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ECHINODERMATA. By: Laura Hein, Jaeyoung Kim Period 3 Rall. Phylum : Echinodermata. Classes: Ophiuroidea: brittle stars Asteroidea: Sea stars Echinoidea: sea urchins sand dollars.

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    1. ECHINODERMATA By: Laura Hein, Jaeyoung Kim Period 3 Rall

    2. Phylum: Echinodermata • Classes: • Ophiuroidea: brittle stars • Asteroidea: Sea stars • Echinoidea: • sea urchins • sand dollars

    3. Classes: cont. • Crinoidea: sea lillies • Holothuroidea: sea cucumbers

    4. Body cavity (coelom) -Echinoderms form their coeloms as outpocketings from the archenteron (embryonic gut), -process=enterocoely. -In most species, the coeloms are trimerous, and initially bilaterally symmetrical. -some coelom departments are similar and may reflect a common evolutionary ancestor within the phylum: - left mesocoel gives rise to most or all of the water vascular system, and one or both somatocoels form the lining of the body cavity. Laura Hein

    5. Body Symmetry • Radial (pentameral) Jaeyoung Kim

    6. Nervous System • Decentralized nervous system • Radial nerves run under the ambulacra (legs) • Central nerve ring surrounds the gut • Eyespots that can detect light • No specialized sensory organs • and no definitive brain Jaeyoung Kim

    7. Circulatory Structures -A Echinoderm has water pumped through its body as part of its very simple circulation system -no specific structures for the circulatory system Laura Hein

    8. Digestive/Excretory System • Tubes grab onto food -> invert their stomach -> secrete/squirt juices (enzymes) that digest -> reabsorb digested food through mouth under the center -> wastes out the aboral anus Jaeyoung Kim

    9. Locomotion • Vascular system consist of a network of hydraulic canals branching into extensions called papullae (tube feet), which provides: • slow movement • feeding • and gas exchange Tube feet uses hydraulics to create negative pressure which acts as a suction force. Jaeyoung Kim

    10. Skeletal type -Biomineral matrix composed of calcium carbonate and several proteins -calcite is composed of numerous tiny crystals lie on same crystal axis within an ossicle -because of this, ossicles are sponge-like microstructures called stereom that is unique to that phylum -Embryologically, echinoderm ossicles are a true endoskeleton, since they are produced by mesenchymal cells and are usually covered by epidermis -However, they act more like an exoskeleton, lying just under the epidermis and enclosing most other tissues in a flexible but tough covering. Laura Hein

    11. Sensory Structures/Features • -rudimentary senses including: • -light sensitive eyespots • sensory tentacles (modified tube feet) at the tips of the arms • small patches of cells sensitive to chemicals or touch. Laura Hein Starfish Tube Feet

    12. Reproductive System • Most are dioecious, with separate male and female individuals, but some are hermaphrodites. • Each arm contains two gonads, which release gametes through openings called gonoducts, located on the central body between the arms. Jaeyoung Kim

    13. Unique Features • Can regenerate lost limbs Jaeyoung Kim

    14. Quiz • 1.Which of the following is not a sensory structure of the echinodermata • A) Light sensitive eyespots • b) Sensory tentacles (modified tube feet) at the tips of the arms • c) Small patches of cells sensitive to chemicals or touch. • d) Taste Buds • 2. Which of these do not belong to the echinodermata phyla? • a) Starfish • b) Brittle Stars • c) Jelly Fish • d) Sea Cucumbers • 3. What kind of circulatory system does the echinodermata possess? • a) No specific structures for the circulatory system • b) A system of capillaries running throughout the body • c) A heart with arteries, blood vessels, veins, and capillaries • d) A simple heart-like organ with no separate ventricles • 4. Free Response: What are the steps to the digestive/excretory system of an echinodermata?

    15. Answers • 1. A • 2. C • 3. A • 4. See slide 8.