How does sea urchin grow?

Sea urchins grow through a process called metamorphosis, starting from a fertilized egg that develops into a free-swimming larva. This larva undergoes several stages, eventually settling on the ocean floor and transforming into the adult form. As they mature, sea urchins feed on algae and other organic materials, which helps them develop their hard spiny exoskeleton. Growth can take several years, depending on the species and environmental conditions.