Question

Sort out the animals on the basis of their symmetry (radial or bilateral): Coelenterates, ctenophores, annelids, arthropods, and echinoderms.

Answer 1

Introduction to symmetry

Symmetry refers to a correspondence of body parts, in size, shape and relative position, on opposite sides of a dividing line. Considering these bases, organisms are of two basic types:

* Asymmetrical: Body cannot be divided into two equal halves by a plane passing through the central axis.

* Symmetrical

* Radially symmetrical: Body can be divided into two equal halves by any plane passing through the central axis.

* Bilaterally symmetrical: Body can be divided into two identical halves only by one plane passing through the central axis.

Classification of organisms based on symmetry

Category of animals	Symmetry
i.Coelenterates	Radial
ii.Ctenophores	Radial
iii.Annelids	Bilateral
iv.Arthropods	Bilateral
v.Echinoderms	Radial