Echinoderms | animals

Echinoderms are radial symmetry, they walk or crawl using tubed feet and suckers for gripping or climbing. Their nervous system is present but they have no brain but they do have nerve rings. Their digestive system is a one-way system starting with the mouth on the underside and ending with the anus. Their circulatory system is fluid filled canals function for gas exchange, feeding and movement. They do not have a heart. their respiratory system takes in oxygen & pass out carbon dioxide. They do have a skeletal system but it is interlocking calcium carbonate plates. Their excretory system goes through diffusion it rids the body of nitrogenous waste which is mainly ammonia. it reproduces sexually. Females releases eggs and sperm into the water. Females can release up to 100 million eggs.

Asteroidea have five arms and live on ocean floors in mostly shallow water. this includes the sea star and asteroids.

Ophiuroidea is your brittle stars and basket stars and they usually live on the ocean floor of deep or shallow water.

Echinoidea have no arms but tubed feet. there mouth scrapes food from rocks. These are sea urchins and sand dollars.

Crinoidea are the earliect of echinoderms. they live on the ocean cloor in deep water. these are your feather stars.

Holothuroidea are you sea cucumbers.