The meadow is home to a variety of organisms: the goshawk, the common starling, the common cress, red clover and the 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 inhabited by 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 absorbed 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?

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.

4.2. Primary consumers

Primary consumers feed on primary producers, i.e. they are 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. 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 it.

4.3. Second and third order consumers

Plant material ( for example, nectar) → fly → spider →

→ shrew → owl

Rosebush sap → aphid → ladybug → spider → insectivorous bird → bird of prey

4.4. Decomposers and detritivores (detritus food chains)

There are two main types of food chains – grazing and detrital. Above were examples of pasture chains in which the first trophic level is occupied by green plants, the second by pasture animals and the third by predators. The bodies of dead plants and animals still contain energy and “building material,” as well as intravital 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 a few 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 them, speeding up 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, a chain starting with detritus:

Detritus → detritivore → predator

Detritivores of forest and coastal communities include earthworm, woodlice, carrion fly larva (forest), polychaete, scarlet fly, holothurian (coastal zone).

Here are two typical detrital food chains in our forests:

Leaf litter → Earthworm → Blackbird → Sparrowhawk

Dead animal → Carrion fly larvae → Grass frog → Common grass snake

Some typical detritivores are earthworms, woodlice, bipeds and smaller ones (<0,5 мм) животные, такие, как клещи, ногохвостки, нематоды и черви-энхитреиды.

5. Food webs

In food chain diagrams, each organism is represented as feeding on other organisms of one type. However, actual food relationships in an ecosystem are much more complex, since an animal may feed on different types of organisms from the same food chain or even from different food chains. This is especially true for predators of the upper trophic levels. Some animals eat both other animals and plants; they are called omnivores (this is the case, in particular, with humans). In reality, food chains are intertwined in such a way that a food (trophic) web is formed. A food web diagram can only show a few of the many possible connections, and it usually includes only one or two predators from each of the upper trophic levels. Such diagrams illustrate nutritional relationships between organisms in an ecosystem and provide the basis for quantitative studies of ecological pyramids and ecosystem productivity.

6. Ecological pyramids.

6.1. Pyramids of numbers.

To study the relationships between organisms in an ecosystem and to graphically represent these relationships, it is more convenient to use ecological pyramids rather than food web diagrams. In this case, the number of different organisms in a given territory is first counted, grouping them by trophic levels. After such calculations, it becomes obvious that the number of animals progressively decreases during the transition from the second trophic level to subsequent ones. The number of plants at the first trophic level also often exceeds the number of animals that make up the second level. This can be depicted as a pyramid of numbers.

For convenience, the number of organisms at a given trophic level can be represented as a rectangle, the length (or area) of which is proportional to the number of organisms living in a given area (or in a given volume, if it is an aquatic ecosystem). The figure shows a population pyramid reflecting the real situation in nature. Predators located at the highest trophic level are called final predators.

Fourth trophic level Tertiary consumers

Food (trophic) chain- a series of species of plants, animals, fungi and microorganisms that are connected to each other by the relationship: food - consumer.

The organisms of the subsequent link eat the organisms of the previous link, and thus a chain transfer of energy and matter occurs, which underlies the cycle of substances in nature. With each transfer from link to link, a large part (up to 80-90%) of the potential energy is lost, dissipated in the form of heat. For this reason, the number of links (types) in the food chain is limited and usually does not exceed 4-5.

Usually, for each link in the chain, you can specify not one, but several other links connected to it by the “food-consumer” relationship. So, not only cows, but also other animals eat grass, and cows are food not only for humans. The establishment of such connections turns the food chain into a more complex structure - a trophic network.

Trophic level

Trophic level- a conventional unit indicating the distance from producers in the trophic chain of a given ecosystem.

In some cases, in a trophic network, it is possible to group individual links into levels in such a way that links at one level act only as food for the next level. This grouping is called a trophic level.

Producers(autotrophic organisms or autotrophs) - organisms capable of synthesizing organic substances from inorganic ones. These are mainly green plants (they synthesize organic substances from inorganic substances during the process of photosynthesis), however, some types of chemotrophic bacteria are capable of purely chemical synthesis of organic matter without sunlight. Producers are the first link in the food chain.

Decomposers- microorganisms (bacteria and fungi) that destroy dead remains of dead creatures, turning them into inorganic compounds and the simplest organic compounds. Decomposers return mineral salts to the soil and water, making them available to autotrophic producers, and thus closing the biotic cycle. Therefore, ecosystems cannot survive without decomposers (unlike consumers, which were probably absent from ecosystems during the first 2 billion years of evolution, when ecosystems consisted of only prokaryotes).

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 eats 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 absorbed 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.

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 features (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 consumer of the third order.

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.