Evolution (Evolution)

by George Jelliss , Crewe, Tuesday, January 27, 2009, 10:11 (5575 days ago) @ David Turell

This article discusses possible causes of the Cambrian explosion - http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&... - Nicholas Butterfield thinks that the appearance of sex and predation and multicellularity led to increased competition. - QUOTES: Until sexual reproduction and violence (in the form of predation) appeared, Butterfield says, life was constrained to a very simple world, defined largely by the physical environment. That's the Precambrian world. /// it was the inevitable encounters of the predator-prey relationship that provided an inexhaustible source of new environments. At the advent of the Cambrian, which led to most of the major groups of animals still around today, the fossil record suddenly reveals wonderful beasts, with claws and shells, /// These defining features all [have to] do with other organisms. Suddenly, to survive, creatures have to move, have to see - what they would like to eat, and what would like to eat them. - "I don't know what caused sex in the first place," he adds, "but one possible explanation for why it persisted was that it allowed the evolution of multicellular organisms. There was a "niche" in the Proterzoic world for large multicellular organisms that had yet to be exploited." And when the multicellular organisms appear on the stage, "this sets up a positive feedback loop whereby organisms respond to new environments" presented by other organisms, "by evolving new morphologies, and those new morphologies introduce new environments which induce newer morphologies. Multicellular organisms can do this," Butterfield says, because there is an essentially inexhaustible supply of new morphology: size, shape, and, by extension, behavior. Asexual eukaryotes and prokaryotes simply can't play this game, because they can't build differentiated multicellular structures."

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GPJ