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Amoebidae

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Amoebidae
Amoeba 3.jpg
Scientific Classification
Genera

Amoebidae is a taxonomic family of unicellular organisms, best known for their type genus, the amoeba. The name amoeba is from the Greek word amoibe which means "change". As an eukaryotic single celled organism, it is the most primitive animal in the kingdom Protista. [1] It is too small to be seen without a scientific device. Its movement is the most primitive form of animal locomotion. The amoeba is a shape shifter. Pelomyxa palustris is the largest amoeba. It is usually found in wet places such as lakes, ponds, puddles, streams, or rivers. It reproduces asexually by fission. Six forms of amoeba are parasites in humans. The most important one is Entamoeba histolytica that causes amebiasis and dysentery. [2]

Contents

Anatomy

An amoeba is a microscopic organism that averages 0.25 mm in length. An amoeba breathes oxygen through its cell membrane. The membrane is made of protein and fat to let substances pass in and out of the cell. Also, the amoeba breathes oxygen through the cell membrane. A nucleus, located centrally, controls the growth and reproduction of the cell and contains the chromosomes. The inside of the amoeba is filled with a fluid called cytoplasm that accounts for most of the amoeba. There are two types of cytoplasm. The clearer cytoplasm, found near the cell membrane is called ectoplasm. The darker cytoplasm found in the interior of the protozoan is called endoplasm. There is a protoplasm in which food and materials float around. [3] The most outstanding feature of the amoeba is the pseudopod which means "false feet". It is a single large tube, located on the anterior end. It functions as feet and mouth to be used for movement and eating food. To eat food, It stretches out and pull back into the body. The amoeba contains a contractile vacuole to excrete water and waste for osmotic equilibrium which means osmolalities inside and outside the cell are equal. Food is stored and digested in what is called a food vacuole. [4]

Reproduction

An amoeba reproduces asexually by a process, binary fission. First, a parent cell stops moving and rounds off. The amoeba creates two nuclei and changes its shape. The cytoplasm contracts to divide the cytoplasm. The cell gets apart into two separate daughter cells. The mother cell and the daughter cell stretch it until it gets cut. Then each starts a new life. If the two cells fail to disconnect the tether, they remain as one cell that has two nuclei. When two amoebas have a problem with disconnecting, the third amoeba gets in between them to cut the umbilical cord. [5]


Ecology

Description

An amoeba usually lives in moist areas around water. More amoebas inhabit locations with higher concentrations of moisture. It avoids light but swims faster in warmer temperature. In unfavorable condtions, the amoeba creates a cyst. This hard walled body exists for a long time until condtions become favorable. The amoeba does not live in an acidic environment.[6] The amoeba exists in a film of water on and between the particles that make up soil. It eats algae, bacteria, plant cells, protozoa and metazoa. There are some parasitic amoeba. They use pseudopods to eat food, and the food is digested in the food vacuole. In higher organic content, the bacterial population increases, which supports higher numbers of amoeba. [7]


Freshwater Lakes & Ponds

The surface - Small Amoebidae like Vannella, Naegleria and Acanthamoeba are seen at the interface between air and water. Amoeba at the interface would be good for the collected bacteria and other prey but would increase a problem with other protists.

The Water Column - A group of amoeba have floating forms with adjunctions which keep the amoeba suspended, so the amoeba can respond quickly. This form is really not as useful as it is on the ground with flagella and cilia. The amoeba seem to be combined as a big group in seawater, and it can also be in freshwater.

The Lake Bottom - Environments have not really changed at the bottom of a lake for years except for the abundant number of amoeba. The density of the amoeba was at its peak in August, September and November. 39 species were found, and 11 new species were found at the bottome of the lake. This means the amoeba community is complex and keeps growing bigger. [8]

Gallery

References

See Also

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