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

6. 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

8. 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

10. 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

12. 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

14. 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

16. 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