Echinodermata

Alyssa Price and Katy Fanning

Period 2

Symmetry

• Echinodermata evolved from animals with bilateral symmetry

• Pentaradial symmetry- arms radiate from the central body (pentamerous), each dividing into five equal segments

• Starfish have no heart, brain, or eyes

• Each arm has its own set of organs

Germ Layers

• Echinodermata have three germ layers: the ectoderm (outer), endoderm (inner), and mesoderm (middle).

• Do not have an external skeleton, but rather have a thin skin layer composed of calcified plates and spines

• The coelom is the secondary body cavity formed by the division of three body cavities

• The coelom is composed of two parts (the perivisceral coelom and the hydrocoel)

Perivisceral coelom contains a watery coelom and the hydrocoel forms the water vascular system.

Movement

• Most Echinodermata are motile • Their movement is controlled by nerve branches in the

arms• Some use water to hold them up and float in shallow

areas• Echinodermata use their water vascular system to move

Reproduction• Females discharge their eggs into the water; Males

discharge their sperm• Gametes float in water until egg and sperm find

each other in water (flagellated sperm)• Females can produce 100 million eggs at once• All echinodermata can regenerate new parts

asexually

Life Cycle

Terms• Tube feet- function of locomotion and feeding; the two

muscles are ampulla and podia: the ampulla are the circular and longitudinal muscles and the podia are the latter muscles

• Spines- make up the outermost skin layer for the function of support

• Pentaradial symmetry- five equal parts around a central axis (usually the mouth)

• Water vascular system- network of canals that function in gas exchange, feeding and locomotion

• Two stomachs (starfish)- one is used for digestion and the other is used to engulf prey

• 5 classes- Echinoidea (sea urchins and sand dollar), Crinoidea (sea lilies), Asteroidea (starfishes), Ophiuroidea (brittle stars), Holothuroidea (sea cucumbers)

Videos

http://www.youtube.com/watch?v=A100m5EpfFI

 

http://www.youtube.com/watch?v=irERi_1OxmE

 

http://www.youtube.com/watch?v=4IRF-pKVtuU