Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Ch. 28.4
Transcript
Echinoderms Ch. 28.4 Phylum ECHINODERMATA Spiny Skin First Phlya with an INTERNAL skeleton ENDOSKELETON: formed from hardened plates of Calcium Carbonate Found only in MARINE environments What is an Echinoderm? Adults have NO anterior or posterior ends No CEPHALIZATION Bodies are still 2 sided (oral surface [where the mouth is]; aboral surface [opposite side]) Spiny skin, internal skeleton, water vascular system, suction-cuplike tube feet Most have 5 part RADIAL symmetry Radial symmetry is similar to spokes of a wheel More closely related to humans than other vertebrates Larva is bilateral Deuterostomes (blastopore develops into an anus) Form and Function in Echinoderms Internal tubes: WATER VASCULAR SYSTEM (carries out body functions such as respiration, circulation, and movement) Sievelike structure called MADREPORITE Tube feet attached to radial canal Muscles help with movement Feeding Can feed by scraping, capture, filtering, predation Respiration and Circulation Thin walled tissue of feet will provide a surface for respiration (some species have ‘skin gills’) Circulation takes place in the water vascular system Excretion Solid wastes released as feces through anus Nitrogen cellular waste are excreted as ammonia (passed into the water via diffusion) Response Don’t have a highly developed nervous system (they don’t even have a ‘head!’) Nerve ring around the mouth with radial nerves Scattered sensory cells that detect light, gravity, and dangerous chemicals Movement Use tube feet and a thin layer of muscle fibers attached to the ENDOSKELETON Reproduction External fertilization Separate sexes Sperm in testes, eggs in ovaries Groups of Echinoderms 7,000 species SEA URCHINS and SAND DOLLARS: large, solid plates; detrivores; burrow or wedge for protection BRITTLE STARS: found on coral reefs; flexible arms that move for defense; can shed their arms; filter feeders or detrivores SEA CUCUMBERS: warty/pickle looking; detritus and suck up food from the sea floor SEA STARS: carnivorous; self repair when damaged SEA LILIES and FEATHER STARS: filter feeders; live near coral reefs Ecology of Echinoderms A change in number of echinoderms can change the ecology Sea urchins help with algae Sea stars help control the number of clams and corals Threat is CROWN of THORNS.
