Oxygen May Not Be Good for You
Especially if you’re anaerobic
Oxygen is a strange element, considering it is responsible for keeping a large chunk of biological life alive, including us humans. Yet it is a highly reactive and dangerous gas, as you will soon realise if you get too much of it.
So where did all this oxygen stuff come from, and how did it come to be of use to us. I mean the Earth for most of it’s life had an atmosphere that was dirty and smelly in human terms, and not conducive to a long and happy life if you were to snort it every day.
There were of course plenty of bacteria and other life forms that didn’t need, or want oxygen, to have a comfortable time, but these tended to be simple life-forms, and it was the arrival of an oxygen-rich environment that allowed the explosion of multicellular and complex life as we know it today.
The initial providers of this oxygen were a form of bacteria, the cyanobacteria, who perfected a little trick called photosynthesis.
Cyanobacteria were crucial in the development of photosynthesis, which led to the production of oxygen as a by-product, and this process fundamentally changed the Earth’s atmosphere and supported the evolution of aerobic life forms, which fundamentally transformed Earth’s atmosphere and set the stage for the evolution of complex life.
The story of how cyanobacteria invented oxygenic photosynthesis and transformed the early Earth is a remarkable tale of evolutionary innovation.
These clever little microscopic organisms, dating back over 3 billion years, stumbled upon the ability to split water molecules and harness the sun’s energy, releasing oxygen as a by-product. At first, this oxygen was toxic to most lifeforms on the planet, but the cyanobacteria evolved to detoxify it, so over time, the cyanobacteria’s oxygen production dramatically changed the atmospheric composition, leading to the “Great Oxidation Event” around 2.4 billion years ago.
This event, though great for the folks who like the taste of oxygen, also had some adverse effects, notably, it also triggered a global ice age that nearly wiped out all life. The increase in oxygen levels led to significant environmental changes, including these severe glaciations known as “Snowball Earth” periods.
Remarkably, the basic process of oxygenic photosynthesis invented by cyanobacteria has been passed down and co-opted by other organisms over billions of years of evolution. From the engulfment of cyanobacteria by other microbes to form algae, to the eventual evolution of land plants, this ancient innovation has coloured our world green, and provided the oxygen we breathe.
Scientists have studied microfossils, genomes, and geochemical signatures to unravel the mysteries of this ancient innovation. The bad news is, they also predict that the Earth may eventually return to an anaerobic state in the distant future, setting the stage for new evolutionary breakthroughs.
Don’t think I’ll wait up!
Sources
Dynamic oxygen levels may have accelerated animal evolution | University of Leeds
How Microbes Evolved to Tolerate Oxygen — PMC (nih.gov)
The Great Oxidation Event: How Cyanobacteria Changed Life (asm.org)
