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From: steve@jplgodo.UUCP (Steve Schlaifer x43171 301/167)
Newsgroups: talk.origins,net.bio
Subject: Re: What's this LIFE stuff?
Message-ID: <829@jplgodo.UUCP>
Date: Mon, 29-Sep-86 14:00:58 EDT
Article-I.D.: jplgodo.829
Posted: Mon Sep 29 14:00:58 1986
Date-Received: Thu, 2-Oct-86 19:52:01 EDT
References: <45500088@uiucdcs> <7670@tekecs.UUCP>
Organization: Jet Propulsion Labs, Pasadena, CA
Lines: 32
Xref: linus talk.origins:119 net.bio:492
Summary: what's the difference between a mule and a solar powered refrigerator

In article <7670@tekecs.UUCP>, mikes@tekecs.UUCP (Michael Sellers) writes:
> There are some general common to all those things we say are alive (though
> most if not all of them have a few notable exceptions):
> 
>   IT MUST METABOLIZE.  All living things use material from their environment
> that, when broken down, is used for the maintenance of the thing itself (or
> for growth or reproduction, etc.).
>   IT MUST REPRODUCE.  All living things are able to reproduce others of their
> kind that are or will become fully functional, independent entities.
>   IT MUST RESPOND TO ITS ENVIRONMENT.  All living things have mechanisms for
> responding to the changes in the environment that are salient to them, as for
> avoidance, food location, life cycle staging, etc.  
>   IT MUST BE AN INDEPENDENT ENTITY, not bound up physically in the structure
> of another living thing.  All living things are entities unto themselves,
> interdependent but not completely dependent on the structure of another.
> 
>   There may be more to this list, but I believe it is fairly complete.

A problem I have had with definitions like this is there are many things
we don't consider to be living that slip through and some we do consider
living that fail to pass.  For the most part, a mule doesn't reproduce
(there are reports of rare exceptions).  A solar powered refrigerator with
automatic sun-tracking and a motorized carriage, on the other hand, satisfies
the other three conditions above as well as the mule does.  Seems to me that
this is a VERY complicated question that cannot be simply defined.
-- 

...smeagol\			Steve Schlaifer
......wlbr->!jplgodo!steve	Advance Projects Group, Jet Propulsion Labs
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