Question

How is radial symmetry advantageous to sedentary organisms?

Answer 1

Hint: Radial symmetry is useful to sedentary organisms. In Radial symmetry sensory receptors are uniformly spread all around the body. Radial Symmetry also helps sedentary organisms to grab food and detect threats in the surroundings.

Complete answer:
The radial symmetry body can be divided into two halves by any of the vertical plane. Characteristic features of radially symmetrical animals are the absence of dorsal and ventral surfaces.

They also do not have anterior or posterior sides. They also have oral (mouth bearing) and aboral sides (sides away from the mouth). The radial symmetry is the characteristic feature of many sedentary organisms like some sponges, sea stars etc. Radial symmetry is advantageous to the slow-moving organisms as in these organisms there is even distribution of all the sensory receptors all over the body. As a result these animals can detect threats from all the directions. Animals with radial symmetry can grab food from all the directions.

Most radially-symmetrical animals are sedentary or move very slowly. The word sessile is mostly used for the organisms that are less attached to the surface or cannot move on their own. Mostly sessile animals possess radial symmetry. Sea anemones and “jellyfishes'' (members of phylum Cnidaria) possess radial symmetry. Some sea stars (members of phylum Echinodermata) also possess radial symmetry.

Note: Almost all of the radially-symmetrical animals have no front and no back. They also have no right and no left. In such animals sense organs are scattered evenly all around the body’s surface. Such animals are very slow-moving and are not attuned to speedy and synchronized movements.