Types of Symmetry Animals


Symmetry is a character used in classification and is defined as – ‘It is a regularly of form, having corresponding position in relation to some central point, axis or plane. With reference to symmetry, a body can be –

1. Asymmetrical or Asymmetry: When the body of the animal doesn’t show any form of symmetry. For example many protozoa.

2. Superficial or Universal Symmetry: It is a rare type of symmetry and an indefinite number of planes may pass through the center of the body and each plane has a structure similar to that of the other. It is found in free-floating protozoa.

3. Radial Symmetry: It is a symmetry in which the body can be divided into a number of radial planes, similar parts arranged around a central axis like the spokes of a cycle wheel. This type of symmetry is found in Sponges, Cnidarians, and Echinoderms.

4. Bilateral Symmetry: In this symmetry body is divided more or less identically into right and left halves by passing a single median plane. The majority of animals show this type of symmetry.

Example: All vertebrate animals and invertebrates Annelida, Arthropoda, Mollusca, etc. show bilateral symmetry.

5. Biradial Symmetry: It is the combination of both bilateral and radial symmetry. It is present in many echinoderms and ctenophores.