What do you think “exo” means in the word exoskeleton? (As a hint, humans have an “endoskeleton.

Outer skeleton

Explanation:

"Exo" means outer and "Endo" means Inner which is why we have an endoskeleton so we have an Inner skeleton and to answer your quest Exo means outer so it means outer skeleton

organisms that lack symmetry are called asymmetrical and belong to phylum porifera/sponges.

organisms with specialized stinging cells belong to phylum cnidaria. stinging cells are called cnidoblast cells.

cnidarians show two morphological forms : polyp (sessile) and medusa (mobile)

filter feeding is observed in porifera members.  

alternation of generation is observed in coelenterata or cnidaria. there is alternation of asexual polyp form and sexual medusoid form. it is also referred as metagenesis.