Why does everybody always seem to forget about the chemistry of evolution? Shells and plates require complex processes to turn calcium carbonate from the sea into shells on the backs of animals. The "Oxygen Revolution" changed life on Earth, allowing higher metabolism (Krebs Cycle) and wiping out life forms to create open niches. Nitrogen and phosphate also contribute to evolution because they allow animals to diversify and grow. DNA changes can’t be ignored either, nor can the switch to heterotrophic feeding that allowed animals to grow in volume instead of spreading out for yet more surface area. And we haven’t even begun to talk about the way the organisms themselves affect their chemical environment and how that environment then affects the organisms. Evolution is very much like a series of reinforcing cycles that once begun are too complicated and powerful to stop. Besides, trying to chemically regulate this planet would be like trying to put out a fire with lighter fluid--who knows what effects it would have on the ecosystem here. Instead of harmless trilobites we might end up with all kinds of mutant life forms completely alien to our understanding and far beyond our control. It was a mistake to "adjust" this planet once for humans and doing it a second time would only create more problems. P-L5 was better left alone!
Leads and Sources
Magazines and Articles:
"When Life Exploded," J. Madeleine Nash. Cover Story Time Magazine December 4, 1995.
"On Embryos and Ancestors," Stephen Jay Gould. Natural History 7/98-8/98, p. 20.
"The Evolution of Life on the Earth," Stephen Jay Gould. Scientific American October 1994, p. 85.
"Breathing Room for Early Animals" (Oxygen), Andrew H. Knoll. Nature Vol. 382, July 11, 1996, p. 111.
"The Big Bang of Animal Evolution," Jeffrey Levinton. Scientific American November 1992.
"Hypersea," Dianna and Mark McMenamin. Discover October 1995, p. 76.
"The Emergence of Animals," Mark McMenamin. Scientific American April 1987, p. 94.
"Life’s Grand Explosions." (theories on why the Cambrian explosion occurred), Lori Oliwenstein. Discover January 1996, p. 42.
"The Molecular Explosion," Henry Gee. Nature Vol. 373, February 16,1995, p. 558.
Internet sites:
The Divisions of Precambrian Time
http://www.ucmp.berkeley.edu/precambrian/precambrian.htmlLife of the Vendian
http://www.ucmp.berkeley.edu/vendian/vendianlife.htmlLearning About the Vendian Animals
http://www.ucmp.berkeley.edu/vendian/critters.htmlOxygen Pulse and the Evolutionary Expansion of the Metazoans
http://www.geocities.com/CapeCanaveral/Hangar/8200/Oxygenation.htmlCambrian Explosion
http://www.carleton.ca/Museum/camex/1ahome.html
Books:
The Emergence of Animals: The Cambrian Breakthrough. Mark and Dianna McMenamin, 1990, Columbia University Press.
Biology: The Science of Life. Wallace, Sanders and Ferl, 4th ed., 1996, Addison-Wesley.