The ecological characteristics of the population do not apply. Populations

THEORETICAL PART

The concept of a population and its main group characteristics.

population- a set of organisms of the same species, jointly inhabiting a common territory, interacting with each other and interbreeding freely. A population is an elementary form of existence of a species in nature. One species of organisms may include several, sometimes many populations, more or less isolated from each other. In populations, to varying degrees, all forms of relationships characteristic of interspecific relations are manifested, but mutualism and competition are most pronounced. There are also specific intraspecific relationships: a) between individuals of different sexes; b) between parent and child generation. The most important property of a population is the ability to reproduce.

A population as a group association of individuals has the following main characteristics:

1) number- the total number of individuals in the allocated territory; the number is not constant, because depends on many factors (reproduction rates, death of individuals as a result of old age, diseases, destruction by predators, migration); if for some reason it is impossible to determine the population size, then its density is determined;

2) population density - the average number (biomass) of individuals per unit area or volume of space occupied by the population;

3) fertility - the number of new individuals (eggs, seeds) that appeared in a population per unit of time, based on a certain number of its members (for example, the number of offspring produced by one female per year; in humans, fertility is usually expressed as the number of births per 1000 people per year); distinguish absolute and specific birth rate; the first is characterized by the total number of individuals born (for example, if in a population of reindeer, numbering 16 thousand heads per year, 2 thousand deer appeared in a year, then this number expresses the absolute birth rate); specific fertility is calculated as the average change in the number per individual over a certain time interval (in this example, it will be, i.e. one newborn per eight members of the population per year);

4) mortality - an indicator reflecting the number of individuals who died in a population over a certain period of time, expressed either as a percentage of the total number of individuals, or as an average number of deaths per 1000 individuals per year; distinguish accordingly absolute and specific mortality; the value of specific fertility or specific mortality is used to compare fertility or mortality in different populations;

5) population growth - the difference between fertility and mortality; growth can be both positive and negative;

6) growth rate is the average population growth per unit of time.

Population research has important practical applications: for example, pest control, wildlife restoration, management biological resources(catching fish, etc.), conservation of rare species.

Population structure.

A population is characterized by a certain organization (structure). It is formed on the basis of the general biological properties of the species, under the influence of populations of other species and abiotic environmental factors.

The structure of the population has an adaptive character. Different populations of the same species have distinctive features that characterize the specific environmental conditions in their habitats.

The structure of a population can be spatial, age, sex, genetic and ecological.

Spatial structure determined by the distribution of individuals in the population area. All individuals in a population have individual and group space. There are certain radii of trophic (feeding) and reproductive activity. There are two opposite processes in the population - isolation and aggregation. Isolation factors - competition between individuals for food with its lack and direct antagonism. This leads to uniform or random distribution of individuals. Aggregation - the association of individuals into groups - although it increases competition between them, it contributes to the survival of the group as a whole due to mutual assistance. Aggregation leads to crowded distribution of individuals in a population. For example, organisms of many species prefer to stay in flocks (birds) or herds (mammals).

Age structure population is determined by the number and ratio of individuals of different ages, reflects the intensity of reproduction, mortality rate, the rate of generational change. In a stable population, groups of different ages are approximately in the same ratio, the birth rate is equal to the death rate, and the population size remains almost unchanged. The growing population is represented mainly by young individuals, here the birth rate exceeds the death rate. If the population is dominated by senile individuals, then its number decreases.

Sex structure- the number and ratio of males and females of the population. Genetic two-factor chromosomal sex determination provides an equal number of sexes. But in some cases, the sex ratio is determined by hormonal factors that act after fertilization, as well as environmental ones. As a result, the sex ratio in the population fluctuates over the years, deviating from 1:1.

genetic structure is determined by the variability and diversity of genotypes, the frequency of variations of individual genes, as well as the division of the population into groups of genetically close individuals, between which there is a constant exchange. The diversity of genotypes depends on the size of the population and external factors affecting its structure. In small, isolated and stable populations, the frequency of inbreeding naturally increases, which reduces genetic diversity and increases the threat of extinction.

ecological structure- this is the subdivision of a population into groups of individuals that interact differently with environmental factors. Groupings are revealed by nutrition (individuals of different sex and age have different food preferences), by orientation behavior, and by physical activity. Often there is a distribution of functions when hunting for prey, when caring for offspring. All populations are also characterized by phenological differentiation (different dates for the beginning and end of seasonal cycles of development and behavior: hibernation, sexual activity, molting, flowering, fruiting, leaf fall, etc.).

Population dynamics.

A population cannot exist without constant changes, due to which it adapts to changing environmental conditions. Changes in the number of organisms over time are called dynamics populations. The concept of population growth is necessary to understand their ability to restore numbers, as well as to understand some of the properties of dynamics.

Any population is theoretically capable of unlimited growth in numbers, if it is not limited by factors external environment. In this case, the population growth rate will depend only on the magnitude biotic potential (b.p.), characteristic of the species. B.P. reflects the theoretical maximum of offspring from one pair or individual per unit of time. B.P. is expressed by the coefficient r and calculated according to the following formula:

where ΔN - population growth;

Δt is the period of time for which there is an increase in ΔN;

N 0 - initial population size.

In nature, the B.P. of a population is never fully realized. Usually, its value is added as the difference between births and deaths in populations:

where in - number of births,

d - the number of dead individuals in the population for the same period of time.

Population growth and growth curves. If the birth rate in a population exceeds the death rate, then the population will grow (if the change due to migration is negligible). To understand the patterns of population growth, it is useful to first consider a model that describes the growth of a bacterial population after inoculation on a fresh culture medium. In this new and favorable environment, conditions for population growth are optimal and exponential growth (J-shaped) is observed. This growth curve is called exponential, or logarithmic (Fig. 1).

Fig.2. Logistic population growth curve (S - shaped)

Eventually, a point is reached where, for several reasons, including diminishing food resources and the accumulation of toxic waste products of metabolism, exponential growth becomes impossible. It begins to slow down so that the growth curve takes on a sigmoid (S-shaped) shape and is called logistic(Fig. 2).

Sigmoid and J-shaped curves are two patterns of population growth. It is assumed that all organisms are very similar to each other, have an equal ability to reproduce and an equal probability of dying, so that the population growth rate in the exponential phase depends only on its size and is not limited by environmental conditions, which remain constant.

In nature, after the exponential phase, the further development of the population proceeds according to the logistic model, while the population growth rate decreases linearly as the population grows up to zero at a certain value of K. The value of K is called biological capacity of the environment(the degree of ability of the natural or natural-anthropogenic environment to ensure the normal functioning of a certain number of organisms without a noticeable violation of the environment itself).

A survival curve can be obtained by starting with a population of newborns and then plotting the number of survivors over time. On the vertical axis, either the absolute number of surviving individuals or their percentage of the original population is usually laid:

Each species has a characteristic survival curve, the shape of which depends in part on the mortality of immature individuals. Typical examples are shown in Figure 3.

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Fig.3. Three Types of Survival Curves

Most animals and plants are subject to senescence, which manifests itself in a decrease in vitality with age after a period of maturity. As soon as aging begins, the probability of death in a certain period of time increases. The immediate causes of death may be different, but they are based on a decrease in the body's resistance to the action of adverse factors (for example, diseases). Curve A in Fig. 2 is very close to the ideal survival curve for a population in which aging is the main factor influencing mortality. An example would be a human population in a modern developed country with a high level of medical care and rational nutrition, where most people live to old age. A curve similar to curve A is also characteristic of annual cultivated plants, when they age simultaneously in a given field.

The Type B curve is characteristic of populations of organisms with high early mortality, such as mountain sheep, or a human population in a country where famine and disease are widespread. A smooth curve of type B can be obtained if mortality is constant throughout the life of the organisms (50% per unit of time). This can be when chance becomes the main factor determining mortality, and individuals die before noticeable aging begins. A similar curve is typical for populations of some animals (for example, hydra) that are not particularly endangered in early age. Most invertebrates and plants also exhibit this type of curve, but high mortality among juveniles causes the initial part of the curve to descend even more steeply.

There are small intraspecific differences in survival curves. They can be due to various reasons and are often associated with gender. In humans, for example, women live slightly longer than men, although the exact reasons for this are unknown.

Drawing survival curves for various kinds, it is possible to determine mortality for individuals different ages and thus find out at what age a given species is most vulnerable. By establishing the causes of death at this age, one can understand how the size of the population is regulated.

Similar information.

Any population is characterized by indicators that are unique to them, has a certain organization and structure. Such features can be expressed by statistical functions, i.e. the population and its properties can be described using the mathematical apparatus. Such, for example, are the structure, density, number, birth rate, and mortality. Some characteristics of populations are interrelated: mortality determines the structure, fertility determines density, and so on.

It should be emphasized that there is a fundamental difference between an individual organism and a population of organisms. Just as a drop of water does not reflect the properties of a river, lake, or ocean, so an individual organism cannot characterize the entire population as a whole.

The only carrier of the characteristics of a population is a group of individuals, but not individual individuals in this group. An individual organism in a population is born, lives, dies, but ecologists are only interested in this as an opportunity to learn the properties of the group as a whole through the study of the behavior of an individual. The special properties inherent in a population reflect its state as a group of organisms as a whole, and not as separate individuals, i.e. the property of a population as a group of organisms is not a mechanical sum of the properties of each individual that composes it.

The Soviet ecologist S.S. Schwartz in his work “Principles and Methods of Modern Ecology” proceeds from the postulate that “the population is the main, and for higher animals it is the only form of existence of the species. Just as the existence of a cell of a multicellular organism is inconceivable outside the organism, so is the existence of individuals outside the population. This does not mean, of course, that the population is an organism higher order, but this means that it is a certain organization (structural whole) of individuals, outside of which they cannot exist.

A population as a biological system has a structure and functions. The structure of a population is characterized by its constituent individuals (number) and their distribution in space. The functions of a population are similar to those of other biological systems. They are characterized by growth, development, the ability to maintain existence in constantly changing conditions.

One of the important parameters that determine the spatial structure is the number of individuals in the population. Observing the properties of different populations, be it animal or plant populations, one can see that their numbers vary greatly. It can be a hundred trees found on a hectare of a pine forest, and millions unicellular algae in the ecosystem of a pond or lake, and a few vultures living on inaccessible rocks, and clouds of starlings over a freshly sown rye field.

Under population size refers to the total number of individuals in a population. The population size cannot be constant and depends on the ratio of the intensity of reproduction and mortality.

population density is defined as the number of individuals of a species per unit area (mainly the earth's surface) or per unit volume ( water environment, experimental culture), for example, 200 trees per 1 ha, 50 people per 1 km 2, 20 tadpoles per 1 m 3 of water. The maximum density for different types of organisms and conditions of existence varies greatly. On one hectare of land, significantly more plantains can live than, say, deer or wild boars. Some species of birds (penguins, seagulls) form the so-called "bird colonies". Huge concentrations of pink flamingos are not uncommon on some lakes equatorial Africa. At the same time, many species of Central European forest songbirds never reach even 1/10 of such a density.

Individuals of living organisms (plants, animals, microorganisms) are usually unevenly distributed in space. Each population occupies a space that provides the means of life for only a certain number of individuals.

V general view three types of distribution of individuals can be distinguished: random, regular (uniform) and group (spotted, crowded, aggregated).

Random distribution is characteristic of populations, the number of individuals of which is small and the potential for competition is small. In this case, the habitat of organisms should be more or less homogeneous. In this case, the strength and direction of the impact of abiotic and biotic factors randomly change in time and space. Random distribution is not very common in nature, although the very action of random natural factors in itself is not uncommon. Such random distribution typical, for example, for spiders living in the forest floor.

Most common in nature group (spotted) distribution. It is characteristic of many organisms that live not only in terrestrial, but also in aquatic ecosystems. With this type of distribution, organisms form various groupings. These groups are formed different reasons: heterogeneity of the environment, local differences in habitats, the influence of daily and seasonal changes in weather conditions; features of the reproduction process, etc.

There are many examples of group distribution. Many fish move from place to place in huge shoals. Waterfowl gather in large flocks, preparing for long-distance flights. North American caribou reindeer form huge herds in the tundra.

The same examples can be given for plants: patchy placement of clover plants in a meadow, patches of mosses and lichens in the tundra, clusters of lingonberry shrubs in a pine forest, extensive spots of oxalis in a spruce forest, strawberry glades on light forest edges, etc.

regular (uniform) distribution can be observed with strong antagonism of individuals (competition), when the probability of finding one individual next to another is extremely small. In nature, this type of distribution is difficult to meet, although it is not uncommon to find the distribution of organisms that deviates from random towards greater regularity.

Regular distribution can most often be observed in agricultural systems artificially created by man - gardens, orchards. So, when planting, you can evenly distribute apple trees in the garden using a measuring tape. In the garden in this way, you can plant bushes of berry crops, some vegetable plants.

An important characteristic in the study of a population is its age structure. The age structure reflects the ratio of different age groups in a population and determines its ability to reproduce. In rapidly growing populations, juveniles make up a large proportion. Therefore, the state of the population after a certain period of time will depend on its current sex and age composition.

If reproduction occurs constantly in a population, then according to the age structure, it is established whether the number is decreasing or increasing.

In most populations, the reproductive capacity of their members (reproductive capacity) changes with age. In modern ecology, when studying the age composition of a population, three ecological age groups are distinguished:

■ pre-reproductive (before reproduction);

■ reproductive (during the breeding season);

■ post-reproductive (after breeding).

The duration of these ages in relation to the total life span varies greatly in different organisms.

Under favorable conditions, the population contains all age groups and maintains a relatively stable level of abundance. The age composition of the population, in addition to the total life expectancy, is affected by the duration of the breeding season, the number of generations per season, the fecundity and mortality of different age groups. For example, in voles, adults can give birth three times a year or more, and juveniles are able to breed after 2-3 months.

Usually, in the initial period of growth (the prereproductive stage), organisms are not able to reproduce. The duration of this period in different species varies greatly - from several minutes in microorganisms to several years in humans, many mammals, and trees. The pre-reproductive period can last for a large part of life, as, for example, in mayflies (larval development in water takes from a year to several years due to the long development of larvae) and a 17-year-old cicada (the pre-reproductive stage reaches several years). However, it is characteristic that the reproductive period in these species is very short (mayflies have several days, the cicada has less than one season), and the post-reproductive period is practically absent, as in many other species.

A different situation is observed in human populations, as well as animals that are kept in artificially created conditions (pets, pets, zoo inhabitants). Individuals in such populations survive until the post-reproductive period. In a modern person, these three "ages" are approximately the same, each of them accounts for about a third of life. In primitive people, the post-reproductive period was much shorter.

Currently, the ratio of age ecological groups in the human population is changing. The number of children, adolescents and pensioners is increasing; unproductive segments of the population. The proportion of children under 15 in most developing countries has increased to 50%, of older people over 65 - up to 15%. Such a change in the ratio of age groups leads to an increase in the burden on the able-bodied part of the population.

Natural populations are not a set of individuals frozen once and for all, but a dynamic unity of interacting organisms. The change in the size, structure and distribution of populations in response to environmental conditions is called population dynamics.

The dynamics of populations in a simplified version can be described by such indicators as fertility and mortality. These are the most important population characteristics, based on the analysis of which one can judge the stability and prospective development of the population.

Fertility - one of the main characteristics of a population and is defined as the number of individuals born in a population over a certain period of time (hour, day, month, year). At the same time, the term "fertility" characterizes the appearance of individuals of any species, regardless of how they were born: whether it is the germination of seeds of plantain or oats, the appearance of cubs from eggs in a chicken or turtle, the birth of offspring in an elephant, whale, or man.

Ecologists distinguish between the maximum birth rate in the absence of limiting environmental factors (it is practically very difficult, if not impossible, to achieve this). Under maximum birth rate is understood as the theoretically possible maximum rate of formation of new individuals in ideal conditions. The reproduction of organisms is restrained only by their physiological characteristics. For example, the theoretical reproduction rate of various species can be quite high in many cases. If we take as a basis such an indicator as the time it takes a species to capture the entire surface of the Earth, then for the cholera bacterium Vibrio cholerae it will be 1.25 days, for diatoms Nitschia putrida- 16.8, for houseflies Musca domestica- 366, for a chicken - about 6,000, for an elephant - 376,000 days. Thus, the maximum birth rate is a theoretical indicator and is constant for a given population.

In contrast to the maximum, ecological, or realized, fertility, fertility (or simply fertility) characterizes the growth or increase in the population size under actual and specific environmental conditions.

The number of individuals born in a given time is called absolute or total fertility.

Due to the fact that the value of the absolute birth rate is directly dependent on the number of populations, ecologists determine the specific birth rate. Specific birth rate is determined by the number of individuals born in a certain time per one individual in the population.

The unit of time may be different depending on the rate and rate of reproduction of the organism. For bacteria, this can be an hour, for insects - a day or a month, for most mammals, this process stretches for months. Suppose a city of 100,000 has 8,000 newborns. The absolute birth rate will be 8,000 per year, and the specific birth rate will be 0.08, or 8%.

The difference between absolute and specific fertility is easily illustrated by an example. A population of 20 protozoa in a certain volume of water increases by division. An hour later, its number increased to 100 individuals. In this case, the absolute birth rate will be 80 individuals per hour, and the specific birth rate (the average rate of change in the number per individual in the population) will be 4 individuals per hour with 20 initial ones.

Mortality - the reciprocal of fertility. This is the number of deaths in a population of individuals per unit of time. . Like fertility, mortality can be expressed in terms of the number of individuals who died during a given period (the number of deaths per unit of time) or as specific mortality for the entire population or part of it. When determining the mortality of a population, all dead individuals are taken into account, regardless of the cause of death (whether they died of old age or died in the claws of a predator, poisoned by pesticides or froze from cold, etc.).

The concept of a population. Population types

population(populus - from lat. people. population) - one of the central concepts in biology and denotes a set of individuals of the same species that has a common gene pool and has a common territory. It is the first superorganismal biological system. From an ecological point of view, a clear definition of the population has not yet been developed. The interpretation of S.S. Schwartz, a population is a grouping of individuals, which is a form of existence of a species and is capable of independently developing indefinitely.

The main property of populations, like other biological systems, is that they are in constant motion, constantly changing. This is reflected in all parameters: productivity, sustainability, structure, distribution in space. Populations have specific genetic and ecological characteristics that reflect the ability of systems to maintain existence in constantly changing conditions: growth, development, stability. The science that combines genetic, ecological and evolutionary approaches to the study of populations is known as population biology.

EXAMPLES. One of several schools of fish of the same species in the lake; microgroups of lily of the valley Keiske in the white birch forest, growing at the bases of trees and in open places; clumps of trees of the same species (Mongolian oak, larch, etc.), separated by meadows, clumps of other trees or shrubs, or swamps.

Ecological population - a set of elementary populations, intraspecific groups confined to specific biocenoses. Plants of the same species in a cenosis are called a coenopopulation. The exchange of genetic information between them occurs quite often.

EXAMPLES. Fish of the same species in all flocks of a common reservoir; forest stands in monodominant forests representing one group of forest types: herbaceous, lichen or sphagnum larch forests (Magadan region, northern Khabarovsk territory); forest stands in sedge (dry) and forb (wet) oak forests (Primorsky Territory, Amur Region); squirrel populations in pine, spruce-fir and broad-leaved forests of one region.

Geographic population- a set of ecological populations inhabiting geographically similar areas. Geographical populations exist autonomously, their ranges are relatively isolated, gene exchange occurs rarely - in animals and birds - during migrations, in plants - when carrying pollen, seeds and fruits. At this level, the formation of geographical races, varieties, subspecies are distinguished.

EXAMPLES. Geographic races of Dahurian larch (Larix dahurica) are known: western (west of the Lena (L. dahurica ssp. dahurica) and eastern (east of the Lena, isolated in L. dahurica ssp. cajanderi), northern and southern races of Kuril larch. Similarly M.A. Shemberg (1986) singled out two subspecies of stone birch: Erman’s birch (Betula ermanii) and woolly birch (B. lanata). at 1000 km, to the north - at 500 km Zoologists distinguish between the tundra and steppe populations of the narrow-skulled vole (Microtis gregalis).The species "common squirrel" has about 20 geographical populations, or subspecies.

Main characteristics of populations

The number and density are the main parameters of the population.

population- the total number of individuals in a given territory or in a given volume.

Density- the number of individuals or their biomass per unit area or volume. In nature, there are constant fluctuations in abundance and density.

Population dynamics and density is determined mainly by fertility, mortality and migration processes. These are indicators that characterize the change in the population over a certain period: month, season, year, etc. The study of these processes and their causes is very important for predicting the state of populations.

Fertility is divided into absolute and specific.

Absolute fertility is the number of new individuals that appeared per unit of time, and specific- the same number, but related to a certain number of individuals. For example, a measure of human fertility is the number of children born per 1,000 people during the year. Fertility is determined by many factors: environmental conditions, food availability, species biology (rate of puberty, number of generations during the season, the ratio of males and females in the population).

According to the rule of maximum birth rate (reproduction), under ideal conditions, the maximum possible number of new individuals appears in populations; birth rate is limited by the physiological characteristics of the species.

EXAMPLE. Dandelion in 10 years is able to fill the entire globe, provided that all of its seeds germinate. Willows, poplars, birches, aspens, and most weeds produce exceptionally abundant seeds. Bacteria divide every 20 minutes and within 36 hours can cover the entire planet in a continuous layer. Fertility is very high in most insect species and low in predators, large mammals.

Mortality, like the birth rate, it can be absolute (the number of individuals who died in a certain time), and specific. It characterizes the rate of population decline from death due to diseases, old age, predators, lack of food, and plays leading role in population dynamics.

There are three types of mortality:

The same at all stages of development; rare, in optimal conditions;

Increased mortality at an early age; characteristic of most species of plants and animals (in trees, less than 1% of seedlings survive to the age of maturity, in fish - 1-2% of fry, in insects - less than 0.5% of larvae);

High death in old age; usually observed in animals whose larval stages take place in favorable little changing conditions: soil, wood, living organisms.

INTRODUCTION………………….……………………………………..……………...3

1. Population - ecological characteristic…………….…………...6

2. Factors of population dynamics……………………....…..9

CONCLUSION…………………………………………….……………………………………………………………………………………………………………………………………………………………………………………….

LIST OF SOURCES…………………………………………………………17

APPENDICES……………………………………………………………….....18

Introduction

Everything is interconnected with everything - says the first ecological law. This means that one cannot take a step without hitting, and sometimes without violating, something from the environment. Each step of a person on an ordinary lawn is dozens of destroyed microorganisms, frightened off insects, changing migration routes, and perhaps even reducing their natural productivity.

Already in the last century, a person's concern for the fate of the planet arose, and in the current century it has come to a crisis in the world ecological system due to increased pressure on the natural environment.

Pollution, exhaustion natural resources and violations of ecological bonds in ecosystems have become global problems. And if humanity continues to follow the current path of development, then its death, according to the leading ecologists of the world, is inevitable in two or three generations.

Despite the Russian state measures to improve the environment, environmental relations continue to develop in an unfavorable direction for nature and society:

a) the departmental approach still prevails, as a result of which each environmental user exploits natural resources based on their departmental interests;

6) the so-called resource approach to ecological use is applied, as a result of which many ecological ties and natural objects that have no resource value remain outside the legal protection.

The interaction of society and nature has crossed the line of the previous balance in the last century, and at the moment it is already impossible to do without proper legal intervention in this area. The demand for the development of a special law on the environmental safety of Russia has become urgent.

Unlike legal literature, where natural objects are examined based on their economic value to society, each natural object should be studied in the aggregate of all its elements that affect the life of the entire environment as a whole.

At present, in the period of the impending ecological crisis on the entire planet, all living people need to solve the problems of transition from exploitation and conquest of nature to its conservation and cooperation with it. Under these conditions, human ecology becomes especially important, since the normal conditions of its existence directly depend on how much a person fits into nature, is able to learn its laws and creatively use them in his life.

Increasingly intensively consuming natural resources with the help of colossally growing in their power technical means, humanity in a progressive form improved the conditions for the development of its civilization and its growth as a biological species Homo sapiens. However, by “conquering” nature, it has largely undermined the natural foundations of its own life, which has created a tense and in many cases crisis situation in the interaction between man and nature, fraught with great dangers for the future of civilization. Interdependent changes have created new links between the global economy and the global ecology. In the past, we have been concerned about the environmental impact of economic growth. Now we cannot help but worry about the consequences of "environmental stress" - the deterioration of soil quality, water regime, the state of the atmosphere and forests - for economic development in the future.

It is now becoming increasingly clear that the sources and causes of pollution are much more diverse, complex and interrelated, and that the effects of pollution are broader, cumulative and chronic than previously thought. In science, even the definition of anthropogenic pollution of the environment has already been formulated. This is a physicochemical and biological change in the quality of the environment (atmospheric air, water, soil) as a result of economic or other activities that exceeds the established standards for harmful effects on the environment and poses a threat to human health, the state of flora and fauna, and material values.

Ecology, like any science, has two aspects. One is the desire for knowledge for the sake of knowledge itself, and in this regard, the search for patterns of development of nature, as well as their explanation, comes first; the other is the application of the collected knowledge to solve problems related to environment. The rapid increase in the importance of ecology is explained by the fact that not one of the issues of great practical importance can currently be solved without taking into account the links between the living and non-living components of nature.

The practical way out of ecology can be seen, first of all, in solving the issues of nature management; it is she who must create the scientific basis for the exploitation of natural resources. We can state that the neglect of the laws underlying natural processes has led to a serious conflict between man and nature.

Population-ecological characteristic

In ecology, a population is a group of individuals of the same species that interact with each other and jointly inhabit a common territory.

A population is a collection of individuals of the same species that exist for a long time in a certain area, interbreed freely and are relatively isolated from other individuals of the same species.

The word "population" comes from the Latin "populus" - people, population. ecological population, thus, can be defined as the population of one species in a certain area.

The population has only it inherent features: number, density, spatial distribution of individuals. There are age, sex, size structure of the population. The ratio of different age and sex groups in a population determines its main functions. The ratio of different age groups depends on two reasons: on the characteristics life cycle type and external conditions.

Compound. Conventionally, three ecological age groups can be distinguished in the population: prereproductive; reproductive; post-reproductive. The duration of these ages in relation to the total life span varies greatly in different organisms.

There are species with a simple age structure, when the population is represented by organisms of the same age, and species with a complex age structure when all age groups are represented in the population or several generations live simultaneously.

The number and density express the quantitative characteristics of the population as a whole. The size of a population is expressed as the number of individuals of a given species living on a unit of area occupied by it. The dynamics of populations over time is determined by the ratio of fertility, mortality, and survival rates, which in turn are determined by living conditions.

Population density is the size of a population per unit of space: the number of individuals, or biomass, of a population per unit area or volume. Density depends on the trophic level at which the population is located. The lower the trophic level, the higher the density.

In many species, under certain conditions, predominantly males or females are born, and sometimes individuals incapable of reproduction. In aphids, for example, generations consisting of only females replace each other in summer. Under adverse conditions, males appear. In some gastropods, polychaete worms, fish, and crustaceans, the sex of an individual changes with age.

There are several ways to define a population. A population is a collection of individuals of the same species for a long time inhabiting certain territory or water area, connected by one degree or another of free crossing and sufficiently isolated from other similar aggregates. As follows from the above definition of a population, it includes the following features inherent in it:

1 Existence over a large number of generations, which distinguishes a population from short-term unstable associations of individuals.

2 The presence of a certain degree of free crossing of individuals. It is this feature of the population that ensures its unity as an evolutionary structure.

3 The degree of free interbreeding within a population is higher than between different (even neighboring) populations.

4 A certain degree of isolation of populations from each other.

The reasons forcing individuals of a population to group within limited areas are extremely numerous and varied, but the main one is the uneven distribution of environmental conditions in geographic space and the similarity of requirements for these conditions in organisms of the same species.

Depending on the size of the occupied territory, three types of populations are distinguished: elementary, ecological and geographical (see Appendix 1)

Ecological characteristics of the population.

1) abundance - the total number of individuals in the allocated territory;

2) population density - the average number of individuals per unit area or volume of space occupied by the population;

3) fertility - the number of new individuals that appeared per unit of time as a result of reproduction;

4) mortality - an indicator that reflects the number of individuals who died in a population over a certain period of time;

5) population growth - the difference between fertility and mortality; growth can be both positive and negative;

6) growth rate - average growth per unit of time.

Similar information.

What is a population?

Definition 1

A population is a set of organisms of the same species, living in a given territory for a long period, having a common gene pool, as well as the ability to easily interbreed, isolated to varying degrees from other populations of this species.

Organisms of each species are represented by several populations inhabiting different territories. Between populations of the same species, there are various relationships that support the species as a whole. However, if for some reason a population becomes isolated from other populations of its own species, this can lead to the formation of a new species of living organisms. Under the influence of environmental conditions, physiological, morphological, and behavioral characteristics of organisms are formed. In this case, the properties of organisms belonging to different populations will differ from each other the stronger, the more dissimilar the conditions of their habitat and the weaker the exchange of individuals between them.

Characteristics of populations

A population is not a random accumulation of individuals of the same species in a common area. This is a complexly organized community with its own structure, composition and complex hierarchy of connections.

The properties that characterize a population can be divided into two types:

1. biological properties - properties inherent in each organism included in the population;
2. group (emergent) properties - properties that are inherent not to individual individuals, but to the population as a whole.

In other words, the association of organisms of the same species into a population (group) is carried out on the basis of its qualitatively new, emergent properties. These properties include:

1. number;
2. population density;
3. the birth rate of organisms in a population;
4. mortality of organisms in a population.

Definition 2

Population size is the total number of individuals of the same species inhabiting a particular area.

The population size changes over time (by years, seasons, from generation to generation) and depends on external and internal factors.

Remark 1

Fluctuations in the number of individuals in a population were called by the Russian biologist S.S. Chetverikov “waves of life”.

The territories (ranges) occupied by different populations can differ significantly from each other in area, so it is not always advisable to compare populations by the absolute number of individuals. In such cases, the population size is expressed as a density.

Definition 3

Population density - the ratio of the number of representatives of one species (or the corresponding biomass) and the volume or area occupied by the population (biomass) of space.

fertility- the number of newly minted individuals that appeared per unit of time as a result of reproduction. The birth rate in a population is determined primarily by the biological characteristics of the species, as well as the average life span of an individual, the sex ratio in the population, food availability, weather conditions, and a number of other factors. There are two types of fertility:

1. maximum (absolute, or physiological) fertility - the theoretically permissible number of individuals that can be born in ideal environmental conditions without any limiting factors, determined only by the physiological potentials of organisms;
2. ecological (realizable) birth rate - the number of individuals born in a certain period in specific environmental conditions.

Mortality is the number of individuals in a population that died in a given time period. It depends primarily on environmental factors and can be very high during natural disasters, during periods of unfavorable climatic conditions or in epidemics. Distinguish:

1. physiological mortality (death of an individual in ideal conditions as a result of physiological old age);
2. environmental mortality (death of an individual in real conditions for various reasons).