Biology 204L Midterm #1 (afternoon) KEY Spring, 2009

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1 Unless otherwise indicated, each question is worth 2 points. YOUR NAME: LAB TA s NAME: Biology 24L Midterm #1 (afternoon) KEY Spring, An enzyme must be capable of conformation change in order to: a. bind to all of the different substrate molecules involved in the many different reactions it catalyzes; b. respond to modulators (if appropriate); c. change its primary conformation (or structure) during the release of the product; d. activate the enzyme-substrate (E-S) complex; e. b & d; f. All of the above 2. Suppose you studied the following enzyme-catalyzed reaction in a reaction vessel: S + E P + E Which of the following statements best accounts for what you would expect to observe if you measured the rate of the reaction before, and after, a positive modulator was added to the reaction mix? a. The rate of the reaction would remain unchanged because positive modulators don t work outside of the cellular environment. b. The rate of the reaction would remain unchanged because enzymes can t respond to modulators outside of the cellular environment. c. The rate of the reaction would increase following addition of the modulator. d. The rate of the reaction would decrease following the addition of the modulator. 3. Negative modulators function by a. Binding to the active site of an enzyme and decreasing the ability of the substrate to bind to it. b. Decreasing the concentration of positive modulators. c. Increasing enzyme-substrate affinity. d. Maintaining a constant enzyme-substrate affinity. e. None of the above. 4. For the following set of reaction rate data, calculate the Q 1 of the reaction: Temperature o C Reaction Rate (if you don t know how to carry out long division by hand, show the problem setup in the space above) The value of the Q 1 for this reaction is approximately: a. 1.8 b. 4.1 c. 3.2 d. 2.6 e. The value cannot be determined from the data. QQ 1 = What do we mean by the term adaptive significance of a physiological process? a. How the process enhances fitness of an organism. b. The evolutionary history of the process. c. What an organism must do to overcome the consequences of the trait, so it can adapt to its environment. d. a & c. e. None of the above.

2 6. Benefit(s) for ectotherms when they acclimate to seasonally changing temperatures include(s): a. dramatic increases in metabolic rate in the winter. b. dramatic decreases in metabolic rate in the winter. c. dramatic decreases in energy expenditure in the winter. d. dramatic increases in body temperature in the winter. e. None of the above. 7. (6 pts.) What is probably the major problem for an animal that allows or is forced to allow its body temperature to vary, and what it the cause of that problem? The major problem is the potential disruption of metabolic pathways due to the Q 1 phenomenon and its impact of the rates of nterconnected metabolic reactions/pathways that have different Q 1 s. 8. Which of the following graphs best represents what you d expect to observe if you monitored the time-course of temperature change in a cool object placed in a warm environment? a 4 b 4 Temperature, o C Temperature, o C Time, min. Time, min. c 4 d 4 Temperature, o C Temperature, o C Time, min. Time, min. 9. EXTRA CREDIT (2 pts.) Give me the equation of the correct answer to the preceding question, and tell me what each term in the equation represents. What represents the driving force in the equation, and what form of energy is caused to move by the driving force? Note: since this is an Extra Credit question, your answer will have to be perfect. So, don t waste time on this question unless you re certain you know the equation. TT oo (tt) = TT aa + (TT oo () TT aa )ee CCCC OR ddtt oo dddd = CC(TT oo TT aa ) where: TT oo = Temperature of the object TT aa = Ambient temperature CC = Conductance Driving force = (TT oo TT aa ) flux of heat

3 1. When an ectotherm maintains its body temperature at its preferred body temperature (T pref ), it: a. maximizes growth rates. b. interferes with its ability to digest its food. c. provides temperature conditions that allow its metabolism to function optimally. d. decreases its fitness. e. a &c. f. All of the above. 11. Which of the following is a correct statement? ANY RESPONSE IS CORRECT a. I want ½ free point. b. I want 1 free point. c. I want 1½ free points. d. I want 2 free points. e. I don t want any free points. 12. (6 pts) Defend or refute the following statement: data from the Baltic Sea starfish conclusively demonstrate that it s better to be an osmoregulator than an osmoconformer. The data show that whether it s better to be an osmoregulator or osmoconformer is determined by the environment. If the solute concentration of the starfish s surroundings remain relatively constant within a homeostatic range, then the lower costs of being an osmoconformer would make it the preferred strategy. If, however, the solute concentration changes either through changes in the water column (say, from a shift in a current, an influx of fresh water from snow melt, etc.) then the higher costs of being an osmoregulator are offset by the benefits. Note to TAs the students need to show in some way that 1. they know the starfish is an osmoconformer. (1 pt.) 2. they understand that there are costs and benefits to osmoconformity and/or osmoregulation (they don t have to use both terms), (2 pts.) 3. they understand that the starfisnh s environment determines whether the costs of being an osmoconformer (or osmoregulator) are outweighed by the corresponding benefits. (3 pts.) 13. Which of the following is(are) potential cost(s) of poikilothermy? a. A high metabolic rate that is required to provide heat for thermoregulation. b. Metabolic disruption due to Q 1 effects on metabolism. c. Energy expended on piloerection and dramatically reduce fitness. d. Adverse effects of norepinephrine on heart function. 14. The fact that most organisms thermoregulate if given the opportunity implies that: a. there are no ecological costs associated with thermoregulation. b. there are no ecological costs associated with thermoconformity. c. the ecological costs of thermoconformity can be severe. d. the ecological costs of thermoregulation can be severe. 15. At temperatures below the Thermal Neutral Zone (TNZ), which of the following is(are) employed by an endotherm trying to maintain its body temperature within homeostatic limits? a. Piloerection b. Shivering c. Nonshivering thermogenesis d. Restricted blood flow to the skin e. a & d. f. b & c. g. a, b, c, & d. 16. For an ectotherm, ecological costs associated with thermoregulation can include: a. metabolic disruption. b. increased risk of predation. c. decreased energy intake. d. dangerous fluctuations in body temperature. e. a & d. f. b & c. g. All of the above.

4 17. Measuring an animal s oxygen consumption rate: a. gives us an estimate of how rapidly the animal is using energy. b. tells us something about the general state of the animal s health. c. is only possible with ectotherms. d. a & b. e. All of the above. 18. (3 pts.) Your text describes two examples of acclimation, one relating to the tanning response. What was the other example, and what would you describe as a major difference between that form of acclimation the example of ectotherm acclimation I presented in lecture? Note: the fact that my lecture example dealt with temperature acclimation and the text s example dealt with another homeostatic parameter doesn t count as a major difference. The other example was either frog acclimation to seasonal temperature change (if they used the older edition of the text) or human acclimation to high altitude and/or low oxygen availability (latest edition of the text). Give em the 3 points for putting one or the other, no matter what else they say. (this questions was just to see if they did the reading 19. (6 pts.) The hormone that helps humans and other mammals acclimate to colder temperatures in the winter is thyroxine_(1 pt). The effect of this hormone in humans is to increase metabolic rate_(2 pts), which it brings about by stimulating expression of what I termed metabolic genes, i.e., the genes that code for the enzymes involved in essentially all of the metabolic pathways in the body. (3 pts) 2. Which of the following graphs represents what you d expect to observe in a true poikilotherm? [Body Fluids] a Body Temperature, o C b Environmental [Solutes] Ambient Temperature, o C [Body Fluids] c Body Temperature, o C d Environmental [Solutes] Ambient Temperature, o C

21. The Lower Critical Temperature (LCT) is reached when: a. piloerection and non-shivering thermogenesis has been minimized. b. the rate of metabolic heat production exceeds the rate of heat loss. c.

5 21. The Lower Critical Temperature (LCT) is reached when: a. piloerection and non-shivering thermogenesis has been minimized. b. the rate of metabolic heat production exceeds the rate of heat loss. c. an endotherm must increase heat production to offset heat losses in order to maintain body temperature within homeostatic limits. d. non-shivering thermogenesis is no longer possible. e. the animal depletes its stores of norepinephrine 22. The slope of the Curve of Thermogenesis below the Lower Critical Temperature is a measure of: a. heat conductance. b. basal metabolic rate. c. body temperature. d. the temperature gradient. e. None of the above. 23. The relative widths of the Thermal Neutral Zone in the naked mole rat, Homo sapiens, and the arctic fox illustrate: a. that all three species are subject to temperature stress in their respective habitats. b. that only humans benefit from the ability to shunt blood when cold-stressed. c. evolutionary adaptation to different degrees of temperature stress imposed by their respective habitats. d. that thermal conductance is greatest in the naked mole rat and lowest in the arctic fox. e. b &c. f. c & d. g. None of the above. 24. (1 pt.) Speaking of naked mole rats: Is that thing butt-ugly, or what? a. Yes. b. No. c. Even its mother couldn t love that face! d. Other Briefly justify your answer. Hint: leave this question for last. Any response is correct. 25. A comparison of thermobiology of ectotherms or endotherms from constant- and variable-temperature environments suggests that a. ectotherms can t survive in variable-temperature environments. b. the ability to acclimate is ecologically/evolutionarily costly. c. constant-temperature habitats favor the ability to acclimate. d. evolution in variable-temperature habitats leads to the loss of acclimation ability. 26. The purpose of superimposing a Q 1 -effect graph on the graph of a summer periwinkle s metabolic response to changing temperature was to a. indicate how a perfect osmoconformer would respond to changing temperature. b. indicate how a perfect thermoregulator would respond to changing temperature. c. give us a null model with which to compare our experimental data. d. indicate how the periwinkle responds to increased thyroxine release by its thyroid gland.

6 27. (4 points) If you compare similarly-sized birds and mammals, you find that the slope of the Curve of Thermogenesis below LCT (Lower Critical Temperature) is less in birds than in mammals. This suggests that Conductance in birds is lower than in similarly-size mammals. 28. (4 points) What is the significance of gene expression in the periwinkle s ability to acclimate to seasonal temperature changes Expression of different alleles of the same genes results in seasonal switches in production of isozymes that function well under one temperature regime, but not the other. The result is that the periwinkle is able to maintain its metabolic rate within homeostatic limits in spite of large seasonal changes in its body temperature. 29. The differences in the physiological response to cold stress exhibited by Australian Aborigines, Alacalufs & Eskimos, and most other human groups are primarily due to a. differences in the way their brain responds to cold stress. b. differences in thyroxine levels. c. differences in the amount of hair on the body surface. d. differences in skin pigmentation. 3. Our discussion of the response to cold stress exhibited by humans from different habitats demonstrated that a. humans cannot respond over evolutionary time scales to changes in habitat conditions. b. the environment plays a critical role in humans evolutionary adaptation to habitat-imposed temperature stresses. c. only human groups whose ancestors evolved in what is now western Europe can use thyroxine to respond to cold conditions. d. only the Australian Aborigine responded in an effective physiological way to cold stress. 31. (5 pts.) Explain the results of the experiment where we had a wolf place its paw in a very cold antifreeze solution, first by describing what s happening physiologically, then explain why (in an ecological/evolutionary context) the wolves respond to cold stress the way they do. What s happening physiologically (3 pts): the wolf s brain is in turns i. causing vasoconstriction in the extremities to reduce heat losses, then ii. causing vasodilation in the extremities to prevent foot pad temperature from dropping too low. iii. Repeating i and ii over time scales of a few minutes. The ecological/evolutionary context (2 pts): i. Wolves must be active year-round, foraging for food, etc., under conditions that expose their legs & feet to extreme cold. ii. Their food base doesn t supply enough energy to allow them to replace the high heat losses that would occur if they kept their leg & food pad temperatures elevated all the time. 32. (5 pts.) Salmon have a unique adaptation, associated with their gill epithelia, that helps them maintain homeostasis. What is that adaptation, and how does it contribute to homeostasis? An ATPase that is capable of transporting NaCl against its concentration gradient. In fresh water this allows the salmon to pump NaCl into its blood, offsetting losses, and in the ocean it allows the salmon to pump NaCl back into the salt water, offsetting diffusion of NaCl into its body.

7 33. When salmon migrate from salt to fresh water, they a. commence eating to ensure they take in enough NaCl and other solutes to maintain homeostasis. b. reduce energy expenditure by reducing urine production rates in their kidneys. c. begin drinking large amounts of water to ensure that they don t dehydrate. d. begin drinking large amounts of water to ensure that they take in enough NaCl and other solutes to maintain homeostasis. e. a & c. f. a & d. g. None of the above. 34. The physiological and behavioral responses we observe in salmon as they migrate from fresh to salt water are examples of: a. Osmoconformity b. Acclimation c. Thermoregulation d. Temperature compensation e. Poikilothermy 35. (12 points) The data used to construct the graphs on the next page were obtained from an experiment involving a sparrowsized bird called the Goldfinch, occupying a habitat in northern Minnesota, where it gets really cold in the winter. The experimental protocol consisted of Capturing 1 birds in the field during July (Summer). Immediately placing the birds in separate temperature-controlled chambers, each set to a constant air temperature of 6 o C. Recording metabolic rate and body temperature over a period of several hours. Repeating the experiment with birds collected in January (Winter). 5 4 Metabolic Rate Summer Winter Time ( hours ) o C ) Body Temperature ( Summer Winter Time ( hours )

8 a. (2 pts) Why does the Metabolic Rate of both groups of birds increase rapidly at the beginning of the experiment? That is, what is the purpose of the increased metabolic rate? To increase heat production in order to maintain body temperature within homeostatic limits in the face of dramatically increased heat losses. b. (4 pts) Propose an explanation for why the Metabolic Rate of the Summer birds decreases starting about.2 hours into the experiment. The Summer birds were unable to increase heat production enough to offset losses, so they became progressively more hypothermic (much as their favorite experimental organism did during the Curve of Thermogenesis experiment when ambient temperature was reduced to close to o C). c. (6 pts) Do the graphs represent acclimation? Defend your answer.. Yes. The winter-captured birds were able to elevate metabolic rate enough to maintain a normal body temperature (a body temperature within homeostatic limits) while the summer birds could not. Clearly, physiological/biochemical changes had occurred in the winter birds that allowed them to thermoregulate at very cold ambient temperatures, and that s the definition of acclimation that I gave them in lecture.

9 Attach bribes (cookies, shots of tequila, plane tickets to Bora-Bora, etc.) here.

Biology 204L Midterm #1 (evening) KEY Spring, 2009

Biology 204L Midterm #1 (evening) KEY Spring, 2009 Unless otherwise indicated, each question is worth 2 points. YOUR NAME: LAB TA s NAME: Biology 24L Midterm #1 (evening) KEY Spring, 29 1. An enzyme must be capable of conformation change in order to: a.