Question

What is the exact difference between grades of organization and symmetry? Explain with examples.

Answer 1

Grades of organization:

1. The grades of organization mean the way an organism has a different body formation.
2. Unicellular organisms, such as amoeba, possess a single cell, resulting in a protoplasmic grade of organization within their body.
3. Some organisms have only cells in their body which is called the cellular grade of organization. e.g. Poriferans.
4. 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:

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’s 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. 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.
6. 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.