phylum echinodermata. characteristics: endoskeleton calcareous (calcium carbonate) ossicles arise...
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PHYLUM ECHINODERMATA
Characteristics: Endoskeleton
Calcareous (calcium carbonate)
Ossicles arise from mesodermal tissue
Pentaradial symmetry as adults
5 sections branch off from disk
Bilateral symmetry as larvae
PHYLUM ECHINODERMATA
Characteristics Water-vascular system
Helps with locomotion, attachment, and feeding
Water-fi lled canals with extensions called tube feet
Includes a ring canal that surrounds the mouth
Complete digestive tract
Nervous system Nerve net Nerve ring Radial nerves
PHYLUM ECHINODERMATA
HistoryShare an ancestor with hemichordates and chordates
Evolved from bilaterally symmetrical ancestors
PHYLUM ECHINODERMATA
Echinoderm AnatomyTube Feet- extensions of the canal system Inside- bulblike ampulla
Contracts & forces water into the tube from the water-filled canals
The tube feet then extend Suction cup at the
distal end Used for locomotion
and/or feeding
PHYLUM ECHINODERMATA
Echinoderm Anatomy Water-Vascular System
Water enters mouth (surrounded by the ring canal)
Ring canal opens to the body through a stone canal (with an opening called a madreporite)
Polian vesicles- sacs connected to the ring canal Function in fluid storage
Canals branch from the ring canal to transport water to the ampulla (internal portion of the tube feet)
PHYLUM ECHINODERMATA
Echinoderm AnatomyHemal system- strands of tissue that encircle the ring canal Circulates fluid using
cilia More than likely helps
to distribute nutrients (definite function is unknown)
PHYLUM ECHINODERMATA
Sea stars1,500 speciesLive on hard
substances, in sand, or in mud
Brightly colored Red, orange, blue, or gray
5 arms- radiate from central disk
Pedicellariae Pincherlike Clean the body surface of
debris Also function in protection
CLASS ASTEROIDEA
Pedicellariae
Maintenance:Diet- snails, bivalves, crustaceans, & corals
Stomach- fills most of the coelom in the central disk 2 regions
Larger, oral stomach (cardiac stomach)- receives ingested food
Smaller, aboral stomach (pyloric stomach)- connects to pyloric cecae (absorb the food)
CLASS ASTEROIDEA
Maintenance Feeding
Force bivalves apart with the tube feet
Clam vs. Sea Star The sea star inserts the
cardiac stomach into the bivalve shell
Gas exchange Diffusion across tissue
Nervous system Nerve ring (encircles the
mouth) Radial nerves extend into the
arms (control the tube feet) Respond to light
(photoreceptors in the arms) & chemicals
CLASS ASTEROIDEA
Reproduction & Regeneration Can regenerate any part
of a broken arm Must at least have a portion
of the central disk remaining Process takes up to a year
to complete Most species are
dioecious 2 gonads in each arm Reproduce externally When one sea star releases
gametes, pheromones stimulate other sea stars to release gametes
CLASS ASTEROIDEA
Basket stars, brittle stars, & serpent stars
> 2,000 speciesLong arms that
give central disk a pentagonal shape
Lack suction disks & ampullasMove like a snake
CLASS OPHIUROIDEA
Sea urchins, sand dollars, & heart urchins
1,000 speciesSea urchins- live on hard
substratesSand dollars & heart
urchins- live in the sand or mud
Move using spines & tube feet
Feed on algae, bryozoans, coral polyps, & dead animal remains
Aristotle’s lantern Chewing apparatus that cuts
food into smaller pieces
CLASS ECHINOIDEA
Sea cucumbers1,500 speciesLack arms- crawl
aroundLack spinesTube feet near the
mouth act as tentacles Covered in mucus to
trap foodProduce toxins to
discourage predators
CLASS HOLOTHUROIDEA
Sea lilies & feather stars
630 speciesSea lilies
Attach permanently to a substrate with a stalk
Crown- unattached end
Feather starsSwim & crawl
Lack nerve ring
CLASS CRINOIDEA