echinoderms “spiny skinned” ex: starfish, sea urchins, sea cucumbers, sand dollars

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Echinoderms “spiny skinned” Ex: starfish, sea urchins, sea cucumbers, sand dollars

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Page 1: Echinoderms “spiny skinned” Ex: starfish, sea urchins, sea cucumbers, sand dollars

Echinoderms“spiny skinned”

Ex: starfish, sea urchins, sea cucumbers, sand dollars

Page 2: Echinoderms “spiny skinned” Ex: starfish, sea urchins, sea cucumbers, sand dollars

Starfish body planCentral disk with radiating arms (usually 5)

Pentaradial symmetry (no head, mouth is on underside of disk)

Rigid body due to calcareous plates and spines

Endoskeleton (embedded in flesh)

Page 3: Echinoderms “spiny skinned” Ex: starfish, sea urchins, sea cucumbers, sand dollars

LocomotionWater vascular systemWater enters via sieve plate, then drawn down a tube

to ring canal (encircles disk)

5 radial canals arise from ring canal connected to tube feet

Tube feet end in ampulla which contracts, thus forcing water into the tube feet and extending the foot. The foot then contracts and pulls the animal forward

Page 4: Echinoderms “spiny skinned” Ex: starfish, sea urchins, sea cucumbers, sand dollars
Page 5: Echinoderms “spiny skinned” Ex: starfish, sea urchins, sea cucumbers, sand dollars

DigestionMove slowly, prey on clams or oysters

Pulls shell apart by pulling in feet in turn until clam is exhausted and relaxes its muscles

Extends stomach into clam inside out and takes in material

Doesn’t need an intestine because all material is digested by the 5 pairs of digestive glands ( 1 pair per arm)

Page 6: Echinoderms “spiny skinned” Ex: starfish, sea urchins, sea cucumbers, sand dollars

RespirationLarge coelom between body wall and digestive

tract are lined by cilia (these open into skin gills which diffuse oxygen in and carbon dioxide out)

Skin gills are protected by spines and pedicillaria (small pincers)

Page 7: Echinoderms “spiny skinned” Ex: starfish, sea urchins, sea cucumbers, sand dollars

ExcretionBy ameboid cells in the coelomic fluid. Engulf

nitrogenous waste then escape through the skin gills

Page 8: Echinoderms “spiny skinned” Ex: starfish, sea urchins, sea cucumbers, sand dollars

Nervous systemSimple because the organism is slow

Ring nerve circles the mouth and branches into 5 radial nerves

Poorly developed sense organs

Sensory cells (touch) are all over the surface

Eyespots at the tip of each arm

Page 9: Echinoderms “spiny skinned” Ex: starfish, sea urchins, sea cucumbers, sand dollars

ReproductionOvaries or testes lie in each arm

Eggs and sperm are released into sea (broadcast method)

Has a free swimming larva (which has cilia and has bilateral symmetry, not radial like the adults)

Regeneration – one arm can turn into a new animal as long as it has most of the central disk