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

This preview shows pages 1–4. Sign up to view the full content.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

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...
View Full Document

{[ snackBarMessage ]}

Page1 / 9

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

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online