Sponges have existed on Earth for over 500 million years and are probably the sister group of all other animals. Porifera means āpore-bearerā and refers to the many pores through which sponges pull in water and food. Today there are approximately 9000 living species which mostly live in the sea.
Cnidarians are radially symmetrical, simple, animals that include jellyfish, corals and anemones. Ā The name Cnidaria comes from the Greek wordĀ knideĀ meaning ānettleā and refers to specialized stinging cells called nematocysts, used for food capture andĀ defence.