Evolutionary advantage of Cambrian O2 production?

[jerrywickey]

Cambrian was the evolutionary advantage of Cambrian micro-organism's ability to liberate oxygen from CO2?

 

Of course we breathe O2 which in does not prebiotically, due to its strong affinity to carbon or hydrogen. Early Cambrian organisms must have liberated oxygen from carbon to give us what we breath today.

 

This process had to be extremely robust to accumulate the tremendous current atmospheric oxygen reservoir in only a few billion years, essentially exhausting atmospheric CO2. Oxygen was a waste product for some very successful organism.

 

However, as the atmospheric CO2 level dropped to half what it started, this theoretical organism must have found an evolutionary advantage to reordering its oxygen producing biochemistry. It had to make this evolutionary choice over much more likely evolutionary choices, given the dwindling CO2 levels.

 

But in fact it did make the evolutionary choice, selecting to continue producing a waste product under increasingly scarce CO2.

 

Any one have any ideas what the evolutionary advantage of producing Cambrian O2?

 

Jerry

[CDarwin]

For one thing, the oxygenation of the atmosphere occurred considerably earlier than the Cambrian. That process was an untended consequence of photosynthesis, whose advantage I should think would be clear as a food source.

[SkepticLance]

The oldest probable fossils of cyanobacteria were stromatolites from Western Australia dated to about 3.6 billion years ago - way before the Cambrian.

 

http://www.fossilmall.com/Science/About_Stromatolite.htm

 

However, the geological record shows that it took about a billion years for the world to convert from an anaerobic atmosphere to a fully aerobic one. It appears that iron compounds absorbed the iron for most of that billion years.

 

This means oxygen was a major part of the Earth's atmosphere for something close to 2 billion years.

 

What was the evolutionary advantage? In short - zero. In fact, it was a major disaster. Most of the organisms living at the time were obligate anaerobes, which meant that oxygen was a toxic polllutant to them. The carnage must have been dreadful.

 

However, there is always a silver lining. In time, new organisms came into being that were able to use oxygen as an energy source, by oxidising organic compounds. This released far more energy per gram of fuel than anaerobic processes, which opened the way for the evolution of high energy organisms. In time, multicellular organisms capable of vigorous movement developed, and the eventual outcome was warm blooded birds and mammals.

 

Humans and our close relatives require a massive energy source, which is not possible without an oxygen atmosphere.

[jerrywickey]

Thanks,

 

That clears some things up. (apparently, I misspoke, is Cambrian the period from half billion years ago to about 1 billion years. I intended to refer to the three billion years prior)

 

What quantity over what period of time would cyano-bacteria need to produce the atmospheric reservoir of O2 we see today?

 

Would it have taken the entire 3 billion years? Or did the cyano-bacteria produce the current level of O2 long before the Cambrian?

 

I am trying to find just how early these O2 producers must have existed. I would like to see just how early this must have taken place.

 

I am learning so much from my early evolution simulation software. I am trying to find a plausible model for entire genetic sequences to be borrowed and exchanged.

 

A process which must have been as common and robust as O2 production is a good starting point for this model.

 

Jerry

[SkepticLance]

To jerry

 

The oxygen content of the atmosphere has varied over time. The cyanobacteria seem to have taken about a billion years to create an atmosphere with large amounts of oxygen, but not what we have today. That happens in its entirety much later, with a world including green plants.

Cyanobacteria are not, of course, plants. They are photosynthetic bacteria.

 

Dates are a bit uncertain. The first organic traces come from Canadian rocks dated to 3.8 billion years ago. That is not proof of life, since the organic molecules present in those rocks might have come from a different source. Personally, I think it makes sense that this is a trace of early life.

 

The Earth came into being about 4 to 4.5 billion years ago, and after a turbulent start (lots of collisions) was geologically reasonably stable at 4 billion years ago. Life probably began 3.5 to 4 billion years ago.

 

The Australian stromatolite fossils are a bit controversial, and some people say they are not true fossils. However, as far as I can make out, those people are a minority. If the stromatolites are true fossils, then we have a clear indication that cyanobacteria were living 3.5 billion years ago.

 

Iron oxides are very rich in strata formed over the next billion years or so, and this is taken as an indication that those chemicals were absorbing oxygen. This probably prevented the air having much oxygen. Younger strata are, by comparison, iron oxide deficient, suggesting that all the available iron had been oxidised.

 

True green plants appear to have arisen about a billion years ago, or perhaps a bit earlier. The first ones would not have left fossil imprints, so the exact date is unsure.

[jerrywickey]

What bioactivity would have been required to free oxygen?

 

Could this have been done entirely by RNA? Or would protein function, perhaps, the earliest protein domains, with catalytic activity have been required?

 

Some process which ultimately enhanced reproductive success, and which had oxygen liberation as a byproduct, could be very complex. But what ever it was must have been simple enough to have arisen with out well evolutionarily developed genetic regulation for protein domain recombination. The likes of which we observe today.

 

Are you aware of any protein domain transfer or recombination mechanisms which are not regulated by well evolutionarily developed genetic regulatory systems?

 

How simple could these bugs have been?

 

Jerry

[SkepticLance]

Jerry

 

You are asking some very difficult questions. I would have to do quite a bit of research to answer those questions for modern day cyanobacteria. Certainly, I could not for the first photosynthesizers. I doubt anyone could, since the fossil record does not include soft tissues, and anything else is speculation.