phylum echinodermata

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Phylum Echinodermata. Echinoderms. Sea Stars Sea Urchins Sand Dollars Sea Cucumbers. Echinoderms. “ Spiny Skin ” 7,000 species Marine Environments Shallow and deep waters Vary in size From 1cm to 1m (3feet) Often brilliantly colored. Echinoderms. Radial Symmetry - PowerPoint PPT Presentation


  • Phylum Echinodermata

  • EchinodermsSea StarsSea UrchinsSand DollarsSea Cucumbers

  • EchinodermsSpiny Skin

    7,000 species

    Marine EnvironmentsShallow and deep waters

    Vary in sizeFrom 1cm to 1m (3feet)

    Often brilliantly colored

  • EchinodermsRadial SymmetryLike cnidarians and ctenophores

    Lack cephalization

    Larvae are bilaterally symmetricalSea StarSea UrchinBrittle Star

  • EchinodermsEchinoderms are deuterostomes, which makes them different from all of the other invertebrates

    Deuterostomes are coelomates whose embryos have radial cleavageanus forms near the blastoporemesoderm arises from outpockets of the endoderm

  • Echinoderms Have:Pentaradial symmetrythe body parts extend from the center along five spokes

    An endoskeleton composed of calcium carbonate plates

    Many small, movable extensions of the water-vascular system called tube feet, which aid in MovementFeedingRespirationExcretion

  • Echinoderm ClassificationCLASSES:

    Crinoidea (kri-NOID-ee-uh)Asteroidea (AS-tuh-ROID-ee-uh)Ophiuroidea (OH-fee-yoor-OID-ee-uh)Echinoidea (EK-uh-NOID-ee-uh)Holothuroidea (HOH-loh-thuh-ROID-ee-uh)

  • Class Crinoidealily-likeExamples: sea lilies, feather starsFive arms extend from the body and branch to form many more armsTube feet gas exchangeCilia on arms direct food to the mouthMouth faces up

  • Class Ophiuroideasnake-tailExamples: basket stars and brittle starsLong, narrow arms help them move quicklyCan break and regenerate easilyLive on the oceans floorEither rake in food with arms or trap it with their tube feet or mucus between their spines

  • Class Echinoideaspinelike,Examples: sea urchins, sand dollarsTest compact, rigid endoskeletonUrchins:Five teeth + their muscles = Aristotles LanternSpines can be sharp and contain venomSand dollars:Burrows into the sandUse spines for locomotion and burrowing

  • Aristotles Lantern

  • Class Holothuroideawater polypExamples: sea cucumbersSoft bodies because the particles that make up their endoskeleton are smallUse tentacles to bring food to the mouth

  • Sea CucumbersEviscerate their gut as a means of self defense

  • Class AsteroideastarlikeExamples: sea starsLive in coastal waters around the worldPrey on oysters, clams, and other foods humans eat

  • Structure and FunctionSea stars typically have 5 arms, but in some species, there may be as many as 24Two rows of tube feet run along the underside of each arm

  • Structure and Function

    On sea stars and sea urchins, pedicellariae, or little pincers, help keep the body surface free of foreign objects, including algae and small animals that might damage its soft tissues

  • Structure and FunctionGas exchange and waste excretion take place by diffusion through the skin gills,

  • Structure and FunctionPrimitive nervous systemNo head = no brainThe nervous system consists mainly of a nerve ring that circles the mouth and a radial nerve that runs from the nerve ring along the length of each armTogether, they coordinate the movements of the tube feet

  • Structure and FunctionSea stars also have a nerve net near the body surface that controls the movements of the spines, pedicellariae, and skin gills.

    Eyespot on each arm responds to light

    Tube feet respond to touch and chemicals

  • Water-Vascular SystemMadreporite-water enters through this small poreStone canal -connects madreporite and ring canalRadial canal -extends down each arm and carries water to hundreds of hollow tube feet---has valves to ensure one way flow

  • Feeding and DigestionMost echinoderms are carnivores.A sea star captures a clam and attaches to both shells with its tube feet, eventually tiring the clams muscles. Once the shell is opened every so slightly, the sea star ejects a portion of its stomach into the clam to digest the tissue.The sea star ejects a portion of its stomach when it feeds. Waste is expelled through anus on aboral surface.

  • ReproductionMost echinoderms are dioecious. Fertilization occurs externally after the organisms spawn.A free-swimming larva called a bipinnaria results and eventually develops into an adult.As long as a portion of the central ring remains intact, a sea star can regenerate.

  • Regeneration

  • Which Class?AsteroideaOphiuroideaHolothuroideaEchinoideaCrinoidea