Examining the Endoskeletons and Body Design of Echinoderms

Activity: Examining Echinoderms

Goals:

1. To examine the endoskeletons of a variety of common echinoderms.
2. To observe the five-point body design of typical echinoderms.
3. To demonstrate the characteristic of radial symmetry.

Background Information: The Phylum Echinodermata gets its name from the Greek language. Echinodermata means “spiny skin.” Many echinoderms actually do have spiny skin, but others do not. Echinoderms are found only in salt water habitats, and cannot be found on land or in fresh water.

All echinoderms show radial symmetry. This means that the creatures have appendages called arms, which point outward from the center of the body like spokes on a bicycle wheel. These appendages usually occur in multiples of five, although there are some exceptions.

In addition to having spiny skin and radial symmetry, echinoderms have a water vascular system and structures called tube feet. Water is pulled into the echinoderm through an opening on the top or dorsal side of the animal. By expanding and contracting chambers within the water vascular system, the echinoderm can force water into the tube feet to extend them. Muscles in the tube feet can retract them. This expanding and contracting of the tube feet allows the echinoderm to walk.

This information was taken from Echinoderms have endoskeletons made of plates that contain calcium. It is this internal skeleton that places echinoderms in position as the phylum closest to the one to which humans belong – the Phylum Chordata. The endoskeletons of echinoderms are beautiful and are prized by collectors.

Materials: Several examples of dried echinoderms and/or their endoskeletons: sea stars, sea urchins, sand dollars, and sea biscuits, and hand lenses

Procedure:

1. Draw a complete dorsal (top) view and ventral (bottom) view of the specimens provided.

2. Describe each echinoderm in the space provided on the chart, using the reference books made available at each lab table.

1. Using a T-chart, explain how the echinoderm specimens are alike and different.

1. Tell how the following characteristics of echinoderms are adaptations for life in a marine environment.

• tube-feet

• radial symmetry

• spiny skin

• water vascular system