Cambrian Explosion: role of oxygen (Introduction)

by David Turell @, Tuesday, December 01, 2015, 15:23 (1579 days ago) @ David Turell

This article explains how oxygen appeared 800-600 million yeas ago in the oceans. Obviously this allowed the development of complex animals, but doesn't explain why or how they developed:

"Our oceans became fully oxygenated at around 800 to 600 million years ago, when atmospheric oxygen reached modern concentrations. Crucially, this allowed for the evolution of animals and the beginning of our modern Earth System. It has long been known that cyanobacteria were the first microorganisms capable of producing oxygen. They did this through photosynthesis - a process that transforms energy from the sun into sugars and oxygen using carbon dioxide and water. Scientists have been trying to work out why it took so long for the Earth's atmosphere to reach modern concentrations of oxygen, when photosynthesis had already evolved by around 2,700 million years ago.


"Early on, these cyanobacteria dominated only terrestrial and coastal environments, and with relatively low impact on the Earth's nutrient cycles. It was only when they properly colonised the oceans that the major, planet-altering event occurred.


"'Rather surprisingly, marine planktonic cyanobacteria are relatively young, only evolving just prior to the origin of complex life - animals. By producing oxygen in vast quantities, these cyanobacteria enabled the development of complex life in our oceans. These biological events are linked - they help explain why it took so long for complex life to evolve on our planet. Cyanobacteria needed to colonise the oceans first',

"'This study shows that several factors contributed to the delay of the oxygenation of the Earth's oceans. Firstly, cyanobacteria evolved in freshwater habitats and not in marine habitats as previously thought, and, second, marine productivity had a huge boost when cyanobacteria were finally able to colonise marine habitats; this allowed for the production of oxygen and carbon burial at unprecedented levels.'

"'The genomic revolution has hugely improved our understanding of the tree of life of cyanobacteria. Without cyanobacteria, complex life on our planet as we know it simply would not have happened.' said Dr Sánchez-Baracaldo."

Comment: Either great planning or lots of lucky sequential chance events.

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