BIOL 111 Lecture Notes - Lecture 54: Water Vascular System, Suction Cup, Echinoderm

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23 Jul 2016
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BIOL 111 Organismal Biology
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!!plate enlarge and more CaCO3 is added
o!it is covered by a thin layer of tissue (nervous tissue, muscle, skin)
!!as an exception, adult echinoderms are pentaradially symmetrical
!!larval echinoderms are bilaterally symmetrical
o!proof of bilaterally symmetrical ancestor
!!the bodies of echinoderms are foreshortens along the anterior-posterior axis
o!the mouth is flopped downward
o!body surfaces are referred to as
!!oralthe mouth surface (faces downwards)
!this advantageous for bottom-feeding
!!aboralthe anal surface (faces upwards)
!!their nervous system is composed of radial nerves and sensory structures in the tube feet
Water Vascular System
!the water vascular system conducts water throughout the body of the echinoderm
!water enters the system through the madreporite
!it travels down the stone canal, around the ring canal and then is distributed to each
radial canal in each tube foot (podium)
!from the radial canals, water flows into sacs called ampulla that are controlled by
muscles
!these muscles can force the water to the bottom of the ampulla in suction cup and create a
suction for grasping
!the ampulla extends through pores in the endoskeleton
!this system can be used for locomotion, feeding, respiration and excretion
o!respiration and excretion also occur through skin gills
!the system contains sensory structures to chemicals and touches
Reproduction
!asexually, they may reproduce by fragmentation or regeneration
o!an arm may be dropped and regenerated to:
!!escape predation
!!decrease chance of infection
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