Do sea urchins have an endoskeleton?

Answer 1

No. echinoderms have no exoskeleton.

Related Information:

Echinoderms are deuterostomes, a group belonging to the Phylum, Chordata but separate from the vertebrates, also of this phylum. While there is a close relationship between the echinoderms and the vertebrates, echinoderms are endoskeletal invertebrates.

Answer 2

invertebrate implies that the animal does not have a skeleton... but not all invertebrates have an exoskeleton (what i think you meant to ask). ex: a worm

Invertebrates can have an endoskeleton (like echinoderms, among them starfish, sea urchins) or an exoskeleton (like insects) while some invertebrates lack a skeleton completely (also some like certain sea cucumbers are entirely soft bodied but ancestors may have had a skeleton or they have have a skeleton whose pieces can be separated to give them flexibility to fit into cavities to avoid predators; so technically these types have a skeleton even though it's not always solid; moreover sponges have spicules to give them firmness although the spicules may not be connected but I think this is not a true skeleton since ancestors of present sponges never had a solid or firm piece of something composed in part of calcium- note many sponges contain silica so I think that would not be a true skeleton on the basis it has no calcium and/or not connected together into one stiff piece).

Note echinoderms are relatively closely related to vertebrates forming much of the taxon deuterostoma and both contain an endoskeleton (insects are a type of protostome and jellyfish lower still next to sponges at the bottom of the evolution tree of large-ish animals).

Answer 3

Yes, all echinoderms have endoskeletons.

Answer 4

Sea Cucumbers.