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GAS EXCHANGE IN ANIMALS

GAS EXCHANGE IN ANIMALS. We will be studying the diversity of adaptations for this process in four animal groups: . Fish. Mammals. Birds. Insects. AN OVERVIEW. Cellular respiration requires O 2 and produces CO 2 :. C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O.

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GAS EXCHANGE IN ANIMALS

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  1. GAS EXCHANGE IN ANIMALS We will be studying the diversity of adaptations for this process in four animal groups: Fish Mammals Birds Insects

  2. AN OVERVIEW • Cellular respirationrequires O2 and produces CO2 : C6H12O6 + 6O2 6CO2 + 6H2O glucose + oxygen  carbon dioxide + water • Gas exchange provides a means of supplying an organism with O2 and removing the CO2

  3. Organism level Cellular level Gas exchange medium (air or water) Circulatory system Gas exchange surface Fuel molecules from food Respiration O2 ATP CO2 CO2

  4. THE SOURCE OF OXYGEN Air • about 21% oxygen • thinner at higher altitudes • easy to ventilate Water • amount of oxygen varies but is always much less than air • even lower in warmer water • harder to ventilate

  5. GAS EXCHANGE SURFACES Diffusion Gases move by diffusion. Diffusion is greater when: • the surface area is large • the distance travelled is small • the concentration gradient is high Gas exchange also requires a moistsurface • O2 and CO2 must be dissolved in water to diffuse across a membrane

  6. GAS EXCHANGE SURFACES Therefore, an efficient gas exchange surface will… • have a large surface area • provide a small distance for gases to diffuse across • be 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 organism • where it lives – water or land • the metabolic demands of the organism – high, moderate or low

  8. TYPES OF GAS EXCHANGE SURFACE

  9. WATER AS A GAS EXCHANGE MEDIUM No problem in keeping the cell membranes of the gas exchange surface moist BUT O2 concentrations in water are low, especially in warmer and/or saltier water SO the gas exchange system must be very efficient to get enough oxygen for respiration

  10. GETTING OXYGEN FROM WATER: FISH GILLS • Gills covered byan operculum (flap) • Fish ventilates gills by alternately opening and closing mouth and operculum water flows into mouth over the gills out under the operculum • Water 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 folds • Gills are thin-walled and in close contact with water: short distance for diffusion • Gills have a very high blood supply to bring CO2 and carry away O2  dark red colour • Gills 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 gases Concurrent flow animation Countercurrent flow animation

  15. CONCURRENT FLOW

  16. COUNTER-CURRENT FLOW

  17. 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 water • Diffusion occurs more quickly so less ventilation of the surface is needed • Less energy is needed to move air through the respiratory system than water

  18. GETTING OXYGEN FROM AIR: MAMMALS, BIRDS & INSECTS BUT as the gas exchange surface must be moist, in terrestrial animals wateris continuously lost from the gas exchange surface by evaporation SO the gas exchange surface is folded into the body to reduce water loss.

  19. WARM-BLOODED ANIMALS Warmth speeds up body’s reactions  enables faster movement etc BUT increases evaporation of water from lungs AND increases demand for energy to stay warm SO higher demand for gas exchange to provide O2 for and remove CO2 from respiration

  20. MAMMAL LUNGS: VENTILATION Two lungs ventilated by movement of diaphragm and ribs

  21. MAMMAL LUNGS: STRUCTURE System of tubes (held open by rings of cartilage) allow air to flow in and out of lungs • Air enters via trachea (windpipe) • Trachea branches into two bronchi (one bronchus to each lung) • Bronchi branch into bronchioles

  22. MAMMAL LUNGS: STRUCTURE Rubber cast of human lungs

  23. MAMMAL LUNGS: STRUCTURE Healthy lungs Smoker’s lungs

  24. MAMMAL LUNGS: STRUCTURE Many alveoli at the end of the bronchioles • walls made of flat cells; only one cell thick • each alveolus lined with moisture • surrounded by capillary network carrying blood

  25. GAS EXCHANGE IN MAMMALS Inhaled air: 21% O2 and 0.04% CO2 Blood arriving: low in O2 and high in CO2 O2 in lung air dissolves in moist lining diffuses into blood diffuses into lung air diffuses into moist lining CO2 in blood Exhaled air: 17% O2 and 4% CO2 Blood leaving: high in O2 and low in CO2

  26. GAS EXCHANGE IN MAMMALS Gas exchange animation

  27. GAS EXCHANGE IN MAMMALS

  28. ENHANCING THE EFFICIENCY OF MAMMAL LUNGS Large surface area • many tiny alveoli • area as big as a tennis court in humans! Short distance for diffusion • alveoli and capillary walls only one cell thick • cells are flattened so very thin • capillaries pressed against alveoli Moist • wet lining of alveolus • system internal to reduce water loss by evaporation

  29. ENHANCING THE EFFICIENCY OF MAMMAL LUNGS Maintaining a concentration gradient • air (with depleted O2 and excess CO2) is exhaled  replaced with fresh inhaled air • blood (having lost CO2 and been enriched with O2) returns to heart to get pumped around body replaced with blood collected from body

  30. BIRD LUNGS Birds have a high demand for oxygen: • warm-blooded so metabolism is high • flight requires a lot of energy Additional 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

  31. BIRD LUNGS Birds have lungs and air sacs: • air sacs are not sites of gas exchange • air sacs enable a one-way flow of air through lungs

  32. Passage of air through lungs: in trachea rear air sacs rear bronchi parabronchi in lungs out trachea front air sacs front bronchi BIRD LUNGS: VENTILATION

  33. BIRD LUNGS Main air tubes through lungs are the parabronchi. Tiny air capillaries loop away from and back to parabronchi  one way flow of air Blood capillaries run alongside air capillaries BUT blood flows in opposite direction to air flow  COUNTER-CURRENT EXCHANGE of gases

  34. ENHANCING THE EFFICIENCY OF BIRD LUNGS Large surface area • many tiny air capillaries Short distance for diffusion • air and blood capillary walls made of flattened, thin cells • air & blood capillaries alongside each other Moist • lining of air capillaries is wet • system is internal to conserve moisture

  35. ENHANCING THE EFFICIENCY OF BIRD LUNGS Maintaining a concentration gradient • Air flows in one direction through lungs regardless of whether the bird is inhaling or exhaling • One way passage in both parabronchi and air capillaries; other wayin blood capillaries  COUNTER-CURRENT EXCHANGE

  36. INSECT TRACHEAL SYSTEM Completely different system! Air tubules (trachea & tracheoles) throughout the body which open to the environment via spiracles

  37. INSECT TRACHEAL SYSTEM • Trachea kept open by circular bands of chitin • Branch to form tracheoles that reach every cell • Ends of the tracheoles are moist • Oxygen delivered directly to respiring cells – insect blood does not carry oxygen

  38. ENHANCING THE EFFICIENCY OF INSECT TRACHEAE • Oxygen delivered directly to respiring cells • Can pump body to move air around in tracheal system BUT • Size of animal limited by relatively slow diffusion rate

  39. DIVERSITY fishgills birdlungs mammallungs insecttracheae

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