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  Topic: The Bathroom Wall, A PT tradition< Next Oldest | Next Newest >  

Posts: 35
Joined: Sep. 2002

(Permalink) Posted: Dec. 31 2008,12:02   

Typical. You left out the very next paragraph.
And thatís exactly what we would expect from evolution! Neurons didnít simply appear out of nowhere, but gradually evolved from cellular processes that were co-opted for new functions. Trichoplax doesnít generate pulses of electrical activity, but it does have cells that must maintain salt balance, and contains pores and pumps to move charged ions in and out of its cells. It doesnít have tightly regulated synapses between neurons, but it does respond to the sensation of chemical signals in its environment by releasing other chemicals via vesicle export, a core process of synaptic activity. Of course, Trichoplax does not make a complex organismal form, nor does it make a brain, so evolution has shaped the predecessors of those functions in novel ways to produce more complex animals, but the molecular predecessors were there in the last common ancestor of both the blob-like microbe-grazer and the genome-sequencing bipedal primate. That these similar molecules are shared is further confirmation of common descent and the pattern of animal evolution, but now a more difficult question remains: what are the details that changed in these lineages to produce our distinctive differences?

  19631 replies since Jan. 17 2006,08:38 < Next Oldest | Next Newest >  

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