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Member (Idle past 5930 days) Posts: 3435 From: Edmonton Alberta Canada Joined: |
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Author | Topic: Is there a border dividing life from non-life? | |||||||||||||||||||
Loudmouth Inactive Member |
quote: I am not speaking for Lam, but I would like to comment. You need to relate "status" to something. To humans, life in general is more important and deserves special consideration. To gravity, the rock and the human are the same, they both are required to act the same. The same goes with every physical, chemical, astrophysical, and natural law. Humans are subject to the same laws that govern the rock, and can not escape any of those laws with their intelligence. The only "status" that humans have is bestowed by humans themselves, not by any external entity or natural law(unless you are religious ). However, this doesn't mean that humans are not "special", only that when considering our self endowed importance it is important to remember that our basic chemical makeup is tied to inanimate objects such as rocks.
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Loudmouth Inactive Member |
quote: From a reductionist view, this doesn't work either. Every chemical process in your body is uniform and predictable. For instance, enzymatic processes are steady, and the kinetics of the reaction are linear. The processes also obey the laws of thermodynamics, the same laws that the rest of the non-life world has to obey.
quote: So snow flakes are unpredictable and non-uniform?
quote: And life is always recognizable as well, yet within the definition of life there is unpredictability and non-uniformity. I think your snowflake analogy fails your test.
quote: But, they are always recognizable as bacteria.
quote: And those same building blocks can be thrown together in random order with non-life mechanisms. Miller illustrated this well, showing the random production of amino acids from inorganic molecules. The same thing can be seen in complex hydrocarbons in oil wells (although oil is from an organic source). However, given the right conditions (eg heat and pressure) carbon, hydrogen, and oxygen will combine into totally new and unpredictable compounds. Life has worked out a way to make this process MORE predictable, in that life creates predictable and uniform proteins, biomolecules, and organic polymers such as DNA and cellulose. I would argue that life is best defined as something predictable and uniform from generation to generation, from cell to cell, and from chemical reaction to chemical reaction. I would put forth that the uniformity and predictability of the reactions that make up the Kreb's Cycle are a perfect example of the predictability and uniformity that life requires. If these reactions were random, then life would not be possible. If the byproducts were not uniform, then life would be impossible. It is the process of copying uniform and predictable chemical reactions through heretible material that makes life possible.
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Loudmouth Inactive Member |
quote: I could also argue the same with the water cycle here on earth. Water does move downhill, but how did that water get to the top of the hill in the first place? By moving water vapor against the grade and dropping it on top of the hill. This is caused by an input of energy, namely the sun. The same thing happens in our bodies. We use sunlight indirectly by using the glucose originally produced through photosynthesis. We then use this energy to drive thermodynamically unfavorable reactions. In this way, creating water vapor that moves uphill is no different than using ATP to create muscle contractions that then move blood. Although this is a reductionist's view, I think it still applies. However, I think "life" is about inheritance and propagation of these pathways into separate pools. That is, my example of rain production happens world wide and is not cordoned off at a certain point. Life is the opposite. With organisms we see the separation of these reactions from the outside environment, and the production of new "thermodynamic islands" through reproduction.
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Loudmouth Inactive Member |
quote: But we do. We see all sorts of different ores and chemicals being formed in the earth through combination of simpler molecules. As far as building blocks being the same, you are completely right. The building blocks for non-life and life are the same, they are atoms.
quote: Actually, you can see the same thing with non-organic chemistry and a petri dish. Add a spot of percholoric acid to one spot. Nothing happens. Add the outside influence of potassium carbonate and you get a new thing, a precipitate, something new that wasn't there before. However, I will grant you that the results do not differ with non-organic material. At the same time, the results do not differ with life either, being that the some of those bacteria will survive and overtake the rest of the population.
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Loudmouth Inactive Member |
quote: Is the air alive then, since we can not predict weather with pinpoint accuracy? For instance, can we predict the number and severity of hurricanes in the year 2006 with the data we have now? Or perhaps weather and living organisms share a similar characteristic, a level of complexity that defies simple predictions. There are simple experiments that give a predictable result when looking at simple organisms. For example, if I add S. cerevisae to wort I will get beer. If I add glucose to a culture of lactobacillus, I will get lactic acid in return. However, your example of mutation is like that of weather. There are multiple pressures and mechanisms that can result in several outcomes. Not knowing an outcome before the environmental change is initiated is not different than not knowing how many hurricanes will develop before the seas start to warm during summer.
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Loudmouth Inactive Member |
quote: Just being nitpicky, but it is possible. Post-translation modification of proteins is quite common, and can include glycosylation, proteolytic cleavage, or conformational changes through binding to another protein. However, all of these modifications are also controlled by DNA/RNA, just not the region specifically coding for the enzyme in question.
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Loudmouth Inactive Member |
quote: And selective pressures always give us a change in allele frequency (or extinction). Given a selective pressure, adaptation is inevitable. The variance in adaptation is no different than the variance in hurricane shape, path, velocity, etc. As far as a hurricane producing a blizzard, this would be the same as bacteria using their cell wall for protein coding instead of DNA.
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Loudmouth Inactive Member |
quote: I think this states the problem better than the other analogies brought up so far. There is a difference between a single neuron firing and consciousness. Also, there is a difference between simple chemical reactions within the cell and life itself. As Mammuthus pointed out, this still doesn't give us the ability to draw a line in the sand between life and non-life, but intuitively it makes perfect sense. We often describe the first life as an imperfect replicator. I think that most investigators involved with abiogenesis would agree that more than one reaction is needed for an imperfect replicator to come about. This would probably include a mechanism for creating nucleotides (RNA or DNA) and a method of elongation through replication. These processes would need to be organized and consume "food", even if it is in the form of simple pyrophosphates or other high energy molecules. Perhaps we should look at life as a self maintaining set of chemical reactions that is able to produce more of itself. This would separate it from fire, since fire is a single, simple reaction that is able to consume food and replicate itself. However, we would still have to include viruses in this definition of life, but I see no problem with that (where the host cell is considered "food"). Narrowing down the minimum set of chemical reactions may be quite difficult, but this seems to be the goal of abiogenesis research and we may have something close to an answer in the near future.
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