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| Excretion and Osmoregulation in Amoeba |
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| Amoeba is a protozoan which forms the simplest of all groups in the animal kingdom. Inspite of being unicellular it is physiologically balanced and performs all the essential processes of an animal. |
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| Carbon dioxide, urea, uric acid and mineral salts are not allowed to collect beyond a certain limit in the organism. Amoeba is fresh water in habitat, these by-products of dissimilation (oxidation of organic substances) are disposed off mainly by diffusion through the general surface which is the cell membrane into surrounding water. |
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| Besides the cell membrane, Amoeba has a simple device known as the contractile vacuole which is an organelle 30 - 50 m in diameter. This small sac lies freely in the cytoplasm of the organism. |
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 excretion |
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osmoregulation |
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| The water content in the organism has to be regulated as there is a constant inflow of excess water. This is because the cell membrane surrounding the animal is semipermeable and as the protoplasm contains a higher concentration of salts than the water outside, water enters the cell by osmosis. This water is more than what is actually required by the animal. To counter this, excess water collects into the contractile vacuole as fast as it enters the body. The vacuole slowly grows larger until it reaches the maximum size. Then the endoplasm in the area surrounding the vacuole contracts and the fluid contents which contain traces of urea and carbon dioxide are discharged out into the surrounding pond water. Thus the contractile vacuole functions effectively as an organelle that performs both excretion and osmoregualtion. |
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Excretion and Osmoregulation
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