Alan fell off a ladder at work and claims his back is in intense pain, even though medical tests find nothing wrong. he does not like to talk about it and keeps quiet other than his report to his attorney. caleb fell off a ladder at work and claims he hurt his back, too, even though medical tests find nothing wrong. he talks about it all of the time in great detail. which diagnosis would seem to fit each man?

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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.