HWs Unit 4

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"Germ-free" laboratory mice birthed and reared in completely sterile environments (this is difficult but possible!) have higher nutritional needs compared to normal mice (ie, they have to eat a LOT more food in order to maintain the same body weight as a "normal" mouse that was not raised in a completely sterile environment). Explain why.

they lack gut microbes that help them digest food and supply vitamins symbiotic gut bacteria aid in digestion by breaking down molecules the host cannot digest and making them available to the host. in some cases, the host organisms provide essential vitamins that otherwise cannot be accessed from the food, such as vitamin K.

How do proton pumps contribute to mineral uptake by roots? A. Roots pump protons out of soil solution to promote diffusion of anions into the root symplast routes. B. Roots pump protons into the soil solution to displace cations from soil particles. C. Mycorhizzal fungi rely on proton pumps to absorb ions following extracellular digestion. D. Mycorhizzal fungi and Rhizobium bacteria use cotransporters to move ions across the gradient produced by root proton pumps. E. All of the above are true

Nitrogen is a mobile nutrient in plant tissues, so it can move within the plant body to areas of need. If a plant were nitrogen-deficient, you would expect to see the greatest impact on: A. Newer leaves B. Older leaves C. How am I supposed to figure this out?

Proton pumps continually pump protons outside of the cell into the environment. What should the anions in the environment do in response? Move into the cell Stay outside of the cell How is this question different from the last one?

The PRIMARY benefit for a plant of associating with Mycorrhizal fungi is: A. increased access to carbon B. increased access to nitrogen and other minerals C. protection from pathogens D. none of these; the fungi are parasitic to the plant

Some plants obtain nitrogen from symbiotic fungi or bacteria.What was the original source of N for the bacteria? A. urea in the soil B. N2 gas C. carbohydrates in the soil D. lipids in the soil E. proteins in the soil

B A few species of bacteria are the only organisms capable of reducing ("fixing") atmospheric nitrogen to make it biologically available. Just as plants and other photosynthesizers are essential as a source of carbon and oxygen for most other forms of life, these bacteria are essential as a soruce of nitrogen for most other forms of life. Nitrogen is used for synthesis of nucleic acids and proteins. Fungi would use nucleid acids and proteins from the soil organic matter; they decompose organisms containgin nitrogen which was orginally made available by the nitrogen-fixing bacteria.

Sodium is not an essential nutrient for plants, but is essential for animals. Given what you know from previous modules, why is this the case?

animals have neurons; plants do not sodium is an essential ion for neuronal function; it is required to set up an electrochemical gradient for action potentials to occur. plants lack a nervous system and presumably use a different set of ions for any necessary electrochemical gradients in their cell function.

Fick's law of diffusion describes the rate of diffusion across a respiratory surface. rate of diffusion = k * A * (P2-P1)/D where k is a diffusion constant (dependent on the gas and T) A is surface area P is partial pressure in either side (1, 2) of the surface D is depth of surface The structures of respiratory organs have been evolutionarily selected to maximize gas exchange. What aspect(s) of respiratory organ structure are most likely to be MAXIMIZED and which MINIMIZED to increase the rate of diffusion?

area for gas exchange: large surface area in lungs/gills/tracheae; partial pressure difference: efficient respiratory organs maintain a high partial pressure difference across the respiratory medium (e.g. cross-current or counter-current flow) distance/depth of the surface (barrier to diffusion) is MINIMIZED in respiratory organs; the greater the depth, the less efficient diffusion is.

Where is partial pressure of CO2 the highest? A. skeletal muscle B. capillary bed in alveolus C. veins D. alveolus (lung air sac) E. all are equal

A carbon dioxide is produced as a result of cellular respiration. all cells use oxygen and produce carbon dioxide as a waste product, but muscle cells can have extremely high levels of cellular respiration, and thus produce large amounts of carbon dioxide, when doing work. in order to move out of the body, the gas must move to areas of lower partial pressure

Circulatory systems are present in: A. All types of animals B. All types of animals with more than two cell layers C. Vertebrates only D. Mammals only

B a circulatory system transports a fluid called blood or hemolymph into close contact with every cell in the body (up to about 0.1 mm), to bring circulatory fluid close enough for diffusion to be efficient for exchanging waste and nutrients. cells in most animals with only two tissue layers (diploblasts) or no true tissues (sponges) are in direct contact with the environment and thus can exchange nutrients and wastes without a circulatory system. all other animals require a circulatory system, which may be either open or closed.

Carnivorous plants have evolved mechanisms that trap and digest small animals. The products of this digestion are used to supplement the plantʹs supply of . A. carbohydrates B. minerals C. water D. energy E. proteins

Ectotherms are always heterotherms A. True B. False

Which requires energy? A. Unloading sugar into young, growing leaves B. Unloading sugar into storage tissues like roots C. Both D. Neither

Radiation differs from conduction in that A. Heat is transferred between two surfaces in contact for radiation. B. Radiation involves the release of heat without necessarily making contact. C. Only radiation can cool an organism.

B Conduction: transfer of heat between two bodies in contact Convection: transfer of heat between a body and moving a liquid/gas Radiation: transfer of heat between two bodies not in contact Evaporation: loss of heat associated with phase change from liquid to gas any process that transfers heat from one object to another (conduction, convection, radiation) can cool one and heat the other, depending on the direction of heat transfer (always from the warmer to the cooler object)

Endotherms are always homeotherms. A. True B. False

B Source of heat Endotherm: obtain heat from metabolic activity (endo="inside") Ectotherm: obtain heat from external sources (ecto="outside") Regulation of body temperature Homeotherm: maintain a relatively constant body temperature as external temperature varies (homeo="same") Heterotherm: usually maintain a relatively constant body temperature but have specific periods where body temperature fluctuates with environmental temperature (hibernation, summer torpor) Poikilotherm: body temperature fluctuates with environmental temperature Endotherms are often homeotherms, but not always. some endothermic animals hibernate or go into seaonal/daily torpors where their body temperatures drop dramatically.

Dehydration has both immediate and long-term effects on blood pressure. What would be a long-term effect of chronic dehydration on blood pressure? A. decrease blood pressure B. increase blood pressure

B chronic dehydration causes the body to respond by increasing blood pressure to compensate for the reduced blood volume. individuals suffering from chronic dehydration can have resulting chronic high blood pressure.

In a saltwater environment, chloride secretory cells in the gills move salts ______ the fish's blood. A. into B. out of

Which kind of fish has to actively drink its surrounding water to maintain electrolyte homeostasis? A. freshwater B. marine

B the seawater is hypertonic to marine fishes (they are hypotonic to the seawater). this means that the water potential in the seawater is lower than the water potential in the fish, and thus they are constantly losing water and gaining solutes. marine fish must therefore constantly drink seawater (and actively pump out solutes) to maintain their water/solute balance. freshwater fish are subject to exactly the opposite problem, and are constantly losing ions and gaining water. they must actively pump in ions from the water and excrete very dilute urine to maintain their water/solute balance.

Endothermy and ectothermy are mutually exclusive modes of thermoregulation. (An animal can only use one method) A. True B. False

B though endothermic animals generate their own body heat, they also congregate together to exchange warmth and/or bask in the sun/lie on warmed rocks to obtain heat from the environment. ectothermic animals obtain heat from the environment, but some flying insects 'shiver' to warm up muscles before flight. shivering generates large amounts of heat as a result of metabolic reactions. honeybees even use metabolic-generated heat to kill invading hornets; the honeybees swarm the hornet and vibrate their flight muscles repeatedly to generate heat that kills the hornet.

Plants have been subjected to strong selection for increasing access to nitrogen. List three adaptations that increase plant access to nitrogen.

mycorrhizal fungi, association with nitrogen-fixing bacteria (legumes), parasitism, carnivory

What makes the "lub" sound of the characteristic lub-dub heartbeat?

the backflow of blood against the closed AV valves as the ventricles contract, blood is forced against the atrioventricular valves causing them to slam shut. this causes the 'lub' sound of the heartbeat.

Which of the following would you expect to have the greatest surface area, and why? mouth; stomach; small intestine; large intestine

two of the most important factors in absorption are large surface area to maximize the space where absorprtion can occur, and a very thin membrane for absoption to occur across. the small intestine has both of these features.

Rank the blood pressure in each of the following types of vessels from LOWEST to HIGHEST. - veins - arteries - capillaries

veins < capillaries < arteries pressure is related to speed, volume, and vessel diameter. there is extremely high pressure in arteries because of the proximity to the ventricles which have just expelled the blood from the heart. there is also a high volume of blood contained in the arteries, which tend to have an intermediate diameter compared to veins (wider) and capillaries (much narrower). there is an intermediate amount of pressure in capillaries, which have very narrow diameters, but massive cross-sectional area and extremely slow movement of blood. there is very low pressure in veins, where blood is moving more slowly and is contained in vessels that are typically wider than arteries

You decide to feed your rabbit, an herbivore, a series of different antibiotics to get over an illness. It temporarily gets better, but then begins to show symptoms of malnutrition. Why might this be?

Symbiotic gut bacteria aid in digestion by breaking down molecules the host cannot digest and making them available to the host. In some cases, the host organisms provide essential vitamins that otherwise cannot be accessed from the food, such as vitamin K. The anitbiotics likely killed both the 'bad' bacteria making the rabbit sick, and the 'good' gut bacteria needed for nutrient acquisition.

In the mammalian kidney the majority of water and solute recovery occurs as the ultrafiltrate passes through the A. proximal convoluted tubule B. Loop of Henle C. distal convoluted tubule D. collecting duct E. ureter

In the pressure-flow mechanism, loading of sucrose into companion cells at the source takes place through A. co-transporters B. ATP-powered pumps C. plasmodesmata D. facilitated diffusion E. none of these

Emperor penguins huddle in close proximity (without direct contact) to thermoregulate as a group, and individuals take turns standing at the outer edge of the group, exposed to the wind. The individuals at the outer edge are subject to more [blank] and less [blank] than those in the middle. A. convection; radiation B. conduction; convection C. radiation; conduction D. conduction; radiation E. convection; conduction

A Conduction: transfer of heat between two bodies in contact Convection: transfer of heat between a body and moving a liquid/gas Radiation: transfer of heat between two bodies not in contact Evaporation: loss of heat associated with phase change from liquid to gas a common misconception about radiation is that the sun is the only source of radiation on Earth. in fact, radiation is the transfer of heat between any two objects that are not in direct contact. in the case of the penguins huddled together, they are exchanging heat through radiation because they are close enough for heat to transfer through the air but not in direct contact (if they were in direct contact, they would exchange heat through conduction). due to the presence of the wind, the penguins at the outer circle are losing heat via convection.

Which type of blood vessel has the most muscular walls? A. arteries B. veins C. capillaries

A arteries have thick bands of muscle and connective tissue to regulate blood flow and to withstand the high arterial pressure. veins are also lined with muscle and connective tissues, though not as thick as around arteries. capillaries have no muscle lining, and are the only blood vessels thin enough to allow efficient gas exchange.

The advantage of excreting nitrogenous wastes as urea rather than as ammonia is that _____. A. urea is less toxic than ammonia B. less nitrogen is removed from the body C. urea can be exchanged for Na+ D. urea does not affect the osmolar gradient E. urea requires more water for excretion than ammonia

A because it is a base and therefore alters pH, ammonia is highly toxic to cells. thus ammonia must be heavily diluted in water for excretion. urea requires additional metabolic reactions to produce from ammonia and therefore is more energetically 'expensive' to produce, however, it is beneficial because its reduced toxicity means it does not have to be diluted in as much water for excretion.

Which of the following is not a use of a countercurrent exchange system? A. The exchange of CO2 and O2 in the human lung B. The reabsorption of salts and water in the mammalian kidney C. The exchange of CO2 and O2 in fish gills D. The flow of blood maintain temperatures in key vertebrate muscles

A countercurrent exchangers are used in the loop of Henle in the kidney, in the capillaries/water flow in fish gills, and to maintain body temperature in arteries/veins in vertebrate limb muscles. they are not present in human lungs, which use a web-like flow of capillaries across air held in a pocket (compared to water pumped unidirectionally across fish gills) the take-home message is that countercurrent exchange is an evoltionarily common but not universal 'solution' to maximize exchange of heat/gas/ions across between two substrates.

Dehydration has both immediate and long-term effects on blood pressure. What would be an immediate effect of dehydration on blood pressure? A. decrease blood pressure B. increase blood pressure

A dehydration results in less water available for blood, meaning a lower volume of blood and thus decreased blood pressure

Large molecules (such as blood cells) are not found in the urine. Why not? A. They are prevented from entering urine at the renal corpuscle B. They are passively removed from urine at the distal convoluted tubule C. They are passively removed from urine at the loop of Henle D. They are actively removed from urine at the loop of Henle E. They are passively removed from urine at the proximal convoluted tubule and collecting duct

A large molecules are not found in urine because they do not exit the blood. they are unable to leave the capillaries in the renal corpuscle based on size selection (pores in the blood vessels are not large enough for them to exit the bloodstream)

In Edgar Allan Poe's short story "The Tell-Tale Heart," a murder victim's heart continued to beat after it was removed from the body. What feature of the heartbeat is the fact behind this fiction? A. Some heart cells can contract spontaneously, requiring no input. B. Nerves controlling heartbeat fire spontaneously, requiring no input. C. Hormones controlling heartbeat are released spontaneously. D. Pulsing of blood in the heart chambers is spontaneous, maintaining the heartbeat.

A muscle cells have action potentials in a nearly identical way to neurons, where influx of sodium causes depolarization; sufficient depolarization generates and action potential which results in muscle contraction. the heart's pacemaker cells are myocardial cells capable of spontaneous depolarization, meaning they can fire without input from a neuron. this is because they are 'leaky' to sodium, so sodium can flow into the cells at a constant background rate. once enough sodium flows in, the membrane depolarization is sufficient to generate and action potential, triggering muscle contraction in the pacemakers cells. the pacemaker cells pass the action potential on to adjacent cells via the specialized gap junctions (intercalated discs) that connect adjacent myocardial cells. though pacemaker cells do not REQUIRE neural input, they are still connected to the nervous system. the sympathetic (fight or flight) and parasympathetic (rest and digest) divisions of the autonomic nervous system can both interact with the pacemaker cells to either speed up or slow down their down their depolarization rate

There are no valves at the point where venous blood flows into the atria. A. True B. False

A the AVs are located between the atria and the ventricles. this valve is open as blood flows and is pumped from the atria into the ventricles. as the ventricles contract, blood is forced against the AV valves causing them to slam shut. this causes the 'lub' sound of the heartbeat. contraction of the ventricles forces blood through the semilunar (pulmonary and aortic) valves. as the ventricle relaxes, the blood in the aortic and pulmonary arteries slams backward against the seminlunar valves, causing them to shut. this causes the 'dub' sound of the heartbeat. there are no valves in the heart at the point where the veins join the atria.

The descending limb of the loop of Henle is permeable to -----, and the thin ascending limb is permeable to -----. A. water; Na+ and Cl− B. Na+ and Cl−; water C. water; urea D. glucose; water

A the descending limb is the portion closer to the glomerulous; the ascending limb is closer to the collecting duct. the descending limb is permeable to water and impermeable to salts; water leaves the tubule due to the higher concentration of solutes in the medulla. the ascending limb is impermeable to water and permeable to salts; salts leave due to either active or passive transport (depending on the location in the tubule)

Which kind of fish produces large amounts of dilute urine to maintain its electrolyte balance? A. freshwater B. marine

A the seawater is hypertonic to marine fishes (they are hypotonic to the seawater). this means that the water potential in the seawater is lower than the water potential in the fish, and thus they are constantly losing water and gaining solutes. marine fish must therefore constantly drink seawater (and actively pump out solutes) to maintain their water/solute balance. freshwater fish are subject to exactly the opposite problem, and are constantly losing ions and gaining water. they must actively pump in ions from the water and excrete very dilute urine to maintain their water/solute balance.

Which of the following statements about C4 plants is/are true? A. The Calvin Cycle takes place deeper in the plant tissue than in C3 plants. B. PEP carboxylase has a higher affinity for CO2 than does rubisco. C. The Calvin Cycle takes place at a different time than initial CO2 fixation. D. The Calvin Cycle takes place at night.

A and B C4 plants alter the LOCATION of CO2 fixation by rubisco. they use an alternate enzyme, PEP carboxylase, for the initial fixation step. PEP carboxylase fixes CO2 into a 4-carbon organic acid. this 4-carbon organic acid is then transported deeper into the plant tissues, away from oxygen, where it is then converted back to CO2 and then fixed by rubisco. these reactions all happen during the day. because they improve the efficiency of rubisco by moving the rubisco reaction to a location lacking oxygen, the reactions are more efficient and stomata don't have to be open for as long during the day to make the needed amounts of sugar. CAM plants alter the TIMING of CO2 fixation by rubisco. they open stomata at night and use an alternate enzyme to fix CO2 to a 4-carbon organic acid at night. however, at night photosynthesis cannot occur because there is no sunlight. the 4-carbon organic acid is stored until the daytime. the plant then closes the stomata during much of the day to avoid losing water, converts the 4-carbon organic acid back to CO2 inside its tissues, and uses rubisco to fix the stored CO2.

Evaporation differs from convection in that A. Evaporation involves the dissipation of heat through the formation of gas. B. Evaporation involves transfer of heat via liquid or gas. C. Evaporation can only cool an organism; convection can cool or heat an organism.

A and C Conduction: transfer of heat between two bodies in contact Convection: transfer of heat between a body and moving a liquid/gas Radiation: transfer of heat between two bodies not in contact Evaporation: loss of heat associated with phase change from liquid to gas any process that transfers heat from one object to another (conduction, convection, radiation) can cool one and heat the other, depending on the direction of heat transfer (always from the warmer to the cooler object) evaporation is different from all of the other mechanisms of heat regulation in that it can only cool an organism because it always involves dissipation (loss) of heat during the phase change from liquid to gas.

Ectotherms are most likely to to use these methods of heat gain: A. conduction B. convection C. radiation D. internal metabolism

A and C the most common sources of heat for ectotherms are basking in the sun (radiation) and lying on rocks and other objects warmed by the sun (conduction). internal metabolism as a source of heat is rare in ectotherms but does occur; some flying insects 'shiver' to warm up muscles before flight. shivering generates large amounts of heat as a result of metabolic reactions.

Use the following information to classify the animal below according to its thermoregulation strategy: Ground squirrels hibernate during the winter. Ground squirrels are: A. Endothermic B. Ectothermic C. Homeothermic D. Heterothermic E. Poikilothermic

A and D

Use the following information to classify the animal below according to its thermoregulation strategy: Hummingbirds have extremely high metabolic rates when active, but exhibit a drop in metabolic rate of almost 95% during cold nights. Hummingbirds are: A. Endothermic B. Ectothermic C. Homeothermic D. Heterothermic E. Poikilothermic

A and D Source of heat Endotherm: obtain heat from metabolic activity (endo="inside") Ectotherm: obtain heat from external sources (ecto="outside") Regulation of body temperature Homeotherm: maintain a relatively constant body temperature as external temperature varies (homeo="same") Heterotherm: usually maintain a relatively constant body temperature but have specific periods where body temperature fluctuates with environmental temperature (hibernation, summer torpor) Poikilotherm: body temperature fluctuates with environmental temperature As birds, hummingbirds are endothermic (generate body heat from metabolic activity); they are heterothermic because they use their metabolism to maintain body temperature during the day, but they also allow their body temperatures to drop dramatically on cold nights.

The heart rate (HR), also called the pulse, is the number of beats per minute The stroke volume (SV) is the amount of blood pumped in a single contraction The cardiac output (CO) is the volume of blood pumped into the systemic circulation per minute and depends on both the heart rate and stroke volume The blood flow through a particular vessel is related to the pressure and resistance in the vessel. Total peripheral resistance (TPR) is a measure of the total resistance across all blood vessels. Blood flow must equal total cardiac output CO = SV x HR BF = P/TPR CO = BF Given this, increasing which of the following will also increase blood pressure, if all other parameters are kept constant? (many) A. Cardiac output B. Heart rate C. Stroke volume D. Total peripheral resistance

A, B, C, and D The heart rate (HR), also called the pulse, is the number of beats per minute The stroke volume (SV) is the amount of blood pumped in a single contraction The cardiac output (CO) is the volume of blood pumped into the systemic circulation per minute and depends on both the heart rate and stroke volume The blood flow through a particular vessel is related to the pressure and resistance in the vessel. Total peripheral resistance (TPR) is a measure of the total resistance across all blood vessels. Blood flow must equal total cardiac output CO = SV x HR BF = P/TPR CO = BF thus since CO = BF, increasing any of the above parameters will increase blood pressure as long as the other parameters are kept constant.

Heterothermy refers to when body temperature varies as a function of environmental conditions (poikilotherms are "extreme" heterotherms). Which of the following are possible in a heterotherm? A. endothermy B. ectothermy C. torpor D. hibernation E. none of these

A, B, C, and D endothermic animals generate their own body heat through metabolism; endothermic animals which hibernate or go into summer torpor (aestivation) allow their body temperatures to change with the environmental conditions and thus qualify as heterotherms. ectothermic animals obtain heat from environmental sources; their body temperatures thus fluctuate with environmental conditions.

The SA node of the heart is: (many) A. enervated by the sympathetic nervous system B. enervated by the parasympathetic nervous system C. capable of depolarizing autonomously (without neural input)

A, B, and C muscle cells have action potentials in a nearly identical way to neurons, where influx of sodium causes depolarization; sufficient depolarization generates and action potential which results in muscle contraction. the heart's pacemaker cells are myocardial cells capable of spontaneous depolarization, meaning they can fire without input from a neuron. this is because they are 'leaky' to sodium, so sodium can flow into the cells at a constant background rate. once enough sodium flows in, the membrane depolarization is sufficient to generate and action potential, triggering muscle contraction in the pacemakers cells. the pacemaker cells pass the action potential on to adjacent cells via the specialized gap junctions (intercalated discs) that connect adjacent myocardial cells. though pacemaker cells do not REQUIRE neural input, they are still connected to the nervous system. the sympathetic (fight or flight) and parasympathetic (rest and digest) divisions of the autonomic nervous system can both interact with the pacemaker cells to either speed up or slow down their down their depolarization rate. if they weren't subject to this control, there would be no way to speed up or slow down heart rate as needed for body function.

Strenuous exercise results in dilation (greater opening) of arterioles in working muscles to increase blood flow to muscles and to skin capillaries to promote body cooling. Which of the following is a mechanism that the body can use to prevent blood pressure from dropping as a result of the change in arteriole dilation? (many) A. Constriction of other arterioles and capillaries - such as those in the digestive tract help balance out the dilation B. Increased cardiac output in terms of heart rate helps balance out the dilation C. Increased cardiac output in terms of blood volume helps balances out the dilation

A, B, and C relaxing arterioles and allowing more blood through the capillaries on its own should cause a drop in blood pressure. however, all of the above reactions occur in response to the relaxation of the skin arterioles. each of these independently can increase blood pressure because: The heart rate (HR), also called the pulse, is the number of beats per minute The stroke volume (SV) is the amount of blood pumped in a single contraction The cardiac output (CO) is the volume of blood pumped into the systemic circulation per minute and depends on both the heart rate and stroke volume The blood flow through a particular vessel is related to the pressure and resistance in the vessel. Total peripheral resistance (TPR) is a measure of the total resistance across all blood vessels. Blood flow must equal total cardiac output CO = SV x HR BF = P/TPR CO = BF

Strenuous exercise results in dilation of arterioles in working muscles to increase blood flow to muscles and to skin capillaries to promote body cooling. Why doesn't blood pressure drop as a result? (many) A. Constriction of other arterioles and capillaries - such as those in the digestive tract help balance out the dilation B. Increased cardiac output in terms of heart rate helps balance out the dilation C. Increased cardiac output in terms of blood volume helps balances out the dilation

Select all of the factors below that will INCREASE oxygen levels in water. (many) A. cooler temperature B. less salinity C. greater depth into the water body D. more wind at the surface E. less rugged terrain (smoother stream flow)

A, B, and D warmer water holds less oxygen than cold water. saltier water holds less oxygen than less salty water. oxygen diffuses into water from the air; thus a greater surface area for water-air interface means more oxygen in the water. wind and turbulence (such as waterfalls, rugged terrain) increases the amount of water exposed to the air surface. once in the water, oxygen moves by diffusion; water that is deeper below the surface will thus have less oxygen due to slow movement by diffusion.

Which of the following is/are true of the pulmonary circuit in a four-chambered, double circulation system? (many) A. the pulmonary circuit pumps oxygen-poor blood into the lungs B. the pulmonary circuit pumps oxygen-rich blood into the body C. blood is pumped through the pulmonary circuit by the left side of the heart D. blood is pumped through the pulmonary circuit by the right side of the heart E. the blood in the pulmonary artery is depleted of oxygen

A, D, and E in a double circulatory system, the pulmonary circuit moves blood to the lungs, and the systemic circuit moves blood to the rest of the body tissues. the pulmonary circuit moves oxygen-depleted blood into the lungs to release carbon dioxide and pick up oxygen. this means the pulmonary artery, which carries blood from the heart to the lungs, carries oxygen-depleted blood. after passing through the capillary beds of the lungs, the blood then returns to the heart, where the systemic circuit pumps oxygen-rich blood to the rest of the body tissues. the pulmonary circuit is served by the right atria and ventricle. the systemic circuit is served by the left atria and ventricle.

How does the application of ice to an injury affect blood flow through the capillaries? A. Decreases blood pressure in capillaries. B. Decreases blood flow by arteriole constriction. C. Increase osmotic pressure outside capillaries. D. Increase blood pressure by increasing fluid loss to interstitial fluid.

B application of ice causes the opposite response to overheating. overheating causes arteriole relaxation and vessel dilation; ice causes local arteriole constriction and thus localized reduced blood flow. because blood is the source of interstitial fluid, application of ice can decrease/prevent swelling by reducing the total amount of blood that moves through the location, and thus reducing the overall amount of interstitial fluid at the site

Blood capillaries must reabsorb all the fluid they emit, or edema (swelling) will occur. A. True B. False

Which of the following is FALSE regarding the lymphatic system? A. the lymphatic system returns fluid to the blood that was lost from the capillaries B. lymphatic vessels are pressurized by the closed circulatory system C. skeletal muscle helps move lymph through the lymphatic system D. lymphatic vessels use one-way valves to prevent backflow of lymph

B because of osmotic pressure and solute concentration differences between the blood and the interstitial fluid, fluid exits the capillaries as they pass through the body tissues. most (~90%) of this fluid returns to the capillaries over the course of their track through the body tissue, but some (~10%) is not reabsorbed. this loss of fluid would eventually cause a severe drop in blood pressure due to less overall volume in the circulatory system, and excess fluid would eventually build up and cause tissue swelling if it were not returned to the circulatory system. return of the fluid to the circulatory system is mediated by the lymphatic system. much like veins, efficient fluid movement through the lymphatic vessels is aided by both movement of adjacent skeletal muscles and by one-way valves that prevent back-flow of fluid through the vessels. the lymphatic system eventually dumps the fluid back into the systemic veins in the circulatory system. though the lymphatic system joins up with these veins in order to return the fluid, the lymphatic system is not part of the closed circulatory system and is not pressurized by it.

The temperature difference between arterial and venous blood nearer to the goose's body: A. allows the goose to lose maximum heat to the environment. B. allows the goose to minimize heat loss to the environment. C. allows the goose's legs to remain cool in freezing water. D. is minimized by the dilation of capillaries in the goose's feet.

B countercurrent exchange maximizes transfer of heat between two countercurrents via a small but consistent heat gradient. as blood moves through arteries from the body to the periphery (foot), it cools; however, because it runs countercurrent to the vein bringing blood back into the body, heat is transferred from the artery to the vein along the entire length of the exchanger. this means that the cooled venous blood is continually being warmed by the warmer arterial blood as it returns; in the absence of the exchanger, the cooled blood would have to be rewarmed by the surrounding tissues and would cost more energy to rewarm and risk chilling the animal. the countercurrent exchanger thus minimizes heat loss to the environment by transferring heat from the artery to the returning vein. dilation of capillaries in the feet would enhance, rather than minimize heat loss.

The kidney has more collecting ducts than distal tubules. A. True B. False

B each nephron empties into a single collecting duct, but a single collecting duct is connected to multiple nephrons. the collecting ducts flow to the ureter. each kidney has a single ureter. the two ureters empty into the single bladder.

Which of the following is a strategy that could be employed by a plant that is EITHER subject to long-term drought OR subjected to extreme flooding? A, increased opening of stomata B. increased cell death C. increased photosynthesis D. increased growth of stems E. increased growth of roots

B of each of the above strategies, only cell death is applicable in the case of EITHER drought OR flooding. in the case of drought, localized cell death of specific leaves and/or branches allows the plant to reduce its overall water needs by reducing its own tissues. in the case of flooding, localized cell death within the roots creates more air space to increase oxygen availability in tissue that would otherwise die from lack of oxygen.

Which of the following statements regarding closed vs open circulatory systems is FALSE? A. Circulatory fluid exits the vessels and directly bathes cells within body cavities in open circulatory systems B. Circulatory fluid can be pumped farther distances in open circulatory systems than in closed circulatory systems C. Circulatory fluid speed and localized pressure can be effeciently controlled in closed but not open circulatory systems D. All vertebrates and some invertebrates have closed circulatory systems E. Circulatory fluid is the same as interstitial fluid in open circulatory systems; they are different fluids in closed circulatory systems

B open circulatory systems are common in invertebrates. vertebrates and some invertebrates (such as annelids and cephalopods) have closed circulatory systems. all circulatory systems have three essential components: a muscular pump (heart), a circulatory fluid (blood or hemolymph), and a series of tubes that the fluid moves through (vessels). the differences between an open and closed circulatory system are that a) the circulatory fluid does not remain within the blood vessels in an open circulatory system and thus b) the circulatory fluid is also the interstitial fluid (fluid in direct contact with the body cells). additional consequences of the open circulatory system are that blood flow rates are slower and blood pressure is not as high as in a closed circulatory system, because the hemolymph moves throughout the entire body volume rather than staying enclosed within vessels. organisms with open circulatory systems can control localized pressure and blood flow to some extent, by compressing sections of the body cavity due to muscle contraction or via additional series of tubes (present in crustaceans) that can affect localized direction of blood flow; however, these adaptations are less efficient at regulating pressure and blood flow compared to a closed system.

What is an example of an animal with an open circulatory system? A. monkey B. beetle C. annelid D. bird E. cnidarian (hydra)

B open circulatory systems are common in invertebrates. vertebrates and some invertebrates (such as annelids and cephalopods) have closed circulatory systems. cnidaria are diploblasts do not have a circulatory system all circulatory systems have three essential components: a muscular pump (heart), a circulatory fluid (blood or hemolymph), and a series of tubes that the fluid moves through (vessels). the differences between an open and closed circulatory system are that a) the circulatory fluid does not remain within the blood vessels in an open circulatory system and thus b) the circulatory fluid is also the interstitial fluid (fluid in direct contact with the body cells). additional consequences of the open circulatory system are that blood flow rates are slower and blood pressure is not as high as in a closed circulatory system, because the hemolymph moves throughout the entire body volume rather than staying enclosed within vessels.

Cardiac muscle fibers can contract without input from the nervous system. What does their anatomy require to create coordinated contraction? A. A lack of troponin-tropomyosin complexes B. Gap junctions to allow depolarization to spread between muscle cells C. A lack of T tubules and minimal sarcoplasmic reticulum D. More glucose

B specialized gap junctions called intercalated discs join cardiac muscle cells to allow spread of the action potential from one cell to the next. absence of troponin-tropomyosin complexes would not spread an action potential from one cell to the next. absence of these complexes would also mean that heart muscle cells would be unable to regulate binding of myosin to actin; once they became contracted, there would be no way to cause them to relax because nothing would block myosin from remaining bound to the actin filaments. absence of T tubules and minimal SR would not propagate action potentials between cells. absence of T tubules would block an action potential from propagating even within a single cell, as T tubules are what carry the action potential into the SR. minimal SR would mean there is little calcium available to release the troponin-tropomyosin complexes from the actin, meaning contraction would be less likely to occur. more glucose would not cause action potentials to propagate from once cell to the next. skeletal muscle is categorized as fast-twitch, slow-twitch, or intermediate. glucose powers fast-twich muscle fibers, which are important for strong bursts of activity but fatigue quickly. cardiac muscle is not skeletal muscle and is not categorized as either fast or slow twitch, so the comparison is not quite appropriate, but cardiac muscle never gets a break so it obviously doesn't fatigue quickly!

There are no valves at the point where blood flows from the ventricles into arteries. A. True B. False

B the atrioventricular valves are located between the atria and the ventricles. this valve is open as blood flows and is pumped from the atria into the ventricles. as the ventricles contract, blood is forced against the atrioventricular valves causing them to slam shut. this causes the 'lub' sound of the heartbeat. contraction of the ventricles forces blood through the semilunar (pulmonary and aortic) valves. as the ventricle relaxes, the blood in the aortic and pulmonary arteries slams backward against the seminlunar valves, causing them to shut. this causes the 'dub' sound of the heartbeat. there are no valves in the heart at the point where the veins join the atria.

Poikilotherms have no ability to regulate body temperature. A. True B. False

B the body temperature of a poikilotherm varies with environmental conditions; however, poikilotherms use many behavioral adaptations to keep their body temperatures relatively consistent during different portions of the day. may reptiles bask in the sun early in the day when it is cold; radiation from the sun warms their body temperatures. as the external temperature rises, they shift to the shade to maintain a fairly constant body temperature. they will alternate between sun a shade throughout the day as conditions change to maintain this body temperature. at night they may return to a burrow where their body temperature drops substantially over night.

If a cell is placed in a 150 mM solution of NaCl, it neither shrinks nor swells. This means that the cell is ____________ with respect to the solution. A. Hypotonic B. Isotonic C. Hypertonic

B tonicity is always definied relative to something else. in this example, because there is no net movement of water or solutes, the cell is isotonic (isoosmotic) to its environment. if water had moved into the cell, the cell would have been hypertonic (hyperosmotic) to its environment, and the environment would have been hypotonic (hypoosmotic) to the cell. if water had moved out of the cell, the cell would have been hypotonic (hypoosmotic) to its environment, and the environment would have been hypertonic (hyperosmotic) to the cell.

Which of the following is/are NOT involved in reabsorption of solutes and water in the loop of Henle? A. countercurrent exchange B. active transport of water C. passive transport of water D. active transport of sodium E. passive transport of sodium F. concentration gradient across the medulla G. changes in the selective permeability of water and ions in different regions of the loop of Henle

B water always moves by osmosis, it is never actively transported. osmoregulation often involves actively transporting ions against their concentration gradients, either directly by ATP-powered pumps, or indirectly via co-transport of another molecules down its concentration gradient (a gradient which is typically first set up by an ATP-powered pump). osmoregulation often involves countercurrent exchangers, which maxmize movement of ions and/or water across a weak, but consistent gradient. the descending limb of the loop of Henle is permeable to water and impermeable to salts; water leaves the tubule due to the higher concentration of solutes in the medulla. the ascending limb is impermeable to water and permeable to salts; salts leave due to either active or passive transport (depending on the location in the tubule) due largely to the concentration gradient established by the juxtamedullary neprhons, the osmotic gradient increases to become more coentrated toward the inner medulla (5) compared to the outer medulla (3). loss of urea from the lower portion of the collecting duct also contributes to this concentration gradient.

Use the following information to classify the animal below according to its thermoregulation strategy: Arctic shrimp are invertibrates which inhabit the arctic ocean. Arctic shrimp are: A. Endothermic B. Ectothermic C. Homeothermic D. Heterothermic E. Poikilothermic

B and C

Which of the following statements about CAM plants is/are true? A. The Calvin Cycle takes place deeper in the plant tissue than in C3 plants. B. PEP carboxylase has a higher affinity for CO2 than does rubisco. C. The Calvin Cycle takes place at a different time than initial CO2 fixation. D. The Calvin Cycle takes place at night.

B and C C4 plants alter the LOCATION of CO2 fixation by rubisco. they use an alternate enzyme, PEP carboxylase, for the initial fixation step. PEP carboxylase fixes CO2 into a 4-carbon organic acid. this 4-carbon organic acid is then transported deeper into the plant tissues, away from oxygen, where it is then converted back to CO2 and then fixed by rubisco. these reactions all happen during the day. because they improve the efficiency of rubisco by moving the rubisco reaction to a location lacking oxygen, the reactions are more efficient and stomata don't have to be open for as long during the day to make the needed amounts of sugar. CAM plants alter the TIMING of CO2 fixation by rubisco. they open stomata at night and use an alternate enzyme to fix CO2 to a 4-carbon organic acid at night. however, at night photosynthesis cannot occur because there is no sunlight. the 4-carbon organic acid is stored until the daytime. the plant then closes the stomata during much of the day to avoid losing water, converts the 4-carbon organic acid back to CO2 inside its tissues, and uses rubisco to fix the stored CO2.

In animals, nitrogenous wastes are produced mostly from the catabolism (breakdown) of: (many) A. urea B. proteins and/or amino acids C. glucose and/or complex sugars D. nucleic acids E. ammonia F. food G. none of these

B and D

In closed circulatory systems, what is/are the advantage/s of a double circulatory system compared to a single circulatory system? (many) A. There can be capillary beds in both the respiratory organ and body systems. B. Oxygenated blood can return to the heart for additional pumping before going to systemic flow. C. Oxygenated blood is kept completely separate from deoxygenated blood in the heart. D. Higher blood pressure can be sustained, supporting terrestrial lifestyles E. In double circulation, the systemic capillary beds receive oxygenated blood, whereas they do not in single circulation F. The double circulation involves contact with the respiratory organ, whereas the single does not.

B and D in all circulatory systems, because capillaries are the only vessels capable of gas exchange, there are capillary beds everywhere that gas exchange must occur: including both the respiratory organ (lungs/gills) and all the body tissues. in fish (single circuit), blood leaves the heart then flows through the gills then directly to the body tissues. there is a substantial drop in both blood pressure once the blood passes through the gills, so blood moving into the tissues does not move as quickly as it does right after exiting the heart. because fish live in a buoyant environment where the effects of gravity are minimized, this lower pressure is still sufficient to move blood efficiently to the body tissues. in contrast, in terrestrial organisms, this decreased pressure would not be sufficient to effectively reach the rest of the body due largely to the effects of gravity. thus the additional chamber of the heart increases both the pressure of the blood entering the body tissues (systemic circuit). this additional pumping step can occur in both a three- and four-chambered heart. oxygenated and deoxygenated blood is only kept fully separate in a four-chambered heart; they mix to some extent in a three-chambered heart (one ventricle, two atria). in a three-chambered heart, the single ventricle pumps to both the pulmonary (lung) and systemic (body) circuits.

Which of the following blood cells can transport oxygen? (select all that apply) A. white blood cells B. lymphocytes only when circulating in blood, not lymph C. red blood cells D. platelets E. thrombocytes

Beavers have relatively little need to conserve water and could therefore be expected to have _______ than humans do. A. Fewer nephrons B. Longer nephron loops C. Shorter nephron loops D. Longer collecting ducts E. Longer proximal and distal tubules

C a longer nephron allows for more reabsorption of water and solutes. thus an animal with ready access to freshwater might be expected to have shorter nephrons. in contrast, an desert animal with less access to freshwater might be expected to have longer nephrons.

Aldosterone is secreted in response to a drop in blood volume. How is it different from how ADH acts? A. ADH acts in response to an increase in blood volume. B. ADH acts in response to a decrease in blood osmolarity. C. ADH acts in response to an increase in blood osmolarity.

C aldosterone leads to reabsorption of additional salt in the distal tubule. this reabsorption of additonal salt also causes reclamation of more water, as water follows the salt by osmois. water and salts are then reabsorbed by the vasa recta. ADH leads to reabsoprtion of additonal water, without reabsorption of additoional salt. this is important because ADH is secreated in response to an increase in blood osmolarity (solute concentration), so water but not solutes must be reclaimed to "dilute" the blood.

Which animal has a double circulatory system? A. earthworm B. fish C. snake D. octopus

C in fish (single circuit), blood leaves the heart then flows through the gills then directly to the body tissues. there is a substantial drop in both blood pressure once the blood passes through the gills, so blood moving into the tissues does not move as quickly as it does right after exiting the heart. because fish live in a buoyant environment where the effects of gravity are minimized, this lower pressure is still sufficient to move blood efficiently to the body tissues. in contrast, in terrestrial organisms, this decreased pressure would not be sufficient to effectively reach the rest of the body due largely to the effects of gravity. thus the additional chamber of the heart increases both the pressure of the blood entering the body tissues (systemic circuit). as a terrestrial vertebrate, snakes have a double circulatory system for the evolutionarily selective reasons described above. though many invertebrates have open circulatory systems, earthworms and octopi both have closed circulatory systems that differ from the vertebrate single or double circulatory systems. the earthworm circulatory system has five pairs of blood vessels called "aortic arches" that pump like hearts to move fluid through the system. they respire through the skin, so there are no lungs to move the blood through. the cephalopod circulatory system has one main systemic heart and a pair of "brachial hearts" in the gills.

Rank the total cross-sectional area in each of the following types of vessels from LOWEST to HIGHEST. A. Veins, arteries, capillaries B. Arteries, capillaries, veins C. Capillaries, veins, arteries D. Veins, capillaries, arteries E. None of these

C pressure is related to speed, volume, and vessel diameter. there is extremely high pressure in arteries because of the proximity to the ventricles which have just expelled the blood from the heart. there is also a high volume of blood contained in the arteries, which tend to have an intermediate diameter compared to veins (wider) and capillaries (much narrower). there is an intermediate amount of pressure in capillaries, which have very narrow diameters, but massive cross-sectional area and extremely slow movement of blood. there is very low pressure in veins, where blood is moving more slowly and is contained in vessels that are typically wider than arteries

Blood moves throughout the body in an open circulatory system, rather slowly and under lower pressure than a closed circulatory system. This is suitable for a sedentary organism, but how do insects power flight with a comparatively slow, low-pressure open circulatory system? A. Insects use anaerobic metabolic pathways to fuel muscle movement in flight. B. Insects convert energy from the sun into metabolic energy. C. Insects use their tracheae to deliver oxygen (via air) to tissues. D. Insects have a larger muscular heart compared to most open-circ-animals.

C the differences between an open and closed circulatory system are that a) the circulatory fluid does not remain within the blood vessels in an open circulatory system and thus b) the circulatory fluid is also the interstitial fluid (fluid in direct contact with the body cells). additional consequences of the open circulatory system are that blood flow rates are slower and blood pressure is not as high as in a closed circulatory system, because the hemolymph moves throughout the entire body volume rather than staying enclosed within vessels. many organisms with open circulatory systems are relatively sedentary, because of these limitations of the open circulatory system (the advantage being that the open system is much less energy-demanding and thus organisms with open systems have lower metabolic demands). insects are very active and quick-moving. they overcome the limitations of the open circulatory system via the tracheae respiratory organs throughout their bodies that deliver oxygen directly to muscles and other tissues with high metabolic demands.

Which of the following is true regarding marine fishes? A. They gain water by osmosis across their gills from the seawater. B. They do not drink seawater. C. They actively transport ions across their gills into the seawater. D. They actively transport water across their gills into the seawater.

C the seawater is hypertonic to marine fishes (they are hypotonic to the seawater). this means that the water potential in the seawater is lower than the water potential in the fish, and thus they are constantly losing water and gaining solutes. marine fish must therefore constantly drink seawater (and actively pump out solutes) to maintain their water/solute balance.

Rank the velocity of blood in each of the following types of vessels from SLOWEST to FASTEST. A. Veins, capillaries, arteries B. Arteries, capillaries, veins C. Capillaries, veins, arteries D. None of the above

C velocity is related to pressure and drag. there is extremely high pressure in arteries because of the proximity to the ventricles which have just expelled the blood from the heart. compared to capillaries, the drag is lower because the overall crossectional area is lower. thus blood moves fastest in arteries. there is very low pressure in veins, which decreases velocity compared to arteries, but there is also very little drag due to the overall low cross-sectional area in veins. thus blood moves at an intermediate speed in veins. there is an intermediate amount of pressure in capillaries but extremely high drag, as arteries are only the width of a single red blood cell. the total cross-sectional area is maximized in capillaries, which thus maximizes drag. thus blood moves slowest in capillaries. this slow movement is important to allow time for gas exchange between the capillaries and the tissues.

How does compression therapy (wrapping) affect tissue swelling? A. Decreases blood pressure in capillaries. B. Decreases blood flow by arteriole constriction. C. Increase osmotic pressure outside capillaries. D. Increase blood pressure by increasing fluid loss to interstitial fluid.

C wrapping increases the pressure in the tissue by constricting the overall volume of the tissue. (wrapping an injury too tightly is dangerous for this reason!) wrapping thus increases the pressure surrounding the capillaries, promoting more movement of interstitial fluid back into the capillaries as they pass through the tissue.

To maintain homeostasis, freshwater fish bring ions into their blood from the water. For freshwater fish, which of the following is/are true of this process? (many) A. it occurs via simple diffusion across the cell membrane B. it occurs via facilitated diffusion through ion channels C. it occurs active transport via ATP-powered ion pumps D. it occurs primarily across the fish gill epithelial tissues E. it occurs primarily across the fish skin

C and D freshwater fish are constantly losing ions and gaining water. they must actively pump in ions from the water, because they move by diffusion down their concentration gradient out of the fish and into the water. diffusion occurs where the physical barrier to diffusion is thin. this occurs at the gills which are optimized to maximize diffusion for gas exchange. thus the gills are also susceptible to loss of ions and gain of water. this does not happen as much across the fish skin which is covered in thick scales and comparatively impermeable to water.

Which of the following best describes the energy requirements for movement of sugar through phloem? A. Energy is required for production of glucose from carbon dioxide; movement of sugar through phloem does not require additional input of energy B. Water is actively pumped into phloem to dilute the high sugar concentration and create turgor pressure required for bulk flow C. Sugar moves between sieve tube cells as a result of ATP-driven transporters D. ATP pumps and cotransport are required for loading companion cells at the sugar source E. All of the above except A

Which statement is correct regarding how CO2 is delivered to rubisco in C3, C4, or CAM plants? A. In CAM plants, CO2 is first stockpiled in cells where rubisco is inactive. B. In C3 plants, CO2 is first stockpiled in cells where rubisco is inactive. C. In C3 plants, CO2 is delivered via three-carbon organic acids. D. In C4 plants, CO2 is delivered via four-carbon organic acids.

D Rubisco catalyzes the reaction that fixes carbon dioxide by attaching CO2 to ribulose bisphosphate (RuBP). However, rubisco can also react with O2 instead of CO2. The reaction with O2 is called photorespiration and it drastically decreases the efficiency of rubisco. Because rubisco also reacts with O2, and O2 is prevalent in the atmosphere, this means that some of the gas exchange/time that stomata are open is 'wasted' because rubisco is carrying out the wrong reaction some of the time. C3 plants use the "normal" CO2 fixation pathway because CO2 is fixed via the Calvin cycle into a 3-carbon sugar C4 plants alter the LOCATION of CO2 fixation by rubisco. they use an alternate enzyme, PEP carboxylase, for the initial fixation step. PEP carboxylase fixes CO2 into a 4-carbon organic acid. this 4-carbon organic acid is then transported deeper into the plant tissues, away from oxygen, where it is then converted back to CO2 and then fixed by rubisco. these reactions all happen during the day. because they improve the efficiency of rubisco by moving the rubisco reaction to a location lacking oxygen, the reactions are more efficient and stomata don't have to be open for as long during the day to make the needed amounts of sugar. CAM plants alter the TIMING of CO2 fixation by rubisco. they open stomata at night and use an alternate enzyme to fix CO2 to a 4-carbon organic acid at night. however, at night photosynthesis cannot occur because there is no sunlight. the 4-carbon organic acid is stored until the daytime. the plant then closes the stomata during much of the day to avoid losing water, converts the 4-carbon organic acid back to CO2 inside its tissues, and uses rubisco to fix the stored CO2.

Based on function, which region of the mammalian heart should have the thickest walls (be the most muscular)? A. The right atrium B. The left atrium C. The right ventricle D. The left ventricle

D atria pump blood into ventricles; ventricles pump blood into arteries. ventricles have thicker walls (more muscle cells) than atria; their contractions are stronger to pump blood much farther. the pulmonary circuit (controlled by the right side of the heart) is relatively short compared to the systemic circuit (controlled by the left side of the heart), which must reach the entire body and return to the heart over a much longer distance. thus natural selection on the heart musculature to reach this much larger distance has resulted in a thicker (more muscular) left ventricle compared to any other compartment of the mammalian heart.

The alternative pathways of photosynthesis using the C4 or CAM systems are said to be compromises. Why? A. C4 plants allow less water loss, but CAM plants allow more water loss. B. C4 compromises on water loss and CAM compromises on photorespiration. C. CAM plants allow more water loss, while C4 plants allow less CO2 into the plant. D. Both minimize photorespiration but expend more ATP during carbon fixation. E. Each one minimizes both water loss and rate of photosynthesis.

D both C4 and CAM pathways are adaptations to minimize photorespiration (inappropriate fixation of O2 by rubisco) and thus minimize water loss in dry environments. however, because C4 and CAM both use a different initial fixation pathway for CO2 which must then be reversed, both use more ATP to fix carbon.

The body fluids of an osmoconformer would be ------ with its ----- environment A. hyperosmotic; freshwater B. hyperosmotic; saltwater C. hypoosmotic; saltwater D. isoosmotic; saltwater E. isoosmotic; freshwater

D by definition, the interstitial fluid of an osmoconformer would be isotonic (same osmolarity) to its environment. it is not a biological requirement that all osmoconformers live in marine environments; however, most osmoconformers do live in seawater. this is because most biological reactions require precise pH and solute concentrations, and do not occur efficiently if conditions move outside of these specific parameters. because the seawater is fairly stable in osmolarity (does not have large swings in solute concentration), these animals are in a relatively stable environment where conditions do not change much.

An aquatic animal with internal solute concentration of about 500 mOsm L-1 is placed in a fluid of solute concentration of about 700 mOsm L-1. Which of the following results is consistent with osmoregulation? A. Passively taking in salts to change its tissue osmolarity to 700 mOsm L-1. B. Passively removing salts to keep tissues at 500 mOsm L-1. C. Pumping in salts to keep tissues at 500 mOsm L-1. D. Pumping out salts to keep tissues at 500 mOsm L-1. E. Pumping out salts to change its tissue osmolarity to 700 mOsm L-1. F. None of the above.

D in this example, there is a lower solute concentration in the animal than in the environment. this means the animal is hypotonic to the environment, or the water potential is lower in the envrionment than in the animal. thus water will tend to move OUT of the animal and into the environment, and salts will tend to move IN to the animal and out of the environment. the animal can combat this effect by taking in large quantities of the solution to bring in water, then using a lot of energy to actively pump the incoming salts out of its body and back into its environment.

Rank the blood pressure in each of the following types of vessels from LOWEST to HIGHEST. A. Veins, arteries, capillaries B. Arteries, capillaries, veins C. Capillaries, veins, arteries D. Veins, capillaries, arteries E. None of these

D pressure is related to speed, volume, and vessel diameter. there is extremely high pressure in arteries because of the proximity to the ventricles which have just expelled the blood from the heart. there is also a high volume of blood contained in the arteries, which tend to have an intermediate diameter compared to veins (wider) and capillaries (much narrower). there is an intermediate amount of pressure in capillaries, which have very narrow diameters, but massive cross-sectional area and extremely slow movement of blood. there is very low pressure in veins, where blood is moving more slowly and is contained in vessels that are typically wider than arteries

All of the following adaptations except for ___________ are seen in desert animals. A. shells, scales, and thick skin B. nocturnal activity pattern C. conservation of metabolic water D. nitrogenous waste excreted as ammonia E. production of concentrated urine

D pretty much any adaptation that decreases loss of water is seen in desert animals. because ammonia is a base is highly toxic to cells, it must be heavily diluted in water for excretion. many desert animals, including desert mammals, convert nitrogenous wastes to uric acid. uric acid is the most energentically costly form of nitrogenous waste disposal; however, it is beneficial because it is nearly insoluble in water and requires almost no water for elimination. this is highly advantageous for animals that live in environments such as deserts where whater is extremely limited or even unavailable.

To maintain homeostasis freshwater fish must _____. A. take in electrolytes through simple diffusion B. excrete large quantities of electrolytes C. consume large quantities of water D. excrete large quantities of water

D the seawater is hypertonic to marine fishes (they are hypotonic to the seawater). this means that the water potential in the seawater is lower than the water potential in the fish, and thus they are constantly losing water and gaining solutes. marine fish must therefore constantly drink seawater (and actively pump out solutes) to maintain their water/solute balance. freshwater fish are subject to exactly the opposite problem, and are constantly losing ions and gaining water. they must actively pump in ions from the water and excrete very dilute urine to maintain their water/solute balance.

Which of the following are subject to hormonal regulation in the mammalian kidney? Select all that apply: A. Proximal tubule B. Descending loop of Henle C. Ascending loop of Henle D. Distal tubule E. Collecting duct F. None of these

D and E

Where does gas exchange occur? Select all that apply. A. within the ventricles of the heart B. arteries C. veins D. capillaries in the lungs E. capillaries in the body

D and E gas exchange occurs only in capillaries. this is related to the properties that control diffusion (surface area, diffusion distance, and partial pressure gradient). in particular, capillaries are the only blood vessesl thin enough to allow efficient diffusion. arteries have thick bands of muscle and connective tissue to regulate blood flow and to withstand the high arterial pressure. veins are also lined with muscle and connective tissues, though not as thick as around arteries. capillaries also maximize surface area fo diffusion in that they are extremely thin (only one blood cell in diameter) networks of vessels that branch to be within 0.1mm of all cells in the body. finally, because they contain either oxygen-rich and carbon dioxide-poor blood at the arterial end of the body tissues capillaries or oxgyen-depleted and carbon dioxide-rich blood at the arterial of the alveolar capillaries, capillaries maximize the partial pressure difference for effective gas exchange.

Anti-diuretic hormone (ADH) is released when plasma osmolarity increases, eventually causing a reduction in urine volume and retaining more water (thus allowing blood plasma concentration to decrease to a normal level). Which of the following are affected directly by ADH? (select all that apply) A. renal tubule cells in the proximal convoluted tubule B. renal tubule cells in the distal convoluted tubule C. aquaporins in tubule cells of the descending Loop of Henle D. aquaporins in tubule cells of the ascending Loop of Henle E. aquaporins in tubule cells of the collecting duct F. strength of the osmotic gradient in the renal medulla

The highest possible concentration of the ultrafiltrate (pre-urine) occurs A. in the cortex of the kidney B. in the medulla of the kidney C. in the proximal convoluted tubule D. at the entry point to the Loop of Henle E. at the apex (bend) in the Loop of Henle F. at the exit point of the Loop of Henle G. the concentration of the ultrafiltrate does not change during the process of forming urine

Which of the following types of organisms is/are isotonic to its environment (does not osmoregulate)? A. Amphibians B. Freshwater fish C. Marine fish D. Terrestrial vertebrates E. Marine jellyfish and sponges

E of these options, only marine jellyfish and sponges do not osmoregulate. most biological reactions require precise pH and solute concentrations, and do not occur efficiently if conditions move outside of these specific parameters. because the seawater is fairly stable in osmolarity (does not have large swings in solute concentration), these animals are in a relatively stable environment where conditions do not change much. this means that even though they are osmoregulators.

Rank the following nitrogenous waste products, from LEAST to MOST energetically "expensive" to produce: - urea - uric acid - ammonia

ammonia < urea < uric acid because it is a base and therefore alters pH, ammonia is highly toxic to cells. thus ammonia must be heavily diluted in water for excretion. urea requires additional metabolic reactions to produce from ammonia and therefore is more energetically 'expensive' to produce, however, it is beneficial because its reduced toxicity means it does not have to be diluted in as much water for excretion. uric acid requires even more reactions to produce from urea, and is thus more 'expensive' to produce than urea; however, it is beneficial because it is nearly insoluble in water and requires almost no water for elimination. this is highly advantageous for animals that live in environments such as deserts where whater is extremely limited or even unavailable.

What makes the "dub" sound of the lub-dub heartbeat?

backflow of blood against the semilunar valves as the ventricle relaxes, the blood in the aortic and pulmonary arteries slams backward against the seminlunar valves, causing them to shut. this causes the 'dub' sound of the heartbeat.

Why is a single-circuit circulatory system physiologically sufficient for fish (eg, why hasn't evolution selected for a double circulatory system)?

in fish (single circuit), blood leaves the heart then flows through the gills then directly to the body tissues. there is a substantial drop in both blood pressure once the blood passes through the gills, so blood moving into the tissues does not move as quickly as it does right after exiting the heart. because fish live in a buoyant environment where the effects of gravity are minimized, this lower pressure is still sufficient to move blood efficiently to the body tissues. in contrast, in terrestrial organisms, this decreased pressure would not be sufficient to effectively reach the rest of the body due largely to the effects of gravity. thus the additional chamber of the heart increases both the pressure of the blood entering the body tissues (systemic circuit).

In turtles and crocodilians, what is the adaptive advantage of the bypass vessel which directs blood returning from the systemic circuit back to the systemic circuit without flowing through the lungs for gas exchange?

in humans, when the body is at rest, the oxygen saturation of hemoglobin is approximately 75% when returning to the heart. thus hemoglobin still has a substantial amount of oxygen bound when returning to the heart when the body is at rest. this is part of the reason we can hold our breath without dying. turtles and crocodilians have a shunt vessel that directs blood from the heart back to the systemic circuit without passing through the pulmonary circuit. this is highly adaptive for when they are submerged under water and circulating blood through the lungs is a waste of time and energy because no gas exchange is possible when underwater. because the blood still contains relatively high levels of oxygen, and because of other specific adaptations that decrease their metabolic needs, turtles and crocodilians are able to survive extended periods of time underwater without breathing. depending on the species, turtles and corocodilians can remain underwater from 30 minutes to up to 3 hours.

Describe the role of the gizzard in digestion. What types of animals have gizzards? What digestive structure do these organisms lack?

the gizzard functions in mechanical breakdown in organisms that lack teeth entirely, or lack teeth that can be used for chewing. it is present in may different types of organisms including birds, reptiles, earthworms, some fish, and crustaceans. many types of animals swallow stones or sand that is stored in the gizzard to aid in mechanical disruption of food.

Rank the following nitrogenous waste products, from LEAST to MOST amount of water lost during excretion: A. urea B. uric acid C. ammonia

uric acid < urea < ammonia because it is a base and therefore alters pH, ammonia is highly toxic to cells. thus ammonia must be heavily diluted in water for excretion. urea requires additional metabolic reactions to produce from ammonia and therefore is more energetically 'expensive' to produce, however, it is beneficial because its reduced toxicity means it does not have to be diluted in as much water for excretion. uric acid requires even more reactions to produce from urea, and is thus more 'expensive' to produce than urea; however, it is beneficial because it is nearly insoluble in water and requires almost no water for elimination. this is highly advantageous for animals that live in environments such as deserts where whater is extremely limited or even unavailable.

According to the pressure-flow hypothesis of phloem transport: A. solute moves from area of high concentration to an area of lower concentration near the sink cells B. the combination of a high turgor pressure in the source and transpiration water loss from the sink moves solutes through phloem conduits C. water is actively transported into the source region of the phloem to create the turgor pressure needed D. the pressure in the phloem of a root is normally greater than the pressure in the phloem of a leaf E. none of these

Many plant roots have specialized associations with specific species of bacteria or fungi to increase access to nitrogen. Which of the following is TRUE of these relationships ? A. The plant provides sugars to the fungi and the bacteria in exchange for access to nitrogen B. The plant relationship with the fungus is mutualistic; the relationship with the bacteria is pathenogenic C. Plant-associated bacteria and fungi both acquire nitrogen from the atmosphere D. All of the above are true E. None of the above are true

Proton pumps continually pump protons outside of the cell into the environment. What should the cations in the environment do in response? A. Move into the cell B. Stay outside of the cell C. Physically distance by remaining 6 feet from the nearest cation

Sandy soils present what sort of tradeoff for a plant? A. Lots of oxygen, but little water B. Lots of water, but little nutrients C. Lots of nutrients, but little oxgyen D. None of these

Which of the following statements about mycorrhizae is/are FALSE? A. Mycorrhizae are parasitic associations of roots and fungi B. The fungus component in mycorrhizae benefits by receiving sugar from plants C. The hyphae of both arbuscular mycorrhizae and ectomycorrhizae extend into the root cortex D. The fungus component in mycorrhizae benefits plants by supplying water and minerals absorbed by the fungal hyphae E. All of the above are true statements

Why are anionic nutrients generally mobile in soils, and thus easily leached, while cationic nutrients are relatively immobile A. Cations interact tightly with clay particles and organic materials B. Cations have a stronger tendency to aggregate than anions do C. Anions are repelled from the surfaces of living roots D. Anions readily form crystals while cations do not E. None of these

You decide to go on a diet and eat NO fats. Your friend warns you that you're misguided and this will cause nutrient deficiencies and lead to health problems. How could this happen, now that you avoid eating fats? A. Decreased absorption of fat-soluble vitamins from foods B. Decreased retention of fat-soluble vitamins in the body C. Decreased absorption of water-soluble vitamins from foods D. Decreased retention of water-soluble vitamins in the body E. None of these

A Fat-soluble vitamins (ADEK) are vitamins best absorbed by the body when accompanied by fat. Lacking fats will decrease the absorption of these vitamins from food. Retention of fat-soluble vitamins in the body will only be impacted if overall fat stores decrease; however, reduced consumption of fat, on its own, will not decrease fat reserves.

In digestion, which of the following is most likely to be digested in a rumen or cecum for a grazer? A. cellulose B. fat-soluble vitamins C. oxygen D. chitin E. fatty-acids

A cellulose, the primary structural carbohydrate in plants, cannot broken down by any animal enzymes. only certain microorganisms produce an enzyme capable of digesting cellulose. thus herbivores rely on a host of mutualistic microorganisms that reside in their digestive tracts to digest cellulosic material. the specialized digestive tract chambers of cows (rumen) and horses (large cecum) house these microorganisms. the rumen is present in foregut fermenters such as cows, the cecum is present in hindgut fermenters such as horses and rabbits. the crop can serve different purposes in different animals. in some animals it functions in food storage for later digestion, but in some herbivorours birds, it functions analogously to the cecum or rumen by housing mutualistic microorganisms that break down cellulosic material.

Why is it important that the xylem is adjacent to the phloem? A. Pressure from xylem water moves nutrients through the phloem. B. The phloem protects the xylem from damage. C. The phloem is a critical component of the cohesion-tension theory. D. The phloem provides a solute potential that drives xylem water movement up the tree.

A transport of sugar depends on a high concentration gradient between source (site of sugar production) and sink (site in need of sugar), which causes large differences in turgor pressure within the phloem at these two different sites. high concentrations of sugar at the source cause water to diffuse from the xylem into the phloem, increasing the turgor pressure. low concentrations of sugar at the sink cause low turgor pressure. this pressure differential drive the movement of sugar from source to sink, with the aid of movement of water down the pressure differential. thus close proximity between xylem and phloem is essential for effective phloem function.

Which of the following is an advantage of a complete digestive tract? A. Digestive steps co-occur in the same place B. A separate opening is not needed for waste C. Digestive enzymes are not needed D. No possible mixing of food and waste

Mutualistic associations of legume plant species with Rhizobium bacteria rely upon: A. Maintenance of low oxygen environment by the plant to enable the bacteria to fix nitrogen B. Fixation of nitrogen by bacteria in exchange for sugar provided by the plant C. Chemical signaling between bacteria and a newly sprouted plant to establish the relationship D. All of the above E. None of the above

Why are many digestive enzymes produced in an inactive form and then activated in the lumen of the digestive tract? A. It helps to break down macromolecules(proteins, carbohydrates, nucleic acids, lipids) faster. B. The temperature of organism changes when food falls into digestive tract, that helps to activate digestive enzymes. C. Digestive enzyme have an inherent inactive period, only after that period can they become activated. D. Digestive enzymes would destroy the cells that produce and secrete them if they were produced in an active form.

D animals eat biological materials and use digestive enzymes to break the material down. thus digestive enzymes are designed to break down nutrients which in many cases are extremely similar to components of the animal cells (lipids, proteins, carbohydrates). if the enzymes were active as soon as a cell produced them, the enzymes could immediately begin digesting components of the cells that made them. the two major strategies for avoiding this type of cell self-destruction are producing enzymes in an inactive form and compartmentalizing digestive reactions when enzymes are active (for example, compartmentalizing the initial digestion of polypeptides to the stomach). the digestive systems of most animals display both of these strategies.

What is the adaptive function of specialized digestive tract chambers in vegetarian animals like cows and horses? A. maintain low pH for stomach enzymes. B. mixing of bile and pancreatic enzymes with food. C. for storage of partially digested plant material. D. housing symbiotic bacteria required for cellulose digestion. E. consolidation of undigested waste before defecation.

D cellulose, the primary structural carbohydrate in plants, cannot broken down by any animal enzymes. only certain microorganisms produce an enzyme capable of digesting cellulose. thus herbivores rely on a host of mutualistic microorganisms that reside in their digestive tracts to digest cellulosic material. the specialized digestive tract chambers of cows (rumen) and horses (large cecum) house these microorganisms.

What is the force behind the process known as "transpiration" in plants? A. Cohesion-tension pulls water up via exporation from leaves. B. Carbon dioxide is absorbed through stomata. C. Water is absorbed into the leaves through stomata. D. Water is absorbed into the roots through root hairs.

A cohesion is attraction among like molecules; in the case of water, cohesion is mediated by hydrogen bonding. surface tension is a force at the air-water interface that causes stronger hydrogen bonding among the water at the interface with the air, causing a concave surface boundary called a meniscus. this surface tension pulls against gravity due to the force of the interactions among the water molecules. when water evaporates out of the stomata in the leaves, it deepens the meniscus causing greater pull on the water below the meniscus (tension) and thus an upward force on all the water in the entire water column, which all interact with each other via hydrogen bonds (cohesion). thus transpiration is driven by evaporation in combination with cohesion and tension in the plant water column from leaf cell to root hair.

Water potential is generally most negative in which of the following parts of a plant? A. mesophyll cells of the leaf B. root hairs C. xylem vessels in leaves D. xylem vessels in roots

A in most cases, water potential follows a gradient where it is highest in the soil and lowest in the leaves. specifically, it is lower in the mesophyll cells of the leaf than in xylem, and because of this gradient it is pulled from the soil into the root hairs, then into the xylem in the roots, up to the xylem in the leaves, and finally into the mesophyll cells of the leaf

How does a longer alimentary canal (digestive tract) create an advantage in processing plant material? A. Increased time of digestion allows for more processing. B. More volume means more food can be consumed. C. It creates positive feedback for decreased enzymatic activity.

A much of the plant matter an animal eats is not broken down by the animal itself, but by the mutualistic microorganisms which reside in its gut. digestion of plant matter, especially cellulosic material, is time-consuming and inefficient, even by the organisms with the necessary enzymes to carry out the reactions. thus a longer alimentary canal provides longer processing time for these microorganisms to digest the plant matter and, importantly, also time for the animal to then absorb the nutrients released (and produced) by the microorganisms.

How does mineral mobility affect the symptoms of deficiency in plants? A. Deficiency of a mobile nutrient usually affects older organs more than young ones B. Deficiency of a mobile nutrient usually affects younger organs more than older ones

A plants are constantly competing for access to light; often older leaves become shaded by competitors over time, and new leaves develop in new locations where the plant can exploit a new source of light. thus when a nutrient becomes limiting, the plant will typically break down structures in old leaves to release nutrients to move into new leaves. any mobile nutrient (present in a structure which can be broken down) in limiting supply will thus move to new leaves at the expense of old leaves; old leaves suffer for lack of mobile nutrients when those nutrients are in short supply. in contrast, any immobile nutrient (present in a structure which cannot be broken down) in limiting supply is stuck in the old leaf and cannot be moved to the new leaves; new leave suffer for lack of immobile nutrients when those nutrients are in short supply.

Plants use proton pumps, cation channels, and anion cotransporter channels to acquire nutrients from the soil. Which of the following requires a direct energy expenditure by the plant? A. proton pump B. cation channel C. anion cotransporter channel

A plants pump protons into the soil to create a high concentration of protons outside the plant. this allows plants to use co-transporters to couple the movement of protons back into the cell (down their concentration gradient) and necessary nutrients into the cell (against their concentration gradients) via a 'coat-tail' effect. the pumping of protons out of the cell requires consumption of ATP. no energy is required by the co-transporter, as the movement of protons back into the cell down the proton concentration gradient allows movement of the nutrient in question against its concentration gradient.

Root pressure can best be described as A. A high pressure potential driven by accumulation of ions and water by osmosis B. The loss of water molecules from menisci, creating a large negative pressure C. The adhesion of water molecules to the sides of xylem, creating a pull upward, and by cohesion with water molecules below D. The movement of water from a region of low water potential to high water potential

A plants typically have a higher solute concentration (lower water potential) than the soil, causing water to move into the plant from the soil. during the day, stomata are open and plants are transpiring as they synthesize sugars from carbon dioxide. at night, in the absence of sunlight to drive photosynthesis, stomata close and transpiration stops. water continues moving into the roots at night because of the lower solute potential in the roots compared to the soil. as water continues to move in but is not transpired out, pressure builds up in the xylem eventually forcing water up the xylem. in short plants, this pressure is strong enough to push water out of the leaves in a process called guttation. root pressure is sufficient to move water up xylem at night and in short plants; however, it is not strong enough to move water up tall trees. movement of water up tall trees occurs as a result of the cohesion-tension model. cohesion is attraction among like molecules; in the case of water, cohesion is mediated by hydrogen bonding. surface tension is a force at the air-water interface that causes stronger hydrogen bonding among the water at the interface with the air, causing a concave surface boundary called a meniscus. this surface tension pulls against gravity due to the force of the interactions among the water molecules. when water evaporates out of the stomata in the leaves, it deepens the meniscus causing greater pull on the water below the meniscus (tension) and thus an upward force on all the water in the entire water column, which all interact with each other via hydrogen bonds (cohesion). thus transpiration is driven by evaporation in combination with cohesion and tension in the plant water column from leaf cell to root hair.

Water flows into the source end of a sieve tube because _____ A. sucrose has been actively transported into the sieve tube, making it hypertonic B. sucrose has been actively transported out of the sieve tube C. water pressure outside the sieve tube forces in water D. the companion cell of a sieve tube actively pumps in water E. sucrose has diffused into the sieve tube, making it hypotonic

A solutes diffuse from areas of high concentration to low concentration, but diffusion is relatively slow. sugar moves much faster though phloem than could be maintained by diffusion alone. instead, sugar is actively transported from the leaf mesophyll cells into the companion cells. sugar in sieve tube cells then quickly moves into sieve tube cells via the shared cytoplasm between companion cells and sieve tube cells. this increase in solute concentration in the phloem cells decreases the solute potential, causing water to diffuse into the phloem from the xylem. the movement of water into the phloem increases the turgor pressure in the phloem cells, which drives phloem cytoplasm (and dissolved sugars) down the phloem from source to sink. this process of active transport of sugars into phloem and the subsequent movement of water into phloem is called phloem loading.

Water moves from an area of [blank] water potential to [blank] water potential. A. high; low B. low; high C. concentrated; dilute D. dilute; concentrated

A water moves from areas of high water potential to areas of low water potential. water potential is related to two phenomena: pressure and solute concentration. A higher pressure means higher water potential; water moves from areas of high pressure (high water potential) to low pressure (low water potential). A higher concentration of solutes means lower water potential; water moves from areas of low solute concentration (high water potential) to high solute concentration (low water potential).

Which of the following is required for acquisition of nutrients from clay-rich soils? (many) A. proton pumps B. facilitated diffusion C. direct diffusion D. osmosis E. none of these

A and B plants pump protons into the soil to create a high concentration of protons outside the plant. this allows plants to use co-transporters to couple the movement of protons back into the cell (down their concentration gradient) and necessary nutrients into the cell (against their concentration gradients) via a 'coat-tail' effect. the proton pumps also are used to add protons to the soil to 'compete' with cations for binding to negatively-charged clay particles; thus protons will displace the cations from the clay in a process called 'cation exchange', which allows plants to more easily absorb the cations

Certain nutrients are considered "essential" in the diets of some animals because _____. (many) A. the nutrients are required for normal organismal function B. only certain foods contain them C. these animals are not able to synthesize these nutrients D. only those animals use those nutrients

A and C any essential nutrient is one that is absolutely required for normal function and which the organism cannot synthesize.

The rate of sugar transport in a plant depends on (select all that apply) A. the difference in turgor pressure between the source and the sink B. the rate of transpiration C. the rate of photosynthesis

A and C transport of sugar depends on a high concentration gradient between source (site of sugar production) and sink (site in need of sugar), which causes large differences in turgor pressure within the phloem at these two different sites. high concentrations of sugar at the source cause water to diffuse from the xylem into the phloem, increasing the turgor pressure. low concentrations of sugar at the sink cause low turgor pressure. this pressure differential drive the movement of sugar from source to sink, with the aid of movement of water down the pressure differential. a high rate of photosynthesis increases the concentration of sugar at the source, which increases the concentration gradient between source and sink.

Under which of the following conditions would the rate of transpiration INCREASE? (many) A. When the weather changes and air becomes drier B. When the temperature of a leaf decreases C. When stomata close at night D. When atmospheric pressure is low

A and D anything that increases evaporation of water from leaves increases transpiration. drier air will increase evaporation, and thus increase traspiration. in addition, low atmospheric pressure increases transpiration in much the same way that water moves from areas of high pressure to areas of low pressure. temperatures decrease in leaves as a RESULT of transpiration, not a cause of it (much like evaporation causes cooling for animals) transpiration occurs through stomata, and thus stomata must be open for transipration to occur. closing stomata at night, or during a drought, decreases transpiration rates.

Which of the following would tend to increase the rate of transpiration? (many) A. When the weather changes and air becomes drier B. When the temperature of a leaf decreases C. When stomata close at night D. When atmospheric pressure is low

in a legume root nodule, the leghemoglobin (many) A. regulates the amount of oxgyen available B. is inactivated by nitrogenase C. is absent in active bacteroids D. protects the nodule from nitrogen E. is produced by the Rhizobium bacteria F. is produced by the plant G. converts nitrogen gas to a biologically available form of nitrogen

A and F

An individual whose ability to absorb carbohydrates is diminished, but can absorb all other nutrients, could have some sort of pathology in which of the following? (Select all that apply): A. Mouth B. Esophagus C. Stomach D. Small intestine E. Liver F. Gallbladder G. Large intestine H. Pancreas

A and H Mouth and pancreas both produce amylases, which break down carbohydrates. a defect in the small intestine is likely to cause more wide-ranging absorption problems than carbohydrates alone

Which of the following is likely to be a sugar sink? (many) A. Fruit B. Flower C. Apical meristem D. New leaf E. Mature leaf F. Root during the middle of the growing season G. Root at the start of the growing season

A, B, C, D, and F a source is any location with a high concentration of sugar that is mobilized to a site in need of sugar. during the growing season, sugar is synthesized via photosynthesis in the leaf mesophyll cells, and transported to locations of new growth and/or sites of storage such as roots. over the course of the growing season, large amounts of sugars are stored in roots and other storage sites. at the end of the growing season, the plant loses leaves and goes dormant, similar to hibernation in some mammals. when the next season begins, sugars in the roots and other storage sites are rapidly mobilized and used to promote growth of new leaves which will then repeat the cycle. bulbs are one specialized sugar storage site; they are a source during the start of the growing season and a sink after new leaves are established by the middle of the growing season. any growing tissue, such as a new leaf, a growing root, an apical meristem, or a developing fruit, is a sink. a mature leaf is a source due to its high rates of photosynthesis.

Soil consists of: (many) A. rock particles of various sizes B. minerals C. microorganisms D. organic matter from dead organisms

A, B, C, and D all of these are components of soil. rock is broken down into smaller and smaller fragments through weathering (combined effects of wind, temperature changes, rain, activity of organisms); minerals such as iron, zinc, and copper are released from rock particles as it is broken down; microorganisms such as a fungi, bacteria, protists, and invertebrates help break down organic matter from dead organisms present in the humus layer of the soil.

Phloem transport of sucrose is often described as going from source to sink. Which of the following is most likely to function as a source? A. a growing root in late summer B. a storage bulb in early spring C. a growing leaf in early spring D. a shoot tip in late fall

B a source is any location with a high concentration of sugar that is mobilized to a site in need of sugar. during the growing season, sugar is synthesized via photosynthesis in the leaf mesophyll cells, and transported to locations of new growth and/or sites of storage such as roots. over the course of the growing season, large amounts of sugars are stored in roots and other storage sites. at the end of the growing season, the plant loses leaves and goes dormant, similar to hibernation in some mammals. when the next season begins, sugars in the roots and other storage sites are rapidly mobilized and used to promote growth of new leaves which will then repeat the cycle. bulbs are one specialized sugar storage site; they are a source during the start of the growing season and a sink after new leaves are established by the middle of the growing season. any growing tissue, such as a new leaf or a growing root, is a sink. a mature leaf is a source due to its high rates of photosynthesis.

Veins always carry deoxygenated blood. A. True B. False

B a vein is any vessel that carries blood into the heart; and artery is any vessel that carries blood away from the heart. the artery that carries blood from the heart to the lungs contains deoxygenated blood, and the vein that carries blood from the lungs to the heart carries oxygenated blood.

Which of the following correctly describes why water is more difficult to respire in compared to air? A. Water is warmer than air, and thus holds less oxygen. B. Water is about 1000x more dense than air, and thus requires more energy to ventilate the respiratory surface (inhale/exhale). C. Water has a higher partial pressure of O2, and thus O2 constantly diffuses into the air (away from aquatic organisms). D. Respiratory surfaces work better in drier conditions, not in moist (or wet) conditions.

B air is less dense and thus takes less work (energy) to move through the respiratory organ. water has a lower partial pressure of oxygen than air does. warmer water holds less oxygen than colder water, but the temperature of a body of water is often cooler than the air. respiratory surfaces tend to be lined in thin mucus, and thus drier air conditions cause drying of these surfaces which can interfere with respiratory function.

The absorption of fats differs from that of carbohydrates in that _____. A. the processing of fats does not require any digestive enzymes, whereas the processing of carbohydrates does B. most absorbed fat first enters the lymphatic system, whereas carbohydrates directly enter the blood C. fat absorption primarily occurs in the stomach, whereas carbohydrates are absorbed from the small intestine D. carbohydrates need to be emulsified before they can be digested, whereas fats do not

B because fats are hydrophobic, they aggregate into globules that are resistant to enzymatic breakdown. thus fats must first be emulsified (broken up and dissolved into aqueous solution with the aid of amphipathic molecules such as bile salts). the emulsified fats are then digested by the enzyme lipase. the resulting fatty acids and monoglycerides are then packaged into protein-coated globules. these globules are large enough that their diffusion into capillaries would clog the capillaries and stop blood flow. thus the globules are instead transported into the lymphatic system, where they eventually join the bloodstream at large veins where there is much less risk of clogging the vessels. digestion of all nutrients requires enzymatic breakdown. the stomach is not involved in absoprtion of any nutrients; its role is purely mechanical and chemical digestion. it is fats that require emulsification, due to their hyrdophobicity, not carbohydrates which are hydrophilic.

The only animals that use skin as a significant portion of their respiratory surface (ie, use skin for gas exchange) are largely aquatic/amphibious. Yet water is a less efficient medium for gas exchange than air. Why do you suppose all skin-ventilated animals reside in/near water? A. having a lot of skin surface area exposes you to greater changes in temperature and other environmenal risks B. the thin membranes required for efficient gas exchange increases the risk of dehydration C. natural selection has increased the efficiency of gas exchange in aquatic animals compared to terrestrial animals D. it is an evolutionary 'accident' based on lack of common ancestry between aquatic and terrestrial vertebrates

B efficient gas exchange requires a thin barrier to diffusion. thus respiratory surfaces are covered by extremely thin membranes. as a consequence, these membranes are also extremely susceptible to evaporation as the same principles that promote efficient diffusion of gasses also promote efficient movement of water.

It is the middle of the fruiting season for apples. Some apples are maturing on the tree; others are only beginning to develop from ovaries. Which of the following should, in principle, allow the tree to maximize the SIZE of the apples on the tree? A. Remove the largest apples from the tree B. Remove the flowers and the smallest apples from the tree C. Add fertilizer

B fruits such as apples are massive sugar sinks; they do not produce sugars but have high concentrations of sugars in their tissues which must be transported from other locations in the plant. apples which are earlier in their development (and flowers containing ovaries which have yet to become fruits) require extremely large amounts of sugar to reach maturity. elimination of smaller apples and flowers diverts this sugar to the existing apples, allowing them to become larger.

What is an example of an animal with an open circulatory system? A. gorilla B. clam C. sponge D. frog

Where is partial pressure of CO2 the highest? A. atmosphere B. skeletal muscle C. capillary bed in alveolus D. alveolus (lung air sac)

B partial pressure is the pressure of a particular amount of gas in a mixture of gasses. it is different from percent because gas is compressible; thus the percent of a gas in a mixture can be the same, but its partial pressure can change based on the overall pressure of the system. just like water's response to pressure, gasses move from areas of high partial pressure to areas of low partial pressure. the partial pressure of carbon dioxide is highest at locations where carbon dioxide is being produced and oxygen is being consumed. of the choices above, this would be at the skeletal muscles.

Iron deficiency is often indicated by yellowing in newly formed leaves. This suggests that iron is _____. A. concentrated in the xylem of older leaves B. relatively immobile nutrient in plants C. concentrated in the phloem of older leaves D. found in leghemoglobin and reduces the amount available to new plant parts E. tied up in formed chlorophyll molecules

B plants are constantly competing for access to light; often older leaves become shaded by competitors over time, and new leaves develop in new locations where the plant can exploit a new source of light. thus when a nutrient becomes limiting, the plant will typically break down structures in old leaves to release nutrients to move into new leaves. any mobile nutrient (present in a structure which can be broken down) in limiting supply will thus move to new leaves at the expense of old leaves; old leaves suffer for lack of mobile nutrients when those nutrients are in short supply. in contrast, any immobile nutrient (present in a structure which cannot be broken down) in limiting supply is stuck in the old leaf and cannot be moved to the new leaves; new leave suffer for lack of immobile nutrients when those nutrients are in short supply.

Moderate soil acidity means there are protons in the soil. Protons help nutrient availability by _____. A. increasing the cation binding to soil particles B. promoting cation exchange C. promoting cellular respiration in root cells D. leaching away the cations from soil after heavy rains

B plants can easily absorb anions from the soil because anions are readily soluble in soil water. in contrast, cations associate tightly with clay particles in soil, which are negatively charged. this makes it difficult for plants to absorb cations from the soil. protons in the soil will 'compete' with cations for binding to negatively-charged clay particles; thus protons will displace the cations from the clay in a process called 'cation exchange', which allows plants to more easily absorb the cations

If ΨP = 0.3 MPa and ΨS = -0.45 MPa, the resulting Ψ is _____. A. +0.15 MPa B. -0.15 MPa C. -0.75 MPa D. +0.75 MPa E. -0.42 MPa

B Ψ (water potential) is the sum of ΨP (pressure potential) and ΨS (solute potential). water moves from areas of high water potential to areas of low water potential. water potential is related to two phenomena: pressure and solute concentration. A higher pressure means higher water potential; water moves from areas of high pressure (high water potential) to low pressure (low water potential). A higher concentration of solutes means lower water potential; water moves from areas of low solute concentration (high water potential) to high solute concentration (low water potential).

Why is it harder to breathe at high elevations? (many) A. The air is "thicker" and more dense. B. The air is "thinner" and holds less oxygen per unit volume. C. The atmospheric pressure is higher, making it more difficult to breathe. D. The atmospheric pressure is lower, resulting in a lower partial pressure for O2.

B and D partial pressure is the pressure of a particular amount of gas in a mixture of gasses. it is different from percent because gas is compressible; thus the percent of a gas in a mixture can be the same, but its partial pressure can change based on the overall pressure of the system. just like water's response to pressure, gasses move from areas of high partial pressure to areas of low partial pressure. because the air is less dense at higher altitudes, the partial pressure of oxygen is lower at higher altitudes. efficient exchange across the respiratory surface depends on a high gradient of partial pressures, but the lowered partial pressure of oxygen at higher altitudes is not much greater than the partial pressure of oxygen in the blood in the alveolar capillaries; thus there is much less exchange of oxygen across the respiratory surface at high altitudes.

Which of the following organs play an accessory role in the digestion of food? (many) A. esophagus B. pancreas C. stomach D. small intestine E. gall bladder F. liver G. large intestine

B, E, and F

As an undergraduate research assistant, your duties involve measuring water potential in experimental soil-plant-atmosphere systems. Assume you make a series of measurements in a system under normal daylight conditions, with stomata open and photosynthesis occurring. Which of the following correctly depicts the trend your measurement data should follow if the cohesion-tension mechanism is operating? A. ψatmosphere<ψleaves=ψroots<ψsoil B. ψsoil<ψroots<ψleaves<ψatmosphere C. ψatmosphere<ψleaves<ψroots<ψsoil D. ψsoil<ψroots=ψleaves<ψatmosphere E. none of these

Clay soils present what sort of tradeoff for a plant? A. Lots of oxygen, but little water B. Lots of water, but little nutrients C. Lots of nutrients, but little oxgyen D. None of these

Nitrifying bacteria can have a strong impact on the nutrient content of soils because: A. they add to the total pool of N by converting N2 to NH3 B. they convert biologically available N into inert N2 C. they transform biologically available N to a form that that washes out of soil easily D. they can outcompete plants for the biologically available N E. None of the above

Which of the following best describes the relationship between movement of water in xylem and the pressure-flow hypothesis? A. Increasing transpiration rates lead to proportional increases in speed of transit through phloem B. Root pressure generally results in greater turgor pressure in the phloem of a root than the turgor pressure in the phloem of a leaf C. Sugar solute moves from area of high concentration at the source to an area of lower concentration near the sink cells; water flows from xylem into phloem as a result of the high sugar solute concentration D. The high concentration of sugar at the source generates high turgor pressure, and loss of water via transpiration from the xylem at the sink then moves solutes through phloem E. None of these are true

Which of the following describes a scenario where a lot of gas will diffuse? A. Small surface area B. Thick membrane C. High partial pressure differences on either side of a membrane D. None of the above

Which of the following is true of fluid transport in vascular plants? A. Movement of water and sugar in plants both require ATP as a energy source B. Xylem plays a role in movement of water, but not movement of sugar C. Water moves due to negative pressure, sugar moves due to positive pressure D. Movement of water and sugar occurs through living cells

Where does chemical digestion of proteins begin? A. esophagus B. pancreas C. stomach D. small intestine E. gall bladder F. liver G. large intestine H. mouth

C Although proteins are physically broken down in the mouth, the stomach begins the chemical breakdown of proteins.

Where is oxygen content the LOWEST? A. In venous blood during rest B. In arterial blood during exercise C. In venous blood during exercise D. In arterial blood during rest

C Arterial blood and venous blood don't engage in oxygen/carbon dioxide exchange. all exchange occurs in capillaries. exercise causes more oxygen to be extracted from hemoglobin so venous blood during exercise has the lowest oxgyen content, after passing through capillaries in tissues with very low oxygen partial pressures, resulting in maximal offloading of oxygen from the hemoglobin into the tissues.

Where does the mass of a tree come from? A. Soil B. Sunlight C. Air D. Water

C all biological compounds contain carbon. plants are capable of 'fixing' atmospheric carbon dioxide to produce sugars, which are the source of carbon for synthesis of biological molecules in the plant. thus the mass of a plant comes from the carbon dioxide in the air.

Clay in soils represents a trade-off in nutrient availability, because A. oxygen levels are exceptionally high, but much of the nitrogen leaches away B. nitrogen levels are exceptionally high, but many of the cations leach away C. cations are less likely to leach out of soil but are difficult for plants to extract D. anions are less likely to leach out of soil but are difficult for plants to extract

C anions are readily soluble in soil water, and thus easily washed (leached) away during heavy rains.. in contrast, cations associate tightly with clay particles in soil, which are negatively charged. this means cations remain bound to clay during rains and do not wash way. plants compensate via a process called cation exchange, where plant cells pump protons into the soil to displace cations from the negatively-charged clay particles, thus freeing the cations for absorption by the plant.

Which of the following is NOT a key component of the cohesion-tension process in xylem? A. Lignin in xylem cell walls B. Open stomata C. Use of ATP D. Water between mesophyll cells

C cohesion is attraction among like molecules; in the case of water, cohesion is mediated by hydrogen bonding. surface tension is a force at the air-water interface that causes stronger hydrogen bonding among the water at the interface with the air, causing a concave surface boundary called a meniscus. this surface tension pulls against gravity due to the force of the interactions among the water molecules. adhesion is attraction among unlike molecules because the water column in a plant is continuous from root to leaf, the menesci (plural of meniscus) are present between the mesophyll cells, not actually within the xylem tubes. thus it is evaporation at these menisci inbetween the leafe mesophyll cells that drive movement via the cohesion-tension process. the cohesion-tension process puts strong negative pressure on the xylem, like sucking on a straw. lignin reinforces the walls of the xylem, which would otherwise collapse as a result of this negative pressure this cohesion-tension model does not require any input of energy on the part of the plant (energy that causes water to evaporate comes from the sun); there is no active transport to move water through xylem. this is because, in most cases, water potential in plants follows a gradient where it is highest in the soil and lowest in the leaves. specifically, it is lower in the mesophyll cells of the leaf than in xylem, and because of this gradient it is pulled from the soil into the roots.

Which of the following is NOT a key component of the cohesion-tension process in xylem? Select all that apply. A. Lignin in xylem cell walls B. Open stomata C. Use of ATP D. Water between mesophyll cells

C cohesion is attraction among like molecules; in the case of water, cohesion is mediated by hydrogen bonding. surface tension is a force at the air-water interface that causes stronger hydrogen bonding among the water at the interface with the air, causing a concave surface boundary called a meniscus. this surface tension pulls against gravity due to the force of the interactions among the water molecules. adhesion is attraction among unlike molecules; in this case the attraction of water to the cell walls of the xylem. when water evaporates out of the stomata in the leaves, it deepens the meniscus causing greater pull on the water below the meniscus (tension) and thus an upward force on all the water in the entire water column, which all interact with each other via hydrogen bonds (cohesion). thus transpiration is driven by evaporation in combination with cohesion and tension in the plant water column from leaf cell to root hair. it is evaporation at menisci in between the leaf mesophyll cells that drive movement via the cohesion-tension process. the cohesion-tension process puts strong negative pressure on the xylem, like sucking on a straw. lignin reinforces the walls of the xylem, which would otherwise collapse as a result of this negative pressure this cohesion-tension model does not require any input of energy on the part of the plant (energy that causes water to evaporate comes from the sun); there is no active transport to move water through xylem. this is because, in most cases, water potential in plants follows a gradient where it is highest in the soil and lowest in the leaves. specifically, it is lower in the mesophyll cells of the leaf than in xylem, and because of this gradient it is pulled from the soil into the roots.

How does hemoglobin binding work? A. Hemoglobin molecules form clumps and accumulate extra oxygen in the pile-up. B. Conformational changes in red blood cells allow for additional oxygen molecules once one is picked up. C. Hemoglobin is more likely to bind to oxygen once one O2 is bound. D. When O2 is bound to hemoglobin, a CO2 molecule can also bind to hemoglobin.

C each hemoglobin protein can bind four oxygen molecules at a time. cooperative binding is the phenomenon where the binding of the first oxygen changes the conformational shape of the rest of the protein and makes it easier for the second, third, and four oxygen molecules to bind. once the hemoglobin protein is fully saturated (bound to 4 oxygen molecules), the reverse is also true: loss of the first oxygen molecules makes it easier for the second, third, and fourth oxygen molecules to leave the hemoglobin protein. each red blood cell contains ~280 million hemoglobin molecules. the phenomenon of cooperative binding occurs at the level of hemoglobin, not red blood cells. most of the carbon dioxide in the bloodstream is converted to carbonic acid by the enzyme carbonic anhydrase. the carbonic acid then dissociates into bicarbonate and a proton. the protons tend to bind to deoxygenated hemoglobin, and the bicarbonate remains in the plasma; thus hemoglobin acts as a pH buffer. if hemoglobin proteins were to clump together, this would distort the shape of the red blood cells and interfere with oxygen binding to hemoglobin. this is what occurs in individuals who suffer from the genetic disorder sickle cell anemia, which results from a mutation in the hemoglobin protein that causes the hemoglobins to clump together.

What is the adaptive advantage of having a double circulation system and three-chambered heart of amphibians, over the single circuit and two-chambered heart of fish? A. There can be capillary beds in both the respiratory organ and body systems. B. The additional chamber increases the pressure of blood flow to the respiratory organ. C. Oxygenated blood can return to the heart for additional pumping before going to systemic flow. D. Oxygenated blood is kept completely separate from deoxygenated blood in the heart.

C in all circulatory systems, because capillaries are the only vessels capable of gas exchange, there are capillary beds everywhere that gas exchange must occur: including both the respiratory organ (lungs/gills) and all the body tissues. in fish (single circuit), blood leaves the heart then flows through the gills then directly to the body tissues. there is a substantial drop in both blood pressure once the blood passes through the gills, so blood moving into the tissues does not move as quickly as it does right after exiting the heart. because fish live in a buoyant environment where the effects of gravity are minimized, this lower pressure is still sufficient to move blood efficiently to the body tissues. in contrast, in terrestrial organisms, this decreased pressure would not be sufficient to effectively reach the rest of the body due largely to the effects of gravity. thus the additional chamber of the heart increases both the pressure of the blood entering the body tissues (systemic circuit). this additional pumping step can occur in both a three- and four-chambered heart. oxygenated and deoxygenated blood is only kept fully separate in a four-chambered heart; they mix to some extent in a three-chambered heart (one ventricle, two atria). in a three-chambered heart, the single ventricle pumps to both the pulmonary (lung) and systemic (body) circuits.

Why are plants like the venus fly trap and pitcher plant carnivorous? A. They need additional carbon than is present in the soil B. They need additional protein than what is present in the soil C. They need additional mineral nutrients than what is present in the soil D. They need additional energy than what is present in the soil

C plants get carbon from carbon dioxide and energy from the sun. they synthesize their own amino acids (building blocks of proteins) from carbon and other nutrients. they also use other nutrients for many other biological functions. these other nutrients are typically minerals obtained from the soil such as nitrogen, potassium, calcium, etc. nitrogen is often the most critically limiting nutrient, as it can only be made biologically available by a few species of bacteria. thus plants which live in extremely nitrogen-poor environments often have carnivorous adaptations to provide an additional sources of nitrogen from other living organisms.

What is the importance of consuming an adequate amount of proteins in the diet? A. They are used as cofactors for metabolic reactions and are required in minute quantities. B. Proteins are necessary to produce urea and other important metabolites. C. Proteins serve a variety of functions, and the body does not store excess quantities of amino acids. D. They are most commonly used to meet energy demands of cells.

C proteins carry out the bulk of chemical reactions and are also essential for structural support in cells. they make up the primary component of muscle and many other tissues. proteins are composed of amino acids, some of which can be synthesized by the body from but some of which cannot. unlike fats and sugars, the body does not store excess amino acids. dietary sources of protein are absolutely required for the essential amino acids and helpful for preventing malnutrition for the nonessential amino acids. vitamins (organic molecules) and mineral (inorganic molecules) are required in minute quantities and often function as cofactors in metabolic reactions cellular energy demands are typically met by either fats or sugars, combined with oxygen as the terminal electron acceptor for oxidative phosphorylation

The companion cells near the source have high concentrations of sucrose. How does this happen? A. Sugar diffuses down its concentration gradient from sites of photosynthesis to the companion cells B. Sugars are actively transported into companion cells via plasmodesmata C. Co-transporters move sugars against their concentration gradient into the companion cells D. Proton pumps actively transport sugars into the companion cells

C sugar is actively transported from the leaf mesophyll cells into the companion cells. sugar in sieve tube cells then quickly moves into sieve tube cells via the shared cytoplasm between companion cells and sieve tube cells. this increase in solute concentration in the phloem cells decreases the solute potential, causing water to diffuse into the phloem from the xylem. the movement of water into the phloem increases the turgor pressure in the phloem cells, which drives phloem cytoplasm (and dissolved sugars) down the phloem from source to sink. this process of active transport of sugars into phloem and the subsequent movement of water into phloem is called phloem loading.

Which of the following promotes oxygen release from hemoglobin? A. A decrease in temperature in body tissue B. A decrease in CO2 levels in body tissue C. A decrease in pH in body tissue D. A decrease in carbonic anhydrase in RBCs

C the Bohr shift causes the hemoglobin-oxygen equilibrium curve (the plot comparing oxygen saturation of hemoglobin against partial pressure of oxygen in the body tissues) to shift toward the right. this means that hemoglobin becomes MORE likely to 'give up' oxygen at any particular partial pressure of oxygen in the body tissue (decreases the affinity of hemoglobin for oxygen). this shift occurs because of lower pH. blood pH can be lowered as a result of increased carbon dioxide; carbon dioxide is converted into carbonic acid in the blood. hemoglobin binds many of the protons released by carbonic acid to buffer the blood, but excess protons beyond what are bound by hemoglobin will lower the blood pH. this occurs when tissues are heavily utilizing oxygen such as during exercise, thus causing greater release of oxygen to the tissues. increased temperature causes a similar effect on the release of oxygen from hemoglobin, but the response to increased temperature is not called the Bohr effect. a decrease in carbonic anyhdrase would decrease the likelihood of Bohr effect occurring, because carbon dioxide would not be converted to carbonic acid as quickly.

The difference between positive pressure ventilation (PPV) and negative pressure ventilation (NPV) is that: A. in PPV, organisms exchange gases only during inhalation; in NPV, organisms exchange gasses only during exhalation B. in PPV, respiration is coupled to a circulatory system; in NPV, respiration occurs through direct gas exchange with tissues C. PPV occurs when air is pushed into the respiratory organ; NPV occurs when air is pulled into the respiratory organ D. PPV occurs only in animals with gills or tracheae, NPV occurs only in animals with lungs

C this is the definition of positive vs negative ventiliation. whether an organism can engage in gas exchange during inhalation only or inhalation and exhalation has to do with the organization of the airways, not the mechanism for bringing air into the airways (review bird vs mammal airway organization). organisms that use direct gas exchange through the skin have no need to 'pump' air anywhere. amphibians are an examples of lunged organisms that use PPV rather than NPV.

Concurrent flow is not as efficient in exchange as countercurrent flow because countercurrent flow provides: A. more diffusion at the beginning of capillary flow than at the end of the capillary by maximizing the concentration gradient at the beginning. B. more diffusion at the end of capillary flow than at the end of the capillary by maximiizing the concentration gradient at the end. C. consistent diffusion across weaker concentration gradients through the entire capillary. D. thinner capillary walls to promote diffusion. E. greater surface area for diffusion.

C when a concentration gradient exists between two adjacent fluids that flow in the same direction, the solutes and water quickly exchange through diffusion (and osmosis) until the concentrations have equalized. once they have equalized, no more net exchange occurs. the end result is 50/50 distribution of solutes across the two adjacent liquids. in contrast, when a concentration gradient exists between two adjacent fluids that flow in OPPOSITE directions, the concentration gradient is maintained across the entire length of the adjacent flow. the gradient is never as strong as the initial gradient that would be seen in concurrent flow; however, because it is maintainied across the entire length of the adjacent flow, this means that the final distribution of solutes can be strongly asymmetric such as 90/10.

Root hairs absorb nutrients from soil against the nutrient concentration gradient. Depending on the nutrient, which of the following can play a role in this process? (many) A. osmosis B. direct diffusion C. facilitated diffusion D. electrochemical gradient E. co-transport

C, D, and E plants pump protons into the soil to create a high concentration of protons outside the plant. this allows plants to use co-transporters to couple the movement of protons back into the cell (down their concentration gradient) and necessary nutrients into the cell (against their concentration gradients) via a 'coat-tail' effect. the proton pumps also are used to add protons to the soil to 'compete' with cations for binding to negatively-charged clay particles; thus protons will displace the cations from the clay in a process called 'cation exchange', which allows plants to more easily absorb the cations

Some of the "dead stuff in our food" makes it into our food chain through the activity of decomposers such as fungi. Fungi are A. photoautotrophs B. photoheterotrophs C. chemoautotrophs D. chemoheterotrophs

D chemoheterotrophs are are organisms which use energy from chemical bonds (chemo) and organic carbon molecules (hetero) to meet their nutritional needs. fungi break down dead organic matter for their source of energy and carbon and thus are chemoheterotrophs

What forces are responsible for capillarity? A. high pressure potentials created by the entry of ions and water during the night, when transpiration rates are low, followed by an influx of water B. cohesion of water molecules in a continuous flow from leaf to root C. gravity and wall pressure (from the sides of xylem cells) D. adhesion of water molecules to the sides of xylem cells, cohesion of water molecules to each other, and surface tension

D cohesion is attraction among like molecules; in the case of water, cohesion is mediated by hydrogen bonding. surface tension is a force at the air-water interface that causes stronger hydrogen bonding among the water at the interface with the air, causing a concave surface boundary called a meniscus. this surface tension pulls against gravity due to the force of the interactions among the water molecules. adhesion is attraction amon unlike molecules; in this case the attraction of water to the cell walls of the xylem. adhesion combined with cohesion and surface tension together cause capillary action, or the movement of water up a narrow tube. capillary action alone is also not sufficient to move water the length of a tall tree.

Which of the following is NOT a reason that an animal's gut is a favorable habitat for mutualistic microorganisms? A. Constant temperature B. Ready supply of nutrients C. Inhospitable conditions for many micro-competitors D. Easy access to bloodstream

D like all life, microorganisms survive better in 'ideal' growth conditions and are in constant competition for access to resources. the gut represents an 'ideal' growth condition for microorganisms because of controlled temperature and ready supply of nutrients, in addition, the inhospitable conditions (high acidity of the stomach, presence of immune cells in the intestines) reduce competition. the gut does not provide easy access to the bloodstream except in cases where the lining of the gut becomes compromised. this can occur in cases of infection, where the tight junctions between intestinal cells becomes compromised. microorganisms which enter the bloodstream can cause massive, systemic infection in the host organism, resulting in an overwhelming immune response that either destroys the microorganism or causes death of the host. neither of these outcomes is advantageous for the microorganism.

Which organism do you think has the most efficient respiratory organ? A. snail B. bird C. snake D. fish E. human

D the partial pressure of oxygen in water is lower than the partial pressure of oxygen in air. in addition, air is less dense and thus takes less work (energy) to move through the respiratory organ. thus fish gills are much more efficient at removing oxygen from water than terrestrial lungs are at removing oxygen from the air as a result of this selective pressure.

Which of the following is not a major activity of the stomach? A. Mechanical digestion B. HCl secretion C. Mucus secretion D. Nutrient absorption E. Enzyme secretion

D the purpose of the stomach is digestion, not absorption. digestion is breakdown of nutrients into smaller components. stomach digestion processes include 1) mechanical breakdown via muscular contractions of the stomach that churns and mixes the food particles and 2) chemical breakdown via enzymatic digestions. stomach enzymes are secreted into the stomach compartment when food enters, and hydrochloric acid is also secreted which activates the protein digestive enzyme pepsin. mucus is also secreted by stomach cells to protect the lining of the stomach from HCl.

Compared to plants from other environments, the cells of many desert plants contain high concentrations of solutes. This helps them survive in their arid surroundings because the high solute concentrations create relatively [blank], which helps retain water and prevent reverse flow of water from roots to soil. A. low pressure potentials B. high pressure potentials C. high solute potentials D. low solute potentials

D Ψ (water potential) is the sum of ΨP (pressure potential) and ΨS (solute potential). water moves from areas of high water potential to areas of low water potential. water potential is related to two phenomena: pressure and solute concentration. A higher pressure means higher water potential; water moves from areas of high pressure (high water potential) to low pressure (low water potential). A higher concentration of solutes means lower water potential; water moves from areas of low solute concentration (high water potential) to high solute concentration (low water potential). desert soil is very dry and thus has very low water potential; this makes it difficulty for plants to absorb water from the soil because the soil may have lower water potential than the plant; this would cause water to move out of the plant and into the soil. as a result of selection in a dry environment, one adaptation in desert plants is very high solute concentrations in their tissues. the higher the solute concentration, the lower the solute potential, and thus the more likely water is to move into the plant from the soil: this low solute potential in the plant can drive the water potential of the plant lower than the water potential of the dry soil.

Water rises in plants primarily by cohesion-tension. Which of the following is not true about the cohesion-tension model? A. The physical forces between water molecules in the capillary-sized xylem cells make it easier to overcome gravity. B. The water potential of the air is more negative than the xylem. C. Water loss by evaporation (transpiration) is the driving force for water movement. D. Cohesion represents the tendency for water molecules to stick together by hydrogen bonds. E. The ʺtensionʺ of this model represents the electrical excitability of the xylem cells.

What is the function of proton pumps localized in the plant plasma membrane? A. to provide channels for ion diffusion B. to transfer phosphorus groups from ATP to proteins C. to transfer metal ions across the plasma membrane D. to transfer anions across the plasma membrane E. to create an electrochemical gradient

Some plants obtain nitrogen from symbiotic fungi or bacteria. What was the original source of N that the FUNGI obtained? A. urea in the soil B. N2 gas C. carbohydrates in the soil D. lipids in the soil E. proteins in the soil

E A few species of bacteria are the only organisms capable of reducing ("fixing") atmospheric nitrogen to make it biologically available. Just as plants and other photosynthesizers are essential as a source of carbon and oxygen for most other forms of life, these bacteria are essential as a soruce of nitrogen for most other forms of life. Nitrogen is used for synthesis of nucleic acids and proteins. Fungi would use nucleid acids and proteins from the soil organic matter; they decompose organisms containgin nitrogen which was orginally made available by the nitrogen-fixing bacteria.

Which of the following soil minerals is most likely leached away during a hard rain (ie, dissolve easily in soil water)? A. H+ B. Ca++ C. K+ D. Na+ E. NO3-

E anions are readily soluble in soil water, and thus easily washed (leached) away during heavy rains.. in contrast, cations associate tightly with clay particles in soil, which are negatively charged. this means cations remain bound to clay during rains and do not wash way.

Which elements are most often the limiting nutrients for plant growth? A. carbon, nitrogen, oxygen B. carbon, potassium, sodium C. carbon, sodium, chlorine D. nitrogen, oxygen, hydrogen E. nitrogen, potassium, phosphorus

E nitrogen, potassium, and phosphorus are all essential macronutrients for plants, meaning they are required in relatively large quantities. macronutrients are typically major components of nucleic acids, proteins, and/or phospholipids, and are thus required for normal function in all cells. nitrogen is highly abundant in the atmosphere as nitrogen gas; however, nitrogen gas is not usable for most organisms. only a few species of bacteria are capable of reducing or 'fixing' nitrogen to become biologically available. oxygen is produced by plant photosynthesis, and required by plant respiration. plants produce enough that it is not limiting. carbon dioxide is required by plants to produce sugars via photosynthesis. it is not limiting in the atmosphere. sodium is not required for most plants.

The Bohr shift on the oxygen-hemoglobin dissociation curve is produced by changes in _____. A. hemoglobin concentration B. the partial pressure of oxygen C. the partial pressure of carbon monoxide D. salts E. pH

E the Bohr shift causes the hemoglobin-oxygen equilibrium curve (the plot comparing oxygen saturation of hemoglobin against partial pressure of oxygen in the body tissues) to shift toward the right. this means that hemoglobin becomes MORE likely to 'give up' oxygen at any particular partial pressure of oxygen in the body tissue (decreases the affinity of hemoglobin for oxygen). this shift occurs because of lower pH. blood pH can be lowered as a result of increased carbon dioxide; carbon dioxide is converted into carbonic acid in the blood. hemoglobin binds many of the protons released by carbonic acid to buffer the blood, but excess protons beyond what are bound by hemoglobin will lower the blood pH. this occurs when tissues are heavily utilizing oxygen such as during exercise, thus causing greater release of oxygen to the tissues. increased temperature causes a similar effect on the release of oxygen from hemoglobin, but the response to increased temperature is not called the Bohr effect.

in a legume root nodule, the nitrogenase: (many) A. regulates the amount of oxygen available B. is inactivated by leghemoglobin C. is absent in active bacteroids D. protects the nodule from nitrogen E. is produced by the Rhizobium bacteria F. is produced by the plant G. converts nitrogen gas to a biologically available form of nitrogen

E and G

Place the following digestion events in sequential order. If two events occur in the same organ, you should set them as equal to one another. - Pepsinogen is cleaved to form pepsin - Polypeptides are cleaved into individual amino acids by proteases - Salivary amylase hydrolyzes starch - Digested food material is compacted and most remaining water absorbed - Parietal cells secrete HCl - Bile salts and pancreatic amylase are secreted

Salivary amylase hydrolyzes starch < Parietal cells secrete HCl = Pepsinogen is cleaved to form pepsin < Bile salts and pancreatic amylase are secreted = Polypeptides are cleaved into individual amino acids by proteases < Digested food material is compacted and most remaining water absorbed this sequence of steps occurs from mouth to large intestine. 1. in the mouth, salivary amylase breaks down complex carbohydrates during chewing. 2. once the food is swallowed and passes through the esophagus into the stomach, the stomach secretes both HCl and pepsinogen. The HCl activates the pepsinogen into pepsin, which breaks down large proteins into polypeptides (shorter chains of amino acids). 3. after digestion in the stomach, the bolus of food moves into the small intestine where the gall bladder secretes bile salts (produced in the liver, stored in the gall bladder) to digest lipids, and the pancreas secretes pancreatic amylyase and other digestive enzymes. these enzymes cause further digestion of material into individual components such as polypeptides broken down into individual amino acids. these nutrients are then absorbed into the blood stream (or moved into the lymph in the case of lipids) in the small intestine. 4. after absorption of nutrients in the small intestine, the digested material moves into the large intestine where water is reabsorbed and the material is compacted for elimination.

Compare and contrast the roles of the cecum, rumen, and crop in digestion. What types of animals have these digestive features?

cellulose, the primary structural carbohydrate in plants, cannot broken down by any animal enzymes. only certain microorganisms produce an enzyme capable of digesting cellulose. thus herbivores rely on a host of mutualistic microorganisms that reside in their digestive tracts to digest cellulosic material. the specialized digestive tract chambers of cows (rumen) and horses (large cecum) house these microorganisms. the rumen is present in foregut fermenters such as cows, the cecum is present in hindgut fermenters such as horses and rabbits. the crop can serve different purposes in different animals. in some animals it functions in food storage for later digestion, but in some herbivorours birds, it functions analogously to the cecum or rumen by housing mutualistic microorganisms that break down cellulosic material.

Rank the following mechanism of gas exchange from LEAST to MOST efficient. - countercurrent flow - concurrent flow - crosscurrent flow

concurrent flow < crosscurrent flow < countercurrent flow when a concentration gradient exists between two adjacent fluids that flow in the same direction, the solutes and water quickly exchange through diffusion (and osmosis) until the concentrations have equalized. once they have equalized, no more net exchange occurs. the end result is 50/50 distribution of solutes across the two adjacent liquids. in contrast, when a concentration gradient exists between two adjacent fluids that flow in OPPOSITE directions, the concentration gradient is maintained across the entire length of the adjacent flow. the gradient is never as strong as the initial gradient that would be seen in concurrent flow; however, because it is maintainied across the entire length of the adjacent flow, this means that the final distribution of solutes can be strongly asymmetric such as 90/10. crosscurrent flow is inbetween countercurrent and concurrent flow. in crosscurrent flow, the exchanging fluids move perpendicular to each other rather than parallel. this arrangement causes more next exchange than in concurrent flow, but not as much as in countercurrent flow.

When an animal cell is placed in a hypotonic solution and water enters the cell via osmosis, the volume of the cell increases until it bursts. Does the same thing happen in plant cells? Why or why not? (please note that LC will not be able to correctly score this question, even if you get it right - don't worry! you'll still get credit for participating)

no, because of the cell wall water moves from areas of high water potential to areas of low water potential. water potential is related to two phenomena: pressure and solute concentration. A higher pressure means higher water potential; water moves from areas of high pressure (high water potential) to low pressure (low water potential). A higher concentration of solutes means lower water potential; water moves from areas of low solute concentration (high water potential) to high solute concentration (low water potential). in the case above, the wall of the plant cell exerts pressure potential against water moving in to cell that balances against the solute potential driving water into the cell. there is no such pressure potential in the case of a mammalian cell that lacks a cell wall, which means water continually moves into the mammalian cell until it bursts.

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