Lab 10

Question Answer
Constraints of echinoderm Remaining in the sea, no terrestrial/freshwater echinoderms
Provide key ecological role in many _____ ecosystems Marine
Echinoderm groups Sea lilies, brittle stars, sea stars, sea urchins, sea cucumbers, sand dollars
Crinoidea = Sea lilies
Crinoidea More plant like, mouth facing upwards, long branched arms that bear tube feet, oldest living class (fossil record 600 years back)
Holothuroidea = Sea cucumbers
Holothuroidea Named due to resemblance with the vegetable
Echinoidea = Sea urchins, Sea dollars
Echinoidea Body is globular or disk shaped, skeletal plates are fused into rigid skeleton called a test
Ophiuroidea = Brittle stars, Basket stars
Ophiuroidea Thin arms; jointed and distinct from body disk
Asteroidea = Sea stars
Asteroidea Body star shaped (5 + arms), arms are relatively thick and not distinct from central body disk, tube feet lie in open grooves, gonads and testes extend into arms
Echinoderms and chordates are under which phyla? Deuterostome
What type of symmetry does echinoderms have? Radial symmetry; originally evolved from bilaterally asymmetrical ancestor and adapted to radial
Success of echinoderms Radial symmetry, coelom, endoskeleton
Type of radial symmetry Pentaradial symmetry
Pentaradial symmetry Involving five or more parts in most echinoderms arranged concentrically around central axis
Defining characteristic Water vascular system
Water vascular system Fluid filled canals and reservoirs
Canals are derived from Coelom
Water vascular system plays a role in: Movement, gas exchange, circulation, feeding
Water vascular system is a ______ system Hydraulic
Description of water v. system Water enters WVS through madreporite, travels down stone canal and around ring canal, flows out each arm through radial canals, water flows into ampullae
Ampullae Bulb-like structures at the top of tube feet
Foot portion Podium
Single tube foot Water held in reserve in relaxed ampulla
When muscles of ampulla contract: Pressure put on the water in it
Water is not compressible so Water is pushed down into podium of tube foot which extends it
Structural support is provided by Endoskeleton
The endoskeleton is Internal skeleton, composed of calcium carbonate plates
Calcium carbonate plates are called Ossicles
Endoskeleton extends past the epidermis of the animal as: Spines
Echinoderms got their name meaning "Spiny skinned"
Plates of skeleton are locked together to form a rigid structure in the species… Sea urchin
Most sea stars and brittle stars can flex their Arms; indicates that the skeleton has gaps and flexible plate junctures
Species that have no real endoskeleton skeleton Sea cucumbers; only tiny remnant ossicles
Sea cucumbers rely on The coelom as hydrostatic skeleton (because they have tiny remnant ossicles)
Most echinoderms use tube feet of water vascular system to Move along surfaces
How are ossicles bound together? Connective tissues; unique property
Ossicles control Thru neurological control can quickly alter degree of stiffness and fluidity; can change from rock hard to liquid
Sea cucumbers with only microscopic ossicles have mutable connective tissue in body wall, therefore… Make most dramatic changes
Feeding strategy Echinodermata Filter feeders, scavengers, grazers, carnivores
Digestive system in echinodermata Complete digestive tract
Exchange of gases occurs across Skin gills
Skin gills are extensions of The coelom (pushed out to surface between spines)
Oxygen moves from water in environment into Coelomic fluid of skin gill (carbon dioxide moves opposite)
Gas exchange also occurs across surface of Fluid filled tube feet
Nutrients from digestive tract are circulated Around body by the coelom
Excretory organs Echinoderms do NOT have any
How does metabolic waste diffuse? Across skin gills and tube feet
Salt concentration of sea stars body is equal to Concentration of salt in seawater where they live
Sexes are Separate
Most echinoderms and fertilization is internal/external? External
They are capable of regenerating Lost parts; e.g., arms in the sea star
Do they have a brain? No
Nervous system varies in groups, generally…. There is a nerve ring surrounding mouth with radial nerves extending to different parts of the body
Sensory cells detect Some dissolved chemicals, water current, light, touch
Sensory structures are relatively simple = Not considered true sensory organs
Each arm has a Short sensory tentacle at its end
Tentacle responds to Chemicals and vibrations in water, and a red photosensitive eyespot
Sea star often lifts end of an arm to Perceive light and movement

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