Biosc 0150 Foundations of Biology I Review 11 Chapter 44 Review Chapter 44 Gas Exchange and Circulation 1 At the Death Valley Nevada the atmospheric pressure is 1 atm 760 mmHg and the air contains 21 oxygen At the top of Mt Everest the atmospheric pressure is 250 mm Hg a Calculate the PO2 at the Death Valley and top of Mt Everest Death Valley 0 21 760 160 mm Hg Mt Everest 0 21 250 mm 53 mm Hg b How much faster would you have to breathe at the top of Mt Everest to obtain the same amount of oxygen as you have in the Death Valley About 3 times faster c Draw a graph that depicts the relationship between the partial pressure of oxygen and elevation d Why do people wear oxygen masks at the top of Mt Everest How does it relate to Fick s law of diffusion Because the partial pressure of oxygen is low meaning the diffusion gradient between the atmosphere and your lung tissues is small This results in low rate of diffusion of oxygen at the alveoli P2 P1 is low thus rate of diffusion is low e Can people climbing Mt Everest acclimatize to the conditions People usually take breaks during their climb to acclimatize Only partial acclimatization is possible and it depends on the physical state training and genetics of people Most people have to use supplementary oxygen sources 2 To obtain oxygen water breathers face a much more challenging environment than air breathers do Why Aquatic animals live in an environment that contains much less oxygen than that of terrestrial animals a Do freshwater or marine environments contain more oxygen Why Freshwater environments contain more oxygen because they have lower concentration of solutes Because seawater has a much higher concentration of solutes it can hold less dissolved gas b Fish in deep body of water have to take in twice as much water as do fish in a shallow pond to get the same amount of oxygen What could account for this Surface area has a large impact on oxygen s ability to diffuse into water The shallow pond has a higher ratio of surface area to volume and therefore would be more oxygen rich This would mean the fish in the shallow pond would not have to work as hard to obtain the needed oxygen Adel Anthony Megan Dr Swigonova Page 1 of 16 Biosc 0150 Foundations of Biology I Review 11 Chapter 44 c Draw a graph relating temperature and gas solubility d Explain why oxygen partial pressures are relatively high in mountain streams and relatively low at the ocean bottom Oxygen partial pressure is high in mountain streams because the water is cold mixes constantly and has a high surface area due to white water Oxygen partial pressure is low at the ocean bottom because the area is far from the surface where gas exchange occurs and there is relatively little mixing 3 Rate of Diffusion k A P2 P1 D a What do all of the variables stand for K is the diffusion constant A is the area for gas b exchange P2 P1 is the difference in partial pressure of gas on either side of the barrier to diffusion and D is the thickness of the barrier to diffusion If A increases what happens to the rate of diffusion If P2 P1 increases If D increases Increasing A Increasing rate of diffusion increasing P2 P1 increasing rate of diffusion increasing D decreasing rate of diffusion c How are high partial pressure gradients maintained They are maintained in part by having am efficient circulatory system in close contact with the gas exchange surface 4 Gills can be external or internal What are the advantages and disadvantages of external versus internal gills in terms of fitness External gills are ventilated passively and are efficient because they are in direct contact with water However they are exposed to predators and mechanical damage Internal gills are protected but have to be ventilated by some type of active mechanism for water flow a Explain why countercurrent exchange is much more efficient than concurrent exchange In countercurrent systems oxygen is transferred along the entire length of the capillaries If concurrent flow occurred oxygen transfer would stop because the partial pressure gradient driving diffusion would fall to 0 partway along the capillary Put another way Countercurrent flow is so efficient because it ensures that a difference in oxygen partial pressure in water versus blood is maintained over the entire gas exchange surface b What part of Fick s law of diffusion does countercurrent exchange maximize The effect of countercurrent exchange is to maximize the P2 P1 term 5 Compare and contrast the problems associated with gas exchange for aquatic and terrestrial animals More specifically compare and contrast the challenges each face in terms of maintaining proper homeostasis For aquatic animals gas exchange disrupts water and electrolyte balance Recall that freshwater and saltwater fish both face challenges in terms of salt exchange and water Adel Anthony Megan Dr Swigonova Page 2 of 16 Biosc 0150 Foundations of Biology I Review 11 Chapter 44 exchange with their environment In this way aquatic animals need and active osmoregulatory system that maintains both electrolyte and water balance Terrestrial animals are different however because all they have to worry about is water loss to their environment They do not lose solutes to the air that they breathe in their respiratory system 6 Suppose that a new pesticide has proven to be very effective in keeping farmers crops from being destroyed by insects This pesticide s mode of action involves dehydrating target insects leaving them incapable of preventing water loss In terms of insect anatomy explain how you think this pesticide works The pesticide could cause the insect s spiracles to be forced open continuously leaving the tracheal system constantly exposed to the drier outside air This leads to water loss and eventual insect death Also it could dissolve the insect s cuticle leaving it unable to prevent water evaporation from its body surface 7 Draw a graph representing air uptake in the human lungs as a function of pressure created by the diaphragm Identify the sign of the graph s slope The graph has a negative slope the y axis should be labeled with air uptake the x axis should be labeled with pressure created by the diaphragm Now draw the graph representing air uptake in frog lungs as a function of pressure created by the diaphragm Does the graph differ from the graph for humans Explain Frogs essentially gulp air into their throats and push it into their lungs via positive pressure Humans on the other hand