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Just wondering ; I get the impression a large number of multicellular organisms are multi-lateral in their physical structure. Why would evolution/mutation have retained multi-lateral symmetry in an organism? What advantage/s does symmetry provide an organism?

EDIT: By multi-lateral symmetry I mean at-least bi-lateral symmetry (as in the case of many beings such as elephants, crabs and fishes), but perhaps more than bi-lateral too (starfish come to mind)

END EDIT:

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Could you explain what you mean by multi-lateral symmetry or give examples? –  kmm Mar 5 '13 at 20:25
    
Similar to: biology.stackexchange.com/questions/5588/… –  kmm Mar 6 '13 at 4:48
    
@Kevin: Thank you. The question you found is very similar; it didn't appear in my search for 'symmetry' 'physiology' when i looked - hence this question posted. –  Everyone Mar 6 '13 at 11:03

2 Answers 2

Signs of symmetry are determined by the environment. Completely isotropic ecological niche corresponds to the maximum degree of symmetry of organisms (spherical symmetry). Asymmetrization on the axis "up-down" took place under the influence of gravity field and lead to radial symmetry. Bilateral symmetry of the multicellular animals arose with movement.

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Evolution works by tinkering, not engineering. Gaining an evolutionary advantage in a simple way is rewarded, as is simplicity generally. Symmetry allows for relatively greater simplicity at the genetic information level (modular body parts driven by repeated application of same genetic instructions). Without symmetry, more genetic information would be needed to construct a similarly complex organism (symmetric like), with the concomitant exposure to increased genetic degradation.

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