The food chain is the sequential transformation of elements of inorganic nature (biogenic, etc.) with the help of plants and light into organic substances (primary production), and the latter - by animal organisms at subsequent trophic (food) links (steps) into their biomass.
The food chain starts with solar energy, and each link in the chain represents a change in energy. All food chains in a community form trophic relationships.
There are various connections between the components of the ecosystem, and first of all they are connected together by the flow of energy and the cycle of matter. The channels through which energy flows through the community are called food chains. The energy of the sun's beam falling on the tops of trees or on the surface of a pond is captured by green plants - whether they are huge trees or tiny algae - and used by them in the process of photosynthesis. This energy goes to the growth, development and reproduction of plants. Plants, as producers of organic matter, are called producers. Producers, in turn, serve as a source of energy for those who feed on plants, and, ultimately, for the entire community.
The first consumers of organic matter are herbivorous animals - consumers of the first order. Predators that eat herbivorous prey act as consumers of the second order. When moving from one link to another, energy is inevitably lost, so there are rarely more than 5-6 participants in the food chain. The decomposers complete the cycle - bacteria and fungi decompose animal corpses, plant remains, turning organic matter into minerals, which are again absorbed by producers.
The food chain includes all plants and animals, as well as the chemical elements contained in the water necessary for photosynthesis. The food chain is a connected linear structure of links, each of which is connected with neighboring links by the relationship "food - consumer". Groups of organisms, for example, specific biological species, act as links in the chain. In water, the food chain begins with the smallest plant organisms - algae - living in the euphotic zone and using solar energy to synthesize organic substances from inorganic chemical nutrients and carbon dioxide dissolved in water. In the process of transferring the energy of food from its source - plants - through a number of organisms that occur by eating some organisms by others, energy is dissipated, part of which is converted into heat. With each next transition from one trophic link (step) to another, up to 80-90% of potential energy is lost. This limits the possible number of steps, or chain links, to usually four or five. The shorter the food chain, the more available energy is stored.
On average, 100 kg of the body of herbivores is formed from 1 thousand kg of plants. Predators eating herbivores can build 10 kg of their biomass from this amount, and secondary predators only 1 kg. For example, a person eats a big fish. Its food is made up of small fish that consume zooplankton, which lives off phytoplankton that captures solar energy.
Thus, to build 1 kg of the human body, 10 thousand kg of phytoplankton are required. Consequently, the mass of each subsequent link in the chain progressively decreases. This pattern is called the rule of the ecological pyramid. There are a pyramid of numbers, reflecting the number of individuals at each stage of the food chain, a biomass pyramid - the amount of organic matter synthesized at each level, and an energy pyramid - the amount of energy in food. All of them have the same direction, differing in the absolute value of digital values. In real conditions, power chains can have a different number of links. In addition, food chains can cross over to form food networks. Almost all species of animals, with the exception of very specialized food, use more than one food source, but several). The greater the species diversity in the biocenosis, the more stable it is. So, in the plant-hare-fox food chain there are only three links. But the fox eats not only hares, but also mice and birds. The general pattern is that at the beginning of the food chain there are always green plants, and at the end - predators. With each link in the chain, organisms become larger, they multiply more slowly, their number decreases. The species that occupy the position of the lower links, although they are provided with food, are themselves intensively consumed (mice, for example, are exterminated by foxes, wolves, owls). Selection goes in the direction of increasing fertility. Such organisms turn into a food base for higher animals without any prospects for progressive evolution.
In any geological epoch, organisms that were at the highest level in food relationships evolved with the greatest speed, for example, in the Devonian - lobe fish - fish-eating predators; in the Carboniferous period - predatory stegocephals. In Permian - reptiles that hunted stegocephalians. Throughout the entire Mesozoic era, mammals were exterminated by predatory reptiles, and only as a result of the extinction of the latter at the end of the Mesozoic did they occupy a dominant position, giving a large number of forms.
Food relationships are the most important, but not the only type of relationships between species in a biocenosis. One species can influence another in different ways. Organisms can settle on the surface or inside the body of individuals of another species, can form a habitat for one or more species, affect air movement, temperature, and illumination of the surrounding space. Examples of relationships that affect species habitats are numerous. Sea acorns are sessile marine crustaceans that often settle on the skin of whales. The larvae of many flies live in cow dung. A particularly large role in creating or changing the environment for other organisms belongs to plants. In thickets of plants, whether it be a forest or a meadow, the temperature fluctuates to a lesser extent than in open spaces, and the humidity is higher.
Often one species is involved in the distribution of another. Animals carry seeds, spores, plant pollen, as well as other smaller animals. Plant seeds can be captured by animals upon accidental contact, especially if the seeds or seedlings have special hooks, hooks (sequence, burdock). When eating fruits, berries that are not digestible, the seeds are excreted along with the droppings. Mammals, birds and insects carry numerous ticks on their bodies.
A connection between two links is established if one group of organisms acts as food for another group. The first link in the chain does not have a precursor, that is, organisms from this group do not use other organisms as food, being producers. Most often in this place there are plants, mushrooms, algae. Organisms of the last link in the chain do not act as food for other organisms.
Each organism has a certain reserve of energy, that is, we can say that each link in the chain has its own potential energy. In the process of eating, the potential energy of food passes to its consumer.
All species that make up the food chain subsist on the organic matter created by green plants. At the same time, there is an important regularity associated with the efficiency of the use and conversion of energy in the process of nutrition. Its essence is as follows.
In total, only about 1% of the radiant energy of the Sun incident on a plant is converted into the potential energy of chemical bonds of synthesized organic substances and can be further used by heterotrophic organisms for nutrition. When an animal eats a plant, most of the energy contained in the food is spent on various life processes, turning into heat and dissipating. Only 5-20% of food energy passes into the newly built substance of the animal's body. If a predator eats a herbivore, then again most of the energy contained in the food is lost. Due to such large losses of useful energy, food chains cannot be very long: they usually consist of no more than 3-5 links (food levels).
The amount of plant matter that serves as the basis of the food chain is always several times greater than the total mass of herbivorous animals, and the mass of each of the subsequent links in the food chain also decreases. This very important pattern is called the rule of the ecological pyramid.
When transferring potential energy from link to link, up to 80-90% is lost in the form of heat. This fact limits the length of the food chain, which in nature usually does not exceed 4-5 links. The longer the trophic chain, the lower the production of its last link in relation to the production of the initial one.
In Baikal, the food chain in the pelagic zone consists of five links: algae - epishura - macrohectopus - fish - seal or predatory fish (lenok, taimen, adults of omul, etc.). Man participates in this chain as the last link, but he can consume the products of lower links, for example, fish or even invertebrates when using crustaceans, aquatic plants, etc. Short trophic chains are less stable and subject to greater fluctuations than long ones. and complex in structure.
2. LEVELS AND STRUCTURAL ELEMENTS OF THE FOOD CHAIN
Usually, for each link in the chain, you can specify not one, but several other links associated with it by the relationship "food - consumer". So grass is eaten not only by cows, but also by other animals, and cows are food not only for humans. The establishment of such links turns the food chain into a more complex structure - food web.
In some cases, in the food web, it is possible to group individual links into levels in such a way that the links of one level act for the next level only as food. Such a grouping is called trophic levels.
Plants (algae) are the initial level (link) of any trophic (food) chain in a reservoir. Plants do not eat anyone (with the exception of a small number of species of insectivorous plants - sundew, oilwort, pemphigus, nepenthes and some others), on the contrary, they are the source of life for all animal organisms. Therefore, the first step in the chain of predators are herbivorous (pasture) animals. They are followed by small carnivores feeding on herbivores, then a link of larger predators. In the chain, each subsequent organism is larger than the previous one. Chains of predators contribute to the stability of the trophic chain.
The food chain of saprophytes is the closing link of the trophic chain. Saprophytes feed on dead organisms. Chemical substances formed during the decomposition of dead organisms are again consumed by plants - producing organisms from which all trophic chains begin.
3. TYPES OF TROPHIC CHAINS
There are several classifications of trophic chains.
According to the first classification, there are three trophic chains in Nature (trophic - means, conditioned by Nature for destruction).
The first trophic chain combines the following free-living organisms:
herbivorous animals;
predators are carnivores;
omnivores, including humans.
The basic principle of the food chain: "Who eats whom?"
The second trophic chain unites living beings that metabolize everything and everyone. This task is performed by reducers. They bring the complex substances of dead organisms to simple substances. The property of the biosphere is that all representatives of the biosphere are mortal. The biological task of decomposers is to decompose the dead.
According to the second classification, there are two main types of food chains - pasture and detrital.
In the pasture trophic chain (grazing chain), autotrophic organisms form the basis, followed by herbivores that consume them (for example, zooplankton feeding on phytoplankton), then predators (consumers) of the 1st order (for example, fish that consume zooplankton), predators of the 2nd order (for example, pike perch, feeding on other fish). Food chains are especially long in the ocean, where many species (for example, tuna) take the place of fourth-order consumers.
In detrital trophic chains (decomposition chains), most common in forests, most of the plant production is not consumed directly by herbivorous animals, but dies off, then being decomposed by saprotrophic organisms and mineralized. Thus, detrital trophic chains start from detritus, go to microorganisms that feed on it, and then to detritus feeders and their consumers - predators. In aquatic ecosystems (especially in eutrophic water bodies and at great depths of the ocean), this means that part of the production of plants and animals also enters the detrital trophic chains.
CONCLUSION
All living organisms that inhabit our planet do not exist on their own, they depend on the environment and experience its effects. This is a precisely coordinated complex of many environmental factors, and the adaptation of living organisms to them determines the possibility of the existence of various forms of organisms and the most diverse formation of their life.
The main function of the biosphere is to ensure the circulation of chemical elements, which is expressed in the circulation of substances between the atmosphere, soil, hydrosphere and living organisms.
All living beings are objects of nourishment for others, i.e. connected with each other by energy relations. Nutritional connections in communities, they are mechanisms for transferring energy from one organism to another. In every community trophic connections are intertwined in a complex net.
Organisms of any species are potential food for many other species.
food webs in biocenoses are very complex, and it seems that the energy entering them can migrate from one organism to another for a long time. In fact, the path of each specific portion of the energy accumulated by green plants is short; it can be transmitted through no more than 4-6 links in a series consisting of sequentially feeding on each other organisms. Such rows, in which it is possible to trace the ways of spending the initial dose of energy, are called food chains. The location of each link in the food chain is called a trophic level. The first trophic level is always producers, creators of organic mass; plant consumers belong to the second trophic level; carnivorous, living at the expense of herbivorous forms - to the third; those consuming other carnivores - to the fourth, and so on. Thus, consumers of the first, second and third orders are distinguished, occupying different levels in the food chains. Naturally, the main role is played by the food specialization of consumers. Species with a wide range of food are included in food chains at different trophic levels.
BIBLIOGRAPHY
Akimova T.A., Khaskin V.V. Ecology. Tutorial. –M.: DONITI, 2005.
Moiseev A.N. Ecology in the modern world // Energy. 2003. No. 4.
Introduction
A prime example of a food chain:
Classification of living organisms regarding their role in the cycle of substances
In any food chain, 3 groups of living organisms are involved:
Producers (manufacturers) | Consumers (consumers) | decomposers (destroyers) |
Autotrophic living organisms that synthesize organic matter from mineral using energy (plants). | Heterotrophic living organisms that consume (eat, process, etc.) living organic matter and transfer the energy contained in it through food chains. | Heterotrophic living organisms that destroy (recycle) dead organic matter of any origin to mineral. |
Relationships between organisms in the food chain
The food chain, whatever it may be, creates close links between a variety of objects, both animate and inanimate. And breaking absolutely any of its links can lead to disastrous results and imbalance in nature. The most important and integral component of any food chain is solar energy. If it doesn't exist, there won't be life. When moving along the food chain, this energy is processed, and each of the organisms makes it their own, transferring only 10% to the next link.
Dying, the organism enters other similar food chains, and thus the circulation of substances continues. All organisms can safely exit one food chain and move into another.
The role of natural zones in the cycle of substances
Naturally, organisms living in the same natural zone create their own special food chains with each other, which cannot be repeated in any other zone. Thus, the food chain of the steppe zone, for example, consists of a wide variety of herbs and animals. The food chain in the steppe practically does not include trees, since there are either very few of them or they are undersized. As for the animal world, artiodactyls, rodents, falcons (hawks and other similar birds) and various kinds of insects predominate here.
Power circuit classification
The principle of ecological pyramids
If we consider specifically the chains starting with plants, then the entire cycle of substances in them comes from photosynthesis, during which solar energy is absorbed. Plants spend most of this energy on their vital activity, and only 10% goes to the next link. As a result, each subsequent living organism needs more and more creatures (objects) of the previous link. This is well shown by ecological pyramids, which are most often used for these purposes. They are pyramids of mass, quantity and energy.
The main condition for the existence of an ecosystem is the maintenance of the circulation of substances and the transformation of energy. It is provided thanks to trophic (food) relationships between species belonging to different functional groups. It is on the basis of these bonds that organic substances synthesized by producers from mineral substances with the absorption of solar energy are transferred to consumers and undergo chemical transformations. As a result of the vital activity of predominantly decomposers, the atoms of the main biogenic chemical elements pass from organic substances to inorganic substances (CO 2, NH 3, H 2 S, H 2 O). Then inorganic substances are used by producers to create new organic substances from them. And they are again involved in the cycle with the help of producers. If these substances were not used repeatedly, life on Earth would be impossible. After all, the reserves of substances absorbed by producers are not unlimited in nature. To implement a full-fledged cycle of substances in an ecosystem, all three functional groups of organisms must be available. And between them there must be constant interaction in the form of trophic links with the formation of trophic (food) chains, or food chains.
A food chain (food chain) is a sequence of organisms in which there is a gradual transfer of matter and energy from a source (previous link) to a consumer (next link).
In this case, one organism can eat another, eat its dead remains or waste products. Depending on the type of initial source of matter and energy, food chains are divided into two types: pasture (grazing chains) and detrital (decomposition chains).
Pasture chains (grazing chains)- food chains that start with producers and include consumers of different orders. In general, a pasture chain can be shown by the following diagram:
Producers -> Consumers of the 1st order -> Consumers of the 2nd order -> Consumers of the 3rd order
For example: 1) meadow food chain: meadow clover - butterfly - frog - snake; 2) the food chain of the reservoir: chlamydomonas - daphnia - gudgeon - pike perch. The arrows in the diagram show the direction of the transfer of matter and energy in the food chain.
Each organism in the food chain belongs to a specific trophic level.
Trophic level - a set of organisms that, depending on the way they eat and the type of food, make up a certain link in the food chain.
Trophic levels are usually numbered. The first trophic level is made up of autotrophic organisms - plants (producers), at the second trophic level are herbivorous animals (consumers of the first order), at the third and subsequent levels - carnivores (consumers of the second, third, etc. orders).
In nature, almost all organisms feed on not one, but several types of food. Therefore, any organism can be at different trophic levels in the same food chain, depending on the nature of the food. For example, a hawk, eating mice, occupies the third trophic level, and eating snakes - the fourth. In addition, the same organism can be a link in different food chains, linking them together. So, a hawk can eat a lizard, a hare or a snake, which are part of different food chains.
In nature, pasture chains in their pure form are not found. They are interconnected by common food links and form food web, or power network. Its presence in the ecosystem contributes to the survival of organisms with a lack of a certain type of food due to the ability to use other food. And the wider the species diversity of individuals in the ecosystem, the more food chains in the food web and the more stable the ecosystem. The loss of one link from the food chain will not disrupt the entire ecosystem, as food sources from other food chains can be used.
Detritus chains (decomposition chains)- food chains that begin with detritus, include detritus feeders and decomposers, and end with minerals. In detrital chains, the substance and energy of detritus are transferred between detritus feeders and decomposers through the products of their vital activity.
For example: a dead bird - fly larvae - mold fungi - bacteria - minerals. If detritus does not require mechanical destruction, then it immediately turns into humus with subsequent mineralization.
Thanks to detrital chains, the cycle of substances is closed in nature. Dead organic substances in detrital chains are converted into minerals, which enter the environment, and from it are absorbed by plants (producers).
Pasture chains are predominantly located in the above-ground, and decomposition chains - in the underground tiers of ecosystems. The relationship between pasture chains and detrital chains is carried out through detritus that enters the soil. Detrital chains are connected with pasture chains through mineral substances extracted from the soil by producers. Due to the interconnection of pasture and detrital chains, a complex food web is formed in the ecosystem, which ensures the constancy of the processes of transformation of matter and energy.
Ecological pyramids
The process of transformation of matter and energy in pasture chains has certain regularities. At each trophic level of the pasture chain, not all of the eaten biomass is used to form the biomass of consumers of this level. A significant part of it is spent on the vital processes of organisms: movement, reproduction, maintaining body temperature, etc. In addition, part of the feed is not absorbed and enters the environment in the form of waste products. In other words, most of the matter and the energy contained in it is lost when moving from one trophic level to another. The percentage of digestibility varies greatly and depends on the composition of the food and the biological characteristics of the organisms. Numerous studies have shown that at each trophic level of the food chain, on average, about 90% of energy is lost, and only 10% goes to the next level. The American ecologist R. Lindeman in 1942 formulated this pattern as 10% rule. Using this rule, you can calculate the amount of energy at any trophic level of the food chain, if its rate is known at one of them. With some degree of assumption, this rule is also used to determine the transition of biomass between trophic levels.
If at each trophic level of the food chain to determine the number of individuals, or their biomass, or the amount of energy contained in it, then it becomes obvious that these values decrease as we move towards the end of the food chain. This pattern was first established by the English ecologist C. Elton in 1927. He called it ecological pyramid rule and offered to express graphically. If any of the above characteristics of trophic levels are depicted as rectangles with the same scale and placed one above the other, then we get ecological pyramid.
Three types of ecological pyramids are known. Pyramid of numbers reflects the number of individuals in each link in the food chain. However, in the ecosystem, the second trophic level ( consumers of the 1st order) can be numerically richer than the first trophic level ( producers). In this case, an inverted pyramid of numbers is obtained. This is due to the participation in such pyramids of individuals that are not equivalent in size. An example is a pyramid of numbers, consisting of a deciduous tree, leaf-eating insects, small insectivores and large birds of prey. biomass pyramid reflects the amount of organic matter accumulated at each trophic level of the food chain. The pyramid of biomass in terrestrial ecosystems is correct. And in the biomass pyramid for aquatic ecosystems, the biomass of the second trophic level, as a rule, is greater than the biomass of the first when it is determined at a particular moment. But since aquatic producers (phytoplankton) have a high rate of production, in the end their biomass per season will still be greater than the biomass of first-order consumers. And this means that the rule of the ecological pyramid is also observed in aquatic ecosystems. energy pyramid reflects patterns of energy expenditure at different trophic levels.
Thus, the stock of matter and energy accumulated by plants in pasture food chains is quickly consumed (eaten away), so these chains cannot be long. They usually include three to five trophic levels.
In the ecosystem, producers, consumers and decomposers are connected by trophic relationships and form food chains: pasture and detrital. In pasture chains, the 10% rule and the ecological pyramid rule apply. Three types of ecological pyramids can be built: numbers, biomass and energy.
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. Specify 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
Topic: Studying the structure of plant and animal cells under a microscope
Goal of the work: to get acquainted with the structural features of the cells of plants and animal organisms, to show the fundamental unity of their structure.
Equipment: microscope , bulb scale skin , epithelial cells from the human oral cavity, teaspoon, coverslip and slide, blue ink, iodine, notebook, pen, pencil, ruler
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 specimen with a cover slip.
3. Remove a little mucus from the inside of the cheek with a teaspoon.
4. Place the slime on a glass slide and tint with blue ink diluted in water. Cover the specimen with a cover slip.
5. Examine both preparations under a microscope.
6. Record the comparison results in Tables 1 and 2.
7. Make a conclusion about the work done.
Option number 1.
Table No. 1 "Similarities and differences between plant and animal cells."
| Features of the structure of the cell | plant cell | animal cage |
| Drawing | ||
| similarities | Nucleus, cytoplasm, cell membrane, mitochondria, ribosomes, Golgi complex, lysosomes, self-renewal, self-regulation abilities. | Nucleus, cytoplasm, cell membrane, mitochondria, ribosomes, lysosomes, Golgi complex, self-renewal, self-regulation abilities. |
| Features of difference | There are plastids (chloroplasts, leukoplasts, chromoplasts), a vacuole, a thick cell wall consisting of cellulose, capable of photosynthesis. Vacuole - contains cell sap and toxic substances (leaves of plants) accumulate in it. | Centriole, elastic cell wall, glycocalyx, cilia, flagella, heterotrophs, storage substance - glycogen, integral cell reactions (pinocytosis, endocytosis, exocytosis, phagocytosis). |
Option number 2.
Table No. 2 "Comparative characteristics of plant and animal cells."
| Cells | Cytoplasm | Core | Dense cell wall | plastids |
| Vegetable | The cytoplasm consists of a thick, viscous substance in which all other parts of the cell are located. It has a special chemical composition. Various biochemical processes take place in it, which ensure the vital activity of the cell. In a living cell, the cytoplasm is constantly moving, flowing throughout the entire volume of the cell; it can increase in size. | contains genetic information that performs the main functions: storage, transmission and implementation of hereditary information with the provision of protein synthesis. | There is a thick cell wall made of cellulose. | Plastids (chloroplasts, leukoplasts, chromoplasts) are present. Chloroplasts are green plastids found in photosynthetic eukaryotic cells. They are used for photosynthesis. Chloroplasts contain chlorophyll, the formation of starch with the release of oxygen. Leukoplasts - synthesize and accumulate starch (the so-called amyloplasts), fats, proteins. They are found in plant seeds, roots, stems and flower petals (attract insects for pollination). Chromoplasts - contain only yellow, orange and reddish pigments from a number of carotenes. They are found in the fruits of plants, give color to vegetables, fruits, berries and flower petals (attract insects and animals for pollination and distribution in nature). |
| Animal | It is present, it consists of a colloidal solution of proteins and other organic substances, 85% of this solution is water, 10% is proteins and 5% is other compounds. | containing genetic information (DNA molecules), performing the main functions: storage, transmission and implementation of hereditary information with the provision of protein synthesis. | Present, cell wall elastic, glycalix | No. |
4. Formulate a 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, a vacuole and plastids; animals, unlike plants, have a thin glycogen membrane (performs pinocytosis, endocytosis, exocytosis, phagocytosis), and there are no vacuoles (except for protozoa).
Lab #2
In nature, any species, population, and even a single individual do not live in isolation from each other and their environment, but, on the contrary, experience numerous mutual influences. Biotic communities or biocenoses - communities of interacting living organisms, which are a stable system connected by numerous internal connections, with a relatively constant structure and an interdependent set of species.
Biocenosis is characterized by certain structures: species, spatial and trophic.
The organic components of the biocenosis are inextricably linked with the inorganic ones - soil, moisture, atmosphere, forming together with them a stable ecosystem - biogeocenosis .
Biogenocenosis- a self-regulating ecological system formed by populations of different species living together and interacting with each other and with inanimate nature in relatively homogeneous environmental conditions.
Ecological systems
Functional systems that include communities of living organisms of different species and their habitats. The connections between the components of the ecosystem arise, first of all, on the basis of food relationships and ways of obtaining energy.
Ecosystem
A set of species of plants, animals, fungi, microorganisms interacting with each other and with the environment in such a way that such a community can be preserved and function for an indefinitely long time. Biotic community (biocenosis) consists of a community of plants ( phytocenosis), animals ( zoocenosis), microorganisms ( microbiocenosis).
All organisms of the Earth and their habitat also represent an ecosystem of the highest rank - biosphere , which has stability and other properties of the ecosystem.
The existence of an ecosystem is possible due to the constant influx of energy from the outside - such an energy source, as a rule, is the sun, although this is not true for all ecosystems. The stability of an ecosystem is ensured by direct and feedback links between its components, the internal circulation of substances and participation in global cycles.
The doctrine of biogeocenoses developed by V.N. Sukachev. The term " ecosystem"Introduced into use by the English geobotanist A. Tensley in 1935, the term" biogeocenosis"- Academician V.N. Sukachev in 1942 biogeocenosis it is necessary to have a plant community (phytocenosis) as the main link, which ensures the potential immortality of biogeocenosis due to the energy produced by plants. ecosystems may not contain phytocenosis.
Phytocenosis
A plant community that has historically developed as a result of a combination of interacting plants in a homogeneous area.
He is characterized:
- a certain species composition,
- life forms
- tiered (aboveground and underground),
- abundance (frequency of occurrence of species),
- accommodation,
- aspect (appearance),
- vitality
- seasonal changes,
- development (change of communities).
Layered (number of floors)
One of the characteristic features of the plant community, which consists, as it were, in its floor-by-floor division both in the above-ground and in the underground space.
Aboveground layering allows better use of light, and underground - water and minerals. Usually, up to five tiers can be distinguished in the forest: the upper (first) - tall trees, the second - low trees, the third - shrubs, the fourth - grasses, the fifth - mosses.
Underground layering - a mirror reflection of the aboveground: the roots of trees go deepest of all, underground parts of mosses are located near the surface of the soil.
According to the method of obtaining and using nutrients All organisms are divided into autotrophs and heterotrophs. In nature, there is a continuous circulation of biogenic substances necessary for life. Chemical substances are extracted by autotrophs from the environment and returned to it through heterotrophs. This process takes on very complex forms. Each species uses only a part of the energy contained in organic matter, bringing its decay to a certain stage. Thus, in the process of evolution, ecological systems have developed chains And power supply .
Most biogeocenoses have a similar trophic structure. The basis of them are green plants - producers. Herbivorous and carnivorous animals are necessarily present: consumers of organic matter - consumers and destroyers of organic residues - decomposers.
The number of individuals in the food chain consistently decreases, the number of victims is greater than the number of their consumers, since in each link of the food chain, with each transfer of energy, 80-90% of it is lost, dissipating in the form of heat. Therefore, the number of links in the chain is limited (3-5).
Species diversity of biocenosis It is represented by all groups of organisms - producers, consumers and decomposers.
Any link broken in the food chain causes a violation of the biocenosis as a whole. For example, deforestation leads to a change in the species composition of insects, birds, and, consequently, animals. On a treeless site, other food chains will develop and another biocenosis will form, which will take more than a dozen years.
Food chain (trophic or food )
Interrelated species that sequentially extract organic matter and energy from the original food substance; moreover, each previous link in the chain is food for the next one.
Food chains in each natural area with more or less homogeneous conditions of existence are composed of complexes of interconnected species that feed on each other and form a self-sustaining system in which the circulation of substances and energy is carried out.
Ecosystem components:
- Producers - autotrophic organisms (mainly green plants) are the only producers of organic matter on Earth. Energy-rich organic matter in the process of photosynthesis is synthesized from energy-poor inorganic substances (H 2 0 and CO 2).
- Consumers - herbivorous and carnivorous animals, consumers of organic matter. Consumers can be herbivores when they use producers directly, or carnivores when they feed on other animals. In the food chain, they most often have serial number from I to IV.
- decomposers - heterotrophic microorganisms (bacteria) and fungi - destroyers of organic residues, destructors. They are also called the orderlies of the Earth.
Trophic (food) level - a set of organisms united by the type of food. The idea of the trophic level allows us to understand the dynamics of energy flow in an ecosystem.
- the first trophic level is always occupied by producers (plants),
- the second - consumers of the first order (herbivorous animals),
- the third - consumers of the second order - predators that feed on herbivorous animals),
- the fourth - consumers of the III order (secondary predators).
There are the following types food chains:
IN pasture chain (eating chains) green plants are the main source of food. For example: grass -> insects -> amphibians -> snakes -> birds of prey.
- detritus chains (decomposition chains) begin with detritus - dead biomass. For example: leaf litter -> earthworms -> bacteria. A feature of detrital chains is also that in them plant products are often not consumed directly by herbivorous animals, but die off and are mineralized by saprophytes. Detrital chains are also characteristic of ecosystems of the ocean depths, the inhabitants of which feed on dead organisms that have descended from the upper layers of the water.
Relationships between species in ecological systems that have developed in the process of evolution, in which many components feed on different objects and themselves serve as food for various members of the ecosystem. Simplified, the food web can be represented as intertwining food chains.
Organisms of different food chains that receive food through an equal number of links in these chains are on one trophic level. At the same time, different populations of the same species included in different food chains can be located on different trophic levels. The ratio of different trophic levels in an ecosystem can be represented graphically as ecological pyramid.
ecological pyramid
A way to graphically display the ratio of different trophic levels in an ecosystem - there are three types:
The abundance pyramid reflects the abundance of organisms at each trophic level;
The biomass pyramid reflects the biomass of each trophic level;
The energy pyramid shows the amount of energy that has passed through each trophic level in a given amount of time.
Ecological pyramid rule
A pattern that reflects a progressive decrease in the mass (energy, number of individuals) of each subsequent link in the food chain.
Pyramid of numbers
An ecological pyramid showing the number of individuals at each food level. The pyramid of numbers does not take into account the size and weight of individuals, life expectancy, metabolic rate, but the main trend is always traced - a decrease in the number of individuals from link to link. For example, in the steppe ecosystem, the number of individuals is distributed as follows: producers - 150000, herbivorous consumers - 20000, carnivorous consumers - 9000 ind./ar. The meadow biocenosis is characterized by the following number of individuals on an area of 4000 m 2: producers - 5,842,424, herbivorous consumers of the 1st order - 708,624, carnivorous consumers of the 2nd order - 35,490, carnivorous consumers of the 3rd order - 3.
Biomass pyramid
The pattern according to which the amount of plant matter that serves as the basis of the food chain (producers) is approximately 10 times greater than the mass of herbivores (consumers of the 1st order), and the mass of herbivores is 10 times greater than the mass of carnivores (consumers of the 2nd order), t i.e. each subsequent food level has a mass 10 times less than the previous one. On average, out of 1000 kg of plants, 100 kg of the body of herbivores is formed. Predators eating herbivores can build 10 kg of their biomass, secondary predators - 1 kg.
energy pyramid
expresses a pattern according to which the flow of energy gradually decreases and depreciates in the transition from link to link in the food chain. So, in the biocenosis of the lake, green plants - producers - create a biomass containing 295.3 kJ / cm 2, consumers of the first order, consuming plant biomass, create their own biomass containing 29.4 kJ / cm 2; consumers of the second order, using consumers of the first order for food, create their own biomass containing 5.46 kJ / cm 2. The loss of energy during the transition from consumers of the 1st order to consumers of the 2nd order, if they are warm-blooded animals, increases. This is explained by the fact that in these animals a lot of energy is spent not only on building their biomass, but also on maintaining a constant body temperature. If we compare the cultivation of a calf and a perch, then the same amount of food energy expended will give 7 kg of beef and only 1 kg of fish, since the calf feeds on grass, and the predatory perch feeds on fish.
Thus the first two types of pyramids have a number of significant drawbacks:
The biomass pyramid reflects the state of the ecosystem at the time of sampling and therefore shows the ratio of biomass at a given moment and does not reflect the productivity of each trophic level (i.e. its ability to form biomass over a given period of time). Therefore, when fast-growing species are among the producers, the biomass pyramid may turn upside down.
The energy pyramid allows you to compare the productivity of different trophic levels, since it takes into account the time factor. In addition, it takes into account the difference in the energy value of various substances (for example, 1 g of fat provides almost twice as much energy as 1 g of glucose). Therefore, the pyramid of energy always tapers upward and is never inverted.
Ecological plasticity
The degree of endurance of organisms or their communities (biocenoses) to the effects of environmental factors. Ecologically plastic species have a wide range of reaction rate , i.e., widely adapted to different habitats (stickleback and eel fish, some protozoa live in both fresh and salt waters). Highly specialized species can exist only in a certain environment: marine animals and algae - in salt water, river fish and lotus plants, water lilies, duckweed live only in fresh water.
Generally ecosystem (biogeocenosis) characterized by the following indicators:
species diversity,
Density of species populations,
Biomass.
Biomass
The total amount of organic matter of all individuals of a biocenosis or species with energy contained in it. Biomass is usually expressed in units of mass in terms of dry matter per unit area or volume. Biomass can be determined separately for animals, plants or individual species. So, the biomass of fungi in the soil is 0.05-0.35 t / ha, algae - 0.06-0.5, roots of higher plants - 3.0-5.0, earthworms - 0.2-0.5 , vertebrates - 0.001-0.015 t/ha.
In biogeocenoses there are primary and secondary biological productivity :
ü Primary biological productivity of biocenoses- the total total productivity of photosynthesis, which is the result of the activity of autotrophs - green plants, for example, a 20-30-year-old pine forest produces 37.8 t / ha of biomass per year.
ü Secondary biological productivity of biocenoses- the total total productivity of heterotrophic organisms (consumers), which is formed through the use of substances and energy accumulated by producers.
Populations. Structure and population dynamics.
Each species on Earth occupies a certain range because it can exist only under certain environmental conditions. However, the habitat conditions within the range of one species can differ significantly, which leads to the disintegration of the species into elementary groups of individuals - populations.
population
A set of individuals of the same species occupying a separate territory within the range of the species (with relatively homogeneous habitat conditions), freely interbreeding with each other (having a common gene pool) and isolated from other populations of a given species, possessing all the necessary conditions to maintain their stability for a long time in changing environmental conditions. The most important characteristics populations are its structure (age, sex composition) and population dynamics.
Under the demographic structure populations understand its sex and age composition.
Spatial structure populations are the features of the distribution of individuals of a population in space.
Age structure population is related to the ratio of individuals of different ages in the population. Individuals of the same age are combined into cohorts - age groups.
IN age structure of plant populations allocate next periods:
Latent - the state of the seed;
Pregenerative (includes the states of a seedling, juvenile plant, immature and virginal plants);
Generative (usually divided into three sub-periods - young, mature and old generative individuals);
Post-generative (includes the states of subsenile, senile plants and the dying phase).
Belonging to a certain age state is determined by biological age- the degree of expression of certain morphological (for example, the degree of dissection of a complex leaf) and physiological (for example, the ability to give offspring) signs.
In animal populations, one can also distinguish various age stages. For example, insects that develop with complete metamorphosis go through the following stages:
larvae,
pupae,
Imago (adult insect).
The nature of the age structure of the populationdepends on the type of survival curve characteristic of a given population.
survival curvereflects the mortality rate in different age groups and is a declining line:
- If the mortality rate does not depend on the age of individuals, the death of individuals occurs evenly in this type, the mortality rate remains constant throughout life ( type I ). Such a survival curve is characteristic of species whose development occurs without metamorphosis with sufficient stability of the born offspring. This type is called type of hydra- it has a survival curve approaching a straight line.
- In species for which the role of external factors in mortality is small, the survival curve is characterized by a slight decrease until a certain age, after which there is a sharp drop due to natural (physiological) mortality ( type II ). The nature of the survival curve close to this type is characteristic of humans (although the human survival curve is somewhat flatter and is somewhere between types I and II). This type is called Drosophila type: this is what Drosophila demonstrates in laboratory conditions (not eaten by predators).
- Many species are characterized by high mortality in the early stages of ontogeny. In such species, the survival curve is characterized by a sharp drop in the region of younger ages. Individuals that have survived the “critical” age demonstrate low mortality and survive to older ages. The type is named oyster type (type III ).
Sex structure populations
The sex ratio is directly related to the reproduction of the population and its sustainability.
There are primary, secondary and tertiary sex ratio in the population:
- Primary sex ratio determined by genetic mechanisms - the uniformity of the divergence of the sex chromosomes. For example, in humans, XY chromosomes determine the development of the male sex, and XX - the female. In this case, the primary sex ratio is 1:1, i.e., equally likely.
- Secondary sex ratio - this is the sex ratio at the time of birth (among newborns). It can differ significantly from the primary one for a number of reasons: the selectivity of eggs for spermatozoa carrying the X- or Y-chromosome, the unequal ability of such spermatozoa to fertilize, and various external factors. For example, zoologists have described the effect of temperature on the secondary sex ratio in reptiles. A similar pattern is characteristic of some insects. So, in ants, fertilization is ensured at temperatures above 20 ° C, and unfertilized eggs are laid at lower temperatures. Males hatch from the latter, and mostly females from the fertilized ones.
- Tertiary sex ratio - sex ratio among adult animals.
Spatial structure populations reflects the nature of the distribution of individuals in space.
Allocate three main types of distribution of individuals in space:
- uniform or uniform(individuals are evenly distributed in space, at equal distances from each other); occurs rarely in nature and is most often caused by acute intraspecific competition (for example, in predatory fish);
- congregational or mosaic(“spotted”, individuals are located in isolated clusters); occurs much more frequently. It is associated with the characteristics of the microenvironment or the behavior of animals;
- random or diffuse(individuals are randomly distributed in space) - can be observed only in a homogeneous environment and only in species that do not show any desire to unite in groups (for example, in a beetle in flour).
Population size denoted by the letter N. The ratio of the increase N to the unit time dN / dt expressesinstantaneous speedchanges in population size, i.e. change in population at time t.Population Growthdepends on two factors - fertility and mortality, provided there is no emigration and immigration (such a population is called isolated). The difference between birth rate b and death rate d and isisolated population growth rate:
Population stability
This is its ability to be in a state of dynamic (i.e., mobile, changing) equilibrium with the environment: environmental conditions change - the population also changes. One of the most important conditions for sustainability is internal diversity. In relation to a population, these are mechanisms for maintaining a certain population density.
Allocate three types of dependence of population size on its density .
First type (I) - the most common, characterized by a decrease in population growth with an increase in its density, which is provided by various mechanisms. For example, many species of birds are characterized by a decrease in fertility (fertility) with an increase in population density; an increase in mortality, a decrease in the resistance of organisms with an increased population density; change in the age of onset of puberty depending on the density of the population.
The third type ( III ) characteristic of populations in which the “group effect” is noted, i.e., a certain optimal population density contributes to better survival, development, and vital activity of all individuals, which is inherent in most group and social animals. For example, for the resumption of populations of heterosexual animals, at least a density is needed that provides a sufficient probability of meeting a male and a female.
Thematic tasks
A1. Biogeocenosis is formed
1) plants and animals
2) animals and bacteria
3) plants, animals, bacteria
4) territory and organisms
A2. Consumers of organic matter in forest biogeocenosis are
1) spruce and birch
2) mushrooms and worms
3) hares and squirrels
4) bacteria and viruses
A3. The producers in the lake are
2) tadpoles
A4. The process of self-regulation in biogeocenosis affects
1) sex ratio in populations of different species
2) the number of mutations that occur in populations
3) predator-prey ratio
4) intraspecific competition
A5. One of the conditions for the sustainability of an ecosystem can be
1) her ability to change
2) variety of species
3) fluctuations in the number of species
4) the stability of the gene pool in populations
A6. Reducers are
2) lichens
4) ferns
A7. If the total mass received by a consumer of the 2nd order is 10 kg, then what was the total mass of producers that became a source of food for this consumer?
A8. Specify the detrital food chain
1) fly - spider - sparrow - bacteria
2) clover - hawk - bumblebee - mouse
3) rye - titmouse - cat - bacteria
4) mosquito - sparrow - hawk - worms
A9. The initial source of energy in the biocenosis is energy
1) organic compounds
2) inorganic compounds
4) chemosynthesis
1) hares
2) bees
3) blackbirds
4) wolves
A11. In one ecosystem you can find oak and
1) gopher
3) lark
4) blue cornflower
A12. Power networks are:
1) relationships between parents and offspring
2) family (genetic) ties
3) metabolism in the cells of the body
4) ways of transferring substances and energy in an ecosystem
A13. The ecological pyramid of numbers reflects:
1) the ratio of biomass at each trophic level
2) the ratio of the masses of an individual organism at different trophic levels
3) food chain structure
4) diversity of species at different trophic levels
