Lecture 5 Notes on Gas Exchange - PDF

Lecture 5: 15 Jan. Gas Exchange Diffusion: Maximizing Fick Reading: 644-651, Box 23., 629-639 If you need review: 654- 677 1 1  Strategies for Breathing Water 1. don’t use much O2 2...

Lecture 5: 15 Jan. Gas Exchange Diffusion: Maximizing Fick Reading: 644-651, Box 23., 629-639 If you need review: 654- 677 1 1  Strategies for Breathing Water 1. don’t use much O2 2 2   P1 − P2  Minimizing X J = D  A   anatomically what does X represent?  X  will selection favour increasing or decreasing X? why? (think mathematics) What do you conclude from the data in 23.7? 22.7 23.7 3 3  Metabolic Rates 1. vs. size 2. air- vs. water-breathers 4 4   P1 − P2  Minimizing X J = D  A   anatomically what does X represent?  X  will selection favour increasing or decreasing X? why? (think mathematics) What do you conclude from the data in 23.7? 22.7 23.7 5 5   P1 − P2  Maximizing A J = D  A   anatomically what does A represent?  X  will selection favour increasing or decreasing A? why? (think mathematics) How do animals increase A? 23.2 6 6  External Gills 23.25 7 7  Internal Gills 23.27 23.26 8 8  Lungs etc. see Box 23.4 23.26 23.29 9 9  How large is A? 30 – 50 m2 23.18 10 10  Allometry of A what’s the allometric exponent? 23.7 11 11  Fish: Unidirectional Ventilation permits countercurrent gas exchange water & blood in gills flow in opposite directions why is that important? 23.10 12 12  Maximizing P1 – P2 countercurrent gas exchange water & blood in gills flow in opposite directions why is that important? 23.10 23.4 13 13  Maximizing P1 – P2: Air Breathers less selective pressure to maximize P1-P2: why? describe airflow relative to blood flow in mammals 22.30 22.3 14 14  Evolution of Lung Ventilation 2. glottis opens; “old” air leaves 1. glottis closed; through dorsal depress buccal surface of buccal cavity; fresh air cavity drawn to buccal floor 3. buccal floor raises, pushing “fresh” air into lunch 23.14 15 15  Ventilation: Mammals 16 16  Bird Ventilation 23.24 23.22 17 17  parabronchi anterior air sac posterior air sac 18 18  Maximizing P1 – P2 countercurrent gas exchange water & blood in gills flow in opposite directions why is that important? 23.10 23.4 19 19  Maximizing P1 – P2: Birds bird ventilation: air flow within gas exchange site (parabronchus air capillaries) unidirectional perpendicular to blood flow (crosscurrent) selective pressure to increase efficiency? 23.5 23.23 20 20 21 21