Q: In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.
The schypozoans and cubozoans of this phylum possess simple sensory organs known as rhopalia. They have a central gastrovascular cavity which functions as mouth, gas-exchange organ, and anus. Some organisms in this phylum are parasitic, including the unusual genus Polypodium which lives inside its hosts cells, but most are predatory animals. First appearing in the Ediacaran period 600 million years ago, most have a life cycle which alternates between a sessile asexual polyp stage and an ambulatory, sexual medusa form. Getting their name from the specialized venomous cells common to many of its members, for ten points, what is this phylum which includes sea anemones, coral polyps, and jellyfish
A:
Science