How do extrusive igneous rocks differ from intrusive igneous rocks?

The difference between intrusive and extrusive igneous is that, intrusive rock is one that forms when magma cools within Earth. Extrusive igneous rock is one that, forms when lava cools on Earths surface.

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.

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