Earth after life

Debate and discussion of any biological questions not pertaining to a particular topic.

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Balanchine
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Earth after life

Post by Balanchine » Sun Feb 24, 2008 12:55 am

Let's suppose that virtually all animal and plant life were quickly obliterated from planet earth. And that this included the oceans down to the level of algae and most plankton. Let's also assume that bacteria would survive in soil and wherever else it managed to find a foothold.

How long would the atmosphere survive?
Are there bacteria that produce oxygen, and if so, would it be enough to sustain human life?
If there were humans able to survive - in salt mines, etc. - would they survive on whatver oxygen remained in the atmosphere, and for how long? (this is also probably a weather/chemistry question too, I'd imagine)

Just curious. Thanks for any input.

An obvious non-biologist,
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mith
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Post by mith » Sun Feb 24, 2008 2:41 am

Living one day at a time;
Enjoying one moment at a time;
Accepting hardships as the pathway to peace;
~Niebuhr

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Re: Earth after life

Post by Balanchine » Sun Feb 24, 2008 2:56 am

Thanks for the link. I see registration is required to read the article, which at this point I'm declining to do... I appreciate your taking the time to reply, though!

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mith
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Post by mith » Sun Feb 24, 2008 3:50 am

You don't need it, this is the first line of the preveiw


The total mass of the atmosphere is estimated to be some 5.5 quadrillion (55 followed by 14 zeros) tons (4.99 quadrillion metric tons).
Living one day at a time;
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Accepting hardships as the pathway to peace;
~Niebuhr

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Re: Earth after life

Post by Balanchine » Sun Feb 24, 2008 3:56 am

Thanks again, Mith... that's a pretty heavy load, I agree. I was just wondering how long it would last if there were no plants to resupply the oxygen, and if there were any bacteria that do and would contribute to the oxygen supply.

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mith
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Post by mith » Sun Feb 24, 2008 4:42 am

Well most oxygen is produced in the ocean by plankton (blue-green algae?) which aren't really plants. So no, we'd be in fine shape.
Living one day at a time;
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Re: Earth after life

Post by Balanchine » Sun Feb 24, 2008 5:44 pm

I'd sort of kind of figured that might be the case. But what, then, would happen if all that algae were gone? Would the existing 20% oxygen in the earth simply remain as it is in the atmosphere? If, say, a million humans survived to try and re-populate the planet, how long would it take them to use up that 20% (leaving aside for the moment the question of where they'd get their food). I wonder....

Thanks again, Mith, for replying.

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Post by mith » Sun Feb 24, 2008 6:03 pm

I was going to do a rough calculation considering how much oxygen people breathe per minute...but then I realized that most oxygen is used in other ways---bacteria, other animals, combustion...etc etc.

http://answers.yahoo.com/question/index ... 223AAK0sWQ

But assume 1 person = 30g/hour

Lifespan = 500000 hours ~ 57 years

Then lifespan consumption ~ 15000kg

You can support around 7 * 10^10 people for 57 years. or around 1million people for 70,000 years.

Of course these numbers are grossly inflated, I'd assume some sort of industrial activity and at least some forms of life present to provide food etc...
Living one day at a time;
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Accepting hardships as the pathway to peace;
~Niebuhr

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Re: Earth after life

Post by Balanchine » Sun Feb 24, 2008 6:08 pm

Mith.... you are the person!

thanks.
B

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mith
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Post by mith » Sun Feb 24, 2008 8:44 pm

Man, I am the man.
Living one day at a time;
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Accepting hardships as the pathway to peace;
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Post by canalon » Mon Feb 25, 2008 8:17 pm

although you have to take into account that human dies way before the O2 level reach 0%. I am not really sure how much would be fatal, considering that if the depletion is slow enough it gives us time to adapt, just as when living at high altitude, but I suspect that we might all be dead long before half the O2 has been used.
Patrick

Science has proof without any certainty. Creationists have certainty without
any proof. (Ashley Montague)

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Re: Earth after life

Post by Balanchine » Mon Feb 25, 2008 8:31 pm

Good point, Canalon, and thanks for responding. Like Mith, you are also The Man. But I'm still wondering about any changes to the 02 over time... does sunlight, for instance, break down oxygen? Would it be absorbed by anything else in the environment - those dead seas, the rocks and earth, etc.?

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