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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

Size Matters: Surface/Volume Ratio unfold the cube’s surfaces 1 cm volume = 1 cm3 S/V=6.0 surface = 6 cm2 unfold the cube’s surfaces 2 cm DB25020.jpg volume = 8 cm3 S/V=3.0 surface = 24 cm2 Larger organisms have less surface area relative to volume than do smaller organisms. Materials inside the larger multicellular body have less contact with surface, so something more than diffusion is needed! Conclusion? Circulation!

Geometry Matters: Surface/Volume Ratio unfold the cube’s surfaces 2 cm volume = 8 cm3 S/V=3.0 surface = 24 cm2 unfold the cube’s surfaces 1 cm DB25020.jpg volume = 8 cm3 S/V=3.5 Larger organisms depending on diffusion for gas exchange get better gas exchange if the body is thinner rather than blockier surface = 28 cm2 Conclusion?

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

Invaginated or Evaginated? Bristleworms (Nereis) have capillary beds in the parapodia for gas exchange http://www.teara.govt.nz/NR/rdonlyres/7D647087-7341-4298-A423-B3D2422B6DEF/144283/p6887pc.jpg Invaginated or Evaginated? ©1996 Norton Presentation Maker, W. W. Norton & Company

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

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 Mucilage surface traps and accumulates food particles Cilia move food-laden mucilage to mouth for digestion

Scallop respiration and feeding (shown with one valve removed) http://www.fao.org/docrep/007/y5720e/y5720e09.jpg http://www.fao.org/docrep/009/y5720f/y5720f1b.jpg The soft tissue anatomy of the calico scallop, Argopecten gibbus, visible following removal of one of the shell valves. Key: AM - adductor muscle; G – gills; O – ovary; T – testis; L – ligament; M – mantle. The inhalant and exhalant chambers of the mantle cavity are identified as IC and EC respectively.

Exploring the incurrent and excurrent siphons of a clam: http://www.youtube.com/watch?v=AzTVh1U7Et4

Evaginated gills surrounded by water bearing oxygen Architeuthis Giant squid Evaginated gills surrounded by water bearing oxygen Mesonychoteuthis hamiltoni Colossal squid http://www.mnh.si.edu/natural_partners/squid4/DispatchImages/20Feb1999/gills_inside_mantle_cavity_labeled.jpg http://www.theage.com.au/ffximage/2007/02/22/squid_narrowweb__300x363,0.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

Delicate gills need protection from predators: shells, opercula Other species evolved internalized respiratory trees… Sea cucumber body systems ©1996 Norton Presentation Maker, W. W. Norton & Company evaginated or invaginated? http://www.marietta.edu/~biol/biomes/images/oceans/sea_cucumber_8178_800.jpg

Tidal flow through anus into respiratory tree of sea cucumber: http://www.youtube.com/watch?v=AzTVh1U7Et4

The tidal flow gas supply is enough to support a friend too… http://www.youtube.com/watch?v=00DXYXVRHkQ&feature=youtu.be

And now for a look inside our gastropod mollusc… http://coris.noaa.gov/glossary/trochophor_larv_186.jpg Trochophore larva: And now for a look inside our gastropod mollusc… http://www.zetnet.co.uk/~pm/photos/snail.jpg http://people.bu.edu/veliger/veliger.jpeg Veliger larva: The shell obviously provides a hard covering for the visceral mass. The snail shown here is a pulmonate, with a vascularized mantle cavity serving as a lung. Vascularizing this led to loss of the gills in most gastropods. The gastropods, are clearly hermaphroditic, and some are self-fertile. Free-living larval stages are the dispersal mechanisms in water (diffusion?)

Adult Sea elephant (snail)… trochophore larva http://en.wikipedia.org/wiki/Trochophore its radula http://tolweb.org/tree/ToLimages/AtlantaPeroni1.jpg gas exchange by simple diffusion veliger larva its proboscis http://tolweb.org/tree/ToLimages/AtlantaSpRadula11.230a.jpg http://tolweb.org/tree/ToLimages/OxygyrusLarva1.jpg http://tolweb.org/tree/ToLimages/ScutataProboscis11.200a.jpg

The slug shows the pneumostome in the mantle for breathing. foot mantle optical tentacles skirt sensory tentacles http://www.nawwal.org/~mrgoff/photojournal/2003/winspr/pictures/05-17slug2.jpg

book gills http://clacc.uchc.edu/Species/Aquatics/HorseshoeCrab/HorseShoeCrab1.jpg http://www.bumblebee.org/invertebrates/images/LimulusDorsal.jpg http://www.bumblebee.org/invertebrates/images/LimulusVentral.jpg

Chelicerata Considerable diversity within a single taxonomic category http://somethingscrawlinginmyhair.com/wp-content/uploads/2007/09/tickdorsalview2007-5-2.jpg http://media-2.web.britannica.com/eb-media/97/46897-004-E3937032.jpg book lungs trachea book gills diffusion http://weblog.pell.portland.or.us/~orc/bugs/argiope_aurantia.jpg http://www.flightglobal.com/blogs/flight-international/scorpion.gif http://farm1.static.flickr.com/40/108057513_ff286d144f.jpg

Argyroneta aquatica, the water spider, traps air with body hairs at surface and brings the air down to the hydrophobic web for later use…sometimes called the “water bell” spider. http://mmem.spschools.org/grade5science/wetland/waterspider.jpeg

Centruroides vittatus (bark scorpion) has a book lung (an evaginated surface like a gill for terrestrial gas exchange) http://www.entomology.umn.edu/cues/tenczar/Cvittatus/Centruroides_vittatus.jpg ©1996 Norton Presentation Maker, W. W. Norton & Company

In an insect respiratory tree, the tracheoles contact every cell. trachea tracheoles spiracles ©1996 Norton Presentation Maker, W. W. Norton & Company See Fig. 45.8 pg 908

Tobacco hornworm: Manduca sexta larva http://farm7.staticflickr.com/6012/5920755746_3b04a39572_o.jpg

The abdominal exoskeletal plates an insect, mostly rigid, move relative to each other by muscle contraction inside, to drive the tidal flow through the spiracles (on the side of the body) http://www.youtube.com/watch?v=v_GP_gIxTCo See also: http://www.youtube.com/watch?v=pYj43gtAKoU

The Cicada Killer Wasp Sphecius speciosus pumps his abdominal segments like a bellows to produce tidal flow through the spiracles on the side of his body. http://www.youtube.com/watch?v=RPKTteHoW-8

An insect gas exchange--an invaginated tracheolar system This is not particularly different from the respiratory tree model But the segmented abdomen and musculature permit tidal air flow trachea spiracle tracheoles ©1996 Norton Presentation Maker, W. W. Norton & Company

Here are two spiracles, one open with sensors functioning. The other is closed to avoid desiccation/predation, etc. ©1996 Norton Presentation Maker, W. W. Norton & Company The convergence with stomata in plant leaves is interesting!

Could this be another example of “ontogeny recapitulating phylogeny”? In larval aquatic stages of arthropod metamorphosis, larvae may demonstrate evaginated gills rather than invaginated tracheoles. Could this be another example of “ontogeny recapitulating phylogeny”? ©1996 Norton Presentation Maker, W. W. Norton & Company

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

Bronchoscopy: Vocal cords, Cartilage ridges, Mucus! http://www.youtube.com/watch?v=DJPV6m52_lM&

The human breathing system: the larger structures ©1996 Norton Presentation Maker, W. W. Norton & Company

The mammalian lung gas exchange fine structure: the alveolus Note the convergence of the oxygen contact feature with spongy mesophyll of plants ©1996 Norton Presentation Maker, W. W. Norton & Company See Fig. 45.10 pg 910

Respiratory Pigments Function: deliver O2 to the cells Hemerythrin – red color but no heme group Fe, low oxygen binding, few inverts, Methylococcus (methanotropic bacterium) Hemocyanin – blue color, Cu group, moderate oxygen binding, most molluscs Hemoglobin – red color, heme Fe group, high oxygen binding, 4 polypeptides, vertebrates and some invertebrates Some organisms have none of these: high surface to body area ratio so exchange occurs at body surface by simple diffusion http://upload.wikimedia.org/ wikipedia/commons/7/79/ Hemerythrin.jpg http://upload.wikimedia.org/ Wikipedia/commons/f/fb/ Hemocyanin2.jpg http://upload.wikimedia.org/wikipedia/ commons/d/d2/Hemoglobin.gif

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

Bird lungs have additional air sacs attached to their lungs anterior sacs lung posterior sacs http://www.strombergschickens.com/images/doves/White_Fantail_Pigeon.jpg

What is the advantage of this apomorphy? lung Bird Lung Function: What is the advantage of this apomorphy? lung anterior air sac posterior air sac inhalation blood flow anterior air sac posterior air sac lung exhalation blood flow See Fig. 45.12 pg 911

SEM of bird lung: note-cells are close to gas exchange surfaces Just as observed in plant leaves ©1996 Norton Presentation Maker, W. W. Norton & Company

Gas Exchange Path for Cooling: Canine Panting http://www.spitzer.caltech.edu/espanol/edu/ir_zoo/images/dog_panting.jpg cool inspired air evap cool expired air cooled arterial blood to brain arterial blood from heart cooled venous blood exg rete What kind of exchange is found in this rete? arterial blood in nose and tongue air temperature venous blood to heart arterial blood to brain exchange rete venous blood in nose and tongue http://www.samrabourn.com/BigWhiteDog.jpg

In wintering aquatic birds, the feet isolate body from cold water ©1996 Norton Presentation Maker, W. W. Norton & Company Feathers provide body insulation

Gas Exchange between the environment and the film of body fluid coating body cells is only the first step in gas exchange for large multicellular animals. The rest of the story involves getting gas exchange between the exchange surfaces and the blood stream and then between the blood stream and the internal body tissues. The rest of the story relates to animal circulation systems which we shall hold off for now...