How do sand dollars get their five-petaled design?

if you look at a sand dollar, you'll find a sort of five-petaled flower or what looks like a leaf design on the top of the shell. How is this exact design created as the shell grows?

How do sand dollars get their five-petaled design?
A sand dollar is an animal in the echinoderm family, related to starfish and urchins. They all have 5-way symmetry.
Reply:Why 5-way symmetry? I don't know, it's just how they evolved? Here is how, anyway, from Wiki:





http://en.wikipedia.org/wiki/S...


http://en.wikipedia.org/wiki/E... (look at physiology) Report It

Reply:5's just magic. five fingers, toes, halfway to the first two digit number. its got balance. its one syllable. five times one equals five. a torso and five things sticking out of it (minus penis).





five. five five. gimmie five!!
Reply:They are live creatures. This is the way they were created. They are a slow moving grazer that feeds on disintegrating organic material found within their sand beds. Sand dollars are in the Echinoid (Echinoderms) class of marine animals. Like its close relative the sea urchin, the sand dollar has five sets of pores arranged in a petal pattern. The pores are used to move sea water into its internal water-vascular system, which allows for movement.





This pattern does not grow onto them, its a part they were created with that just gets bigger as it grows. Like your own arm or leg.
Reply:genetics
Reply:elves...

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