1. Sea Star, Sea Urchin, Sea Cucumber
Phylum Echinodermata
Sea Star, Sea Urchin, Sea Cucumber

2. General Characteristics
Spiny skinned
pentaradial symmetry = as adults have five similar parts arranged in circle around a central point
exclusively marine, adapted to a bottom-dwelling existence
examples include sea stars (‘starfish’), sea urchins, sand dollars, sea cucumbers

3. most species reproduce sexually, have separate sexes, and have external fertilization. Note that the larvae of echinoderms are ciliated and bilaterally symmetric .
Many echinoderms are recognized by their pentaradial (five-fold) symmetry. It is important to understand that the radial symmetry of echinoderms is superficial and almost certainly secondarily derived. This means that the ancestor of echinoderms (the ancestor it shares in common with all other bilaterians) was likely bilaterally symmetric. If we look carefully at a typical echinoderm like the sea star we will note that the five part organization can be divided into mirror-image right and left halves - the hallmark of bilateral symmetry.
An easy way to see this is to find the madreporite and imagine a line connecting it to the tip of the arm opposite the madreporite. This line will divide the animal into right and left halves.

5. Muscular/ Skeletal System
Mouth on the bottom side of organism (oral surface). Other side= aboral surface
have an internal skeleton (endoskeleton) composed of interlocking calcium carbonate plates

6. Water Vascular System Contains a water vascular system
Water enters body through a sieve plate (=madreporite) The water is transport through the ring canal and the radial canal to power the tube feet
have tube feet, which are versatile structures used for locomotion, gas exchange, feeding, attachment, and sensory reception!
Tube feet:..\..\..\Lesson Videos\Biology 11\Arthropods and Echinoderms\Starfish or Sea Star (Asteroidea).flv

8. Digestion Use tube feet to open bivalves, to capture preys
Sea stars and sea urchins
contain pedicellaria
= grasping appendages
(food gathering, cleaning, & defense against predators)
Sea stars can flip its stomach out of the mouth and digest/ eat the food outside its body. It will flip its stomach back in when finished.

9. Herbivores (e.g. sea urchins) have 5-part jaws to scrape algae
Some are filter feeders (sea lillies, brittle stars)
Some detritus feeders

10. Respiration
Diffusion through tube feet
Circulatory
Done by digestive gland and fluid in body (located in pseudocoelem)
Excretory
Solid food waste anus
Nitrogen waste tube feet, gill, all over body

11. Nervous System
No brain (radial symmetry)
Nerve rings around mouth; eyespot; statocysts
Movement
Use tube feet
Reproduction
Echinoderm sexes are generally separate
Fertilization and development of young are external, larval stage in life cycle

12. Class Asteroida (Sea Stars)
5-26 arms
eyespots located on tip of each arm
push stomachs out of body through mouth to devour prey
can regenerate lost or damaged arm, but is very slow
gills protrude through skin

14. Crown of thorns starfish
Reading and species file
Video:..\..\..\Lesson Videos\Biology 11\Arthropods and Echinoderms\Crown-of-Thorns starfish.flv

15. Know your anatomy

16. Worksheet time