The structure of any system is the pattern in the relationship and connections of its parts. Under species structure biocenosis understand the diversity of species in it and the ratio of their number or mass. Each specific biocenosis is characterized by a strictly defined species composition. Wherever the conditions of the abiotic environment approach optimal for life, species-rich communities arise, for example, tropical forests, coral reefs, river valleys in arid regions, etc. An increase in species diversity as one moves from north to south was formulated by A. Wallace in 1859 . and received the name Wallace's rule. It concerns both the species and the communities that make up them. The species composition of biocenoses depends on both the duration of their existence and the history of each biocenosis.

Young, emerging communities, as a rule, have a smaller set of species than long-established, mature ones. Biocenoses created by man (vegetable gardens, orchards, fields, etc.) are usually poorer in species in comparison with natural systems similar to them (forest, meadow, steppe). However, even the most impoverished biocenoses include several dozen species of organisms that belong to different systematic and ecological groups. Moreover, some types of biocenosis can be represented by numerous populations, while others are small. Hence it follows that in any biocenosis one or several species can be distinguished, which determine its appearance. Thus, the appearance of a forest or steppe biocenosis is represented by one or several plant species. In the forest - pine, spruce; in the feather-grass-fescue steppe - feather-grass and fescue. To assess the quantitative ratio of species in biocenoses, ecological literature uses diversity index, calculated by Shannon's formula:

where is the sign of the sum,

pi is the share of each species in the community (by number or mass),

log 2 Pi is the binary logarithm of pi.

To assess the role of a particular species in the species structure of the biocenosis, different indicators based on quantitative accounting are used. An abundance of species - this is the number of individuals of a given species per unit area or volume of occupied space. For example, the number of birds nesting per 1 km 2 of the steppe area, or the number of small crustaceans per 1 dm 3 of water in a reservoir, etc. To calculate the abundance of a species, instead of the number of individuals, the value of their total biomass is sometimes used. The abundance of a species as an indicator changes over time (seasonal, annual and random fluctuations in numbers) and in space (from one biocenosis to another). It is not always easy to pinpoint the abundance of species. In this regard, in practice, they are often limited to the use of a less accurate point estimate, highlighting five degrees of abundance: 0 - no; 1 - rarely and absent-mindedly; 2 - often; 3 - abundant; 4 - very abundant.

Frequency of occurrence characterizes the uniformity or uneven distribution of the species in the biocenosis. Calculated as the percentage of the number of samples and counting sites where the species occurs to the total number of such samples or sites. You can calculate the frequency for one sample and for all samples of a given biocenosis and, on this basis, construct a histogram of frequencies.

Consistency. Represents the following ratio, expressed as a percentage:

where p is the number of samples containing the species under study,

P is the total number of samples taken.

Depending on the value of C, there are the following categories of species:

permanent species are found in more than 50% of samples;

additional species are found in 25-50% of samples;

random species are found in less than 25% of samples.

The abundance and occurrence of the species are not directly related. The species may be small in number, but the occurrence is rather high, or numerous, but with a low occurrence. In a forest that consists of dozens of plant species, usually one or two of them provide up to 90% of the timber. These species are called dominant and dominant. They occupy a leading, dominant position in the biocenosis. Terrestrial biocenoses, as a rule, are named after the dominant species: birch forest, feather grass-fescue steppe, sphagnum bog.

Dominance degree - This is an indicator that reflects the ratio of the number of individuals of a given species to the number of individuals of all species of the group under consideration. So, if out of 200 birds registered in a given territory, 100 are finches, the degree of dominance of this species among birds will be 50%.

In all biocenoses, small forms prevail numerically - bacteria and other microorganisms. When comparing species of different sizes, the indicator of dominance in numbers cannot reflect the characteristics of the community. It is calculated not for the community as a whole, but for individual groupings, within which the difference in size can be neglected.

Species that live off dominants are named predominants. For example, in a pine forest these are insects, squirrels, and murine rodents feeding on a pine tree.

However, not all dominant species have the same effect on the biocenosis. The biocenosis also contains the so-called edifiers - species that by their life activity to the greatest extent create an environment for the entire community and without which, in this regard, the existence of most other species is impossible. They are community builders. Removal of the edificator species from the biocenosis entails a change in the physical environment, primarily the microclimate of the biotope. The edificators of terrestrial biocenoses are certain types of plants: in birch forests - birch, in pine forests - pine, in the steppes - cereals (feather grass, fescue, etc.). Spruce in the taiga zone forms dense, heavily shaded forests. Only plants that are adapted to conditions of strong shading, high air humidity, and acidic podzolized soils can live under its canopy. In accordance with this, a specific animal population is also formed in the spruce forests. In this case, the spruce acts as a powerful edifier that determines a certain biocenosis.

In pine forests, the edificator is pine. However, in comparison with spruce, pine is a weaker edifier, since the pine forest is comparatively light and sparsely. The species composition of plants and animals is much richer and more diverse here than in the spruce forest.

Edificator species are found in almost any biocenosis. In some cases, animals are also edificators. In the territories occupied by marmot colonies, it is their burrowing activity that determines for the most part the nature of the landscape, the microclimate and the conditions for the growth of plants.

In addition to a relatively small number of dominant species, the biocenosis includes; as a rule, a significant number of small and even rare forms. There is a definite connection between the number of dominant species and the general species composition of the community. With a decrease in the number of species, the abundance of individual forms usually increases sharply, biocenotic connections weaken, the most competitive species get the opportunity to reproduce without hindrance. The more specific the environmental conditions, the poorer the species composition of the community and the higher the number of individual species.

Thus, all the species that make up the biocenosis are to a certain extent associated with the dominant species and edificators. Within the biocenosis, to one degree or another close groupings, complexes of populations that depend on edificator plants or on other elements of the biocenosis are formed; peculiar structural units of the biocenosis - consortia - are created. The term "consortium" was first introduced by L.G. Ramensky (1952).

A consortium is a set of populations of organisms, the vital activity of which within one biocenosis is trophically or topically related to the central species - an autotrophic plant. The edificator is usually the central species - the main species that determines the characteristics of the biocenosis. The populations of the remaining species of the consortium form its core, due to which there are species that destroy the organic matter created by autotrophs. Populations of an autotrophic plant, for example birch, on the basis of which a consortium is formed, are called determinant, and the views united around it - consorts(fig. 2).

biocenosis ecological niche organism

Rice. 2.

Rice. 3.

Central view (consortium determinant); I, II, III - concentrates _ - consorts, among them: I - phytophages, epiphytes, symbionts; II, III - zoophages (after V.V. Mazin, 1966)

Each consortium, as we can see, covers a large number of species. Number their it is also great because the determinants are represented in biocenoses (ecosystems) by a different age composition. Often, each age stage of organisms is accompanied by its own consortium population. So, stem pests affect mostly adult spruce, and at the same time, rust fungi more affect young specimens. With the age of the spruce, the composition of its consorts, feeding on root secretions, changes.

The composition of the consortium is the result of a long process of selecting species that can exist in the habitat of the determinant. Each consortium is a special structural unit of the biocenosis, ecosystem.

Send your good work in the knowledge base is simple. Use the form below

Students, graduate students, young scientists who use the knowledge base in their studies and work will be very grateful to you.

Posted on http://www.allbest.ru/

Introduction

1. Biocenosis - general information and concepts

2. The structure of the biocenosis

3. Modern problems of biocenoses and ways to solve them

Conclusion

Bibliography

Introduction

A biocenosis is a historically formed set of animals, plants, fungi and microorganisms that inhabit a relatively homogeneous living space (a certain area of ​​land or water area), and are connected with each other and their environment. The concept of "biocenosis" is one of the most important in ecology, since it implies that living things form complexly organized systems on Earth, outside of which they cannot stably exist.

Biocenosis is one of the main objects of ecology research. Problems of stability of biocenoses, a decrease in the number of populations, the disappearance of entire species of living organisms are acute problems facing mankind today. Therefore, the study of biocenoses, their structure and conditions of sustainability is an important ecological task, which has been and continues to be given great attention by ecologists of all countries of the world, including Russian scientists.

In this work, I will dwell in detail on such issues as the properties and structure of the biocenosis, the conditions for their stability, as well as the main modern problems and ways to solve them. It should be noted that in the mind of a person who is not a specialist in the field of ecology, there is confusion in the concepts of "biocenosis", "ecosystem", "biogeocenosis", "biosphere", so I will briefly dwell on the issue of similarities and differences between these concepts and their interrelationships. Biocenosis is one of the main objects of ecology research. Ecologists from all countries of the world, including Russian scientists, have paid and continue to pay great attention to the study of biocenoses. In the process of working on the abstract, I used textbooks written by well-known foreign ecologists: Y. Odum, V. Tishler; and by Russian authors: Korobkin V.I., Peredelsky L.V., as well as modern electronic resources indicated in the list of references.

1. Bioc enosis - general information and concepts

Biocenosis (from the Greek vYapt - "life" and kpint - "common") is a historically formed set of animals, plants, fungi and microorganisms that inhabit a relatively homogeneous living space (a certain area of ​​land or water area), and are interconnected and their environment. Biocenoses have arisen on the basis of the biogenic cycle and provide it in specific natural conditions. Biocenosis is a dynamic system capable of self-regulation, the components of which (producers, consumers, reducers) are interconnected.

The most important quantitative indicators of biocenoses are biodiversity (the total number of species in it) and biomass (the total mass of all types of living organisms in a given biocenosis).

The concept of "biocenosis" is one of the most important in ecology, since it implies that living things form complexly organized systems on Earth, outside of which they cannot stably exist. The main function of a community is to ensure equilibrium in an ecosystem based on a closed cycle of substances.

Biocenoses can include thousands of species of various organisms. But not all of them are equally significant. Removal from the community of some of them does not have a noticeable effect on them, while the removal of others leads to significant changes.

Some types of biocenosis can be represented by numerous populations, while others are small. The scale of biocenotic groupings of organisms is very different - from communities of lichen cushions on tree trunks or a decaying stump to the population of entire landscapes: forests, steppes, deserts, etc.

The organization of life at the biocenotic level is subordinated to the hierarchy. With an increase in the scale of communities, their complexity and the proportion of indirect, indirect connections between species increase.

Natural associations of living beings have their own laws of functioning and development, i.e. are natural systems.

Thus, being, like organisms, structural units of living nature, biocenoses, nevertheless, develop and maintain their stability on the basis of other principles. They are systems of the so-called frame type - without special control and coordinating centers, and are also built on numerous and complex internal connections.

The most important features of systems related to the supraorganic level of organization of life, for example, according to the classification of the German ecologist W. Tischler, are the following:

1) Communities always arise, are made up of ready-made parts (representatives of various species or whole complexes of species) available in the environment. This is the way of their occurrence differs from the formation of a separate organism, which occurs through the gradual differentiation of the simplest initial state.

2) Parts of the community are interchangeable. Parts (organs) of any organism are unique.

3) If the whole organism maintains constant coordination, the consistency of the activity of its organs, cells and tissues, then the superorganic system exists mainly due to the balancing of oppositely directed forces.

4) Communities are based on the quantitative regulation of the number of some species by others.

5) The limiting dimensions of an organism are limited by its internal hereditary program. The sizes of the superorganic systems are determined by external factors.

A homogeneous natural living space (part of the abiotic environment) occupied by a biocenosis is called a biotope. It can be a piece of land or a body of water, a seashore or a mountainside. A biotope is an inorganic environment, which is a necessary condition for the existence of a biocenosis. Biocenosis and biotope closely interact with each other.

The scale of biocenoses can be different - from communities of lichens on tree trunks, moss bumps in a swamp or decaying stump to populations of entire landscapes. So, on land, one can distinguish a biocenosis of a dry (not flooded with water) meadow, a biocenosis of a white moss pine forest, a biocenosis of a feather-grass steppe, a biocenosis of a wheat field, etc.

Distinguish between the concepts of "species richness" and "species diversity" of biocenoses. Species richness is a general set of species of a community, which is expressed by a list of representatives of different groups of organisms. Species diversity is an indicator reflecting not only the qualitative composition of the biocenosis, but also the quantitative relationships of species.

Distinguish between poor and species-rich biocenoses. The species composition of biocenoses, in addition, depends on the duration of their existence, the history of each biocenosis. Young, just emerging communities usually include a smaller set of species than long-established, mature ones. Biocenoses created by man (fields, orchards, vegetable gardens) are also poorer in species than natural systems similar to them (forest, steppe, meadow). Man maintains the uniformity and species poverty of agrocenoses with a special complex system of agrotechnical measures.

Almost all terrestrial and most aquatic biocenoses include microorganisms, plants and animals. The stronger the differences between two adjacent biotopes, the more heterogeneous the conditions at their borders and the stronger the border effect is. The number of a particular group of organisms in biocenoses strongly depends on their size. The smaller the individuals of the species, the higher their number in biotopes.

Groups of organisms of different sizes live in a biocenosis at different scales of space and time. For example, the life cycles of unicellular organisms can occur within an hour, and the life cycles of large plants and animals are stretched over tens of years.

Naturally, in all biocenoses, the smallest forms, bacteria and other microorganisms, prevail numerically. In each community, it is possible to distinguish a group of main species, the most numerous in each size class, the connections between which are decisive for the functioning of the biocenosis as a whole. The dominant species (productivity) are the dominants of the community. Dominants dominate the community and constitute the “species core” of any biocenosis.

For example, when studying a pasture, it was found that the maximum area in it is occupied by a bluegrass plant, and among the animals grazing there, there are most of all cows. This means that bluegrass dominates among producers, while cows dominate among consumers.

In the richest biocenoses, almost all species are few in number. In tropical forests, it is rare to find several trees of the same species nearby. In such communities, outbreaks of mass reproduction of certain species do not occur; biocenoses are highly stable.

The totality of all types of a community makes up its biodiversity. Typically, a community consists of several main species with a high abundance and many rare species with a small abundance.

Biodiversity is responsible for the equilibrium state of the ecosystem, and therefore for its sustainability. The closed cycle of nutrients (biogens) occurs only due to biological diversity.

Substances that are not assimilated by some organisms are assimilated by others, therefore the release of nutrients from the ecosystem is small, and their constant presence ensures the balance of the ecosystem.

Human activity greatly reduces the diversity in natural communities, which requires predictions and forecasts of its consequences, as well as effective measures to maintain natural systems.

1.1 Biocenosis, ecosystem, biosphere

Ecosystem (from ancient Greek pkpt - dwelling, habitation and ueufzmb - system) is a biological system consisting of a community of living organisms (biocenosis), their habitat (biotope), a system of connections that exchange matter and energy between them. Thus, the biocenosis is the main component of the ecosystem, its biotic component.

The ecological view of the world is based on the idea that every living creature is surrounded by many different factors influencing it, which form its habitat in a complex - a biotope. Consequently, a biotope is an area of ​​a territory that is homogeneous in terms of living conditions for certain species of plants or animals (a slope of a ravine, an urban forest park, a small lake or part of a large one, but with uniform conditions - the coastal part, deep-water part).

Organisms characteristic of a particular biotope constitute a vital community, or biocenosis (animals, plants and microorganisms of a lake, meadow, coastal strip).

The biocenosis forms a single whole with its biotope, which is called an ecological system (ecosystem). An example of natural ecosystems is an anthill, lake, pond, meadow, forest, city, farm. The classic example of an artificial ecosystem is the spaceship. species spatial trophic biocenosis

Close to the concept of ecosystem is the concept of biogeocenosis. Supporters of the ecosystem approach in Zapkada, incl. Y. Odum, consider these concepts to be synonyms. However, a number of Russian scientists do not share this opinion, seeing a number of differences. Of particular importance for the identification of ecosystems are the trophic relationships of organisms that regulate the entire energy of biotic communities and the ecosystem as a whole.

Attempts to create a classification of the ecosystems of the globe have been undertaken for a long time, but there is still no convenient, universal classification. The point is that due to the huge variety of types of natural ecosystems, because of their lack of rank, it is very difficult to find that single criterion, based on which, one can develop such a classification.

If a puddle, a hummock in a swamp, or a sand dune with fixed vegetation can be a separate ecosystem, then, naturally, all possible variants of hummocks, puddles, etc. can be calculated. does not seem possible. Therefore, ecologists decided to focus on large combinations of ecosystems - biomes. A biome is a large biosystem that is characterized by some dominant vegetation type or other landscape feature. According to the American ecologist R. Whittaker, the main type of community of any continent, distinguished by physiognomic characteristics of vegetation, is the biome. Moving from the north of the planet to the equator, there are nine main types of land biomes: tundra, taiga, temperate deciduous forest biome, temperate steppe, Mediterranean ooze vegetation, desert, tropical savannah and grassland biome, tropical or thorny woodland, tropical forest biome ...

The main components of ecosystems are:

1) inanimate (abiotic) environment. These are water, minerals, gases, as well as organic substances and humus;

2) biotic components. These include: producers or producers (green plants), consumers, or consumers (living things that feed on producers), and decomposers or decomposers (microorganisms).

The biomass created by organisms (the substance of the bodies of organisms) and the energy contained in them are transferred to other members of the ecosystem: animals eat plants, these animals are eaten by other animals. This process is called the food, or trophic, chain. In nature, food chains often intersect to form a food web. Examples of food webs: plant - herbivore - carnivore; cereal - field mouse - fox, etc. and the food web are shown in Fig. 1.

Rice. 1. Food web and direction of flow of matter

The biosphere is the shell of the Earth, inhabited by living organisms, under their influence and occupied by the products of their vital activity. The biosphere is the global ecosystem of the Earth. It penetrates into the entire hydrosphere, the upper part of the lithosphere and the lower part of the atmosphere, that is, it inhabits the ecosphere. The biosphere is a collection of all living organisms. It is home to over 3,000,000 species of plants, animals, fungi and bacteria. Man is also a part of the biosphere, his activity surpasses many natural processes.

The state of equilibrium in the biosphere is based on the interaction of biotic and abiotic environmental factors, which is maintained due to the continuous exchange of matter and energy between all components of ecosystems.

In the closed cycles of natural ecosystems, along with others, two factors must participate: the presence of decomposers and the constant supply of solar energy. In urban and artificial ecosystems, there are few or no decomposers; therefore, liquid, solid and gaseous wastes accumulate, polluting the environment.

1.3 History of the study of biocenosis

In the late 70s. XIX century. German hydrobiologist Karl Möbius studied complexes of benthic animals - clusters of oysters (oyster banks). He observed that together with oysters there were also such animals as starfish, echinoderms, bryozoans, worms, ascidians, sponges, etc. The scientist concluded that these animals live together, in the same habitat, not by chance. They need the same conditions as oysters. Such groupings appear due to similar requirements for environmental factors. Complexes of living organisms constantly occurring together in different points of the same water basin in the presence of the same conditions of existence, Möbius called biocenoses. The term "biocenosis" (from the Greek bios - life and koinos - general) was introduced by him into the scientific literature in 1877 in the book "Die Auster und die Austernwirthschaft" to describe all organisms that inhabit a certain territory (biotope), and their relationship.

The merit of Möbius is that he not only established the presence of organic communities and proposed a name for them, but also managed to reveal many patterns of their formation and development. Thus, the foundations were laid for an important direction in ecology - biocenology (ecology of communities).

It should be noted that the term “biocenosis” has become widespread in the scientific literature in German and Russian, and in English-speaking countries it corresponds to the term “community”. However, strictly speaking, the term “community” is not synonymous with the term “biocenosis”. If a biocenosis can be called a multi-species community, then a population (a component of a biocenosis) is a single-species community.

2. The structure of the biocenosis

The structure of the biocenosis is multifaceted, and when studying it, various aspects are distinguished. Based on this, the structures of the biocenosis are subdivided into the following types:

1) species;

2) spatial, in turn subdivided into vertical (tiered) and horizontal (mosaic) organization of the biocenosis;

3) trophic.

Each biocenosis consists of a certain set of living organisms belonging to different species. But it is known that individuals of the same species are combined into natural systems called populations. Therefore, the biocenosis can also be defined as the totality of populations of all types of living organisms inhabiting common habitats.

The biocenosis includes a set of plants in a certain area - phytocenosis; a set of animals living within a phytocenosis - a zoocenosis; microbocenosis - a set of microorganisms that inhabit the soil. Sometimes, as a separate constituent element in the biocenosis, they include mycocenosis - a collection of fungi. Examples of biocenoses are deciduous, spruce, pine or mixed forest, meadow, swamp, etc.

A specific biocenosis includes not only organisms that constantly inhabit a certain territory, but also those that have a significant impact on it. For example, many insects breed in water bodies, where they serve as an important source of food for fish and some other animals. At a young age, they are part of the aquatic biocenosis, and in adulthood they lead a terrestrial lifestyle, i.e. act as elements of land biocenoses. Hares can eat in the meadow and live in the forest. The same applies to many species of forest birds that seek food for themselves not only in the forest, but also in the adjacent meadows or swamps.

2.1 Species structure of biocenosis

The species structure of a biocenosis is a combination of its constituent species. In some biocenoses, animal species may predominate (for example, the biocenosis of a coral reef), in other biocenoses, plants play the main role: the biocenosis of a floodplain meadow, feather grass steppe, spruce, birch, and oak forests.

A simple indicator of biocenosis diversity is the total number of species, or species richness. If any kind of plant (or animal) quantitatively predominates in the community (has a large biomass, productivity, abundance or abundance), then such a species is called a dominant, or dominant species (from Latin dominans - dominant). There are dominant species in any biocenosis. For example, in the spruce forest, using the main share of solar energy, they increase the greatest biomass, shade the soil, weaken the movement of air and create a lot of inconveniences for the life of other inhabitants of the forest.

The number of species (species diversity) in different biocenoses is different and depends on their geographic location. The most famous pattern of changes in species diversity is its decrease from the tropics towards high latitudes. The closer to the equator, the richer and more diverse the flora and fauna. This applies to all forms of life, from algae and lichens to flowering plants, from insects to birds and mammals.

In the rain forests of the Amazon basin, on an area of ​​about 1 hectare, up to 400 trees of more than 90 species can be counted. In addition, many trees support other plants. Up to 80 species of epiphytic plants grow on the branches and trunk of each tree.

In contrast to the tropics, the pine forest biocenosis in the temperate zone of Europe can include a maximum of 8-10 tree species per hectare, and in the north of the taiga region, 2-5 species are present on the same area.

The poorest biocenoses in terms of the set of species are alpine and arctic deserts, the richest are tropical forests. Panama's rainforests are home to three times as many species of mammals and birds as Alaska.

Biocenoses are not isolated from each other. Although one can visually distinguish one plant community from another, for example, a dry forest biocenosis from a wet meadow biocenosis, which is replaced by a swamp, it is rather difficult to draw a clear boundary between them. Almost everywhere there is a kind of transitional strip of various widths and lengths, because rigid, sharp boundaries in nature are a rare exception. They are characteristic mainly of communities subject to intense anthropogenic impact.

In the early 30s. XX century American naturalist A. Leopold proclaimed the need to take into account the so-called "edge effect" in the activities of the hunting industry. In this case, the forest edge meant not only the edge of the forest, but also any border between two biocenoses, even between two massifs of different crops. On both sides of this conventional feature, the relative species diversity of plants and animals increases, the forage and protective conditions for game improve, the disturbance factor is weakened, and most importantly, this zone has increased productivity. Such a transitional strip (or zone) between adjacent physiognomically distinguishable communities is called an ecotone.

More or less sharp boundaries between biocenoses can be observed only in cases of a sharp change in the factors of the abiotic environment. For example, such boundaries exist between aquatic and terrestrial biocenoses, in places where there is a sharp change in the mineral composition of the soil, etc. Often the number of species in the ecotone exceeds their number in each of the bordering biocenoses. This tendency to an increase in the diversity and density of living organisms at the boundaries of biocenoses is called the marginal (marginal, boundary) effect. The edge effect is most clearly manifested in the zones separating the forest from the meadow (the zone of shrubs), the forest from the swamp, etc.

2.2 Spatial structure of biocenosis

Species can be distributed differently in space in accordance with their needs and habitat conditions. Such a distribution of the species that make up the biocenosis in space is called the spatial structure of the biocenosis. Distinguish between its vertical and horizontal structures.

1) The vertical structure of the biocenosis is formed by its individual elements, special layers, which are called tiers. Tier - co-growing groups of plant species differing in height and position in the biocenosis of assimilating organs (leaves, stems, underground organs - tubers, rhizomes, bulbs, etc.). As a rule, different tiers are formed by different life forms (trees, shrubs, shrubs, grasses, mosses). The layering is most clearly expressed in forest biocenoses (Fig. 2).

The first, arboreal, layer usually consists of tall trees with high foliage, which is well lit by the sun. Unused light can be absorbed by trees forming a second, sub-log, tier.

Rice. 2. Tiers of the forest biocenosis

The understory layer is made up of shrubs and shrub forms of tree species, for example, hazel, mountain ash, buckthorn, willow, apple tree, etc. In open places in normal ecological conditions, many shrub forms of such species as mountain ash, apple, pear, would have the appearance of trees of the first size. However, under the forest canopy, in conditions of shade and lack of nutrients, they are doomed to exist in the form of undersized, often not barking seeds and fruits of trees. As the forest biocenosis develops, such species will never enter the first tier. This is how they differ from the next layer of the forest biocenosis.

Young small (from 1 to 5 m) trees, which in the future will be able to enter the first tier, belong to the understorey layer. These are the so-called forest-forming species - spruce, pine, oak, hornbeam, birch, aspen, ash, black alder, etc. These species can reach the first tier and form biocenoses with their own dominance (forests).

Under the canopy of trees and shrubs, there is a grass-dwarf shrub layer. This includes forest grasses and shrubs: lily of the valley, oxalis, strawberries, lingonberries, blueberries, ferns.

The ground layer of mosses and lichens forms a moss-lichen layer.

So, in the forest biocenosis stand out stand, undergrowth, undergrowth, grass cover and moss-lichen layer.

Similar to the distribution of vegetation over the tiers, in biocenoses, different species of animals also occupy certain levels. Soil worms, microorganisms, earth-moving animals live in the soil. In leaf litter, on the soil surface, various centipedes, ground beetles, ticks and other small animals live. Birds nest in the upper canopy of the forest, and some can feed and nest below the upper tier, others in the bushes, and still others near the ground. Large mammals live in the lower tiers.

Layering is inherent in oceans and seas biocenoses. Different types of plankton keep different depths depending on the light. Different types of fish live at different depths depending on where they find their food.

2) Individuals of living organisms are unevenly distributed in space. Usually they make up groupings of organisms, which is an adaptive factor in their life. Such groups of organisms determine the horizontal structure of the biocenosis - the horizontal distribution of individuals that form various kinds of patterning, spotting of each species.

There are many examples of such a distribution: these are numerous herds of zebras, antelopes, elephants in the savannah, coral colonies on the seabed, schools of sea fish, schools of migratory birds; thickets of reeds and aquatic plants, accumulations of mosses and lichens on the soil in the forest biocenosis, spots of heather or lingonberry in the forest.

The elementary (structural) units of the horizontal structure of plant communities include microcenosis and microgrouping.

The microcenosis is the smallest structural unit of the horizontal division of the community, which includes all the layers. Almost every community includes a complex of microcommunities or microcenoses.

Microgrouping - concentration of individuals of one or several species within a layer, intra-layer mosaic spots. For example, in the moss layer, various moss spots can be distinguished with the dominance of one or several species. The herb-dwarf shrub layer contains bilberry, bilberry-oxalis, and blueberry-sphagnum microgroups.

Mosaicity is essential for the life of a community. Mosaicity allows for a more complete use of various micro-habitats. Individuals forming groups are characterized by a high survival rate, they use food resources most efficiently. This leads to an increase and variety of species in the biocenosis, contributes to its stability and vitality.

2.3 Trophic structure of biocenosis

The interaction of organisms that occupy a certain place in the biological cycle is called the trophic structure of the biocenosis.

In the biocenosis, three groups of organisms are distinguished.

1. Producers (from Latin producens - producing) - organisms synthesizing from inorganic substances (mainly water and carbon dioxide) all the organic substances necessary for life, using solar energy (green plants, cyanobacteria and some other bacteria) or energy oxidation of inorganic substances (sulfur bacteria, iron bacteria, etc.). Usually, producers are understood as green chlorophyll-bearing plants (autotrophs) that provide primary production. The total dry weight of phytomass (plant mass) is estimated at 2.42 x 1012 tons. This is 99% of all living matter on the earth's surface. And only 1% is accounted for by heterotrophic organisms. Therefore, only vegetation the planet Earth owes the existence of life on it. It was green plants that created the necessary conditions for the emergence and existence of, first, a variety of prehistoric animals, and then man. When the plants died, they accumulated energy in coal deposits, peat and even oil.

Producer plants give a person food, raw materials for industry, medicines. They purify the air, retain dust, soften the temperature regime of the air, and muffle noise. Thanks to vegetation, there is a huge variety of animal organisms that inhabit the Earth. Producers are the first link in food value and are at the heart of ecological pyramids.

2. Consumables (from Lat. Consumo - I consume), or consumers, are heterotrophic organisms that feed on ready-made organic matter. Consumers themselves cannot build organic matter from inorganic and receive it ready-made, feeding on other organisms. In their organisms, they convert organic matter into specific forms of proteins and other substances, and into the environment they release waste generated in the course of their life.

Grasshopper, hare, antelope, deer, elephant, i.e. herbivores are first-order consumers. A toad grabbing a dragonfly, a ladybug feeding on aphids, a wolf hunting a hare - these are all second-order consumers. A stork eating a frog, a kite carrying a chicken into the sky, a snake swallowing a swallow are third-order consumers.

3. Reducers (from Latin reducens, reducentis - restoring, restoring) - organisms that destroy dead organic matter and turn it into inorganic substances, and they, in turn, are assimilated by other organisms (producers).

The main reducers are bacteria, fungi, protozoa, i.e. heterotrophic microorganisms in the soil. If their activity decreases (for example, when a person uses pesticides), the conditions for the production process of plants and consumers deteriorate. Dead organic remains, be it a tree stump or the corpse of an animal, do not disappear into anywhere. They rot. But dead organics cannot rot by themselves. Reducers (destructors, destroyers) act as "gravediggers". They oxidize dead organic residues to C0 2, H 2 0 and simple salts, i.e. to inorganic components, which can again be involved in the circulation of substances, thereby closing it.

3. Modern problems and ways to solve them

The most acute problem of biocenoses is the reduction of populations of various living organisms up to the disappearance of whole species of animals, plants and microorganisms. This leads to disruption of the stability of biocenoses and poses a threat to the entire biosphere of the planet.

Each species participates in the circulation of substances, maintains a dynamic balance in natural ecosystems. Therefore, the loss of any biological species is highly undesirable for the biosphere.

The loss of species has occurred as a result of evolutionary processes. Due to human activities, the planet's biological resources are being lost much faster. Tens of thousands of plant and animal species are endangered. The reasons for this situation are:

1) loss of habitat: destruction of forests, drainage of swamps and floodplain lakes, plowing of steppes, change and shallowing of river beds, reduction of the area of ​​sea estuaries suitable for nesting, molting and wintering of waterfowl, road construction, urbanization and other changes resulting from human economic activity;

2) pollution of the environment with toxic chemicals and xenobiotics, oil and oil products, salts of heavy metals, solid household waste;

3) the spread of introduced species of plants and animals, actively occupying vast territories and displacing the natural inhabitants of ecosystems. Unintentional, accidental dispersal of animals has increased with the development of transport;

4) merciless exploitation of natural resources - minerals, soil fertility, aquatic ecosystems, overhunting of animals, birds and aquatic organisms.

Active, sometimes urgent, measures must be taken to protect endangered species. One of the most effective methods of animal protection is the creation of reserves or sanctuaries. On the territory of the Russian Federation, there are more than 150 nature reserves in which a large number of animals have been preserved. Among them are the Amur tiger, saiga, goral, Bukhara deer, kulan and others. Zoos throughout the country are helping to breed endangered species.

In order to preserve and increase the number of rare species, states on all continents of the Earth are adopting laws regarding the protection and use of the animal world. In the Russian Federation, such a law was adopted on June 25, 1980. To account for rare species both in Russia and in other countries of the world, the so-called Red Data Books are being created. Endangered species of animals around the world need separate registration, for this the International Red Book has been created.

It is necessary to use natural resources rationally, including in agriculture. Limit deforestation, as well as hunting and fishing, and completely ban rare and endangered species.

Conclusion

Biocenosis is one of the main objects of ecology research. A biocenosis is a collection of populations of plants, animals and microorganisms. The main function of the biocenosis is to ensure equilibrium in the ecosystem based on a closed cycle of substances. The place occupied by the biocenosis is called a biotope. Types of biocenosis structures: species, spatial (vertical (tiered) and horizontal (mosaic) organization of the biocenosis) and trophic. The species structure of the biocenosis covers all species living in it. The spatial structure includes a vertical structure - tiers and horizontal - microcenoses and microassociations. The trophic structure of the biocenosis is represented by producers, consumers and decomposers. The transfer of energy from one species to another by eating them is called the food (trophic) chain. The place of an organism in the food chain associated with its food specialization is called the trophic level. The trophic structure of the biocenosis and ecosystem is usually displayed by graphic models in the form of ecological pyramids. Distinguish between ecological pyramids of numbers, biomass and energy. The rate of fixation of solar energy determines the productivity of biocenoses. The set of environmental factors within which a species lives is called an ecological niche.

Humanity is now facing an acute problem of the disappearance of species of various living organisms, leading to a violation of the stability of biocenoses and the biosphere as a whole. To prevent a decline in the number of populations and the extinction of entire species, it is necessary to take urgent and active measures: entering endangered species in the Red Data Books; creation of nature reserves and national parks; restriction of hunting, fishing and deforestation; rational use of all natural resources.

Bibliography

1. Korobkin V.I., Peredelsky L.V. Ecology. - R.-on-Don, 2001 - 576 p.

2. Odum Y. Ecology: in 2 volumes. Vol. 1 - M., 1986 - 328 p .; T. 2 - M., 1986 - 376 p.

3. Articles from the electronic resource "Wikipedia": Biocenosis, Biosphere, Ecosystem

4. Tishler V. Agricultural ecology. - M., 1971 - 455 p.

Posted on Allbest.ru

Similar documents

The concept and criteria for assessing population density, the main factors affecting its value. Population density structure. The essence and structure of biocenosis, types of food chains. Components of the species diversity of the biocenosis. Ecosystem and its dynamics.

summary, added 11/24/2010


Study of the biosphere as a global ecosystem, the impact of human activities on it. Analysis of the species structure of the biocenosis. Basic principles of environmental protection. Environmental consequences of pollution caused by the nuclear industry. Methods for protecting the atmosphere.

test, added 04/01/2010


Study of the theory of cultural biocenosis of the Malthusians, who argued that the moment will soon come when the population will exceed the maximum food productivity of the biosphere and there will be famine all over the world. The law of agriculture of the XXI century.

article added on 04/13/2011


Study of the biocenosis of the border of the forest ecosystem and the agroecosystem as a result of the interaction of natural and artificial ecosystems. Human interaction with the environment in agricultural production. Species composition of phytocenosis and zoocenosis.

report added on 07/18/2010


General laws of the action of environmental factors on organisms. The most important abiotic factors and organisms adaptations to them. Basic living environments. The concept and structure of biocenosis. Mathematical modeling in ecology. Biological productivity of ecosystems.

tutorial, added 04/11/2014


The concept of "productivity of ecosystems", its types, classification of ecosystems by productivity. Four consecutive steps (or stages) of the production process of organic matter. Species composition and saturation of biocenosis. Environmental standardization.

test, added 09/27/2009


The concept of trophic structure as the totality of all food addictions in an ecosystem. Community activism factors. Types of food for living organisms. Distribution of ranges of the solar spectrum. Diagram of the cycle of matter and the flow of energy in the ecosystem.

presentation added on 02/08/2016


The history of the development of ecology. Species and spatial structure of biocenosis. Natural resources of the earth. Types of pollution of the hydrosphere and biosphere with production and consumption waste. The role of biotechnology and government agencies in environmental protection.

test, added 06/02/2010


Acquaintance with the interpretation of the concept of biocenosis; identification of its constituent parts and main participants. Characterization of the essence and methods of environmental risk management, familiarization with its anthropogenic, natural and man-made factors of occurrence.

test, added 04/27/2011


Consideration of the principles of the Bari Commoner's theory, the laws of minimum, necessity, the energy pyramid, the concept of succession (successive change of communities by sex by the influence of time), biocenosis, tolerance, environmental resistance, stability of the natural community.

2. Biogeocenosis (ecosystem). Functional blocks of the ecosystem.

Ecosystem classification.

4. Food chains and nutritional levels. Rule 10%.

Ecosystem productivity and energy.

Ecosystem dynamics.

THE CONCEPT OF BIOCENOSIS. STRUCTURE OF BIOCENOSIS.

Communities or biocenoses - it is a historically formed set of populations of plants (phytocoenosis), animals (zoocenosis) and microorganisms (microbocenosis) interacting with each other and inhabiting a relatively homogeneous living space (land or water body). This term was proposed in 1877. by the German zoologist K. Moebius.

Biocenosis structure:

Species

Spatial

Ecological

Species structure of biocenosis- characterizes the species diversity of living organisms in the community.

According to the species composition, biocenoses are:

· Simple - characterized by a small composition of species (field with agricultural crops, tundra zone, desert zone);

· Complex - characterized by a wide variety of species (forest, meadow, river, etc.);

· Unstable - a community where the species diversity is not constant;

· Stable - a community where the species composition is constant, unchanged.

Spatial structure characterizes the distribution of species in a living community. Species in the space of biocenosis can be located in two planes:

· Vertically (tiered);

· Horizontally (mosaic, mottling, synusia).

Tier - co-growing groups of plant species differing in height and position in the biocenosis of assimilating organs (leaves, stems, underground organs).

The layering is most clearly expressed in forest biocenoses:

tall trees - shrubs and shrub forms of tree species (mountain ash, buckthorn, willow, etc.) - shrubs (blueberries, lingonberries, cranberries, etc.) - herbaceous vegetation (lily of the valley, oxalis, strawberries) - mosses, lichens ...

Layering is also characteristic of underground parts of plants.

Species occupying different tiers do not compete with each other.

In accordance with the longline arrangement of plants, animals are also arranged in a tiered arrangement. For example, soil worms, microorganisms, earth-moving animals live in the soil; in leaf litter, on the soil surface, various centipedes, ground beetles, ticks and other small animals live; Birds nest in the upper forest canopy, and different species of birds build nests and feed in different tiers - on the ground (wagtail), in bushes (robin, nightingale), in tree crowns (rooks, magpies).

In each tier, certain conditions are created for the life of various species. The species occupying one tier in the community compete with each other for natural space and food resources.

The horizontal distribution of individuals of the species in the space within the layer is formed by various kinds of patterning, spotting, mosaicism of each species. For example, in the moss layer, various moss spots can be distinguished with the dominance of one or several species. In the grass-dwarf shrub layer, spots can be distinguished blueberry, blueberry-oxalis, blueberry-sphagnum, etc.

Ecological structure biocenosis characterizes the quantitative and qualitative ratios of species in the community. In each community, 1, 2 or 3 species are distinguished, prevailing in the biocenosis. They are called dominant or dominant, and the species living off the dominant - predominant... Typically, the dominant species are species - edifiers, that is, species that create conditions for the existence of other species of the dominant species, numerically prevailing in the cenosis.

BIOGEOCENOSIS (ECOSYSTEM). FUNCTIONAL BLOCKS OF THE ECOSYSTEM.

Biocenoses function under certain environmental conditions, the totality of which is called a biotope. Biocenosis and biotope form an interconnected unity - biogeocenosis. Thus, biogeocenosis is a natural system of interconnected living organisms and their surrounding abiotic environment.

Biogeocenosis is a system of functionally interconnected populations of plants, animals, microorganisms and their habitat, characterized by metabolism and circulation of substances, a constant influx of solar energy within the community.

Each biogeocenosis has the following functional blocks:

· abiotic environment- inanimate components of nature, from where the biocenosis (living organisms) takes everything necessary for life and where it releases waste products;

· block of producers- autotrophic organisms that create organic matter from inorganic by means of photosynthesis (plants, algae, some bacteria) or chemosynthesis (a number of bacteria). The main producers in aquatic and terrestrial ecosystems are green plants;

· reducers- heterotrophic organisms that feed on dead organic matter of plants and animals and subject it to mineralization and return decay products to the abiotic environment, suitable for use by producers. Reducers include mainly bacteria and fungi, as well as some animals (for example, earthworms).

CLASSIFICATION OF ECOSYSTEMS

Depending on the origin and composition, biogeocenoses are divided into:

· Terrestrial ecosystems (forest, meadow, field, etc.);

· Marine and oceanic ecosystems (seas, oceans, bays, etc.);

· Freshwater ecosystems (river, lake, marsh, artificial reservoir ecosystem, pond, etc.).

By the amount of energy expended for the existence of biogeocenoses are divided into:

· Natural - existing due to the energy of the sun (forest, meadow, water, etc.);

· Partially subsidized by human energy - fields, farms, artificial reservoirs, rural settlements;

· Artificial ecosystems - exist at the expense of large energy investments (protected ground, livestock complexes, cities, fish farming lines).

4. FOOD CHAINS AND NUTRITIONAL LEVELS. RULE 10%.

Living organisms in a community are linked by food links.

Food chain- this is the transfer of substances and the energy contained in them from autotrophs to heterotrophs, which occurs as a result of eating by some organisms of others. Chains come in a variety of lengths, but typically contain 2 to 5 links. Food chains can be: short (plant - cow) and simple, long (plant - insect - frog - stork - fox - golden eagle, etc.) and complex (plant - snail - bird - predator)

Insect - frog - stork - fox)

Bird is a predator)

There are two types of food chains: grazing and detrital.

1. Grazing chain (grazing chain) begins with aftotrophic photosynthetic organisms (plants), e.g. green plant → herbivorous animals.

2. Detrital chain (decomposition chain) begins with dead plant remains, corpses and animal excrement - detritus. Such food chains are typical for communities on the bottom of deep lakes and oceans, for forests. For example, leaf litter - centipedes - thrush - hawk.

The set of organisms united by one type of food and occupying a certain position in the food chain is called trophic level.

The rejection of organic matter from the fields is 75 - 95% - when growing agricultural crops. crops, the humus content decreases, i.e. natural fertility decreases, which leads to disruption of the natural natural cycle.

Rule 10% - the transition from one trophic level to another 10% of matter and energy does not disturb the balance in the ecosystem.

This rule can be viewed as a pyramid of biomass of organic matter.

Meadow biomass - 1000 t.

First order consumables - 100t.

Second order consumables - 10t.

Third order consumables - 1t.

Species structure and functions of species

Definition 1

The species structure is one of the most important characteristics of biocenoses. The concept of species structure usually includes the species composition of organisms in a certain territory (biota in general, flora and fauna) and indicators of the number of species (vegetation and animal population).

Each species performs in the structure of the biocenosis a function specific only to it, since the ecological niches of the two species cannot be completely repeated. However, there are some more general functions in the performance of which organisms of different types can participate. For example, in the field of the functional structure of biocenoses, these are the functions of producers, consumers and reducers. Each of them can be performed by a different number of species of organisms, up to one (however, the biocenosis in this case turns out to be unstable). In general, the greater the number of species in the ecosystem (and individually - at each trophic level), the more intensive the cycle of substances, the better the trophic and other conditions of consumers, the higher the productivity, fewer free ecological niches, the more stable the biocenosis (ecosystem).

Finished works on a similar topic

• Course work Species structure of biocenoses RUB 450
• abstract Species structure of biocenoses 240 RUB
• Test Species structure of biocenoses RUB 250

Subdivision of types of biocenosis by number

Remark 1

In terms of abundance, all species forming a biocenosis can be subdivided into several groups. Each of them performs a specific function that ensures the stability of the biocenosis.

Dominant species.

Dominant - predominance in numbers, biomass or productivity. Usually these are the few species that are most intensively involved in the circulation of substances and the conversion of energy. There are not so many of them at every trophic level and in every major taxonomic group. The proportion of dominants in the species structure of the biocenosis may differ, but usually amounts to more than 50%, but less than 90%. The number of individuals at which a species should be classified as dominant is also very conditional and depends on the total number of species in a given group. For example, in a community of birds (usually there are at least 40 species in an ecosystem), the dominant species are those whose number exceeds 5% of the total number of avifauna. Usually there are 3-5 such species, rarely less or more. Often, dominants are also edificators.

Edificators (or builders) are organisms (usually plants) with a pronounced environment-forming ability, due to which there are various consumers (predominants) and associated trophic or spatial relationships.

The group of subdominants, the number of individuals of each of whose species is usually several times lower than that of dominants, usually includes the largest number of species. Since the species diversity of dominantra is small, subdominants usually play a reserve role in the biocenosis. In the case of a sharp decrease in the number of any of the dominant species, the biocenotic role characteristic of it under normal conditions begins to be played by the most corresponding subdominants. Thus, the functional structure of the ecosystem is protected from destruction. This is one of the manifestations of the principle of ecological substitution.

The principle of biological substitution: a newly introduced species always develops its ecological niche, turns out to be more competitive, displaces less competitive species and often causes reverse successions or even destruction of ecosystems. These are the results of the dispersal of the muskrat, raccoon dog, American mink, Amur sleeper, American maple, and various other animals and plants, both specially and accidentally imported to new places.

The GF principle. Gause (1934) or the principle of competitive exclusion: two species with the same ecological properties, i.e. when their ecological niches completely coincide, they cannot coexist.

The principle of duplication is one of the mechanisms for maintaining the stability of ecosystems, when a species that has disappeared permanently or temporarily is functionally replaced by an ecologically similar backup species from the same or a neighboring link in the trophic chain.

Rare species. In natural biocenoses, there are always a large number of rare species, the number of which is 2-3 orders of magnitude or more lower than that of the dominants from the corresponding taxonomic groups. Low abundance is one of the specific properties of these species, since they are not numerous in any biocenosis. The ecological niches of these organisms are very specific; the reserves of resources necessary for life are usually small. All this determines the natural "rarity" of such species (should not be confused with species that become rare due to human fault). These organisms perform in biocenoses subtle, not yet fully understood functions, and, like all other members of the biocenosis, contribute to its stabilization and stability.

Biocenosis- a set of populations of plants, animals and microorganisms. The place occupied by the biocenosis is called a biotope. The species structure of the biocenosis covers all species living in it. The spatial structure includes a vertical structure - tiers and horizontal - microcenoses and microassociations. The trophic structure of the biocenosis is represented by producers, consumers and decomposers. The transfer of energy from one species to another by eating them is called the food (trophic) chain. The place of an organism in the food chain associated with its food specialization is called the trophic level. The trophic structure of the biocenosis and ecosystem is usually displayed by graphic models in the form of ecological pyramids. Distinguish between ecological pyramids of numbers, biomass and energy. The rate of fixation of solar energy determines the productivity of biocenoses. The set of environmental factors within which a species lives is called an ecological niche. The trend towards an increase in the diversity and density of living organisms at the boundaries of biocenoses (in ecotones) is called the edge effect.

Biocenosis concept

Organisms do not live on Earth as independent individuals. They form regular complexes in nature. German hydrobiologist K. Möbius in the late 70s. XIX century. studied complexes of benthic animals - oyster clusters (oyster banks). He observed that together with oysters there were also such animals as starfish, echinoderms, bryozoans, worms, ascidians, sponges, etc. The scientist concluded that these animals live together, in the same habitat, not by chance. They need the same conditions as oysters. Such groupings appear due to similar requirements for environmental factors. Complexes of living organisms constantly occurring together in different points of the same water basin in the presence of the same conditions of existence, Möbius called biocenoses. The term "biocenosis" (from the Greek bios - life and koinos - general) was introduced by him into the scientific literature in 1877.

The merit of Möbius is that he not only established the presence of organic communities and proposed a name for them, but also managed to reveal many patterns of their formation and development. Thus, the foundations were laid for an important direction in ecology - biocenology (ecology of communities).

The biocenotic level is the second (after the population) supra-organismal level of organization of living systems. A biocenosis is a fairly stable biological formation capable of self-sustaining its natural properties and species composition under external influences caused by changes in climatic and other factors. The stability of the biocenosis is determined not only by the stability of the populations included in it, but also by the peculiarities of the interaction between them.

- these are historically established groupings of plants, animals, fungi and microorganisms that inhabit a relatively homogeneous living space (land or water body).

So, each biocenosis consists of a certain set of living organisms belonging to different species. But it is known that individuals of the same species are combined into natural systems called populations. Therefore, the biocenosis can also be defined as the totality of populations of all types of living organisms inhabiting common habitats.

It should be noted that the term “biocenosis” has become widespread in the scientific literature in German and Russian, and in English-speaking countries it corresponds to the term “community”. However, strictly speaking, the term “community” is not synonymous with the term “biocenosis”. If a biocenosis can be called a multi-species community, then a population (a component of a biocenosis) is a single-species community.

The biocenosis includes a set of plants in a certain area - phytocenosis(from the Greek phyton - plant); a set of animals living within the phytocenosis - zoocenosis(from the Greek zoon - animal); microbocenosis(from the Greek mikros - small + bios - life) - a set of microorganisms that inhabit the soil. Sometimes, as a separate constituent element in the biocenosis, they include mycocenosis(from the Greek. mykes - mushroom) - a collection of mushrooms. Examples of biocenoses are deciduous, spruce, pine or mixed forest, meadow, swamp, etc.

A homogeneous natural living space (part of the abiotic environment) occupied by a biocenosis is called biotope. It can be a piece of land or a body of water, a seashore or a mountainside. A biotope is an inorganic environment, which is a necessary condition for the existence of a biocenosis. Biocenosis and biotope closely interact with each other.

The scale of biocenoses can be different - from communities of lichens on tree trunks, moss bumps in a swamp or decaying stump to populations of entire landscapes. So, on land, one can distinguish a biocenosis of a dry (not flooded with water) meadow, a biocenosis of a white moss pine forest, a biocenosis of a feather-grass steppe, a biocenosis of a wheat field, etc.

A specific biocenosis includes not only organisms that constantly inhabit a certain territory, but also those that have a significant impact on it. For example, many insects breed in water bodies, where they serve as an important source of food for fish and some other animals. At a young age, they are part of the aquatic biocenosis, and in adulthood they lead a terrestrial lifestyle, i.e. act as elements of land biocenoses. Hares can eat in the meadow and live in the forest. The same applies to many species of forest birds that seek food for themselves not only in the forest, but also in the adjacent meadows or swamps.

Species structure of biocenosis

Species structure of biocenosis Is a set of its constituent types. In some biocenoses, animal species may predominate (for example, the biocenosis of a coral reef), in other biocenoses, plants play the main role: the biocenosis of a floodplain meadow, feather grass steppe, spruce, birch, and oak forests. The number of species (species diversity) in different biocenoses is different and depends on their geographic location. The most famous pattern of changes in species diversity is its decrease from the tropics towards high latitudes. The closer to the equator, the richer and more diverse the flora and fauna. This applies to all forms of life, from algae and lichens to flowering plants, from insects to birds and mammals.

In the rain forests of the Amazon basin, on an area of ​​about 1 hectare, up to 400 trees of more than 90 species can be counted. In addition, many trees support other plants. Up to 80 species of epiphytic plants grow on the branches and trunk of each tree.

An example of species diversity is one of the volcanoes in the Philippines. Its slopes are home to more arboreal species than the rest of the United States!

In contrast to the tropics, the pine forest biocenosis in the temperate zone of Europe can include a maximum of 8-10 tree species per hectare, and in the north of the taiga region, 2-5 species are present on the same area.

The poorest biocenoses in terms of the set of species are alpine and arctic deserts, the richest are tropical forests. Panama's rainforests are home to three times as many species of mammals and birds as Alaska.

A simple indicator of biocenosis diversity is the total number of species, or species richness. If any species of plant (or animal) quantitatively prevails in the community (has a large biomass, productivity, abundance or abundance), then this species is called dominant, or dominant species(from Latin dominans - dominant). There are dominant species in any biocenosis. For example, in the spruce forest, using the main share of solar energy, they increase the greatest biomass, shade the soil, weaken the movement of air and create a lot of inconveniences for the life of other inhabitants of the forest.

Spatial structure of biocenosis

Species can be distributed differently in space in accordance with their needs and habitat conditions. Such a distribution of the species that make up the biocenosis in space is called the spatial structure of the biocenosis. Distinguish between its vertical and horizontal structures.

Vertical structure biocenosis is formed by its individual elements, special layers, which are called tiers. Tier - co-growing groups of plant species, differing in height and position in the biocenosis of assimilating organs (leaves, stems, underground organs - tubers, rhizomes, bulbs, etc.). As a rule, different tiers are formed by different life forms (trees, shrubs, shrubs, grasses, mosses). The layering is most clearly expressed in forest biocenoses (Fig. 1).

First, arboreal, layer usually consists of tall trees with high foliage, which is well lit by the sun. Unused light can be absorbed by trees forming a second, sub-log, tier.

Underbrush tier are shrubs and shrub forms of tree species, for example, hazel, mountain ash, buckthorn, willow, forest apple, etc. In open places in normal ecological conditions, many shrub forms of such species as mountain ash, apple, pear, would have the appearance of trees of the first size. However, under the forest canopy, in conditions of shade and lack of nutrients, they are doomed to exist in the form of undersized, often not barking seeds and fruits of trees. As the forest biocenosis develops, such species will never enter the first tier. This is how they differ from the next layer of the forest biocenosis.

Rice. 1. Tiers of the forest biocenosis

TO tier of undergrowth young small (from 1 to 5 m) trees, which in the future will be able to go to the first tier, are included. These are the so-called forest-forming species - spruce, pine, oak, hornbeam, birch, aspen, ash, black alder, etc. These species can reach the first tier and form biocenoses with their own dominance (forests).

Under the canopy of trees and shrubs is located herb-shrub layer... This includes forest grasses and shrubs: lily of the valley, oxalis, strawberries, lingonberries, blueberries, ferns.

The soil layer of mosses and lichens forms moss-lichen layer.

So, in the forest biocenosis stand out stand, undergrowth, undergrowth, grass cover and moss-lichen layer.

Similar to the distribution of vegetation over the tiers, in biocenoses, different species of animals also occupy certain levels. Soil worms, microorganisms, earth-moving animals live in the soil. In leaf litter, on the soil surface, various centipedes, ground beetles, ticks and other small animals live. Birds nest in the upper canopy of the forest, and some can feed and nest below the upper tier, others in the bushes, and still others near the ground. Large mammals live in the lower tiers.

Layering is inherent in oceans and seas biocenoses. Different types of plankton keep different depths depending on the light. Different types of fish live at different depths depending on where they find their food.

Individuals of living organisms are unevenly distributed in space. Usually they make up groupings of organisms, which is an adaptive factor in their life. Such groupings of organisms determine horizontal structure of biocenosis- horizontal distribution of individuals forming various kinds of patterning, spotting of each species.

There are many examples of such a distribution: these are numerous herds of zebras, antelopes, elephants in the savannah, coral colonies on the seabed, schools of sea fish, schools of migratory birds; thickets of reeds and aquatic plants, accumulations of mosses and lichens on the soil in the forest biocenosis, spots of heather or lingonberry in the forest.

The elementary (structural) units of the horizontal structure of plant communities include microcenosis and microgrouping.

Microcenosis(from the Greek micros - small) - the smallest structural unit of the horizontal division of the community, which includes all the tiers. Almost every community includes a complex of microcommunities or microcenoses.

Microgrouping - concentration of individuals of one or several species within a layer, intra-layer mosaic spots. For example, in the moss layer, various moss spots can be distinguished with the dominance of one or several species. The herb-dwarf shrub layer contains bilberry, bilberry-oxalis, and blueberry-sphagnum microgroups.

Mosaicity is essential for the life of a community. Mosaicity allows for a more complete use of various micro-habitats. Individuals forming groups are characterized by a high survival rate, they use food resources most efficiently. This leads to an increase and variety of species in the biocenosis, contributes to its stability and vitality.

Trophic structure of biocenosis

The interaction of organisms that occupy a certain place in the biological cycle is called trophic structure of biocenosis.

In the biocenosis, three groups of organisms are distinguished.

1.Producers(from Latin producens - producing) - organisms that synthesize from inorganic substances (mainly water and carbon dioxide) all organic substances necessary for life, using solar energy (green plants, cyanobacteria and some other bacteria) or the energy of oxidation of inorganic substances (sulfur bacteria , iron bacteria, etc.). Usually, producers are understood as green chlorophyll-bearing plants (autotrophs) that provide primary production. The total dry weight of phytomass (plant mass) is estimated at 2.42 x 10 12 tons. This is 99% of all living matter on the earth's surface. And only 1% is accounted for by heterotrophic organisms. Therefore, only vegetation the planet Earth owes the existence of life on it. It was green plants that created the necessary conditions for the emergence and existence of, first, a variety of prehistoric animals, and then man. When the plants died, they accumulated energy in coal deposits, peat and even oil.

Producer plants give a person food, raw materials for industry, medicines. They purify the air, retain dust, soften the temperature regime of the air, and muffle noise. Thanks to vegetation, there is a huge variety of animal organisms that inhabit the Earth. Producers are the first link in food value and are at the heart of ecological pyramids.

2.Consumptions(from Latin consumo - I consume), or consumers, are heterotrophic organisms that feed on ready-made organic matter. Consumers themselves cannot build organic matter from inorganic and receive it ready-made, feeding on other organisms. In their organisms, they convert organic matter into specific forms of proteins and other substances, and into the environment they release waste generated in the course of their life.

Grasshopper, hare, antelope, deer, elephant, i.e. herbivores are first-order consumers. A toad grabbing a dragonfly, a ladybug feeding on aphids, a wolf hunting a hare - these are all second-order consumers. A stork eating a frog, a kite carrying a chicken into the sky, a snake swallowing a swallow are third-order consumers.

3. Reducers(from Latin reducens, reducentis - returning, restoring) - organisms that destroy dead organic matter and turn it into inorganic substances, and they, in turn, are assimilated by other organisms (producers).

The main reducers are bacteria, fungi, protozoa, i.e. heterotrophic microorganisms in the soil. If their activity decreases (for example, when a person uses pesticides), the conditions for the production process of plants and consumers deteriorate. Dead organic remains, be it a tree stump or the corpse of an animal, do not disappear into anywhere. They rot. But dead organics cannot rot by themselves. Reducers (destructors, destroyers) act as "gravediggers". They oxidize dead organic residues to C0 2, H 2 0 and simple salts, i.e. to inorganic components, which can again be involved in the circulation of substances, thereby closing it.