ECHINODERMATA By: Laura Hein, Jaeyoung Kim Period 3 Rall http://www.palaeos.org/images/thumb/5/5a/Acanthaster_planci.jpg/340px-Acanthaster_planci.jpg
Phylum: Echinodermata • Classes: • Ophiuroidea: brittle stars • Asteroidea: Sea stars • Echinoidea: • sea urchins • sand dollars http://people.hws.edu/mitchell/cards01/LEI2.html
Classes: cont. • Crinoidea: sea lillies • Holothuroidea: sea cucumbers http://people.hws.edu/mitchell/cards01/LEI2.html
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
Body Symmetry • Radial (pentameral) http://webs.lander.edu/rsfox/rsfoximages3/lab1_x550_x_595x.gif Jaeyoung Kim
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 http://www.brocku.ca/MeadProject/Angell/Angell_1906/images/ang01_06.gif
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 http://tolweb.org/Echinodermata Laura Hein
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 http://image.tutorvista.com/content/animal-kingdom/starfish-anatomy.jpeg Jaeyoung Kim
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
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. http://www.esu.edu/~milewski/intro_biol_two/lab__13_echinoderm/images/aster_ossicle_diagr.jpg Laura Hein
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. http://www.sfdj.com/learn/13.jpg Laura Hein Starfish Tube Feet
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 http://egate.mcgehee.k12.la.us/faculty/jenniferz/biology/starfish%20B/STARFISH%20project/rep.%20diagram%20pic.gif
Unique Features • Can regenerate lost limbs http://www.esu.edu/~milewski/intro_biol_two/lab__13_echinoderm/images/aster_diagr_water_vasc.jpg Jaeyoung Kim
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?
Answers • 1. A • 2. C • 3. A • 4. See slide 8.