Given the distribution of the 30 or so animal phyla across the earth's various ecosystems, what would be the most likely habitat for the origin of animals?

Seems like an open ended question, the habitat organ was the ocean, more specifically is probably the sea floor, since that it is where sponges (basal animals) live

Control variable- changedependant variable- stays the samechanging- food itemsdependant- presences of proteins