15. Diffusion (complete)

15. Diffusion (complete) - 2/27/11 Initial setup 1. Open...

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2/27/11 1 Initial setup 1. Open Mathematica player and RandomWalkCircles 5 simulation 2. Adjust the stimulation window to fill the screen as here 3. Open your Google account and use the link emailed to you to open “Diffusion data” spreadsheet 4. Play with the simulation according to the instructions on the handout. In-class activities: computer simulations for understanding the fundamental principles governing diffusion as a physical process Group homework: several problems for illustrating the role of diffusion in biological systems. Homework assignment will be posted on the class website. Due next Friday. Learning objectives : 1) To visualize how the random movement of molecules can result in their net movement down a concentration gradient; 2) To gain a quantitative perspective of how the diffusion works as a physical process; and 3) To analyze how the limits of diffusion have affected the evolution and functioning of large multicellular organisms in eukaryotic lineages. Multicellular eukaryotes: The limits of diffusion Diffusion in Cells Diffusion works fine across membranes, organelles, and most cells In general, no need to evolve special mechanisms for facilitating the movement of most molecules via diffusion over short distances. (Exception: the challenge of membrane permeability) Independent origins of eukaryotic multicellularity - > 20 origins Basal “Photosynthetic” “Heterotrophic” unicellular flagellate Basal flagellated eukaryotes Likely origin of multicellularity in some lineages
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15. Diffusion (complete) - 2/27/11 Initial setup 1. Open...

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