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प्रश्न
What is the exact difference between grades of organization and symmetry? Explain with examples.
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उत्तर
Grades of organization:
- The grades of organization mean the way an organism has a different body formation.
- Unicellular organisms, such as amoeba, possess a single cell, resulting in a protoplasmic grade of organization within their body.
- Some organisms have only cells in their body which is called the cellular grade of organization. For example, Poriferans.
- Some organisms possess tissues, such as Coelenterata. They are supposed to possess tissue-grade organization. Certain things possess organs; they are classified as having an organization - organ grade. For example, Platyhelminthes. All other higher animals possess organ-system grade organization.
Symmetry:
- Symmetry, on the other hand, shows the base of the body formation.
- The symmetry can be understood by taking an imaginary cut through the animal’s body.
- Based on the symmetry, there can be three types.
- In asymmetric animals, there is no symmetry in any plane. e.g. Amoeba.
- Bilateral symmetry is a condition in which an imaginary axis can traverse a single median plane, hence divide the body into two equal halves. The majority of animals have bilateral symmetry, resulting in the symmetrical arrangement of their organs on both sides.
- The imaginary plane passing through the central axis of a body may produce many equal halves. The organs of these animals are organised in a radial configuration around an imaginary circle. For example, Cnidaria and some Echinodermata.
Both grades of organization and symmetry are the bases for classifying animals into different phyla.
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