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What is the exact difference between grades of organization and symmetry ? Explain with examples. |
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Answer» Solution :I. Grades of organization : (1) The grades of organization mean the way an organism has different bodyformation . (2) UNICELLULAR organisms like amoeba have a single cell in the body and hence the organization in its body is CALLED protoplasmic grade of organization . (3) Some organisms have onlycells in their body which is called cellular grade of organization . e.g. Poriferans. (4) Somehave tissues e.g. Coelenterates . They are said to have tissue grade organization . Some have organs , they are said to have organization - organ grade. e. g. Plathyheminthes . All other higher ANIMALS have organ - system grade organization . II. Symmetry : (1) Symmetry on the other hand shows the base of the body formation . (2) The symmetry can be understood by taking an imaginary cut through the animal body. (3) Based on the symmetry there can be three types. (4) In asymmetric animals, there is no symmetry in any plane . e.g. Amoeba. (5) The bilateral symmetry is the one in whichan imaginary axis can pass through only one median plane to divide the body into two equal halves. Most of the animals have bilateral symmetryand hence their organs are arranged in symmetric way on both the sides. (6) The imaginary cut passing through the CENTRAL axis but any plane of body can give more than one equal half. The organs of such animals are arranged in a radius of an imaginary circle.e.g. Cnidarians and some echinoderms. Both grades of organization and symmetry are the bases for classifying animals into different phyla. |
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