Class crinoidea sea lilies feather stars stalked

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Class Crinoidea (Sea Lilies, Feather Stars)Stalked, flowerlike sea lilies and feather stars have branched arms that radiate from the cuplikecentral disc in multiples of five.These filter feeding, ancient echinoderms lack spines, a madreporite,pedicellaria, and suckers on their tube feet.Sessile sea lilies typically live at depth and attach theirlong jointed stalk to a substrate with root-like projections calledcirri.In contrast, feather star adultsmay lack a stalk and be free-swimming with motile, gripping cirri and a mouth and anus on the oralupper surface.The skeleton is composed of plates (Fig. 7.180).1.Observe the preserved specimens on display and note thearmsandcirri.
121Class Echinoidea (Sea Urchins, Sand Dollars, & Sand Biscuits)Sand dollars and spiny sea urchins are herbivorous echinoderms that look as though their arms werefolded back on themselves and fixed into a rigid calcareous skeleton ortest.The test may be globularand covered with long, sharp, movable spines, tube feet equipped with suckers,and pedicellaria.Inthe center of the test lies the mouth and anus.A large gut fills much of the test cavity, except duringspawning periods (Figs. 7.180, 7.189 - 7.193 in atlas).1.Observe the preserved and live specimens on display and note thetest.If live urchins areavailable, observe them under the stereomicroscope to see thepedicellaria, tube feet, andspinesmoving.Class Holothuroidea (Sea Cucumbers)As their name implies, sea cucumbers have oblong shape, warty/spiny skin that can be papery toleathery in thickness, and vary in length from an inch up to several feet.These soft-bodieddetritivores have tube feet but lack arms, pedicellaria, and an endoskeleton, except for the fewscattered plates in the body wall.The mouth surrounded with tentacles is at one end of the body andthe anus is at the other, the latter often bearing a complex called therespiratory tree,whichfunctions in gas exchange (Figs. 7.194 - 7.196 in atlas).1.Observe the different species of sea cucumbers on display, noting the different textures ofskin andtentaclesaround the mouth if possible.
122Class Ophiuroidea (Brittle Stars, Basket Stars)Brittle and basket stars have a skeleton in the form of plates and a central disc which is distinctly setoff from the highly flexible, jointed arms that are attached to the disc.Ophiuroids are unique in thatthey have an incomplete digestive tract and lack pedicellaria, digestive glands in arms, andambulaccral grooves.Tube feet have a sensory function as well as used in food collection andlocomotion (Fig. 7.180 in atlas).1.Observe the specimens on display.Note the many arms on the basket star.Class Asteroidea (Sea Stars)Sea stars usually have short spines, pedicellaria, and 5 arms not distinctly set off from a central disc(some species have as many as 50 arms!).Movement in the arms is possible as the ossicles areseparate, thus permitting predaceous sea stars to feed on a variety of bivalves.Some sea stars feed

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Term
Summer
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Bacteria, Cladistics, Iris Diaphragm

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