Plant food chain. Food chain in nature. Definition and composition
The transfer of energy by living organisms eating each other is called a food chain. These are specific relationships between plants, fungi, animals, and microorganisms that ensure the circulation of substances in nature. Also called a food chain.
Structure
All organisms feed, i.e. receive energy that powers life processes. The trophic chain system is formed by links. A link in the food chain is a group of living organisms connected to a neighboring group through the “food-consumer” relationship. Some organisms are food for other organisms, which in turn are also food for a third group of organisms.
There are three types of links:
- producers - autotrophs;
- consumers - heterotrophs;
- decomposers (destructors) - saprotrophs.
Rice. 1. Links in the food chain.
All three links form one chain. There can be several consumers (consumers of the first, second order, etc.). The basis of the chain can be producers or decomposers.
Producers include plants that transform organic substances with the help of light into organic substances, which, when eaten by plants, enter the body of the first-order consumer. The main feature of the consumer is heterotrophy. At the same time, consumers can consume both living organisms and dead ones (carrion).
Examples of consumers:
- herbivores - hare, cow, mouse;
- predators - leopard, owl, walrus;
- scavengers - vulture, Tasmanian devil, jackal.
Some consumers, including humans, occupy an intermediate position, being omnivores. Such animals can act as consumers of the first, second and even third order. For example, a bear eats berries and small rodents, i.e. is simultaneously a consumer of the first and second orders.
Reducers include:
- mushrooms;
- bacteria;
- protozoa;
- worms;
- insect larvae.
Rice. 2. Decomposers.
Decomposers feed on the remains of living organisms and their metabolic products, returning inorganic substances into the soil that producers consume.
Species
Food chains can be of two types:
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- pasture (grazing chain);
- detrital (decomposition chain).
Pasture chains are characteristic of meadows, fields, seas, and reservoirs. The beginning of the grazing chain is autotrophic organisms - photosynthetic plants.
Next, the chain links are arranged as follows:
- First-order consumers are herbivores;
- second-order consumers are predators;
- third-order consumers are larger predators;
- decomposers.
In marine and oceanic ecosystems, grazing chains are longer than on land. They may include up to five consumer orders. The basis of marine chains is photosynthetic phytoplankton.
The following links are formed by several consumers:
- zooplankton (crustaceans);
- small fish (sprats);
- large predatory fish (herring);
- large predatory mammals (seals);
- apex predators (killer whales);
- decomposers.
Detritus chains are characteristic of forests and savannas. The chain begins with decomposers that feed on organic remains (detritus) and are called detriophages. These include microorganisms, insects, and worms. All these living organisms become food for top predators, for example, birds, hedgehogs, and lizards.
Examples of two types of food chains:
- pasture : clover - hare - fox - microorganisms;
- detrital : detritus - fly larvae - frog - snake - hawk - microorganisms.
Rice. 3. Example of a food chain.
The top of the food chain is always occupied by a predator, which is the last-order consumer in its range. The number of top predators is not regulated by other predators and depends only on external factors environment. Examples are killer whales, monitor lizards, and large sharks.
What have we learned?
We found out what food chains there are in nature and how the links are located in them. All living organisms on Earth are interconnected food chains, through which energy is transmitted. Autotrophs produce themselves nutrients and are food for heterotrophs, which, when dying, become a breeding ground for saprotrophs. Decomposers can also become food for consumers and produce a nutrient medium for producers without interrupting the food chain.
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Living organisms require energy and nutrients to exist. Autotrophs transform the radiant energy of the Sun in the process of photosynthesis, synthesizing from carbon dioxide and water organic matter.
Heterotrophs use these organic substances in the process of nutrition, ultimately decomposing them again into carbon dioxide and water, and the energy accumulated in them is spent on various processes of the life of organisms. Thus, the light energy of the Sun turns into chemical energy of organic substances, and then into mechanical and thermal energy.
All living organisms in the ecological system according to the type of nutrition can be divided into three functional groups- producers, consumers, decomposers.
1. Producers- these are green autotrophic plants that produce organic substances from inorganic ones and are capable of accumulating solar energy.
2. Consumers- These are heterotrophic animals that consume ready-made organic substances. First order consumers can use organic matter from plants (herbivores). Heterotrophs that use animal food are divided into consumers of orders II, III, etc. (carnivores). They all use energy chemical bonds, stored in organic matter by producers.
3. Decomposers- These are heterotrophic microorganisms, fungi, that destroy and mineralize organic residues. Thus, decomposers, as it were, complete the cycle of substances, forming inorganic substances to enter a new cycle.
The sun provides a constant supply of energy, and living organisms eventually dissipate it as heat. During the life activity of organisms, a constant cycle of energy and substances occurs, and each species uses only part of the energy contained in organic substances. As a result, there are power circuit - trophic chains, food chains, representing a sequence of species that extract organic matter and energy from the original food substance, with each previous link becoming food for the next (Fig. 98).
Rice. 98. General scheme food chain
In each link, most of the energy is consumed in the form of heat and is lost, which limits the number of links in the chain. But most chains begin with a plant and end with a predator, and the largest one at that. Decomposers break down organic matter at every level and are the final link in the food chain.
Due to the decrease in energy at each level, there is a decrease in biomass. The trophic chain usually has no more than five levels and is an ecological pyramid, with a wide base at the bottom and tapering at the top (Fig. 99).
Rice. 99. Simplified diagram of the ecological pyramid of biomass (1) and pyramid of numbers (2)
Ecological pyramid rule reflects the pattern according to which in any ecosystem the biomass of each subsequent link is 10 times less than the previous one.
There are three types of ecological pyramids:
A pyramid reflecting the number of individuals at each level of the food chain - pyramid of numbers;
Pyramid of biomass of organic matter synthesized at each level - mass pyramid(biomass);
- energy pyramid, showing the amount of energy flow. Typically the power chain consists of 3-4 links:
plant → hare → wolf;
plant → vole → fox → eagle;
plant → caterpillar → tit → hawk;
plant → gopher → viper → eagle.
However, in real conditions in ecosystems, various food chains intersect with each other, forming branched networks. Almost all animals, with the exception of rare ones specialized types, use a variety of food sources. Therefore, if one link in the chain falls out, there is no disruption to the system. The greater the species diversity and the richer the food webs, the more stable the biocenosis.
In biocenoses, two types of trophic networks are distinguished: pasture and detritus.
1. IN grassland type food web the flow of energy goes from plants to herbivores, and then to consumers of a higher order. This gorging network. Regardless of the size of the biocenosis and habitat, herbivorous animals (terrestrial, aquatic, soil) graze, eat up green plants and transfer energy to the next levels (Fig. 100).
Rice. 100. Pasture food network in a terrestrial biocenosis
2. If the flow of energy begins with dead plant and animal remains, excrement and goes to the primary detritivores - decomposers, partially decomposing organic matter, then such a trophic network is called detrital, or network of decomposition(Fig. 101). Primary detritivores include microorganisms (bacteria, fungi), small animals (worms, insect larvae).
Rice. 101. Detrital food chain
In terrestrial biogeocenoses, both types of trophic chain are present. In aquatic communities, the grazing chain predominates. In both cases, the energy is fully used.
Trophic chains form the basis of relationships in living nature, but food connections are not the only type of relationship between organisms. Some species can participate in the distribution, reproduction, settlement of other species, and create appropriate conditions for their existence. All the numerous and varied connections between living organisms and environment ensure the existence of species in a stable, self-regulating ecosystem.
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§ 71. Ecological systems§ 73. Properties and structure of biocenoses
Introduction
A striking example of a power chain:
Classification of living organisms regarding their role in the cycle of substances
Any food chain involves 3 groups of living organisms:
Producers (manufacturers) | Consumers (consumers) | Decomposers (destroyers) |
Autotrophic living organisms that synthesize organic matter from mineral matter using energy (plants). | Heterotrophic living organisms that consume (eat, process, etc.) living organic matter and transfer the energy contained in it through food chains. | Heterotrophic living organisms that destroy (process) dead organic matter of any origin into mineral matter. |
Connections between organisms in the food chain
The food chain, whatever it may be, creates close connections between various objects of both animate and inanimate nature. And the rupture of absolutely any link can lead to disastrous results and an imbalance in nature. The most important and integral component of any power chain is solar energy. Without it, there will be no life. When moving along the food chain, this energy is processed, and each organism makes it its own, passing only 10% to the next link.
When dying, the body enters other similar food chains, and thus the cycle of substances continues. All organisms can easily leave one food chain and move into another.
The role of natural areas in the cycle of substances
Naturally, organisms living in the same natural area, create their own special food chains with each other, which cannot be repeated in any other zone. Thus, the food chain of the steppe zone, for example, consists of a wide variety of grasses and animals. The food chain in the steppe practically does not include trees, since there are either very few of them or they are stunted. As for the animal world, artiodactyls, rodents, falcons (hawks and other similar birds) and various kinds insects.
Classification of power circuits
The principle of ecological pyramids
If we consider specifically the chains starting with plants, then the entire cycle of substances in them comes from photosynthesis, during which solar energy is absorbed. Plants spend most of this energy on their vital functions, and only 10% goes to the next link. As a result, each subsequent living organism requires more and more creatures (objects) of the previous link. This is clearly demonstrated by ecological pyramids, which are most often used for these purposes. They are pyramids of mass, quantity and energy.
Every organism must receive energy to live. For example, plants consume energy from the sun, animals eat plants, and some animals eat other animals.
A food (trophic) chain is the sequence of who eats whom in a biological community () to obtain nutrients and energy that support life.
Autotrophs (producers)
Autotrophs- living organisms that make their own food, that is, their own organic compounds, from simple molecules such as carbon dioxide. There are two main types of autotrophs:
- Photoautotrophs (photosynthetic organisms) such as plants process energy from sunlight to produce organic compounds - sugars - from carbon dioxide in the process. Other examples of photoautotrophs are algae and cyanobacteria.
- Chemoautotrophs obtain organic substances due to chemical reactions that involve inorganic compounds (hydrogen, hydrogen sulfide, ammonia, etc.). This process is called chemosynthesis.
Autotrophs are the basis of every ecosystem on the planet. They make up the majority of food chains and webs, and the energy obtained through photosynthesis or chemosynthesis supports all other organisms in ecological systems. When it comes to their role in food chains, autotrophs can be called producers or producers.
Heterotrophs (consumers)
Heterotrophs, also known as consumers, cannot use solar or chemical energy to produce their own food from carbon dioxide. Instead, heterotrophs obtain energy by consuming other organisms or their byproducts. People, animals, fungi and many bacteria are heterotrophs. Their role in food chains is to consume other living organisms. There are many species of heterotrophs with different ecological roles, from insects and plants to predators and fungi.
Destructors (reducers)
Another consumer group should be mentioned, although it does not always appear in food chain diagrams. This group consists of decomposers, organisms that process dead organic matter and waste, turning them into inorganic compounds.
Decomposers are sometimes considered a separate trophic level. As a group, they feed on dead organisms coming from different trophic levels. (For example, they are able to process decaying plant matter, the body of a squirrel malnourished by predators, or the remains of a deceased eagle.) In a sense, the trophic level of decomposers runs parallel to the standard hierarchy of primary, secondary, and tertiary consumers. Fungi and bacteria are key decomposers in many ecosystems.
Decomposers, as part of the food chain, play important role in maintaining a healthy ecosystem, since thanks to them, nutrients and moisture are returned to the soil, which are later used by producers.
Levels of the food (trophic) chain
Diagram of the levels of the food (trophic) chain
A food chain is a linear sequence of organisms that transfer nutrients and energy from producers to top predators.
The trophic level of an organism is the position it occupies in the food chain.
First trophic level
The food chain starts with autotrophic organism or producer, producing its own food from a primary energy source, usually solar or energy from hydrothermal vents at mid-ocean ridges. For example, photosynthetic plants, chemosynthetic plants, etc.
Second trophic level
Next come the organisms that feed on autotrophs. These organisms are called herbivores or primary consumers and consume green plants. Examples include insects, hares, sheep, caterpillars and even cows.
Third trophic level
The next link in the food chain are animals that eat herbivores - they are called secondary consumers or carnivorous (predatory) animals(for example, a snake that feeds on hares or rodents).
Fourth trophic level
In turn, these animals are eaten by larger predators - tertiary consumers(for example, an owl eats snakes).
Fifth trophic level
Tertiary consumers are eaten quaternary consumers(for example, a hawk eats owls).
Every food chain ends with an apex predator or superpredator - an animal with no natural enemies (for example, a crocodile, polar bear, shark, etc.). They are the "masters" of their ecosystems.
When any organism dies, it is eventually eaten by detritivores (such as hyenas, vultures, worms, crabs, etc.) and the rest is decomposed by decomposers (mainly bacteria and fungi), and energy exchange continues.
Arrows in a food chain show the flow of energy, from the sun or hydrothermal vents to top predators. As energy flows from body to body, it is lost at each link in the chain. The collection of many food chains is called food web.
The position of some organisms in the food chain may vary because their diet is different. For example, when a bear eats berries, it acts as a herbivore. When it eats a plant-eating rodent, it becomes a primary predator. When a bear eats salmon, it acts as a superpredator (this is due to the fact that salmon is the primary predator because it feeds on herring, which eats zooplankton, which feeds on phytoplankton, which generate their own energy from sunlight). Think about how people's place in the food chain changes, even often within a single meal.
Types of food chains
In nature, as a rule, there are two types of food chains: pasture and detritus.
Grassland food chain
Grassland food chain diagram
This type of food chain begins with living green plants to feed the herbivores on which carnivores feed. Ecosystems with this type of chain are directly dependent on solar energy.
Thus, the grazing type of food chain depends on the autotrophic capture of energy and its movement along the links of the chain. Most ecosystems in nature follow this type of food chain.
Examples of grazing food chains:
- Grass → Grasshopper → Bird → Hawk;
- Plants → Hare → Fox → Lion.
Detrital food chain
Detrital food chain diagram
This type of food chain begins with decaying organic material - detritus - which is consumed by detritivores. Then, predators feed on detritivores. Thus, such food chains are less dependent on direct solar energy than grazing ones. The main thing for them is the influx of organic substances produced in another system.
For example, this type of food chain is found in decomposing litter.
Energy in the food chain
Energy is transferred between trophic levels when one organism feeds on and receives nutrients from another. However, this movement of energy is inefficient, and this inefficiency limits the length of food chains.
When energy enters a trophic level, some of it is stored as biomass, as part of the body of organisms. This energy is available for the next trophic level. Typically, only about 10% of the energy that is stored as biomass at one trophic level is stored as biomass at the next level.
This principle of partial energy transfer limits the length of food chains, which typically have 3-6 levels.
At each level, energy is lost in the form of heat, as well as in the form of waste and dead matter that decomposers use.
Why does so much energy leave the food web between one trophic level and the next? Here are some of the main reasons for inefficient energy transfer:
- At each trophic level, a significant portion of energy is dissipated as heat as organisms perform cellular respiration and move around in daily life.
- Some organic molecules that organisms feed on cannot be digested and are excreted as feces.
- Not all individual organisms in a trophic level will be eaten by organisms from the next level. Instead, they die without being eaten.
- Feces and uneaten dead organisms become food for decomposers, who metabolize them and convert them into their energy.
So, none of the energy actually disappears - it all ends up producing heat.
Food chain meaning
1. Food chain studies help understand feeding relationships and interactions between organisms in any ecosystem.
2. Thanks to them, it is possible to evaluate the mechanism of energy flow and the circulation of substances in the ecosystem, as well as understand the movement of toxic substances in the ecosystem.
3. Studying the food chain provides insight into biomagnification issues.
In any food chain, energy is lost every time one organism is consumed by another. In this regard, there should be much more plants than herbivorous animals. There are more autotrophs than heterotrophs, and therefore most of them are herbivores rather than carnivores. Although there is intense competition between animals, they are all interconnected. When one species goes extinct, it can affect many other species and have unpredictable consequences.
In living nature there are practically no living organisms that do not eat other creatures or are not food for someone. Thus, many insects feed on plants. The insects themselves are prey for larger creatures. Certain organisms are the links from which the food chain is formed. Examples of such “dependence” can be found everywhere. Moreover, in any such structure there is a first initial level. As a rule, these are green plants. What are some examples of food? What organisms can be links? How does the interaction between them occur? More on this later in the article.
General information
The food chain, examples of which will be given below, is a certain set of microorganisms, fungi, plants, animals. Each link is at its own level. This “dependence” is built on the principle “food - consumer”. At the top of many food chains is man. The higher the population density in a particular country, the fewer links will be contained in the natural sequence, since people are forced in such conditions to eat plants more often.
Number of levels
How does interaction occur within ecological pyramids?
How does the food chain work? The examples given above show that each subsequent link should be more high level development than the previous one. As already mentioned, relationships in any ecological pyramid are built on the “food-consumer” principle. Due to the consumption of some organisms by others, energy is transferred from lower to higher levels. The result occurs in nature.
Food chain. Examples
Conventionally, several types of ecological pyramids can be distinguished. There is, in particular, a grazing food chain. Examples that can be seen in nature are sequences where the transfer of energy occurs from lower (protozoan) organisms to higher (predator) organisms. Such pyramids, in particular, include the following sequences: “caterpillars-mice-vipers-hedgehogs-foxes”, “rodents-predators”. The other, detrital food chain, examples of which will be given below, is a sequence in which the biomass is not consumed by predators, but a process of decay with the participation of microorganisms takes place. It is believed that this ecological pyramid begins with plants. This is, in particular, what the forest food chain looks like. Examples include the following: “fallen leaves—rotting with the participation of microorganisms,” “dead (carnivorous)—predators—centipedes—bacteria.”
Producers and consumers
In a large body of water (ocean, sea), planktonic organisms are food for Cladocera (animal filter feeders). They, in turn, are prey for predatory mosquito larvae. A certain type of fish feeds on these organisms. They are eaten by larger predatory individuals. This ecological pyramid is an example of a sea food chain. All organisms acting as links are at different trophic levels. At the first stage there are producers, at the next - consumers of the first order (consumers). By the third trophic level include 2nd order consumers (primary carnivores). They, in turn, serve as food for secondary predators - third-order consumers, and so on. As a rule, ecological pyramids of land include three to five links.
open water
Beyond the shelf sea, in the place where the slope of the continent breaks off more or less abruptly towards the deep-sea plain, the open sea begins. This area has predominantly blue and clear water. This is due to the absence of inorganic suspended compounds and a smaller volume of microscopic planktonic plants and animals (phyto- and zooplankton). In some areas, the surface of the water has a particularly bright blue color. For example, in such cases they talk about so-called ocean deserts. In these zones, even at a depth of thousands of meters, using sensitive equipment, traces of light (in the blue-green spectrum) can be detected. The open sea is characterized by the complete absence of various larvae of benthic organisms (echinoderms, mollusks, crustaceans) in the composition of zooplankton, the number of which sharply decreases with distance from the coast. Both in shallow water and in wide open spaces, the only source of energy is sunlight. As a result of photosynthesis, phytoplankton uses chlorophyll to form organic compounds from carbon dioxide and water. This is how the so-called primary products are formed.
Links in the sea food chain
Organic compounds synthesized by algae are transferred indirectly or directly to all organisms. The second link in the food chain in the sea is animal filter feeders. The organisms that make up phytoplankton are microscopically small in size (0.002-1mm). They often form colonies, but their size does not exceed five millimeters. The third link is carnivores. They are filter feeders. In the shelf, as well as in the open seas, there are quite a lot of such organisms. These, in particular, include siphonophores, ctenophores, jellyfish, copepods, chaetognaths, and carinarids. Among fish, herring should be classified as filter feeders. Their main food is the large aggregations that form in northern waters. The fourth link is considered to be predatory large fish. Some species are of commercial importance. The final link should also include cephalopods, toothed whales and seabirds.
Nutrient transfer
The transfer of organic compounds within food chains is accompanied by significant energy losses. This is mainly due to the fact that most of it is spent on metabolic processes. About 10% of the energy is converted into body matter by the organism. Therefore, for example, the anchovy, which feeds on planktonic algae and is part of an exceptionally short food chain, can develop in such huge quantities as it does in the Peruvian Current. The transfer of food into the twilight and deep zones from the light zone is due to active vertical migrations of zooplankton and individual species fish Animals moving up and down different times days they end up at different depths.
Conclusion
It should be said that linear food chains are quite rare. Most often, ecological pyramids include populations belonging to several levels at once. The same species can eat both plants and animals; carnivores can feed on both first- and second-order consumers; Many animals consume living and dead organisms. Due to the complexity of linkages, the loss of a species often has virtually no effect on the state of the ecosystem. Those organisms that took the missing link for food may well find another source of food, and other organisms begin to consume the food of the missing link. This way the community as a whole maintains balance. It will be more stable ecological system, which contains more complex chains nutrition, consisting of a large number of links, including many different types.
