The park is one of the types of artificial biocenosis. Artificial biocenosis characteristic features

In nature, all living organisms are in constant relationship with each other. What is it called? Biocenosis is an established set of microorganisms, fungi, plants and animals, which has historically formed in a relatively homogeneous living space. Moreover, all these living organisms are connected not only with each other, but also with their environment. Biocenosis can exist both on land and in water.

Origin of the term

The concept was first used by the famous German botanist and zoologist Karl Möbius in 1877. He used it to describe the totality and relationships of organisms inhabiting a certain area, which is called a biotope. Biocenosis is one of the main objects of study of modern ecology.

The essence of relationships

Biocenosis is a relationship that has arisen on the basis of a biogenic cycle. It is he who provides it in specific conditions. What is the structure of the biocenosis? This dynamic and self-regulating system consists of the following interrelated components:

Producers (aphtotrophs), which are producers of organic substances from inorganic ones. Some bacteria and plants in the process of photosynthesis convert solar energy and synthesize organic matter, which is consumed by living organisms, called heterotrophs (consumers, decomposers). Producers capture carbon dioxide from the atmosphere, which is emitted by other organisms, and produce oxygen.
Consumers, which are the main consumers of organic substances. Herbivores eat plant foods, which in turn become a meal for carnivorous predators. Due to the process of digestion, consumers carry out the primary grinding of organic matter. This is the initial stage of its disintegration.
Decomposers, finally decomposing organic substances. They dispose of waste and corpses of producers and consumers. Decomposers are bacteria and fungi. The result of their vital activity is mineral substances, which are again consumed by producers.

Thus, it is possible to trace all the connections in the biocenosis.

Basic concepts

All members of the community of living organisms are usually called certain terms derived from Greek words:

the totality of plants in a particular area, - phytocenosis;
all types of animals living within the same area - zoocenosis;
all microorganisms living in the biocenosis - microbiocenosis;
fungal community - mycocenosis.

Quantitative indicators

The most important quantitative indicators of biocenoses:

biomass, which is the total mass of all living organisms in specific natural conditions;
biodiversity, which is the total number of species in the biocenosis.

Biotope and biocenosis

In the scientific literature, such terms as "biotope", "biocenosis" are often used. What do they mean and how do they differ from each other? In fact, the totality of living organisms included in a particular ecological system is commonly called a biotic community. Biocenosis has the same definition. This is a set of populations of living organisms living in a certain geographical area. It differs from others in a number of chemical (soil, water) and physical (solar exposure, altitude, area size) indicators. A section of the abiotic environment occupied by a biocenosis is called a biotope. So both of these concepts are used to describe communities of living organisms. In other words, biotope and biocenosis are practically the same thing.

Structure

There are several types of biocenosis structures. All of them characterize it according to different criteria. These include:

The spatial structure of the biocenosis, which is divided into 2 types: horizontal (mosaic) and vertical (tiered). It characterizes the living conditions of living organisms in specific natural conditions.
The species structure of the biocenosis, which is responsible for a certain diversity of the biotope. It is a collection of all populations that are part of it.
Trophic structure of biocenosis.

Mosaic and layered

The spatial structure of the biocenosis is determined by the location of living organisms of different species relative to each other in the horizontal and vertical directions. Layering ensures the most complete use of the environment and a uniform distribution of species along the vertical. Thanks to this, their maximum productivity is achieved. So, in any forests, the following tiers are distinguished:

ground (mosses, lichens);
grassy;
shrubby;
woody, including trees of the first and second magnitude.

The corresponding arrangement of animals is superimposed on the tiering. Due to the vertical structure of the biocenosis, plants most fully use the light flux. Thus, light-loving trees grow in the upper tiers, and shade-tolerant trees grow in the lower ones. Different horizons are also distinguished in the soil, depending on the degree of saturation with roots.

Under the influence of vegetation, the biocenosis of the forest creates its own microenvironment. In it, not only an increase in temperature is observed, but also a change in the gas composition of the air. Such transformations of the microenvironment favor the formation and layering of fauna, including insects, animals, and birds.

The spatial structure of the biocenosis also has a mosaic structure. This term refers to the horizontal variability of flora and fauna. Mosaic in area depends on the diversity of species and their quantitative ratio. It is also influenced by soil and landscape conditions. Often, a person creates an artificial mosaic, cutting down forests, draining swamps, etc. Because of this, new communities form in these territories.

Mosaic is inherent in almost all phytocenoses. Within them, the following structural units are distinguished:

Consortia, which are a collection of species united by topical and trophic links and dependent on the core of this grouping (central member). Most often, its basis is a plant, and its components are microorganisms, insects, animals.
Synusia, which are a group of species in a phytocenosis belonging to close life forms.
Parcels, representing the structural part of the horizontal section of the biocenosis, which differs from its other components in its composition and properties.

Spatial structure of the community

A good example for understanding vertical layering in living beings are insects. Among them there are such representatives:

soil inhabitants - geobias;
inhabitants of the surface layer of the earth - herpetobia;
bryobia living in mosses;
located in the herbage of phyllobia;
living on trees and shrubs aerobia.

Horizontal structure is caused by a number of different reasons:

abiogenic mosaic, which includes factors of inanimate nature, such as organic and inorganic substances, climate;
phytogenic, associated with the growth of plant organisms;
eolian-phytogenic, which is a mosaic of abiotic and phytogenic factors;
biogenic, associated primarily with animals that are able to dig the ground.

Species structure of biocenosis

The number of species in the biotope directly depends on the stability of the climate, the time of existence and the productivity of the biocenosis. So, for example, in a tropical forest, such a structure will be much wider than in a desert. All biotopes differ from each other in the number of species inhabiting them. The most numerous biogeocenoses are called dominant. In some of them, it is simply impossible to determine the exact number of living beings. As a rule, scientists determine the number of different species concentrated in a particular area. This indicator characterizes the species richness of the biotope.

This structure makes it possible to determine the qualitative composition of the biocenosis. When comparing territories of the same area, the species richness of the biotope is determined. In science, there is the so-called Gause principle (competitive exclusion). In accordance with it, it is believed that if in a homogeneous environment there are 2 types of similar living organisms together, then when constant conditions one of them will gradually replace the other. At the same time, they have a competitive relationship.

The species structure of the biocenosis includes 2 concepts: "wealth" and "diversity". They are somewhat different from each other. Thus, species richness is the total set of species living in a community. It is expressed by a list of all representatives of different groups of living organisms. Species diversity is an indicator that characterizes not only the composition of the biocenosis, but also the quantitative relationships between its representatives.

Scientists distinguish between poor and rich biotopes. These types of biocenosis differ among themselves in the number of representatives of communities. The age of the biotope plays an important role in this. Thus, young communities that began their formation relatively recently include a small set of species. Every year the number of living beings in it can increase. The poorest are biotopes created by man (gardens, orchards, fields).

Trophic structure

The interaction of various organisms that have their own specific place in the cycle of biological substances is called the trophic structure of the biocenosis. It consists of the following components:

Features of biocenoses

Populations and biocenoses are the subject of careful study. Thus, scientists have found that most aquatic and almost all terrestrial biotopes contain microorganisms, plants and animals. They established the following feature: the greater the difference in two neighboring biocenoses, the more heterogeneous the conditions at their boundaries. It has also been established that the abundance of a certain group of organisms in a biotope largely depends on their size. In other words, the smaller the individual, the greater the abundance of this species. It has also been established that groups of living creatures of different sizes live in a biotope on different scales of time and space. So, the life cycle of some unicellular organisms takes place within one hour, and a large animal - within decades.

Number of species

In each biotope, a group of main species is distinguished, the most numerous in each size class. It is the connections between them that are decisive for the normal life of the biocenosis. Those species that prevail in terms of numbers and productivity are considered to be the dominants of this community. They dominate it and are the core of this biotope. An example is grass bluegrass, which occupies the maximum area in a pasture. She is the main producer of this community. In the richest biocenoses, almost always all types of living organisms are few in number. So, even in the tropics, several identical trees are rarely found in one small area. Since such biotopes are distinguished by their high stability, outbreaks of mass reproduction of some representatives of the flora or fauna are rare in them.

All types of community constitute its biodiversity. The biotope has certain principles. As a rule, it consists of several main species, characterized by high abundance, and a large number of rare species characterized by a small number of its representatives. This biodiversity is the basis for the equilibrium state of a particular ecosystem and its sustainability. It is thanks to him that a closed cycle of biogens occurs in the biotope ( nutrients).

Artificial biocenoses

Biotopes are formed not only naturally. In their life, people have long learned to create communities with properties that are useful to us. Examples of human-made biocenosis:

man-made canals, reservoirs, ponds;
pastures and fields for crops;
drained swamps;
renewable gardens, parks and groves;
field-protective forest plantations.

Inhabiting a relatively homogeneous living space (a certain piece of land or water area), and connected with each other and their environment. Biocenoses arose on the basis of biogenic cycle and provide it in specific natural conditions. Biocenosis is a dynamic system capable of self-regulation, the components of which (producers, consumers, decomposers) are interconnected. One of the main objects of ecology research. 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).

Types of biocenoses: 1) Natural (river, lake, meadow, etc.) 2) Artificial (pond, garden, etc.)

There are 2 types (types) of biocenosis: natural and artificial ( see slide 3). Try to determine what is the difference between these biocenoses. Give examples.

Natural biocenosis is the one created by nature. For example, a lake, a forest.

Artificial biocenosis is the one created by man. For example, a garden, a vegetable garden.

Natural biocenoses.

The composition of the inhabitants in each of them is not accidental, it depends on the conditions of the given territory and is adapted to them. Biocenoses can be rich in species and poor, for example: in the tundra there is a poor species composition, and in tropical forests- rich.

The higher the number of species, the more resistant the biocenosis to various interventions.

The stability of biocenoses is also determined by their layering - spatial and temporal.

What do you think these terms mean?

Tiers - floors.

Spatial - located in space (triple dimension).

Temporal - located in time (changes over time)

Spatial layering is characteristic of both animals and plants. Each tier is mastered by individuals of its own species, but this does not prevent different animals from being in other tiers. However, the main stages of animal life take place in certain tiers. For example, bird nests are located in some tiers, while foraging may occur in others.

Temporary layering occurs in connection with nutritional habits, the construction of nests and houses, and reproduction. For example, the timing of the arrival of birds depends on the availability of food. In addition, in cases of prolonged cold weather, birds do not start building nests and laying eggs for a long time.

In natural biocenoses, the species composition is preserved for a long time, and certain relationships are established between different species. Organisms are distinguished as producers, consumers and decomposers. Try to define the term "producers"

Producers - those who produce (produce) something.

What organisms do you think could be producers?

Plants, because they produce oxygen and organic matter.

Plants that produce organic substances from inorganic substances are called producers.

If producers are organisms that produce a substance, then who are consumers?

Consumers are those organisms that consume a substance.

Herbivorous animals that create organic substances, but of animal origin, are called order consumers.

So, we found out who the producers and consumers are. Think and say, who are the decomposers and what role should they play?

Decomposers are organisms that process the remains of dead animals and plants.

Decomposers are organisms that feed on the remains of dead plants and animals. These include bacteria, fungi, and some animals such as worms.

In the natural biocenosis, self-regulation of the number of individuals of each group occurs.

What features do you think the artificial biocenosis will have?

Only what man has planted will grow there, only a few species of animals will live.

Artificial biocenoses

Agriculture has led to the destruction of natural and the creation of artificial biocenoses (agrobiocenoses). The cultivation of plants of the same species over large areas, for example, potatoes, wheat, has led to a sharp reduction in the links between species. Agrobiocenosis is not very stable, because there is no tiering (both temporal and spatial).

Cultivated plants form a specific composition of the inhabitants of the animal world with a predominance of herbivorous species, mainly pests. All individuals are characterized by good adaptability to the rapid change of vegetation, omnivorous.

To fight them, a person uses various methods, uses pesticides, while polluting the environment, destroying along with harmful and beneficial animals. To maintain the stability of artificial biocenoses, large financial costs are required.

For example, consider the biocenosis of a reservoir .

The producers here are all types of plants, which in most cases are located in the upper layers. Microscopic algae form phytoplankton.

Consumers of the first order are microscopic animals that form zooplankton, which feed on phytoplankton and directly depend on its development.

Consumers of the second order - fish that feed on crustaceans and insects.

Consumers of the second order are predatory fish.

Consumers can live at various depths, including the bottom.

The remains of the vital activity of all organisms sink to the bottom and become food for decomposers, decomposing them to inorganic substances.

In the process of everyday life, not every person notices his interaction with various people. Rushing to work, it is unlikely that anyone, except perhaps a professional ecologist or biologist, will pay special attention to the fact that he crossed a square or park. Well, passed and passed, so what? But this is already a biocenosis. Each of us can recall examples of such involuntary, but constant interaction with ecosystems, if we only think about it. We will try to consider in more detail the question of what biocenoses are, what they are and what they depend on.

What is a biocenosis?

Most likely, few people remember that they studied biocenoses at school. Grade 7, when this topic is taught in biology, has remained far in the past, and completely different events are remembered. Recall what a biocenosis is. This word is formed by the fusion of two Latin words: "bios" - life and "cenosis" - common. This term denotes a set of microorganisms, fungi, plants and animals living in the same territory, interconnected and interacting with each other.

Any biological community includes the following components of the biocenosis:

microorganisms (microbiocenosis);
vegetation (phytocenosis);
animals (zoocenosis).

Each of these components plays an important role and can be represented by individuals of different species. However, it should be noted that phytocenosis is the leading component that determines microbiocenosis and zoocenosis.

When did this concept appear?

The concept of "biocenosis" was proposed by the German hydrobiologist Möbius at the end of the 19th century, when he studied the habitats of oysters in the North Sea. During the study, he found that these animals can only live in strictly defined conditions, characterized by depth, current speed, salinity and water temperature. In addition, Möbius noted that strictly certain types of marine plants and animals live in the same territory along with oysters. Based on the data obtained, in 1937 the scientist introduced the concept we are considering to denote the association of groups of living organisms living and coexisting in the same territory, due to historical development species and long The modern concept of "biocenosis" biology and ecology interpret a little differently.

Classification

Today, there are several signs according to which biocenosis can be classified. Examples of classification based on size:

macrobiocenosis (sea, mountains, oceans);
mesobiocenosis (swamp, forest, field);
microbiocenosis (flower, old stump, leaf).

Also, biocenoses can be classified depending on the habitat. The following three types are recognized as the main ones:

nautical;
freshwater;
ground.

Each of them can be divided into subordinate, smaller and local groups. Thus, marine biocenoses can be subdivided into benthic, pelagic, shelf and others. Freshwater biological communities are river, marsh and lake. Terrestrial biocenoses include coastal and inland, mountain and plain subtypes.

The simplest classification of biological communities is their division into natural and artificial biocenoses. Among the former, there are primary ones, formed without human influence, as well as secondary ones, which have undergone a change due to the influence of natural elements or the activities of human civilization. Let's take a closer look at their features.

Natural biological communities

Natural biocenoses are associations of living beings created by nature itself. Such communities are natural systems that form, develop and function according to their own special laws. The German ecologist W. Tischler identified the following features that characterize such formations:

1. Communities arise from ready-made elements that can act as representatives certain types, as well as entire complexes.

2. Individual parts of the community may be replaceable. Thus, one species can be displaced and completely replaced by another that has similar requirements for the conditions of existence, without negative consequences for the entire system.

3. Due to the fact that interests in the biocenosis various kinds are opposite, then the entire supraorganismal system is based and exists due to the balancing of forces directed oppositely.

In addition, in biological communities there are edificators, that is, animal or plant species that create the necessary conditions for the life of other beings. So, for example, in steppe biocenoses, feather grass is the most powerful edificator.

In order to assess the role of a particular species in the structure of a biological community, indicators based on quantitative accounting are used, such as its abundance, frequency of occurrence, Shannon diversity index and species saturation.

Biocenosis (from Greek bios - life, koinos - general) is an organized group of interconnected populations of plants, animals, fungi and microorganisms living together in the same environmental conditions.

The concept of "biocenosis" was proposed in 1877 by the German zoologist K. Möbius. Mobius, studying oyster jars, came to the conclusion that each of them is a community of living beings, all members of which are in close relationship. Biocenosis is a product of natural selection. Its survival, stable existence in time and space depends on the nature of the interaction of the constituent populations and is possible only with the obligatory receipt of the radiant energy of the Sun from outside.

Each biocenosis has a certain structure, species composition and territory; it is characterized by a certain organization of food relations and a certain type of metabolism

But no biocenosis can develop on its own, outside and independently of the environment. As a result, certain complexes, aggregates of living and non-living components, are formed in nature. The complex interactions of their individual parts are supported on the basis of versatile mutual fitness.

A space with more or less homogeneous conditions, inhabited by one or another community of organisms (biocenosis), is called a biotope.

In other words, a biotope is a place of existence, a habitat, a biocenosis. Therefore, a biocenosis can be considered as a historically established complex of organisms, characteristic of a particular biotope.

Any biocenosis forms a dialectical unity with a biotope, a biological macrosystem of an even higher rank - a biogeocenosis. The term "biogeocenosis" was proposed in 1940 by V.N. Sukachev. It is practically identical to the term "ecosystem" widely used abroad, which was proposed in 1935 by A. Tensley. There is an opinion that the term "biogeocenosis" to a much greater extent reflects the structural characteristics of the macrosystem under study, while the concept of "ecosystem" primarily includes its functional essence. In fact, there is no difference between these terms. Undoubtedly, V.N. Sukachev, formulating the concept of "biogeocenosis", combined in it not only the structural, but also the functional significance of the macrosystem. According to V.N. Sukachev, biogeocenosis- this is set of homogeneous natural phenomena over a known extent of the earth's surface- atmosphere, rocks, hydrological conditions, vegetation, fauna, the world of microorganisms and soil. This set is distinguished by the specifics of the interactions of its constituent components, their special structure and a certain type of exchange of matter and energy between themselves and with other natural phenomena.

Biogeocenoses can be of various sizes. In addition, they are very complex - it is sometimes difficult to take into account all the elements, all the links in them. These are, for example, such natural groupings as a forest, a lake, a meadow, etc. An example of a relatively simple and clear biogeocenosis can be a small reservoir, a pond. Its non-living components include water, substances dissolved in it (oxygen, carbon dioxide, salts, organic compounds) and soil - the bottom of a reservoir, which also contains a large number of various substances. The living components of the reservoir are divided into producers of primary products - producers (green plants), consumers - consumers (primary - herbivorous animals, secondary - carnivores, etc.) and decomposers - destructors (microorganisms), which decompose organic compounds to inorganic. Any biogeocenosis, regardless of its size and complexity, consists of these main links: producers, consumers, destroyers and components of inanimate nature, as well as many other links. Connections of various orders arise between them - parallel and intersecting, tangled and intertwined, etc.

In general, biogeocenosis represents an internal contradictory dialectical unity that is in constant motion and change. “Biogeocenosis is not the sum of biocenosis and the environment,” N.V. Dylis points out, “but a holistic and qualitatively isolated phenomenon of nature, acting and developing according to its own laws, the basis of which is the metabolism of its components.”

Living components of biogeocenosis, i.e. balanced animal and plant communities (biocenoses), are the highest form of existence of organisms. They are characterized by a relatively stable composition of fauna and flora and have a typical set of living organisms that retain their main features in time and space. The stability of biogeocenoses is supported by self-regulation, that is, all elements of the system exist together, never completely destroying each other, but only limiting the number of individuals of each species to a certain limit. That is why such relationships have historically developed between animal, plant and microorganism species that ensure development and keep their reproduction at a certain level. Overpopulation of one of them may arise for some reason as an outbreak of mass reproduction, and then the established ratio between the species is temporarily disturbed.

To simplify the study of biocenosis, it can be conditionally divided into separate components: phytocenosis - vegetation, zoocenosis - fauna, microbiocenosis - microorganisms. But such fragmentation leads to an artificial and actually incorrect separation from a single natural complex of groups that cannot exist independently. In no habitat can there be a dynamic system that would consist only of plants or only of animals. Biocenosis, phytocenosis and zoocenosis must be considered as biological units of different types and stages. This view objectively reflects the real situation in modern ecology.

In the conditions of scientific and technological progress, human activity transforms natural biogeocenoses (forests, steppes). They are replaced by crops and plantings cultivated plants. This is how special secondary agrobiogeocenoses, or agrocenoses, are formed, the number of which on Earth is constantly increasing. Agrocenoses are not only agricultural fields, but also shelterbelts, pastures, artificially regenerated forests in clearings and fires, ponds and reservoirs, canals and drained swamps. Agrobiocenoses in their structure are characterized by a small number of species, but their high abundance. Although there are many specific features in the structure and energy of natural and artificial biocenoses, there are no sharp differences between them. In a natural biogeocenosis, the quantitative ratio of individuals of different species is mutually dependent, since it has mechanisms that regulate this ratio. As a result, a stable state is established in such biogeocenoses, maintaining the most favorable quantitative proportions of its constituent components. There are no such mechanisms in artificial agrocenoses; there, a person completely took care of streamlining the relationship between species. Much attention is paid to the study of the structure and dynamics of agrocenoses, since in the foreseeable future there will be practically no primary, natural, biogeocenoses.

Trophic structure of biocenosis

The main function of biocenoses - maintaining the circulation of substances in the biosphere - is based on the nutritional relationships of species. It is on this basis that organic substances synthesized by autotrophic organisms undergo multiple chemical transformations and eventually return to the environment in the form of inorganic waste products, which are again involved in the cycle. Therefore, with all the diversity of species that make up different communities, each biocenosis necessarily includes representatives of all three principal ecological groups of organisms - producers, consumers and decomposers . The completeness of the trophic structure of biocenoses is an axiom of biocenology.

Groups of organisms and their relationships in biocenoses

According to participation in the biogenic cycle of substances in biocenoses, three groups of organisms are distinguished:

1) Producers(producers) - autotrophic organisms that create organic substances from inorganic ones. The main producers in all biocenoses are green plants. The activity of producers determines the initial accumulation of organic substances in the biocenosis;

ConsumersIorder.

This trophic level is composed by direct consumers of primary production. In the most typical cases, when the latter is created by photoautotrophs, these are herbivorous animals. (phytophages). Species and ecological forms representing this level are very diverse and adapted to nutrition. different types vegetable feed. Due to the fact that plants are usually attached to the substrate, and their tissues are often very strong, many phytophages have evolved a gnawing type of mouth apparatus and various adaptations for grinding and grinding food. These are the dental systems of the gnawing and grinding type in various herbivorous mammals, the muscular stomach of birds, which is especially well expressed in granivorous ones, and so on. n. The combination of these structures determines the possibility of grinding solid food. Gnawing mouth apparatus is characteristic of many insects, etc.

Some animals are adapted to feed on plant sap or flower nectar. This food is rich in high-calorie, easily digestible substances. The oral apparatus of species that feed in this way is arranged in the form of a tube, with the help of which liquid food is absorbed.

Adaptations to nutrition by plants are also found at the physiological level. They are especially pronounced in animals that feed on the coarse tissues of the vegetative parts of plants, which contain a large amount of fiber. Cellulolytic enzymes are not produced in the body of most animals, and the breakdown of fiber is carried out by symbiotic bacteria (and some protozoa of the intestinal tract).

Consumers partly use food to support life processes (“breathing costs”), and partly build their own body on its basis, thus carrying out the first, fundamental stage in the transformation of organic matter synthesized by producers. The process of creation and accumulation of biomass at the consumer level is denoted as , secondary products.

ConsumersIIorder.

This level combines animals with a carnivorous type of food. (zoophages). Usually, all predators are considered in this group, since their specific features practically do not depend on whether the prey is a phytophage or a carnivore. But strictly speaking, only predators that feed on herbivorous animals and, accordingly, represent the second stage of the transformation of organic matter in food chains, should be considered second-order consumers. The chemicals that make up the tissues of an animal organism are quite homogeneous, so the transformation during the transition from one level of consumers to another is not as fundamental as the transformation of plant tissues into animals.

With a more careful approach, the level of consumers of the second order should be divided into sublevels according to the direction of the flow of matter and energy. For example, in the trophic chain "cereals - grasshoppers - frogs - snakes - eagles", frogs, snakes and eagles constitute successive sublevels of consumers of the second order.

Zoophages are characterized by their specific adaptations to the nature of their diet. For example, their mouthparts are often adapted for grasping and holding live prey. When feeding on animals that have dense protective covers, adaptations are developed for their destruction.

At the physiological level, adaptations of zoophages are expressed primarily in the specificity of the action of enzymes "tuned" to the digestion of food of animal origin.

ConsumersIIIorder.

The most important in biocenoses are trophic relationships. Based on these connections of organisms in each biocenosis, the so-called food chains are distinguished, which arise as a result of complex nutritional relationships between plant and animal organisms. Food chains unite directly or indirectly a large group of organisms into a single complex, interconnected by relationships: food - consumer. The food chain usually consists of several links. Organisms of the next link eat the organisms of the previous link, and thus a chain transfer of energy and matter is carried out, which underlies the cycle of substances in nature. With each transfer from link to link, a large part (up to 80 - 90%) of the potential energy is lost, dissipating in the form of heat. For this reason, the number of links (species) in the food chain is limited and usually does not exceed 4-5.

A schematic diagram of the food chain is shown in fig. 2.

Here, the food chain is based on species - producers - autotrophic organisms, mainly green plants that synthesize organic matter (they build their bodies from water, inorganic salts and carbon dioxide, assimilating the energy of solar radiation), as well as sulfur, hydrogen and other bacteria that use organic matter for the synthesis substances energy oxidation of chemicals. The next links in the food chain are occupied by consumer species-heterotrophic organisms that consume organic matter. Primary consumers are herbivorous animals that feed on grass, seeds, fruits, underground parts of plants - roots, tubers, bulbs and even wood (some insects). Secondary consumers include carnivores. Carnivores, in turn, are divided into two groups: feeding on mass small prey and active predators, often attacking prey larger than the predator itself. At the same time, both herbivores and carnivores have a mixed diet. For example, even with an abundance of mammals and birds, martens and sables also eat fruits, seeds and pine nuts, and herbivorous animals consume some amount of animal food, thus obtaining the essential amino acids of animal origin they need. Starting at the producer level, there are two new ways to use energy. First, it is used by herbivores (phytophages), which eat directly the living tissues of plants; secondly, they consume saprophages in the form of already dead tissues (for example, during the decomposition of forest litter). Organisms called saprophages, mainly fungi and bacteria, obtain the necessary energy by decomposing dead organic matter. In accordance with this, there are two types of food chains: the chains of eating and the chains of decomposition, fig. 3.

It should be emphasized that the food chains of decomposition are no less important than the chains of grazing. On land, these chains begin with dead organic matter (leaves, bark, branches), in water - dead algae, fecal matter and other organic residues. Organic residues can be completely consumed by bacteria, fungi and small animals - saprophages; in this case, gas and heat are released.

Each biocenosis usually has several food chains, which in most cases are difficult to intertwine.

Quantitative characteristics of biocenosis: biomass, biological productivity.

Biomass and biocenosis productivity

The amount of living matter of all groups of plant and animal organisms is called biomass. The rate of biomass production is characterized by the productivity of the biocenosis. There are primary productivity - plant biomass formed per unit time during photosynthesis, and secondary - biomass produced by animals (consumers) that consume primary products. Secondary production is formed as a result of the use by heterotrophic organisms of the energy stored by autotrophs.

Productivity is usually expressed in units of mass per year in terms of dry matter per unit area or volume, which varies significantly in different plant communities. For example, 1 hectare of pine forest produces 6.5 tons of biomass per year, and a sugarcane plantation - 34-78 tons. In general, the primary productivity of the world's forests is the highest compared to other formations. A biocenosis is a historically established complex of organisms and is part of a more general natural complex - an ecosystem.

The rule of ecological pyramids.

All species that make up the food chain subsist on the organic matter created by green plants. At the same time, there is an important regularity associated with the efficiency of the use and conversion of energy in the process of nutrition. Its essence is as follows.

Only about 0.1% of the energy received from the Sun is bound in the process of photosynthesis. However, due to this energy, several thousand grams of dry organic matter per 1 m 2 per year can be synthesized. More than half of the energy associated with photosynthesis is immediately consumed in the process of respiration of the plants themselves. The other part of it is transferred through a number of organisms along food chains. But when animals eat plants, most of the energy contained in food is spent on various life processes, while turning into heat and dissipating. Only 5 - 20% of food energy passes into the newly built substance of the animal's body. The amount of plant matter that serves as the basis of the food chain is always several times greater than the total mass of herbivorous animals, and the mass of each of the subsequent links in the food chain also decreases. This very important rule is called ecological pyramid rule. The ecological pyramid, which is a food chain: cereals - grasshoppers - frogs - snakes - an eagle is shown in fig. 6.

The height of the pyramid corresponds to the length of the food chain.

The transition of biomass from the underlying trophic level to the overlying one is associated with the loss of matter and energy. On average, it is believed that only about 10% of the biomass and the energy associated with it passes from each level to the next. Because of this, the total biomass, production and energy, and often the number of individuals progressively decrease as one ascends the trophic levels. This regularity was formulated by Ch. Elton (Ch. Elton, 1927) as a rule ecological pyramids (Fig. 4) and acts as the main limiter for the length of food chains.

The totality of living beings included in the ecological system is called the biotic community, or biocenosis. Consequently, biocenosis- a set of populations of all types of living organisms inhabiting a certain geographical area that differs from other neighboring areas in terms of chemical composition soils, waters, as well as a number of physical indicators (altitude above sea level, solar radiation, etc.). This refers to the totality of living beings - plants, animals, microorganisms, adapted to cohabitation in a given territory. The concept of "biocenosis" is one of the most important in ecology, since it follows from it that living beings form complex organized systems outside of which they cannot sustainably exist. The main function of the community is to ensure balance in the ecosystem based on a closed cycle of substances.

The composition of biocenoses can include thousands of species of various organisms. But not all of them are equally significant. The removal of some of them from the community 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 scales of biocenotic groupings of organisms are very different - from communities of lichen pillows 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 subject to hierarchy. With an increase in the scale of communities, their complexity and the proportion of indirect, indirect relationships 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, are formed and maintain their stability on the basis of other principles. They are systems of the so-called frame type- without special managing and coordinating centers, and are also built on numerous and complex internal connections.

The most important features of systems related to a non-organismal level of life organization, for example, according to the classification of a German ecologist V. Tischler, are the following:

Communities always arise, are made up of ready-made parts (representatives of various species or entire complexes of species) that are present in the environment. In this way, the way they arise differs from the formation of a separate organism, which occurs through the gradual differentiation of the simplest initial state.
Community parts are interchangeable. Parts (organs) of any organism are unique.
If a whole organism maintains constant coordination, the consistency of the activity of its organs, cells and tissues, then the supraorganismal system exists mainly due to the balancing of oppositely directed forces.
Communities are based on the quantitative regulation of the abundance of some species by others.
The maximum dimensions of an organism are limited by its internal hereditary program. The dimensions of supraorganismal systems are determined by external causes.

Within the phytocenosis, each species behaves relatively independently. From the point of view of continuity, species meet together not because they have adapted to each other, but because they have adapted to a common habitat. Any variation in habitat conditions causes changes in the composition of the community.

Multifaceted, and when studying it, various aspects are distinguished.

Species and spatial structure of the biocenosis

There are concepts of "species richness" and "species diversity" of biocenoses. Species richness- a common set of community species, which is expressed by a list of representatives of different groups of organisms. Species diversity- an indicator that reflects not only the qualitative composition of the biocenosis, but also the quantitative relationships of species.

There are 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, gardens, orchards) are also poorer in species than natural systems similar to them (forest, steppe, meadow). The monotony and species poverty of agrocenoses is supported by a special complex system of agrotechnical measures.

Almost all terrestrial and most aquatic biocenoses include both plants and animals in their composition. The stronger the differences between two neighboring biotopes, the more heterogeneous the conditions at their boundaries and the more pronounced the boundary effect. population of one or another group of organisms in biocenoses strongly depends on their size. The smaller the individuals of species, the higher their abundance in biotopes.

Groups of organisms of different sizes live in a biocenosis at different scales of space and time. For example, life cycles unicellular can take place within an hour, and the life cycles of large plants and animals stretch for decades.

Naturally, in all biocenoses, the smallest forms - bacteria and other microorganisms - predominate numerically. In each community, it is possible to single out a group of main, most numerous species in each size class, the relationships between which are decisive for the functioning of the biocenosis as a whole. The species that prevail in terms of abundance (productivity) are community dominators. 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 plant - bluegrass, and among the animals grazing there, most of all are cows. This means that bluegrass dominates among producers, and 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 side by side. In such communities, outbreaks of mass reproduction of individual species do not occur; biocenoses are highly stable.

The totality of all types of community makes it biodiversity. Typically, a community consists of a few major species with high numbers and many rare species with low numbers.

Biodiversity is responsible for the equilibrium state of the ecosystem, and, consequently, for its sustainability. A closed cycle of nutrients (biogens) occurs only due to biological diversity. Substances that are not assimilated by some organisms are assimilated by others, so the output of biogens 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 forecasts and foresight of its consequences, as well as effective measures to maintain natural systems.

The area of \u200b\u200bthe abiotic environment that the biocenosis occupies is called biotope.

The spatial structure of the terrestrial biocenosis consists of its plant part - phytocenosis, the distribution of the ground and underground plant masses. Animals are also predominantly confined to one or another layer of vegetation (Fig. 1).

Rice. 1. Distribution of ungulates by feeding tiers (De la Fuente, 1972): 1 - giraffe; 2 - gerenuk antelope; 3 - dik-dik antelope; 4 - rhinoceros; 5 - elephant; 6 - zebra; 7 - giu; 8 - Grant's gazelle; 9 - antelope bubal