Target: to reveal the features of abiotic environmental factors and consider their influence on living organisms.

Tasks: to acquaint students with environmental factors of the environment; to reveal the features of abiotic factors, to consider the influence of temperature, light and moisture on living organisms; to distinguish different groups of living organisms depending on the influence of different abiotic factors on them; complete a practical task to determine the groups of organisms, depending on the abiotic factor.

Equipment: computer presentation, assignments in groups with pictures of plants and animals, practical assignment.

DURING THE CLASSES

All living organisms inhabiting the Earth are influenced by environmental factors.

Environmental factors Are individual properties or elements of the environment that directly or indirectly affect living organisms, at least during one of the stages of individual development. Environmental factors are manifold. There are several qualifications, depending on the approach. This is according to the influence on the vital activity of organisms, according to the degree of variability over time, according to the duration of action. Consider the classification of environmental factors based on their origin.

We will consider the impact of the first three abiotic factors environment, since their influence is more significant - it is temperature, light and humidity.

For example, in the May beetle, the larval stage takes place in the soil. It is influenced by abiotic environmental factors: soil, air, indirectly moisture, chemical composition of the soil - light does not affect it at all.

For example, bacteria are able to survive in the most extreme conditions - they are found in geysers, hydrogen sulfide springs, very salty water, at the depth of the World Ocean, very deep in the soil, in the ice of Antarctica, on the highest peaks (even Everest 8848 m), in the bodies of living organisms.

TEMPERATURE

Most plant and animal species are adapted to a fairly narrow temperature range. Some organisms, especially at rest or suspended animation, are able to withstand fairly low temperatures. Temperature fluctuations in water are usually less than on land, so the temperature tolerance limits for aquatic organisms are worse than for terrestrial ones. The metabolic rate depends on the temperature. Basically, organisms live at temperatures from 0 to +50 on the surface of sand in the desert and up to -70 in some areas of Eastern Siberia. The average temperature range is from +50 to –50 in terrestrial habitats and from +2 to +27 in the World Ocean. For example, microorganisms can withstand cooling down to –200, certain types of bacteria and algae can live and multiply in hot springs at temperatures of + 80, +88.

Distinguish animal organisms:

with a constant body temperature (warm-blooded);
with inconsistent body temperature (cold-blooded).

Organisms with variable body temperature (fish, amphibians, reptiles)

In nature, the temperature is not constant. Organisms that live in temperate latitudes and are exposed to temperature fluctuations are less tolerant of constant temperatures. Sharp fluctuations - heat, frost - are unfavorable for organisms. Animals have developed adaptations to combat cooling and overheating. For example, with the onset of winter, plants and animals with variable body temperatures fall into a state of winter dormancy. Their metabolic rate drops sharply. In preparation for winter, a lot of fat and carbohydrates are stored in the tissues of animals, the amount of water in the fiber decreases, sugars and glycerin accumulate, which prevents freezing. So the frost resistance of wintering organisms increases.

In the hot season, on the contrary, physiological mechanisms are activated that protect against overheating. In plants, the evaporation of moisture through the stomata increases, which leads to a decrease in the temperature of the leaves. In animals, the evaporation of water through the respiratory system and skin increases.

Organisms with a constant body temperature. (birds, mammals)

These organisms underwent changes in the internal structure of their organs, which contributed to their adaptation to a constant body temperature. This, for example, is a 4-chambered heart and the presence of one aortic arch, providing complete separation of arterial and venous blood flow, intensive metabolism due to the supply of oxygenated arterial blood to tissues, feather or hair cover of the body, which helps to preserve heat, well-developed nervous activity) ... All this allowed the representatives of birds and mammals to remain active during sudden temperature changes and to master all habitats.

In natural conditions, the temperature is very rarely kept at the level of favorableness for life. Therefore, plants and animals develop special adaptations that weaken sharp fluctuations in temperature. Animals such as elephants have a larger auricle compared to its mammoth ancestor in colder climates. The auricle, in addition to the organ of hearing, performs the function of a thermoregulator. In plants, to protect against overheating, a waxy coating, dense cuticle appears.

LIGHT

Light provides all life processes on Earth. For organisms, the wavelength of the perceived radiation, its duration and intensity of exposure are important. For example, in plants, a decrease in the length of daylight hours and the intensity of illumination lead to autumn leaf fall.

By relation to the light of the plant divided into:

light-loving- have small leaves, highly branching shoots, a lot of pigment - cereals. But increasing the intensity of light beyond optimal suppresses photosynthesis, so it is difficult to get good harvests in the tropics.
shade-loving e - have thin leaves, large, located horizontally, with fewer stomata.
shade-tolerant- plants capable of living in good lighting and shading conditions

An important role in the regulation of the activity of living organisms and their development is played by the duration and intensity of exposure to light. - photoperiod. In temperate latitudes, the development cycle of animals and plants is confined to the seasons of the year, and the length of daylight serves as a signal to prepare for a change in temperature, which, unlike other factors, always remains constant in a certain place and at a certain time. Photoperiodism is a triggering mechanism that includes physiological processes leading to the growth and flowering of plants in spring, fruiting in summer, and shedding of leaves in autumn in plants. In animals, the accumulation of fat by autumn, reproduction of animals, their migration, migration of birds and the onset of the dormant stage in insects. ( Student message).

In addition to seasonal changes, there are also daily changes in the illumination regime, the change of day and night determines the daily rhythm of the physiological activity of organisms. An important adaptation that ensures the survival of an individual is a kind of "biological clock", the ability to sense time.

Animals, the activity of which depends from time of day, come with day, night and twilight lifestyle.

HUMIDITY

Water is a necessary component of the cell, therefore its amount in certain habitats is a limiting factor for plants and animals and determines the nature of the flora and fauna of a given area.

Excess moisture in the soil leads to waterlogging of the soil and the appearance of marsh vegetation. Depending on the moisture content of the soil (amount of precipitation), the species composition of the vegetation changes. Broad-leaved forests give way to small-leaved, then forest-steppe vegetation. Further, there is low grass, and at 250 ml per year - a desert. Precipitation throughout the year may not fall evenly, living organisms have to endure long droughts. For example, the plants and animals of the savannah, where the intensity of the vegetation cover, as well as the intensive feeding of ungulates, depends on the rainy season.

In nature, daily fluctuations in air humidity also occur, which affect the activity of organisms. There is a close relationship between humidity and temperature. Temperature affects the body more strongly when humidity is high or low. Plants and animals have developed adaptations to varying humidity. For example, in plants - a powerful root system is developed, the cuticle of the leaf is thickened, the leaf blade is reduced or turned into needles and thorns. In saxaul, photosynthesis is carried out by the green part of the stem. Plants stop growing during a drought period. Cacti store moisture in the extended part of the stem; needles instead of leaves reduce evaporation.

Animals have also developed adaptations that allow them to tolerate a lack of moisture. Small animals - rodents, snakes, turtles, arthropods - extract moisture from food. The source of water can be a fat-like substance, for example, in a camel. In hot weather, some animals are rodents, turtles go into hibernation, which lasted for several months. Plants are ephemeral by the beginning of summer, after a short flowering, they can shed their leaves, die off the ground parts and so survive a period of drought. At the same time, bulbs and rhizomes are preserved until the next season.

By plant relation to water divide:

aquatic plants high humidity;
near-water plants, terrestrial water;
land plants;
plants in dry and very dry places, live in places with insufficient moisture, can tolerate a short drought;
succulents- juicy, accumulate water in the tissues of their bodies.

In relation to to the water of animals divide:

moisture-loving animals;
intermediate group;
dry-loving animals.

Types of organisms adaptability to fluctuations in temperature, humidity and light:

warm-bloodedness – maintaining a constant body temperature by the body;
hibernation - prolonged sleep of animals in the winter season;
suspended animation - a temporary state of the body, in which life processes are slowed down to a minimum and all visible signs of life are absent (observed in cold-blooded animals and in winter and during a hot period of time);
frost resistance b - the ability of organisms to tolerate negative temperatures;
resting state - the adaptive property of a perennial plant, which is characterized by the cessation of visible growth and vital activity, the dying off of terrestrial shoots in herbaceous forms of plants and leaf abscission in woody forms;
summer calm- the adaptive property of early flowering plants (tulip, saffron) of tropical regions, deserts, semi-deserts.

(Student messages.)

Let's make output, to all living organisms, i.e. plants and animals are affected by abiotic environmental factors (factors of inanimate nature), especially temperature, light and moisture. Depending on the influence of factors of inanimate nature, plants and animals are divided into different groups and they develop adaptations to the influence of these abiotic factors.

Practical assignments in groups:(Annex 1)

1. TASK: Of the listed animals, name cold-blooded (ie, with a variable body temperature).

2. TASK: From the listed animals name warm-blooded (ie with constant body temperature).

3. TASK: select from the proposed plants those that are light-loving, shade-loving and shade-tolerant and write down in the table.

4. ASSIGNMENT: Select animals that are day, nocturnal and crepuscular.

5. TASK: select plants belonging to different groups in relation to water.

6. TASK: select animals belonging to different groups in relation to water.

Tasks on the topic "abiotic environmental factors", answers(

Introduction

1. Light as an environmental factor. The role of light in the life of organisms

2. Temperature as an environmental factor

3. Humidity as an environmental factor

4. Edaphic factors

5. Different living environments

Conclusion

List of used literature

Introduction

There is a huge variety of living environments on Earth, which provides a variety of ecological niches and their "settlement". However, despite this diversity, there are four qualitatively different living environments that have a specific set of environmental factors, and therefore require a specific set. adaptations... These are the living environments: ground-air (land); water; the soil; other organisms.

Each species is adapted to a specific set of environmental conditions - an ecological niche.

Each species is adapted to its specific environment, to a specific food, predators, temperature, water salinity and other elements of the external world, without which it cannot exist.

A complex of factors is required for the existence of organisms. The body's need for them is different, but each to a certain extent limits its existence.

The absence (lack) of some environmental factors can be compensated by other close (similar) factors. Organisms are not “slaves” of environmental conditions - they, to a certain extent, adapt themselves and change environmental conditions so as to weaken the lack of certain factors.

The absence in the environment of physiologically necessary factors (light, water, carbon dioxide, nutrients) cannot be compensated (replaced) by others.

1. Light as an environmental factor. The role of light in the life of organisms

Light is one of the forms of energy. According to the first law of thermodynamics, or the law of conservation of energy, energy can pass from one form to another. According to this law, organisms are a thermodynamic system constantly exchanging energy and matter with the environment. Organisms on the Earth's surface are exposed to the flow of energy, mainly solar energy, as well as long-wave thermal radiation from space bodies. Both of these factors determine the climatic conditions of the environment (temperature, rate of evaporation of water, movement of air and water). Sunlight with an energy of 2 cal falls on the biosphere from space. 1cm 2 in 1 min. This is the so-called solar constant. This light, passing through the atmosphere, is weakened and no more than 67% of its energy can reach the Earth's surface on a clear noon, i.e. 1.34 cal. per cm 2 in 1 min. Passing through cloud cover, water and vegetation, sunlight is further weakened, and the distribution of energy in it significantly changes in different parts of the spectrum.

The degree of attenuation of sunlight and cosmic radiation depends on the wavelength (frequency) of the light. Ultraviolet radiation with a wavelength of less than 0.3 microns hardly passes through the ozone layer (at an altitude of about 25 km). Such radiation is dangerous for a living organism, in particular for protoplasm.

In living nature, light is the only source of energy, all plants, except bacteria photosynthesize, i.e. synthesize organic substances from inorganic substances (that is, from water, mineral salts and CO 2 - with the help of radiant energy in the process of assimilation). All organisms are dependent on terrestrial photosynthesizing food i.e. chlorophyll-bearing plants.

Light as an environmental factor is divided into ultraviolet with a wavelength of 0.40 - 0.75 microns and infrared with a wavelength longer than these magnitudes.

The effect of these factors depends on the properties of the organisms. Each type of organism is adapted to a particular spectrum of light wavelength. Some types of organisms have adapted to ultraviolet, while others to infrared.

Some organisms are able to distinguish between wavelengths. They have special light-perceiving systems and have color vision, which are of great importance in their life. Many insects are sensitive to shortwave radiation, which humans cannot perceive. Night butterflies perceive ultraviolet rays well. Bees and birds accurately locate and navigate the terrain even at night.

Organisms also react strongly to the intensity of light. According to these characteristics, plants are divided into three ecological groups:

1. Light-loving, sun-loving or heliophytes - which are able to develop normally only under the sun's rays.

2. Shade-loving, or sciophytes - these are plants of the lower tiers of forests and deep-sea plants, for example, lilies of the valley and others.

With a decrease in light intensity, photosynthesis also slows down. All living organisms have threshold sensitivity to light intensity, as well as to other environmental factors. The threshold sensitivity to environmental factors is not the same for different organisms. For example, intense light inhibits the development of Drosophila flies, even causes their death. Cockroaches and other insects do not like light. In most photosynthetic plants, at low light intensity, protein synthesis is inhibited, and in animals, biosynthesis processes are inhibited.

3. Shade-tolerant or facultative heliophytes. Plants that grow well in both shade and light. In animals, these properties of organisms are called light-loving (photophiles), shade-loving (photophobes), euryphobic - stenophobic.

2. Temperature as an environmental factor

Temperature is the most important environmental factor. Temperature has a huge impact on many aspects of the life of organisms, their geography of distribution, reproduction and other biological properties of organisms, depending mainly on temperature. Range, i.e. the temperature range in which life can exist ranges from about -200 ° C to + 100 ° C, sometimes the existence of bacteria in hot springs at a temperature of 250 ° C is found. In fact, most organisms can survive in an even narrower temperature range.

Certain types of microorganisms, mainly bacteria and algae, are able to live and multiply in hot springs at temperatures close to the boiling point. The upper temperature limit for hot spring bacteria is around 90 ° C. Temperature variability is very important from an environmental point of view.

Any species is able to live only within a certain temperature range, the so-called maximum and minimum lethal temperatures. Outside of these critical extreme temperatures, cold or heat, the death of the organism occurs. Somewhere between them, there is an optimal temperature at which the vital activity of all organisms, living matter as a whole, is active.

According to the tolerance of organisms to the temperature regime, they are divided into eurythermal and stenothermal, i.e. able to withstand temperature fluctuations within wide or narrow ranges. For example, lichens and many bacteria can live at different temperatures, or orchids and other thermophilic plants in tropical zones are stenothermal.

Some animals are able to maintain a constant body temperature, regardless of the ambient temperature. Such organisms are called homeothermal. In other animals, body temperature changes depending on the ambient temperature. They are called poikilothermic. Depending on the way organisms adapt to the temperature regime, they are divided into two ecological groups: cryophylls - organisms adapted to the cold, to low temperatures; thermophiles - or thermophilic.

3. Humidity as an environmental factor

Originally, all organisms were aquatic. Having conquered the land, they have not lost their dependence on water. Water is an integral part of all living organisms. Humidity is the amount of water vapor in the air. There is no life without moisture or water.

Humidity is a parameter that characterizes the content of water vapor in the air. Absolute humidity is the amount of water vapor in the air and depends on temperature and pressure. This amount is called relative humidity (i.e. the ratio of the amount of water vapor in the air to the saturated amount of vapor under certain conditions of temperature and pressure.)

In nature, there is a daily rhythm of humidity. Humidity fluctuates vertically and horizontally. This factor, along with light and temperature, plays an important role in regulating the activity of organisms and their distribution. Humidity also changes the effect of temperature.

Drying air is an important environmental factor. Especially for terrestrial organisms, the drying effect of the air is of great importance. Animals adapt, moving to protected places and leading an active lifestyle at night.

Plants absorb water from the soil and evaporate almost completely (97-99%) through the leaves. This process is called transpiration. Evaporation cools the leaves. Due to evaporation, ions are transported through the soil to the roots, ions are transported between cells, etc.

A certain amount of moisture is absolutely essential for terrestrial organisms. Many of them need a relative humidity of 100% for normal life, and vice versa, an organism in a normal state cannot live for a long time in absolutely dry air, because it constantly loses water. Water is an essential part of living matter. Therefore, the loss of water in a known amount leads to death.

Plants of a dry climate adapt by morphological changes, reduction of vegetative organs, especially leaves.

Land animals also adapt. Many of them drink water, others suck it through the integument of the body in a liquid or vapor state. For example, most amphibians, some insects and ticks. Most of the desert animals never drink; they satisfy their needs at the expense of water supplied with food. Other animals get water from fat oxidation.

Water is absolutely essential for living organisms. Therefore, organisms spread throughout the habitat depending on their needs: aquatic organisms in water live constantly; hydrophytes can only live in very humid environments.

From the point of view of ecological valence, hydrophytes and hygrophytes belong to the group of stenogigers. Humidity strongly affects the vital functions of organisms, for example, 70% relative humidity was very favorable for field maturation and fertility of female migratory locusts. With favorable reproduction, they cause enormous economic damage to crops in many countries.

For ecological assessment of the distribution of organisms, the indicator of climate dryness is used. Dryness serves as a selective factor for the ecological classification of organisms.

Thus, depending on the characteristics of the humidity of the local climate, the species of organisms are distributed into ecological groups:

1. Hydatophytes are aquatic plants.

2. Hydrophytes are terrestrial aquatic plants.

3. Hygrophytes are terrestrial plants living in conditions of high humidity.

4. Mesophytes are plants that grow with medium moisture

5. Xerophytes are plants growing with insufficient moisture. They, in turn, are divided into: succulents - succulent plants (cacti); sclerophytes are plants with narrow and small leaves, and rolled into tubes. They are also subdivided into euxerophytes and stipaxerophytes. Euxerophytes are steppe plants. Stipaxerophytes are a group of narrow-leaved turf grasses (feather grass, fescue, fine-legged, etc.). In turn, mesophytes are also divided into mesohygrophytes, mesoxerophytes, etc.

While being inferior to temperature, humidity is, nevertheless, one of the main environmental factors. Throughout most of the history of living nature, the organic world was represented exclusively by the water norms of organisms. Water is an integral part of the vast majority of living things, and almost all of them need an aquatic environment to reproduce or merge gametes. Land animals are forced to create an artificial aquatic environment in their bodies for fertilization, and this leads to the fact that the latter becomes internal.

Humidity is the amount of water vapor in the air. It can be expressed in grams per cubic meter.

4. Edaphic factors

Edaphic factors include the entire set of physical and chemical properties of the soil that can have an environmental impact on living organisms. They play an important role in the life of those organisms that are closely related to the soil. Plant especially depends on edaphic factors.

The main properties of the soil affecting the life of organisms include its physical structure, i.e. slope, depth and granulometry, the chemical composition of the soil itself and the substances circulating in it - gases (in this case, it is necessary to find out the conditions for its aeration), water, organic and mineral substances in the form of ions.

The main characteristic of soil, which is of great importance for both plants and burrowing animals, is its particle size.

Ground soil conditions are determined by climatic factors. Even at shallow depths, complete darkness reigns in the soil, and this property is a characteristic feature of the habitat of those species that avoid light. As it sinks into the soil, temperature fluctuations become less and less significant: during the diurnal changes, they quickly fade, and, starting from a known depth, its seasons of differences are smoothed out. Daily temperature differences disappear already at a depth of 50 cm. As the soil sinks into the soil, the oxygen content in it decreases, and CO 2 increases. At a considerable depth, conditions approach anaerobic, where some anaerobic bacteria live. Already earthworms prefer an environment with a higher content of CO 2 than in the atmosphere.

Soil moisture is an extremely important characteristic, especially for the plants growing on it. It depends on numerous factors: the rain regime, the depth of the layer, as well as the physical and chemical properties of the soil, the particles of which, depending on their size, the content of organic matter, etc. The flora of dry and wet soils is not the same and the same crops cannot be grown on these soils. The fauna of the soil is also very sensitive to its moisture and, as a rule, does not tolerate too much dryness. Earthworms and termites are well-known examples. The latter are sometimes forced to supply their colonies with water, making underground galleries at great depths. However, too high a water content in the soil kills large numbers of insect larvae.

Mineral substances necessary for plant nutrition are found in the soil in the form of ions dissolved in water. At least traces of over 60 chemical elements can be found in the soil. CO2 and nitrogen are abundant; the content of others, such as nickel or cobalt, is extremely low. Some ions are poisonous for plants, others, on the contrary, are vital. The concentration of hydrogen ions in the soil - pH - is, on average, close to neutral. The flora of such soils is especially rich in species. Calcareous and saline soils have an alkaline pH of about 8-9; on sphagnum peat bogs, acidic pH can drop to 4.

Some ions are of great ecological importance. They can cause the elimination of many species and, conversely, contribute to the development of very peculiar forms. Limestone soils are very rich in Ca +2 ion; a specific vegetation called calciphyte develops on them (in the edelweiss mountains; many types of orchids). In contrast to this vegetation, there is calcephobic vegetation. It includes chestnut, bracken fern, most heathers. Such vegetation is sometimes called flint, since the soil, which is poor in calcium, contains correspondingly more silicon. In fact, this vegetation does not directly favor silicon, but simply avoids calcium. Some animals have an organic need for calcium. It is known that chickens stop laying eggs in hard shells if the chicken coop is located in an area where the soil is poor in calcium. The limestone zone is abundantly inhabited by shell-like gastropods (snails), which are widely represented here in terms of species, but they almost completely disappear on the granite massifs.

On soils rich in ion 0 3, a specific flora, called nitrophilic, also develops. Organic residues often found on them, containing nitrogen, are decomposed by bacteria, first to ammonium salts, then to nitrates, and finally to nitrates. Plants of this type form, for example, dense thickets in the mountains near pastures for livestock.

The soil also contains organic matter from the decomposition of dead plants and animals. The content of these substances decreases with increasing depth. In the forest, for example, an important source of their input is litter from fallen leaves, and the litter from deciduous species in this respect is richer than coniferous. It feeds on destructive organisms - saprophytic plants and animal saprophages. Saprophytes are mainly represented by bacteria and fungi, but among them one can find higher plants that have lost chlorophyll as a secondary adaptation. Such are, for example, orchids.

5. Different living environments

According to the majority of authors studying the origin of life on Earth, the evolutionary primary environment of life was precisely the aquatic environment. We find quite a few indirect confirmations of this position. First of all, most organisms are not capable of active life without water entering the body, or at least without maintaining a certain fluid content inside the body.

Perhaps the main distinguishing feature of the aquatic environment is its relative conservatism. For example, the amplitude of seasonal or daily temperature fluctuations in the aquatic environment is much less than in the ground-air one. The bottom topography, the difference in conditions at different depths, the presence of coral reefs, etc. create a variety of conditions in the aquatic environment.

The features of the aquatic environment result from the physicochemical properties of water. Thus, the high density and viscosity of water are of great ecological importance. The specific gravity of water is comparable to that of the body of living organisms. The density of water is about 1000 times that of air. Therefore, aquatic organisms (especially those actively moving) are faced with a large force of hydrodynamic resistance. For this reason, the evolution of many groups of aquatic animals was in the direction of the formation of body shape and types of movement that reduce drag, which leads to a decrease in energy consumption for swimming. Thus, a streamlined body shape is found in representatives of various groups of organisms living in water - dolphins (mammals), bony and cartilaginous fish.

The high density of water is also the reason that mechanical vibrations (vibrations) are well distributed in the aquatic environment. This was important in the evolution of the senses, spatial orientation and communication between aquatic inhabitants. Four times faster than in air, the speed of sound in aquatic environment determines the higher frequency of echolocation signals.

Due to the high density of the aquatic environment, its inhabitants are deprived of the obligatory connection with the substrate, which is characteristic of terrestrial forms and is associated with the forces of gravity. Therefore, there is a whole group of aquatic organisms (both plants and animals) that exist without an obligatory connection with the bottom or other substrate, "hovering" in the water column.

The ground-air environment is characterized by a huge variety of living conditions, ecological niches and organisms inhabiting them.

The main features of the nasal-air environment are a large amplitude of changes in environmental factors, inhomogeneity of the environment, the action of gravitational forces, and low air density. The complex of physical, geographical and climatic factors inherent in a certain natural zone leads to the evolutionary formation of morphophysiological adaptations of organisms to life in these conditions, a variety of life forms.

The atmospheric air is characterized by low and variable humidity. This circumstance largely limited (limited) the possibilities of mastering the ground-air environment, and also directed the evolution of water-salt metabolism and the structure of the respiratory organs.

Soil is the result of the activity of living organisms.

An important feature of the soil is also the presence of a certain amount of organic matter. It is formed as a result of the dying off of organisms and is part of their excretions (secretions).

The conditions of the soil habitat determine such properties of the soil as its aeration (that is, saturation with air), humidity (presence of moisture), heat capacity and thermal regime (daily, seasonal, annual temperature variation). The thermal regime, in comparison with the ground-air environment, is more conservative, especially at great depths. In general, the soil is characterized by fairly stable living conditions.

Vertical differences are typical for other soil properties, for example, the penetration of light, of course, depends on the depth.

Soil organisms are characterized by specific organs and types of movement (burrowing limbs in mammals; the ability to change body thickness; the presence of specialized head capsules in some species); body shape (round, volkovate, worm-like); strong and flexible covers; reduction of eyes and disappearance of pigments. Among the soil inhabitants, saprophagia is widely developed - eating the corpses of other animals, rotting remains, etc.

Conclusion

The exit of one of the environmental factors beyond the minimum (threshold) or maximum (extreme) values (characteristic of the type of zone of tolerance) threatens the death of the organism even with an optimal combination of other factors. Examples are: the appearance of an oxygen atmosphere, ice age, drought, pressure changes when divers rise, etc.

Each environmental factor has a different effect on different types of organisms: an optimum for some may be a pessimum for others.

Organisms on the Earth's surface are exposed to the flow of energy, mainly solar energy, as well as long-wave thermal radiation from space bodies. Both of these factors determine the climatic conditions of the environment (temperature, rate of evaporation of water, movement of air and water).

Drying air is an important environmental factor. Especially for terrestrial organisms, the drying effect of the air is of great importance.

While being inferior in value to temperature, humidity is, nevertheless, one of the main environmental factors. Throughout most of the history of living nature, the organic world was represented exclusively by the water norms of organisms.

List of used literature

1. Dedu I.I. Ecological encyclopedic dictionary. - Chisinau: ITU Publishing House, 1990 .-- 406 p.

2. Novikov G.A. Fundamentals of general ecology and nature protection. - L .: Publishing house Leningrad. University, 1979 .-- 352 p.

3. Radkevich V.A. Ecology. - Minsk: Higher school, 1983 .-- 320 p.

4. Reimers N.F. Ecology: theory, laws, rules, principles and hypotheses. -M .: Young Russia, 1994 .-- 367 p.

5. Ricklefs R. Fundamentals of General Ecology. - M .: Mir, 1979 .-- 424 p.

6. Stepanovskikh A.S. Ecology. - Kurgan: GIPP "Trans-Urals", 1997. - 616 p.

7. Khristoforova N.K. Fundamentals of Ecology. - Vladivostok: Dalnauka, 1999.-517 p.

These are any environmental factors to which the body reacts with adaptive reactions.

Environment is one of the main ecological concepts, which means a complex of environmental conditions that affect the vital activity of organisms. In a broad sense, the environment is understood as the totality of material bodies, phenomena and energy that affect the body. A more specific, spatial understanding of the environment as the immediate environment of the organism is also possible - its habitat. Habitat is everything among which an organism lives, it is a part of nature that surrounds living organisms and exerts a direct or indirect influence on them. Those. elements of the habitat, which are not indifferent for a given organism or species and in one way or another affect it, are factors in relation to it.

The components of the environment are diverse and changeable, therefore living organisms constantly adapt and regulate their vital activity in accordance with the ongoing variations in the parameters of the external environment. Such adaptations of organisms are called adaptation and allow them to survive and reproduce.

All environmental factors are divided into

Abiotic factors - factors of inanimate nature acting directly or indirectly on the organism - light, temperature, humidity, the chemical composition of the air, water and soil environment, etc. ...
Biotic factors - all forms of influence on the body from the surrounding living beings (microorganisms, the influence of animals on plants and vice versa).
Anthropogenic factors are various forms of human society activity that lead to changes in nature as the habitat of other species or directly affect their lives.

Environmental factors affect living organisms

as stimuli causing adaptive changes in physiological and biochemical functions;
as constraints that make it impossible to exist in these conditions;
as modifiers that cause structural and functional changes in organisms, and as signals indicating changes in other environmental factors.

In this case, it is possible to establish the general nature of the impact of environmental factors on a living organism.

Any organism has a specific set of adaptations to environmental factors and happily exists only within certain limits of their variability. The most favorable level of the factor for life is called optimal.

At low values or with excessive exposure to the factor, the vital activity of organisms drops sharply (noticeably inhibited). The range of action of the environmental factor (area of tolerance) is limited by the points of minimum and maximum, corresponding to the extreme values of this factor, at which the existence of an organism is possible.

The upper level of the factor, beyond which the vital activity of organisms becomes impossible, is called the maximum, and the lower one is called the minimum (Fig.). Naturally, each organism has its own maxima, optima and minima of environmental factors. For example, the housefly can withstand temperature fluctuations from 7 to 50 ° C, and the human roundworm lives only at the temperature of the human body.

The points of optimum, minimum and maximum constitute three cardinal points that determine the possibilities of the body's reaction to this factor. The extreme points of the curve, expressing the state of oppression with a lack or excess of a factor, are called areas of pessimum; pessimal values of the factor correspond to them. Sublethal values of the factor lie near the critical points, and lethal zones of the factor lie outside the tolerance zone.

Environmental conditions under which any factor or their combination goes beyond the comfort zone and has a depressing effect are often called extreme, boundary (extreme, difficult) in ecology. They characterize not only ecological situations (temperature, salinity), but also such habitats where conditions are close to the limits of the possibility of existence for plants and animals.

A complex of factors simultaneously affects any living organism, but only one of them is limiting. The factor that sets the framework for the existence of an organism, species or community is called limiting (limiting). For example, the spread of many animals and plants to the north is limited by a lack of warmth, while in the south the limiting factor for the same species may be a lack of moisture or necessary food. However, the limits of the organism's endurance in relation to the limiting factor depend on the level of other factors.

For the life of some organisms, conditions are required that are limited by narrow limits, that is, the optimum range is not constant for the species. The optimum action of the factor is different for different species. The range of the curve, that is, the distance between the threshold points, shows the zone of action of the ecological factor on the organism (Fig. 104). Under conditions close to the threshold effect of the factor, organisms feel depressed; they may exist, but they do not reach full development. Plants usually do not bear fruit. In animals, on the other hand, sexual maturity is accelerated.

The magnitude of the range of action of the factor, and especially the optimum zone, makes it possible to judge the endurance of organisms in relation to a given element of the environment, testifies to their ecological amplitude. In this regard, organisms that can live in a fairly diverse environment are called zribiontic (from the Greek "evros" - broad). For example, the brown bear lives in a cold and warm climate, in dry and humid regions, and eats a variety of plant and animal foods.

In relation to particular environmental factors, a term is used that begins with the same prefix. For example, animals that can live in a wide temperature range are called eurythermal, and organisms that can live only in narrow temperature ranges are stenothermal. According to the same principle, an organism can be euryhydride or stenohydride, depending on its response to fluctuations in humidity; euryhaline or stenohaline - depending on the ability to tolerate different values of the salinity of the environment, etc.

There are also concepts of ecological valence, which is the ability of an organism to inhabit a variety of environments, and ecological amplitude, reflecting the width of the factor range or the width of the optimum zone.

The quantitative patterns of the reaction of organisms to the action of an ecological factor differ in accordance with the conditions of their habitation. Stenobionticity or eurybionticity does not characterize the specificity of a species in relation to any ecological factor. For example, some animals are confined to a narrow temperature range (i.e., stenothermal) and at the same time can exist in a wide range of environmental salinity (euryhaline).

Environmental factors affect a living organism simultaneously and jointly, and the action of one of them depends to a certain extent on the quantitative expression of other factors - light, humidity, temperature, surrounding organisms, etc. This pattern is called the interaction of factors. Sometimes the lack of one factor is partially compensated by the intensification of the activity of another; the partial substitutability of the action of environmental factors is manifested. At the same time, none of the factors necessary for the body can be completely replaced by another. Phototrophic plants cannot grow without light under the most optimal temperature or nutritional conditions. Therefore, if the value of at least one of the necessary factors goes beyond the tolerance range (below the minimum or above the maximum), then the existence of the organism becomes impossible.

Environmental factors that are pessimal under specific conditions, that is, those that are most distant from the optimum, especially make it difficult for the species to exist under these conditions, despite the optimal combination of other conditions. This dependence is called the law of limiting factors. Such factors deviating from the optimum are of paramount importance in the life of a species or individual individuals, determining their geographic range.

Identification of limiting factors is very important in agricultural practice to establish ecological valence, especially during the most vulnerable (critical) periods of ontogenesis of animals and plants.

Any properties or components of the external environment that affect organisms are called environmental factors... Light, heat, concentration of salts in water or soil, wind, hail, enemies and pathogens - all these are environmental factors, the list of which can be very large.

Among them there are abiotic related to inanimate nature, and biotic associated with the influence of organisms on each other.

Environmental factors are extremely diverse, and each species, experiencing their influence, responds to it in different ways. Nevertheless, there are some general laws that govern the response of organisms to any environmental factor.

The main one is optimum law... It reflects how living organisms transfer different strengths of the action of environmental factors. The strength of the impact of each of them is constantly changing. We live in a world with variable conditions, and only in certain places on the planet are the values of some factors more or less constant (in the depths of caves, at the bottom of the oceans).

The law of the optimum is expressed in the fact that any environmental factor has certain limits of positive influence on living organisms.

When deviating from these limits, the sign of the effect changes to the opposite. For example, animals and plants do not tolerate extreme heat and severe frosts; average temperatures are optimal. Likewise, drought and constant heavy rains are equally unfavorable for the crop. The law of the optimum indicates the measure of each factor for the viability of organisms. On the graph, it is expressed by a symmetric curve showing how the vital activity of the species changes with a gradual increase in the influence of the factor (Fig. 13).

Figure 13. Scheme of the action of environmental factors on living organisms. 1,2 - critical points
(to enlarge the image, click on the picture)

In the center under the curve - optimum zone... At optimal values of the factor, organisms actively grow, feed, and multiply. The more the value of the factor deviates to the right or to the left, that is, in the direction of decreasing or increasing the force of action, the less favorable it is for organisms. The curve representing vital activity slopes sharply down on either side of the optimum. There are two pessimum zones... When the curve intersects the horizontal axis, there are two critical points... These are such values of the factor that organisms can no longer withstand, death occurs outside of them. The distance between the critical points shows the degree of tolerance of organisms to a change in the factor. Conditions close to critical points are especially difficult for survival. Such conditions are called extreme.

If you draw the curves of the optimum of any factor, for example, temperature, for different species, then they will not coincide. Often what is optimal for one species is pessimum for another or even outside the critical points. Camels and jerboas could not live in the tundra, and reindeer and lemmings in the hot southern deserts.

The ecological diversity of species is also manifested in the position of critical points: in some they are close together, in others they are widely spaced. This means that a number of species can live only in very stable conditions, with a slight change in environmental factors, while others can withstand wide fluctuations. For example, a touch-me-not plant withers if the air is not saturated with water vapor, and feather grass tolerates changes in humidity well and does not die even in drought.

Thus, the law of optimum shows us that for each species there is a measure of the influence of each factor. Both a decrease and an increase in exposure beyond this measure leads to the death of organisms.

To understand the relationship of species with the environment, it is equally important limiting factor.

In nature, organisms are simultaneously influenced by a whole complex of environmental factors in different combinations and with different strengths. It is not easy to isolate the role of each of them. Which one matters more than the others? What we know about the law of optimum allows us to understand that there are no entirely positive or negative, important or secondary factors, and everything depends on the strength of the influence of each.

The law of the limiting factor states that the most significant factor is the one that deviates most from the values that are optimal for the body.

It is on him that the survival of individuals depends in this particular period. In other periods of time, other factors may become limiting, and during life organisms meet with a variety of limitations of their vital activity.

The laws of optimum and limiting factor are constantly faced by the practice of agriculture. For example, the growth and development of wheat, and, consequently, the harvest is constantly limited either by critical temperatures, or by a lack or excess of moisture, or by a lack of mineral fertilizers, and sometimes by such catastrophic effects as hail and storms. It takes a lot of effort and money to maintain optimal conditions for crops, and at the same time, in the first place, to compensate or mitigate the effect of the limiting factors.

The habitat of various species is surprisingly varied. Some of them, for example, some small mites or insects, spend their whole life inside a leaf of a plant, which for them is the whole world, others master huge and varied spaces, such as reindeer, whales in the ocean, migratory birds.

Depending on where representatives of different species live, they are affected by different complexes of environmental factors. On our planet, there are several main living environments, very different in terms of living conditions: water, ground-air, soil. The organisms themselves, in which others live, also serve as a habitat.

Aquatic life environment. All aquatic inhabitants, despite the differences in lifestyle, must be adapted to the main features of their environment. These features are determined, first of all, by the physical properties of water: its density, thermal conductivity, ability to dissolve salts and gases.

Density water determines its significant buoyancy. This means that the weight of organisms is lightened in water and it becomes possible to lead permanent life in the water column, without sinking to the bottom. Many species, mostly small ones, incapable of rapid active swimming, seem to soar in water, being in suspension in it. The collection of such small aquatic inhabitants is called plankton... Plankton includes microscopic algae, small crustaceans, fish eggs and larvae, jellyfish and many other species. Planktonic organisms are carried by currents unable to resist them. The presence of plankton in the water makes possible a filtration type of nutrition, i.e. strain, with the help of various devices, small organisms and food particles suspended in the water. It is developed in both swimming and sedentary benthic animals such as sea lilies, mussels, oysters and others. A sedentary lifestyle would be impossible for aquatic inhabitants if there were no plankton, which, in turn, is possible only in an environment with sufficient density.

The density of the water makes it difficult to actively move in it, therefore, fast-swimming animals, such as fish, dolphins, squids, must have strong muscles and a streamlined body shape. Due to the high density of water, the pressure increases strongly with depth. Deep-sea creatures can withstand pressures that are thousands of times higher than those on land.

Light penetrates into the water only to a shallow depth; therefore, plant organisms can exist only in the upper horizons of the water column. Even in the cleanest seas, photosynthesis is possible only down to depths of 100-200 m. At great depths, there are no plants, and deep-sea animals live in complete darkness.

Temperature regime softer in water than on land. Due to the high heat capacity of water, temperature fluctuations in it are smoothed out, and aquatic inhabitants do not face the need to adapt to severe frosts or forty-degree heat. Only in hot springs can the water temperature approach the boiling point.

One of the difficulties of aquatic life is limited oxygen... Its solubility is not very high and, moreover, greatly decreases when the water is polluted or heated. Therefore, in reservoirs sometimes there are zamora- mass death of inhabitants due to lack of oxygen, which occurs for various reasons.

Salt composition the environment is also very important for aquatic organisms. Marine species cannot live in freshwater, and freshwater species cannot live in the seas due to cell disruption.

Ground-air environment of life. This environment has a different set of features. It is generally more complex and varied than the aquatic one. It contains a lot of oxygen, a lot of light, sharper changes in temperature in time and in space, significantly weaker pressure drops and often a moisture deficit. Although many species can fly, and small insects, spiders, microorganisms, seeds and plant spores are carried by air currents, organisms feed and reproduce on the surface of the earth or plants. In such a low-density environment as air, organisms need support. Therefore, in terrestrial plants, mechanical tissues are developed, and in terrestrial animals, the internal or external skeleton is more pronounced than in aquatic animals. Low air density makes it easier to move around in it.

MS Gilyarov (1912-1985), a prominent zoologist, ecologist, academician, founder of extensive studies of the world of soil animals, passive flight mastered about two-thirds of the inhabitants of the land. Most of them are insects and birds.

Air is a poor conductor of heat. This facilitates the ability to preserve the heat generated inside organisms and maintain a constant temperature in warm-blooded animals. The very development of warm-bloodedness became possible in the terrestrial environment. The ancestors of modern aquatic mammals - whales, dolphins, walruses, seals - once lived on land.

Terrestrial inhabitants have a wide variety of adaptations associated with providing themselves with water, especially in arid conditions. In plants, this is a powerful root system, a waterproof layer on the surface of leaves and stems, and the ability to regulate water evaporation through the stomata. In animals, these are also different features of the structure of the body and integuments, but, in addition, the corresponding behavior contributes to maintaining the water balance. They can, for example, migrate to watering holes or actively avoid particularly drying out conditions. Some animals can live their entire life on dry food, such as jerboas or the well-known clothes moth. In this case, the water needed by the body arises due to the oxidation of the constituent parts of the food.

Many other environmental factors play an important role in the life of terrestrial organisms, for example, the composition of the air, winds, and the relief of the earth's surface. Weather and climate are especially important. Inhabitants of the ground-air environment must be adapted to the climate of the part of the Earth where they live and withstand the variability of weather conditions.

Soil as a living environment. The soil is a thin layer of the land surface, processed by the activities of living beings. Solid particles are penetrated in the soil by pores and cavities filled partly with water and partly with air, therefore, small aquatic organisms can also inhabit the soil. The volume of small cavities in the soil is a very important characteristic. In loose soils, it can be up to 70%, and in dense soils - about 20%. A huge variety of microscopic creatures live in these pores and cavities or on the surface of solid particles: bacteria, fungi, protozoa, roundworms, arthropods. Larger animals make their own tunnels in the soil. The entire soil is permeated with plant roots. The depth of the soil is determined by the depth of root penetration and the activity of burrowing animals. It is no more than 1.5-2 m.

The air in the soil cavities is always saturated with water vapor, and its composition is enriched with carbon dioxide and depleted in oxygen. In this way, the living conditions in the soil resemble the aquatic environment. On the other hand, the ratio of water to air in soils is constantly changing depending on weather conditions. Temperature fluctuations are very sharp at the surface, but quickly smoothed out with depth.

The main feature of the soil environment is the constant supply of organic matter, mainly due to dying plant roots and falling leaves. It is a valuable source of energy for bacteria, fungi and many animals, so the soil - the most vibrant environment... Her hidden world is very rich and varied.

By the appearance of different species of animals and plants, one can understand not only in what environment they live, but also what kind of life they lead in it.

If we have before us a four-legged animal with strongly developed muscles of the thighs on the hind limbs and much weaker ones on the front ones, which, moreover, are shortened, with a relatively short neck and a long tail, then we can say with confidence that this is a land jumper, capable of to fast and maneuverable movements, an inhabitant of open spaces. This is how the famous Australian kangaroos, desert Asian jerboas, African jumpers, and many other jumping mammals - representatives of various orders living on different continents, look like. They live in the steppes, prairies, savannas - where fast movement on the ground is the main means of escape from predators. The long tail serves as a balancer during fast turns, otherwise the animals would lose their balance.

The thighs are strongly developed on the hind limbs and in jumping insects - locusts, grasshoppers, fleas, leaf beetles.

A compact body with a short tail and short limbs, of which the front ones are very powerful and look like a shovel or a rake, blind eyes, a short neck and short, as it were, trimmed fur tell us that we have in front of us an underground animal burrowing holes and galleries ... It can be a forest mole, and a steppe mole rat, and the Australian marsupial mole, and many other mammals leading a similar lifestyle.

Burrowing insects - bears also have a compact, stocky body and powerful forelimbs, similar to a reduced bucket of a bulldozer. In appearance, they resemble a small mole.

All flying species have developed wide planes - wings in birds, bats, insects, or expanding folds of skin on the sides of the body, like gliding flying squirrels or lizards.

Organisms that disperse by passive flight, with air currents, are characterized by small sizes and very diverse shapes. However, they all have one thing in common - the strong development of the surface compared to the body weight. This is achieved in different ways: due to long hairs, bristles, various outgrowths of the body, its lengthening or flattening, and the lightening of the specific gravity. This is how small insects and plant fly fruits look like.

The external similarity that occurs among representatives of different unrelated groups and species as a result of a similar lifestyle is called convergence.

It mainly affects those organs that directly interact with the external environment, and is much less pronounced in the structure of the internal systems - the digestive, excretory, nervous.

The shape of the plant determines the features of its relationship with the external environment, for example, the way it endures the cold season. Trees and tall shrubs have the tallest branches.

The shape of a liana - with a weak trunk entwining other plants, can be found in both arboreal and herbaceous species. These include grapes, hops, meadow dodder, tropical vines. Curling around the trunks and stems of erect species, liana-like plants bring their leaves and flowers to the light.

Under similar climatic conditions on different continents, a similar appearance of vegetation appears, which consists of different, often completely unrelated species.

The external form, which reflects the way it interacts with the habitat, is called the life form of the species. Different species may have similar life forms if they lead a close lifestyle.

The life form is developed during the secular evolution of species. Those species that develop with metamorphosis naturally change their life form during the life cycle. Compare, for example, a caterpillar and an adult butterfly or frog and its tadpole. Some plants can take on different life forms depending on the growing conditions. For example, linden or bird cherry can be both an upright tree and a bush.

Communities of plants and animals are more stable and more complete if they include representatives of different life forms. This means that such a community makes fuller use of the resources of the environment and has more diverse internal connections.

The composition of life forms of organisms in communities serves as an indicator of the characteristics of their environment and the changes occurring in it.

Aircraft engineers take a close look at the different life forms of flying insects. Models of machines with flapping flight were created, according to the principle of movement in the air of Diptera and Hymenoptera. Modern technology has been used to construct walking machines, as well as robots with lever and hydraulic movement, as in animals of different life forms. Such cars are able to move on steep slopes and off-road.

Life on Earth developed under conditions of a regular change of day and night and the alternation of seasons due to the rotation of the planet around its axis and around the Sun. The rhythm of the external environment creates periodicity, that is, the repetition of conditions in the life of most species. Both critical, difficult periods for survival and favorable ones are regularly repeated.

Adaptation to periodic changes in the external environment is expressed in living beings not only by a direct reaction to changing factors, but also in hereditarily fixed internal rhythms.

Daily rhythms. Circadian rhythms adapt organisms to the change of day and night. Plants have intensive growth, blooming of flowers are timed to a certain time of the day. Animals greatly change their activity during the day. On this basis, day and night species are distinguished.

The daily rhythm of organisms is not only a reflection of changes in external conditions. If you place a person, or animals, or plants in a constant, stable environment without changing day and night, then the rhythm of life processes is preserved, close to the daily one. The body, as it were, lives according to its internal clock, counting the time.

The daily rhythm can capture many processes in the body. In humans, about 100 physiological characteristics obey the daily cycle: heart rate, breathing rhythm, hormone secretion, secretions of the digestive glands, blood pressure, body temperature and many others. Therefore, when a person is awake instead of sleep, the body is still tuned to a night state and sleepless nights have a bad effect on health.

However, diurnal rhythms are manifested not in all species, but only in those in whose life the change of day and night plays an important ecological role. Inhabitants of caves or deep waters, where there is no such change, live according to different rhythms. Yes, and among terrestrial inhabitants, the daily frequency is not detected in everyone.

In experiments under strictly constant conditions, fruit flies-Drosophila maintain a diurnal rhythm for tens of generations. This periodicity is inherited from them, like many other species. So deeply adaptive reactions associated with the daily cycle of the external environment.

Violations of the daily rhythm of the body during night work, space flights, diving, etc. are a serious medical problem.

Annual rhythms. Annual rhythms adapt organisms to seasonal changes in conditions. In the life of species, periods of growth, reproduction, molting, migrations, deep dormancy regularly alternate and repeat in such a way that organisms meet the critical season in the most stable state. The most vulnerable process - reproduction and rearing of young animals - falls on the most favorable season. This periodicity of the change in the physiological state during the year is largely congenital, that is, it manifests itself as an internal annual rhythm. If, for example, Australian ostriches or a wild dingo dog are placed in a Northern Hemisphere zoo, their breeding season will begin in the fall, when it is spring in Australia. The restructuring of the internal annual rhythms takes place with great difficulty, through a number of generations.

Preparing for reproduction or overwintering is a long process that begins in organisms long before the onset of critical periods.

Abrupt short-term weather changes (summer frosts, winter thaws) usually do not disturb the annual rhythms of plants and animals. The main environmental factor that organisms respond to in their annual cycles is not random weather changes, but photoperiod- changes in the ratio of day and night.

The length of daylight hours regularly changes throughout the year, and it is these changes that serve as an accurate signal of the approach of spring, summer, autumn or winter.

The ability of organisms to respond to changes in the length of the day is called photoperiodism.

If the day is shortened, the species begin to prepare for winter, if it lengthens, for active growth and reproduction. In this case, the factor of changing the length of the day and night is not important for the life of organisms, but its signal value, indicating the upcoming profound changes in nature.

As you know, the length of the day strongly depends on the geographical latitude. In the northern hemisphere in the south, the summer day is much shorter than in the north. Therefore, the southern and northern species react differently to the same amount of day change: the southern ones begin to reproduce with a shorter day than the northern ones.

ENVIRONMENTAL FACTORS

Ivanova T.V., Kalinova G.S., Myagkova A.N. "General biology". Moscow, "Education", 2000

Topic 18. "Habitat. Environmental factors." Chapter 1; pp. 10-58
Topic 19. "Populations. Types of relationships between organisms." chapter 2 §8-14; p. 60-99; chapter 5 § 30-33
Topic 20. "Ecosystems." chapter 2 §15-22; pp. 106-137
Topic 21. "Biosphere. Cycles of substances." chapter 6 §34-42; pp. 217-290

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1. Light as an environmental factor. The role of light in the life of organisms

In living nature, light is the only source of energy, all plants except bacteria? photosynthesize, i.e. synthesize organic substances from inorganic substances (that is, from water, mineral salts and CO 2 - with the help of radiant energy in the process of assimilation). All organisms are dependent on terrestrial photosynthesizing food i.e. chlorophyll-bearing plants.

Light as an environmental factor is divided into ultraviolet with a wavelength of 0.40 - 0.75 microns and infrared with a wavelength longer than these magnitudes.

Organisms also react strongly to the intensity of light. According to these characteristics, plants are divided into three ecological groups:

1. Light-loving, sun-loving or heliophytes - which are able to develop normally only under the sun's rays.

2. Shade-loving, or sciophytes - these are plants of the lower tiers of forests and deep-sea plants, for example, lilies of the valley and others.

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