PHYLUM ECHINODERMATA
•Sea Stars, Sea Urchins, Sand Dollars, and Sea Cucumbers
•“______________________________ _______________________________”
•7,000 species
•Marine Environments
–Shallow and deep waters
•Vary in size
–From 1cm to 1m (3feet)
•Often brilliantly colored
•Radial Symmetry
–Like _______________________________ ______________ _______________________________
•Lack _______________________________
•Larvae are _______________________________symmetrical
•Echinoderms are __________________________, which makes them different from all of the other invertebrates
•Deuterostomes are coelomates whose
–embryos have radial cleavage
–anus forms near the blastopore
–mesoderm arises from outpockets of the endoderm
Echinoderms Have:
•Pentaradial symmetry
–the body parts extend from the center along five spokes
•An _______________________________composed of calcium carbonate plates
•Many small, movable extensions of the water-vascular system called ____________________ ___________________,
which aid in
–________________________________________
–________________________________________
–________________________________________
–________________________________________
Echinoderm Classification
•CLASSES:
Class ________________________________________
•“lily-like”
•Examples: sea lilies, feather stars
–Five arms extend from the body and branch to form many more arms
–Tube feet  gas exchange
–Cilia on arms direct food to the mouth
–Mouth faces up
Class ________________________________________
•“snake-tail”
•Examples: basket stars and brittle stars
–Long, narrow arms help them move quickly
•Can break and regenerate easily
–Live on the ocean’s floor
–Either rake in food with arms or trap it with their tube feet or mucus between their spines
Class ________________________________________
•“spinelike,”
•Examples: sea urchins, sand dollars
–Test –compact, rigid endoskeleton
–Urchins:
•Five teeth + their muscles = Aristotle’s Lantern
•Spines can be sharp and contain venom
–Sand dollars:
•Burrows into the sand
•Use spines for locomotion and burrowing
Class ________________________________________
•“water polyp”
•Examples: sea cucumbers
–Soft bodies because the particles that make up their endoskeleton are small
–Use tentacles to bring food to the mouth
Sea Cucumbers
•Eviscerate their gut as a means of self defense
Class ________________________________________
•“starlike”
•Examples: sea stars
–Live in coastal waters around the world
–Prey on oysters, clams, and other foods humans eat
Structure and Function
•Sea stars typically have five arms, but in some species, there may be as many as _______________.
•Two rows of tube feet run along the underside of each arm
•On sea stars and sea urchins, _____________________________________________, or little pincers, help keep the
body surface free of foreign objects, including algae and small animals that might damage its soft tissues
•Gas exchange and waste excretion take place by diffusion through the ___________________ __________________,
•Primitive nervous system; no head = no brain
•The nervous system consists mainly of a _________________________ _____________________that circles the mouth
and a _____________________ _____________________that runs from the nerve ring along the length of each arm
•Together, they coordinate the movements of the tube feet
•Sea stars also have a ___________________________
______________________________near the body surface that
controls the movements of the spines, pedicellariae, and skin gills.
•Eyespot on each arm responds to light
•Tube feet respond to touch and chemicals
Water-Vascular System
_______________________________-water enters through this small pore
_____________________________ _____________________________-connects madreporite and ring canal
_____________________________ _____________________________-extends down each arm and carries water to
hundreds of hollow tube feet---has valves to ensure one way flow
Feeding and Digestion
•Most echinoderms are carnivores.
•A sea star captures a clam and attaches to both shells with its tube feet, eventually tiring the clam’s
muscles. Once the shell is opened every so slightly, the sea star ejects a portion of its stomach into the
clam to digest the tissue.
•The sea star ejects a portion of its stomach when it feeds.
•Waste is expelled through anus on aboral surface.
Reproduction
•Most echinoderms are dioecious.
•Fertilization occurs externally after the organisms spawn.
•A free-swimming larva called a bipinnaria results and eventually develops into an adult.
•As long as a portion of the central ring remains intact, a sea star can __________________________.
Sea Star
Anatomy
What Class?