A food chain is the transfer of energy from its source through a series of organisms. All living beings are connected because they serve as food sources for other organisms. All power chains consist of three to five links. The first are usually producers - organisms that are capable of producing organic substances from inorganic ones. These are plants that obtain nutrients through photosynthesis. Next come consumers - these are heterotrophic organisms that receive ready-made organic substances. These will be animals: both herbivores and predators. The final link in the food chain is usually decomposers - microorganisms that decompose organic matter.
The food chain cannot consist of six or more links, since each new link receives only 10% of the energy of the previous link, another 90% is lost in the form of heat.
What are food chains like?
There are two types: pasture and detrital. The first ones are more common in nature. In such chains, the first link is always the producers (plants). They are followed by consumers of the first order - herbivores. Next are second-order consumers - small predators. Behind them are consumers of the third order - large predators. Further, there may also be fourth-order consumers, such long food chains usually found in oceans. The last link is the decomposers.
The second type of power circuit is detrital- more common in forests and savannas. They arise due to the fact that most of the plant energy is not consumed by herbivores, but dies, then undergoing decomposition by decomposers and mineralization.
Food chains of this type begin from detritus - organic remains of plant and animal origin. The first-order consumers in such food chains are insects, for example, dung beetles, or scavenger animals, for example, hyenas, wolves, vultures. In addition, bacteria that feed on plant residues can be first-order consumers in such chains.
In biogeocenoses, everything is connected in such a way that most species of living organisms can become participants in both types of food chains.
Food chains in deciduous and mixed forests
Deciduous forests are mostly found in the Northern Hemisphere of the planet. They are found in Western and Central Europe, in Southern Scandinavia, in the Urals, in Western Siberia, East Asia, North Florida.
Deciduous forests are divided into broad-leaved and small-leaved. The former are characterized by trees such as oak, linden, ash, maple, and elm. For the second - birch, alder, aspen.
Mixed forests are those in which both coniferous and deciduous trees grow. Mixed forests are characteristic of temperate climate zone. They are found in the south of Scandinavia, in the Caucasus, in the Carpathians, on Far East, in Siberia, in California, in the Appalachians, near the Great Lakes.
Mixed forests consist of trees such as spruce, pine, oak, linden, maple, elm, apple, fir, beech, and hornbeam.
Very common in deciduous and mixed forests pastoral food chains. The first link in the food chain in forests is usually numerous types of herbs and berries, such as raspberries, blueberries, and strawberries. elderberry, tree bark, nuts, cones.
First-order consumers will most often be herbivores such as roe deer, moose, deer, rodents, for example, squirrels, mice, shrews, and hares.
Second-order consumers are predators. Usually these are fox, wolf, weasel, ermine, lynx, owl and others. A striking example The fact that the same species participates in both grazing and detrital food chains will be a wolf: it can both hunt small mammals and eat carrion.
Second-order consumers can themselves become prey for larger predators, especially birds: for example, small owls can be eaten by hawks.
The closing link will be decomposers(rotting bacteria).
Examples of food chains in a deciduous-coniferous forest:
- birch bark - hare - wolf - decomposers;
- wood - chafer larva - woodpecker - hawk - decomposers;
- leaf litter (detritus) - worms - shrews - owl - decomposers.
Features of food chains in coniferous forests
Such forests are located in northern Eurasia and North America. They consist of trees such as pine, spruce, fir, cedar, larch and others.
Here everything is significantly different from mixed and deciduous forests.
The first link in this case will not be grass, but moss, shrubs or lichens. This is due to the fact that in coniferous forests there is not enough light for a dense grass cover to exist.
Accordingly, animals that will become consumers of the first order will be different - they should feed not on grass, but on moss, lichens or shrubs. It can be some types of deer.
Despite the fact that shrubs and mosses are more common, they are still found in coniferous forests. herbaceous plants and bushes. These are nettle, celandine, strawberry, elderberry. Hares, moose, and squirrels usually eat this kind of food, which can also become consumers of the first order.
Second-order consumers will be, as in mixed forests, predators. These are mink, bear, wolverine, lynx and others.
Small predators such as mink can become prey for third-order consumers.
The closing link will be rotting microorganisms.
In addition, in coniferous forests they are very common detrital food chains. Here the first link will most often be plant humus, which feeds soil bacteria, becoming, in turn, food for single-celled animals that are eaten by mushrooms. Such chains are usually long and can consist of more than five links.
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Energy transfer in an ecosystem occurs through the so-called food chains. In turn, a food chain is the transfer of energy from its original source (usually autotrophs) through a number of organisms, by eating some by others. Food chains are divided into two types:
Scots pine => Aphids => Ladybugs => Spiders => Insectivores
birds => Birds of prey.
Grass => Herbivorous mammals => Fleas => Flagellates.
2) Detrital food chain. It originates from dead organic matter (the so-called detritus), which is either consumed by small, mainly invertebrate animals, or decomposed by bacteria or fungi. Organisms that consume dead organic matter are called detritivores, decomposing it - destructors.
Grassland and detrital food chains usually exist together in ecosystems, but one type of food chain almost always dominates the other. In some specific environments (for example, underground), where the vital activity of green plants is impossible due to the lack of light, only detrital food chains exist.
In ecosystems, food chains are not isolated from each other, but are closely intertwined. They make up the so-called food webs. This happens because each producer has not one, but several consumers, which, in turn, can have several food sources. The relationships within a food web are clearly illustrated by the diagram below.
Food web diagram.
In food chains, so-called trophic levels. Trophic levels classify organisms in the food chain according to their types of life activity or sources of energy. Plants occupy the first trophic level (the level of producers), herbivores (consumers of the first order) belong to the second trophic level, predators that eat herbivores form the third trophic level, secondary predators form the fourth, etc. first order.
Flow of energy in an ecosystem
As we know, energy transfer in an ecosystem occurs through food chains. But not all the energy from the previous trophic level is transferred to the next one. An example is the following situation: net primary production in an ecosystem (that is, the amount of energy accumulated by producers) is 200 kcal/m^2, secondary productivity (energy accumulated by first-order consumers) is 20 kcal/m^2 or 10% from the previous trophic level, the energy of the next level is 2 kcal/m^2, which is equal to 20% of the energy of the previous level. As can be seen from this example, with each transition to a higher level, 80-90% of the energy of the previous link in the food chain is lost. Such losses are due to the fact that a significant part of the energy during the transition from one stage to another is not absorbed by representatives of the next trophic level or is converted into heat, unavailable for use by living organisms.
Universal model of energy flow.
Energy intake and expenditure can be viewed using universal energy flow model. It applies to any living component of an ecosystem: plant, animal, microorganism, population or trophic group. Such graphical models, connected to each other, can reflect food chains (when the energy flow patterns of several trophic levels are connected in series, a diagram of the energy flow in the food chain is formed) or bioenergetics in general. The energy entering the biomass in the diagram is designated I. However, part of the incoming energy does not undergo transformation (in the figure it is indicated as NU). For example, this occurs when some of the light passing through plants is not absorbed by them, or when some of the food passing through the digestive tract of an animal is not absorbed by its body. Assimilated (or assimilated) energy (denoted by A) is used for various purposes. It is spent on breathing (in the diagram - R) i.e. to maintain the vital activity of biomass and to produce organic matter ( P). Products, in turn, take different forms. It is expressed in energy costs for biomass growth ( G), in various secretions of organic matter in external environment (E), in the body's energy reserves ( S) (an example of such a reserve is fat accumulation). The stored energy forms the so-called working loop, since this part of the production is used to provide energy in the future (for example, a predator uses its energy reserve to search for new victims). The remaining part of the production is biomass ( B).
The universal energy flow model can be interpreted in two ways. Firstly, it can represent a population of a species. In this case, the channels of energy flow and connections of the species in question with other species represent a diagram of the food chain. Another interpretation treats the energy flow model as an image of some energy level. The biomass rectangle and energy flow channels then represent all populations supported by the same energy source.
In order to clearly show the difference in approaches to interpreting the universal model of energy flow, we can consider an example with a population of foxes. Part of the foxes' diet consists of vegetation (fruits, etc.), while the other part consists of herbivores. To emphasize the aspect of intrapopulation energetics (the first interpretation of the energetic model), the entire fox population should be depicted as a single rectangle, if metabolism is to be distributed ( metabolism- metabolism, metabolic rate) fox populations into two trophic levels, that is, to display the relationship between the roles of plant and animal food in metabolism, it is necessary to construct two or more rectangles.
Knowing the universal model of energy flow, it is possible to determine the ratio of energy flow values at different points of the food chain. Expressed as a percentage, these ratios are called environmental efficiency. There are several groups of environmental efficiencies. The first group of energy relations: B/R And P/R. The proportion of energy spent on respiration is large in populations of large organisms. When exposed to stress from the external environment R increases. Magnitude P significant in active populations of small organisms (for example algae), as well as in systems that receive energy from the outside.
The following group of relations: A/I And P/A. The first of them is called efficiency of assimilation(i.e., the efficiency of using the supplied energy), the second - efficiency of tissue growth. Assimilation efficiency can vary from 10 to 50% or higher. It can either reach a small value (when the energy of light is assimilated by plants), or have large values (when the energy of food is assimilated by animals). Typically, the efficiency of assimilation in animals depends on their food. In herbivorous animals, it reaches 80% when eating seeds, 60% when eating young foliage, 30-40% when eating older leaves, 10-20% when eating wood. In carnivorous animals, the efficiency of assimilation is 60-90%, since animal food is much more easily absorbed by the body than plant food.
The efficiency of tissue growth also varies widely. It reaches its greatest values in cases where organisms are small in size and the conditions of their habitat do not require large energy expenditures to maintain the temperature optimal for the growth of organisms.
The third group of energy relations: P/B. If we consider P as the rate of increase in production, P/B represents the ratio of production at a particular point in time to biomass. If products are calculated for a certain period of time, the value of the ratio P/B is determined based on the average biomass over this period of time. IN in this case P/B is a dimensionless quantity and shows how many times the production is more or less than biomass.
It should be noted that the energy characteristics of an ecosystem are influenced by the size of the organisms inhabiting the ecosystem. A relationship has been established between the size of an organism and its specific metabolism (metabolism per 1 g of biomass). The smaller the organism, the higher its specific metabolism and, therefore, the lower the biomass that can be supported at a given trophic level of the ecosystem. With the same amount of energy used, organisms large sizes accumulate more biomass than small ones. For example, with equal energy consumption, the biomass accumulated by bacteria will be much lower than the biomass accumulated by large organisms (for example, mammals). A different picture emerges when considering productivity. Since productivity is the rate of biomass growth, it is greater in small animals, which have higher rates of reproduction and biomass renewal.
Due to the loss of energy within food chains and the dependence of metabolism on the size of individuals, each biological community acquires a certain trophic structure, which can serve as a characteristic of the ecosystem. The trophic structure is characterized either by the standing crop or by the amount of energy fixed per unit area per unit time by each subsequent trophic level. The trophic structure can be depicted graphically in the form of pyramids, the base of which is the first trophic level (the level of producers), and subsequent trophic levels form the “floors” of the pyramid. There are three types of ecological pyramids.
1) Number pyramid (indicated by number 1 in the diagram) It displays the number of individual organisms at each trophic level. The number of individuals at different trophic levels depends on two main factors. The first of them is more high level specific metabolism in small animals compared to large ones, which allows them to have a numerical superiority over large species and higher rates of reproduction. Another of the above factors is the existence of upper and lower limits on the size of their prey among predatory animals. If the prey is much larger in size than the predator, then it will not be able to defeat it. Small prey will not be able to satisfy the energy needs of the predator. Therefore, for each predatory species there is an optimal size of prey. However, there are exceptions to this rule (for example, snakes use venom to kill animals larger than themselves). Pyramids of numbers can be pointed downward if the producers are much larger than the primary consumers in size (an example is a forest ecosystem, where the producers are trees and the primary consumers are insects).
2) Biomass pyramid (2 in the diagram). With its help, you can clearly show the ratios of biomass at each of the trophic levels. It can be direct if the size and lifespan of producers reaches relatively large values (terrestrial and shallow-water ecosystems), and reversed when producers are small in size and have a short life cycle (open and deep water bodies).
3) Pyramid of energy (3 in the diagram). Reflects the amount of energy flow and productivity at each trophic level. Unlike pyramids of numbers and biomass, the pyramid of energy cannot be reversed, since the transition of food energy to higher trophic levels occurs with large energy losses. Consequently, the total energy of each previous trophic level cannot be higher than the energy of the next one. The above reasoning is based on the use of the second law of thermodynamics, so the pyramid of energy in an ecosystem serves as a clear illustration of it.
Of all the trophic characteristics of an ecosystem mentioned above, only the energy pyramid provides the most complete picture of the organization of biological communities. In the population pyramid, the role of small organisms is greatly exaggerated, and in the biomass pyramid, the importance of large ones is overestimated. In this case, these criteria are unsuitable for comparing the functional role of populations that differ greatly in the ratio of metabolic intensity to the size of individuals. For this reason, it is energy flow that serves as the most suitable criterion for comparing individual components of an ecosystem with each other, as well as for comparing two ecosystems with each other.
Knowledge of the basic laws of energy transformation in an ecosystem contributes to a better understanding of the functioning processes of the ecosystem. This is especially important due to the fact that human intervention in its natural “work” can lead to the destruction of the ecological system. In this regard, he must be able to predict the results of his activities in advance, and an understanding of energy flows in the ecosystem can provide greater accuracy of these predictions.
Introduction
1. Food chains and trophic levels
2. Food webs
3. Freshwater food connections
4. Forest food connections
5. Energy losses in power circuits
6. Ecological pyramids
6.1 Pyramids of numbers
6.2 Biomass pyramids
Conclusion
Bibliography
Introduction
Organisms in nature are connected by a commonality of energy and nutrients. The entire ecosystem can be likened to a single mechanism that consumes energy and nutrients to do work. Nutrients initially originate from the abiotic component of the system, to which they ultimately return either as waste products or after the death and destruction of organisms.
Within an ecosystem, energy-containing organic substances are created by autotrophic organisms and serve as food (a source of matter and energy) for heterotrophs. 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, supplying it with raw materials and energy. This sequence is called a food chain, and each link is called a trophic level.
The purpose of the essay is to characterize food connections in nature.
1. Food chains and trophic levels
Biogeocenoses are very complex. They always have many parallel and complexly intertwined power circuits, and total number species are often measured in hundreds and even thousands. Almost always different types They feed on several different objects and themselves serve as food for several members of the ecosystem. The result is a complex network of food connections.
Each link in the food chain is called a trophic level. The first trophic level is occupied by autotrophs, or the so-called primary producers. Organisms of the second trophic level are called primary consumers, the third - secondary consumers, etc. There are usually four or five trophic levels and rarely more than six.
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 organic molecules, from which fabrics are constructed. 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 the land most Primary production is supplied by more highly organized forms related to gymnosperms and angiosperms. They form forests and meadows.
Primary consumers feed on primary producers, i.e. they are herbivores. On land, typical herbivores include many insects, reptiles, birds and mammals. Most important groups herbivorous mammals are rodents and ungulates. The latter include grazing animals such as horses, sheep, large cattle, adapted for running on the tips of the fingers.
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 them.
Plant material (e.g. nectar) → fly → spider →
→ shrew → owl
Rosebush sap → aphid → ladybug→ spider → insectivorous bird → bird of prey
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 " construction 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 urine, feces and animal carcasses are consumed within a few weeks, while fallen trees and the 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 cellulose, 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.
2. 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.
3. Freshwater food connections
The food chains of a fresh water body consist of several successive links. For example, protozoa, which are eaten by small crustaceans, feed on plant debris and the bacteria that develop on them. The crustaceans, in turn, serve as food for fish, and the latter can be eaten by predatory fish. Almost all species do not feed on one type of food, but use different food objects. Food chains are intricately intertwined. An important general conclusion follows from this: if any member of the biogeocenosis falls out, then the system is not disrupted, since other food sources are used. The greater the species diversity, the more stable the system.
The primary source of energy in aquatic biogeocenosis, as in most ecological systems, is sunlight, thanks to which plants synthesize organic matter. Obviously, the biomass of all animals existing in a reservoir completely depends on the biological productivity of plants.
Most living organisms eat organic food, this is the specificity of their life activity on our planet. Among this food are plants, the meat of other animals, their products and dead matter ready for decomposition. The process of nutrition itself in different species of plants and animals occurs in different ways, but the so-called They are always formed. They transform matter and energy, and nutrients can thus pass from one creature to another, carrying out the cycle of substances in nature.
In the woods
Forests of various kinds cover quite a lot of land surface. These are lungs and a tool for cleansing our planet. It is not for nothing that many progressive modern scientists and activists today oppose mass deforestation. The food chain in the forest can be quite diverse, but, as a rule, it includes no more than 3-5 links. In order to understand the essence of the issue, let us turn to the possible components of this chain.
Producers and consumers
- The first are autotrophic organisms that feed on inorganic food. They take energy and matter to create their own bodies, using gases and salts from their environment. An example is green plants that get their food from sunlight through photosynthesis. Or numerous types of microorganisms that live everywhere: in the air, in the soil, in the water. It is the producers who, for the most part, constitute the first link in almost any food chain in the forest (examples will be given below).
- The second are heterotrophic organisms that feed on organic matter. Among them are those of the first order that directly provide nutrition through plants and bacteria producers. Second order - those who eat animal food (predators or carnivores).
Plants
As a rule, the food chain in the forest begins with them. They act as the first link in this cycle. Trees and shrubs, grasses and mosses extract food from inorganic substances using sunlight, gases and minerals. A food chain in a forest, for example, may begin with a birch tree, the bark of which is eaten by a hare, which in turn is killed and eaten by a wolf.
Herbivores
Animals that feed on plant foods are found in abundance in various forests. Of course, for example, it is very different in its content from the lands of the middle zone. The jungle is home to various species of animals, many of which are herbivores, which means they form the second link in the food chain, feeding on plant foods. From elephants and rhinoceroses to barely visible insects, from amphibians and birds to mammals. So, in Brazil, for example, there are more than 700 species of butterflies, almost all of them are herbivores.
The fauna, of course, is poorer in the forest belt of central Russia. Accordingly, there are much fewer power supply options. Squirrels and hares, other rodents, deer and moose, hares - this is the basis for such chains.
Predators or carnivores
They are called that because they eat flesh, feeding on the meat of other animals. They occupy a dominant position in the food chain, often being the final link. In our forests these are foxes and wolves, owls and eagles, sometimes bears (but in general they belong to those who can eat both plant and animal food). A food chain can involve either one or several predators that eat each other. The final link, as a rule, is the largest and most powerful carnivore. In the middle forest, this role can be performed, for example, by a wolf. There are not too many such predators, and their population is limited by the nutritional base and energy reserves. Since, according to the law of conservation of energy, during the transition of nutrients from one link to the next, up to 90% of the resource can be lost. This is probably why the number of links in most food chains cannot exceed five.
Scavengers
They feed on the remains of other organisms. Oddly enough, there are also quite a lot of them in the natural forest: from microorganisms and insects to birds and mammals. Many beetles, for example, use the corpses of other insects and even vertebrates as food. And bacteria are capable of decomposing the dead bodies of mammals in a fairly short time. Scavenger organisms play a huge role in nature. They destroy matter, converting it into inorganic substances, releasing energy, using it for their life activity. If it were not for scavengers, then, probably, the entire earthly space would be covered with the bodies of animals and plants that have died throughout time.
In the woods
To create a food chain in a forest, you need to know about the inhabitants who live there. And also about what these animals can eat.
- Birch bark - insect larvae - small birds - birds of prey.
- Fallen leaves are bacteria.
- Butterfly caterpillar - mouse - snake - hedgehog - fox.
- Acorn - mouse - fox.
- Cereals - mouse - eagle owl.
There is also a more authentic one: fallen leaves - bacteria - earthworms - mice - mole - hedgehog - fox - wolf. But, as a rule, the number of links is no more than five. The food chain in a spruce forest is slightly different from those in a deciduous forest.
- Cereal seeds - sparrow - wild cat.
- Flowers (nectar) - butterfly - frog - snake.
- Fir cone - woodpecker - eagle.
Food chains can sometimes intertwine with each other, forming more complex, multi-level structures that unite into a single forest ecosystem. For example, the fox does not disdain to eat both insects and their larvae, and mammals, thus several food chains intersect.
Who eats what
Make up a food chain that tells about the characters in the song “A grasshopper sat in the grass.”
Animals that eat plant foods are called herbivores. Those animals that eat insects are called insectivores. Larger prey is hunted by predatory animals, or raptors. Insects that eat other insects are also considered predators. Finally, there are omnivores (they eat both plant and animal foods).
What groups can animals be divided into based on their feeding methods? Fill out the chart.
Power circuits
Living things are connected to each other in a food chain. For example: Aspen trees grow in the forest. Hares eat their bark. A hare can be caught and eaten by a wolf. It turns out this food chain: aspen - hare - wolf.
Compose and write down power supply circuits.
a) spider, starling, fly
Answer: fly - spider - starling
b) stork, fly, frog
Answer: fly - frog - stork
c) mouse, grain, owl
Answer: grain - mouse - owl
d) slug, mushroom, frog
Answer: mushroom - slug - frog
d) hawk, chipmunk, cone
Answer: cone - chipmunk - hawk
Read short texts about animals from the book "With Love for Nature." Identify and write down the type of food animals eat.
In autumn, the badger begins to prepare for winter. He eats up and gets very fat. He eats everything he comes across: beetles, slugs, lizards, frogs, mice, and sometimes even small hares. He eats wild berries and fruits.
Answer: badger is omnivorous
In winter, the fox catches mice and sometimes partridges under the snow. Sometimes she hunts for hares. But hares run faster than a fox and can run away from it. In winter, foxes come close to human settlements and attack poultry.
Answer: carnivorous fox
At the end of summer and autumn, the squirrel collects mushrooms. She pins them on tree branches so that the mushrooms dry out. The squirrel also stuffs nuts and acorns into hollows and cracks. All this will be useful to her during the winter lack of food.
Answer: squirrel is herbivorous
The wolf is a dangerous beast. In summer he attacks various animals. It also eats mice, frogs, and lizards. Destroys bird nests on the ground, eats eggs, chicks, and birds.
Answer: carnivorous wolf
The bear breaks apart rotten stumps and looks for fatty larvae of woodcutter beetles and other insects that feed on wood. He eats everything: he catches frogs, lizards, in a word, whatever he comes across. Digs plant bulbs and tubers from the ground. You can often meet a bear in berry fields, where he greedily eats the berries. Sometimes a hungry bear attacks moose and deer.
Answer: the bear is omnivorous
Based on the texts from the previous assignment, compose and write down several power circuits.
1. strawberry - slug - badger
2. tree bark - hare - fox
3. grain - bird - wolf
4. wood - beetle larvae - woodcutter - bear
5. young shoots of trees - deer - bear
Draw a food chain using the pictures.
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