When two species compete for the same ecological niche, they cannot coexist because they are competing for the exact same resources. One species is always slightly better adapted for the niche than the other, so over time the disadvantaged species will either go extinct or shift to a different ecological niche. This situation highlights the concept of .

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.

the endomembrane system i think