Our planet Earth is heterogeneous in composition, state of the constituent substance, physical properties and processes taking place in it. In general, heterogeneity is the main property and driving force of the entire Universe, including our planet.

In the direction towards the center of the Earth, the following shells, or, in other words, the geosphere, can be distinguished: atmosphere, hydrosphere, biosphere, earth's crust, mantle and core. Sometimes inside the solid Earth, the lithosphere is distinguished, which unites the earth's crust and the upper mantle, the asthenosphere, or a partially molten layer in the upper mantle, and the subastenospheric mantle. Below we will show that the last classification of the upper geospheres of the solid Earth is more justified when considering geodynamic processes.

The three outer shells (atmosphere, hydrosphere, and biosphere) have very variable or even indefinite boundaries, but in comparison with other geospheres, they are most accessible to direct observation. The geospheres of the solid Earth, with the exception of the uppermost layer of the earth's crust, are studied mainly by indirect, geophysical methods, therefore, many questions still remain unresolved. It is enough to compare the radius of the Earth - 6370 km and the depth of the deepest drilled well - less than 15 km to imagine how little we have direct information about the composition of the planet's matter.

Let's consider the main physical characteristics of individual geospheres.

Population stability

The concept of sustainability can be called one of the fundamental concepts in ecology. Indeed, the practical meaning of all bioecological investigations is given only by the knowledge of the limits of resistance of a particular biological system to possible human impact. What is the permissible level of human impact on nature, at which it is still capable of self-healing? Perhaps this is one of the most important questions that an ecologist must answer.

At the same time, there is still no definiteness with the concept of "sustainability" in environmental science. There are many approaches to what can be considered sustainability, and even more - what properties of natural objects can be considered sustainability criteria. In other words, what changes in what properties of a particular biological system (organism, population, ecosystem) indicate loss of stability?

We will return to the issue of sustainability in one of the next lessons on ecosystem sustainability. In the meantime, I would like to outline the main points. Most often, stability is understood as the ability of a system to adequately respond to changes in external conditions. The stability of a population is its ability to be in a state of dynamic (that is, mobile, changing) equilibrium with the environment: environmental conditions change - the population also changes adequately. Conditions return to their initial value - the population also restores its properties. Stability presupposes the ability to maintain its properties, despite external changes.

One of the most important conditions for sustainability (by the way, this is the answer to one of the tasks, if someone still remembers it) is inner diversity. Although the debate of scientists about how structural and functional diversity relates to the stability of a system does not subside, there is no doubt that the more diverse the system, the more stable it is. For example, the more diverse in their genetic inclinations the individuals of the population, the more chances that when conditions change in the population, there will be individuals capable of existing under these conditions.

Diversity is a common property that ensures the sustainability of biological systems. At the same time, there are also specific mechanisms for maintaining stability. With regard to the population, these are, first of all, the mechanisms for maintaining a certain population density.

There are three types of dependence of the population size on its density.

The first type (I) is perhaps one of the most common. As can be seen from the figure, type I is characterized by a decrease in population growth with an increase in its density. This is provided by various mechanisms. First of all, this is a decrease in the birth rate with an increase in population density. Such a dependence of fertility (fertility) on population density has been noted, for example, for many bird species. Another mechanism is an increase in mortality, a decrease in the resistance of organisms at an increased population density. Even in the human population, large gatherings of people (crowd in the bazaar, crowding in public transport) cause stress - these are "rudiments" of the density control mechanism left to us from our ancestors. Another curious mechanism is the change in the age of puberty depending on the population density.

The second type (II) is characterized by a constant growth rate of the number, which drops sharply when the maximum number is reached. A similar pattern has been described in lemmings. When the maximum density was reached, they began to migrate en masse; reaching the sea, many lemmings drowned.

Intraspecific competition is one of the most important factors in maintaining the population size. It can manifest itself in various forms, from the struggle for nesting sites to cannibalism.

Finally, the third type (III) is the type characteristic of populations in which the so-called "group effect" is noted, that is, a certain optimal population density contributes to better survival, development, and vital activity of all individuals. In this case, the most favorable is a certain optimal, and not the minimum density. To a certain extent, the group effect is characteristic of most group, and even more so social (that is, having a "social structure" of the population, division of roles) animals. For example, for the resumption of populations of heterosexual animals, at a minimum, density is necessary, providing a sufficient probability of a meeting between a male and a female.

The maintenance of a certain spatial structure by the population is closely related to the regulation of density, and especially to a decrease in intraspecific competition. We have already noted in previous lessons that spatial structure is important for optimal use of resources and for reducing competition within a population for these resources.

However, it should be taken into account that the stability of the population is not limited to density regulation. Optimal density is extremely important for optimal use of resources (as the density increases, resources may not be sufficient), but this is not a guarantee of a sustainable population. As we have noted, sustainability has a lot to do with internal diversity. Therefore, maintaining the genetic structure of the population is very important. Consideration of the evolutionary and genetic mechanisms for maintaining the genetic structure, perhaps, is not included in our tasks, however, those interested can be advised to look at the Hardy-Weinberg law.

We have considered far from all the mechanisms that ensure the stability of populations. However, in my opinion, we can already draw an important conclusion that those species and populations that can maintain their structure under changing conditions have been preserved evolutionarily. Moreover, it is obvious that the stability limits are not infinite. If the level of impact (for example, from a person - directly, or indirectly through a change in the habitat) exceeds the limits of stability, the population is threatened with death.

Glossary

ORGANISM

any living being, an integral system, a real bearer of life, characterized by all its properties; comes from one primordium (zygote, spore, seed, etc.); is individually susceptible to evolutionary and environmental factors.

POPULATION

a set of individuals of the same species, having a common gene pool and inhabiting a certain space.

ECOSYSTEM

a single natural complex formed by living organisms and their habitat.

POPULATION (Population) DENSITY

the average number of individuals in a population (species) per unit area or volume of space.

nonspecific (general) reaction of tension of a living organism to any strong effect exerted on it.

COMPETITION

rivalry, any antagonistic relationship determined by the desire to better or sooner achieve a goal in comparison with other members of the community. Competition arises for space, food, light, female, etc. Competition is one of the manifestations of the struggle for existence.

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1. General concept of ecology

Ecology (from the Greek oikos - house, dwelling, residence and ... logic), a science that studies the relationship of organisms with the environment, that is, a set of external factors that affect their growth, development, reproduction and survival. To some extent, conditionally, these factors can be divided into "abiotic" or physicochemical (temperature, humidity, day length, the content of mineral salts in the soil, etc.), and "biotic", due to the presence or absence of other living organisms (in including food items, predators or competitors).

The focus of ecology is on what directly connects the body with the environment, allowing it to live in certain conditions. Ecologists are interested in, for example, what the body consumes and what it secretes, how fast it grows, at what age it starts reproducing, how many offspring it produces, and what is the probability of these offspring surviving to a certain age. Most often, the objects of ecology are not individual organisms, but populations, biocenoses, and ecosystems. Examples of ecosystems could be a lake, sea, woodland, a small puddle, or even a rotting tree trunk. The entire biosphere can be considered as the largest ecosystem.

In modern society, under the influence of the media, ecology is often interpreted as purely applied knowledge about the state of the human environment, and even as this state itself (hence such ridiculous expressions as "bad ecology" of a particular area, "environmentally friendly" products or products). Although the problems of the quality of the environment for humans, of course, are of very important practical importance, and their solution is impossible without knowledge of ecology, the range of tasks of this science is much wider. In their works, environmental specialists try to understand how the biosphere is arranged, what is the role of organisms in the circulation of various chemical elements and the processes of energy transformation, how different organisms are interconnected with each other and with their habitat, which determines the distribution of organisms in space and the change in their number over time ... Since objects of ecology are, as a rule, aggregates of organisms or even complexes that include, along with organisms, inanimate objects, it is sometimes defined as the science of supraorganic levels of organization of life (populations, communities, ecosystems and the biosphere), or as the science of the living appearance of the biosphere.

The term "ecology" was proposed in 1866 by the German zoologist and philosopher E. Haeckel, who, while developing a classification system for biological sciences, discovered that there is no special name for the field of biology, which studies the relationship of organisms with the environment. Haeckel also defined ecology as the "physiology of relationships", although "physiology" was understood in this very broadly - as the study of the most diverse processes occurring in living nature.

Undoubtedly, the forerunner of ecology can be called the German naturalist A. Humboldt, many of whose works are now rightfully considered ecological. It is Humboldt who is credited with the transition from the study of individual plants to the knowledge of the vegetation cover, as some kind of integrity. Having laid the foundations of the "geography of plants", Humboldt not only stated the differences in the distribution of different plants, but also tried to explain them, linking them with the peculiarities of the climate.

Charles Darwin's works, primarily his theory of natural selection as a driving force of evolution, played an outstanding role in preparing the scientific community for the subsequent perception of ecological ideas. Darwin proceeded from the fact that any species of living organisms can increase its number exponentially (according to an exponential law, if we use the modern formulation), and since resources to maintain a growing population soon begin to be insufficient, competition between individuals necessarily arises (struggle for existence ). The winners in this struggle are the individuals that are most adapted to the given specific conditions, that is, those who have managed to survive and leave a viable offspring. Darwin's theory retains its enduring importance for modern ecology, often setting the direction of the search for certain relationships and allowing us to understand the essence of different "survival strategies" used by organisms in certain conditions.

The 1920s-1940s were very important for the transformation of ecology into an independent science. At this time, a number of books on various aspects of ecology were published, specialized journals began to appear (some of them still exist), and ecological societies emerged. But the most important thing is that the theoretical basis of the new science is gradually being formed, the first mathematical models are proposed and a methodology is being developed that allows one to set and solve certain problems. At the same time, two rather different approaches that exist in modern ecology were formed: the population approach, which focuses on the dynamics of the number of organisms and their distribution in space, and the ecosystem approach, which concentrates on the processes of the circulation of matter and the transformation of energy.

In the second half of the 20th century. completing the formation of ecology as an independent science, which has its own theory and methodology, its own range of problems, and its own approaches to their solution. Mathematical models are gradually becoming more realistic: their predictions can be verified by experiment or observations in nature. The experiments and observations themselves are increasingly planned and carried out so that the results obtained would make it possible to accept or refute a hypothesis put forward in advance. A notable contribution to the formation of the methodology of modern ecology was made by the work of the American researcher Robert MacArthur (1930-1972), who successfully combined the talents of a mathematician and a biologist-naturalist. MacArthur studied the regularities of the ratio of the numbers of different species included in one community, the choice of the most optimal prey by the predator, the dependence of the number of species inhabiting the island on its size and distance from the mainland, the degree of permissible overlap of ecological niches of coexisting species, and a number of other problems. Noting the presence in nature of a certain recurring regularity ("pattern"), MacArthur proposed one or several alternative hypotheses explaining the mechanism of this regularity, built the corresponding mathematical models, and then compared them with empirical data. MacArthur formulated his point of view very clearly in the book Geographical Ecology (1972), written by him when he was terminally ill, a few months before his untimely death.

The approach developed by MacArthur and his followers was focused primarily on clarifying the general principles of the structure (structure) of any communities. However, within the framework of the approach that became widespread somewhat later, in the 1980s, the main attention was shifted to the processes and mechanisms that resulted in the formation of this structure. For example, when studying the competitive displacement of one species by another, ecologists began to be primarily interested in the mechanisms of this displacement and those features of species that predetermine the outcome of their interaction. It turned out, for example, that when different plant species compete for elements of mineral nutrition (nitrogen or phosphorus), the winner is often not the species that, in principle (in the absence of resource scarcity), can grow faster, but the one that is able to maintain at least minimal growth with lower concentration in the environment of this element.

Researchers began to pay special attention to the evolution of the life cycle and different survival strategies. Since the possibilities of organisms are always limited, and organisms have to pay with something for each evolutionary acquisition, clearly expressed negative correlations (so-called "tradeoffs") inevitably arise between individual traits. It is impossible, for example, for a plant to grow very quickly and at the same time form reliable means of protection against herbivores. The study of such correlations makes it possible to find out how, in principle, the very possibility of the existence of organisms under certain conditions is achieved.

In modern ecology, some problems that have a long history of research are still relevant: for example, the establishment of general regularities in the dynamics of the abundance of organisms, an assessment of the role of various factors limiting the growth of populations, and the elucidation of the causes of cyclical (regular) fluctuations in numbers. Significant progress has been made in this area - for many specific populations, mechanisms for regulating their numbers have been identified, including those that generate cyclical changes in numbers. Research on predator-prey relationships, competition, as well as mutually beneficial cooperation of different types - mutualism - continues.

A new direction in recent years is the so-called macroecology - a comparative study of different species on a large scale (comparable to the size of continents).

At the end of the 20th century, tremendous progress was made in the study of the cycle of matter and the flow of energy. First of all, this is associated with the improvement of quantitative methods for assessing the intensity of certain processes, as well as with the growing possibilities of large-scale application of these methods. An example is the remote (from satellites) determination of the chlorophyll content in the surface waters of the sea, which makes it possible to draw up maps of the phytoplankton distribution for the entire World Ocean and estimate the seasonal changes in its production.

2. Environmental factors: definitions, groups, examples

Environmental factors (environmental factors) are any properties or components of the external environment that affect organisms.

Environmental factors are divided into abiotic, i.e. factors of inorganic, or inanimate, nature, and biotic - generated by the vital activity of organisms.

The set of abiotic factors within a homogeneous area is called an ecotope, the whole set of factors, including biotic ones, is called a biotope.

Abiotic factors include:

climatic - light, heat, air, water (including precipitation in various forms and air humidity);

Edaphic, or soil-ground, - the mechanical and chemical composition of the soil, its water and temperature regime;

Topographic - relief conditions.

Climatic and edaphic factors are largely determined by the geographic location of the ecotope - its distance from the equator and from the ocean and altitude.

Among environmental factors, there are also direct and indirect differences.

Direct environmental factors directly affect plants. Examples of direct factors: moisture, temperature, nutrient richness of the soil, etc.

Indirect environmental factors act on plants indirectly - through direct environmental factors. Examples of indirect factors: latitude and distance from the ocean, relief (altitude and slope exposure), soil texture. Ascending the mountains changes the climate (precipitation and temperature regime); the exposure and steepness of the slope affect the intensity of heating of the soil surface and the mode of its moisture. The mechanical composition of the soil (the ratio of sandy, clayey and silty particles) affects plants and soil fauna through the moisture regime and dynamics of nutrients. In addition, direct abiotic environmental factors are divided into conditions and resources.

Conditions are environmental factors that organisms do not consume. These include temperature, air humidity, water salinity, the reaction of the soil solution, the content of pollutants in water and soil that are not used by plants as nutrients.

Resources are environmental factors that are consumed by organisms. Therefore, one stronger organism can "eat" more resources, and another weaker organism will have less of them.

For plants, resources are light, water, mineral nutrients, carbon dioxide; for animals - plant biomass, live animals or dead organic matter. Oxygen is a necessary resource for the vast majority of organisms.

Space can be a resource. Plants for the life cycle must receive a certain area "under the sun" and a certain amount of soil for the consumption of water and mineral nutrients (nutritional area). Herbivorous animals need a plot of "pasture" (for aphids it will be part of a leaf, for a school of horses - ten hectares of steppe, for a herd of elephants - tens of square kilometers), carnivores - a hunting allotment.

Occasionally, a purely physical lack of space is also possible. So, crocuses even push "extra" bulbs out of the ground. In mussel settlements, the shells are so tightly pressed against each other that a new challenger cannot squeeze in between them.

The variety of conditions for the existence of organisms in different parts of the planet and in different ecotopes explains biological diversity - the diversity of living organisms.

3. Sex structure of the population

The genetic mechanism of sex determination provides a split of offspring by sex in a 1: 1 ratio, the so-called sex ratio. But this does not mean that the same ratio is typical for the population as a whole. Sex-linked traits often define significant differences in physiology, ecology, and behavior between females and males. Due to the different viability of the male and female organisms, this primary ratio often differs from the secondary and especially from the tertiary, which is characteristic of adults. So, in humans, the secondary sex ratio is 100 girls to 106 boys, by the age of 16-18 this ratio is leveled out due to increased male mortality and by the age of 50 it is 85 men per 100 women, and by the age of 80 - 50 men per 100 women ...

The sex ratio in a population is established not only by genetic laws, but also to a certain extent under the influence of the environment.

The ratio of individuals by sex and especially the proportion of breeding females in the population are of great importance for the further growth of its numbers. In most species, the sex of the future individual is determined at the time of fertilization as a result of recombination of sex chromosomes. This mechanism provides an equal ratio of zygotes based on sex, but it does not follow from this that the same ratio is typical for the population as a whole. Sex-linked traits often define significant differences in physiology, ecology, and behavior between males and females. The consequence of this is a higher probability of death of representatives of any sex and a change in the sex ratio in the population.

Environmental and behavioral differences between males and females can be very pronounced. For example, males of mosquitoes of the Culicidae family, unlike blood-sucking females, either do not feed at all in the imaginal period, or are limited to licking dew, or consume plant nectar. But even if the lifestyle of males and females is similar, they differ in many physiological characteristics: growth rates, periods of puberty, resistance to temperature changes, starvation, etc.

Differences in mortality appear even in the embryonic period. For example, muskrats in many areas have one and a half times more females among newborns than males. In populations of Megadyptes antipodes penguins, no such difference is observed when chicks emerge from eggs, but by the age of ten, only one female remains for every two males. In some bats, the proportion of females in the population after hibernation sometimes decreases to 20%. Many other species are distinguished, on the contrary, by a higher mortality rate for males (pheasants, mallard ducks, great tits, many rodents).

Thus, the sex ratio in a population is established not only according to genetic laws, but also to a certain extent under the influence of the environment.

In red forest ants (Formica rufa), males develop from eggs laid at temperatures below +20 ° C, and at higher temperatures, almost exclusively females. The mechanism of this phenomenon is that the musculature of the sperm receptacle, where sperm is stored after copulation, is activated only at high temperatures, ensuring the fertilization of the laid eggs. From unfertilized eggs in Hymenoptera, only males develop.

The influence of environmental conditions on the sex structure of populations in species with alternating sexual and parthenogenetic generations is especially evident. Daphnia Daphnia magna reproduce parthenogenetically at optimal temperatures, but males appear in populations at higher or lower temperatures. The appearance of a bisexual generation in aphids can be influenced by changes in the length of daylight hours, temperature, an increase in population density, and other factors.

Among flowering plants, there are many dioecious species, in which there are males and females: species of willows, poplars, white doze, small sorrel, perennial woodworm, field thistle, etc. There are also species with female dioeciousness, when some individuals have bisexual flowers, and others are female, that is, with an undeveloped androecium. Usually androsteril flowers are smaller than bisexual flowers. This phenomenon occurs in the families of labiates, cloves, teasers, bell-flowers, etc. Examples of species with female dioeciousness are Marshall thyme, oregano, field mint, ivy budra, wilted resin, forest geranium, etc. Populations of such species are genetically heterogeneous. In them, cross-pollination is facilitated, proteroandria is more often observed - earlier maturation of anthers in comparison with pistils. Within the range of species, the sex structure of plant populations is more or less constant, but changes in external conditions change the sex ratio. Thus, in the dry year of 1975 in the Trans-Urals, the number of female forms sharply decreased, for example, in steppe sage by 10 times, in medicinal asparagus by 3 times.

In some species, sex is initially determined not by genetic, but by environmental factors. For example, in Arisaema japonica plants, the sex depends on the accumulation of nutrient reserves in the tubers. Large tubers grow specimens with female flowers, small ones with male ones.

The sex structure of the population is determined by the differential equation proposed by R.A. Poluektovym.

where x o, x + is the number of males and females, respectively; d t - time interval; b o and b + are the fertility of males and females of one sex group, respectively, d o and d + are the fertility of males and females of another sex group of individuals, respectively. To determine P. with. a significant role is played by the sex index:

where n + is the number of females, N is the total number of individuals in the population.

4. Zones of ecological damage

Environmental damage means a significant regional or local violation of environmental conditions, which leads to the destruction of local ecological systems, local economic infrastructure, seriously threatens the health and life of people and causes significant economic damage.

Environmental damages are:

1. Sharp, sudden, catastrophic, associated with emergency situations (ES), which, in turn, are subdivided into:

* natural disasters and natural disasters (earthquakes, volcanic eruptions, landslides, floods, wildfires, hurricanes, heavy snowfalls, avalanches, epidemics, mass reproduction of harmful insects, etc.);

* anthropogenic (technogenic) disasters (industrial and communication accidents, explosions, collapses, destruction of buildings and structures, fires, etc.).

2. Prolonged in time, when the defeat is a long, gradually fading consequence of emergency situations, catastrophes, or, conversely, arises and is detected as a result of gradually increasing negative changes. The scale of such defeats can objectively be no less catastrophic.

Long-term ecological damages in nature are usually the result of catastrophic (spontaneous or anthropogenic) disturbances of the environment, have a fading character and are accompanied by successions.

Lasting anthropogenic environmental damage in the technosphere can also be a fading consequence of man-made disasters - emergency chemical and radiation contamination. But there are those that are gradually developing as a result of chronic technogenic pollution or environmental errors and miscalculations in the creation of new economic facilities and the transformation of territories.

There are no clear boundaries between some natural and anthropogenic environmental damage. Thus, it is often impossible to establish the true cause of a forest fire; landslides and floods can be the result of technical accidents, and the destruction of buildings is the result of tectonic shifts.

Of course, all regional and local ecological damages make a significant contribution to the global disturbance of the ecosphere, to the degradation of the natural environment on the planet.

In accordance with the Law of the Russian Federation "On Environmental Protection", a distinction is made between zones of an ecological emergency (areas of the territory where stable negative changes in the natural environment occur) and zones of ecological disaster (where these changes are deeply irreversible). More than 400 such zones are registered in the Russian Federation. Technogenic (anthropogenic) disasters pose the greatest environmental hazard, because entail injury and death of a large number of people, huge economic losses and significant pollution of the natural environment. Armed conflicts and terrorism, especially with the use of nuclear, chemical or bacteriological (biological) weapons, pose a great environmental threat.

Zones of an ecological emergency (ZBES) - areas of the territory where there are persistent negative changes in the environment that threaten the health of the population, the state of natural ecosystems, genetic funds of plants and animals.

Zones of ecological disaster (ZEZ) - areas of the territory where profound irreversible changes in the natural environment have occurred, resulting in a deterioration in public health, disruption of natural balance, destruction of natural ecosystems, degradation of flora and fauna.

The most ecologically dangerous are technogenic accidents and disasters, which are accompanied by the release of harmful chemical and radioactive materials into the environment (Chernobyl, Chelyabinsk-65).

5. Protected areas

The basis of territorial nature protection in Russia is the system of specially protected natural areas (SPNA). The status of protected areas is currently determined by the Federal Law "On Specially Protected Natural Areas", adopted by the State Duma on February 15, 1995. According to the Law "Specially Protected Natural Areas - areas of land, water surface and air space above them, where natural complexes and objects are located, which have their own environmental, scientific, cultural, aesthetic, recreational and health-improving value, which are withdrawn by decisions of state authorities in whole or in part from economic use and for which a special protection regime has been established. "

Russia inherited from the USSR a rather complex system of PA categories, which was formed evolutionarily. The Law distinguishes the following categories:

State natural reserves, including biosphere reserves;

National parks;

Natural parks;

State nature reserves;

Natural monuments;

Dendrological parks and botanical gardens;

Health-improving areas and resorts.

Among these territories, only nature reserves, national parks and wildlife sanctuaries of federal significance have federal status (sanctuaries may also be local), other forms of territory protection usually have a local status and are not considered here. In addition, the Law postulates the possibility of creating other categories of protected areas, which is already being implemented. Traditionally, nature reserves are the highest form of protection of natural areas in our country.

The reserves are organized by a decree of the Federal Government and are under the joint management of the Federation and its Subject, on the territory of which they are located - the current legislation of the country does not imply purely federal ownership of natural objects. The territories of the reserves are completely withdrawn from economic use and cannot be alienated, in addition, the reserves have a scientific department that constantly studies their natural complexes. The tasks of the reserves are limited to the protection and research of natural complexes, education, participation in environmental expertise, and training of relevant personnel. Usually, a zone is allocated on the territory of the reserve, completely closed for any impact. Often along the boundaries of reserves, their buffer zones are located, performing a buffer function due to restrictions on certain types of economic activities. In the status of reserves, the most effective regime for the protection of territories is implemented. As of January 1, 1998, there were 98 reserves in Russia with a total area of \u200b\u200b32.9 million hectares. The territory of these higher forms of protection accounted for 2.1% of the total area of \u200b\u200bthe country.

National parks, unlike nature reserves, along with the tasks of protecting and studying natural complexes, should provide tourism and recreation for citizens. On their territory, land plots of other users and owners may be retained with the national park's pre-emptive right to purchase such land. As of January 1, 1998, 32 natural national parks with a total area of \u200b\u200b6.7 million hectares were operating in Russia. The territory of these higher forms of protection was 0.2% of the total area of \u200b\u200bthe country.

National natural parks are a new form of territory protection for Russia. The first two (Losiny Ostrov and Sochi) were created only in 1983, 12 out of 32 in the last five years. The implementation of the legal status of national parks is still facing serious opposition from economic entities, whose activities are limited by this status. So far, this form cannot be considered an effective method of territorial protection of wildlife, however, public attention and trends known in other countries give enough hope for the gradual realization of the potential of this form of protection of natural complexes.

Natural reserves differ from the previous categories in that their lands can be either alienated or not alienated from owners and users, they can be both federal and local subordination. Among the reserves of federal significance, zoological ones play the greatest role, other forms - landscape, botanical, forest, hydrological, geological - are less widespread. As of September 1, 1994, there were 59 hunting and complex reserves of federal significance in the country with a total area of \u200b\u200b62.0 million hectares. Their main function is to protect the hunting fauna. Hunting is always prohibited, but very significant restrictions on forest exploitation, construction and some other types of economic activities are often introduced. These reserves are usually pretty well guarded.

The importance of protected areas in preserving the diversity of flora and fauna depends on the geographical location of this specially protected area, its area and the diversity of the territories represented on it. It should be noted that these factors are interrelated. In the south and in the mountains, with equal areas, the diversity is higher than in the north and on the plains. Since in Russia usually larger reserves are characteristic of the northern territories, this somewhat compensates for the differences in their role in the protection of biota. Usually, the diversity of habitats, even in protected areas in old-developed regions, is somewhat increased. The fact is that here reserves are organized most often on previously used lands - the forests here were at least partially covered by felling and burnt-out areas, steppe and meadow areas were often already plowed up and, of course, served as hayfields and pastures, often having anthropogenic origin, violations of the relief - ravines , road embankments, ponds, etc. Naturally, the mosaic nature of the vegetation cover is higher here and there is a fairly significant number of species - human companions - weeds and other synanthropes. In addition, islets of preserved nature among the anthropogenic landscape have increased attractiveness for many species of animals and they keep almost exclusively on them, not found anywhere around the reserves.

Determine the fertility index, mortality equation, population viability and build age pyramids for two populations of wood mice.

Table 1

TROPHIC CHAIN	Plants - »» Mouse - »» Hedgehog - »» Fox
Biomass to abundance in the food chain



NUMBER OF MICE BY AGE FOR THE 1ST AND 2ND POPULATION






Mortality at the age from 0 to 10 months,% (1st population / 2nd population)
The number of births (of the number of births),% (1st pop / 2nd pop)
Biomass of producers in the food chain, kg / ha.

Calculation progress

Building age pyramids of populations

To build the age pyramids of the mouse population, it is necessary to calculate the number of individuals for each age group in summer. Based on the number of age groups of the spring population and data on fertility and mortality from the conditions of the task, we make a calculation for the 1st population taking into account the following indicators: - mice of age groups 2-4 months (86 individuals), 4-6 months (60 ), 6-8 months (43), 8-10 months (36 individuals) \u003d 225;

Underyearlings is the number of cubs born (the number of breeding ones increases by 2 times) \u003d 225 * 2 \u003d 450;

The percentage of surviving individuals between the ages of 0 and 10 months -75%. According to the condition of the task, it is known that the mortality rate of mice at the age of 0 to 2 months is 25%. All individuals of the population are taken as 100%, which means that surviving individuals: 100% - 25% \u003d 75% or 0.75;

The calculation is made in table 2

Table 2 - Calculation of the size of the first population of mice

	Number of individuals
		Calculation progress
		(86 + 60 + 43 + 36) x 2

According to table 2, we calculate for the 1st population of mice:

The number of all age groups of the mouse population in spring - 445;

The number of all age groups of the population of mice in the summer - 777

for the 2nd population, the calculation taking into account the following indicators: - mice of age groups 2-4 months (86 individuals), 4-6 months (60), 6-8 months (43), 8-10 months (36 individuals) ) \u003d 225;

Underyearlings - this is the number of cubs born (the number of breeding ones increases by 0.5 times) \u003d 225 * 0.5 \u003d 113; - the percentage of surviving individuals at the age from 0 to 10 months -68%. According to the condition of the task, it is known that the mortality rate of mice at the age from 0 to 2 months is 32%. We take all individuals of the population as 100%, which means that surviving individuals: 100% - 35% \u003d 68% or 0.68;

The calculation is made in table 3

Table 3 - Calculation of the size of the second population of mice

	Number of individuals
		Calculation progress
		(86 + 60 + 43 + 36) x 0.5

According to table 3, we calculate for the 2nd population of mice:

the number of all age groups of the mouse population in spring - 445

the number of all age groups of the population of mice in the summer is 409.

We build age pyramids for summer mouse populations (Figures 1 and 2). To do this, we plot the number of individuals on the abscissa, and the age periods on the ordinate. So, when constructing a pyramid for the summer population of the bank vole, the abundance value for the age group 0-2 months -450 individuals is divided in half and one half is deposited to the left of 0, the other - to the right as a horizontal rectangle. Similarly, we complete the rectangles for the rest of the age groups.

Calculation of population indicators and assessment of population viability

We calculate such population indicators as the fertility index and the mortality equation using formulas 1 and 2.

We calculate the fertility index for the first mouse population:

where n is the number of newborns in 2 months (450);

N is the total number of summer mice populations (777).

We calculate the fertility index for the second mouse population:

The mortality equation for mouse populations is calculated:

1st population

where N 1 - the number of all age groups of the population in the spring (445);

N 2 - the number of all age groups of the population in summer (777);

V (t 2 - t 1) - the number of individuals born in 2 months. (450);

t 2 - t 1 is the number of days in two months (61).

2nd population

where N1 is the number of all age groups of the population in spring (445);

N2 is the number of all age groups of the population in summer (409);

V (t2 - t1) is the number of individuals born in 2 months. (113);

t2 - t1 - number of days in two months (61).

The assessment of the viability of populations is carried out by comparing the indicators given in table 4 and reference table 5

Table 4 - Determination of the viability of the population

Table 5 - Indicators of viability of mouse populations

Output: according to table 3, we determine that the 1st population of mice is more viable than the 2nd population of mice

7. Task 2

For a more viable mouse population, based on the results of task 1, draw up a diagram of the food chain for a population of wood mice, calculate the number of its species and build a population pyramid.

Given: The mouse population is included in the following food chain: herbaceous plants, mouse, hedgehog, fox.

We accept that in this food chain, representatives of each subsequent level feed only on organisms of the previous level. The biomass of producers in this food chain is 150 kg / ha. The ratios of biomass and number are taken as follows: 1 herbaceous shoot - 5 g; 1 mouse - 10g; 1 hedgehog -500 g; 1 fox - 5000 g

Calculation progress

A simple example of a food chain (plants - mouse - hedgehog - fox) gives the following sequence: vegetation - vegetation-eating animal - smaller carnivorous animal - larger carnivorous animal. In this chain, there is a unidirectional flow of matter and energy from one group of organisms to another. Let's build a food chain for populations.

The biomass of producers (trophic level I), according to the assignment, is 15000 kg / ha. To simplify calculations, we assume that animals of each trophic level feed only on organisms of the previous level. Taking into account the rule of energy transfer from one trophic level to another (Lindemann's law), we calculate the biomass for subsequent trophic levels (Table 6).

The ratio of biomass and number is taken as follows: 1 herbaceous plant shoot - 5 g; 1 mouse - 10 g; 1 snake - 100 g; 1 hawk - 2000 g. We determine the number of species by the ratio of the weight of one individual and the calculated biomass:

The number of producers (plants)

15,000 kg / ha: 0.005 kg \u003d 3,000,000 individuals,

Number of 1st order consumers (mice)

1500 kg / ha: 0.01 kg \u003d 150,000 individuals

Number of consumers of the 2nd order (hedgehog)

150 kg / ha: 0.5 kg \u003d 300 individuals

number of consumers of the 3rd order (foxes)

15 kg / ha: 5 kg \u003d 3 individuals

Table 6 - Calculation of biomass and abundance for the food chain

To build a pyramid of numbers on the abscissa axis, we postpone the number, on the ordinate axis - trophic levels, starting from the 1st from the bottom up. The value of the abundance for the entire trophic level is divided in half and one half is deposited to the left of 0, the other to the right in the form of a horizontal rectangle. Similarly, we complete the rectangles for the remaining trophic levels, superimposing them one on top of the other from bottom to top.

population fertility food

List of references

1. Ivonin VM, Water Ecology: Textbook. allowance - Rostov-n / D: SKNTs, 2000.

2. Ecology / Edited by prof. V.V. Denisov. - M.IKTs "Mart"; Rostov n / a: Publishing center "Mart"; 2006. -

3. Zasoba V.V. Methodical instructions for conducting practical exercises in the discipline "Ecology". - Novocherkassk. : NGMA, 1996.

4. Zasoba V.V., Levchenko E.N., Bogatova E.S. Instructions for the abstract on the discipline "Ecology". - Novocherkassk: NGMA, 1998.

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Population dynamics

Population size and density change over time. The capacity of the medium fluctuates on a seasonal and long-term scale, which determines the dynamics of density even at a constant level of reproduction. In populations, there is a constant influx of individuals from the outside and the eviction of some of them outside the population. This determines the dynamic nature of a population as a system composed of many separate organisms. They differ from each other in age, sex, genetic characteristics and role in the functional structure of the population. The numerical ratio of different categories of organisms in a population is called demographic structure.

The age structure of a population is determined by the ratio of different age groups (cohorts) of organisms in the population. Age reflects the lifetime of a given group in the population (absolute age of organisms) and the stage state of an organism (biological age). Population growth rates are determined by the proportion of individuals at reproductive age. The percentage of immature organisms reflects the potential for reproduction in the future.

The age structure changes over time, which is associated with different mortality rates in different age groups. In species for which the role of external factors is small (weather, predators, etc.), the survival curve is characterized by a slight decrease until the age of natural death, and then sharply decreases. In nature, this type is rare (mayflies, some large vertebrates, humans). Many species are characterized by increased mortality at the initial stages of ontogenesis. In such species, the survival curve drops sharply at the beginning of development, and then there is a low mortality rate of animals that have survived a critical age. With an even distribution of mortality by age, the nature of survival is presented as a diagonal straight line. This type of survival is primarily characteristic of species that develop without metamorphosis with sufficient independence of the offspring. The ideal survival curve was found for the inhabitants of Ancient Rome.

The sex structure of a population not only determines reproduction, but also contributes to the enrichment of the gene pool. Genetic exchange between individuals is characteristic of almost all taxa. But there are organisms that reproduce vegetatively, parthenogenetically or miosis. Therefore, a clear sex structure is expressed in the higher groups of animals. Sexual structure is dynamic and related to age, since the ratio of males and females varies in different age groups. In this regard, distinguish between primary, secondary and tertiary sex ratio.

The primary sex ratio is determined genetically (based on the different quality of chromosomes). In the process of fertilization, various combinations of chromosomes are possible, which affects the sex of the offspring. After fertilization, other influences are switched on, in relation to which a differentiated reaction is manifested in zygotes and embryos. So, in reptiles and insects, the formation of males or females occurs in certain temperature ranges. For example, fertilization in ants takes place at temperatures above 20˚C, and at a lower temperature, unfertilized eggs are laid, from which only males hatch. As a result of such influences on the nature of development and the unequal mortality rate of newborns of different sex, the ratio of males to females (secondary sex ratio) differs from genetically determined. The tertiary sex ratio characterizes this indicator among adult animals and is formed as a result of different mortality rates of males and females in the process of ontogenesis.

The ability of a population to reproduce means the potential for a constant increase in its numbers. This growth can be thought of as an ongoing process, the extent of which depends on the rate of reproduction. The latter is defined as the specific increase in the number per unit of time: r \u003d dN / Ndt,

where r is the instantaneous (in a short period of time) specific growth rate of the population, N is its size, and t is the time during which the change in population was taken into account. The indicator of the instantaneous specific growth rate of the population r is defined as the reproductive (biotic) potential of the population. Exponential growth is possible only if r is constant. But population growth is never realized in this form. The growth of the population is limited by a complex of environmental factors and is formed as a result of the ratio of fertility and mortality. The real growth of the population is slow for some time, then it increases and reaches a plateau determined by the capacity of the land. This reflects the balance of the breeding process with food and other resources.

The number of populations does not remain constant even when reaching a plateau; regular rises and falls in numbers are found, which are cyclical. Depending on this, several types of population dynamics are distinguished.

1. The stable type is characterized by a small amplitude and a long period of fluctuations in numbers. Outwardly, it is perceived as stable. This type is characteristic of large animals with a long life span, late onset of sexual maturity and low fertility. This corresponds to a low mortality rate. For example, ungulates (the period of fluctuations in numbers 10-20 years), cetaceans, hominids, large eagles, some reptiles.

2. The labile (fluctuating) type is distinguished by regular fluctuations in numbers with a period of the order of 5-11 years and a significant amplitude (tens, sometimes hundreds of times). Seasonal changes in abundance associated with the frequency of reproduction are characteristic. This type is characteristic of animals with a life expectancy of 10-15 years, earlier puberty and high fertility. These include large rodents, lagomorphs, some predators, birds, fish and insects with a long development cycle.

3. The ephemeral (explosive) type of dynamics is characterized by an unstable number with deep depressions, followed by outbreaks of mass reproduction, in which the number increases hundreds of times. Its changes are carried out very quickly. The total cycle length is usually up to 4-5 years, of which the peak of the number takes most often 1 year. This type of dynamics is characteristic of short-lived (no more than 3 years) species with imperfect adaptation mechanisms and high mortality (small rodents and many species of insects).

Environmental strategies. Different types of dynamics reflect different life strategies. This is the basis for the concept of environmental strategies. Its essence boils down to the fact that the survival and reproduction of the species is possible either by improving adaptations or by increasing reproduction, which compensates for the death of individuals and in critical situations allows you to quickly restore the number. The first path is called the K-strategy. It is characteristic of large forms with a long life span. Their number is limited mainly by external factors. K-strategy means selection for quality - increasing adaptability and resistance, and r-strategy - selection for quantity through compensation for large losses with high reproductive potential (maintaining the stability of the population through a rapid change of individuals). This type of strategy is characteristic of small animals with high mortality and high fertility. Species with an r-strategy (r is the population growth rate) easily colonize habitats with unstable conditions and are distinguished by a high level of energy consumption for reproduction. Their survival is determined by high reproduction, which allows them to quickly recover losses.

There are a number of transitions from r to K strategy. Each species, in its adaptation to the conditions of existence, combines different strategies in various combinations.

For plants, L.G. Ramenskiy (1938) identified 3 types of strategies: violet (competitive species with high vitality and the ability to quickly master space); patient (species that are resistant to adverse influences and therefore capable of assimilating habitats inaccessible to others) and expired (species capable of rapid reproduction, actively dispersing and assimilating places with disturbed associations).

Factors of population dynamics. 1) A complex of abiotic factors that are mainly influenced by climate and weather are related to the population density independent. They act at the level of the organism and therefore their effect is not related to the number or density. The action of these factors is one-sided: organisms can adapt to them, but are not able to exert the opposite effect. The effect of the influence of climatic factors is manifested through mortality, which increases as the force of the influence of the factor deviates from the optimum. The mortality and survival rate is determined only by the strength of the factor, taking into account the adaptive capabilities of the organism and some characteristics of the environment (the presence of shelters, the softening effect of associated factors, etc.). So, if the winter temperature is low and there is little snow, the number of small rodents will be low. The same applies to forest chicken birds fleeing from frost in snow holes. The climate can also affect indirectly through changes in feeding conditions. Thus, good vegetation of plants promotes the reproduction of herbivores. The relationship of abiotic factors with the structure of the population can be expressed in the selective mortality of certain groups of animals (young animals, migrants, etc.). Based on changes in population structure, the level of reproduction can change (as a secondary effect). However, the effect of climatic factors does not lead to the creation of a stable balance. These factors are not able to respond to changes in density, that is, to act on the principle of feedback. Therefore, meteorological conditions are classified as modifying factors.

2) Factors depending on population density include the impact on the level and dynamics of the abundance of food, predators, pathogens, etc. Acting on the size of populations, they themselves are influenced by them and therefore belong to the category of regulatory factors. The effect of the action appears with some delay. As a result, the population density exhibits regular fluctuations around the optimal level.

One of the forms is the relationship between the consumer and his food. The role of food boils down to the fact that high food supply causes an increase in the birth rate and a decrease in mortality in the consumer population. As a result, their numbers are growing, which leads to the eating of food. There is a deterioration in consumer living conditions, a fall in the birth rate and an increase in mortality. As a result, the pressure on the forage population decreases.

Trophic cycles of abundance arise in conditions of a predator-prey relationship. Both populations affect the number and density of each other, there is the formation of repeated rises and falls in the number of both species, and the number of the predator lags behind the dynamics of the prey population.

Population cycles. The dynamics of fertility and mortality is manifested through the mechanisms of autoregulation, i.e., the population takes part in the formation of a response to the influence of factors in the form of types of population dynamics. The autoregulation system works on the principle of cybernetics: information about the density ↔ the mechanisms of its regulation. Such a control system already contains a source of constant fluctuations. This is expressed in a cycle of population dynamics: amplitude (swing range) and period (cycle duration).

Maintaining an optimal density by regulating the rate of reproduction and mortality is closely related to the structure of the population. As the structure becomes more complex, the regulatory mechanisms become more complex (behavior is also important in higher vertebrates). Their effectiveness is based on the different quality of individuals in the composition of the population: the level of reproduction varies depending on the position in the general structure. The severity of stress is different in individuals of different ranks. In a number of species, high-ranking individuals become breeding residents. Fluctuations in numbers affect the spatial structure of the population: an increase in density is compensated by dispersal from the core of the population and the creation of settlements on the periphery. Depending on the nature of seasonal changes in numbers, the demographic structure of the population, the intensity of reproduction and the level of survival change.

Thus, the dynamics of the number of animals is the interaction of the population with the conditions of its life. Changes in numbers occur under the influence of a complex set of factors, the action of which is transformed through intrapopulation mechanisms. At the same time, fluctuations are associated with the dynamics of the population structure and its parameters.

The dynamics of cenopopulations is expressed in changes in population parameters. With regard to plants, population cycles are considered from the standpoint of changes in the structure and functions of populations. The dynamics of the number of animals is associated with individuals. In plants, this is more difficult, since both individuals and clones (aggregates of individuals of vegetative origin) can act as elements of the population. The structure of cenopopulations can be considered in several aspects: population composition (quantitative ratio of elements), structure (mutual arrangement of elements in space), functioning (set of connections between elements). The dynamics of cenopopulations includes changes over time in all aspects of the structure (abundance, biomass, seed production, age spectrum and composition). The number and density of cenopopulations depend on the ratio of fertility and mortality. Fertility in flowering plants corresponds to the potential seed productivity (number of ovules per shoot). Actual seed production (the number of full-fledged ripe seeds per shoot) reflects the real level of population reproduction. It reflects the processes of population self-maintenance. Factors limiting seed productivity: insufficient pollination, lack of resources, the influence of phytophages and diseases. Vegetative reproduction is of great importance - the separation of structural parts and their transition to independent existence.

Changes in the level of reproduction and mortality form the dynamics of the structure, biomass and functioning of cenopopulations. Density affects the intensity of plant growth, the state of seed production and vegetative growth. With an increase in density, mortality increases, and in some cases the type of survival also changes. At low densities, mortality is high, since the influence of external factors is significant here. With an increase in density, the "group effect" is formed, and when thickening above a certain threshold, mortality increases again as a result of overlapping phytogenic zones and mutual oppression. The density-dependent mortality is directed against the unlimited growth of the population and stabilizes its number within the limits close to the optimum.

The gradual rise in living standards over the past two centuries has led to an increase in life expectancy. From tables compiled by the statistician W. Farr for England and Wales and relating to 1838-1854, it follows that the average life expectancy at that time was equal to 40.9 years. With the development of medicine and hygiene, the average life expectancy increased to 49.2 years (1900–1902). In the USA in 1945, the average life expectancy reached 65.8, i.e. increased over five decades by about 16 years.

Briefly about the main

The ecological interaction between the environment and the community determines the size of the population. This value serves as an indicator of how successfully the community subjugates the environment (as a result of conscious activity or in some other way).

The accelerated population growth began about 8,000 years ago. During the Paleolithic and Mesolithic eras, the population density was less than 1 person per 3 km2. In the Neolithic era, when man began to cultivate the land, the density increased by about 10 times; in the Bronze and Iron Ages - another 10 times. The total number of people in the Neolithic era is estimated at about 5 million, and in the period of the appearance of the first large cities - at 20-40 million.

It took the modern species Homo sapiens about 20 thousand years to reach 200 million (during the Roman Empire). In the next 1500 years (by 1600 AD) the world's population increased to 500 million, after another 200 years it more than doubled (about 1 billion in 1800).

The size of the human population is regulated not only by biological, but also by cultural factors.

Population growth should be viewed as a process associated with the balance of three demographic factors - fertility, mortality and migration.

The standard of living of a particular human community depends on the way in which this community achieves equilibrium under certain environmental conditions. This balance can be achieved through higher overall mortality or higher morbidity, as well as through strenuous work, poor health or lack of material wealth. To characterize the equilibrium, you can use various criteria (including those that determine the level of consumption, working capacity, energy or monetary income per capita), as well as different demographic indicators. The indicators of infant mortality and average life expectancy deserve special attention.

test questions

1. What factors determine the density of the population and its size?

2. What processes regulate population size?

3. What are the measures to regulate the size of human populations?

Literature

Mandatory

1. Khrisanfova E.N., Perevozchikov I.V. Anthropology. - M .: Higher school, 2002.

2. Khomutov A.E. Anthropology. - Rostov n / a: Phoenix, 2004.

Additional

1. Bigon M., Harper J., Townsend K. Ecology. Individuals, populations and communities. T.

No living organism of any kind exists separately from others - they all form groups called populations. There are rather complex interactions within a population, but both in relations with other populations and with the environment, the population acts as a kind of integral structure. Therefore, the lowest level of organization of living matter, considered in ecology, is the population level.

The main characteristic of a population is its total number or density (number per unit of space occupied by the population). It is usually expressed either in the number of individuals or in their biomass. The size determines the size of the population. It is characteristic that in nature there are certain lower and upper limits for the size of the population. The upper limit is determined by the flow of energy in the ecosystem, which includes the population, the trophic level it occupies, and the physiological characteristics of the organisms forming the population (the size and intensity of metabolism). The lower limit is usually determined purely statistically - if the number is too small, the probability of fluctuations that can lead to the complete death of the population increases sharply.

One of the basic ecological principles is the assertion that in an unlimited stationary and favorable environment for organisms, the size of the population grows exponentially. However, as already mentioned, this is never observed in nature - the population size is always limited from above. Light, food, space, other organisms, etc. can act as a limiting factor (or limiting factors).

The dynamics of changes in the total population size is determined by two processes - birth and death.

The birth process is characterized by fertility - the ability of a population to increase in size. Maximum (absolute, physiological) fertility is the maximum possible number of offspring produced by one individual in ideal environmental conditions in the absence of any limiting factors and is determined only by the physiological capabilities of the organism. Ecological fertility (or simply fertility) is associated with an increase in the population in real-life environmental conditions. It depends both on the size and composition of the population, and on the physical conditions of the environment.

The process of population decline is characterized by mortality. By analogy with fertility, they distinguish: minimum mortality, associated with physiological life expectancy, and ecological, which characterizes the probability of death of an individual in real conditions. It is obvious that environmental mortality is much higher than physiological.

Considering the dynamics of an isolated population, we can assume that fertility and mortality rates are generalized parameters that characterize the interaction of the population with the environment.

What determines the stability of the population. Chapter i. the stability of an isolated population. Stability and vitality of populations

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