Ahhh, Life…

March 24th, 2006

A study out in Science today uses the new field of bioinformatics to determine how organisms went from anaerobic to having metabolic processes dependent on oxygen. The intricate tale that they weave describes the steps that must have been necessary, yet were so unlikely to occur at times. You see, we live in a caustic environment. Oxygen is incredibly reactive, and although we and most life on Earth depend on it, it is a corrosive bath in which we have fought through time to be able to survive.

There are many steps as yet undetermined, but the authors, Raymond and Segre, found through their analyses that there has to have been a distinct procession of chemical steps that pushed life to higher metabolic complexity. When life began on earth, it was dominated by anaerobic organisms that were able to capitalize on the reductive molecules available at the time. However, they lacked the metabolic pathways to be able to oxidize the large supply of H2O. So, it wasn’t until the evolution of photosynthesis that organisms began to take advantage of electron-donating water, releasing oxygen into the atmosphere. The shift to oxygen then moved evolution more rapidly as organisms had to create new ways of protecting themselves from the ravages of such a reactive compound. At the same time the atmosphere and oceans were filling with oxygen released as a metabolic by-product of the growing populations of photosynthesizing organisms. The anaerobes became relegated to pockets within the environment as oxygen became more and more plentiful. Oxygen soon supplanted other reactive chemicals that organisms had relied upon for so long, and forced organisms to find ways to use organic materials in order to reduce oxygen to water. This led to the development of respiration, which uses both aerobic and anaerobic processes to create energy. Respiration created new problems for cellular organisms to deal with, requiring even more creative metabolic solutions, and thus spurred evolution to advance once again. Since then the fight to live dependant upong oxygen has given rise to eukaryotic, multi-cellular, organisms – the plants and then the animals.

All the diversity we see around us has come from the fight to survive in one way or another. Whether it be to out-smart oxygen or a cunning predator, life is always full of incredible solutions. And, it is able to respond quickly to environmental challenges, leading ever onward on its unknown path.

I haven’t figured out how to embed images in my posts yet (is moveable type really as complicated as it seems? or is it just that they have a crap help section?), so here is the link to the graphic relation of these processes. You may not be able to see it if you are not subscribed to Science.)

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