Problem 5

Background and context

All animals have body symmetry. Animals can be symmetrical or asymmetrical.

Asymmetrical -- They have no symmetry. They can't be divide into two equal parts in any plane. e.g., sponges

Symmetrical --- Animals can be divide into two equal parts.

This is of two types:  a) Bilateral symmetry   b) Radial symmetry

Radial symmetry - When any plane cut through its longitudinal axis, it will produce two equal halves. It means any line passing through centre of animal, will divide into two equal parts. Mostly found in aquatic animals. e.g., Simple sponge, sea anemone, starfish.

Bilateral symmetry --- When a plane cut from front(anterior) to back(posterior) separates it into two similar parts -left part and right part. Left and right parts are not identical bu mirror images of each other. It can divide into left and right part in only on plane. e.g.  Arthropods, Vertebrates.