Nature is amazing and diverse, and everything in it is interconnected and balanced. The number of individuals of any species of animals, insects, fish is constantly regulated.
It is impossible to imagine that the number of any species of individuals is constantly increasing. To prevent this from happening, there is natural selection and many other environmental factors that constantly regulate this number. All of you have probably heard such an expression as an ecological pyramid. What it is? What types of ecological pyramids exist? What rules is it based on? You will receive answers to these and other questions below.
The ecological pyramid is... Definition
So, everyone knows that in biology there are food chains when some animals, usually predators, feed on other animals.
The ecological pyramid is about the same system, but, in turn, is much more global. What does she represent? An ecological pyramid is a kind of system that reflects in its composition the number of creatures, the mass of individuals, and plus the energy inherent in them at each level. The peculiarity is that with the increase of each level, the indicators are significantly reduced. By the way, this is exactly what the rule of the ecological pyramid is connected with. Before talking about it, it is worth understanding what this scheme looks like.
pyramid rule
If you imagine it schematically in the figure, then it will be something similar to the pyramid of Cheops: a quadrangular pyramid with a pointed top, where the smallest number of individuals is concentrated.
The rule of the ecological pyramid defines one very interesting pattern. It consists in the fact that the base of the ecological pyramid, namely the vegetation that forms the basis of nutrition, is about ten times larger than the mass of animals that eat plant foods.
Moreover, each next level is also ten times less than the previous one. So it turns out that the extreme upper level contains the smallest mass and energy. What gives us this regularity?
The role of the pyramid rule
Based on the rule of the ecological pyramid, many problems can be solved. For example, how many eagles can grow when there is a certain amount of grain, when frogs, snakes, grasshoppers and an eagle are involved in the food chain.
Based on the fact that only 10% of the energy is transferred to the highest level, such problems can be easily solved. We learned what ecological pyramids are, revealed their rules and patterns. But we will now talk about what ecological pyramids exist in nature.
Types of ecological pyramids
There are three types of pyramids. Based on the initial definition, it can already be concluded that they are related to the number of individuals, their biomass and the energy contained in them. In general, about everything in order.
Pyramid of numbers
The name speaks for itself. This pyramid reflects the number of individuals located at all levels separately. But it is worth noting that in ecology it is used quite rarely, since there are a very large number of individuals at the same level, and it is quite difficult to give a complete structure of the biocenosis.
All this is much easier to imagine in one specific example. Let's say there are 1000 tons of green plants at the base of the pyramid. This vegetation is eaten by grasshoppers. Their number, for example, is somewhere around thirty million. Ninety thousand frogs can eat all these grasshoppers. The frogs themselves are the food of 300 trout. This is the amount of fish one person can eat in a year. What do we get? And it turns out that at the base of the pyramid there are millions of blades of grass, and at the top of the pyramid there is only one person.
Just here we can observe how, when moving from one level to each subsequent level, the indicators decrease. The mass, the number of individuals decreases, the energy contained in them decreases. Not to mention that there are exceptions. For example, sometimes there are reversed eco-pyramids of numbers. Suppose insects live on a certain tree in the forest. All insectivorous birds feed on them.
biomass pyramid
The second scheme is the biomass pyramid. It is also a ratio. But in this case it is the ratio of masses. As a rule, the mass at the base of the pyramid is always much larger than at the highest trophic level, and the mass of the second level is higher than the mass of the third level, and so on. If organisms at different trophic levels do not differ much in size, then in the figure it just looks like a quadrangular pyramid tapering upwards. One of the American scientists explained the structure of this pyramid using the following example: the weight of vegetation in a meadow is much greater than the mass of individuals consuming these plants, the weight of herbivores is higher than the weight of carnivores of the first level, the weight of the latter is higher than the weight of carnivores of the second level, and so on.
For example, one lion weighs quite a lot, but this individual is so rare that compared to the mass of other individuals, its own mass is negligible. Exceptions are also found in such pyramids, when the mass of producers is less than the mass of consumers. Let's take a water system as an example. The mass of phytoplankton, even taking into account high productivity, is less than the mass of consumers, such as whales. Such pyramids are called inverted or inverted.
energy pyramid
And finally, the third type of ecological pyramid is the energy one. It reflects the speed with which the mass of food passes through the chain, as well as the amount of this energy. This law was formulated by R. Lindemann. It was he who proved that with a change in the trophic level, only 10% of the energy that was at the previous level passes.
The initial energy percentage is always 100%. But if only a tenth of it goes to the next trophic level, then where does most of the energy go? Its main part, namely 90%, is spent by individuals to ensure all life processes. So there is a pattern here too. Through the upper trophic levels, where there is a smaller mass and number of individuals, much less energy also flows through than it passes through the lower levels. This may explain the fact that there are not so many predators.
Disadvantages and advantages of ecological pyramids
Despite the number of different types, almost each of them has a number of disadvantages. These are, for example, pyramids of numbers and biomass. What is their disadvantage? The fact is that the construction of the first one causes some difficulties if the spread in the number of different levels is too large. But the difficulty lies not only in this.
The energy pyramid is able to compare productivity, as it takes into account the most important time factor. And, of course, it is worth saying that such a pyramid is never inverted. Because of this, it is a kind of standard.
The role of the ecological pyramid
The ecological pyramid is what helps us understand the structure of the biocenosis, describe the state of the system. Also, these schemes help in determining the allowable amount of fish catch, the number of animals shot.
All this is necessary in order not to violate the overall integrity and sustainability of the environment. The pyramid, in turn, helps us understand the organization of functional communities, as well as compare different ecosystems in terms of their productivity.
Ecological pyramid as a ratio of features
Based on the above types, we can conclude that the ecological pyramid is a kind of ratio of indicators related to abundance, mass and energy. The levels of the ecological pyramid are different in all respects. Higher scores have lower levels, and vice versa. Do not forget about inverted schemes. Here consumers outnumber producers. But there is nothing surprising in this. Nature has its own laws, exceptions can be anywhere.
The energy pyramid is the simplest and most reliable, as it takes into account the most important time factor. Due to this, it is it that is considered to be a certain standard. The role of ecological pyramids is very important for maintaining the balance of natural ecosystems and ensuring their sustainability.
Lindemann's rule (10%)
The through flow of energy, passing through the trophic levels of the biocenosis, is gradually extinguished. In 1942, R. Lindemann formulated the law of the pyramid of energies, or the law (rule) of 10%, according to which from one trophic level of the ecological pyramid it moves to another, higher level (along the "ladder": producer - consumer - decomposer) on average about 10% of the energy received at the previous level of the ecological pyramid. The reverse flow associated with the consumption of substances and the energy produced by the upper level of the ecological pyramid of energy by its lower levels, for example, from animals to plants, is much weaker - no more than 0.5% (even 0.25%) of its total flow, and therefore we can say about the cycle of energy in the biocenosis is not necessary.
If energy is lost tenfold during the transition to a higher level of the ecological pyramid, then the accumulation of a number of substances, including toxic and radioactive ones, increases in approximately the same proportion. This fact is fixed in the biological amplification rule. It is true for all cenoses. In aquatic biocenoses, the accumulation of many toxic substances, including organochlorine pesticides, correlates with the mass of fats (lipids), i.e. clearly has an energy background.
Ecological pyramids
To visualize the relationship between organisms of different species in the biocenosis, it is customary to use ecological pyramids, distinguishing between the pyramids of abundance, biomass and energy.
Among the ecological pyramids, the most famous and frequently used are:
§ Pyramid of numbers
§ Pyramid of biomass
Pyramid of numbers. To build a pyramid of abundance, the number of organisms in a certain territory is counted, grouping them according to trophic levels:
§ producers - green plants;
§ primary consumers - herbivores;
§ secondary consumers - carnivores;
§ tertiary consumers - carnivores;
§ ha-e consumers ("ultimate predators") - carnivores;
§ decomposers - destructors.
Each level is conventionally depicted as a rectangle, the length or area of which corresponds to the numerical value of the number of individuals. By placing these rectangles in a subordinate sequence, they get an ecological pyramid of abundance (Fig. 3), the basic principle of which was first formulated by the American ecologist Ch. Elton Nikolaikin N. I. Ecology: Proc. for universities / N. I. Nikolaykin, N. E. Nikolaykina, O. P. Melekhova. - 3rd ed., stereotype. - M .: Bustard, 2004 ..
Rice. Fig. 3. Ecological pyramid of abundance for a meadow overgrown with cereals: numbers - number of individuals
Data for population pyramids are easily obtained by direct sampling, but there are some difficulties:
§ Producers vary greatly in size, although one cereal or algae has the same status as one tree. This sometimes violates the correct pyramidal shape, sometimes even giving inverted pyramids (Fig. 4) Ibid .;
Rice.
§ The range of abundance of different species is so wide that it is difficult to maintain scale in a graphic representation, but in such cases a logarithmic scale can be used.
Biomass pyramid. The ecological pyramid of biomass is built similarly to the pyramid of abundance. Its main meaning is to show the amount of living matter (biomass - the total mass of organisms) at each trophic level. This avoids the inconveniences typical of population pyramids. In this case, the size of the rectangles is proportional to the mass of living matter of the corresponding level, per unit area or volume (Fig. 5, a, b) Nikolaykin N. I. Ecology: Proc. for universities / N. I. Nikolaykin, N. E. Nikolaykina, O. P. Melekhova. - 3rd ed., stereotype. - M.: Bustard, 2004 .. The term "biomass pyramid" arose due to the fact that in the vast majority of cases the mass of primary consumers living at the expense of producers is much less than the mass of these producers, and the mass of secondary consumers is much less than the mass of primary consumers. It is customary to show the biomass of destructors separately.
Rice. Fig. 5. Pyramids of biomass of biocenoses of the coral reef (a) and the English Channel (b): numbers - biomass in grams of dry matter per 1 m 2
Sampling determines standing biomass or standing yield (ie, at a given point in time), which does not contain any information about the rate of production or consumption of biomass.
The rate of creation of organic matter does not determine its total reserves, i.e. the total biomass of all organisms at each trophic level. Therefore, errors may occur in further analysis if the following are not taken into account:
* Firstly, if the rate of biomass consumption (loss due to eating) and the rate of its formation are equal, the standing crop does not indicate productivity, i.e. about the amount of energy and matter passing from one trophic level to another, higher one, for a certain period of time (for example, for a year). So, on a fertile, intensively used pasture, the yield of grasses on the vine may be lower, and the productivity is higher than on a less fertile, but little used for grazing;
* secondly, small-sized producers, such as algae, are characterized by a high growth and reproduction rate, balanced by their intensive consumption by other organisms and natural death. Therefore, their productivity can be no less than that of large producers (for example, trees), although the biomass on the vine can be small. In other words, phytoplankton with the same productivity as a tree will have a much lower biomass, although it could support the life of animals of the same mass.
One of the consequences of what has been described is "inverted pyramids" (Fig. 3, b). Zooplankton of biocenoses of lakes and seas most often has a greater biomass than its food - phytoplankton, however, the rate of reproduction of green algae is so high that during the day they restore all the biomass eaten by zooplankton. Nevertheless, in certain periods of the year (during spring flowering), the usual ratio of their biomasses is observed (Fig. 6) Nikolaikin NI Ecology: Proc. for universities / N. I. Nikolaykin, N. E. Nikolaykina, O. P. Melekhova. - 3rd ed., stereotype. - M .: Bustard, 2004 ..
Rice. Fig. 6. Seasonal changes in the lake biomass pyramids (on the example of one of the Italian lakes): numbers - biomass in grams of dry matter per 1 m 3
Seeming anomalies are devoid of pyramids of energies, which are considered below.
Energy Pyramid. The most fundamental way to reflect the relationships between organisms of different trophic levels and the functional organization of biocenoses is the energy pyramid, in which the size of the rectangles is proportional to the energy equivalent per unit time, i.e. the amount of energy (per unit area or volume) that has passed through a certain trophic level during the accepted period (Fig. 7) Ibid.. One more rectangle can be reasonably added from below to the base of the pyramid of energy, reflecting the flow of solar energy.
The pyramid of energies reflects the dynamics of the passage of a mass of food through the food (trophic) chain, which fundamentally distinguishes it from the pyramids of abundance and biomass, which reflect the statics of the system (the number of organisms at a given moment). The shape of this pyramid is not affected by changes in the size and intensity of the metabolism of individuals. If all sources of energy are taken into account, then the pyramid will always have a typical shape (in the form of a pyramid with the top up), according to the second law of thermodynamics.
Rice. 7. Pyramid of energy: numbers - the amount of energy, kJ * m -2 * r -1
Energy pyramids allow not only to compare different biocenoses, but also to identify the relative importance of populations within the same community. They are the most useful of the three types of ecological pyramids, but the data to build them is the most difficult to obtain.
One of the most successful and illustrative examples of classical ecological pyramids are the pyramids depicted in Fig. 8 Nikolaikin N. I. Ecology: Proc. for universities / N. I. Nikolaykin, N. E. Nikolaykina, O. P. Melekhova. - 3rd ed., stereotype. - M.: Bustard, 2004 .. They illustrate the conditional biocenosis proposed by the American ecologist Y. Odum. The "biocenosis" consists of a boy who eats only veal and calves who eat only alfalfa.
Rice.
rule 1% Ecology. Lecture course. Compiled by: Candidate of Technical Sciences, Associate Professor Tikhonov AI, 2002. Pasteur's points, as well as the law of the pyramid of energies by R. Lindemann, gave rise to the formulation of the rules of one and ten percent. Of course, 1 and 10 are approximate numbers: about 1 and about 10.
"Magic Number" 1% arises from the ratio of energy consumption possibilities and the "capacities" needed to stabilize the environment. For the biosphere, the share of possible consumption of total primary production does not exceed 1% (which also follows from R. Lindemann's law: about 1% of net primary production in energy terms is consumed by vertebrates as consumers of higher orders, about 10% by invertebrates as consumers of lower orders and the remaining some are bacteria and saprophage fungi). As soon as humanity, on the verge of the past and our centuries, began to use a greater amount of biosphere production (now at least 10%), the Le Chatelier-Brown principle ceased to be satisfied (apparently, from about 0.5% of the total energy of the biosphere): vegetation did not give biomass growth in accordance with the increase in CO 2 concentration, etc. (an increase in the amount of carbon bound by plants was observed only in the last century).
Empirically, the consumption threshold of 5 - 10% of the amount of a substance, which, when passing through it, leads to noticeable changes in the systems of nature, is quite recognized. It was adopted mainly on an empirical-intuitive level, without distinguishing between the forms and nature of control in these systems. Approximately, it is possible to divide the emerging transitions for natural systems with an organismic and consortium type of control, on the one hand, and population systems, on the other. For the former, the quantities of interest to us are the threshold for exiting the stationary state up to 1% of the energy flow (the "norm" of consumption) and the self-destruction threshold - about 10% of this "norm". For population systems, exceeding on average 10% of the withdrawal volume leads to the exit of these systems from the stationary state.
ecological pyramids.
Trophic chains can theoretically consist of a large number of links, but practically do not exceed 5–6 links, since as a result of the action second law of thermodynamics the energy dissipates quickly.
The second law of thermodynamics is also known as the law of increase. entropy(gr. entropia turn, change). According to this law, energy cannot be created or destroyed - it is transferred from one system to another and turns from one form to another.
In trophic chains, the amount of plant matter that serves as the basis of the food chain is approximately 10 times greater than the mass of herbivorous animals, and each subsequent food level also has a mass 10 times less. This pattern is called the 10% rule: on average, no more than 1/10 of the energy received from the previous level is transferred to the next trophic level. Therefore, if about one percent of solar energy is accumulated in plants, then, for example, at the 4th trophic level, its share will be only 0.001%.
Trophic chains are very unstable systems , since the accidental loss of any link destroys the entire chain. Sustainability of natural communities is provided by the presence of complex branched multi-species food webs . In such networks, when any link fails, energy begins to move along detour paths. The more species in the biogeocenosis, the more reliable and stable it is.
For a visual representation of the magnitude of the energy transfer coefficient from level to level in the food chains of ecosystems, ecological pyramids of several types are used.
Ecological pyramid -this is a graphical (or diagrammatic) representation of the relationship between the volumes of organic matter or energy at adjacent levels in the food chain.
The graphic model of the pyramid was developed in 1927 by an American zoologist Charles Elton.
The base of the pyramid is the first trophic level - the level of producers, and the next "floors" of the pyramid are formed by subsequent levels - consumers of various orders. The height of all blocks is the same, and the length is proportional to the number, biomass or energy at the corresponding level. There are three ways to build ecological pyramids
The most widespread are the following types of ecological pyramids:
Pyramids of Elton's numbers;
Pyramids of biomass;
Energy pyramids.
Lindemann principle. In 1942, based on the generalization of extensive empirical material, the American ecologist Lindeman formulated the principle of biochemical energy conversion in ecosystems, which received the name in ecological literature law 10%.
Lindemann principle - the law of the pyramid of energies (the law of 10 percent), according to which, on average, about 10% of the energy received by the previous level of the ecological pyramid passes from one trophic level through food chains to another trophic level. The rest of the energy is lost in the form of thermal radiation, movement, etc. Organisms, as a result of metabolic processes, lose about 90% of all energy in each link of the food chain, which is spent on maintaining their vital functions.
Pyramids of Elton's numbers are presented in the form average number of individuals required for the nutrition of organisms at subsequent trophic levels.
Pyramid of numbers(numbers) reflects the number of individual organisms at each level (Fig. 35).
For example, to feed one wolf, you need at least a few hares that he could hunt; to feed these hares, you need a fairly large number of various plants.
For example, to represent the trophic chain:
OAK LEAF - CATERRIP - TIT
the pyramid of numbers for one tit (third level) depicts the number of caterpillars (second level) that it eats in a certain time, for example, in one light day. At the first level of the pyramid, as many oak leaves are depicted as required to feed the number of caterpillars that are shown at the second level of the pyramid.
Pyramids of biomass and energy express the ratio of the amount of biomass or energy at each trophic level.
The biomass pyramid is based on displaying the results of weighing the dry mass of organic matter at each level, and the energy pyramid is based on calculations of the biochemical energy transferred from the lower to the higher level. These levels on the biomass (or energy) pyramid plot are depicted as rectangles of equal height, the width of which is proportional to the amount of biomass transferred to each subsequent (overlying) level of the trophic chain under study.
GRASS (809) - HERBIVORS (37) - CARNIVORES-1 (11) - CARNIVORS-2 (1.5),
where values of dry biomass (g/sq. m) are given in parentheses.
2. Pyramid of biomass – the ratio of the masses of organisms of different trophic levels. Usually, in terrestrial biocenoses, the total mass of producers is greater than each subsequent link. In turn, the total mass of first-order consumers is greater than second-order consumers, and so on. If the organisms do not differ too much in size, then the graph usually shows a stepped pyramid with a tapering top. So, for the formation of 1 kg of beef, 70-90 kg of fresh grass is needed.
In aquatic ecosystems, it is also possible to obtain an inverted or inverted biomass pyramid, when the biomass of producers is less than that of consumers, and sometimes decomposers. For example, in the ocean, with a fairly high productivity of phytoplankton, its total mass at the moment may be less than that of consumer consumers (whales, large fish, mollusks)
Pyramids of numbers and biomass reflect static systems, i.e., characterize the number or biomass of organisms in a certain period of time. They do not provide complete information about the trophic structure of the ecosystem, although they allow solving a number of practical problems, especially those related to maintaining the stability of ecosystems.
The pyramid of numbers makes it possible, for example, to calculate the allowable value of catching fish or shooting animals during the hunting period without consequences for their normal reproduction.
3. Pyramid of energy reflects the amount of energy flow, the rate of passage of a mass of food through the food chain. The structure of the biocenosis is largely influenced not by the amount of fixed energy, but food production rate (Fig. 37).
It has been established that the maximum amount of energy transferred to the next trophic level can in some cases be 30% of the previous one, and this is at best. In many biocenoses, food chains, the value of the transferred energy can be only 1%.
Rice. 37. Energy Pyramid: energy flow through the pasture food chain (all figures are in kJ per square meter x year)
Note that the ecological pyramids are a clear illustration of the Lindemann principle and with their help reflect an essential feature of energy processes in ecosystems, namely: due to a relatively small share of energy (on average, about a tenth) transferred to the next level, very little energy remains in ecosystem, and the rest returns to the geosphere. So, with a 4-level trophic chain, only a ten thousandth of the biochemical energy remains in the ecosystem. The negligible fraction of energy remaining in an ecosystem explains why food chains in real natural ecosystems have no more than 5–6 levels.
An ecological pyramid is a graphic representation of the relationship between producers and consumers of all levels (herbivores, predators; species that feed on other predators) in an ecosystem.
The American zoologist Charles Elton proposed in 1927 to schematically depict these relationships.
In a schematic representation, each level is shown as a rectangle, the length or area of \u200b\u200bwhich corresponds to the numerical values \u200b\u200bof the food chain link (Elton's pyramid), their mass or energy. Rectangles arranged in a certain sequence create pyramids of various shapes.
The base of the pyramid is the first trophic level - the level of producers, the subsequent floors of the pyramid are formed by the next levels of the food chain - consumers of various orders. The height of all blocks in the pyramid is the same, and the length is proportional to the number, biomass or energy at the corresponding level.
Ecological pyramids are distinguished depending on the indicators on the basis of which the pyramid is built. At the same time, for all the pyramids, the basic rule is established, according to which in any ecosystem there are more plants than animals, herbivores than carnivores, insects than birds.
Based on the rule of the ecological pyramid, it is possible to determine or calculate the quantitative ratios of different plant and animal species in natural and artificially created ecological systems. For example, 1 kg of the mass of a sea animal (seal, dolphin) needs 10 kg of eaten fish, and these 10 kg already need 100 kg of their food - aquatic invertebrates, which, in turn, need to eat 1000 kg of algae and bacteria to form such a mass. In this case, the ecological pyramid will be stable.
However, as you know, there are exceptions to every rule, which will be considered in each type of ecological pyramids.
Types of ecological pyramids
Pyramids of numbers - at each level, the number of individual organisms is postponed
The pyramid of numbers reflects a clear pattern discovered by Elton: the number of individuals that make up a sequential series of links from producers to consumers is steadily decreasing (Fig. 3).
For example, to feed one wolf, you need at least a few hares that he could hunt; to feed these hares, you need a fairly large number of various plants. In this case, the pyramid will look like a triangle with a wide base tapering upwards.
However, this form of a pyramid of numbers is not typical for all ecosystems. Sometimes they can be reversed, or inverted. This applies to forest food chains, when trees serve as producers, and insects as primary consumers. In this case, the level of primary consumers is numerically richer than the level of producers (a large number of insects feed on one tree), so the pyramids of numbers are the least informative and least indicative, i.e. the number of organisms of the same trophic level largely depends on their size.
Biomass pyramids - characterizes the total dry or wet mass of organisms at a given trophic level, for example, in units of mass per unit area - g / m2, kg / ha, t / km2 or per volume - g / m3 (Fig. 4)
Usually, in terrestrial biocenoses, the total mass of producers is greater than each subsequent link. In turn, the total mass of first-order consumers is greater than second-order consumers, and so on.
In this case (if the organisms do not differ too much in size), the pyramid will also look like a triangle with a wide base tapering upwards. However, there are significant exceptions to this rule. For example, in the seas, the biomass of herbivorous zooplankton is significantly (sometimes 2-3 times) greater than the biomass of phytoplankton, which is represented mainly by unicellular algae. This is explained by the fact that algae are very quickly eaten away by zooplankton, but the very high rate of division of their cells protects them from complete eating.
In general, terrestrial biogeocenoses, where producers are large and live relatively long, are characterized by relatively stable pyramids with a wide base. In aquatic ecosystems, where producers are small in size and have short life cycles, the biomass pyramid can be reversed or inverted (pointed downwards). So, in lakes and seas, the mass of plants exceeds the mass of consumers only during the flowering period (spring), and in the rest of the year the situation may be reversed.
Pyramids of numbers and biomass reflect the statics of the system, i.e., they characterize the number or biomass of organisms in a certain period of time. They do not provide complete information about the trophic structure of the ecosystem, although they allow solving a number of practical problems, especially those related to maintaining the stability of ecosystems.
The pyramid of numbers makes it possible, for example, to calculate the allowable value of catching fish or shooting animals during the hunting period without consequences for their normal reproduction.
Pyramids of energy - shows the amount of energy flow or productivity at successive levels (Fig. 5).
In contrast to the pyramids of numbers and biomass, which reflect the statics of the system (the number of organisms at a given moment), the pyramid of energy, reflecting the picture of the speed of passage of a mass of food (amount of energy) through each trophic level of the food chain, gives the most complete picture of the functional organization of communities.
The shape of this pyramid is not affected by changes in the size and intensity of the metabolism of individuals, and if all sources of energy are taken into account, then the pyramid will always have a typical appearance with a wide base and a tapering top. When building a pyramid of energy, a rectangle is often added to its base, showing the influx of solar energy.
In 1942, the American ecologist R. Lindeman formulated the law of the pyramid of energies (the law of 10 percent), according to which, on average, about 10% of the energy received by the previous level of the ecological pyramid passes from one trophic level through food chains to another trophic level. The rest of the energy is lost in the form of thermal radiation, movement, etc. Organisms, as a result of metabolic processes, lose about 90% of all the energy that is expended to maintain their vital activity in each link of the food chain.
If a hare ate 10 kg of plant matter, then its own weight could increase by 1 kg. A fox or a wolf, eating 1 kg of hare, increases its mass by only 100 g. In woody plants, this proportion is much lower due to the fact that wood is poorly absorbed by organisms. For grasses and algae, this value is much higher, since they do not have hard-to-digest tissues. However, the general regularity of the process of energy transfer remains: much less energy passes through the upper trophic levels than through the lower ones.
Consider the transformation of energy in an ecosystem using the example of a simple pasture trophic chain, in which there are only three trophic levels.
level - herbaceous plants,
level - herbivorous mammals, for example, hares
level - predatory mammals, for example, foxes
Nutrients are created in the process of photosynthesis by plants, which from inorganic substances (water, carbon dioxide, mineral salts, etc.) using the energy of sunlight form organic substances and oxygen, as well as ATP. Part of the electromagnetic energy of solar radiation is then converted into the energy of chemical bonds of synthesized organic substances.
All organic matter created during photosynthesis is called gross primary production (GPP). Part of the energy of gross primary production is spent on respiration, resulting in the formation of net primary production (NPP), which is the very substance that enters the second trophic level and is used by hares.
Let the runway be 200 conventional units of energy, and the costs of plants for respiration (R) be 50%, i.e. 100 conventional units of energy. Then the net primary production will be equal to: NPP = WPP - R (100 = 200 - 100), i.e. at the second trophic level, hares will receive 100 conventional units of energy.
However, for various reasons, hares are able to consume only a certain proportion of NPP (otherwise, resources for the development of living matter would disappear), but a significant part of it, in the form of dead organic residues (underground parts of plants, hard wood of stems, branches, etc. .) is not able to be eaten by hares. It enters detritus food chains and (or) is decomposed by decomposers (F). The other part goes to building new cells (population size, growth of hares - P) and ensuring energy metabolism or respiration (R).
In this case, according to the balance approach, the balance equation of energy consumption (C) will look like this: C = P + R + F, i.e. The energy received at the second trophic level will be spent, according to Lindemann's law, for population growth - P - 10%, the remaining 90% will be spent on breathing and removing undigested food.
Thus, in ecosystems with an increase in the trophic level, there is a rapid decrease in the energy accumulated in the bodies of living organisms. From this it is clear why each subsequent level will always be less than the previous one and why food chains usually cannot have more than 3-5 (rarely 6) links, and ecological pyramids cannot consist of a large number of floors: to the final link of the food chain in the same way as to the top floor of the ecological pyramid will receive so little energy that it will not be enough in case of an increase in the number of organisms.
Such a sequence and subordination of groups of organisms connected in the form of trophic levels is the flow of matter and energy in the biogeocenosis, the basis of its functional organization.
Each ecosystem is made up of several trophic (food) levels, forming a certain structure. trophic structure usually depicted as ecological pyramids.
In 1927, the American ecologist and zoologist Charles Elton proposed a graphical model ecological pyramid. The base of the pyramid is the first trophic level, consisting of producers. Above are the levels of consumers of various orders. In other words, looking at the ecological pyramid, we understand how all its members are related in a given ecosystem according to several factors.
Levels are displayed ecological pyramid in the form of several rectangular or trapezoidal tiers, the size of which is correlated either with the number of participants in each level of the food chain, or with their mass, or with energy.
Three types of ecological pyramids
1. Pyramid of numbers (or numbers) tells us the number of living organisms at each level. For example, to feed one owl, 12 mice are needed, and they, in turn, need 300 ears of rye. It often happens that the pyramid of numbers is inverted (such a pyramid is otherwise called inverted). It can describe, say, a forest food chain in which trees are producers and insects are primary consumers. One tree is food for myriads of insects.
2. Biomass pyramid describes the ratio of the masses of organisms of several trophic levels. As a rule, in biocenoses on land, the mass of producers is much greater than in each subsequent link in the food chain, and the mass of consumers of the first level exceeds the mass of consumers of the second level, etc.
Aquatic ecosystems can also be characterized by inverted biomass pyramids, in which the mass of consumers is greater than the mass of producers. Oceanic zooplankton feeding on phytoplankton far exceeds it in terms of total mass. It would seem that with such a rate of absorption, phytoplankton would have to disappear, however, it is saved by a high growth rate.
3. energy pyramid explores the amount of energy flow through the food chain from the base level to the highest. The structure of the biocenosis is highly dependent on the rate of food production at all trophic levels. The American scientist Raymond Lindeman found that up to 90% of the energy received by him is lost at each level (the so-called "Law of 10%").
Why do we need ecological pyramids?
Pyramids of numbers and biomass describe the ecosystem in its statics, since they calculate the number or mass of participants in the ecosystem for a fixed time period. They are not intended to provide information about the trophic structure of the ecosystem in dynamics, however, they allow solving problems related to maintaining the stability of the ecosystem and foreseeing possible dangers.
A classic example of a violation of stability is the importation of rabbits to the Australian continent. Due to the high rate of reproduction, their numbers became so huge that they harmed agriculture, depriving sheep and cattle of food - thus, only one species consumers (rabbits) monopolized the producer (grass) in this ecosystem.
energy pyramid, unlike the above pyramids, is dynamic, it conveys the rate of passage of the amount of energy through all trophic levels. Its task is to give an idea of the functional organization ecosystems.
