How is a living organism different from a non-living thing?

In strict physical sense, (the definition satisfactory to me) , a life form is an integrated system (consisting of many parts),which is semi-stable(stability = capacity to maintain its integrity, semi  =  over a limited period of time)  with information carrying capacity to remember what can keep it in its semi-stable state. The capacity to maintain that integrity and information  carrying capacity is what I think is the essential difference between living and non-living. And that information processing capability is called consciousness. Clarification: information is closely associated with entropy and energy.

Although not sure whether I agree with your assessment, still trying. Organisms are complex chemical systems, organized in ways that promote reproduction and some measure of sustainability or survival. The same laws that govern non-living chemistry govern the chemical processes of life. It is generally the phenomena of entire organisms that determine their fitness to an environment and therefore the survivability of their DNA-based genes. Organisms clearly owe their origin, metabolism, and many other internal functions to chemical phenomena, especially the chemistry of large organic molecules. Organisms are semi-closed chemical systems. Although they are individual units of life (as the definition requires), they are not closed to the environment around them. To operate they constantly take in and release energy. Autotrophs produce usable energy (in the form of organic compounds) using light from the sun or inorganic compounds while heterotrophs take in organic compounds from the environment. Apart from the fact that no life forms made from inorganic molecules are known. Earth, to be a living organism would have to be made up of metabolic cells, or be a giant cell in itself ( interesting thought.. ) . Basking in the energy of sun at a safe distance with its friends. In the latter case , the earths crust, atmosphere, etc. may act as some sort of a membrane and every thing inside take up metabolic roles. One reason why this doesn't seem like a viable option is the lack of a medium which can carry any raw materials, finished goods, or waste of metabolism from one cell site to other. looks like a cell, with a nucleus. The Mantle is far too large and too solid to allow any form of transfer of material, ( apart from the occasional transfer through vents for lava delivery ). This, for me is a sufficient reason to believe that earth or any material which does not have a cellular structure is not a living organism. I have not included viruses in the answer for they give me headaches.

The thought you got to post the question clearly shows that you are a living organism in perfect condition. Thought is not the only defining character of living organisms...there are many more..One of the main defining character is metabolism..non living things don't have metabolism...but living things do have metabolism. a living organism is made up of many atoms like non living things do..but the only difference is..the atoms are not in correct order..it is like having all the parts of a car put in wrong order..n expecting the car to run..there is no single essential difference between a living organism and a non living organism..but they are a group of differences which make them unique..!

While I entirely agree that the distinction between living and non-living is not sharp, this does not mean that, away does the grey zone, there is not a distinction. It is a common fallacy of untrained thinkers in the Western tradition to believe that you must be able to sort everything into binary classes- good/bad, black/white, tree/bush, conservative/liberal. A common derivative is "if you are not for us, you are against us". Many things have indeterminate areas. There is no sharp line between the desert and the forest, but that does not mean that desert and forest do not exist, that each does not have its own distinctive fauna, each of which does best in its own land and Bradley when it crosses that indeterminate transition zone into the other. So I do believe in separating the definitely living (me) from the definitely non-living (a brick). But I do not believe you can draw a hard line between the tow, and make definite statements about those close to the dividing line (viruses). When considering such uncertainties, you have to ask what difference would it make if you were able to be certain. If I came up with a definitive statement that, according to my judgement, viruses definitely are, or ar not, alive, how would you change your actions? If I said they were alive, would you set up a society to ban cruelty to viruses? I doubt it. So if the distinction would have no effect, it is not one that matters. So let the uncertainty remain. Consciousness is another, though completely distinct, uncertain question. I would say that, in my opinion, to be conscious a being has to be in the "definitely living" area. But what consciousness is, and who has it, is an indeterminate area. In this case, we might make moral decisions based on whether something is conscious. So it is worth trying to investigate this further. But I never expect a black/white distinction. Like most emergent properties, consciousness us soft edged.

There is a pretty sharp and sudden divide between living and non-living things -> that divide is the ability of living things to multiply. Earth cannot multiply hence in that context it is not a living thing. Exchange and conversion of matter and energy are not exclusive for living things - just awesome processes that drive the engine called Universe. Another difference is the ability of living things to react to changes in their environment - the ability to process information and take action. Consciousness ? Well that's easy. :) It's like a laptop, a TV set, the Internet if you like. All you need are the right parts, build in the right way and into the right system. Pretty easy. Sad thing is that science knows about a lot of those parts, how they come to be, how each of them works but has no idea how their organization leads consciousness. Science does not know even if those parts are the only ones which (after arranged and combined) allow for consciousness to arise.

In order for a system to be 'living' it must simultaneously possess metabolism and heredity, though there are always complications. A fire has metabolism, but lacks heredity; if a spark from one fire starts another, no characteristics are transferred (the fire cannot replicate as a distinct individual, apart from other fires). A crystal has heredity, but lacks metabolism;  a repeating unit cell of atoms can be made from a seed in a solution, but once made they are frozen in place, undergoing no metabolism. A system with both features, however, would be alive. The complications come from how indirect things can get. Viruses are parasites that need others to reproduce, and some would say that they are therefore not alive, but why is the same not true of males (or, in most cases, females)? A prion can convert other proteins into duplicates of itself without reproducing from scratch. Parts of viruses can be considered dead in some environments but, in the right conditions, they can self-assemble into functional virus all over again. 'Living' is then a quality like 'weather', not localized to a few particular parts.

Biology has classically concerned with the the study of certain things because reductionism is useful to understand things in detail, but you can also go the other way and take an holistic approach. - http://en.wikipedia.org/wiki/Ecology and http://en.wikipedia.org/wiki/Systems_biology are what you get when you study life at different size and time scales. - Taking it further, http://en.wikipedia.org/wiki/Astronomy would be the largest scale at which you can study life. - Genetics and natural selection can also be understood as http://en.wikipedia.org/wiki/Cybernetics - thus, are abstract, and detached from carbon-based life forms. - Life is governed by http://en.wikipedia.org/wiki/Thermodynamics processes, just as anything else in the universe. So, from a more holistic approach, life can be seen as a characteristic, not a particular phenomena. Since all things at all scales are systems, all things can exhibit life. Finally, http://en.wikipedia.org/wiki/Consciousness is probably the most inscrutable of all mysteries. Even if we understand the mechanics of it, it's still a subjective experience, so maybe will never leave the terrain of http://en.wikipedia.org/wiki/Metaphysics. It's like trying to argue whether a rock falls in love. The biologist would say: it clearly doesn't, because it does not have a nervous system and such and such things that happen on the body of somebody who falls in love... The philosopher would say: how do you know what is love? You can describe the mechanics of it, but would be it?

Living things are generally open systems that perpetuate themselves through ingesting, processing and maintaining, then excreting anything that does not keep that system within viable boundaries of being able to continue this process. There's usually some way of multiplying involved too in order to allow further life to take over, and increase population. As our technology improves, it is becoming more and more difficult to see where the dilineation lies, especially as we find tools that extend our capabilities. Do they become alive while they become part of us as an organism? The definition of alive and dead will only get blurrier. Consciousness to me is merely a way of abstracting sensory experience in a way that allows us to formulate that experience in non-automatic ways - primarily through transactional communication with other living (and possibly non-living) things. It's really just an extension of our sensory experience - think of it as another sense - consciousness.

Like water flows..... and fire grows.....  Every non living thing shows.. that it has life..:)