Biogeocenosis is a homogeneous area of the earth's surface with a certain composition of living organisms and certain living conditions, which are united by the metabolism and energy into a single natural complex.
In each biogeocenosis, there are species that prevail in number or occupy a large area. They are called dominant species. However, not all dominant species have the same effect on biogeocenosis. Those that determine the composition, structure and properties of an ecosystem by creating an environment for the entire community are called edificators. And now consider the biogeocenosis of the oak forest.
Among the terrestrial biogeocenoses, one of the most complex is a broad-leaved forest, for example, an oak forest. Oak grove is a perfect and stable ecological system capable of existing for centuries under constant external conditions. The biogeocenosis of oak forests consists of more than a hundred species of plants and several thousand species of animals.
Oak plants. In terrestrial biogeocenoses, higher plants create the main biological products. In the forest, these are predominantly perennial tree species.
Between plants there is an increased competition for the basic living conditions: space, light, water with minerals dissolved in it. As a result of long-term natural selection, oak forest plants have developed adaptations that allow different species to exist together. This is clearly manifested in the layering characteristic of oak forests.
The upper tier is formed by the most light-loving tree species: oak, ash, linden. Below are the less light-loving trees accompanying them: maple, apple, pear, etc. Even lower is the undergrowth layer formed by various shrubs: hazel, buckthorn, viburnum, etc. Finally, a layer of herbaceous plants grows on the soil. The lower the tier, the more shade-tolerant the plants forming it.
Due to the complex layering, the total area of plant leaves growing on each hectare reaches 4–6 hectares. Net production in the form of an increase in organic matter is almost 10 t/ha per year.
Food chains in oak forests. The richness and diversity of plants becomes the reason for the development of consumers from the animal world in oak forests, from the simplest to higher vertebrates - birds and mammals.
Food chains in the forest are intertwined in a very complex food web, so the loss of any one species of animal usually does not significantly disrupt the entire system. The disappearance, for example, in most of our oak forests of all large herbivorous ungulates: bison, deer, roe deer, elk would have little effect on the overall ecosystem, since their biomass has never been large and has not played a significant role in the general circulation of substances. But if herbivorous insects disappeared, the consequences would be very serious, since insects perform an important function of pollinators in biogeocenosis, participate in the destruction of litter and serve as the basis for the existence of many subsequent links in food chains.
Ecological systems
- Biogeocenosis
- Reservoir and oak forest as examples of biogeocenoses
- Changes in biogeocenoses
- Biogeocenoses created by man
- Nutritional connections
- Energy losses in power circuits
Biogeocenosis.
Biogeocenosis is a stable community of plants, animals and microorganisms that are in constant interaction with the components of the atmosphere, hydrosphere and lithosphere. The energy of the Sun, mineral substances of the soil and gases of the atmosphere, water enter this community, and heat, oxygen, carbon dioxide, and waste products of organisms are released from it. The main functions of biogeocenosis are the accumulation and redistribution of energy and the circulation of substances. Biogeocenosis is an integral self-regulating and self-sustaining system. It includes the following mandatory components: inorganic (carbon, nitrogen, carbon dioxide, water, mineral salts) and organic substances (proteins, carbohydrates, lipids, etc.); autotrophic organisms - producers of organic substances; heterotrophic organisms - consumers of ready-made organic substances of plant - consumers (consumers of the first order) and animal (consumers of the second and subsequent orders) origin. Heterotrophic organisms include decomposers - reducers, or destructors, which decompose the remains of dead plants and animals, turning them into simple mineral compounds.
Speaking of biocenoses, only interconnected living organisms that live in a given area are considered. Biocenoses are characterized by species diversity, i.e. the number of species of living organisms that form it; population density, i.e. the number of individuals of a given species, per unit area or per unit volume (for aquatic and soil organisms); biomass - the total amount of animal organic matter, expressed in units of mass.
Biomass is formed as a result of the binding of solar energy. The efficiency with which plants assimilate solar energy varies in different biocenoses. The total production of photosynthesis is called primary production. Plant biomass is used by first-order consumers - herbivorous animals - as a source of energy and material for creating biomass; moreover, it is used extremely selectively (Fig. 17.7), which reduces the intensity of the interspecific struggle for existence and contributes to the conservation of natural resources. Herbivorous animals, in turn, serve as a source of energy and material for consumers of the second order - predators, etc. Figure 17.8 shows comparative data on the productivity of various biogeocenoses. The greatest amount of biomass is formed in the tropics and in the temperate zone, very little - in the tundra and the ocean.
Organisms that are part of biogeocenoses are influenced by inanimate nature - abiotic factors, as well as from wildlife - biotic influences.
Biocenoses are integral, self-regulating biological systems, which include living organisms living in the same territory.
The energy of sunlight is assimilated by plants, which are subsequently used by animals as food.
Nutritional connections .
Energy losses in power circuits
All species that make up the food chain subsist on the organic matter created by green plants. In this case, 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.
In total, only about 1% of the radiant energy of the Sun incident on a plant is converted into the potential energy of chemical bonds of synthesized organic substances and can be further used by heterotrophic organisms for nutrition. When an animal eats a plant, most of the energy contained in the food is spent on various life processes, turning into heat and dissipating. Only 5-20% of food energy passes into the newly built substance of the animal's body. If a predator eats a herbivore, then again most of the energy contained in the food is lost. Due to such large losses of useful energy, food chains cannot be very long: they usually consist of no more than 3-5 links (food levels).
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 HH o This very important pattern is called the rule of the ecological pyramid.
Reservoir and oak forest as examples of biogeocenoses
1. Biogeocenosis of fresh water.
Any natural body of water, such as a lake or a pond, with its plant and animal population is a separate biogeocenosis. This natural system, like other biogeocenoses, has the ability for self-regulation and continuous self-renewal.
Plants and animals inhabiting the reservoir are unevenly distributed in it. Each species lives in the conditions to which it is adapted. The most diverse and favorable conditions for life are created in the coastal zone. Here the water is warmer, as it warms up with the sun's rays. It is sufficiently oxygenated. The abundance of light penetrating to the bottom ensures the development of many higher plants. Small algae are also numerous. Most of the animals live in the coastal zone. Some are adapted to life on aquatic plants, others actively swim in the water column (fish, predatory swimming beetles and water bugs). Many are found at the bottom (barley, toothless, larvae of some insects - caddisflies, dragonflies, mayflies, a number of worms, etc.). Even the surface film of water serves as a habitat for species specially adapted to it. In quiet backwaters, you can see predatory water strider bugs running on the surface of the water and swirling beetles swimming quickly in circles. The abundance of food and other favorable conditions attract fish to the coastal zone.
In the deep near-bottom parts of the reservoir, where sunlight weakly penetrates, life is poorer and more monotonous. Photosynthetic plants cannot exist here. The lower layers of water remain cold due to weak mixing. Here the water contains little oxygen.
Special conditions are also created in the thickness of the water in open areas of the reservoir. It is inhabited by a mass of the smallest plant and animal organisms, which are concentrated in the upper, warmer and well-lit layers of water. Various microscopic algae develop here; algae and bacteria feed on numerous protozoa - ciliates, as well as rotifers and crustaceans. This whole complex of small organisms suspended in water is called plankton. In the circulation of substances and in the life of a reservoir, plankton plays a very important role.
2. Food connections and stability of pond biogeocenosis.
Consider, due to what the system of inhabitants of the reservoir exists and how it is maintained. Food chains consist of several consecutive links. For example, plant residues and bacteria developing on them are fed by protozoa, which are eaten by small crustaceans. The crustaceans, in turn, serve as food for fish, and the latter can be eaten by predatory fish. Almost all species do not feed on one type of food, but use different food objects. Food chains are intricately intertwined. An important general conclusion follows from this: if any member of the biogeocenosis falls out, then the system is not disturbed, since other food sources are used. The greater the species diversity, the more stable the system.
The primary source of energy in aquatic biogeocenosis, as in most ecological systems, is sunlight, thanks to which plants synthesize organic matter. Obviously, the biomass of all animals existing in a reservoir completely depends on the biological productivity of plants.
Often the reason for the low productivity of natural water bodies is the lack of minerals (especially nitrogen and phosphorus) necessary for the growth of autotrophic plants, or the unfavorable acidity of the water. The application of mineral fertilizers, and in the case of an acidic environment, the liming of reservoirs, contributes to the reproduction of plant plankton, which feed on animals that serve as food for fish. In this way, the productivity of fishery ponds is increased.
3. Biogeocenosis of broad-leaved forest.
Summary of other presentations
"Evidence of the evolution of the organic world" - They are divergent in nature. Comparative anatomical (morphological) evidence of evolution. Evidence groups for the evolutionary process. Grade 11. What do the terms mean? Archeopteryx. The peculiarity of the fauna and flora of the islands testifies in favor of evolution. Molecular biological and cytological. Paleontological evidence for evolution Fossil forms. Conclusion: A. Wallace identified 6 zoogeographic areas for the distribution of animals and plants on our planet. Stages of embryonic development of vertebrates. Embryological.
"Ecosystem structure" - Terrestrial biogeocenosis. stream ecosystem. Together with the factors of inanimate nature, the community forms an ecosystem. Biology Grade 11 Completed by Viktor Arkhipkin. Ecological structure of the ecosystem. Oak ecosystem. Producers or autotrophs (producers of non-protein toxins). Water as an ecosystem.
"Natural selection and evolution" - In a population from generation to generation, the phenotype changes in one direction. It is observed during long-term preservation of constant environmental conditions. The concept of natural selection. Draw a table. Driving form of selection. Content. Observed in changing environmental conditions. The population remains phenotypically homogeneous. Within a population, several distinctly different phenotypic forms arise.
"Organism as a biosystem" - Humoral regulation. The body as a biosystem. Homework. Chemotrophs are bacteria. In algae, fungi, and protozoa, calcium ions play an important role. An organism has a certain individual stock of hereditary information. Multicellular Plants Animals Mushrooms Man. Multicellular organism. Nervous regulation Faster Addressed to a strictly defined organ. unicellular organisms.
"Archaean era in biology" - Head: Ivanova N.N. MOU secondary school No. 43. Presentation on theme: "The Archean Era". 11th grade student "A". Completed by: Dzhurik Kristina Alexandrovna. Biology Presentation! Reproduction methods: Asexual Sexual. In the Archean era, the first living organisms arose.
"The main directions of evolution" - The main directions of evolution of the organic world. Fundamentals of Darwin's teachings. Evolution of the organic world. Completed by: Litvinova E, 11th grade. 2008
Among the terrestrial biogeocenoses, one of the most complex is a broad-leaved forest, such as an oak forest. oak brava - a perfect and stable ecological system capable of existing for centuries under constant external conditions. The biogeocenosis of oak forests consists of more than a hundred species of plants and several thousand species of animals.
oak forest plants
In terrestrial biogeocenoses, higher plants create the main biological products. In the forest, these are predominantly perennial tree species (Figure 39).
Figure 39. Biogeocenosis of a broad-leaved forest.A characteristic feature of the deciduous forest is the species diversity of vegetation. Between plants there is an increased competition for the basic living conditions: space, light, water with minerals dissolved in it. As a result of long-term natural selection, oak forest plants have developed adaptations that allow different species to exist together. This is clearly manifested in the layering characteristic of oak forests.
The upper tier is formed by the most light-loving tree species: oak, ash, linden. Below are the accompanying less light-loving trees: maple, apple, pear, etc. Even lower is the undergrowth layer formed by various shrubs: hazel, euonymus, buckthorn, viburnum, etc.
Finally, a layer of herbaceous plants grows on the soil. The lower the tier, the more shade-tolerant the plants forming it.
Layering is also expressed in the location of root systems. The trees of the upper tiers have the deepest root system and can use water and minerals from the deep layers of the soil.
The oak forest is characterized by high biological productivity. Due to its complex multilayered, the total area of leaves of plants growing on each hectare reaches 4-6 hectares. Such a powerful photosynthetic apparatus captures and transforms about 1% of the annual influx of solar radiation into potential energy of organic matter. The latter in the middle latitudes is about 3.8 10 7 kJ/ha. Almost half of the synthesized substance is consumed by the plants themselves in the process of respiration. Net production in the form of an increase in organic matter in the aboveground parts of plants is 5-6 t/ha per year. To this should be added 3-4 t/ha of annual growth of underground parts. Thus, the production of oak forests reaches almost 10 t/ha per year.
Food chains in oak forests.
The richness and diversity of plants, producing a huge amount of organic matter that can be used as food, cause the development in oak forests of numerous consumers from the animal world, from protozoa to higher vertebrates - birds and mammals.
Food chains in the forest are intertwined in a very complex food web, so the loss of any one species of animal usually does not significantly disrupt the entire system. The value of different groups of animals in the biogeocenosis is not the same. The disappearance, for example, in most of our oak forests of all large herbivorous ungulates; bison, deer, roe deer, elk - would have little effect on the overall ecosystem, since their numbers, and therefore biomass, have never been large and have not played a significant role in the general circulation of substances. But if herbivorous insects disappeared, the consequences would be very serious, since insects perform an important function of pollinators in biogeocenosis, participate in the destruction of litter and serve as the basis for the existence of many subsequent links in food chains.
Self-regulation in forest biogeocenosis.
The process of self-regulation in the oak forest is manifested in the fact that the entire diverse population of the forest exists together, without completely destroying each other, but only limiting the number of individuals of each species to a certain level. The importance of such population regulation in the life of a forest can be seen from the following example. Several hundred species of insects feed on oak leaves, but under normal conditions, each species is represented by such a small number of individuals that even their common activity does not cause significant harm to the tree and forest. Meanwhile, all insects are highly prolific. The number of eggs laid by one female is rarely less than 100. Many species are capable of producing 2-3 generations per summer. Consequently, in the absence of limiting factors, the number of any kind of insect would increase very quickly and would lead to the destruction of the ecological system.
Mineralization of organic residues.
Of great importance in the life of the forest are the processes of decomposition and mineralization of the mass of dying leaves, wood, animal remains and their metabolic products. Of the total annual increase in the biomass of above-ground parts of plants, about 3-4 tons per 1 ha naturally die off and fall off, forming the so-called forest litter. A significant mass is also made up of dead underground parts of plants. With the litter, most of the minerals and nitrogen consumed by plants return to the soil.
Animal remains are very quickly destroyed by dead beetles, skin beetles, larvae of carrion flies and other insects, as well as putrefactive bacteria. It is more difficult to decompose cellulose and other durable substances that make up a significant part of plant litter. But they also serve as food for a number of organisms, such as fungi and bacteria, which have special enzymes that break down fiber and other substances into easily digestible sugars.
Figure 40. Comparison of the general structure of terrestrial and aquatic biogeocenoses:
I - plants producing organic matter: a - higher plants; b - algae;
II - animals - consumers of organic matter: a - herbivorous, b - carnivorous, c - eating mixed food.
As soon as the plants die, their substance is completely used by the destroyers. A significant part of the biomass is made up of earthworms, which do a great job of decomposing and moving organic matter in the soil. The total number of insects, shell mites, worms and other invertebrates reaches many tens and even hundreds of millions per hectare. The role of bacteria and lower, saprophytic fungi is especially great in the decomposition of litter.
OAK ECOSYSTEM: EXCURSION
1. Oak forest as a natural community (biogeocenosis), is one of the most complex among terrestrial biogeocenoses. Well, firstly, what is biogeocenosis? Biogeocenosis is a complex of interconnected species (populations of different species) living in a certain area with more or less uniform conditions of existence. This definition will be needed for later use. Oak forest is a perfect and stable ecological system capable of existing for centuries under constant external conditions. The biogeocenosis of oak forests consists of more than a hundred species of plants and several thousand species of animals. It is clear that with such a variety of species inhabiting the oak forest, it will be difficult to shake the stability of this biogeocenosis by exterminating one or more species of plants or animals. It is difficult, because as a result of the long coexistence of plant and animal species from disparate species, they became a single and perfect biogeocenosis - an oak forest, which, as mentioned above, is capable of existing for centuries under unchanged external conditions.
2. The main components of biogeocenosis and the relationship between them; Plants are the main link in an ecosystem. The vast majority of biogeocenosis is based on green plants, which, as you know, are the producer of organic matter (producers). And since in the biogeocenosis there are necessarily herbivorous and carnivorous animals - consumers of living organic matter (consumers) and, finally, destroyers of organic residues - mainly microorganisms that bring the breakdown of organic substances to simple mineral compounds (decomposers), it is not difficult to guess why plants are the main link in the ecosystem. But because in the biogeocenosis everyone consumes organic substances, or compounds formed after the decay of organic substances, and it is clear that if plants, the main source of organic matter, disappear, then life in the biogeocenosis will practically disappear.
3. Circulation of substances in biogeocenosis. Significance in the cycle of plants using solar energy The cycle of substances in biogeocenosis is a necessary condition for the existence of life. It arose in the process of the formation of life and became more complicated in the course of the evolution of living nature. On the other hand, in order for the circulation of substances to be possible in the biogeocenosis, it is necessary to have organisms in the ecosystem that create organic substances from inorganic ones and convert the energy of solar radiation, as well as organisms that use these organic substances and again turn them into inorganic compounds. All organisms are divided into two groups according to the method of nutrition - autotrophs and heterotrophs. Autotrophs (mainly plants) use inorganic compounds from the environment to synthesize organic substances. Heterotrophs (animals, humans, fungi, bacteria) feed on ready-made organic substances synthesized by autotrophs. Therefore, heterotrophs depend on autotrophs. In any biogeocenosis, all reserves of inorganic compounds would very soon run out if they were not renewed in the course of the life of organisms. As a result of respiration, decomposition of animal corpses and plant residues, organic substances turn into inorganic compounds, which return back to the natural environment and can again be used by autotrophs. Thus, in biogeocenosis, as a result of the vital activity of organisms, there is a continuous flow of atoms from inanimate nature to living nature and vice versa, closing in a cycle. For the circulation of substances, an influx of energy from the outside is necessary. The source of energy is the sun. The movement of matter caused by the activity of organisms occurs cyclically, it can be used repeatedly, while the flow of energy in this process is unidirectional. The radiation energy of the Sun in the biogeocenosis is converted into various forms: into the energy of chemical bonds, into mechanical and, finally, into internal. From all that has been said, it is clear that the circulation of substances in biogeocenosis is a necessary condition for the existence of life and plants (autotrophs) in it the most important link.
4. Diversity of species in the biogeocenosis, their adaptability to living together. A characteristic feature of the oak forest is the species diversity of vegetation. As mentioned above, the biogeocenosis of oak forests consists of more than a hundred plant species and several thousand animal species. Between plants there is an increased competition for the basic living conditions: space, light, water with minerals dissolved in it. As a result of long-term natural selection, oak forest plants have developed adaptations that allow different species to exist together. This is clearly manifested in the layering characteristic of oak forests. The upper tier forms the most light-loving tree species: oak, ash, linden. Below are the less light-loving trees accompanying them: maple, apple, pear, etc. Even lower is the undergrowth layer formed by various shrubs: hazel, euonymus, buckthorn, viburnum, etc. Finally, a layer of herbaceous plants grows on the soil. The lower the tier, the more shade-tolerant the plants forming it. Layering is also expressed in the location of root systems. The trees of the upper tiers have the deepest root system and can use water and minerals from the deep layers of the soil.
7. Changes in biogeocenosis in spring: in the life of plants and animals.
Spring changes in plant life.
Some willows, alders, and hazels are blooming before their leaves have opened; on thawed patches, even through the snow, sprouts of the first spring plants make their way. By mid-spring, almost all trees have leaves. The flowering period of plants and flowers. In general, plants come alive from winter calm.
Spring changes in the life of animals.
Migratory birds arrive, overwintered insects appear, some animals wake up from hibernation. The period of formation of pairs and the marriage period.
8. Possible directions of biogeocenosis change. Any biogeocenosis develops and evolves. The leading role in the process of changing terrestrial biogeocenoses belongs to plants, but their activity is inseparable from the activity of the other components of the system, and the biogeocenosis always lives and changes as a whole. The change goes in certain directions, and the duration of the existence of various biogeocenoses is very different. An example of a change in an insufficiently balanced system is the overgrowth of a reservoir. Due to the lack of oxygen in the bottom water layers, part of the organic matter remains unoxidized and is not used in the further circulation. In the coastal zone, the remains of aquatic vegetation accumulate, forming peaty deposits. The pond is shrinking. Coastal aquatic vegetation spreads to the center of the reservoir, peat deposits are formed. The lake gradually turns into a swamp. The surrounding terrestrial vegetation is gradually advancing on the site of the former reservoir. Depending on local conditions, a sedge meadow, a forest, or another type of biogeocenosis may appear here. Oak forest can also turn into a different type of biogeocenosis. For example, after cutting down trees, it can turn into a meadow, a field (agrocenosis) or something else.
9. Influence of human activity on biogeocenosis; measures to be taken to protect it. Man has recently become very active in influencing the life of biogeocenosis. The economic activity of people is a powerful factor in the transformation of nature. As a result of this activity, peculiar biogeocenoses are formed. These include, for example, agrocenoses, which are artificial biogeocenoses resulting from human agricultural activities. Examples are artificially created meadows, fields, pastures. Artificial biogeocenoses created by man require tireless attention and active intervention in their life. Of course, there are many similarities and differences in artificial and natural biogeocenoses, but we will not dwell on this. A person also influences the life of natural biogeocenoses, but, of course, not as much as on agrocenoses. Forest areas created for planting young trees, as well as for limiting hunting, can serve as an example. Reserves and national parks created to protect certain species of plants and animals can also serve as an example. Mass societies are also being created that promote the preservation and protection of the environment, such as the "green" society, etc.
10. Conclusion. Using the example of an excursion walk through a natural biogeocenosis - an oak forest, they found out and disassembled why the oak forest is integral and stable, what are the main components of a biogeocenosis, what is their role and what connections exist between them, they also disassembled why the circulation of substances in a biogeocenosis is a necessary condition for the existence of life, they also found out how the whole variety of species living in an oak forest does not conflict with each other, allowing each other to develop normally, we sorted out what food connections exist in an oak forest and sorted out such a concept as an ecological pyramid, substantiated the factors causing a change in numbers and such a phenomenon as self-regulation, found out which changes occur in the biogeocenosis in the spring and sorted out the possible directions of evolution of the biogeocenosis, as well as how a person affects life in biogeocenoses. In general, on the example of oak forests, the life of biogeocenoses was completely dismantled.
Producers, or manufacturers, - these are autotrophs, which in the course of life synthesize organic compounds from inorganic substances, using carbon dioxide as a source of carbon. Biomass formed in an ecosystem by autotrophic organisms is called primary products. It serves as food and a source of energy for the rest of the organisms in the community.
The main producers are green plants, although photosynthetic and chemosynthetic bacteria also contribute to the formation of the primary production of the ecosystem. Each large ecosystem or any biogeocenosis is characterized by its own specific plants that carry out photosynthesis, i.e., their producers.
consumers, or consumers, - These are heterotrophic organisms that use the biomass synthesized by producers for their own vital activity. By eating and processing plants, consumers receive energy and form secondary products ecosystems.
Consumers are a variety of living organisms - from microscopic bacteria to large mammals, from protozoa to humans. From the point of view of the structure of the ecosystem and the role that different consumers play in maintaining its equilibrium state, all consumers can be divided into several subgroups, which we will do a little later when we analyze the nutritional relationships of ecosystems.
decomposers, or decomposers, recycle dead organic matter detritus) to mineral compounds that can again be used by producers. Many organisms, such as, for example, earthworms, centipedes, termites, ants, etc., feed on plant and animal remains, and part of the wood rots and decomposes during the life of fungi and bacteria. When fungi and other decomposers die, they themselves turn into detritus and serve as food and energy source for other decomposers.
Thus, despite the diversity of ecosystems, they all have structural similarity. Each ecosystem capable of independent existence has its own producers, various types of consumers and decomposers (Fig. 76).
Oak ecosystem. Consider, as an example, an oak forest, a very stable terrestrial ecosystem (Fig. 77). Oak forest is a typical broad-leaved forest with a longline structure, in which many hundreds of plant species and several thousand species of animals, microorganisms and fungi coexist.
The upper tree layer is formed by large (up to 20 m) perennial oaks and lindens. These light-loving plants, growing quite freely, create favorable conditions for the formation of the second tree layer, represented by undersized and less light-loving pear, maple, and apple trees.
Rice. 76. Necessary components of an ecosystem
Shrub vegetation is formed under the canopy of two tiers. Hazel, euonymus, viburnum, hawthorn, blackthorn, elder, buckthorn - this is not a complete list of plants that form the third tier up to a height of 2–4 m.
The next, herbaceous layer is made up of numerous shrubs and semi-shrubs, ferns, seedlings of trees and various herbs. Moreover, during the year in the oak forest there is a change in the grass cover. In the spring, when there is still no foliage on the trees and the soil surface is brightly lit, light-loving primroses bloom: lungwort, corydalis, anemone. In the summer they are replaced by shade-tolerant plants.
In the ground layer, which is only a few centimeters high from the soil surface, lichens, mosses, mushrooms, and low grasses grow.
Hundreds of plant species ( producers), using the energy of the sun, create a green biomass of oak forests. Oak forests are very productive: during the year, on an area of 1 hectare, they create up to 10 tons of plant mass growth.
Dead roots and fallen leaves form a litter in which numerous decomposers: earthworms, larvae of flies and butterflies, dung beetles and carnivores, wood lice and centipedes, springtails, mites, nematodes. Feeding, these organisms not only transform detritus, but also form the soil structure. The activity of diggers such as moles, mice and some large invertebrates keeps the soil from caking. Numerous soil protozoa live in drops of water between soil particles, and fungi form a symbiosis with plant roots and participate in the decomposition of detritus.
Rice. 77. Oak forest ecosystem
Despite the fact that annually 3–4 tons of dead plants enter 1 hectare of the soil surface in an oak forest, almost all of this mass is destroyed as a result of the activity of decomposers. A special role in this processing belongs to earthworms, of which there are a huge number in oak forests: several hundred individuals per 1 m2.
The fauna of the upper tiers of the oak forest is diverse. Dozens of species of birds nest in the crowns of trees. Nests are built by magpie and jackdaw, song thrush and chaffinch, great tit and blue tit. In the hollows, the eagle owl and the common owl hatch their chicks. Hobbies and sparrowhawks intimidate small songbirds. The bushes are inhabited by robin and blackbird, pied flycatcher and nuthatch. Even lower are the nests of warbler and wren. A gray squirrel moves along all tiers in search of food. Butterflies, bees, wasps, flies, mosquitoes, beetles - more than 1600 species of insects are closely related to oak! Grasshoppers and beetles, spiders and haymakers, mice, shrews and hedgehogs share their place under the sun in the grass layer. The largest consumers of this ecosystem are roe deer, fallow deer and wild boar.
The stability of this and any other ecosystem is ensured by a complex system of relationships between all the organisms that make up it.
Review questions and assignments
1. What is biogeocenosis?
2. Tell us about the spatial structure of the ecosystem.
3. What are the required components of any ecosystem?
4. In what relationship are the inhabitants of biocenoses with each other? Describe these connections.
5. Describe the species composition and spatial structure of the oak forest ecosystem.
Think! Execute!
1. What are the common features of the biogeocenoses of a deciduous forest and a freshwater reservoir.
2. Is the existence of a biocenosis consisting only of plants possible? Justify your point of view.
3. Do research on the topic "My home as an example of an ecosystem."
4. Develop a tour route that allows you to demonstrate the species, spatial and ecological structures of a typical ecosystem in your region (group project).
Work with computer
Refer to the electronic application. Study the material and complete the assignments.
25. Food connections. Circulation of matter and energy in ecosystems
Remember!
What are the essential components of any ecosystem?
Living organisms are in constant interaction with each other and with environmental factors, forming a stable self-regulating and self-sustaining ecosystem. The features of the species composition of this system are determined by historical and climatic conditions, and the relationships of organisms with each other and with the environment are built on the basis of eating behavior.
In the oak forest ecosystem we have considered, deer eat herbaceous plants and leaves of shrubs, squirrels are not averse to eating acorns and mushrooms, a hedgehog eats an earthworm, and an eagle owl catches mice and voles during night hunting. Numerous insects, oak acorns, wild apple and pear fruits, seeds and berries are excellent food for birds. Dead organic remains fall to the ground. Bacteria develop on them, which are consumed by protozoa, which, in turn, serve as food for numerous small soil invertebrates. All types of organisms are connected with each other by a complex system. food relationships.
When studying the structure of any ecosystem, it becomes obvious that its stability depends on the diversity food links, existing between different species of this community. Moreover, the greater the species diversity, the more stable the structure. Imagine a system in which predator and prey are represented by only single species, let's say "fox - hare". The disappearance of hares will inevitably lead to the death of predators, and the ecosystem, having lost two of its components, will begin to collapse. If, however, a fox can use both rodents, frogs, and small birds as food in a given ecosystem, then the loss of one food source will not lead to the destruction of the entire structure, and the vacant ecological niche will soon be occupied by other organisms with similar environmental requirements.
Get acquainted with figures 198, 200-202 with groups of organisms living together in biocenoses. What are the connections between them?
Various types of established relationships of organisms in biocenoses contribute to the preservation of their species composition and the maintenance of the optimal number of species populations that make up the biocenosis.
The structure of the biocenosis is expressed in the species composition of its population and the quantitative ratio of organisms by species (species structure), in the regular distribution of organisms of different species relative to each other in the occupied space (spatial structure), in food (trophic) and other relationships of organisms.
Species structure of biocenosis. Any biocenosis is formed by its characteristic species of organisms with a certain number of each of them. The total number of species in one biocenosis can reach several tens of thousands. Coral reefs and tropical forests are especially rich in species of organisms (Fig. 197, 1, 2). For biocenoses that have developed in harsh living conditions of organisms, for example, in the Arctic, a much smaller number of species is characteristic (Fig. 197, 3).
Rice. 197. Biocenoses rich and poor in species: 1 - coral reef; 2 - tropical forest; 3 - polar tundra
The number of organisms of each species in the biocenosis is different. Species with the largest number, or dominant (dominant), constitute its "species core". In some spruce forests, for example, in sorrel spruce forests, spruce dominates from trees, from herbaceous plants - sour, from birds - kinglet, robin, chaffinch, and from mammals - red and red-gray voles (Fig. 198).
Rice. 198. Numerous species of organisms of the spruce-sorrel forest: 1 - common spruce; 2 - common sorrel; 3 - finch; 4 - red-gray vole
The number of small species in biocenoses is always greater than the number of numerous ones. Small species create species richness of biocenoses and increase the diversity of its relationships. The same species serve as a reserve for replacing the dominant species when environmental conditions change. The richer the species composition of the biocenosis, the better its stability in relation to changing environmental conditions is ensured.
Spatial structure of biocenosis. The distribution of organisms in terrestrial biocenoses is mainly associated with layering, or the vertical arrangement of vegetation.
The tiered, or vertical, composition of biocenoses is most clearly expressed in forests, where there can be up to 5-6 tiers of plants (Fig. 199). So, in broad-leaved forests, or oak forests, oak, linden and other tall deciduous trees with large leaves form the first (upper) tier. Less light-loving, for example, Norway maple, elm and other companion trees of oak - this is the second tier. Hazel (hazel), honeysuckle, euonymus, wild rose, viburnum, buckthorn and other shrubs - the third tier (undergrowth). Perennial herbaceous plants (corydalis, anemone, goose onion, lungwort, May lily of the valley, green zelenchuk, European hoof, raven eye) form the fourth tier. Mosses, lichens and fungi grow in the lower (fifth) layer of the broad-leaved forest and are rare, without forming a continuous cover.
Rice. 199. Longline distribution of plants in the biocenosis of a broad-leaved forest - oak forest
The tiered structure of the forest allows plants to use sunlight more efficiently: light-loving plants form the upper tier, and plants of other tiers have adapted to life in conditions with low light or develop and bloom in early spring before the leaves bloom on the trees (scillas, anemones, corydalis, goose onions) .
The vertical distribution of animals and other organisms is associated with the tiers of biocenoses (Fig. 200). So, in the crowns of trees of the first and second tiers of the forest, various leaf-eating insects, insectivorous birds (thrushes, orioles, cuckoos), small animals (squirrels, dormice) live. There are also birds of prey here, such as the Sparrowhawk. The population of animals of the lower tier of the forest is especially diverse. Moose, hares, wild boars, hedgehogs, forest mice, wolves, foxes and other animals live here.
Rice. 200. Longline distribution of animals in the mixed forest biocenosis
Many animals, due to their mobility, live in several tiers. For example, the common squirrel builds nests and feeds its young in trees, and collects food for itself both in trees and bushes, and on the ground. Black grouse, capercaillie, hazel grouse feed mainly in the lower tier of the forest, spend the night in trees, and breed their offspring on the ground.
The distribution of animals by tiers in the biocenosis reduces competition between them in food, the choice of places for building nests. So, the pied flycatcher preys on insects in the crowns of trees, and the garden redstart hunts in shrubs and above the soil. Great spotted woodpecker and nuthatch feed on insects and their larvae, usually in the middle layer of the forest. However, they do not compete with each other: the woodpecker extracts insects, their larvae and pupae from under the bark of trees, and the nuthatch collects insects from the surface of the bark.
Layering, like floors, is also observed in the location of the roots. The roots of the trees of the upper tiers go deepest into the soil. In each layer of the soil there are bacteria and fungi, due to which organic residues are converted into humus (humus) and its mineralization. Many insects, mites, worms and other animals live here either permanently or temporarily. The number of species and individuals of animals associated with the soil exceeds the number of terrestrial ones. The soil population is most numerous in places where the soil is rich in organic matter and has a great influence on soil formation.
Food (trophic) structure of biocenosis. All organisms of biocenoses are interconnected by the “food-consumer” relationship, and each of them is included in one or another link in the food chain - a sequential series of organisms that feed on each other. There are two main types of food chains: pasture (grazing chains) and detrital (decomposition chains).
The basis of pasture food chains are plants (autotrophic organisms) and animals (heterotrophic organisms). Herbivorous animals, such as locusts, leaf beetles, crossbills, waxwings, voles, hares, deer are first-order consumers; carnivores (frogs, toads, lizards, snakes, insectivorous birds, many birds of prey and animals) are second-order consumers; and predatory animals that feed on second-order consumers are third-order consumers (Fig. 201).
Rice. 201. Pasture food chain oak forest
In detrital food chains (from Latin detritus - worn, small organic particles), the food source of first-order consumer organisms is the remains of decomposed animals, plants, fungi, along with the bacteria they contain. Detrital food chains are most common in forests (Fig. 202). Thus, a significant part of plant production (leaf litter) is not consumed directly by herbivorous animals, but dies off and undergoes decomposition and mineralization by saprotrophs (from the Greek sapros - rotten) - decay bacteria. Earthworms, centipedes, mites, insect larvae that feed on detritus serve as food for consumers of the next link.
Rice. 202. Deciduous forest detrital food web
So, the species, spatial and nutritional (trophic) structures of the biocenosis form the basis for maintaining its integrity. The species composition of organisms is formed in accordance with the environmental conditions in which this or that natural community exists. The species that make up the biocenosis, distributed over tiers and connected to each other by food chains, ensure the long-term existence of various natural communities on our planet.
Lesson learned exercises
- What is the structure of the biocenosis expressed in?
- How does the species structure of the biocenosis differ from the spatial and food (trophic)?
- What species of biocenosis organisms are considered dominant?
- What is the role of small species in the biocenosis?
- What is the vertical distribution of organisms associated with in biocenoses?
- What are food chains? How do pasture food chains differ from detrital food chains?
Make up several pasture and detrital food chains from the listed organisms and their metabolic products: herbaceous plants, leaves of trees and shrubs, plant litter, earthworms, butterfly caterpillars, slugs, blowfly larvae, frogs, snakes, a dead crow, tits, hawks, hedgehogs .
The life of forest plants has its own characteristics. The trees that form the forest grow more or less close together, influencing each other and the rest of the forest vegetation. Plants in the forest are arranged in tiers, which can be compared to floors. The upper, first tier is represented by the main trees of the first degree of significance (spruce, pine, oak). The second tier is formed by trees of the second size (bird cherry, mountain ash, apple tree). The third tier consists of shrubs, for example, wild rose, hazel, viburnum, euonymus. The fourth tier is a herbaceous cover, and the fifth is mosses and lichens. The access of light to plants of different tiers is not the same. The crowns of the trees of the first tier are better lit. From the upper to the lower tiers, the illumination decreases, as the plants of the upper tiers retain a fraction of the sun's rays. Mosses and lichens occupying the fifth tier receive a very small amount of light. These are the most shade-tolerant plants in the forest.
Different forests have a different number of tiers. For example, in a dark spruce forest, only two or three tiers are distinguishable. On the first tier are the main trees (spruces), on the second - a small number of herbaceous plants, and the third is formed by mosses. Other woody and shrubby plants do not grow in the second tier of the spruce forest, as they cannot stand strong shading. Also, grass cover is not observed in the spruce forest.
The tiered arrangement is typical not only for the aboveground parts of plants, but also for their underground organs - the roots. Tall trees have roots that penetrate deep into the ground, while the root system of trees of the second tier is shorter and forms a conditionally second tier of roots. The roots of other forest plants are even shorter and are located in the upper layers of the soil. Thus, plants in the forest absorb nutrients from different soil layers.
Trees of the first magnitude (oak, pine, spruce) close with their crowns and form a forest canopy, under which a small fraction of sunlight penetrates. Therefore, the herbaceous plants of the forest, as a rule, are shade-tolerant and have wide leaf blades. Many of them do not withstand exposure to direct sunlight and may die in open space. A feature of the grasses of the broad-leaved forest is flowering in early spring, when there are no foliage on the trees yet. With the help of broad leaves, forest plants accumulate organic matter in low light and deposit them in underground organs, for example, lungwort in rhizomes. In gloomy spruce thickets, flowers of herbaceous plants have white corollas so that they are visible from afar to pollinating insects. For example, such flowers are found in lily of the valley, wintergreen, septenary, gout, minik. But, despite these adaptations, the flowers of forest grasses often do not pollinate and do not form seeds. Therefore, the reproduction of many herbaceous plants is carried out by dividing the rhizomes, for example, in oxalis, lily of the valley, kupena, sedmichnik, minnik. This explains the placement of these herbs in groups in the forest.
Forest litter covering the soil consists of fallen leaves or needles, respectively, in deciduous or coniferous forests, as well as bark and branches of trees, dead grass patches, mosses. Loose forest litter is moist, which is favorable for the development of molds and hat fungi. Myceliums of various fungi densely permeate the litter, gradually converting organic matter into humus and mineral salts to feed the green plants of the forest.
