Abiotic (from Greek - lifeless) are components and phenomena of inanimate, inorganic nature that directly or indirectly affect living organisms. In accordance with the existing classification, the following abiotic factors are distinguished:

climatic (solar radiation, light and light conditions, temperature, humidity, precipitation, wind, pressure, etc.),

· edaphic (soil) mechanical and chemical composition of the soil, moisture capacity, water, air and thermal regime of the soil, groundwater level, etc.,

· orographic or topographic (relief (refers to indirectly acting environmental factors, since it does not directly affect the life of organisms); exposure (location of relief elements in relation to the cardinal points and prevailing winds that bring moisture); altitude),

· hydrographic (aquatic environment) – factors of the aquatic environment (salinity, temperature, oxygen content, organic matter content, etc.),

· chemical (gas composition of the atmosphere, salt composition of water).

Some of the most important abiotic factors are light, temperature, and humidity.

Light. Solar radiation serves as the main source of energy for all processes occurring on Earth. In relation to light, the following ecological groups of plants are distinguished: photophilous(light), shade-loving(shadow), shade-tolerant. Shade-loving plants do not tolerate strong light and live under the forest canopy in constant shade. These are mainly forest herbs. Shade-tolerant plants can live in good light, but can easily tolerate some shading. These include most forest plants. Light-loving plants are mainly plants of meadows and other open spaces. Light is a condition for the orientation of animals. Animals are divided into diurnal, nocturnal and crepuscular species. The light regime also affects the geographical distribution of animals. Thus, certain species of birds and mammals settle in high latitudes with long polar days in the summer, and in the fall, when the days shorten, they migrate or migrate south.

Temperature. One of the most important environmental factors. It determines the level of activity of organisms, affects metabolic processes, reproduction, development, and other aspects of their life. The distribution of organisms depends on it. It should be noted that depending on body temperature, poikilothermic and homeothermic organisms are distinguished. Poikilothermic organisms (from the Greek - various and heat) are cold-blooded animals with an unstable internal body temperature, varying depending on the ambient temperature. These include all invertebrates, and vertebrates include fish, amphibians and reptiles. Their body temperature, as a rule, is 1–2° C higher than the external temperature or equal to it. When the environmental temperature increases or decreases beyond optimal values, these organisms fall into torpor or die. The lack of perfect thermoregulatory mechanisms in poikilothermic animals is due to the relatively weak development of the nervous system and low level of metabolism compared to homeothermic organisms. Homeothermic organisms are warm-blooded animals whose temperature is more or less constant and, as a rule, does not depend on the ambient temperature. These include mammals and birds, in which the constancy of temperature is associated with a higher level of metabolism compared to poikilothermic organisms. In addition, they have a thermal insulating layer (feather, fur, fat layer). Their temperature is relatively high: in mammals it is 36–37° C, and in birds at rest – up to 40–41° C.

Adaptations in plants that smooth out the harmful effects of high and low temperatures:

· intensity of transpiration (as the temperature decreases, the evaporation of water through the stomata occurs less intensely and, as a result, heat transfer decreases and, vice versa);

accumulation of salts in cells that change the plasma coagulation temperature,

· the property of chlorophyll to prevent the penetration of the hottest rays of the sun.

· the accumulation of sugar and other substances in the cells of frost-resistant plants that increase the concentration of cell sap makes the plant more resilient and is of great importance for their thermoregulation.

The influence of thermal conditions can also be seen in animals:

· Bergmann's rule: “as we move away from the poles to the equator, the sizes of systematically similar animals with unstable body temperatures increase, and with constant ones they decrease.” One of the reasons for this phenomenon is an increase in temperature in the tropics and subtropics. In small forms, the relative surface area of ​​the body increases and heat transfer increases, which has a negative effect in temperate and high latitudes, primarily on animals with unstable body temperature. The body temperature of organisms has a significant shape-forming effect.

· Physiological adaptations: fat deposits, down, feathers and fur in birds and mammals; in the Arctic, in the mountains, most insects are dark in color, which contributes to increased absorption of sunlight.

· Allen's rules: “animals with a constant body temperature in cold climatic zones tend to reduce the area of ​​protruding parts of the body, since they give off the greatest amount of heat to the environment.” In mammals, at low temperatures, the size of the tail, limbs, and ears is relatively reduced, and hair develops better.

Water. Also the most important and irreplaceable environmental factor. All physiological processes occur with the participation of water. Living organisms use aqueous solutions (such as blood and digestive juices) to maintain their physiological processes. It limits the growth and development of plants more often than other environmental factors.

Introduction

Main abiotic factors and their characteristics

Literature

Introduction

Abiotic environmental factors are components and phenomena of inanimate, inorganic nature that directly or indirectly affect living organisms. Naturally, these factors act simultaneously and this means that all living organisms fall under their influence. The degree of presence or absence of each of them significantly affects the viability of organisms, and varies differently for different species. It should be noted that this greatly affects the entire ecosystem as a whole and its sustainability.

Environmental factors, both individually and in combination, when affecting living organisms, force them to change and adapt to these factors. This ability is called ecological valency or plasticity. The plasticity, or environmental valency, of each species is different and has a different effect on the ability of living organisms to survive under changing environmental factors. If organisms not only adapt to biotic factors, but can also influence them, changing other living organisms, then this is impossible with abiotic environmental factors: the organism can adapt to them, but is not able to have any significant reverse influence on them.

Abiotic environmental factors are conditions that are not directly related to the life activity of organisms. The most important abiotic factors include temperature, light, water, composition of atmospheric gases, soil structure, composition of nutrients in it, terrain, etc. These factors can affect organisms both directly, for example light or heat, and indirectly, for example, terrain, which determines the action of direct factors, light, wind, moisture, etc. More recently, the influence of changes in solar activity on biosphere processes has been discovered.

1. Main abiotic factors and their characteristics

Among the abiotic factors are:

Climatic (the influence of temperature, light and humidity);

Geological (earthquake, volcanic eruption, glacial movement, mudflows and avalanches, etc.);

Orographic (features of the terrain where the studied organisms live).

Let us consider the action of the main direct abiotic factors: light, temperature and the presence of water. Temperature, light and humidity are the most important environmental factors. These factors naturally change both throughout the year and day, and in connection with geographic zoning. Organisms exhibit zonal and seasonal adaptation to these factors.

Light as an environmental factor

Solar radiation is the main source of energy for all processes occurring on Earth. In the spectrum of solar radiation, three regions can be distinguished, different in biological action: ultraviolet, visible and infrared. Ultraviolet rays with a wavelength of less than 0.290 microns are destructive to all living things, but they are retained by the ozone layer of the atmosphere. Only a small portion of longer ultraviolet rays (0.300 - 0.400 microns) reaches the Earth's surface. They make up about 10% of radiant energy. These rays are highly chemically active; at high doses they can damage living organisms. In small quantities, however, they are necessary, for example, for humans: under the influence of these rays, vitamin D is formed in the human body, and insects visually distinguish these rays, i.e. see in ultraviolet light. They can navigate by polarized light.

Visible rays with a wavelength of 0.400 to 0.750 microns (they account for most of the energy - 45% - of solar radiation) reaching the Earth's surface are especially important for organisms. Green plants, due to this radiation, synthesize organic matter (carry out photosynthesis), which is used as food by all other organisms. For most plants and animals, visible light is one of the important environmental factors, although there are those for which light is not a prerequisite for existence (soil, cave and deep-sea types of adaptation to life in the dark). Most animals are able to distinguish the spectral composition of light - have color vision, and plants have brightly colored flowers to attract pollinating insects.

Infrared rays with a wavelength of more than 0.750 microns are not perceived by the human eye, but they are a source of thermal energy (45% of radiant energy). These rays are absorbed by the tissues of animals and plants, causing the tissues to heat up. Many cold-blooded animals (lizards, snakes, insects) use sunlight to increase their body temperature (some snakes and lizards are ecologically warm-blooded animals). Light conditions associated with the Earth's rotation have distinct daily and seasonal cycles. Almost all physiological processes in plants and animals have a daily rhythm with a maximum and minimum at certain hours: for example, at certain hours of the day, a plant flower opens and closes, and animals have developed adaptations to night and day life. Day length (or photoperiod) is of great importance in the life of plants and animals.

Plants, depending on their living conditions, adapt to the shade - shade-tolerant plants or, on the contrary, to the sun - light-loving plants (for example, cereals). However, strong, bright sun (above optimal brightness) suppresses photosynthesis, making it difficult to produce high yields of protein-rich crops in the tropics. In temperate zones (above and below the equator), the development cycle of plants and animals is confined to the seasons of the year: preparation for changes in temperature conditions is carried out on the basis of a signal - changes in day length, which at a certain time of the year in a given place is always the same. As a result of this signal, physiological processes are turned on, leading to plant growth and flowering in the spring, fruiting in the summer and shedding leaves in the fall; in animals - to molting, fat accumulation, migration, reproduction in birds and mammals, and the onset of the resting stage in insects. Animals perceive changes in day length using their visual organs. And plants - with the help of special pigments located in the leaves of plants. Irritations are perceived through receptors, as a result of which a series of biochemical reactions occur (activation of enzymes or release of hormones), and then physiological or behavioral reactions appear.

The study of photoperiodism in plants and animals has shown that the reaction of organisms to light is based not simply on the amount of light received, but on the alternation of periods of light and darkness of a certain duration during the day. Organisms are able to measure time, i.e. have biological clock - from unicellular organisms to humans. The biological clock - are also governed by seasonal cycles and other biological phenomena. The biological clock determine the daily rhythm of activity of both whole organisms and processes occurring even at the cellular level, in particular cell divisions.

Temperature as an environmental factor

All chemical processes occurring in the body depend on temperature. Changes in thermal conditions, often observed in nature, deeply affect the growth, development and other manifestations of the life of animals and plants. There are organisms with an unstable body temperature - poikilothermic and organisms with a constant body temperature - homeothermic. Poikilothermic animals are entirely dependent on the temperature of the environment, while homeothermic animals are able to maintain a constant body temperature regardless of changes in environmental temperature. The vast majority of terrestrial plants and animals in a state of active life cannot tolerate negative temperatures and die. The upper temperature limit of life is not the same for different species - rarely above 40-45 O C. Some cyanobacteria and bacteria live at temperatures of 70-90 O C, some mollusks (up to 53 O WITH). For most terrestrial animals and plants, the optimum temperature conditions fluctuate within rather narrow limits (15-30 O WITH). The upper threshold of life temperature is determined by the temperature of protein coagulation, since irreversible protein coagulation (disturbance of protein structure) occurs at a temperature of about 60 o WITH.

In the process of evolution, poikilothermic organisms have developed various adaptations to changing temperature conditions of the environment. The main source of thermal energy in poikilothermic animals is external heat. Poikilothermic organisms have developed various adaptations to low temperatures. Some animals, for example, Arctic fish, live constantly at a temperature of -1.8 o C, contain substances (glycoproteins) in tissue fluid that prevent the formation of ice crystals in the body; insects accumulate glycerol for these purposes. Other animals, on the contrary, increase the body's heat production due to active muscle contraction - this way they increase body temperature by several degrees. Still others regulate their heat exchange due to the exchange of heat between the vessels of the circulatory system: the vessels coming from the muscles are in close contact with the vessels coming from the skin and carrying cooled blood (this phenomenon is characteristic of cold-water fish). Adaptive behavior involves many insects, reptiles and amphibians selecting places in the sun to warm themselves or changing different positions to increase the heating surface.

In a number of cold-blooded animals, body temperature can vary depending on the physiological state: for example, in flying insects, the internal body temperature can rise by 10-12 o C or more due to increased muscle work. Social insects, especially bees, have developed an effective way of maintaining temperature through collective thermoregulation (a hive can maintain a temperature of 34-35 o C, necessary for the development of larvae).

Poikilothermic animals are able to adapt to high temperatures. This also occurs in different ways: heat transfer can occur due to the evaporation of moisture from the surface of the body or from the mucous membrane of the upper respiratory tract, as well as due to subcutaneous vascular regulation (for example, in lizards, the speed of blood flow through the vessels of the skin increases with increasing temperature).

The most perfect thermoregulation is observed in birds and mammals - homeothermal animals. In the process of evolution, they acquired the ability to maintain a constant body temperature due to the presence of a four-chambered heart and one aortic arch, which ensured complete separation of arterial and venous blood flow; high metabolism; feathers or hair; regulation of heat transfer; a well-developed nervous system acquired the ability to live actively at different temperatures. Most birds have a body temperature slightly above 40 o C, and in mammals it is slightly lower. Very important for animals is not only the ability to thermoregulate, but also adaptive behavior, the construction of special shelters and nests, the choice of a place with a more favorable temperature, etc. They are also able to adapt to low temperatures in several ways: in addition to feathers or hair, warm-blooded animals use trembling (microcontractions of externally motionless muscles) to reduce heat loss; the oxidation of brown adipose tissue in mammals produces additional energy that supports metabolism.

The adaptation of warm-blooded animals to high temperatures is in many ways similar to similar adaptations of cold-blooded animals - sweating and evaporation of water from the mucous membrane of the mouth and upper respiratory tract; in birds - only the latter method, since they do not have sweat glands; dilation of blood vessels located close to the surface of the skin, which increases heat transfer (in birds, this process occurs in non-feathered areas of the body, for example through the crest). Temperature, as well as the light regime on which it depends, naturally changes throughout the year and in connection with geographic latitude. Therefore, all adaptations are more important for living at low temperatures.

Water as an environmental factor

Water plays an exceptional role in the life of any organism, since it is a structural component of the cell (water accounts for 60-80% of the cell's mass). The importance of water in the life of a cell is determined by its physicochemical properties. Due to polarity, a water molecule is able to attract any other molecules, forming hydrates, i.e. is a solvent. Many chemical reactions can only occur in the presence of water. Water is present in living systems thermal buffer , absorbing heat during the transition from a liquid to a gaseous state, thereby protecting the unstable structures of the cell from damage during the short-term release of thermal energy. In this regard, it produces a cooling effect when evaporating from the surface and regulates body temperature. The thermal conductivity properties of water determine its leading role as a climate thermoregulator in nature. Water slowly heats up and slowly cools: in summer and during the day, the water of the seas, oceans and lakes heats up, and at night and in winter it also slowly cools. There is a constant exchange of carbon dioxide between water and air. In addition, water performs a transport function, moving soil substances from top to bottom and back. The role of humidity for terrestrial organisms is due to the fact that precipitation is distributed unevenly on the earth's surface throughout the year. In arid areas (steppes, deserts), plants obtain water with the help of a highly developed root system, sometimes very long roots (for camel thorn - up to 16 m), reaching the wet layer. The high osmotic pressure of cell sap (up to 60-80 atm), which increases the suction power of the roots, helps retain water in the tissues. In dry weather, plants reduce water evaporation: in desert plants, the integumentary tissues of the leaves thicken, or a waxy layer or dense pubescence develops on the surface of the leaves. A number of plants achieve a decrease in moisture by reducing the leaf blade (leaves turn into spines, often plants completely lose leaves - saxaul, tamarisk, etc.).

Depending on the requirements for the water regime, the following ecological groups are distinguished among plants:

Hydratophytes are plants that constantly live in water;

Hydrophytes - plants that are only partially immersed in water;

Helophytes - marsh plants;

Hygrophytes are terrestrial plants that live in excessively moist places;

Mesophytes - prefer moderate moisture;

Xerophytes are plants adapted to constant lack of moisture; Among xerophytes there are:

Succulents - accumulating water in the tissues of their body (succulent);

Sclerophytes - lose a significant amount of water.

Many desert animals are able to survive without drinking water; some can run quickly and for a long time, making long migrations to watering places (saiga antelopes, camels, etc.); Some animals obtain water from food (insects, reptiles, rodents). Fat deposits of desert animals can serve as a kind of water reserve in the body: when fats are oxidized, water is formed (fat deposits in the hump of camels or subcutaneous fat deposits in rodents). Low-permeability skin coverings (for example, in reptiles) protect animals from moisture loss. Many animals have switched to a nocturnal lifestyle or hide in burrows, avoiding the drying effects of low humidity and overheating. Under conditions of periodic dryness, a number of plants and animals enter a state of physiological dormancy - plants stop growing and shed their leaves, animals hibernate. These processes are accompanied by reduced metabolism during dry periods.

abiotic nature biosphere solar

Literature

1. http://burenina.narod.ru/3-2.htm

Http://ru-ecology.info/term/76524/

Http://www.ecology-education.ru/index.php?action=full&id=257

Http://bibliofond.ru/view.aspx?id=484744

Tutoring

Need help studying a topic?

Our specialists will advise or provide tutoring services on topics that interest you.
Submit your application indicating the topic right now to find out about the possibility of obtaining a consultation.

Abiotic factors. Temperature

Abiotic factors- all components and phenomena of inanimate nature.

Temperature refers to climatic abiotic environmental factors. Most organisms are adapted to a rather narrow temperature range, since the activity of cellular enzymes ranges from 10 to 40 ° C; at low temperatures, reactions proceed slowly.

Animal organisms are distinguished:

• with a constant body temperature ( warm-blooded, or homeothermic);
• with unstable body temperature ( cold-blooded, or poikilothermic).

Plants and animals have special adaptationscooling, allowing adaptation to temperature fluctuations.

Organisms whose body temperature changes depending on the temperature of the environment (plants, invertebrate animals, fish, amphibians and reptiles) have various adaptations to maintain life. Such animals are called cold-blooded, or poikilothermic. The lack of a thermoregulation mechanism is due to poor development of the nervous system, low metabolic rate and the absence of a closed circulatory system.

The body temperature of poikilothermic animals is only 1-2 °C higher than the ambient temperature or equal to it, but it can increase as a result of absorption of solar heat (snakes, lizards) or muscular work (flying insects, fast-swimming fish). Sharp fluctuations in environmental temperature can lead to death.

With the onset of winter, plants and animals enter a state of winter dormancy. Their metabolic rate drops sharply. In preparation for winter, a lot of fat and carbohydrates are stored in animal tissues, the amount of water in fiber decreases, sugars and glycerin accumulate, which prevents freezing.

Species with an unstable body temperature are capable of entering an inactive state when the temperature drops. Slowing down metabolism in cells greatly increases the resistance of organisms to adverse weather conditions. The transition of animals into a state of torpor, like the transition of plants into a state of rest, allows them to endure the winter cold with minimal losses, without spending a lot of energy.

To protect organisms from overheating in the hot season, special physiological mechanisms are activated: in plants, the evaporation of moisture through the stomata increases; in animals, the evaporation of water through the respiratory system and skin increases.

In poikilothermic organisms, internal body temperature follows changes in environmental temperature. Their metabolic rate either increases or decreases. Such species are the majority on Earth.

Organisms with a constant body temperature are called warm-blooded, or homeothermic. These include birds and mammals.

The body temperature of such animals is stable, it does not depend on the temperature of the environment, due to the presence of thermoregulation mechanisms. The constancy of body temperature is ensured by the regulation of heat production and heat transfer.

When there is a threat of overheating of the body, skin vessels dilate, sweating and heat transfer increase. When there is a threat of cooling, the skin vessels narrow, the fur or feathers rise - heat transfer is limited.

With significant changes in external temperature and sudden changes in heat production, the temperature of internal organs in warm-blooded animals may deviate from normal values ​​from 0.2-0.3 to 1-3 °C.

Sweating is characteristic only of humans, monkeys and equids. In other homeothermic animals, the most effective mechanism for heat loss is thermal panting. The ability to increase heat production is most pronounced in birds, rodents and some other animals.

Homeotherms are able to maintain a constant body temperature under any environmental conditions. Their metabolism always runs at a high speed, even if the outside temperature is constantly changing. For example, polar bears in the Arctic or penguins in Antarctica can withstand frosts of 50 degrees, which is a difference of 87-90 degrees compared to their own temperature.

Adaptations of organisms to different temperature conditions. Both warm-blooded and cold-blooded animals, in the process of evolution, have developed various adaptations to changing temperature conditions of the environment.The main source of thermal energy in organisms with unstable body temperature is external heat.

It takes two to three weeks for overwintered snakes to bring their metabolism to a sufficient intensity. Typically, snakes crawl out and bask in the sun repeatedly throughout the day, and return to their burrows at night.

With the onset of winter, plants and animals with unstable body temperatures enter a state of winter dormancy. Their metabolic rate decreases sharply. In preparation for winter, a lot of fats and carbohydrates are stored in the tissues.

In autumn, plants reduce their consumption of substances by storing sugar and starch. Their growth stops, the intensity of all physiological processes slows down sharply, and the leaves fall off. During the first frosts, plants lose a significant amount of water, becoming frost-resistant and entering a state of deep dormancy.

During the hot season, overheating protection mechanisms are activated. In plants, water evaporation increases through the stomata, and in animals - through the respiratory system and skin.

If the plants are sufficiently supplied with water, the stomata are open day and night. However, in many plants the stomata are open only during the day in the light and close at night. In dry, hot weather, plant stomata close even during the day, and the release of water vapor from the leaves into the air stops. When favorable conditions occur, the stomata open and normal plant activity is restored.

The most perfect thermoregulation is observed in animals with a constant body temperature. Regulation of heat transfer by skin vessels and well-developed higher nervous activity allowed birds and mammals to remain active during sudden temperature changes and to master almost all habitats.

Complete division of blood into venous and arterial, intensive metabolism, feathers or body hair that help retain heat.

Of great importance for warm-blooded animals is not only the ability to thermoregulate, but also adaptive behavior, the construction of special shelters and nests.

In nature, one of the important limiting environmental factors is temperature. The influence of temperature on most organisms is manifested in the regulation of biochemical and physiological processes of life. Temperature can influence the behavior and geographic distribution of organisms. The temperature factor is characterized by wide geographical, seasonal and daily fluctuations. The limits of tolerance for any species are the temperatures at which protein denaturation occurs. This leads to loss of enzyme activity and an irreversible change in the colloidal properties of the cytoplasm. The range of tolerated temperatures varies greatly among different species, but, as a rule, is in the range from 0 to +50 °C.

Poikilothermic and homeothermic organisms

Depending on the method of thermoregulation, two groups of organisms are distinguished: poikilothermic and homeothermic.

Poikilothermic organisms(from Greek poikilos- changeable, changing, thermo- heat) - organisms whose body temperature is not constant and changes with the temperature of the environment. These include all plants, fungi, protists, invertebrate animals, fish, amphibians and reptiles.

Homeothermic organisms(from Greek homoios- identical, similar, thermo- heat) - organisms capable of maintaining a relatively constant body temperature when the ambient temperature changes. These include birds and mammals (including humans). Homeothermic organisms are able to remain active over a wide range of temperatures. Poikilo thermal organisms go into torpor at low temperatures, and some desert inhabitants also go into torpor at high temperatures.

Do homeothermic organisms always maintain a constant body temperature? It is known that some species of mammals and birds are capable of falling into torpor, which is superficially similar to the cold torpor of poikilothermic animals. At the same time, their body temperature drops almost to the level of ambient temperature. Irregular torpor is observed in swallows, swifts, many rodents, and some marsupials due to sudden cold weather, rain or snowfall. Seasonal torpor, which is commonly called hibernation, typical for marmots, gophers, hedgehogs, bats, and brown bears. The above-mentioned species of birds and mammals are classified into a separate group heterothermic animals(from Greek heteros- different, different, thermo- warm).

Adaptation of plants to different temperature conditions

The life activity of plants largely depends on the ambient temperature. According to the need for heat, they are divided into three ecological groups: heat-loving, mesothermic and cold-resistant.

Heat-loving plants grow in tropical, subtropical zones and well-warmed habitats of the temperate zone. Heat-loving plants have developed adaptations to high temperatures. Mesothermic and cold-resistant plants, inhabiting temperate and cold zones, are forced to adapt to low temperatures. All plant adaptations to temperature can be divided into three types: biochemical, physiological and morphological.

Biochemical adaptations

At high temperatures, the content of protective substances (organic acids, salts, mucus) increases in the cytoplasm of the cells of heat-loving plants. They prevent the coagulation of the cytoplasm and neutralize toxic substances.

In cold-resistant plants, at low temperatures, carbohydrates (mainly glucose) accumulate in the cell sap, which lowers the freezing point of water.

Physiological adaptations

Effective protection of plants from overheating is enhanced transpiration (evaporation of water) due to the large number of stomata.

In desert and steppe plants, a short development cycle allows them to avoid high temperatures. Their entire growing season occurs in early spring. And they survive the summer heat in a state of rest. Annual plants in which the dormant state occurs in the form of seeds are called ephemera(poppy). Perennials experiencing an unfavorable period in the form of bulbs, tubers or rhizomes are called ephemeroids(tulip).

An extreme measure in the fight against cold or heat is the transition of plants to a state suspended animation(reversible suspension of life processes) due to dehydration. For example, mosses and lichens can remain in this state for a long time.

Morphological adaptations

The effect of high temperatures on plants in the subtropical and tropical zones is reduced by increasing the reflection of sunlight and reducing the light-absorbing surface.

Increased reflection of sunlight is facilitated by the light color of the leaves, their shiny or pubescent surface.

Reducing light absorption is achieved through modification of leaf blades. These can be thorns (cacti) or small (saxaul), dissected (palm trees), rolled (feather grass) leaves.

The vertical arrangement of leaves relative to the sun's rays counteracts overheating of plants. A change in the angle of their inclination can occur when the leaf blade is rotated.

Adaptations in plants of cold climates manifest themselves in the form of the formation of dwarf life forms (birch, willow). Creeping (dwarf cedar, Turkestan juniper) and cushion-shaped (alpine and arctic cushion plants) life forms are also found. Such plants are less exposed to wind, are better covered with snow in winter, and use the heat of the soil more fully in summer.

Adaptation of animals to different temperature conditions

The diversity of animal adaptations to unfavorable temperature conditions is explained by different methods of thermoregulation in poikilothermic and homeothermic organisms. All animal adaptations according to the mechanism of action are divided into biochemical, physiological, morphological and behavioral.

Biochemical adaptations

In poikilothermic animals, when hypothermia occurs, “biological antifreezes” (substances that lower the freezing point of water) accumulate in body fluids. Such substances in fish are glycoproteins, in insects - glycerol, high concentrations of glucose.

Arctic and Antarctic fish have an increased content of unsaturated fatty acids in their fat composition, which reduces their solidification temperature.

In homeothermic organisms, the fight against hypothermia occurs by increasing the metabolic rate. In mammals, the breakdown of special adipose tissue (brown fat) increases. It is rich in mitochondria and penetrated by numerous blood vessels.

Physiological adaptations

In poikilothermic organisms, regulation of heat exchange occurs due to the structural features of the circulatory system.

The presence of arteriovenous “heat exchangers” is of great importance for thermoregulation in poikilothermic animals. The vessels coming from the muscles are in close contact with the vessels coming from the skin. The blood of the skin warms the blood of the muscles, and it enters deep into the body warm. Having given up its heat, the cooled muscle blood is again directed to the surface of the body. When the ambient temperature increases in lizards, for example, the speed of blood flow through the vessels increases.

At high temperatures, in both poikilothermic and homeothermic organisms, heat transfer increases due to the evaporation of moisture from the surface of the body (sweating). Moisture can evaporate through the mucous membranes of the oral cavity and upper respiratory tract (thermal shortness of breath, etc.).

When exposed to low temperatures, animals may experience muscle tremors. They can also hibernate.

In mammals with short and sparse hair, vascular reactions play an important role in thermoregulation. The expansion or contraction of small superficial vessels of the skin increases or decreases heat transfer.

Morphological adaptations

Thermal insulating covers help reduce heat loss in organisms. Reptiles have horns, birds have feathers, and mammals have hair. Subcutaneous fat, especially pronounced in inhabitants of cold climates (pinnipeds and cetaceans), contributes to heat retention.

Behavioral adaptations

There are two types of behavioral adaptations in poikilothermic animals. This is an active selection of places with the most favorable temperature conditions and a change of positions.

In the first case, insects, reptiles and amphibians actively search for sunlit places. Having received the required amount of heat, animals move into the shade or hide in burrows and maintain their temperature through muscle contractions. In aquatic animals, movement occurs between shallow, well-warmed areas and deeper, cooler areas.

Changing postures allows you to change the surface of the body heated by the sun's rays. For example, marine iguanas on the Galapagos Islands early in the morning or in cloudy weather take a “prostrate” pose, pressing their whole body against the substrate. This provides maximum solar heating surface area. When overheated, they assume an “elevated” posture. Their chest and front part of the body are raised above the substrate. This reduces the heating surface, and the body is blown by the wind.

Homeothermic animals are also characterized by adaptive behavior. It manifests itself in the form of choosing places for protection from cold or heat, and seasonal migrations. Animals can bury themselves in the snow, form close aggregations of individuals to reduce energy costs for thermoregulation, etc.

Temperature can have a limiting effect on organisms due to protein denaturation. This leads to loss of enzyme activity and an irreversible change in the colloidal properties of the cytoplasm. Depending on the method of thermoregulation, organisms are divided into poikilothermic and homeothermic. In relation to different environmental temperature conditions, organisms have developed biochemical, physiological, morphological, and in animals also behavioral adaptations.

Biology. General biology. Grade 11. Basic level Sivoglazov Vladislav Ivanovich

22. Abiotic environmental factors

Remember!

What is a habitat?

What factors are classified as inanimate factors?

In the process of historical development, organisms adapt to a certain set of abiotic factors, which become mandatory conditions for their existence. Moreover, in the process of life, organisms themselves participate in the formation of an abiotic (non-living) environment. During photosynthesis, plants absorb carbon dioxide and release oxygen into the atmosphere, filter-feeding animals purify water, green spaces prevent soil erosion, and legumes enrich the soil with nitrogen—there are many similar examples.

Let us consider the influence of the main abiotic factors on living organisms.

Temperature. Temperature is one of the most important abiotic factors that operates always and everywhere. It is temperature that determines the rate of biochemical reactions and affects most physical processes.

Although the optimal temperature regime for most species is between +15 and +30 °C, there are organisms that can withstand very high or low temperatures. For example, some bacteria and algae live in hot springs at temperatures of +85–87 °C. The resting stages of development of organisms - cysts, insect pupae, bacterial spores, plant seeds - withstand temperature changes well.

All invertebrates and most vertebrates are cold-blooded organisms that are unable to maintain a constant body temperature. Their temperature depends on the thermal regime of the environment. Therefore, in the cold season, the activity of such animals is greatly reduced. Birds and Mammals – warm-blooded animals, they have an almost constant body temperature, independent of the ambient temperature. Maintaining a high body temperature in warm-blooded organisms is ensured by a high level of metabolism, perfect thermoregulation and good thermal insulation.

Since temperature is subject to daily and seasonal fluctuations, organisms are forced to adapt to such changes. In the cold season, mammals develop thicker and longer fur, fat actively accumulates in the subcutaneous fatty tissue, which provides thermal insulation, and in birds the mass of feathers increases in winter. Some animals have developed behavioral adaptations to the seasonal decrease in temperature: migration, flight, digging holes and searching for shelters. In deserts, where daytime soil temperatures can reach +60–70 °C, animals bury themselves in the sand or hide in holes. In plants during the hot season, evaporation from the surface of leaves increases.

Humidity. Water is necessary for life for all living organisms. Moreover, if loss of moisture is especially dangerous for terrestrial animals and plants, then for organisms living in water, on the contrary, excess water in the body can upset the salt balance. Therefore, aquatic organisms develop various adaptations for removing excess water, for example, contractile vacuoles in the ciliate slipper.

For terrestrial living organisms, humidity is one of the most important factors that determines their distribution. Throughout life, water is inevitably lost by the body, so its reserves must be constantly replenished. Depending on environmental conditions, organisms have developed various adaptations to supply themselves with water and conserve moisture. Such drought-resistant plants as camel thorn, saxaul, and desert wormwood have a very deep root system (Fig. 67). Other desert and semi-desert plants have narrow, hard leaves covered with a waxy coating, which significantly reduces water loss through evaporation. Some succulent plants (cacti, euphorbia) have highly developed water-storing tissue, and their leaves are transformed into spines or scales (Fig. 68). Interesting are the adaptations of some steppe plants that manage to grow and bloom in a short wet spring period. They survive the dry season in the form of seeds, bulbs, and tubers.

Animals that live in low humidity conditions also have certain adaptations. Many of them never drink and use only the liquid that is in their food. The dense chitinous cover of terrestrial arthropods prevents the evaporation of moisture. In the process of evolution, having switched to a terrestrial existence, reptiles completely lost their skin glands. A number of animals (insects, camels, marmots) use metabolic water, which is formed during the breakdown of fat, for their life. In arachnids, in the course of adaptation to saving moisture, the metabolism has changed - dehydrated metabolic products (almost dry crystals of uric acid) are released.

Rice. 67. Root system of camel thorn

Adaptive behavioral features are of great importance for animals in arid regions - searching for shelter, nocturnal lifestyle. When the air is very dry, many desert animals hide in holes and tightly close the entrance to them. The air in a closed room is quickly saturated with water vapor, which prevents further loss of moisture by the body. During periods of drought, many rodents, turtles, snakes, and some insects hibernate.

Light. The main source of energy for living organisms is sunlight. Its biological effect depends on the intensity, duration of action, spectral composition, daily and seasonal frequency.

Rice. 68. Cacti are plants with highly developed water-storing tissue

Ultraviolet part of the spectrum promotes the formation of vitamin D in animals. These rays are perceived by the visual organs of insects, and in plants, ultraviolet provides the synthesis of pigments and vitamins. Visible part of the spectrum most significant for organisms. Thanks to illumination, animals orient themselves in space, and photosynthesis occurs in plants. Infrared rays– a source of thermal energy, which is very important for cold-blooded organisms.

Depending on the requirements for lighting conditions, plants are divided into light-loving, shade-tolerant and shade-loving. Light-loving plants are inhabitants of open areas; they do not tolerate even slight shading (for example, steppe plants, white acacia). In diffused light, most ferns and mosses grow in shaded places, and the record holder for living in dark conditions is seaweed.

An important factor in the life of plants and animals is the length of daylight and the change of seasons. For many organisms, changes in day length serve as a signal for changes in physiological activity. This phenomenon is called photoperiodism. In the process of evolution, animals and plants have developed certain biological rhythms– daily and seasonal. The length of the day determines the timing of flowering and ripening of fruits in plants, the migration of birds, the change of fur in mammals, the beginning of the mating season, preparation for hibernation, etc. The lifestyle of nocturnal and daytime animals is significantly different. Plants' flowers open and close at certain times.

Many biochemical and physiological processes in the human body have a rhythmic nature. More than a hundred different parameters are known that change with a 24-hour rhythm (body temperature, blood pressure, hormone secretion, etc.). The study of human biorhythms is very important for organizing an optimal work and rest regime, developing measures for the prevention and treatment of various diseases.

The distribution of certain species is determined not only by light, humidity and temperature, but also by other abiotic environmental parameters. For example, only certain types of plants that can withstand high soil salinity can live in the coastal strip of the ocean, and the wind affects the settlement and migration of spiders and flying insects.

Review questions and assignments

1. What adaptations to changes in environmental temperature do plants and animals have?

2. Tell us about the adaptations of living organisms to a lack of water.

3. Thanks to what part of the solar radiation spectrum do photosynthesis occur in plants?

4. Tell us what you know about the biological rhythms of living organisms.

Think! Do it!

1. What climatic conditions and soil are typical for your region?

2. Why do you think, with constant directed changes in abiotic environmental conditions, the adaptation of living organisms to these changes cannot be endless?

3. Why do poultry farms and greenhouses use additional artificial lighting to increase the length of daylight hours?

4. Solve the problem of placing indoor plants depending on the ecological characteristics of the species.

Work with computer

Refer to the electronic application. Study the material and complete the assignments.

Repeat and remember!

Plants

The most characteristic representatives of shade-loving plants are algae that live in the water column. Light, passing through the water column, gradually dissipates, so algae living at different depths have a different set of pigments. The role of auxiliary pigments, the appearance of which masks the main photosynthetic pigment – ​​chlorophyll, increases significantly. As a result, instead of the green color characteristic of plants, algae may have other colors.

The most deep-sea plants are red algae (purple algae), a large group (about 4 thousand species) of mainly marine inhabitants. Externally, red algae are very diverse: there are unicellular, colonial, filamentous, lamellar; the dissected thalli of some resemble corals or vegetative organs of higher plants. Multicellular forms are attached to stones and shells by thread-like outgrowths - rhizoids.

The color of algae (from pink to dark red) is determined by a unique set of pigments. Besides chlorophyll A And b, chlorophyll present d, no longer found in any plants, carotenoids, as well as blue pigment (phycocyanin) and red (phycoerythrin). The water column absorbs orange-red rays, allowing blue-green rays to pass through, which can be used by red-brown pigments. Due to the presence of red pigment, algae of this group can settle at significant depths (up to 200 m), inaccessible to most other algae. The chromatophores (chloroplasts) of scarlet mushrooms are disc-shaped.

Agar-agar is extracted from red algae, which is used in the food industry for the preparation of jelly, marmalade, marshmallows and other products, in paper production, and in microbiological laboratories (for the preparation of nutrient media).

Animals

Amniotes: life in conditions of moisture deficiency. True proto-terrestrial vertebrates (reptiles, birds, mammals) form a group of amniotes. Cyclostomes, fish and amphibians belong to primary aquatic animals - anamnia. Amniotes have fundamental differences from anamnias. This is due to the peculiarities of their water metabolism and reflects the ability of amniotes to develop in a ground-air environment under conditions of moisture deficiency. Let us recall the main characteristic features of this group of vertebrates.

The body's protection from moisture loss through evaporation from the surface of the skin led to the formation of a horny substance in the epidermis, i.e., to keratinization of the skin. In all amniotes (except mammals), the number of skin glands is sharply reduced. Such skin becomes less permeable to water and gases. The breathing function is almost entirely transferred to the lungs. The lungs are located deep in the body cavity, and special airways lead to them - the trachea and bronchi. As the respiratory system changes, the circulatory system also changes. The appearance of a complete or incomplete septum in the ventricle leads to the separation of the second, pulmonary circulation.

In the excretory system of amniotes, it is not the trunk (primary) but the pelvic (secondary) kidneys that function. The structure of these buds ensures water conservation. The nephrons of the pelvic kidneys have long convoluted tubules, along which water is reabsorbed from urine into the blood.

All amniotes undergo internal fertilization. The developing embryo is protected by germinal membranes.