The layered structure of the Earth's shells and the composition of the atmosphere; light regime as a factor of the ground-air environment; adaptation of organisms to different light regimes; temperature conditions in the ground-air environment, temperature adaptations; air pollution
The ground-air environment is the most difficult in terms of environmental conditions of life. Life on land required such morphological and biochemical adaptations, which turned out to be possible only with a sufficiently high level of organization of both plants and animals. On fig. 2 shows a diagram of the shells of the Earth. The outer part can be attributed to the ground-air environment lithosphere and the bottom atmosphere. The atmosphere, in turn, has a fairly pronounced layered structure. The lower layers of the atmosphere are shown in fig. 2. Since the bulk of living beings live in the troposphere, it is this layer of the atmosphere that is included in the concept of the ground-air environment. The troposphere is the lowest part of the atmosphere. Its height in different areas is from 7 to 18 km, it contains the bulk of water vapor, which, condensing, form clouds. In the troposphere, there is a powerful movement of air, and the temperature drops by an average of 0.6 ° C with a rise for every 100 m.
The Earth's atmosphere consists of a mechanical mixture of gases that do not chemically act on each other. All meteorological processes take place in it, the totality of which is called climate. The upper boundary of the atmosphere is conditionally considered to be 2000 km, i.e. its height is V 3 part of the Earth's radius. Various physical processes continuously take place in the atmosphere: temperature and humidity change, water vapor condenses, fogs and clouds appear, the sun's rays heat the atmosphere, ionizing it, etc.
The bulk of the air is concentrated in the 70 km layer. Dry air contains (in%): nitrogen - 78.08; oxygen - 20.95; argon - 0.93; carbon dioxide - 0.03. There are very few other gases. These are hydrogen, neon, helium, krypton, radon, xenon - most of the inert gases.
Atmospheric air is one of the main vital elements of the environment. It reliably protects the planet from harmful cosmic radiation. Under the influence of the atmosphere on Earth, the most important geological processes take place, which ultimately form the landscape.
Atmospheric air belongs to the category of inexhaustible resources, but the intensive development of industry, the growth of cities, the expansion of space exploration increase the negative anthropogenic impact on the atmosphere. Therefore, the issue of protecting atmospheric air is becoming increasingly important.
In addition to air of a certain composition, living organisms inhabiting the ground-air environment are affected by air pressure and humidity, as well as solar radiation and temperature.
Rice. 2.
Light mode, or solar radiation. For the implementation of vital processes, all living organisms need energy coming from outside. Its main source is solar radiation.
The effect of different parts of the spectrum of solar radiation on living organisms is different. It is known that in the spectrum of sunlight emit ultraviolet, visible And infrared area, which, in turn, consist of light waves of different lengths (Fig. 3).
Among the ultraviolet rays (UFL), only long-wave (290-300 nm) rays reach the Earth's surface, and short-wave (less than 290 nm), destructive for all living things, are almost completely absorbed at a height of about 20-25 km by the ozone screen - a thin layer of the atmosphere containing molecules 0 3 (see Fig. 2).
Rice. 3. The biological effect of different parts of the spectrum of solar radiation: 1 - protein denaturation; 2 - intensity of wheat photosynthesis; 3 - spectral sensitivity of the human eye. The area of ultraviolet radiation that does not penetrate is shaded.
through the atmosphere
Long-wave ultraviolet rays (300-400 nm), which have high photon energy, have high chemical and mutagenic activity. Large doses of them are harmful to organisms.
In the range of 250–300 nm, UV radiation has a powerful bactericidal effect and causes the formation of anti-rachitis vitamin D in animals, i.e., in small doses, UV radiation is necessary for humans and animals. At a length of 300-400 nm, UV rays cause a tan in humans, which is a protective reaction of the skin.
Infrared rays (IRL) with a wavelength of more than 750 nm have a thermal effect, are not perceived by the human eye and provide the thermal regime of the planet. These rays are especially important for cold-blooded animals (insects, reptiles), which use them to increase body temperature (butterflies, lizards, snakes) or for hunting (ticks, spiders, snakes).
Currently, many devices have been manufactured that use one or another part of the spectrum: ultraviolet irradiators, household appliances with infrared radiation for quick cooking, etc.
Visible rays with a wavelength of 400-750 nm are of great importance for all living organisms.
Light as a condition for plant life. Light is essential for plants. Green plants use solar energy in this region of the spectrum, capturing it in the process of photosynthesis:
Due to the different need for light energy, plants develop various morphological and physiological adaptations to the light regime of their habitat.
Adaptation is a system for regulating metabolic processes and physiological characteristics that ensures maximum adaptability of organisms to environmental conditions.
In accordance with adaptations to the light regime, plants are divided into the following ecological groups.
- 1. Light-loving- having the following morphological adaptations: strongly branching shoots with shortened internodes, rosette; the leaves are small or with a strongly dissected leaf blade, often with a waxy coating or pubescence, often turned with an edge towards the light (for example, acacia, mimosa, sophora, cornflower, feather grass, pine, tulip).
- 2. Shade-loving- constantly in conditions of strong shading. Their leaves are dark green in color, arranged horizontally. These are plants of the lower tiers of forests (for example, wintergreens, two-leaved mink, ferns, etc.). With a lack of light, deep-sea plants (red and brown algae) live.
- 3. shade-tolerant- can tolerate shading, but also grow well in the light (for example, forest grasses and shrubs growing both in shady places and on the edges, as well as oak, beech, hornbeam, spruce).
In relation to the light, plants in the forest are arranged in tiers. In addition, even in the same tree, the leaves capture light differently depending on the tier. As a rule, they constitute sheet mosaic, i.e. arranged in such a way as to increase the leaf surface for better light capture.
The light regime varies depending on the geographical latitude, time of day and season. In connection with the rotation of the Earth, the light regime has a distinct daily and seasonal rhythm. The reaction of the body to a change in lighting mode is called photoperiodism. In connection with photoperiodism in the body, the processes of metabolism, growth and development change.
The phenomenon associated with photoperiodism in plants phototropism- the movement of individual plant organs towards the light. For example, the movement of a sunflower basket during the day following the sun, opening the inflorescences of a dandelion and bindweed in the morning and closing them in the evening, and vice versa - opening flowers of night violet and fragrant tobacco in the evening and closing them in the morning (daily photoperiodism).
Seasonal photoperiodism is observed in latitudes with the change of seasons (temperate and northern latitudes). With the onset of a long day (in spring), active sap flow is observed in plants, the buds swell and open. With the onset of a short autumn day, the plants shed their leaves and prepare for winter dormancy. It is necessary to distinguish between "short day" plants - they are common in the subtropics (chrysanthemums, perilla, rice, soybeans, cocklebur, hemp); and plants of the "long day" (rudbeckia, cereals, cruciferous, dill) - they are distributed mainly in temperate and subpolar latitudes. "Long day" plants cannot grow in the south (they do not produce seeds), and the same applies to "short day" plants if grown in the north.
Light as a condition for animal life. For animals, light is not a factor of paramount importance, as for green plants, since they exist due to the energy of the sun accumulated by these plants. Nevertheless, animals need light of a certain spectral composition. Basically, they need light for visual orientation in space. True, not all animals have eyes. In primitives, these are simply photosensitive cells or even a place in the cell (for example, the stigma in unicellular organisms or the "light-sensitive eye").
Figurative vision is possible only with a sufficiently complex structure of the eye. For example, spiders can distinguish the contours of moving objects only at a distance of 1-2 cm. The eyes of vertebrates perceive the shape and size of objects, their color and determine the distance to them.
Visible light is a conventional concept for different animal species. For a person, these are rays from purple to dark red (recall the colors of the rainbow). Rattlesnakes, for example, perceive the infrared part of the spectrum. Bees, on the other hand, distinguish multicolor ultraviolet rays, but do not perceive red ones. The spectrum of visible light for them is shifted to the ultraviolet region.
The development of the organs of vision largely depends on the ecological situation and environmental conditions of organisms. So, in permanent inhabitants of caves, where sunlight does not penetrate, the eyes can be completely or partially reduced: in blind ground beetles, bats, some amphibians and fish.
The ability for color vision also depends on whether the organisms are diurnal or nocturnal. Dogs, cats, hamsters (which feed by hunting at dusk) all see in black and white. The same vision is in night birds - owls, nightjars. Diurnal birds have well-developed color vision.
Animals and birds also have adaptations for daytime and nocturnal lifestyles. For example, most ungulates, bears, wolves, eagles, larks are active during the day, while tigers, mice, hedgehogs, owls are most active at night. The length of daylight hours affects the onset of the mating season, migrations and flights in birds, hibernation in mammals, etc.
Animals navigate with the help of their organs of vision during long-distance flights and migrations. Birds, for example, choose the direction of flight with amazing accuracy, overcoming many thousands of kilometers from nesting to wintering grounds. It has been proven that during such long-distance flights, birds are at least partially oriented by the Sun and stars, i.e., astronomical light sources. They are capable of navigation, changing orientation in order to get to the desired point on the Earth. If the birds are transported in cages, then they correctly choose the direction for wintering from anywhere in the world. Birds do not fly in continuous fog, as they often go astray during the flight.
Among insects, the ability for this kind of orientation is developed in bees. They use the position (height) of the Sun as a guide.
Temperature regime in the ground-air environment. Temperature adaptations. It is known that life is a way of existence of protein bodies, therefore the boundaries of the existence of life are the temperatures at which the normal structure and functioning of proteins is possible, on average from 0°C to +50°C. However, some organisms have specialized enzyme systems and are adapted to active existence at temperatures outside these limits.
Species that prefer cold (they are called cryophiles), can maintain cell activity down to -8°... -10°C. Bacteria, fungi, lichens, mosses, and arthropods can endure hypothermia. Our trees also do not die at low temperatures. It is only important that during the period of preparation for winter, the water in the plant cells passes into a special state, and does not turn into ice - then the cells die. Plants overcome hypothermia by accumulating substances in their cells and tissues - osmotic protectors: various sugars, amino acids, alcohols, which “pump out” excess water, preventing it from turning into ice.
There is a group of species of organisms whose optimum life is high temperatures, they are called thermophiles. These are various worms, insects, mites that live in deserts and hot semi-deserts, these are bacteria from hot springs. There are springs with a temperature of + 70 ° C, containing living inhabitants - blue-green algae (cyanobacteria), some types of mollusks.
If, however, we take into account latent(long-term dormant) forms of organisms, such as spores of some bacteria, cysts, spores and seeds of plants, they can withstand greatly abnormal temperatures. Bacterial spores can withstand temperatures up to 180°C. Many seeds, plant pollen, cysts, unicellular algae withstand freezing in liquid nitrogen (at -195.8°C) and then long-term storage at -70°C. After thawing and placing in favorable conditions and sufficient nutrient medium, these cells can become active again and begin to multiply.
The temporary suspension of all vital processes of the body is called suspended animation. Anabiosis can occur in animals both with a decrease in the temperature of the environment, and with its increase. For example, in snakes and lizards, when the air temperature rises above 45 ° C, thermal torpor occurs. In amphibians at water temperatures below 4 ° C, vital activity is practically absent. From the state of anabiosis, living beings can return to normal life only if the structure of macromolecules in their cells (primarily DNA and proteins) is not disturbed.
Resistance to temperature fluctuations in terrestrial inhabitants is different.
Temperature adaptations in plants. Plants, being immobile organisms, are forced to adapt to those temperature fluctuations that exist in their habitats. They have specific systems that protect against hypothermia or overheating. transpiration- this is a system for the evaporation of water by plants through the stomatal apparatus, which saves them from overheating. Some plants have even acquired resistance to fires - they are called pyrophytes. Fires often occur in savannahs, bush thickets. Savannah trees have thick bark impregnated with refractory substances. Their fruits and seeds have thick, lignified skins that crack when set on fire, which helps the seeds to fall into the ground.
Temperature adaptations of animals. Animals, compared with plants, have greater ability to adapt to changes in temperature, as they are able to move, have muscles and produce their own internal heat. Depending on the mechanisms of maintaining a constant body temperature, there are poikilothermic(cold-blooded) and homoiothermal(warm-blooded) animals.
Poikilothermic are insects, fish, amphibians, reptiles. Their body temperature changes with the temperature of the environment.
Homeothermic- animals with a constant body temperature, able to maintain it even with strong fluctuations in outside temperature (these are mammals and birds).
The main ways of temperature adaptations:
- 1) chemical thermoregulation- increase in heat production in response to a decrease in ambient temperature;
- 2) physical thermoregulation- the ability to retain heat due to hair and feathers, the distribution of fat reserves, the possibility of evaporative heat transfer, etc.;
3) behavioral thermoregulation- the ability to move from places of extreme temperatures to places of optimum temperatures. This is the main way of thermoregulation in poikilothermic animals. When the temperature rises or falls, they tend to change their posture or hide in the shade, in a hole. Bees, ants, termites build nests with a well-regulated temperature inside them.
In warm-blooded animals, the thermoregulation system has improved significantly (although it is weak in young and chicks).
To illustrate the perfection of thermoregulation in higher animals and humans, we can give the following example. About 200 years ago, Dr. C. Blegden in England set up the following experiment: together with his friends and a dog, he spent 45 minutes in a dry chamber at +126°C without health consequences. Fans of the Finnish bath know that it is possible to spend some time in a sauna with a temperature of more than + 100 ° C (for everyone - their own), and this is good for health. But we also know that if a piece of meat is kept at this temperature, it will cook.
Under the action of cold in warm-blooded animals, oxidative processes are intensified, especially in the muscles. Chemical thermoregulation comes into play. Muscle tremors are noted, leading to the release of additional heat. Lipid metabolism is especially enhanced, since fats contain a significant supply of chemical energy. Therefore, the accumulation of fat reserves provides better thermoregulation.
The increased production of heat production is accompanied by the consumption of a large amount of food. So, birds remaining for the winter need a lot of food, they are not afraid of frost, but starvation. With a good harvest, spruce and pine crossbills, for example, even in winter breed chicks. People - residents of harsh Siberian or northern regions - from generation to generation developed a high-calorie menu - traditional dumplings and other high-calorie foods. Therefore, before following the fashionable Western diets and rejecting the food of the ancestors, one must remember the expediency existing in nature, which underlies the long-term traditions of people.
An effective mechanism for regulating heat transfer in animals, as in plants, is the evaporation of water through sweating or through the mucous membranes of the mouth and upper respiratory tract. This is an example of physical thermoregulation. A person in extreme heat can allocate up to 12 liters of sweat per day, while dissipating heat 10 times more than normal. Part of the excreted water must be returned through drinking.
Warm-blooded animals, like cold-blooded animals, are characterized by behavioral thermoregulation. In the burrows of animals living underground, temperature fluctuations are the smaller, the deeper the hole. Skillfully built nests of bees maintain an even, favorable microclimate. Of particular interest is the group behavior of animals. For example, penguins in severe frost and snowstorm form a "turtle" - a dense pile. Those who found themselves on the edge gradually make their way inside, where the temperature is maintained at about +37°C. In the same place, inside, cubs are placed.
Thus, in order to live and reproduce in certain conditions of the ground-air environment, animals and plants in the process of evolution have developed a wide variety of adaptations and systems to correspond to this habitat.
Air pollution. Recently, an increasingly significant external factor that changes the ground-air habitat has become anthropogenic factor.
The atmosphere, like the biosphere, has the property of self-purification, or maintaining balance. However, the volume and speed of modern atmospheric pollution exceed the natural possibilities of their neutralization.
Firstly, it is natural pollution - various dust: mineral (products of weathering and destruction of rocks), organic (aeroplankton - bacteria, viruses, plant pollen) and space (particles entering the atmosphere from space).
Secondly, these are artificial (anthropogenic) pollution - industrial, transport and domestic emissions into the atmosphere (dust of cement plants, soot, various gases, radioactive contamination, pesticides).
According to rough estimates, 1.5 million tons of arsenic have been released into the atmosphere over the past 100 years; 1 million tons of nickel; 1.35 million tons of silicon, 900 thousand tons of cobalt, 600 thousand tons of zinc, the same amount of copper and other metals.
Chemical enterprises emit carbon dioxide, iron oxide, nitrogen oxides, chlorine. Of the pesticides, organophosphorus compounds are especially toxic, from which even more toxic ones are obtained in the atmosphere.
As a result of emissions in cities where ultraviolet radiation is reduced and there is a large crowd of people, the air basin is degraded, one of the manifestations of which is smog.
Smog happens "classical"(a mixture of toxic fogs that occur during slight cloudiness) and " photochemical» (a mixture of caustic gases and aerosols, which is formed without fog as a result of photochemical reactions). The most dangerous is London and Los Angeles smog. It absorbs up to 25% of solar radiation and 80% of ultraviolet rays, the urban population suffers from this.
The ground-air environment is the most difficult for the life of organisms. The physical factors that make it up are very diverse: light, temperature. But organisms have adapted over the course of evolution to these changing factors and have developed adaptation systems to ensure extreme adaptability to environmental conditions. Despite the inexhaustibility of air as an environmental resource, its quality is rapidly deteriorating. Air pollution is the most dangerous form of environmental pollution.
Questions and tasks for self-control
- 1. Explain why the ground-air environment is the most difficult for the life of organisms.
- 2. Give examples of adaptations in plants and animals to high and low temperatures.
- 3. Why does temperature have a strong influence on the vital activity of any organisms?
- 4. Analyze how light affects the life of plants and animals.
- 5. Describe what photoperiodism is.
- 6. Prove that different waves of the light spectrum have different effects on living organisms, give examples. List the groups into which living organisms are divided according to the way they use energy, give examples.
- 7. Comment on what seasonal phenomena in nature are connected with and how plants and animals react to them.
- 8. Explain why air pollution poses the greatest danger to living organisms.