Invertebrates 5
Phylum Echinodermata, and a
wee bit of Chordata
Branchpoints:
Protostomes vs.
deuterostomes
Phylum Echinodermata:
Spiny-skinned
Echinodermata: 4 key features
 Calcareous internal
skeleton
 Parts: Plates, spines and
pedicellariae
 Why “internal”?
 Water vascular system
(controls tube feet)
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Derived from coelom
Layout
Tube foot control
Other functions
 Symmetry: Pentamerous
radial symmetry as
adults/ bilateral as larvae
 Mutable connective tissue
Body plan: Other aspects
 Perivisceral coelom
 Houses organs
 Gas exchange
 Hydrostatic skeleton
 Digestive system
 Can be highly branched
 Complete in some
 Nervous system
 No brain
 Branches parallel water
vascular system
 Sensory
 Eye spots
 Receptors associated with
tube feet
Class Asteroidea:
sea stars
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Body plan
Feeding
Respiration
Protection
Class Echinoidea:
Sea urchins and others
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Body plan
Feeding
Respiration
Protection
Class Ophioroidea:
Brittle stars, basket stars
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Body plan
Feeding
Respiration
Protection
Class Crinoidea
Sea lilies
Class Holothuroidea:
Sea cucumbers
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Body plan
Feeding
Respiration
Protection
Phylum Chordata
 Our closest invertebrate relatives are
slimy sacs that pump seawater
Parting shot: Your closest
invertebrate relatives