16. Plants

16. Plants - 2/27/11 1 Class announcements 1. Next Friday...

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Unformatted text preview: 2/27/11 1 Class announcements 1. Next Friday HW5. Diffusion homework due. Available at GAE homeworks link 2. Next Fridays GAE bring 2 calculators for each group. Simulation #3-#5 Class results Concentration gradient = C (Particle number) x (Distance of 4 circles) Particles past circle 4 Ficks First Law of Diffusion e.g., a membrane (Negative sign means down the gradient, but biologists often drop the sign.) area x J = -D C x J = flux (diffusion rate) D = diffusion coefficient C = concentration difference x = distance J Simulation #6 Class results Two (of many) possibilities include: 1) t is directly proportional to x (the plot of t vs. x is a straight line) 2) t is directly proportional to x squared (the plot is parabolic) Not enough data for 80 s 2/27/11 2 Ficks Second Law of Diffusion C t = D 2 C x 2 Einsteins solution - time-to-diffuse equation t = ( x ) 2 2 D t = time x = mean distance traveled D = diffusion coefficient Adapted from www.npl.co.uk/educate-+-explore/beginners-guides-posters/einstein-and-blackboard HELP ME, 207! Movement of small diffusible molecules Distance ( x) Time (t) Typical Structure 10 nm 100 ns Cell membrane 1 m 1 ms Bacteria 10 m 100 ms Eukaryotic cell 300 m 1.5 min Sea urchin embryo 1 mm 16.6 min Volvox 2 cm 4.6 days Human heart wall 10 cm 82.7 days Squid giant axon For example, glucose - molecular weight: 180 Da diffusion coefficient: 7.0 x 10-6 cm 2 /sec t = ( x ) 2 2 D The Evolution of Plants - They Made the Land Green The easy life of an aquatic alga Bathed in nutrients Supported against gravity Extensive transport often not necessary Gametes, offspring transmitted by water No problem of desiccation 2/27/11 3 Plausible selection pressures for colonizing the land ~470 million years ago: More direct sun for photosynthesis (sufficient ozone for UV filtration) Inorganic nutrients available on land Initially, an absence of herbivores The harsh life of a land plant Land plants must ______________ ______________ ______________ ______________ ______________ www.izix.com Where are the plants? Animals fossilized in the Burgess Shale following the Cambrian Radiation 540 million years ago C & R Fig. 32.13 Plants evolved as the conquerors of the land Colonization of terrestrial environments First- plants evolved as a new monophyletic lineage with novel adaptations for surviving on the land....
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16. Plants - 2/27/11 1 Class announcements 1. Next Friday...

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