AP BIOLOGY

Detailed explanation-1: -The bilateral symmetry of Cnidaria is thought to be inherited from the common ancestors of both cnidarians and triploblastic bilaterians. The secondary radial symmetry of Cnidaria evidently is a result of the adaptation to the sessile mode of life.

Detailed explanation-2: -The body plans cnidarians generally have radial symmetry (Fig. 3.25 A). Because the tentacles of corals, jellyfish, and sea anemones have this radial structure, they can sting and capture food coming from any direction.

Detailed explanation-3: -Cnidarians have radial symmetry. Echinoderms are bilateral animals that have a 5-part radial symmetry as adults.

Detailed explanation-4: -Cnidarians are radially or biradially symmetric, a general type of symmetry believed primitive for eumetazoans. They have achieved the tissue level of organization, in which some similar cells are associated into groups or aggregations called tissues, but true organs do not occur.