15 - & ±& ² ± ³& ´ ³ ´ The Evolution of...

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Unformatted text preview: & ± & ² ± ³ & ´ ³ ´ The Evolution of Plants - They Made the Land Green 1. Next Friday – HW5. Diffusion homework due. Available at Homework Assignment link. Simulations #3-#5 – Class results Concentration gradient = Δ C (Particle number) Δ x (Distance of 4 circles) Diffusion rate = Particles past circle 4 Fick’s First Law of Diffusion e.g., a membrane (Negative sign means diffusion happens down the gradient, but biologists often drop the sign.) area Δ x J = -D Δ C Δ x J = flux (“diffusion rate”) amount/area-time D = diffusion coefficient Δ C = concentration difference Δ 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) & ± & ² ± ³ & ´ & ´ Fick’s Second Law of Diffusion ∂ C t = D 2 C x 2 Einstein’s solution - “time-to-diffuse equation” t = ( Δ x ) 2 2 D t = time Δ 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 For example, glucose - molecular weight: 180 Da diffusion coefficient: 7.0 x 10-6 cm 2 /sec t = ( Δ x ) 2 2 D Typical Structure Distance (x) Time (t) Cell membrane 10 nm 71 ns Bacterium 1 µ m 0.71 ms Eukaryotic cell 10 µ m 71 ms Sea urchin embryo 300 µ m 64 s Volvox 1 mm 12 min Mammalian heart wall 2 cm 3.3 days Squid giant axon 10 cm 82.6 days The Evolution of Plants - They Made the Land Green Where are the plants? Animals fossilized in the Burgess Shale following the Cambrian Radiation 540 million years ago C & R Fig. 32.13 & ± & ² ± ³ & ´ µ ´ Plants evolved as the first conquerors of the land Colonization of terrestrial environments • First- plants evolved as a new monophyletic lineage with novel adaptations for surviving on the land. • Later- existing lineages of animals modified pre-existing structures for terrestrial survival. www.palaeos.com/Plants/Images/early-dev.jpg 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 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...
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15 - & ±& ² ± ³& ´ ³ ´ The Evolution of...

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