AP BIOLOGY

Detailed explanation-1: -Echinodermata. Hint: Sea anemone is free-swimming marine animals. They have a soft and simple body made up of only two germ layers. They also have a central gut cavity in which the mouth leads to the gut.

Detailed explanation-2: -Answer and Explanation: The only animal in this list that does not belong to the echinoderm phylum is B) sea squirt.

Detailed explanation-3: -Examples of echinoderms include sea stars, sea urchins, sea cucumbers, brittle stars, and feather stars (Fig. 3.83). Although they may appear very different, echinoderms all have two major defining characteristics that set them apart from all other animals: a water vascular system and five-sided radial symmetry.

Detailed explanation-4: -Living representatives include the classes Crinoidea (sea lilies and feather stars), Echinoidea (sea urchins), Holothuroidea (sea cucumbers), Asteroidea (starfishes, or sea stars), Ophiuroidea (basket stars and serpent stars, or brittle stars), and Concentricycloidea (sea daisies; discovered in the 1980s).