AP BIOLOGY

Detailed explanation-1: -The phylum Cnidaria (pronounced “nih DARE ee uh”) includes soft-bodied stinging animals such as corals, sea anemones, and jellyfish (Fig. 3.23 A). The phylum’s name is derived from the Greek root word cnid-meaning nettle, a stinging plant. Cnidarians are found in many aquatic environments.

Detailed explanation-2: -All jellyfish are Cnidaria, an animal phylum that contains jellies, sea anemones, and corals, among others. There are more than 10, 000 species of Cnidaria, and less than 4, 000 of these are Medusazoa-those animals we think of as jellyfish.

Detailed explanation-3: -Cnidarians have two body forms-polyp and medusa-which often occur within the life cycle of a single cnidarian. The body of a medusa, commonly called a jellyfish, usually has the shape of a bell or an umbrella, with tentacles hanging downward at the margin.

Detailed explanation-4: -Throughout their lifecycle, jellyfish take on two different body forms: medusa and polyps. Polyps can reproduce asexually by budding, while medusae spawn eggs and sperm to reproduce sexually.

Detailed explanation-5: -The polyp phase is a stalked organism which remains attached to some hard surface, and looks much like a Hydra. The medusa is the free-swimming phase which is usually thought of as a jellyfish. This stage has a gelatinous umbrella, called a bell, with the mouth located underneath.