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Life on Earth

  1. Jun 30, 2005 #1
    Accorinding to a lot of data and information, it seems that the possibility of producing life is too small. Does it mean that the life on Earth is not formed 'accidentially'? I do not mean that there must be a God (as it is not a religious forum). However, does the too small possiblity means that there is acutally an undiscovered law governing the universe? What do you think?
     
  2. jcsd
  3. Jun 30, 2005 #2
    Some believe the origins of biomolecules came from debris from outer space.
     
  4. Jun 30, 2005 #3
    Life came from cells,
    Cell is composed of chemical elements
    Chemical elements are divided into organic and inorganic ones
    Although there wouldnot have been many organic elements on early earth, from small amount of them small parts of cell were created, then under some conditions of primitive environment, they needed to divide to survive and grow.
     
  5. Jun 30, 2005 #4

    wolram

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    For life to be universal it must have a plan, at least to get to the single cell
    stage, AFAIK no one can make life from a chemistry set, so it seems to me
    that life would be a very rare occurence.
     
  6. Jun 30, 2005 #5
    it doesn't really help prove god, or 'intentional' life, it does however help disprove the liklyhood of living creatures on similiar worlds, what sort of planet would be better for life???
     
  7. Jun 30, 2005 #6
    That's true, and I haven't heard anything on this for ages. Comets contain some organic molecules... something cyanide and something else I can't remember, but it is thought that comets may be kind of 'starter packs' for life. Sounds groovy.
     
  8. Jun 30, 2005 #7

    DaveC426913

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    I still say this doesn't answer the question. So what if the molecules came from comets? How does that explain *how* life came to be?
     
  9. Jun 30, 2005 #8
    There have been several theories submitted as to how life on Earth began. For example, Stanley Miller in 1953 developed a simple experiment to prove how life may come into existance. Assuming that this process had happened after reduced molecules existed in Earth's atmosphere, Miller set up a flask of water that connected to another flask containing Hydrogen, Ammonia, and Methane. He placed small electrodes in the flask containing the gases to simulate lightning.

    When he heated the flask with water, water vapor would travel to the smaller flask with the gas and electrodes. Next the gas would be condensed back into liquid and sent back to the original flask of water and the system would circulate. He later found that his water flask found copious amounts of formaldehyde and hydrogen cyanide, precursors to life.

    Now this account is far from extensive and there is a lot to the story. For example, some people argued that the gasses he assumed to exist in early Earth are not completely accurate. However there have been more demonstrations to prove their theories.

    There is a plethora of information on the subject and I think a reason why some find it difficult to simulate is because the atmosphere of our Earth and what not is much different from when it first birthed life. As for other hidden laws we may not know of , I agree in general that this is true, because I believe that we still have much to learn in science.
     
  10. Jun 30, 2005 #9
    I wasn't trying to. I was just commenting that I had heard this theory. Explaining how to get from organic molecules to human beings is a job I'm not qualified to do. Someone else might want to, but I imagine that would be a veeeeeery long post.
     
  11. Jun 30, 2005 #10
    THAT'S THE FELLAS! Yeah, they were found to be in comets too.
     
  12. Jun 30, 2005 #11

    Moonbear

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    The problem of trying to use probability to justify that life started out as something other than a random process is that probability uses information about past occurrences to predict future occurrences of something. So, if we only know life started once (or that's our best guess anyway), that's not much of a data set to use for predicting trends or probabilities. Since we still don't know exactly how that first life came to exist, how can we really say much about the odds of it happening again? The reality is that life DID come into existence; any probability estimates are only for the chance that it can independently happen again in the future. Think of it like playing the lottery. Your odds of winning in the future could be something like 1 in 16 million (made up number). So, you could argue that you would need to buy 16 million tickets before you would win. But, that's not how it really happens. Every so often you hear of the case where some lucky person who never buys tickets walks into a convenience store and buys one ticket with the dollar in change he got from buying a jug of milk and hits the jackpot. Does that mean there was some intelligent plan or non-randomness involved? Absolutely not. The nature of true randomness is that if your odds are 1 in 16 million, you could hit it on the first try or on the 16-millionth try, or any try in between.

    The other issue I have is that there is non-randomness in the formation of chemical bonds, yet when people predict the probability of life forming, they seem to assume it had to happen through all of the necessary elements simultaneously colliding and forming life in one instant. For example, we know that all amino acids have both a common structure and R-groups that make them distinct from one another. Chemists would have a really hard time conducting any experiments or synthesizing any new compounds if chemical reactions were completely random and nothing could be predicted about the behavior of elements or compounds when they are mixed together. This does not require that there is intelligence involved in those reactions happening just because they are non-random. A molecule won't just react with any other molecule it happens to bump into, there have to be certain conditions met, but once those conditions are met, there's a very high probability that two molecules will react.

    So, just because there is a low probability of something happening a second time, and because some aspects of it are not explained by total randomness, this does not mean the only explanation is an intelligent force. It's not an either/or situation.
     
  13. Jun 30, 2005 #12

    wolram

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    This is from wikipidia
    On September 28, 1969, a meteorite that fell over Murchison, Victoria, Australia was found to contain over 90 different amino acids, nineteen of which are found in Earth life. Comets and other icy outer-solar-system bodies are thought to contain large amounts of complex carbon compounds (such as tholins) formed by these processes, in some cases so much so that the surfaces of these bodies are turned dark red or as black as asphalt. The early Earth was bombarded heavily by comets,
    So may be life or its basic building blocks were formed in space, but step 2
    finding a friendly host would be the next difficulty, step 3 evolving cellular
    structure, i think would be a matter of time and a lot of it.
     
  14. Jun 30, 2005 #13

    vanesch

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    Just as a teaser: quantum theory could play a role, in that if quantum theory is correct "all the way up", then this leads to a vastly more complicated universe (many worlds) than we observe. The devellopment of life then derives from the quantum version of the anthropological principle. The only requirement for the anthropological principle to work is that the observed universe must be only a tiny spec of the ontological universe. Now, this can be the case classically (if the universe is infinite), or you can even obtain it for a smaller scale universe, if you allow for quantum superpositions.
    Then it doesn't matter how terribly SMALL the a priori probabilities are for live to emerge: multiplied with the mindboggling size of the universe (in whatever version, which makes it much bigger than the *observable* universe), you can make them arbitrarily big. Which means that life happens *somewhere*. And if you're alive, then that somewhere must be here (that's the anthropological principle).

    Now, I realise that the anthropological principle is not liked much because it sounds like a non-falsifiable statement. It isn't, really: but we don't know enough of the true a-priori probabilities for life to emerge. Nevertheless, it is not non-falsifiable, because it makes some definite predictions: for instance, if the anthropological principle is to be invoked, this means that there are no extraterrestrial life forms in the observable universe (otherwise that would make TWO of them in a small patch of the universe (namely only about 15 billion light years across), leading to necessarily FINITE probabilities that cannot be too small, and the invocation of the anthropological principle is not necessary). Too bad for Tom Cruise :-)

    cheers,
    Patrick.
     
  15. Jun 30, 2005 #14
    A low probability for some event does not mean that it does not happen unless there is "something special".
    If you throw a dice you will witness an event that had a probability of 1/6. Throw 10 dice and you will witness an event that had a probability of only 0.000000017
     
  16. Jun 30, 2005 #15

    wolram

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    all this about probabilities reminded me of the fallen tree, one probability
    was a pink elephant in a flying saucer knocked it down, the other that the
    wind blew it down.
     
  17. Jun 30, 2005 #16
    Life schmife.

    You don't need a cell to magically appear out of primordial soup. What you need, is a replicator. Period. Once you have a replicator, "random" doesn't really apply in the same way. The replicator catalyzes its own synthesis, and the whole ball of wax takes off.

    Nucliec acid, baby, nucleic acid!

    If you go to pubmed and search on 'prebiotic chemistry' you'll find lots of neat chemistry that has been done in the last 5 - 10 years. Miller and Urey were great, but there are all sorts of shiny new experiments - things like how certain clays in lakebeds catalyze the formation of oligonucleotides. Things like how hydrothermal vents might catalyze the formation of oligonucleotides. They've managed to simulate reasonable conditions to make a 50-mer, (50 nucleotides long) which can then catalyze its own synthesis.

    And since oligonucleotides (like this 50-mer) can base pair with individual nucleotides - any sequence should automatically *catalyze* its own synthesis to a limited extent.

    So, to make the first replicator, all you need is an oligonucleotide! You can worry about cell membranes and proteins, later.

    Nucleic acid. I'm tellin' ya.
     
  18. Jun 30, 2005 #17

    saltydog

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    Can you describe the chemical environment in which this synthesis occurred?
    How about a reference? You can embed the link in the post by choosing the goggles on the tool bar, input a name for the link, then the actual link.
     
    Last edited: Jun 30, 2005
  19. Jun 30, 2005 #18
    Here's a review article from 2004:

    Orig Life Evol Biosph. 2004 Dec;34(6):549-70. Related Articles, Links

    Montmorillonite, oligonucleotides, RNA and origin of life.

    Ertem G.

    http://nai.nasa.gov/nai2005/abstracts/947 - NAI2005ABS.doc.pdf

    Also see:

    http://www.ncbi.nlm.nih.gov/entrez/...ve&db=PubMed&dopt=Abstract&list_uids=12458736

    This sort of research shows what sorts of steps *might* have happened on the early Earth. There are still too many unknowns to say with any certainty where life began (lake beds, hydrothermal vents, etc), and so on. I hope you find the references useful.
     
  20. Jun 30, 2005 #19
    Sorry - didn't see your first question.

    This research doesn't deal with the formation of organic molecules; they assume organics are present (either due to Miller Urey type stuff, meteorites, or other events). So, if you are wondering about how reactive the atmosphere was, or something like that - I don't know if that applies.

    Assuming organic reactants are present: In my understanding, the important feature in this line of experiments is montmorillonite. This is a clay found in some lakes. Whether a first replicator formed on montmorillonite or not is an open question. Anyway, in these experiments, researchers vary the concentrations of certain ions (looking at whether Na or K are more conducive to polymerization, for example); they vary the reactants, whether the nucleotides are mono, di, or tri phosphate, the reactions are aqueous, around pH8. Conditions are fiddled with, as the question of how the first replicator may have come about, is very interesting.

    Here is one example of a set of conditions that has been used:

    "Oligomers of adenylic acid of up to the 11-mer in length are formed by the reaction of the phosphorimidazolide of adenosine (ImpA) in pH 8 aqueous solution at room temperature in the presence of Na(+)-montmorillonite. <snip> The exchangeable cation associated with the montmorillonite effects the observed catalysis with Li+, Na+, NH4+, and Ca2+ being the more effective while Mg2+ and Al3+ are almost ineffective catalysts. "
     
  21. Jul 1, 2005 #20

    Danger

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    Oh great... I had to be on my 14th beer before I ran across this. Now I'll have to come back to it tomorrow to read it properly. :grumpy: The one thing that I notice about Wooly's comments is that he seems to echo a lot of non-scientists/creationists/SF critics who marvel at how perfect the Earth is for us to live on, and thus must have been designed for us. They all seem to miss the point that it's perfect for us because this is where we evolved. If we had started on Venus instead, we'd probably have a sulphur/silicon metabolism and think that Earth was a frigid near-vacuum environment. Those critters that live on undersea volcanic vents would probably hold the same opinion about surface conditions if they were sentient. Although it's one of the most practical, workable situations, no rule says that life has to be Earth-like, or even carbon based. Even something that resembles us superficially but uses levorotating sugars instead of dextrorotating would be a completely different life form.
     
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