04 respiration in animals


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  • 04 respiration in animals

    1. 1. GAS EXCHANGE IN ANIMALS We will be studying the diversity of adaptations for this process in two animal groups: Mammals Fish
    2. 2. AN OVERVIEW <ul><li>Cellular respiration requires O 2 and produces CO 2 : </li></ul>C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O <ul><li>Gas exchange provides a means of supplying an organism with O 2 and removing the CO 2 </li></ul>glucose + oxygen  carbon dioxide + water
    3. 3. THE SOURCE OF OXYGEN <ul><li>Air </li></ul><ul><li>about 21% oxygen </li></ul><ul><li>thinner at higher altitudes </li></ul><ul><li>Water </li></ul><ul><li>amount of oxygen varies but is always much less than air </li></ul><ul><li>even lower in warmer water </li></ul><ul><li>harder to ventilate </li></ul>
    4. 4. GAS EXCHANGE SURFACES <ul><li>Gases move by diffusion . </li></ul>Diffusion <ul><li>Diffusion is greater when: </li></ul><ul><li>the surface area is large </li></ul><ul><li>the distance travelled is short </li></ul><ul><li>the concentration gradient is high </li></ul><ul><li>Gas exchange also requires a moist surface </li></ul><ul><li>O 2 and CO 2 must be dissolved in water to diffuse across a membrane </li></ul>
    5. 5. GAS EXCHANGE SURFACES <ul><li>… and will be organised or operate in a way that maintains a favourable concentration gradient for the diffusion of both gases. </li></ul>A circulatory system may operate in tandem with the gas exchange system to maintain the concentration gradient
    6. 6. <ul><li>Depends on: </li></ul><ul><li>the size of the organism </li></ul><ul><li>where it lives – water or land </li></ul><ul><li>the metabolic demands of the organism – high, moderate or low </li></ul>STRUCTURE OF THE GAS EXCHANGE SURFACE
    8. 8. WATER AS A GAS EXCHANGE MEDIUM <ul><li>No problem in keeping the cell membranes of the gas exchange surface moist </li></ul>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
    9. 9. GETTING OXYGEN FROM WATER: FISH GILLS <ul><li>Gills covered by an operculum (flap) </li></ul><ul><li>Fish ventilates gills by alternately opening and closing mouth and operculum  water flows into mouth  over the gills  out under the operculum </li></ul><ul><li>Water difficult to ventilate  gills near surface of body </li></ul>
    10. 10. GETTING OXYGEN FROM WATER: FISH GILLS <ul><li>Each gill made of four bony gill arches. </li></ul><ul><li>Gill arches lined with hundreds of gill filaments that are very thin and flat . </li></ul>
    11. 11. GETTING OXYGEN FROM WATER: FISH GILLS <ul><li>Gill filaments have folds called lamellae that contain a network of capillaries . </li></ul><ul><li>Blood flows through the blood capillaries in the opposite direction to the flow of water. </li></ul>
    12. 12. ENHANCING THE EFFICIENCY OF FISH GILLS <ul><li>Gills have a very large surface area: four arches with flat filaments with lamellae folds </li></ul><ul><li>Gills are thin-walled and in close contact with water: short distance for diffusion </li></ul><ul><li>Gills have a very high blood supply to bring CO 2 and carry away O 2  dark red colour </li></ul><ul><li>Gills are moist : fish live in water! </li></ul>
    13. 13. ENHANCING THE EFFICIENCY OF FISH GILLS <ul><li>Fresh water flows over gills in one direction . </li></ul><ul><li>COUNTER-CURRENT FLOW: water and blood in the gills flow in opposite directions </li></ul><ul><li> maintains a favourable concentration gradient for diffusion of both gases </li></ul>Concurrent flow animation Countercurrent flow animation
    16. 17. GETTING OXYGEN FROM AIR: MAMMALS, BIRDS & INSECTS <ul><li>As a gas exchange medium, air has many advantages over water: </li></ul><ul><li>Air has a much higher oxygen concentration than water </li></ul><ul><li>Diffusion occurs more quickly so less ventilation of the surface is needed </li></ul><ul><li>Less energy is needed to move air through the respiratory system than water </li></ul>
    17. 18. <ul><li>BUT </li></ul><ul><li>as the gas exchange surface must be moist, in terrestrial animals water is continuously lost from the gas exchange surface by evaporation </li></ul><ul><li>SO </li></ul><ul><li>the gas exchange surface is folded into the body to reduce water loss . </li></ul>GETTING OXYGEN FROM AIR: MAMMALS, BIRDS & INSECTS
    18. 19. WARM-BLOODED ANIMALS <ul><li>Warmth speeds up body’s reactions </li></ul><ul><li> enables faster movement etc </li></ul><ul><li>BUT </li></ul><ul><li>increases evaporation of water from lungs </li></ul><ul><li>AND </li></ul><ul><li>increases demand for energy to stay warm </li></ul><ul><li>SO </li></ul><ul><li>higher demand for gas exchange to provide O 2 for and remove CO 2 from respiration </li></ul>
    19. 20. MAMMAL LUNGS: VENTILATION <ul><li>Two lungs ventilated by movement of diaphragm and ribs </li></ul>
    20. 21. MAMMAL LUNGS: STRUCTURE <ul><li>Air enters via trachea (windpipe) </li></ul><ul><li>Trachea branches into two bronchi (one bronchus to each lung) </li></ul><ul><li>Bronchi branch into bronchioles </li></ul>System of tubes (held open by rings of cartilage ) allow air to flow in and out of lungs
    21. 22. MAMMAL LUNGS: STRUCTURE <ul><li>Healthy lungs </li></ul>Smoker’s lungs
    22. 23. MAMMAL LUNGS: STRUCTURE <ul><li>Many alveoli at the end of the bronchioles </li></ul><ul><li>walls made of flat cells ; only one cell thick </li></ul><ul><li>each alveolus lined with moisture </li></ul><ul><li>surrounded by capillary network carrying blood </li></ul>
    23. 24. GAS EXCHANGE IN MAMMALS <ul><li>Inhaled air: 21% O 2 and 0.04% CO 2 </li></ul><ul><li>Blood arriving: low in O 2 and high in CO 2 </li></ul>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
    24. 25. GAS EXCHANGE IN MAMMALS Gas exchange animation