Consumers 1.2.3 4 order examples. Food chain. Functional organization of ecosystems

Within an ecosystem, energy-containing organic substances 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 can be transferred through a number of organisms - each subsequent one feeds on the previous one, which supplies it with raw materials and energy. This sequence is called food chain, and each of its links is trophic level(Greek trophos - food). The first trophic level is occupied by autotrophs, or so-called primary producers. Organisms of the second trophic level are called primary consumers, third - secondary consumers etc. There are usually four or five trophic levels and rarely more than six - for reasons described in Sect. 12.3.7 and 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 single-celled organisms that make up the phytoplankton of the surface layers of oceans and lakes. On land, most of the primary production is supplied by more highly organized forms related to gymnosperms and angiosperms. They form forests and meadows.

Primary consumers

Primary consumers feed on primary producers, i.e. herbivores. On land, typical herbivores include many insects, reptiles, birds and mammals. The most important groups of herbivorous mammals are rodents and ungulates. The latter include grazing animals such as horses, sheep, and cattle, which are adapted to running on their toes.

In aquatic ecosystems (freshwater and marine), herbivorous forms are usually represented by mollusks and small crustaceans. Most of these organisms—cladocerans, copepods, crab larvae, barnacles, and bivalves (such as mussels and oysters)—feed by filtering tiny primary producers from the water, as described in Section 1. 10.2.2. Together with protozoa, many of them form the bulk of the zooplankton that feed on phytoplankton. Life in oceans and lakes depends almost entirely on plankton, since almost all food chains begin with them.

Consumers of the second third order

In typical carnivore food chains, carnivores are larger at each trophic level:

Plant material (eg nectar) fly → spider → shrew owl

Rosebush juice → aphids → ladybug → spider → insectivorous bird → bird of prey

Decomposers and detritivores (detritus food chains)

There are two main types of food chains - grazing and detrital. We gave examples above pasture chains, in which the first trophic level is occupied by green plants, the second by grazing animals (the term "grazing" is used in a broad sense and includes all organisms that feed on plants), and the third by carnivores. The bodies of dead plants and animals still contain energy and “building material,” as well as intravital excretions, 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 decomposers. They release digestive enzymes onto dead bodies or waste products and absorb the products of their digestion. The rate of decomposition may vary. Organic matter from urine, feces and animal carcasses is consumed within weeks, while fallen trees and branches can take many years to decompose. A very significant role in the decomposition of wood (and other plant debris) is played by fungi, which secrete the enzyme cellulase, 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 ( detritivores) feed on it, accelerating the decomposition process. Since both true decomposers (fungi and bacteria) and detritivores (animals) are involved in this process, both are sometimes called decomposers, although in reality this term refers only to saprophytic organisms.

Larger organisms can, in turn, feed on detritivores, and then a different type of food chain is created - a chain starting with detritus:

Detritus → detritivore → predator

Some detritivores of forest and coastal communities are shown in Fig. 12.5.

Here are two typical detrital food chains in our forests:

Leaf litter → Earthworm → Lumbricus sp. → Blackbird → Sparrowhawk Turdus merula Accipiter nisus Dead animal → Carrion fly larvae → Calliphora vomitoria, etc. → Common frog → Common grass snake Rana temporaria Natrix natrix

Some typical terrestrial detritivores are earthworms, woodlice, bipeds and smaller ones (

In ecology, to analyze a system, an elementary structural unit is chosen as an object of study, which is subjected to comprehensive study. A necessary condition for constructing a structural unit is that it retains all the properties of the system.

The concept of “system” means a set of interconnected, mutually influencing, interdependent components that do not come together by chance, but constitute a single whole.

For natural ecosystems, the object of study is a biogeocenosis, the structural diagram of which is presented in Fig. 1.

Fig.1. Scheme of biogeocenosis (ecosystem), according to V.N. Sukachev

In accordance with the structural diagram, the biogeocenosis includes two main blocks:

biotope - a set of abiotic environmental factors or the entire complex of inanimate nature factors;

(ecotope is a term close to biotope, but emphasizing environmental factors external to the community, not only abiotic, but also biotic)

biocenosis - a collection of living organisms.

Biotope, in turn consists of a set of climatic (climatope) and soil-ground (edaphoto) and hydrological (hydrotope) environmental factors.

Biocenosis includes plant communities (phytocenosis ), animals (zoocenosis) and microorganisms (microbocenosis ).

The arrows in Fig. 1 indicate channels for transmitting information between various components of the biogeocenosis.

One of the most important properties of biogeocenosis is interrelation and interdependence of all its components.

It is quite clear that climate entirely determines the state and regime of soil and ground factors and creates a habitat for living organisms.

In turn, the soil to some extent determines climatic characteristics (for example, its reflectivity (albedo), and, consequently, the warming and humidity of the air depends on the color of the soil surface), and also affects animals, plants and microorganisms.

All living organisms are closely connected with each other by various food, spatial or environment-forming relationships, being for each other either a source of food, or a habitat, or a factor of mortality.

The role of microorganisms (primarily bacteria) in the processes of soil formation, mineralization of organic matter and often acting as pathogens of plant and animal diseases is especially important.

2.2. Functional organization of ecosystems.

The main function of ecosystems is to maintain the cycle of substances in the biosphere, which is based on the nutritional relationships of species.

Despite the huge diversity of species that make up various communities, each ecosystem necessarily includes representatives of three functional groups of organisms - producers, consumers and decomposers.

The basis of the vast majority of biogeocenoses is producers (manufacturers) - these are autotrophic organisms (from the Greek “auto” - self and “tropho” - food) , which have the ability to synthesize organic substances from inorganic ones, 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, using solar energy, are able to create organic substances through the process of photosynthesis.

Photoautotrophic organisms include plants, as well as blue-green algae (cyanobacteria).

However, not all plants are producers, for example:

some fungi (cap mushrooms, molds), as well as some flowering species (for example, podelnik), which do not contain chlorophyll, are not capable of photosynthesis and therefore feed on ready-made 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 chemoautotrophic organisms is small 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 to consumers and decomposers.

Consumers (consumers) - these are heterotrophic organisms (from the Greek “hetero” - different) , which use living organic matter as food to obtain and store energy.

The main source of energy for heterotrophic organisms is the energy released during the breakdown of chemical bonds of organic substances created by autotrophic organisms.

Thus, heterotrophs are entirely dependent on autotrophs.

Depending on the power sources, there are:

First-order consumers (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 types of insects consume all parts of plants;

In aquatic ecosystems, zooplankton (small animals that move primarily with the flow of water) feed on phytoplankton (microscopic, usually single-celled algae).

Second-order consumers (zoophagous) are carnivorous organisms that feed exclusively on herbivorous organisms (phytophagous).

Examples of secondary consumers are:

insectivorous mammals, birds and spiders that eat insects;

seagulls eating shellfish and crabs;

fox eating hares;

tuna feeding on herring and anchovies.

Third-order consumers are predators that feed only on carnivorous organisms.

Examples of tertiary consumers are:

a hawk or falcon that feeds on snakes and stoats;

sharks feeding on other fish.

Meet consumers of the fourth and higher orders.

In addition, there are many types with mixed type of nutrition :

when a person eats fruits and vegetables, he is a consumer of the first order;

when a person eats the meat of a herbivorous animal, he is a secondary consumer;

when a person eats fish that feed on other animals, which in turn eat algae, then the person acts as a third-order consumer.

Euryphages are omnivorous organisms that feed on both plant and animal foods.

For example: pigs, rats, foxes, cockroaches and humans.

Decomposers (destroyers)- these are heterotrophic organisms that feed on dead organic matter and mineralize it into simple inorganic compounds.

There are two main types of decomposers: detritivores and destructors.

Detritivores are organisms that directly consume dead plant and animal remains (detritus).

Detritivores include: jackals, vultures, crabs, termites, ants, earthworms, centipedes, etc.

Decomposers 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 animal residues, as they gravitate toward substrates with a slightly alkaline reaction.

Mushrooms, on the contrary, prefer slightly acidic substrates, so they take a major part in the decomposition of plant residues.

Thus, Each living organism within the biogeocenosis performs a specific function, i.e. occupies a certain ecological niche in a complex system of ecological relationships with other organisms and inanimate factors.

For example, in different parts of the world and in different territories there are species that are not systematically identical, but are ecologically similar and perform the same functions in their biogeocenoses:

The herbaceous and forest vegetation of Australia differs significantly in species composition from the vegetation of a similar climatic region in Europe or Asia, but as producers in their biogeocenoses they perform the same functions, i.e. occupy basically the same ecological niches;

antelopes in the savannas of Africa, bison in the prairies of America, kangaroos in the savannas 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 systematically close, settling nearby in the same biogeocenosis, perform unequal functions, i.e. occupy different ecological niches:

two species of water bugs in the same body of water play different roles: one species leads a predatory lifestyle and is a tertiary consumer, while the other feeds on dead and decaying organisms and is a decomposer. 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 feeds on plant foods and is a primary consumer, and the adult frog is a typical carnivore and is a 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 certain ecological niches.

The food chain has a certain structure. It includes producers, consumers (first, second order, etc.) and decomposers. More details about consumers will be discussed in the article. In order to thoroughly understand who consumers of the 1st order, 2nd order and beyond are, we first briefly consider the structure of the food chain.

Structure of the food chain

The next link in the chain and, accordingly, the tier of the food pyramid are consumers (of several orders). This is the name given to organisms that producers consume as food. They will be discussed in detail below.

And finally, decomposers are the final tier of the food pyramid, the last link in the chain, “orderly” organisms. This is an integral and very important component of the ecosystem. They process and decompose high-molecular organic compounds into inorganic ones, which are then reused by autotrophs. Most of them are organisms of fairly small size: insects, worms, microorganisms, etc.

Who are consumers

As mentioned above, consumers are located on the second tier of the food pyramid. These organisms, unlike producers, do not have the ability for photo- and chemosynthesis (the latter is understood as the process by which archaea and bacteria obtain the energy necessary for the synthesis of organic substances from carbon dioxide). Therefore, they must feed on other organisms - those who have such an ability, or their own kind - other consumers.

Animals are consumers of the 1st order

This link in the food chain includes heterotrophs, which, unlike decomposers, are not capable of decomposing organic substances into inorganic ones. The so-called primary consumers (1st order) are those that directly feed on the biomass producers themselves, that is, producers. These are primarily herbivores - so-called phytophages.

This group includes both giant mammals, such as elephants, and small insects - locusts, aphids, etc. It is not difficult to give examples of consumers of the 1st order. These are almost all animals bred by humans in agriculture: cattle, horses, rabbits, sheep.

Among wild animals, the beaver is a phytophagous animal. It is known that it uses tree trunks to build dams, and uses their branches for food. Some species of fish, such as grass carp, are also herbivores.

Plants are consumers of the first order

To summarize, we can draw the following conclusion: consumers are organisms that feed on plants.

Consumers of the second order and beyond

In turn, consumers of the 3rd order are those who eat consumers of the previous order, that is, larger predators, of the 4th are those who eat consumers of the third. Above the fourth level, the food pyramid, as a rule, does not exist, since energy losses from the producing organism to the consumer at the previous levels are quite large. After all, they are inevitable at every level.

It is also often difficult, and sometimes impossible, to draw a clear boundary between consumers of certain orders. After all, some animals are simultaneously consumers of different levels.

Also, many of them are omnivores, for example a bear, that is, consumers of the first and second order at the same time. The same applies to a person who is omnivorous, although due to different views, traditions or living conditions, he may, for example, eat food only of plant origin.

The meadow is home to a variety of organisms: goshawk, common starling, common cress, red clover and cabbage white butterfly. Which named organisms can be used to make up a food chain, compose it. Identify the second-order consumer in this chain. Select pairs of organisms that enter into competitive relationships with each other.

Answer

Food chain: common cress → cabbage white butterfly → common starling → goshawk. The second-order consumer is the common starling. Competitors include common cress and meadow clover.

The reservoir is home to a variety of organisms: perch, pike, single-celled green algae (chlorella), daphnia, and tadpoles. Make a food chain from the named organisms. Specify a third-order consumer. Select pairs of organisms that engage in predator-prey relationships.

Answer

Food chain: chlorella → daphnia → tadpoles → perch → pike. The third-order consumer is perch. Tadpoles and daphnia, perch and tadpoles, pike and perch enter into predator-prey relationships.

Make a food chain using all the named representatives: great tit, apple beetle, hawk, apple flowers. Identify the second-order consumer in the constructed chain.

Answer

Food chain: apple blossoms → apple beetle → great tit → hawk. The second-order consumer is the great tit.

Make a food chain using all of the following objects: humus, cross spider, hawk, great tit, housefly. Identify the third-order consumer in the constructed chain.

Answer

Food chain: humus → housefly → cross spider → great tit → hawk. The third-order consumer is the great tit.

1. The pasture food chain of biogeocenosis includes producers and consumers. 2. The first link in the food chain is producers. 3. Second-order consumers eat plant foods. 4. Producers in the dark phase of photosynthesis form ATP molecules. 5. Decomposers destroy organic substances formed only by consumers into inorganic ones.

Answer

3. Second-order consumers eat animal food (first-order consumers).
4. Producers form ATP in the light phase of photosynthesis, and in the dark phase they form glucose.
5. Decomposers destroy organic substances formed not only by consumers, but also by producers.

Find errors in the given text. Indicate the numbers of the sentences in which they are made, write the correct answer.
1. The food chain of biogeocenosis includes producers, consumers and decomposers. 2. The first link in the food chain is consumers. 3. Consumers in the light accumulate energy acquired during photosynthesis. 4. In the dark phase of photosynthesis, oxygen is released. 5. Decomposers contribute to the release of energy accumulated by consumers and producers.

Answer

2. The first link in the food chain is producers.
3. Producers in the light accumulate energy acquired during photosynthesis.
4. In the dark phase of photosynthesis, oxygen is not released.

Why can granivorous birds at different periods of life (dispersal, reproduction) occupy the place of consumers of the first and second orders in food chains?

Answer

Granivorous birds themselves feed on grains (they are consumers of the first order), and their chicks are fed with insects (at this moment they are consumers of the second order).

Blood-sucking insects are common inhabitants of many biocenoses. Explain in what cases they occupy the position of consumers of the II, III and even IV orders in food chains.

Answer

A blood-sucking insect is a second-order consumer if it feeds on the blood of a first-order consumer (a herbivore, for example, a cow).
A blood-sucking insect is a consumer of the third order if it feeds on the blood of a consumer of the second order (a small predator, for example, a fox).
A blood-sucking insect is a fourth-order consumer if it feeds on the blood of a third-order consumer (a large predator, for example, a tiger).

Why are owls classified as second-order consumers in a forest ecosystem, and mice as first-order consumers?

Food chains and trophic levels are considered integral components of the biological cycle. There are many elements involved. Next, let's take a closer look at the trophic levels of the ecosystem.

Terminology

A food chain is the movement of energy contained in plant foods through a number of organisms as a result of them eating each other. Only plants form organic matter from inorganic matter. A trophic level is a complex of organisms. Interaction occurs between them in the process of transferring nutrients and energy from the source. Trophic chains (trophic level) presuppose a certain position of organisms at one or another stage (link) during this movement. Marine and terrestrial biological structures differ in many ways. One of the main ones is that in the former the food chains are longer than in the latter.

steps

The first trophic level is represented by autotrophs. They are also called producers. The second trophic level consists of the original consumers. At the next stage are consumers who consume herbivorous organisms. These consumers are called secondary. These include, for example, primary predators, carnivores. Also, the 3rd trophic level includes consumers of the 3rd order. They, in turn, consume weaker predators. As a rule, there is a limited number of trophic levels - 4 or 5. There are rarely more than six. This food chain is usually closed by decomposers or decomposers. They are bacteria, microorganisms that decompose organic residues.

Consumers: general information

They are not just "eaters" that the food chain contains. They satisfy their needs through a feedback (positive) feedback system. Consumers influence higher trophic levels of the ecosystem. So, for example, the consumption of vegetation in African savannas by large herds of antelopes, together with fires during the dry period, helps to increase the rate of return of nutrients to the soil. Subsequently, during the rainy season, herbaceous regeneration and production increases.

Odum's example is quite interesting. It describes the effects of consumers on producers in a marine ecosystem. Crabs, which consume detritus and algae, "look after" their grasses in several ways. They break up the soil, thereby increasing the circulation of water near the roots and introducing oxygen and necessary elements into the anaerobic coastal zone. In the process of constantly processing bottom silts rich in organic matter, crabs help improve conditions for the development and growth of benthic algae. One trophic level consists of organisms that obtain energy through the same number of steps.

Structure

Food consumed at each trophic level is not completely 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. Within a biological system, organic compounds containing energy are produced by autotrophic organisms. These substances are a source of energy and necessary components for heterotrophs. A simple example is the following: an animal consumes plants. In turn, the animal can be eaten by another larger representative of the fauna. This way energy can be transferred through several organisms. The next one uses the previous one, which supplies energy and nutrients. It is this sequence that forms the food chain, in which the trophic level is the link.

1st order producers

The initial trophic level contains autotrophic organisms. These mainly include green spaces. Some prokaryotes, in particular blue-green algae, as well as a few species of bacteria, also have the ability to photosynthesize. However, their contribution to the trophic level is insignificant.

Thanks to the activity of photosynthetics, solar energy is converted into chemical energy. It consists of 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 are the main producers in aquatic ecosystems. They are often represented by small unicellular organisms that form phytoplankton in the surface layers of lakes and oceans. Most of the primary production on land comes in more highly organized forms. They belong 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, detritus and pasture structures are distinguished. Examples of the latter are described above. They contain green plants on the first level, grazing animals on the second, and predators on the third. However, the bodies of dead plants and animals still contain energy and “building material” along with intravital excretions (urine and feces). All these organic materials are subject to decomposition due to the activity of microorganisms - bacteria and fungi. They live on organic debris as saprophytes.

Organisms of this type are called decomposers. They secrete digestive enzymes onto waste products or dead bodies, and then absorb the digestion products. Decomposition can occur at different rates. Consumption of organic compounds from feces, urine, and animal corpses occurs over several weeks. However, fallen branches or trees can take years to decompose.

Detritivores

Fungi play a significant role in the process of wood decay. They secrete the enzyme cellulase. It has a softening effect on the wood, which makes it possible for small animals to penetrate and absorb the material. Fragments of decayed material are called detritus. Many small living organisms (detritivores) feed on it and accelerate the process of destruction.

Since two types of organisms (fungi and bacteria, as well as animals) participate in decomposition, they are often combined under one name - “decomposers”. But in reality, this term applies only to saprophytes. Detritivores, in turn, can be consumed by larger organisms. In this case, a chain of a different type is formed - starting with detritus. Detritivores of coastal and forest communities include woodlice, earthworm, carrion fly larva, scarlet fly, sea cucumber, and polychaete.

food web

In systems diagrams, each organism can be represented as consuming others of a particular type. But the food connections existing in the biological structure have a much more complex structure. This is because an animal can consume a variety of different types of organisms. Moreover, they may belong to the same food chain or belong to different ones. This is especially evident among predators located 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, this is how humans are. In the existing biological system, intertwined food chains are quite common. As a result, a new multicomponent structure is formed - a network. The diagram can only reflect some of all possible connections. As a rule, it contains only one or two predators belonging to the upper trophic levels. In the flow of energy and circulation within a typical structure, there can be two exchange paths. On the one hand, interaction occurs between predators, on the other, between decomposers and detritivores. The latter can consume dead animals. At the same time, living decomposers and detritivores can act as food for predators.