Sea stars and sea
urchins have common
Echinoderm features.

Organisms grouped in phylum Echinodermata have spiny skin and radial symmetry and move with the use of a water vascular system and tube feet. View the slideshow to learn how to draw an Echinoderm. The slideshow features the sea star. You will then use this information to draw a sea urchin.

Spiny Skin When drawing an Echinoderm such as a sea star, the main external (outer) characteristic you must draw is its spiny skin. Notice the rough texture of the sea star shown above. Sieve Plate Another external feature found on sea stars is its sieve plate. The sieve plate, also called a madreporite, is found on the dorsal (top) part of the sea star and is off centered. It is where water enters the sea star. It's easily found because it is lighter in color than the rest of the sea star skin. Radial Canal From the sieve plate, water enters the radial canal (dashed circle in the center of the sea star) and then branches out into each arm through water vessels (dashed lines), completing the water vascular system. Ampullae Along the water vessels are ampullae, which are the light blue sacs in the image above. They control the water pressure. Tube Feet The water vascular system controls the tube feet, shown the image above as emerging through the sea star's open arm groove.

Use the Echinoderm Drawing worksheet to sketch and label the characteristic features of a sea urchin. Once the worksheet is completed, submit your work to your teacher.