That may seem an almost silly question to ask. I mean, duh An organism is such a common concept that it can be taken for granted, no?

But, I'm hard pressed to give a good or robust definition, and Bloom doesn't provide a definition for me (at least not in the pages I've read so far); yet it seems a critical thing to understand given the fact that he lists the superorganism as concept number two in his list of the foundations underlying the Lucifer Principle.

I might attempt this def: An organism is a living entity.

But that begs the questions: What does it mean to be living? And, what does it mean to be an entity? (This is where things delve into stuff like complex adaptive systems and the identity of an organism.)

Life could be expressed as the ability to:

Grow
Reproduce
Utilize nutrients/metabolites
Exhibit Homeostasis
Respond to stimuli

An entity is any single organism.

Groups of organisms working together in an (ideally) altruistic manner would be a super-entity.

Edited by: ZachSylvanus at: 11/9/02 2:34:15 pm

There is a conflict in the biological world whether viruses are considered "living" or not. My zoology prof doesn't think so. Funny, isn't it?

B

Its not really so much funny as interesting.

They don't really grow, but they do reproduce (albeit using a host-cell's systems), they don't utilize energy (the host cell reproduces the virus' genetic material at cost to itself), they don't really have any sense of homeostasis (if thrown into an environment not adapted to, it is destroyed rather than attempting to overcome the stress), and they don't really respond to stimuli....

I would like to offer Dawkins' definition of 'organism', but first, share a fascinating question: why organism at all?

Quote:

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We do not at present appreciate the organism for the remarkable phenomenon it is. We are accustomed to asking, of any widespread biological phenomenon, 'what is its survival value?' But we do not say, 'What is the survival value of packaging life up into discrete units called organisms?' We accept it as a given feature of the way life is. ...the organism becomes the automatic subject of our questions about the survival value of other things: 'In what way does the behaviour pattern benefit the individual doing it? In what way does this morphological structure benefit the individual it is attached to?' (ep, 5)

. . . I am not necessarily objecting to this focus of attention on individual organisms, merely calling attention to it as something that we take for granted. Perhaps we should stop taking it for granted and start wondering about the individual organism, as something that needs explaining it its own right, just as we found sexual reproduction to be something that needs explaining in its own right. (ep, 5)

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Later in The Extended Phenotype, Dawkins offers a definition:

Quote:

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The organism has the following attributes. It is either a single cell, or if it is a multicellular its cells are close genetic kin of each other: they are descended from a single stem cell, which means that they have a more recent common ancestor with each other than with the cells of any other organism. The organism is a unit with a life cycle which, however complicated it may be, repeats the essential character-
istics of previous life cycles, and may be an improvement on previous life cycles. The organism either consist of germ-line cells, or it contains germ-line cells as a subset of its own cells, or, as in the case of a sterile social insect worker, it is in a position to work for the welfare of germ-line cells in closely related organisms. (ep, 263)

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Personally, I consider virii alive, although I understand the argument that they are not. I also have my own, simple definition of life: "Life is that which is capable of evolution by natural selection, and the products of evolution by natural selection".

I though it had to do with sexual gratification. Boy, I've sure learned a lot on this site!

Another defintion that redirects the emphasis away from selection and survival benefits to directly address Dawkins suggestion to take the organism as something that needs explaining in its own right: "Life is that which exhibits autopoiesis."

I think that, or similar definitions offered systemicists, answers the question: why an organism? Because adaptive systems emerge as discrete entities in open thermodynamic systems (creating the conditions under which selection can operate).

PS: I'd cast my vote against a virus as a living thing.

Quote:

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An entity is any single organism.

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Unfortunately, that sets up a circular definition, i.e. an organism is an entity, an entity is an organism. Plus, I think it's possible for something to be an entity without being an organism, i.e. it can be an object, at least in a basic or general sense.