Adaptations for Gas Exchange

Respiratory surfaces
1. Properties: Large surface area. Thin(Short diffusion path) Moist. Has a concentration gradient . permeable
As an organism gets bigger, its surface area gets smaller
1. The volume of an organism increases much faster than the surface area
  1. Larger organisms have had to evolve systems and organs to increase the avaliable surface for gas exchange. They also need a system to transport gases to and from the exchange surface
Earthworm Adaptations
1. They carry out gas exchange by diffusion
2. Large S.A
  1. Blood containing haemoglobin (high affinity for oxygen)
3. Well developed Capillary network
  1. Low metabollic rate
Human Lungs
1. Inspiration
  1. Intercostals contract. Ribcage moves up and out. Diaphragm muscles contract and flatten. Volume of thorax increases. Pressure of air in thorax reduces below atmospheric
2. Expiration
  1. Intercostals relax. Rib cage moves in and down. Diaphragm muscles relax and become dome shaped. Volume of thorax decreases. Pressure of air in thorax increases above atmospheric
Insect gas exchange
1. Relies on diffusion
2. During periods of movement, the abdomen ventilate the trachea
3. Simple respiratory system with spiracles, oxygen enters spiracles as they are valve like openings
Large terrestrial animals adaptations
1. Largely folded exchange surface
2. Internal lungs to avoid desiccation
3. Layer of moisture around lungs for gases to dissolve in
4. Constant blood supply = conc gradient maintained
Fish
1. high metabollic rate
2. Cartilaginous Fish use Parallel/ concurrent flow- where water and blood flow across the gills in the same direction
3. Bony fish use counter current flow- where blood and water flow across the gills in opposite directions
  1. In this Equilibrium is NOT reached
    1. The % of oxy in water is always higher than the blood so conc gradient is maintained
4. Gill Adaptations
  1. Large s.a
  2. Short diffusion path
  3. Rich supply of blood vessels
  4. Ventilation mechanism to maintain conc gradient
5. Ventillation (fish)
  1. WATER IN:
    1. Mouth open, opercular valve closed, floor of mouth lowered, volume increases insde mouth cavity, pressure in cavity lowers, water flows in from a HIGH pressure to a LOW pressure
  2. WATER OUT:
    1. Mouth closed, opercular valve open, floor of mouth raised, volume decreases inside mouth cavity, pressure in cavity increases, water is forced OVER THE GILLS and out the OPERCULAR VALVE
Stomatal opening
1. Stomata open because...
  1. 1. K+ ions are pumped into guard cells by active transport- which requires ATP
  2. 2. Starch is converted into malate ions inside guard cells
  3. 3. Malate ions and K+ lower the W.P inside guard cells
  4. 4. Water moves into the guard cells by osmosis down a W.P gradient
  5. 5. The guard cells become turgid
  6. 6. due to the thickened inner wall of the guard cell, the cells curve apart and the stomata open

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Adaptations for Gas Exchange

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	Created by megan.daye4 almost 10 years ago