paleo@ecsvax.UUCP (Constantine A. LaPasha) (02/13/89)
(maybe a bit late, but my 2 cents worth...) There are a few problems with reductionism as a complete method for studying and characterizing biological (and many physical) systems. As I understand it, reductionist thinking goes something like this: if I understand the little pieces well enough, I can then put them together using some underlying principles (rules) and understand the way the whole works. Now, understanding the pieces of the problem (system) is important, and needs to be studied. But the problem comes when we try to put the parts back together. Many biological systems are not linear. That is, the rules needed to explain how the parts work together are nonlinear. We can sometimes approximate nonlinear systems with linear systems, but this does not always work, and may hide some of the most interesting behaviors of the system. Nonlinear systems have some interesting properties, like sensitivity to initial conditions. (In other words, minute differences in the values of the starting conditions of the system get magnified as you follow the behavior of the system until the behavior of two systems starting at nearly the same initial conditions no longer resemble each other -- conversly, similar behavior can be obtained from very different initial conditions.) So what? We would like to think that if we know the state of a system now, and understand all the parts, and the relations between the parts, we could predict the state of the system (behavior) at some future time. Unfortunately, for nonlinear systems, predictions for even the simplest, best understood systems are good for only the short term - long term predictions don't work well. Another interesting property of nonlinear systems is that the same system can act very differently when the constants in the equations are changed slightly. Small changes in some constants can cause drastic differences in the behavior of the system. So... the same mechanism (nonlinear system) can sometimes explain very different behaviors of a system - you don't need to invoke different mechanisms to get different behaviors. (an example is heart rhythm - normal rhythm and fibrilation can be explained by the same equations if the constants are silghtly altered) Oh well... so if I understand all the little pieces of the puzzle, AND how they all relate to each other, and I put it all together, I STILL can't predict how the system is going to behave... May sound depressing, but actually I think it is very exciting! Maybe the varying rates of extinction are due to slight changes in the constants governing this system...hmm... too long winded, but maybe worth some discussion.. BTW- the study of the behavior of nonlinear systems has come to be referred to as chaos -- ===================================================================== Kostya LaPasha paleo@uncecs.edu or paleo@ecsvax.uncecs.edu == computers get the munchies too - memory hungry, want chips... === ==========NCSU is not responsible...=================================
dd@beta.lanl.gov (Dan Davison) (02/13/89)
In article <6390@ecsvax.UUCP>, paleo@ecsvax.UUCP (Constantine A. LaPasha) writes: > (maybe a bit late, but my 2 cents worth...) > BTW- the study of the behavior of nonlinear systems has come to > be referred to as chaos Well, not really. The Center for Non-Linear Studies here at Los Alamos National Laboratory sort of falls into two camps, jokingly referred to as the "chaos-ers" and the "soliton-ers". So there is more to non-linear studies than meets the eye. By the way, The Santa Fe Institute (1120 Canyon Road, Santa Fe, NM 87501) sponsors meetings and workshops on a wide range of non-linear studies and publish a newsletter four times a year. The last issue covers economics, the aids-immune system interactions, the Matrix of Biological Knowledge effort, "Complexity, Entropy, and the Physics of Information: A Manifesto", and news about a Complex Systems summer school. If you are interested in this area, I suggest contacting the Santa Fe Institute. (You might mail to the attention of Ms. Ginger Richardson). dan davison/theoretical biology/t-10 ms k710/los alamos national laboratory los alamos, nm 875545/dd@lanl.gov (arpa)/dd@lanl.uucp(new)/..cmcl2!lanl!dd The NRA: defending your right to shoot small schoolchildren with automatic weapons (and teflon bullets, too!)