Texas A&M University (TAMU) BIOL112 Introductory Biology II Exam 3 Practice

Starfish and sea cucumbers belong to the phylum Echinodermata, which is characterized by several distinct features. Members of this phylum are known for their radial symmetry, a water vascular system that aids in movement and feeding, and an endoskeleton composed of calcareous ossicles. Echinoderms typically exhibit a unique ability to regenerate lost body parts and have a pentaradial symmetry as adults, which is a hallmark of their body plan. This phylum includes not only starfish and sea cucumbers but also sea urchins and sea lilies, all of which share these common characteristics. The classification of these organisms under Echinodermata highlights their evolutionary relationship and ecological importance within marine ecosystems.