1. Chapter 15
Section 4 Echinoderms
Bellringer
Echinoderms include marine animals such as sea stars, sea urchins, and sea cucumbers. All these organisms are slow moving bottom dwellers. How do you think they protect themselves from predators?

2. Chapter 15
Section 4 Echinoderms
Objectives
Describe the endoskeleton, nervous system, and water vascular system of echinoderms.
Explain how an echinoderm’s body symmetry changes with age.
Describe five classes of echinoderms.

3. Chapter 15
Section 4 Echinoderms
Echinoderms
Echinoderms are spiny invertebrates that live in the ocean.
Sea stars, sea urchins, and sand dollars are some familiar members of this group.
Echinoderms eat shellfish, dead plants or animals, or algae that they scrape off rocks.

4. Chapter 15 Characteristics The name echinoderm means “spiny skinned.”
Section 4 Echinoderms
Characteristics
The name echinoderm means “spiny skinned.”
The spines are actually on the animals endoskeleton. An endoskeleton in an internal skeleton made of bone or cartilage.
Adult echinoderms have radial symmetry. Larvae have bilateral symmetry.

5. Chapter 15 The Nervous System
Section 4 Echinoderms
The Nervous System
All echinoderms have a simple nervous system similar to that of a jellyfish. Around the mouth is a circle of nerve fibers called the nerve ring.
Sea stars have a radial nerve that runs from the nerve ring to the tip of each arm.

6. Sea Star Nervous System
Chapter 15
Section 4 Echinoderms
Sea Star Nervous System

7. Chapter 15 Water Vascular System
Section 4 Echinoderms
Water Vascular System
The water vascular system is a system of canals filled with a watery fluid that circulates throughout the body of an echinoderm.
Echinoderms use their water vascular system to move, eat, breathe, and sense its environment.

8. Chapter 15
Section 4 Echinoderms

9. Chapter 15 Kinds of Echinoderms
Section 4 Echinoderms
Kinds of Echinoderms
There are five major classes of echinoderms. Sea stars are the most familiar class.
Brittle Stars and Basket Stars Brittle stars and basket stars look like sea stars. But these echinoderms have long, slim arms and are often smaller than sea stars. They don’t have suckers on their tube feet.

10. Kinds of Echinoderms, continued
Chapter 15
Section 4 Echinoderms
Kinds of Echinoderms, continued
Sea Urchins and Sand Dollars Sea urchins and sand dollars are round. Their endoskeletons form a solid, shell-like structure.
Sea Lilies and Feather Stars Sea lilies and feather stars have 5 to 200 feathery arms.
Sea Cucumbers Like sea urchins and sand dollars, sea cucumbers have no arms. A sea cucumber has a soft, leathery body.