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In Stentor, a narrow elongate shape permits faster diffusion. http://micro.magnet.fsu.edu/primer/techniques/hoffmangallery/images/stentor.jpg 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.
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 http://www.microscopy-uk.org.uk/mag/imagsmall/amoebafeeding3.jpg
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
Nudibranch Flabellina verrucosa http://www.sciencephoto.com/image/108117/530wm/C0043905-Nudibranch-SPL.jpg
Argopecten gibbus the Calico scallop, a bivalve mollusc ©1996 Norton Presentation Maker, W. W. Norton & Company Ciliated surfaces move water across gills for gas exchange
Mexican Axolotl Ambystoma mexicanum See Fig. 45.4 pg 906 http://images.nationalgeographic.com/wpf/media-live/photos/000/007/cache/mexican-axolotl_780_600x450.jpg
Perca flavescens oxygenated water deoxygenated, carbonated water http://www.tnfish.org/PhotoGalleryFish_TWRA/FishPhotoGallery_TWRA/images/YellowPerchMeltonHillNegus_jpg.jpg oxygenated water operculum deoxygenated, carbonated water http://courses.washington.edu/chordate/453photos/gut_photos/aseptal_gills2.jpg Muscular operation of operculum system moves water into mouth, over evaginated gills, and out from trailing edge of operculum See Fig. 45.5 pg 907
How do evaginated gills work? oxygenated ©1996 Norton Presentation Maker, W. W. Norton & Company filament enlarged… deoxygenated
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. 45.5 pg 907
Counter-current is more efficient than concurrent exchange water water 100 70 40 15 100 85 70 55 53 90 60 30 5 5 20 35 50 52 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. 45.6 pg 907
Vertebrates evolved an invaginated gas exchange system: The alveolate lung ©1996 Norton Presentation Maker, W. W. Norton & Company Notice in this sequence how exchange surface area increases!
Tidal flow in “blind pouch” exchange system warms, humidifes, traps particles ©1996 Norton Presentation Maker, W. W. Norton & Company closes glottis for swallowing exhaled air vibrates cords for voice mucus, particles swallowed cartilage ridges keep airway open cilia lift mucus with particles upward
The human breathing system: the larger structures ©1996 Norton Presentation Maker, W. W. Norton & Company
The mammalian lung gas exchange fine structure: the alveolus ©1996 Norton Presentation Maker, W. W. Norton & Company See Fig. 45.10 pg 910
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 ©1996 Norton Presentation Maker, W. W. Norton & Company
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. 45.11 pg 911