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2. In Stentor, a narrow elongate shape permits faster diffusion.
In Stentor, a narrow elongate shape permits faster diffusion.
Myonemes along body wall allow shape contraction to mix cell contents.
Exterior circulation by cilia helps move fresh water for gas exchange, nutrients closer to body, for exchange by diffusion.

3. Gas Exchange in Unicellular Organisms
Size matters: microorganisms use simple diffusion for gas exchange
Altering shape may make diffusion uptake a shorter, faster path
diffusion

4. Unicellular animals use diffusion
Simple aquatic multicellular animals exchange gas through skin with capillary exchange with blood system…evaginated
Unicellular animals use diffusion
©1996 Norton Presentation Maker, W. W. Norton & Company
..or invaginated
Air breathers use lungs or tracheal systems

5. Nudibranch Flabellina verrucosa

6. Argopecten gibbus the Calico scallop, a bivalve mollusc
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Ciliated surfaces move water across gills for gas exchange

7. Mexican Axolotl Ambystoma mexicanum
See Fig pg 906

8. Perca flavescens oxygenated water deoxygenated, carbonated water
oxygenated
water
operculum
deoxygenated,
carbonated water
Muscular operation of operculum system moves water into mouth, over evaginated gills, and out from trailing edge of operculum
See Fig pg 907

9. How do evaginated gills work?
oxygenated
©1996 Norton Presentation Maker, W. W. Norton & Company
filament enlarged…
deoxygenated

10. Gill filament shows counter-current exchange design:
oxygenated water
water and blood flow in opposite directions
blood return to heart
blood from heart
deoxygenated water
©1996 Norton Presentation Maker, W. W. Norton & Company
See Fig pg 907

11. Counter-current is more efficient than concurrent exchange water water
blood
blood
100 50
Percent O2 Saturation
water
blood
100 50
Percent O2 Saturation
water
blood
Countercurrent flow maximizes:
Oxygen removal from water
Blood oxygen content
This efficient system is needed because oxygen solubility is very low in water (10 mg/L) compared to in air (286 mg/L).
See Fig pg 907

12. Vertebrates evolved an invaginated gas exchange system:
The alveolate lung
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Notice in this sequence how exchange surface area increases!

13. Tidal flow in “blind pouch” exchange system
warms, humidifes,
traps particles
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closes glottis for swallowing
exhaled air vibrates cords for voice
mucus, particles swallowed
cartilage ridges keep airway open
cilia lift mucus with particles upward

14. The human breathing system: the larger structures
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15. The mammalian lung gas exchange fine structure: the alveolus
©1996 Norton Presentation Maker, W. W. Norton & Company
See Fig pg 910

16. How the alveolate lung works inhalation exhalation
“Artificial respiration” is possible because of this!
inhalation
exhalation
Notice this is not a counter-current mechanism and is inefficient compared to gills
Terrestrial animals do not need efficient exchange because air holds much oxygen compared to water
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17. contracts to drop floor
The ventilation movement in vertebrates with lungs has two parts
lungs nearly empty
lungs nearly full
rib muscles lift
contracts to drop floor
©1996 Norton Presentation Maker, W. W. Norton & Company
For many singers and public speakers, the first lesson is re-learning how to breathe!
See Fig pg 911