The sea urchin is a marine echinoderm with a spherical body covered in spines. Sea urchins originated about 450 million years ago during the Ordovician period, and have since adapted to changing environments and conditions over millions of years to maintain their place in evolutionary history. Sea urchins move slowly, crawling with their tube feet and sometimes using their spines to propel themselves. They feed primarily on algae, but they can also eat slow-moving animals.
