Plan.
1. Introduction. Ecosystem and the ecosystem method in ecology.
2. The general structure of ecosystems.
3. The biotic component of ecosystems.
3.1. The sun as a source of energy.
4. Food chains and trophic levels.
4.1. Primary producers.
4.2. Primary Consumers.
4.3. Consumables of the second and third order.
4.4. Reducers and detritophages.
5. Food Networks.
6. Ecological pyramids.
6.1. Pyramids of numbers.
6.2. Pyramids of biomass.
7. The abiotic component of the ecosystem.
7.1. Edaphic factors.
7.2. Climatic factors.
7.2.1. Shine.
7.2.2. Temperature.
7.2.3. Humidity and salinity.
9. List of used literature.
1. Introduction. Ecosystem and the ecosystem method in ecology.
The first definition of the ecosystem as a combination of living organisms with their habitat was given by Tansley in 1935. With the ecosystem approach to the study of ecology, scientists focus on the flow of energy and the circulation of substances between the biotic and abiotic components of the ecosphere. The ecosystem approach highlights the community organization of all communities, regardless of the habitat and systematic position of their constituent organisms. At the same time, the concept of homeostasis (self-regulation) finds application in the ecosystem approach, from which it becomes clear that violation of regulatory mechanisms, for example, as a result of environmental pollution, can lead to biological imbalance. The ecosystem approach is also important in the future development of evidence-based agricultural practices.
2. The general structure of ecosystems.
Ecosystems consist of living and nonliving components, called biotic and abiotic, respectively. The totality of living organisms of the biotic component is called community. Ecosystem research includes, inter alia, elucidating and describing the close relationships that exist between the community and the abiotic component.
It is useful to subdivide the biotic component into autotrophic and heterotrophic organisms. Thus, all living organisms fall into one of two groups. Autotrophs synthesize the organic substances they need from simple inorganic substances and make, with the exception of chemotrophic bacteria, using photosynthesis, using light as an energy source. Heterotrophs need a source of organic matter and (with the exception of some bacteria) use the chemical energy contained in the food they eat. Heterotrophs in their existence depend on autotrophs, and an understanding of this dependence is necessary for understanding ecosystems.
The non-living, or abiotic, component of the ecosystem mainly includes 1) soil or water and 2) climate. Soil and water contain a mixture of inorganic and organic substances. The properties of the soil depend on the parent rock on which it lies, and from which it is partially formed. The concept of climate includes such parameters as illumination, temperature and humidity, which largely determines species composition organisms successfully developing in this ecosystem. The degree of salinity is also very significant for aquatic ecosystems.
3. Biotic component of ecosystems
Organisms in an ecosystem are related energy and nutrients . The whole ecosystem can be likened to a single mechanism that consumes energy and nutrients to do the job. Nutrients originally come from the abiotic component of the system, into which, in the end, they return either as waste products, or after the death and destruction of organisms. Thus, in the ecosystem there is a cycle of nutrients, in which both the living and non-living components participate. Such cycles are called biogeochemical cycles.
The driving force of these cycles is, ultimately, the energy of the sun. Photosynthetic organisms directly use the energy of sunlight and then transfer it to other representatives of the biotic component. The result is a flow of energy and nutrients through the ecosystem. It should also be noted that the climatic factors of the abiotic component, such as temperature, atmospheric movement, evaporation and precipitation, are also regulated by the influx of solar energy.
Energy can exist in the form of various interconvertible forms, such as mechanical, chemical, thermal, and electrical energy. The transition from one form to another is called energy conversion.
Thus, all living organisms are energy converters, and each time when energy is converted, part of it is lost in the form of heat. In the end, all the energy entering the biotic component of the ecosystem is dissipated as heat. Studying the flow of energy through ecosystems is called ecosystem energy.
In fact, living organisms do not use heat as a source of energy for work - they use light and chemical energy.
Studying the flow of energy through ecosystems is called ecosystem energy.
3.1. The sun as a source of energy
The primary source of energy for ecosystems is the sun. The sun is a star radiating a huge amount of energy into space. Energy is distributed in outer space in the form of electromagnetic waves, and a small part of it, about 10.5 * 10 6 kJ / m 2 per year, is captured by the Earth. About 40% of this amount is immediately reflected from the clouds, atmospheric dust and the surface of the Earth without any heat effect. Another 15% are absorbed by the atmosphere (in particular, the ozone layer in its upper parts) and turn into thermal energy or consumed by the evaporation of water. The remaining 45% is absorbed by plants and the earth's surface. On average, this is 5 * 10 6 kJ / m 2 per year, although the actual amount of energy for a given area depends on geographical latitude. Most of the energy is re-emitted by the earth's surface and heats the atmosphere about two-thirds of the energy enters the atmosphere this way. And only a small part of the energy that came from the Sun is absorbed by the biotic component of the ecosystem.
4. Food chains and trophic levels
Inside an ecosystem, organic substances containing energy are created by autotrophic organisms and serve as food (a source of matter and energy) for heterotrophs. A typical example of an animal eating plants. This animal, in turn, can be eaten by another animal, and in this way there can be a transfer of energy through a number of organisms - each subsequent one feeds on the previous one, supplying, supplying him raw materials and energy. This sequence is called the food chain, and each link is called the trophic level. The first trophic level is occupied by autotrophs, or the so-called primary producers. Organisms of the second trophic level are called primary consumers, the third - secondary consumers, etc. Usually there are four or five trophic levels and rarely more than six.
4.1. Primary producers
The primary producers are autotrophic organisms, mainly green plants. Some prokaryotes, namely blue-green algae and a few species of bacteria, also photosynthesize, but their contribution is relatively small. Photosynthetics convert solar energy (light energy) into chemical energy contained in the organic molecules that make up the tissue. Chemosynthesizing bacteria, which extract energy from inorganic compounds, also make a small contribution to the production of organic matter.
IN aquatic ecosystems the main producers are algae - often small unicellular organisms that make up the phytoplankton of the surface layers of oceans and lakes. On the land most primary products are supplied by more highly organized forms related to gymnosperms and angiosperms. They form forests and meadows.
4.2. Primary Consumers
Primary consumers feed on primary producers, that is, they are herbivores. On land, typical insectivores are many insects, reptiles, birds and mammals. The most important groups of herbivorous mammals are rodents and ungulates. The latter include pasture animals such as horses, sheep, cattle, adapted to run at your fingertips.
In aquatic ecosystems (freshwater and marine), herbivorous forms are usually represented by mollusks and small crustaceans. Most of these organisms - branched and copepods, crab larvae, barnacles and bivalve mollusks (for example, mussels and oysters) - feed by filtering out the smallest primary producers from water. Together with the simplest, many of them make up the bulk of zooplankton feeding on phytoplankton. Life in the oceans and lakes is almost completely dependent on plankton, since almost all food chains begin with it.
4.3. Consumables of the second and third order
Plant material ( e.g. nectar) → fly → spider →
→ shrew → owl
Rose bush juice → aphids → ladybug → spider → insectivorous bird → bird of prey
4.4. Reducers and detritophages (detrital food chains)
There are two main types of food chains - pasture and detrital. Above were given examples of pasture chains in which the first trophic level is occupied by green plants, the second by pasture animals and the third by predators. The bodies of dead plants and animals still contain energy and “building material”, as well as intravital secretions, such as urine and feces. These organic materials are decomposed by microorganisms, namely fungi and bacteria, living as saprophytes on organic residues. Such organisms are called reducers. They secrete digestive enzymes into dead bodies or waste products and absorb the products of their digestion. The decomposition rate may vary. The organic matter of urine, feces, and animal corpses is consumed in a few weeks, while fallen trees and branches can decompose for many years. A very significant role in the decomposition of wood (and other plant residues) is played by fungi that secrete the cellulase enzyme, which softens the wood, and this allows small animals to penetrate and absorb the softened material.
Pieces of partially decomposed material are called detritus, and many small animals (detritophages) feed on it, accelerating the decomposition process. Since both true reducers (fungi and bacteria) and detritophages (animals) are involved in this process, both of them are sometimes called reducers, although in reality this term refers only to saprophytic organisms.
Larger organisms, in turn, can feed on detritophages, and then a different type of food chain is created - a chain, a chain starting with detritus:
Detritus → Detritophagus → Predator
Detritophages of forest and coastal communities include earthworm, wood lice, carrion fly larva (forest), polychaete, scarlet, holothuria (coastal zone).
Here are two typical detrital food chains in our forests:
Litter → Earthworm → Blackbird → Sparrowhawk
Dead animal → Larvae of carrion flies → Grass frog → Common
Some typical detritophages are earthworms, wood lice, two-legged and smaller (<0,5 мм) животные, такие, как клещи, ногохвостки, нематоды и черви-энхитреиды.
5. Food Networks
In the schemes of food chains, each organism is presented as feeding on other organisms of one type. However, real food connections in the ecosystem are much more complicated, because an animal can feed on organisms of different types from the same food chain or even from different food chains. This is especially true for predators of the upper trophic levels. Some animals feed on both other animals and plants; they are called omnivores (such, in particular, is man). In fact, food chains are intertwined in such a way that a food (trophic) network is formed. Only a few of the many possible relationships can be shown in a food web diagram, and it usually includes only one or two predators of each of the upper trophic levels. Such schemes illustrate the nutritional relationships between organisms in an ecosystem and serve as the basis for a quantitative study of ecological pyramids and ecosystem productivity.
6. Ecological pyramids.
6.1. Pyramids of numbers.
To study the relationships between organisms in the ecosystem and to graphically represent these relationships, it is more convenient to use ecological pyramids rather than food network schemes. At the same time, the number of different organisms in a given territory is first calculated by grouping them by trophic levels. After such calculations, it becomes obvious that the number of animals progressively decreases with the transition from the second trophic level to the next. The number of plants of the first trophic level also often exceeds the number of animals making up the second level. This can be displayed as a pyramid of numbers.
For convenience, the number of organisms at a given trophic level can be represented as a rectangle, the length (or area) of which is proportional to the number of organisms living in this area (or in this volume, if it is an aquatic ecosystem). The figure shows the pyramid of numbers, reflecting the real situation in nature. Predators located at the highest trophic level are called final predators.
Fourth Trophic Level Tertiary Consumers
Third trophic level Secondary consumers
Second Trophic Level Primary Consumers
First trophic Primary producers
level
6.2. Pyramids of biomass.
The inconvenience associated with the use of population pyramids can be avoided by constructing biomass pyramids, which take into account the total mass of organisms (biomass) of each trophic level. The determination of biomass includes not only the counting of numbers, but also the weighing of individual individuals, so this is a more time-consuming process, requiring more time and special equipment. Thus, the rectangles in the pyramids of biomass represent the mass of organisms of each trophic level, referred to a unit of area or volume.
When sampling - in other words, at a given point in time - the so-called standing biomass, or standing crop, is always determined. It is important to understand that this value does not contain any information about the rate of biomass formation (productivity) or its consumption; otherwise, errors may occur for two reasons:
1. If the rate of biomass consumption (loss due to eating) approximately corresponds to the rate of its formation, then the standing crop does not necessarily indicate productivity, ie about the amount of energy and substance passing from one trophic level to another for a given period of time, for example, for a year. For example, in a fertile, intensively used pasture, the yield of grass can be lower, and productivity is higher than in a less fertile, but little used for grazing.
2. A producer of small sizes, such as algae, is characterized by a high rate of renewal, i.e. high growth and reproduction rate, balanced by their intensive consumption in food by other organisms and natural death. Thus, although the standing biomass can be small compared with large producers (e.g. trees), productivity can be no less, since trees accumulate biomass for a long time. In other words, phytoplankton with the same productivity as a tree will have a much lower biomass, although it could support the life of the same mass of animals. In general, populations of large and long-lived plants and animals have a lower update rate than small and short-lived ones and accumulate matter and energy for a longer time. Zooplankton has a greater biomass than phytoplankton, which it feeds on. This is characteristic of planktonic communities of lakes and seas at certain times of the year; the biomass of phytoplankton exceeds the biomass of zooplankton during spring "flowering", but in other periods the opposite ratio is possible. Such apparent anomalies can be avoided by applying energy pyramids.
7. Abiotic ecosystem component
Abiotic i.e. inanimate, the ecosystem component is subdivided into edaphic (soil), climatic, topographic, and other physical factors, including the effects of waves, sea currents, and fire.
7.1. Edaphic factors.
Soil science is called soil science. Already in early works, the importance of soil as a source of plant nutrients was emphasized. Although we have included the soil in the section on abiotic factors, it is more correct to consider it as the most important link between the biotic and abiotic components of terrestrial ecosystems. Soil is a layer of substance lying on top of rocks of the earth's crust. The composition of the soil includes four important structural components: the mineral base (usually 50-60% of the total soil composition), organic matter (up to 10%), air (15-20%) and water (25-35%).
The mineral skeleton of the soil is an inorganic component that was formed from the parent rock as a result of its weathering. The mineral fragments that form the substance of the soil skeleton are different - from boulders and stones to sand grains and tiny particles of clay. Skeletal material is usually randomly divided into shallow soil (particles less than 2 mm) and larger fragments. Particles less than 1 micron in diameter are called colloidal. The mechanical and chemical properties of the soil are mainly determined by those substances that relate to shallow soil.
The organic matter of the soil is formed by the decomposition of dead organisms, their parts (for example, fallen leaves), excreta and feces. Dead organic material is used in food together by detritophages, which eat it and thus contribute to its destruction, and reducers (fungi and bacteria) that complete the decomposition process. Not completely decomposed organic residues are called litter, and the final decomposition product - an amorphous substance in which it is no longer possible to recognize the original material - was called humus. The color of humus varies from dark brown to black. Chemically, this is a very complex mixture of variable composition, formed by various types of organic molecules; humus mainly consists of phenolic compounds, carboxylic acids and fatty acid esters. Humus, like clay, is in a colloidal state; its individual particles firmly adhere to clay and form a clay-humus complex. Like clay, humus has a large particle surface and high cation exchange ability. This ability is especially important for low clay soils. Anions in humus are carboxyl and phenolic groups. Due to its chemical and physical properties, humus improves the structure of the soil and its aeration, and also increases the ability to retain water and nutrients.
7.2. Climatic factors.
7.2.1. Shine
Light is necessary for life, since it is a source of energy for photosynthesis, however, there are other aspects of its effect on living organisms. The light intensity, its quality (wavelength, or color) and the duration of illumination (photoperiod) can have different effects.
The need for light for plants significantly affects the structure of communities. The distribution of aquatic plants is limited to the surface layers of water. In terrestrial ecosystems, in the process of competition for light, plants developed certain strategies, for example, rapid growth in height, using other plants as a support, increasing the surface of leaves.
7.2.2. Temperature
The main source of heat is solar radiation; they may also be geothermal springs, but they play an important role in only a few habitats.
Temperature, as well as light intensity, largely depends on geographical latitude, season, time of day, and slope exposure. However, narrow local differences in temperature are often encountered; this is especially true for micro-habitats with their own microclimate. Vegetation also has some effect on temperature. For example, a different temperature occurs under the forest canopy or to a lesser extent inside separate groups of plants, as well as under the leaves of a single plant.
7.2.3. Humidity and salinity.
Water is essential for life and can be an important limiting factor in terrestrial ecosystems. Water comes from the atmosphere in the form of precipitation: rain, snow, rain with snow, hail or dew. In nature there is a continuous cycle of water - hydrological the cycle on which its distribution on the land surface depends. Terrestrial plants absorb water mainly from the soil. Rapid drainage, a small amount of precipitation from the soil, strong evaporation, or a combination of all these factors can lead to desiccation of soils, and with abundance, on the contrary, they can be constantly wetted. Thus, the amount of water in the soil depends on the water holding capacity of the soil itself and on the balance between the amount of precipitation and the combined result of evaporation and transpiration. Evaporation occurs both from the surface of wet vegetation and from the surface of the soil.
8. Conclusion. Efficient use of ecosystems.
“Harvesting” means the removal from the ecosystem of those organisms or parts thereof that are used for food (or for other purposes). At the same time, it is desirable that the ecosystem produce the most suitable food products. This can be achieved by increasing crop yields, reducing morbidity and interference from other organisms, or using a culture more adapted to the conditions of a given ecosystem.
Studying the productivity of ecosystems, we are dealing with the flow of energy passing through an ecosystem. Energy enters the biotic component of the ecosystem of primary producers. The rate of energy storage by primary producers in the form of organic matter that can be used in food is called primary production. This is an important parameter, since it determines the total energy flow through the biotic component of the ecosystem, and hence the number (biomass) of animal organisms that can exist in the ecosystem.
Inside an ecosystem, organic substances containing energy are created by autotrophic organisms and serve as food (a source of matter and energy) for heterotrophs. A typical example: an animal eats plants. This animal, in turn, can be eaten by another animal, and in this way energy transfer can occur through a number of organisms - each subsequent one feeds on the previous one, supplying it with raw materials and energy. This sequence is called food chain, and each of its links - trophic level (Greek trophos - nutrition). The first trophic level is occupied by autotrophs, or the so-called primary producers. Organisms of the second trophic level are called primary consumersthird - secondary consumers etc. There are usually four or five trophic levels and rarely more than six - for the reasons described in section 12.3.7 and the obvious from fig. 12.12. Below is a description of each link in the food chain, and their sequence is shown in Fig. 12.4.
Primary producers
The primary producers are autotrophic organisms, mainly green plants. Some prokaryotes, namely blue-green algae and a few species of bacteria, also photosynthesize, but their contribution is relatively small. Photosynthetics convert solar energy (light energy) into chemical energy contained in the organic molecules that make up their tissues. Chemosynthetic bacteria, which extract energy from inorganic compounds, also make a small contribution to the production of organic matter.
In aquatic ecosystems, the main producers are algae - often small unicellular organisms that make up the phytoplankton of the surface layers of oceans and lakes. On land, most of the primary production comes from more highly organized forms related to gymnosperms and angiosperms. They form forests and meadows.
Primary Consumers
Primary consumers are fed by primary producers, i.e. this herbivores. On land, typical herbivores are many insects, reptiles, birds and mammals. The most important groups of herbivorous mammals are rodents and ungulates. The latter include pasture animals, such as horses, sheep, cattle, adapted to run at your fingertips.
In aquatic ecosystems (freshwater and marine), herbivorous forms are usually represented by mollusks and small crustaceans. Most of these organisms - branched and copepods, crab larvae, barnacles and bivalve mollusks (for example, mussels and oysters) - feed by filtering out the smallest primary producers from water, as described in Sec. 10.2.2. Together with the simplest, many of them make up the bulk of zooplankton feeding on phytoplankton. Life in the oceans and lakes is almost completely dependent on plankton, since almost all food chains begin with it.
Consumables of the second third order
In typical predator food chains, carnivores are larger at each of the following trophic levels:
Plant material (e.g. nectar) fly → spider → shrew owl
Rose bush juice → aphids → ladybug → spider → insectivorous bird → bird of prey
Reducers and detritophages (detrital food chains)
There are two main types of food chains - pasture and detrital. We have given examples above. pasture chainswhere green plants occupy the first trophic level, pasture animals occupy the second (the term "pasture" is used in a broad sense and includes all organisms that feed on plants) and the third are predators. The bodies of dead plants and animals still contain energy and "building material", as well as intravital secretions, such as urine and feces. These organic materials are decomposed by microorganisms, namely fungi and bacteria, living as saprophytes on organic residues. Such organisms are called reducers. They secrete digestive enzymes into dead bodies or waste products and absorb the products of their digestion. The decomposition rate may vary. The organic matter of urine, feces, and animal corpses is consumed in a few weeks, while fallen trees and branches can decompose for many years. A very significant role in the decomposition of wood (and other plant residues) is played by fungi that secrete the cellulase enzyme, which softens the wood, and this allows small animals to penetrate and absorb the softened material.
Pieces of partially decomposed material are called detritus, and many small animals ( detritophages) feed on it, accelerating the decomposition process. Since both true reducers (fungi and bacteria) and detritophages (animals) are involved in this process, both of them are sometimes called reducers, although in reality this term refers only to saprophytic organisms.
Larger organisms, in turn, can feed on detritophages, and then a different type of food chain is created - a chain starting with detritus:
Detritus → Detritophagus → Predator
Some detritophages of forest and coastal communities are shown in Fig. 12.5.
Here are two typical detrital food chains in our forests:
Litter → Earthworm → Lumbricus sp. → Blackbird → Sparrow-hawk Turdus merula Accipiter nisus Dead animal → Larvae of carrion flies → Calliphora vomitoria and others → Twig frog → Common Rana temporaria Natrix natrix
Some typical terrestrial detritophages are earthworms, wood lice, bipedal and smaller (
In ecology, to analyze the system, an elementary structural unit is selected as an object of study, which is subjected to comprehensive study. A necessary condition for constructing a structural unit is that it preserves all the properties of the system.
The concept of "system" means a combination of not accidentally caught together, but constituting a single whole interconnected, interdependent, interdependent components.
For natural ecosystems, a biogeocenosis, the structural diagram of which is shown in Fig. 1, is taken as an object of study.
Fig. 1. Scheme of biogeocenosis (ecosystem), according to V.N.Sukachev
In accordance with the structural diagram of the biogeocenosis includes two main blocks:
biotope -the totality of abiotic environmental factors or the whole complex of factors of inanimate nature;
(ecotope is a term close to a biotope, but with emphasis on environmental factors external to the community, not only abiotic but also biotic)
biocenosis -totality of living organisms.
Biotope, in turn consists of a combination of climate (climatop) and soil (edafotop) and hydrological (hydrotope) environmental factors.
Biocenosis includes plant communities (phytocenosis ), animals (zoocenosis) and microorganisms (microbocenosis ).
The arrows in Fig. 1 indicate the channels of information transfer between the various components of the biogeocenosis.
One of the most important properties of biogeocenosis is interconnection and interdependence of all its components.
It is quite clear that the climate completely determines the state and regime of soil and soil factors, and creates a habitat for living organisms.
In turn, the soil to some extent determines the climatic features (for example, its reflectivity (albedo) and, consequently, the warmth and humidity of the air depend on the coloring of the soil surface), and also affects animals, plants and microorganisms.
All living organisms are closely interconnected by various food, spatial or environment-forming relationships, being for each other either a food source, or a habitat, or a mortality factor.
Particularly important is the role of microorganisms (primarily bacteria) in the processes of soil formation, mineralization of organic substances and often acting as pathogens of diseases of plants and animals.
2.2. Functional organization of ecosystems.
The main function of ecosystems is to maintain the circulation of substances in the biosphere, which is based on the nutritional relationships of species.
Despite the huge variety of species that make up the various communities, each ecosystem necessarily includes representatives of three functional groups of organisms - producers, consumers and reducers.
The basis of the vast majority of biogeocenoses is producers (manufacturers) - these are autotrophic organisms (from the Greek “auto” - itself and “tropho” - food) , which have the ability to synthesize organic matter from inorganic, using solar energy or the energy of chemical bonds.
Depending on the source of energy used, two types of organisms are distinguished: photoautotrophs and chemoautotrophs.
Photoautotrophs are organisms that are able to create organic matter through photosynthesis using solar energy.
Photoautotrophic organisms include plants, as well as blue-green algae (cyanobacteria).
However, not all plants are producers, for example:
some mushrooms (hat, mold), as well as some flower species (for example, scapegoat) that do not contain chlorophyll, are not capable of photosynthesis and therefore feed on prepared organic substances.
Chemoautotrophs are organisms that use the energy of chemical bonds as an energy source for the formation of organic substances.
Chemoautotrophic organisms include: hydrogen, nitrifying bacteria, iron bacteria, etc.
The group of chemoautotroph organisms is not numerous and does not play a fundamental role in the biosphere.
Only producers (producers) are able to produce energy-rich food for themselves, i.e. are self-feeding. Moreover, they directly or indirectly provide nutrients with nutrients and reducers.
Consumers (consumers) - these are heterotrophic organisms (from the Greek. “hetero” - different) , which use living organic matter as food for energy production and storage.
The main source of energy for heterotrophic organisms is the energy released during the splitting of the chemical bonds of organic substances created by autotrophic organisms.
Thus, heterotrophs are entirely dependent on autotrophs.
Depending on the power sources, they distinguish:
Consumables of the first order (phytophages) are herbivorous organisms that feed on different types of plant food (producers).
Examples of primary consumers are:
birds eat seeds, buds and foliage;
deer and hares feed on branches and leaves;
grasshoppers and many other species of insects consume all parts of plants;
in aquatic ecosystems, zooplankton (small animals moving mainly with the flow of water) feeds on phytoplankton (microscopic, usually unicellular algae).
Second-order consumables (zoophages) are carnivorous organisms that feed exclusively on herbivorous organisms (phytophages).
Examples of secondary consumers are:
insectivorous mammals, birds and spiders eating insects;
gulls eating shellfish and crab;
fox eating hare;
tuna feeding on herring and anchovies.
Third order consumables are predators that feed only on carnivores.
Examples of tertiary consumers are:
hawk or falcon feeding on snakes and ermines;
sharks feeding on other fish.
Meet fourth and higher orders.
In addition, there are many types with mixed type of food :
when a person eats fruits and vegetables, then he is a consumer of the first order;
when a person eats the meat of a herbivorous animal, then he is a secondary consumer;
when a person eats fish that feeds on other animals, which in turn eat algae, the person acts as a third-order consumer.
Euriphages are omnivorous organisms that feed on both plant and animal food.
For instance: pigs, rats, foxes, cockroaches and humans.
Reducers (destroyers)- These are heterotrophic organisms that feed on dead organic matter and mineralize it to simple inorganic compounds.
There are two main types of reducers: detritophages and destructors.
Detritophages are organisms that directly consume dead plant and animal debris (detritus).
Detritophages include: jackals, vultures, crabs, termites, ants, earthworms, millipedes, etc.
Destructors are organisms that decompose complex organic compounds of dead matter into simpler inorganic substances, which are then used by producers.
The main destructors are: bacteria and fungi.
In this case, bacteria take part in the decomposition of residues of animal origin, since they gravitate to substrates with a slightly alkaline reaction.
And mushrooms, on the contrary, prefer slightly acid substrates, so they take a major part in the decomposition of plant residues.
In this way, each living organism as part of a biogeocenosis performs a specific function, i.e. occupies a certain ecological niche in a complex system of environmental relations with other organisms and factors of inanimate nature.
So, for example, in different parts of the world and in different territories, there are systematically different, but ecologically similar species that perform the same functions in their biogeocenoses:
the grassy and forest vegetation of Australia in species composition differs significantly from the vegetation of a similar climatic region of Europe or Asia, but as producers in their biogeocenoses they perform the same functions, i.e. in principle, they occupy identical ecological niches;
antelopes in the savannahs of Africa, bison on the prairies of America, kangaroos in the savannahs of Australia, being consumers of the first order, perform the same functions, i.e. occupy similar ecological niches in their biogeocenoses.
At the same time, species that are often closely related in a systematic way, settling nearby in the same biogeocenosis, perform different functions, i.e. occupy different ecological niches:
two species of water bugs in the same reservoir play a different role: one species leads a predatory lifestyle and is a tertiary consumer, and the other feeds on dead and decaying organisms and is a reducer. This leads to a decrease in competitive tension between them.
In addition, the same species at different periods of its development can perform different functions, i.e. occupy various ecological niches:
the tadpole eats plant food and is the primary consumer, and the adult frog, the typical carnivore, is the second-order consumer;
among algae, there are species that function either as autotrophs or as heterotrophs. As a result, at certain periods of their lives, they perform various functions and occupy various ecological niches.
Food chains and trophic levels are considered integral components of the biological cycle. It involves many elements. Next, we consider in more detail the trophic levels of the ecosystem.
Terminology
The food chain is the movement of energy that is contained in plant foods through a number of organisms due to their eating each other. Only plants form organic matter from inorganic matter. The trophic level is a complex of organisms. Between them there is an interaction in the process of transferring nutrients and energy from the source. Trophic chains (trophic level) suggest a certain position of organisms at one or another stage (link) during this movement. Marine and terrestrial biological structures have many differences. One of the main ones is that in the first food chains are longer than in the second.
Steps
The first trophic level is represented by autotrophs. They are also called producers. The second trophic level consists of the initial consumers. At the next stage are consumers who consume herbivorous organisms. These consumers are called secondary. These, for example, include primary predators, carnivores. Also in the 3rd trophic level are consumers of the 3rd order. They consume, in turn, weaker predators. As a rule, there is a limited number of trophic levels - 4 or 5. Rarely more than six. This food chain is usually closed by reducers or destructors. They are bacteria, microorganisms that decompose organic residues.
Consumers: general information
They are not just “eaters” that the food chain contains. Satisfaction of their needs by them is carried out through a feedback system (positive). Consumers influence the trophic levels of the ecosystem above. So, for example, the consumption of vegetation in the African savannahs by large herds of antelopes together with fires in the dry period contributes to an increase in the rate of return of nutrients to the soil. Subsequently, during the rainy season, the restoration of grassy plants and their production increases.
An interesting example is Odum. It describes the impact of consumers on producers in the marine ecosystem. Crabs that consume detritus and algae "look after" their herbs in several ways. They break the soil, thus enhancing the circulation of water near the roots and introducing oxygen and necessary elements into the anaerobic coastal zone. In the process of continuous processing of bottom silts, rich in organic matter, crabs contribute to improving the conditions for the development and growth of benthic algae. Organisms that receive energy through the same number of steps comprise one trophic level.
Structure
Food consumed at each trophic level is not fully assimilated. This is due to its significant losses at the stages of metabolic processes. In this regard, the production of organisms included in the next trophic level is less than in the previous one. Inside a biological system, organic compounds containing energy are formed by autotrophic organisms. These substances are a source of energy and necessary components for heterotrophs. The following example is simple: an animal consumes plants. In turn, the beast can be eaten by another larger representative of the fauna. Thus, energy transfer through several organisms can take place. The next one uses the previous one, supplying energy and nutrients. It is this sequence that forms the food chain, in which the trophic level acts as a link.
1st order producers
The initial trophic level contains autotrophic organisms. They mainly include green spaces. Some prokaryotes, in particular blue-green algae, as well as a few species of bacteria, also have the ability to photosynthesis. However, their contribution to the trophic level is insignificant.
Thanks to the activity of photosynthetics, solar energy is converted into chemical energy. It lies in organic molecules, from which, in turn, tissues are built. A relatively small contribution to the production of organic matter is made by chemosynthetic bacteria. They extract energy from inorganic compounds. Algae act as the main producers in aquatic ecosystems. Often they are represented by small unicellular organisms that form phytoplankton in the surface layers of lakes and oceans. Most of the primary production on land is delivered in more highly organized forms. They relate to gymnosperms and angiosperms. Due to them, meadows and forests are formed.
Consumers 2, 3 orders
Food chains can be of two types. In particular, detrital and pasture structures are distinguished. The examples of the latter are described above. In them, on the first level there are green plants, on the second - pasture animals, on the third - predators. However, the bodies of dead plants and animals still contain energy and "building material" along with intravital secretions (urine and feces). All these organic materials are decomposed due to the activity of microorganisms - bacteria and fungi. They live on organic debris as saprophytes.
Organisms of this type are called reducers. They secrete digestive enzymes to waste products or to dead bodies, and then digestion products are absorbed. Decomposition can occur at different rates. The consumption of organic compounds of feces, urine, animal corpses is carried out for several weeks. At the same time, fallen branches or trees can decompose for years.
Detritophages
A significant role in the process of rotting wood belongs to mushrooms. They secrete the enzyme cellulase. It has a softening effect on wood, which makes it possible for small animals to penetrate and absorb material. Fragments of the decomposed material are called detritus. Many small living organisms (detritophages) feed on it and accelerate the destruction process.
Since the decomposition involves two types of organisms (fungi and bacteria, as well as animals), they are often combined under the same name - "reducers". But in reality, this term applies only to saprophytes. Detritophages, in turn, can be absorbed by larger organisms. In this case, a different type of chain is formed - starting with detritus. Detritophages of coastal and forest communities include wood lice, earthworm, carrion fly larva, purplish, holothuria, and polychaete.
Food network
In systems diagrams, each organism can be represented as consuming others belonging to a certain type. But the nutritional relationships that exist in the biological structure have a much more complex structure. This is due to the fact that the animal can consume organisms of various types. Moreover, they can belong to one food chain or belong to different ones. This is especially evident among predators at high levels of the biological cycle. There are animals that consume other fauna and plants at the same time. Such individuals belong to the category of omnivores. In particular, such is man. In the existing biological system, the interweaving of food chains is quite common. As a result, a new multicomponent structure is formed - the network. Only some of all possible relationships can be reflected in the diagram. As a rule, it contains only one or two predators belonging to the upper trophic levels. In the flow of energy and the cycle within the framework of a typical structure, two paths of exchange can exist. On the one hand, the interaction is between predators, and on the other, between reducents and detritus. The latter can consume dead animals. At the same time, living reducers and child-eaters can act as food for predators.
Organic moleculessynthesized by autotrophs serve as a source of nutrition (matter and energy) for heterotrophic animals. These animals, in turn, are eaten by other animals and in this way there is a transfer of energy through a number of organisms, where each subsequent one feeds on the previous one. This sequence is called the food chain, and each link in the chain corresponds to a certain trophic level (from the Greek. Troph - food). The first trophic level is always autotrophs, called producers (from the Latin. Producere - to produce). The second level is herbivorous (phytophages), which are called consumers (from lat. Consumo - “devour”) of the first order; the third level (for example, predators) is second-order consumers, etc.
In an ecosystem, usually happens 4-5 trophic levels and rarely more than 6. This is partly due to the fact that at each level a part of the substance and energy is lost (incomplete eating of food, respiration of consumers, “natural” death of organisms, etc.); such losses are shown in the figure and are discussed in more detail in the corresponding article. However, judging by recent research, food chain lengths are also limited by other factors. Perhaps the essential role is played by the availability of preferred food and territorial behavior, which reduces the density of the distribution of organisms, and, therefore, the number of consumers of higher orders in a particular habitat. According to existing estimates, in some ecosystems up to 80% of primary production is not consumed by phytophages. Dead plant material becomes the prey of organisms that feed on detritus (detritophagous) or reducers (destructors). In this case, they talk about detrital food chains. Detrital food chains predominate, for example, in rainforests.
Producers
Almost all producers - photoautotrophs, i.e. green plants, algae and some prokaryotes, for example cyanobacteria (formerly they were called blue-green algae). The role of chemoautotrophs on a biosphere scale is negligible. The microscopic algae and cyanobacteria that make up phytoplankton are the main producers of aquatic ecosystems. On the contrary, large plants predominate at the first trophic level of terrestrial ecosystems, for example, trees in forests, grasses in savannahs, steppes, fields, etc.
The flow of energy and the circulation of substances in a typical food chain. Please note that between predators and detritophages, as well as reducers, a two-way exchange is possible: detritophages feed on dead predators, and predators in some cases eat live detritophages and reducers. Phytophages - consumers of the first order; carnivores - consumers of the second, third, etc. orders.First-Order Consumables
On land, the main phytophages - insects, reptiles, birds and mammals. In fresh and sea water these are usually small crustaceans (daphnia, sea acorns, crab larvae, etc.) and bivalve mollusks; most of them are filtering machines that filter out producers, as described in the corresponding article. Together with the simplest, many of them are part of zooplankton - a collection of microscopic drifting heterotrophs that feed on phytoplankton. The life of oceans and lakes is almost completely dependent on planktonic organisms, which constitute virtually the beginning of all food chains in these ecosystems.
Consumables of the second, third and subsequent orders
Second order consumables eat phytophages, i.e. are carnivorous organisms. Third-order consumables and higher-order consumers are also carnivores. These consumers can be divided into several environmental groups:
Here are two examples based on food chain photosynthesis:
Plant (leaves) -\u003e Slug - "Frog -" Already - * - "Ermine
Plant (phloem juice) - "Aphids -\u003e ladybug -\u003e - »Spider - ^ Starling -\u003e Hawk