The main signs of a living organism. The main features of wildlife

Laboratory workshop. The method of breeding and keeping cultures of the simplest animals, and their application in the educational process

You can find free-living protozoa in nature in almost every body of water - in a pond, ditch, swamp, in the coastal parts of large bodies of water, etc. They are found in the thickness and at the bottom; on various underwater objects, on aquatic plants, among rotting plant debris and in the soil.

The small size of the protozoa makes it difficult to work with them. However, their abundance in nature and easy accessibility, as well as the simplicity of their maintenance and breeding, favor working with them.

Living cultures of protozoa are necessary for a teacher in the study of protozoa, which begins the course of zoology, in the study of cellular life forms in the section of cytology of general biology, in circle work and when students perform extra-class individual work and excursions to study the aquatic fauna. In the process of studying the cultures of protozoa, they get acquainted with free-living single-celled organisms, learn to find them in nature, maintain and breed cultures of protozoa in the laboratory and at home as live food for some fry of aquarium fish. They get acquainted in detail with their structure, the way of life of the most important representatives of the protozoa, their reproduction and relationships with other forms, get acquainted with the signs of classes and orders of the simplest.

The experience of many biology teachers convinces that, when studying the simplest, students can breed ciliates on various nutrient media, observe the formation of digestive vacuoles when "feeding" them with paints that are harmless to them, conduct experiments that clarify the behavior of ciliates, depending on the effect on them various irritants: crystals of table salt, pieces of bacterial film, light, as well as the rate of reproduction of ciliates, depending on the ambient temperature.

In all cases, when possible, acquaintance with an animal should begin with an examination of it in its living form. Considering a live animal versus studying a fixed animal has a number of advantages:

1. The student sees the natural color of the animal, the natural shape of the body, characteristic postures, can observe the way the animal moves and its reaction to external stimuli.

2. Observing living animals, one can best understand one of the most important principles of a living organism - the unity of form and function.

Various free-living protozoa - amoeba, euglena, ciliates (sarcodes, flagellates and ciliates) often live together. Therefore, along with special methods of work, there are a number of general conditions for breeding the simplest a number of general rules:

1. Collecting protozoa in nature just before class is unreliable.

2. Handouts in the required quantity and quality composition are provided only by cultivation, i.e. the creation of conditions favorable for life and reproduction of the simplest.

3. To obtain a prefabricated culture of protozoa, only glassware made of transparent (not greenish-bottle) glass is used. You can use any glassware, jars, glasses, yogurt, Koch dishes, Petri dishes with a capacity of 300 ml to 3-4 liters. Any metal utensil is unsuitable due to the harmful effect on animals of metal dissolved in water, even in negligible doses.

Water. Tap water is not suitable because it is chlorinated. It can be used only after dechlorination, for which it is left in a glass vessel for 7-10 days for chlorine to escape, stirring from time to time with a glass rod. During this time, it is saturated with oxygen. Before use, filter the water through a folded paper filter, adding fresh water as it evaporates, keeping, if possible, the same level.

The most reliable water for breeding protozoa is rain, melt, lake, pond water, it is preliminarily boiled, and then filtered through a thick silk sieve or folded paper filter.

Conditions for keeping crops. The development of protozoa largely depends on the temperature of the water and lighting:

1. The most favorable temperature is in the range of 18-23 ° C, a sharp change in temperature negatively affects.

2. Banks with culture are placed near the window, but protected from the unfavorable effects of direct sunlight (curtains, a screen, a cardboard plate).

3. Eliminate any possibility of chemical contamination of the water.

4. Do not transfer jars with cultures from one place to another in order to avoid shaking the liquid.

5. Keep jars covered with glass plates to reduce evaporation of water and contamination of the culture with dust.

Nutrient medium for protozoa... Bacteria most often serve as food for protozoa, therefore a nutrient medium rich in bacteria is prepared for the cultivation of bacteria. Usually rice, soil and manure infusions are used.

1. Rice (wheat). In a flask with water, grains of rice or wheat are boiled for several minutes, water is boiled in the flask at the same time, then cooled, filtered and placed in Petri dishes (Koch) and 5-6 grains are placed in each.

2. Soil infusion: 1/4 jars are poured with garden soil and 3/4 of raw water.

3. Manure infusion: 100 g of horse manure, aged for 10 days in a cool place (in the basement), add 1 liter of boiling water with constant stirring.

4. Mixed infusion: 100g. soil land + 50g manure + 1 liter of boiled hot water.

The culture media are left open for 7-10 days for bacteria to grow in them.

Introduction of the simplest into the culture. They take three cans and fill them with water from different reservoirs - ditches, puddles, ponds; silt, fresh and decaying vegetation are placed on the bottom. Water is poured through a net of nylon fabric to get rid of predatory animals (crustaceans, worms) that feed on ciliates, then add this water in an amount of 200-500 ml into a vessel with a nutrient medium.

The combined culture of the protozoa is set up no later than a month before using it in the classroom. From time to time it is viewed, for which they take samples with a pipette from different places - from the bottom, from the water column, from the surface of the film, then the species composition of the protozoa is noted.

The protozoa should be caught in a reservoir with a net made of dense material. They must be collected from various parts of the reservoir - from the bottom, from the thickness, from the surface, and placed in separate jars, providing them with an appropriate label indicating where and when the sample was taken, from which reservoir and from which part of it (from the bottom, from the water).

Cultures of protozoa, taken in summer and autumn, can be kept without great difficulty throughout the year, although protozoa can be found in nature in winter - there are cysts of these animals in the silt at the bottom of the reservoir of thickets.

Study of cultures. The amoeba and ciliates of the trumpeter are examined under a magnifying glass, and the rest under a microscope.

The glasses for the preparation (object and coverslip) must be clean and dry, therefore, when starting work, they must be wiped well. Hold the glass with two fingers (most conveniently with the thumb and forefinger) by its opposite edges, without touching the surface of the glass with your fingers to avoid contamination.

Pipette a drop of culture onto a glass slide; holding the cover glass in a slightly inclined position in this way, apply its lower edge to the slide at the base of the drop and gently lower it onto the drop.

The culture drop should not be very large so that the glass slide does not float on it. Remove excess liquid with filter paper.

In cases where large enough objects are filtered (amoeba protea, volvox, ciliate trumpeter) and there is a danger of damaging them by covering with a cover glass, then small "legs" are made on liquid glass from wax or plasticine, lifting the cover glass. The wax is warmed between the fingers of the hand and scratched on it with each of the four corners of the cover glass, the glass is placed on the drop with the legs down.

Breeding ciliates. Usually, ciliates are bred in vitro. For feeding the fry, the most commonly used shoe is P. caudatum, the size of which usually ranges from 0.1 to 0.3 mm.

For breeding shoes, it is best to take a pure culture of ciliates. If it is impossible to acquire a pure culture, then you can breed it yourself.

Slippers are found in almost every body of water. They are obtained in this way: water from reservoirs is poured into three glass jars; in one of them they put twigs taken from the bottom, rotting leaves and other decaying plant residues, in the other they collect various plants (duckweed, elodea), in the third - silt taken from the bottom. Thus, three banks will create different conditions for the life of shoes. After filling the jars with water, you need to look through and remove from them all crustaceans, insects and their larvae, since most of these animals eat ciliates.

In summer, you can also take a sample from the bottom of a dried-up reservoir, and in winter - soil from under the ice. Banks are placed in a bright place (not under direct sunlight) at room temperature and covered with glass.

After the jars have stood for 2-3 days, shake them slightly and look at the light. At the same time, it is possible to determine whether there are many shoes in the vessel and whether there are any of its enemies - aquatic insects and crustaceans.

Taking a drop from a jar onto a glass slide, examine it with a microscope or magnifying glass. The slipper is easy to distinguish from other animals by their quick, fluid movement. Their body is spindle-shaped, resembling the sole of a shoe.

Under a low magnification of the microscope, it is clearly visible how, when moving forward, they rotate around their axis.

Ciliates often accumulate in masses on pieces of organic debris of the leaf or on the surface bacterial film, where they feed on bacteria. Under uneven illumination of the vessel, the overwhelming majority of shoes are concentrated at a more illuminated wall.

If reproduction is not fast enough, you can add 1-2 drops of boiled milk to the water, but usually after 2-3 days, ciliates are quite enough. In this case, take a drop of water from the wall located on the cardinal side, and carefully examine it under a microscope at low magnification.

If no animals are found in the sample, except for shoes, then the culture is suitable for mass reproduction. Otherwise, a large drop of water with the maximum concentration of ciliates is located on a clean glass, and next to it from the cardinal direction is a drop of fresh settled water. Both drops are connected by means of a sharpened match by a water bridge; the shoes rush towards fresh water and light at a greater speed than all other microorganisms. Shoes reproduce very quickly, so at the beginning there is no need for large quantities of them for breeding.

When breeding shoes, you can use various vessels, glass jars are most convenient. The best is water with a temperature of about 26 ° C, fairly good results are obtained at room temperature, but the culture can be kept at a much lower temperature (4-10 ° C and even lower). Prolonged maintenance of culture at optimal temperature leads to their rapid reproduction, and then to their rapid disappearance.

It is best to use three-liter jars when breeding ciliates. In one of them, water is settled, topped up instead of decreasing, and in two, the culture of ciliates is maintained. From them, in turn, the shoes are taken from the places of their greatest concentration using a rubber bulb with a glass tip.

The slipper can be grown on a banana peel. The peel of ripe intact bananas is dried and then stored in a dry room; the dried peel is washed and a small amount (1-3 cm 3) is placed in the culture.

The simplest is to breed shoes with skimmed cheese or boiled milk. Milk should be added in 1-3 drops every few days (less is better than more). If a sediment forms at the bottom or turbidity on the walls of the vessel, the jar should be washed, pour settled water and place a culture of shoes in it. It is always necessary to keep in stock the culture of slippers, which can be used to replace the dead one, since the culture on milk is very unstable (it is especially easy to die with its excess). In a milk solution, the shoes feed on lactic acid bacteria that multiply there in a huge (amount).

You can breed shoes with hay infusion. To do this, put 10 g of meadow hay or a liter of water in a clean saucepan or flask and boil for 15-20 minutes. During this time, all protozoa and their cysts die, but bacterial spores remain. After boiling, the cooled infusion is filtered through a funnel with cotton wool, poured into vessels and covered with cotton-gauze swabs. After 2-3 days, hay sticks develop from the spores, which serve as food for ciliates. In this form, culture can be added to the infusions as needed. It persists for a month.

The shoe can be bred on dried lettuce leaves, placed in a bag of gauze, and on baker's yeast.

Slippers serve as natural orderlies of fresh floors, destroying bacteria.

To obtain a pure culture, it is necessary to free the culture from bacteria and organic particles suspended in water. A rich culture of ciliates is placed in a cylinder, cotton wool is placed on top of the sludge liquid and then, carefully, fresh water is added to the cotton wool. After half an hour, most of the shoes are moved into fresh water and together with it they are transferred with a pear into a vessel with settled water.

Euglena- small unicellular animal organisms belonging to the group of green flagellates such as sarcomastia lophora. Just like other representatives of the flagellate class, they are characterized by the presence of flagella. Euglena has special organelles - chromatophores containing chlorophyll, with the help of which they, like plants, synthesize carbohydrates in the light from inorganic substances. This feature of euglena brings them closer to plants and at the same time distinguishes euglena as a completely special type of food for fry of a number of fish, in particular herbivorous ones.

The flagellate breeder. Numerous species of the genus Euglena are often found in lakes, ponds, ditches and puddles. Many of they are inhabited by reservoirs rich in organic matter. Of particular interest are euglena, obtained from permanent and temporary puddles, they have the advantage that they can be kept dry. In addition, they are more susceptible to cultivation on media composed of distilled water, i.e., with a certain chemical composition.

Many species of euglena live in water bodies, differing both in size and in body shape. The most common E. visidis is green euglena. Its body has a fusiform shape, the posterior end is pointed. There is a flagellum in front, at its base there is a bright red stigma-eye spot. Outside, euglena is covered with a membrane, inside are visible green chromatophores and colorless nuclei of paramila, which is the product of assimilation.

Euglene can be obtained in puddles using a water net, but it is much more convenient to breed them in culture.

As a nutrient medium, you can use the infusion, on soil taken from the bottom of the reservoir (in particular, dry), where these organisms are common. However, it is more convenient to use special environments: Knop and Beneke.

Composition of Knop's medium: distilled water, 1000 ml, MgSO 4 -0-25 g, Ca (NO3) 2 - 1.0 g, KHPO-0.25 g, KC1-0.12 g. FeCb - traces.

Composition of Beneke's medium: distilled water - 1500 ml, NHNO 3 - 0.3 g, CaCl - 0.15 g, KHPO - 0.15 g, MgSCb - 0.15 g. On these nutrient media, euglena reproduce slowly. The addition of organic matter is required. As one of them, you can use a broth made from finely chopped pieces of meat (without fat), followed by filtering through cotton wool. The broth can be stored in a glass container in the refrigerator. Euglen can also be bred in hay infusion prepared for ciliates.

After 5-7 days, the liquid turns green due to the huge number of flagellates multiplying in it. 1/4 l of fresh solution should be poured into the culture once a month; it should be kept in the light. Thanks to the positive phototaxis of euglena, it is easy to increase their concentration by picking up a green film, which is clearly visible with the naked eye, which forms on the surface of water in places most brightly illuminated by the sun or a beam of artificial illumination with a pipette. The euglena obtained in this way should be separated from the liquid by filtering it through a sieve. The extinction of a culture is noticed by its clarification, as well as by the powdery sediment at the bottom of the vessel, which is encystated euglena.

Breeding amoebas. Common amoeba (A. proteus) is one of the largest amoebas, it reaches a size in the active state of 0.2-0.5 mm. Amoebas are found in small freshwater bodies of water - ponds, ditches, puddles, swamps, rich in decaying plant remains, mainly in the bottom layer of water or directly in the mud of stagnant bodies of water. It is well cultivated in laboratory conditions in Petri dishes on infusions of rice or birch branches, even better - in soil infusion.

Amoeba is studied at school (grade 6). In the classroom, live amoebas are examined. In the warm season, amoebas can be collected for practice directly v nature. Samples from reservoirs are taken with a plankton net, passing them near the silt surface. The silt is slightly stirred up by the movement of the net and is collected in the last one. You can also lower an excursion bucket into the water with a hole down, tilt the quadrangular aquarium vessel sharply, the outgoing air will raise the silt from the bottom, which is scooped up by the vessel. The use of the material is possible after the sample brought from the reservoir has calmly stood for several hours.

Amoeba is also collected by gently scraping with a scalpel the superficial plaque on the underside of floating leaves of aquatic vegetation (egg capsules, water lilies, duckweed).

It is not difficult to cultivate large amoebas in the laboratory. From suitable reservoirs (best of all from a reservoir where amoebas are found) take water together with silt and decaying residues, then filtered. The culture becomes more abundant if it is fed, for this, hay infusion is prepared - chopped hay is poured with water and left for 3-4 days for the development of hay sticks, then water filtered from the pond is poured.

The culture of amoeba develops even better on specially prepared nutrient media: on rice, soil infusion.

1. Filtered pond water is poured in a thin layer into Petri dishes, 5-6 grains of rice are placed in each dish. After a few days, a cloud forms around the grains - bacteria grow, which serve as food for amoeba. In the cups prepared in this way, live amoebas are introduced, which live and reproduce well. If there is a culture of ciliates tetrahimenes in the laboratory, then every 3-4 days, a little bit of live tetrachimenes should be added to Petri dishes, which are readily eaten by amoebas. Re-sowing of crops should be carried out in 1.5-2 months.

2. To prepare the soil infusion, fill a glass jar 1/4 with garden soil and 3/4 with raw water, leave it open for 7-10 days so that as many bacteria as possible develop in it, and then on this culture

you can breed amoebas.

3. Manure infusion is prepared from horse manure kept in a cool dry place (in the basement) for 10 days. Gradually pour about 100 g of such manure with one liter, boiling water with constant stirring. You can successfully use a mixed infusion: 100 g of soil + 50 g of manure per 1 liter of water.

4. The best results are achieved with a mixture of soil infusion and infusion of young tree branches (birch). Simultaneously with the infusion, an infusion of young deciduous trees is prepared on the garden soil. After 7-10 days, drain both infusions in equal parts into one vessel. A rich microflora will develop here in 5-7 days. Pour the nutrient medium into several Petri dishes (Koch dishes - crystallizers) and populate with amoebas, catching them with a pipette from a sample brought from the reservoir.

Field observations: Counting soil invertebrates.

Equipment:traps - jars with steep edges (you can use plastic jars from under mayonnaise, sour cream or glass jars 0.5 l), 7% acetic acid solution, spatula, strainer, 2 jars 1- 2L for collecting insects.

Traps (usually 10 pieces) are buried in the soil in the most typical area of ​​the studied ecosystem at a distance of 1 - 1.5 m from each other. The jar is buried in such a way that its edges are just below the surface of the earth. A fixing liquid (7% acetic acid solution) is poured onto the bottom of the can (2-3 cm). The diary records the time when the traps were set and their number. The fishing line is usually checked once a day. When checking, the trapped insects are collected in a separate jar. Removing insects from the fixing liquid can be carried out either with tweezers or by filtering the liquid from the trap through a strainer, from which the remaining insects are transferred to a separate jar. After the check, the diary records the check time, weather conditions and the number of traps checked. Traps filled to the brim with water (for example, after rain) are considered inoperative. For example, in a line of 10 traps, in a day only 9 traps were not flooded with water. Thus, the abundance of insects in the remaining jars will be equal to 9 trap days. Collecting insects in another day with all traps working, will add up to the first 19 trap-days. The abundance of insects is usually recalculated for 10 trap-days. Those. if in 19 trap-days 190 specimens of ants were caught in jars, then their abundance is 100 individuals per 10 trap-days.

As with birds, identifying insects and other invertebrates requires some skill. At the same time, the definition of most insects by species is often only within the power of specialist entomologists. Therefore, in order to characterize this group of animals, one can restrict the identification of collected specimens to larger taxa - orders or families. Usually, representatives of the same insect family are characterized by similar ecological functions in ecosystems, which allows them to be considered as a single component of the biocenosis. For example, the overwhelming majority of representatives of the ground beetle family are predators, leaf beetles are herbivorous, etc. The appendix contains brief illustrated tables to identify the main orders and families of insects.

Study of the animal population of the reservoir

The role of zooplankton in the transformation of energy and the biotic circulation of substances, which determines the productivity of water bodies, is very great. In most of the lakes, the main flow of energy goes through plankton. When solving general and specific issues related to the problem of studying the productivity of zooplankton communities, reliable data on the number and biomass of the species populations that make up the community are necessary, and in determining productivity, accurate data on the age composition of populations of mass species, individual weight of animals, their fertility and the duration of the development of individual stages. To obtain these data, long-term observations on water bodies are required.

The methodology for conducting long-term and short-term studies, as well as the degree of generalization, can vary greatly. However, there are strict principles for collecting, processing and evaluating results that ensure the reliability of data obtained from studies of various durations.

Equipment:Standard quantitative Jedi net (upper ring diameter - 18 cm, lower - 2 cm) made of gas No. 49-56 (for collecting crustaceans) or No. 64-70 (for catching rotifers); high-quality Apstein net: nets for plankton; plankton digger; jars (0.251; formalin; microscope; slides and coverslips; tweezers; tray; pipette; Bogorov's chamber.

With the help of the network, samples of phyto- and zooplankton are taken on the surface and at a depth of up to 2-3 meters. To determine the qualitative composition, two samples are taken from each horizon (the interval is 50 cm). Samples can be processed both live and fixed. For fixation, formalin or 70% alcohol is used.

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More than 2 million animals live on Earth, and this list is constantly growing.

The science that studies the structure, behavior, features of the vital activity of animals is called zoology.

The sizes of animals range from a few microns to 30 m. Some of them are visible only through a microscope, such as amoeba and ciliates, while others are giants. These are whales, elephants, giraffes. The habitat of animals is very diverse: it is water, land, soil and even living organisms.

Having common features with other representatives of eukaryotes, animals also have significant differences. Animal cells are devoid of membranes and plastids. They feed on ready-made organic substances. A significant number of animals move actively and have special organs of movement.

Animal kingdom divided into two subkingdoms: unicellular (protozoa) and multicellular.

Rice. 77. The simplest: 1 - amoeba; 2 - green euglena; 3 - foraminifera (shells); 4 - ciliate shoe ( 1 - large core; 2 - small core; 3 - cellular mouth; 4 - cell pharynx; 5 - digestive vacuole; 6 - powder; 7 - contractile vacuoles; 8 - cilia)

The simplest are divided into several types, the most widespread and significant of them are Sarcodes, Flagellates, Sporozoans and Ciliates.

Sarcodes (Roots). The amoeba is a typical representative of the sarcode. Amoeba is a free-living freshwater animal that does not have a constant body shape. The amoeba cell, when moving, forms pseudopodia, or pseudopods, which also serve to capture food. In the cell, the nucleus and digestive vacuoles are clearly visible, which are formed at the site of food capture by the amoeba. In addition, there is also contractile vacuole, through which excess water and liquid metabolic products are removed. Amoeba reproduces by simple division. Breathing occurs across the entire surface of the cell. Amoeba has irritability: a positive reaction to light and food, a negative reaction to salt.

Conch amoeba - foraminifera have an external skeleton - a shell. It consists of an organic layer saturated with limestone. The shell has numerous holes - holes through which pseudopodia protrude. The size of the shells is usually small, but in some species it can reach 2-3 cm. The shells of dead foraminifera form deposits on the seabed - limestone. Other shell amoebas also live there - radiolarians (beams). Unlike foraminifera, they have an internal skeleton, which is located in the cytoplasm and forms needles - rays, often of an openwork design. In addition to organic matter, the skeleton contains strontium salts - the only case in nature. These needles form a mineral called celestine.

Flagellate. These microscopic animals have a constant body shape and move with the help of flagella (one or more). Euglena green - a unicellular organism that lives in water. Its cell has a fusiform shape, at the end of it there is one flagellum. A contractile vacuole and a light-sensitive ocellus (stigma) are located at the base of the flagellum. In addition, the cell contains chromatophores containing chlorophyll. Therefore, euglena photosynthesizes in the light, in the dark it feeds on ready-made organic substances.

After several asexual generations, cells appear in erythrocytes, from which gametes develop. For further development, they must enter the intestines of the Anopheles mosquito. When a mosquito bites a patient with malaria, blood gametes enter the digestive tract, where sexual reproduction and the formation of sporozoites take place.

Ciliates- the most complexly organized representatives of the protozoa, there are more than 7 thousand species. One of the most famous representatives - ciliate shoe. It is a rather large unicellular animal that lives in fresh water bodies. Its body resembles the footprint of a shoe and is covered with a dense shell with cilia, the synchronous movement of which ensures the movement of the ciliates. It has a cellular mouth surrounded by cilia. With their help, the ciliate creates a stream of water, with which bacteria and other small organisms that it feeds on enter the "mouth". A digestive vacuole is formed in the body of the ciliate, which can move throughout the cell. Undigested food residues are thrown out through a special place - powder. The ciliate has two nuclei - a large and a small one. The small nucleus takes part in the sexual process, and the large one controls the synthesis of proteins and cell growth. The shoe reproduces both sexually and asexually. Asexual reproduction is replaced by sexual reproduction after several generations. Further (§ 58-65) the multicellular organisms of the animal kingdom are considered.

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Section 56. Seed plants§ 58. The kingdom of animals. Multicellular: sponges and coelenterates

The main advantage of cultured cells is the ability to observe cells in vivo using a microscope.

It is essential that when working with cell cultures in the experiment, healthy cells are used, and they remain viable throughout the entire experiment. In experiments on a whole animal, the state of the kidneys, for example, can be assessed only at the end of the experiment, and, moreover, usually only qualitatively.

Cell cultures are a genetically homogeneous population of cells that grow under constant conditions. Moreover, the researcher can change these conditions within certain limits, which allows him to assess the effect on cell growth of various factors - pH, temperature, concentration of amino acids, vitamins, etc. Growth can be assessed over a short period of time or by an increase in the number or size cells, or by the incorporation of radioactive precursors into cellular DNA.

These real advantages over whole animal studies place cell cultures as an experimental system on a par with microbial cultures.

Moreover, when working with cell cultures, significant results can be obtained using a very small number of cells. Experiments requiring the use of 100 rats or 1000 people to clarify a particular issue can be performed with equal statistical reliability on 100 cultures on coverslips. That. one cell can replace an entire clinic of patients. This is an important advantage when it comes to humans, and, moreover, removes many of the ethical problems that arise when it is necessary to use a large group of animals for an experiment.

Since cells in culture are readily available for various biochemical manipulations, when working with them, radioactive precursors, poisons, hormones, etc. can be introduced at a given concentration and for a given period. The amount of these compounds can be an order of magnitude less than in experiments on a whole animal. The danger that the test compound is metabolized by the liver, stored in the muscles, or excreted by the kidneys also disappears. When using cell cultures, as a rule, it is easy to establish that, at a certain concentration, the substance added to the culture is in contact with the cells for a given period of time. This ensures that real values ​​of the rate of incorporation or metabolism of the compounds under study are obtained.

Cell culture is used in various scientific and practical fields:

Genetics
The ability of cells to grow in culture has led to the development of the following methods:

• Cloning
• Cell storage and fusion
• Receiving and working with mutant cells.

Immunology
Hybridoma technology: cells synthesizing antibodies of interest to scientists are fused with myeloma cells, which produce antibodies with unknown specificity.
The resulting hybridomas made it possible to establish the production of monoclonal antibodies: a mouse is immunized with a crude antigen preparation and then its spleen cells hybridize with myeloma cells. Among the resulting hybrid cells, there is at least one that produces antibodies specific to the original antigen.

Biotechnology
Cell cultures can be a valuable source of hormones and other secreted materials. Cell cultures are already becoming important producers of the species-specific antiviral agent interferon.

Virology and cell transformation
Advances in virology are largely driven by the ability to grow viruses in cell cultures.
As a result of the application of these methods, it turned out that viruses can not only infect and kill cells, but can also cause changes in the nature of cell growth - a phenomenon known as viral cell transformation. These changes, leading to the appearance of cells that do not respond to their neighbors in the way that is characteristic of untransformed cells, are of particular interest due to the fact that they can help to understand the nature of transformation, since similar changes that occur with cells in vitro play a certain role in tumor induction.
Since most viral diseases are currently treated by the administration of antisera, the cultivation of viruses is essential both for the identification of viruses and for their use in vaccine production.
These tasks are solved mainly using cell cultures.

The type of protozoa includes about 25 thousand species of unicellular animals living in water, soil, or organisms of other animals and humans. Having a morphological similarity in the structure of cells with multicellular organisms, protozoa differ significantly from them in functional terms.

If the cells of a multicellular animal perform special functions, then the cell of the simplest is an independent organism capable of metabolism, irritability, movement and reproduction.

The simplest are organisms at the cellular level of organization. In morphological terms, the simplest is equivalent to a cell, but physiologically it is a whole independent organism. The overwhelming majority of them are microscopically small (from 2 to 150 microns). However, some of the living protozoa reach 1 cm, and the shells of a number of fossil rhizopods are up to 5-6 cm in diameter.The total number of known species exceeds 25 thousand.

The structure of the simplest is extremely diverse, but they all have features characteristic of the organization and function of the cell. Common in the structure of the structure of the protozoa are two main components of the body - the cytoplasm and the nucleus.

Cytaplasm

The cytoplasm is limited by the outer membrane, which regulates the entry of substances into the cell. In many protozoa, it is complicated by additional structures that increase the thickness and mechanical strength of the outer layer. Thus, formations such as pellicle and shell arise.

The cytoplasm of protozoa usually splits into 2 layers - the outer one is lighter and denser - ectoplasm and internal, equipped with numerous inclusions, - endoplasm.

General cellular organelles are localized in the cytoplasm. In addition, a variety of special organelles can be present in the cytoplasm of many protozoa. Various fibrillar formations are especially widespread - supporting and contractile fibers, contractile vacuoles, digestive vacuoles, etc.

Core

Protozoa have a typical cell nucleus, one or more. The nucleus of the protozoa has a typical two-layer nuclear envelope. Chromatin material and nucleoli are distributed in the nucleus. The nuclei of protozoa are characterized by exceptional morphological diversity in size, the number of nucleoli, the amount of nuclear juice, etc.

Features of the life of protozoa

Unlike somatic cells, multicellular protozoa are characterized by the presence of a life cycle. It is composed of a number of successive stages, which in the existence of each species are repeated with a certain regularity.

Most often, the cycle begins with the zygote stage corresponding to the fertilized egg of multicellular organisms. This stage is followed by single or multiple repeated asexual reproduction, carried out by cell division. Then sex cells (gametes) are formed, the pairwise fusion of which again gives a zygote.

An important biological feature of many protozoa is the ability to encysting. In this case, the animals are rounded, discard or draw in the organelles of movement, emit a dense shell on their surface and fall into a state of rest. In an encystated state, protozoa can tolerate abrupt changes in the environment, maintaining their viability. When conditions favorable for life return, the cysts open and the protozoa emerge from them in the form of active, mobile individuals.

According to the structure of the organelles of movement and the characteristics of reproduction, the type of protozoa is divided into 6 classes. The main 4 classes: Sarcodes, Flagellates, Sporozoans and Infusoria.

Modern science divides all nature into living and nonliving. At first glance, this division may seem simple, but sometimes it is quite difficult to decide whether a particular one is actually alive or not. Everyone knows that the main properties, signs of living things are growth and reproduction. Most scientists use seven life processes or signs of living organisms that distinguish them from inanimate nature.

What is typical for all living things

All living things:

• Consist of cells.
• They have different levels of cellular organization. Tissue is a group of cells that perform a common function. An organ is a group of tissues that perform a common function. An organ system is a group of organs that perform a common function. An organism is any living being in a complex.
• They use the energy of the Earth and the Sun, which they need for life and growth.
• React to the environment. Behavior is a complex set of reactions.
• Are growing. Cell division is the orderly formation of new cells that grow to a certain size and then divide.
• They multiply. Reproduction is not essential for the survival of individual organisms, but it is essential for the survival of the entire species. All living things reproduce in one of the following ways: asexual (the production of offspring without the use of gametes), sexual (the production of offspring by connecting the sex cells).
• Adapt and adapt to environmental conditions.

The main signs of living organisms

• Motion. All living things can move and change their position. This is more evident in animals that can walk and run, and less evident in plants, parts of which can move to track the movement of the sun. Sometimes the movement can be so slow that it is very difficult to see it.

• Breathing is a chemical reaction that takes place inside a cell. It is the process of releasing energy from nutrients in all living cells.
• Sensitivity is the ability to detect changes in the environment. All living things are able to respond to stimuli such as light, temperature, water, gravity, and so on.

• Growth. All living things are growing. The constant increase in the number of cells and the size of the body is called growth.
• Reproduction is the ability to reproduce and transmit genetic information to your offspring.

• Excretion - getting rid of waste and toxins. As a result of many chemical reactions taking place in cells, it is necessary to get rid of metabolic products that can poison cells.
• Nutrition - the consumption and use of nutrients (protein, carbohydrates, and fats) needed for growth, tissue repair, and energy. In different types of living beings, this happens in different ways.

All living things are made of cells

What are the main traits The first thing that makes living organisms unique is that they are all made up of cells, which are considered the building blocks of life. Cells are amazing, despite their small size, they can work together to form such large body structures as tissues and organs. Cells are also specialized - for example, liver cells are located in the organ of the same name, while brain cells function only in the head.

Some organisms are made of just one cell, like many bacteria, while others are made up of trillions of cells, like humans. are very complex creatures with incredible cellular organization. This organization begins with DNA and extends to the entire body.

Reproduction

The main signs of a living (biology describes this even in a school course) also include such a concept as reproduction. How do all living organisms get to the Earth? They do not appear out of thin air, but through reproduction. There are two main ways of producing offspring. The first is the well-known sexual reproduction. This is when organisms produce offspring by combining their gametes. Humans and many animals fall into this category.

Another type of reproduction is asexual: organisms produce offspring without gametes. Unlike sexual reproduction, where the offspring has a different genetic makeup, not the same as that of either parent, the asexual method produces offspring that are genetically identical to their parent.

Growth and development

The main signs of a living also imply growth and development. When offspring are born, they don't stay that way forever. The person himself can be an excellent example. As people grow, they change, and the more time passes, the more these differences are noticeable. If we compare an adult and a baby with whom he once came into this world, then the differences are simply colossal. Organisms grow and develop throughout life, but these two terms (growth and development) do not mean the same thing.

Growth is when size changes, from small to large. For example, with age, all organs of a living organism grow: fingers, eyes, heart, and so on. Development implies the possibility of change or transformation. This process begins even before birth, when the first cell appears.

Energy

Growth, development, cellular processes and even reproduction can occur only if living organisms accept and can use energy, which is also included in the main features of a living being. All life energies ultimately come from the sun, and this force energizes everything on Earth. Many living organisms, such as plants and some algae, use the sun to produce their own food.

The process of converting sunlight into chemical energy is called photosynthesis, and the organisms that can produce it are called autotrophs. However, many organisms cannot create their own food, and therefore have to feed on other living organisms for energy and nutrients. Organisms that feed on other organisms are called heterotrophs.

Responsiveness

When listing the main features of living nature, it is important to note the fact that all living organisms have an inherent ability to respond in a certain way to various environmental stimuli. This means that any change in the environment triggers certain reactions in the body. For example, such as the Venus flytrap will close its bloodthirsty petals quite quickly if an unsuspecting fly lands there. If possible, the turtle will come out to bask in the sun, and not remain in the shade. When a person hears a rumbling in his stomach, he will go to the refrigerator to make a sandwich, and so on.

Irritants can be external (outside the human body) or internal (inside the body), and they help living organisms to maintain balance. They are represented as various senses in the body, such as sight, taste, smell and touch. The speed of response can vary from organism to organism.

Homeostasis

The main features of living organisms include regulation called homeostasis. For example, temperature regulation is very important for all living things, because body temperature affects such an important process as metabolism. When the body gets too cold, these processes slow down and the body can die. The opposite happens if the body overheats, the processes are accelerated, and all this leads to the same destructive consequences.

What do living things have in common? They must have all the basic characteristics of a living organism. For example, a cloud can grow in size and move from one place to another, but it is not a living organism, since it does not have all of the above characteristics.