>>Common amoeba, its habitat, structural features and life activity
Single-celled animals, or Protozoa
§ 3. Common amoeba, its habitat, structural features and vital functions
Habitat, structure and movement of amoeba. The common amoeba is found in the sludge at the bottom of ponds with polluted water. It looks like a small (0.2-0.5 mm), barely visible to the naked eye, colorless gelatinous lump, constantly changing its shape (“amoeba” means “changeable”). The details of the amoeba's structure can only be seen under a microscope.
The body of the amoeba consists of semi-liquid cytoplasm with a small vesicular nucleus enclosed inside it. An amoeba consists of one cell, but this cell is a whole organism leading an independent existence.
Lesson content lesson notes supporting frame lesson presentation acceleration methods interactive technologies Practice tasks and exercises self-test workshops, trainings, cases, quests homework discussion questions rhetorical questions from students Illustrations audio, video clips and multimedia photographs, pictures, graphics, tables, diagrams, humor, anecdotes, jokes, comics, parables, sayings, crosswords, quotes Add-ons abstracts articles tricks for the curious cribs textbooks basic and additional dictionary of terms other Improving textbooks and lessonscorrecting errors in the textbook updating a fragment in a textbook, elements of innovation in the lesson, replacing outdated knowledge with new ones Only for teachers perfect lessons calendar plan for a year guidelines discussion programs Integrated LessonsAmoebas are a detachment of the smallest single-celled organisms from the subclass of rhizomes of the class Sarcodae, such as sarcomastigophores. Distinctive feature All representatives of this group of protozoa have the ability to form pseudopods (pseudopodia) for movement and capture of food. Pseudopodia are outgrowths of the cytoplasm, the shape of which is constantly changing.
Amoeba is considered one of the simplest forms of life. However, from a physiological point of view, an amoeba cell is quite complex arranged system. In the body of the amoeba, functions characteristic of higher multicellular organisms, – breathing, excretion, digestion.
All amoebas have an irregular shape, which is constantly changing due to the formation of pseudopods. This adaptation, as mentioned above, was formed in the process of evolution for nutrition and movement. These organisms lack a dense membrane around the cell. There is only a special molecular layer called plasma membrane, which is a constituent element of living cytoplasm.
The internal structure of the amoeba has characteristics. The cytoplasm is divided into an internal part (endoplasm) and an external part (ectoplasm). Endoplasm has a granular structure, and ectoplasm has an approximately uniform consistency. The endoplasm contains a large nucleus, contractile and digestive vacuoles, and fatty inclusions.
Organisms in this group feed on protozoa, bacteria, and algae. With the help of pseudopodia, food is captured by the amoeba and enters its endoplasm, where a digestive vacuole is formed in which food particles are digested. The release of undigested residues, as well as waste products, occurs in amoebas through the entire surface of the body through ordinary diffusion.
The function of the contractile vacuole is to remove excess water from the body of the individual. When the vacuole contracts, it pushes water out.
Amoebas reproduce asexually by binary fission. A constriction forms in the mother cell, and the cytoplasm is divided into two approximately equal parts with a nucleus in each. The nuclei of young individuals are formed as a result of mitotic division of the nucleus of the mother cell. Two young amoebas gradually grow and at a certain stage divide again, giving rise to new individuals.
Animals, like all organisms, are on different levels organizations. One of them is cellular, and its typical representative is the amoeba proteus. We will consider the features of its structure and life activity in more detail below.
Subkingdom Unicellular
Despite the fact that this systematic group unites the most primitive animals, its species diversity already reaches 70 species. On the one hand, these are indeed the most simply structured representatives of the animal world. On the other hand, these are simply unique structures. Just imagine: one, sometimes microscopic, cell is capable of carrying out all vital processes: breathing, movement, reproduction. Amoeba Proteus (the photo shows its image under a light microscope) is a typical representative of the subkingdom Protozoa. Its dimensions barely reach 20 microns.
Amoeba Proteus: a class of protozoa
The very species name of this animal indicates the level of its organization, since proteus means “simple.” But is this animal so primitive? Amoeba Proteus is a representative of a class of organisms that move using non-permanent projections of the cytoplasm. Colorless blood cells that form human immunity move in a similar way. They are called leukocytes. Their characteristic movement is called amoeboid.
In what environment does amoeba proteus live?
The amoeba proteus, which lives in polluted waters, does no harm to anyone. This habitat is the most suitable because it is where protozoa occupy their important role in the power circuit.
Structural features
Amoeba Proteus is a representative of the class, or rather the subkingdom, Unicellular. Its size barely reaches 0.05 mm. It can be seen with the naked eye in the form of a barely noticeable jelly-like lump. But all the main organelles of the cell will be visible only under a light microscope at high magnification.
The surface apparatus of the amoeba Proteus cell is presented which has excellent elasticity. Inside there is a semi-liquid content - cytoplasm. She moves all the time, causing the formation of pseudopods. Amoeba is a eukaryotic animal. This means that its genetic material is contained in the nucleus.
Protozoan movement
How does Amoeba Proteus move? This occurs with the help of non-permanent outgrowths of the cytoplasm. It moves, forming a protrusion. And then the cytoplasm smoothly flows into the cell. The pseudopods are retracted and formed elsewhere. For this reason, amoeba Proteus does not have permanent shape bodies.
Nutrition
Amoeba Proteus is capable of phagocytosis and pinocytosis. These are the processes of cell absorption of solid particles and liquids, respectively. It feeds on microscopic algae, bacteria and similar protozoa. The amoeba proteus (the photo below demonstrates the process of capturing food) surrounds them with its pseudopods. Next, the food ends up inside the cell. A digestive vacuole begins to form around it. Thanks to digestive enzymes, particles are broken down, absorbed by the body, and undigested residues are removed through the membrane. By phagocytosis, blood leukocytes destroy pathogenic particles that penetrate the body of humans and animals every moment. If these cells did not protect organisms in this way, life would be practically impossible.
In addition to specialized nutritional organelles, inclusions may also be found in the cytoplasm. It's fickle cellular structures. They accumulate in the cytoplasm when there is a need for this the necessary conditions. And they are spent when a vital need arises. These are starch grains and lipid droplets.
Breath
Amoeba Proteus, like all unicellular organisms, does not have specialized organelles for the respiration process. It uses oxygen dissolved in water or other liquid, if we are talking about amoebas that live in other organisms. Gas exchange occurs through the surface apparatus of the amoeba. Cell membrane is permeable to oxygen and carbon dioxide.
Reproduction
Amoeba is characterized by cell division in two. This process is carried out only in warm time of the year. It occurs in several stages. First the nucleus divides. It is stretched and separated using a constriction. As a result, two identical ones are formed from one nucleus. The cytoplasm between them is torn. Its sections separate around the nuclei, forming two new cells. ends up in one of them, and in the other its formation occurs anew. Division occurs through mitosis, so the daughter cells are an exact copy of the mother cells. The process of amoeba reproduction occurs quite intensively: several times a day. So the lifespan of each individual is very short.
Pressure regulation
Most amoebas live in aquatic environments. A certain amount of salts is dissolved in it. Much less of this substance is in the cytoplasm of the protozoan. Therefore, water must come from an area with a higher concentration of the substance to the opposite one. These are the laws of physics. In this case, the amoeba’s body would burst from excess moisture. But this does not happen due to the action of specialized contractile vacuoles. They remove excess water with salts dissolved in it. At the same time, they ensure homeostasis - maintaining constant internal environment body.
What is a cyst
Amoeba proteus, like other protozoa, has adapted in a special way to survive unfavorable conditions. Her cell stops feeding, the intensity of all vital processes decreases, and metabolism stops. The amoeba stops dividing. It is covered with a dense shell and in this form endures an unfavorable period of any duration. This happens periodically every autumn, and with the onset of warmth, the single-celled organism begins to intensively breathe, feed and reproduce. The same thing can happen in the warm season with the onset of drought. The formation of cysts has another significance. It lies in the fact that in this state, amoebas carry the wind over significant distances, dispersing this biological species.
Irritability
Of course, oh nervous system in these simplest single-celled organisms there is no speech, because their body consists of only one cell. However, this property of all living organisms in the amoeba Proteus manifests itself in the form of taxis. This term means a response to stimuli various kinds. They can be positive. For example, an amoeba clearly moves towards food objects. This phenomenon can essentially be compared to the reflexes of animals. Examples of negative taxis are the movement of the amoeba Proteus from bright light, from an area of high salinity or mechanical stimuli. This ability is primarily of defensive value.
So, amoeba proteus is a typical representative of the subkingdom Protozoa or Unicellular. This group of animals is the most primitively structured. Their body consists of one cell, but it is capable of performing the functions of the whole organism: breathing, eating, reproducing, moving, responding to irritations and unfavorable environmental conditions. Amoeba Proteus is part of the ecosystems of fresh and salt water bodies, but can also live in other organisms. In nature, it is a participant in the cycle of substances and the most important link in the food chain, being the basis of the plankton of many reservoirs.
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 excretion is carried out directly through the 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.
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
