2 Diversity Echinodermata means “spiny skin” Echinoderms usually inhabit shallow coastal waters and ocean trenchesorganisms in this class include:Sea starsBrittle starsSand dollarsSea cucumbers
3 Characteristicschange from a free-swimming bilaterally symmetrical larva to a bottom-dwelling adult with radial symmetry.Most have five radial appendages or multiples which is known as pentaradial symmetrythey have an endoskeleton that is made up of calcium plates, may include protruding spines
4 Have small feet called tube feet that aid in movement, feeding, respiration, & excretion. Do not have circulatory, respiratory or excretory systems.Have a nervous system but no head or brain.There are two sexes and they can produce sexually and asexually.
5 Evolution & Classification Echinoderms are from the Cambrian period & date back to over 500 million years agoscientist believe that they evolved from bilaterally symmetrical ancestor.The inferred ancestral larva is very similar to the modern Sea star larva.
7 Body Symmetry evolved from animals with bilateral symmetry adult echinoderms possess radial symmetryAll echinoderms exhibit fivefold radial symmetry in portions of their body at some stage of life (5 parts around central axis), even if they have secondary bilateral symmetryLARVAE ~ bilateralADULTS ~ radial
8 Body Plan of the Sea Star oral surface: mouth located on the underside of the bodyaboral surface: top of the bodyossicles: sharp protective spines made of calcium plates, covered with thin epidermal layerpedicellariae: tiny forceps that protect and clean the body surface
9 Water-Vascular System Used in locomotion, food capture, & respirationNetwork of canals – run throughout body ending w/tube feetVarying internal water pressure can extend or contract tube feetTube feet end in small suction cups
10 Water Vascular SystemWater enters madreporite on aboral surface into a short, straight stone canalStone canal connects to circular canal around the mouth = ring canal.Enters five radial canals extending down each arm
11 Water Vascular SystemRadial canals carry water to hundreds of paired tube feet.Bulb-like sacs or ampulla on tube feet contract & create suction
12 Other Body Systems No circulatory, excretory, or respiratory systems No head or brainEyespots on the tips of each arm detect light
16 Surfaces Mouth on oral surface (bottom / ventral) Anus on aboral surface (top / dorsal)
17 Feeding & Digestion uses feet eat mollusks, worms, and slow-moving animalsenzymes help digest food
18 Other Body Partsfluid in coelom surrounds the organs & distributes nutrients & oxygenskin gills: protect coelom lining; gases are exchangednerve ring: surrounds mouth & branches off into nerve cords in each arm.Eyespots: on each arm that responds to lighttentacles: responds to touch
19 Reproduction each arm produces sperm & egg occurs externally bipinnaria: free-swimming larva that develops from fertilized eggssettles in the bottom and develops into an adult through metamorphosisreproduce asexually by regenerating lost parts
20 Taxonomists have divided 6,000 species of echinoderms into five classes:
21 Classes of echinoderms CrinoideaAsteroideaOphiuroideaEchinoideaHolothuroidea
22 Crinoidea (“lilylike”) They include:Sea liliesFeather starsCrinoidea are sessilethey have long stalks that attach to rocks or to the ocean floorfeather stars eventually detach themselvesSticky tube feet that are at the end of each arm catch food and serve as a respiratory surface.
23 Asteroidea (“star-like”) starfish or sea stars belong in this classfound all over coastal shores around the worldprey on oysters, clams, and other sea food that is used by people
24 Ophiuroidea (“snakelike”) largest echinoderm classincludes basket stars & brittle starsprimarily reside under stones & in crevices and holes of coral reefshave thin brittle arms that break off & regenerate themselves quicklyfeed by raking food off the ocean floor with their arms and bottom of tube feetalso trap food with mucous strands between their spines.
25 Echinoidea (“hedgehoglike”) sand dollars & sea urchinstest: rigid endoskeleton that the internal organs are compacted inAristotle’s lantern: complex jaw-like mechanism that is used to grind their foodlocomotion: tube feetprotection: barbs on their long spines that are sometimes venomous
26 Sand dollars live along seacoasts & sandy areas flat, round shape bodies; and adaptation for shallow burrowinglocomotion: short spines (also aid in burrowing & cleaning their bodies)use tubes to filter food out of water
27 Holothuroidea sea cucumbers belong in this class bodies are soft how they feed: tentacles around the mouth sweep up sediment from the waterprotection: eject internal organs through the anus.Lost parts are later regenerated.Process called evisceration
28 Other Unique Features Echinoderms can REGENERATE ex: sea cucumbers can eject a portion of gut in response to predators and regenerate when safeWater vascular system (described earlier) is unique to echinoderms
29 Other Unique FeaturesCrinoids and some brittle stars = passive filter-feeders, absorbing suspended particles from passing watersea urchins = grazerssea cucumbers = deposit feedersstarfish = active hunters
30 More Unique FeaturesAutonomy = The spontaneous self amputation of an appendage when the organism is injured or under attack. The autotomized part is usually regenerated.“arms” → multiples of 5; some have more because of regeneration
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