phylum echinodermata (means spiny skinned)

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PHYLUM ECHINODERMATA (means spiny skinned). ex: seastars, sea urchins, sand dollars, sea cucumbers, sea lilies. Seastars. Characteristics:. 1. Radial (pentamerous) symmetry. 2. Internal skeleton (endoskeleton). 3. Complete digestive system. - PowerPoint PPT Presentation


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1PHYLUM ECHINODERMATA(means spiny skinned)ex: seastars, sea urchins, sand dollars, sea cucumbers, sea liliesCharacteristics:1. Radial (pentamerous) symmetry2. Internal skeleton (endoskeleton)3. Complete digestive system4. Water vascular system with tube feet (hold or sense)5. Highly regenerative - can eviscerate6. Separate sexes; external fertilization

Seastars 12PHYLUM ECHINODERMATA(means spiny skin)ex: seastars, sea urchins, sand dollars, sea cucumbers, sea lilies

Why are they considered advanced?1. endoskeleton of calcium carbonate plates2. bilaterally symmetric larvae3. water vascular system instead of muscles is a big advantage in predatory situations4. highly regenerative - can regrow lost or damaged body parts5. separate sexes; external fertilization 23Why are they considered simple?

1. Light-sensitive eyes located at the end of each ray do not provide vision because there is no brain nor head.2. They have reduced internal organs - no respiratory, circulatory, excretory. No nervous system.4. Adults have pentamerous (5-fold) radial symmetry (associated with sedentary lifestyle)5. Respiration is by diffusion through the skin.3. Nerve net (no nervous system) exhibit complex behavior 34

Seastars are predators and eat a variety of organisms. The seastar can open a clam shell a few millimeters wide.Then by everting its stomach into the shell, the clam is digested and absorbed. Seastar Eating a Clam Missing parts from injuries or evisceration are quickly replaced. Any portion of the central disk will regenerate a new seastar - a fact that oyster fishermen learned too late!SEA STARS ASTEROIDEA45Brittle stars have long flexible arms extending from a central diskBrittle stars eat particulate organic matterBRITTLESTARS - OPHIUROIDEA

Gray Brittle Stars (Ophiura luetkenii) on the move56Sea urchins use tube feet and spines to moveSea urchins graze on seaweeds, seagrasses and algaeMouth has complex system of jaws & muscles Aristotles LanternSEA URCHINS- ECHINOIDEA 67Sea cucumbers are deposit feeders

Some secrete toxic substancesSome expel their gut and other internal organs - eviscerationMissing parts from evisceration are quickly replacedSEA CUCUMBERS - HOLOTHUROIDEA

78Crinoids are suspension feedersSea lilies are deep waterFeather stars perch and crawl on hard bottom shallow to deep waterUpside down brittle starFEATHER STARS OR SEA LILIES- CRINOIDEA 8SEASTAR DISSECTION9

Seastar DissectionSeastar External AnatomySeastar Anatomy InternalSeastar Dissection


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