13.3 study biol 101

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The Gap to be bridged: Invention of novel complex structures:

1. Mutation and natural selection might be expected to function more robustly in a system that already contains populations of reproducing organisms with genomic info.

2. Features of bird wing, shape, feather distribution, and flight feather structure suggest that this will be a major design challenge for mutation and selection.

3. Preening and flight behaviors must be also evolved at the same time.

4. Mutation and selection must generate the entire developmental process that gives rise to the flight feather in a bird.

5. Keratin is arranged in a higher-order polymers and fibers within feather structure.

6. Feather developments involve changes to the skin layers, follicle production, selective growth and death of certain keratinocytes, and a whole series of induction events to generate the pattern of barbs and barbules on a feather.

7. Many concurrent structural and regulatory gene activities required to generate a feather form an irreducibly complex system.

Bridging the Gap I: Random mutation in primitive feather keratinocytes:

1. In the neo-Darwinian synthesis, the source of structural and functional variations in a population result from the variant forms of alleles at specific genetic loci (genes)

2. The synthesis requires that these variations or mutations are entirely random; no outside intelligent force guides or directs their frequency or site of appearance.

3. The majority of mutations in a population of organisms are slightly harmful or no effect what so ever.

4. Mutations do not generate whole new elements of information; they simply alter existing elements of info.

5. Under rare environmental conditions, altered genetic elements may be of positive value to a population of organisms.

Bridging the Gap II: Natural selection in Primitive Feather Keratinocytes.

1. The process of natural selection works to increase the frequency of individuals in a population whose genetic makeup best suits them to leave the most offspring for the next generation.

2. Natural selection works at the level of the individual; it averages out the effects of harmful and rare beneficial mutations in determining which individuals will survive.

3. Natural selection is more effective in larger populations within small geographic areas, where competition is most intense; in sparse distributions of individuals, selection doesn't have an effect.

4. Natural selection is most effective in primitive, poorly adapted individuals in which many positive options for moving forward exist.

5. Natural selections directional progress depends on the stability of environmental conditions; cyclical environmental changes result in cyclical directions of selection.

6. Natural selection is blind and mindless. It does not build systems by coordinating multiple, simultaneous genetic changes.