Phylum Enchinodermata is more advanced than Phylum Mollusca?

Of the phyla we have discussed to this point, which one has the most complex nervous system?

Regeneration of lost parts of a sea star also serves in 

Echinoderms are monecious with external fertilization.

The 180°, counterclockwise twisting of the visceral mass, mantle, and mantle cavity of gastropods is called

Sea cucumbers will eviscerate intestines if disturbed.

Mollusk blood is referred to as

How many groups of mollusks branched off the original common ancestor?

For a sea star to regenerate from a severed arm what must still be in tact on that arm?

Sea urchins possess