Question

Give a detail account on symmetry and coelom that you have studied.

Answer 1

Symmetry:
It is a plane of arrangement of body parts.

• Radial symmetry and bilateral symmetry are the two types of symmetry.

1. In radial symmetry the body parts are arranged around the central axis. If the animal is cut through the central axis in any direction, it can be divided into similar halves.

Example: Hydra, jelly fish and star fish.

2. In bilateral symmetry, the body parts are arranged along a central axis. If the animal is cut through the central axis, we get two identical halves.

Example: Frog.

Coelom:
It is a fluid-filled body cavity. It separates the digestive tract from the body wall.

• A true body cavity or coelom is one that is located within the mesoderm. Based on the nature of the coelom, animals are divided into 3 groups.

a)Coelomates or Eucoelomates have a true coelom.
Example: Earthworm, Frog.
b) Pseudocoelomates have a false body cavity.
Example: Roundworm.
c)Acoelomates do not have a body cavity.
Example: Tapeworm.