Subject: What criteria unambiguously define biological evolution?

What are the identifiable criteria by which the term "evolution" 
(in its biological context)is unambiguously differentiated from all other 
words?  Particularly from (biological) "variation", "extinction", 
"devolution", etc.

Prior to the unraveling of the DNA double helix by Crick and Watson in the 
1950s, the best scientist's could offer were imprecise 'descriptions' as 
"change over time", "descent with modifcation", etc.  However, with their 
establishment of the Dogma of Microbiology -- that "DNA -> RNA -> 
PROTEIN" -- science is now, for the first time, in a position to provide a 
superior 'explanatory' definition for this key term.   

As a preliminary, I've drafted the following:  

    "BIOLOGICAL EVOLUTION is the postulated process involving the     
    appearance and accumulation of new, increasingly complex, biologically 
    beneficial genetic code in a pre-existing (simpler) gene pool by     
    naturalistic mass/energy interactions."

    This encompasses the criteria that appear to be both 'necessary' and 
'sufficient' to give the word "evolution" its own (unambiguous and unique) 
meaning.  Your comments and further suggestions will be appreciated.
    

Re: What criteria unambiguously define biological evolution?