Echinoderms

What are echinoderms?

spiny skininternal skeleton

water vascular system

tube feet

Form and FunctionWater Vascular

system Filled with fluidrespirationCirculation movementMadreporite

◦ 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 Urchinsuse a 5 part jaw-like structure to scrape algae from rock

Sea Liliesuse tube feet to capture floating plankton

Sea Cucumbersmove like bulldozers taking in sand and detritus

Sea Starsfeed 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 ringsRadialScattered

sensory cells ◦ detect

light gravity chemicals released

by potential prey

Movementdependant 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

Reproductionexternal fertilizationare either male or

femaleSperm and eggs

released into the water for fertilization

Larva have bilateral symmetry

develop radial symmetry

Groups of Echinoderms

Sea Urchins and Sand DollarsLarge 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 StarsCommon

◦ especially on coral reefs

slender, flexible armsrapidly escape

predatorsshed one or two arms

◦ keep moving when ◦ distract predators

Are filter feeders ◦ detritivores

Nocturnal

Sea Cucumbers warty moving

picklesAre detritus

feeders, ◦ organic matter ◦ remains of plants ◦ remains of

animals.Roam across

deep sea floorherds of

hundreds of thousands

Sea Starscreep 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 feederslong feathery armsCommon 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 EchinodermsSea 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