1, Echinoderm is a kind of echinoderms, which is an invertebrate living in shallow water. The main feature is that the body is spherical, disc-shaped or heart-shaped, without wrists. The endoskeleton heals with each other to form a strong shell. Most species have a complex chewing device in their mouths, which is called Aristotle's partial tooth. It has teeth and can chew food. The digestive tube is tubular and coiled in the body, feeding on algae, corals and worms. Polymorphism, the individual develops through sea urchin larvae (long wrists), and then metamorphoses into juvenile sea urchins, reaching the need of sexual maturity 1-2 years. It can be divided into regular sea urchins and irregular sea urchins, with a total of 22 orders. There are more than 900 species belonging to 225 genera. There are about 100 known species and 7,000 fossil species in China.

2. It is distributed in the intertidal zone to the seabed several thousand meters deep, mostly concentrated in the rocky seabed or sandy seabed in the coastal zone, or widely distributed or limited to specific sea areas, which varies from species to species. Sea urchin is the earliest model organism used in the history of biological science, and its eggs and embryos play an important role in the development of early developmental biology. It is one of the longest-lived marine life on earth.