answers (1)

NAME: BIO 152 229 Exam 2 7/8/10 1. (10 points) The two largest marine predators are killer whales (orcas) and big sharks. Assume that a killer whale and a shark of the same size are capable of swimming at the same maximum velocity and that one is chasing the other. Which one would be able to escape from the other? Explain why. If the whale and the shark are the same size and have the same maximum velocity then who eats whom, or who catches whom, is a matter of endurance rather than brute force of muscle activity. Therefore, a good way to explain it is to consider the physiological systems of the two species: sharks are heterothermic regulators (they have counter-current exchange vessels to trap heat from active muscles in their core), whales are endotherms with high body temperatures; sharks are fish and have gills to derive oxygen from seawater, whales are mammals that breathe air; they are both quite well streamlined for rapid velocity in water. The whale should be able to catch the shark every time because: a) endothermic whales have much higher body temp than heterothermic sharks. The Q-10 effect would allow greater rates of protein activity (like muscle proteins), metabolism, and energy production in the whale’s muscles than in the shark’s. Higher temp plus more ATP to burn means faster and stronger acting muscles. b) the lungs of the air-breathing whale can do gas exchange at much higher rates than the gills of the shark. There is much less oxygen in water, water is viscous and relatively slow to move across gill filaments; air has 21% oxygen, has practically zero viscosity, and moves in and out of respiratory systems very, very quickly, guaranteeing rapid and extensive O2 -- CO2 exhange. Bottom line: the killer whale catches the shark eventually. 2. (10 points) There are a few species of insects that live in the arctic region of far northern Alaska. Adults do not fly south for the winter but rather stay in the extremely low temperature environment and reappear in the spring. Moreover, the adults cannot dig deep enough into the ground to get below the freezing level. If insects not adapted to extreme cold are introduced to Alaska, they freeze solid in the winter and do not survive. How can the adapted insects survive the winter? Arctic insects often have ‘antifreeze’ in their hemolymph. As described in the article on antifreeze compounds (“insect and fish antifreeze.docx”) and in lecture audio, arctic insects have enough of these inhibitors of ice-formation to keep ice crystals from forming in hemolymph and killing the animal. Without the ‘antifreeze’ they certainly would not survive such low temperatures as are found in far northern Alaska. 3. (10 points) Explain the changes that need to occur in water and electrolyte balance as young salmon move from freshwater to salt water and eventually back to fresh water to spawn. Specifically, state when the animal should drink or not drink water, when cells in the gill epithelium should excrete or import electrolytes, and what the consequences of each change are. When young salmon swim from the freshwater rivers where they hatched and enter the salt water of the ocean they must have ways to resist taking in lots of sodium to their blood and interstitial fluid. And when they leave the ocean and enter freshwater rivers to have babies, they must do the opposite: avoid losing most of their sodium to the nearly sodium-free river water and/or taking in huge amounts of water that diffuses into their bodies because of the high sodium concentration. Since these fish are osmoregulators (they have to be to survive in either fresh or seawater) they must keep the concentration of sodium in their bodies at a near-constant value (homeostasis) as well as keep water at a near-constant concentration. When going from fresh to salt water, the ‘chloride’ cells of their gills use active transport to move sodium ions from their blood and dump them into the ocean water. They also must be able to resist extensive water loss: pumping sodium out into the seawater makes the ‘concentration’ of water inside the fish higher and thus there is a greater force driving the water out of the fish by diffusion through tissues. Fish counter this water-loss tendency by not drinking seawater, excreting very low-volume urine and having water-resistant skin. The urinary system cooperates to excrete large amounts of salt (and nitrogen waste) in small volumes of water. When they move from the ocean back into freshwater rivers they must reverse these processes. The chloride cells produce new sodium pumps on the other side of the gills so that now they pump sodium out of the water and into the fish interstitial fluid so as to maintain their homeostatic body volume and water concentration. Water moves into the fish because of the newly increased salt concentration so they have to get rid of excess water. They excrete a much higher volume of urine, meaning their kidneys are no longer conserving water by concentrating urine but rather now don’t concentrate it but pee it out copiously so as to reduce the amount of water in the fish to homeostatic levels. 4 In midsummer, you are fishing at a lake. You are catching the most fish at the inlet of a stream into the lake, where logs and branches are creating turbulent flow and mixing the deep water with the shallow water near the surface of the lake. What is the probable reason the fish are congregating in this area? This area has higher oxygen content, aiding gill oxygen uptake. Stirring up water helps oxygen dissolve it it. This area is warmer, which stimulates metabolism. This area is cooler, which stimulates metabolism. This area has a lower oxygen content, which helps to transfer oxygen into the fish's gills. None of the above apply. 5 You prop open the gill covers of a fish, tie a string around its tail, and tow it backward through the water. This action forces water to flow in the back of the gill covers, from back to front over the gills, and out through the fish's mouth. What effect would this backward movement have on gas exchange? It would reduce efficiency of gas exchange. The water would be moving in the opposite direction across the gill filaments thus eliminating the benefit of counter-current exchange. It would increase efficiency of gas exchange. The only effect would be the fish's discomfort from this treatment. The fish would be unable to control its body temperature. 6 When you are jogging, your muscles are using more oxygen and releasing more carbon dioxide into the blood than when you are at home on the couch. Which of the following would occur during your jog? Blood pH would increase (become more basic/less acid) by at least 1 pH unit. The concentration of bicarbonate ions (HCO3-) in the blood would decrease. The medullary respiratory center would increase the rate of breathing. Blood pH would decrease because of all the CO2 in it. Decreased pH signals the medullary respiratory cells to increase the number of breaths per minute so as to ‘blow off’ more carbon dioxide and thus bring pH back up towards normal. All of the above answers apply. 7 Which of the following mechanisms play a role in regulating human heart rate? Chemical messengers in the blood, such as epinephrine Nerves originating from the medulla (lower part of the brain) Pacemaker cells within the heart All of the above Only A and C 8 Blood is pumped at high pressures in arteries from the heart to ensure that all parts of the body receive adequate blood flow. Capillary beds, however, would hemorrhage under direct arterial pressures. How does the design of the circulation network contribute to reducing blood pressure to avoid this scenario? Blood flow through the capillaries is essentially frictionless, and this reduces the amount of pressure on their walls. The total cross-sectional diameter of the arterial circulation increases with progression from artery to arteriole to capillary, leading to a reduced blood pressure. Fluid flowing through a pipe at a certain pressure will slow down if the pipe divides such that the two or more pipes formed have a greater volume (total X-sectional area of all the capillaries) and thus pressure is reduced. Fluid loss from the arteries is high enough that pressure drops off significantly by the time blood reaches the capillaries. All of the above answers apply. 9 Why is it more difficult to obtain enough oxygen via respiration from water than from air? The density of water makes ventilating the respiratory tissues more difficult. It’s harder, takes more energy, to suck in water than air. The viscosity of water is less than that of air. The solubility of oxygen in water is less than in air. All of the above answers apply. Only 1 and 3 apply. 10 Premature infants may not produce surfactants in the alveoli of their lungs. What implications does this have for their health and survival? The partial pressure of oxygen drops significantly in the absence of these surfactants, and the child may suffer brain damage from oxygen deprivation. The surface tension of fluids in the lungs may be too high for the lungs to expand fully during inhalation. The surfactants greatly reduce surface tension of the water layer in the very thin, weak lung alveoli. If tension were not reduced it would cause alveoli to be flattened and be unable to open. Surfactants are necessary to trap pollutants and other material that enters the lungs during inhalation; thus, lung disease is more likely. Surfactants raise the surface tension of alveolar fluids so that deoxygenated air does not get trapped in the lungs during exhalation. 11 The dinosaurs that birds evolved from had teeth yet birds don’t have teeth. What’s the likeliest adaptive value to birds of the loss of teeth during their evolution? The food they eat does not require much grinding and tearing. The loss of the weight of teeth allows birds to fly better. Birds have lost lots of organs to lose weight – one of their ovaries, for instance, and teeth, and others. Bird beaks are too weak to support tooth attachment. Birds must breathe so rapidly they require an open pathway for air to flow in and out of their lungs. 12 Air flows in only one direction through the lungs of which animals? Frogs. Cats. Flying insects. Alligators. There’s an article on this in the website collection as well as in Bb. 13 Which system plays the greatest role in the homeostatic function of helping to regulate volume and composition of blood and interstitial fluid? Muscular system. Reproductive system Urinary system. This is the system that measures and controls fluid. the nervous system plays minor roles, mostly in helping regulat the kidneys. Nervous system 14 Why do endothermic animals have, on the average, quicker and stronger muscular responses than terrestrial ectotherms? Endotherms have bigger muscles per unit body mass than do ectotherms. Cellular proteins change shape faster at higher temperatures. The Q-10 effect – everything goes fsster at higher temp and muscle contraction depends on protein shape change (eg myosin and actin). ATP can be produced faster by endotherms. Almost all ectotherms are not predators and they therefore don’t need fast, strong muscles. 15 During the production of urine, animals using hydrostatic pressure to filter blood must also Regulate their body temperatures. Have closed circulatory systems. You can’t have blood pressure without a closed system. Have active transport pumps in the cells of their glomerulus capillaries. Use the movement of cilia to force liquid from blood into proximal tubules. 16 Of the following statements all but one are both true and support the hypothesis that lizards have the ability to sense their body temperature. Which statement is not true? They release water on to their body surface when in a hot environment. Lizrds don’t do this. Besides, they do do 2 and 3. They move to a cooler location when overheated. They become more active when in a cool environment. None of the above; all are true. 17 What is the likeliest reason there are few to no flying insects in the winter? Their offspring cannot survive in winter. Their food supplies are absent in winter. They can’t generate enough energy to fly. Ectotherm insects can’t get their muscles warm enough for the Q-10 effect to make muscle action possible. Only a few insects are endotherms or heterotherms and even these aren’t very good at it, having to warm up their muscles before they take off. Predators need increased food intake and thus wipe out all the insects. 18 Because marine invertebrates are osmoconformers they _____. must drink large amounts of seawater to regulate their hemolymph osmolarity. regulate their solute concentrations by excreting urine with a much higher osmolarity of electrolytes than seawater. excrete large amounts of water in their urine. don’t need to actively regulate the concentration of dissolved substances within their tissues. They’re osmoconformers, meaning they couldn’t care less. 19 Which is an adaptation of kangaroo rats that allows them to live in very dry deserts? They get all their water from the leaves they feed on. They allow their body temperatures to rise during the heat of the day. They have extremely dilute urine. They have a nasal countercurrent system with long exit passages that cool air, drying it out before it is exhaled. This system allows them to lose only a tiny fraction of the water on the surface of their lung alveoli (which must be wet to allow gases to dissolve. During exhalation almost all the water evaporated from their alveoli condenses on the convoluted trachea surface. 20 When an alligator chases you why must it catch you within a short period of time if it is to be a successful predator and have you for dinner? It is so heavy it tires quickly when it runs. Its legs are too short to propel its body rapidly on land. It cannot take in enough oxygen across its gills to generate enough ATP energy to run faster than a human. Alligators quickly use up their ATP stores and must rely mostly on anaerobic ATP production (glycolysis) after that. Anaerobic ATP production (glycolysis) is a lot slower than aerobic, the kind you, as an endotherm, do. 21 Compared to other cells in marine fish gills, chloride cells have a very high content of mitochondria. “Chloride cells” are the ones that remove salt from the fish’s blood. How does a very large number of mitochondria relate to the functional role of chloride cells? Mitochondria produce the ATP necessary to carry out active transport by the gill chloride cells. If no mitochondria, then no ATP, no Na+/K+ pump. During ATP production in mitochondria, fresh water is formed. Chloride ions released by chloride cells are used by the fish as food. Mitochondria contain the organism’s genetic material and thus must be active at all times. 22 In which pair of locations must active transport occur in an insect that has Malpighian tubules. Active transport is the use of ATP energy to transport molecules from a lower concentration region to a higher concentration region Flame cells and Malpighian tubule cells. Blood vessel cells and hindgut cells. Malpighian tubule cells and hindgut cells. These are the places insects use AT to move waste molecules INTO the Malpighian tubules and to remove valuable, non-waste molecules from the hindgut. Tracheole cells and Malpighian tubule cells. 23 Urine in the collecting ducts of the kidney is concentrated by removal of water. What causes the water to be removed from urine? The osmotic concentration outside the cells of the collecting ducts is much higher than the osmotic concentration in the urine. Outside the CT duct cells is a lot of urea, more concentrated the farther down the CT. Active transport uses ATP energy to move water from the ducts. Urea molecules diffuse into the urine forcing water molecules to move out. The high hydrostatic pressure of the liquid in the collecting duct forces water to move out of the duct. 24 What effect does antidiuretic hormone (ADH) have on the nephron of mammalian kidneys? It increases water permeability of the descending limb of the loop of Henle. It decreases water permeability of the descending limb of the loop of Henle. It increases water permeability of the collecting duct. “Antidiuretic” means to reduce loss of water through excretion. That means ADH must help remove even more water from the urine before it gets to the bladder. If water permeability is INCREASED, and there’s lots of urea outside (Q#23), more water will be removed from urine faster. It decreases water permeability of the collecting duct. 25 When and why is a snake more or less active? Less active in winter because the food supply is decreased. Less active in winter because it does not need to avoid predators. More active in summer because that is the period for mating. More active in summer because it can gain body heat by conduction. Snakes are ectotherms so to be active it must warm up (the old Q-10 again). No matter how eager it is to mate, it first has to warm up (literally, not just being friendly, please!)