EVERYDAY SCIENCE

Detailed explanation-1: -Are all cnidarians sessile? No, they can be free-swimming or sessile. Where do jellyfish digest their prey? Digestive enzymes break down food in the gastrovascular cavity (external digestion).

Detailed explanation-2: -Yes, Cnidaria are generally both sessile and motile. Most species of Cnidaria have two basic forms, a sessile polyp, and a mobile medusa. This allows the animal the ability to move around and find a good space to live and feed, then develop into a sessile form.

Detailed explanation-3: -Cnidarians are radially symmetrical (i.e., similar parts are arranged symmetrically around a central axis). They lack cephalization (concentration of sensory organs in a head), their bodies have two cell layers rather than the three of so-called higher animals, and the saclike coelenteron has one opening (the mouth).

Detailed explanation-4: -Answer and Explanation: The option that is NOT correct is: (a) The adult body is bilaterally symmetrical. The adult cnidarians are not bilaterally symmetrical.

Detailed explanation-5: -They have two different morphologies: a polyp stage and a medusa stage (not all classes will have both through out their life time). Both stages have radial symmetry. The polyp stage tends to be sessile and the medusa stage is mobile. Some species of Cnidarians have bioluminescence.