phylum echinodermata "spiny skin" strangest group in animal kingdom closest invert...
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Phylum Echinodermata"Spiny Skin"
Strangest group in animal kingdom
Closest invert relationto the Chordates
Endoskeletonjust under skin
Lack sensory organs
No brain
No clear excretoryor circulatory systems
Phylum Echinodermata"Spiny Skin"
Possess water vascular systemfor movement and feeding
Larval stages are bilaterally symmetrical
Undergo metamorphosisto become a radial adult
Sea stars, brittle stars, sea urchins, basket stars, sea cucumbers, sand dollars
Class EchinoideaSea urchin
Sand dollar
Class Asteroideasea star
Class Holothuroideasea cucumber
Class Ophiuroideabrittle star
Body Plan - External Anatomy
Body Plan - External Anatomy
Madreporite Plate
Sensory Tentacles
Spiny Skin
Body Plan - External Anatomy
Body Plan - External AnatomyOral View
Dermal Spines
Tube Feet
Peristome
Mouth
Internal AnatomyLack many common organ systems
Nervous SystemDecentralized nervous system with: 1) central ring of ganglia 2) nerve net 3) radial nerves
Amazing ability to regenerate arms and some organsAutotomy - can intentionally lose an arm to avoid predation
Water Vascular SystemUsed for locomotion, feeding, waste removal and respirationSystem composed of canals connecting tube feetWater enters through Madreporite, then passes through stone canal to ring canalHydraulic system allows for powerful but slow movement
RespirationClass Holothuroidea - use respiratory tree
Class Asteroidea - use combination of gills and tube feet
Digestive System
Complete systemFood travels from mouth to cardiac stomach to pyloric stomach, to intestine to anusCan continually digest and ingest food
Reproductive SystemSeparate sexes but impossible to tell differenceGonads present in arms
Life CycleBilateral larva --> Metamorphosis --> Radial Adult