bacterial flagelem (sorry about spelling)

Originally posted by Raging Atheist
uh huh... care to elaborate?

Originally posted by waterbuckat


 

It was basically showin how it couldn't of evolved from something else because there is nothing else like it in the world that scientists have discovered and there must of been a creator.  Which would be god............  sorry if I didn't answer what you were looking for, I don't know too much on the subject

In other words, you need to show how a bacterial flagellum can be built by small changes in successive generations, each of which would survive because it is of selective advantage to that individual.

To contradict the notion that a naturalistic evolutionary path to the flagellum cannot be conceived, I would like to describe such a path, even though it cannot be any more than a speculation, so it is vulnerable to the "just-so" criticism. We start with an initial bacterial species with no flagellum and living in moving water. It can extract some nutrients from the mud it contacts, but only if it sticks around long enough to carry out certain biochemical reactions. Some bacteria evolve a surface protein that attaches to molecules on a solid support like rock or sand grains in the mud and prevents the cell from being swept away by currents; and this strain of bacteria prospers and multiplies. The next development is that after using up all the nutrients within reach, the bacteria run into a metabolic dead end, until some cells evolve hair-like projections fastened to the cell wall that allow them stick to their sand grains but to forage nutrients over a wider area without being swept away by the water currents. (These are similar in structure and function to modern bacterial pili.) The next step is that these hair-like projections get longer (allowing a wider area for foraging nutrients) until some bacteria die when water currents spin them around and twist off their hair-like projections. Then some bacteria evolve a mechanism that allows the projections to rotate with respect to the surface of the bacteria so that the hair-like projections don't get twisted when the current spins the cells. When these molecular swivels become efficient, bacteria whose growth is prevented by limiting energy supplies evolve a mechanism for converting the mechanical energy of rotational motion at the base of the hair projections into ATP; they do this by borrowing components of the F1 ATPase already evolved to convert rotation into ATP. When this mechanism for converting rotational energy into ATP has evolved, some bacteria that have become detached from their sand grains evolve a mechanism for running the conversion mechanism backwards, i.e. so that ATP is used to generate rotation of the hair projection to provide motility. Voila, a primitive flagellum, evolved by multiple sequential steps, in which each individual component is dispensable when added because the earlier versions of the complex provide a function different that of the modern homolog, motility. Obviously I don't claim that this is necessarily the true evolutionary path that led to the bacterial flagella since we have no way to access that path, but I offer this scenario to show the worthlessness of the idea that no such path is conceivable. (Also, there is some evidence for sequence similarity between archaeal bacterial protein components of flagella and pili [Bayley & Jarrell J Mol Evol 46:370, 1998]).

To contradict the notion that a naturalistic evolutionary path to the flagellum cannot be conceived, I would like to describe such a path, even though it cannot be any more than a speculation, so it is vulnerable to the "just-so" criticism.