posted by Laurel .
What is the "Oxygen Catastrophe"
Why was it so important for life on this planet?
Most articles are hard to understand.
This is one of the more readable articles I could find:
The oxygen catastrophe refers to a time about 2.7 billion years ago when organisms that support photosynthesis appeared, and began consuming carbon dioxide and adding oxygen to the atmosphere. This eventually caused the class of anaerobic organisms to become extinct. (Some such organisms, for which oxygen is toxic, still exist as a class of bacteria, in places where there is no air). The time of the catastrophe can be pinpointed by the sudden appearance of iron oxide in age-dated rocks.
It was not a "catstrophe" for animals that use the oxidation of food as a source for energy, but rather marked the beginning of their evolution.