In the external environment, the intestinal amoeba is well preserved, in some cases it can multiply, but still a favorable place for it is the intestines of a person or another living organism. Inanimate organic substrates (bacteria, the remains of various foods) are used as food, while the amoeba does not secrete an enzyme that breaks down proteins into amino acids. Due to this, in most cases there is no penetration into the intestinal wall, which means that the host is not harmed. This phenomenon is called carrier. With a weakening of immunity and a combination of other circumstances, the amoeba penetrates under the intestinal mucosa and begins to multiply intensively.

The structure of the intestinal amoeba

The intestinal amoeba is a type of protozoan. The structure of the intestinal amoeba consists of a body and a nucleus. The body contains protoplasm (a liquid substance with specialized living structures) and one, two, rarely several nuclei. Protoplasm has two layers: inner (endoplasm) and outer (ectoplasm). The nucleus is like a bubble.

There are two phases of existence of the intestinal amoeba: a vegetative individual (trophozoites) and a cyst. Trophozoites have a well-defined nucleus with a diameter of 20-40 µm. Amoeba constantly changes its shape due to the appearance of pseudopods, with the help of which movement and food capture occur. Due to the shape of pseudopodia, nuclei, their number, one or another type of amoeba is identified. Her movements are slow, reminiscent of marking time. Reproduction occurs by fission first nuclei, then protoplasm.

Life cycle of the intestinal amoeba

The life cycle of the intestinal amoeba begins with the infection of the host organism by the fecal-oral route. With unwashed hands, vegetables, fruits, thanks to various carriers (flies, cockroaches), amoeba cysts enter the inside of a person. Thanks to their shell, they pass through the aggressive environment of the stomach and duodenum intact, getting into the intestines. Its enzymes dissolve the shell, giving way to the intestinal amoeba.

The vegetative stage of development has the following forms: tissue, luminal and pre-cystic. Of these, the tissue phase is the most mobile; it is at this time that the amoeba is most invasive. The other two are immobile. From the translucent form, part of the amoeba passes into the pre-cystic form, while the other part penetrates under the intestinal mucosa, forming a pathogenic tissue form. As a result of its vital activity, the latter secretes cytolysins, which melt tissues and create conditions for reproduction. The cyst is immobile, during defecation, it leaves the intestines. With a strong infection, up to 300 million individuals per day leave the body.

Intestinal amoeba cysts

After several cycles of reproduction, when unfavorable conditions occur for a vegetative individual, it becomes covered with a shell, forming a cyst. Cysts of the intestinal amoeba are round or oval in shape, 10-30 microns in size. Sometimes they contain a supply of nutrients. At different stages of development, cysts have a different number of nuclei: from two to eight. They come out with feces, with a strong infection in large quantities and have the ability to persist for a long time. Once again inside a living organism, they burst, turning into an amoeba.

Symptoms

A large accumulation of intestinal amoeba, which happens when a person’s immunity decreases after suffering stress, viral infections, respiratory diseases, causes a disease called amoebiasis. More often it happens intestinal and extraintestinal. Intestinal leads to ulcerative lesions of the large intestine and, as a result, a protracted course. In this case, the amoeba, along with the blood, penetrates into other internal organs, more often into the liver, and damages them, causing extraintestinal abscesses.

Symptoms of amoebiasis, in the first place, are loose stools, which can be crimson in color. Pain occurs in the right upper abdomen, because. localization of these organisms occurs in the upper part of the large intestine. The temperature may rise, chills, jaundice may appear.

Intestinal amoeba in children

The mechanism of intestinal amoeba infection in children is the same as in adults, and the source is unwashed hands, flies, dirty toys and household items. Amoebiasis can be asymptomatic, manifest, in acute or chronic form. Asymptomatic is invisible to the child. The manifest form is evidenced by deterioration of health, weakness, loss of appetite. The temperature may be normal or slightly elevated. Diarrhea appears, defecation occurs several times a day, increasing up to 10-20 times. Mucus with blood appears in the fetid liquid stool. Raspberry color of feces is not always. There are paroxysmal pains in the right side of the abdomen, aggravated before emptying. Without treatment, the acute stage lasts a month and a half, gradually subsiding. After the remission stage, it flares up with renewed vigor.

Diagnostics

Diagnosis of intestinal amoeba occurs, starting with finding out the patient's history: what symptoms, how long ago they appeared, whether the patient was in countries with a hot, humid climate and low sanitary culture. It is there that the amoeba is widespread and it is from there that it can be imported.

Blood, feces and urine are analyzed. Pathogens are found in feces, and it is important to identify the vegetative form of the amoeba. The analysis must be done no later than 15 minutes after a bowel movement. Also, amoebas can be detected in tissues during sigmoidoscopy - a visual examination of the rectal mucosa using a special device. The sigmoidoscope makes it possible to see ulcers or fresh scars on its inner surface. Not detecting traces of mucosal lesions does not yet indicate the absence of amoebiasis, tk. they may be in the higher sections of the intestine. There is a blood test to detect antibodies to amoebas, it will confirm or refute the diagnosis.

With the help of ultrasound, fluoroscopy, tomography, the localization of abscesses in extraintestinal amoebiasis is determined. Intestinal amoebiasis is differentiated from ulcerative colitis, and amoebic abscesses are differentiated from abscesses of a different nature.

The difference between intestinal amoeba and dysentery

The difference between the intestinal amoeba and the dysentery amoeba is in its structure: the shell of the dysentery amoeba is double-circuit, refracting light, it has 4 nuclei (in the intestinal - 8), located eccentrically, it includes blood cells, which is not in the intestinal. The dysenteric amoeba is more energetic in movement.

Treatment

Treatment of intestinal amoeba is carried out depending on the severity and form of the disease. The drugs used to eliminate the disease are divided into amoebocides of universal action (metronidazole, tinidazole) and direct, aimed at a specific localization of the pathogen: in the intestinal lumen (chiniofon (yatren), mexaform, etc.); in the intestinal wall, liver and other organs (emetine hydrochloride, dehydroemetine, etc.). Antibiotics of the tetracycline series are indirect amoebocides that affect amoeba in the intestinal lumen and in its walls.

Asymptomatic intestinal amoebiasis is treated with yatren. During an acute outbreak, metronidazole or tinidazole is given. In severe form, metronidazole is combined with yatren or tetracycline antibiotics, dehydroemetine may be added. In the case of extraintestinal abscesses, treat with metronidazole with yatren or chingamine with dehydroemetine. Dispensary observation is carried out during the year.

This gelatinous unicellular creature is so small that it can only be seen under a microscope. The main amoeba species live in freshwater rivers and ponds. But there are species that live at the bottom of salty reservoirs, in moist soil and food. The amoeba is constantly changing its shape. She moves, pushing forward first one of her half, then the other. Like many jelly-like organisms, the amoeba moves in such a way that it forms a shape called a “false leg,” or pseudopodia. When the pseudopodia reaches the food, it envelops it and takes it into the main body. This is how the amoeba eats. She doesn't have a mouth. Amoeba belongs to the class of protozoa, which are the lowest rank of living beings. She has neither lungs nor gills. But it sucks in oxygen from the water, releases carbon dioxide, digests food, as more complex animals do. Probably, the amoeba also has feelings. When touched or when aroused, she immediately curls up into a tiny ball. Amoeba avoids bright light, too hot or cold water. In an adult amoeba, the nucleus, a tiny dot in the center of the protoplasm, divides into two parts. After that, the amoeba itself bifurcates, forming new independent organisms. When they reach full size, they begin to divide again. In their structure, the protozoa are extremely diverse. The smallest ones are 2-4 microns in diameter (a micrometer is 0.001 mm). Their most common sizes are in the range of 50-150 microns, some reach 1.5 mm and are visible with the naked eye.

The amoeba has the simplest structure. The body of the amoeba is a lump of semi-liquid cytoplasm with a nucleus in the middle. The entire cytoplasm is divided into two layers: the outer, viscous - ectoplasm and the inner, much more liquid - endoplasm. These two layers are not sharply demarcated and can turn into each other. The amoeba does not have a hard shell, and it is able to change the shape of the body. When an amoeba crawls over a leaf of an aquatic plant, protrusions of the cytoplasm are formed in it in the direction in which it moves. Gradually, the rest of the cytoplasm of the amoeba flows into them. Such protrusions are called pseudopodia or pseudopodia. With the help of pseudopodia, the amoeba not only moves, but also captures food. With pseudopodia, it covers a bacterium or microscopic algae, soon the prey is inside the body of the amoeba, and a bubble is formed around it - a digestive vacuole. Undigested food remains are thrown out after a while.

Fig.1. amoeba proteus

1 - core; 2 - digestive vacuoles; 3 - contractile vacuole; 4 - pseudopods; 5 - undigested food debris thrown out

In the cytoplasm of the amoeba, a light bubble is usually visible, which either appears or disappears. This is a contractile vacuole. It collects excess water that accumulates in the body, as well as the liquid waste products of the amoeba. The amoeba, like all other protozoa, breathes over the entire surface of the body.

Fig.2. Euglena green

1 - flagellum; 2 - eye spot; 3 - contractile vacuole; 4 - chromatophores; 3 - core

The most complex structure of the simplest ciliates. Unlike the amoeba, their body is covered with the thinnest shell and has a more or less constant shape. The support fibers that run in different directions also support and determine the shape of the body. However, the body of ciliates can quickly contract, change its shape, and then return to its original shape. The contraction is carried out with the help of special fibers, similar in many respects to the muscles of multicellular animals. Ciliates can move very quickly. So, a shoe in a second overcomes a distance exceeding the length of its body by 10-15 times. At the same time, many cilia that cover the entire body of the ciliate make fast rowing movements, up to 30 per second (at room temperature). In the ectoplasm of the shoe there are many trichocyst sticks. When irritated, they are thrown out, turning into long threads, and hit the enemy attacking the ciliate. Instead of those thrown out in the ectoplasm, new trichocysts are formed. On one side, approximately in the middle of the body, the shoe has a deep oral cavity leading to a small tubular pharynx.

Fig.3. Infusoria slipper

1 - cilia; 2 - digestive vacuoles; 3 - large nucleus (macronucleus); (micronucleus); 5 - mouth opening and pharynx; 6 - undigested food residues thrown out; 7 - trichocysts; 8 - contractile vacuole

Through the pharynx, food enters the endoplasm, where it is digested in the resulting digestive vacuole. In ciliates, unlike amoebas, undigested food residues are thrown out in a certain place in the body. Their contractile vacuole is more complex and consists of a central reservoir and conducting channels. The ciliates have two types of nuclei: large - macronucleus and small - micronucleus. Some ciliates may have several macro- and micronuclei. The macronucleus differs from the micronucleus in a significantly larger number of chromosomes. And therefore, it contains a lot of deoxyribonucleic acid (DNA), which is part of the chromosomes.

Rice. 4. Planktonic ciliates

1 - Liliomorplia viridis; 2 - Marituja pelagica; h - Tintinnopsis beroidea; 4 - Mucophrya pelagica (Suctoria).
1, 2, 4 - planktonic ciliates of Lake Baikal; 3 - sea view



This class includes unicellular animals, which are characterized by a variable body shape. This is due to the formation of pseudopods, which serve to move and capture food. Many rhizopods have an internal or external skeleton in the form of shells. After death, these skeletons settle to the bottom of water bodies and form silt, gradually turning into chalk.

A typical representative of this class is the common amoeba (Fig. 1).

The structure and reproduction of the amoeba

Amoeba - one of the most simply arranged animals, devoid of a skeleton. Lives in silt at the bottom of ditches and ponds. Externally, the body of the amoeba is a grayish gelatinous lump 200-700 microns in size, which does not have a permanent shape, which consists of cytoplasm and a vesicular nucleus and does not have a shell. In the protoplasm, an outer, more viscous (ectoplasm) and an inner granular, more liquid (endoplasm) layer is distinguished.

On the body of the amoeba, outgrowths that change their shape are constantly formed - false legs (pseudopodia). The cytoplasm gradually overflows into one of these protrusions, the false leg attaches to the substrate at several points, and the amoeba moves. Moving, the amoeba encounters unicellular algae, bacteria, small unicellular, covers them with pseudopods so that they are inside the body, forming a digestive vacuole around the swallowed piece in which intracellular digestion occurs. Undigested residues are thrown out in any part of the body. The method of capturing food with the help of false legs is called phagocytosis. The fluid enters the body of the amoeba through the resulting thin tubular channels, i.e. by pinocytosis. The end products of vital activity (carbon dioxide and other harmful substances and undigested food residues) are excreted with water through a pulsating (contractile) vacuole, which removes excess fluid every 1-5 minutes.

The amoeba does not have a special respiratory organelle. It absorbs the oxygen necessary for life by the entire surface of the body.

Amoebas reproduce only asexually (mitosis). Under unfavorable conditions (for example, when a reservoir dries up), amoeba retract pseudopodia, become covered with a strong double membrane and form cysts (encysted).

When exposed to external stimuli (light, change in the chemical composition of the environment), the amoeba responds with a motor reaction (taxis), which, depending on the direction of movement, can be positive or negative.

Other members of the class

Many species of Sarcodidae live in marine and fresh waters. Some sarcodes on the surface of the body have a skeleton in the form of a shell (shell rhizomes, foraminifers). The shells of such sarcodes are riddled with pores from which pseudopodia protrude. In shell rhizomes, reproduction is observed by multiple division - schizogony. Sea rhizomes (foraminifera) are characterized by alternation of asexual and sexual generations.

The skeletalized Sarcodidae are among the oldest inhabitants of the Earth. Chalk and limestone were formed from their skeletons. Each geological period is characterized by its own foraminifera, and they often determine the age of geological layers. The skeletons of certain types of shell rhizomes accompany the deposition of oil, which is taken into account in geological surveys.

dysenteric amoeba(Entamoeba histolytica) is the causative agent of amoebic dysentery (amebiasis). Discovered by F. A. Lesh in 1875

Localization. The human intestine.
. Common, but more common in countries with hot climates.

Morphological features and life cycle. In the human intestine, the following forms occur in the life cycle:

• cysts - 1, 2, 5-10 (Fig. 2).
• small vegetative form living in the intestinal lumen (forma minuta) - 3, 4;
• large vegetative form that lives in the lumen of the intestines (forma magna) - 13-14
• tissue, pathogenic, large vegetative form (forma magna) - 12;

A characteristic feature of the cysts of the dysenteric amoeba is the presence of 4 nuclei in them (a distinctive species feature), the size of the cysts is from 8 to 18 microns.

The dysenteric amoeba usually enters the human intestine in the form of cysts. Here, the shell of the swallowed cyst dissolves and a four-core amoeba comes out of it, which quickly divides into 4 single-core small (7-15 microns in diameter) vegetative forms (f. minuta). This is the main form of existence of E. histolytica.

The small vegetative form lives in the lumen of the large intestine, feeds mainly on bacteria, multiplies and does not cause disease. If the conditions are not favorable for the transition to the tissue form, then the amoeba, getting into the lower intestines, encysts (turns into a cyst) with the formation of a 4-nuclear cyst and is excreted into the external environment with feces.

If the conditions favor the transition to the tissue form (E. histolytica forma magna), the amoeba increases in size to an average of 23 microns, sometimes reaching 30 or even 50 microns, and acquires the ability to secrete hyaluronidase, proteolytic enzymes that dissolve tissue proteins and penetrate into the walls intestines, where it intensively multiplies and causes damage to the mucosa with the formation of ulcers. In this case, the walls of blood vessels are destroyed and bleeding occurs in the intestinal cavity.

When amoebic lesions of the intestine appear, small vegetative forms located in the intestinal lumen begin to turn into a large vegetative form. The latter is characterized by large sizes (30-40 microns) and the structure of the nucleus: the chromatin of the nucleus forms radial structures, a large lump of chromatin, the karyosome, is located strictly in the center, forma magna begins to feed on erythrocytes, i.e., becomes an erythrophage. Blunt broad pseudopodia and jerky locomotion are characteristic.

Amoebas that reproduce in the tissues of the intestinal wall - a tissue form - getting into the intestinal lumen, in structure and size become similar to a large vegetative form, but are not able to swallow erythrocytes.

When treating or increasing the protective reaction of the body, a large vegetative form (E. histolytica forma magna) again turns into a small one (E. histolytica forma minuta), which begins to encyst. Subsequently, either recovery occurs, or the disease becomes chronic.

The conditions necessary for the transformation of some forms of the dysenteric amoeba into others have been studied by the Soviet protistologist V. Gnezdilov. It turned out that various unfavorable factors - hypothermia, overheating, malnutrition, overwork, etc. - contribute to the transition of forma minuta to forma magna. A necessary condition is also the presence of certain types of intestinal bacteria. Sometimes an infected person sheds cysts for many years without showing signs of illness. These people are called cyst carriers. They are a great danger, as they serve as a source of infection for others. During the day, one cyst carrier releases up to 600 million cysts. Cystocarriers are subject to identification and mandatory treatment.

The only one source of disease amoebiasis - man. Faecal cysts contaminate soil and water. Since feces are often used as fertilizer, cysts end up in the garden and garden, where they pollute vegetables and fruits. Cysts are resistant to the external environment. They enter the intestines with unwashed vegetables and fruits, through unboiled water, dirty hands. Flies, cockroaches, which contaminate food, serve as mechanical carriers.

Pathogenic action. With the introduction of an amoeba into the intestinal wall, a serious disease develops, the main symptoms of which are: bleeding ulcers in the intestines, frequent and loose stools (up to 10-20 times a day) mixed with blood and mucus. Sometimes, through the blood vessels, a dysenteric amoeba - an erythrophage can be carried into the liver and other organs, causing the formation of abscesses there (focal suppuration). In the absence of treatment, mortality reaches 40%.

Laboratory diagnostics. Microscopy: smears of feces. In the acute period, the smear contains large vegetative forms containing erythrocytes; cysts are usually absent because f. magna is unable to encyst. In the chronic form or cystic carriage, quadrinuclear cysts are found in the feces.

Prevention: personal - washing vegetables and fruits with boiled water, drinking only boiled water, washing hands before eating, after going to the toilet, etc .; public - the fight against contamination of soil and water with feces, the destruction of flies, sanitary and educational work, examination for cystic carriage of persons working in public catering enterprises, treatment of patients.

Non-pathogenic amoebae include intestinal and oral amoebae.

Intestinal amoeba (Entamoeba coli).

Localization. The upper part of the large intestine lives only in the intestinal lumen.

Geographic distribution. Found in approximately 40-50% of the population of various regions the globe.

. The vegetative form has a size of 20-40 microns, but sometimes larger forms are also found. There is no sharp boundary between ecto- and endoplasm. It has a characteristic way of locomotion - it simultaneously releases pseudopodia from different sides and, as it were, "marks time". The nucleus contains large clumps of chromatin, the nucleolus lies eccentrically, and there is no radial structure. It does not secrete a proteolytic enzyme, does not penetrate the intestinal wall, feeds on bacteria, fungi, plant and animal food residues. The endoplasm contains many vacuoles. Erythrocytes are not swallowed, even if they are contained in the intestines in large quantities (in patients with bacterial dysentery). In the lower part of the digestive tract, it forms eight- and two-core cysts.

Mouth amoeba (Entamoeba gingivalis).

Localization. Oral cavity, plaque in healthy people and those with diseases of the oral cavity, carious cavities of the teeth.

Geographic distribution. Everywhere.

Morphophysiological characteristics. The vegetative form has sizes from 10 to 30 microns, strongly vacuolized cytoplasm. The type of movement and the structure of the nucleus resemble a dysenteric amoeba. Erythrocytes do not swallow, feed on bacteria, fungi. In addition, nuclei of leukocytes or the so-called salivary bodies are found in the vacuoles, which, after staining, can resemble erythrocytes. It is believed that the cyst does not form. Pathogenic action is currently denied. It is found in the dental plaque of healthy people in 60-70%. It is more common in people with diseases of the teeth and oral cavity.

Amoeba vulgaris (Proteus) is a species of protozoan animals from the genus Amoeba of the subclass of the rhizopod of the class Sarcodidae of the sarcomastigophora type. This is a typical representative of the amoeba genus, which is a relatively large amoeboid organism, the distinctive feature of which is the formation of many prolegs (10 or more in one individual). The shape of the common amoeba when moving due to pseudopodia is very variable. So, pseudopods constantly change appearance, branch, disappear and form again. If the amoeba releases pseudopodia in a certain direction, it can move at speeds up to 1.2 cm per hour. At rest, the shape of the amoeba proteus is spherical or elliptical. In free swimming near the surface of water bodies, the amoeba acquires a star shape. Thus, there are floating and locomotor forms. The habitat of this species of amoeba is fresh water bodies with stagnant water, in particular, swamps, rotting ponds, and aquariums. Amoeba proteus is found all over the globe. The sizes of these organisms range from 0.2 to 0.5 mm. The structure of the amoeba proteus has characteristic features. The outer shell of the body of the common amoeba is the plasmalemma. Under it is the cytoplasm with organelles. The cytoplasm is divided into two parts - the outer (ectoplasm) and the inner (endoplasm). The main function of the transparent, relatively homogeneous ectoplasm is the formation of pseudopodia for food trapping and locomotion. All organelles are enclosed in a dense granular endoplasm, and food is digested there. The ordinary amoeba is fed by phagocytosis of the smallest protozoa, including ciliates, bacteria, unicellular algae. Food is captured by pseudopodia - outgrowths of the cytoplasm of the amoeba cell. When the plasmalemma and the food particle come into contact, an impression is formed, which turns into a bubble. Digestive enzymes are intensively released there. This is how the process of formation of the digestive vacuole occurs, which then passes into the endoplasm. The amoeba obtains water by pinocytosis. At the same time, an invagination is formed on the surface of the cell, like a tube, through which fluid enters the body of the amoeba, then a vacuole is formed. When water is absorbed, this vacuole disappears. The release of undigested food residues occurs in any part of the body surface when a vacuole transferred from the endoplasm merges with the plasma membrane. In the endoplasm of the common amoeba, in addition to digestive vacuoles, contractile vacuoles, one relatively large discoidal nucleus and inclusions (fat drops, polysaccharides, crystals) are located. Organelles and granules in the endoplasm are in constant motion, picked up and carried by currents of the cytoplasm. In a newly formed pseudopod, the cytoplasm shifts to its edge, and in a shortening one, on the contrary, it goes deep into the cell. Amoeba Proteus reacts to irritation - to food particles, light, negatively - to chemicals (sodium chloride). Reproduction of the amoeba is asexual by cell division in half. Before the division process begins, the amoeba stops moving. First, the nucleus divides, then the cytoplasm. The sexual process is absent.

outer membrane, and one or more nuclei. The light and dense outer layer is called ectoplasm, and the inner one is called endoplasm. In the endoplasm of the amoeba there are cellular organelles: contractile and digestive vacuoles, mitochondria, ribosomes, elements of the Golgi apparatus, endoplasmic reticulum, supporting and contractile fibers.

Respiration and excretion

Cellular respiration of the amoeba occurs with the participation of oxygen, when it becomes less than in the external environment, new molecules enter the cell. Accumulated as a result of vital activity, harmful substances and carbon dioxide are removed to the outside. Fluid enters the body of the amoeba through thin tubular channels, this process is called. Contractile vacuoles pump out excess water. Gradually filling up, they are sharply reduced and pushed out about once every 5-10 minutes. Moreover, vacuoles can form in any part of the body. The digestive vacuole approaches the cell membrane and opens outward, as a result of which undigested residues are released into the external environment.

Food

The amoeba feeds on unicellular algae, bacteria and smaller unicellular organisms, bumping into them, it flows around them and includes them in the cytoplasm, forming a digestive vacuole. It receives enzymes that break down proteins, lipids and carbohydrates, this is how intracellular digestion occurs. After digestion, food enters the cytoplasm.

reproduction

Amoebas reproduce asexually by fission. This process is no different from cell division, which occurs during the growth of a multicellular organism. The only difference is that the daughter cells become independent organisms.

First, the nucleus is doubled so that each daughter cell has its own copy of the hereditary information. The core is first stretched, then lengthened and pulled in the middle. Forming a transverse groove, it is divided into two halves, which form two nuclei. They diverge in different directions, and the body of the amoeba is divided into two parts by a constriction, forming two new unicellular organisms. One nucleus enters each of them, and the formation of the missing organelles also occurs. The division can be repeated several times in one day.

Cyst formation

Unicellular organisms are sensitive to changes in the external environment; under adverse conditions, a large amount of water is released from the cytoplasm on the surface of the body of the amoeba. The secreting water and substances of the cytoplasm form a dense membrane. This process can occur in the cold season, when the reservoir dries up, or in other conditions unfavorable for the amoeba. The organism passes into a resting state, forming a cyst in which all vital processes are suspended. Cysts can be carried by the wind, which contributes to the settlement of amoebae. When favorable conditions occur, the amoeba leaves the cyst shell and becomes active.

Sources:

• Biotutorials, Amoeba vulgaris

Reproduction is a natural property of living beings. It is sexual and asexual - i.e. with the participation of only one individual, in the absence of an individual of the opposite sex. The latter is found in certain types of plants and fungi, as well as in the simplest organisms.

Instruction

Asexual reproduction occurs without the exchange of genetic information between two individuals of different sexes. It is characteristic of the simplest unicellular organisms - amoebas, ciliates-shoes. They have no variability; for thousands of years, the daughter individuals completely copy the parent ones.

One of the ways of asexual reproduction is division, when two daughters (for example, amoeba) are formed from one individual. In this case, the nucleus of the organism begins to divide first, and then the cytoplasm splits in two. This method is also common among bacteria.

A starfish reproduces in a fragmented way: the "mother" organism is divided into parts, and each of them becomes a full-fledged new starfish.

Another way is reproduction by spores. Here we are talking about multicellular organisms - fungi and plants. With asexual reproduction, only one plant is involved in this process. It forms spores or separates viable parts of the vegetative body, and from them daughter individuals are formed under favorable circumstances.

Vegetative propagation in plants occurs with the help of vegetative organs - leaves, roots and. Violet, for example, propagates by leaves, and raspberries by roots. This phenomenon is especially common among wild plants. Vegetative reproduction is natural and artificial when it is carried out by a person.

Often, under natural conditions, certain types of plants reproduce by the same organs: tulips, lilies, daffodils, onions and garlic - bulbs; dahlias, Jerusalem artichoke, potatoes - tubers; - creeping shoots (whiskers); Ivan tea, horsetail, yarrow - rhizomes.

To create an environment in the oral cavity that is unfavorable for the reproduction of bacteria, eat more berries, watermelons, citrus fruits and other fruits and vegetables rich in vitamin C. Regular consumption of such foods again has a beneficial effect. Do not replace natural vitamin C with an artificial supplement, it can cause indigestion.

Do not forget about green tea, which successfully washes away bacteria from the surface of the gums and teeth. This drink is rich in flavonoids, which not only rid the mouth of bad breath, but also whiten teeth and improve metabolism.

You should pay attention to dairy products. Like yogurt, they reduce hydrogen sulfide levels in the mouth and freshen breath. Also, the substances contained in fermented milk products do not allow fermentation bacteria to multiply and the oral cavity unsuitable for their life.

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