Geoscience Reference
In-Depth Information
CHAPter 4
Cyanobacteria: The Great Liberators
Try to imagine something so profound, so fundamental, that it changed
the whole world. Think of something so revolutionary, that it forever
changed the chemistry of the atmosphere, the chemistry of oceans and
the nature of life itself. hat about the Great Plague, the Renaissance,
or World War II? These were important events indeed, and they all
changed the course of human culture, but their influence outside the
human realm was small. hat about the extinction that killed the dino-
saurs 65 million years ago, or the great Permian extinction some 250
million years ago, which laid waste to perhaps 95% of all animal species
on the planet? We're getting closer. Each of these major extinctions
indeed changed the course of animal evolution, but still, they did not
fundamentally alter the fabric of life or the surface chemistry of Earth.
hat then, you might ask, did?
It was the evolution of cyanobacteria. These tiny unassuming crea-
tures, which we met in the last chapter, completely changed everything.
As we discussed, the evolution of cyanobacteria brought the biological
production of oxygen to Earth for the first time. This led, in turn, to the
eventual accumulation of oxygen in the atmosphere and to the wide-
spread evolution of oxygen-utilizing organisms. These points will be
explored in detail in subsequent chapters. The importance of cyano-
bacteria, however, goes beyond this. As we have learned, cyanobacteria
were the first photosynthetic organisms on Earth to use water as a source
 
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