The Visitor leaves the finished map and steps onto a bacterial cell to watch its motor. Darwin tied his theory to complex organs forming through numerous, successive, slight modifications. Michael Behe's 1996 book Darwin's Black Box named the flagellum as the leading example of a system that functions when all its components are present, and called this irreducible complexity.
The Visitor opens the motor to see the parts.
The Flagellum
- The flagellum is a proton-driven rotary motor built from dozens of distinct proteins. The structural proteins are commonly cited at about 25 to 30 (approximate).
- Its regulon spans more than 50 genes in at least 17 operons, and over 60 genes when the full regulatory hierarchy and chemotaxis are counted (Chilcott and Hughes 2000; Chevance and Hughes 2008). The genes switch on in early, middle, and late classes, in step with assembly.
- Speed: about 300 turns per second (about 18,000 rpm) in E. coli, and above 100,000 rpm in Vibrio alginolyticus (Berg 2003; Sowa and Berry 2008).
- The page assigns each of eight parts one job:
- Basal body: the anchor, with L, P, MS, and C rings.
- MotA/MotB: the proton channel and power source, about 8 to 12 complexes per motor.
- C-ring and switch (FliM, FliN, FliG): the rotor, which also receives the direction signal.
- Type III secretion system: exports flagellin to the growing tip.
- Hook (FlgE): a universal joint of about 120 subunits that carries torque.
- Filament (flagellin): a hollow propeller of about 20,000 monomers.
- Cap (FliD): guides flagellin insertion at the tip.
- CheY: connects sensory input to motor direction, switching rotation from counterclockwise (run) to clockwise (tumble).
- The article page presents the mainstream reply of co-option (parts that once served other functions) and responds that the type III secretion system shares a set of components with the flagellum, so integration of the whole machine is the open question the site raises.
Whole-Cell Coherence
- Return to the finished map. The technical brief pairs systems by dependency: DNA and Error Correction, Epigenetics and Histones, RNA Regulation and Ribozymes, Signaling and Differentiation, Enzymes and Protein Folding.
- The article page names the pack's central idea, Deep Sophistication: complexity is a quantity, and sophistication is a quality. The article describes components that speak to each other in compatible languages, built to a unified specification and operating simultaneously across twelve channels.
- The site's position: the first cell that worked already had all twelve systems, and the question for each visitor is whether chance is a coherent explanation for that degree of coordination.
- Read the What Mainstream Biology Says section on the article page and say in your own words where you agree and where you want to look further.
The rotor spins in the wall and the filament turns behind it. The full motor runs on its own page: open the flagellum animation.
Pick any two systems on the map and describe how each one relies on the other.
Sample answer: Histones control whether the epigenetic machinery can reach the genome, and epigenetics writes marks on histones. Other pairs from the technical brief work as well.
Each learner draws the twelve-node map from memory, adds an arrow for every dependency they can name, and compares with the live map at the coherence page.
Twelve systems in one cell lean on each other, and the flagellum shows the same pattern in a single machine of more than 50 coordinated genes.
The Visitor holds the finished map and the flagellum side by side.
See the map