They have males and females and are live-bearing. Their excretory system consists of segmented, paired nephridia like annelids. They also share the presence and structure of their cuticle, their ciliated reproductive tract, and their musculature with Phylum Annelida. However, their respiratory system of tracheal tubes directly to the various organs, their open circulatory system, and their chitinous exoskeleton which must periodically be molted are shared with Phylum Arthropoda. This phylum fits in here, but we'll come back to it later because it needs a longer discussion.
Echinoderms are more closely related to chordates than any of the other invertebrate phyla.
By pumping fluid from one part of the hydraulic system to another, echinoderms can create a strong suction in the tube feet, aiding in movement and feeding. They have sexual reproduction with males and females. Much to the chagrin of early oyster fishermen, starfish are also capable of asexual reproduction by regeneration . Starfish prey on oysters, thus the oyster fishermen would cut up starfish to try to kill them, only to find the starfish population in their oyster beds had increased because one arm can regenerate a whole new starfish. The clam, however, must use its muscles to hold itself shut, and muscles can't work forever without getting fatigued, so eventually the clam's muscles will get tired and relax.