation alone causes strong fluctuations in its humidity, which often negatively affects plants. It has a harmful effect and is too high level groundwater, because this leads to waterlogging of the soil, depletion of oxygen and enrichment in mineral salts. Constant soil moisture, regardless of the vagaries of the weather, ensures an optimal groundwater level.
Temperature conditions. Distinctive feature The land-air environment is characterized by a large range of temperature fluctuations. In most land areas, daily and annual temperature ranges are tens of degrees. Changes in air temperature are especially significant in deserts and subpolar continental regions. For example, the seasonal temperature range in deserts Central Asia 68-77°C, and daily 25-38°C. In the vicinity of Yakutsk, the average January temperature is 43°C, the average July temperature is +19°C, and the annual range is from -64 to +35°C. In the Trans-Urals, the annual variation in air temperature is sharp and is combined with great variability in the temperatures of the winter and spring months in different years. The coldest month is January, the average air temperature ranges from -16 to -19°C, in some years it drops to -50°C, the warmest month is July with temperatures from 17.2 to 19.5°C. Maximum positive temperatures are 38-41°C.
Temperature fluctuations at the soil surface are even more significant.
Land plants occupy a zone adjacent to the soil surface, i.e., to the “interface” on which the transition of incident rays from one medium to another or in another way - from transparent to opaque. A special thermal regime is created on this surface: during the day there is strong heating due to the absorption of heat rays, at night there is strong cooling due to radiation. From here, the ground layer of air experiences the sharpest daily temperature fluctuations, which are most pronounced over bare soil.
The thermal regime of plant habitats, for example, is characterized based on temperature measurements directly in the vegetation cover. In herbaceous communities, measurements are taken inside and on the surface of the grass stand, and in forests, where there is a certain vertical temperature gradient, at a number of points at different heights.
Resistance to temperature changes in the environment in terrestrial organisms varies and depends on the specific habitat where their life takes place. Thus, terrestrial leafy plants mostly grow in a wide temperature range, i.e. they are eurythermic. Their life span in the active state extends, as a rule, from 5 to 55°C, while these plants are productive between 5 and 40°C. Plants of continental regions, which are characterized by a clear diurnal temperature variation, develop best when the night is 10-15 ° C colder than the day. This applies to most plants in the temperate zone - with a temperature difference of 5-10 ° C, and tropical plants with an even smaller amplitude - about 3 ° C (Fig. 5.30)
In poikilothermic organisms, with increasing temperature (T), the duration of development (t) decreases more and more rapidly. The development rate Vt can be expressed by the formula Vt = 100/t.
To reach a certain stage of development (for example, in insects - from an egg), i.e. pupation, the imaginal stage, always requires a certain amount of temperature. The product of effective temperature (temperature above the zero point of development, i.e. T-To) by the duration of development (t) gives a species-specific thermal constant development c=t(T-To). Using this equation, you can calculate the time of onset of a certain stage of development, for example, of a plant pest, at which its control is effective.
Plants, as poikilothermic organisms, do not have their own stable body temperature. Their temperature is determined by the thermal balance, i.e., the ratio of energy absorption and release. These quantities depend on many properties such as environment(the size of the arrival of radiation, the temperature of the surrounding air and its movement), and the plants themselves (color and other optical properties of the plant, the size and location of the leaves, etc.). The primary role is played by the cooling effect of transpiration, which prevents severe overheating of plants in hot habitats. As a result of the above reasons, the temperature of plants usually differs (often quite significantly) from the ambient temperature. Three situations are possible here: the plant temperature is higher than the ambient temperature, lower than it, equal to or very close to it. The excess of plant temperature over air temperature occurs not only in highly heated, but also in colder habitats. This is facilitated by the dark color or other optical properties of plants, which increase the absorption of solar radiation, as well as anatomical and morphological features that help reduce transpiration. Arctic plants can warm up quite noticeably (Fig. 5.31).
Another example is the dwarf willow - Salix arctica in Alaska, whose leaves are 2-11 °C warmer than the air during the day and even at night during the polar “24-hour day” - by 1-3 °C.
For early spring ephemeroids, the so-called “snowdrops,” heating of the leaves provides the opportunity for fairly intense photosynthesis on sunny but still cold spring days. For cold habitats or those associated with seasonal temperature fluctuations, an increase in plant temperature is ecologically very important, since physiological processes thereby become independent, to a certain extent, from the surrounding thermal background.
A decrease in the temperature of plants compared to the surrounding air is most often observed in highly illuminated and heated areas of the terrestrial sphere (desert, steppe), where the leaf surface of plants is greatly reduced, and increased transpiration helps remove excess heat and prevents overheating. IN general outline we can say that in hot habitats the temperature of the above-ground parts of plants is lower, and in cold habitats it is higher than the air temperature. The coincidence of plant temperature with the ambient air temperature is less common - in conditions that exclude a strong influx of radiation and intense transpiration, for example, in herbaceous plants under the canopy of forests, and in open areas - in cloudy weather or during rain.
In general, terrestrial organisms are more eurythermic than aquatic ones.
In the ground-air environment, living conditions are complicated by the existence weather changes. Weather is the continuously changing state of the atmosphere at the earth's surface, up to approximately an altitude of 20 km (the boundary of the troposphere). Weather variability is manifested in the constant variation of the combination of environmental factors such as temperature and humidity, cloudiness, precipitation, wind strength and direction, etc. (Fig. 5.32).
Weather changes, along with their regular alternation in the annual cycle, are characterized by non-periodic fluctuations, which significantly complicate the conditions for the existence of terrestrial organisms. In Fig. Figure 5.33 uses the example of the codling moth caterpillar Carpocapsa pomonella to show the dependence of mortality on temperature and relative humidity. Light, temperature and air humidity usually determine not the maximum, but the average degree of opening of stomata in plants, since the coincidence of all conditions promoting their opening rarely happens.
The long-term weather regime characterizes climate of the area. The concept of climate includes not only the average values of meteorological phenomena, but also their annual and daily movements, deviation from it, their repeatability. The climate is determined by the geographical conditions of the area.
The main climatic factors are temperature and humidity, measured by precipitation and water vapor saturation in the air. Thus, in countries remote from the sea, there is a gradual transition from a humid climate through a semiarid intermediate zone with occasional or periodic dry periods to an arid territory, which is characterized by prolonged drought, salinization of soil and water (Fig. 5.34).
Each habitat is characterized by a certain ecological climate, i.e., the climate of the ground layer of air, or ecoclimate.
Big influence climatic factors are influenced by vegetation. Thus, under the forest canopy, air humidity is always higher, and temperature fluctuations are less than in the clearings. The light regime of these places is also different. Different plant associations form their own regime of light, temperature, humidity, i.e. phytoclimate.
For full specifications climatic conditions Ecoclimate or phytoclimate data is not always sufficient for a given habitat. Local elements environments (relief, exposure, vegetation, etc.) very often change the regime of light, temperature, humidity, air movement in a particular area in such a way that it can differ significantly from the climatic conditions of the area. Local climate modifications that develop in the surface layer of air are called microclimate. For example, the living conditions surrounding insect larvae living under the bark of a tree are different than in the forest where the tree grows. The temperature of the southern side of the trunk can be 10 - 15°C higher than the temperature of its northern side. Burrows, tree hollows, and caves inhabited by animals have a stable microclimate. There are no clear differences between ecoclimate and microclimate. It is believed that ecoclimate is the climate of large areas, and microclimate is the climate of individual small areas. Microclimate influences living organisms of a particular territory or locality (Fig. 5.35).
The presence of many microclimates in one area ensures the coexistence of species with different requirements for the external environment.
Geographical zonality and zonality. The distribution of living organisms on Earth is closely related to geographic zones and zones. The belts have a latitudinal extension, which, naturally, is primarily due to radiation boundaries and the nature of atmospheric circulation. On the surface of the globe, 13 geographic zones are distinguished, spreading across continents and oceans (Fig. 5.36).
These are like arctic, antarctic, subarctic, subantarctic, north and south moderate, north and south subarctic, north and south tropical, north and south subequatorial And equatorial. Inside the belts there are geographical zones, where, along with radiation conditions, the moisture content of the surface and the ratio of heat and moisture characteristic of a given zone are taken into account. Unlike the ocean, where the supply of moisture is complete, on the continents the ratio of heat and moisture can have significant differences. From here, geographic zones extend to continents and oceans, and geographic zones extend only to continents. Distinguish latitudinal And meridial or longitudinal natural zones. The former stretch from west to east, the latter - from north to south. In the longitudinal direction, latitudinal zones are divided into subzones, and in the latitude - on provinces.
The founder of the doctrine of natural zonality is V.V. Dokuchaev (1846-1903), who substantiated zonality as a universal law of nature. All phenomena within the biosphere are subject to this law. The main reasons for zonation are the shape of the Earth and its position relative to the sun. In addition to latitude, the distribution of heat on Earth is influenced by the nature of the relief and the height of the area above sea level, the ratio of land and sea, sea currents, etc.
Subsequently, the radiation basis for the formation of the zonality of the globe was developed by A. A. Grigoriev and M. I. Budyko. To establish a quantitative characteristic of the relationship between heat and moisture for various geographical zones, they determined some coefficients. The ratio of heat and moisture is expressed by the ratio of the surface radiation balance to the latent heat of evaporation and the amount of precipitation (radiation dryness index). A law was established, called the law of periodic geographical zoning (A. A. Grigorieva - M. I. Budyko), which states: that with the change of geographical zones, similar geographical(landscape, natural) zones and some of them general properties are repeated periodically.
Each zone is confined to a certain range of indicator values: a special nature of geomorphological processes, a special type of climate, vegetation, soil and animal life. In the territory former USSR The following geographical zones were noted: icy, tundra, forest-tundra, taiga, mixed forests. Russian plain, monsoon mixed forests of the Far East, forest-steppes, steppes, semi-deserts, temperate zone deserts, deserts subtropical zone, Mediterranean and humid subtropics.
One of important conditions the variability of organisms and their zonal distribution on earth is variability chemical composition environment. In this regard, the teaching of A.P. Vinogradov about biogeochemical provinces, which are determined by the zonality of the chemical composition of soils, as well as the climatic, phytogeographical and geochemical zonality of the biosphere. Biogeochemical provinces are areas on the Earth's surface that differ in content (in soils, waters, etc.) chemical compounds, which are associated with certain biological reactions on the part of the local flora and fauna.
Along with horizontal zoning in the terrestrial environment, high-rise or vertical zonality.
The vegetation of mountainous countries is richer than on the adjacent plains, and is characterized by an increased distribution of endemic forms. Thus, according to O. E. Agakhanyants (1986), the flora of the Caucasus includes 6,350 species, of which 25% are endemic. The flora of the mountains of Central Asia is estimated at 5,500 species, of which 25-30% are endemic, while on the adjacent plains south- There are 200 species of plants in the deserts.
When climbing into the mountains, the same change of zones is repeated as from the equator to the poles. At the foot there are usually deserts, then steppes, deciduous forests, coniferous forests, tundra and, finally, ice. However, there is still no complete analogy. As you climb the mountains, the air temperature decreases (the average air temperature gradient is 0.6 °C per 100 m), evaporation decreases, ultraviolet radiation and illumination increase, etc. All this forces plants to adapt to dry or wet conditions. The dominant plants here are cushion-shaped life forms and perennials, which have developed adaptation to strong ultraviolet radiation and reduced transpiration.
The fauna of the high mountain regions is also unique. Low air pressure, significant solar radiation, sharp fluctuations in day and night temperatures, and changes in air humidity with altitude contributed to the development of specific physiological adaptations in the body of mountain animals. For example, in animals the relative volume of the heart increases, the content of hemoglobin in the blood increases, which allows more intensive absorption of oxygen from the air. Rocky soil complicates or almost eliminates the burrowing activity of animals. Many small animals (small rodents, pikas, lizards, etc.) find refuge in rock crevices and caves. Among the birds typical for mountainous regions are mountain turkeys (sulars), mountain finches, larks, and large birds - bearded vultures, vultures, and condors. Large mammals in the mountains are inhabited by rams, goats (including snow goats), chamois, yaks, etc. Predators are represented by species such as wolves, foxes, bears, lynxes, snow leopards (irbis), etc.
Life occurs on a large expanse of the diverse surface of the globe.
Biosphere- This is the shell of the Earth where living organisms exist.
The biosphere includes:
The lower part of the atmosphere (the air envelope of the Earth)
Hydrosphere (water shell of the Earth)
The upper part of the lithosphere (the solid shell of the Earth)
Each of these shells of the Earth has special conditions that create different living environments. Various conditions Living environments give rise to a variety of forms of living organisms.
Environments of life on Earth. Rice. 1.
Rice. 1. Habitats of life on Earth
The following habitats on our planet are distinguished:
Ground-air (Fig. 2)
Soil
Organic.
Rice. 2. Ground-air environment a habitat
Life in each environment has its own characteristics. There is enough oxygen and sunlight in the ground-air environment. But often there is not enough moisture. In this regard, plants and animals of arid habitats have special adaptations for obtaining, storing and economically using water. There are significant temperature changes in the land-air environment, especially in areas with cold winters. In these areas, the entire life of the organism changes noticeably throughout the year. Autumn leaf fall, the flight of birds to warmer regions, the change of fur of animals to thicker and warmer ones - all this is the adaptation of living beings to seasonal changes in nature. For animals living in any environment, movement is an important problem. In the ground-air environment, you can move on the Earth and in the air. And animals take advantage of this. The legs of some are adapted for running: ostrich, cheetah, zebra. Others - for jumping: kangaroo, jerboa. Of every 100 animals living in this environment, 75 can fly. These are most insects, birds and some animals, for example, a bat. (Fig. 3).
Rice. 3. Bat
The champion in flight speed among birds is the swift. 120 km/h is his usual speed. Hummingbirds flap their wings up to 70 times per second. The flight speed of different insects is as follows: for the lacewing - 2 km/h, for the housefly - 7 km/h, for the cockchafer - 11 km/h, for the bumblebee - 18 km/h, and for the hawkmoth butterfly - 54 km/h h. Our bats are small in stature. But their relatives, the fruit bats, reach a wingspan of 170 cm.
Large kangaroos jump up to 9 meters.
What distinguishes birds from all other creatures is their ability to fly. The entire body of the bird is adapted for flight. (Fig. 4). Birds' forelimbs turned into wings. So the birds became bipedal. The feathered wing is much more adapted for flight than the flight membrane of bats. Damaged wing feathers are quickly restored. Wing lengthening is achieved by lengthening the feathers, not the bones. The long, thin bones of flying vertebrates can break easily.
Rice. 4. Skeleton of a pigeon
As an adaptation for flight, a bone developed on the sternum of birds. keel. This is the support for the bony flight muscles. Some modern birds lack a keel, but at the same time they have lost the ability to fly. Nature has tried to eliminate all the extra weights in the structure of birds that interfere with flight. The maximum weight of all large flying birds reaches 15-16 kg. And for flightless animals, such as ostriches, it can exceed 150 kg. Bird bones in the process of evolution they became hollow and light. At the same time, they retained their strength.
The first birds had teeth, but then heavy the dental system has completely disappeared. Birds have a horny beak. In general, flying is an incomparably faster method of movement than running or swimming in water. But energy costs are approximately twice as high as when running and 50 times higher than when swimming. Therefore, birds must consume quite a lot of food.
Flight may be:
waving
Soaring
Birds of prey have mastered soaring flight to perfection. (Fig. 5). They use warm air currents rising from the heated earth.
Rice. 5. Griffon Vulture
Fish and crustaceans breathe through gills. These are special organs that extract dissolved oxygen from water, which is necessary for breathing.
A frog, while underwater, breathes through its skin. Mammals that have mastered water breathe through their lungs; they need to periodically rise to the surface of the water to inhale.
Aquatic beetles behave in a similar way, only they, like other insects, do not have lungs, but special breathing tubes - tracheas.
Rice. 6. Trout
Some organisms (trout) can only live in oxygen-rich water. (Fig. 6). Carp, crucian carp, and tench can withstand a lack of oxygen. In winter, when many reservoirs are covered with ice, fish may die, that is, their mass death from suffocation. To allow oxygen to enter the water, holes are cut in the ice. There is less light in the aquatic environment than in the air-terrestrial environment. In the oceans and seas at a depth of 200 meters - the kingdom of twilight, and even lower - eternal darkness. Accordingly, aquatic plants are found only where there is enough light. Only animals can live deeper. Deep-sea animals feed on the dead remains of various marine inhabitants falling from the upper layers.
A feature of many sea animals is swimming device. In fish, dolphins and whales these are fins. (Fig. 7), seals and walruses have flippers. (Fig. 8). Beavers, otters, and waterfowl have membranes between their toes. The swimming beetle has swimming legs that look like oars.
Rice. 7. Dolphin
Rice. 8. Walrus
Rice. 9. Soil
The soil environment is home to a variety of bacteria and protozoa. (Fig. 9). Mushroom myceliums and plant roots are also located here. The soil was also inhabited by a variety of animals: worms, insects, animals adapted to digging, for example, moles. The inhabitants of the soil find in it the conditions necessary for them: air, water, food, mineral salts. There is less oxygen and more carbon dioxide in the soil than in fresh air. And there is too much water here. The temperature in the soil environment is more equal than on the surface. Light does not penetrate the soil. Therefore, the animals inhabiting it usually have very small eyes or no visual organs at all. Their sense of smell and touch helps.
The formation of soil began only with the appearance of living beings on Earth. Since then, over millions of years, there has been a continuous process of its formation. Solid rocks in nature are constantly destroyed. The result is a loose layer consisting of small pebbles, sand, and clay. It contains almost no nutrients needed by plants. But still, unpretentious plants and lichens settle here. Humus is formed from their remains under the influence of bacteria. Plants can now settle in the soil. When they die, they also produce humus. So gradually the soil turns into a living environment. Various animals live in the soil. They increase its fertility. Thus, soil cannot appear without living beings. At the same time, both plants and animals need soil. Therefore, in nature everything is interconnected.
1 cm of soil is formed in nature in 250-300 years, 20 cm in 5-6 thousand years. That is why the destruction and destruction of the soil should not be allowed. Where people have destroyed plants, the soil is eroded by water and strong winds blow. The soil is afraid of many things, for example, pesticides. If you add more than normal, they accumulate in it, polluting it. As a result, worms, microbes, and bacteria die, without which the soil loses fertility. If too much fertilizer is applied to the soil or it is watered too much, excess salts accumulate in it. And this is harmful to plants and all living things. To protect the soil, it is necessary to plant forest strips in the fields, properly plow on the slopes, and carry out snow retention in winter.
Rice. 10. Mole
The mole lives underground from birth to death and does not see white light. As a digger, he has no equal. (Fig. 10). Everything he has is suited for digging in the best possible way. The fur is short and smooth so as not to cling to the ground. The mole's eyes are tiny, about the size of a poppy seed. Their eyelids close tightly when necessary, and some moles have eyes that are completely overgrown with skin. The mole's front paws are real shovels. The bones on them are flat, and the hand is turned out so that it is more convenient to dig the earth in front of you and rake it back. He breaks through 20 new moves per day. The underground labyrinths of moles can extend over vast distances. Moles have two types:
Nesting areas in which he rests.
Feeders, they are located close to the surface.
A sensitive sense of smell tells the mole in which direction to dig.
The body structure of the mole, zokor and mole rat suggests that they are all inhabitants of the soil environment. The front legs of the mole and zokor are the main tool for digging. They are flat, like shovels, with very large claws. But the mole rat has ordinary legs. It bites into the soil with its powerful front teeth. The body of all these animals is oval, compact, for more convenient movement through underground passages.
Rice. 11. Roundworms
1. Melchakov L.F., Skatnik M.N. Natural history: textbook. for 3.5 grades avg. school - 8th ed. - M.: Education, 1992. - 240 pp.: ill.
2. Bakhchieva O.A., Klyuchnikova N.M., Pyatunina S.K. and others. Natural history 5. - M.: Educational literature.
3. Eskov K.Yu. and others. Natural history 5 / Ed. Vakhrusheva A.A. - M.: Balass.
1. Encyclopedia Around the World ().
2. Gazetteer ().
3. Facts about the mainland of Australia ().
1. List the environments of life on our planet.
2. Name the animals of the soil habitat.
3. Like animals different environments habitats adapted to movement?
4. * Prepare a short report about the inhabitants of the land-air environment.
Ecological features of the ground-air habitat - section Ecology, GENERAL ECOLOGY The ground-air habitat is significantly more complex in its...
The ground-air habitat is much more complex in its environmental conditions than the aquatic environment. To live on land, both plants and animals needed to develop a whole complex of fundamentally new adaptations.
The density of air is 800 times less than the density of water, so life suspended in the air is practically impossible. Only bacteria, fungal spores and plant pollen are regularly present in the air and can be transported over significant distances by air currents, but all have a main function life cycle– reproduction occurs on the surface of the earth, where nutrients are available. Land dwellers are forced to have developed support system,
supporting the body. In plants, these are a variety of mechanical tissues; animals have a complex bone skeleton. Low air density determines low resistance to movement. Therefore, many terrestrial animals were able to use the environmental benefits of this feature of the air environment during their evolution and acquired the ability for short-term or long-term flight. Not only birds and insects, but even individual mammals and reptiles have the ability to move in the air. In general, at least 60% of terrestrial animal species can actively fly or glide using air currents.
The life of many plants largely depends on the movement of air currents, since it is the wind that carries their pollen and pollination occurs. This method of pollination is called anemophilia. Anemophily is characteristic of all gymnosperms, and among angiosperms, wind-pollinated plants make up at least 10% of the total number of species. Characteristic of many species anemochory– settlement using air currents. In this case, it is not the germ cells that move, but the embryos of organisms and young individuals - seeds and small fruits of plants, insect larvae, small spiders, etc. Anemochorous seeds and fruits of plants have either very small sizes (for example, orchid seeds) or various wing-like and parachute-like appendages , thanks to which the ability to plan increases. Organisms passively transported by wind are collectively called aeroplankton by analogy with planktonic inhabitants of the aquatic environment.
The low density of air causes very low pressure on land compared to the aquatic environment. At sea level it is 760 mm Hg. Art. As altitude increases, the pressure decreases and at an altitude of approximately 6000 m is only half of what is usually observed at the Earth's surface. For most vertebrates and plants, this is the upper limit of distribution. Low pressure in the mountains leads to a decrease in oxygen supply and dehydration of animals due to an increase in respiration rate. In general, the vast majority of terrestrial organisms are much more sensitive to changes in pressure than aquatic inhabitants, since pressure fluctuations in the terrestrial environment usually do not exceed tenths of an atmosphere. Even large birds capable of rising to heights of more than 2 km find themselves in conditions in which the pressure differs by no more than 30% from the ground level.
Except physical properties air environment, its chemical characteristics are also very important for the life of terrestrial organisms. The gas composition of the air in the surface layer of the atmosphere is uniform everywhere, due to the constant mixing of air masses by convection and wind flows. On modern stage evolution of the Earth's atmosphere, the composition of the air is dominated by nitrogen (78%) and oxygen (21%), followed by the inert gas argon (0.9%) and carbon dioxide (0.035%). The higher oxygen content in the terrestrial-air habitat, compared to the aquatic environment, contributes to an increase in the level of metabolism in terrestrial animals. It was in the terrestrial environment that physiological mechanisms arose, based on the high energy efficiency of oxidative processes in the body, providing mammals and birds with the opportunity to maintain their body temperature and physical activity at a constant level, which gave them the opportunity to live only in warm, but also in cold regions of the Earth . Currently, oxygen, due to its high content in the atmosphere, is not one of the factors limiting life in the terrestrial environment. However, under certain conditions, its deficiency may occur in the soil.
The concentration of carbon dioxide can vary in the surface layer within fairly significant limits. For example, if there is no wind in major cities and industrial centers, the content of this gas can be tens of times higher than the concentration in natural undisturbed biocenoses, due to its intensive release during the combustion of organic fuel. Increased concentrations of carbon dioxide can also occur in areas of volcanic activity. High concentrations of CO 2 (more than 1%) are toxic to animals and plants, but low levels of this gas (less than 0.03%) inhibit the process of photosynthesis. The main natural source of CO 2 is the respiration of soil organisms. Carbon dioxide comes from the soil into the atmosphere, and it is emitted especially intensively by moderately moist, well-warmed soils with a significant amount of organic material. For example, the soils of a beech broadleaf forest emit from 15 to 22 kg/ha of carbon dioxide per hour, sandy sandy soils - no more than 2 kg/ha. There are daily changes in the content of carbon dioxide and oxygen in the surface layers of air, caused by the rhythm of animal respiration and plant photosynthesis.
Nitrogen, which is the main component of the air mixture, is inaccessible to direct absorption for most inhabitants of the ground-air environment due to its inert properties. Only some prokaryotic organisms, including nodule bacteria and blue-green algae, have the ability to absorb nitrogen from the air and involve it in the biological cycle of substances.
The most important environmental factor in terrestrial habitats is sunlight. All living organisms require energy from outside to exist. Its main source is sunlight, which accounts for 99.9% of the total energy balance on the Earth’s surface, and 0.1% is the energy of the deep layers of our planet, the role of which is quite high only in certain areas of intense volcanic activity, for example in Iceland or Kamchatka in the Valley of Geysers. If we take solar energy reaching the surface of the Earth's atmosphere as 100%, then about 34% is reflected back into outer space, 19% is absorbed when passing through the atmosphere, and only 47% reaches land-air and water ecosystems in the form of direct and diffuse radiant energy. Direct solar radiation is electromagnetic radiation with wavelengths from 0.1 to 30,000 nm. The share of scattered radiation in the form of rays reflected from clouds and the Earth's surface increases with a decrease in the height of the Sun above the horizon and with an increase in the content of dust particles in the atmosphere. The nature of the impact of sunlight on living organisms depends on their spectral composition.
Short-wave ultraviolet rays with wavelengths less than 290 nm are destructive to all living things, because have the ability to ionize and split the cytoplasm of living cells. These dangerous rays are 80–90% absorbed by the ozone layer, located at altitudes of 20 to 25 km. Ozone layer, which is a collection of O 3 molecules, is formed as a result of the ionization of oxygen molecules and is thus a product of photosynthetic activity of plants on a global scale. This is a kind of “umbrella” that covers terrestrial communities from harmful ultraviolet radiation. It is assumed that it arose about 400 million years ago, due to the release of oxygen during photosynthesis of ocean algae, which made it possible for life to develop on land. Long-wave ultraviolet rays, with wavelengths between 290 and 380 nm, are also highly chemically reactive. Prolonged and intense exposure to them harms organisms, but many of them need small doses. Rays with wavelengths of about 300 nm cause the formation of vitamin D in animals, with wavelengths from 380 to 400 nm - lead to the appearance of tanning as a protective reaction of the skin. In the area of visible sunlight, i.e. perceived by the human eye, includes rays with wavelengths from 320 to 760 nm. Within the visible part of the spectrum there is a zone of photosynthetically active rays - from 380 to 710 nm. It is in this range of light waves that the process of photosynthesis occurs.
Light and its energy, which largely determine the temperature of the environment in a particular habitat, affect gas exchange and evaporation of water by plant leaves, stimulate the work of protein synthesis enzymes and nucleic acids. Plants need light for the formation of the chlorophyll pigment, the formation of the structure of chloroplasts, i.e. structures responsible for photosynthesis. Under the influence of light, plant cells divide and grow, flowering and fruiting. Finally, the distribution and abundance of certain plant species, and, consequently, the structure of the biocenosis, depend on the intensity of light in a particular habitat. In low light conditions, such as under a canopy of broadleaf or spruce forest, or in the morning and evening hours, light becomes an important limiting factor that can limit photosynthesis. On a clear summer day in an open habitat or in the upper part of the tree canopy in temperate and low latitudes, illumination can reach 100,000 lux, while 10,000 lux is sufficient for the success of photosynthesis. With very high illumination, the process of bleaching and destruction of chlorophyll begins, which significantly slows down the production of primary organic matter during photosynthesis.
As you know, as a result of photosynthesis, carbon dioxide is absorbed and oxygen is released. However, in the process of plant respiration during the day, and especially at night, oxygen is absorbed, and CO 2, on the contrary, is released. If you gradually increase the light intensity, the rate of photosynthesis will correspondingly increase. Over time, a moment will come when photosynthesis and respiration of the plant will precisely balance each other and the production of pure biological matter, i.e. not consumed by the plant itself in the process of oxidation and respiration for its needs, cease. This state in which the total gas exchange of CO 2 and O 2 is equal to 0 is called compensation point.
Water is one of the absolutely necessary substances for the successful course of the photosynthesis process and its deficiency negatively affects the course of many cellular processes. Even a lack of moisture in the soil for several days can lead to serious losses in the harvest, because... A substance that inhibits tissue growth, abscisic acid, begins to accumulate in plant leaves.
The optimal air temperature for photosynthesis of most plants in the temperate zone is about 25 ºС. At higher temperatures, the rate of photosynthesis slows due to increased costs of respiration, loss of moisture through evaporation to cool the plant, and decreased CO2 consumption due to decreased gas exchange.
Plants experience various morphological and physiological adaptations to the light regime of the ground-air habitat. According to the requirements for the level of lighting, all plants are usually divided into the following environmental groups.
Photophilous or heliophytes– plants of open, constantly well-lit habitats. The leaves of heliophytes are usually small or with a dissected leaf blade, with a thick outer wall of epidermal cells, often with a waxy coating to partially reflect excess light energy or with dense pubescence allowing for effective heat dissipation, with a large number of microscopic holes - stomata, through which gas- and moisture exchange with the environment, with well developed mechanical fabrics and tissues capable of storing water. The leaves of some plants from this group are photometric, i.e. capable of changing their position depending on the height of the Sun. At noon, the leaves are positioned edge-on to the sun, and in the morning and evening - parallel to its rays, which protects them from overheating and allows the use of light and solar energy to the required extent. Heliophytes are part of communities in almost all natural zones, but their greatest number is found in the equatorial and tropical zones. These are plants of tropical rainforests of the upper tier, plants of savannas of West Africa, steppes of Stavropol and Kazakhstan. For example, these include corn, millet, sorghum, wheat, cloves, and euphorbias.
Shade-loving or sciophytes– plants of the lower tiers of the forest, deep ravines. They are able to live in conditions of significant shading, which is the norm for them. The leaves of sciophytes are arranged horizontally, they are usually dark green in color and larger in size compared to heliophytes. The epidermal cells are large, but with thinner outer walls. Chloroplasts are large, but their number in cells is small. The number of stomata per unit area is less than that of heliophytes. To shade-loving plants of moderate climate zone belong to mosses, mosses, herbs from the ginger family, common oxalis, bifolia, etc. They also include many plants of the lower tier of the tropical zone. Mosses, as plants of the lowest forest layer, can live at illumination of up to 0.2% of the total on the surface of the forest biocenosis, mosses - up to 0.5%, and flowering plants can develop normally only at illumination of at least 1% of the total. In sciophytes, the processes of respiration and moisture exchange occur with less intensity. The intensity of photosynthesis quickly reaches a maximum, but with significant illumination it begins to decrease. The compensation point is located in low light conditions.
Shade-tolerant plants can tolerate significant shading, but they also grow well in the light and are adapted to significant seasonal changes in illumination. This group includes meadow plants, forest herbs and shrubs growing in shaded areas. They grow faster in intensely lit areas, but develop quite normally in moderate lighting.
The attitude towards the light regime changes in plants throughout their life. individual development– ontogeny. Seedlings and young plants of many meadow grasses and trees are more shade-tolerant than adult plants.
In the life of animals, the visible part of the light spectrum also plays a fairly important role. Light for animals is necessary condition visual orientation in space. The primitive eyes of many invertebrates are simply individual light-sensitive cells that allow them to perceive certain fluctuations in illumination, the alternation of light and shadow. Spiders can distinguish the contours of moving objects at a distance of no more than 2 cm. Rattlesnakes are able to see the infrared part of the spectrum and are able to hunt in complete darkness, focusing on the heat rays of the prey. In bees, the visible part of the spectrum is shifted to shorter wavelengths. They perceive a significant portion of ultraviolet rays as colored, but do not distinguish red ones. The ability to perceive colors depends on the spectral composition at which a given species is active. Most mammals leading a twilight or nocturnal lifestyle do not distinguish colors well and see the world in black and white (representatives of the canine and feline families, hamsters, etc.). Living in twilight leads to an increase in eye size. Huge eyes, capable of capturing insignificant amounts of light, are characteristic of nocturnal lemurs, tarsiers, and owls. They have the most advanced visual organs cephalopods and higher vertebrates. They can adequately perceive the shape and size of objects, their color, and determine the distance to objects. The most perfect three-dimensional binocular vision is characteristic of humans, primates, and birds of prey - owls, falcons, eagles, and vultures.
The position of the Sun is an important factor in the navigation of various animals during long-distance migrations.
Living conditions in the ground-air environment are complicated by weather and climate changes. Weather is the continuously changing state of the atmosphere near the earth's surface up to an altitude of approximately 20 km (the upper limit of the troposphere). Weather variability is manifested in constant fluctuations in the values of the most important environmental factors, such as temperature and humidity, the amount of liquid water falling on the soil surface due to precipitation, the degree of illumination, wind speed, etc. Weather characteristics are characterized not only by fairly obvious seasonal changes, but also non-periodic random fluctuations over relatively short periods of time, as well as in the daily cycle, which especially negatively affect the lives of land dwellers, since it is extremely difficult to develop effective adaptations to these fluctuations. The life of the inhabitants of large bodies of water on land and sea is affected by weather to a much lesser extent, affecting only surface biocenoses.
The long-term weather regime characterizes climate terrain. The concept of climate includes not only the values of the most important meteorological characteristics and phenomena averaged over a long time interval, but also their annual course, as well as the probability of deviation from the norm. The climate depends, first of all, on the geographical conditions of the region - latitude, altitude, proximity to the Ocean, etc. The zonal diversity of climates also depends on the influence of monsoon winds carrying warm, moist air masses from tropical seas to the continents, and on the trajectories of cyclones. and anticyclones, from the influence of mountain ranges on the movement of air masses, and from many other reasons that create an extraordinary variety of living conditions on land. For most terrestrial organisms, especially for plants and small sedentary animals, it is not so much the large-scale features of the climate that are important natural area in which they live, but the conditions that are created in their immediate habitat. Such local climate modifications, created under the influence of numerous locally distributed phenomena, are called microclimate. Differences between temperature and humidity in forest and grassland habitats, on northern and southern slopes of hills, are widely known. A stable microclimate occurs in nests, hollows, caves and burrows. For example, in the snow den of a polar bear, by the time the cub appears, the air temperature can be 50 °C higher than the ambient temperature.
The land-air environment is characterized by significantly greater temperature fluctuations in the daily and seasonal cycle than the water environment. On vast spaces temperate latitudes of Eurasia and North America located at a considerable distance from the Ocean, the temperature amplitude in annual progress can reach 60 and even 100 °C, due to very cold winters and hot summers. Therefore, the basis of flora and fauna in most continental regions are eurythermal organisms.
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In the ground-air environment, the operating environmental factors have a number of characteristic features: higher light intensity compared to other environments, significant temperature fluctuations, changes in humidity depending on the geographical location, season and time of day. The impact of the factors listed above is inextricably linked with the movement of air masses - wind.
In the process of evolution, living organisms of the land-air environment have developed characteristic anatomical-morphological, physiological, behavioral and other adaptations. Let us consider the features of the impact of basic environmental factors on plants and animals in the ground-air environment of life.
Low air density determines its low lifting force and insignificant support. All inhabitants of the air are closely connected with the surface of the earth, which serves them for attachment and support. For most organisms, staying in the air is associated only with settling or searching for prey. The low lifting force of air determines the maximum mass and size of terrestrial organisms. The largest animals living on the surface of the earth are smaller than the giants of the aquatic environment.
Low air density creates little resistance to movement. The ecological benefits of this property of the air environment were used by many land animals during evolution, acquiring the ability to fly: 75% of all species of land animals are capable of active flight.
Due to the mobility of air that exists in the lower layers of the atmosphere, the vertical and horizontal movement of air masses, passive flight of certain types of organisms is possible, anemochory is developed - settlement with the help of air currents. Wind-pollinated plants have a number of adaptations that improve the aerodynamic properties of pollen.
Their floral integument is usually reduced and the anthers are not protected from the wind in any way. Vertical convection air currents and weak winds play a major role in the dispersal of plants, animals and microorganisms. Storms and hurricanes have a significant environmental impact on terrestrial organisms.
In areas where strong winds constantly blow, the species composition of small flying animals is usually poor, since they are not able to resist powerful air currents. The wind causes a change in the intensity of transpiration in plants, which is especially pronounced during hot winds that dry out the air, and can lead to the death of plants. The main ecological role of horizontal air movements (winds) is indirect and consists in enhancing or weakening the impact of such important environmental factors on terrestrial organisms. factors such as temperature and humidity.
Ground-air environment (Fig. 7.2). The very name of this environment indicates its heterogeneity. Some of its inhabitants are adapted only to terrestrial movement - they crawl, run, jump, climb, leaning on the surface of the earth or on plants. Other animals can move and fly in the air. Therefore, the organs of movement of the inhabitants of the ground-air environment are diverse. It moves on the ground thanks to the work of the muscles of the body; a panther, a horse, a monkey use all four limbs for this, a spider uses eight, and a dove and an eagle use only two hind ones. Their forelimbs - wings - are adapted for flight.
Dense body coverings help protect land animals from drying out: chitinous cover in insects, scales in lizards, shells in terrestrial mollusks, skin in mammals. The respiratory organs of land animals are hidden inside the body, which prevents water from evaporating through their thin surfaces. Material from the site
Terrestrial animals of temperate latitudes are forced to adapt to significant temperature fluctuations. They escape from the heat in burrows, in the shade of trees. Mammals cool their bodies by evaporating water through the oral epithelium (dogs) or by sweating (humans). With the approach of cold weather, the fur of animals thickens, they accumulate reserves of fat under the skin. In winter, some of them, such as marmots and hedgehogs, hibernate, which helps them survive the lack of food. To escape winter hunger, some birds (cranes, starlings) fly to warmer climes.
On this page there is material on the following topics:
Report on land and air animals
Ground-air habitat biology
Ground-air habitat abstract
Lesson-presentation on the surrounding world 3rd grade inhabitants of the ground-air environment
Animals of the land-air habitat
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