GENERAL HISTOLOGY

Detailed explanation-1: -Echinoderms take many forms of symmetry. Pentameral symmetry is the major form and the other forms are derived from it. However, the ancestors of echinoderms, which originated from Cambrian period, were believed to be bilaterians. Echinoderm larvae are bilateral during their early development.

Detailed explanation-2: -The larvae of echinoderms are bilaterally symmetrical. As they mature, they become radially symmetrical.

Detailed explanation-3: -Echinoderms have a spiny endoskeleton. They have radial symmetry as adults but bilateral symmetry as larvae. Echinoderms have a unique water vascular system with tube feet. This allows slow but powerful movement.

Detailed explanation-4: -Although the echinoderms show both radial and bilateral symmetry in their life cycle, they are classified as bilaterally symmetric and not radially symmetric because they are evolved from bilaterally symmetrical organisms.