tivol at tivol at
Mon Oct 17 23:46:00 EST 1994

Bill Poulin asks about oxygen and the history of lower plants.
Dear Bill,
	When I took biology, the plant groups you mention were thought to be
the *decendants* of blue-green algae, not their *ancestors*.  As to your
question; it is my understanding that the earth's atmosphere had no free
oxygen until after the blue-green algae produced it.  In fact, a seminar on
superoxide dismutase started with the exposition of the plot of the blue-
green algae to take over the world by producing this toxin (O2).  Unfortu-
nately for them (but lucky for the rest of us) the rest of the biosphere was
up to the task of stopping this dastardly plot by "inventing" SOD.  I'm sure
there are many botanical experts out there who will be only too glad to cor-
rect any innacuracies in this post.
				Bill Tivol

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