I was following a post on the origins of life and began thinking about that age-old question, what is life? Koshland gave us the "P(rogram), I(mprovisation), C(ompartmentalization), E(nergy), R(egeneration), A(daptability), S(eclusion)" definition. Has anyone developed a simpler one? Discussions on the topic would be easier if we had an accurate, simpler definition.
He called them the seven pillars of life. Here is basically what they are; 1. Program - Life has some kind of organized plan to operate through such as the nucleic acid and amino acid system. 2. Improvization - A living thing can change its plan in response to its environment. 3. Compartmentalization - A living thing must have separated spaces for necessary reactions to prevent other ingredients from messing up the reactions. 4. Energy - Living things require energy. 5. Regeneration - Living things must have a system to repair or restore damaged or lost components or processes. 6. Adaptability - A living thing responses to changes, dangers, and needs. 7. Seclusion - Chemical pathways must be separated.
Yes, I think Origin of Life would be an appropriate category.
well, one way to simplify would be to combine Improvisation and Adaptability as well as Compartmentalization and Seclusion. The terms in each pair seem to be describing the same thing. The definition from Wikipedia is the one I learned in highschool
quote:Homeostasis: Regulation of the internal environment to maintain a constant state; for example, electrolyte concentration or sweating to reduce temperature.
Organization: Being structurally composed of one or more cells, which are the basic units of life.
Metabolism: Consumption of energy by converting chemicals and energy into cellular components (anabolism) and decomposing organic matter (catabolism). Living things require energy to maintain internal organization (homeostasis) and to produce the other phenomena associated with life.
Growth: Maintenance of a higher rate of synthesis than catabolism. A growing organism increases in size in all of its parts, rather than simply accumulating matter. The particular species begins to multiply and expand as the evolution continues to flourish.
Adaptation: The ability to change over a period of time in response to the environment. This ability is fundamental to the process of evolution and is determined by the organism's heredity as well as the composition of metabolized substances, and external factors present.
Response to stimuli: A response can take many forms, from the contraction of a unicellular organism to external chemicals, to complex reactions involving all the senses of higher animals. A response is often expressed by motion, for example, the leaves of a plant turning toward the sun (phototropism) and chemotaxis.
Reproduction: The ability to produce new organisms. Reproduction can be the division of one cell to form two new cells. Usually the term is applied to the production of a new individual (either asexually, from a single parent organism, or sexually, from at least two differing parent organisms), although strictly speaking it also describes the production of new cells in the process of growth.
Personally, I feel that the reason life is so hard to define is because it is really more of a continuum than a cut and dry categorical difference. Viruses are often not considered alive because they are acellular and cannot reproduce without using the proteins from a cell. However, they are subject to natural selection to the same degree as any living organism. Prions are even less life-like because they have no nucleic acid, and reproduce by changing the conformation of other proteins. The range of what we would call "emergent properties" (i.e. traits that seem to be something more than the sum of the constituent parts, for example, cognition) is vast for cellular organisms as well. At an atomic level, we are made from nearly the same proportions of elements as a bacterium, and yet, we can do some many more things. Does this mean we are more alive than a bacterium?
I know this has gone a bit out of the strictly scientific definition and into a more philosophical look at the question, but it always seems to go that way. May I ask why you want to define life?
"There are three kinds of lies: lies, damned lies, and statistics."
I was following a post on abiogenisis and thinking about what it took to create the first living cell. I realized how difficult it is to actually talk about life because the definition is so complicated. My aim was not to try and define life but to see if someone has come up with a simpler definition in recent years so it would be easier to talk about.
quote: I was following a post on abiogenisis and thinking about what it took to create the first living cell. I realized how difficult it is to actually talk about life because the definition is so complicated. My aim was not to try and define life but to see if someone has come up with a simpler definition in recent years so it would be easier to talk about.
Wouldn't the logical answer to your question would be something like: the first cell would have to be very similar to another existing structure that did not quite meet whatever definition of cell you were using?
This sounds a bit like you think life did not begin until the first cell formed.
I suspect there is no good definition for life because it's not a "real" concept. In the same way that intuitively we consider 'cold' to have real meaning but, in the physically reality, it is nothing more than a lower value of temperature, there isn't any difference in reality between chemistry and life. Life is simply a complex form of it.
As such, you can define it if you like; but that definition will never be a natural classification of reality.
I'm not exactly sure what you mean by "surface" catalysis?
I was trying to exclude, for example, the way that water is required to catalyze the reaction of hydrogen and oxygen in the presence of a spark, which makes more water but which we would wish to exclude from the definition of life. I forget what that's called, but it's called something else.
Is anyone round here a chemist?
I can see it excluding all males.
Why? I am male, and the chemicals of which I am constituted do indeed catalyze their own synthesis.