Monday, August 3, 2009

Why physicists and biologists need each other

I really enjoyed reading the rest of Chapter 1 of Biological Physics in preparation for thursday's class discussion. Section 1.3 has a nice discussion of the relationship between physical and biological sciences. Physicists seek the universal and simple in any system. In contrast, biologists when confronted with the complexities of the biosphere are more likely to emphasise "frozen accidents of history" and focus on details.

Figure 1.4 is nice but does not scan well and so I don't reproduce it here.

How does one synthesize these complementary approaches? First appreciate the value of each. Nelson suggests 3 steps for scientific advance:
"a) select a simplified but real model system for study
b) represent this system by a mathematical model with as few parameters and variables as possible.
c) deduce from the mathematical model some nonobvious, quantitative, and experimentally testable predictions."
He emphasises that a) and b) are inductive whereas c) is deductive.
a) and b) require a thorough knowledge of the biology.
Physicists need to be wary of proposing models that "lead to a large body of both theory and experiment culminating in irrelevant results."

Nelson points out that the best models may lead "to postulating entities whose very existence wasn't obvious from the observed phenomena."
Historical examples of this include:
Max Delbruck's deduction of the existence of a hereditary molecule (chapter 3)

the discovery of ions pumps and ion channels in cells (chapter 11,12)

George Gamow's proposal to find the genetic code

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