Question

What is radial symmetry? Which animal taxa are radially symmetric? How might radial symmetry be advantageous to these types of organisms? What is bilateral symmetry, who has it, and what advantages does it convey to those animals? How do sponges fit in to all this?

Answer 1

Radial symmetry - The arrangement of body parts of an organism in such a way that it produces two equal halves when cut along any plane along the main axis. The animals possessing radial symmetry can take food from all directions. The receptors are equally distributed throughout the body which helps such animals to detect the danger of predators from all directions.

Bilateral symmetry - The arrangement of body parts of an organism in such a way that it produces two equal halves along only one plane of the main axis. Bilateral symmetry aids in faster movements in a particular direction that is forward, which helps such animals to escape their predators. The head remains ahead than the rest of the body and the processing unit lies there, which helps in early detection of stimulus and produce quicker responses moving forward. The bodies of such organisms are streamlined and the energy consumption moving forward is reduced.

Sponges are asymmetrical as they have a cellular level of organization, which are not arranged in radial or bilateral symmetry.