Amoeba
Classification of Amoeba
Phylum - Protozoa
Subphylum - Sarcomastigophora
Class - Sarcodina
Subclass - Rhizopoda
Order - Amoebida
Genus - Amoeba
Phylum - Protozoa
Subphylum - Sarcomastigophora
Class - Sarcodina
Subclass - Rhizopoda
Order - Amoebida
Genus - Amoeba
Amoeba was discovered by Russel von Rosenhoff (1755). They named it "Little Proteus", because it keeps changing its shape like Proteus, a fictional sea god of the British.
Many species of amoeba are known but Amoeba proteus is most commonly found. Other widespread species are Amoeba radiosa, Amoeba discoides and Amoeba verrucosa.
Habitat and Habits
There are different species of amoeba that are found in sea, freshwater, or wet soil. Amoeba Proteus crawls slowly and continuously in ponds, puddles, drains, lakes, etc. all over the world, often in the bottom and surface moss and bottom mud. It feeds on algae, bacteria, etc., and reacts to various stimuli. In this reproduction is by simple binary fission.
Culture of Amoeba
Amoeba can be cultured for laboratory study. For this, leaves, grass, wheat grains, or banana peels are boiled in distilled water and kept in an open vessel for 2-3 days. Innumerable bacteria grow in the water of the utensil, then after bringing half-rotten leaves from a pond or puddle, wash them a little and put some clean ones in the utensil. Innumerable amoebas are formed in the water of the vessel within 5-7 days. Take a drop from the bottom of the dish using a dropper put it on a slide and observe under a microscope.
Shape and Structure of Amoeba
Shape, Size, and Color
Amoeba Proteus is up to 0.6 mm. But amoebas of other species are 0.2 to 0.5 mm in diameter. Under the microscope, the living amoeba looks like a colorless, but shiny and asymmetric drop of jelly-like substance. By watching continuously for some time, it will be known that its shape keeps on changing all the time.
Pseudopodia
1. Small protuberances of protoplasm continuously form here and there on the surface of the living amoeba and merge back into the body.
2. Therefore, the shape of the body is asymmetric and always changing and there is no fixed surface ventral surface, or anterior or posterior end of the body. The protuberances are called pseudopodia = “false feet” because the locomotion continues to occur due to their formation. They are also helpful in taking food.
3. In most of the species of Amoeba, it is like a finger, wide and rounded at the ends. Such feet are called lobopodia.
4. In active amoeba, the pseudopods sometimes appear as wrinkles, merging at the temporary posterior end. Such a wrinkled end is called a postpod or uroid.
Amoeba's unicellular body, like a normal cell, has three major parts-
- Plasma Membrane
- Cytoplasm
- Nucleus
Plasma Membrane
Amoeba's body is covered by a thin living tissue called plasmalemma. It is 1 - 2μ thick. It is made up of double layers of protein and lipid molecules, it is surrounded by microfilament-like molecules of mucoproteins called microvilli, due to which the plasmalemma is sticky. This membrane is firm but flexible due to which the body of the amoeba continues to grow. It also can regenerate.
Cytoplasm
The cytoplasm contains a basic fluid called a matrix. It is divided into two parts ectoplasm and endoplasm-
1. Ectoplasm: Thick, sticky, and jelly-like plasma gel layer of fibrous and granular protoplasm on the inner side and, Between it and the protoplasm, there is a thin and bright hyaline layer of non-granular, clear, colorless, and transparent aqueous liquid. Probably the organism slides here and there freely on the hyaline layer. There is a thick hyaline cap of the hyaline layer at the top of the feet.
2. Endoplasm: It is the granular, relatively less fibrous, and more liquid central body of the protoplasm. It is also called plasma sol. In this, there are clear motions of fluid flow, which are called cyclosis.
Apart from this, vacuoles are also found in the cytoplasm which is of three types – Contractile vacuole, Food vacuole, and Water vacuole.
(a) Contractile vacuole - This vacuole works for osmosis control, in this the unnecessary amount of water from the cytoplasm keeps on collecting continuously, due to which it keeps on taking it out, hence it sometimes appears big and sometimes small.
(b) Food vacuoles – This vacuole is related to nutrition. These are numerous non-contractile granules that are visible here and there throughout the endoplasm. These are not permanent formations, each food vessel is formed as a result of the food inside and after digestion of the food present in it, it ends by cutting outside.
(c) Water vacuoles - These are colorless and transparent non-contractile vesicles filled with small amounts of water in the endoplasm.
Nucleus
In the endoplasm of amoeba, a nucleus is found in its central part. All the functions of amoeba (metabolism, reproduction, inheritance, etc.) are under the control of the nucleus. Therefore, if amoeba is cut into pieces in such a way that some pieces have parts of the nucleus and some do not, then the pieces with parts of the nucleus will regenerate to become complete amoeba, but the other pieces will be destroyed.
In addition to the above organelles, the endoplasm contains regular-shaped vesicles of an excretory substance called carbonyl diurea. These are called biurets and triurets, depending on the shape.
How many amoebas are there in the world and ocean? - If seen, there are different species of amoeba in the world which are found in the sea, freshwater, or wet soil. Amoeba Proteus is a species of Amoeba that crawls slowly and continuously in ponds, puddles, drains, lakes, etc., often in the bottom and surface moss and bottom mud. It feeds on algae, bacteria, etc., and reacts to various stimuli. In this reproduction is by simple binary fission. So it can be said that amoebas are found in very large numbers in the world because we cannot see them without a microscope, so we cannot find out their exact number.
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