Amoeba Proteus is a single-celled animal that combines the functions of a cell and an independent organism. Outwardly, an ordinary amoeba resembles a small gelatinous lump only 0.5 mm in size, constantly changing its shape due to the fact that the amoeba constantly forms outgrowths - the so-called pseudopods, and, as it were, flows from place to place.
For such a variability in the shape of the body, the common amoeba was given the name of the ancient Greek god Proteus, who knew how to change his appearance.
The structure of the amoeba
The amoeba organism consists of a single cell, and contains a cytoplasm surrounded by a cytoplasmic membrane. The cytoplasm contains the nucleus and vacuoles - the contractile vacuole, which acts as an excretory organ, and the digestive vacuole, which serves to digest food. The outer layer of the cytoplasm of the amoeba is more dense and transparent, the inner one is more fluid and granular.
Amoeba proteus lives at the bottom of small fresh water bodies - in ponds, puddles, ditches with water.
amoeba nutrition
The common amoeba feeds on other unicellular animals and algae, bacteria, microscopic remains of dead animals and plants. Flowing along the bottom, the amoeba encounters prey, and envelops it from all sides with the help of pseudopods. At the same time, a digestive vacuole is formed around the prey, into which digestive enzymes begin to flow from the cytoplasm, due to which food is digested and then absorbed into the cytoplasm. The digestive vacuole moves to the cell surface anywhere, and merges with the cell membrane, after which it opens to the outside, and undigested food residues are thrown into the external environment. Digestion of food in one digestive vacuole takes the amoeba Proteus from 12 hours to 5 days.
Selection
In the process of life of any organism, including the amoeba, harmful substances are formed that must be excreted. To do this, the common amoeba has a contractile vacuole, into which dissolved harmful waste products constantly enter from the cytoplasm. After the contractile vacuole is filled, it moves to the cell surface and pushes the contents out. This process is repeated constantly - after all, the contractile vacuole is filled in a few minutes. Together with harmful substances, excess water is also removed during the excretion process. In protozoa living in fresh water, the concentration of salts in the cytoplasm is higher than in the external environment, and water constantly enters the cell. If excess water is not removed, the cell will simply burst. In protozoa, living in salty, sea water, there is no contractile vacuole; in them, harmful substances are removed through the outer membrane.
Breath
Amoeba breathes oxygen dissolved in water. How does this happen and why is breathing necessary? In order to exist, any living organism needs energy. If plants receive it in the process of photosynthesis, using the energy of sunlight, then animals receive energy as a result of chemical reactions of oxidation of organic substances that come with food. The main participant in these reactions is oxygen. In protozoa, oxygen enters the cytoplasm through the entire surface of the body and participates in oxidation reactions, while the energy necessary for life is released. In addition to energy, carbon dioxide, water and some other chemical compounds are formed, which are then excreted from the body.
amoeba reproduction
Amoebas reproduce asexually by dividing the cell in two. In this case, the nucleus first divides, then a constriction appears inside the amoeba, which divides the amoeba into two parts, each of which contains a nucleus. Then, along this constriction, the parts of the amoeba are separated from each other. If conditions are favorable, then the amoeba divides about once a day.
Under adverse conditions, for example, when a reservoir dries up, a cold snap, a change in the chemical composition of the water, and also in the fall, the amoeba turns into a cyst. In this case, the body of the amoeba becomes rounded, the pseudopods disappear, and its surface is covered with a very dense shell that protects the amoeba from drying out and other adverse conditions. Amoeba cysts are easily carried by the wind, and thus the amoeba colonizes other water bodies.
When environmental conditions become favorable, the amoeba leaves the cyst and begins to lead a normal, active lifestyle, feed and multiply.
Irritability
Irritability is a property of all animals to respond to various influences (signals) of the external environment. In an amoeba, irritability is manifested by the ability to respond to light - the amoeba crawls away from bright light, as well as to mechanical irritation and changes in salt concentration: the amoeba crawls away from the mechanical stimulus or from a salt crystal placed next to it.
One of the representatives of unicellular animals (protozoa) that have the ability to move independently using the so-called "pseudo-legs" is called Amoeba vulgaris or Proteus. It belongs to the type of rhizopods because of its inconstant appearance, forming, changing and disappearing pseudopods.
It has the form of a small, colorless, gelatinous lump, barely visible to the naked eye, about 0.5 mm in size, the main characteristic of which is the variability of shape, hence the name - “amoeba”, which means “changeable”.
It is impossible to examine in detail the structure of an ordinary amoeba cell without a microscope.
Any body of fresh standing water is an ideal habitat for an amoeba, especially ponds with a high content of rotting plants and swamps in which bacteria live in large numbers.
At the same time, it will be able to survive in the moisture of the soil, in a drop of dew, in the water inside a person, and even in an ordinary rotting leaf of a tree, it can notice an amoeba, amoeba, in other words, they directly depend on water.
The presence of a large number of microorganisms and unicellular algae is a clear sign of the presence of proteus in the water, as it feeds on them.
When negative conditions for existence occur (the onset of autumn, the drying up of a reservoir), the protozoan stops eating. Acquiring the shape of a ball, a special shell appears on the body of a unicellular - a cyst. The body can stay inside this film for a long time.
In the state of a cyst, the cell waits out drought or cold (while the protozoan does not freeze and dry out), until the environmental conditions change or the cyst is carried by the wind to a more favorable place, the life of the amoeba cell stops.
This is how the amoeba is protected from adverse conditions, when the habitat becomes suitable for life, the proteus leaves the shell and continues to lead a normal life.
There is an ability to regenerate, when the body is damaged, it can complete the destroyed place, the main condition for this process is the integrity of the core.
The structure and metabolism of the simplest
To examine the internal structure of a unicellular organism, a microscope is needed. It will allow you to see that the structure of the body of an amoeba is a whole organism that is able to independently perform all the functions necessary for survival.
Her body is covered with a thin film, which is called, and containing semi-liquid cytoplasm. The inner layer of the cytoplasm is more liquid and less transparent than the outer one. It contains the nucleus and vacuoles
The digestive vacuole is used for digestion and disposal of undigested residues. begins to be carried out with contact with food, a “food cup” appears on the surface of the cell body. When the walls of the “calyx” close, digestive juice enters there, this is how a digestive vacuole appears.
The resulting nutrients as a result of digestion are used to build the body of the proteus.
The digestion process can take from 12 hours to 5 days. This type of nutrition is called phagocytosis. To breathe, the protozoan absorbs water over the entire surface of the body, from which it then releases oxygen.
To perform the function of excreting excess water, as well as regulating pressure inside the body, the amoeba has a contractile vacuole, through which waste products can also sometimes be released. This is how amoeba respiration occurs, the process is called pinocytosis.
Movement and reaction to stimuli
For movement, the common amoeba uses a pseudopod, their other name is pseudopodia or rhizopod (because of its similarity to plant roots). They can form anywhere on the surface of the body. When the cytoplasm overflows to the edge of the cell, a bulge appears on the surface of the proteus, a false leg is formed.
In several places, the leg is attached to the surface, the remaining cytoplasm gradually flows into it.
Thus, there is a movement, the speed of which is approximately 0.2 mm per minute. The cell may form several pseudopodia. The body reacts to various stimuli, i.e. has the ability to feel.
reproduction
Eating, the cell grows, increases, the process for which all creatures live - reproduction begins.
Reproduction of the common amoeba, the simplest process known to science, occurs asexually, and involves division into parts. Reproduction begins from the stage when the amoeba nucleus begins to stretch and narrow in the middle until it splits into two parts. At this time, the body of the cell itself is also divided. In each of these parts remains on the core.
In the end, the cytoplasm between the two parts of the cell is torn, and the resulting new cellular organism is separated from the parent, in which the contractile vacuole remains. The division stage is also due to the fact that the proteus stops eating, digestion stops, the body takes on a rounded appearance.
Thus, proteus multiplies. During the day, the cell can multiply several times.
Value in nature
Being an important element of any ecosystem, the amoeba regulates the number of bacteria and microorganisms in its habitat. This keeps the waterways clean.
Thus, being part of the food chain, it feeds on small fish, crustaceans and insects for which it is food.
The body of the amoeba proteus (Fig. 16) is covered with a plasma membrane. All actions of the amoeba are controlled by the nucleus. The cytoplasm is in constant motion. If its microflows rush to one point on the surface of the amoeba, a protrusion appears there. It increases in size, becomes an outgrowth of the body. This is a pseudopod that attaches itself to silt particles. All the contents of the amoeba gradually flow into it. This is how the amoeba moves from place to place.
Amoeba proteus is an omnivore. Its food is bacteria, unicellular plants and animals, as well as decaying organic particles. Moving, the amoeba encounters food and flows around it from all sides, and it ends up in the cytoplasm (Fig. 16). A digestive vacuole is formed around food, where digestive secrets enter, digesting food. This way of capturing food is called cellular ingestion.
The amoeba can also feed on liquid food, using another method - cellular drinking. It happens like this. Outside, a thin tube is pushed into the cytoplasm, into which liquid food is sucked. A digestive vacuole is formed around it.
| Rice. 16. The structure and nutrition of the amoeba |
Selection
As in Bodo, the vacuole with undigested food remnants moves to the surface of the body of the amoeba and its contents are thrown out. The release of harmful substances of vital activity and excess water occurs with the help of a contractile (pulsating) vacuole.
Breath
Respiration in an amoeba is carried out in the same way as in a bodo ( cm.Bodo - flagellate animal).
Each type of protozoan animal has its own structure, its own form, including very complex and bizarre ones. It is not formed by chance, and persists for a very long time: at the bottom of the ocean, in sediments formed tens of millions of years ago, exactly the same foraminifera shells are found.
This is possible because in each species the construction of the organism is carried out according to a certain plan, a certain program. This program is written in a special code on long molecules stored in the cell nucleus, just like computer programs are written on a magnetic hard disk. Before reproduction, a copy is written off from the program and passed on to offspring. These programs can be called genetically fixed, or innate. material from the site
The cell nucleus contains not only programs how to build it, but also how to act. They determine the actions of the animal - its behavior. Just as some of the simplest body shape programs lead to a simple form, while others to a complex one, so behavioral programs can be both simple and complex. The diversity of animals in terms of the complexity of the behavioral program is no less than the diversity of their forms.
The amoeba also responds to many signals by launching its behavior programs. Thus, she recognizes different types of microscopic organisms that serve her food; moves away from bright light; determines the concentration of substances in the environment; away from constant mechanical irritation.
Origin of Sarcode
In the limits of the flagellates, there is a shaky border (a distinctive feature) between the two kingdoms - plants and animals. At first glance, it seems that there is a sharp difference between animal flagellates and sarcodes: the former move with the help of flagella, the latter with the use of prolegs. But it turns out that Sarcodidae, previously considered the oldest protozoa, are now considered as evolutionary descendants of animal flagellates. The fact is that flagella appear in many Sarcodidae during reproduction, as, for example, in the germ cells of radiolarians and foraminifers. Therefore, flagella were once also found in Sarcodidae. Moreover, animal flagellates (for example, the flagellated amoeba) are known, taking the form of an amoeba to capture food with the help of prolegs. All this allows us to consider that the Sarcodidae originated from the ancient flagellates and lost their flagella during further evolution.
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Taxonomy of amoeba proteus
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The general structure of the amoeba proteus
Questions about this item:
Amoeba is a genus of single-celled eukaryotic organisms (they belong to the simplest). They are considered animal-like because they feed heterotrophically.
The structure of amoebas is usually considered on the example of a typical representative - the common amoeba (Proteus amoeba).
Amoeba ordinary (hereinafter amoeba) lives at the bottom of freshwater reservoirs with polluted water. Its size ranges from 0.2 mm to 0.5 mm. In 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 outgrowths) 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 prolegs and the movement of the amoeba occurs due to the movement of the cytoplasm, which gradually flows into the 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 the life processes characteristic of multicellular animals. The amoeba feeds, breathes, releases substances, and reproduces.
The amoeba cytoplasm is not homogeneous. A more transparent and dense outer layer is isolated ( eqtplasma) and a more granular and fluid inner layer of the cytoplasm ( endoplasm).
In the cytoplasm of the amoeba there are various organelles, the nucleus, as well as the digestive and contractile vacuoles.
The amoeba feeds on various unicellular organisms and organic residues. Food is wrapped around the pseudopods and is inside the cell, formed digestiveand Ivacuole. It receives various enzymes that break down nutrients. Those that the amoeba needs then enter the cytoplasm. Unnecessary food residues remain in the vacuole, which approaches the surface of the cell and everything is thrown out of it.
The "organ" of excretion in the 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 the entire surface of the body. Oxygen comes into it from water, carbon dioxide comes out of it. The process of respiration consists in the oxidation of organic substances in mitochondria with oxygen. 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 then used for various life processes.
For the amoeba, only asexual reproduction is described by dividing in two. Only large, i.e. grown, individuals divide. First, the nucleus divides, after which the amoeba cell divides by constriction. That daughter cell that does not receive a contractile vacuole forms one subsequently.
With the onset of cold weather or drought, the amoeba forms cyst. Cysts have a dense shell that performs a protective function. They are quite light and can be carried by the wind over long distances.
The amoeba is able to react to light (creeps away from it), mechanical irritation, the presence of certain substances in the water.
Amoeba proteus or common amoeba- lat. Amoeba proteus. Amoeba proteus or is a huge amoeboid organism, a representative of the class lobous amoeba, belongs to the type protozoa. Found in fresh waters, aquariums.
In a drop of water taken from a pond, swamp, ditch or aquarium, when viewed under a microscope, a whole world of living beings opens up. Among them are tiny translucent invertebrates, constantly changing the shape of their body.
An ordinary amoeba, like a ciliate shoe, is the simplest animal in its structure. To examine an ordinary amoeba, you need to place a drop of water with amoebas under a microscope. The entire body of an ordinary amoeba consists of a tiny gelatinous lump of living matter - protoplasm with a nucleus inside. From the course of botany it is known that a lump of protoplasm with a nucleus is a cell. So, an ordinary amoeba is a unicellular invertebrate animal. Its body consists only of protoplasm and nucleus.
Observing the amoeba Proteus under a microscope, we notice that after a while the shape of its body changes. Amoeba Proteus does not have a permanent body shape. Therefore, it received the name "amoeba", which means "changeable" in Greek.
Also under a microscope, you can see that it slowly creeps onto the darkened part of the glass. Bright sunlight quickly kills common amoebas. If you add a crystal of table salt to a drop of water, the amoeba stops moving, retracts the pseudopods and acquires a spherical shape. Thus, ordinary amoebas reduce the surface of the body, which is affected by a salt solution harmful to them. This means that ordinary amoeba are able to respond to external stimuli. This ability is called irritability. It connects the common amoeba with the external environment and has a protective value.
Common amoebas can be found even in ditches and puddles that have formed recently. When the reservoir in which ordinary amoeba and other protozoa live begins to dry up, they do not die, but are covered with a dense shell, turning into a cyst. In this state, amoeba and other protozoa can tolerate both high temperatures (up to +50, +60 °) and strong cooling (up to - 273 degrees). The cysts are carried by the wind over considerable distances. When such a cyst again finds itself in favorable conditions, it begins to feed and multiply. Thanks to this adaptation, ordinary amoeba survive unfavorable living conditions for them and settle throughout the planet. The movement of the amoeba occurs with the help of pseudopods.
The amoeba feeds on bacteria, algae, microscopic fungi. With the help of pseudopods (because of which the amoeba moves), it captures food.
Amoeba Proteus, like all animals, needs oxygen. Amoeba respiration is carried out due to the assimilation of oxygen from water and the release of carbon dioxide.
Common amoeba reproduce by division. In this case, the core of the amoeba lengthens, and then divides in half.
