Biology at the Lyceum. Laws of ecosystem organization Can plants act as consumers
Any set of organisms and inorganic components in which the cycle of matter can be maintained is called an ecological system or ecosystem.
Natural ecosystems can be of different volume and length: a small puddle with its inhabitants, a pond, an ocean, a meadow, a grove, a taiga, a steppe - all these are examples of ecosystems of different scales. Any ecosystem includes a living part - a biocenosis and its physical environment. Smaller ecosystems are part of ever larger ones, up to the general ecosystem of the Earth. The general biological cycle of matter on our planet also consists of the interaction of many more particular cycles.
An ecosystem can ensure the circulation of matter only if it includes the four components necessary for this: reserves of biogenic elements, producers, consumers and decomposers.
Producers are green plants that create organic matter from biogenic elements, that is, biological products, using solar energy flows.
Consumers - consumers of this organic matter transforming it into new forms. Animals usually act as consumers. Distinguish consumers of the first order - herbivorous species and the second order - carnivores.
Decomposers - organisms that finally destroy organic compounds to mineral ones. The role of decomposers in biocenoses is performed mainly by fungi and bacteria, as well as other small organisms that process the dead remains of plants and animals.
Life on Earth has been going on for about 4 billion years, without interruption precisely because it takes place in the system of biological cycles of matter. The basis of this is plant photosynthesis and food relations of organisms in biocenoses.
However, the biological cycle of matter requires a constant expenditure of energy.
Unlike chemical elements, repeatedly involved in living bodies, the energy of the sun's rays, delayed by green plants, cannot be used by organisms indefinitely.
According to the first law of thermodynamics, energy does not disappear without a trace, it is stored in the world around us, but it passes from one form to another. According to the second law of thermodynamics, any transformation of energy is accompanied by the transition of part of it to a state where it can no longer be used for work. In the cells of living beings, the energy that provides chemical reactions, with each reaction, it partially turns into heat, and the heat is dissipated by the body in the surrounding space. The complex work of cells and organs is thus accompanied by energy losses from the body. Each cycle of the circulation of substances, depending on the activity of the members of the biocenosis, requires more and more energy.
Thus, life on our planet is carried out as a constant circulation of substances, supported by the flow of solar energy. Life is organized not only in biocenoses, but also in ecosystems in which close connection between living and non-living components of nature.
The diversity of ecosystems on Earth is associated both with the diversity of living organisms and the conditions of the physical, geographical environment. Tundra, forest, steppe, desert or tropical communities have their own characteristics of biological cycles and connections with environment. Aquatic ecosystems are also extremely diverse. Ecosystems differ in the rate of biological cycles and in the total amount of matter involved in these cycles.
The basic principle of ecosystem stability - the circulation of matter supported by the flow of energy - essentially ensures the endless existence of life on Earth.
According to this principle, sustainable artificial ecosystems, and production technologies that conserve water or other resources. Violation of the coordinated activity of organisms in biocenoses usually entails serious changes in the cycles of matter in ecosystems. This is the main reason for such environmental disasters, as a fall in soil fertility, a decrease in plant yields, the growth and productivity of animals, the gradual destruction of the natural environment.
Ending. See No. 16, 17/2002
"Swamp as an Ecosystem"
swamp myrtle(Chamaedaphna calycalata) usually has a height of about 25 cm, sometimes up to 1 m. Like wild rosemary, new shoots of myrtle appear annually only from renewal buds on the tops of last year's branches. It blooms in May with small white flowers collected in apical one-sided brushes. Myrtle has another name - cassandra. Cassandra in mythology Ancient Greece Daughter of King Priam of Troy. From Apollo, who was in love with her, she received the gift of divination, but, having rejected his love, she was punished by the fact that no one believed her predictions, although they always came true.
Podbel-whiteleaf (Andromeda polifolia) - a small (up to 30 cm) evergreen shrub with narrow long leaves, grows in more watered areas of the swamps. As sphagnum mosses grow, it develops abundantly branching adventitious roots concentrated in the uppermost moss layer. The Latin name of Podbela - Andromeda - is associated with Greek mythology. In the reign of Cepheus, the king of Ethiopia, a sea monster appeared that devastated the country, eating people. Kefey, in order to get rid of the punishment of the gods, decided to sacrifice his beautiful daughter Andromeda. However, Perseus, in love with her, defeated the monster, saved the girl and married her. Since then, Andromeda has blossomed with happiness. Podbel blooms with delicate pink bells from April to June, coloring the still faded swamp in pinkish color.
Heather(Calluna vulgaris) - a strongly branching evergreen shrub from 30 cm to 1 m high. Dense brushes of numerous small purple flowers located on the tops of the shoots usually appear late, in July-August, but remain on the bushes for a long time. Thickets of this ornamental shrub are eagerly visited by bees and other insects. Heather honey is tart and bitter.
Several species are found in swamps. cotton grass(Eriophorum), belonging to the sedge family ( Cyperaceae). These are herbs 30-50 cm high. The name comes from the white puffs that appear after flowering at the ends of the stems. Cotton grass blooms in April-May with inconspicuous flowers. Instead of petals, there are straight, smooth, inconspicuous bristles, greatly elongating towards the end of flowering. They form a white fluffy brush, at the base of which lie black trihedral fruitlets. Together with the fluffs, the seeds are carried by the wind over long distances.
The problem of lack of mineral nutrition was solved by some flowering plants by the transition to insectivorousness, i.e. use along with autotrophic and heterotrophic types of nutrition. Such plants include sundews, pemphigus, and butterflies. Two species are common in the swamp sundews– English(Drosera anglica) And round-leaved(D. rotundifolia) - differing in the shape of the leaves, which serve as trapping devices for them. In the English sundew they are long-leaved, lanceolate, in the round-leaved they are rounded. There are different types of sundews and habitat conditions. Sundew round-leaved prefers drier places and the neighborhood of pine. The English sundew is more moisture-loving and grows on flooded hollows with a water level of at least 2 cm from the surface.
Sundew is a perennial plant. In early spring, a bud wintering in the thickness of the moss appears on the surface and gives rise to leaves, as well as a long stalk with an inflorescence of small white flowers. To take the kidney out, the sundew grows every spring to the thickness of the increased moss cover. From the preserved sundew rosettes, one can accurately measure the growth of sphagnum over a number of years.
The leaves of sundews of both species are covered with numerous (up to 200 on each leaf) red glandular hairs with droplets of a light liquid similar to dew. Hence the name of the plant (from the Greek drosos- dew). The glands on the hairs, in contact with the victim, begin to secrete a digestive fluid containing substances similar in composition to pepsin in the human stomach. Sundew assimilates only proteins, it does not need fats and carbohydrates. The digestion process is very slow, over several days. Experiments with sundew have shown that the sensitivity of the glands of sundew is much higher than that of the nerve endings at the tip of the human tongue.
Approaching the outskirts of raised bogs, where mineral-enriched waters flow, you can see plants adapted to mesotrophic nutrition: marsh calla, three-leaf watch, marsh cinquefoil and others.
Task 8. Establish the affiliation of the discovered plant species to families. Fill the table.
The most common representative of the tree layer in the raised bog is Scotch pine(Pinus sylvestris). However, its growth is suppressed by an abundance of water, a small amount of mineral nutrients, and the depletion of peat in oxygen. Pine trees growing in swamps differ from upland ones in their structure, which was discussed at the beginning of the 20th century. wrote V.N. Sukachev. They have shorter needles, in which there are more resin passages, smaller cones and seeds, a different shape of the trunk. Their wood is dense, so it does not collapse for a long time, annual rings are thin, and the growth of the stem in height is very slow.
Task 9. Visually determine the height of the pine and calculate the age by the whorls on the stems. Compare the age and height of plants in drier and wetter parts of the bed.
From other plants in the swamps can be found fluffy birch(Betula pubescens), which together with pine forms sparse forest stands. The height of a birch and the diameter of its trunk depend on the place of growth.
Task 10. Determine the layering of the raised bog plants. Write the names of plant species in the appropriate columns of the table.
Answer the question: how would you explain the limited species composition of the vegetation of the swamp ecosystem?
5. Consumers
The fourth stage of the excursion is devoted to the species diversity of consumers and their adaptation to the environment. The fauna of invertebrates is diverse and depends on the habitat: a lake (water surface, water column, bottom and bottom sediments), woody vegetation and open air space.
Before starting the story about the entomofauna of swamps, the teacher distributes tables to students. 1 and 2 and asks them to fill in the empty columns during the excursion - enter the names of the animals considered and defined to the genus or indicate the presence of a particular group of animals with a “+” sign (tasks 11 and 12).
It is advisable to start observing the fauna of invertebrates from the lake.
On the surface of the water, students can see predatory insects that feed on small animals that accidentally land on the water surface. These insects include big water strider(Gerris rufoscutellatus) And armored water strider(G. thoracicus), and spinners(Gurinus). These insects have aquatic larvae, the development of which is not necessarily associated with this particular reservoir. This is confirmed by the fact that in swamp lakes there are no suitable conditions for the development of the mentioned insects. So, for example, the larva of the whirlpool has tracheal gills and lives in the bottom substrate, which, under swamp conditions, is very depleted in oxygen; The water strider usually lays its eggs on the leaves of aquatic plants, and there are no leaves of higher aquatic plants suitable for laying in lakes.
A special group of relatively large and very active predators are smoothies(Notonecta glauca) and various types rowers(Corixa). Gladysh lives in the near-surface layers, because. the air supply that it carries with it greatly increases buoyancy. Rowers are less mobile. They carry a supply of air under their elytra and can stay underwater longer. These species require submerged or floating aquatic vegetation to which they can attach. These insects can also be migrants, as they fly actively in the evening.
In the water column, water mites different types make up a large group of aquatic predators, preying mainly on small lower crustaceans (daphnia, cyclops, etc.), as well as small insect larvae. These consumer species, due to their absolute inedibility, close short food chains.
The study of deep (more than 1 m) near-bottom layers of water and bottom sediments shows the poverty of the fauna. This is due to the low water temperature and high acidity, which does not contribute to the bacterial decomposition of bottom plant sediments and the oxygen saturation of the environment. Microscopic studies of such deposits reveal amoebae with silicate shells ( Arcella). In the bog ecosystem, these species are detritivores. It is unlikely that you will be able to meet aquatic mollusks, since their calcareous shells quickly break down in acidic environment. Consequently, representatives of annelids - leeches, the main consumers of aquatic mollusks - will also be difficult to detect.
The students then continue along the ridge, and the teacher talks about invertebrates that live out of the water.
Microscopic mites, representatives of the arachnid class, live in the surface layer of sphagnum. The lower layers of moss are inhabited by rotifers, small crustaceans and tardigrades, which do not play any significant role in soil formation. Due to the fact that the bog vegetation of the raised bog is represented mainly by bryophytes and wind-pollinated flowering plants, pollinating insects will occur sporadically. On marsh cinquefoil(Comarum palustre) you can find some species of bumblebees, as well as bee and bumblebee flies. There will be a border effect at the border between swamp and forest, and a greater diversity of pollinating insects associated with certain forage plants can be expected.
Raised bogs are breeding grounds for various species of "non-malarial" mosquitoes. It will be interesting for students to learn that the method of observing tagged individuals has established the settlement of mosquitoes from a reservoir at distances of up to 18 km. Swamp conditions unsuitable for species Anopheles while mosquito larvae Culex constitute the main link in the food chain. The teacher can name the distinguishing features of mosquito genera Culex And Anopheles. It is important to remind students that in adult mosquitoes there is a food differentiation by sex, as a result of which males and females belong to different trophic levels. Males are consumers of the 1st order, feeding on plant sap; females, as blood-sucking insects, are consumers of subsequent orders in other food chains.
The open space above the swamp is a great hunting ground for dragonflies, which are active predators that forage in flight. More often than others in the swamp you can meet a clearly visible large dragonfly flat(Libellula depressa), as well as similar dragonfly four-spotted(L.quadrimaculatum), which has a more elongated abdomen and non-blackened bases of the first pair of wings.
It is known that all dragonflies go through the larval stage of incomplete transformation in water. The larvae breathe with oxygen dissolved in water with the help of internal (rectal) gills (Dragonflies) or with the help of three external tracheal abdominal gills (Dragonflies). Larvae of all species of dragonflies are active predators, and sometimes rather large aquatic animals - tadpoles, fish fry - become their prey. However, due to the depletion of water in oxygen and the poverty of the food supply, dragonfly larvae are rare in the swamp ecosystem.
Moving along the ridge towards the edge of the swamp, the teacher talks about tree pests and demonstrates the damage caused by them. A few trees in a depressed state grow on the raised bog: Scotch pine, downy birch, willows. It is with them that some consumers of plant products are associated.
Traces of the Great Spotted and Black Woodpeckers indicate that the pines are infested with barbel larvae. You can find their larval passages and "cradles" under the dead bark. Brownish flour is clearly visible under the bark of dead pines. typographer bark beetle(Ips typographus), located parallel to the axis of the tree, the uterine passages, as well as many flight holes. Under the bark of dead pines, one can also see bipedal predatory centipedes.
The bark of some birches is perforated birch sapwood(Scolytus ratzeburgi) is the largest representative of the bark beetle family ( Ipidae). Birch aphids and moth caterpillars are always found on birch leaves.
On birch and pine, one can also see other active consumers of plant products - birch and pine sawfly caterpillars, which are easily distinguished from Lepidoptera caterpillars by visual features: well-defined simple eyes, 11 pairs of legs (8 abdominal + 3 pectoral).
And, finally, if you look at the leaves of birch and willow, you can find traces of the activity of small insects, their larvae, as well as mites. These are traces of bites, gnaws, eating away of the mesophyll (mining), i.e. everything that usually escapes the eye during a cursory examination.
By moving along the ridge to the edge of the swamp, the teacher can demonstrate to the students the result of the work of a black tree ant on the wood of some spruces. At the same time, the central part of the trunk at their base often turns into parchment dust.
The teacher may recommend that students collect a small herbarium of damaged leaves during the excursion, and then determine the species of their consumers in the laboratory. Similarly, under laboratory conditions, it is useful to consider the population of sphagnum mosses - microscopic herbivorous and predatory mites.
It should be noted once again that the raised bog is a unique community where plants can act as consumers of the 2nd and even 3rd orders: sundew growing along the ridges, and pemphigus in lakes.
The story about the consumers of the marsh ecosystem would be incomplete without mentioning the vertebrates. Their species diversity is relatively low. Consumers of lakes floating near the surface and flying insects are pond frogs (Rana esculenta), the abundance of which in summer directly depends on the biomass of the above-mentioned insects. At some distance from the water's edge - on the ridges - there are two closely related species: grass frog(R. temporaria) And moor frog(R.arvalis). The class of reptiles is represented viviparous lizard(Lacerta viviparia) And common viper(Vipera berus), the wintering grounds of which are confined to raised bogs.
Of the birds on the raised bog in the Moscow region, you can meet mallard(Anas platyrhynchos), which is a consumer of the 1st order. Consumers of the 2nd order are represented common cuckoo(Cuculus canorus), catching insects in the air, some species of woodpeckers, meadow pipit(Anthus pratensis), wagtails(Motacilla sp.), collecting small invertebrates from the surface. On the border of the swamp and the forest, it is possible to meet with siskin(spinus spinus) And oatmeal-remez(Emberiza rustica). It should be noted that the food base of most of the listed bird species is not limited to invertebrates and they also willingly consume plant buds, their seeds and berries, which is justified in the conditions of poor nutrition offered by the swamp ecosystem. Birds of prey are rare in the Moscow region, and their ecological niche (consumers of the 3rd order) is apparently occupied by seagulls(Larus minutes). Of the mammals, the swamp can be visited moose(Alces alces).
6. Reducers
The role of decomposers in the bog ecosystem is not as great as in other ecosystems, which is due to the peculiarities of abiotic factors. Still at the roots of some angiosperms you can see mycorrhiza. In summer and autumn, fruiting bodies of various mushrooms grow in the swamp (in autumn - boletus and boletus). The activity of bacteria in swamps is reduced, because. phenols secreted by mosses inhibit microbiological processes. The low rate of decomposition of organic matter, in turn, contributes to the accumulation of peat in the bog ecosystem.
Due to the fact that the tour is quite long and informative, theoretical basis the organization of the swamp ecosystem can be given in front of her in a class lesson.
For knowledge testing obtained during the excursion, the teacher gives students assignments. Assignments can be completed in groups and then discussed in class. With a creative approach to completing the task, students can make drawings, collages, diagrams.
Tasks to test the knowledge gained on the excursion
1. Prove that the swamp is an ecosystem.
2. Prove that the swamp is an ecosystem that is stable over time.
3. Make a description of the swamp as an ecosystem according to the plan: soil features, water regime, features of flora and fauna.
4. Imagine that while walking in the forest you met a swamp on the way. What will you do to determine its type? On what grounds can one distinguish an upland bog from a lowland one?
5. Using two or three examples, show the adaptability of plants to the abiotic factors of the swamp.
6. Draw a diagram of the food web of the inhabitants of the raised bog.
7. Seminar on the topic "Value, use and protection of the wetland ecosystem"
Preparation for the seminar begins two weeks before it takes place. At the booth Research students” the title of the topic of the seminar, a list of questions and a list of recommended literature are posted. Students are offered the following topics for preparing messages.
1. The role of swamps in the regulation of the hydrological regime of the landscape.
2. The role of swamps in the regulation of geochemical processes in the biosphere.
3. The role of swamps in the conservation of biological and landscape diversity of the biosphere.
4. The use of the swamp by man.
To control the progress of preparation for the seminar, the teacher conducts consultations, during which he analyzes and corrects the work done, gives recommendations and reviews the completed assignments.
The seminar begins with an introductory speech by the teacher, who formulates the main objectives of the lesson, gives brief description topic, emphasizes its practical significance. Using herbarium material, tables, slides, the teacher activates the knowledge gained by students on the excursion about the swamp as an ecosystem. Students recall the basic relationships between plants and animals in an ecosystem. With the help of a teacher, students formulate the conclusion that in the food chains of biogeocenosis, organic matter is synthesized and repeatedly transformed, as a result of which there is a continuous circulation of substances in the biosphere.
Then the teacher introduces students to the biological productivity of swamps, reveals the main differences between the true growth of forests and swamps. If in the forest the true growth is concentrated in trees (they grow), then in the swamp it turns into peat by about 10–20%. Due to this swamps grow up. The rest of the growth (80–90%) decomposes, splits into chemical elements and enters the next cycle. Substances that have passed into peat are excluded from the circulation of substances in nature.
In students' reports on the biospheric functions of the swamp ecosystem, the following meanings of swamps are considered.
1. Formation of groundwater and groundwater resources.
2. Regulation of flood water runoff.
3. Protection against the penetration of salt water into underground and surface fresh water.
4. Detention of suspended particles.
5. Accumulation of animal nutrients.
6. Removal of toxic substances.
7. Global carbon storage.
8. Maintenance of microclimate.
9. Conservation of plant and animal habitats, including rare species.
In the stories of students about the practical significance of swamps, questions of human use should be raised:
- medicinal plants;
– gene pool of some plant and animal species for selection;
- berries and mushrooms.
Students can also talk about the various uses of peat (construction, papermaking, agriculture, medicine, fuel).
The teacher supplements the students' messages with a story about the methods of peat extraction (milling, excavation, hydraulic), draws the children's attention to the negative consequences of land reclamation. Finishing the review of the properties of peat, the teacher talks about the ability of peat to conserve objects of human life, traces of material culture.
To consolidate the studied material, the teacher before the start of the lesson offers the students the following questions, which they must answer at the end of the lesson (or at home).
1. Why does the level of groundwater decrease when swamps are drained?
2. How do swamps regulate flood water runoff?
3. There is an opinion that forests are the lungs of the planet, streams and rivers are its circulatory system, and swamps act as the liver and lungs on Earth. Do you agree with this statement? Justify your answer.
4. How can the accumulation of nutrients and the removal of toxic substances in bottom sediments swamps?
5. Which of the plant and animal species living in the swamp are listed in the Red Book?
6. How do you understand the statement that the swamp is a global carbon store?
7. How can the disappearance of swamps contribute to the greenhouse effect?
Phytophages and carnivores
The structure of the living matter of the ecosystem. Biotic structure. Autotrophs and heterotrophs
Ecosystem. Ecosystem features
Ecosystem homeostasis. ecological successions. Types of natural and anthropogenic successions. The concepts of climax, stability and variability of ecosystems.
populations in an ecosystem.
Producers. Consumers I, II order. Detritophages. Reducers.
Phytophages and carnivores.
The structure of the living matter of the ecosystem. Biotic structure. Autotrophs and heterotrophs.
Ecosystem. Ecosystem features.
Topic 3. Ecosystem. Structure of ecosystems
Bioconsumption. Population size and sustainability of the biosphere
The concepts of noosphere and technosphere
The term "ecosystem" was proposed by the English ecologist A. Tensley in 1935.
Ecosystem is any set of interacting living organisms and environmental conditions.
“Any unit (biosystem) that includes all co-functioning organisms (biotic community) in a given area and interacts with the physical environment in such a way that the energy flow creates well-defined biotic structures and the circulation of substances between living and non-living parts, is ecological system, or ecosystem"(Yu. Odum, 1986).
Ecosystems are, for example, anthills, forest area, farm area, cabin spaceship, a geographic landscape, or even the entire globe.
Ecologists also use the term "biogeocenosis", proposed by the Russian scientist V.N. Sukachev. This term refers to the totality of plants, animals, microorganisms, soil and atmosphere on a homogeneous land area. Biogeocenosis is one of the ecosystem options.
Between ecosystems, as well as between biogeocenoses, there are usually no clear boundaries, and one ecosystem gradually passes into another. Large ecosystems are made up of smaller ecosystems.
Rice. "Matryoshka" of ecosystems
On fig. the "matryoshka" of ecosystems is shown. The smaller the size of an ecosystem, the more closely the organisms that make up it interact. An organized team of ants lives in an anthill, in which all responsibilities are distributed. There are hunter ants, guards, builders.
The anthill ecosystem is part of the forest biogeocenosis, and the forest biogeocenosis is part of the geographical landscape. The composition of the forest ecosystem is more complex; representatives of many species of animals, plants, fungi, and bacteria live together in the forest. The connections between them are not as close as those of ants in an anthill. Many animals spend only part of their time in the forest ecosystem.
Within the landscape, different biogeocenoses are connected by aboveground and underground movement of water, in which minerals are dissolved. Water with mineral substances moves most intensively within the catchment basin - a reservoir (lake, river) and the slopes adjacent to it, from which aboveground and groundwater flow into this reservoir. The ecosystem of the catchment basin includes several different ecosystems - forest, meadow, arable land. The organisms of all these ecosystems may not have direct relationships and are connected through underground and aboveground water flows that move to the reservoir.
Within the landscape, plant seeds are transferred, animals move. A fox hole or a wolf's lair is located in one biogeocenosis, and these predators hunt in a large area consisting of several biogeocenoses.
Landscapes are combined into physical and geographical regions (for example, the Russian Plain, the West Siberian Lowland), where different biogeocenoses are connected by a common climate, geological structure territory and the possibility of resettlement of animals and plants. Relationships between organisms, including humans, in the ecosystems of a physical-geographic region and the biosphere are carried out through changes in the gas composition of the atmosphere and chemical composition reservoirs.
Finally, all the ecosystems of the globe are connected through the atmosphere and the World Ocean, into which the products of the vital activity of organisms enter, and form a single whole - biosphere.
The ecosystem includes:
1) living organisms (their totality can be called a biocenosis or biota of an ecosystem);
2) non-living (abiotic) factors - atmosphere, water, nutrients, light;
3) dead organic matter - detritus.
Of particular importance for the allocation of ecosystems are trophic , i.e. nutritional relationships of organisms that regulate the entire energy of biotic communities and the entire ecosystem as a whole.
First of all, all organisms are divided into two large groups - autotrophs and heterotrophs.
autotrophic organisms use inorganic sources for their existence, thereby creating organic matter from inorganic matter. Such organisms include photosynthetic green plants of land and aquatic environment, blue-green algae, some bacteria due to chemosynthesis, etc.
Since organisms are quite diverse in types and forms of nutrition, they enter into complex trophic interactions with each other, thereby performing the most important ecological functions in biotic communities. Some of them produce products, others consume, and others transform it into an inorganic form. They are called respectively: producers, consumers and decomposers.
Producers- producers of products that all other organisms then feed on - these are terrestrial green plants, microscopic marine and freshwater algae that produce organic substances from inorganic compounds.
Consumers are consumers of organic matter. Among them there are animals that consume only plant foods - herbivores(cow) or eating only the meat of other animals - carnivores(predators), as well as those who use both - “ omnivores"(man, bear).
Reducers (destructors)- restorers. They return substances from dead organisms back to inanimate nature, decomposing organic matter into simple inorganic compounds and elements (for example, into CO 2 , NO 2 and H 2 O). Returning to the soil or aquatic environment biogenic elements, they thereby complete the biochemical cycle. This is done mainly by bacteria, most other microorganisms and fungi. Functionally, decomposers are the same consumers, so they are often called microconsumers.
A.G. Bannikov (1977) believes that insects also play an important role in the decomposition of dead organic matter and in soil-forming processes.
Microorganisms, bacteria and other more complex forms, depending on the habitat, are divided into aerobic, i.e. living in the presence of oxygen, and anaerobic living in an oxygen-free environment.
All living organisms are divided into two groups according to the method of nutrition:
autotrophs(from Greek. autos- myself and tropho- nutrition);
heterotrophs(from Greek. heteros- another).
Autotrophs use inorganic carbon ( inorganic energy sources) and synthesize organic substances from inorganic ones, these are the producers of the ecosystem. According to the source (used) energy, they, in turn, are also divided into two groups:
Photoautotrophs- solar energy is used for the synthesis of organic substances. These are green plants that have chlorophyll (and other pigments) and absorb sunlight. The process by which it is absorbed is called photosynthesis.
(Chlorophyll is a green pigment that causes the color of plant chloroplasts to be green. With its participation, the process of photosynthesis is carried out.
Choroplasts are green plastids found in plant cells and some bacteria. They are used for photosynthesis.)
Chemoautotrophs used for the synthesis of organic substances chemical energy. These are sulfur bacteria and iron bacteria that obtain energy from the oxidation of sulfur and iron compounds (chemosynthesis). Chemoautotrophs play a significant role only in groundwater ecosystems. Their role in terrestrial ecosystems is relatively small.
Heterotrophs they use the carbon of organic substances that are synthesized by producers, and together with these substances they receive energy. Heterotrophs are consumers(from lat. consumo- I consume), consuming organic matter, and decomposers, decomposing it to simple compounds.
Phytophages(herbivores). These include animals that feed on living plants. Phytophages include both small animals such as aphids or grasshoppers and giants such as elephants. Phytophages include almost all agricultural animals: cows, horses, sheep, rabbits. There are phytophages among aquatic organisms, for example, grass carp, eating plants that overgrow irrigation canals. Important phytophage - beaver. It feeds on tree branches, and from the trunks it builds dams that regulate the water regime of the territory.
Zoophages(predators, carnivores). Zoophages are varied. These are small animals that feed on amoebas, worms or crustaceans. And big ones, like a wolf. Predators that feed on smaller predators are called second-order predators. There are predatory plants (dew, pemphigus) that use insects as food.
Symbiotrophs. These are bacteria and fungi that feed on the root secretions of plants. Symbiotrophs are very important for the life of the ecosystem. Threads of fungi that entangle the roots of plants help the absorption of water and minerals. Symbiotrophic bacteria absorb gaseous nitrogen from the atmosphere and bind it into compounds available to plants (ammonia, nitrates). This nitrogen is called biological (in contrast to the nitrogen of mineral fertilizers).
Symbiotrophs also include microorganisms (bacteria, unicellular animals) that live in the digestive tract of phytophagous animals and help them digest food. Animals such as cows, without the help of symbiotrophs, are not able to digest the grass they eat.
Detritophages are organisms that feed on dead organic matter. These are centipedes, earthworms, dung beetles, crayfish, crabs, jackals and many others.
Some organisms use both plants and animals as food, and even detritus, and are euryphages (omnivores) - bear, fox, pig, rat, chicken, crow, cockroaches. Euryphage is also a man.
decomposers- organisms that, by their position in the ecosystem, are close to detritophages, since they also feed on dead organic matter. However, decomposers - bacteria and fungi - break down organic matter to mineral compounds, which return to the soil solution and are again used by plants.
Reducers need time to process corpses. Therefore, in the ecosystem there is always detritus - a supply of dead organic matter. Detritus is leaf litter on the surface of forest soil (remains 2–3 years), the trunk of a fallen tree (remains 5–10 years), soil humus (remains hundreds of years), deposits of organic matter on the bottom of the lake - sapropel - and peat in the swamp ( preserved for thousands of years). The longest lasting detritus are coal and oil.
On fig. the structure of the ecosystem, which is based on plants - photoautotrophs, is shown, and the table shows examples of representatives of different trophic groups for some ecosystems.
Rice. Ecosystem structure
Organic substances created by autotrophs serve as food and a source of energy for heterotrophs: phytophage consumers eat plants, first-order predators eat phytophages, second-order predators eat first-order predators, etc. This sequence of organisms is called food chain, its links are located at different trophic levels (represent different trophic groups).
The trophic level is the location of each link in the food chain. The first trophic level is producers, all the rest are consumers. The second trophic level is herbivorous consumers; the third is carnivorous consumers feeding on herbivorous forms; fourth - consumers consuming other carnivores, etc. therefore, it is possible to divide consumers by levels: consumers of the first, second, third, etc. orders (Fig.).
Rice. Nutritional relationships of organisms in biogeocenosis
Only consumers specializing in a certain type of food are clearly distributed by levels. However, there are species that eat meat and plant foods (humans, bears, etc.), which can be included in food chains at any level.
On fig. five examples of food chains are given.
Rice. Some food chains in ecosystems
The first two food chains represent natural ecosystems - terrestrial and aquatic. In the terrestrial ecosystem, predators such as the fox, wolf, eagles, feeding on mice or ground squirrels, close the chain. In the aquatic ecosystem, solar energy, assimilated mainly by algae, passes to small consumers - daphnia, then to small fish (roach) and, finally, to large predators - pike, catfish, pike perch. In agricultural ecosystems, the food chain can be complete, when farm animals are bred (third example), or shortened, when plants are grown that are directly used by humans as food (fourth example).
The above examples simplify the real picture, since the same plant can be eaten by different herbivores, and they, in turn, become victims of different predators. A leaf of a plant can be eaten by a caterpillar or a slug, a caterpillar can become a victim of a beetle or an insectivorous bird, which can at the same time peck at the beetle itself. The beetle can also become a victim of a spider. Therefore, in real nature, it is not food chains that are formed, but food webs.
When energy moves from one trophic level to another (from plants to phytophages, from phytophages to first-order predators, from first-order predators to second-order predators), about 90% of energy is lost with excrement and breathing costs. In addition, phytophages eat only about 10% of the plant biomass, the rest replenishes the supply of detritus and then it is destroyed by decomposers. Therefore, secondary biological production is 20-50 times less than primary.
Rice. Main types of ecosystems
Any set of organisms and inorganic components in which the circulation of substances can take place is called ecosystem. To maintain the circulation of substances in the system, it is necessary to have a stock of inorganic molecules in an assimilated form and three functionally different ecological groups of organisms: producers, consumers, and decomposers.
Consumers (From lat. Consume - to use) are heterotrophic organisms (all living creatures that need food of organic origin) that consume the organic matter of producers or other consumers and transform it into new forms.
Depending on the power sources, consumers are divided into three main classes:
- phytophages(herbivores) are consumers of the 1st order feeding exclusively on living plants. For example, birds eat seeds, buds, and leaves.
- - predators(carnivores) - 2nd order consumers that feed exclusively on herbivorous animals (phytophages), as well as 3rd order consumers that feed only on carnivores.
- - euryphages(omnivorous) that can eat both plant and animal food. Examples are pigs, rats, foxes, cockroaches, and humans.
The term "consumer (of the first, second, and so on) order" allows you to more accurately indicate the place of the organism in the food chain. Reducers (for example, fungi, decay bacteria) are also heterotrophs, they are distinguished from consumers by the ability to completely decompose organic substances (proteins, carbohydrates, lipids, and others) to inorganic (carbon dioxide, ammonia, urea, hydrogen sulfide), completing the cycle of substances in nature, creating a substrate for the activities of producers.
A single organism can be a consumer of different orders in different trophic chains, for example, an owl eating a mouse is both a consumer of the second and third orders, and a mouse is of the first and second, since the mouse eats both plants and herbivorous insects.
The presence of four interconnected blocks: producer - consumer of the first order - consumer of the second order - decomposer is always traced. It is this functional chain that is meant when speaking of trophic or food chains in an ecosystem.
Ecological role of consumers consists in the processing of biomass accumulated by producers and the creation of a new, additional biomass. At the expense of producers, they increase their biomass, spending, of course, part of the energy to ensure their vital activity, in particular, releasing it in one form or another into the environment (Fig. 36 - 3). In fact, they redistribute matter and energy in time and space.
Consumers not only use the biomass of predecessors to increase their own, but often simply destroy it, making life easier for decomposers.
The general importance of consumers in the cycle of substances idiosyncratic and ambiguous. They are not necessary in the direct cycle process: artificial closed model systems composed of green plants and soil microorganisms, in the presence of moisture and mineral salts, can exist indefinitely due to photosynthesis, destruction of plant residues and involvement of released elements in a new cycle. But this is only possible under stable laboratory conditions. In a natural environment, the probability of the death of such simple systems from many causes increases. The “guarantors” of the stability of the cycle are, first of all, the consumers.
In the process of their own metabolism, heterotrophs decompose the organic substances obtained in the composition of food and, on this basis, build the substances of their own body. The transformation of substances primarily produced by autotrophs in consumer organisms leads to an increase variety of living matter. Diversity is a necessary condition for the stability of any cybernetic system against the background of external and internal disturbances (Ashby's principle). Living systems - from the organism to the biosphere as a whole - operate according to the cybernetic principle of feedback. In the following text, we will repeatedly meet with the importance of various forms of biological diversity (biological heterogeneity) for the sustainable functioning of ecosystems.
Animals, which make up the bulk of consumer organisms, are characterized by mobility, the ability to actively move in space. This is how they effectively participate in the migration of living matter, its dispersion over the surface of the planet, which, on the one hand, stimulates the spatial settlement of life, and on the other hand, serves as a kind of “guarantee mechanism” in case of the destruction of life in any place due to various reasons.
An example of such a "spatial guarantee" is the well-known catastrophe on about. Krakatau: as a result of the volcanic eruption in 1883, life on the island was completely destroyed, but within only 50 years it recovered - about 1200 species were recorded. The settlement proceeded mainly at the expense of Java, Sumatra and neighboring islands, which were not affected by the eruption, from where, in different ways, plants and animals repopulated the island covered with ash and frozen lava flows. At the same time, films of cyanobacteria appeared first (after 3 years) on volcanic tuff and ash. The process of establishing sustainable communities on the island continues; forest cenoses are still in the early stages of succession and are greatly simplified in structure.
Note that the division of living organisms into producers, consumers and decomposers is the first level of biological heterogeneity.
Finally, the role of consumers, primarily animals, is extremely important, as regulators of the intensity of matter and energy flows along trophic chains. The ability for active autoregulation of biomass and the rate of its change at the level of ecosystems and populations of individual species is ultimately realized in the form of maintaining the correspondence between the rates of creation and destruction of organic matter in global cycle systems. Not only consumers participate in such a regulatory system, but the latter (especially animals) are distinguished by the most active and rapid reaction to any disturbances in the biomass balance of adjacent trophic levels.
IN biocenoses living organisms are closely connected not only with each other, but also with inanimate nature. This connection is expressed through matter and energy.
Metabolism, as you know, is one of the main manifestations of life. talking modern language, organisms are open biological systems, since they are connected with the environment by a constant flow of matter and energy passing through their bodies. The material dependence of living beings on the environment was realized in ancient Greece. The philosopher Heraclitus figuratively expressed this phenomenon in the following words: “Our bodies flow like streams, and matter is constantly renewed in them, like water in a stream.” The material-energy connection of the organism with the environment can be measured.
The supply of food, water, oxygen to living organisms is the flow of matter from environment. Food contains the energy necessary for the functioning of cells and organs. Plants absorb energy directly sunlight, store it in chemical bonds organic compounds, and then it is redistributed through food relations in biocenoses.
V. N. Sukachev
(1880 – 1967)
Major Russian botanist, academician
The founder of biogeocenology - the science of natural ecosystems
The flows of matter and energy through living organisms in the processes of metabolism are extremely high. A person, for example, during his life consumes tens of tons of food and drink, and through the lungs - many millions of liters of air. Many organisms interact with the environment even more intensively. Plants spend from 200 to 800 or more grams of water to create each gram of their mass, which they extract from the soil and evaporate into the atmosphere. Substances needed for photosynthesis, plants are obtained from soil, water and air.
With such an intensity of matter flows from inorganic nature to living bodies, the reserves of compounds necessary for life are nutrients– would have been exhausted long ago on Earth. However, life does not stop, because biogenic elements are constantly returned to the environment surrounding organisms. This happens in biocenoses, where, as a result of nutritional relations between species, synthesized by plants organic matter are eventually broken down again to such compounds that can be reused by plants. This is how biological cycle of substances.
Thus, the biocenosis is part of an even more complex system, which, in addition to living organisms, also includes their inanimate environment, which contains matter and energy necessary for life. Biocenosis cannot exist without material-energy connections with the environment. As a result, the biocenosis represents a certain unity with it.
A. Tansley
(1871 – 1955)
English botanist, introduced the concept of "ecosystem" into science
Any combination of organisms and inorganic components in which the circulation of matter can be maintained is called ecological system, or ecosystem.
Natural ecosystems can be of different volume and length: a small puddle with its inhabitants, a pond, an ocean, a meadow, a grove, a taiga, a steppe - all these are examples of ecosystems of different scales. Any ecosystem includes a living part - a biocenosis and its physical environment. Smaller ecosystems are part of ever larger ones, up to the general ecosystem of the Earth. The general biological cycle of matter on our planet also consists of the interaction of many more particular cycles. An ecosystem can ensure the cycle of matter only if it includes the four components necessary for this: reserves of biogenic elements, producers, consumers And decomposers(Fig. 1).
Rice. 1. Necessary components of the ecosystem
Producers- these are green plants that create organic matter from biogenic elements, that is, biological products, using solar energy flows.
Consumers- consumers of this organic matter, processing it into new forms. Animals usually act as consumers. Distinguish consumers of the first order - herbivorous species and the second order - carnivorous animals.
decomposers- organisms that finally destroy organic compounds to mineral ones. The role of decomposers in biocenoses is mainly performed by fungi and bacteria, as well as other small organisms that process the dead remains of plants and animals (Fig. 2).
Rice. 2. Destroyers of dead wood (bronzovka beetle and its larva; stag beetle and its larva; large oak barbel and its larva; odorous woodworm butterfly and its caterpillar; red flat beetle; millipede kisyak; black ant; wood lice; earthworm)
Life on Earth has been going on for about 4 billion years, without interruption precisely because it takes place in the system of biological cycles of matter. The basis of this is plant photosynthesis and food relations of organisms in biocenoses. However, the biological cycle of matter requires a constant expenditure of energy. Unlike chemical elements, which are repeatedly involved in living bodies, the energy of the sun's rays, retained by green plants, cannot be used by organisms indefinitely.
According to the first law of thermodynamics, energy does not disappear without a trace, it is stored in the world around us, but it passes from one form to another. According to the second law of thermodynamics, any transformation of energy is accompanied by the transition of part of it to a state where it can no longer be used for work. In the cells of living beings, the energy that provides chemical reactions is partially converted into heat during each reaction, and the heat is dissipated by the body in the surrounding space. The complex work of cells and organs is thus accompanied by energy losses from the body. Each cycle of the circulation of substances, depending on the activity of the members of the biocenosis, requires more and more energy.
Thus, life on our planet is carried out as a permanent matter cycle supported flow of solar energy. Life is organized not only into biocenoses, but also into ecosystems, in which there is a close relationship between living and non-living components of nature.
The diversity of ecosystems on Earth is associated both with the diversity of living organisms and the conditions of the physical, geographical environment. Tundra, forest, steppe, desert or tropical communities have their own characteristics of biological cycles and relationships with the environment. Aquatic ecosystems are also extremely diverse. Ecosystems differ in the rate of biological cycles and in the total amount of matter involved in these cycles.
The basic principle of ecosystem stability - the circulation of matter supported by the flow of energy - essentially ensures the endless existence of life on Earth.
According to this principle, both sustainable artificial ecosystems and production technologies can be organized in which water or other resources are saved. Violation of the coordinated activity of organisms in biocenoses usually entails serious changes in the cycles of matter in ecosystems. This is the main reason for such environmental disasters, as a fall in soil fertility, a decrease in plant yields, the growth and productivity of animals, the gradual destruction of the natural environment.
