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Re: Cannibalism (and yes it is on topic)

From: Beth Fulton <beth.fulton@m...>
Date: Tue, 27 Jun 2000 19:46:06 +1000
Subject: Re: Cannibalism (and yes it is on topic)

G'day Karl,

 >Overall, I consider the concept of bio-organic spaceships (especially
 >if they are supposed to have evolved naturally) to be so far out that
 >discussing them in the same paragraph as the laws of thermodynamics
 >really make sense.

I'd have to agree with you, multicellular animals actively living in a 
vacuum is more unlikely than FTL. ;)

 >Still, FWIW:
 >1) IIRC the efficiency in converting food into body mass of
 >life is markedly different for warm-blooded and cold-blooded animals.

Well there's actually two sides to it, if you mean straight assimilation

(amount of ingested food used in the body vs dumped as detritus) then 
you're looking at about 80% being assimilated. If you're actually
at how much of the consumption makes it to production (growth) once
taken out all the other metabolic activities then you get down to about
5 - 
30 %. With very large slow growing animals having a growth efficiency of

round about 5% (or less for the really big marine mammals), whereas the 
super fast growing larvae have growth efficiencies of about 30% or a bit

more. All up 20% comes out as about average though.

 >Which class do the Savasku belong to ?

Ohh I'd love to see the mission details for that assignment... ;)

 >2) The laws of thermodynamics don't deal with the conversion of
 >materials, but with the conversion of energy. The main source of waste
 >biological is the need for energy, which is obtained by chemically 
 >high-energy-molecules (sugars, fats etc.) into low-energy 'waste'
 >molecules (carbon dioxide, water) which are of no use and excreted. If
 >Savasku have available 'unlimited' energy (from a biological
 >fusion-reactor, say), they may be able to make use of all the target 
ships' mass.

While I may very well accept the complete use of consumed mass for
game-wise (its simple to remember), I wouldn't support it on biological 
grounds. First up, biology does follow the laws of thermodynamics and so
can't see catabolism (material breakdown) liberating 100% of energy used
anabolism to create that organic structure in the first place. Thus
see some deterioration in the amount of mass produced for the amount 
consumed (as you don't get 100% of the energy out so you can't build the

exact same amount again). However, more importantly <given your
fusion-reactor idea... which I guess is no weirder than a biological
in space in the first place ;)> each organism has an internal ratio of 
nutrients and so some are going to be in excess when others are
As a consequence you're always going to have some waste material (the 
excess) regardless. So biologically you're just not going to see 100% 
conversion, but like I said this doesn't stop its adoption in a game
the KISS principle).



Elizabeth Fulton
c/o CSIRO Division of Marine Research
GPO Box 1538
Phone (03) 6232 5018 International +61 3 6232 5018
Fax 03 6232 5053 International +61 3 6232 5053


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