Morphological adaptations - adaptations of animals to environmental factors. Behavioral adaptations of organisms to the action of ecological factors. Examples Types of behavioral adaptation
Behavioral adaptations - these are the features of behavior developed in the process of evolution that allow them to adapt and survive in the given environmental conditions.
Typical example - winter dream of a bear.
Also examples are 1) the creation of shelters, 2) movement in order to select the optimum temperature conditions, especially in conditions of extreme t. 3) the process of tracking down and pursuing prey from predators, and from prey - in response reactions (for example, hiding).
common for animals way of adapting to bad times- migration. (Saiga saigas annually leave for the winter in the snowless southern semi-deserts, where winter grasses are more nutritious and accessible due to the dry climate. However, in summer, semi-desert herbage quickly burns out, therefore, during the breeding season, saigas move to more humid northern steppes).
Examples 4) behavior when searching for food and a sexual partner, 5) mating, 6) feeding offspring, 7) avoiding danger and protecting life in case of a threat, 8) aggression and threatening postures, 9) care for offspring, which increases the likelihood of cub survival, 10) uniting in flocks, 11) imitation of injury or death in the event of a threat of attack.
21. Life forms, as a result of the adaptation of organisms to the action of a complex of environmental factors. Classification of life forms of plants according to K.Raunkier, I.G.Serebryakov, animals according to D.N.Kashkarov.
The term "life form" was introduced in the 80s by E. Warming. He understood life form as "a form in which the vegetative body of a plant (individual) is in harmony with the external environment throughout its life, from cradle to coffin, from seed to death." This is a very deep definition.
Life forms as types of adaptive structures demonstrate: 1) a variety of ways to adapt different plant species even to the same conditions,
2) the possibility of similarity of these paths in plants that are completely unrelated, belonging to different species, genera, families.
-> The classification of life forms is based on the structure of vegetative organs and reflects II and convergent paths of ecological evolution.
According to Raunkier: applied his system to find out the relationship between life forms of plants and climate.
He singled out an important feature that characterizes the adaptation of plants to the transfer of an unfavorable season - cold or dry.
This sign is the position of the renewal buds on the plant in relation to the level of the substrate and snow cover. Raunkier attributed this to protecting the kidneys during unfavorable times of the year.
1)phanerophytes- the buds hibernate or endure the dry period "open", high above the ground (trees, shrubs, woody vines, epiphytes).
-> they are usually protected by special bud scales, which have a number of devices to preserve the growth cone and young leaf primordia enclosed in them from moisture loss.
2)chamephites- the buds are located almost at the level of the soil or not higher than 20-30 cm above it (shrubs, semi-shrubs, creeping plants). In cold and dead climates, these kidneys very often receive additional protection in winter, in addition to their own kidney scales: they hibernate under the snow.
3)cryptophytes- 1) geophytes - buds are located in the ground at a certain depth (they are divided into rhizomatous, tuberous, bulbous),
2) hydrophytes - buds hibernate under water.
4)hemicryptophytes- usually herbaceous plants; their renewal buds are at the level of the soil or are sunk very shallowly, in the litter formed by leaf waste - another additional "cover" for the buds. Among the hemicryptophytes, Raunkier distinguishes " irotogeiicryptophytes"with elongated shoots, dying off annually to the base, where the renewal buds are located, and rosette hemicryptophytes, in which shortened shoots can overwinter at the entire soil level.
5)terophytes- special group; these are annuals in which all vegetative parts die off by the end of the season and there are no overwintering buds - these plants renew the next year from seeds that overwinter or survive a dry period on the soil or in the soil.
According to Serebryakov:
Having used and generalized the classes proposed at different times, he proposed calling a peculiar habitus a life form - (characteristic form, appearance org-ma) opgroups of plants, arising as a result of growth and development in opr conditions - as an expression of adaptability to these conditions.
The basis of its classification is a sign of the lifespan of the whole plant and its skeletal axes.
A. Woody plants
1. Trees
2. Shrubs
3. Shrubs
B. Semi-woody plants
1.Subshrubs
2.Subshrubs
B. Ground grasses
1.Polycarpic herbs (perennial herbs, bloom many times)
2. Monocarpic herbs (live for several years, bloom once and die off)
D. Water grasses
1. Amphibious herbs
2.Floating and underwater grasses
The life form of a tree turns out to be an extrusion of adaptations to conditions that are most favorable for growth.
AT forests of the humid tropics- the most tree species (up to 88% in the Amazon region of Brazil), and in the tundra and highlands there are no real trees. In the area of taiga forests trees are represented by only a few species. No more than 10–12% of total number species make up trees and in the flora of the temperate forest zone of Europe.
According to Kashkarov:
I. Floating forms.
1. Purely aquatic: a) nekton; b) plankton; c) benthos.
2. Semi-aquatic:
a) diving b) not diving; c) only getting food from the water.
II. Burrowing forms.
1. Absolute excavators (who spend their whole lives underground).
2. Relative excavations (coming to the surface).
III. ground forms.
1. Not making holes: a) running; b) jumping; c) crawling.
2. Making holes: a) running; b) jumping; c) crawling.
3. Animals of rocks.
IV. Wood climbing forms.
1. Not descending from the trees.
2. Only climbing trees.
V. Air forms.
1. Obtaining food in the air.
2. Searching for food from the air.
In appearance birds, to a significant extent, their confinement to habitat types and the nature of movement when obtaining food are manifested.
1) woody vegetation;
2) open land spaces;
3) swamps and shoals;
4) water spaces.
In each of these groups, specific forms are distinguished:
a) getting food by climbing (pigeons, parrots, woodpeckers, passerines)
b) foraging in flight (long-winged, in the forests - owls, nightjars, over water - tube-nosed);
c) feeding while moving on the ground (on open spaces- cranes, ostriches; forest - most chicken; in swamps and shallows - some passerines, flamingos);
d) those who obtain food by swimming and diving (loons, copepods, gooses, penguins).
22. The main environments of life and their characteristics: land-air and water.
ground-air- most animals and plants live.
It is characterized by 7 main abiotic factors:
1.Low air density makes it difficult to maintain the shape of the body and provokes the image of the support system.
EXAMPLE: 1. Aquatic plants do not have mechanical tissues: they appear only in terrestrial forms. 2. Animals must have a skeleton: a hydroskeleton (in roundworms), or the external skeleton (in insects), or the internal (in mammals).
The low density of the medium facilitates the movement of animals. Many terrestrial species are capable of flight.(birds and insects, but there are also mammals, amphibians and reptiles). The flight is associated with the search for prey or resettlement. The inhabitants of the land spread only on the Earth, which serves as their support and attachment point. In connection with active flight in such organisms modified forelimbs and developed pectoral muscles.
2) Mobility of air masses
*Provides the existence of aeroplankton. It consists of pollen, seeds and fruits of plants, small insects and arachnids, spores of fungi, bacteria and lower plants.
This ecological group of org-in adapted due to the large variety of wings, outgrowths, cobwebs, or due to very small sizes.
* method of pollination of plants by wind - anemophilia- Har-n for birches, firs, pines, nettles, grasses and sedges.
* settling with the help of the wind: poplars, birches, ash trees, lindens, dandelions, etc. The seeds of these plants have parachutes (dandelions) or wings (maple).
3) Low pressure, norm=760 mm. The pressure drops, compared with the aquatic habitat, are very small; thus, at h=5800 m it is only half of its normal value.
=> almost all land inhabitants are sensitive to strong pressure drops, i.e. they are stenobionts in relation to this factor.
The upper limit of life for most vertebrates is 6000 m, because pressure drops with height, which means that the solubility of o in the blood decreases. To maintain a constant concentration of O 2 in the blood, the respiratory rate must increase. However, we exhale not only CO2, but also water vapor, so frequent breathing should invariably lead to dehydration of the organism. This simple dependence is not characteristic only for rare species organisms: birds and some invertebrates, mites, spiders and springtails.
4) Gas composition has a high content of O 2: it is more than 20 times higher than in the aquatic environment. This allows the animals to have very high metabolic rates. Therefore, only on land could arise homoiothermy- the ability to maintain a constant t of the body due to internal energy. Thanks to homoithermy, birds and mammals can remain active in the most severe conditions.
5) Soil and relief are very important, first of all, for plants. For animals, the structure of the soil is more important than its chemical composition.
*For ungulates that make long migrations on dense ground, the adaptation is a decrease in the number of fingers and => a decrease in the S-support.
* For the inhabitants of free-flowing sands, an increase in Spov-ti support (fan-toed gecko) is characteristic.
* Soil density is also important for burrowing animals: prairie dogs, marmots, gerbils and others; some of them develop digging limbs.
6) Significant water shortage on land provokes the development of various adaptations aimed to conserve water in the body:
The development of respiratory organs capable of absorbing O 2 from the air environment of the integument (lungs, trachea, lung sacs)
Development of waterproof covers
The change will highlight the system and metabolic products (urea and uric acid)
Internal fertilization.
In addition to providing water, precipitation also plays an ecological role.
*Snow value reduces fluctuations in t at depths of 25 cm. Deep snow protects plant buds. For black grouse, hazel grouse and tundra partridges, snowdrifts are a place to spend the night, i.e. at 20–30 o below zero at a depth of 40 cm, it remains ~0 °С.
7) Temperature regime more variable than water. ->many land dwellers eurybiont to this f-ru, i.e., they are able to exist in a wide range of t and demonstrate very different ways of thermoregulation.
Many animal species that live in areas where winters are snowy molt in autumn, changing the color of their coat or feathers to white. It is possible that such a seasonal molt of birds and animals is also an adaptation - a camouflage coloration, which is typical for the hare, weasel, arctic fox, tundra partridge and others. However, not all white animals change color seasonally, which reminds us of the neopremism and the impossibility of considering all the properties of the body as beneficial or harmful.
Water. Water covers 71% of the S of the earth or 1370 m3. The main mass of water - in the seas and oceans - 94-98%, polar ice contains about 1.2% of water and a very small proportion - less than 0.5%, in fresh waters of rivers, lakes and swamps.
About 150,000 species of animals and 10,000 plants live in the aquatic environment, which is only 7 and 8% of the total number of species on Earth. So on land, evolution was much more intense than in water.
In the seas-oceans, as in the mountains, is expressed vertical zonation.
All inhabitants of the aquatic environment can be divided into three groups.
1) Plankton- countless accumulations of tiny organisms that cannot move on their own and are carried by currents in the top layer of sea water.
It consists of plants and living organisms - copepods, eggs and larvae of fish and cephalopods, + unicellular algae.
2) Nekton- a large number of org-in freely floating in the thickness of the oceans. The largest of them are blue whales and giant shark feeding on plankton. But there are also dangerous predators among the inhabitants of the water column.
3) Benthos- the inhabitants of the bottom. Some deep-sea inhabitants are deprived of the organs of vision, but most can see in dim light. Many residents lead an attached lifestyle.
Adaptations of aquatic organisms to high water density:
Water has a high density (800 times the density of air) and viscosity.
1) Plants have very poorly developed or absent mechanical tissues- they are supported by the water itself. Most are buoyant. Har-but active vegetative reproduction, the development of hydrochoria - the removal of peduncles above the water and the spread of pollen, seeds and spores by surface currents.
2) The body has a streamlined shape and is lubricated with mucus, which reduces friction when moving. Adaptations for increasing buoyancy have been developed: accumulations of fat in tissues, swim bladders in fish.
In passively swimming animals - outgrowths, spikes, appendages; the body flattens, reduction of skeletal organs occurs.
different ways movement: bending of the body, with the help of flagella, cilia, jet mode of locomotion (cephalomollusks).
In benthic animals, the skeleton disappears or is poorly developed, the size of the body increases, the reduction of vision is common, and the development of tactile organs.
Adaptations of hydrobionts to water mobility:
Mobility is caused by ebbs and flows, sea currents, storms, different levels of elevations of river beds.
1) In flowing waters, plants and animals are firmly attached to stationary underwater objects.. The bottom surface for them is primarily a substrate. These are green and diatom algae, water mosses. From animals - gastropods, barnacles + hide in crevices.
2) Different body shapes. In fish flowing through the waters, the body is round in diameter, and in fish living near the bottom, the body is flat.
Adaptations of hydrobionts to water salinity:
Natural reservoirs are characterized by a certain chemical composition. (carbonates, sulfates, chlorides). In fresh water bodies, the salt concentration is not > 0.5 g /, in the seas - from 12 to 35 g / l (ppm). With a salinity of more than 40 ppm, the reservoir is called g hyperhaline or oversalted.
1) * In fresh water (hypotonic environment) osmoregulation processes are well expressed. Hydrobionts are forced to constantly remove the water penetrating into them, they homoiosmotic.
* In salt water (isotonic medium), the concentration of salts in the bodies and tissues of hydrobionts is the same as the concentration of salts dissolved in water - they poikiloosmotic. -> Inhabitants of salt water bodies have not developed osmoregulatory functions, and they could not populate fresh water bodies.
2) Aquatic plants are able to absorb water and nutrients from the water - "broth", the entire surface, therefore, their leaves are strongly dissected and conductive tissues and roots are poorly developed. The roots serve to attach to the underwater substrate.
Typically maritime and typically freshwater species – stenohaline, cannot tolerate changes in salinity. Euryhaline species a little. They are common in brackish waters (pike, bream, mullet, coastal salmon).
Adaptation of hydrobionts to the composition of gases in water:
In water, O 2 is the most important environmental factor. Its source is atm-ra and photosynthetic plants.
When water is stirred and t decreases, the O 2 content increases. *Some fish are very sensitive to O2 deficiency (trout, minnow, grayling) and therefore prefer cold mountain rivers and streams.
*Other fish (crucian carp, carp, roach) are unpretentious to the content of O 2 and can live at the bottom of deep water bodies.
* Many aquatic insects, mosquito larvae, lung mollusks are also tolerant to the content of O 2 in water, because from time to time they rise to the earth and swallow fresh air.
Carbon dioxide enough in water - almost 700 times > than in air. It is used in plant photosynthesis and goes to the formation of calcareous skeletal formations of animals (mollusk shells).
Identifying limiting factors is of great practical value. First of all, for growing crops: applying the necessary fertilizers, liming the soil, reclamation, etc. allow to increase productivity, improve soil fertility, improve the existence of cultivated plants.
- What does the prefix "evry" and "steno" mean in the species name? Give examples of eurybionts and stenobionts.
Wide tolerance limit of the species in relation to abiotic environmental factors, denoted by adding prefixes to the name of the factor "evry. The inability to tolerate significant fluctuations in factors or a low endurance limit is characterized by the prefix "steno", for example, stenothermic animals. Small temperature changes have little effect on eurythermal organisms and can be fatal for stenothermic ones. The species adapted to low temperatures is cryophilic(from the Greek krios - cold), and to high temperatures - thermophilic. Similar patterns apply to other factors as well. Plants may be hydrophilic, i.e. demanding on water and xerophilic(dry-hardy).
In relation to content salts in the habitat, eurygales and stenogals are distinguished (from Greek gals - salt), to illumination - euryphotes and stenophots, in relation to to the acidity of the environment- Euryionic and stenionic species.
Since eurybionty makes it possible to populate a variety of habitats, and stenobiontism sharply narrows the range of places suitable for the species, these 2 groups are often called evry - and stenobionts. Many terrestrial animals living in a continental climate are able to withstand significant fluctuations in temperature, humidity, and solar radiation.
Stenobionts include- orchids, trout, Far Eastern hazel grouse, deep-sea fish).
Animals that are stenobiont simultaneously with respect to several factors are called stenobionts in the broad sense of the word ( fish that live in mountain rivers and streams that cannot tolerate too high temperatures and low oxygen content, inhabitants of the humid tropics, unadapted to low temperatures and low air humidity).
The eurybionts are Colorado potato beetle, mouse, rats, wolves, cockroaches, reeds, wheatgrass.
- Adaptation of living organisms to environmental factors. Types of adaptation.
adaptation ( from lat. adaptation - adaptation ) - this is an evolutionary adaptation of the organisms of the environment, expressed in a change in their external and internal features.
Individuals that for some reason have lost the ability to adapt, in the conditions of changes in the regimes of environmental factors, are doomed to elimination, i.e. to extinction.
Types of adaptation: morphological, physiological and behavioral adaptations.
Morphology is the doctrine of the external forms of organisms and their parts.
1.Morphological adaptation- this is an adaptation that manifests itself in adaptation to fast swimming in aquatic animals, to survival in conditions of high temperatures and moisture deficiency - in cacti and other succulents.
2.Physiological adaptations consist in the features of the enzymatic set in the digestive tract of animals, determined by the composition of the food. For example, the inhabitants of dry deserts are able to provide the need for moisture due to the biochemical oxidation of fats.
3.Behavioral (ethological) adaptations appear in the most various forms. For example, there are forms of adaptive behavior of animals aimed at ensuring optimal heat exchange with the environment. Adaptive behavior can be manifested in the creation of shelters, movement in the direction of more favorable, preferred temperature conditions, choosing places with optimal humidity or illumination. Many invertebrates are characterized by a selective attitude towards light, which manifests itself in approaching or moving away from the source (taxis). Diurnal and seasonal migrations of mammals and birds are known, including migrations and flights, as well as intercontinental movements of fish.
Adaptive behavior can be manifested in predators in the process of hunting (tracking and chasing prey) and in their prey (hiding, obfuscating the trail). The behavior of animals during the mating season and during the rearing of offspring is exceptionally specific.
There are two types of adaptation to external factors. Passive way of adaptation- this adaptation by the type of tolerance (tolerance, endurance) consists in the emergence of a certain degree of resistance to this factor, the ability to maintain functions when the force of its influence changes .. This type of adaptation is formed as a characteristic species property and is realized at the cellular and tissue level. The second type of fixture active. In this case, the body, using specific adaptive mechanisms, compensates for the changes caused by the influencing factor, so that the internal environment remains relatively constant. Active adaptations are adaptations of a resistant type (resistance) that maintain the homeostasis of the internal environment of the body. An example of a tolerant type of adaptation is poikiloosmotic animals, an example of a resistant type is homoyosmotic .
- Define a population. Name the main group characteristics of the population. Give examples of populations. Growing, stable and dying populations.
population- a group of individuals of the same species that interact with each other and jointly inhabit a common territory. The main characteristics of the population are as follows:
1. Number - total individuals in a certain area.
2. Population density - the average number of individuals per unit area or volume.
3. Fertility - the number of new individuals that appeared per unit of time as a result of reproduction.
4. Mortality - the number of dead individuals in the population per unit of time.
5. Population growth - the difference between fertility and mortality.
6. Growth rate - average growth per unit of time.
Populations are characterized by a certain organization, the distribution of individuals over the territory, the ratio of groups by sex, age, and behavioral characteristics. It is formed, on the one hand, on the basis of common biological properties species, and on the other hand, under the influence of abiotic environmental factors and populations of other species.
The structure of the population is unstable. The growth and development of organisms, the birth of new ones, death from various causes, changes in environmental conditions, an increase or decrease in the number of enemies - all this leads to a change in various ratios within the population.
Increasing or growing population- this is a population in which young individuals predominate, such a population is growing in number or is being introduced into the ecosystem (for example, countries of the "third" world); More often than not, there is an excess of births over deaths and the population grows to such an extent that an outbreak can occur. mass reproduction. This is especially true for small animals.
With a balanced intensity of fertility and mortality, a stable population. In such a population, mortality is compensated by growth and its number, as well as its range, are kept at the same level. . Stable population - this is a population in which the number of individuals of different ages varies evenly and has the character of a normal distribution (as an example, we can name the population of Western Europe).
Decreasing (dying) population is a population in which the death rate exceeds the birth rate . A declining or dying population is a population dominated by older individuals. An example is Russia in the 1990s.
However, it cannot shrink indefinitely either.. At a certain level of abundance, the intensity of mortality begins to fall, and fecundity increases. . Ultimately, a declining population, having reached a certain minimum size, turns into its opposite - a growing population. The birth rate in such a population gradually increases and at a certain moment levels off with mortality, i.e., the population becomes stable for a short period of time. Decreasing populations are dominated by old individuals that are no longer able to reproduce intensively. Such age structure indicates unfavorable conditions.
- Ecological niche of the organism, concepts and definitions. Habitat. Mutual arrangement of ecological niches. The ecological niche of man.
Any kind of animal, plant, microbe is able to normally live, feed, reproduce only in the place where it has been "registered" by evolution over many millennia, starting from its ancestors. To refer to this phenomenon, biologists have borrowed term from architecture - the word "niche" and they began to say that each type of living organism occupies its own, unique ecological niche in nature.
Ecological niche of an organism- this is the totality of all its requirements for environmental conditions (the composition and regimes of environmental factors) and the place where these requirements are met, or the totality of the set biological characteristics and physical parameters environment that determine the conditions for the existence of a particular species, its transformation of energy, the exchange of information with the environment and their own kind.
The concept of an ecological niche is usually used when using the relationships of ecologically close species belonging to the same trophic level. The term "ecological niche" was proposed by J. Grinnell in 1917 to characterize the spatial distribution of species, that is, the ecological niche was defined as a concept close to the habitat. C. Elton defined an ecological niche as the position of a species in a community, emphasizing the particular importance of trophic relationships. A niche can be thought of as part of an imaginary multi-dimensional space (hypervolume), the individual dimensions of which correspond to the factors necessary for the species. The more the parameter varies, i.e. adaptation of a species to a particular environmental factor, the wider its niche. The niche can also increase in the case of weakened competition.
habitat of the species- this is the physical space occupied by a species, organism, community, it is determined by the totality of the conditions of the abiotic and biotic environment, providing the entire development cycle of individuals of the same species.
The habitat of the species can be designated as "spatial niche".
The functional position in the community, in the ways of processing matter and energy in the process of nutrition, is called trophic niche.
Figuratively speaking, if a habitat is, as it were, the address of organisms of a given species, then a trophic niche is a profession, the role of an organism in its habitat.
The combination of these and other parameters is commonly called an ecological niche.
ecological niche(from the French niche - a recess in the wall) - this is the place occupied by a biological species in the biosphere, includes not only its position in space, but also its place in trophic and other interactions in the community, as it were, the “profession” of the species.
Niche ecological fundamental(potential) is an ecological niche in which a species can exist in the absence of competition from other species.
Ecological niche realized (real) – ecological niche, part of a fundamental (potential) niche that a species can defend in competition with other species.
According to the relative position of the niches of the two types, they are divided into three types: non-contiguous ecological niches; contiguous but not overlapping niches; contiguous and overlapping niches.
Man is one of the representatives of the animal kingdom, a biological species of the class of mammals. Despite the fact that it has many specific properties (mind, articulate speech, labor activity, biosociality, etc.), it has not lost its biological essence and all the laws of ecology are valid for it to the same extent as for other living organisms. . Man has his own, only his own, ecological niche. The space in which the human niche is localized is very limited. As a biological species, a person can live only within the land of the equatorial belt (tropics, subtropics), where the hominid family arose.
- Formulate the fundamental law of Gause. What is a "life form"? What ecological (or life) forms are distinguished among the inhabitants of the aquatic environment?
Both in the plant and in the animal world, interspecific and intraspecific competition is very widespread. There is a fundamental difference between them.
Rule (or even law) Gause: two species cannot occupy the same ecological niche at the same time and therefore necessarily crowd out each other.
In one of the experiments, Gause bred two types of ciliates - Paramecium caudatum and Paramecium aurelia. As food, they regularly received one of the types of bacteria that does not multiply in the presence of paramecium. If each type of ciliate was cultivated separately, then their populations grew according to a typical sigmoid curve (a). At the same time, the number of paramecia was determined by the amount of food. But when coexisting, paramecia began to compete, and P. aurelia completely replaced its competitor (b).
Rice. Competition between two closely related species of ciliates occupying a common ecological niche. a - Paramecium caudatum; b - P. aurelia. 1. - in one culture; 2. - in a mixed culture
With the joint cultivation of ciliates, after a while only one species remained. At the same time, ciliates did not attack individuals of another type and did not emit harmful substances. The explanation lies in the fact that the studied species differed in unequal growth rates. In the competition for food, the fastest breeding species won.
When breeding P. caudatum and P. bursaria no such displacement occurred, both species were in equilibrium, the latter being concentrated on the bottom and walls of the vessel, and the former in free space, i.e., in a different ecological niche. Experiments with other types of ciliates have demonstrated the regularity of the relationship between prey and predator.
Gauze principle is called the principle elimination competitions. This principle leads either to the ecological separation of closely related species, or to a decrease in their density where they are able to coexist. As a result of competition, one of the species is ousted. The Gause principle plays a huge role in the development of the concept of a niche, and also forces ecologists to look for answers to a number of questions: How do similar species coexist? How big must be the differences between species in order for them to coexist? How do you avoid competitive exclusion?
The life form of the species it is a historically developed complex of its biological, physiological and morphological properties, which determines a certain reaction to the influence of the environment.
Among the inhabitants of the aquatic environment (hydrobionts), the classification distinguishes the following life forms.
1.Neuston(from the Greek neuston - able to swim) – collection of marine and freshwater organisms that live near the surface of the water , for example, mosquito larvae, many protozoa, water strider bugs, and from plants, the well-known duckweed.
2. Closer to the surface of the water inhabits plankton.
Plankton(from Greek planktos - soaring) - floating organisms capable of making vertical and horizontal movements mainly in accordance with the movement water masses. Allocate phytoplankton photosynthetic free-swimming algae and zooplankton- small crustaceans, larvae of mollusks and fish, jellyfish, small fish.
3.Nekton(from the Greek nektos - floating) - free-floating organisms capable of independent vertical and horizontal movement. Nekton lives in the water column - these are fish, in the seas and oceans, amphibians, large aquatic insects, crustaceans, and reptiles ( sea snakes and turtles) and mammals: cetaceans (dolphins and whales) and pinnipeds (seals).
4. Periphyton(from Greek peri - around, about, phyton - plant) - animals and plants attached to the stems of higher plants and rising above the bottom (mollusks, rotifers, bryozoans, hydras, etc.).
5. Benthos ( from the Greek benthos - depth, bottom) - benthic organisms leading an attached or free lifestyle, including: living in the thickness of the bottom sediment. These are mainly mollusks, some lower plants, crawling insect larvae, worms. The bottom layer is inhabited by organisms that feed mainly on decaying remains.
- What is biocenosis, biogeocenosis, agrocenosis? The structure of biogeocenosis. Who is the founder of the doctrine of biocenosis? Examples of biogeocenoses.
Biocenosis(from Greek koinos - common bios - life) is a community of interacting living organisms, consisting of plants (phytocenosis), animals (zoocenosis), microorganisms (microbocenosis) adapted to coexist in a given territory.
The concept of "biocenosis" - conditional, since organisms cannot live outside the environment of existence, but it is convenient to use it in the process of studying ecological relationships between organisms. Depending on the area, the attitude to human activity, the degree of saturation, usefulness, etc. there are biocenoses of land, water, natural and anthropogenic, saturated and unsaturated, full-membered and non-full-membered.
Biocenoses, like populations - this is a supra-organismal level of life organization, but of a higher rank.
The sizes of biocenotic groups are different- these are also large communities of lichen pillows on tree trunks or a rotting stump, but this is also a population of steppes, forests, deserts, etc.
The community of organisms is called biocenosis, and the science that studies the community of organisms - biocenology.
V.N. Sukachev the term has been proposed (and generally accepted) to refer to communities biogeocenosis(from Greek bios - life, geo - Earth, cenosis - community) - it is a set of organisms and natural phenomena characteristic of a given geographical area.
The structure of biogeocenosis includes two components biotic - community of living plant and animal organisms (biocenosis) - and abiotic - a set of non-living environmental factors (ecotope, or biotope).
Space with more or less homogeneous conditions, which occupies a biocenosis, is called a biotope (topis - place) or ecotope.
Ecotop includes two main components: climatetop- the climate in all its diverse manifestations and edaphotop(from the Greek edafos - soil) - soil, relief, water.
Biogeocenosis\u003d biocenosis (phytocenosis + zoocenosis + microbocenosis) + biotope (climatotop + edaphotop).
Biogeocenoses - these are natural formations (they contain the element "geo" - the Earth ) .
Examples biogeocenoses there may be a pond, a meadow, a mixed or single-species forest. At the level of biogeocenosis, all processes of transformation of energy and matter in the biosphere take place.
Agrocenosis(from Latin agraris and Greek koikos - common) - a community of organisms created by man and artificially supported by him with increased productivity (productivity) of one or more selected plant or animal species.
Agrocenosis differs from biogeocenosis main components. It cannot exist without human support, as it is an artificially created biotic community.
- The concept of "ecosystem". Three principles of functioning of ecosystems.
ecological system- one of the most important concepts of ecology, abbreviated as an ecosystem.
Ecosystem(from the Greek oikos - dwelling and system) - this is any community of living beings, together with their habitat, connected inside complex system relationships.
Ecosystem - these are supraorganismal associations, including organisms and inanimate (inert) environment, which are in interaction, without which it is impossible to maintain life on our planet. This is a community of plant and animal organisms and an inorganic environment.
Based on the interaction of living organisms that form an ecosystem, with each other and with their habitat, in any ecosystem, interdependent aggregates are distinguished biotic(living organisms) and abiotic(inert or inanimate nature) components, as well as environmental factors (such as solar radiation, humidity and temperature, atmospheric pressure), anthropogenic factors and others.
To abiotic components of ecosystems include inorganic substances - carbon, nitrogen, water, atmospheric carbon dioxide, minerals, organic substances found mainly in the soil: proteins, carbohydrates, fats, humic substances, etc., which have entered the soil after the death of organisms.
To the biotic components of the ecosystem include producers, autotrophs (plants, chemosynthetics), consumers (animals) and detritophages, decomposers (animals, bacteria, fungi).
The textbook complies with the Federal State educational standard secondary (complete) 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 per 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 world? 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
Talk to electronic application. Study the material and complete the assignments.
Repeat and remember!
Human
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 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 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 features of the interaction of individuals with each other and with the 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 refer those options 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 related to adaptation to specific situation, but as if facing the future. Among them are exploratory, imitative and playful behavior.
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In the process of evolution, as a result of natural selection and the struggle for existence, adaptations (adaptations) of organisms to certain living conditions arise. Evolution itself is essentially a continuous process of formation of adaptations, occurring according to the following scheme: intensity of reproduction -> struggle for existence -> selective death -> natural selection -> fitness.
Adaptations affect different aspects of the life processes of organisms and therefore can be of several types.
Morphological adaptations
They are associated with a change in the structure of the body. For example, the appearance of membranes between the toes in waterfowl (amphibians, birds, etc.), a thick coat in northern mammals, long legs and a long neck in marsh birds, a flexible body in burrowing predators (for example, in weasels), etc. In warm-blooded animals, when moving north, an increase in the average body size (Bergmann's rule) is noted, which reduces the relative surface and heat transfer. In bottom fish, a flat body is formed (stingrays, flounder, etc.). In plants in northern latitudes and highland areas, creeping and cushion-shaped forms are frequent, less damaged by strong winds and better warmed by the sun in the soil layer.
Protective coloration
Protective coloration is very important for animal species that do not have effective means of protection against predators. Thanks to her, animals become less visible on the ground. For example, female birds hatching eggs are almost indistinguishable from the background of the area. Bird eggs are also colored to match the color of the area. patronizing coloration have bottom fish, most insects and many other animal species. In the north, white or light coloration is more common, helping to camouflage in the snow (polar bears, snowy owls, arctic foxes, cubs of pinnipeds - white pups, etc.). A number of animals developed a coloration formed by the alternation of light and dark stripes or spots, making them less visible in bushes and dense thickets (tigers, young wild boars, zebras, spotted deer, etc.). Some animals are able to change color very quickly depending on the conditions (chameleons, octopuses, flounder, etc.).
Disguise
The essence of disguise is that the shape of the body and its color make animals look like leaves, knots, branches, bark or thorns of plants. Often found in insects that live on plants.
Warning or threatening coloration
Some types of insects that have poisonous or odorous glands have a bright warning color. Therefore, predators that once encountered them remember this color for a long time and no longer attack such insects (for example, wasps, bumblebees, ladybugs, Colorado beetles and a number of others).
Mimicry
Mimicry is the coloring and body shape of harmless animals that mimics their venomous counterparts. For example, some non-venomous snakes look like poisonous ones. Cicadas and crickets resemble large ants. Some butterflies have large spots on their wings that resemble the eyes of predators.
Physiological adaptations
This type of adaptation is associated with the restructuring of metabolism in organisms. For example, the emergence of warm-bloodedness and thermoregulation in birds and mammals. In more simple cases- this is an adaptation to certain forms of food, the salt composition of the environment, high or low temperatures, humidity or dryness of soil and air, etc.
Biochemical adaptations
Behavioral adaptations
This type of adaptation is associated with a change in behavior in certain conditions. For example, caring for offspring leads to better survival of young animals and increases the resilience of their populations. AT mating periods many animals form separate families, and in winter they unite in flocks, which facilitates their food or protection (wolves, many species of birds).
Adaptations to periodic environmental factors
These are adaptations to environmental factors that have a certain periodicity in their manifestation. This type includes daily alternations of periods of activity and rest, states of partial or complete anabiosis (dropping leaves, winter or summer diapauses of animals, etc.), animal migrations caused by seasonal changes etc.
Adaptations to extreme living conditions
Plants and animals that live in deserts and polar regions also acquire a number of specific adaptations. In cacti, the leaves have evolved into spines (to reduce evaporation and protect against being eaten by animals), and the stem has evolved into a photosynthetic organ and reservoir. Desert plants have a long root system that allows them to extract water from great depths. Desert lizards can survive without water by eating insects and obtaining water by hydrolyzing their fats. In northern animals, in addition to thick fur, there is also a large supply of subcutaneous fat, which reduces body cooling.
Relative nature of adaptations
All adaptations are expedient only for certain conditions in which they have developed. When these conditions change, adaptations can lose their value or even harm the organisms that have them. The white color of hares, which protects them well in the snow, becomes dangerous during winters with little snow or strong thaws.
The relative nature of adaptations is also well proven by paleontological data, which testify to the extinction of large groups of animals and plants that did not survive the change in living conditions.
Reactions to unfavorable environmental factors only under certain conditions are detrimental to living organisms, and in most cases they have an adaptive value. Therefore, these responses were called by Selye "general adaptation syndrome". In later works, he used the terms "stress" and "general adaptation syndrome" as synonyms.
Adaptation- this is a genetically determined process of formation of protective systems that provide an increase in stability and the flow of ontogenesis in unfavorable conditions for it.
Adaptation is one of the most important mechanisms that increases the stability of a biological system, including a plant organism, in the changed conditions of existence. The better the organism is adapted to some factor, the more resistant it is to its fluctuations.
The genotypically determined ability of an organism to change metabolism within certain limits, depending on the action of the external environment, is called reaction rate. It is controlled by the genotype and is characteristic of all living organisms. Most of the modifications that occur within the limits of the reaction norm are of adaptive significance. They correspond to changes in the habitat and provide better survival of plants under fluctuating environmental conditions. In this regard, such modifications are of evolutionary importance. The term "reaction rate" was introduced by V.L. Johansen (1909).
The greater the ability of a species or variety to modify in accordance with the environment, the wider its rate of reaction and the higher the ability to adapt. This property distinguishes resistant varieties of agricultural crops. As a rule, slight and short-term changes in environmental factors do not lead to significant violations. physiological functions plants. This is due to their ability to maintain the relative dynamic balance of the internal environment and the stability of the basic physiological functions in a changing external environment. At the same time, sharp and prolonged impacts lead to disruption of many functions of the plant, and often to its death.
Adaptation includes all processes and adaptations (anatomical, morphological, physiological, behavioral, etc.) that increase stability and contribute to the survival of the species.
1.Anatomical and morphological adaptations. In some representatives of xerophytes, the length of the root system reaches several tens of meters, which allows the plant to use groundwater and not experience a lack of moisture in conditions of soil and atmospheric drought. In other xerophytes, the presence of a thick cuticle, pubescence of leaves, and the transformation of leaves into spines reduce water loss, which is very important in conditions of lack of moisture.
Burning hairs and spines protect plants from being eaten by animals.
Trees in the tundra or at high mountain heights look like squat creeping shrubs, in winter they are covered with snow, which protects them from severe frosts.
In mountainous regions with large diurnal temperature fluctuations, plants often have the form of flattened pillows with densely spaced numerous stems. This allows you to keep moisture inside the pillows and a relatively uniform temperature throughout the day.
At the swamps and aquatic plants a special air-bearing parenchyma (aerenchyma) is formed, which is a reservoir of air and facilitates the breathing of plant parts immersed in water.
2. Physiological and biochemical adaptations. In succulents, an adaptation for growing in desert and semi-desert conditions is the assimilation of CO 2 during photosynthesis along the CAM pathway. These plants have stomata closed during the day. Thus, the plant keeps domestic reserves water from evaporation. In deserts, water is the main factor limiting plant growth. The stomata open at night, and at this time, CO 2 enters the photosynthetic tissues. The subsequent involvement of CO2 in the photosynthetic cycle occurs in the daytime already with closed stomata.
Physiological and biochemical adaptations include the ability of stomata to open and close, depending on external conditions. The synthesis in cells of abscisic acid, proline, protective proteins, phytoalexins, phytoncides, an increase in the activity of enzymes that counteract the oxidative breakdown of organic substances, the accumulation of sugars in cells and a number of other changes in metabolism contribute to an increase in plant resistance to adverse environmental conditions.
The same biochemical reaction can be carried out by several molecular forms of the same enzyme (isoenzymes), while each isoform exhibits catalytic activity in a relatively narrow range of some environmental parameter, such as temperature. The presence of a number of isoenzymes allows the plant to carry out the reaction in a much wider range of temperatures, compared with each individual isoenzyme. This enables the plant to successfully perform vital functions under changing temperature conditions.
3. Behavioral adaptations, or avoidance of an adverse factor. An example is ephemera and ephemeroids (poppy, starflower, crocuses, tulips, snowdrops). They go through the entire cycle of their development in the spring for 1.5-2 months, even before the onset of heat and drought. Thus, they kind of leave, or avoid falling under the influence of the stressor. In a similar way, early-ripening crop varieties form a crop before the onset of unfavorable conditions. seasonal events: August fogs, rains, frosts. Therefore, the selection of many agricultural crops is aimed at creating early ripe varieties. Perennial plants overwinter as rhizomes and bulbs in the soil under snow, which protects them from freezing.
Adaptation of plants to unfavorable factors is carried out simultaneously at many levels of regulation - from a single cell to a phytocenosis. The higher the level of organization (cell, organism, population), the greater the number of mechanisms simultaneously involved in the adaptation of plants to stress.
Regulation of metabolic and adaptive processes inside the cell is carried out with the help of systems: metabolic (enzymatic); genetic; membrane. These systems are closely related. Thus, the properties of membranes depend on gene activity, and the differential activity of the genes themselves is under the control of membranes. The synthesis of enzymes and their activity are controlled at the genetic level, at the same time, enzymes regulate the nucleic acid metabolism in the cell.
On the organism level to the cellular mechanisms of adaptation, new ones are added, reflecting the interaction of organs. Under unfavorable conditions, plants create and retain such a number of fruit elements that are provided in sufficient quantities with the necessary substances to form full-fledged seeds. For example, in inflorescences of cultivated cereals and in crowns fruit trees under adverse conditions, more than half of the laid 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 are sharply accelerated. At the same time, the substances necessary for plants move from them to young organs, responding to the survival strategy of the organism. Thanks to the recycling of nutrients from the lower leaves, the younger ones, the upper leaves, remain viable.
There are mechanisms of regeneration of lost organs. For example, the surface of the wound is covered with a secondary integumentary tissue (wound periderm), the wound on the trunk or branch is healed with influxes (calluses). With the loss of the apical shoot, dormant buds awaken in plants and lateral shoots develop intensively. Spring restoration of leaves instead of fallen ones in autumn is also an example of natural organ regeneration. Regeneration as a biological device that provides vegetative propagation of plants by root segments, rhizomes, thallus, stem and leaf cuttings, isolated cells, individual protoplasts, is of great practical importance for crop production, fruit growing, forestry, ornamental gardening, etc.
The hormonal system is also involved in the processes of protection and adaptation at the plant level. For example, under the influence of unfavorable conditions in a plant, the content of growth inhibitors sharply increases: ethylene and abscissic acid. They reduce metabolism, inhibit growth processes, accelerate aging, fall of organs, and the transition of the plant to a dormant state. Inhibition of functional activity under stress under the influence of growth inhibitors is a characteristic reaction for plants. At the same time, the content of growth stimulants in the tissues decreases: cytokinin, auxin and gibberellins.
On the population level selection is added, which leads to the appearance of more adapted organisms. The possibility of selection is determined by the existence of intrapopulation variability in plant resistance to various environmental factors. An example of intrapopulation variability in resistance can be the unfriendly appearance of seedlings on saline soil and an increase in the variation in germination time with an increase in the action of a stressor.
View in modern view consists of a large number of biotypes - smaller ecological units, genetically identical, but showing different resistance to environmental factors. AT various conditions not all biotypes are equally vital, and as a result of competition, only those of them that best meet the given conditions remain. That is, the resistance of a population (variety) to a particular factor is determined by the resistance of the organisms that make up the population. Resistant varieties have in their composition a set of biotypes that provide good productivity even in adverse conditions.
At the same time, in the process of long-term cultivation, the composition and ratio of biotypes in the population changes in varieties, which affects the productivity and quality of the variety, often not for the better.
So, adaptation includes all processes and adaptations that increase the resistance of plants to adverse environmental conditions (anatomical, morphological, physiological, biochemical, behavioral, population, etc.)
But to choose the most effective way adaptation is the main time during which the body must adapt to new conditions.
With the sudden action of an extreme factor, the response cannot be delayed, it must follow immediately in order to exclude irreversible damage to the plant. With long-term impacts of a small force, adaptive rearrangements occur gradually, while the choice of possible strategies increases.
In this regard, there are three main adaptation strategies: evolutionary, ontogenetic and urgent. The task of the strategy is the efficient use of available resources to achieve the main goal - the survival of the organism under stress. The adaptation strategy is aimed at maintaining the structural integrity of vital macromolecules and the functional activity of cellular structures, maintaining vital activity regulation systems, and providing plants with energy.
Evolutionary or phylogenetic adaptations(phylogeny - the development of a biological species in time) - these are adaptations that arise during the evolutionary process on the basis of genetic mutations, selection and are inherited. They are the most reliable for plant survival.
Each species of plants in the process of evolution has developed certain needs for the conditions of existence and adaptability to the ecological niche it occupies, a stable adaptation of the organism to the environment. Moisture and shade tolerance, heat resistance, cold resistance and others ecological features specific plant species were formed as a result of long-term action of the relevant conditions. Thus, heat-loving and short-day plants are characteristic of southern latitudes, less heat-demanding and long-day plants are characteristic of northern latitudes. Numerous evolutionary adaptations of xerophyte plants to drought are well known: economical use of water, deep-seated root system, shedding of leaves and transition to a dormant state, and other adaptations.
In this regard, varieties of agricultural plants show resistance precisely to those environmental factors against which breeding and selection of productive forms is carried out. If the selection takes place in a number of successive generations against the background of the constant influence of some unfavorable factor, then the resistance of the variety to it can be significantly increased. It is natural that the varieties bred by the Research Institute of Agriculture of the South-East (Saratov) are more resistant to drought than the varieties created in the breeding centers of the Moscow region. In the same way in ecological zones with unfavorable soil and climatic conditions, resistant local plant varieties have formed, and endemic plant species are resistant to the stressor that is expressed in their habitat.
Characterization of the resistance of spring wheat varieties from the collection of the All-Russian Institute of Plant Industry (Semenov et al., 2005)
| Variety | Origin | Sustainability |
| Enita | Moscow region | Medium drought resistant |
| Saratovskaya 29 | Saratov region | drought resistant |
| Comet | Sverdlovsk region. | drought resistant |
| Karazino | Brazil | acid resistant |
| Prelude | Brazil | acid resistant |
| Kolonias | Brazil | acid resistant |
| Thrintani | Brazil | acid resistant |
| PPG-56 | Kazakhstan | salt tolerant |
| Osh | Kyrgyzstan | salt tolerant |
| Surkhak 5688 | Tajikistan | salt tolerant |
| Messel | Norway | Salt tolerant |
In a natural environment, environmental conditions usually change very quickly, and the time during which the stress factor reaches a damaging level is not enough for the formation of evolutionary adaptations. In these cases, plants use not permanent, but stressor-induced defense mechanisms, the formation of which is genetically predetermined (determined).
Ontogenetic (phenotypic) adaptations are not associated with genetic mutations and are not inherited. The formation of such adaptations requires a relatively long time, so they are called long-term adaptations. One of these mechanisms is the ability of a number of plants to form a water-saving CAM-type photosynthesis pathway under conditions of water deficit caused by drought, salinity, low temperatures, and other stressors.
This adaptation is associated with the induction of the expression of "inactive" in normal conditions phosphoenolpyruvate carboxylase gene and genes of other enzymes of the CAM pathway of CO 2 uptake, 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 water consumption.
In field crops, for example, in corn, aerenchyma is absent under normal growing conditions. But under conditions of flooding and a lack of oxygen in the tissues in the roots, some of the cells of the primary cortex of the root and stem die (apoptosis, or programmed cell death). In their place, cavities are formed, through which oxygen is transported from the aerial part of the plant to the root system. The signal for cell death is the synthesis of ethylene.
Urgent adaptation occurs with rapid and intense changes in living conditions. It is based on the formation and functioning of shock protective systems. Shock defense systems include, for example, the heat shock protein system, which is formed in response to rapid rise temperature. These mechanisms provide short-term conditions for survival under the action of a damaging factor and thus create the prerequisites for the formation of more reliable long-term specialized adaptation mechanisms. An example of specialized adaptation mechanisms is the new formation of antifreeze proteins at low temperatures or the synthesis of sugars during the overwintering of winter crops. At the same time, if the damaging effect of the factor exceeds the protective and reparative capabilities of the body, then death inevitably occurs. In this case, the organism dies at the stage of urgent or at the stage of specialized adaptation, depending on the intensity and duration of the action of the extreme factor.
Distinguish specific and non-specific (general) plant responses to stressors.
Nonspecific reactions do not depend on the nature of the acting factor. They are the same under the action of high and low temperatures, lack or excess of moisture, high concentrations of salts in the soil or harmful gases in the air. In all cases, the permeability of membranes in plant cells increases, respiration is disturbed, the hydrolytic decomposition of substances increases, the synthesis of ethylene and abscisic acid increases, and cell division and elongation are inhibited.
The table shows a complex of nonspecific changes occurring in plants under the influence of various environmental factors.
Change physiological parameters in plants under stress conditions (according to G.V., Udovenko, 1995)
| Options | The nature of the change in parameters under conditions | |||
| droughts | salinity | high temperature | low temperature | |
| The concentration of ions in tissues | growing | growing | growing | growing |
| Water activity in the cell | Falling down | Falling down | Falling down | Falling down |
| Osmotic potential of the cell | growing | growing | growing | growing |
| Water holding capacity | growing | growing | growing | — |
| Water scarcity | growing | growing | growing | — |
| Protoplasm permeability | growing | growing | growing | — |
| Transpiration rate | Falling down | Falling down | growing | Falling down |
| Transpiration efficiency | Falling down | Falling down | Falling down | Falling down |
| Energy efficiency of breathing | Falling down | Falling down | Falling down | — |
| Breathing intensity | growing | growing | growing | — |
| Photophosphorylation | Decreases | Decreases | — | Decreases |
| Stabilization of nuclear DNA | growing | growing | growing | growing |
| Functional activity of DNA | Decreases | Decreases | Decreases | Decreases |
| Proline concentration | growing | growing | growing | — |
| Content of water-soluble proteins | growing | growing | growing | growing |
| Synthetic reactions | Suppressed | Suppressed | Suppressed | Suppressed |
| Ion uptake by roots | Suppressed | Suppressed | Suppressed | Suppressed |
| Transport of substances | Depressed | Depressed | Depressed | Depressed |
| Pigment concentration | Falling down | Falling down | Falling down | Falling down |
| cell division | slows down | slows down | — | — |
| Cell stretch | Suppressed | Suppressed | — | — |
| Number of fruit elements | Reduced | Reduced | Reduced | Reduced |
| Organ aging | Accelerated | Accelerated | Accelerated | — |
| biological harvest | Downgraded | Downgraded | Downgraded | Downgraded |
Based on the data in the table, it can be seen that the resistance of plants to several factors is accompanied by unidirectional physiological changes. This gives reason to believe that an increase in plant resistance to one factor may be accompanied by an increase in resistance to another. This has been confirmed by experiments.
Experiments at the Institute of Plant Physiology of the Russian Academy of Sciences (Vl. V. Kuznetsov et al.) have shown that short-term heat treatment of cotton plants is accompanied by an increase in their resistance to subsequent salinization. And the adaptation of plants to salinity leads to an increase in their resistance to high temperatures. Heat shock increases the ability of plants to adapt to the subsequent drought and, conversely, in the process of drought, the body's resistance to high temperature increases. Short-term exposure to high temperatures increases resistance to heavy metals and UV-B radiation. The preceding drought favors the survival of plants in conditions of salinity or cold.
The process of increasing the body's resistance to a given environmental factor as a result of adaptation to a factor of a different nature is called cross-adaptation.
To study the general (nonspecific) mechanisms of resistance, of great interest is the response of plants to factors that cause water deficiency in plants: salinity, drought, low and high temperatures, and some others. At the level of the whole organism, all plants react to water deficiency in the same way. Characterized by inhibition of shoot growth, increased growth of the root system, the synthesis of abscisic acid, and a decrease in stomatal conductance. After some time, the lower leaves rapidly age, and their death is observed. All these reactions are aimed at reducing water consumption by reducing the evaporating surface, as well as by increasing the absorption activity of the root.
Specific reactions are reactions to the action of any one stress factor. So, phytoalexins (substances with antibiotic properties) are synthesized in plants in response to contact with pathogens (pathogens).
The specificity or non-specificity of responses implies, on the one hand, the attitude of a plant to various stressors and, on the other hand, the characteristic reactions of plants of different species and varieties to the same stressor.
The manifestation of specific and nonspecific responses of plants depends on the strength of stress and the rate of its development. Specific responses occur more often if the stress develops slowly, and the body has time to rebuild and adapt to it. Nonspecific reactions usually occur with a shorter and stronger effect of the stressor. The functioning of nonspecific (general) resistance mechanisms allows the plant to avoid large energy expenditures for the formation of specialized (specific) adaptation mechanisms in response to any deviation from the norm in their living conditions.
Plant resistance to stress depends on the phase of ontogeny. The most stable plants and plant organs in a dormant state: in the form of seeds, bulbs; woody perennials - in a state of deep dormancy after leaf fall. Plants are most sensitive at a young age, since growth processes are damaged in the first place under stress conditions. The second critical period is the period of gamete formation and fertilization. The effect of stress during this period leads to a decrease in the reproductive function of plants and a decrease in yield.
If stress conditions are repeated and have a low intensity, then they contribute to the hardening of plants. This is the basis for methods for increasing resistance to low temperatures, heat, salinity, and an increased content of harmful gases in the air.
Reliability plant organism is determined by its ability to prevent or eliminate failures at different levels biological organization: molecular, subcellular, cellular, tissue, organ, organism and population.
To prevent disruptions in the life of plants under the influence of adverse factors principles redundancy, heterogeneity of functionally equivalent components, systems for the repair of lost structures.
The redundancy of structures and functionality is one of the main ways to ensure the reliability of systems. Redundancy and redundancy has multiple manifestations. At the subcellular level, the reservation and duplication of genetic material contribute to the increase in the reliability of the plant organism. This is provided, for example, by the double helix of DNA, by increasing the ploidy. The reliability of the functioning of the plant organism under changing conditions is also maintained due to the presence of a variety of messenger RNA molecules and the formation of heterogeneous polypeptides. These include isoenzymes that catalyze the same reaction, but differ in their physical and chemical properties and the stability of the molecular structure under changing environmental conditions.
At the cellular level, an example of redundancy is an excess of cellular organelles. Thus, it has been established that a part of the available chloroplasts is sufficient to provide the plant with photosynthesis products. The remaining chloroplasts, as it were, remain in reserve. The same applies to general content chlorophyll. The redundancy also manifests itself in a large accumulation of precursors for the biosynthesis of many compounds.
At the organismic level, the principle of redundancy is expressed in the formation and laying at different times of more shoots, flowers, spikelets than is required for the change of generations, in a huge amount of pollen, ovules, seeds.
At the population level, the principle of redundancy is manifested in a large number of individuals that differ in resistance to a particular stress factor.
Repair systems also work at different levels - molecular, cellular, organismal, population and biocenotic. Reparative processes go with the expenditure of energy and plastic substances, therefore, reparation is possible only if a sufficient metabolic rate is maintained. If metabolism stops, then reparation also stops. In extreme conditions of the external environment, the preservation of respiration is especially important, since it is respiration that provides energy for reparation processes.
The regenerative ability of cells of adapted organisms is determined by the resistance of their proteins to denaturation, namely, the stability of the bonds that determine the secondary, tertiary, and quaternary structure of the protein. For example, the resistance of mature seeds to high temperatures is usually associated with the fact that, after dehydration, their proteins become resistant to denaturation.
The main source of energy material as a substrate for respiration is photosynthesis, therefore, the energy supply of the cell and related reparation processes depend on the stability and ability of the photosynthetic apparatus to recover from damage. To maintain photosynthesis under extreme conditions in plants, the synthesis of thylakoid membrane components is activated, lipid oxidation is inhibited, and the plastid ultrastructure is restored.
At the organismic level, an example of regeneration is the development of replacement shoots, the awakening of dormant buds when growth points are damaged.
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