MadSci Network: General Biology

Re: Does entropy apply to living things?

Date: Sat Nov 13 21:24:46 1999
Posted By: Eric Maass, Operations Manager, semiconductors / communication products
Area of science: General Biology
ID: 940898333.Gb

Yes, entropy does apply to living things.  In fact, you might think of the tendency for entropy to increase over time as 
the "engine" that allows life and change in general to exist.

You might want to think of entropy as a measure of how "messy" things are.  Now, there are many ways to have things 
messy, but only a few ways to have them neat -- so, if you just let things proceed sort of randomly, things will tend to 
get more messy.

If Humpty Dumpty sits on a wall, and falls off - the result is kind of messy.  It is easy to go from the neat state before 
he fell, to a messy state afterwards.  However, it is very hard to go from that messy state back to the neat state -- all 
the king's horses and all the king's men can't put Humpty Dumpty together again.

Similarly, it is rather easy for you and your group of friends to make your bedroom or living room a mess...but a lot 
more, unpleasant work might be involved in making the room neat again afterwards. So, you can blame the law relating 
to entropy tending to increase for why cleaning your bedroom isn't so much fun.

Now, relating this to living things - most, if not all, of the processes that are involved in what we call "life" involve an 
increase in entropy overall.    Our cells that make up our bodies use diffusion, in which oxygen and nutrients diffuse 
across the cell membrane (the outside of the cell).  Diffusion proceeds by a process involving an increase in entropy - 
the oxygen and nutrients diffuse from where they are in greater concentration to where they are in lesser 
concentration - increasing the "messiness".  All of the chemical reactions that go on in our bodies, like getting energy 
from the food we have eaten, involve increases in entropy as the energy is released and used.

While life itself seems very structured and orderly -- so it may seem like entropy is not being increasing -- the fact is, 
life itself increases the entropy of the system as a whole (I often have referred to babies as "entropy machines").

Here are two earlier Mad Scientist answers that might explain these concepts further: 

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