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Echinoderms

Echinoderms. Section 38.1. Echinoderms. Examples : sea stars, sand dollars, sea urchins, & sea cucumbers Marine environments Brilliantly colored Radial symmetry. 4 Unique Characteristics:. Ossicles : calcium carbonate plates that make up exoskeleton

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Echinoderms

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  1. Echinoderms Section 38.1

  2. Echinoderms • Examples: sea stars, sand dollars, sea urchins, & sea cucumbers • Marine environments • Brilliantly colored • Radial symmetry

  3. 4 Unique Characteristics: • Ossicles: calcium carbonate plates that make up exoskeleton • Water-vascular system: network of water-filled canals inside body

  4. 3. Tube feet: small, movable extension of w-v system which aid in movement, feeding, respiration, & excretion 4.Pentaradial symmetry: body parts extend from center along 5 spokes

  5. Classification • 6 classes of echinoderms (only 5 discussed in textbook): • Class Crinoidea • Class Ophiuroidea • Class Echinoidea • Class Holothuroidea • Class Asteroidea

  6. Class Crinoidea • Examples: sea lilies, feather stars • Crinoid means “lily-like” • 5 main arms that branch to form up to 200 more arms • Filter feeders • Mouth faces up

  7. Class Ophiuroidea • Largest class with examplessuch asbasket stars & brittle stars • Ophiuroidea means “snake-tail” • Live on bottom of ocean • Regeneration of broken arms • Long, narrow arms allow for quick movement

  8. Class Echinoidea • Examples: sea urchins & sand dollars • Echinoidea means “spinelike” • Test: compact, rigid endoskeleton that surrounds internal organs • Spines can have barbs or venom

  9. Class Holothuroidea • Example: sea cucumber • Holothuroidea means “water polyp” • Armless • Ossicles are not connected thus soft bodies • Tentacles around mouth to capture prey

  10. Class Asteroidea • Example: sea star (starfish) • Asteroidea means “starlike” • Variety of sizes, shapes, and colors • Compete with humans for oysters, clams, etc

  11. Sea Stars Section 38.1 continued

  12. External Structure • Several arms extending from central region • Two rows of tube feet on underneath side of each arm • Oral surface: side where mouth is located • Starfish = underside • Aboral surface: side opposite of mouth

  13. Rough texture due to short spines • Pedicellariae: tiny pinchers surrounding of each spine that keep body free of foreign objects

  14. Water-Vascular System • Network of water-filled canals that are connected to the tube feet • Water movement: • Madreporite (sievelike plate on aboral surface)  stone canal  ring canal (encircles mouth)  radial canal (extends to each arm)  tube feet • Ampulla: bulblike sac at end of tube feet that allows for movement and suction

  15. Feeding & Digestion • Prey: mollusks, worms, clams • Cardiac stomach: can be turned inside out through mouth during feeding • Digestive pathway: • Mouth  cardiac stomach  pyloric stomach  digestive glands in each arm  anus

  16. Other Body Structures • No circulatory, excretory, or respiratory systems! • Skin gills: thin walls of tube feet that allow gas exchange • Nervous system = nerve ring (around mouth), radial nerves (length of each arm), eyespots (end of each arm), tentacles

  17. Reproduction & Development • Separate sexes – each arm has sex organs • External fertilization • After 2 months of swimming they settle to bottom of ocean and metamorphous into adult • Regeneration (asexual) • As long as part of the central region stays in tact

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