EVERYDAY SCIENCE

Detailed explanation-1: -This phylum is also called Coelenterata. Animals belonging to this phylum are aquatic and exclusively marine. They are generally attached to rocks, i.e., they are sessile. Hydra is the only freshwater organism under this phylum.

Detailed explanation-2: -Hydras belong to the phylum Coelenterata (also called Cnidaria), which includes corals, sea anemones, and jellyfish. Coelenterates are primarily marine animals, but hydras are found in freshwater ponds, lakes, and streams.

Detailed explanation-3: -The best-known freshwater coelenterates, the hydra, have lost the medusa stage entirely. In hydra, polyps may produce new polyps by asexual budding or may temporarily switch to sexual reproduction using gonads. Fertilized eggs derived directly from polyps may then hatch to produce new polyps.

Detailed explanation-4: -Hydra, genus of invertebrate freshwater animals of the class Hydrozoa (phylum Cnidaria). The body of such an organism consists of a thin, usually translucent tube that measures up to about 30 millimetres (1.2 inches) long but is capable of great contraction.

Detailed explanation-5: -Solution : Hydra is a fresh water polyp like coelenterate whereas Aurelia, Obelia and Physalia are marine coelenterates.