echinoderms section 38.1. echinoderms  examples: sea stars, sand dollars, sea urchins, & sea...

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  • EchinodermsSection 38.1

  • EchinodermsExamples: sea stars, sand dollars, sea urchins, & sea cucumbersMarine environmentsBrilliantly colored Radial symmetry

  • 4 Unique Characteristics:Ossicles: calcium carbonate plates that make up exoskeleton

    Water-vascular system: network of water-filled canals inside body

  • 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

  • Classification6 classes of echinoderms (only 5 discussed in textbook):

    Class CrinoideaClass OphiuroideaClass EchinoideaClass HolothuroideaClass Asteroidea

  • Class CrinoideaExamples: sea lilies, feather starsCrinoid means lily-like5 main arms that branch to form up to 200 more armsFilter feeders Mouth faces up

  • Class OphiuroideaLargest class with examples such as basket stars & brittle starsOphiuroidea means snake-tailLive on bottom of oceanRegeneration of broken armsLong, narrow arms allow for quick movement

  • Class EchinoideaExamples: sea urchins & sand dollarsEchinoidea means spinelikeTest: compact, rigid endoskeleton that surrounds internal organsSpines can have barbs or venom

  • Class HolothuroideaExample: sea cucumberHolothuroidea means water polypArmlessOssicles are not connected thus soft bodiesTentacles around mouth to capture prey

  • Class AsteroideaExample: sea star (starfish)Asteroidea means starlikeVariety of sizes, shapes, and colorsCompete with humans for oysters, clams, etc

  • Sea StarsSection 38.1 continued

  • External StructureSeveral arms extending from central regionTwo rows of tube feet on underneath side of each arm

    Oral surface: side where mouth is locatedStarfish = undersideAboral surface: side opposite of mouth

  • Rough texture due to short spinesPedicellariae: tiny pinchers surrounding of each spine that keep body free of foreign objects

  • Water-Vascular SystemNetwork 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

  • Feeding & DigestionPrey: mollusks, worms, clamsCardiac stomach: can be turned inside out through mouth during feeding

    Digestive pathway:Mouth cardiac stomach pyloric stomach digestive glands in each arm anus

  • Other Body StructuresNo circulatory, excretory, or respiratory systems!Skin gills: thin walls of tube feet that allow gas exchangeNervous system = nerve ring (around mouth), radial nerves (length of each arm), eyespots (end of each arm), tentacles

  • Reproduction & DevelopmentSeparate sexes each arm has sex organsExternal fertilizationAfter 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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