Adapted animals. Forms of adaptations
Ecology
In the wild, in order to survive, you need to be able to adapt. Many animals follow this golden rule, which is why their populations thrive. Some adaptations arose millions of years ago and are still successfully used by representatives of the animal world. Find out about these most important adaptations thanks to which we can witness such things today great variety fauna on the planet.
1) Flocks, herds, groups
Among all the adaptations of the animal world, perhaps the most important is the habit of living in a group. Animals benefit greatly from living side by side with members of their own species. They help each other get food, defend themselves from enemies and take care of their offspring together. Countless species form groups, colonies, herds, flocks, complex communities or free associations. However, the most common groups in the animal kingdom are groups called "nuclear families", which includes a male, a female and their offspring, or a male, several females and their offspring, or a group of females and their offspring, or other combinations.
2) Flight
Animals have adapted to move around in different ways while living on the planet, including walking, swimming, climbing or jumping. But the most remarkable of the adaptations to movement can be called flight. Flight not only allows animals to move long distances much faster than when walking or running on the surface, the ability to fly allows them to hide from enemies, find new territories, and look for food sources that would otherwise be inaccessible. Flight not only changed the lives of many animals, it also completely changed our lives, transformed human society, gave me many opportunities.
3) Migrations
This adaptation is found in many living things, especially birds and insects. Nothing in nature is more impressive than the movement of entire populations of animals that move in large groups from one place to another. The reasons for migrations can be very different, but are usually associated with a lack of food and the search for new, more food-rich places, and animals often migrate in order to mate and produce offspring. Some living beings are capable of migrating over amazingly long distances, covering thousands of kilometers every year. For example, the Arctic tern migrates every year from breeding grounds in the Arctic to wintering grounds in Antarctica, covering a distance of 40 thousand kilometers.
4) Camouflage
The ability to blend into their surroundings and become undetected is very helpful in evading predators, especially for those animals that are small enough to have no other means of defense against enemies in their arsenal. Many living creatures use camouflage. Some species of animals, including scorpionfish and tree frog, can change their appearance to suit their environment. Others have evolved into something completely different from an animal, such as a branch or leaf. Zebras are animals that also use camouflage to deceive a potential enemy. To a lion, a zebra looks like a mass of black and white stripes, but not a tempting treat.
5) Hibernation
Getting out of bed on cold and cloudy winter days is not a pleasant experience, which is why some animals prefer to spend the entire winter hibernating. This is an ingenious way to escape the cold and survive in harsh conditions where resources are very scarce. Many animals hibernate, including chipmunks, hedgehogs, bats and bears. Some animals, such as the American black bear, sleep all winter, but they are fairly easy to wake up. Other animals, e.g. most Mammals that hibernate in winter sleep so soundly that they go into suspended animation and many bodily functions are suspended. Waking them up is very difficult, if not impossible.
6) Conservation of resources
For animals that live in places where resources such as food and water are very scarce for long periods, the ability to store fat and water in their bodies helps them survive. This amazing feature has bactrian camel, which lives in the arid regions of Central and East Asia, where the air temperature in summer varies from minus 5 to 40 degrees Celsius. These camels have adapted perfectly to such harsh conditions. First, their humps are filled with fat, which turns into energy and water needed to survive the harsh seasons. Moreover, these camels do not sweat at all until their body temperature rises to 40 degrees.
7) Deceptive resizing
Many animals have adapted to appear larger in order to scare off enemies. For example, puffer fish can swell and almost double in size in order to intimidate the enemy and gain advantages. In case of danger, these fish pump air and water into their very elastic belly and become round like balls. In a bloated state, it is difficult for these fish to move, but this is no longer so important, since they become not particularly attractive in appearance as lunch.
8) Wool
For us humans, body hair does not have any special meaning. important, and we can live perfectly well without them. However, for most animals in the wild, fur is an important protective element. Take the musk ox, for example. Wool is vital to these animals, which live in the very cold conditions of Alaska. The dense, shaggy coat hangs all the way to the ground, giving the bull the necessary protection from the cold, allowing these creatures to withstand extremely low temperatures. Fur helps animals survive in winter average temperature minus 35 degrees Celsius. Animals shed their winter fur and exchange it for lighter summer fur when the air temperature rises to 5-10 degrees Celsius.
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Rice. 33. Winter coloring of a hare
So, as a result of the action driving forces evolution, organisms develop and improve adaptations to conditions environment. The consolidation of various adaptations in isolated populations can ultimately lead to the formation of new species.
Review questions and assignments
1. Give examples of the adaptation of organisms to living conditions.
2. Why do some animals have bright, unmasking colors, while others, on the contrary, have protective colors?
3. What is the essence of mimicry?
4. Does the action apply? natural selection on animal behavior? Give examples.
5. What are biological mechanisms the emergence of adaptive (hiding and warning) coloration in animals?
6. Are physiological adaptations factors that determine the level of fitness of the organism as a whole?
7. What is the essence of the relativity of any adaptation to living conditions? Give examples.
Think! Do it!
1. Why is there no absolute adaptation to living conditions? Give examples to prove relative character any device.
2. Boar cubs have a characteristic striped coloring, which disappears with age. Give similar examples of color changes in adults compared to offspring. Can this pattern be considered common to the entire animal world? If not, then for which animals and why is it characteristic?
3. Gather information about animals with warning colors that live in your area. Explain why knowledge of this material is important for everyone. Make an information stand about these animals. Give a presentation on this topic to primary school students.
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Refer to the electronic application. Study the material and complete the assignments.
Repeat and remember!
Human
Behavioral adaptations are innate, unconditional reflex behavior. Innate abilities exist in all animals, including humans. A newborn baby can suck, swallow and digest food, blink and sneeze, and react to light, sound and pain. These are examples unconditioned reflexes. Such forms of behavior arose in the process of evolution as a result of adaptation to certain, relatively constant conditions environment. Unconditioned reflexes are inherited, so all animals are born with a ready-made complex of such reflexes.
Each unconditioned reflex occurs in response to a strictly defined stimulus (reinforcement): some - to food, others - to pain, others - to the appearance of new information etc. The reflex arcs of unconditioned reflexes are constant and pass through the spinal cord or brain stem.
One of the most full classifications unconditioned reflexes is the classification proposed by Academician P.V. Simonov. The scientist proposed dividing all unconditioned reflexes into three groups, differing in the characteristics of the interaction of individuals with each other and with the environment. Vital reflexes(from Latin vita - life) are aimed at preserving the life of the individual. Failure to comply with them leads to the death of the individual, and implementation does not require the participation of another individual of the same species. This group includes food and drinking reflexes, homeostatic reflexes (maintaining constant temperature body, optimal breathing rate, heart rate, etc.), defensive, which, in turn, are divided into passive-defensive (running away, hiding) and active-defensive (attack on a threatening object) and some others.
TO zoosocial, or role-playing reflexes include those variants of innate behavior that arise during interaction with other individuals of their own species. These are sexual, child-parent, territorial, hierarchical reflexes.
The third group is self-development reflexes. They are not related to adaptation to a specific situation, but seem to be directed to the future. These include exploratory, imitative and playful behavior.
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The correspondence of the structure of organs to the functions performed (for example, the perfection of the aircraft of birds, bats, insects) has always attracted human attention and prompted researchers to use the principles of the organization of living beings when creating many machines and instruments. The harmonious relationships between plants and animals and their environment are no less striking.
The facts indicating the adaptability of living beings to living conditions are so numerous that it is not possible to give any complete description of them. Let us give just some striking examples of adaptive coloration?
It is especially important to protect eggs, larvae, and chicks.protective coloration. In open nesting birds (grouse, eider, black grouse), the female sitting on the nest is almost indistinguishable from the surrounding background. The pigmented shells of the eggs also match the background. It is interesting that in birds nesting in hollows, females often have bright colors (tits, woodpeckers, parrots).
An amazing resemblance to twigs is observed in stick insects. The caterpillars of some butterflies resemble twigs, and the body of some butterflies resembles a leaf. Here the protective coloring is combined with the protective shape of the body. When the stick insect freezes, it is difficult to detect its presence even at close range - it blends so much with the surrounding vegetation. Every time we get into the forest, meadows, or fields, we don’t even notice how many insects are hiding on the bark, leaves, and grass.
The zebra and tiger have dark and light stripes on their bodies that coincide with the alternation of shadow and light in the surrounding area. In this case, the animals are hardly noticeable even in open space from a distance of 50-70 m. Some animals (flounder, chameleon) are even capable of quickly changing their protective color due to the redistribution of pigments in the chromatophores of the skin. The effect of protective coloration increases when it is combined with appropriate behavior: at the moment of danger, many insects, fish, birds freeze, taking a resting pose.
A very bright warning color (usually white, yellow, red, black) is characteristic of well-protected poisonous stinging forms. Having tried several times to taste the soldier bug, ladybug, and wasp, the birds eventually give up attacking the brightly colored victim.
Interesting examples of adaptation are related tomimicry(from the Greek mimos - actor). Some defenseless and edible animals imitate species that are well protected from predators. For example, some spiders resemble ants, and wasp flies are similar in appearance to wasps.
These and many other examples indicate the adaptive nature of evolution.
Relativity of fitness.
In the pre-Darwinian period of the development of biology, the adaptability of living beings served as proof of the existence of God: without an omnipotent creator, nature itself would not have been able to so intelligently arrange living beings and so wisely adapt them to the environment. The prevailing opinion was that each individual device is absolute, since it corresponds to a specific purpose laid down by the creator: the mouth parts of the butterfly are extended into a proboscis so that it can use them to get nectar hidden in the depths of the corolla; A thick stem is necessary for the cactus to store water, etc.
The adaptation of organisms to the environment was developed in the process of long historical development under the influence of natural causes and not absolute, but relative, since environmental conditions often change faster than adaptations are formed. Corresponding to a specific habitat, adaptations lose their significance when it changes. The following facts can be evidence of the relative nature of fitness:
protective devices against some enemies are ineffective against others (for example, poisonous snakes, dangerous for many animals, are eaten by mongooses, hedgehogs, pigs);
the manifestation of instincts in animals may turn out to be inappropriate (moths collect nectar from light flowers, clearly visible at night, but they also fly towards the fire, although they die in the process);
an organ that is useful in some conditions becomes useless and even relatively harmful in another environment (the membranes between the toes of mountain geese, which never land on the water);
More advanced adaptations to a given habitat are also possible. Some species of animals and plants multiplied quickly and spread widely in completely new areas globe, where they were accidentally or intentionally introduced by humans.
Thus, the relative nature of fitness contradicts the statement of absolute expediency in living nature.
Reactions to unfavorable environmental factors are detrimental to living organisms only under certain conditions, but in most cases they have adaptive significance. Therefore, these responses were called “general adaptation syndrome” by Selye. In later works, he used the terms “stress” and “general adaptation syndrome” as synonyms.
Adaptation is a genetically determined process of the formation of protective systems that ensure increased stability and the course of ontogenesis in unfavorable conditions for it.
Adaptation is one of the most important mechanisms that increases the stability of a biological system, including plant organism, in changed conditions of existence. The better an organism is adapted to a certain 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 norm. It is controlled by the genotype and is characteristic of all living organisms. Most modifications that occur within the normal range of reaction have adaptive significance. They correspond to changes in the environment and ensure better plant survival under fluctuating environmental conditions. In this regard, such modifications have evolutionary significance. The term “reaction norm” was introduced by V.L. Johannsen (1909).
The greater the ability of a species or variety to be modified in accordance with the environment, the wider its reaction rate and the higher its ability to adapt. This property distinguishes resistant varieties of crops. As a rule, slight and short-term changes in environmental factors do not lead to significant disturbances in the physiological functions of plants. This is due to their ability to maintain relative dynamic equilibrium internal environment and stability of basic physiological functions in a changing external environment. At the same time, sudden 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 contribute to increased stability and contribute to the survival of the species.
1.Anatomical and morphological devices. 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, pubescent leaves, and the transformation of leaves into spines reduce water loss, which is very important in conditions of lack of moisture.
Stinging hairs and spines protect plants from being eaten by animals.
Trees in the tundra or at high mountain altitudes look like squat creeping shrubs; in winter they are covered with snow, which protects them from severe frosts.
In mountainous regions with large daily temperature fluctuations, plants often have the form of spread out pillows with numerous stems densely spaced. This allows you to maintain moisture inside the pillows and a relatively uniform temperature throughout the day.
In the swamp 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 via the CAM pathway. These plants have stomata that are closed during the day. Thus, the plant preserves its 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 CO 2 in the photosynthetic cycle occurs during the day when the stomata are closed.
Physiological and biochemical adaptations include the ability of stomata to open and close, depending on external conditions. Synthesis in cells of abscisic acid, proline, protective proteins, phytoalexins, phytoncides, increased activity of enzymes that counteract oxidative breakdown organic matter, the accumulation of sugars in cells and a number of other changes in metabolism help to increase the resistance of plants to unfavorable environmental conditions.
The same biochemical reaction can be carried out by several molecular forms of the same enzyme (isoenzymes), with each isoform exhibiting 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 reactions in a much wider temperature range compared to each individual isoenzyme. This enables the plant to successfully perform vital functions in changing conditions. temperature conditions.
3. Behavioral adaptations, or avoidance of an unfavorable factor. An example is ephemera and ephemeroids (poppy, chickweed, crocuses, tulips, snowdrops). They go through their entire development cycle in the spring in 1.5-2 months, even before the onset of heat and drought. Thus, they seem to leave, or avoid falling under the influence of the stressor. Similarly, early ripening varieties of agricultural crops form a harvest before the onset of unfavorable seasonal phenomena: August fogs, rains, frosts. Therefore, the selection of many agricultural crops is aimed at creating early ripening varieties. Perennials overwinter in the form of 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 an individual cell to a phytocenosis. The higher the level of organization (cell, organism, population), the larger number mechanisms simultaneously participates in the adaptation of plants to stress.
Regulation of metabolic and adaptation processes inside the cell is carried out using systems: metabolic (enzymatic); genetic; membrane These systems are closely interconnected. 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, while at the same time enzymes regulate nucleic acid metabolism in the cell.
On organismal level new ones are added to the cellular mechanisms of adaptation, reflecting the interaction of organs. IN unfavorable conditions plants create and retain the amount of fruit elements that sufficient quantity provided with the necessary substances to form full-fledged seeds. For example, in the inflorescences of cultivated cereals and in the crowns fruit trees in unfavorable conditions, more than half of the established ovaries may 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 sharply accelerate. At the same time, substances needed by plants move from them to young organs, responding to the organism’s survival strategy. Thanks to recycling nutrients Of the lower leaves, the younger ones, the upper leaves, remain viable.
Mechanisms for regeneration of lost organs operate. For example, the surface of a wound is covered with secondary integumentary tissue (wound periderm), a wound on a trunk or branch is healed with nodules (calluses). When the apical shoot is lost, dormant buds awaken in plants and side shoots intensively develop. The regeneration of leaves in the spring instead of those that fell in the fall is also an example of natural organ regeneration. Regeneration as a biological device that provides vegetative propagation of plants by segments of the root, rhizome, thallus, stem and leaf cuttings, isolated cells, and individual protoplasts has a great practical significance for plant growing, fruit growing, forestry, ornamental gardening, etc.
The hormonal system also participates 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 abscisic acid. They reduce metabolism, inhibit growth processes, accelerate aging, organ loss, and the plant’s transition to a dormant state. Inhibition of functional activity under stress conditions under the influence of growth inhibitors is a characteristic reaction for plants. At the same time, the content of growth stimulants in tissues decreases: cytokinin, auxin and gibberellins.
On population level selection is added, which leads to the emergence 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 uneven emergence of seedlings on saline soil and the increase in variation in germination timing with increasing stressors.
View in modern idea consists of a large number of biotypes - smaller ecological units that are genetically identical, but exhibit different resistance to environmental factors. IN different conditions not all biotypes are equally vital, and as a result of competition, only those that best meet the given conditions remain. That is, the resistance of a population (variety) to one or another factor is determined by the resistance of the organisms that make up the population. Resistant varieties include a set of biotypes that provide good productivity even in unfavorable conditions.
At the same time, during long-term cultivation of varieties, the composition and ratio of biotypes in the population changes, 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 unfavorable environmental conditions (anatomical, morphological, physiological, biochemical, behavioral, population, etc.)
But to choose the most effective way adaptation is the main thing is the time during which the body must adapt to new conditions.
In the event of a sudden action of an extreme factor, the response cannot be delayed; it must follow immediately to avoid irreversible damage to the plant. With prolonged exposure to a small force, adaptive changes occur gradually, and the choice of possible strategies increases.
In this regard, there are three main adaptation strategies: evolutionary, ontogenetic And urgent. The goal of the strategy is efficient 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, preserving life regulation systems, and providing plants with energy.
Evolutionary or phylogenetic adaptations(phylogeny - the development of a biological species over 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.
In the process of evolution, each plant species has developed certain needs for living conditions and adaptability to the ecological niche it occupies, a stable adaptation of the organism to its habitat. Moisture and shade tolerance, heat resistance, cold resistance and others environmental features specific plant species were formed as a result of prolonged action of appropriate conditions. Thus, heat-loving and short-day plants are characteristic of southern latitudes, less demanding of heat and long-day plants - for northern ones. Numerous evolutionary adaptations of xerophyte plants to drought are well known: economical use of water, deep-lying root system, shedding 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 the background of which breeding and selection of productive forms is carried out. If 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 at 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-climatic conditions, resistant local plant varieties have formed, and endemic plant species are resistant precisely to the stressor that is expressed in their habitat.
Characteristics of resistance of spring wheat varieties from the collection of the All-Russian Institute of Plant Growing (Semyonov et al., 2005)
Variety | Origin | Sustainability |
Enita | Moscow region | Moderately drought resistant |
Saratovskaya 29 | Saratov region | Drought resistant |
Comet | Sverdlovsk region | Drought resistant |
Karasino | Brazil | Acid resistant |
Prelude | Brazil | Acid resistant |
Colonias | Brazil | Acid resistant |
Trintani | Brazil | Acid resistant |
PPG-56 | Kazakhstan | Salt resistant |
Osh | Kyrgyzstan | Salt resistant |
Surkhak 5688 | Tajikistan | Salt resistant |
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 stress-induced ones rather than permanent ones. 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 this kind of adaptation takes a relatively long time, which is why they are called long-term adaptations. One of these mechanisms is the ability of a number of plants to form a water-saving CAM-type photosynthetic pathway under conditions of water deficiency caused by drought, salinity, and low temperatures and other stressors.
This adaptation is associated with the induction of the expression of the phosphoenolpyruvate carboxylase gene, which is “inactive” under normal conditions, and the genes of other enzymes of the CAM pathway of CO 2 assimilation, with the biosynthesis of osmolytes (proline), with the activation of antioxidant systems and changes in the daily rhythms of stomatal movements. All this leads to very economical use of water.
In field crops, for example, corn, aerenchyma is absent under normal growing conditions. But under conditions of flooding and a lack of oxygen in the tissues of 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 aboveground part of the plant to root system. The signal for cell death is ethylene synthesis.
Urgent adaptation occurs with rapid and intense changes in living conditions. It is based on the formation and functioning of shock defense 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 conditions survival under the influence of a damaging factor and thereby 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 a factor exceeds the protective and reparation 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 extreme factor.
Distinguish specific And nonspecific (general) plant responses to stressors.
Nonspecific reactions do not depend on nature active factor. They are the same under the influence of high and low temperatures, lack or excess of moisture, high concentration of salts in the soil or harmful gases in the air. In all cases, the permeability of membranes in plant cells increases, respiration is impaired, the hydrolytic breakdown of substances increases, the synthesis of ethylene and abscisic acid increases, and cell division and elongation are inhibited.
The table presents a complex of nonspecific changes that occur in plants under the influence of various environmental factors.
Change physiological parameters in plants under stress conditions (according to G.V. Udovenko, 1995)
Options | The nature of changes in parameters under conditions | |||
drought | salinity | high temperature | low temperature | |
Ion concentration in tissues | Growing | Growing | Growing | Growing |
Water activity in the cell | Falls | Falls | Falls | Falls |
Osmotic potential of the cell | Growing | Growing | Growing | Growing |
Water holding capacity | Growing | Growing | Growing | — |
Water shortage | Growing | Growing | Growing | — |
Permeability of protoplasm | Growing | Growing | Growing | — |
Transpiration rate | Falls | Falls | Growing | Falls |
Transpiration efficiency | Falls | Falls | Falls | Falls |
Energy efficiency of breathing | Falls | Falls | Falls | — |
Breathing intensity | Growing | Growing | Growing | — |
Photophosphorylation | Decreasing | Decreasing | — | Decreasing |
Stabilization of nuclear DNA | Growing | Growing | Growing | Growing |
Functional activity of DNA | Decreasing | Decreasing | Decreasing | Decreasing |
Proline concentration | Growing | Growing | Growing | — |
Content of water-soluble proteins | Growing | Growing | Growing | Growing |
Synthetic reactions | Depressed | Depressed | Depressed | Depressed |
Absorption of ions by roots | Suppressed | Suppressed | Suppressed | Suppressed |
Transport of substances | Depressed | Depressed | Depressed | Depressed |
Pigment concentration | Falls | Falls | Falls | Falls |
Cell division | Braking | Braking | — | — |
Cell stretching | Suppressed | Suppressed | — | — |
Number of fruit elements | Reduced | Reduced | Reduced | Reduced |
Aging of organs | Accelerated | Accelerated | Accelerated | — |
Biological harvest | Demoted | Demoted | Demoted | Demoted |
Based on the table data, it can be seen that plant resistance 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 salinity. 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, during drought the body's resistance to high temperatures increases. Short-term exposure to high temperatures increases resistance to heavy metals and UV-B irradiation. Previous drought promotes plant survival in salinity or cold conditions.
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 general (nonspecific) resistance mechanisms great interest represents 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 respond to water deficiency in the same way. Characterized by inhibition of shoot growth, increased growth of the root system, abscisic acid synthesis, and decreased stomatal conductance. After some time, the lower leaves age rapidly 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- These 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.
The specificity or non-specificity of response reactions implies, on the one hand, the attitude of the plant to various stressors and, on the other hand, the specificity of plant reactions various types and varieties to the same stressor.
The manifestation of specific and nonspecific plant responses depends on the strength of stress and the speed of its development. Specific responses occur more often if stress develops slowly, and the body has time to rebuild and adapt to it. Nonspecific reactions usually occur with a more short-term and strong action 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 ontogenesis. The most stable plants and plant organs are 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 growth processes are damaged first. The second critical period is the period of gamete formation and fertilization. Stress during this period leads to a decrease in the reproductive function of plants and a decrease in yield.
If stressful conditions are repeated and have low intensity, then they contribute to plant hardening. This is the basis for methods of increasing resistance to low temperatures, heat, salinity, and increased levels of harmful gases in the air.
Reliability of a plant organism is determined by its ability to prevent or eliminate failures in different levels biological organization: molecular, subcellular, cellular, tissue, organ, organismal and population.
To prevent disruptions in plant life under the influence of unfavorable factors, the following principles are used: redundancy, heterogeneity of functionally equivalent components, systems for repairing lost structures.
Redundancy of structures and functionality- one of the main ways to ensure system reliability. Redundancy and redundancy have diverse manifestations. At the subcellular level, the redundancy and duplication of genetic material contribute to increasing the reliability of the plant organism. This is ensured, for example, by the double helix of DNA and an increase in ploidy. The reliability of the functioning of a 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 portion of the available chloroplasts is sufficient to provide the plant with photosynthetic products. The remaining chloroplasts seem to remain in reserve. The same applies to the total chlorophyll content. Redundancy is also manifested in the large accumulation of precursors for the biosynthesis of many compounds.
At the organismal level, the principle of redundancy is expressed in the formation and in the laying of more at different times than is required for the change of generations, the number of shoots, flowers, spikelets, etc. a huge number pollen, ovules, seeds.
At the population level, the principle of redundancy manifests itself in a large number of individuals that differ in resistance to a particular stress factor.
Reparation systems also operate at different levels - molecular, cellular, organismal, population and biocenotic. Repair processes require energy and plastic substances, so repair is possible only if sufficient metabolic rate is maintained. If metabolism stops, repair also stops. IN extreme conditions external environment especially great value has preservation of respiration, since it is respiration that provides energy for repair processes.
The restorative 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 due to 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 the associated repair processes depend on the stability and ability of the photosynthetic apparatus to recover after damage. To maintain photosynthesis under extreme conditions in plants, the synthesis of thylakoid membrane components is activated, lipid oxidation is inhibited, and the ultrastructure of plastids is restored.
At the organismal level, an example of regeneration can be the development of replacement shoots, the awakening of dormant buds when growth points are damaged.
Strictly speaking, physical, chemical and physiological processes do not occur in isolation, but in close interaction.
But for the convenience of study, we will allow discussions about physiological adaptations as conditional independent phenomena. Physiological adaptation processes underlie all known adaptive phenomena. To prove this thesis, it is enough to mention that any type of adaptation at the very beginning involves the perception of a stimulus using sensory systems. In other words, the body's response begins with the activation of functions nervous system with subsequent vegetative and somatic changes, which are based on physical, chemical and physiological processes.
Morphological adaptations are developed over a long period of time and remain in all members of the population. Physiological adaptations are developed in a shorter period of time. And according to the activation mechanism, they are urgent. Physiological adaptations are designed to ensure an immediate response of the body to the action of an unfavorable environmental factor. They start and stop quickly. According to their time characteristics, they can be fast and fleeting, slow and long. Any physiological process is controlled by the nervous and humoral systems. The nervous system initiates a rapid response to a change in stimulus. The humoral mechanism controls protracted adaptation processes.
Under physiological adaptation V pure form researchers understand the adaptability of thermoregulation, heart function, water exchange, gas exchange and maintaining the electrical balance of the nervous system (A. D. Slonim, 1971; K. Schmidt-Nielsen, 1982).
The ability to maintain relative constancy of body temperature, i.e. homeothermy, was the most important evolutionary acquisition(aromorphosis). This aromorphosis allowed warm-blooded mammals and birds to occupy ecological niches inaccessible to poikilothermic animals (the Arctic, deserts, tropics).
In polar mammals, adaptation to low temperature conditions is extreme. The difference between ambient temperature and body temperature polar wolf and arctic fox reaches 74°C. In snow partridge, this difference exceeds 80°C.
The survival of animals at low environmental temperatures is determined by two factors: the heat-insulating properties of integumentary tissues and the ability of animals to increase metabolism when cooled. The last property of animals is based on the vegetative reactions of the body and is well developed in polar animals. Thus, in a polar bear, the basal metabolism increases at an air temperature of -50°C, in an arctic fox - at -40°C, in rodents - at 15°C.
Temperatures below -50°C are considered critically dangerous even for polar animals, although individual representatives, for example, the Eskimo husky or the Arctic fox, maintain their body temperature at 38-40°C even at an air temperature of about -80°C.
Even more tenacious is the snow goat that lives in the mountains of Alaska. It has probably the most perfect mechanism for maintaining body temperature and maintaining viability in conditions of extremely low environmental temperatures. Its metabolism remains unchanged over a wide range of external temperatures: from +20°C to -20°C. Only at -30°C was it possible to register an increase in metabolism in this animal. In 50-degree frost, a snow goat increases oxygen consumption by 30%, which is enough for active image life. For comparison, we note that when the environmental temperature drops in autumn to 5-6°C, a hedgehog’s metabolism increases 3-5 times compared to summer conditions.
The constancy of body temperature is the result of heat production and heat transfer. In warm-blooded animals, the main source of heat is numerous biochemical processes that require energy.
The energy from the chemical bonds of nutrients is eventually converted into thermal energy. Energy production ensures basal metabolism (the performance of all physiological systems in a state of physiological rest) and productive exchange(job skeletal muscles, fetal growth, lactopoiesis).
The main heat generators of the animal body are:
- muscles (up to 50% of the body’s total heat production);
- liver (15-20% heat);
- lungs and kidneys (7-12% heat);
- gastrointestinal tract (10% heat).
In ruminants, a significant part of the heat production belongs to symbiotic microorganisms of the forestomach and large intestine. Ciliates, bacteria and fungi inhabiting these sections digestive tract, hydrolyze up to 80% of fiber, 70% of protein and 60% of dietary lipids.
In poikilothermic animals, internal heat production usually exceeds its own needs. Therefore in natural environment habitat, a significant part of the metabolic heat is released in external environment. Even under normal temperature conditions, poikilotherms are much more likely to overheat than to overcool. When the environmental temperature decreases, the metabolism of cold-blooded animals decreases without negative consequences. When the air temperature drops to a critical value, animals hibernate.
In warm-blooded animals, the response to a decrease in environmental temperature is different. They increase metabolism and, therefore, heat production. The regulator of this vital mechanism is the hypothalamus.
The afferent flow resulting from the excitation of cold receptors (Krause bodies) through the thalamus and hypothalamus activates the production of adenocorticotropic hormone (ACTH) and thyroid-stimulating hormone (TSH) by the pituitary gland. Under the influence of ACTH, the adrenal glands release catecholamines into the blood, and the thyroid gland secretes thyroid hormones T3 and T4. Adrenaline and thyroxine in the liver and muscles enhance thermogenesis due to the oxidation of ATP. As a result, an additional amount of heat is released, which warms the animal’s body.
In addition, under the influence of adrenaline, the activity of the heart muscle is activated. As a result of increased blood circulation, the surface of the body receives more blood and additional heat is generated, which increases skin temperature and inhibits the formation of receptor potential in Krause's corpuscles. The afferent flow from cold receptors weakens, and the stimulating influence of the thalamus ceases.
However, the basal metabolism has some inertia. Therefore, heat production remains elevated for some time after the cessation of the cold factor.
Heat removal is based on four physical phenomena: radiation, convection, conduction and evaporation. In comfortable temperature conditions, the main way to remove heat from the animal’s body is radiation and conduction. The latter route of heat transfer can become the main one when the animal comes into contact with a colder environment (for example, when a dog lies in the snow or a pig rolls in the mud).
Radiation becomes the main method of heat transfer in animals that stand still. Thermal radiation reveals the hidden animal to those predators that have the appropriate reception mechanism. Snakes are very sensitive to heat rays. Some of them detect the presence of a rat or other rodent even when the victim’s body temperature exceeds the ambient temperature by only 0.01 ° C. Such a high thermal sensitivity of snakes is justified in desert conditions, where the inhabitants strive to ensure that the temperature of the surface of their body differs as little as possible from the hot surface of the earth.
In the heat the main and most in an efficient way The removal of excess thermal energy is the evaporation of water. When transitioning from a liquid state to a gaseous state (steam), energy is absorbed. To evaporate 1 g of water, about 600 cal of thermal energy is required. Through evaporation, heat is released from the surface of the skin and through the mucous membranes of the respiratory organs. In males individual species Animals additionally experience evaporation of water from the mucous membrane of the penis - thermal erection of stallions, donkeys, camels, elephants. Under heat stress in dogs, many species of birds, as well as in ruminants in the hot zone, heat transfer sharply increases due to increased evaporation through the mucous membranes of the upper respiratory tract.
Animals use different techniques cooling your body.
Reptiles increase heat transfer due to the evaporation of water from the surface of the skin, canines use thermal shortness of breath, and the American antelope ground squirrel rubs its head with saliva to cool due to the subsequent evaporation of saliva.
For the vast majority of animal species, under conditions of thermal comfort, the main place of water evaporation during thermoregulation is the skin. According to G. Tangle, a lactating cow with a live weight of 300 to 800 kg evaporates from 6 to 16 liters of water through the skin. Evaporation through the skin in horses accounts for 5-8 liters, in adult pigs - 2.0-2.5 liters, in shorn sheep - about 2.5 liters of water. Thus, the daily heat transfer due to the evaporation of water through the skin in a cow reaches 9600 kcal, in horses - up to 4800 kcal, in pigs and sheep it ranges from 1200 to 1500 kcal per head.
Obviously, the heat transfer path used by the animal’s body is determined by the force thermal factor. M. Kovalchikova and K. Kovalchik (1978) provide the following data on the influence of environmental temperature on the removal of heat from the body using the example of a domestic pig.
Up to an air temperature of 30°C, the main method of heat transfer in a pig is respiration and radiation. When the difference between the animal's body temperature and the ambient temperature becomes minimal or disappears altogether, the radiation of heat stops. The main way to get rid of excess heat is evaporation. In pigs important role The limbs, ears and tail play a role in thermoregulation. Interestingly, at an ambient temperature of 5°C, the temperature of the protruding parts of the animal’s body is significantly lower than at a temperature of 25°C. Thus, the temperature of the ears at 5°C is only 15°C; at an air temperature of 15°C, the temperature of the ears rose to 27°C; at 25°C, the ears heat up to a temperature of 36°C.
Similar changes occur with the temperature of the pig's tail. In general, due to changes in the blood supply to different areas of the skin of a pig, the total heat loss from the surface of the body under unfavorable conditions changes within 70%.
In northern animals sharp decline ambient temperature, breathing becomes rare, slow, but deep. Due to changes in breathing, heat transfer from the body is reduced.
With short-term exposure to low temperatures on animals for which cold is not a habitual factor (gerbils, rats, mice), on the contrary, the respiratory rate increases due to increased metabolism and increased heat production. But with a long stay in conditions of low temperatures (compatible with life), in these animals, like in the northern aborigines, breathing slows down over time.
When the ambient temperature rises to values exceeding the upper limit of the temperature comfort zone, all animal species develop polypnea(hyperpnea, physiological shortness of breath). In this situation, polypnea acts as a factor of physical thermoregulation. There is a tight feedback between polypnea and sweating. Polypnea is most pronounced in animals with poorly developed sweat glands. Thermal shortness of breath is especially pronounced in predators, in which the respiratory rate increases by two orders of magnitude and reaches 600 in 1 minute. In hedgehogs, the respiratory rate reaches 240 per minute, in mice it is even higher. In cows, sheep and goats, polypnea may be prolonged (all hot day), but their respiratory rate does not exceed 200 per minute. Prolonged polypnea leads to acapnia- a decrease in CO 2 content in the blood and a change in the acid-base balance of the body (alkalosis).
Humans have well-developed sweat glands. Therefore, his breathing rate, even at an ambient temperature of 70-80°C (sauna temperature), is about 50-60 per minute.
The reaction of the heart is also indicative. vascular system to changes in ambient temperature. Changes in breathing rate are accompanied by changes in heart rate. The reactions of the heart to cooling vary from animal to animal. In animals adapted to cold, a decrease in heart rate is recorded. But in animals that are not adapted to the effects of cold, the exact opposite response of the heart is noted - tachycardia. For example, cooling only the tail to -4°C in laboratory rats causes an increase in heart rate by 50-100%.
In addition to the heart muscle, the vascular system is also responsive to the thermal factor. In animals accustomed to cold, spasms of peripheral vessels are detected during sudden cooling. Southerners in this situation demonstrate the exact opposite reaction. They have vasodilation, i.e., increased blood circulation in peripheral vessels. In this regard, it would be appropriate to mention “walruses” - people who regularly swim in open water in winter. A short-term immersion in an ice hole causes hyperemia of the skin vessels (severe redness of the skin). When in severe frost“walruses” crawl out of the ice hole, their body is red and steam comes from them. This suggests that the surface temperature of the human body in these extreme conditions is much higher than the ambient temperature.
In conditions of high temperatures in animals, blood flow to the heat exchange organs (ears, tail, limbs) increases. These organs are characterized by special structure vascular system. They have arterial-venous heat exchangers. Such specific blood supply systems are described in the limbs of dogs, in the skin of cattle, and in the tail of rodents.
The parallel and close arrangement of arteries and veins allows excess heat to be effectively removed from the body. Arterial blood has a temperature close to physiological body temperature. In the countercurrent, part of the thermal energy is taken away by the venous blood. Veins are located close to the surface, often just under the skin. Consequently, due to the increase in the temperature of the venous blood, some heating of the surface of the limb, tail or other part of the body occurs. For animals in low temperature conditions, this heat redistribution is of great importance. Due to the counter-current mechanism, the limbs are protected from frostbite and remain operational in extreme environmental temperature conditions.
In cattle and related animal species, a countercurrent circulatory mechanism is present in the intercostal muscles. The arteries of these muscles extend to the surface of the body on the back and sides, where they branch and form anastomoses with the veins - the so-called “miraculous network”. With hyperpnea (shortness of breath), the intercostal muscles give off heat to the adjacent blood vessels. Due to the high heat capacity of blood, muscles are effectively cooled. The body surface temperature rises, resulting in the dissipation of this heat into the external environment.
Thus, due to chemical and physical thermoregulation, homeothermic animals maintain body temperature and maintain high functional activity even under conditions of extreme temperatures.