echinoderms and molluscs
TRANSCRIPT
Echinoderms and Molluscs
Phylum Echinodermata
Includes sea stars, brittle stars, sand dollars, sea urchins, & sea cucumbers
• Start life as bilateral, free-swimming larva and change to sessile or sedentary adult
• Adults have radial symmetry • Have a true coelom (body cavity)• Capable of extensive regeneration • Have a nervous system but no head or brain
in adults
Phylum Echinodermata
• No circulatory, respiratory, or excretory systems • Tube feet on the underside of arms help in moving &
feeding • One-way digestive system consists of mouth with
oral spines, gut, & anus • Separate sexes • Reproduce sexually & asexually • Includes 5 classes:
* Crinoidea - sea lilies & feather stars * Asteriodea – sea stars * Ophiuroidea - basket stars & brittle stars * Echinoidea - sea urchins & sand dollars * Holothuroidea - sea cucumbers
Phylum Mollusca• have a true coelom (body cavity)
Similar larval stage as Echinoderms• Bilateral Symmetry
• Characteristics of Mollusks· Visceral Mass (organs)· Foot (muscle, movement)· Shell in most· Radula - tongue-like structure, sharp· Gills for respiration· Most have separate sexes
• Types of Mollusks· Gastropods - snails, slugs, nudibranchs ("stomach foot")· Bivalves - clams, oysters ("two doors")· Cephalopods - nautilus, cuttlefish, squid, octopus ("head foot")