Population species. Population-species level

The combination of individuals in a population, and the latter into species according to the degree of genetic and ecological unity, leads to the emergence of new properties and features in wildlife. A population is a system of individuals of the same species that occupy a certain space for a long time and reproduce themselves over a large number of generations. A species is a system of populations of individuals that have a number of common morpho-physiological features that are capable of interbreeding with the formation of fertile offspring. A population is an elementary structure at the population-species level, and an elementary phenomenon at this level is a change in the genotypic composition of a population; the elemental material at this level is mutations. Relations between individuals within a population and species play a special role. At the same time, populations act as the main evolutionary units, which are genetically open systems (individuals from different populations sometimes interbreed, thus, genetic information is exchanged). Populations and species are capable of long-term existence and independent evolutionary development. The life of an individual in this case depends on population processes. Population-species integrity is associated with the interaction of individuals within populations and is maintained by the exchange of genetic material in the process of sexual reproduction.

6. Biogeocenotic (ecosystem) level. Principles of sustainability of biogeocenosis.

Populations of different species form complex communities - biocenoses. Biocenoses - a set of plants, animals, fungi and prokaryotes that inhabit areas of land or water and are in certain relationships with each other. Together with specific areas of the earth's surface occupied by biocenoses and the adjacent atmosphere, they form an ecosystem (biogeocenosis). An ecosystem is an interdependent complex of living and non-living (inert) components interconnected by the metabolism and energy. The name "biogeocenosis" is used only in relation to natural systems. In general, the life of a biogeocenosis is mainly regulated by forces acting within the system itself, i.e. we can talk about self-regulation of biogeocenosis. Biogeocenosis is an open system that has energy "inputs" and "outputs" that connect neighboring biogeocenoses, the exchange of substances between which can be carried out both in gaseous and in liquid and solid phases, as well as in the form of living matter (for example, animal migration) . The current state of ecosystems is the result of a long evolution and adaptation of organisms to each other and to the conditions of existence. All ecosystem groups are a product of the joint historical development of species that differ and adapt to each other. The primary basis for the functioning of the ecosystem are plants and prokaryotes - autotrophs, synthesizing organic substances necessary for life from inorganic substances (water, carbon dioxide, nitrogen compounds). Autotrophs use the energy of photosynthesis (green plants) or chemosynthesis (bacteria). They are producers that create a living environment for heterotrophs that consume ready-made organic substances and are incapable of synthesizing them from inorganic ones. Heterotrophs are animals and fungi. These consumers, in turn, are divided into consumers - (herbivorous animals and predators) and decomposers (fungi, microorganisms that decompose organic matter.) Populations of different species in ecosystems affect each other according to the principle of direct and feedback. In ecosystems, food (trophic) chains are distinguished - through them, the transformation of matter and energy occurs. During the transition of energy from one link to another, up to 80-90% of it is lost in the form of heat, so the chains usually include no more than 4-5 links, and the production of each subsequent link is less than the previous one. The totality of all organisms united by a single type of nutrition form a trophic level. In the ecosystem, the pyramid rule is implemented: the production of each subsequent trophic level is approximately 10 times less than the previous one. The composition of the food of each species may include other different species, and each species can serve as food for other different species, i.e. Food chains intertwine to form food webs. The ecosystem implements the principles of stability and balance:

sustainability principle: the more trophic levels in an ecosystem and the more diverse they are, the more stable the ecosystem;

balance principle: there is a balance between species in an ecosystem, and a deviation from it in one direction or another can lead to disaster.

Human economic activity has led to dramatic changes in all components of biocenoses. Natural biocenoses are being replaced by artificial ones - agrobiocenoses, urban biocenoses. Agrobiocenosis (and urban biocenosis) is a secondary biogeocenosis that can exist only with constant renewal by man.

6. Biogeocenotic (ecosystem) level. Principles of sustainability of biogeocenosis.

sustainability principle: the more trophic levels in an ecosystem and the more diverse they are, the more stable the ecosystem;

balance principle: there is a balance between species in an ecosystem, and a deviation from it in one direction or another can lead to disaster.

biospheric level

The biosphere is the unity of all biogeocenoses, a system covering all the phenomena of life on Earth. This term was introduced in 1875 by the geologist E. Suess (), but it became widespread in the 20s of the twentieth century, when the teachings of V.I. Vernadsky about the biosphere. According to Vernadsky, the biosphere is those parts of the earth's shells (litho-, hydro- and atmosphere) that have been influenced by living organisms throughout geological history and bear traces of their vital activity. The biosphere arose during the formation of the earth's crust and currently occupies a space from approximately 10 km below the Earth to 33 km above it. It should be noted a very narrow range of physical conditions for the existence of life, and in a certain sense, the uniqueness of the environment in which life is possible. At the same time, Life gradually, slowly adapting, captured a significant part of the Earth, and this capture continues.

Vernadsky's biogeochemical approach allows us to consider the entire set of living organisms as a certain type - living matter. In addition to it, the biosphere contains inanimate or inert matter, as well as a bio-inert substance that is complex in nature, including both living organisms and inanimate matter modified by them (soils, silts, natural waters). The most important feature of the biosphere is the presence of biotic cycles of matter. As a result of the ability to transform energy and metabolism, as well as to reproduce and disperse, living organisms cause biogenic migration of atoms. At the same time, as Vernadsky pointed out, the biogenic migration of chemical elements in the biosphere tends to its maximum manifestation. The vital activity of organisms is one of the most important geological factors. The originality of this factor is associated primarily with evolution. “Due to the evolution of species, continuously going on and never stopping, the reflection of living matter on the environment changes dramatically ... The evolution of species turns into the evolution of the biosphere” (V.I. Vernadsky).

Modern natural science, in the course of studying the interaction of biocenoses in the biosphere, introduces a new concept - "coevolution", meaning the mutual adaptation of species. Co-evolution is a promising concept in the natural and social sciences, in which the decisive role in existence is played not by struggle, but by consistency, the cooperation of different species that are not genetically related. Energy, information and social concepts of the biosphere are currently being intensively developed.

Population-species standard of living The work was done by a 10th grade student Anastasia Davidovich Biology teacher: Yandyshev G.I.

Species A species is a collection of individuals that are similar in terms of species criteria to such an extent that they can naturally interbreed and produce fertile offspring.

Morphological criterion Morphological criterion involves the description of the external features of individuals that are part of a particular species. In appearance, size and color of plumage, for example, it is easy to distinguish a large spotted woodpecker from a green one.

Physiological criterion The physiological criterion consists in the similarity of life processes, primarily in the possibility of crossing between individuals of the same species with the formation of fertile offspring. There is a physiological isolation between different species.

Geographic criterion Geographic criterion is based on the fact that each species occupies a certain territory or water area. In other words, each species is characterized by a certain geographical area.

Ecological criterion The ecological criterion is based on the fact that each species can exist only under certain conditions, performing the corresponding function in a certain biogeocenosis. In other words, each species occupies a specific ecological niche.

Genetic criterion The genetic criterion is based on the difference between species according to karyotypes, that is, according to the number, shape and size of chromosomes. The vast majority of species are characterized by a strictly defined karyotype.

Biochemical criterion The biochemical criterion makes it possible to distinguish species by biochemical parameters (composition and structure of certain proteins, nucleic acids and other substances). It is known that the synthesis of certain macromolecular substances is inherent only in certain groups of species.

Population as a Structural Unit of a Species A set of individuals of the same species living in the same area and interbreeding freely is called a population. A population is the elementary structural unit of a species. Individuals of the same species, within the range, are not distributed evenly, but in clusters - populations, between which there are breaks. Thus, a species exists as a collection of populations. Individuals of one population are more similar to each other than representatives of other populations.

Population as a unit of evolution A population is the smallest of groups of individuals capable of evolutionary development, therefore it is called an elementary unit of evolution. A single organism cannot be a unit of evolution. Evolution occurs only in a group of individuals.

Speciation Speciation is the most complex process in the development of living matter. The emergence of a new species is always accompanied by a rupture of ties with the parent species and transformation into a new, separate set of populations and organisms. A new species may be formed from one population or a group of adjacent populations.

Biodiversity Conservation Adopt effective economic, social and other appropriate incentive measures to promote the conservation of biological diversity and the sustainable use of biological resources. Contribute to the restoration of disturbed ecosystems and the restoration of endangered or endangered species. Develop new or strengthen existing strategies, plans or action programs for the protection of biological diversity and the sustainable use of biological resources. Promote environmentally sound and sustainable development in areas adjacent to protected areas.

In modern biology, living matter is usually considered as a hierarchical structure. Each level is a system of interconnected elements. At the same time, a separate structural unit is at the same time a set of “details” of a lower order. The population-species level of life organization is one of such steps in the hierarchical ladder of organisms. It is on it that all evolutionary changes begin to manifest themselves in full measure.

Hierarchical model

Living systems are usually combined into four groups:

Molecular genetic level. It houses such components of living organisms as lipids, carbohydrates, proteins and nucleic acids. This level cannot yet be called alive, but the macromolecules that make it up form the basis for the next stage of development.

ontogenetic level. Cells, organs, tissues, and from hydra to humans are located here. It is at this level that life first arises.

Population-species level. This article is devoted to the presentation of its features.

Biogeocenotic level. Includes communities of organisms, biocenoses and the biosphere. This is the level at which the organization of living matter reaches its greatest complexity.

Some Features

The structures located at each of the levels are systemic. They tend to consist of a certain number of elements, constantly interact with the environment, manage internal processes with the help of self-regulation. They have a boundary that defines where the system ends and the outside world begins. The population-species level is a structure with similar properties. The boundary separating it from its environment is not some physical structure, but complex relationships of individuals and genetic factors.

The population-species level of life organization is the most important for understanding evolutionary processes. It is at this stage that all the main selection mechanisms are clearly visible. The main elements of a level are species and population.

Selection criteria

There are many types of living beings on our planet. The differences between them are determined by a whole set of characteristics. All of them are different variants of the similarity of individuals of the same species:

Lack of main

Any of these features, taken separately and found in a group of individuals, does not guarantee that we have the described element, which constitutes the population-species standard of living. Only all the parameters taken together make it possible to assert that the group of organisms under consideration constitutes a single whole. By morphological features, the so-called twin species may be similar. An example of them are roundworms, which are generally identical in structure, but differ in habitat. It also happens that individuals of the same species differ in appearance. A common example is the mismatch in color and size of females and males of some birds or insects.

A single habitat area in isolation from other indicators can also lead to erroneous assignment of individuals to one species. The range is often fragmented due to some landscape characteristics. Conversely, individuals of completely different species often live together in the same territory.

Definition

Similar examples can be found for any of the listed parameters. The elements that make up the population-species level of life organization can be distinguished only by using the entire set of features. The most significant is the free interbreeding of individuals and fertile offspring. Based on these features, a definition of the concept can be derived. A species is a collection of individuals that are similar in internal and external structure, as well as the course of life processes, occupying one area and able to freely interbreed with each other, leaving offspring capable of reproduction.

Subdivisions

The population-species level, examples of which are found in any territory, is that step in the hierarchy of life where all the mechanisms of natural selection are fully deployed. It is here that the so-called unit of evolution is located. which is also a structural element of the view. The latter is rather a systematic unit. In nature, it is impossible to find a species that is not divided into populations.

This element, which is included in the population-species level, has several characteristics:

all individuals belong to the same species;
they inhabit a relatively isolated range within the territory of a given species;
individuals interbreed freely and leave fertile offspring.

Indicators

The division of a species into populations most often occurs as a result of the geographical or biological isolation of one group of individuals from others. In the first case, they are separated by mountains, lakes, rivers or other natural barriers. In the second, as a result of slightly different needs in environmental conditions, differences in behavior or the presence of mutations, the possibility of crossing individuals of different groups disappears.

Populations have a set of indicators such as numbers, births, deaths, and growth. The first is the collection of all individuals. The population is distinguished by the ability to self-regulate its numbers. The limiting factor is the resistance of the environment: as a result of an increase in the number of individuals, the food supply in the given territory decreases, and other conditions worsen. The answer to this will be a decrease in the number - its restoration to a certain average level.

Important indicators of this element included in the population-species are the birth rate and mortality. They represent the number of appeared and dead individuals for a certain period, respectively. The difference between them is called growth. It is negative and positive. In the first case, the population decreases, and in the second - increases.

Structure

Individuals of the element under consideration, which is included in the population-species level of life organization, differ in sex and age. These indicators formed the basis for identifying the relevant structures. The ratio of males and females, as a rule, is one to one, however, due to the influence of external factors, disharmony in this parameter may occur. The simultaneous presence in the population of individuals of different ages contributes to its greater adaptability. At the same time, an increase in the number of “young animals” makes it possible to predict an increase in the population size in the future.

There is also a behavioral structure that is characteristic exclusively for animals. Individuals in a population can be solitary or form flocks, families, and herds. The former, sooner or later, look for societies of their own kind, since otherwise reproduction is impossible. The flock is characterized by the presence of a large number of imitative reactions, a clear internal order, and a developed alarm system. During the breeding season, as a rule, it breaks up into pairs. In the family, the relationship between offspring and parents becomes stronger. A good example of this type of behavioral structure is a lion pride consisting of one male, several females and their cubs.

The herd is the most permanent association of animals. It is characterized by the presence of a strict hierarchy headed by a leader.

Evolution unit

As already noted, the population-species level of organization is that step in the hierarchy of living systems at which the evolutionary process can be fully traced. Change starts with the population. Individuals, its components, have a gene pool, that is, the totality of the hereditary material of all organisms. It is characterized by the ability to directed change. The population is called the unit of evolution, since an individual organism cannot change during its life due to the fixed set of its genes.

evolutionary material

Changes in the gene pool occur as a result of the appearance and accumulation of mutations. They appear quite rarely and can affect any symptom. Distinguish between dominant and recessive mutations. The first, having appeared, immediately appear. Individuals with a new trait are then subjected to natural selection. If the mutation is beneficial, then it is fixed. Gradually, the number of individuals with this trait increases in the population.

Recessive mutations, which occur in nature much more often than dominant ones, are initially inactive. They accumulate in the gene pool over an often quite long period. When a certain level of concentration of such mutations is reached, they can manifest themselves as a new trait, and the process will proceed similarly to that described above.

Also, the appearance of various characteristics of individuals is possible on the basis of mixing (combination) of the material available in the gene pool as a result of free crossing. In this case, the number of possible variations will be the greater, the more impressive the size of the population.

Directed Change

In relatively calm, that is, constant, conditions, individuals with a different set of traits coexist in a population. At the same time, a certain average composition of genes is maintained. In the case when individuals are subject to the constant influence of aggressive organisms, only the most adapted organisms will survive. This is how the vigilantly “controlling” population-species level works. Examples of its impact constitute the entire evolution of the animal world. Such changes in the gene pool are a necessary prerequisite for all larger transformations.

In the natural hierarchy, it is impossible to single out the most important and necessary structures. Each higher level of development is impossible without the "developments" of the previous ones. However, a new step is always qualitatively different from the simple sum of singularities of the underlying ones. Thus, the population-species becomes the "field of activity" of natural selection, the main evolutionary process.

A population is a collection of individuals of the same species that has all the necessary conditions to maintain its own population for an indefinitely long time in constantly changing environmental conditions.

population - the main elementary structure at the population-species level, and the elementary phenomenon at this level is a change in the genotypic composition of the population; elementary material this level - mutations.

In the synthetic theory of evolution, the elementary factors operating at this level are singled out: the mutation process, external conditions (population waves, isolation), and natural selection. Each of these factors can have a certain effect on the population and cause changes in the genotypic composition of the population.

At the population-species level, free interbreeding between individuals within a population and species plays a special role. Species are the smallest genetically closed systems, since the crossing of individuals of different species in nature in the vast majority of cases does not lead to the appearance of fertile offspring.

Populations are integral, although they consist of many individuals. Their integrity is ensured by the interaction of individuals in populations and is recreated through the exchange of genetic material in the process of sexual reproduction.

Population characteristics:

1. number - the total number of individuals in a given territory or in a given volume. The population size depends on the ratio of the intensity of reproduction and mortality.

2. Density is the number of individuals (or biomass) per unit area (or volume).

3. spatial distribution of individuals in a population, which is uniform, random and group. Knowledge of the spatial distribution of individuals is of great importance in assessing the population density and identifying dominant species.

4. fertility - the number of new individuals that appeared in the population for a certain period of time. Distinguish between maximum and realized fertility.

5. mortality - the number of dead individuals in a population for a certain period of time.

6. age structure of the population - the ratio of age groups, allocated according to the ability of individuals to reproduce.

Biogeocenotic level. Includes biocenoses, biogeocenoses and the biosphere.

Biocenosis- a set of plants, animals, fungi and microorganisms that inhabit an area of the environment with more or less homogeneous conditions of existence and are characterized by certain relationships with each other.

Biocenosis is formed by species capable of coexistence. The adaptation of members of the biocenosis to living together is expressed in a certain similarity of requirements for abiotic environmental conditions and relationships with each other.

Characteristics of the biocenosis.

1. species structure - the diversity of species in the biocenosis and the ratio of their abundance or mass. The species composition of biocenoses depends on the duration and history of the existence of communities.

2. spatial structure. Allocate the horizontal and vertical structure of the biocenosis. The vertical structure of the biocenosis is expressed in layers and reduces competition for light resources between plants. The horizontal structure is expressed in the mosaic nature of communities and reflects its complex structure associated with micro-differences in the community habitat.

3. the relationship of organisms in the biocenosis - the glue that does not allow the community to break up into separate parts, these are all the interactions that the organisms of the biocenosis enter into. The determining relationships in the communities of living beings are food (trophic), which are observed when one species feeds on another, either its remains or waste products. Food relations determine the ecological niches of living organisms that are part of the community. Gause's rule: two different species cannot occupy the same ecological niche. Another important type of relationship is the relationship of place - these are any changes in the living conditions of one species as a result of the life of another. In addition to those listed, other types of relationships in the biocenosis are distinguished.

Biocenoses are included as components in even more complex systems (communities) - biogeocenoses.

Biogeocenosis (ecosystem, ecological system) ~ an interdependent complex of living and abiotic components interconnected by the metabolism and energy.

Biogeocenosis is one of the most complex natural systems. Biogeocenoses consist of abiotic components (biotope) and biotic components (biocenosis). The abiotic components of biogeocenoses are the atmosphere, solar energy, soil, and water. The components of the biocenosis are plants, animals, microorganisms and fungi. From the point of view of the trophic structure, the biotic components of biogeocenosis are divided into autotrophs and heterotrophs. Autotrophs - green plants and microorganisms, chemosynthetics that produce organic matter. Autotrophic plants and microorganisms represent the living environment for heterotrophs - consumers of ready-made organic matter (animals, fungi, most bacteria, viruses).

Characteristics of biogeocenosis.

1. integrity. Biogeocenosis is an integral system. The loss of one or more components of the biogeocenosis can lead to an irreversible imbalance and the death of the biogeocenosis as a system.

2. Self-organization and self-regulation. The life of biogeocenosis is regulated by forces acting within the system itself.

3. the structure of biogeocenosis, expressed in internal connections and interaction with the environment. Species in biogeocenosis act on each other not only according to the principle of direct, but also feedback (including through changes in abiotic conditions). At the same time, a biogeocenosis is a rather isolated system that has substance and energy outlet channels that connect neighboring biogeocenoses.

4. stability. Biogeocenosis is a balanced, interconnected and time-resistant system, which is the result of a long and deep adaptation of its constituent components. Its stability is proportional to the diversity of its components: the more diverse the biogeocenosis, the more stable it is, as a rule, in time and space. For example, biogeocenoses represented by tropical forests are much more stable than biogeocenoses in the temperate or arctic zones, since tropical biogeocenoses consist of a much larger variety of plant and animal species than temperate, and even more so, arctic biogeocenoses.

The whole set of biogeocenoses interconnected by the circulation of substances and energy on the surface of our planet forms the biosphere of the Earth.

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