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| B. Evolutionary advances |
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| (Biological Contributions) |
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| • | Not terribly more complex than the |
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| cnidarians and ctenophores except |
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| • | 1. Bilateral
symmetry |
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| • | 2.
Cephalization |
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| • | 3.
Ladder-like nervous system with ganglia |
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| • | 4.
Triploblastic |
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| • | 5. Excretory
system (protonephridia) |
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| • | 6. Increased
complexity in musculature |
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