Compare and contrast the support systems of cicadas and sea urchins?

Well, honey, cicadas and sea urchins both have support systems, but they're as different as night and day. Cicadas rely on their exoskeleton for structure and protection, while sea urchins have an endoskeleton made of calcium carbonate plates. So, in a nutshell, cicadas wear their support on the outside, while sea urchins keep it all on the inside.