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Author Topic:   What is life?
Member (Idle past 4452 days)
Posts: 174
From: Oregon
Joined: 12-28-2008

Message 5 of 33 (503410)
03-18-2009 4:38 PM
Reply to: Message 3 by alaninnont
03-18-2009 3:05 PM

Re: some expansion please
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
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."

This message is a reply to:
 Message 3 by alaninnont, posted 03-18-2009 3:05 PM alaninnont has replied

Replies to this message:
 Message 6 by alaninnont, posted 03-18-2009 8:02 PM Stagamancer has not replied

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