Echinoderms

What are echinoderms? spiny skin internal skeleton water vascular system tube feet

Form and Function Water Vascular system Filled with fluid respiration Circulation movement Madreporite ◦ sieve like structure ◦ opening to outside

5 part radial symmetry bilaterally symmetrical deuterostomes ◦ blastopore develops into the anus

Sea stars ◦ Tube Feet  muscles pull up the center of the suction cup  Tube feet allow them to walk and pull open prey.

Sea Urchins use a 5 part jaw-like structure to scrape algae from rock

Sea Lilies use tube feet to capture floating plankton

Sea Cucumbers move like bulldozers taking in sand and detritus

Sea Stars feed on mollusks ◦ Pry open shells ◦ Push stomach out of its mouth ◦ Secretes enzymes to digest mollusks in their own shells ◦ Pulls stomach and partially digested prey back in

Respiration and Circulation surface respiration ◦ tube feet ◦ skin gills water vascular system ◦ carry oxygen, food and waste

Excretion Digestive waste ◦ anus Nitrogen-containing cellular waste ◦ tube feet ◦ skin gills

Nervous System not highly developed nerve rings Radial Scattered sensory cells ◦ detect  light  gravity  chemicals released by potential prey

Movement dependant on the type of endoskeleton Most use tube feet with other forms of locomotion

Sand Dollars and Sea Urchins movable spines

Sea Stars and Brittle Stars have flexible joints

Sea Cucumbers plates over a soft muscular body wall

Reproduction external fertilization are either male or female Sperm and eggs released into the water for fertilization Larva have bilateral symmetry develop radial symmetry

Groups of Echinoderms

Sea Urchins and Sand Dollars Large solid plates around internal organs Are detritivores ◦ eat algae Defense ◦ burrowing in the sand (sand dollar) ◦ wedging in rocks (sea urchins) ◦ using sharp spines

Brittle Stars Common ◦ especially on coral reefs slender, flexible arms rapidly escape predators shed one or two arms ◦ keep moving when ◦ distract predators Are filter feeders ◦ detritivores Nocturnal

Sea Cucumbers warty moving pickles Are detritus feeders, ◦ organic matter ◦ remains of plants ◦ remains of animals. Roam across deep sea floor herds of hundreds of thousands

Sea Stars creep slowly along the sea floor carnivorous ◦ prey on bivalves pieces will grow into a new animal ◦ Must contain a portion of the central body

Sea Lilies and Feather Stars oldest class of echinoderms filter feeders long feathery arms Common in tropical oceans

Sea lilies live attached to the ocean bottom by long, stem-like stalks

Feather stars live on coral reefs and use their tube feet to catch plankton

Ecology of Echinoderms Sea urchins ◦ help control algae and other marine life Sea stars ◦ predators to control the population of other organisms

Crown-of-Thorns sea stars threaten coral reefs Have poisonous spines Feeds almost exclusively on corals destroyed extensive areas of the Great Barrier Reef in Australia