The evolution of adaptation is the main result of natural selection. Classification of adaptation: morphological, physiological-biochemical, ethological, specific adaptations: congruences and cooperations. Relativity of organic expediency.
Answer: Adaptation is any feature of an individual, population, species or community of organisms that contributes to success in competition and provides resistance to abiotic factors. This allows organisms to exist in these environmental conditions and leave offspring. Adaptation criteria are: viability, competitiveness and fertility.
Types of adaptation
All adaptations are divided into accommodation and evolutionary adaptations. Accommodations are a reversible process. They occur when there is a sudden change in environmental conditions. For example, during relocation, animals enter a new environment for them, but gradually get used to it. For example, a person who has moved from the middle lane to the tropics or the Far North experiences discomfort for some time, but eventually gets used to new conditions. Evolutionary adaptation is irreversible and the resulting changes are genetically fixed. This includes all the adaptations that natural selection acts on. For example, protective coloring or fast running.
Morphological adaptations manifested in the advantages of the structure, patronizing coloration, warning coloration, mimicry, disguise, adaptive behavior.
The advantages of the structure 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.
Mimicry is the result of homologous (same) mutations in different species that help unprotected animals survive.
Camouflage - adaptations in which the shape of the body and color of animals merge with surrounding objects
Physiological adaptations- acquisition of specific features of metabolism in different environmental conditions. They provide functional benefits to the body. They are conditionally divided into static (constant physiological parameters - temperature, water-salt balance, sugar concentration, etc.) and dynamic (adaptation to fluctuations in the action of the factor - changes in temperature, humidity, illumination, magnetic field, etc.). Without such adaptation, it is impossible to maintain a stable metabolism in the body in constantly fluctuating environmental conditions. Let's give some examples. In terrestrial amphibians, a large amount of water is lost through the skin. However, many of their species penetrate even into deserts and semi-deserts. The adaptations that develop in diving animals are very interesting. Many of them can do without oxygen for a relatively long time. For example, seals dive to a depth of 100-200 and even 600 meters and stay under water for 40-60 minutes. The chemical organs of insects are amazingly sensitive.
Biochemical adaptations provide the optimal course of biochemical reactions in the cell, for example, the ordering of enzymatic catalysis, the specific binding of gases by respiratory pigments, the synthesis of the necessary substances under certain conditions, etc.
Ethological adaptations are all behavioral responses aimed at the survival of individuals and, therefore, the species as a whole. These reactions are:
Behavior when searching for food and a sexual partner,
Pairing,
rearing offspring,
Avoiding danger and protecting life in the event of a threat,
Aggression and threatening postures
Indifference and many others.
Some behavioral responses are inherited (instincts), others are acquired during life (conditioned reflexes).
Species adaptations are found in the analysis of a group of individuals of the same species, they are very diverse in their manifestation. The main ones are different congruences, the level of mutability, intraspecific polymorphism, the level of abundance and the optimal population density.
Congruences represent all the morphophysiological and behavioral features that contribute to the existence of the species as an integral system. Reproductive congruences ensure reproduction. Some of them are directly related to reproduction (correspondence of the genital organs, feeding adaptations, etc.), while others are only indirectly (various signal signs: visual - wedding attire, ritual behavior; sound - birdsong, the roar of a male deer during the rut and others; chemical - various attractants, for example, insect pheromones, secretions from artiodactyls, cats, dogs, etc.).
Congruences include all forms of intraspecific cooperation, - constitutional, trophic and reproductive. constitutional cooperation expressed in the coordinated actions of organisms in adverse conditions, which increase the chances of survival. In winter, the bees gather in a ball, and the heat they give off is spent on co-warming. In this case, the highest temperature will be in the center of the ball and individuals from the periphery (where it is colder) will constantly strive there. Thus, there is a constant movement of insects and together they will safely overwinter. Penguins also huddle together in a close group during incubation, sheep in cold weather, etc.
Trophic cooperation consists in the association of organisms for the purpose of obtaining food. Joint activity in this direction makes the process more productive. For example, a pack of wolves hunts much more efficiently than a single individual. At the same time, in many species there is a division of duties - some individuals separate the chosen victim from the main herd and drive it into an ambush where their relatives hid, etc. In plants, such cooperation is expressed in the joint shading of the soil, which helps to retain moisture in it.
Reproductive cooperation increases the success of reproduction and promotes the survival of offspring. In many birds, individuals gather on leks, and in such conditions it is easier to search for a potential partner. The same thing happens in spawning grounds, pinniped rookeries, etc. The probability of pollination in plants increases when they grow in groups and the distance between individual individuals is small.
The law of organic expediency, or Aristotle's law
1. The deeper and more versatile science studies living forms, the more fully they are revealed. expediency, that is, the purposeful, harmonious, as it were, reasonable nature of their organization, individual development and relationship with the environment. Organic expediency is revealed in the process of understanding the biological role of specific features of living forms.
2. Expediency is inherent in all types. It is expressed in the subtle mutual correspondence of the structures and purpose of biological objects, in the adaptability of living forms to the conditions of life, in natural focus features of individual development, in the adaptive nature of the forms of existence and behavior of biological species.
3. Organic expediency, which became the subject of analysis of ancient science and served as the basis for teleological and religious interpretations of living nature, received a materialistic explanation in Darwin's doctrine of creative role natural selection, manifested in the adaptive nature of biological evolution.
This is the modern formulation of those generalizations, the origins of which go back to Aristotle, who put forward ideas about the final causes.
The study of specific manifestations of organic expediency is one of the most important tasks of biology. Having found out what this or that feature of the biological object under study serves for, what is the biological significance of this feature, thanks to Darwin's evolutionary theory, we are approaching the answer to the question of why and how it arose. Let us consider the manifestations of organic expediency on examples related to various fields of biology.
In the field of cytology bright, good example organic expediency - cell division in plants and animals. The mechanisms of equational (mitosis) and reduction (meiosis) division determine the constancy of the number of chromosomes in the cells of a given plant or animal species. Doubling of the diploid set in mitosis maintains the constancy of the number of chromosomes in dividing somatic cells. Haploidization of the chromosome set during the formation of germ cells and its restoration during the formation of a zygote as a result of the fusion of germ cells ensure the preservation of the number of chromosomes during sexual reproduction. Deviations from the norm, leading to polyploidization of cells, i.e., to the multiplication of the number of chromosomes against the normal one, are cut off by the stabilizing effect of natural selection or serve as a condition for genetic isolation, isolation of the polyploid form with its possible transformation into a new species. At the same time, cytogenetic mechanisms come into play again, causing the preservation of the chromosome set, but already at a new, polyploid, level.
In the process of individual development of a multicellular organism, cells, tissues and organs of various functional purposes are formed. The correspondence of these structures to their purpose, their interaction in the process of development and functioning of the organism are characteristic manifestations of organic expediency.
An extensive area of examples of organic expediency is provided by adaptations for the reproduction and distribution of living forms. Let's name some of them. For example, bacterial spores are highly resistant to adverse environmental conditions. Flowering plants are adapted to cross-pollination, in particular with the help of insects. The fruits and seeds of a number of plants are adapted for distribution with the help of animals. Sexual instincts and instincts for caring for offspring are characteristic of animals of the most diverse levels of organization. The structure of caviar and eggs ensures the development of animals in the appropriate environment. The mammary glands provide adequate nutrition for offspring in mammals.
Modern concepts of the species. reality of existence and biological significance types.
Answer: A species is one of the main forms of organization of life on Earth and the main unit of classification of biological diversity. The variety of modern species is enormous. According to various estimates, about 2-2.5 million species currently live on Earth (up to 1.5-2 million animal species and up to 500 thousand plant species). The process of describing new species is continuously ongoing. Every year, hundreds and thousands of new species of insects and other invertebrates and microorganisms are described. The distribution of species by classes, families and genera is very uneven. There are groups with a huge number of species and groups - even of high taxonomic rank - represented by a few species in modern fauna and flora. For example, a whole subclass of reptiles is represented by only one species - the tuatara.
At the same time, the modern species diversity is much less than the number of extinct species. Due to human activities, a huge number of species die out every year. Since the conservation of biodiversity is an indispensable condition for the existence of mankind, this problem is becoming global today. K. Linnaeus laid the foundations of modern taxonomy of living organisms (The System of Nature, 1735). K. Linnaeus found that within a species, many essential features change gradually, so that they can be arranged in a continuous series. K. Linnaeus considered species as objectively existing groups of living organisms, quite easily distinguishable from each other.
The biological concept of the species. The biological concept was formed in the 30s-60s of the XX century. based on the synthetic theory of evolution and data on the structure of species. It was developed with the greatest completeness in Mayr's book Zoological Species and Evolution (1968). Mayr formulated the biological concept in the form of three points: species are determined not by differences, but by isolation; species do not consist of independent individuals, but of populations; Species are defined based on their relationship to populations of other species. The decisive criterion is not crossbreeding fertility, but reproductive isolation.” Thus, according to the biological concept A species is a group of actually or potentially interbreeding populations that are reproductively isolated from other such populations. This concept is also called polytypical. The positive side of the biological concept is a clear theoretical base, well developed in the works of Mayr and other supporters of this concept. However, this concept is not applicable to sexually reproducing species and in paleontology. The morphological concept of a species was formed on the basis of a typological, more precisely, on the basis of a multidimensional polytypic species. At the same time, it represents a step forward compared to these concepts. According to her, the view is a set of individuals that have a hereditary similarity of morphological, physiological and biochemical features, freely interbreed and give fertile offspring, adapted to certain living conditions and occupying a certain area in nature - an area. Thus, two concepts of species are mainly discussed and applied in the current literature: biological and morphological (taxonomic).
The Reality of Existence and the Biological Significance of Species.
To exist for the objects of biological science means to have subject-ontological characteristics of biological reality. Proceeding from this, the problem of the existence of a gene, species, etc. "is resolved in the language of this level by constructing appropriate experimental and "observational" methods, hypotheses, concepts that assume these entities as elements of their objective reality." Biological reality was formed taking into account the existence of various levels of "living", which is a complex hierarchy of the development of biological objects and their relationships.
Biodiversity is the main source of satisfaction for many human needs and serves as the basis for its adaptation to changing environmental conditions. The practical value of biodiversity lies in the fact that it is essentially an inexhaustible source of biological resources. These are, first of all, food products, medicines, sources of raw materials for clothing, production of building materials, etc. Biodiversity is of great importance for the organization of human recreation.
Biodiversity provides genetic resources for agriculture, constitutes the biological basis for world food security and is a necessary condition for the existence of mankind. A number of wild plants related to crops are very important for the economy at the national and global levels. For example, Ethiopian varieties of Californian barley provide protection against disease-causing viruses worth $160 million. USA per year. Genetic disease resistance achieved with wild wheat varieties in Turkey is estimated at $50 million
Adaptations of organisms to temperature. Living organisms in the course of a long evolution have developed a variety of adaptations that allow you to regulate metabolism with changes in ambient temperature. This is achieved: 1) by various biochemical and physiological changes in the body, which include changes in the concentration and activity of enzymes, dehydration, lowering the freezing point of body solutions, etc.; 2) maintenance of body temperature at a more stable temperature level than the temperature of the environment, which allows you to save the current for this species of bio chemical reactions.[ ...]
Temperature adaptations. Plants, invertebrates and lower vertebrates - fish, amphibians and reptiles - are unable to maintain any specific body temperature. They depend more on the heat coming from outside than on the heat generated in the exchange processes. At the same time, in the entire range of changes, the body temperature differs little (at the level of tenths or no more than 1-2 °) from the temperature of the environment. These organisms can be referred to as ectotherms, i.e. subject to outside temperature. Some of them have a limited ability for short-term thermal stabilization due to the heat of biochemical reactions and intense muscle activity. But only true endotherms - birds and mammals - can maintain a constantly high body temperature with significant changes in ambient temperature. They have the means of effective regulation of heat transfer and heat production of the body. In some of them, the corresponding mechanisms reach high power and perfection. Thus, the arctic fox, snowy owl, and white goose easily endure extreme cold without a drop in body temperature and while maintaining a temperature difference between the body and the environment of 100 ° or more. Due to the thickness of subcutaneous fat and the peculiarities of the peripheral circulation, many pinnipeds and whales are perfectly adapted to a long stay in ice water.[ ...]
The biochemical breakdown of a substance depends on a number of chemical and physical factors, such as the presence of various functional groups in the molecule, the size of the molecule and its structure, the solubility of the substance, isomerization, polymerization, the formation of intermediate products and their interaction, etc. This decay is also determined by biological factors - the complexity of metabolism in microorganisms, the variability of bacterial strains, the influence of the environment and the duration of adaptation of microbes, etc. The mechanism of adaptation is still unknown. The terms and limits of adaptation of microorganisms are different - from several hours to 200 days or more.[ ...]
biochemical changes. It is well known that temperature changes have a significant impact on the rate of metabolic reactions and the overall intensity of metabolism. An increase in temperature in the tolerant range leads to an increase in the intensity of metabolism, and a decrease in temperature leads to its decrease. Meanwhile, the basic metabolic processes in the body must be maintained at a certain level, which can change only within fairly narrow limits, otherwise metabolic homeostasis disorders that are incompatible with life occur. It should be especially emphasized that for the normal course of metabolic processes, both the level of oncoming temperature changes and their speed are important. A sharply pronounced and rapidly developing decrease in temperature can lead to such a slowdown in metabolic processes, which is no longer able to ensure the normal course of the main life processes. Comparable in severity and speed, but opposite in direction, a change in temperature, i.e., its increase, can also lead to such an increase in the intensity of metabolic processes, which is difficult or impossible to provide with oxygen. All this made fish and other ectothermic animals face the need to develop various mechanisms for controlling the intensity of metabolic processes that would ensure the maintenance of the level of metabolic activity relatively independent of the ambient temperature. key role at the same time, enzymes play - catalysts for countless chemical reactions, the totality of which makes up metabolism. Since almost all cellular reactions are catalyzed by enzymes, the regulation of metabolism is reduced to the regulation of the type and intensity of enzymatic functions.[ ...]
Adaptation to stable temperatures is accompanied in poikilothermic animals by compensatory changes in the level of metabolism, which normalize vital functions in the corresponding temperature regimes. Such adaptations are revealed by comparing closely related species, geographic populations of the same species, and seasonal conditions of individuals of the same population. The general pattern of adaptive shifts in metabolism is that animals adapted to a lower temperature have a higher metabolic rate than those adapted to a higher temperature (Fig. 4.8). This applies both to the general level of metabolism and to individual biochemical reactions. It has been shown, for example, that the level and reactivity to temperature changes of the amyllytic activity of the moor frog pancreatic extract differs in different geographical populations of this species. If the activity at 35°С is taken as 100%, then at 5°С the frogs from the population of the Yamal Peninsula will have an activity of 53.7, and in the population from the vicinity of Yekaterinburg it will be only 35%.[ ...]
Adaptation (adaptation) or bringing the body into line with the environment (about the purified water) causes a sharp increase in the intensity and efficiency of biochemical purification. Adaptation is especially important in those cases where the waste to be treated is a new synthetic substance that did not previously exist in nature. Sometimes adaptation takes several months. Adaptation time can be reduced if seeding with already adapted microflora is carried out. The ability of microorganisms to oxidize organic substances is determined by the activity of their enzymes, each of which selectively catalyzes one reaction. the set of enzyme systems depends on the content and concentration of wastewater impurities, and the rate of enzyme formation depends on the physiological activity of microorganisms.[ ...]
In the biochemical oxidation of arenes, the partial pressure of oxidizing oxygen plays an important role. An increase in pressure to a certain limit (depending on the composition of the biocenosis) leads to an increase in the reaction rate. In this case, the rate of the process is limited by the solubility of oxygen in the aqueous phase and the adaptation of microorganisms. Compared to other microorganisms, Nocardia corallina, N. oraca, N. actinomorpha are easier than others to adapt to the increased pressure of the oxidizing gas.[ ...]
The adaptation of microbial cenoses to industrial pollution is based on a variety of genetically heterogeneous biological mechanisms. Destructor microbes, on the biochemical properties of which the oxidizing ability of the biocenosis depends, can change either phenotypically, temporarily acquiring the ability to ferment certain compounds, or genotypically - with the formation of new forms of microbes, which have the ability to synthesize a new enzyme hereditarily fixed. Regulatory mechanisms ensure proper coordination of the metabolic activity of individual enzyme systems, prevent excessive production of enzymes, intermediates and end products, and allow bacteria to economically and expediently use individual chemicals. This amazing harmony of cellular metabolism is one of the most interesting problems of associative relations of microbes.[ ...]
Substances dissolved in water oxidize faster than in a dispersed state. The presence of functional groups promotes biological oxidation, and the tertiary carbon atom worsens it. The presence of a double tie in some cases facilitates the biodegradation of the compound.[ ...]
Physiological and biochemical adaptation of a person to noise is impossible.[ ...]
Physiological and biochemical adaptation of a person to noise is impossible. Loud noise is a physical drug for a person. Musical noise of 120-130 decibels (dB) is comparable to a lightning strike or a jet plane taking off (100 dB).[ ...]
The possibility of biochemical destruction of chlorophos by activated sludge at a concentration of the latter in the range of 25-500 mg / dm3 is shown in the work. Preliminary adaptation of the microflora made it possible to significantly intensify this process.[ ...]
A number of experiments were carried out to study the biochemical activity of silts obtained both from one culture and from a mixture of cultures. The experimental technique was as follows. Activated sludge of a certain concentration was introduced into a microaerator containing 1 liter of sterile industrial waste water, the sludge liquid was aerated for various periods of time, and then the aeration was stopped; after 30 min. sedimentation, the liquid was siphoned and used for chemical analysis, and the activated sludge was filled with fresh waste water. In some cases, the same activated sludge was used without prior adaptation to treat wastewater of a different composition.[ ...]
The specific gravity of the biochemical component in the instantaneous temperature adaptation, apparently, less than the physiological component, because it is easier for the body to avoid an unfavorable temperature regime than to resort to the "switching on" of biochemical mechanisms. Another thing is when it comes to gradual and rather long-term (days, weeks, months), say, seasonal changes in the temperature regime of a reservoir or its thermal pollution. Here, along with physiological and biochemical changes, they come to the fore, ensuring the restoration of functional activity and normal functioning of the body under a new temperature regime by compensating for the intensity of metabolism (metabolic acclimation). Since the intensity of the main metabolic processes that provide the body with energy and "building" material (the formation of intermediate substances; the synthesis of nucleic acids, proteins, lipids and carbohydrates) necessary for normal life is determined by enzymes, enzymes acquire a decisive role in biochemical adaptation to constantly changing temperature conditions.[ ...]
Since all biochemical processes take place with the participation of enzymes, upon admission organic matter of a different chemical composition and structure, the vital activity of microorganisms can be completely disrupted due to the toxic effect, or for some time there is an adaptation (adaptation) of microorganisms to changed conditions. The consequence of this is the development of new enzymes, under the influence of which a new type of organic pollution begins to decompose. Depending on the chemical nature of the pollution, its concentration, the number of microorganisms, the rate of their reproduction and other external factors, the adaptation period can last from several days to several months.[ ...]
In the absence of biochemical treatment facilities, river silt taken below the wastewater discharge (at a distance of about 0.5 km) or domestic wastewater, the microflora of which must be previously adapted, can be used for infection. To adapt the microflora, domestic waste water is diluted with tap water to a bichromate oxidizability equal to 50-60 mg O g / l, and industrial waste is added to it in such an amount that the dichromate oxidizability of the mixture is 100-150 mg O g / l. The solution is placed in a thermostat at 30°C or kept at room temperature. After 2 days, the liquid becomes cloudy, sometimes a film appears on its surface, which indicates the abundant development of microflora (checking under a microscope is desirable). When the bichromate oxidizability decreases by 50-60%, water from the production waste is added again and after 2-3 days the liquid with adapted microflora is filtered, proceeding as described above.[ ...]
Determination of BOD of biochemically treated wastewater. Wastewater that has undergone biochemical treatment in appropriate plants has some features that should be emphasized. The values of the BOD of such waters are negligible, and in the course of determination, only hardly oxidizable (“biochemically rigid”) compounds are biochemically oxidized by oxygen. Therefore, the curve showing the increase in BOD over time (by day) is relatively flat (the rate of oxidation is insignificant). Under these conditions, the use of adapted microflora is especially important in order not to overly delay the process, and the adaptation of the introduced microflora should be carried out precisely on this water, which has undergone biochemical purification, and not on untreated water. These waters contain a lot of nitrites, and therefore the removal of the latter with sulfamic acid or sodium azide is necessary. An excess of sulfamic acid will not hurt, as it decomposes without forming oxidizing substances.[ ...]
Physiological adaptations are manifested, for example, in the features of the enzymatic set in the digestive tract of animals, which is determined by the composition of the food. Thus, a camel is able to provide moisture needs by biochemical oxidation of its own fat.[ ...]
Physiological adaptations. The heat produced by living organisms as a by-product of biochemical reactions can serve as a source of an increase in their body temperature. Therefore, many organisms, using physiological processes, can change their body temperature within certain limits. This ability is called thermoregulation.[ ...]
About to +100 C, since biochemical reactions in cells proceed in aqueous solutions. This, however, is not entirely true. The main factors that determine the temperature limits of active life or the preservation of the viability of organisms are the temperature stability of proteins, cell membranes and other macromolecular complexes of the cell, as well as the balance of biochemical reactions in the processes of cellular metabolism. Proteins are complex biopolymers, the functional activity of which depends on the spatial structure of the molecule, which is supported by many bonds - strong (covalent and ionic) and weak, including hydrogen ones, sensitive to temperature. At low temperatures, these bonds are stable, so adaptation to life at temperatures close to zero is achieved mainly by shifting the temperature optimum of enzyme activity and harmonizing it in the entire complex of enzymes and regulatory mechanisms.[ ...]
Finally, another way of biochemical adaptation is the production of homologous enzymes, which are characterized by more or less pronounced independence from temperature changes in the tolerant range for the species. A vivid example of this kind of adaptation is provided by Gilichthys mirabilis pyruvate kinase (Fig. 16), whose ability to bind phosphoenol-pyruvate (substrate) is practically independent of temperature over a rather significant range. This is an example of the production of a eurythermal enzyme, which differs significantly in the degree of temperature dependence of K in comparison with the stenothermic isoenzymes of rainbow trout pyruvate kinase.[ ...]
The calculation of any facilities for biochemical treatment of industrial wastewater is carried out according to the full biochemical oxygen demand. The BOD5 value does not give any indication of the oxygen demand, since it depends on the degree of adaptation of the microbes to the compounds contained in the wastewater, on the number of microbes taken for infection, and on the dilution adopted. So, BOD5 1 mg of a substance, according to various authors, varies for formaldehyde from 0.33 to 1.1; for acetaldehyde from 0.66 to 0.91; for furfural from 0.28 to 0.77; for methyl alcohol from 0.12 to 0.96; for acetic acid from 0.34 to 0.77. In table. 44 provides data on the total biochemical oxygen demand for a number of organic compounds, obtained by domestic specialists.[ ...]
The strategy and specific ways of biochemical adaptation to ever-fluctuating environmental factors, including the temperature factor, are discussed in detail in an excellent monograph by P. Khochachka and J. Therefore, we will limit ourselves to a brief summary of the main ideas and factual data indicating the critical importance of biochemical foundations. temperature adaptation of fish.[ ...]
Biochemical adaptation strategy.[ ...]
The influence of organic toxic substances on biochemical processes is very diverse. Many of them serve as a source of carbon for microorganisms, as a result of which they can be processed at significant concentrations in the purified sewage. However, the process of their biochemical oxidation proceeds slowly, especially at its beginning; as the microorganisms adapt, the intensity of the process increases and after a certain period of time reaches its maximum value. The duration of the adaptation period depends on the type of toxic substances and their concentration; it usually takes up to two months and only sometimes more.[ ...]
Irritants are factors that cause biochemical and physiological changes (adaptations).[ ...]
The considered technological scheme of biochemical treatment facilities is the simplest in terms of instrumentation, but it is advisable to use it only if industrial wastewater has a stable composition and unchanged basic parameters: flow rate, pH, temperature, pollutant content, pollution composition. The practice of operating treatment facilities at chemical enterprises has shown that most often industrial wastewater has a variable composition, which destabilizes the technological mode of operation of treatment facilities, adversely affects activated sludge, and prevents the latter from adapting to pollutants. Therefore, it is more expedient to use the technological scheme of treatment facilities with preliminary averaging of industrial wastewater entering them (Fig. 4.5).[ ...]
Molecular mechanisms of temperature adaptation include changes in the primary structure of enzymes, using such fundamental mechanisms as gene activation, transcription, translation and assembly of new enzyme variants (isoenzymes), changes in the concentrations of individual isoenzymes adapted to certain temperatures, changes in the kinetic properties of a given enzyme, change in cofactors and microenvironment in which enzymes function, conformational changes leading to the appearance of "instant", or functional, isoenzymes. The choice of a strategy and specific mechanisms for the biochemical adaptation of fish is determined primarily by the rate of onset and duration of temperature changes, as well as species ecological and age characteristics fish.[ ...]
During the commissioning of biochemical treatment facilities, the gradual adaptation (adaptation) of activated sludge microorganisms to the oxidation of pollutants in wastewater is mandatory.[ ...]
Oxidation work of aeration tank No. 1. Experiments on biochemical wastewater treatment, as a rule, begin with the treatment of wastewater with a small concentration of organic substances in order to adapt the microflora of the sludge to specific pollutants. Obtaining stable cleaning results allows you to change the mode of operation of the structure.[ ...]
According to Mills' research, in order to optimize biochemical treatment processes, an increase in the concentration of activated sludge must be combined with thermobiosis. Thermobiosis refers to the functioning and, accordingly, adaptation of microorganisms at temperatures above 30 °C, when thermophilic processes begin to predominate in the metabolism of microorganisms, accompanied, in particular, by accelerated growth, accelerated biochemical oxidation of contaminants, and an increase in enzymatic activity. Thermotolerant microorganisms (Pseudomonas, Bacterium, Sarcina) predominated among thermophiles in compacted silts. With this ratio - about 1: 800, eurythermic thermophiles play a subordinate role in the biochemical oxidation of industrial pollution.[ ...]
The basis for the development of methods for two- and multi-stage biochemical wastewater treatment is the idea of cultivating activated sludge at treatment plants adapted to the oxidation of certain groups of organic pollutants. It is believed that the closer the adaptation (specialization) of activated sludge to this species pollution, the more successful the process of biochemical purification. One of the ways for the engineering implementation of this idea is the creation of a staged biochemical treatment, at each stage of which a certain culture of activated sludge functions. It is clear that the greater the difference in the rates of biochemical oxidation of individual wastewater components, the higher their initial concentrations, the more effective the use of a stepwise treatment scheme.[ ...]
It has been established that with an increase in the temperature of the waste water, the rate of the biochemical reaction increases. However, in practice it is maintained within the range of 20-30 °C. Exceeding the specified temperature can lead to the death of microorganisms. At lower temperatures, the cleaning rate decreases, the process of adaptation of microbes to new types of pollution slows down, the processes of nitrification, flocculation and activated sludge deposition worsen. Increasing the temperature within the optimal limits accelerates the process of decomposition of organic substances by 2-3 times. With an increase in the temperature of the waste water, the solubility of oxygen decreases, therefore, in order to maintain the required concentration in water, more intensive aeration is required.[ ...]
In water containing domestic pollution, in the absence of preliminary adaptation of the bacterial flora, the STEK emulsifier at concentrations of 10–30 mg/l caused an insignificant increase, and at a concentration of 100 mg/l, a slight decrease in biochemical oxygen consumption. Statistical processing of the results of two parallel series of experiments (5 experiments per series) - control and affected by STEK at a concentration of 5 mg / l - did not show significant differences between the values of the VPC calculated from the series at different times of the experiment (the experiment was carried out for 20 days ).[ ...]
For each particular drain, activated sludge must be gradually adapted. With the adaptation of the sludge and ensuring the desired ratio of bacteria and protozoa, the efficiency of biochemical treatment increases, and the increase in excess activated sludge decreases. Even after adaptation, harmful ¡substances contained in wastewater can be in concentrations above the limit and have a toxic effect on sludge microorganisms.[ ...]
The monograph deals with a wide range of issues on genetically determined biochemical polymorphism in humans. Introduced historical sketch study of genetic and biochemical variability in populations and analyzed their own results of the study of biochemical polymorphism in a significant number of genetic systems of enzymes and other blood proteins. Gene-geographic maps have been compiled that significantly expand the picture of genetic and anthropological differentiation on the territory of the USSR. It contains new information about the formation of ethnic groups and anthropological types of North Asia and adjacent territories in space and time. The data on human evolutionary adaptation at the biochemical level are critically analyzed. An assessment is given of one of the most important factors of genetic dynamics - the rate of the mutation process in some populations of the USSR.[ ...]
Permanent components of urban wastewater are surfactants. In relation to biochemical oxidation, they are divided into "soft" and "hard". Rigid surfactants practically do not undergo biochemical oxidation. The ability of surfactants to biochemical oxidation is determined by their chemical structure. Anionic surfactant alkyl sulfates with a normal hydrocarbon chain are easily subjected to biochemical oxidation. Surfactants with a branched hydrocarbon chain containing a benzene ring and nonionic surfactants are the most resistant to biochemical oxidation. The ability to biochemically oxidize surfactants can be increased with the adaptation of microorganisms, which should begin with the introduction of small amounts of surfactants (about 5 mg/l).[ ...]
The high structural and accompanying functional heterogeneity of fish hemoglobin are among the most important biochemical mechanisms of wide adaptation to a diverse range of changing factors, both internal and external. The presence in the body of complex, multicomponent hemoglobin, each of which has its own optimal conditions for functioning, increases its reactive ability to attach and release oxygen, i.e., ultimately contributes to the optimal supply of oxygen to the body under different physiological and constantly changing environmental conditions. [ . ..]
The composition of industrial wastewater is varied. Very often, the substances contained in wastewater greatly slow down the process of biochemical oxidation, and sometimes have a toxic effect. However, it is known that microorganisms can adapt (adapt) to various compounds, including even toxic ones. When determining the biochemical oxygen demand of industrial effluents, the preliminary adaptation of the microflora is of decisive importance. Adaptation takes some time.[ ...]
Another important adaptive response that occurs during long-term or short-term oxygen deficiency in the environment, but already at the biochemical (molecular) level, is a change in the affinity of hemoglobin for oxygen. Already at the beginning of this century, A. Krogh and I. Leich showed that the adaptation of fish to a reduced oxygen content is carried out by increasing the affinity of hemoglobin for oxygen. Comparing the value of oxygen tension in water, necessary for half-saturation of blood in sedentary freshwater fish (carp, eel), often found with oxygen deficiency in natural habitats, with highly mobile oxyphilic trout, they found that in sedentary fish this value is 3-5 times lower than those of high mobility. The same dependence was also revealed when comparing two species of marine fish differing in their activity level - bottom flounder and pelagic cod, however, in this case, the differences reached only a twofold value (Fig. 18) ■ Research of this plan was continued on marine fish by R. Root , who came to the conclusion that the blood of highly active fish has an increased oxygen capacity in comparison with the blood of low-active fish. According to some experts, the degree of affinity of hemoglobin for oxygen is the most important factor, which determines the level of resistance of fish to oxygen deficiency. The existence of a relationship between the values of P o and P95 of blood and the level of threshold and critical /e02 (Fig. 19) for many marine and freshwater fish species belonging to different ecological groups in terms of activity was revealed.[ ...]
Summarizing the experimental data presented in this chapter, it must be recognized that fish have highly effective physiological and biochemical mechanisms for adapting to long-term or short-term oxygen deficiency in the environment (exogenous hypoxia) or resulting from strenuous muscular work and other conditions. stressful situations(endogenous hypoxia).[ ...]
In reservoirs with large temperature differences, the amplitude of which reaches several tens of degrees, eurythermal fish live. If the adaptation of stenothermic fish is based on behavior and active choice of habitats, then the adaptation of eurythermal fish is based on deep biochemical mechanisms (changes in the concentration of enzymes, their activity, and the proportion of individual isoforms of a particular enzyme). Thermal isoenzymes show high affinity for substrates at temperatures close to the "upper range" for this species (approximately 15-20°C), and quickly lose it at low temperatures (approximately 10°C and below). On the contrary, "cold" isoenzymes bind the substrate best at temperatures below 10°C, and at higher temperatures show less affinity for it than the "thermal" variants.[ ...]
If you carefully read the three previous chapters, then you probably noticed that when an organism adapts to changes in various environmental conditions, unidirectional and quite commensurate changes in the same biochemical parameters are often observed. It turns out that the adaptation of an organism to any one environmental factor can contribute to its adaptation to other factors, increase resistance to them. This phenomenon is called cross-adaptation. First of all, let's turn to the facts, and then we will try to understand the molecular basis of human cross-adaptation and its practical significance.[ ...]
Ecological ideas about evolutionary processes in populations, called microevolution by N.V. Timofeev-Resovsky, were largely developed by the Ural school of ecologists under the leadership of S.S. Schwartz. According to these ideas, the microevolutionary process goes through the following stages: 1) the occurrence of morphological changes in the population during adaptation to specific habitat conditions; 2) the accumulation of physiological changes following this; 3) biochemical changes in the body and, accordingly, changes in genetic information; 4) formation of new subspecies; 5) the formation of new species.[ ...]
Many benthic fish of deep lakes living in completely deoxygenated waters or with a significant deficiency of oxygen, fish of tropical swamps or small freezing lakes constantly encounter acute oxygen deficiency and have been forced to improve the possibilities of anaerobic metabolism during their long evolution. Under these conditions, biochemical mechanisms of adaptation at the molecular level come to the fore, because only they can ensure the long-term survival of fish in such extreme conditions as constant oxygen deficiency or even its short-term absence.[ ...]
When establishing the maximum permissible concentration of a harmful substance in the air of the working area, the most important and critical step is to determine the minimum effective (threshold) concentration (PC) in a long-term (chronic) experiment. White rats are used as experimental animals. Usually, the results of exposure to 2-3-fold concentrations are studied, with the help of which subthreshold (maximum inactive) and threshold (minimum effective) concentrations (AUC and PC) are established according to functional, biochemical and other indicators. The subthreshold and threshold concentrations established as a result of a long experiment make it possible to reveal the features of the impact of harmful substances and the features of animal adaptation to this effect. Taking into account the revealed features, MPC values are chosen. The transition to them is made by multiplying the threshold concentrations by the safety factor, the value of which depends on the toxicity of the substance and varies from 3 to 20.[ ...]
In accordance with modern concepts, the main mechanism for regulating metabolic processes is a change in the activity of individual enzymes or enzyme systems that ensure the normal course of metabolism. In turn, the regulation of enzymatic activity is carried out in three main ways: 1) by changing the activity of enzymes ("modulation" strategy); 2) changing the concentrations of enzymes ("quantitative" strategy); 3) changing the set of enzymes ("qualitative" strategy). The share of each of these mechanisms of biochemical adaptation in the development of three temporary forms of compensation for temperature effects: immediate, delayed and long-term is not the same.[ ...]
Physiologists distinguish between individual resistance parameters: frost and cold resistance, heat and drought resistance, resistance to salinity, and diseases. But the number of types of resistance is growing: gas resistance (03, B02, Sh4), resistance to heavy metals (mercury, copper, cadmium, etc.), herbicides, hydrocarbons and other technogenic factors "appeared". If this "factorial" principle of resistance classification is developed, then it is possible to come to the existence of resistance to individual temperatures (-25? -5° +40? +50°) or various concentrations of chemical agents. From the point of view of the specific mechanisms of resistance, it is necessary to look for many individual ways of adaptation in the cell. Such a task seems to us too complicated and generally unrealistic. It is difficult to imagine that a cell has a specific resistance to some substance, which it natural conditions not met before. It is probably more rational to proceed from the position that the mechanisms of a living system's response to external influences were subjected to natural selection in evolution, and therefore the biochemical strategy of cell adaptation should be more uniform and more rational. Therefore, it is more reasonable to consider certain types of stability as particular manifestations general principles reliability of a living system (Grodzinsky, 1983).
General ideas about biochemical mechanisms
Adaptations of living organisms to the environment
There are 3 types of adaptive mechanisms:
1. Adaptation of macromolecular components of cells or body fluids.
There are 2 types of such a device:
- quantity change(concentrations) of existing types of macromolecules, such as enzymes;
- formation of new types of macromolecules, for example, new isoenzymes that replace previously existing macromolecules.
2. Adaptation of the microenvironment in which macromolecules function. For example, the osmotic properties of the medium or the composition of dissolved substances change.
3. Adaptation at the functional level. In this case, the change in the efficiency of macromolecular systems, especially enzymes, is not associated with a change in the number of macromolecules present in the cell or their types. In this case, adaptation is provided by a change in the use of already existing macromolecular systems in accordance with the current local needs for a particular activity. This is carried out at the level of metabolic regulation by increasing or decreasing the activity of enzymes.
Adaptive changes in enzyme systems
2 main functions of enzymes: catalytic and regulatory.
Reasons for the need to implement adaptation by changing the set of enzymes or their concentration:
1. change in the needs of the body when the environment changes or the transition to a new stage of development;
2. change in the physical factors of the environment (temperature, pressure, etc.);
3. change in the chemical factors of the environment.
Adaptations at the level of the microenvironment of macromolecules
The importance of osmoregulation.
· Selection of certain types of solutes as "osmotic effectors".
· The importance of the lipid environment of macromolecules.
· Ensuring the pH value.
With proper regulation of the microenvironment of macromolecules, adaptation of the organism to changes in the external environment may not require any change in the macromolecules themselves.
Adaptation by changing metabolic activity
This adaptation may be in response to:
1. changing energy needs;
2. change in oxygen supply;
3. the impact of factors associated with migration and starvation;
4. change in the physical conditions of the environment;
5. change in hormonal status.
Rate of biochemical adaptation
The more time allowed for adaptive change, the greater the choice of possible adaptive mechanisms.
genetic adaptation happens over many generations. There are mutations in regulatory genes, amino acid substitutions with the formation of new isoenzymes, the emergence of new molecules.
Example: the appearance of glycoprotein polypeptide "antifreeze" in marine bony fish living among the ice.
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 resilience biological system, including the 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 have evolutionary significance. 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 basic 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 areas with large diurnal temperature fluctuations, the 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 propagation of plants by root segments, rhizomes, thallus, stem and leaf cuttings, isolated cells, individual protoplasts, has a large practical value for plant growing, 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 objective of the strategy is effective use available resources to achieve the main goal - the survival of the body 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(phylogenesis - development species in time) 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 of breeding research institutes Agriculture South-East (Saratov), are more resistant to drought than 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)
| Variety | Origin | Sustainability |
| Enita | Moscow region | Medium drought resistant |
| Saratovskaya 29 | Saratov region | drought resistant |
| Comet | Sverdlovsk region. | drought resistant |
| Karazino | Brazil | acid resistant |
| Prelude | Brazil | acid resistant |
| Kolonias | Brazil | acid resistant |
| Thrintani | Brazil | acid resistant |
| PPG-56 | Kazakhstan | salt tolerant |
| Osh | Kyrgyzstan | salt tolerant |
| Surkhak 5688 | Tajikistan | salt tolerant |
| Messel | Norway | Salt tolerant |
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)
| Parameters | The nature of the change in parameters under conditions | |||
| droughts | salinity | high temperature | low temperature | |
| The concentration of ions in tissues | growing | growing | growing | growing |
| Water activity in the cell | Falling down | Falling down | Falling down | Falling down |
| Osmotic potential of the cell | growing | growing | growing | growing |
| Water holding capacity | growing | growing | growing | — |
| Water scarcity | growing | growing | growing | — |
| Protoplasm permeability | growing | growing | growing | — |
| Transpiration rate | Falling down | Falling down | growing | Falling down |
| Transpiration efficiency | Falling down | Falling down | Falling down | Falling down |
| Energy efficiency of breathing | Falling down | Falling down | Falling down | — |
| Breathing intensity | growing | growing | growing | — |
| Photophosphorylation | Decreases | Decreases | — | Decreases |
| Stabilization of nuclear DNA | growing | growing | growing | growing |
| Functional activity of DNA | Decreases | Decreases | Decreases | Decreases |
| Proline concentration | growing | growing | growing | — |
| Content of water-soluble proteins | growing | growing | growing | growing |
| Synthetic reactions | Suppressed | Suppressed | Suppressed | Suppressed |
| Ion uptake by roots | Suppressed | Suppressed | Suppressed | Suppressed |
| Transport of substances | Depressed | Depressed | Depressed | Depressed |
| Pigment concentration | Falling down | Falling down | Falling down | Falling down |
| cell division | slows down | slows down | — | — |
| Cell stretch | Suppressed | Suppressed | — | — |
| Number of fruit elements | Reduced | Reduced | Reduced | Reduced |
| Organ aging | Accelerated | Accelerated | Accelerated | — |
| biological harvest | Downgraded | Downgraded | Downgraded | Downgraded |
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 this 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 plant responses 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 non-specific (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 under stress conditions the growth processes are damaged in the first place. 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 more shoots, flowers, spikelets than is required for the 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, as a rule, is 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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In the process of evolution, as a result of natural selection and the struggle for existence, adaptations (adaptations) of organisms to certain living conditions arise. Evolution itself is essentially a continuous process of formation of adaptations, occurring according to the following scheme: intensity of reproduction -> struggle for existence -> selective death -> natural selection -> fitness.
Adaptations affect different aspects of the life processes of organisms and therefore can be of several types.
Morphological adaptations
They are associated with a change in the structure of the body. For example, the appearance of membranes between the toes in waterfowl (amphibians, birds, etc.), a thick coat in northern mammals, long legs and a long neck in marsh birds, a flexible body in burrowing predators (for example, in weasels), etc. In warm-blooded animals, when moving north, an increase in the average body size (Bergmann's rule) is noted, which reduces the relative surface and heat transfer. In bottom fish, a flat body is formed (stingrays, flounder, etc.). Plants in the northern latitudes and high mountain regions often have creeping and cushion-shaped forms, less damaged by strong winds and better warmed by the sun in the soil layer.
Protective coloration
Protective coloration is very important for animal species that do not have effective means of protection against predators. Thanks to her, animals become less visible on the ground. For example, female birds hatching eggs are almost indistinguishable from the background of the area. Bird eggs are also colored to match the color of the area. Bottom fish, most insects and many other animal species have a protective coloration. In the north, white or light coloration is more common, helping to camouflage in the snow (polar bears, polar owls, arctic foxes, pinniped cubs - white pups, etc.). A number of animals developed a coloration formed by alternating light and dark stripes or spots, making them less noticeable in bushes and dense thickets (tigers, young wild boars, zebras, spotted deer, etc.). Some animals are able to change color very quickly depending on the conditions (chameleons, octopuses, flounder, etc.).
Disguise
The essence of disguise is that the shape of the body and its coloring make animals look like leaves, knots, branches, bark or thorns of plants. Often found in insects that live on plants.
Warning or threatening coloration
Some types of insects that have poisonous or odorous glands have a bright warning color. Therefore, predators that once encountered them remember this color for a long time and no longer attack such insects (for example, wasps, bumblebees, ladybugs, Colorado potato beetles and a number of others).
Mimicry
Mimicry is the coloring and body shape of harmless animals that mimics their venomous counterparts. For example, some non-venomous snakes look like poisonous ones. Cicadas and crickets resemble large ants. Some butterflies have large spots on their wings that resemble the eyes of predators.
Physiological adaptations
This type of adaptation is associated with the restructuring of metabolism in organisms. For example, the emergence of warm-bloodedness and thermoregulation in birds and mammals. In simpler cases, this is an adaptation to certain forms of food, the salt composition of the environment, high or low temperatures, humidity or dryness of soil and air, etc.
Biochemical adaptations
Behavioral adaptations
This type of adaptation is associated with a change in behavior in certain conditions. For example, caring for offspring leads to better survival of young animals and increases the resilience of their populations. During the mating season, many animals form separate families, and in winter they unite in flocks, which facilitates their food or protection (wolves, many species of birds).
Adaptations to periodic environmental factors
These are adaptations to environmental factors that have a certain periodicity in their manifestation. This type includes daily alternations of periods of activity and rest, states of partial or complete anabiosis (dropping leaves, winter or summer diapauses of animals, etc.), animal migrations caused by seasonal changes, etc.
Adaptations to extreme living conditions
Plants and animals that live in deserts and polar regions also acquire a number of specific adaptations. In cacti, the leaves have evolved into spines (to reduce evaporation and protect against being eaten by animals), and the stem has evolved into a photosynthetic organ and reservoir. Desert plants have a long root system that allows them to extract water from great depths. Desert lizards can survive without water by eating insects and obtaining water by hydrolyzing their fats. In northern animals, in addition to thick fur, there is also a large supply of subcutaneous fat, which reduces body cooling.
Relative nature of adaptations
All adaptations are expedient only for certain conditions in which they have developed. When these conditions change, adaptations can lose their value or even harm the organisms that have them. The white color of hares, which protects them well in the snow, becomes dangerous during winters with little snow or strong thaws.
The relative nature of adaptations is also well proven by paleontological data indicating extinction. large groups animals and plants that have not survived the change in living conditions.
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