The [Ninja Turtles] henchmen Bebop and Rocksteady have hijacked the musical genres for us just like the Lone Ranger hijacked the William Tell Overture for our parents.

- xkcd

Tuesday, April 05, 2005

Quick Riff

Just to make sure I don't let myself start neglecting this again.

I watched the NCAA Championship last night and saw Illinois lose. It was a painful loss as they had three good shots at the basket and, had any of them dropped, they might have won. Oh well, they played a good game and came back to keep it close and make UNC work. Hopefully they can continue to keep the program growing and, between them and Mich St., we can keep the Big 10 basketball program strong.

On a slightly more intellectual note, I have been reading a few papers about heterochrony in embryo development. Heterochrony is pretty much what it sounds like, the changing order of developmental points in the embryo. For instance, whether the limbs or internal organs start to develop first. This also touches on an older biological idea, "ontogeny recapitulates phylogeny," the Biogenetic Law developed by Haeckel.

I am guessing it is fairly unusual but this notion was actually explored in my high school freshman honors biology course. We had to "synthesize" (that is in quotes because it was part of this moderately bizarre project that was supposed to explore six levels of cognition; bonus points to anyone who can tell me what they are) the meaning of the statement and some evidence to support it. I think that was the first assignment where I just looked blankly at the piece of paper because I'd never even heard of those words before.

Leaving the personal narrative for some science, the idea is, roughly, that you can deduce phylogenetic information about your ancestors by watching the embryonic progresion. For example, human embryos have, at an early stage, features that seem to be precursors to gills. The original idea was that you could look back at the embryo development and see how it progresses from one celled organism to 2, to 64, through some aquatic ancestor, right past dogs, apes, and on to humans. That idea has pretty much been shot to hell. As organisms evolve, thedevelopmental process is still subject to selective pressures just like every other aspect of life. Some key evolutionary differences are attributed to the rearranging of developmental stages (humans and neotany). However, like most ideas, there are parts that can be salvaged from it. The relative sequence of different events can be used to compare organisms to understand how they diverged. Additionally, the evidence can be part of a suite of evidence to argue for the relative evolutionary placement of two organisms.

This is longer than what I intended (and also somewhat plagaristic since I haven't cited anyone -- I'll do that this afternoon) but the gist is that ontogeny (the individula organism's development) does have some value in understanding phylogeny. Understanding the limitations and details will follow later today or tomorrow.


Post a Comment