Presentation on theme: "GAS EXCHANGE IN ANIMALS"— Presentation transcript:
1 GAS EXCHANGE IN ANIMALS We will be studying the diversity of adaptations for this process in four animal groups:FishMammalsBirdsInsects
2 AN OVERVIEW Cellular respiration requires O2 and produces CO2 : C6H12O6 + 6O2 6CO2 + 6H2Oglucose + oxygen carbon dioxide + waterGas exchange provides a means of supplying an organism with O2 and removing the CO2
3 Gas exchange medium (air or water) Organism levelCirculatory systemCellular levelGas exchange surfaceFuel moleculesfrom foodRespirationO2ATPCO2CO2
4 THE SOURCE OF OXYGEN Air about 21% oxygen thinner at higher altitudes easy to ventilateWateramount of oxygen varies but is always much less than aireven lower in warmer waterharder to ventilate
5 GAS EXCHANGE SURFACES Gases move by diffusion. Diffusion Diffusion is greater when:the surface area is largethe distance travelled is smallthe concentration gradient is highGas exchange also requires a moist surfaceO2 and CO2 must be dissolved in water to diffuse across a membrane
6 GAS EXCHANGE SURFACESTherefore, an efficient gas exchange surface will…have a large surface areaprovide a small distance for gases to diffuse acrossbe moist…and will be organised or operate in a way that maintains a favourable concentration gradient for the diffusion of both gases.A circulatory system may operate in tandem with the gas exchange system to maintain the concentration gradient
7 STRUCTURE OF THE GAS EXCHANGE SURFACE Depends on:the size of the organismwhere it lives – water or landthe metabolic demands of the organism – high, moderate or low
9 WATER AS A GAS EXCHANGE MEDIUM No problem in keeping the cell membranes of the gas exchange surface moistBUTO2 concentrations in water are low, especially in warmer and/or saltier waterSOthe gas exchange system must be very efficient to get enough oxygen for respiration
10 GETTING OXYGEN FROM WATER: FISH GILLS Gills covered by an operculum (flap)Fish ventilates gills by alternately opening and closing mouth and operculum water flows into mouth over the gills out under the operculumWater difficult to ventilate gills near surface of body
11 GETTING OXYGEN FROM WATER: FISH GILLS Each gill made of four bony gill arches.Gill arches lined with hundreds of gill filaments that are very thin and flat.
12 GETTING OXYGEN FROM WATER: FISH GILLS Gill filaments are have folds called lamellae that contain a network of capillaries.Blood flows through the blood capillaries in the opposite direction to the flow of water.
13 ENHANCING THE EFFICIENCY OF FISH GILLS Gills have a very large surface area: four arches with flat filaments with lamellae foldsGills are thin-walled and in close contact with water: short distance for diffusionGills have a very high blood supply to bring CO2 and carry away O2 dark red colourGills are moist: fish live in water!
14 ENHANCING THE EFFICIENCY OF FISH GILLS Fresh water flows over gills in one direction.COUNTER-CURRENT FLOW: water and blood in the gills flow in opposite directions maintains a favourable concentration gradient for diffusion of both gasesConcurrent flow animationCountercurrent flow animation
18 GETTING OXYGEN FROM AIR: MAMMALS, BIRDS & INSECTS As a gas exchange medium, air has many advantages over water:Air has a much higher oxygen concentration than waterDiffusion occurs more quickly so less ventilation of the surface is neededLess energy is needed to move air through the respiratory system than water
19 GETTING OXYGEN FROM AIR: MAMMALS, BIRDS & INSECTS BUTas the gas exchange surface must be moist, in terrestrial animals water is continuously lost from the gas exchange surface by evaporationSOthe gas exchange surface is folded into the body to reduce water loss.
20 WARM-BLOODED ANIMALS Warmth speeds up body’s reactions enables faster movement etcBUTincreases evaporation of water from lungsANDincreases demand for energy to stay warmSOhigher demand for gas exchange to provide O2 for and remove CO2 from respiration
21 MAMMAL LUNGS: VENTILATION Two lungs ventilated by movement of diaphragm and ribs
22 MAMMAL LUNGS: STRUCTURE System of tubes (held open by rings of cartilage) allow air to flow in and out of lungsAir enters via trachea (windpipe)Trachea branches into two bronchi (one bronchus to each lung)Bronchi branch into bronchioles
23 MAMMAL LUNGS: STRUCTURE Rubber cast of human lungs
25 MAMMAL LUNGS: STRUCTURE Many alveoli at the end of the bronchioleswalls made of flat cells; only one cell thickeach alveolus lined with moisturesurrounded by capillary network carrying blood
26 GAS EXCHANGE IN MAMMALS Inhaled air: 21% O2 and 0.04% CO2Blood arriving: low in O2 and high in CO2O2 in lung airdissolves in moist liningdiffuses into blooddiffuses into lung airdiffuses into moist liningCO2 in bloodExhaled air: 17% O2 and 4% CO2Blood leaving: high in O2 and low in CO2
29 ENHANCING THE EFFICIENCY OF MAMMAL LUNGS Large surface areamany tiny alveoliarea as big as a tennis court in humans!Short distance for diffusionalveoli and capillary walls only one cell thickcells are flattened so very thincapillaries pressed against alveoliMoistwet lining of alveolussystem internal to reduce water loss by evaporation
30 ENHANCING THE EFFICIENCY OF MAMMAL LUNGS Maintaining a concentration gradientair (with depleted O2 and excess CO2) is exhaled replaced with fresh inhaled airblood (having lost CO2 and been enriched with O2) returns to heart to get pumped around body replaced with blood collected from body
31 BIRD LUNGS Birds have a high demand for oxygen: warm-blooded so metabolism is highflight requires a lot of energyAdditional challenge:air at higher altitude is thinner lower in O2…yet some species have been seen flying over Mt Everest!Birds have a very efficient gas exchange system to cope with low O2 supply & high O2 demand
32 BIRD LUNGS Birds have lungs and air sacs: air sacs are not sites of gas exchangeair sacs enable a one-way flow of air through lungs
33 BIRD LUNGS: VENTILATION Passage of air through lungs:in trachea rear air sacs rear bronchiparabronchi in lungsout trachea front air sacs front bronchi
34 BIRD LUNGS Main air tubes through lungs are the parabronchi. Tiny air capillaries loop away from and back to parabronchi one way flow of airBlood capillaries run alongside air capillariesBUTblood flows in opposite direction to air flow COUNTER-CURRENT EXCHANGE of gases
36 ENHANCING THE EFFICIENCY OF BIRD LUNGS Large surface areamany tiny air capillariesShort distance for diffusionair and blood capillary walls made of flattened, thin cellsair & blood capillaries alongside each otherMoistlining of air capillaries is wetsystem is internal to conserve moisture
37 ENHANCING THE EFFICIENCY OF BIRD LUNGS Maintaining a concentration gradientAir flows in one direction through lungs regardless of whether the bird is inhaling or exhalingOne way passage in both parabronchi and air capillaries; other way in blood capillaries COUNTER-CURRENT EXCHANGE
38 INSECT TRACHEAL SYSTEM Completely different system!Air tubules (trachea & tracheoles) throughout the body which open to the environment via spiracles
39 INSECT TRACHEAL SYSTEM Trachea kept open by circular bands of chitinBranch to form tracheoles that reach every cellEnds of the tracheoles are moistOxygen delivered directly to respiring cells – insect blood does not carry oxygen
40 ENHANCING THE EFFICIENCY OF INSECT TRACHEAE Oxygen delivered directly to respiring cellsCan pump body to move air around in tracheal systemBUTSize of animal limited by relatively slow diffusion rate