What role did cyanobacteria play in the transformation of Earth's early atmosphere?
1 Answer
Funny you should ask - just doing a course on this subject now myself! They changed the atmosphere profoundly and changed th course of biological evolution.
Explanation:
Cyanobacteria probably formed a partnership with chloroplast bacteria around 2 billion years ago - the chloroplasts were engulfed by the cyanobacteria and formed a symbiotic relationship. Together they discovered photosynthesis - the ability to harvest energy from the sun and turn it, plus CO2 and water, into nutrients. The first photosynthesizes were anoxic, but the second generation could withstand oxygen. Once they got going, they took over like gangbusters. They started to release huge amounts of oxygen as a waste product, first in the oceans and then later into the atmosphere.
This caused the Earth's first extinction event when all of the earlier prokaryotic cells who thrived in an oxygen poor world to die off. It also allowed eukaryotic cells (those having a DNA nucleus, like us and all animals) to evolve and utilize oxygen to metabolize. This sent biological evolution off in a whole new direction including eukaryotes combining together to form multi-cellular more complex organism - like clams, fish and humans much, much later on.
See link: http://anesthesiology.pubs.asahq.org/article.aspx?articleid=1922558
Gradually the oxygen level increased to today's levels and it also formed the protective ozone layer that shields us from harmful UV radiation. This also allowed critters, our distant relatives, to crawl on to the land, which up until about 400 million years ago was uninhabited due to high UV radiation.
Finally, I just learned this cool fact myself, the abundance of oxygen also gave rise to thousands of new minerals on Earth. See pic of the copper oxide mineral malachite that most people are familiar with.
The oxygen byproducts of early life created minerals! In turn, its also thought that clay minerals may have played a role in getting the first biomolecules going on Earth- crazy!
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