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    X. Starfish - The Dermatologic Nightmare: Echinoderms and Early Chordates

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    Róisín Blanks
    This document discusses echinoderms and early chordates. It describes the classification and characteristics of starfish and other classes of echinoderms like brittle stars, sea urchins, and sea cucumbers. It notes starfish use their tube feet to exert force and everting their stomach to digest prey. Sea cucumbers can expel their internal organs when threatened. The document then discusses chordates and the four characteristics they share, including a notochord. It briefly outlines the subphyla of tunicates, which are sessile, and lancelets, which possess all four chordate traits and live on sandy coasts.

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    X. Starfish - The Dermatologic Nightmare: Echinoderms and Early Chordates

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    Róisín Blanks
    30 views4 pages
    This document discusses echinoderms and early chordates. It describes the classification and characteristics of starfish and other classes of echinoderms like brittle stars, sea urchins, and sea cucumbers. It notes starfish use their tube feet to exert force and everting their stomach to digest prey. Sea cucumbers can expel their internal organs when threatened. The document then discusses chordates and the four characteristics they share, including a notochord. It briefly outlines the subphyla of tunicates, which are sessile, and lancelets, which possess all four chordate traits and live on sandy coasts.

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    Lecture_Notes_-_Lecture_7_Echinoderms_and_Early_Chordates_p_33-36_

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    This document discusses echinoderms and early chordates. It describes the classification and characteristics of starfish and other classes of echinoderms like brittle stars, sea urchins, and sea cucumbers. It notes starfish use their tube feet to exert force and everting their stomach to digest prey. Sea cucumbers can expel their internal organs when threatened. The document then discusses chordates and the four characteristics they share, including a notochord. It briefly outlines the subphyla of tunicates, which are sessile, and lancelets, which possess all four chordate traits and live on sandy coasts.

    Copyright:

    © All Rights Reserved
    Download as DOC, PDF, TXT or read online from Scribd
    Download as doc, pdf, or txt
    30 views4 pages

    X. Starfish - The Dermatologic Nightmare: Echinoderms and Early Chordates

    Uploaded by

    Róisín Blanks
    This document discusses echinoderms and early chordates. It describes the classification and characteristics of starfish and other classes of echinoderms like brittle stars, sea urchins, and sea cucumbers. It notes starfish use their tube feet to exert force and everting their stomach to digest prey. Sea cucumbers can expel their internal organs when threatened. The document then discusses chordates and the four characteristics they share, including a notochord. It briefly outlines the subphyla of tunicates, which are sessile, and lancelets, which possess all four chordate traits and live on sandy coasts.

    Copyright:

    © All Rights Reserved
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    Download as doc, pdf, or txt
    of 4

    Echinoderms and Early Chordates 35

    X. STARFISH – THE DERMATOLOGIC NIGHTMARE


    A. Classification
    Kingdom Animalia
    Phylum Echinodermata (spine + skin)
    Class Asteroidea – sea stars
    Class Ophiuroidea – brittle stars, basket stars
    Class Echinoidea – sea urchins, sand dollars, sea biscuits
    Class Holothuroidea – sea cucumbers

    B. Characteristics:
    1. pentamerous radial symmetry but larva = bilateral symmetry

    2. endoskeleton with calcareous plates or ossicles and spines

    3. water vascular system – tube feet produce a suction to allow the animal to hold onto
    objects = hydraulic system of animal kingdom

    4. locomotion by tube feet

    5. deuterostome development pattern

    6. complete digestive system – however in some, undigested materials are expelled through
    mouth

    C. Review of Development Patterns:


    1. protostome – arthropods, molluscs, annelids

    gastrula stage

    2. deuterostome – echinoderms, chordates

    gastrula stage
    Echinoderms and Early Chordates 36

    D. Class Asteroidea
    1. characteristics:
    a. thick arms not marked off from central disc that are equipped with pedicellariae =
    cleaning pinchers

    b. external body structures

    c. digestive system

    Note: starfish are predatory and use tube feet to exert 1,300 g of force for
    30 minutes and the adductor muscles of the clam fatigue. The starfish
    then everts its stomach and inserts it into the clam's shell and digest the
    clam. Undigested materials are expelled through the mouth.

    d. reproduction – reproduce asexually and sexually

    Note: autotomy = ability to break off part of their own bodies (e.g., injured arm
    throw it away and make a new one)

    2. Examples – sea stars = typical starfish

    E. Class Ophiuroidea – Brittle stars


    Note: highest numbers of species and most abundant group of echinoderms

    F. Class Echinoidea
    examples:
    1. heart urchins
    2. sand dollar
    Note: urchins and sand dollars have 5 teeth (used to feed on detritus, algae,
    and some prey items) – shake a sand dollar and 5 doves fall out –
    doves = teeth
    Echinoderms and Early Chordates 37

    G. Class Holothuroidea – sea cucumbers


    1. characteristics:
    a. soft body with leathery body wall
    b. plant-like appearance
    c. oral tentacles
    d. body plan

    2. Sea cucumber trivia:


    Note:
    If threatened, sea cucumbers can regurgitate or expel all of their visceral
    organs (respiratory tree tubules, digestive organs, and gonads ) = "puke out their
    guts". They promptly grow a whole new gut. Would-be predators get entangled and
    may be fatally immobilized by sticky, toxic secretions associated with the Cuverian
    tubules of the respiratory tree.

    XI. THE ONES WITH A BACKBONE


    A. Classification
    Kingdom Animalia
    Phylum Chordata
    Subphylum Urochordata – tunicates
    Subphylum Cephalochordata – lancelets
    Subphylum Vertebrata – vertebrates
    Note:
    have 4 chordate characteristics + segmented backbone
    contain 8 Classes

    B. Characteristics: 4 major chordate characteristics


    1. notochord – support structure = our spinal column

    2. dorsal tubular nerve cord = our spinal cord

    3. pharyngeal gill slits

    4. postanal tail – extending beyond anus

    Note: all chordates possess these at some point in their development


    Echinoderms and Early Chordates 38

    C. Subphylum Urochordata (tail + cord) – sea squirts or tunicates


    1. characteristics – sessile with tough tunic or covering
    2. body plan

    D. Subphylum Cephalochordata – Amphioxus or lancelet


    1. characteristics – sandy bottoms of coasts – possess all 4 chordate characteristics
    2. body plan

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