BIO1011 Lecture Notes - Lecture 17: Bilateria, Notochord, Neural Tube
5 Jul 2018
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1. LECTURE 17 – ANIMAL DIVERSITY III
33.5 ECHINODERMS AND CHORDATES ARE
DEUTEROTSOMES
ECHINODERMS
Sea stars (commonly known star fish).
Are coelomates
Thin epidermis covers an endoskeleton of hard calcareous plates, and most species are
prickly from skeletal bumps and spines.
Water vascular system: a network of hydraulic canals branching into extensions called
tube feet that function in locomotion and feeding.
Sexual reproduction involves separate male and female individuals that release their
gametes into the water.
Descendant of symmetrical ancestors, yet on first inspection most species seem to have
a radially symmetrical form.
Echinoderm large have bilateral symmetry.
ASTEROIDEA: SEA STARS AND SEA DAISES
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Have arms radiating from a central disk; the undersurfaces of the arms bear tube feet.
Combination of muscular and chemical actions, tube feet can attach to or detach from a
substrate.
Ability to begin the digestive process outside of its body allows a sea star to consume
bivalves and other prey species that are much larger than its mouth.
Ophiuroidea: Brittle Stars
Distinct central disk and long, flexible arms.
Move primary by lashing their arms in serpentine movement.
Echinoidea: Sea Urchins and Sand Dollars
Sea urchins have no arms, but they do have five radially arranged groups of tube feet
that function in slow movement.
Have muscles that pivot their long spines, which aid locomotion.
Crinoidea: Sea Lilies and Feather stars
Attached to the substance by stalk; feather stars crawl about using their long, flexible
arms.
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Document Summary
Thin epidermis covers an endoskeleton of hard calcareous plates, and most species are prickly from skeletal bumps and spines. Water vascular system: a network of hydraulic canals branching into extensions called tube feet that function in locomotion and feeding. Sexual reproduction involves separate male and female individuals that release their gametes into the water. Descendant of symmetrical ancestors, yet on first inspection most species seem to have a radially symmetrical form. Have arms radiating from a central disk; the undersurfaces of the arms bear tube feet. Combination of muscular and chemical actions, tube feet can attach to or detach from a substrate. Ability to begin the digestive process outside of its body allows a sea star to consume bivalves and other prey species that are much larger than its mouth. Distinct central disk and long, flexible arms. Move primary by lashing their arms in serpentine movement.
