Name _________________________________________________________ Introduction to Echinoderms Echinoderms are invertebrates with an internal skeleton and a system of fluid-­‐filled tubes called a water vascular system. ALL echinoderms live in salt water. Echinoderms have 5-­part symmetry, which means that, these organisms have arms or rays in multiples of five (think of spokes coming off of a wheel). There are five major classes of organisms in this phylum: Sea Urchins (Echinodea), Sea Cucumbers (Holothuroidea), Sand Dollars (Echinarachinus), Brittle Stars (Ophiuroidea), and Sea Stars (Asteroidea). The name Echinoderm means “spiny skin” (echino – spiny, derm – skin). Body Structure Echinoderms do not have a heart, brain, or eyes, but they do have sensory tube feet and a light-­‐sensitive organ on their bodies to help them navigate and find food. The skin of most echinoderms is stretched over a flexible, internal skeleton, endoskeleton, made of hardened plates. These plates give the animal a bumpy texture. Movement The internal system of fluid-­‐filled tubes in echinoderms is called the water vascular system. You can see a sea star’s water vascular system in the image to the right. Portions of the tubes in this system can contract, or squeeze together, forcing water into structures called tube feet. The tube feet then propel the echinoderm through its habitat and help it move its food to its mouth. Echinoderms Movie – watch the Echinoderm movie (on Ms. Bell’s website) and answer the questions. 1. Describe the 5-­‐part symmetry of echinoderms. 2. Give a basic description of the skeleton of a sea star. 3. If Urchins do not have eyes, how do they know where to go? 4. How would you describe urchin feeding habits? (Circle one): Predator Scavenger Grazer 5. Why is it bad for the kelp forest to have an over abundance of urchins? 6. Where in the ocean are sea cucumbers found? _________________________________________________________________ 7. What do Sea Cucumbers eat? How do Sea Cucumbers eat? 8. How do Brittle Stars eat? What do Brittle Stars eat? 9. Very generally, how do the tube feet work? 10. How could the light sensing organ on the sea star help it find food? 11. Very generally, how do sea stars eat?