Name: Comparative Physiology 2007 Second Midterm Exam 1) 8 pts 2) 14 pts 3) 12 pts 4) 17 pts 5) 10 pts 6) 8 pts 7) 12 pts 8) 10 pts 9) 9 pts Total
1. Cells I and II, shown below, are found in the gills of teleost fishes. I. Outside world II. Tu Outside world bul ar lu me n of wh at??? A. Which cell type, I. or II., is found in salt water fishes and which, I or II, is found in fresh water fishes? (4 pts.) I - Salt water II - Fresh water B. Explain why saltwater fishes need the cell type you identified in their gills. (4 pts.) They are hypoosmotic to heir environment, so they gain salt and need to excrete it. 2. Answer the following questions (16 pts.): A. List two food groups or food categories that are present in a modern western diet but appear to have been largely or totally absent from the diet of humans before the development of agriculture and animal domestication. (2 pts.) Cereal grains, refined sugars, refined oils, dairy products, meat with high fat content. B. Briefly define "thrifty genotype". (5 pts.) Genotype that allows an individual to store energy during times of plenty and to be very efficient with energy use during periods of famine.
C. The paper by Cordain and colleagues (2005) argues that the single biggest threat to public health in the United State is our diet. (2 pt.) D. Humans have evolved a great capacity to stockpile extra energy in the form of adipose. Although we all know that obesity is dangerous, the prevalence of overweight individuals increases each year. Propose an explanation for why repeated public health warnings about diet have not been successful in improving the diet of most Americans. (5 pts.) We evolved to like foods with high levels of useful energy. Prior to the invention of agriculture and state societies, famine was always a real possibility. Individuals that were able to store extra energy as fat were the ones that survived to reproduce. Thus, the desire to eat high calorie food is very strong. 3. In an aquatic environment, large mobile organisms (e.g., fishes) tend to be streamlined. Using your knowledge of hydro/aerodynamics, drag, and flow separation explain and/or speculate as to why the following statements are true: (8 pts.) A. Sessile aquatic organisms (i.e., sea anemones, sponges) tend to be circular (shaped like a cylinder) in cross-section. (3 pts.) Flow can come from any direction. There is a need to minimize drag in all directions. B. Many sessile aquatic organisms (i.e., starfish, sponges) have a dimpled (small bumps) body surface. (3 pts.) Dimples reduce parasite drag by creating a turbulent boundary layer. C. In a terrestrial environment, large mobile organisms (e.g., elephants, hippos, humans) are not streamlined. (3 pts.) Air has low density and viscosity, and running speeds are relatively low, so drag is not a problem for large terrestrial animals.
D. When swimming fast for long distances dolphins porpoise (repeatedly jump out of the water), but tuna do not? (3 pts.) They must come to the surface to breathe and drag is less in air than in water. 4. What question, related to the topics we have discussed during the second part of this course, would you investigate if you had the resources and time? (7 pts.) Explain why you believe this is an important question. (5 pts.) Explain how you would investigate this topic. (5 pts.)
5. Many or most mammals have energetically optimal speeds in each of their locomotor gaits. Provide two possible explanations for this pattern. (10 pts.) EXPLANATION 1 - The force-velocity relationship of muscle may result in an optimal speed in each gait. There is an intermediate speed of shortening at which power and efficiency of contraction are maximized. There could be an intermediate running speed in each gait in which muscle shortening speed matched the most economical speed. EXPLANATION 2 - There is natural frequency of ventilation that is most economical for any rate of ventilation. There is also a natural frequency of limb movement. There may be a single frequency in each gait in which locomotion and ventilation are most compatible and do not result in interference. 6. Most animals use one of three compounds to eliminate the nitrogenous wastes that result from the metabolism of amino acids. (8 pts.) A. Of the three main nitrogenous waste compounds used by animals, which one requires the most water to eliminate nitrogen? Ammonia (NH 3 ) or Ammonium (NH 4 + ) B. Which nitrogenous compound is the most toxic? Ammonia (NH 3 ) or Ammonium (NH 4 + ) C. Which one requires the most energy for synthesis? Uric Acid D. Which compound has the lowest solubility? Uric Acid
7. Answer the following questions about muscle contractile physiology. (12 pts.) A. From the perspective of muscle contraction, explain why mammals that are specialized for running have less muscle in their forelimbs than their hindlimbs. There is a division of labor between the hindlimbs and forelimbs such that the hindlimbs do most of the acceleration and the forelimbs do most of the deceleration during the running cycle. During deceleration the muscle of the forelimb is stretched when active and a muscle that is stretched when active is able to produce 2-3 times more force then a shortening muscle. Because of this the forelimbs need less cross-sectional area in order to produce the same force as the hindlimbs, which are shortening when active in order to accelerate the animal when running. B. What aspects of muscle contraction explain why longer legs reduce the cost of transport? All else being equal if an animals legs were longer fewer strides would be needed to cover a distance or run at a given speed then if the animals legs were shorter. If fewer strides were made then less ATP would be used to turn on and off the muscle contraction and this would reduce the cost of transport. The cost of transport would also be reduced by the fact that the contractions could be made at a slower velocity and muscles do work more efficiently at slower velocities. C. What characteristic of muscle contraction makes energy savings through elastic storage and recovery of energy possible? When an elastic element is placed in series with a muscle the elastic element can do the shortening as the muscle contracts isometrically. A muscle can produce more force when it contracts isometrically (active but not shortening) then when it is contracting concentrically (active and shortening). Because of this fewer muscle need to be recruited and less ATP is used during a running cycle. 8. Sustained hovering flight appears to be difficult for birds because few species do it. Hummingbirds, however, do it routinely. List three mechanisms of generating lift that might help explain why hummingbirds can generate enough lift to hover. Pick one of the three mechanisms and explain how it works. (10 pts.) Wing Tip Vortex or Delayed Stall A delayed stall causes the formation of a leading-edge vortex that gradually increases the velocity of flow down the wing on the upper edge of the wing. This reduces pressure over the upper surface of the wing and increases the lift over the wing.
Wing Rotation or Magnus Affect When the wings angle is rotated a vortex similar to that of putting backspin on a ball is created. This pulls the boundary layer over the wing creating upward lift. Wake Capture As the wing moves through the air, it leaves whirlpools or vortices of air bind it. When the wing is rotated back over its original path of motion it intersects its own wake (whirlpools of vortices of air) and captures this energy in the form of lift. 9. Answer these multiple choice questions. (9 pts.) A. The dominant terrestrial vertebrate fauna during the Mesozoic was the following: A) mice and other rodents D) Archosaurs B) Synapsids E) Anapsids C) Snakes and Lizards F) Flying reptiles, such as pterosaurs D) Crocodiles D) Archosaurs 2) All nonavian reptiles have two aortas, a right and a left. The function of the left aorta is best described by the following: A) The left aorta servers to reduce systemic arterial blood pressure B) The left aorta enables a greater volume of blood to be ejected from the heart in any given period of time, thereby reducing the work of the heart C) The left aorta serves to carry carbon dioxide to the stomach D) The left aorta helps prevent the animals from freezing in the more Northerly areas of their distribution by reducing blood flow to the skin. C) The left aorta serves to carry carbon dioxide to the stomach 3) The only vertebrate known to have a neurologically controlled valve in the heart is the following: A) birds E) pythons B) sharks F) alligators C) swordfish G) tenrecs D) no vertebrates have neurologically controlled valves in the heart F) Alligators