The biological term "population" was first used in 1903 by a biologist from Denmark Wilhelm Ludwig Johansen (1857 - 1927) to indicate a group growth of one plant species.
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General concept
What is a population? She (the ancient Latins said: populus, from modern English. population- population) is a collection of representatives a specific type of living organisms, a long time period living or growing in one territorial space, apart from individuals of other groups that are similar in terms of similar characteristics.
The term is used in various fields of natural sciences: ecology, medicine, demography.
If we take, for example, then in the appropriate terminology, the concept defined as a community of animals or plants of the same species with a single gene pool(we will consider this term below), capable of stable self-reproduction. In biology, it is understood as a group of organisms within a particular species.
The simplest example is the human population on Earth. If we take examples from the animal world: sika and red deer, brown and polar bear, cod and haddock in the seas of the Arctic Ocean basin. From the world of plants: different types of pine and spruce, aspen and linden, oak and elm.
What parameters are characteristic of each population? The generally accepted criteria are:
- common habitat (range);
- uniform origin of the community of organisms;
- the relative isolation of this community from other similar groups (the so-called interpopulation barriers);
- observance of the principle of panmixia (free crossing) within the group, in other words, equal probability of meeting all existing genotypes within the range.
Population types
Species of living organisms in wildlife a great many. First of all, you need to highlight two global populations - animals and plants. And already in them the subspecies of a particular group of organisms are determined.
In biology, geographically determined groups are structurally distinguished, for example, the settlement of squirrels in the forests of the Ulyanovsk region. Grouped animals of the same subspecies (in our case, squirrels) living in a geographically homogeneous space. Such a territory is called a habitat.
In turn, the geographic populations are subdivided into smaller - ecological (proteins in coniferous and mixed forests of one region), and those - into even smaller ones - elementary or local (the same proteins, but already in different parts one forest).
According to the ability to reproduce, there is a subdivision into:
- Permanent that do not need an influx of individuals of their own species from the outside to maintain the number at the level necessary for a full-fledged existence.
- Semi-dependent, in which a certain number of such individuals from the outside comes from outside, but even without them, the population is able to exist for a long time.
- Temporary, in them the mortality rate of representatives is higher than the species fertility, and the existence is directly dependent on the influx of individuals from the outside. Temporary populations are often formed in places with an unfavorable climate and an unstable food supply.
Attention! A population is very similar to a living organism, as a biosystem, it also has an organized structure that has its own integrity, a genetic program of self-reproduction and special characteristic mechanisms of self-regulation and adaptation.
Population structure
The structure of the predominant number of existing species settlements is determined by the representatives that form them, and the placement of the latter in the habitat (remembering squirrels - the total number and percentage of heterosexual animals in the forest). To make it clearer, consider the points.
So, the structure of the population is
Spatial - the distribution of individuals over the area occupied - how many squirrels are running and where. It, in turn, is subdivided into:
- Random (if the forest is the same for all squirrels, and they jump in the same natural environment). In this case, there are few animals; they do not get lost in "groups" and do not live in a heap in a watery place.
- Uniform. It is found mainly in animals living in conditions of fierce competition for food resources and habitats. Some species predatory fish, birds and mammals (bears, for example) anxiously guard their hunting grounds and do not favor strangers.
- Group. The most common in nature. Here we will consider the example of plants. Some trees have large, heavy fruits (nuts, acorns, plane trees, etc.), which, falling next to the tree, immediately sprout, forming groups. And even lilies of the valley! But, they owe this vegetative mode of reproduction (offshoots from rhizomes). These growth features are caused by the fact that the environmental conditions are heterogeneous, habitats are limited, the species has characteristic biological qualities and breeding options.
Sexual - the ratio of heterosexual specimens (how many squirrels-boys and squirrels-girls are in the forest).
Age is the most understandable. How many individuals of different ages. In any species, and sometimes in each population within the species, there are different ratios of age groups. As a rule, the following ecological ages are distinguished:
- pre-reproductive (organisms that have not reached puberty);
- reproductive (sexually mature);
- post-reproductive (representatives who have lost the ability to reproduce).
For animals and plants, this structure has significant differences, but this is a separate topic for consideration.
Genetic structure of the population due to variability and diversity of genotypes(roughly speaking, the difference in squirrels in color and size, and their variations when mating with subsequent offspring).
The ecological structure consists in dividing a species into groups of individual representatives, interacting in their own way with the conditions of the habitat. It is here that the local population often manifests itself. The thing is that the difference between a type and a separate group of representatives existing in special conditions common area residence, very conditional.
Basically, the system functions like practically any biological system. Accordingly, it is characterized by: growth, development, survival in changing environmental conditions. This determines the presence of certain parameters.
Squirrel population
Parameters
Most of the existing populations are characterized by: number, density, fertility and mortality. All these characteristics are also closely related and interdependent.
Population size- the total number of representatives of the species living in the territory. Density, respectively, is the number of individuals of a given species per unit area of the range.
In many large groups, the average number does not change too much annually, due to the fact that:
- approximately the same number of representatives die from natural causes;
- the intensity of reproduction of organisms increases with a low population density, and with an increase, accordingly, it decreases;
- constantly changing natural conditions and climatic factors create obstacles for the high realization of reproductive potential.
But, even with a certain stability, fluctuations are characteristic of the population size. The main reasons for these fluctuations associated with changes in the conditions of existence. Namely:
These periodic fluctuations lead to changes in the total number, which consist of the following phenomena:
- fertility;
- mortality;
- immigration (introduction - an influx of individuals from the outside);
- emigration (eviction of representatives of the species).
The so-called population waves are associated with these factors.
Important! Population waves are sudden, significant numerical changes.
Example: a reduction in the number of foxes as a result of shooting (abiotic factor) leads to a population increase in field mice (voles).
Populations are characterized by abundance, density, fertility and mortality.
Gene pool
But of particular importance is the effective number - the number of sexually mature representatives of the species capable of producing offspring. It is they who form the gene pool. And now we will consider this concept specifically.
What is the gene pool of a population(gene pool). This is a collection of all the traits (genes) of a species and their variations, which are inherited. It is thanks to genes that proteins from Siberia differ from proteins from Canada. Gene variations (alleles) determine the ability of organisms to adapt to constantly changing characteristics environment... The greater the diversity of genes, the more the organism is able to adapt to life.
In biology, there is such a thing as an ideal population. But, it is purely theoretical and is used to model processes. Ideal population can be defined as a hypothetical panmictic (i.e., individuals of which have the same chances of interbreeding), with an infinitely growing number that persists over generations and is independent of natural selection, external factors and mutations.
What is the main role of the concept for the existence of living organisms on the planet? In ecology, it is defined as an elementary unit of the process microevolution(intraspecific small gene changes in several generations, leading to certain changes in the individual, both external and internal), responding to changing environmental factors by restructuring the gene pool.
Population functioning and dynamics of its number in nature
Population as a form of species existence in nature
Output
Based on the above , we summarize. A population is a collection of representatives of one species living in a common territory, freely interbreeding, possessing a single gene pool, having its own structure, characteristics and parameters similar to existing biosystems, and being an elementary microevolutionary unit.
INTRODUCTION …………………. ………………………………… .. …………… ... 3
1. Population - ecological characteristic…………….…………...6
2. Factors of population dynamics …………………… ....… ..9
CONCLUSION ……………………………………………. …………………… 14
LIST OF SOURCES ……………………………………………………… 17
APPENDICES …………………………………………………………… ..... 18
Introduction
Everything is interconnected with everything - says the first environmental law. This means that a step cannot be taken without touching, and sometimes without disturbing anything from the environment. Each step of a person on an ordinary lawn is dozens of killed microorganisms, frightened off insects, changing migration routes, and maybe reducing their natural productivity.
Already in the last century, a person's anxiety about the fate of the planet arose, and in the current century it has come to a crisis of the world ecological system due to an increase in the load on the natural environment.
Environmental pollution, depletion of natural resources and disruption of ecological ties in ecosystems have become global problems. And if humanity continues to follow the current path of development, then its death, according to the world's leading ecologists, is inevitable in two or three generations.
Despite the The Russian state measures to improve the environment, environmental relations continue to develop in a direction that is unfavorable for nature and society:
a) the departmental approach still prevails, as a result of which each environmental user exploits natural resources, proceeding from 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 do not have resource value remain outside the legal protection.
The interaction of society and nature crossed the line of the previous equilibrium in the last century, and at the moment it is already impossible to do without proper legal interference in this area. The requirement for the development of a special law on the environmental safety of Russia has become urgent.
Unlike legal literature, where natural objects are studied based on their economic value for 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 the present time, 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 preservation and cooperation with it. Under these conditions, human ecology becomes especially important, since the normal conditions of his existence directly depend on how much a person fits into nature, is able to cognize its laws and use them creatively in his life.
Consuming natural resources more and more intensively with the help of colossally increasing in power technical means, mankind in a progressive form improved the conditions for the development of its civilization and its growth as a biological species Homo sapiens. However, “conquering” nature, it significantly undermined the natural foundations of its own life, which created a tense and, in many cases, a crisis situation in the interaction of 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 environment. In the past, we have been concerned about the environmental impact of economic growth. Now we cannot but be concerned about the consequences of "environmental stress" - 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 the effects of pollution are broader, cumulative and chronic than previously thought. Science has even formulated a definition of anthropogenic pollution of the environment. This is a physicochemical and biological change in the quality of the environment ( atmospheric air, waters, soil) as a result of economic or other activities that exceed the established standards for harmful effects on the environment and poses a threat to human health, the state of flora and fauna, material values.
Ecology, like any science, has two aspects. One is the striving for knowledge for the sake of knowledge itself, and in this regard, the search for the laws of the development of nature, as well as their explanation, is put in the first place; the other is the application of the knowledge gathered to solve environmental problems. The rapid increase in the importance of ecology is explained by the fact that none of the issues of great practical importance at the present time can be solved without taking into account the links between living and nonliving components of nature.
A practical way out of ecology can be seen primarily in the solution of issues of nature management; it is she who must create the scientific basis for the exploitation of natural resources. We can state that the disregard for the laws underlying natural processes has led to a serious conflict between man and nature.
Population-ecological characteristics
A population in ecology 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 one species, existing for a long time in a certain territory, freely interbreeding and relatively isolated from other individuals of the same species.
The word "population" comes from the Latin "populus" - people, population. Ecological population thus, it can be defined as the population of one species in a certain area.
The population has only its inherent features: number, density, spatial distribution of individuals. Distinguish the age, sex, size structure of the population. The ratio of groups of different age and sex in a population determines its main functions. The ratio of different age groups depends on two reasons: on the characteristics of the species life cycle and on external conditions.
Structure. Conventionally, three ecological age groups can be distinguished in the population: pre-reproductive; reproductive; post-reproductive. The duration of these ages in relation to the total life span varies greatly in different organisms.
Species with a simple age structure are distinguished, 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.
Abundance and density express the quantitative characteristics of the population as a whole. The size of a population is expressed by the number of individuals of a given species living on a unit of the area it occupies. The dynamics of the population size 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 of area or volume. The 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, mainly males or females are born, and sometimes individuals incapable of reproduction. In aphids, for example, in the summer, generations, consisting of the same females, replace each other. Under unfavorable conditions, males appear. Some gastropods, polychaete worms, fish, crustaceans, the sex of the individual changes with age.
There are several options for defining a population. A population is a set of individuals of one species for a long time inhabiting a certain territory or water area, connected by one or another degree of free crossing and sufficiently isolated from other similar populations. 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 the 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 crossing 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 the population to group within limited areas are extremely numerous and varied, but the main one is the uneven distribution of ecological 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) number - the total number of individuals in the allocated area;
2) population density - the average number of individuals per unit area or volume of the 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 reflecting the number of individuals killed in a population over a certain period of time;
5) population growth - the difference between fertility and mortality; the gain can be both positive and negative;
6) growth rate - average growth per unit of time.
Similar information.
Area- a part of the land surface or water area, within which individuals of a given species (genus, family, or a certain type of community) are distributed and go through the full cycle of their development.
Endemic- a species that occupies an insignificant territory.
■ Examples of endemic species: relict plants of ginkgo and metasequoia, platypus, echidna, coelacanth fish.
❖ Causes of endemism:
■ geographic isolation (on oceanic islands, in mountainous areas or isolated bodies of water);
■ climatic and soil conditions;
■ biotic factors (competition, predation, symbiosis).
Cosmopolitan- a species found in most of the inhabited areas of the Earth, widespread everywhere.
■ Examples of cosmopolitans: weeds (large plantain, shepherd's purse, etc.), aquatic and marsh plants (duckweed, cattail), as well as housefly, city sparrow, gray rat and other animals that settle after humans.
❖ Factors influencing the formation and characteristics of the area:
■ ecological plasticity of the species;
■ its ability to reproduce and settle;
■ historical age;
■ speed of speciation.
Continuous area- this is the area within which individuals of the species are found in all habitats suitable for their life.
Discontinuous range- This is an area that breaks up into several isolated territories, so far from each other that the exchange of pollen or spores between plants or the migration of animals living in these territories is impossible.
Ecological niche of the species Is a complex of living conditions of a species, i.e. a set of all environmental factors (including microclimate), within which a species can exist in nature.
■ Two species cannot occupy the same ecological niche, so one of the species either creates a new ecological niche or disappears.
Populations and their main characteristics
Population- this is a set of individuals of the same species, for a long time inhabiting a certain part of the range, relatively isolated from other groups of individuals of the same species and interacting with each other (competing, helping each other, freely interbreeding, etc.).
■ Population is an elementary form of existence and evolution of a species.
The role of populations in evolution: due to the spatial disunity of populations, the species exists in a variety of environmental conditions and is subjected to the action of natural selection of different intensities and in different directions, which leads to the formation of new varieties, subspecies and types of organisms.
The main characteristics of the populations: area, abundance, density, fertility, mortality, spatial, ecological, sex and age structures, genetic heterogeneity.
The size of a stable population is limited by maximum and minimum values.
■ The maximum population size is determined by environmental resources (amount of food, water, etc.).
■ The minimum population size is at least several hundred individuals. With a smaller number, any accidental cause (fire, flood, drought, severe frosts, etc.) can lead to the extinction of the population.
Population homeostasis- the property of a population to maintain its size at some optimal average level.
Population density- the average number of individuals per unit area or volume of space occupied by the population.
With an increase in the number of individuals, the population density, as a rule, increases. It can remain unchanged only with the expansion of the range due to the dispersal of individuals.
Population density regulation is achieved:
■ in plants - due to intraspecific competition, leading to self-thinning (in this case, not only the density changes, but also the vegetative power of individual individuals);
■ in animals through complex behavioral and physiological mechanisms and manifests itself only in cases of limited environmental resources and the impossibility of finding them in other territories (in small reservoirs where there are no other fish species, adult perches feed on their own juveniles).
Fertility (absolute)- the number of new individuals in the population that appeared per unit of time as a result of reproduction.
Specific fertility- the average number of individuals born in the population per unit of time per 1, 100 or 1000 individuals of the population. This indicator allows you to compare the birth rate in populations with different numbers.
The value of the birth rate of each species was determined historically as an adaptation to compensate for the decline in populations and depends on:
■ sex ratio in the population (its sex structure);
■ the ratio of age groups (its age structure);
■ frequency of reproductive cycles (breeding cycles);
■ fertility of individuals (which, in turn, depends on the degree of development of care for the offspring and the provision of eggs with nutrients).
Usually, the birth rate in each population is balanced by its characteristic mortality.
Biotic potential characterizes the theoretically possible number of offspring from one pair (or one individual) for a certain period of time (for example, for the entire life cycle or for a year).
■ Examples: the number of many insects and crustaceans (aphids, daphnia) per year. can increase by 10 10 -10 30 times; the number large mammals even under the most favorable conditions, it can increase only by 1.05-1.1 times per year.
Specific mortality- the number of individuals that died in the population per unit of time per individual.
Survival curve- a graph showing the percentage of individuals who survived to a particular age.
Survival types of organisms(determined by the mortality of individuals).
■ increased mortality of individuals in the early period of life (in fish);
■ uniform death of individuals at all periods of life (in hydras, some worms, etc.);
■ survival of individuals to the maximum age and mass death at later periods of life (most insects); less common; leads to breeding outbreaks.
Population structure
Spatial structure population characterizes the features of the distribution of individuals in the occupied territory. It depends on the size of the population and its age and sex structure, can change throughout the year and is determined by the properties of the habitat and the biological characteristics of the species.
❖ Types of spatial structure of populations:
■ accidental
distribution over the territory;
■ uniform
distribution over the territory;
■ group
distribution, when individuals live in groups: families, herds, colonies, harems. This distribution is most common, as it helps to better defend against predators, search for and get food.
Ecological structure characterizes the attitude of different groups of organisms of one population to environmental conditions (for example, individuals of one plant population differ in size, the number of leaves and flowers, do not bloom at the same time, their fruits also do not ripen at the same time, etc.).
■ Such a difference in individuals allows the population to survive as a whole under the onset of various unfavorable conditions, although one or another part of the individuals may die in this case.
Gender structure expresses the ratio of the number of males and females in a population. It usually differs from the 1: 1 ratio determined by the genetic mechanism, which is mainly due to the different vitality of males and females.
■ The predominance of the proportion of females over males ensures more intensive growth of the population.
■ Since males and females of many species differ in their feeding habits, behavior, etc., a change in the sex structure of a population to one degree or another changes its role in the ecosystem.
■ In human populations, the sex ratio at birth is 100 girls to 106 boys, by the age of 18 it becomes 1: 1, by the age of 50 there are 85 men for 100 women, by the age of 80 the sex ratio becomes 2: 1 (100 women for 50 men).
Age structure of the population reflects the ratio of different age groups in the population. It depends on the life expectancy of individuals, the time of onset of their sexual maturity, the number of offspring in the litter, the number of offspring per season, etc.
■ The presence of a large number of individuals of younger age groups in the population indicates its well-being. The predominance of old individuals in the population indicates that this population is ending its existence.
■ The age structure reflects the adaptive nature of individuals, since the resistance to the environment in individuals of different ages is not the same (adult May beetles live for several weeks, and their larvae in the soil for three years).
❖ Types of ecological age:
■ pre-reproductive;
■ reproductive;
■ post-reproductive.
Population dynamics
Population growth Is the difference between fertility and. mortality. It can be positive (the population is increasing) and negative (the population is decreasing).
Growth rate- the average population growth per unit of time. In most species, it depends on the population density. The highest growth rate is observed at a certain optimal population density or when the population enters a new, unoccupied ecological niche.
Growth in numbers. Any population, if it is not limited by environmental factors (limited resources, diseases, predators, etc.), is theoretically capable of unlimited growth in numbers. In this case, the rate (rate) of population growth depends only on the value biotic potential , and the growth of the population itself occurs in geometric progression(exponentially) and is called exponential.
Exponential growth conditions... Really exponential growth of the population can occur only for a limited period of time in the following cases:
■ the population is in conditions of surplus environmental resources (food, breeding grounds) and is not affected by adverse factors;
■ the population finds itself in a new environment, where it has no enemies and competitors (example: rabbits in Australia);
■ the population exists in artificially created laboratory conditions (bacteria, yeast, etc.).
The growth of the population leads to an increase in its density. But at the same time, as the population density increases, the limited resources of the environment begin to affect, and the conditions for reproduction and growth of individuals become less favorable, which leads to a slowdown in population growth.
Logistic type of population growth- a type of growth with limited resources, characterized by a decrease in the growth rate as the population density increases.
Medium capacity- optimal population density in specific environmental conditions.
■ If the density of the population matches the capacity of the environment, then the size of the population will fluctuate around the average level.
■ If the density of the population exceeds the capacity of the environment, then the size of the population and its density decrease.
Regulation of the population size.Two groups of factors affecting population size:
■ modifying, independent of the population density (this, as a rule, abiotic environmental factors; for example, a harsh winter leads to the death of animals and birds feeding on the ground, etc.);
■ regulating, depending on the population density (as a rule, these are different biotic factors: fertility, mortality, migration, behavioral factors, depletion of environmental resources, etc.).
Migrations- these are regular daily or seasonal movements of animals between significantly different, spatially separated habitats. They are caused by changes in the conditions of existence in habitats or changes in the requirements of animals for these conditions at different stages of development.
The role of migrations:
■ allow organisms for a certain time to use the optimal environmental conditions in those places where the permanent residence of organisms of this species is impossible;
■ lead to the development of new biotopes and the expansion of the general range of the species;
■ lead to the exchange of individuals between populations, which can change their structure and basic properties, prevent the death of a population on the verge of extinction, or, conversely, lead to a sharp decline;
■ increase the unity and overall stability of the species;
■ contribute to success in the struggle for existence.
In the absence of migration, the change in population size depends on the ratio of fertility and mortality.
Examples of physiological and behavioral factors regulating the size and density of the population:
■ with a high population density in some animal species (rodents), the concentration of the hormone adrenaline in the blood increases, causing aggressiveness (fights) and various hormonal disorders (in females, embryo resorption may occur), which ultimately leads to a decrease in the population size;
■ chemical interaction individuals (for example, tadpoles release substances into the water that retard the growth of other tadpoles);
■ tagging(the secret of scent glands, scratches on trees, singing of male birds, etc.), security an individual site of the territory and avoidance reproduction of "alien" individuals on it allows the most rational use of the space occupied by the population. At the same time, the excess part of the population does not multiply or is forced to move out of the occupied space.
The multiplicity of mechanisms for regulating the number leads to the fact that in nature there is very rarely a catastrophic increase in numbers, the undermining of resources (lack of food, shelters, space) and the death of the population.
1. The concept of population: statistical indicators of the population, the concept of genotype and gene pool
A set of individuals with hereditary similarities in morphological, physiological and biochemical characteristics, capable of crossing with the formation of fertile offspring, adapted to certain living conditions and occupying a certain territory (area) in nature is called biological species... Species often occupy a large area, within which individuals are unevenly distributed, in groups - populations.
Population - a set of individuals of one species, capable of self-reproduction, which exists for a long time in a certain part of the range relatively apart from other populations of the same species. The term "population" comes from the Latin word "populus" (people) and literally means "population". A population is precisely that cell of the biota, which is the basis of its existence: self-reproduction of living matter takes place in it, it ensures the survival of the species, i.e. is a structural unit of a species and a unit of evolution. Contacts between individuals of the same population are carried out more often than between individuals of different populations. For example, the level of panmixia (free crossing) within a population is higher than between individuals of different populations.
Areal. The space in which a population or a species as a whole occurs throughout its entire life is called an area of distribution. The area can be continuous or broken (disjunctive), if between its parts there are various barriers (water, orographic, etc.), spaces not inhabited by representatives of this species.
2.Static indicators of the population
Quantitative indicators (characteristics) of the population can be divided into static and dynamic. Static indicators characterize the state of the population on this moment time. The main ones are: the number and density, as well as indicators of the structure. The dynamic indicators of the population reflect the processes taking place in the population over a certain period of time. The main ones are: fertility, mortality, population growth rate.
Abundance is the number of animals or plants within a certain spatial unit: area, river basin, sea area, region, district, etc. Population size can vary significantly over time. It depends on the biotic potential of the species and external conditions. The number of certain animals is determined by various methods. For example, by counting from an airplane or helicopter when flying over an area. The size of the human population is determined by a census of the population of the entire state, its administrative divisions. The importance of the size and structure of the population (ethnic, professional, age, gender, etc.) is of great economic and environmental importance.
Density is the number of individuals or biomass of a population per unit area or volume. The larger the animal, the more area it needs to get food, therefore, the larger the body size of the individual, the lower the population density.
The population is characterized by a certain structural organization - the ratio of groups of individuals by sex, age, size, distribution of individuals over the territory, etc. In this regard, various structures of the population are distinguished: sexual, age, size, genetic, spatial-ethological, etc. The structure of a population is formed, on the one hand, on the basis of the general biological properties of the species, on the other hand, under the influence of environmental factors.
Sex structure (sex composition) - the quantitative ratio of males and females in a population. The sex ratio of a population is established according to genetic laws as a result of recombination of sex chromosomes, and then it is influenced by the environment. In theory, the sex ratio should be the same: 50% of the total population should be males, and 50% should be females. The actual sex ratio depends not only on genetic and physiological features kind, but also from action various factors environment (for example, in fish - from the pH value of the environment; in red forest ants from eggs laid at temperatures below 20 ° C, males develop, and with more high temperature- females).
Distinguish between primary, secondary and tertiary relationships. The primary ratio is the ratio observed during the formation of germ cells (gametes). Usually it is 1: 1. This ratio is determined by the genetic mechanism of sex determination. The secondary ratio is the ratio observed at birth. Tertiary ratio is the ratio observed in adult sexually mature individuals.
For example, in humans, in the secondary ratio, boys are somewhat prevalent, in the tertiary ratio - women: for 106 boys, 100 girls are born, by the age of 16 ... 18, due to increased male mortality, this ratio is leveled out and by the age of 50 it is 85 men per 100 women. and by the age of 80 - 50 men and 100 women.
The genetic structure of a population is characterized by varying degrees of genetic diversity of individuals. The set of all genes concentrated in the chromosomes of one organism is called a genotype. If the ratio of genotypes in a population is constant across generations, then the population is stable, there is a genotypic balance in it. The set of genes that individuals of a particular population have is called a gene pool. Despite the variability in its structural parts, the population as an integral system steadily preserves the gene pool inherited from the ancestral population.
The relative spatial isolation of the population leads to its reproductive isolation - the limitation of the freedom of crossing of individuals of different populations. This isolation ensures the uniqueness of the gene pool of the population and the possibility of its independent evolution. However, there are no completely isolated populations in nature and migration (outflow and inflow) of genes can occur, leading to changes in their genetic structure.
Age structure (age composition) - the ratio in the population of individuals of different age groups. The absolute age composition expresses the number of certain age groups at a certain point in time. The relative age composition expresses the proportion or percentage of individuals of a given age group in relation to the total population. The age composition is determined by such indicators as: time to puberty, life expectancy, duration of the breeding period, mortality, etc.
Depending on the ability of an individual to reproduce, three groups are distinguished: pre-reproductive (individuals that are not yet able to reproduce), reproductive (individuals that can reproduce) and post-reproductive (individuals that are no longer able to reproduce).
The ratio of individuals in the population for these conditions is called the age spectrum of the population, which reflects the quantitative ratios of different age groups. By age spectrum the ability of the population to self-support and its resistance to external influences are assessed. To compare the number of individuals of different ages in populations, histograms of age structures are constructed (see Fig.).
The most viable are populations in which all ages are represented relatively evenly. Such populations are called normal. If senile individuals prevail in the population, this indicates the presence of negative factors that disrupt reproductive functions. Such populations are called regressive or endangered.
Age structure of populations:
Invasive (growing); 2 - normal (stable);
Regressive (shrinking)
Populations, represented mainly by young individuals, are considered to be invading, or invasive. Their vitality does not cause concern, but there is a high probability of outbreaks of excessively high numbers of individuals. It is especially dangerous if such populations are represented by species that were previously absent here.
The spatial and ethological structure determines the nature of the distribution of individuals within the range. It depends on the characteristics of the environment and ethology (behavior) of the species.
There are three main types of distribution of individuals in space: uniform (regular), uneven (aggregated, group, mosaic) and random (diffuse).
With a uniform distribution, individuals are placed at more or less equal intervals, for example, trees in a pine forest. In reality, a uniform distribution of individuals is rare in nature.
Uneven (group, mosaic) distribution is manifested in the formation of groups of individuals, between which there are large unpopulated territories. It is typical for populations living in conditions of uneven distribution of environmental factors or consisting of individuals leading a group lifestyle (for example, a herd of mammals, a colony of birds). Group placement provides populations with a higher resistance to unfavorable conditions.
In a random (diffusion) distribution, individuals are unevenly distributed, and their encounters with each other are random. This type of distribution is widespread among plants and many animal species. Random distribution is the result of probabilistic processes and weak social ties between individuals.
Over large geographical areas, over time, individuals of the same population, when distributed, can form combinations of these three types of distribution. For example: trees - from group to uniform. The dispersal of aphids or the Colorado potato beetle at first may be random, and as they multiply, it acquires a group or uniform character.
According to the type of use of space, all mobile animals are subdivided into sedentary and nomadic. The sedentary way of life is characterized by an intensive type of use of the territory, i.e. individual individuals or their groups have been exploiting resources for a long time in a relatively limited space. It has a number of biological advantages, such as free orientation in familiar territory when looking for food or shelter, the ability to create food reserves (squirrel, field mouse). Its disadvantages include the depletion of food resources with an excessively high population density.
Species characterized by a nomadic way of life are characterized by an extensive type of use of the territory, in which resources are usually consumed by groups of individuals constantly moving within a vast area.
According to the form of coexistence, animals are distinguished by a solitary lifestyle, family, in colonies, flocks, herds.
The spread of organisms outside the population is called dispersal. Settlement patterns reflect how a population occupies an ever-increasing space. Among them, the following are distinguished: anemochoria (spread by the wind), hydrochoria (by water), phytochoria (by plants), zoochoria (by animals) and anthropochoria (by humans).
3.Water living environment
From an ecological point of view, the environment -these are natural bodies and phenomena with which the organism is in direct or indirect relations. Habitat is a part of nature that surrounds living organisms (individual, population, community) and has a certain effect on them.
On our planet, living organisms have mastered four main habitats: aquatic, ground-air, soil and organismic (i.e., formed by the living organisms themselves).
Aquatic life environment
The aquatic life environment is the most ancient. Water ensures the course of metabolism in the body and the normal functioning of the body as a whole. Some organisms live in water, others have adapted to a constant lack of moisture. The average water content in the cells of most living organisms is about 70%.
4.Specific properties of water as a habitat
A characteristic feature of the aquatic environment is high density -it is 800 times the density of the air. In distilled water, for example, it is equal to 1 g / cm 3... With increasing salinity, the density increases and can reach 1.35 g / cm 3... All aquatic organisms experience high pressure increasing by 1 atmosphere for every 10 m depth. Some of them, such as angler fish, cephalopods, crustaceans, sea stars and others, live at great depths at a pressure of 400 ... 500 atm.
The density of water provides the ability to rely on it, which is important for skeletal forms of aquatic organisms.
The following factors also affect the biont of aquatic ecosystems:
1.dissolved oxygen concentration;
2.water temperature;
.transparency, characterized by the relative change in the intensity of the light flux with depth;
.salinity, that is, the percentage (by weight) of salts dissolved in water, mainly NaCl, KC1 and MgS04 ;
.availability of nutrients, primarily compounds of chemically bound nitrogen and phosphorus.
The oxygen regime of the aquatic environment is specific. Oxygen in water is 21 times less than in the atmosphere. The oxygen content in the water decreases with an increase in temperature, salinity, depth, but increases with an increase in the flow rate. Among aquatic organisms, there are many species belonging to euryoxybionts, i.e., organisms capable of carrying a low oxygen content in water (for example, some species of mollusks, carp, crucian carp, tench, and others).
Stenoxybionts, for example, trout, mayfly larvae and others, can exist only with a sufficiently high water saturation with oxygen (7 ... 11 cm 3/ l), and therefore are bioindicators of this factor.
Lack of oxygen in water leads to catastrophic events -deaths (winter and summer), accompanied by the death of aquatic organisms.
The temperature regime of the aquatic environment is characterized by relative stability in comparison with other environments. IN fresh water temperate latitudes, the temperature of the surface layers ranges from 0.9 ° C to 25 ° C, i.e. the amplitude of temperature changes is within 26 ° С (except for thermal sources, where the temperature can reach 140 ° С). At a depth in fresh water bodies, the temperature is constantly 4 ... 5 ° С.
The light regime of the aquatic environment differs significantly from the terrestrial-air environment. There is little light in water, as it is partially reflected from the surface and partially absorbed when passing through the water column. Particles suspended in water also prevent light from passing through. In connection with this, three zones are distinguished in deep water bodies: light, twilight and a zone of eternal darkness.
According to the degree of illumination, the following zones are distinguished:
the littoral zone (the water column where sunlight reaches the bottom);
limnic zone (the water column to a depth where only 1% of sunlight penetrates and where photosynthesis is attenuated);
euphotic zone (the entire illuminated water column, including the littoral and limnic zones);
profundal zone (bottom and water column, where sunlight does not penetrate).
In relation to water, the following ecological groups are distinguished among living organisms: hygrophiles (moisture-loving), xerophiles (dry-loving) and mesophiles (intermediate group). In particular, among plants, hygrophytes, mesophytes and xerophytes are distinguished.
Hygrophytes -plants of wet habitats that cannot tolerate water scarcity. These include, for example: pond, water lily, reed.
Xerophytes are plants in dry habitats that can tolerate overheating and dehydration. Distinguish between succulents and sclerophytes. Succulents -xerophytic plants with succulent, fleshy leaves (for example, aloe) or stems (for example, cactus), in which water-storage tissue is developed. Sclerophytes are xerophytic plants with rigid shoots, due to which, with a water deficit, they do not observe an external picture of wilting (for example, feather grass, saxaul).
Mesophytes -plants of moderately humid habitats; intermediate group between hydrophytes and xerophytes.
IN aquatic environment there are about 150,000 animal species (about 7% of their total) and 10,000 plant species (about 8% of the total). Organisms that live in water are called aquatic organisms.
According to the type of habitat and way of life, aquatic organisms are grouped into the following ecological groups.
Plankton -suspended organisms floating in water, passively moving due to the current. Distinguish between phytoplankton (unicellular algae) and zooplankton (unicellular animals, crustaceans, jellyfish, etc.). A special species of plankton is the ecological group Neuston -inhabitants of the surface film of water at the border with the air environment (for example, water striders, bugs, and others).
Nekton -animals actively moving in water (fish, amphibians, cephalopods, turtles, cetaceans, etc.). Active swimming of aquatic organisms, united in this ecological group, directly depends on the density of the water. Rapid movement in the water column is possible only in the presence of a streamlined body shape and highly developed muscles.
Benthos -organisms living on the bottom and in the ground, it is divided into phytobenthos (attached algae and higher plants) and zoobenthos (crustaceans, molluscs, starfish, etc.).
5. Varieties of smog and their features
Smog (English Smoke - smoke, fog - thick fog) - visible air pollution of any nature. Smog occurs under certain conditions: a large amount of dust and gases in the air and the long-term existence of anticyclonic weather conditions (areas with high atmospheric pressure) when pollutants accumulate in the surface layer of the atmosphere. Smog causes choking, asthma attacks, allergic reactions, eye irritation, damage to vegetation, buildings and structures.
There are three types of smog: ice (Alaskan type); wet (London type); dry or photochemical (Los Angeles type).
The most studied is wet smog. It is common in areas with high relative humidity and frequent fogs. This promotes the mixing of pollutants and the interaction of chemical reactions. These pollutants, directly emitted into the atmosphere, are called primary pollutants. The main toxic components of wet smog are most often CO 2and SO 2... In a notorious case, in 1952, wet smog in London claimed more than 4,000 lives.
Photochemical smog is secondary air pollution caused by the decomposition of primary pollutants by sunlight. The main toxic component is ozone.
Ice smog occurs when very low temperatures and anticyclone. In this case, the emission of even small amounts of pollutants leads to the formation of a thick fog, consisting of the smallest ice crystals and, for example, sulfuric acid.
Air is mainly a mixture of O 2and N 2... At high flame temperatures, molecules in the air can disintegrate and even molecules of relatively inert N 2undergo reactions:
According to the equation, an oxygen atom is formed, which is included in the equation. Once formed in the flame, an oxygen atom will be recreated and participate in the entire chain of reactions leading to the formation of NO. If we sum up these two reactions, we get:
The equation shows how nitrogen oxides are formed in a flame. They appear because the fuel is burned in air and not in oxygen O 2... In addition, some fuels contain nitrogen compounds as impurities, and as a result, the combustion products of these impurities serve as a source of other nitrogen oxides. Oxidation of nitric oxide in smog produces nitrogen dioxide, a brown gas. This color means that the gas absorbs light (with a wavelength of at least 310nm.), Is photochemically active and undergoes dissociation:
Thus, according to the equation, nitrogen oxide appears again, but also a single and reactive oxygen atom, which can react to form ozone - O3 :
Ozone is the only pollutant that most clearly characterizes photochemical smog. However, Oh 3which presents such a problem is not emitted by the vehicle (or any major pollutant). It is a secondary pollutant.
In summary, VOCs released by the use of gasoline-based fuels contribute to the conversion of NO to NO. 2(and underlie photochemical smog).
In the process of oxidation of hydrocarbons in the atmosphere, the role of the OH * radical should be especially noted. Consider the oxidation of methane (CH 4) as a simple example of this process:
These reactions show the conversion of nitric oxide (NO) to dioxide (NO 2) and a simple alkane of the CH 4into an aldehyde (in this case formaldehyde HCHO). In this case, the OH * radical is reproduced at the end of the reaction chain, therefore, it can be considered a catalyst in some way. Despite the fact that the reaction takes place in photochemical smog, the effect of the OH * radical on large and complex organic molecules is quite effective. Aldehydes can also be attacked by OH * radicals.
Methyl radical (CH 3*) from the equation can be returned to the equation.
An important addition to this series of reactions is the following:
leading to the formation of irritating eyes of peroxyacetylnetrate (PAN).
6. Environmental law and its main sources
Environmental law is a branch of law that regulates public relations in the field of interaction between society and nature.
Environmental law is an important tool used by the state in the interests of the conservation and rational use of the natural environment.
The sources of environmental law are the following regulatory legal acts: 1) the Constitution of the Russian Federation; 2) laws and codes in the field of nature protection; 3) decrees and orders of the President on issues of ecology and nature management; government environmental acts; 4) normative acts of ministries and departments; 5) regulatory decisions of local self-government bodies.
- The constitutional foundations of environmental protection are enshrined in the Constitution of the Russian Federation, adopted on December 12, 1993.The Constitution proclaims the right of citizens to land and other natural resources, enshrines the right of every person to a favorable environment (ecological safety) and to compensation for damage caused to his health. It also defines the organizational and control functions of the supreme and local authorities for the rational use and protection of natural resources, establishes the responsibilities of citizens in relation to nature, the protection of its wealth.
2. Laws and codes in the field of environmental protection constitute the natural resource legal basis. These include laws on land, subsoil, air protection, protection and use of wildlife, etc. The system of environmental legislation is headed by the Federal Law "On Environmental Protection" dated January 10, 2002, No. 7-FZ. In matters of environmental protection, the norms of other laws should not contradict the Constitution of Russia and this legislative act.
1. The Land Code of the Russian Federation (2001) regulates the protection of land and the protection of the natural environment from possible harmful effects when using land. The main legal functions of land protection: preservation and improvement of soil fertility, preservation of the fund of agricultural land. Damage, pollution, contamination and depletion of land are considered environmental violations. The Code regulates the sale and purchase of land and other land transactions.
2. The Water Code of the Russian Federation (1995) regulates legal relations in the field of rational use and protection of water bodies, establishes responsibility for violation of water legislation. Legal regulations are aimed at protecting waters from pollution, clogging and depletion.
3. The legal basis for the protection of atmospheric air is reflected in the Law of the Russian Federation "On Environmental Protection" (2002), as well as the Law "On the Protection of Atmospheric Air" (1982). The most important general measures for the protection of the air basin are the establishment of standards for maximum permissible harmful effects (MPC, MPE) and payments for emissions of pollutants into the atmosphere.
4. Legal protection people involved in the use of nuclear and radiation installations and radioactive substances is guaranteed by the Law of the Russian Federation "On Radiation Safety of the Population" (1995) (as well as the Federal Law "On the Use of atomic energy»).
In the event of an accident, the Law guarantees compensation for damage to the health and property of citizens, establishes compensation for the increased risk to those living near nuclear and radiation installations in the form of improved social conditions.
5. The Law of the Russian Federation "On Subsoil" (1992) establishes legal relations in the study, use and protection of subsoil. Among the environmental and legal violations affecting the subsoil as part of the natural environment, the Law primarily refers to their pollution.
6. The Fundamentals of Forestry Legislation (1977) stipulates the requirements for forest management. The main legal norms are aimed at the use of forests as a natural resource, reproduction of forests, conservation and protection of forests, etc.
7. Law of the Russian Federation "On Animal World" (1995). It contains environmental, legal and administrative norms, taking into account new economic relations. According to the Law, environmental violations include: illegal fishing, destruction of rare and endangered animals, etc.
8. The Law of the Russian Federation "On Production and Consumption Waste" (1998) defines the legal basis for handling production and consumption waste in order to prevent their harmful effects on human health and the environment.
9. The most important environmental requirements are also reflected in the Law of the Russian Federation "On the Sanitary and Epidemiological Welfare of the Population" (1999) and the Fundamentals of the Legislation of the Russian Federation on Health Protection (1993).
Federal Law "On Natural Medicinal Resources, Medical and Recreational Areas and Resorts" dated 23.02.95 No. 26-FZ;
Federal Law "On Specially Protected natural areas"dated 03/14/95 (as revised on 12/30/2001) No. 33-FZ;
Federal Law "On Ecological Expertise" dated 23.11.95 (as amended on 15.04.98) No. 174-FZ;
Federal Law "On the Use of Atomic Energy" dated November 21, 1995 (as amended on March 28, 2002) No. 170-FZ;
Federal Law "On the Continental Shelf" dated November 30, 1995 (as amended on June 30, 2003) No. 187-FZ;
Decrees and orders of the President, decisions of the Government cover a wide range of environmental issues. An example is the Presidential Decree of April 1, 1996 on the concept of the transition of the Russian Federation to sustainable development.
- Normative acts of environmental ministries and departments are issued on a wide variety of issues of rational use and protection of the natural environment, in the form of decrees, instructions, orders and are considered mandatory for all individuals and legal entities.
- Regulatory decisions of local administrative bodies (city halls, rural and settlement bodies) supplement and concretize the existing normative legal acts on environmental protection.
The current Federal Law "On Environmental Protection" (2002) significantly expands the powers of the state authorities of the constituent entities of the Russian Federation and local governments in the field of relations related to environmental protection. In particular, the constituent entities of the Federation are given the right to develop and issue laws and other regulations in the field of environmental protection, taking into account geographical, natural, socio-economic and other peculiarities, to restrict or prohibit economic and other anti-ecological activities in their territories, etc.
genetic structure population
List of sources used
Ecology: Textbook for technical universities / Tsvetkova, Alekseev et al. Ed. L.I. Tsvetkova. - M .: Publishing house ASV; SPb .: Khimizdat, 1999 .-- 488 p.
Korobkin V.I., Peredelsky. Ecology in questions and answers.
V.I. Korobkin, L.V. Peredelsky Ecology for university students.
Www. ekolog.org
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Populations and their ecological characteristics.
Within the range of a certain species, the conditions for the existence of organisms are not the same, therefore, there will be differences between the structural groupings of the species. For example, the river perch species has coastal and deep-sea populations. The number of populations depends mainly on the size of the area and the variety of living conditions. Groups of spatially adjacent populations can form a geographic race, or subspecies. The unity of individuals in the population ensures free interbreeding - panmixia... Each population is characterized by certain characteristics that emphasize it ecological features. The section of ecology that studies the conditions of formation, structure and dynamics of development of populations of certain species is usually calledpopulation ecology.
Ecological characteristics of populations is a list of features that describe the interaction of populations with a complex of environmental factors in a particular habitat.
Any population of a species occupies a certain territory, which is usually called population area... The area of the population can have different sizes, depends largely on the degree of mobility of individuals. Each population is characterized by number of -the number of individuals that is part of the population and occupies a certain area or volume in the biocenosis. Any population is theoretically capable of unlimited growth in size, but it is limited by the resources that are necessary for normal functioning. The number of individuals in the population fluctuates within certain limits, but it should not be below a certain limit. A decrease in numbers below this limit can lead to the extinction of the population. The population size is determined fertility, mortality, their ratio in the form of natural growth, as well as immigration (population) and emigration (eviction). Fertility is the number of individuals in the population, is born per unit of time, and mortality- the number of individuals of the population that die during the same time. If the birth rate prevails over the death rate, then there will be positive natural growth and the population size will increase. In accordance with the size of the population area and the number of individuals, the density is calculated populations. Population density is determined by the average number of individuals per unit area or volume. For each complex of environmental conditions, there is a certain optimal population density determined by the capacity of the habitat. The population density can be displayed through such a metric as biomass. Population biomass - mass of individuals of a population per unit area or volume.
2. Population structure.
Within a population, groups can be distinguished that determine its characteristic structure..
Population structure - dividing the population into groups of individuals that differ in certain properties (size, sex, location, behavior, etc.).
Distinguish the following types of population structure:
1) sex structure- the ratio of individuals of different sexes;
2) age structure - distribution of individuals of the population by age groups;
3) spatial structure- distribution of individuals of the population over the territory that it occupies;
4) ethological structure- a system of relationships between individuals, which is manifested in their behavior; so, the main forms of organization of animal populations are a single way of life (for example, most spiders, mallard duck) and a group way of life in the form of families (truths of lions), colonies (in wild rabbits, coastal swallows), flocks (in locusts, wolves ), herds (in ungulates, cetaceans).
3.PopulationsNo Waves .
Population waves - These are periodic or non-periodic changes in the population size under the influence of various factors. This concept was introduced by S.S. Chetverikov. Population waves are one of the causes of gene drift, causes the following phenomena : growth of genetic homogeneity (homozygosity) of the population; changes in the concentration of rare alleles, preservation of alleles that reduce the viability of individuals; change in the gene pool in different populations. All these phenomena lead to evolutionary transformations of the genetic structure of the population, and in the future to a change in the species.
Population waves are seasonal and non-seasonal:
Seasonal population waves - due to peculiarities life cycles or seasonal changes in climatic factors;
Off-season population waves - caused by changes in various environmental factors.
The population itself can maintain its size indefinitely. At the population level, there are self-regulation processes that adjust the population density to the capacity of the habitat and are manifested in the form of waves of life.
The main mechanisms for regulating the population size are:
1) regulation by relationships with populations of other species (for example, the number of lynx depends on the number of hares);
2) regulation by dispersal (migration of proteins);
3) regulation of social behavior (in social insects, separate female queens and males participate in reproduction, the number of which is regulated in the process of reproduction);
4) regulation of territorial behavior (marking of territory in bears, bison, tigers)
5) regulation by overpopulation and stressful behavior (the phenomenon of cannibalism in seagulls).
Due to long-term adaptation to the conditions of existence, the populations have developed mechanisms to avoid unlimited growth in numbers, and contribute to maintaining the population density at a relatively constant level.
4.Population homeostasis - ϶ᴛᴏ maintaining the population size at a certain level, optimal for a given habitat. Population homeostasis is influenced by abiotic factors, as well as interspecies and intraspecific relationships. 5. Ecosystems, their structure and properties.
Ecosystem-a set of organisms of different species and their habitat, associated with the exchange of matter, energy and information. Home aquarium, lake on the outskirts of the village, steppe gully, woodland, cabin spaceship, our whole planet is all ecosystems of a single biosphere. The concept of "ecosystem" was proposed in 1935 by A. Tesli. The functioning of the ecosystem provides an "internal" biological circulation of substances between abiotic and biotic parts. Ecosystems are open biosystems, and in this regard, for their existence in time, "external" flows of energy, matter and information are needed as part of the general geological cycle.
Biogeocenoses are close to ecosystems.
Biogeocenosisit is a certain territory with homogeneous living conditions, inhabited by interconnected populations of different species, united by a circle of substances and a flow of energy. The concept of biogeocenosis was introduced by V.M. Sukachov (1940). The overwhelming majority of biogeocenoses are based on photosynthetic organisms that form plant groups. Biogeocenosis, in contrast to an ecosystem, is a specific, territorial concept, because it occupies a limited area with homogeneous living conditions and with a corresponding phytocenosis (plant groupings).
The ecosystem is distinguished biotic and abiotic parts... The biotic part of an ecosystem is a collection of interconnected living organisms that form a biocenosis. Biocenosis is a grouping of interconnected populations of organisms of different species inhabiting a site with homogeneous living conditions. This concept was proposed by the German hydrobiologist K. Miobius. The basis of biocenoses is phytocenosis(plant groupings) with which zoocenoses (groupings of animals) and microbiocenoses (groupings of microorganisms) are associated. Biocenoses exist in a certain area of the environment, which is usually called biotope.
The biotic part of the ecosystem constitute various ecological groups of organisms united by spatial and trophic relationships - producers, consumers and reducers.
Producers - populations of autotrophic organisms capable of synthesizing organic substances from inorganic ones. These are green plants, cyanobacteria, photosynthetic and chemosynthetic bacteria. In aquatic ecosystems, algae are the main producers, and on land, plant seeds.
Reducers- populations of heterotrophic organisms, which in the process of their vital activity decompose dead organic matter to minerals, which are then used by producers. These are heterotrophic saprophytic organisms - bacteria and fungi that secrete enzymes and organic residues and absorb their cleavage products. Detritivores participate in the decomposition of organic compounds (they consume crushed organic matter, for example, earthworms, fly larvae), saprophages eat animal and human droppings, for example, dung beetles), necrophages (eat animal corpses, for example, dung beetles).
Part abiotic part biogeocenosis includes the following components:
Inorganic substances-compounds that are included in the biogenic migration of substances (for example, CO 2, O 2, nitrogen, water, hydrogen sulfide, etc.);
Organic matter-connections that connect the abiotic and biotic parts of the ecosystem;
Microclimate, or climatic regime - a set of conditions that determine the existence of organisms (illumination, temperature regime, humidity, terrain, etc.).
Main properties ecosystems are: integrity, self-reproduction, sustainability, self-regulation, etc. Relationships between populations in ecosystems . The composition and structure of groupings, their stability and change depend on complex relationships between populations of different species. There are the following types of links between individual populations of different species in ecosystems:
Indirect- populations of one species affect the population of another indirectly, through the populations of the third (predators, eating prey, affect plant populations);
Trophic- these are food connections (predator-prey);
Topical- these are spatial connections (orchids on tree trunks);
Antibiotic relationships(predation, competition, grazing) - each of the interacting populations of different species experiences Negative influence other;
Neutral relationships- the existence of populations of different species on a common territory does not entail any consequences for each of them (predators of different species);
6. Self-regulation of ecosystems. Agrocenoses. Self-regulation– the ability to restore internal balance after any natural or anthropogenic impact. Fluctuations in quantitative and qualitative indicators characterizing ecosystems occur around certain average (optimal) values. Ecosystem stability implies persistence (homeostasis) populations of each of its species. Regulatory factors that smooth out fluctuations in the number of individual species are intraspecific and interspecific relationships... The state of equilibrium of a population is determined by the ratio of limiting factors that predetermine the resistance of the environment, on the one hand, and the biotic potential of reproduction, on the other. The ecosystem only strives for sustainability, but never achieves it: first, they change external conditions secondly, species change habitats.
Control of knowledge and skills:
1) What is population structure?
2) What are the types of population structure?
3) How is the population size regulated?
4) What is the main factor influencing the homeostasis of the population?
5) what is the difference between an ecosystem and a biogeocenosis?
Homework: retelling of the synopsis͵ §28.29, (30-33.47) prepare messages, Lek.№ 25.
Populations and their ecological characteristics. - concept and types. Classification and features of the category "Populations and their ecological characteristics." 2017, 2018.
