Captain Jack
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I'm reading up a little about plant biology and a book states all the oxygen on earth was produced by plants. Is that being literal (there was little or no oxygen on earth until plants evolved) or is it just saying that over time all oxygen will have gone through the cycle and is likely now all from plants?
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Asklepios
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There was very little oxygen in the atmosphere when the Earth was first 'formed.' Wasn't till early form of photosynthetic life came about that the atmosphere became enriched in oxygen.

http://en.m.wikipedia.org/wiki/Histo...and_atmosphere


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miser
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When I was a child I remember reading in a book that before the planet was filled with oxygen, there was carbon dioxide. The book had an illustration of plants and animals in this environment. However, I've never come across anything like this since, so I'm hesitant to believe it.

What I can say is that 2.3 billion years ago, there was what's called the Great Oxygen Event, which is when the earth suddenly went from having little oxygen to having enough to support oxygen-breathing life (aerobic organisms).

The oxygen was produced by cyanobacteria, which absorbed carbon dioxide and released oxygen (through photosynthesis). They had been doing this for a long time (many millions of years), but the oxygen would be absorbed by things on the earth's surface. Eventually these things couldn't absorb any more oxygen, so suddenly the oxygen started filling the atmosphere, allowing aerobic life to evolve.
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Eloades11
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(Original post by Captain Jack)
I'm reading up a little about plant biology and a book states all the oxygen on earth was produced by plants. Is that being literal (there was little or no oxygen on earth until plants evolved) or is it just saying that over time all oxygen will have gone through the cycle and is likely now all from plants?
It sounds like a silly book if you ask me. I can't really add to what the others have said, but cyanobacteria was producing oxygen long before the plants came along. A good proportion of the oxygen in our atmosphere is down to photosynthesising bacteria, but the proportions are almost impossible to measure.

It's quite possible it's all gone through the cycle again through plants, but that could be said the same for water and a lot of other elements, it's not that significant. The water from my eyes may have previously come from the Queen's toilet ect ect...
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Gwilym101
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The elements pre-date plants by billions of years.

In the early earth there was very little pure oxygen in the atmosphere, so early plants utilised abundant gases such as Carbon Dioxide to create food and expelled oxygen as a waste product. As time passed, the atmosphere because more and more enriched with oxygen.
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Captain Jack
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(Original post by Asklepios)
There was very little oxygen in the atmosphere when the Earth was first 'formed.' Wasn't till early form of photosynthetic life came about that the atmosphere became enriched in oxygen.

http://en.m.wikipedia.org/wiki/Histo...and_atmosphere


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(Original post by AlphaNick)
there must have been at least a tiny bit of oxygen on Earth beforehand, considering Earth was compromised of all elements up to iron (and beyond a little bit) it would be strange if it didn't have some oxygen.
(Original post by miser)
When I was a child I remember reading in a book that before the planet was filled with oxygen, there was carbon dioxide. The book had an illustration of plants and animals in this environment. However, I've never come across anything like this since, so I'm hesitant to believe it.

What I can say is that 2.3 billion years ago, there was what's called the Great Oxygen Event, which is when the earth suddenly went from having little oxygen to having enough to support oxygen-breathing life (aerobic organisms).

The oxygen was produced by cyanobacteria, which absorbed carbon dioxide and released oxygen (through photosynthesis). They had been doing this for a long time (many millions of years), but the oxygen would be absorbed by things on the earth's surface. Eventually these things couldn't absorb any more oxygen, so suddenly the oxygen started filling the atmosphere, allowing aerobic life to evolve.
(Original post by Eloades11)
It sounds like a silly book if you ask me. I can't really add to what the others have said, but cyanobacteria was producing oxygen long before the plants came along. A good proportion of the oxygen in our atmosphere is down to photosynthesising bacteria, but the proportions are almost impossible to measure.

It's quite possible it's all gone through the cycle again through plants, but that could be said the same for water and a lot of other elements, it's not that significant. The water from my eyes may have previously come from the Queen's toilet ect ect...
(Original post by Gwilym101)
The elements pre-date plants by billions of years.

In the early earth there was very little pure oxygen in the atmosphere, so early plants utilised abundant gases such as Carbon Dioxide to create food and expelled oxygen as a waste product. As time passed, the atmosphere because more and more enriched with oxygen.
Thanks everyone - this is all quite fascinating. I'd never really given it much thought before.

I was wondering, probably ridiculously, what would happen if people cutting down forests and trees. Will the quality / level of oxygen eventually decline to a point where it starts to affect our health, and in such an event, would it not take years to turn it back around? I'm thinking many years into the future when the human population is even greater. Total science fiction nonsense because I'm sure that even if the human population were to triple, our oxygen consumption would barely scratch the surface.

I do love the fact that animals and other organisms that require oxygen couldn't have existed until the bacteria and plants created enough to sustain them.
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miser
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(Original post by Captain Jack)
Thanks everyone - this is all quite fascinating. I'd never really given it much thought before.

I was wondering, probably ridiculously, what would happen if people cutting down forests and trees. Will the quality / level of oxygen eventually decline to a point where it starts to affect our health, and in such an event, would it not take years to turn it back around? I'm thinking many years into the future when the human population is even greater. Total science fiction nonsense because I'm sure that even if the human population were to triple, our oxygen consumption would barely scratch the surface.

I do love the fact that animals and other organisms that require oxygen couldn't have existed until the bacteria and plants created enough to sustain them.
Yeah, cutting down trees could certainly affect the planet's oxygen levels. The Amazon rainforest alone contributes 20% of the world's oxygen. I expect we'd have technology in the future to recover oxygen without trees though. We've already created artificial leaves that photosynthesise. If we manufactured enough of things like that, I think we could survive okay.

It's also the case that humans can, over time and through generations, adapt to low-oxygen environments like mountain regions.
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Captain Jack
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(Original post by miser)
I expect we'd have technology in the future to recover oxygen without trees though. We've already created artificial leaves that photosynthesise. If we manufactured enough of things like that, I think we could survive okay.
:eek:
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Kallisto
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(Original post by Captain Jack)
I'm reading up a little about plant biology and a book states all the oxygen on earth was produced by plants. Is that being literal (there was little or no oxygen on earth until plants evolved) or is it just saying that over time all oxygen will have gone through the cycle and is likely now all from plants?
I might be wrong, but before the first plants were emerged on earth, water was already in existence. And water also consists of oxygen...
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The Master Cheif
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Some prokyrotic organism like cynobactria where production O2 as an result of photosynthesis before the Cambrian explosion when eukroyotic plant organism took to land.
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Captain Jack
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(Original post by The Master Cheif)
Some prokyrotic organism like cynobactria where production O2 as an result of photosynthesis before the Cambrian explosion when eukroyotic plant organism took to land.
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