MadSci Network: General Biology

Re: How does a living organism differ from fire???

Date: Sun Feb 6 08:49:37 2000
Posted By: Rob Welton, Graduate Student, Molecular Biology and Genetics
Area of science: General Biology
ID: 949365279.Gb


Interesting question, and one that many scientists have struggled with over 
the years.  I too was perplexed by this question.  Certainly fire does 
consume nutrients, grows and produces waste products, but is it alive?  To 
answer your question, I decided to find out what the current definition of 
"life" is.  In researching this, I found no real good answer.  So I will 
list here what criteria the science community currently uses to define 
life.  Much of this information I retrieved from an old Introduction to 
Biology text (Biology 3ed, Peter Raven and George Johnson, Mosby, New York, 

Criteria that one may think of that define life include:

1.  Movement
2.  Sensitivity
3.  Death
4.  Complexity

Some of these can be applied to fire and many other things that are 
considered 'nonliving'.  For example, water moves, but is not living; fire 
can die, if it is extinguished or its source of fuel is removed.  But, on 
the other hand, these criteria are not possessed by all forms of life, 
therefore they are neither necessary nor sufficient for life.

Scientists have further refined the criteria to include:

1.  Cellular organization
2.  Growth and metabolism
3.  Reproduction

Again, fire can fit into some but not all of these categories.  It grows, 
it can be said it metabolizes in that it converts matter to energy and 
possibly reproduces (spreads).  Although these criteria are certainly 
necessary for life, they are not sufficient.  There is one additional 
criteria that defines life HEREDITY.  Living organisms have the ability to 
pass on their genes to their offspring.  Fire cannot do this.

So to make a long story short, Fire may seem to fit some of these criteria, 
but not all.  In defining life as we know it, one must consider the latter 
4 criteria that I have listed.  

I hope this helps.

Rob Welton

Note:  Here are two previous Mad Scientist answers that discuss this subject:
Is fire a living thing?>
,which gives a similar conclusion, and
 What is the meaning of life?,
which discusses that alternate perspective, that fire CAN be considered a form of life.

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