Lecture 7
Animal of the day dytiscus. A water beetle
· Found in freshwater lakes and streams
· Have tracheae which hold air. Beetle traps a bubble of air under their wing.
o Air bubble acts as a alveolus
o When pO2 in the bubble drops below threshold the beetle will go to the surface and trap another air bubble
· When we plot body mass along with heart rate we see the larger the animal is the lower their heart rate is
o The smaller the animal is the faster the heart rate is
· In every other animal group the respiratory gasses are extremely important
o Chemosensors play an important role in sending information about blood gasses
· Cellular respiration- oxidative metabolism… the use of oxygen and the production of carbon dioxide
o Cellular respiration is the fundamental end point in respiration
· Partial pressure is the percentage of a gas times the total pressure
· In water oxygen is relatively poorly soulable in water, nitrogen is worse
o Only 34molecular oxygen in water, 17 of nitrogen, co2 is very soluable so it’s a 1018 ml/L
o H2O+CO2<->H2CO3<->H+ +HCO3-
o Gasses are more soluble in cold water than they are in warm water!
§ Soluablility in sea water of oxygen is lower than the solubility in fresh water
· Amount of oxygen dissolves in water depends on how much oxygen is available in a gaseous stage.
o Gas will transfer between the air and water depending on the relative amount of oxygen in the air and in the water
· Respiratory gas transport
o Oxygen is moved in the blood by convection
§ Diffusion driven by concentration gradients oxygen moves from circulatory medium to cells
o Cells produce carbon dioxide
§ This is diffused into the blood circulation
§ Which is carried back to respiratory exchange surface into the rest of the world
