Re: Different Forms of Life (Copy)

From: TomHendricks474 (tomhendricks474_at_cs.com)
Date: 09/23/04 

Date: Thu, 23 Sep 2004 17:50:35 +0000 (UTC)

>> > IMO the more we know about life, the more we will
>> > see how locked in it is to certain conditions.
>> > Sci-fi lets' us imagine anything as does early
>> > unproven speculation. But as the origin becomes
>> > deciferable, we'll find it limits what life is
>> > and where it can be, much much much more than
>> > most think now.
>>
>> Interestingly, the last few decades has taken the opposite
>direction.
>> Extremophiles are now found deep in the rocky mantle, high
>in the atmosphere
>> and around oceanic vents, where we used to assume life was
>impossible. If
>> life has evolved elsewhere, I think we'll find it can
>thrive in even more
>> extremely diverse and "inhospitable" (from our viewpoint)
>habitats than ones
>> just here on this planet. If I were a betting man and
>thought that any of
>> this can be proven in my lifetime, I'd even propose a
>wager that whatever
>> life we find will not have DNA, nor anything we'd consider
>a variant, as its
>> base. Regards, Brett.

TH
I don't think so. The extremophiles on planet earth took
4 billion years to evolve that ability. Our common
ancestor probably was formed in a very specific
set of circumstances that began with a heat cycle
and water in liquid form (which limits the heat cycle
to an amazingly short short short temp range - and
if its also a wet/dry cycle, then we are left with
an almost exact temp range of near 100C to allow for
water and steam both.

Further an important clue is that nucleic acids
absorb UV at 260nm. IF that is indeed a key element then
life is almost point-on specific.
Your scenario of anything goes would have to be supported by some 'for
instance' before I would
change my mind on this.

-----
>I completely agree on all points, Brett. It may well turn
>out that the primary criterion for life is the necessity for
>complexity, and it may be achieved over many paths and
>materials. ...tonyC

TH
Again that is hard to support with facts. The complexity
comes from ways to survive the heat cycle IMO.
So life is not a first event, it is a reaction to what
comes before it. You can't begin in the middle of the
process. Life cannot come before certain earlier instances. Life cannot exist
without the heat cycle
that produces the monomers for it, stirs the
primordial soup pot, powers it with endless cyclic
energy in a reasonably constant form (with enough
variation to make variants and have some variants more
stable - that lead to even more stable variants) and
selects some variants over others through UV damage, etc.

Relevant Pages

  • Re: Different Forms of Life (Copy)
    ... The extremophiles on planet earth took ... > and water in liquid form (which limits the heat cycle ... > element then life is almost point-on specific. ... > variation to make variants and have some variants more ...
    (sci.bio.evolution)
  • Re: No Grace Period for Metabolism Either
    ... >> how that would lead to life. ... >> We have taken the heat cycle for granted. ... (One can see the sun cycle in every living thing ... Note how all life shuts down in low energy, and speeds up in high - its clear ...
    (sci.bio.evolution)
  • Re: Not Hydrothermal Vents
    ... >It's not unreasonable to assume that hydrothermal vents have been a constant ... but the sun heat cycle has been more consistent over a longer ... It is conceivable with lots of fluke factor that life could adjust to moving ... >throughout the oceans have also existed since that time. ...
    (sci.bio.evolution)
  • Re: Ventists - what about UV repair? (resend)
    ... hyperthermophilic bacteria and archaea at the roots of the ... ``Extremophiles, especially hyperthermophiles, possess slow ... specialised organisms had more-or-less stayed put in their ... Even Woese agrees that the earliest forms of life constituted a community ...
    (sci.bio.evolution)
  • Photolysis Inhibited by Amino Acids
    ... hypothesis to explain origin of life" if yes than how much is ihas been ... If you do not have a heat cycle, ... The heat cycle should be a law. ... forced on a chemical system by the sun heat cycle. ...
    (sci.bio.evolution)