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04   respiration in animals
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04 respiration in animals

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  • http://www.youtube.com/watch?v=XEIRlw5rCUk&feature=related
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04   respiration in animals 04 respiration in animals Presentation Transcript

  • GAS EXCHANGE IN ANIMALS We will be studying the diversity of adaptations for this process in two animal groups: Mammals Fish
  • AN OVERVIEW
    • Cellular respiration requires O 2 and produces CO 2 :
    C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O
    • Gas exchange provides a means of supplying an organism with O 2 and removing the CO 2
    glucose + oxygen  carbon dioxide + water
  • THE SOURCE OF OXYGEN
    • Air
    • about 21% oxygen
    • thinner at higher altitudes
    • Water
    • amount of oxygen varies but is always much less than air
    • even lower in warmer water
    • harder to ventilate
  • GAS EXCHANGE SURFACES
    • Gases move by diffusion .
    Diffusion
    • Diffusion is greater when:
    • the surface area is large
    • the distance travelled is short
    • the concentration gradient is high
    • Gas exchange also requires a moist surface
    • O 2 and CO 2 must be dissolved in water to diffuse across a membrane
  • GAS EXCHANGE SURFACES
    • … 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
    • Depends on:
    • the size of the organism
    • where it lives – water or land
    • the metabolic demands of the organism – high, moderate or low
    STRUCTURE OF THE GAS EXCHANGE SURFACE
  • TYPES OF GAS EXCHANGE SURFACE
  • WATER AS A GAS EXCHANGE MEDIUM
    • No problem in keeping the cell membranes of the gas exchange surface moist
    BUT O 2 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
  • 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 operculum
    • Water difficult to ventilate  gills near surface of body
  • 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 .
  • GETTING OXYGEN FROM WATER: FISH GILLS
    • Gill filaments 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.
  • 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 CO 2 and carry away O 2  dark red colour
    • Gills are moist : fish live in water!
  • 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
  • CONCURRENT FLOW
  • COUNTER-CURRENT FLOW
  •  
  • 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
    • BUT
    • as the gas exchange surface must be moist, in terrestrial animals water is continuously lost from the gas exchange surface by evaporation
    • SO
    • the gas exchange surface is folded into the body to reduce water loss .
    GETTING OXYGEN FROM AIR: MAMMALS, BIRDS & INSECTS
  • 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 O 2 for and remove CO 2 from respiration
  • MAMMAL LUNGS: VENTILATION
    • Two lungs ventilated by movement of diaphragm and ribs
  • MAMMAL LUNGS: STRUCTURE
    • Air enters via trachea (windpipe)
    • Trachea branches into two bronchi (one bronchus to each lung)
    • Bronchi branch into bronchioles
    System of tubes (held open by rings of cartilage ) allow air to flow in and out of lungs
  • MAMMAL LUNGS: STRUCTURE
    • Healthy lungs
    Smoker’s lungs
  • 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
  • GAS EXCHANGE IN MAMMALS
    • Inhaled air: 21% O 2 and 0.04% CO 2
    • Blood arriving: low in O 2 and high in CO 2
    O 2 in lung air dissolves in moist lining diffuses into blood CO 2 in blood diffuses into moist lining diffuses into lung air Exhaled air: 17% O 2 and 4% CO 2 Blood leaving: high in O 2 and low in CO 2
  • GAS EXCHANGE IN MAMMALS Gas exchange animation