Trophic levels: types, meaning, schemes and definition of the food chain. Food chains in biology Animal food chain examples 3

Target: expand knowledge of biotic environmental factors.

Equipment: herbarium plants, stuffed chordates (fish, amphibians, reptiles, birds, mammals), insect collections, animal wet preparations, illustrations of various plants and animals.

Progress:

1. Use the equipment and make up two power circuits. Remember that a chain always starts with a producer and ends with a decomposer.

Plants → insects→lizard → bacteria

Plants → grasshopper→ frog → bacteria

Recall your observations in nature and make two food chains. Sign producers, consumers (1st and 2nd orders), decomposers.

Violet → Springtails→predatory mites→carnivorous centipedes→ bacteria

Producer - consumer1 - consumer2 - consumer2 - decomposer

Cabbage→ slug→ frog →bacteria

Producer - consumer1 - consumer2 - decomposer

What is a food chain and what underlies it? What determines the stability of the biocenosis? Formulate a conclusion.

Conclusion:

food (trophic) chain- rows of species of plants, animals, fungi and microorganisms that are related to each other by relationships: food - consumer (a sequence of organisms in which there is a phased transfer of matter and energy from source to consumer). Organisms of the next link eat the organisms of the previous link, and thus a chain transfer of energy and matter is carried out, 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, dissipating in the form of heat. For this reason, the number of links (species) in the food chain is limited and usually does not exceed 4-5. The stability of the biocenosis is determined by the diversity of its species composition. Producers- organisms capable of synthesizing organic substances from inorganic, that is, all autotrophs. Consumers- heterotrophs, organisms that consume ready-made organic substances created by autotrophs (producers). Unlike reducers

, consumers are not able to decompose organic substances to inorganic ones. Decomposers- microorganisms (bacteria and fungi) that destroy the dead remains of living beings, turning them into inorganic and simple organic compounds.

3. Name the organisms that should be in the missing place of the following food chains.

1) Spider, fox

2) caterpillar tree eater, snake hawk

3) caterpillar

4. From the proposed list of living organisms, make a food web:

grass, berry bush, fly, titmouse, frog, snake, hare, wolf, decay bacteria, mosquito, grasshopper. Indicate the amount of energy that passes from one level to another.

1. Grass (100%) - grasshopper (10%) - frog (1%) - already (0.1%) - decay bacteria (0.01%).

2. Shrub (100%) - hare (10%) - wolf (1%) - decay bacteria (0.1%).

3. Grass (100%) - fly (10%) - titmouse (1%) - wolf (0.1%) - decay bacteria (0.01%).

4. Grass (100%) - mosquito (10%) - frog (1%) - already (0.1%) - decay bacteria (0.01%).

5. Knowing the rule of energy transfer from one trophic level to another (about 10%), build a biomass pyramid of the third food chain (task 1). Plant biomass is 40 tons.

Grass (40 tons) - grasshopper (4 tons) - sparrow (0.4 tons) - fox (0.04).

6. Conclusion: what do the rules of ecological pyramids reflect?

The rule of ecological pyramids very conditionally conveys the pattern of energy transfer from one level of nutrition to the next, in the food chain. For the first time, these graphic models were developed by C. Elton in 1927. According to this pattern, the total mass of plants should be an order of magnitude greater than that of herbivorous animals, and the total mass of herbivorous animals should be an order of magnitude greater than the first level predators, and so on. to the very end of the food chain.

Lab #1

In ecosystems, producers, consumers and decomposers are united by complex processes of the transfer of substances and energy, which is contained in food, created mainly by plants.

The transfer of the potential energy of food created by plants through a number of organisms by eating some species by others is called a trophic (food) chain, and each link is called a trophic level.

All organisms that eat the same type of food belong to the same trophic level.

In Fig.4. a diagram of the trophic chain is presented.

Fig.4. Food chain diagram.

First trophic level form producers (green plants) that accumulate solar energy and create organic substances in the process of photosynthesis.

At the same time, more than half of the energy stored in organic substances is consumed in the processes of plant life, turning into heat and dissipating in space, and the rest enters the food chain and can be used by heterotrophic organisms of subsequent trophic levels when feeding.

Second trophic level form consumers of the 1st order - these are herbivorous organisms (phytophages) that feed on producers.

Consumers of the first order spend most of the energy contained in food to ensure their life processes, and use the rest of the energy to build their own body, thereby transforming plant tissues into animals.

Thus , consumers of the 1st order carry out the first, fundamental stage in the transformation of organic matter synthesized by producers.

Primary consumers can serve as a source of nutrition for consumers of the 2nd order.

Third trophic level form consumers of the 2nd order - these are carnivorous organisms (zoophages), which feed exclusively on herbivorous organisms (phytophages).

Consumers of the 2nd order carry out the second stage of the transformation of organic matter in food chains.

However, the chemicals that make up the tissues of animal organisms are quite homogeneous and therefore the transformation of organic matter during the transition from the second trophic level of consumers to the third is not as fundamental as when moving from the first trophic level to the second, where plant tissues are transformed into animals.

Secondary consumers can serve as a source of nutrition for consumers of the 3rd order.

Fourth trophic level form consumers of the 3rd order - these are carnivores that feed only on carnivorous organisms.

Last level of the food chain occupied by decomposers (destructors and detritophages).

decomposers-destructors (bacteria, fungi, protozoa) in the course of their life activity decompose the organic remains of all trophic levels of producers and consumers to mineral substances, which again return to the producers.

All links in the food chain are interconnected and interdependent.

Between them, from the first to the last link, the transfer of substances and energy is carried out. However, it should be noted that when energy is transferred from one trophic level to another, it is lost. As a result, the food chain cannot be long and most often consists of 4-6 links.

However, such food chains do not usually occur in nature in their pure form, since each organism has several food sources, i.e. eats several types of food, and is itself used as food by numerous other organisms from the same food chain or even from different food chains.

For example:

omnivorous organisms eat both producers and consumers, i.e. are at the same time consumers of the first, second, and sometimes third order;

the mosquito, which feeds on the blood of humans and predatory animals, is at a very high trophic level. But mosquitoes feed on the swamp sundew plant, which, thus, is both a producer and a consumer of a high order.

Therefore, almost any organism that is part of one trophic chain can simultaneously be part of other trophic chains.

Thus, trophic chains can branch and intertwine many times, forming complex food webs or trophic (food) webs in which the multiplicity and diversity of food relationships acts as an important mechanism for maintaining the integrity and functional stability of ecosystems.

In Fig.5. a simplified diagram of a food network for a terrestrial ecosystem is shown.

Human intervention in the natural communities of organisms, through the intentional or unintentional elimination of a species, often has unpredictable negative consequences and leads to a violation of the stability of ecosystems.

Fig.5. Food web diagram.

There are two main types of food chains:

grazing chains (grazing chains or or consumption chains);

detritus chains (decomposition chains).

Pasture chains (grazing chains or consumption chains) are the processes of synthesis and transformation of organic substances in trophic chains.

Pasture chains start with producers. Living plants are eaten by phytophages (first-order consumers), and phytophages themselves are food for carnivores (second-order consumers), which third-order consumers can eat, etc.

Examples of grazing chains for terrestrial ecosystems:

3 links: aspen → hare → fox; plant → sheep → human.

4 links: plants → grasshoppers → lizards → hawk;

plant flower nectar → fly → insectivorous bird →

predatory bird.

5 links: plants → grasshoppers → frogs → snakes → eagle.

Examples of grazing chains for aquatic ecosystems: →

3 links: phytoplankton → zooplankton → fish;

5 links: phytoplankton → zooplankton → fish → predatory fish →

predator birds.

Detrital chains (decomposition chains) are processes of gradual destruction and mineralization of organic substances in trophic chains.

Detrital chains begin with the gradual destruction of dead organic matter by detritivores, which sequentially replace each other in accordance with a specific type of nutrition.

At the last stages of degradation processes, reducers-destructors function, mineralizing the remains of organic compounds to simple inorganic substances, which are again used by producers.

For example, during the decomposition of dead wood, successively replace each other: beetles → woodpeckers → ants and termites → destructor fungi.

Detrital chains are most common in forests, where most (about 90%) of the annual increase in plant biomass is not consumed directly by herbivorous animals, but dies off and enters these chains in the form of leaf litter, then being decomposed and mineralized.

In aquatic ecosystems, most of the matter and energy is included in pasture chains, and in terrestrial ecosystems, detrital chains are of the greatest importance.

Thus, at the level of consumers, the flow of organic matter is divided into different groups of consumers:

living organic matter follows pasture chains;

dead organic matter goes along detrital chains.

What are food chains

All living creatures of our planet are interconnected by one of the strongest bonds - food. That is, someone is food for someone or, in scientific terms, a food base. Herbivores eat plants, the herbivores themselves are eaten by predators, which in turn can also be eaten by other, larger and stronger predators. These peculiar food connections in biology are commonly called food chains. Understanding how the ecosystem of the food chain works gives biologists an idea of the various nuances of living organisms, helps to explain the behavior of some animals, to understand where the legs grow from certain habits of our four-legged friends.

Types of food chains

In general, two main types of food chains are distinguished: the grazing chain (it is also a pasture food chain) and the detrital food chain, which is also called the decomposition chain.

pasture food chain

The pasture food chain is generally simple and understandable, its essence is briefly described at the beginning of the article: plants serve as food for herbivores and are called producers in scientific terminology. Herbivores that eat plants are called consumers (from Latin this word is translated as "consumers") of the first order. Small predators are consumers of the second order, and larger ones are already of the third. In nature, there are also longer food chains, with five or more links, such are found mainly in the oceans, where larger (and voracious) fish eat smaller ones, which in turn eat even smaller ones, and so on down to algae. Closes the links of the food chain is a special happy link, which no longer serves as food for anyone. Usually this is a person, of course, provided that he is careful and does not try to swim with sharks or walk with lions)). But seriously, such a closing link in biology is called a decomposer.

Detrital food chain

But here everything happens a little the other way around, namely, the energy flow of the food chain goes in the opposite direction: large animals, whether they are predators or herbivores, die and decompose, smaller animals feed on their remains, various scavengers (for example, hyenas), which in their turn also die and decompose, and their mortal remains likewise serve as food, either for even smaller lovers of carrion (for example, some species of ants), or for various special microorganisms. Microorganisms, processing the remains, secrete a special substance called detritus, hence the name of this food chain.

A more visual diagram of the power circuit is shown in the picture.

What is the length of the power chain

The study of the length of the food chain provides scientists with answers to many questions, for example, about how favorable the environment for animals is. The more favorable the habitat, the longer the natural food chain will be due to the abundance of various animals that serve as food for each other. But the longest food chain is in fish and other inhabitants of the ocean depths.

What is at the heart of the food chain

At the heart of any food chain are food connections and energy, which is transferred from eating one representative of the fauna (or flora) to others. Thanks to the energy received, consumers can continue their livelihoods, but in turn also become dependent on their food (food base). For example, when the famous migration of lemmings takes place, serving as food for various Arctic predators: foxes, owls, there is a reduction in the population of not only the lemmings themselves (who die en masse during these very migrations), but also predators that feed on lemmings, and some of them even migrate along with them.

Food chains, video film

And in addition, we offer you an educational video about the importance of food chains in biology.

Every organism must receive energy for life. For example, plants consume energy from the sun, animals feed on plants, and some animals feed on other animals.

A food (trophic) chain is a sequence of who eats whom in a biological community () to obtain nutrients and energy that support life.

Autotrophs (producers)

Autotrophs- living organisms that produce their 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 convert 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 matter through chemical reactions involving inorganic compounds (hydrogen, hydrogen sulfide, ammonia, etc.). This process is called chemosynthesis.

Autotrophs are the backbone of every ecosystem on the planet. They make up the majority of food chains and webs, and the energy derived from photosynthesis or chemosynthesis sustains all other organisms in ecological systems. When it comes to their role in food chains, autotrophs can be called producers or manufacturers.

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 by-products. Humans, animals, fungi and many bacteria are heterotrophs. Their role in food chains is to consume other living organisms. There are many types of heterotrophs with different ecological roles, from insects and plants to predators and fungi.

Destructors (reducers)

Another group of consumers 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 supplied at various trophic levels. (For example, they are able to process decaying plant matter, the body of a squirrel undereaten by predators, or the remains of a dead 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 an important role in maintaining a healthy ecosystem, because thanks to them, nutrients and moisture return to the soil, which are further used by producers.

Food (trophic) chain levels

Scheme of food (trophic) chain levels

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 that produces its own food from a primary source of energy, usually solar or hydrothermal energy from mid-ocean ridges. For example, photosynthetic plants, chemosynthetic and.

Second trophic level

This is followed by 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 eat quaternary consumers(for example, a hawk eats owls).

Each food chain ends with a top predator or superpredator - an animal without natural enemies (for example, a crocodile, a polar bear, a shark, etc.). They are the "masters" of their ecosystems.

When an organism dies, it is eventually eaten by detritus feeders (such as hyenas, vultures, worms, crabs, etc.), and the rest is decomposed with the help of decomposers (mainly bacteria and fungi), and energy exchange continues.

Arrows in the 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 every link in the chain. The collection of many food chains is called food web.

The position of some organisms in the food chain can vary because their diet differs. 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 a primary predator, since it feeds on herring, and she eats zooplankton, which feeds on phytoplankton that produce 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, two types of food chains are distinguished: pasture and detrital.

pasture food chain

Diagram of a pasture food chain

This type of food chain begins with living green plants that are meant to feed on herbivorous animals that feed on predators. Ecosystems with this type of circuit are directly dependent on solar energy.

Thus, the grazing type of the 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.

Pasture food chain examples:

Grass → Grasshopper → Bird → Hawk;
Plants → Hare → Fox → Lion.

detritus food chain

Diagram of the detritus food chain

This type of food chain starts with decaying organic material - detritus - which is consumed by detritus feeders. Then, predators feed on detritophages. 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 decaying bedding.

Energy in the food chain

Energy is transferred between trophic levels when one organism feeds on another and receives nutrients from it. However, this movement of energy is inefficient, and this inefficiency limits the length of food chains.

When energy enters the 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, which are used by decomposers.

Why does so much energy exit the food web between one trophic level and another? Here are some of the main reasons for inefficient power transfer:

At each trophic level, a significant amount of energy is dissipated as heat as organisms perform cellular respiration and move about in daily life.
Some organic molecules that organisms feed on cannot be digested and pass out in the form of 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, which metabolize them and convert them into their own energy.

So, none of the energy actually disappears - all this eventually leads to the release of heat.

Importance of the food chain

1. Food chain studies help understand food 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 to understand the movement of toxic substances in the ecosystem.

3. Studying the food chain allows you to understand the problems of biomagnification.

In any food chain, energy is lost each time one organism is consumed by another. In this regard, there must be many more plants than herbivorous animals. There are more autotrophs than heterotrophs, and therefore most of them are herbivores rather than predators. 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.

To receive energy for vital processes, all beings must eat. The diversity of the animal world was also reflected in the ways of eating: someone eats fresh meat, someone eats berries and grass, and someone can eat both. Find out who eats what and how they get their food.

Nutrition methods

Our planet is inhabited by very different animals: from the simplest microorganisms to such giants as the African elephant or the blue whale. To move, breathe, reproduce, all animals must regularly receive the usual food.

Depending on the method of nutrition, animals are divided into the following groups:

Herbivores

Animals that eat only plant foods. Domestic animals include horses, sheep, cows, goats. Among wild animals - hares, roe deer, deer, moose. Their teeth have a special structure that helps them easily pluck and grind tough plants.

Since plant foods are not high in calories, herbivores have to spend a lot of time eating them every day.

Who eats what: food chains

All animals, one way or another, are connected with each other in the food chain: someone eats plants, and someone else eats other animals.

Since plants are the main food of herbivores, they occupy the first place in the food chain.

Only plants are able to synthesize nutrients from water and carbon dioxide under the influence of the sun. As such, they are an excellent food source for many animal species.

Rice. 3. Plants are a valuable source of food.

Second place is given to herbivorous animals.

The third place is occupied by predatory representatives of the animal world.

An example of a food chain: grain - mouse - fox.

At first glance, it may seem that life on Earth would be much more pleasant if there were no insects, snakes, frogs. But they are all important links in the food chain. Without them on the planet, such a fragile ecological balance would be upset: sick animals would spread infections, infecting other animals and people, plants would not be pollinated and crops would be lost. Absolutely all animals on Earth are of great value!

What have we learned?

When studying one of the important topics of the program of the world around us for grade 3, we learned which groups animals are divided into depending on the way they eat. All carnivores, herbivores and omnivores are closely related in the food chain.

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