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Hands on Activities for Understanding Ammonite Sutures

Hands on Activities for Understanding Ammonite Sutures. Clint Cowan Carleton College On the Cutting Edge - Professional Development for Geoscience Faculty Teaching Paleontology in the 21st Century. Goals. Short term / Lower Level goals Spatial reasoning / Visualization

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Hands on Activities for Understanding Ammonite Sutures

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  1. Hands on Activities for Understanding Ammonite Sutures Clint Cowan Carleton College On the Cutting Edge - Professional Development for Geoscience Faculty Teaching Paleontology in the 21st Century

  2. Goals • Short term / Lower Level goals • Spatial reasoning / Visualization • Implicit or Explicit: • 2D to 3D Reasoning • Using biological actualism • Understanding shell growth in Molluscs • Understanding preservation (steinkerns,casts & original material) • “Complexity” in a simple system

  3. Supplies • Fossil Ammonites www.stonesbones.com • Between $50 - $150 per (depends size, etc.) • Nautilus shells: www.SeaShellCity.com • Between $15 - $50 per (depends size, etc.) • Glass plates from local handyman • Play-Doh, food coloring (Kmart) • Tubing, syringes, cover slips, Glycerol - lab supplies

  4. For complex sutures, many students have trouble physically relating the septum to the suture

  5. It helps to go back and forth between the Nautilus and the ammonoid…

  6. Prove you know it by building it… Making a fluted or convolute edge to your chamber wall really drives the concept home

  7. “Oh yeah!” The sutures are only visible where the phragmacone has been chipped/worn away

  8. One year, a student simply couldn’t get it… until we buffed away part of the phragmacone of the Nautilus to expose the edge of a chamber wall, and that did it… Filling some chambers with Play-Doh helps get the steinkern point across, too.

  9. Jordy, show me how and where the animal adds new shell material to grow…

  10. SHOW ME: growth lines sutures ornamentation (?) What are the relationships (if any) between these?

  11. How are color (or for a clam, a periostracum) secreted ?

  12. Then I hit them with a 20 minute ppt presentation about biomineralization, with an emphasis on the Mollusks.

  13. How do sutures get to be dendritic ? (NOTE: this is not the same question as what is the purpose of dendritic sutures) complex shape = complex explanation?

  14. The Hele-Shaw Cell Technique borrowed from: The Center for Polymer Studies at Boston University “Exploring Patterns in Nature” website Two glass plates, one with a hole drilled in the center Cover slips Plastic tubing that fits snugly in the hole in the glass plate, and syringes that fit snug-but-easy inside the tubing Glycerin, Food Coloring Binder Clips Windex and Paper Towels (critical)

  15. 1 regular binder clip at each corner keeps the whole thing together 2 glass plates ~ 8” square top plate has hole drilled in it Two stacked micro cover slips in each corner (2 x 150 µm = 300µm gap put a piece of white paper underneath for better visibility

  16. Did ammonites somehow run the biological equivalent of a Hele-Shaw experiment?

  17. Goals • Long term Higher Level goals (Essay) • Functional Morphology • Natural Selection • Driven vs. Passive Trends • Argument Construction • Familiarization with Peer-Reviewed Literature (sources)

  18. Thinking more about complex sutures: What would the biological parts be that are analogous to our experimental Hele-Shaw apparatus? You have: cameral fluid, visceral fluid, membrane between them, and space between inside of phragmacone and body membrane This always comes up: What did the ‘backside’ of the soft animal look like? How do organisms “secrete” minerals?

  19. Did the animal re-run a Hele-Shaw experiment each time it scooted forward?

  20. … or … did the animal run a Hele-Shaw only the first time it scooted forward and created the first septum, and then the rump remembers the shape (was cast in that fluted configuration)?

  21. How do sutures increase in length to accommodate increased circumference of phragmacone as creature grows? S-t-r-e-t-c-h-i-n-g ? or Adding new bits ?

  22. Is the dendrite shape (in detail) coded for genetically? isn’t this how ammonite species are recognized? So … yes….it must be… but what is coded? 8 Teams in lab each ran a Hele-Shaw experiment using the same fluids and set-up…. Were the dendrites identical between the teams ? (close enough to recognize them as the same species?) (… or is the Hele-Shaw not really a good analogy?)

  23. Questions for further study • What benefit (if any) did complex sutures impart ? • They must be coded for if they are selected for… • If they are selected for, then they must provide some benefit (increased fitness) • Is the data on ancestor-decendent lineages robust enough to be able to say complexity increases? Where does this data come from? • If sutures start out simple, is there any way to change except toward more complex ? (random walk away from a left wall S.J. Gould’s “Full House”)

  24. Why did the more simply-sutured Nautilus survive? (rules of the game during ‘normal’ times and at times of environmental perturbation (at extinction events))

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