Post on 17-Dec-2015
Phylum: Echinodermata
Echinos = SpinyDerma = SkinAta= to bear
“bears spiny skin”
Zoology Chapter 16
Phylum Echinodermata
• 5 Classes– Class Crinoidea
• Sea lilies• Feather stars
– Class Asteroidea• Sea Stars
– Class Ophiuroidea• Brittle Stars
– Class Echinoidea• Sea Urchins (venomous)• Sand Dollars
– Class Holothuroidea• Sea cucumbers
Characteristics
• Calcareous endoskeleton– Ossicles- “small bones”
• Adults with pentaradial symmetry (5 points)– Larvae with bilateral symmetry
• Water-vascular system
Water-vascular system • Composed of water-filled
canals • Used in
– Attachment– Feeding– Locomotion– Respiration– Circulation of nutrients and
wastes
• Extends to each arm and tube feet– Tube feet act as suction cups
• Contract & expand
Digestion
• Complete digestive tract• Eat clams– Tube feet open shell– Stomach forced through mouth – Stomach into opening between clam’s shells– Digestive enzymes break down tissue– Sea Star sucks out predigested food
• Eat algae
Nervous System
• Nerve Net• Nerve Ring• Radial Nerves• Eyespots– Sea stars on each arm
Regeneration & Reproduction
Reproduction• Mostly dioecious; but no sexes• Sexual & Asexual• 2 Gonads are present in each armsRegeneration • Broken arms• New body from broken arm• Pearl Diver Story• A form of Asexual Reproduction