Phylum Echinodermata: Echinoderms A. General Characteristics 1. Echin- Spiny Dermis- Skin Dermis- Skin 2. Pentaradial: 5 part radial symmetry 3. Water.

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  • Phylum Echinodermata: EchinodermsA. General Characteristics1. Echin- Spiny Dermis- Skin2. Pentaradial: 5 part radial symmetry3. Water Vascular System: System of internal tubesinternal network of fluid filled canals connected to tube-feet. Involved in many processes:feedingrespirationinternal transportelimination of wastesmovement4. Tube-Feet: suction cup-like structures.

  • StructureB. Structure1. No anterior, posterior, or brain2. Two sides:a. aboral- top of the bodyb. oral- side where the mouth is located (hint to remember: orajel, oralB floss)3. Spiny skinned

  • MovementC. Water Vascular System1. Sieve Plate (madreporite): located on the aboral surface water enters into the starfish2. Ring Canal: Surrounds the mouth Surrounds the mouth3. Stone canal: carries water into the ring canal.4. Five Radial Canals: These extend from the ring canal to each body segment. Water moves from the ring canal into these radial canals. This is how water reaches the rest of the body.5. Tube-Feet: Suction cup like structures When water is pushed in- tube feet expands When water is pulled out- The ampulla shrinks creating a vacuum suctioning to what it is touching. 6. Ampulla: Muscular sac at the base of each tube foot that contains fluid.Hint: This is how a dropper works.

  • Feeding/ExcretionFeeds on mollusks, worms, and other slow moving animalsD. Feeding Process:1. use tube feet to pry open shells of mollusks2. Once the shells are open, it flips its stomach out of its mouth it pours out enzymes to digest the meat of the mollusk in its own shell3. when partially digested, the starfish pulls its stomach back into its mouth to finish its mealE. Excretion Process;1. diffusion through the thin walls of the tube feet2. diffusion through the skin gills.

  • Respiration/Nervous SystemsF. Respiration1. Exchange of oxygen(O2) and carbon dioxide (CO2) occurs through diffusion of skin gills and tube feet.G. Nervous System1. Nerve Ring: surrounds the mouth2. Radial Nerves: connects to the nerve ring. they extend into each arm. 3. Eyespots: located at the end of each arm, detect light4. Tube feet: sense touch5. Scattered sensory cells: sense chemicals

  • Reproductive SystemH. Reproduction1. Separate Sexes:a. produce egg or sperm which fill the arms during the reproductive season.b. eggs and sperm are released into open waterc. starfish detect gametes of their own speciesd. respond by releasing their gametes (egg or sperm) into the water.e. fertilization occurs in the open water. 2. Regenerationa. this can occur if part of the central disc is present

  • anatomy of a starfish

  • ring canal Circular canal in which filtered water enters through the madreporite and branches out into the radiated canals.

    rectal cecum Lateral duct of the terminal part of the digestive tract, where waste is stored before being expelled through the anus.

    anus Terminal orifice of the digestive tract allowing waste to be ejected; most of the undigested food is regurgitated rather than expelled through the anus.

    stomach Dilated section of the digestive tract preceding the intestine; it receives food to be digested.

    gonad Each of the two glands located in each arm, producing gametes (spermatozoids or ovules) depending on the sex of the starfish.

    pyloric cecum Radiated duct of the digestive tract producing digestive enzymes and also allowing digested food to be stored.

  • gonopore Dorsal opening through which gametes (spermatozoids and ovules) are expelled into the water to be fertilized.

    intestine Section of the digestive tract between the stomach and the anus where absorption of nutrients is carried out and waste is transformed into fecal matter.

    radial canal Canal running the length of the arm; it receives water from the annular canal, which then passed into the tube feet.

    ampulla Bulb that contracts to let water enter the tube foot, allowing it to extend; when it dilates, the foot retracts.

    esophagus Muscular membranous channel of the anterior section of the digestive tract; it allows food to reach the stomach.

    mouth Anterior cavity of the digestive tract located on the ventral surface that allows food to be ingested.


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