Adaptation- this is an adaptation of the body to environmental conditions due to a complex of morphological, physiological, and behavioral characteristics.
Different organisms adapt to different environmental conditions, and as a result, moisture-loving hydrophytes and "dry-bearers" - xerophytes(Fig. 6); saline soil plants halophytes; shade tolerant plants sciophytes), and requiring full sunlight for normal development ( heliophytes); animals that live in deserts, steppes, forests or swamps are nocturnal or diurnal. Groups of species with a similar attitude to environmental conditions (that is, living in the same ecotopes) are called environmental groups.
The ability to adapt to adverse conditions in plants and animals differ. Due to the fact that animals are mobile, their adaptations are more diverse than those of plants. Animals can:
– avoid adverse conditions (birds fly to warmer climes because of winter starvation and cold, deer and other ungulates wander in search of food, etc.);
- fall into suspended animation - a temporary state in which life processes are so slowed down that their visible manifestations are almost completely absent (stupor of insects, hibernation of vertebrates, etc.);
- adjust to life adverse conditions(wool and subcutaneous fat save them from frost, desert animals have devices for economical use of water and cooling, etc.). (Fig. 7).
Plants are inactive and lead an attached lifestyle. Therefore, only the last two variants of adaptations are possible for them. Thus, plants are characterized by a decrease in the intensity of vital processes during unfavorable periods: they shed their leaves, hibernate as dormant organs buried in the soil - bulbs, rhizomes, tubers, and remain in the state of seeds and spores in the soil. In bryophytes, the entire plant has the ability to anabiosis, which, in a dry state, can persist for several years.
Plant resistance to adverse factors increases due to special physiological mechanisms: changes in osmotic pressure in cells, regulation of the intensity of evaporation with the help of stomata, the use of “filter” membranes for selective absorption of substances, etc.
Adaptations different organisms produced at different rates. They occur most rapidly in insects that can adapt to the action of a new insecticide in 10–20 generations, which explains the failure of chemical control of insect pest population density. The process of developing adaptations in plants or birds occurs slowly, over centuries.
The observed changes in the behavior of organisms are usually associated with hidden traits that they had, as it were, "in reserve", but under the influence of new factors, they appeared and increased the resistance of species. Such hidden features explain the resistance of some tree species to the action of industrial pollution (poplar, larch, willow) and some weed species to the action of herbicides.
The composition of the same ecological group often includes organisms that are not similar to each other. This is due to the fact that different types of organisms can adapt to the same environmental factor in different ways.
For example, they experience cold differently warm-blooded(they are called endothermic, from the Greek words endon - inside and terme - heat) and cold-blooded (ectothermic, from the Greek ectos - outside) organisms. (Fig. 8.)
The body temperature of endothermic organisms does not depend on the ambient temperature and is always more or less constant, its fluctuations do not exceed 2–4 o even during the most severe frosts and the most intense heat. These animals (birds and mammals) maintain their body temperature by internal heat production based on intensive metabolism. They keep their body heat at the expense of warm “fur coats” made of feathers, wool, etc.
Physiological and morphological adaptations are supplemented by adaptive behavior (selection of wind-protected places for lodging for the night, construction of burrows and nests, group overnight stays with rodents, close groups of penguins warming each other, etc.). If the ambient temperature is very high, then endothermic organisms are cooled by special adaptations, for example, by evaporation of moisture from the surface of the mucous membranes of the oral cavity and upper respiratory tract. (For this reason, in the heat, the dog's breathing quickens and he sticks out his tongue.)
The body temperature and mobility of ectothermic animals depends on the ambient temperature. Insects and lizards become lethargic and inactive in cool weather. At the same time, many animal species have the ability to choose a place with favorable conditions for temperature, humidity and sunlight (lizards bask on illuminated rock slabs).
However, absolute ectothermy is observed only in very small organisms. Most cold-blooded organisms are still capable of poor regulation of body temperature. For example, in actively flying insects - butterflies, bumblebees, the body temperature is maintained at 36–40 ° C even at air temperatures below 10 ° C.
Similarly, species of the same ecological group in plants differ in their appearance. They can also adapt to the same environmental conditions different ways. So, different types of xerophytes save water in different ways: some have thick cell membranes, others have pubescence or a wax coating on the leaves. Some xerophytes (for example, from the labiaceae family) emit vapors of essential oils, which envelop them like a “blanket”, which reduces evaporation. root system in some xerophytes it is powerful, it goes into the soil to a depth of several meters and reaches the groundwater level (camel thorn), in others it is superficial, but highly branched, which allows collecting precipitation water.
Among the xerophytes there are shrubs with very small hard leaves that can be shed in the driest season (caragana shrub in the steppe, desert shrubs), turf grasses with narrow leaves (feather grass, fescue), succulents(from the Latin succulentus - juicy). Succulents have succulent leaves or stems that accumulate a supply of water, and easily tolerate high air temperatures. Succulents include American cacti and saxaul growing in the Central Asian deserts. They have a special type of photosynthesis: stomata open for a short time and only at night, during these cool hours, plants store carbon dioxide, and during the day they use it for photosynthesis with closed stomata. (Fig. 9.)
A variety of adaptations to survive unfavorable conditions on saline soils is also observed in halophytes. Among them there are plants that are able to accumulate salts in their bodies (soleros, swede, sarsazan), secrete excess salts on the surface of the leaves with special glands (kermek, tamariks), “keep” salts out of their tissues due to the “root barrier” impervious to salts "(wormwood). In the latter case, the plants have to be content with a small amount of water and they have the appearance of xerophytes.
For this reason, one should not be surprised that under the same conditions there are plants and animals that are different from each other, which have adapted to these conditions in different ways.
1. What is adaptation?
2. Due to what animals and plants can adapt to adverse environmental conditions?
2. Give examples environmental groups plants and animals.
3. Tell us about the different adaptations of organisms to experiencing the same adverse environmental conditions.
4. What is the difference between adaptations to low temperatures in endothermic and ectothermic animals?
Adaptation of a person to a new environment for him is a complex socio-biological process, which is based on a change in the systems and functions of the body, as well as habitual behavior. Human adaptation refers to the adaptive reactions of his body to changing environmental factors. Adaptation manifests itself at different levels of organization of living matter: from molecular to biocenotic. Adaptation develops under the influence of three factors: heredity, variability, natural / artificial selection. There are three main ways that organisms adapt to their environment: the active way, the passive way, and the avoidance of adverse effects.
active path- strengthening of resistance, development of regulatory processes that allow to carry out all the vital functions of the body, despite the deviation of the environmental factor from the optimum. For example, maintaining a constant body temperature in warm-blooded animals (birds, humans), optimal for the flow of biochemical processes in cells.
passive way- subordination of the vital functions of the organism to changes in environmental factors. For example, under unfavorable environmental conditions, the transition to a state of anabiosis (hidden life), when the metabolism in the body almost completely stops (winter dormancy of plants, preservation of seeds and spores in the soil, stupor of insects, hibernation, etc.).
Avoidance of adverse conditions- production by the body life cycles and behaviors that avoid adverse effects. For example, seasonal migrations of animals.
Usually, the adaptation of a species to the environment takes place by one or another combination of all three. possible ways adaptation.
Adaptations can be divided into three main types: morphological, physiological, ethological.
Morphological adaptations- changes in the structure of the organism (for example, the modification of a leaf into a thorn in cacti to reduce water loss, bright colors of flowers to attract pollinators, etc.). Morphological adaptations in animals lead to the formation of certain life forms.
Physiological adaptations- changes in the physiology of the body (for example, the ability of a camel to provide the body with moisture by oxidizing fat reserves, the presence of cellulose-degrading enzymes in cellulose-destroying bacteria, etc.).
Ethological (behavioral) adaptations- changes in behavior (for example, seasonal migrations of mammals and birds, hibernation in winter, mating games in birds and mammals during the breeding season, etc.). Ethological adaptations are characteristic of animals.
Living organisms are well adapted to periodic factors. Non-periodic factors can cause disease and even death of a living organism. A person uses this by applying antibiotics and other non-periodic factors. However, the duration of their exposure can also cause adaptation to them.
The environment has a huge impact on a person. In this regard, the problem of adapting a person to his environment is becoming increasingly important. In social ecology, this problem is of paramount importance. At the same time, adaptation is only the initial stage, at which reactive forms of human behavior predominate. The person does not stop at this stage. He shows physical, intellectual, moral, spiritual activity, transforms (for worse or worse) his environment.
Human adaptation is divided into genotypic and phenotypic. Genotypic adaptation: a person outside of his consciousness can adapt to changing environmental conditions (temperature changes, food taste, etc.), that is, if the adaptation mechanisms are already in the genes. Phenotypic adaptation is understood as the inclusion of consciousness, one's personal qualities of a person in order to adapt the body to a new environment, to maintain balance in new conditions.
The main types of adaptation include physiological, adaptation to activity, adaptation to society. Let's focus on physiological adaptation. Under the physiological adaptation of a person is understood the process of maintaining the functional state of the body as a whole, ensuring its preservation, development, performance, maximum life expectancy. Great importance in physiological adaptation is attached to acclimation and acclimatization. It is clear that a person's life in the Far North differs from his life at the equator, since these are different climatic zones. Moreover, a southerner, having lived for a certain time in the north, adapts to it and can live there permanently and vice versa. Acclimation is the initial, urgent stage of acclimatization under changing climatic and geographical conditions. In some cases, a synonym for physiological adaptation is acclimatization, that is, the adaptation of plants, animals and humans to new climatic conditions for them. Physiological acclimatization occurs when a person, with the help of adaptive reactions, increases working capacity, improves well-being, which can deteriorate sharply during the period of acclimation. When new conditions are replaced by old ones, the body can return to its previous state. Such changes are called acclimatization. The same changes that, in the process of adapting to a new environment, have passed into the genotype and are inherited, are called adaptive.
Adaptation of the body to living conditions (city, village, other locality). is not limited to climatic conditions. A person can live in the city and in the countryside. Many people prefer the metropolis with its noise, pollution, frantic pace of life. Objectively, living in a village, where clean air, a calm, measured rhythm, is more favorable for people.
The same area of adaptation includes moving, for example, to another country. Some quickly adapt, overcome the language barrier, find a job, others with great difficulty, others, having adapted outwardly, experience a feeling called nostalgia.
We can highlight the adaptation to the activity. Different types of human activity impose different requirements on the individual (some require perseverance, diligence, punctuality, others require speed of reaction, the ability to make decisions independently, etc.). However, a person can cope with these and other types of activity quite successfully. There is an activity that is contraindicated for a person, but he can perform it, as adaptation mechanisms work, which is called the development of an individual style of activity.
Particular attention should be paid to adaptation to society, other people, and the team. A person can adapt to a group by assimilating its norms, rules of conduct, values, etc. The mechanisms of adaptation here are suggestibility, tolerance, conformity as forms of submissive behavior, and on the other hand, the ability to find one’s place, find a face, and show determination.
We can talk about adaptation to spiritual values, to things, to states, for example, to stressful ones, and to many other things. In 1936, the Canadian physiologist Selye published the message "Syndrome caused by various damaging elements", in which he described the phenomenon of stress - a general non-specific reaction of the body aimed at mobilizing its defenses under the influence of irritating factors. In the development of stress, 3 stages were distinguished: 1. stage of anxiety, 2. stage of resistance, 3. stage of exhaustion. G. Selye formulated the theory of the General Adaptation Syndrome (GAS) and adaptive diseases as a consequence of the adaptive reaction, according to which GAS manifests itself whenever a person feels danger to himself. The visible causes of stress can be injuries, postoperative conditions, etc., changes in abiotic and biotic environmental factors. In recent decades, the number of anthropogenic environmental factors with a high stress effect has significantly increased (chemical pollution, radiation, exposure to computers during systematic work with them, etc.). The stress factors of the environment should also include negative changes in modern society: increase, change in the ratio of urban and rural population, rising unemployment, crime.
Organisms' adaptations to their environment are called adaptation. Adaptations are any changes in the structure and functions of organisms that increase their chances of survival.
The ability to adapt is one of the main properties of life in general, as it provides the very possibility of its existence, the ability of organisms to survive and reproduce. Adaptations manifest themselves at different levels: from the biochemistry of cells and the behavior of individual organisms to the structure and functioning of communities and ecological systems. Adaptations arise and develop in the course of the evolution of species.
The main mechanisms of adaptation at the level of the organism: 1) biochemical- manifest themselves in intracellular processes, such as a change in the work of enzymes or a change in their number; 2) physiological– for example, increased sweating with increasing temperature in a number of species; 3) morpho-anatomical- features of the structure and shape of the body associated with lifestyle; 4) behavioral- for example, the search for favorable habitats by animals, the creation of burrows, nests, etc.; 5) ontogenetic- acceleration or deceleration individual development facilitating survival under changing conditions.
Environmental environmental factors have various effects on living organisms, i.e., they can affect how irritants, causing adaptive changes in physiological and biochemical functions; as limiters, causing the impossibility of existence in these conditions; as modifiers, causing morphological and anatomical changes in organisms; as signals, indicating changes in other environmental factors.
General laws of the action of environmental factors on organisms
Despite the wide variety of environmental factors, a number of general patterns can be identified in the nature of their impact on organisms and in the responses of living beings.
The law of optimum.
Each factor has certain limits of positive influence on organisms (Fig. 1). The result of the action of a variable factor depends primarily on the strength of its manifestation. Both insufficient and excessive action of the factor negatively affects the life of individuals. The beneficial effect is called zone of optimum ecological factor or simply optimum for organisms of this species. The stronger the deviation from the optimum, the more pronounced the inhibitory effect of this factor on organisms. (pessimum zone). The maximum and minimum tolerated values of the factor are critical points behind beyond which existence is no longer possible, death occurs. The endurance limits between critical points are called ecological valency living beings in relation to a specific environmental factor.
Rice. one. Scheme of the action of environmental factors on living organisms
Representatives different types differ greatly from each other both in the position of the optimum and in ecological valency. For example, arctic foxes in the tundra can tolerate fluctuations in air temperature in the range of more than 80 °C (from +30 to -55 °C), while warm-water crustaceans Copilia mirabilis withstand changes in water temperature in the range of no more than 6 °C (from +23 up to +29 °C). One and the same force of manifestation of a factor can be optimal for one species, pessimal for another, and go beyond the limits of endurance for the third (Fig. 2).
The wide ecological valence of a species in relation to abiotic environmental factors is indicated by adding the prefix "evry" to the name of the factor. eurythermal species - enduring significant temperature fluctuations, eurybatic– wide pressure range, euryhaline– different degree of salinization of the environment.
Rice. 2. The position of the optimum curves on the temperature scale for different species:
1, 2 - stenothermic species, cryophiles;
3–7 – eurythermal species;
8, 9 - stenothermic species, thermophiles
The inability to endure significant fluctuations in the factor, or narrow ecological valence, is characterized by the prefix "steno" - stenothermal, stenobate, stenohaline species, etc. In a broader sense, species whose existence requires strictly defined environmental conditions are called stenobiont, and those who are able to adapt to different environmental situation, – eurybiontic.
Conditions approaching critical points in one or several factors at once are called extreme.
The position of the optimum and critical points on the factor gradient can be shifted within certain limits by the action of environmental conditions. This occurs regularly in many species as the seasons change. In winter, for example, sparrows withstand severe frosts, and in summer they die from cooling at temperatures just below zero. The phenomenon of shifting the optimum with respect to any factor is called acclimation. With regard to temperature, this is a well-known process of thermal hardening of the body. Temperature acclimation requires a significant period of time. The mechanism is a change in the cells of enzymes that catalyze the same reactions, but with different temperatures(so called isoenzymes). Each enzyme is encoded by its own gene, therefore, it is necessary to turn off some genes and activate others, transcription, translation, assembly of a sufficient amount of a new protein, etc. The overall process takes an average of about two weeks and is stimulated by changes in the environment. Acclimation, or hardening, is an important adaptation of organisms that occurs under gradually impending adverse conditions or when they enter territories with a different climate. She is in these cases integral part overall process acclimatization.
The textbook complies with the Federal State educational standard medium (full) general education recommended by the Ministry of Education and Science of the Russian Federation and included in the Federal List of Textbooks.
The textbook is addressed to students in grade 11 and is designed to teach the subject 1 or 2 hours a week.
Modern design, multi-level questions and tasks, Additional Information and the possibility of parallel work with an electronic application contribute to the effective assimilation of educational material.
Rice. 33. Winter coloring of a hare
So, as a result of the action driving forces evolution in organisms, adaptations to environmental conditions arise and improve. Fixation in isolated populations of various adaptations can eventually lead to the formation of new species.
Review questions and assignments
1. Give examples of the adaptability of organisms to the conditions of existence.
2. Why do some animals have a bright, unmasking color, while others, on the contrary, are patronizing?
3. What is the essence of mimicry?
4. Does the action of natural selection extend to the behavior of animals? Give examples.
5. What are the biological mechanisms for the emergence of adaptive (concealing 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! Execute!
1. Why is there no absolute adaptation to living conditions? Give examples proving the relative nature of any device.
2. Boar cubs have a characteristic striped coloration that disappears with age. Give similar examples of color changes in adults compared to offspring. Can this pattern be considered common to the entire animal kingdom? If not, for which animals and why is it typical?
3. Gather information about warning color animals 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 in front of elementary school students.
Work with computer
Refer to the electronic application. Study the material and complete the assignments.
Repeat and remember!
Man
Behavioral adaptations are innate unconditioned reflex behavior. Innate abilities exist in all animals, including humans. A newborn baby can suck, swallow and digest food, blink and sneeze, 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 environmental conditions. Unconditioned reflexes are inherited, so all animals are born with a ready-made complex of such reflexes.
Each unconditioned reflex occurs to a strictly defined stimulus (reinforcement): some - to food, others - to pain, others - to the appearance new information etc. The reflex arcs of unconditioned reflexes are constant and pass through the spinal cord or brain stem.
One of the most complete classifications of unconditioned reflexes is the classification proposed by Academician P. V. Simonov. The scientist proposed to divide all unconditioned reflexes into three groups, differing in the characteristics of the interaction of individuals with each other and with environment. Vital reflexes(from lat. vita - life) are aimed at preserving the life of the individual. Failure to comply with them leads to the death of the individual, and the implementation does not require the participation of another individual of the same species. This group includes food and drink reflexes, homeostatic reflexes (maintaining a constant body temperature, optimal breathing rate, heart rate, etc.), defensive ones, which, in turn, are divided into passive-defensive (runaway, 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 when interacting with other individuals of their species. These are sexual, parent-child, territorial, hierarchical reflexes.
The third group is reflexes of self-development. They are not connected with adaptation to a specific situation, but, as it were, turned to the future. Among them are exploratory, imitative and playful behavior.
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arises in the process of evolution to solve the environmental problems of the organism, presented by the environment. They are a changing, improving, sometimes disappearing adaptation of organisms to specific environmental factors. As a result of the development of adaptation, a state of adaptation (or correspondence of the morphology, physiology, and behavior of organisms) to the ecological niches they occupy is achieved, which represent the entire set of environmental conditions and lifestyle of a given organism. That. adaptation can be considered a broad basis for the emergence or disappearance of organs, the divergence (divergence) of species, the formation of new populations and species, and the complication of organization.
The process of developing adaptation occurs constantly and many signs of the body are involved in it. [show] .
The evolution of birds from reptiles included, for example, successive changes bones, muscles, integuments, limbs.
An increase in the sternum, a restructuring of the histological structure of the bones, which, along with strength, gave them lightness, the development of plumage, which led to better aerodynamic properties and thermoregulation, the transformation of a pair of limbs into wings, provided a solution to the problem of flight.
Some representatives of birds subsequently developed adaptations to a terrestrial or aquatic lifestyle (ostrich, penguin), while secondary adaptations also captured a number of characters. Penguins, for example, changed their wings to fins, and their covers became waterproof.
However, an adaptation is formed only if there is a type of hereditary information in the gene pool that contributes to a change in structures and functions in the required direction. Thus, mammals and insects use lungs and tracheas, respectively, for breathing, which develop from different primordia under the control of different genes.
Adaptation sometimes leads to a new mutation, which, being included in the genotype system, changes the phenotype in the direction of a more effective solution of environmental problems. This way of occurrence of adaptation is called combinative.
Different adaptations can be used to solve one ecological problem. Thus, thick fur serves as a means of thermal insulation in bears, arctic foxes, and in cetaceans, the fatty subcutaneous layer.
There are several classifications of adaptation.
According to the mechanism of action allocate
Passive protection devices
- protective coloration. Thanks to the protective coloration, the organism becomes difficult to distinguish and, therefore, protected from predators.
- Bird eggs laid on sand or on the ground are gray and brown with spots, similar to the color of the surrounding soil. In cases where eggs are not available to predators, they are usually devoid of coloration.
- Butterfly caterpillars are often green, the color of the leaves, or dark, the color of the bark or earth.
- Bottom fish are usually painted to match the color of the sandy bottom (stingrays and flounders). At the same time, flounders also have the ability to change color depending on the color of the surrounding background.
- The ability to change color by redistributing the pigment in the integument of the body is also known in terrestrial animals (chameleon).
- Desert animals, as a rule, have a yellow-brown or sandy-yellow color.
- Monochromatic protective coloration is characteristic of both insects (locust) and small lizards, as well as large ungulates (antelopes) and predators (lion).
- Dissecting protective coloration in the form of alternating light and dark stripes and spots on the body. Zebras and tigers are hard to see already at a distance of 50-40 m due to the coincidence of the stripes on the body with the alternation of light and shadow in the surrounding area. Dissecting coloring violates ideas about the contours of the body.
- frightening (warning) coloring - also provides protection for organisms from enemies.
Bright coloration is usually characteristic of poisonous animals and warns predators about the inedibility of the object of their attack. The effectiveness of warning coloration was the cause of a very interesting imitation phenomenon - mimicry. [show] .
Mimicry is the resemblance of a defenseless and edible species to one or more unrelated species that are well protected and have a warning color. The phenomenon of mimicry is common in butterflies and other insects. Many insects mimic stinging insects. Beetles, flies, butterflies are known, copying wasps, bees, bumblebees.
Mimicry is also found in vertebrates - snakes. In all cases, the similarity is purely external and is aimed at forming a certain visual impression in potential enemies.
For mimic species, it is important that their numbers be small compared to the model they imitate, otherwise the enemies will not develop a stable negative reflex to warning coloration. The low number of mimic species is supported by a high concentration of lethal genes in the gene pool.
- the similarity of the body shape with the environment - beetles are known that resemble lichens, cicadas, similar to the thorns of those shrubs among which they live. Stick insects look like a small brown or green twig.
Protective action patronizing coloring or body shape increases when combined with the appropriate behavior. For example, moth caterpillars in a defensive posture are similar to a plant branch. Selection destroys individuals whose behavior unmasks them.
- high fecundity
- other means of passive protection
- The development of spines and needles in plants protects them from being eaten by herbivores.
- Poisonous substances that burn hairs (nettle) play the same role.
- Calcium oxalate crystals, formed in the cells of some plants, protect them from being eaten by caterpillars, snails and even rodents.
- Formations in the form of a hard chitinous cover in arthropods (beetles, crabs), shells in mollusks, scales in crocodiles, shells in armadillos and turtles protect them well from many enemies. The quills of the hedgehog and porcupine serve the same.
Active protection devices, movement,
looking for food or a breeding partner
- improvement of the apparatus of movement, nervous system, sense organs, the development of means of attack in predatory
The chemical organs of insects are amazingly sensitive. Males gypsy moth attracts the smell of the aromatic gland of the female from a distance of 3 km. In some butterflies, the sensitivity of taste receptors is 1000 times greater than the sensitivity of human tongue receptors. Nocturnal predators, such as owls, see perfectly in the dark. Some snakes have a well-developed ability to thermolocation. They distinguish objects at a distance if the difference in their temperatures is only 0.2 ° C.
Adaptations to the social way of life - the division of "labor" in bees.
Depending on the nature of the change
- adaptation with the complication of morphophysiological organization
- the emergence of lobe-finned fish on land in the Devonian, which allowed them to give rise to terrestrial vertebrates
For lobe-finned fish, the limbs were used for crawling along the bottom of reservoirs. Swallowing air and using oxygen by protrusion of the intestinal wall - primitive lungs - provided an opportunity to compensate for the lack of oxygen in the waters of that time. These structures allowed some fish to leave the waters for a while. Initially, such exits were made, apparently, on rainy days or wet nights. This is exactly what the American catfish (Ictalurus nebulosis) currently does. Subsequently, these structures developed into the lungs and limbs of land animals. Subsequently, the whole organization of fish underwent profound changes in the process of adaptation to life on land.
Such changes during the development of a new habitat, expanding the range of functions based on structures that previously performed other functions, but changed in such a direction and to such an extent that they were able to take on new functions - is called pre-adaptation.
The phenomenon of pre-adaptation once again emphasizes the adaptive nature of evolution, based on the selection of useful hereditary changes and progressive transformations of existing structures in the process of mastering new environmental conditions.
By fixture scale
- specialized adaptations . With the help of specialized adaptations, the organism solves specific problems in the narrow local conditions of the life of the species. For example, the structural features of the anteater's tongue provide food for ants.
- common adaptations - allow you to solve many problems in a wide range environmental conditions. These include the internal skeleton of vertebrates and the external arthropods, hemoglobin as an oxygen carrier, etc. Such adaptations contribute to the development of various ecological niches, provide significant ecological and evolutionary plasticity, and are found in representatives of large taxa of organisms. Thus, the primary horny cover of the ancestral forms of reptiles in the process of historical development gave the covers of modern reptiles, birds, and mammals. The scale of adaptation is revealed in the course of evolution of the group of organisms in which it arose for the first time.
Thus, the structure of living organisms is very finely adapted to the conditions of existence. Any species trait or property is adaptive in nature and appropriate in a given environment, in given living conditions.
Relativity and expediency of fitness of organisms
Adaptations arise in response to a specific ecological task, so they are always relative and expedient. The relativity of adaptation lies in the limitation of their adaptive value to certain living conditions. Thus, the adaptive value of the pigmentation of moth butterflies in comparison with light forms is evident only on sooty tree trunks.
When environmental conditions change, adaptations may turn out to be useless or even harmful to the organism. The constant growth of rodent incisors is a very important feature, but only when eating solid food. If a rat is kept on soft food, the incisors, without wearing out, grow to such a size that feeding becomes impossible.
None of the adaptive features provides absolute security for their owners. Due to mimicry, most birds do not touch wasps and bees, but among them there are species that eat both wasps and bees, and their imitators. The hedgehog and the secretary bird eat without harm poisonous snakes. The shell of terrestrial turtles reliably protects them from enemies, but birds of prey lift them into the air and smash them on the ground.
The biological expediency of the organization of living beings is manifested in the harmony between the morphology, physiology, behavior of organisms of different species and their habitat. It also lies in the amazing consistency of the structure and functions of individual parts and systems of the body itself. Supporters of the theological explanation of the origin of life saw biological expediency as a manifestation of the wisdom of the creator of nature. The teleological explanation of biological expediency proceeds from the principle of the "ultimate goal", according to which life develops in a directed way due to an inherent striving towards a known goal. Since the time of J. B. Lamarck, there have been hypotheses linking biological expediency with the principle of an adequate response of organisms to changes in external conditions and the inheritance of such "acquired traits." A convincing argument in favor of the expediency of changes under the influence of the environment has long been recognized as the fact that microorganisms are "addicted" to drugs - sulfonamides, antibiotics. The experience of V. and E. Lederberg showed that this is not so.
In a Petri dish on the surface of a solid nutrient medium, the microbe forms colonies (1). With a special stamp (2), the imprint of all colonies was transferred to the medium with lethal dose antibiotic (3). If at least one colony grew under these conditions, then it came from a colony of microbes that were also resistant to this drug. Unlike other colonies on the first Petri dish (4), it grew in the antibiotic tube (5). If the number of original colonies was large, then among them, as a rule, there was also a stable one. Thus, we are not talking about the directed adaptation of the microbe, but about the state of pre-adaptation, which is due to the presence in the genome of the microorganism of an allele that blocks the action of the antibiotic. In some cases, "resistant" microbes synthesize an enzyme that destroys the drug, in others, the cell wall becomes impermeable to the drug.
The emergence of strains of microorganisms resistant to drugs is facilitated by the wrong tactics of doctors who, wanting to avoid side effects prescribed low, sub-lethal doses of drugs. It is also possible to explain the appearance of forms resistant to poisons among insects and mammals - among mutant organisms there is a stable form that undergoes positive selection under the action of a poisonous substance. For example, the resistance of rats to the warfarin used to kill them depends on the presence of a certain dominant allele in the genotype.
The possibility of "direct adaptation" of organisms to the environment, "alteration of nature by assimilating conditions" was argued by some biologists as early as the 40-50s of the current century. The points of view given above correspond to idealistic views, and cannot explain biological expediency without drawing on the idea, if not of God, then of a special goal or program for the development of life that existed even before its occurrence.
The biological expediency of the structure and functions of organisms develops in the process of life development. It is a historical category. This is evidenced by the change in the types of organization that occupy a dominant position in organic world planets. Thus, the dominance of amphibians for almost 75 million years was replaced by the dominance of reptiles, which lasted for 150 million years. During periods of dominance of any group, there are several waves of extinction that change the relative species composition corresponding large taxon.
The emergence of any adaptation and biological expediency as a whole is explained by the work in nature for more than 3.5 billion years of natural selection. Of the many random deviations, it preserves and accumulates hereditary changes that have adaptive value. This explanation makes it possible to understand why biological expediency, when viewed in space and time, is a relative property of living beings and why, under specific living conditions, individual adaptations reach only the degree of development that is sufficient to survive in comparison with competitors' adaptations.
