Echinoderm is the name given to a member of the phylum Echinodermata. They have radial symmetry and this includes sea urchins, sand dollars, sea stars and sea cucumbers. It is suggested that they are related to the chordates which is the answer.
<h2>Operational </h2>
Explanation:
The operational definition is the description of a specific process, or set of validation tests, accessible to more persons than the definer (i.e., said to be publicly accessible), where it can be repeatedly measured or tested
Operational definitions are also used to define system states or (nonspecific) physical objects by the description of a specific process of preparation which can be repeated
For example in the given example experimenter is using the case of hitting a punching bag to measure the level of aggression in someone
Protection, sensory perception, storage, absorption, sunscreen, dilation, and constriction
