AP BIO evolutionary connection help.?

Question

A recent revival of the anti-evolutionary "intelligent design" argument holds that biochemical pathways are too complex to have evolved, because all intermediate steps in a given pathway must be present to produce the final product. Critique this argument. How could you use the diversity of metabolic pathways that produce the same or similar products to support your case?

Answer 1

(They're asking about intelligent design in AP BIO now? Just great.)



>"A recent revival of the anti-evolutionary "intelligent design" argument holds that biochemical pathways are too complex to have evolved, because all intermediate steps in a given pathway must be present to produce the final product. Critique this argument."



This argument ignores three *basic* concepts: repurposing, scaffolding, and coevolution. Let's look at each:



1. Repurposing. It is not necessary for all the "intermediate steps" in a pathway to be present to produce the *final result*. What matters is whether the intermediate steps produce *ANY result*! I.e. if the intermediate steps, taken separately, produce any beneficial functions AT ALL, then this is all that is necessary to explain the evolution of those intermediate steps independent of the full pathway.



For example, a bacterial flagellum may require all its current proteins to function *as a flagellum*. But if simpler subsets of these proteins serve other functions ... such as the secretory system useful to the bacterium for infecting host cells ... then such protein structures can evolve, and then get *repurposed* when the more useful function within the flagellum emerges. So it is a bogus argument to the fact that removing any of these parts disables *the flagellum*, because they evolved for other purposes besides the flagellum.





2. Scaffolding. Consider a protein A that provides some critical function. Two other proteins B+C when combined, also produce the same function, but not as well. But an additional protein provides a small improvement until the combination B+C+D provides the function better than A does. So the original protein A is not needed any more, and becomes disabled (or even disappears) in the genome. One might look at the remaining proteins B, C, D and conclude that they could not have evolved piecemeal because the function now requires all three of them. But that is based on lack of knowledge of A, the "scaffold", that was providing the function all along until this combination replaced it.



To pick a simple example to illustrate this. Primates have no ability to create their own Vitamin C, while other mammals (like cats and dogs) can produce their own Vitamin C. Why? Because primates emerged from a line of fruit eaters ... so the fruit provides a "scaffold" by which the ability to manufacture Vitamin C is no longer necessary. We can still find the *gene* for producing Vitamin C in our genome ... but it is disabled.





3. Coevolution. This is usually seen as evolution between two *species* that evolve in response to each other ... but it can also apply to two or more *structures* or *proteins* that evolve in response to each other. So proteins A,B, C may provide separate functions, but when combined may collectively produce a certain function. But improvements to A may produce corresponding improvements to B and C ... and vice versa. The result after a long time, would be that A, B, and C while once slightly useful in combination, are now absolutely interdependent on each other (the way that a specific flower and its pollinator can go from being loosely cooperative, to being absolutely dependent on each other).



At that point it is bogus to point to the interdepenence of A, B, and C as making it *impossible* for them to have evolved separately. They DIDN'T evolve separately ... they evolved together ... they once were not interdependent, and now they are.

Answer 2

That argument has always seemed odd to me. Behe talks about the complicated Rube Goldberg interactions of molecules in the cell as if such unnecessarily complicated mechanisms were more easily explained by an intelligent designer. They aren't. They are in fact the reason that simple, random changes to the DNA code can improve the ability of the organism to survive and reproduce in its environment.



Consider computer code, written by an intelligent designer to accomplish some specific task. Change a letter here or there in the code and you're most likely to end up making the program unexecutable. A few changes might still allow some functionality, but it's hard to imagine a random change that would improve the functionality of the program. That's because the code was written by an intelligent designer, and if that designer wants to improve the functionality of the program she can do it herself. Each letter and word of code has meaning, and is important to the proper functioning of the program as designed.



The DNA -> RNA -> Protein -> functionality system of cells doesn't work like that. DNA doesn't code directly for any particular functional result. Rather, DNA establishes the blocks used to build proteins, and different blocks may or may not change the shape of the proteins - either slightly or significantly. It is the shape of the proteins that lets them serve their functions in the cell - for instance by binding simultaneously with two other molecules so those molecules can bind with each other.



So picture an early, relatively simple cell. It already has a network of interacting proteins floating around, interacting with each other and with other molecules in Rube Goldberg ways, doing things necessary for the cell's continued functioning. Now picture a piece of mRNA, recently transcribed from a gene, getting reverse-transcribed back into a new position in the DNA. This is called gene duplication, and results in two copies of the same gene. Both are putting out the same protein. The protein from the second copy may not do anything useful, but it happens anyway. Now suppose there's a small copying error in the second gene causing it to put out a protein with a slightly different shape. The protein from the first gene is still performing its function, so the second gene is free to mutate. The newly modified protein goes out into the cell and interacts with the existing Rube Goldberg systems of molecules. Possibly it does something useful, possibly not. If it does something detrimental, then the individual will be less likely to survive and reproduce, and the mutation will get weeded out of the population over time. If the mutation instead does do something useful, then the individual with the mutation will be more likely to survive and reproduce, and the proportion of individuals in the population with the mutation will increase from generation to generation until eventually everyone has the mutation. This will likely mean an increase in the complexity of one of the Rube Goldberg interactions, or else the addition of a new simple interaction. Thus, if no intelligent designer were present, we'd expect to see populations in which the complexity of interacting Rube Goldberg systems goes up over time. We would not expect to see the sparse, to-the-point lines of intelligently designed code in a computer program. We do in fact see the former and not the latter.

Answer 3

Some structures are imperfectly suited to their use. An excellent example of an imperfect design is the eye of vertebrate animals, in which photoreceptors face backward, toward the wall of the eye. As a result, the nerve fibers extend not backward, toward the brain, but forward into the eye chamber, where they slightly obstruct light.

If it was an "intelligent design" why would it do such bad work???

Answer 4

There goes secretsauce upset again at students getting some inquiry based learning ("They're asking about intelligent design in AP BIO now? Just great"). He wants educators to be in the interesting position of not teaching students, but instead conditioning them to recite the “correct” answers without a second thought to other possible explanations.



What are the Darwinists afraid of? A little critical analysis never hurt anyone who had the evidence on their side.



Responding to Darwinists Claiming to Have Explained Away the Challenge of Irreducible Complexity:

http://www.discovery.org/a/3408

Answer 5

look up the Dover v Kitzmiller case and Ken Miller's testimony...

cite that in your answer as well