Am 21.05.2012 12:51, schrieb Invisible:

> In particular, the purpose of leaves is to absorb as much sunlight as
> possible. Given that task, you would /expect/ leaves to evolve to be
> huge flat sheets. You would /not/ expect leaves to evolve holes and cuts
> in them. You certainly wouldn't expect to see long, thin, pointy leaves
> which hardly soak up any light at all.

Once again, your expectations suffer from oversimplification.

One other purpose of leaves, for instance, is gas exchange: Somehow the 
plant needs to take up carbon dioxide and give off oxygen. "Fractal" 
shapes are better suited to this, as they allow for better average 
airflow across the surface.

For some plants, the leaves also serve the purpose of collecting water 
from dew or rainfall; others use them to store water; yet others protect 
the earth from erosion by heavy rain, and some need to manage to cope 
with heavy snow.

And then there are secondary design criteria to be met; one of them is 
self-defense: Small or "fractal" leaves provide better barriers against 
the spread of degenerative diseases; certain structures might make life 
more difficult for parasites (e.g. hindering migration from one side of 
the leaf to the other), and/or make the respective predators' life easier.

Furthermore, leaves must be lightweight to allow for faster growth of 
the plant, yet robust enough to withstand the prevailing wind speeds. 
And in extremely hot or cold environments their surface must be limited 
for better temperature management.

And I bet I only touched the surface of it.

> But plants of course are not designed by human thinking. They are
> designed by a far more reliable process: trial and error. The vast
> number of plants with weird shaped leaves demonstrates beyond question
> that this /works/, and that it provides some sort of advantage. But...
> what?

See above.

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