Echinoderms are easy to keep in a salt water aquarium.  

Background:

Echinoderms are invertebrates which are characterized by an external skeleton covered with sharp spines, radial symmetry, and tube feet.  

Starfish walk using their tube feet to move themselves along a surface. Their tube feet have suckers on the ends, which they use to attach themselves to rocks and to trap prey items. 

Starfish can regrow their arms if they are damaged or eaten by predators. In fact, in some cases an entire sea star can be regenerated from just a single arm! 

Look at specimens of sea cucumbers, sea urchins, sea biscuits, sand dollars, and starfish to see the similarities.  Use agfa loupes (these are magnifiers which you can buy from a camera supply store) or magnifying glasses to examine the specimens.  Have have each child take a different echinoderm and draw what they see under the loupe. Do not have them draw the entire animal, only a part.  Everyone in the class tries to guess what their drawing is of.  

It is important that the students understand the concept of radial symmetry during this part of the unit.  Each child can make their own sea urchin out of self-hardening clay and toothpicks.  Look for elaboration in the detail they add to the sea urchin such as coloring the tips of the spines. 

Have the students cut out starfish patterns out of sandpaper.  They can use them to make starfish rubbings.

Starfish dissection activity

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