Phylum echinodermata

KINGDOM ANIMALIA
PHYLUM ECHINODERMATA

1. Phylum Echinodermata

2. GENERAL CHARACTERISTICS echino = “bumpy” or“spiny derm = “ skin  Echinoderms are radically symmetrical equal units arranged in a circle around a central disk Many have five equal units so we can specify that they have pentamerous radical symmetry as adults  Calcareous endoskeleton, often bearing visible spines .

3. Distribution & Habitat, Reproduction Found worldwide All found on the bottom of the sea Echinoderms have the ability to regenerate new parts asexually. They also have separate sexes with reproductive organs in each arm. Seahorses: males give birth Sexual reproduction involves releasing gametes into the water (external fertilization).

4. UNIQUE FEATURES External skeletons There is no head Usually have mouth on the underside Anus usually on top

5. Symmetry Bilateral Symmetry - Common of free moving organisms Radial Symmetry - Common of sessile (non-moving,/attached Echinodermata Symmetry - Free moving and radial symmetry Pentaradial Symmetry – body radially symmetrical in 5 parts or multiples of 5

6. Class Asteroidea Most have 5 arms from a central disk, though can have up to 50 Each arm carries an equal share of organ systems Mouth is located in the center of oral surface which is directed downward Includes: sea stars or starfish

7. Class Crinoidea Most primitive of the echinoderms Unusual in that the oral surface is directed upward bears a number of arms  Along the length of the arms are branches called pinnules Feather stars and Sea lilies

8. Class Echinoidea Includes: Sea Urchins & Sand Dollars Body structure forms a round, rigid body with movable spins and pedicellarie Locomotion achieved by movable spines Mouth is on the bottom, anus on the top Spines: sharp, hollow and sometime contain venom

9. Class Holothuroidea Sea Cucumbers Similar body plan to a sea urchin, just stretched out from mouth to anus Lies on sides, oral and aboral surfaces are at the ends Some excrete toxic substance as defense mechanism Some expulse gut and other internal organs out of the mouth or anus, called evisceration

10. Class Ophiuroidea Includes: Brittle Stars Legs proportionally longer and thinner than sea starts Allows for better movement Organs in central disc Eat organic matter and small animals they find on the bottom