Final answer:
Echinoderms lack a centralized nervous system, an external skeleton, respiratory and excretory systems, and do not possess a heart for fluid circulation. They feature pentamerous radial symmetry, a water vascular system for movement and respiration, and a complete digestive system within their internal calcareous endoskeleton.
Step-by-step explanation:
The characteristics not found in the phylum Echinodermata include a centralized nervous system, an external skeleton, respiratory and excretory systems, and a heart for circulating fluids within the body. Echinoderms, such as sea stars and sea urchins, are characterized by their pentamerous radial symmetry, water vascular system, and a complete digestive system. Their body wall includes an endoskeleton of calcareous ossicles, often with surface spines, but they lack a hard external skeleton.
Echinoderms have a water vascular system that aids in respiration and locomotion. Their physiology includes an open circulatory system without a heart, and oxygen and wastes are diffused through the thin walls of their tube feet. They also possess a coelom and use pheromones for communication, with some species having simple eyes or ocelli to detect light. The ability to regenerate lost body parts is another notable characteristic of echinoderms.