Monday, July 30, 2007

Poop - relieving the pressure of natural selection!!

One of the purposes of this blog is to gather together some of the neat things I come across while studying complex adaptive systems. Here is an example:

Endozoochory is the dispersal of seeds through animal ingestion and excretion. This is a strategy used by some plants to improve the odds of their species surviving: get yourself eaten by a creature, but make sure your seeds resist being digested by that creature. When the creature has its next poop, it returns your seeds to the earth along with their own personal pile of fertilizer!!

This is neat because it shows how the creature and the plant really help each other out. The more the creature eats, the more the plant flourishes; the more it flourishes, the more the creature *can* eat next year, and so on.

The immediate result is that the plant should thrive around the creature's home - call it site A.

But going a step further, suppose the creature is migratory: then the plant also gets the chance to colonize sites along the creature's migratory paths. Let's say that the plant starts out only at site A, but there are also sites B & C which are inaccessible to the plant (maybe because it's too far away for a random gust of wind to blow the seed over from A.) Over time, as the creature migrates from A to B, it carries the seeds of the plant and poops them out along its path (essentially planting its own lunch for next year's migration...) The result of this process is that the plant is able to spread to B.

And finally, the really big payoff is that the plant gets the chance to colonize areas visited by *other* creatures who happen to pass through site B - creatures it never would have met in site A! Such a creature never visits site A but does visit sites B & C: once it finds the plant growing in B and eats it, the creature can spread the plant to C.

And now realize that at each previously-inaccessible site, there's probably a few more creatures which can eat the plant, and that they each have their own set of sites that they visit...You can see what a powerful means of reproduction endozoochory is.

PS: This spread of a seed through the world via excrement reminds me an awful lot of Facebook gimmicks (and contagious diseases; and catchy tunes; and parasites; and fashion trends; etc...): Suppose a group "A" is all the people who routinely check out brand new Facebook gimmicks - this is just a tiny subset of all the people out there who use Facebook. But if just one person from group A adds a new Facebook gimmick to their page, all of their friends (group B) suddenly see it; when someone from group B adopts the gimmick, all of her friends (group C) suddenly see it; etc. In the end, the gimmick propagates far beyond just the people in group A.

The point of all this is that if you are like my sister's boyfriend and loathe Facebook, then at last you can point to this blog and say that people who use Facebook are simply shovelling crap from one person to another.

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