Hoping for new life

I already told you about my struggle on growing Mediterranean tree species in Austria. Well, our orange trees are doing pretty well, but I am starting to loose my faith on the survival of the pine tree. I think it might have frozen as we were in Spain last Christmas.

I'm afraid the day will come when I'll have to accept the evidence and throw my little pine away. Knowing that I will be very sad about it, I decided to make up to myself for it by letting new life sprout before the day comes. Just in case.

It all started in the Paleoproterozoic, around 3000 million years ago, as the ice cap of the Makganyene glaciation (which might have covered the whole planet) retreated and left space for a vast ancestral ocean.

Two types of living organisms survived under the ice and rapidly populated this ocean. Archaea, which used several sources of energy such as sulphur or ammonia and produced methane as waste product, and a new kind of bacteria, the Cyanobacteria, able to obtain their energy through photosynthesis, a process that converts sunlight and carbon dioxide (CO₂) into energy, releasing oxygen (O₂) as a waste product.



These cyanobacteria were so successful at reproducing and colonising the ocean that they actually changed the composition of the atmosphere and were going to shape the world for the next 3000 million years. Before cyanobacteria existed, there was not much oxygen in the atmosphere. Free oxygen in large amounts was in fact poisonous to most of the living creatures at the time, especially to archaea. Most life on Earth vanished in what is known as the Oxygen Catastrophe^(*).

But serious stress factors like this great oxidizing event are notably the source of big evolutionary pushes: a whole new kind of bacterial organisms evolved, aerobic bacteria, which used oxygen (now available in huge amounts) as a source of energy, producing carbon dioxide as a waste product. And that's not all. By an outstanding touch of genius, some Archaea, facing a serious problem in this new and poisonous oxygen-rich environment, incorporated cyanobacteria or proteobacteria (a kind of aerobic bacteria) through the cellular membrane into their cellular bodies and used part of the energy produced by them to keep themselves alive. This brilliant trick, known as endosymbiosis, would be the origin of the eukaryotic cells, which contain several membrane-bound structures, each one specialising in a different function.

Those Archaea that associated with aerobic bacteria (which needed oxygen) were the basis for the fauna, to which we humans ^(**) belong as well. From Archaea that associated with cyanobacteria (which produced oxygen through photosynthesis) would originate the flora, that is, multi-celled living creatures able to obtain energy from sunlight through photosynthesis.

^(***)

I've been thinking about this long story, this long evolutive path, as I was sowing orange and lemon seeds to give plant life another chance. Now wake up!, you little seeds. Wake up from your long sleep, let sunshine and water put you in alert and consummate once again the miracle of life for me!

^(*) This Oxygen Catastrophe in the Paleoproterozoic raised the atmospherical oxygen concentration to 4%. To reach the current level of 21% a colonisation of the land masses by plants and woods would be needed.

^(**) Not all Archaea disappeared in the Paleoproterozoic. In fact, a great number of them are alive and well, living in the most incredible places. Big colonies of Methanobrevibacter smithii, for instance, live in the human gut and help us with digestion.

^(***) Taronger is the Catalan word for "orange tree".