Read about the great oxygenation event. Life used to exist without oxygen. And oxygen was toxic to it. Cyanobacteria then emerged to which oxygen wasn’t toxic anymore? How were Cyanobacteria protected from Oxygen? Did the process happen in stages? What were the stages?
In: 3
From what I understand, it was still quite toxic, but not as directly. It basically out-competed all the other microbial life and then decimated itself in an ice age as explained towards the end of [this video](https://youtu.be/H476c8UjLXY)
It’s only because a small fraction survived that we exist.
The chemistry of breaking water apart for energy with the sun’s light could have kept going, the oxygen didn’t become a factor as much until the seas were saturated by it. But it caused temperatures to drop covering the oceans in ice thereby cutting off the sun to most areas. Mutations evolved to help a little but it was ultimately the oxygen changing the atmosphere that got them.
From what I remember (and I have no clue from where, so don’t trust me too much), cyanobacteria evolved to squirt out oxygen as a method of killing off their competition.
The oxygen they put out was used to poison competing bacteria to death.
Similar to how modern day snakes are immune to their own venom, cyanobacteria were at least partially immune to their own “poison”, oxygen.
As for how it happened, I’m not sure, but most kinds of things like this happen because an organism starts excreting waste, then they evolve to resist their waste a bit, which lets them use the waste to ward off competition, so the waste gets more toxic, so they evolve to be even more immune, evolve to make their waste even more toxic, and so on.
Again, this is all coming from a very vague memory from years ago, so don’t trust me too much.
Some cyanobacteria ancestors had a random mutation that caused them to free oxygen from a water or CO2 molecule, creating a free oxygen atom. The bacteria that could tolerate the oxygen being free was able to create baby bacteria that could also tolerate that little bit of oxygen.
As time went on, more and more free oxygen built up and the bacteria that could tolerate it (through random mutation) were the only ones able to create more baby bacteria, so the new baby bacteria was able to tolerate more oxygen.
That cycle repeated for many generations, we call the process “survival of the fittest.”. The survival of the oxygen tolerant babies is known as ‘selection’ of the fittest.
Latest Answers