Download - Echinoderms
Echinoderms
Section 29.1
Animal Classification
Animals
Invertebrates
Vertebrates
SpongesCnidariansWormsMollusksArthropodsEnchinoderms
Ectotherms(cold-blooded)
Endotherms(warm-blooded)
FishesAmphibiansReptiles
BirdsMammals
Echinoderms
What is an Echinoderm?
Echinoderm (Greek word) “echinos” – spiny “derma” – skin
Rays – long, tapering arms that are covered with short, rounded spines
What is an Echinoderm?
Pedicellariae (PEH dih sih LAHR ee ee) – modified spines into pincerlike appendages
Echinoderms have radial symmetry
Water Vascular System
Water vascular system – a hydraulic system that operates under water pressure
Water enters and leaves the water vascular system of a sea star through the madreporite
Water Vascular System
Madreporite (mah druh POHR ite) – a sievelike, disk-shaped opening on the upper surface of an echinoderm’s body
Water Vascular System
Tube feet – hollow, thin-walled tubes that end in a suction cup
Tube feet look somewhat like miniature droppers
Water Vascular System
Ampulla – the round, muscular structure works like the bulb of a dropper
Tube feet also function in gas exchange and excretion
Varied Nutrition
Sea stars are carnivorous and prey on worms and clams
Brittle stars and sea cucumbers feed on dead and decaying matter that drifts down to the ocean floor
Simple Nervous System
Echinoderms have no head or brain, but they do have a central nerve ring
Each radial nerve branches into a nerve net that provides sensory information to the animal
Simple Nervous System
Sea stars have eyespots located at the tip of each arm
Diversity of Echinoderms
Sea stars Most species of sea stars have five rays, but
some can have up to 40 rays
Diversity of Echinoderms
Brittle stars Brittle stars are extremely fragile This adaptation helps the brittle star to distract a
predator
Diversity of Echinoderms
Sea urchins Globe-shaped Do not have rays Look like pin cushions
Sand dollars Disk-shaped Do not have rays A living sand dollar is
covered with hair-like spines
Diversity of Echinoderms
Sea cucumbers When threatened, they may expel their organs
(intestines) through the anus The organs may rupture and is regenerated in a
few weeks