1. Echinoderms
“spiny skin”

2. Echinoderms: Main Characteristics
• Spiny Skin
– Endoskeleton
– Musculoskeletal
• 5 part radial symmetry
– Penta-radial
– What was the advantage of
radial symmetry
• Tube feet: Movement
– Water-vascular system
• Benthic organisms

4. Classes
• Asteroidea: Sea Stars
• Ophiuroidea: brittle
stars
• Echinoidea: sea urchins
and sand dollars
• Holothuroidea: Sea
cucumbers
• Crinoidea: Sea Lilies and
feather stars

5. Class Asteroidea: Sea Stars
• Aster = star, oides = in
the form of
• Large Coelome
• Circulatory system:
– use diffusion & cilia to
move gas, nutrients and
waste
• Respiratory system:
– Dermal branchi on skin

6. Diagram the arm of the starfish

7. Asteroidea
• Digestive System:
– Mouth on underside
– Opens into cardiac
stomach
• Folds out of body into prey
to secrete enzymes
– Opens into the pyloric
system
• Nutrients diffuse out of the
pyloric stomach
• Eat:
– mollusks, crustaceans,
polychaetes, coral, detritus

9. The Water Vascular System
• Who can explain how hydraulics work?
• Water Vascular System:
– Made up of a series of water-filled canals that run
down the arms from a canal ring in the center
• Radial canal – ampullae – tubed feet

10. Water Vascular System

11. Asteroidea vs. Ophiuroidea
• Sea Star vs. Brittle Star
– Both can regenerate
arms
• Sea Stars:
– Arms attached to arms
– Carnivores: Active
Predators
• Brittle Star
– Arms NOT attached to
arms
– Not active predators: eat
plankton

12. Echinoidea: Sea Urchins
• Same structure, longer
spines than starfish
– Move by means of tube
feet
• Feeding
– Herbivores, feed on
algae and marine plants
– Grazers
– Scrape food
• Roles:
– Control algae

13. Sea Cucumbers
• Elongated Body Plan
– Long sea urchin
• Tube feet to move
• Separate sexes
• Take organic nutrients out
of sand
– Use oral tentacles
• Defense:
– release internal organs
– Tubules called cuvierian
tubules: sticky and
poisonous

14. Work on Study Packet