Complex power circuit. NOD “Food chains in the forest” (preparatory group)

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

The transfer of potential food energy 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 use 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.

Fig.4. Food chain diagram.

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

At the same time, more than half of the energy stored in organic substances is consumed in the life processes of plants, turning into heat and dissipating in space, and the rest goes into food chains and can be used by heterotrophic organisms of subsequent trophic levels for nutrition.

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

Consumers of the first order most of The energy contained in food is spent to ensure their life processes, and the rest of the energy is used to build their own body, thereby transforming plant tissue into animal tissue.

Thus , 1st order consumers 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 2nd order consumers.

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

Second-order consumers carry out the second stage of transformation of organic matter in food chains.

However, the chemical substances from which the tissues of animal organisms are built 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 during the transition 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 third-order consumers.

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 detritivores).

Reducers-destructors (bacteria, fungi, protozoa) in the process of their life activity decompose organic remains of all trophic levels of producers and consumers into mineral substances, which are returned to the producers.

All links of the food chain are interconnected and interdependent.

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

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

For example:

Omnivorous organisms consume both producers and consumers as food, i.e. are simultaneously consumers of the first, second, and sometimes third order;

a mosquito that feeds on the blood of humans and predatory animals is at a very high trophic level. But the swamp sundew plant feeds on mosquitoes, which is thus 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 connections acts as an important mechanism for maintaining the integrity and functional stability of ecosystems.

In Fig.5. shows a simplified diagram of a power network for a terrestrial ecosystem.

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

Fig.5. Scheme of the trophic network.

There are two main types of trophic chains:

pasture chains (grazing chains or consumption chains);

detrital chains (decomposition chains).

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

Pasture chains begin with producers. Living plants are eaten by phytophages (consumers of the first order), and the phytophages themselves are food for carnivores (consumers of the second order), which can be eaten by consumers of the third order, etc.

Examples of grazing chains for terrestrial ecosystems:

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

4 links: plants → grasshoppers → lizards → hawk;

nectar of plant flower → fly → insectivorous bird →

bird of prey.

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 →

birds of prey.

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

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

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

For example, when dead wood decomposes, they successively replace each other: beetles → woodpeckers → ants and termites → destructive fungi.

Detrital chains are most common in forests, where most (about 90%) of the annual increase in plant biomass is not consumed directly by herbivores, but dies and enters these chains in the form of leaf litter, then undergoing decomposition and mineralization.

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

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

living organic matter follows grazing chains;

dead organic matter goes along detrital chains.

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

References

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 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, making 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 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 are cladocerans and copepods, crab larvae, barnacles and bivalves(for example, mussels and oysters) - feed by filtering the smallest 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. Examples were given above pasture chains, in which the first trophic level is occupied by green plants, the second by grazing 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 decomposed by microorganisms, namely fungi and bacteria, living as saprophytes on organic residues. Such organisms are called decomposers. They secrete digestive enzymes into 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 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 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 because 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 fresh water bodies 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.

All living beings on our planet are connected to each other by one of the strongest connections - food. That is, someone is food for someone else, or, in scientific terms, a food source. Herbivores eat plants, the herbivores themselves are eaten by predators, which in turn can also be eaten by other, larger and stronger predators. In biology, these peculiar food connections are usually called food chains. Understanding how the food chain ecosystem works gives biologists an understanding of the various nuances of living organisms, helps explain the behavior of some animals, and understands where the legs come from for certain habits of our four-legged friends.

Types of power circuits

In general, there are two main types of food chains: the grazing chain (also known as the grazing food chain) and the detrital food chain, which is also called the decomposition chain.

Pastoral 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 in scientific terminology are called producers. 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 of the third order. In nature, there are also longer food chains, numbering five or more links, these 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. The links in the food chain are closed by 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 of nutrition 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 predators or herbivores, die and decompose, their remains feed on smaller animals, various scavengers (for example, hyenas), which in their turn also die and decompose, and their mortal remains similarly 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, release 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 does the length of the power circuit mean?

Studying the length of the food chain gives scientists answers to many questions, for example, how favorable the environment is for animals. The more favorable the habitat, the longer the natural food chain will be due to the abundance of different animals serving each other as food. But the longest food chain is for fish and other inhabitants of the ocean depths.

What is the basis of the food chain?

The basis of any food chain is food connections and energy, which is transferred with the consumption of one representative of the fauna (or flora) to another. Thanks to the energy received, consumers can continue their life activities, but in turn also become dependent on their food (feed supply). For example, when the famous migration of lemmings occurs, 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 same migrations) but also the predators that feed on lemmings, and some of them even migrate with them.

Power circuits, video film

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

For me, nature is a kind of well-oiled machine, in which every detail is provided. It’s amazing how well everything is thought out, and it’s unlikely that a person will ever be able to create something like this.

What does the term "power chain" mean?

According to the scientific definition, this concept includes the transfer of energy through a number of organisms, where the producers are the first link. This group includes plants that absorb inorganic substances from which they synthesize nutritious organic compounds. They feed on consumers - organisms that are not capable of independent synthesis, and therefore are forced to eat ready-made organic matter. These are herbivores and insects that act as “lunch” for other consumers - predators. As a rule, the chain contains about 4-6 levels, where the closing link is represented by decomposers - organisms that decompose organic matter. In principle, there can be much more links, but there is a natural “limiter”: on average, each link receives little energy from the previous one - up to 10%.

Examples of food chains in a forest community

Forests have their own characteristics, depending on their type. Coniferous forests are not distinguished by rich herbaceous vegetation, which means that the food chain will have a certain set of animals. For example, a deer enjoys eating elderberry, but it itself becomes prey for a bear or lynx. The broad-leaved forest will have its own set. For example:

• bark - bark beetles - tit - falcon;
• fly - reptile - ferret - fox;
• seeds and fruits - squirrel - owl;
• plant - beetle - frog - snake - hawk.

It is worth mentioning scavengers who “recycle” organic remains. There are a great variety of them in forests: from the simplest unicellular organisms to vertebrates. Their contribution to nature is enormous, since otherwise the planet would be covered with animal remains. They transform dead bodies into inorganic compounds that plants need, and everything starts anew. In general, nature is perfection itself!

Target: expand knowledge about biotic environmental factors.

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

Work progress:

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

Plants → insects→lizard → bacteria

Plants → grasshopper→ frog → bacteria

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

Violet → Springtails→predatory mites→predatory 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 a biocenosis? State your conclusion.

Conclusion:

Food (trophic) chain- a series of species of plants, animals, fungi and microorganisms that are connected to each other by the relationship: food - consumer (a sequence of organisms in which a gradual transfer of matter and energy occurs 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 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. The stability of a biocenosis is determined by the diversity of its species composition. Producers- organisms capable of synthesizing organic substances from inorganic ones, that is, all autotrophs. Consumers- heterotrophs, organisms that consume ready-made organic substances created by autotrophs (producers). Unlike decomposers

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

1) Spider, fox

2) tree-eater-caterpillar, snake-hawk

3) caterpillar

4. From the proposed list of living organisms, create a trophic network:

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

1. Grass (100%) - grasshopper (10%) - frog (1%) - snake (0.1%) - rotting bacteria (0.01%).

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

3. Grass (100%) - fly (10%) - tit (1%) - wolf (0.1%) - rotting bacteria (0.01%).

4. Grass (100%) - mosquito (10%) - frog (1%) - snake (0.1%) - rotting bacteria (0.01%).

5. Knowing the rule for the transfer of energy from one trophic level to another (about 10%), build a pyramid of biomass for 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. These graphic models were first developed by Charles 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 that of first-level predators, etc. to the very end of the food chain.

Laboratory work No. 1

Topic: Studying the structure of plant and animal cells under a microscope

Purpose of the work: get acquainted with the structural features of plant and animal cells, show the fundamental unity of their structure.

Equipment: microscope , onion scale skin , epithelial cells from the human oral cavity, teaspoon, cover glass and slide glass, blue ink, iodine, notebook, pen, pencil, ruler

Work progress:

1. Separate a piece of the skin covering it from the scales of the bulb and place it on a glass slide.

2. Apply a drop of a weak aqueous solution of iodine to the preparation. Cover the preparation with a coverslip.

3. Use a teaspoon to remove some mucus from the inside of your cheek.

4. Place the mucus on a slide and tint with blue ink diluted in water. Cover the preparation with a coverslip.

5. Examine both preparations under a microscope.

6. Enter the comparison results in tables 1 and 2.

7. Draw a conclusion about the work done.

Option #1.

Table No. 1 “Similarities and differences between plant and animal cells.”

Option number 2.

Table No. 2 “Comparative characteristics of plant and animal cells.”

4. State your conclusion.

Conclusion: _All plants and animals are made up of cells. A cell is an elementary unit of structure and vital activity of all living organisms. A plant cell has a thick cellulose membrane, vacuole and plastids; animals, unlike plants, have a thin glycogen membrane (carries out pinocytosis, endocytosis, exocytosis, phagocytosis), and there are no vacuoles (except in protozoa).

Laboratory work No. 2