Environmental factors are very diverse, and each species, experiencing their influence, responds to it differently. There are general laws that govern the responses of organisms to any environmental factor.

1. Law of Optimum

Reflects how living organisms tolerate different strengths of environmental factors.

The law of optimum is expressed in the following: any environmental factorhas certain limits of positive effect on living organisms.

For example, animals and plants do not tolerate extreme heat and severe frost; Medium temperatures are optimal. On the graph, the law of optimum is expressed by a symmetrical curve showing how the life activity of a species changes with a constant increase in the influence of the factor.

Curves similar to the one shown in this figure are called tolerance curves (from the Greek tolerance - patience, stability).

In the center under the curve - optimum zone. At optimal values ​​of the factor, organisms actively grow and reproduce. When the curve slopes down on either side of the optimum - pessimum zones. When the curve intersects the horizontal axis, there are 2 critical points. These are the values ​​of the factor that organisms can no longer withstand, beyond which death occurs. Conditions close to critical points are especially difficult for survival. Such conditions are called extreme.

Curves with very sharp peaks mean that the range of conditions under which the body's activity reaches its maximum is very narrow. Flat curves correspond to a wide tolerance range.

Organisms with wide margins of resistance have a chance of becoming more widespread.

But during the life of an individual, its tolerance may change if the individual falls into other external conditions, then after a while the body gets used to it and adapts to them.

Changes in the physiological optimum, or shifts in the dome of the tolerance curve - adaptation or acclimatization . For example, the ecotype of jellyfish.

2. Law of the minimum.

Formulatedn founder of the science of mineral fertilizers Justus Liebig(1803-1873).

Liebig discovered that plant yield can be limited by any of the basic nutrients if that element is in short supply.

Law of the minimum. The successful survival of living organisms depends on a complex of conditions; The limiting factor is the factor that deviates the most from the optimal values ​​for the body.

For example, oxygen is a factor of physiological necessity for all animals, but from an ecological point of view it becomes limiting only in certain habitats. Fish are dying in the river - you need to measure the oxygen concentration. Birds are dying due to another factor.

Currently, the number of environmental factors that have one or another effect on living organisms is quite large. And if the effect of some (ambient temperature, humidity, etc.) is already very well known to scientists, then, for example, the change in gravitational forces has not yet been fully studied. At the same time, a number of patterns can be traced in the nature of the impact of all environmental factors.

The concept of the law of optium

The law of optimum formulated by V. Shelford describes the presence of an optimal value of an environmental factor at which the existence of an individual organism or a biocenosis as a whole is possible. Outside the optimum zone there are zones of oppression, beyond which the existence of life is not possible.

The different attitudes of organisms to the effects of various environmental factors are very important. Thus, the body exhibits its maximum capabilities when the factors comprehensively reach the optimum point.

As shown in the figure, between the critical points there is a certain zone of environmental tolerance, within which the organism can still somehow exist. In the nai to a greater extent this characteristic depends on the habitat of living organisms.

Diversity of individual reactions of organisms to environmental factors

As is known, the optimum zones for various organisms are within different limits. Those organisms for which they have a significant range are called eurybionts. Organisms with a narrow tolerance range are called stenobionts. For example, in an environment that is relatively stable in its properties, stenobionts predominate, while in a dynamic environment more eurybionts have a chance to survive.

However, as a rule, environmental valence does not remain the same for an organism throughout its life. For example, insect larvae are stenobionts in relation to temperature, while adult insects can be eurybionts.

Note 1

It is worth noting that the effect of each environmental factor has a different effect on the functions of the body. For example, high temperature in cold-blooded organisms can increase the metabolic rate, but at the same time slow it down motor activity. Crab larvae live in fresh water are not capable, while adult individuals are very often found in the estuarine zone of rivers.

Interaction of environmental factors

Scientists have long proven the possibility of shifting endurance limits relative to any environmental factor depending on the strength of the simultaneous influence of other factors. For example, species that have adapted to live in a wide range of temperature conditions may not be able to withstand fluctuations in soil moisture or water salinity. At the same time, some environmental factors can easily enhance or mitigate the effect of other factors. For example, reducing air humidity can mitigate excess heat. And an increase in the amount of moisture and a decrease in air temperature can slow down the process of plant withering.

Increased concentration carbon dioxide in the air can compensate for the lack of light to ensure photosynthesis, etc. However, this does not mean that the factors are interchangeable. For example, optimal soil conditions will not compensate complete absence light, which will soon lead to the death of the plant.

Note 2

Based on all of the above, it follows that the existence of living organisms on our planet is possible only with an optimal balance of environmental factors.

Biotic factors.

Biotic factors are a set of influences of the life activity of some organisms on the life activity of others, as well as on inanimate nature.

Classification of biotic interactions:

1. Neutrality - no population affects another.

2. Competition is the use of resources (food, water, light, space) by one organism, which thereby reduces the availability of this resource for another organism.

Competition can be intraspecific and interspecific. If the population size is small, then intraspecific competition is weak and resources are available in abundance. At high population densities, intense intraspecific competition reduces resource availability to a level that inhibits further growth, thereby regulating population size.

Interspecific competition is an interaction between populations that adversely affects their growth and survival. When the Carolina squirrel was brought to Britain from North America, its numbers decreased common squirrel, because the Carolina squirrel turned out to be more competitive.

Competition can be direct and indirect.

Direct is intraspecific competition associated with the struggle for habitat, in particular the protection of individual areas in birds or animals, expressed in direct collisions. If there is a lack of resources, it is possible to eat animals of their own species (wolves, lynxes, predatory bugs, spiders, rats, pike, perch, etc.)

Indirect - between shrubs and herbaceous plants in California. The type that settles first excludes the other type. Fast-growing, deep-rooted grasses reduced the soil moisture content to levels unsuitable for shrubs. And the tall bushes shaded the grasses, preventing them from growing due to lack of light.

Inside the owner. Viruses, bacteria, primitive fungi - plants. Worms are animals. High fertility. Does not lead to the death of the owner, but inhibits vital processes

4. Predation - the eating of one organism (prey) by another organism (predator).

Predators can eat herbivores and also weak predators. Predators have wide range food, easily switch from one prey to another more accessible one.

Predators often attack weak prey. The mink destroys sick and old muskrats, but does not attack adult individuals.

Ecological balance is maintained between prey-predator populations.

5. Symbiosis - cohabitation of two organisms different types in which organisms benefit each other. According to the degree of partnership, symbiosis is:

Commensalism - one organism feeds at the expense of another without harming it. Cancer - sea anemone. The sea anemone attaches to the shell, protecting it from enemies, and feeds on leftover food.

Mutualism - both organisms benefit, but they cannot exist without each other. Lichen - mushroom + algae. The fungus protects the algae, and the algae feeds it.

Under natural conditions, one species will not lead to the destruction of another species.

General patterns effects of environmental factors

Due to the extreme diversity of environmental factors, different types of organisms, experiencing their influence, respond to it differently, however, it is possible to identify a number general laws(patterns) of the action of environmental factors. Let's look at some of them.

1. The law of optimum is expressed in the fact that any environmental factor has limits of positive influence on living organisms.

The impact of environmental factors is constantly changing. Only in certain places planets, the values ​​of some of them are more or less constant (constant). For example: at the bottom of the oceans, in the depths of caves, the temperature and water regimes, lighting mode.

Let's consider the operation of the law of optimum using a specific example: animals and plants do not tolerate both extreme heat and severe frost; average temperatures are optimal for them - the so-called optimum zone. The greater the deviation from the optimum, the more this environmental factor inhibits the vital activity of the organism. This zone is called the pessimum zone. It has critical points - “maximum factor value” and “minimum factor value”; beyond their limits, the death of organisms occurs. The distance between the minimum and maximum values ​​of the factor is called the ecological valence or tolerance of the organism (Fig. 1).

An example of the manifestation of this law: roundworm eggs develop at t° = 12-36°, and the optimal temperature for their development is t° = 30°. That is, the ecological tolerance of roundworms according to temperature conditions ranges from 12° to 36°.

By the nature of tolerance the following types:

Eurybiont - having a broad ecological valency in relation to abiotic environmental factors; are divided into eurythermal (tolerating significant temperature fluctuations), eurybate (tolerating a wide range of pressure indicators), euryhaline (tolerating varying degrees salinity of the environment).

Stenobiont - unable to tolerate significant fluctuations in the manifestation of a factor (for example, polar bears are stenothermic, pinnipeds mammals living at low temperatures).

2. The law of ecological individuality of species was formulated in 1924 by the Russian botanist L.G. Ramensky: the ecological spectra (tolerance) of different species do not coincide; each species is specific in its ecological capabilities. This law can be illustrated in Fig. 2.

3. The law of the limiting (limiting) factor states that the most significant factor for the body is the one that deviates most from its optimal value. The law was established in 1905 by the English scientist Blacker.

It is on this minimally (or maximally) represented environmental factor at a given moment that the survival of the organism depends. At other times, other factors may be limiting. During their lives, individuals of species encounter a variety of limitations to their life activities. Thus, the factor limiting the spread of deer is the depth of the snow cover; moths of the winter cutworm (a pest of vegetable and grain crops) - winter temperature etc.

This law is taken into account in practice agriculture. The German chemist J. Liebig established that the productivity of cultivated plants, first of all, depends on the nutrient (mineral element) that is most poorly represented in the soil. For example, if phosphorus in the soil contains only 20% of the required norm, and calcium - 50%, then the limiting factor will be the lack of phosphorus; It is necessary, first of all, to add phosphorus-containing fertilizers to the soil.

J. Liebig called this rule the “rule of the minimum”, as he studied the effect of insufficient doses of fertilizers. Later it turned out that an excess of mineral salts in the bud also reduces yield, since this disrupts the ability of the roots to absorb salt solutions.

Limiting environmental factors determine the geographic range of a species. The nature of these factors may be different. Thus, the movement of the species to the north may be limited by a lack of heat, to arid regions - by a lack of moisture or too much high temperatures. A factor limiting the spread may also be biotic relationships, for example, the territory being occupied by a stronger competitor or the lack of pollinators for plants. Thus, pollination of figs depends entirely on a single species of insect - the wasp Blastophaga psenes. The homeland of this tree is the Mediterranean. Figs introduced to California did not bear fruit until pollinating wasps were introduced there. The distribution of legumes in the Arctic is limited by the distribution of the bumblebees that pollinate them. On Dikson Island, where there are no bumblebees, legumes are not found, although temperature conditions the existence of these plants there is still permissible.

To determine whether a species can exist in a given geographic area, it is necessary first to determine whether any environmental factors exceed the limits of its ecological valency, especially during the most vulnerable period of development.

Identification of limiting factors is very important in agricultural practice, since by directing the main efforts to their elimination, one can quickly and effectively increase plant yields or animal productivity. Thus, on highly acidic soils, the wheat yield can be slightly increased by using various agronomic influences, but the best effect will be obtained only as a result of liming, which will remove the limiting effects of acidity. Knowledge of limiting factors is thus the key to controlling the life activities of organisms. IN different periods the lives of individuals act as limiting various factors environment, therefore skillful and constant regulation of the living conditions of grown plants and animals is required.

4. The law of ambiguous action: the action of each environmental factor is ambiguous at different stages of organism development. Examples of its manifestation can be the following data:

Water is vital for the development of tadpoles, but for an adult frog it is not a vital condition;

Critical minimum temperature for adult individuals of the moth moth = -22°, and for caterpillars of this species the critical value is t = -7°.

Each factor affects different body functions differently. The optimum for some processes may be a pessimum for others. Thus, air temperature from +40 to +45°C in cold-blooded animals greatly increases the rate of metabolic processes in the body, but inhibits motor activity, and the animals fall into thermal stupor. For many fish, the water temperature that is optimal for the maturation of reproductive products is unfavorable for spawning, which occurs at a different temperature range.

Life cycle, in which during certain periods the organism primarily performs certain functions (nutrition, growth, reproduction, settlement, etc.), is always consistent with seasonal changes in a complex of environmental factors. Mobile organisms can also change habitats to successfully carry out all their vital functions.

5. The law on direct and indirect factors: environmental factors, based on their impact on organisms, are divided into direct and indirect.

Direct environmental factors act on organisms directly, directly (wind, rain or snow, the composition of the mineral components of the soil, etc.).

Indirect environmental factors act indirectly, redistributing direct factors. For example: relief (indirect factor) “redistributes” the action of such direct factors as wind, precipitation, nutrients; the physical properties of the soil (mechanical composition, moisture capacity, etc.) as indirect factors “redistribute” the action of direct factors - chemical properties.

6. The law of interaction of environmental factors: the optimal zone and limits of endurance of organisms in relation to any factor can shift depending on the combination with which other factors the influence is carried out.

So, it is easier to endure the heat in dry, rather than in humid air; frost is less tolerated in combination with windy weather, etc.

This pattern is taken into account in agricultural practice to maintain optimal conditions vital activity of cultivated plants. For example, if there is a threat of frost on the soil, which occurs in middle lane even in May, the plants are watered abundantly at night.

7. V. Shelfold’s law of tolerance.

Most fully and in the most general view the entire complexity of environmental factors on an organism is reflected by the law of tolerance: the absence or impossibility of prosperity is determined by a deficiency (in qualitative or quantitative terms) or, conversely, an excess of any of a number of factors, the level of which may be close to the limits tolerated by a given organism. These two limits are called tolerance limits.

Regarding the action of one factor, this law can be illustrated as follows: a certain organism is capable of existing at temperatures from -5°C to 25°C, i.e. its tolerance range lies within these temperatures. Organisms whose life requires conditions limited to a narrow range of temperature tolerance are called stenothermic, and those capable of living in a wide range of temperatures are called eurythermal.

Similar to temperature, other limiting factors act, and organisms, in relation to the nature of their influence, are called, respectively, stenobionts and eurybionts. For example, they say: an organism is stenobiotic in relation to humidity, or eurybiontic in relation to climatic factors. Organisms that are eurybiont to the main climatic factors are the most widespread on Earth.

The range of tolerance of the organism does not remain constant - it, for example, narrows if any of the factors is close to any limit, or during the reproduction of the organism, when many factors become limiting. This means that the nature of the action of environmental factors under certain conditions can change, i.e. it may or may not be limiting.

9. Classification of living organisms by the nature of nutrition (autotrophs, heterotrophs, mixotrophs), by the method of obtaining food. Life forms of plants (phanerophytes, chamephytes, cryptophytes, etc.). Life forms of animals. Classification of organisms by participation in the biological cycle (producers, consumers, decomposers).

Modern ideas about plant and animal populations. Classification and structure of populations. Population dynamics.

Certain types external structure, which arose as adaptations to the ecological conditions of the habitat, are called life forms of organisms.

Among the adaptations of organisms to environmental conditions that arose as a result of evolution, the most obvious can be considered adaptations (adaptations) that manifest themselves in the features of the external structure of plants and animals. They are called morphological (from the Greek morphe? form). Certain types external structure, which arose as adaptations to the ecological conditions of habitats, are called life forms of organisms.

The life forms of plants and animals are very diverse. They are distinguished by a combination of structural characteristics and lifestyle. So, the most widespread life forms plants? trees, shrubs, herbs. The latter are divided into aquatic and terrestrial, among which, in turn, various forms are also distinguished. Vivid examples adaptations to harsh conditions environments provide life forms of plants such as succulents (in arid climate), lianas (with a lack of light), dwarf trees and cushion plants (in tundras, highlands with low temperatures and dryness with strong winds).

The life forms of animals are distinguished according to different characteristics for different systematic groups. Thus, for animals, one of the main characteristics for identifying life forms, in addition to the habitat, is considered to be methods of movement (walking, running, jumping, swimming, crawling). Characteristics the external structure of ground jumpers, for example, are long hind limbs with highly developed muscles of the thighs, long tail, short neck. These usually include residents open spaces: Asian jerboas, Australian kangaroos, African jumpers and other jumping mammals living on different continents.

The life forms of birds are distinguished by the type of their habitat and the method of obtaining food, but in fish? mainly by body shape. The life forms of the inhabitants of reservoirs are also distinguished by the type of their habitat. Thus, in the water column, small organisms form plankton (from the Greek planktos? wandering), that is, a collection of organisms living in suspension and unable to resist currents. The inhabitants of the soil form benthos (from the Greek benthos? depth). Individual life forms include organisms living near the surface film of water or on various solid substrates.

Similar life forms arose as a result of evolution occurring in similar ecological conditions in systematically different organisms: for example, kangaroos and jerboas, dolphins and fish, birds and bats, worms and snakes, etc.

It cannot be assumed that, having undergone a number of profound changes in the process of evolution and achieving great diversity, wildlife frozen in an unchanged form. She keeps changing. And this ability of organisms to change is the most important factor ensuring compliance between organisms and their environment.

Population is a collection of individuals of the same species occupying a certain area, freely interbreeding with each other, having a common origin, genetic basis and, to one degree or another, isolated from other populations of a given species.

The most important property of populations is self-reproduction. Even despite spatial separation, populations are able to maintain their existence in a given habitat indefinitely. They are groupings of individuals of the same species that are stable in time and space. The term “population” does not apply to a flock of fish or sparrows. Such groups can easily disintegrate under the influence external factors or mingle with others. In other words, they are unable to reproduce themselves sustainably. This is only possible for large groups that have the basic properties of the species and are represented by all categories of individuals composing it. These are, for example, all the perch in a lake or all the pine trees in a forest.

Obviously, the sets of conditions in different habitats may differ somewhat. Under the influence different conditions In individual populations, properties can arise and accumulate that distinguish them from each other. This may manifest itself in small deviations in the structure of organisms belonging to different populations, their physiological indicators (remember the phenomenon of acclimatization) and other characteristics. Thus, populations, like individual organisms, exhibit variability. As among organisms, among populations it is impossible to find two completely identical.

Variability, as you already know, most important factor evolution. Population variability increases the internal diversity of a species. This, in turn, increases the resistance of the species to local (local) changes in living conditions, allows it to penetrate and gain a foothold in new conditions and areas. We can say that existence in the form of populations enriches the species, ensures its integrity and constant self-maintenance of the basic species properties.

Populations living in different parts of the species' range (the general area of ​​distribution of the species) do not live in isolation. Do they interact with populations of other species, forming biotic communities with them? complete systems even more high level organizations. In each community, the population of a given species plays its assigned role, occupying a certain ecological niche and, together with populations of other species, ensuring the sustainable functioning of the community.

Ecologists who study ecological systems view populations as their basic elements. It is through the functioning of populations that conditions are created that support life.

The nature and extent of use is determined not by individual organisms, but by populations. various types resources. The circulation of substances depends on populations, energy metabolism between living and inanimate nature. Joint activities populations determines many important properties of biotic communities and ecological systems.

Based on the above, we can give a broader definition of population. Population? a relatively isolated group of organisms of the same species, which has the ability to self-maintain species properties and performs a certain role in the community of living organisms.

The population has not only biological properties its constituent organisms, but also its own, which are inherent only to this group of individuals as a whole. Like an individual organism, a population grows, improves, and supports itself. However, group properties, for example abundance, fertility, mortality, age composition, can only characterize the population as a whole and are not applicable to its individual individuals.

The organisms that make up a population are connected to each other by various relationships: they jointly participate in reproduction, they can compete with each other for certain types of resources, they can eat each other or together defend themselves from a predator. Internal relationships in populations are very complex. Therefore, the reactions of individual individuals to changes in certain environmental factors and population reactions often do not coincide. The death of individual organisms (for example, from predators) can improve the qualitative composition of the population (the weak die, the strong remain), and increase its ability to self-sustain in numbers. Here we are faced with one very important rule, applicable to environmental objects consisting of many elements connected to each other by various relationships: about the state ecological object(be it a population, community or ecosystem) cannot always be judged by the state of its individual elements.

Demographic indicators. Population characteristics such as abundance, fertility, mortality, and age composition are called demographic indicators. Knowing them is very important for understanding the laws governing the life of populations and predicting the constant changes occurring in them.

The study of demographic indicators is of great importance practical significance. Thus, when harvesting wood, it is very important to know the rate of forest restoration in order to correctly plan the intensity of felling. Some animal populations are used to obtain valuable food or fur raw materials. The study of other populations (for example, small rodents, among which pathogens of diseases dangerous to humans circulate) is important from a medical point of view.

In all these cases, we are primarily interested in changes in the population as a whole, in predicting these changes and in regulating them (for example, reducing the number of agricultural pests). Essential for this is knowledge of the causes and rates of population changes, as well as the ability to measure these natural objects.

11. 300 thousand – 3 million

The object of study of demecology, or population ecology, serves the population. It is defined as a group of organisms of the same species (within which individuals can exchange genetic information), occupying a specific space and functioning as part of a biotic community. Each individual of the population is a carrier of a unique adaptive complex, but since there is interaction between members of the population, the entire group as a whole, i.e. population influences the properties of the biotic community. We can say that the species that make up a biotic community participate in its life activity in the form of populations.

The population is characterized by a number of characteristics; their only carrier is the group, but not the individuals in this group. The most important property of a population is density, i.e. the number of individuals assigned to a certain unit of space.

The main results of the review of factors that control population density can be formulated in the form of four conclusions.

1. Factors of population dynamics are divided into modifying and regulating. Modifying factors can act directly and indirectly (for example, through changes in the population size of a predator). A biotic factors often have a modifying effect.

2. According to the nature of reactions to factors of population dynamics, one should distinguish, on the one hand, equilibrium populations and, on the other, opportunistic ones. The former are characterized by low fertility, long duration life of individuals, low rates of population renewal, relative independence of individuals from climatic conditions. Opportunistic populations, on the contrary, are distinguished by high fertility of individuals, shorter life expectancy of individuals, often a large number of generations per year, and greater dependence of individuals on climatic conditions.

Regulation of the number of equilibrium populations is determined primarily by biotic factors. Among them, the main factor is often intraspecific competition, as, for example, in birds that fight for places convenient for nesting.

Regulation of the number of opportunistic populations is determined primarily by abiotic factors. When favorable climatic conditions the rapid development of individuals allows them to multiply greatly in a short period of time; towards the end of the favorable period, the combined effects of climate, predators and disease rapidly reduce the population size.

3. In areas with a relatively stable and favorable climate for reproduction, biotic factors play a major role; in areas with a less favorable climate and especially with a distinct winter period, climatic factors play a decisive role.

4. Finally, the stability of populations depends on the degree of complexity of the ecosystem. The more complex the ecosystem, the larger number interacting species, the more stable the populations.

12. Community is a collection of organisms of all species living in a certain territory and interacting with each other.

Properties -

1) Species composition

2) The ratio of species by abundance

3) Types – widespread, common, rare, isolated.

4) The ratio of species by type of nutrition: producers, consumers, herbivores, predators, scavengers, decomposers.

Related information.

Environmental factors are dynamic, variable in time and space. The warm season regularly gives way to the cold season, fluctuations in temperature and humidity are observed during the day, day follows night, etc. All these are natural (natural) changes in environmental factors. Also, as mentioned above, people can intervene in them, changing either the regimes of environmental factors (absolute values ​​or dynamics) or their composition (for example, developing, producing and using plant protection products that previously did not exist in nature, mineral fertilizers, etc. ).

Despite the variety of environmental factors, the different nature of their origin, their variability in time and space, it is possible to identify general patterns of their impact on living organisms.

The concept of optimum. Liebig's law of the minimum

Each organism, each ecosystem develops under a certain combination of factors: moisture, light, heat, the presence and composition of nutritional resources. All factors act on the body simultaneously. The body's reaction depends not so much on the factor itself, but on its quantity (dose). For each organism, population, ecosystem, there is a range of environmental conditions - a range of stability within which the life activity of objects occurs ( Fig.2).

Fig.2.

In the process of evolution, organisms have developed certain requirements for environmental conditions. The dose of factors at which the body achieves the best development and maximum productivity corresponds to optimal conditions. With a change in this dose towards a decrease or increase, the organism is depressed and the greater the deviation of the values ​​of factors from the optimum, the greater the decrease in viability, until its death. Conditions under which vital activity is maximally suppressed, but the organism still exists, are called pessimal. For example, in the south the limiting factor is moisture availability. Thus, in Southern Primorye, optimal forest conditions are characteristic of the northern slopes of the mountains in their middle part, and pessimal conditions are characteristic of the dry southern slopes with a convex surface.

The fact that limiting the dose (or absence) of any of the substances necessary for the plant, related to both macro and microelements, leads to the same result - a slowdown in growth and development, has been discovered and studied German chemist Eustace von Liebig. The rule he formulated in 1840 is called Liebig’s law of minimum: the greatest influence on plant endurance is exerted by those factors that are at a minimum in a given habitat.2 At the same time, Yu. Liebig, conducting experiments with mineral fertilizers, drew a barrel with holes, showing that the bottom hole in the barrel determines the level of liquid in it.

The law of the minimum is true for both plants and animals, including humans, who in certain situations have to use mineral water or vitamins to compensate for the lack of any elements in the body.

A factor whose level is close to the endurance limits of a particular organism is called limiting. And it is to this factor that the body adapts (develops adaptations) in the first place. For example, normal survival of sika deer in Primorye occurs only in oak forests on the southern slopes, because here the thickness of the snow is insignificant and provides the deer with a sufficient food supply for winter period. The limiting factor for deer is deep snow.

Subsequently, clarifications were made to Liebig's law. An important amendment and addition is the law of ambiguous (selective) action of a factor on various functions of the body: any environmental factor has an uneven effect on the functions of the body; the optimum for some processes, such as respiration, is not optimal for others, such as digestion, and vice versa.

E. Rübel in 1930 established the law (effect) of compensation (interchangeability) of factors: the absence or deficiency of some environmental factors can be compensated by another close (similar) factor.

For example, a lack of light can be compensated for a plant by an abundance of carbon dioxide, and when shellfish build shells, the missing calcium can be replaced with strontium. However, the compensatory capabilities of the factors are limited. Not a single factor can be completely replaced by another, and if the value of at least one of them goes beyond the upper or lower limits of the body’s endurance, the existence of the latter becomes impossible, no matter how favorable the other factors are.

In 1949 V.R. Williams formulated the law of irreplaceability of fundamental factors: the complete absence of fundamental environmental factors (light, water, etc.) in the environment cannot be replaced by other factors.

This group of refinements of Liebig's law includes a slightly different rule of phase reactions "benefit - harm": low concentrations of a toxicant act on the body in the direction of enhancing its functions (stimulating them), while higher concentrations inhibit or even lead to its death.

This toxicological pattern is true for many (for example, it is known medicinal properties low concentrations snake venom), but not all toxic substances.

The history of environmental knowledge goes back many centuries. Already primitive people needed to have certain knowledge about plants and animals, their way of life, relationships with each other and with environment. As part of the general development of the natural sciences, there was also an accumulation of knowledge that now belongs to the field of environmental science. Ecology emerged as an independent discipline in the 19th century.

The term Ecology (from the Greek eco - house, logos - teaching) was introduced into science by the German biologist Ernest Haeckel.

In 1866, in his work “General Morphology of Organisms,” he wrote that this is “... the sum of knowledge related to the economics of nature: the study of the entire set of relationships between an animal and its environment, both organic and inorganic, and, above all, its friendly or hostile relations with those animals and plants with which it directly or indirectly comes into contact.” This definition classifies ecology as a biological science. At the beginning of the 20th century. the formation of a systematic approach and the development of the doctrine of the biosphere, which is a vast field of knowledge, including many scientific areas of both the natural and humanitarian cycles, including general ecology, led to the spread of ecosystem views in ecology. The main object of study in ecology has become the ecosystem.

An ecosystem is a collection of living organisms that interact with each other and with their environment through the exchange of matter, energy and information in such a way that unified system remains stable for a long time.

The ever-increasing human impact on the environment has made it necessary to once again expand the boundaries of environmental knowledge. In the second half of the 20th century. scientific and technological progress has entailed a number of problems that have received global status, thus, in the field of view of ecology, the issues of comparative analysis of natural and man-made systems and the search for ways of their harmonious coexistence and development have clearly emerged.

Accordingly, the structure of environmental science differentiated and became more complex. Now it can be represented as four main branches, further divided: Bioecology, geoecology, human ecology, applied ecology.

Thus, we can define ecology as a science about the general laws of functioning of ecosystems of various orders, a set of scientific and practical issues of the relationship between man and nature.

2. Environmental factors, their classification, types of effects on organisms

Any organism in nature experiences the effects of a wide variety of components external environment. Any properties or components of the environment that influence organisms are called environmental factors.

Classification of environmental factors. Environmental factors (ecological factors) are diverse, have different natures and specific actions. The following groups of environmental factors are distinguished:

1. Abiotic (factors of inanimate nature):

a) climatic - lighting conditions, temperature conditions, etc.;

b) edaphic (local) - water supply, soil type, terrain;

c) orographic - air (wind) and water currents.

2. Biotic factors are all forms of influence of living organisms on each other:

Plants Plants. Plants Animals. Plants Mushrooms. Plants Microorganisms. Animals Animals. Animals Mushrooms. Animals Microorganisms. Mushrooms Mushrooms. Fungi Microorganisms. Microorganisms Microorganisms.

3. Anthropogenic factors are all forms of activity of human society that lead to changes in the habitat of other species or directly affect their lives. The impact of this group of environmental factors is rapidly increasing from year to year.

Types of impact of environmental factors on organisms. Environmental factors have various impacts on living organisms. They may be:

Stimuli that contribute to the emergence of adaptive (adaptive) physiological and biochemical changes ( hibernation, photoperiodism);

Limiters that change the geographical distribution of organisms due to the impossibility of existence in given conditions;

Modifiers that cause morphological and anatomical changes in organisms;

Signals indicating changes in other environmental factors.

General patterns of action of environmental factors:

Due to the extreme diversity of environmental factors, different types of organisms, experiencing their influence, respond to it differently, however, it is possible to identify a number of general laws (patterns) of the action of environmental factors. Let's look at some of them.

1. Law of optimum

2. The law of ecological individuality of species

3. Law of the limiting (limiting) factor

4. The law of ambiguous action

3. Patterns of action of environmental factors on organisms

1) Optimum rule. For an ecosystem, an organism or a certain stage of it

development there is a range of the most favorable value of the factor. Where

factors are favorable; population density is maximum. 2) Tolerance.

These characteristics depend on the environment in which the organisms live. If she

stable in its own way

yours, it has a greater chance for organisms to survive.

3) Rule of interaction of factors. Some factors may enhance or

mitigate the effect of other factors.

4) Rule of limiting factors. A factor that is deficient or

excess negatively affects organisms and limits the possibility of manifestation. strength

the action of other factors. 5) Photoperiodism. Under photoperiodism

understand the body's reaction to the length of the day. Reaction to changes in light.

6) Adaptation to the rhythm of natural phenomena. Adaptation to daily and

seasonal rhythms, tidal phenomena, solar activity rhythms,

lunar phases and other phenomena that repeat with strict frequency.

Ek. valence (plasticity) - ability to org. adapt to dep. environmental factors environment.

Patterns of the action of environmental factors on living organisms.

Environmental factors and their classification. All organisms are potentially capable of unlimited reproduction and dispersal: even species leading an attached lifestyle have at least one developmental phase in which they are capable of active or passive dispersal. But at the same time species composition organisms living in different climatic zones, does not mix: each of them has a specific set of species of animals, plants, and fungi. This is explained by the limitation of excessive reproduction and dispersal of organisms by certain geographical barriers (seas, mountain ranges, deserts, etc.), climatic factors (temperature, humidity, etc.), as well as relationships between individual species.

Depending on the nature and characteristics of the action, environmental factors are divided into abiotic, biotic and anthropogenic (anthropic).

Abiotic factors are components and properties of inanimate nature that directly or indirectly affect individual organisms and their groups (temperature, light, humidity, gas composition of air, pressure, salt composition of water, etc.).

A separate group of environmental factors includes various shapes human economic activities that change the state of the habitat of various species of living beings, including humans themselves (anthropogenic factors). For relatively short period human existence as biological species, its activities have radically changed the face of our planet and this impact on nature is increasing every year. The intensity of the action of some environmental factors can remain relatively stable over long historical periods of development of the biosphere (for example, solar radiation, gravity, salt composition of sea water, gas composition of the atmosphere, etc.). Most of them have variable intensity (temperature, humidity, etc.). The degree of variability of each environmental factor depends on the characteristics of the organisms’ habitat. For example, the temperature on the soil surface can vary significantly depending on the time of year or day, weather, etc., while in reservoirs at depths of more than several meters there are almost no temperature differences.

Changes in environmental factors can be:

Periodic, depending on the time of day, time of year, the position of the Moon relative to the Earth, etc.;

Non-periodic, for example, volcanic eruptions, earthquakes, hurricanes, etc..;

Directed over significant historical periods of time, for example, changes in the Earth's climate associated with a redistribution of the ratio of land areas and the World Ocean.

Each of the living organisms constantly adapts to the entire complex of environmental factors, that is, to the habitat, regulating life processes in accordance with changes in these factors. Habitat is a set of conditions in which certain individuals, populations, or groupings of organisms live.

Patterns of influence of environmental factors on living organisms. Despite the fact that environmental factors are very diverse and different in nature, some patterns of their influence on living organisms, as well as the reactions of organisms to the action of these factors, are noted. Adaptations of organisms to environmental conditions are called adaptations. They are produced at all levels of organization of living matter: from molecular to biogeocenotic. Adaptations are not constant because they change during the historical development of individual species depending on changes in the intensity of environmental factors. Each type of organism is adapted to certain living conditions in a special way: there are no two close species that are similar in their adaptations (the rule of ecological individuality). Thus, the mole (Insectivorous series) and the mole rat (Rodents series) are adapted to exist in the soil. But the mole digs passages with the help of its forelimbs, and the mole rat digs with its incisors, throwing the soil out with its head.

Good adaptation of organisms to a certain factor does not mean the same adaptation to others (the rule of relative independence of adaptation). For example, lichens, which can settle on substrates poor in organic matter (such as rock) and withstand dry periods, are very sensitive to air pollution.

There is also the law of optimum: each factor has a positive effect on the body only within certain limits. The intensity of influence of an environmental factor that is favorable for organisms of a certain type is called the optimum zone. The more the intensity of the action of a certain environmental factor deviates from the optimal one in one direction or another, the more pronounced its inhibitory effect on organisms will be (pessimum zone). The intensity of the impact of an environmental factor, due to which the existence of organisms becomes impossible, is called the upper and lower limits of endurance (critical points of maximum and minimum). The distance between the limits of endurance determines the ecological valency of a certain species relative to a particular factor. Consequently, environmental valence is the range of intensity of the impact of an environmental factor in which the existence of a certain species is possible.

The broad ecological valency of individuals of a certain species relative to a specific environmental factor is denoted by the prefix “eur-”. Thus, arctic foxes are classified as eurythermic animals, since they can withstand significant temperature fluctuations (within 80°C). Some invertebrates (sponges, sponges, echinoderms) belong to eurybatherous organisms, therefore they settle from coastal zone to great depths, withstanding significant pressure fluctuations. Species that can live in a wide range of fluctuations of various environmental factors are called eurybiontnyms. Narrow ecological valence, that is, the inability to withstand significant changes in a certain environmental factor, is denoted by the prefix “stenothermic” (for example, stenothermic, stenobiontny, etc.).

The optimum and limits of the body's endurance relative to a certain factor depend on the intensity of the action of others. For example, in dry, windless weather it is easier to withstand low temperatures. So, the optimum and limits of endurance of organisms in relation to any environmental factor can shift in a certain direction depending on the strength and in what combination other factors act (the phenomenon of interaction of environmental factors).

But the mutual compensation of vital environmental factors has certain limits and none can be replaced by others: if the intensity of the action of at least one factor goes beyond the limits of endurance, the existence of the species becomes impossible, despite the optimal intensity of the action of others. Thus, a lack of moisture inhibits the process of photosynthesis even with optimal illumination and CO2 concentration in the atmosphere.

A factor whose intensity of action exceeds the limits of endurance is called limiting. Limiting factors determine the territory of distribution of a species (area). For example, the spread of many animal species to the north is hampered by a lack of heat and light, and to the south by a similar lack of moisture.

Thus, the presence and prosperity of a certain species in a given habitat is determined by its interaction with a whole range of environmental factors. Insufficient or excessive intensity of action of any of them makes it impossible for the prosperity and very existence of individual species.

Environmental factors are any components of the environment that affect living organisms and their groups; they are divided into abiotic (components of inanimate nature), biotic (various forms of interaction between organisms) and anthropogenic (various forms of human economic activity).

Adaptations of organisms to environmental conditions are called adaptations.

Any environmental factor has only certain limits of positive influence on organisms (the law of optimum). The limits of the intensity of the action of a factor at which the existence of organisms becomes impossible are called the upper and lower limits of endurance.

The optimum and limits of endurance of organisms in relation to any environmental factor can vary in a certain direction depending on the intensity and in what combination other environmental factors act (the phenomenon of interaction of environmental factors). But their mutual compensation is limited: not a single vital factor can be replaced by others. An environmental factor that goes beyond the limits of endurance is called limiting, it determines the range of a certain species.

ecological plasticity of organisms

Ecological plasticity of organisms (ecological valence) is the degree of adaptability of a species to changes in environmental factors. It is expressed by the range of values ​​of environmental factors within which a given species maintains normal life activity. The wider the range, the greater the environmental plasticity.

Species that can exist with small deviations of the factor from the optimum are called highly specialized, and species that can withstand significant changes in the factor are called broadly adapted.

Environmental plasticity can be considered both in relation to a single factor and in relation to a complex of environmental factors. The ability of species to tolerate significant changes in certain factors is indicated by the corresponding term with the prefix “every”:

Eurythermic (plastic to temperature)

Eurygolinaceae (salinity of water)

Euryphotic (plastic to light)

Eurygygric (plastic to humidity)

Euryoic (plastic to habitat)

Euryphagous (plastic to food).

Species adapted to slight changes in this factor are designated by the term with the prefix “steno”. These prefixes are used to express the relative degree of tolerance (for example, in a stenothermic species, the ecological temperature optimum and pessimum are close together).

Species that have broad ecological plasticity in relation to a complex of environmental factors are eurybionts; species with low individual adaptability are stenobionts. Eurybiontism and isthenobiontism characterize various types adaptations of organisms to survival. If eurybionts develop for a long time in good conditions, then they can lose ecological plasticity and develop the traits of stenobionts. Species that exist with significant fluctuations in the factor acquire increased ecological plasticity and become eurybionts.

For example, in aquatic environment more stenobionts, since its properties are relatively stable and the amplitudes of fluctuations of individual factors are small. In a more dynamic air-ground environment, eurybionts predominate. Warm-blooded animals have a broader ecological valency than cold-blooded animals. Young and old organisms tend to require more uniform environmental conditions.

Eurybionts are widespread, and stenobiontism narrows their ranges; however, in some cases, due to their high specialization, stenobionts own vast territories. For example, the fish-eating bird osprey is a typical stenophage, but in relation to other environmental factors it is a eurybiont. In search of the necessary food, the bird is able to fly long distances, so it occupies a significant range.

Plasticity is the ability of an organism to exist in a certain range of environmental factor values. Plasticity is determined by the reaction norm.

According to the degree of plasticity in relation to individual factors, all types are divided into three groups:

Stenotopes are species that can exist in a narrow range of environmental factor values. For example, most plants of moist equatorial forests.

Eurytopes are broadly flexible species capable of colonizing various habitats, for example, all cosmopolitan species.

Mesotopes occupy an intermediate position between stenotopes and eurytopes.

It should be remembered that a species can be, for example, a stenotopic according to one factor and a eurytopic according to another and vice versa. For example, a person is a eurytope in relation to air temperature, but a stenotop in terms of the oxygen content in it.