Amoeba vulgaris is a type of protozoan eukaryotic creature, a typical representative of the genus Amoeba.
Taxonomy. The species of common amoeba belongs to the kingdom - Animals, phylum - Amoebozoa. Amoebas are united in the class Lobosa and order - Amoebida, family - Amoebidae, genus - Amoeba.
Characteristic processes. Although amoebas are simple, single-celled creatures that do not have any organs, they possess all vital processes. They are able to move, get food, reproduce, absorb oxygen, and remove metabolic products.
Structure
The common amoeba is a unicellular animal, the body shape is uncertain and changes due to the constant movement of the pseudopods. The dimensions do not exceed half a millimeter, and the outside of its body is surrounded by a membrane - plasmalem. Inside there is cytoplasm with structural elements. Cytoplasm is a heterogeneous mass, where two parts are distinguished:
- External - ectoplasm;
- internal, with a granular structure - endoplasm, where all intracellular organelles are concentrated.
The common amoeba has a large nucleus, which is located approximately in the center of the animal's body. It has nuclear sap, chromatin and is covered with a membrane with numerous pores.
Under a microscope it can be seen that the common amoeba forms pseudopodia into which the cytoplasm of the animal is poured. At the moment of pseudopodia formation, endoplasm rushes into it, which in the peripheral areas becomes denser and turns into ectoplasm. At this time, on the opposite part of the body, ectoplasm partially transforms into endoplasm. Thus, the formation of pseudopodia is based on the reversible phenomenon of the transformation of ectoplasm into endoplasm and vice versa.
Breath
Amoeba receives O 2 from water, which diffuses into internal cavity through the outer integument. The whole body participates in the respiratory act. Oxygen entering the cytoplasm is necessary to break down nutrients into simple components that Amoeba proteus can digest, and also to obtain energy.
Habitat
Inhabits fresh water in ditches, small ponds and swamps. Can also live in aquariums. Amoeba vulgaris culture can be easily propagated in the laboratory. It is one of the large free-living amoebas, reaching 50 microns in diameter and visible to the naked eye.
Nutrition
The common amoeba moves with the help of pseudopods. She covers one centimeter in five minutes. While moving, amoebas encounter various small objects: unicellular algae, bacteria, small protozoa, etc. If the object is small enough, the amoeba flows around it from all sides and it, along with a small amount of liquid, ends up inside the cytoplasm of the protozoa.
Amoeba vulgaris nutritional diagram The process of absorption of solid food by the common amoeba is called phagocytosis. Thus, digestive vacuoles are formed in the endoplasm, into which food enters from the endoplasm. digestive enzymes and intracellular digestion occurs. Liquid digestion products penetrate the endoplasm, a vacuole with undigested food remains approaches the surface of the body and is thrown out.
In addition to digestive vacuoles, the body of amoebas also contains a so-called contractile, or pulsating, vacuole. This is a bubble of watery liquid that periodically grows, and when it reaches a certain volume, it bursts, emptying its contents out.
The main function of the contractile vacuole is to regulate osmotic pressure inside the protozoan body. Due to the fact that the concentration of substances in the cytoplasm of the amoeba is higher than in fresh water, a difference in osmotic pressure is created inside and outside the body of the protozoa. That's why fresh water penetrates the body of the amoeba, but its quantity remains within the limits physiological norm, as the pulsating vacuole “pumps” excess water out of the body. This function of vacuoles is confirmed by their presence only in freshwater protozoa. In marine animals it is either absent or reduced very rarely.
In addition to the osmoregulatory function, the contractile vacuole partially performs an excretory function, excreting along with water into environment metabolic products. However, the main function of selection is carried out directly through outer membrane. The contractile vacuole probably plays a certain role in the process of respiration, since water penetrating into the cytoplasm as a result of osmosis carries dissolved oxygen.
Reproduction
Amoebas are characterized by asexual reproduction, carried out by dividing in two. This process begins with mitotic division of the nucleus, which lengthens longitudinally and is separated by a septum into 2 independent organelles. They move away and form new nuclei. The cytoplasm with the membrane is divided by a constriction. The contractile vacuole does not divide, but enters one of the newly formed amoebae; in the second, the vacuole forms independently. Amoebas reproduce quite quickly; the division process can occur several times during the day.
In the summer, amoebas grow and divide, but with the arrival of autumn cold, due to the drying up of water bodies, it is difficult to find nutrients. Therefore, the amoeba turns into a cyst, finding itself in critical conditions and becomes covered with a durable double protein shell. At the same time, cysts easily spread with the wind.
Meaning in nature and human life
Amoeba proteus is an important component of ecological systems. It regulates the number of bacterial organisms in lakes and ponds. Cleanses aquatic environment from excessive pollution. It is also an important component food chains. Single-celled organisms are food for small fish and insects.
Scientists use the amoeba as a laboratory animal, conducting many studies on it. The amoeba cleans not only reservoirs, but also by settling in human body, it absorbs destroyed particles epithelial tissue digestive tract.
Amoebas are a genus of single-celled eukaryotic organisms (classified as protozoa). They are considered animal-like because they feed heterotrophically.
The structure of amoebas is usually considered using the example of a typical representative - the common amoeba (Amoebae Proteus).
The common amoeba (hereinafter referred to as amoeba) lives at the bottom of freshwater bodies of polluted water. Its size ranges from 0.2 mm to 0.5 mm. By appearance The amoeba looks like a shapeless, colorless lump that can change its shape.
The amoeba cell does not have a hard shell. It forms protrusions and invaginations. Protrusions (cytoplasmic projections) are called pseudopods or pseudopodia. Thanks to them, the amoeba can move slowly, as if flowing from place to place, and also capture food. The formation of pseudopods and the movement of the amoeba occurs due to the movement of the cytoplasm, which gradually flows into a protrusion.
Although the amoeba is a unicellular organism and there can be no talk of organs and their systems, it is characterized by almost all life processes characteristic of multicellular animals. Amoeba eats, breathes, secretes substances, and reproduces.
The cytoplasm of the amoeba is not homogeneous. Produces a more transparent and dense outer layer (ekTplasma) and a more granular and liquid inner layer of cytoplasm ( endoplasm).
The amoeba's cytoplasm contains various organelles, a nucleus, as well as digestive and contractile vacuoles.
Amoeba feeds on various unicellular organisms and organic debris. Food is grasped by pseudopods and ends up inside the cell, forming digestiveand Ivacuole. It receives various enzymes that break down nutrients. Those that the amoeba needs then enter the cytoplasm. Unnecessary food debris remains in a vacuole, which approaches the surface of the cell and everything is thrown out of it.
The “organ” of excretion in an amoeba is contractile vacuole. It receives excess water, unnecessary and harmful substances from the cytoplasm. The filled contractile vacuole periodically approaches the cytoplasmic membrane of the amoeba and pushes its contents out.
The amoeba breathes over the entire surface of the body. Oxygen comes into it from water, and carbon dioxide comes from it. The process of respiration involves oxidation by oxygen organic matter in mitochondria. As a result, energy is released, which is stored in ATP, and water and carbon dioxide are also formed. The energy stored in ATP is further spent on various vital processes.
For amoeba, only an asexual method of reproduction is described by dividing in two. Only large, i.e. grown, individuals are divided. First, the nucleus divides, after which the amoeba cell divides through the constriction. The daughter cell that does not receive a contractile vacuole subsequently forms one.
With the onset of cold weather or drought, the amoeba forms cyst. Cysts have a dense shell that performs protective function. They are quite light and can be carried by the wind to long distances.
Amoeba is able to react to light (crawls away from it), mechanical irritation, and the presence of certain substances in water.
Amoebaordinary(lat. Amoeba proteus)
or amoeba proteus(rhizopod) - amoeboid organism, representative of the class Lobosa(lobosal amoebas). Polypodial form (characterized by the presence of numerous (up to 10 or more) pseudopodia - pseudopodia). Pseudopodia constantly change their shape, branch, disappear and reappear.
Cell structure
A. proteus is externally covered only with plasmalemma. The cytoplasm of the amoeba is clearly divided into two zones, ectoplasm and endoplasm (see below).
Ectoplasm, or hyaloplasm, lies in a thin layer directly under the plasmalemma. Optically transparent, free of any inclusions. The thickness of the hyaloplasm in different parts of the amoeba’s body is different. On the lateral surfaces and at the base of the pseudopodia this is usually a thin layer, and at the ends of the pseudopodia the layer noticeably thickens and forms the so-called hyaline cap, or cap.
Endoplasm, or granuloplasm - the internal mass of the cell. Contains all cellular organelles and inclusions. When observing a moving amoeba, a difference in the movement of the cytoplasm is noticeable. The hyaloplasm and peripheral portions of the granuloplasm remain practically motionless, while its central part is in continuous motion; cytoplasmic currents with organelles and granules involved in them are clearly visible. In a growing pseudopodia, the cytoplasm moves to its end, and from shortening ones - to central part cells. The mechanism of hyaloplasm movement is closely related to the process of transition of the cytoplasm from a sol to a gel state and changes in the cytoskeleton.
Nutrition
Amoeba Proteus feeds by phagocytosis, absorbing bacteria, single-celled algae and small protozoa. The formation of pseudopodia underlies food capture. On the surface of the amoeba’s body, contact occurs between the plasmalemma and the food particle, and a “food cup” is formed in this area. Its walls close, and digestive enzymes begin to flow into this area (with the help of lysosomes). Thus, a digestive vacuole is formed. Then it passes into the central part of the cell, where it is picked up by cytoplasmic currents. In addition to phagocytosis, amoeba is characterized pinocytosis- swallowing liquid. In this case, an invagination in the form of a tube is formed on the surface of the cell, through which a drop of liquid enters the cytoplasm. The forming vacuole with liquid is detached from the tube. After the liquid is absorbed, the vacuole disappears.
Defecation
Endocytosis (excretion). The vacuole with undigested food remains approaches the surface of the cell and merges with the membrane, thus throwing the contents out.
Osmoregulation
A pulsating contractile vacuole is periodically formed in the cell - a vacuole containing excess water and removing it out.
Reproduction
Only agamic, binary fission. Before division, the amoeba stops crawling, its dictyosomes, Golgi apparatus and contractile vacuole disappear. First, the nucleus divides, then cytokinesis occurs. The sexual process is not described.
Causes indigestion and colitis (bloody diarrhea).
The cytoplasm is completely surrounded by a membrane, which is divided into three layers: outer, middle and inner. In inner layer, which is called endoplasm, contains the necessary elements for an independent organism:
- ribosomes;
- elements of the Golgi apparatus;
- supporting and contractile fibers;
- digestive vacuoles.
Digestive system
A unicellular organism can actively reproduce only in moisture; in the dry habitat of the amoeba, nutrition and reproduction are impossible.
Respiratory system and response to irritation
Amoeba proteus
Amoeba division
The most favorable living environment is found in the reservoir and human body . Under these conditions, the amoeba multiplies quickly, actively feeds on bacteria in bodies of water and gradually destroys the tissues of the organs of its permanent host, which is a person.
Amoeba reproduces asexually. Asexual reproduction involves cell division and the formation of a new one-celled organism.
It is noted that one adult can divide several times a day. This determines the greatest danger for a person who suffers from amoebiasis.
That is why, at the first symptoms of the disease, doctors strongly recommend seeking help from a specialist rather than starting self-medication. Incorrectly selected drugs can even cause harm to the patient more harm than benefit.
In contact with
Amoebas, testate amoebas, foraminifera
The rhizopods are characterized by movement organelles such as lobopodia or rhizopodia. A number of species form an organic or mineral shell. The main method of reproduction is asexual through mitotic cell division in two. Some species exhibit alternation of asexual and sexual reproduction.
The rhizomes class includes the following orders: 1) Amoebas, 2) Testate amoebas, 3) Foraminifera.
Amoeba squad (Amoebina)
rice. 1.
1 - nucleus, 2 - ectoplasm, 3 - endoplasm,
4 - pseudopodia, 5 - digestive
vacuole, 6 - contractile vacuole.
Amoeba proteus (Fig. 1) lives in fresh water bodies. Reaches a length of 0.5 mm. It has long pseudopodia, one nucleus, a formed cellular mouth and no powder.
rice. 2.
1 - pseudopodia of amoeba,
2 - food particles.
It feeds on bacteria, algae, particles of organic substances, etc. The process of capturing solid food particles occurs with the help of pseudopodia and is called phagocytosis (Fig. 2). A phagocytotic vacuole is formed around the captured food particle, digestive enzymes enter it, after which it turns into a digestive vacuole. The process of absorption of liquid food masses is called pinocytosis. In this case, solutions of organic substances enter the amoeba through thin channels that are formed in the ectoplasm by invagination. A pinocytosis vacuole is formed, it detaches from the channel, enzymes enter it, and this pinocytosis vacuole also becomes a digestive vacuole.
In addition to the digestive vacuoles, there is a contractile vacuole that removes excess water from the amoeba’s body.
It reproduces by dividing the mother cell into two daughter cells (Fig. 3). Division is based on mitosis.
rice. 3.
Under unfavorable conditions, the amoeba encysts. Cysts are resistant to desiccation, low and high temperatures, water currents and air currents transported over long distances. Once in favorable conditions, the cysts open and amoebas emerge.
Dysenteric amoeba (Entamoeba histolytica) lives in the human large intestine. Can cause a disease - amoebiasis. IN life cycle Dysenteric amoeba is divided into the following stages: cyst, small vegetative form, large vegetative form, tissue form. The invasive (infecting) stage is the cyst. The cyst enters the human body orally along with food or water. In the human intestine, amoebas emerge from cysts, having small sizes (7-15 microns), feeding mainly on bacteria, multiplying and not causing diseases in humans. This is a small vegetative form (Fig. 4). When it enters the lower parts of the large intestine, it becomes encysted. Cysts released in feces can end up in water or soil, then on food products. The phenomenon in which dysenteric amoeba lives in the intestines without causing harm to the host is called cyst carriage.
rice. 4.
A - small vegetative form,
B - large vegetative form
(erythrophage): 1 - core,
2 - phagocytosed erythrocytes.
Laboratory diagnosis of amebiasis - examination of fecal smears under a microscope. IN acute period diseases, large vegetative forms (erythrophages) are detected in the smear (Fig. 4), with chronic form or cyst carrier - cysts.
Mechanical carriers of dysentery amoeba cysts are flies and cockroaches.
Intestinal amoeba (Entamoeba coli) lives in the lumen of the large intestine. The intestinal amoeba feeds on bacteria, plant and animal debris, without causing any harm to the host. Never swallows red blood cells, even if they are in large quantities in the intestines. Forms cysts in the lower part of the large intestine. Unlike the four-nucleated dysenteric amoeba cysts, intestinal amoeba cysts have eight or two nuclei.
rice. 5.
A - arcella (Arcella sp.),
B - diffusion (Difflugia sp.).
Order Testacea (Testacea)
Representatives of this order are freshwater benthic organisms; some species live in the soil. They have a shell, the size of which varies from 50 to 150 microns (Fig. 5). The shell can be: a) organic (“chitinoid”), b) made of silicon plates, c) encrusted with grains of sand. They reproduce by dividing cells in two. In this case, one daughter cell remains in the mother shell, the other builds a new one. They lead only a free lifestyle.
Order Foraminifera
rice. 6.
A - planktonic foraminifera Globigerina
(Globigerina sp.), B - multi-chambered calcareous
Elphidium sp. shell.
Foraminifera live in marine waters and are part of the benthos, with the exception of the families Globigerina (Fig. 6A) and Globorotalidae, which lead a planktonic lifestyle. Foraminifera have shells whose sizes vary from 20 microns to 5-6 cm; in fossil species of foraminifera - up to 16 cm (nummulites). The shells are: a) calcareous (the most common), b) organic from pseudochitin, c) organic, encrusted with grains of sand. Calcareous shells can be single-chambered or multi-chambered with an aperture (Fig. 6B). The partitions between the chambers are pierced with holes. Very long and thin rhizopodia emerge both through the mouth of the shell and through numerous pores piercing its walls. In some species, the shell wall does not have pores. The number of cores is from one to many. They reproduce asexually and sexually, which alternate with each other. Sexual reproduction- isogamous type.
Foraminifera play important role in the formation of sedimentary rocks (chalk, nummulitic limestones, fusuline limestones, etc.). Foraminifera have been known in fossil form since the Cambrian period. Each geological period is characterized by its own widespread species of foraminifera. These types are guiding forms for determining the age of geological strata.
