Answer:
Differences:
Cnidarians have groups of similar cells that work together as tissues, while sponges have no tissues, only disconnected regions of specialized cells.
Similarities:
They contain nematocyst (cells that sting)
some are sessile/free swimming
Some corals have a symbiotic relationship with algae, they need to grow in shallow waters so that light can penetrate for the algae to photosynthesize.