On Sat, 12 Apr 2008 16:30:58 -0700 (PDT), Gareth Wilson
<wilsong2@[EMAIL PROTECTED]
> wrote:
>I've just read a paper which discusses bottlenecks in the evolution of
>intelligent life. It points out that oxygen-producing photosynthesis
>evolved only once and might be one of the less likely steps towards
>the modern biosphere. So, suppose it never evolved. The productive
>base of the biosphere becomes the other types of photosynthesis, which
>don't use water as an electron donor and don't produce oxygen. After
>billions of years of evolution, what does life on Earth look like? One
>possibility is a sulphur-hydrogen sulphide cycle. There are already
>bacteria that use photosynthesis to release sulphur from hydrogen
>sulphide, and other bacteria that "burn" glucose using sulphur or
>sulphates instead of oxygen, producing hydrogen sulphide. You could
>easily imagine "plants" doing the former and "animals" doing the
>latter - except the amount of energy involved is a fraction of what
>you get with oxygen and water. Any other suggestions?
Besides the sulphur bacteria you mention, methanogens
<http://en.wikipedia.org/wiki/Methanogen>,
which combine carbon
monoxide with hydrogen to release methane are well known and flourish
in extreme environments where there is no oxygen. They are believed to
have thrived on Earth billions of years ago before cyanobacteria
became a dominant life form and released large quantities of a deadly
new poison known as oxygen into the atmosphere.
--
Cause, really, nothing says "I'm a counter culture
rebel, fighting the establishment" like an Aibo on
a skateboard.
- Seen on Slashdot
Roberto Castillo
robertocastillo@[EMAIL PROTECTED]
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