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Biology LibreTexts

7.E: Patterning Class Activity and Discussion

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  • Assignment 1

    Choose one of the stories from How the Snake Lost It's Legs. and summarize the information for the class.

    End your summary with at least one "future directions" question for us to consider in class.

    Assignment 2

    The questions below were originally written for students reading Endless Forms by Sean Carroll. However, the questions in bold are discussion questions that can be answered without these books.

    The "Reading Guide" questions are appropriate for short homework answers and the "Discussion Guide" questions are appropriate for open in-class or online discussion.

    Discussion Questions

    1. Do you think our "sense of wonder and beauty is diminshed or enhanced by scientific understanding?"
    2. Why do we think it is "easy" for butterflies to evolve new wing patterns but less easy to evolve new biochemical pathways (like new pigments for example)?
    3. What kinds of lab experiments can give us insight into butterfly wing Evo-Devo?
    4. What is the difference between morphological convergence and genetic convergence?
    5. What changes besides protein changes in MC1R could lead to changes in animal coloration?
    6. Can convergent evolution of a trait be driven by different genetic mutations?
    7. Why do we know more about coloration in fruit flies than in zebras and leopards?
    8. Draw a butterfly wing with a maximum ground plan and one with fewer pattern elements.
    9. What are three butterfly wing inventions?
    10. How is Bicyclus an example of plasticity? What is the switch that regulates this plasticity?
    11. Explain the genetics and selection driving melanism in rock pocket mice.
    12. What is Bard's model for zebra striping?

    Endless Forms Reading Guide: Chapter 8

    1. What is Batesian mimicry?
    2. What are the serial homologs in a butterfly wing?
    3. What is a wing scale? Is it homologous or homoplasious to a fish scale?
    4. What is an eyespot focus and why do we call it an organizer?

    Endless Forms Reading Guide: Chapter 9

    1. What is disruptive coloration?
    2. What is melanin?
    3. What genetic changes drive melanism? Are these cis-regulatory or exonic? Why don't they affect other developmental processes?
    4. What is the significance of MC1R in humans?
    5. What causes white spots on mammals?
    6. What is fitness?
    7. What is a selection coefficient?
    8. Give two reasons why we might not see spotted mice in nature.

    In-class Activity (Mini-Lab)

    Reaction Diffusion Simulator

    Note: If possible this is ideally run in a computer lab or with loaner laptops. Otherwise, ask students ahead of time to bring in at least one laptop per group. Students can follow the questions below or can be given minimal instructions and just "play" with the simulation.

    In the Turing Model, the pattern is changed by adjusting the speed of diffusion, the strength of interaction, and the rate of degradation. In the Grey-Scott model simulation, the feed rate is related to the speed of diffusion and the death rate is related to the rate of degredation.

    1. To see the a "boring" pattern, choose a feed rate of 0.006 and a death rate of 0.028. Click anywhere on the canvas.
    2. Choose the present "Solitons" and click anywhere on the canvas. This feed/death rate combination produces a field of equally spaced spots. How does this relate to the Turing model?
    3. Adjust the feed rate to 0.02 and the death rate to 0.058, how does this affect the spot pattern you saw in Solitons?
    4. Can you adjust the feed and death rates to produce stripes?
    5. What happens if you click on the canvas while a pattern is being generated. What would this represent biologically?
    6. What kinds of biochemical/molecular properties might affect feed and death rates?