Re: Why is it macroevolution?
r norman wrote:
I wonder how many times people will repeat this until it sinks in.
OTOH, on the TO website, there is little if any mention of the distinction.
There is only chemistry, but still we
have organic and inorganic.
Absolutely, each with their own quirks and particularities. The people
that have studied chemistry will know that many things cannot be
explained by "mix 2 atoms/molecules together=more complex compound."
Really? Are you sure about that?
Let's take a look at what happens when you mix a simple ion- hydroxide-
with another hydrogen atom.
Is a water molecule more complex than the two components I mentioned
above? Does water exhibit any complex behavior that is not seen in the
ions? Nashton says no, but I think most would disagree. A "simple"
water molecule has emergent properties that H+ and OH- cannot even
approach- and these properties are essential for life.
Water, for example, has variable density, while those ions do not. Why
is this important? Water is densest at about 4C. That, by the way, is
the temperature at which the standard density of water applies (1g/cc)
and the temperature at which the calorie applies (the amount of energy
to raise 1cc of water by from 3.5C to 4.5C).
Consider what would happen if ice was denser than water. As the
uppermost layer of water froze in winter, it would sink. Would it melt
in Spring? Probably not, unless the water was quite shallow. In the
ocean it would accumulate from year to year, until only a few
centimeters of liquid water appeared in summers. The planet would be an
iceball. This property of water is not seen in its component ions.
Water molecules also exhibit cohesion and adhesion. When you put a
straw into a glass of water, you can see the water rise up a short
distance. This happens because water is sticky stuff- it sticks to the
inside surface of the straw, and water molecules stick to one another
(more on that soon). Who cares? Well, trees, for one. Trees don't have
a pumping organ like a heart to bring water all the way up to the
leaves where it's needed for photosynthesis. They rely on a process of
evapotranspiration to generate a "suction" that draws water from ground
level to the top of the tree. This could not happen if the water
molecules didn't stick to the inside of the vascular tissue of the
plant, and to one another. We certainly don't see that behavior in
hydroxyl or hydrogen ions. By the way, this also generates the surface
tension you see in water. That's why insects like water striders can
run around on the tops of ponds.
How do water molecules stick together? There are weak bonds between the
oxygens of one water molecule and the hydrogen of an adjacent water
molecule. This is certainly a property we don't see in the component
ions. These hydrogen bonds are what hold the two strands of DNA
together- a rather important function of an emergent property, most
people would think.
The fact that large numbers of water molecules are held together by
hydrogen bonds (which are always breaking and reforming) gives water
another important emergent property: a high specific heat. At 4C
(there's that important temperature again) water has a specific heat of
1 calorie (a little over 4 joules). That is pretty darn high, and
that's pretty darn important too. I ask my students if they think it
takes a lot of energy to heat up water, or a little, and they almost
always say it takes just a little energy. So I give them this
assignment: go home, take 2 identical pans, fill one with water, and
put them both on the stove over high heat for 30 seconds- then press
their hands on the bottom of the pans. Obviously, water has a much
higher specific heat than any metal commonly used for cookware. This
also makes it an excellent heat sink and temperature buffer. It's one
of the more important ways organisms maintain a livable body
temperature. We surely don't see that property in the two ions
Another thing you don't see in the ions is the solvent property of
water. Remember that every chemical reaction in your body has to take
place in solution. Would this be possible using hydroxyl or hydrogen
ions? Not a chance.
Yes, there are in fact things that cannot yet be explained by
chemistry. But some people would have us stop looking. And, in fact, a
whole range of things vital to living systems *can* be explained by
looking at "mix two atoms/molecules --> more complex molecule". They
range from the simple (variable density) to the complex
(double-stranded structure of DNA).
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