The main ways and forms of adaptation of living organisms to environmental conditions. Photoperiodism. Forms of adaptation Anatomical morphological adaptation examples

Reactions to unfavorable environmental factors only under certain conditions are detrimental to living organisms, and in most cases they have an adaptive value. Therefore, these responses were called by Selye "general adaptation syndrome". In later works, he used the terms "stress" and "general adaptation syndrome" as synonyms.

Adaptation- this is a genetically determined process of formation of protective systems that provide an increase in stability and the flow of ontogenesis in unfavorable conditions for it.

Adaptation is one of the most important mechanisms that increases the stability of a biological system, including a plant organism, in the changed conditions of existence. The better the organism is adapted to some factor, the more resistant it is to its fluctuations.

The genotypically determined ability of an organism to change metabolism within certain limits, depending on the action of the external environment, is called reaction rate. It is controlled by the genotype and is characteristic of all living organisms. Most of the modifications that occur within the limits of the reaction norm are of adaptive significance. They correspond to changes in habitat and provide better survival of plants under fluctuating environmental conditions. In this regard, such modifications are of evolutionary importance. The term "reaction rate" was introduced by V.L. Johansen (1909).

The greater the ability of a species or variety to modify in accordance with the environment, the wider its rate of reaction and the higher the ability to adapt. This property distinguishes resistant varieties of agricultural crops. As a rule, slight and short-term changes in environmental factors do not lead to significant violations of the physiological functions of plants. This is due to their ability to maintain the relative dynamic balance of the internal environment and the stability of the main physiological functions in a changing external environment. At the same time, sharp and prolonged impacts lead to disruption of many functions of the plant, and often to its death.

Adaptation includes all processes and adaptations (anatomical, morphological, physiological, behavioral, etc.) that increase stability and contribute to the survival of the species.

1.Anatomical and morphological adaptations. In some representatives of xerophytes, the length of the root system reaches several tens of meters, which allows the plant to use groundwater and not experience a lack of moisture in conditions of soil and atmospheric drought. In other xerophytes, the presence of a thick cuticle, pubescence of leaves, and the transformation of leaves into spines reduce water loss, which is very important in conditions of lack of moisture.

Burning hairs and spines protect plants from being eaten by animals.

Trees in the tundra or at high mountain heights look like squat creeping shrubs, in winter they are covered with snow, which protects them from severe frosts.

In mountainous regions with large diurnal temperature fluctuations, plants often have the form of flattened pillows with densely spaced numerous stems. This allows you to keep moisture inside the pillows and a relatively uniform temperature throughout the day.

In marsh and aquatic plants, a special air-bearing parenchyma (aerenchyma) is formed, which is an air reservoir and facilitates the breathing of plant parts immersed in water.

2. Physiological and biochemical adaptations. In succulents, an adaptation for growing in desert and semi-desert conditions is the assimilation of CO 2 during photosynthesis along the CAM pathway. These plants have stomata closed during the day. Thus, the plant keeps the internal water reserves from evaporation. In deserts, water is the main factor limiting plant growth. The stomata open at night, and at this time, CO 2 enters the photosynthetic tissues. The subsequent involvement of CO2 in the photosynthetic cycle occurs in the daytime already with closed stomata.

Physiological and biochemical adaptations include the ability of stomata to open and close, depending on external conditions. The synthesis in cells of abscisic acid, proline, protective proteins, phytoalexins, phytoncides, an increase in the activity of enzymes that counteract the oxidative breakdown of organic substances, the accumulation of sugars in cells and a number of other changes in metabolism contribute to an increase in plant resistance to adverse environmental conditions.

The same biochemical reaction can be carried out by several molecular forms of the same enzyme (isoenzymes), while each isoform exhibits catalytic activity in a relatively narrow range of some environmental parameter, such as temperature. The presence of a number of isoenzymes allows the plant to carry out the reaction in a much wider range of temperatures, compared with each individual isoenzyme. This enables the plant to successfully perform vital functions in changing temperature conditions.

3. Behavioral adaptations, or avoidance of an adverse factor. An example is ephemera and ephemeroids (poppy, starflower, crocuses, tulips, snowdrops). They go through the entire cycle of their development in the spring for 1.5-2 months, even before the onset of heat and drought. Thus, they kind of leave, or avoid falling under the influence of the stressor. In a similar way, early-ripening varieties of agricultural crops form a crop before the onset of adverse seasonal events: August fogs, rains, frosts. Therefore, the selection of many agricultural crops is aimed at creating early ripe varieties. Perennial plants overwinter as rhizomes and bulbs in the soil under snow, which protects them from freezing.

Adaptation of plants to unfavorable factors is carried out simultaneously at many levels of regulation - from a single cell to a phytocenosis. The higher the level of organization (cell, organism, population), the greater the number of mechanisms simultaneously involved in the adaptation of plants to stress.

Regulation of metabolic and adaptive processes inside the cell is carried out with the help of systems: metabolic (enzymatic); genetic; membrane. These systems are closely related. Thus, the properties of membranes depend on gene activity, and the differential activity of the genes themselves is under the control of membranes. The synthesis of enzymes and their activity are controlled at the genetic level, at the same time, enzymes regulate the nucleic acid metabolism in the cell.

On the organism level to the cellular mechanisms of adaptation, new ones are added, reflecting the interaction of organs. Under unfavorable conditions, plants create and retain such a number of fruit elements that are provided in sufficient quantities with the necessary substances to form full-fledged seeds. For example, in the inflorescences of cultivated cereals and in the crowns of fruit trees, under adverse conditions, more than half of the laid ovaries can fall off. Such changes are based on competitive relations between organs for physiologically active and nutrients.

Under stress conditions, the processes of aging and falling of the lower leaves are sharply accelerated. At the same time, the substances necessary for plants move from them to young organs, responding to the survival strategy of the organism. Thanks to the recycling of nutrients from the lower leaves, the younger ones, the upper leaves, remain viable.

There are mechanisms of regeneration of lost organs. For example, the surface of the wound is covered with a secondary integumentary tissue (wound periderm), the wound on the trunk or branch is healed with influxes (calluses). With the loss of the apical shoot, dormant buds awaken in plants and lateral shoots develop intensively. Spring restoration of leaves instead of fallen ones in autumn is also an example of natural organ regeneration. Regeneration as a biological device that provides vegetative reproduction of plants by root segments, rhizomes, thallus, stem and leaf cuttings, isolated cells, individual protoplasts, is of great practical importance for crop production, fruit growing, forestry, ornamental gardening, etc.

The hormonal system is also involved in the processes of protection and adaptation at the plant level. For example, under the influence of unfavorable conditions in a plant, the content of growth inhibitors sharply increases: ethylene and abscissic acid. They reduce metabolism, inhibit growth processes, accelerate aging, fall of organs, and the transition of the plant to a dormant state. Inhibition of functional activity under stress under the influence of growth inhibitors is a characteristic reaction for plants. At the same time, the content of growth stimulants in the tissues decreases: cytokinin, auxin and gibberellins.

On the population level selection is added, which leads to the appearance of more adapted organisms. The possibility of selection is determined by the existence of intrapopulation variability in plant resistance to various environmental factors. An example of intrapopulation variability in resistance can be the unfriendly appearance of seedlings on saline soil and an increase in the variation in germination time with an increase in the action of a stressor.

A species in the modern view consists of a large number of biotypes - smaller ecological units, genetically identical, but showing different resistance to environmental factors. Under different conditions, not all biotypes are equally vital, and as a result of competition, only those of them remain that best meet the given conditions. That is, the resistance of a population (variety) to a particular factor is determined by the resistance of the organisms that make up the population. Resistant varieties have in their composition a set of biotypes that provide good productivity even in adverse conditions.

At the same time, in the process of long-term cultivation, the composition and ratio of biotypes in the population changes in varieties, which affects the productivity and quality of the variety, often not for the better.

So, adaptation includes all processes and adaptations that increase the resistance of plants to adverse environmental conditions (anatomical, morphological, physiological, biochemical, behavioral, population, etc.)

But to choose the most effective way of adaptation, the main thing is the time during which the body must adapt to new conditions.

With the sudden action of an extreme factor, the response cannot be delayed, it must follow immediately in order to exclude irreversible damage to the plant. With long-term impacts of a small force, adaptive rearrangements occur gradually, while the choice of possible strategies increases.

In this regard, there are three main adaptation strategies: evolutionary, ontogenetic and urgent. The task of the strategy is the efficient use of available resources to achieve the main goal - the survival of the organism under stress. The adaptation strategy is aimed at maintaining the structural integrity of vital macromolecules and the functional activity of cellular structures, maintaining vital activity regulation systems, and providing plants with energy.

Evolutionary or phylogenetic adaptations(phylogeny - the development of a biological species in time) - these are adaptations that arise during the evolutionary process on the basis of genetic mutations, selection and are inherited. They are the most reliable for plant survival.

Each species of plants in the process of evolution has developed certain needs for the conditions of existence and adaptability to the ecological niche it occupies, a stable adaptation of the organism to the environment. Moisture and shade tolerance, heat resistance, cold resistance and other ecological features of specific plant species were formed as a result of long-term action of the relevant conditions. Thus, heat-loving and short-day plants are characteristic of southern latitudes, less heat-demanding and long-day plants are characteristic of northern latitudes. Numerous evolutionary adaptations of xerophyte plants to drought are well known: economical use of water, deep root system, shedding of leaves and transition to a dormant state, and other adaptations.

In this regard, varieties of agricultural plants show resistance precisely to those environmental factors against which breeding and selection of productive forms is carried out. If the selection takes place in a number of successive generations against the background of the constant influence of some unfavorable factor, then the resistance of the variety to it can be significantly increased. It is natural that the varieties bred by the Research Institute of Agriculture of the South-East (Saratov) are more resistant to drought than the varieties created in the breeding centers of the Moscow region. In the same way, in ecological zones with unfavorable soil and climatic conditions, resistant local plant varieties were formed, and endemic plant species are resistant to the stressor that is expressed in their habitat.

Characterization of the resistance of spring wheat varieties from the collection of the All-Russian Institute of Plant Industry (Semenov et al., 2005)

In a natural environment, environmental conditions usually change very quickly, and the time during which the stress factor reaches a damaging level is not enough for the formation of evolutionary adaptations. In these cases, plants use not permanent, but stressor-induced defense mechanisms, the formation of which is genetically predetermined (determined).

Ontogenetic (phenotypic) adaptations are not associated with genetic mutations and are not inherited. The formation of such adaptations requires a relatively long time, so they are called long-term adaptations. One of such mechanisms is the ability of a number of plants to form a water-saving CAM-type photosynthesis pathway under conditions of water deficit caused by drought, salinity, low temperatures, and other stressors.

This adaptation is associated with the induction of expression of the phosphoenolpyruvate carboxylase gene, which is inactive under normal conditions, and the genes of other enzymes of the CAM pathway of CO2 uptake, with the biosynthesis of osmolytes (proline), with the activation of antioxidant systems, and with changes in the daily rhythms of stomatal movements. All this leads to very economical water consumption.

In field crops, for example, in corn, aerenchyma is absent under normal growing conditions. But under conditions of flooding and a lack of oxygen in the tissues in the roots, some of the cells of the primary cortex of the root and stem die (apoptosis, or programmed cell death). In their place, cavities are formed, through which oxygen is transported from the aerial part of the plant to the root system. The signal for cell death is the synthesis of ethylene.

Urgent adaptation occurs with rapid and intense changes in living conditions. It is based on the formation and functioning of shock protective systems. Shock defense systems include, for example, the heat shock protein system, which is formed in response to a rapid increase in temperature. These mechanisms provide short-term survival conditions under the action of a damaging factor and thus create the prerequisites for the formation of more reliable long-term specialized adaptation mechanisms. An example of specialized adaptation mechanisms is the new formation of antifreeze proteins at low temperatures or the synthesis of sugars during the overwintering of winter crops. At the same time, if the damaging effect of the factor exceeds the protective and reparative capabilities of the body, then death inevitably occurs. In this case, the organism dies at the stage of urgent or at the stage of specialized adaptation, depending on the intensity and duration of the action of the extreme factor.

Distinguish specific and non-specific (general) plant responses to stressors.

Nonspecific reactions do not depend on the nature of the acting factor. They are the same under the action of high and low temperatures, lack or excess of moisture, high concentrations of salts in the soil or harmful gases in the air. In all cases, the permeability of membranes in plant cells increases, respiration is disturbed, the hydrolytic decomposition of substances increases, the synthesis of ethylene and abscisic acid increases, and cell division and elongation are inhibited.

The table shows a complex of nonspecific changes occurring in plants under the influence of various environmental factors.

Changes in physiological parameters in plants under the influence of stressful conditions (according to G.V., Udovenko, 1995)

Based on the data in the table, it can be seen that the resistance of plants to several factors is accompanied by unidirectional physiological changes. This gives reason to believe that an increase in plant resistance to one factor may be accompanied by an increase in resistance to another. This has been confirmed by experiments.

Experiments at the Institute of Plant Physiology of the Russian Academy of Sciences (Vl. V. Kuznetsov and others) have shown that short-term heat treatment of cotton plants is accompanied by an increase in their resistance to subsequent salinization. And the adaptation of plants to salinity leads to an increase in their resistance to high temperatures. Heat shock increases the ability of plants to adapt to subsequent drought and, conversely, in the process of drought, the body's resistance to high temperature increases. Short-term exposure to high temperatures increases resistance to heavy metals and UV-B radiation. The preceding drought favors the survival of plants in conditions of salinity or cold.

The process of increasing the body's resistance to a given environmental factor as a result of adaptation to a factor of a different nature is called cross-adaptation.

To study the general (nonspecific) mechanisms of resistance, of great interest is the response of plants to factors that cause water deficiency in plants: salinity, drought, low and high temperatures, and some others. At the level of the whole organism, all plants react to water deficiency in the same way. Characterized by inhibition of shoot growth, increased growth of the root system, the synthesis of abscisic acid, and a decrease in stomatal conductivity. After some time, the lower leaves rapidly age, and their death is observed. All these reactions are aimed at reducing water consumption by reducing the evaporating surface, as well as by increasing the absorption activity of the root.

Specific reactions are reactions to the action of any one stress factor. Thus, phytoalexins (substances with antibiotic properties) are synthesized in plants in response to contact with pathogens (pathogens).

The specificity or non-specificity of responses implies, on the one hand, the attitude of a plant to various stressors and, on the other hand, the characteristic reactions of plants of different species and varieties to the same stressor.

The manifestation of specific and nonspecific responses of plants depends on the strength of stress and the rate of its development. Specific responses occur more often if the stress develops slowly, and the body has time to rebuild and adapt to it. Nonspecific reactions usually occur with a shorter and stronger effect of the stressor. The functioning of nonspecific (general) resistance mechanisms allows the plant to avoid large energy expenditures for the formation of specialized (specific) adaptation mechanisms in response to any deviation from the norm in their living conditions.

Plant resistance to stress depends on the phase of ontogeny. The most stable plants and plant organs in a dormant state: in the form of seeds, bulbs; woody perennials - in a state of deep dormancy after leaf fall. Plants are most sensitive at a young age, since growth processes are damaged in the first place under stress conditions. The second critical period is the period of gamete formation and fertilization. The effect of stress during this period leads to a decrease in the reproductive function of plants and a decrease in yield.

If stress conditions are repeated and have a low intensity, then they contribute to the hardening of plants. This is the basis for methods for increasing resistance to low temperatures, heat, salinity, and an increased content of harmful gases in the air.

Reliability of a plant organism is determined by its ability to prevent or eliminate failures at different levels of biological organization: molecular, subcellular, cellular, tissue, organ, organismal and population.

To prevent disruptions in the life of plants under the influence of adverse factors, the principles redundancy, heterogeneity of functionally equivalent components, systems for the repair of lost structures.

The redundancy of structures and functionality is one of the main ways to ensure the reliability of systems. Redundancy and redundancy has multiple manifestations. At the subcellular level, the reservation and duplication of genetic material contribute to the increase in the reliability of the plant organism. This is provided, for example, by the double helix of DNA, by increasing the ploidy. The reliability of the functioning of the plant organism under changing conditions is also supported by the presence of various messenger RNA molecules and the formation of heterogeneous polypeptides. These include isoenzymes that catalyze the same reaction, but differ in their physicochemical properties and the stability of the molecular structure under changing environmental conditions.

At the cellular level, an example of redundancy is an excess of cellular organelles. Thus, it has been established that a part of the available chloroplasts is sufficient to provide the plant with photosynthesis products. The remaining chloroplasts, as it were, remain in reserve. The same applies to the total chlorophyll content. The redundancy also manifests itself in a large accumulation of precursors for the biosynthesis of many compounds.

At the organismic level, the principle of redundancy is expressed in the formation and laying at different times of a greater number of shoots, flowers, spikelets than is required for a change of generations, in a huge amount of pollen, ovules, seeds.

At the population level, the principle of redundancy is manifested in a large number of individuals that differ in resistance to a particular stress factor.

Repair systems also work at different levels - molecular, cellular, organismal, population and biocenotic. Reparative processes go with the expenditure of energy and plastic substances, therefore, reparation is possible only if a sufficient metabolic rate is maintained. If metabolism stops, then reparation also stops. In extreme conditions of the external environment, the preservation of respiration is especially important, since it is respiration that provides energy for reparation processes.

The reductive ability of cells of adapted organisms is determined by the resistance of their proteins to denaturation, namely, the stability of the bonds that determine the secondary, tertiary, and quaternary structure of the protein. For example, the resistance of mature seeds to high temperatures is usually associated with the fact that, after dehydration, their proteins become resistant to denaturation.

The main source of energy material as a substrate for respiration is photosynthesis, therefore, the energy supply of the cell and related reparation processes depend on the stability and ability of the photosynthetic apparatus to recover from damage. To maintain photosynthesis under extreme conditions in plants, the synthesis of thylakoid membrane components is activated, lipid oxidation is inhibited, and the plastid ultrastructure is restored.

At the organismic level, an example of regeneration is the development of replacement shoots, the awakening of dormant buds when growth points are damaged.

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Basically, adaptation systems in one way or another relate to the cold, which is quite logical - if you manage to survive in a deep minus, other dangers will not be so terrible. The same, by the way, applies to extremely high temperatures. Who is able to adapt, most likely will not disappear anywhere.

Arctic hare are the largest hares in North America, which for some reason have relatively short ears. This is a great example of what an animal can sacrifice to survive in harsh conditions - while long ears can help hear a predator, short ones reduce the release of precious heat, which is much more important for Arctic hare.

Frogs from Alaska, the species Rana sylvatica, perhaps even outdid the Antarctic fish. They literally freeze into the ice in winter, thus waiting out the cold season, and come back to life in the spring. Such a “cryosleep” is possible for them due to the special structure of the liver, which doubles during hibernation, and the complex biochemistry of blood.

Some praying mantis species, unable to spend all day in the sun, cope with the lack of heat through chemical reactions in their own bodies, concentrating flashes of heat inside for short-term heating.

A cyst is a temporary form of existence of bacteria and many unicellular organisms, in which the body surrounds itself with a dense protective shell in order to protect itself from an aggressive external environment. This barrier is very effective - in some cases, it can help the host survive for a couple of decades.

Nototheniform fish live in Antarctic waters so cold that normal fish would freeze to death there. Sea water freezes only at a temperature of -2 ° C, which cannot be said about completely fresh blood. But Antarctic fish secrete a natural antifreeze protein that prevents ice crystals from forming in the blood - and survive.

Megathermia - the ability to generate heat using body mass, thereby surviving in cold conditions even without antifreeze in the blood. This is used by some sea turtles, remaining mobile when the water around them almost freezes.

Asian mountain geese, when crossing the Himalayas, rise to great heights. The highest flight of these birds was recorded at an altitude of 10 thousand meters! Geese have complete control over their body temperature, even changing their blood chemistry as needed to survive in the icy and thin air.

Mudskippers are not the most common type of fish, although they belong to rather banal gobies. At low tide, they crawl along the silt, getting their own food, climbing trees on occasion. In their way of life, mudskippers are much closer to amphibians, and only fins with gills give out fish in them.

To survive in adverse climatic conditions, plants, animals and birds have some features. These features are called "physiological adaptations," examples of which can be seen in virtually every mammalian species, including humans.

Why do we need physiological adaptation?

Living conditions in some parts of the world are not entirely comfortable, however, there are various representatives of wildlife. There are several reasons why these animals did not leave the hostile environment.

First of all, climatic conditions could change when a certain species already existed in a given area. Some animals are not adapted to migration. It is also possible that the territorial features do not allow migration (islands, mountain plateaus, etc.). For a certain species, the changed living conditions still remain more suitable than in any other place. And physiological adaptation is the best solution to the problem.

What is meant by adaptation?

Physiological adaptation is the harmony of organisms with a specific habitat. For example, a comfortable stay in the desert of its inhabitants is due to their adaptation to high temperatures and lack of access to water. Adaptation is the appearance of certain signs in organisms that allow them to get along with any elements of the environment. They arise in the process of certain mutations in the body. Physiological adaptations, examples of which are well known in the world, are, for example, the ability to echolocation in some animals (bats, dolphins, owls). This ability helps them navigate in a space with limited lighting (in the dark, in water).

Physiological adaptation is a set of body reactions to certain pathogenic factors in the environment. It provides organisms with a greater likelihood of survival and is one of the methods of natural selection of strong and resistant organisms in a population.

Types of physiological adaptation

Adaptation of the organism is distinguished genotypic and phenotypic. The genotypic is based on the conditions of natural selection and mutations, which led to changes in the organisms of a whole species or population. It was in the process of this type of adaptation that the modern species of animals, birds and humans were formed. The genotypic form of adaptation is hereditary.

The phenotypic form of adaptation is due to individual changes in a particular organism for a comfortable stay in certain climatic conditions. It can also develop due to constant exposure to an aggressive environment. As a result, the body acquires resistance to its conditions.

Complex and cross adaptations

Complex adaptations are manifested in certain climatic conditions. For example, the body's adaptation to low temperatures during a long stay in the northern regions. This form of adaptation develops in each person when moving to another climatic zone. Depending on the characteristics of a particular organism and its health, this form of adaptation proceeds in different ways.

Cross-adaptation is a form of body habituation in which the development of resistance to one factor increases the resistance to all factors of this group. The physiological adaptation of a person to stress increases his resistance to some other factors, such as cold.

On the basis of positive cross-adaptations, a set of measures was developed to strengthen the heart muscle and prevent heart attacks. Under natural conditions, those people who more often faced stressful situations in their lives are less susceptible to the consequences of myocardial infarction than those who led a calm lifestyle.

Types of adaptive reactions

There are two types of adaptive reactions of the body. The first type is called "passive adaptations". These reactions take place at the cellular level. They characterize the formation of the degree of resistance of the organism to the effects of a negative environmental factor. For example, a change in atmospheric pressure. Passive adaptation allows you to maintain the normal functionality of the body with small fluctuations in atmospheric pressure.

The most well-known physiological adaptations in animals of the passive type are the protective reactions of the living organism to the effects of cold. Hibernation, in which life processes slow down, is inherent in some species of plants and animals.

The second type of adaptive reactions is called active and implies protective measures of the body when exposed to pathogenic factors. In this case, the internal environment of the body remains constant. This type of adaptation is inherent in highly developed mammals and humans.

Examples of physiological adaptations

The physiological adaptation of a person is manifested in all non-standard situations for his environment and lifestyle. Acclimatization is the most famous example of adaptations. For different organisms, this process takes place at different speeds. Some take a few days to get used to the new conditions, for many it will take months. Also, the rate of habituation depends on the degree of difference with the habitual environment.

In aggressive habitats, many mammals and birds have a characteristic set of body reactions that make up their physiological adaptation. Examples (in animals) can be observed in almost every climate zone. For example, desert dwellers accumulate reserves of subcutaneous fat, which oxidizes and forms water. This process is observed before the onset of the drought period.

Physiological adaptation in plants also takes place. But she is passive. An example of such an adaptation is the shedding of leaves by trees when the cold season sets in. The places of the kidneys are covered with scales, which protect them from the harmful effects of low temperatures and snow with wind. Metabolic processes in plants slow down.

In combination with morphological adaptation, the physiological reactions of the organism provide it with a high level of survival under adverse conditions and with drastic changes in the environment.

These are the optimal proportions of the body, the location and density of the hair or feather cover, etc. The appearance of an aquatic mammal - a dolphin - is well known. His movements are light and precise. Independent speed in water reaches 40 kilometers per hour. The density of water is 800 times that of air. The torpedo-shaped shape of the body avoids the formation of eddies of water flows around the dolphin.