The simplest organism is the amoeba proteus, although there are different types amoeba It got its name in honor of Proteus - the character Greek mythology, a feature of which was to change their appearance. The creature is a prokaryote because it is not a bacterium, as many people think. This is a colorless organism of a heterotrophic type, a eukaryote, which is able to feed on microorganisms and unicellular algae. Despite its simplicity and short life cycle, this type of animal plays important role in nature.
Description
According to the classification, the common amoeba belongs to the kingdom "Animals", the sub-kingdom "Protozoa", a class of free-living sarcodes. The structure of the creature is primitive, and it moves thanks to the temporarily appearing protrusions of the cytoplasm (they also call the rhizome). The body of Proteus consists of only a single cell, which is an independent and complete organism.
Amoeba is a eukaryote, a single-celled independent animal. Its characteristic is as follows: the body is semi-liquid, the size reaches 0.2-0.7 mm in length, and the creature can be clearly seen only under a microscope. Over the entire surface, the amoebic cell is covered with cytoplasm, which protects the “insides”. Above is the cytoplasmic membrane. In amoeba, the structure of the cytoplasm is two-layered. The outer layer is transparent and dense, the inner one is granular and fluid. In the cytoplasm are the contractile vacuole of the amoeba (due to it, unnecessary substances are released to the outside), the nucleus and the digestive vacuole. When moving, the shape of the cytoplasm is constantly changing. After examining the images, scientists determined that Proteus has more than five hundred chromosomes, so small that it is impossible to observe them.
Breathing is carried out by the whole body. The skeleton is missing. Amoeba reproduction is asexual. The amoebic cell also does not have a sense organ (including respiration).
However, the single-celled amoeba breathes, is sensitive to chemicals, irritants of the mechanical type and avoids sunlight.
One of the features of the animal is the ability to regenerate. This means that in case of damage, the cell will be able to repair itself by completing the missing fragments. The only condition is the complete preservation of the core, since it is the carrier of all information about the structure. Without a nucleus, the amoebic organism will simply die.
The movement of amoebas occurs with the help of pseudopodia, the so-called non-permanent outgrowths of the cytoplasm, which are also called pseudopodia. The cell membrane is very elastic and can be stretched anywhere. To form a pseudopod, the cytoplasm first bulges outward from the body, so that they look like thick tentacles. After - the same actions are performed, only in the reverse order - the cytoplasm moves inward, the pseudopod hides and appears in another part of the body. It is this method of movement that prevents the animal from having a permanent body shape. Despite their small size, creatures move relatively quickly - about 10 mm / hour.
The amoeba moves with the help of pseudopods, which is why it does not have a permanent body shape.
How do unicellular organisms eat and breathe?
The amoebic life cycle depends entirely on how the animal feeds and what the environment is like. The diet of the proteus includes the remains of decay, unicellular algae, bacteria, as well as microorganisms of a suitable size. Amoeba nutrition occurs by capturing the “prey” with pseudopods and pulling it inside the body. A vacuole forms around the food, into which the digestive juice then enters. Interestingly, the process of capture and further digestion can occur in any part of the body and even in several parts at the same time. The nutrients obtained during digestion enter the cytoplasm and are spent on building the body of the amoeba. In the process of resorption of algae and bacteria, protozoa immediately bring out the remnants of vital activity, and this can also occur in any part of the cytoplasm.
Like all protozoa of the unicellular class, proteas lack special organelles. Respiration in an amoeba occurs due to the absorption of oxygen dissolved in water (or liquid) by a surface apparatus. cell membrane animal is permeable, and through it freely pass carbon dioxide and oxygen.
How do they reproduce?
To produce offspring, asexual reproduction is used with the division of the body into two identical parts. More details on how many stages a cell goes through during division.
The process occurs only in the warm season and includes several stages:
- The nucleus undergoes division first. It protrudes, stretches, constrictions appear in it, with the help of which it then divides into two completely identical parts. In this case, there is a discrepancy between the daughter chromosomes to the opposite poles of the mother cell.
- Next, the division of the cytoplasm between the two nuclei occurs. Its zones are located and concentrated around the nuclei, thereby forming two new cells.
- Since in the body of an amoeba there is only a single copy of the contractile vacuole, it goes to only one new cage. In the other, it is re-formed. A more detailed description of the process of division and divergence of chromosomes is shown in the figure.
Cell division in this way is called mitosis, so the resulting two organisms are a copy of the "mother". There is no sexual process, so the exchange of chromosomes also does not occur.
Common amoebas reproduce very quickly. Judging by time, the creature divides into 2 cells every 3 hours, so the amoebic organism lives a little.
Features of existence and development
The life cycle is simple. The only cell, which is part-time and the body of an animal, grows in the process of development, and upon reaching the adult state, “reproduces”, dividing into two bodies asexually with a divergence of maternal chromosomes for “children”. Getting into conditions that are negative for life (cold season, drying up of a reservoir), such a cell is able to “die” for a while. At the same time, the body undergoes changes: pseudopodia are retracted, water is released from the cytoplasm and covers the entire amoebic organism, forming a double membrane, followed by the formation of a cyst. Protea freezes. When the environment becomes habitable, the creature is "reborn", the amoeba cyst ruptures, the prolegs are released (to move around), and the creature reproduces. You can learn in detail what an amoeba is in the video.
The animal is of great importance in nature. It is a source of food for multicellular organisms (worms, crustaceans, fish fry, and various molluscs feed on amoebas). The protea living in reservoirs in the process of life cleans reservoirs by eating various types of microorganism, bacteria and rotting parts of algae, the simplest testate amoebae are involved in the formation of chalk deposits and limestones.
Habitat "Amoeba ordinary"
The common amoeba is found in the mud at the bottom of ponds with polluted water. It looks like a small (0.2-0.5 mm), barely noticeable with a simple eye a colorless gelatinous lump, constantly changing its shape ("amoeba" means "changeable"). It is possible to consider the details of the amoeba structure only under a microscope.
The structure and movement of the "Amoeba ordinary"
The body of the amoeba consists of a semi-liquid cytoplasm with a small bubble-like nucleus enclosed inside it. The amoeba consists of one cell, but this cell is a whole organism leading an independent existence.
The cytoplasm of the cell is in constant motion. If the current of the cytoplasm rushes to one point on the surface of the amoeba, a protrusion appears on its body in this place. It increases, becomes an outgrowth of the body - a pseudopod, the cytoplasm flows into it, and the amoeba moves in this way. Amoeba and other protozoans capable of forming pseudopods are classified as rhizopods. They got this name for the external resemblance of the pseudopods to the roots of plants.
Nutrition "Ameba ordinary"
An amoeba can simultaneously form several pseudopods, and then they surround food - bacteria, algae, and other protozoa. Digestive juice is secreted from the cytoplasm surrounding the prey. A vesicle is formed - a digestive vacuole.
Digestive juice dissolves some of the substances that make up food and digests them. As a result of digestion, nutrients are formed that seep from the vacuole into the cytoplasm and go to build the body of the amoeba. Undissolved residues are thrown out anywhere in the body of the amoeba.
Breath "Ameba ordinary"
The amoeba breathes oxygen dissolved in water, which penetrates into its cytoplasm through the entire surface of the body. With the participation of oxygen, the decomposition of complex nutrients cytoplasm into simpler ones. In this case, the energy necessary for the life of the body is released.
Isolation of harmful substances of vital activity and excess water "Amoeba vulgaris"
Harmful substances are removed from the body of the amoeba through the surface of its body, as well as through a special vial - contractile vacuole. The water surrounding the amoeba constantly penetrates into the cytoplasm, liquefying it. The excess of this water with harmful substances gradually fills the vacuole. From time to time the contents of the vacuole are thrown out.
So from environment amoeba receives food, water, oxygen. As a result of the life of the amoeba, they undergo changes. Digested food serves as material for building the body of the amoeba. The resulting substances harmful to the amoeba are removed to the outside. going on amoeba metabolism. Not only the amoeba, but also all other living organisms cannot exist without metabolism both inside their body and with the environment.
Reproduction "Amoeba ordinary"
The nutrition of the amoeba leads to the growth of its body. The grown amoeba begins to reproduce. Reproduction begins with a change in the nucleus. It is stretched, the transverse groove is divided into two halves, which diverge into different sides two new nuclei are formed. The body of the amoeba is divided into two parts by a constriction. Each of them gets one nucleus. The cytoplasm between both parts is torn, and two new amoebas are formed. The contractile vacuole remains in one of them, while in the other it reappears. So, the amoeba reproduces by dividing in two. During the day, division can be repeated several times.
Cyst
Amoeba feeding and reproduction occurs throughout the summer. In autumn, when cold weather sets in, the amoeba stops eating, its body becomes rounded, a dense protective shell is released on its surface - a cyst is formed. The same thing happens when the pond where the amoeba lives dries up. In the state of the cyst, the amoeba endures unfavorable living conditions. When favorable conditions occur, the amoeba leaves the cyst shell. She releases pseudopods, begins to feed and multiply. Cysts carried by the wind contribute to the settlement of amoebas.
Protozoa in a drop of pond water (under a microscope).
Rhizome class unites the simplest unicellular animals, whose body is devoid of a dense shell, and therefore does not have a permanent shape. They are characterized by the formation of pseudopods, which are temporarily formed outgrowths of the cytoplasm that promote movement and capture of food.
Habitat, structure and movement of the amoeba. The common amoeba is found in the silt at the bottom of the ponds with contaminated water. It looks like a small (0.2-0.5 mm), colorless gelatinous lump, barely visible to the naked eye, constantly changing its shape ("amoeba" means "changeable"). The details of the structure of the amoeba can only be examined under a microscope.
The body of the amoeba consists of a semi-liquid cytoplasm with a small vesicle enclosed inside it core. Amoeba consists of one cell, but this cell is a whole organism leading an independent existence.
Cytoplasm cells are in constant motion. If the current of the cytoplasm rushes to one point on the surface of the amoeba, a protrusion appears on its body in this place. It increases, becomes an outgrowth of the body - a pseudopod, the cytoplasm flows into it, and the amoeba moves in this way. Amoeba and other protozoa capable of forming pseudopods are classified as rhizopods. They got this name for the external resemblance of the pseudopods to the roots of plants.
Vital activity of Amoeba.
Nutrition. An amoeba can simultaneously form several pseudopods, and then they surround food - bacteria, algae, and other protozoa. Digestive juice is secreted from the cytoplasm surrounding the prey. A vesicle is formed - a digestive vacuole. Digestive juice dissolves some of the substances that make up food and digests them. As a result of digestion, nutrients are formed that seep from the vacuole into the cytoplasm and go to build the body of the amoeba. Undissolved residues are thrown out anywhere in the body of the amoeba.
Amoeba Breath. Amoeba breathes oxygen dissolved in water, which penetrates into its cytoplasm through the entire surface of the body. With the participation of oxygen, complex food substances of the cytoplasm are decomposed into simpler ones. In this case, the energy necessary for the life and activity of the body is released.
Release of harmful substances life activity and excess water. Harmful substances are removed from the body of the amoeba through the surface of its body, as well as through a special bubble - the contractile vacuole. The water surrounding the amoeba constantly penetrates into the cytoplasm, liquefying it. The excess of this water with harmful substances gradually fills the vacuole. From time to time the contents of the vacuole are thrown out. So, from the environment, food, water, oxygen enter the body of the amoeba. As a result of the life of the amoeba, they undergo changes. The digested food serves as material for building the body of the amoeba. The substances harmful to the amoeba are removed outside. There is a metabolism. Not only amoeba, but also all other living organisms cannot exist without metabolism both inside their body and with the environment.
Amoeba reproduction. The feeding of the amoeba leads to the growth of its body. The grown amoeba begins to reproduce. (? Probably due to exceeding a certain mass of her body.) Reproduction begins with a change in the nucleus. It is stretched, the transverse groove is divided into two halves, which diverge in different directions - two new nuclei are formed. The body of the amoeba is divided into two parts by a constriction. Each of them gets one nucleus. The cytoplasm between both parts is torn, and two new amoebas are formed. The contractile vacuole remains in one of them, while in the other it reappears. So the amoeba reproduces by dividing in two. During the day, division can be repeated several times.
Division (reproduction) of Amoeba.
Cyst. The amoeba feeds and reproduces throughout the summer. In autumn, when cold weather sets in, the amoeba stops eating, its body becomes rounded, a dense protective shell is released on its surface - a cyst is formed. The same thing happens when the pond dries up where amoebas live. In the state of a cyst, the amoeba endures unfavorable living conditions for it. When favorable conditions occur, the amoeba leaves the cyst shell. She releases pseudopods, begins to feed and multiply. Cysts carried by the wind contribute to the dispersal (spread) of amoebae.
Possible additional questions for self-study.
- What makes the Cytoplasm systematically flow from one part of the Amoeba to another, forcing it to move in a given direction?
- How does the membrane of the cytoplasm of Amoeba recognize nutrients, as a result of which the amoeba purposefully forms pseudopods and a digestive vacuole?
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 travels to the cell surface anywhere, and fuses with cell wall, 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 do not remove, the cell will simply burst. In protozoa, living in salty, sea water there is no contractile vacuole, they have harmful substances 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 get it in the process of photosynthesis, using energy sunlight, then animals receive energy as a result chemical reactions oxidation organic matter received 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 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 unfavorable conditions, for example, when a reservoir dries up, a cold snap, a change chemical composition 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 conditions external environment become favorable, the amoeba leaves the cyst and begins to conduct normal, active image life, food and reproduction.
Irritability
Irritability is a property of all animals to respond to various influences (signals) of the external environment. In the amoeba, irritability is manifested by the ability to respond to light - the amoeba crawls away from bright light, as well as mechanical irritation and changes in salt concentration: the amoeba crawls away from the mechanical stimulus or from the salt crystal placed next to it.
