Positive feedback differs from negative feedback in that

Positive feedback differs from negative feedback in that

A) the effector's response increases some parameter (such as body temperature), whereas in negative feedback it can only decrease the parameter.
B) positive feedback benefits the organism, whereas negative feedback is detrimental.
C) the positive feedback's effector responses are in the same direction as the initiating stimulus rather than opposite to it.
D) positive feedback systems have only effectors, whereas negative feedback systems have only receptors.
E) positive feedback systems have control centers that are lacking in negative feedback systems.


Answer: C

Which process in the nephron is least selective?

Which process in the nephron is least selective? 

A) reabsorption
B) active transport
C) secretion
D) salt pumping by the loop of Henle
E) filtration


Answer: E

Connective tissues typically have

Connective tissues typically have 

A) many densely packed cells with direct connections between the membranes of adjacent cells.
B) a supporting material such as chondroitin sulfate.
C) relatively few cells and a large amount of extracellular matrix.
D) the ability to transmit electrochemical impulses.
E) the ability to shorten upon stimulation.


Answer: C

Antidiuretic hormone (ADH) functions at the cellular level by

Antidiuretic hormone (ADH) functions at the cellular level by 

A) causing an increase in the number of aquaporin molecules of collecting duct cells.
B) decreasing the speed at which filtrate flows through the nephron, leading to increased reabsorption of water.
C) triggering the synthesis of an enzyme that makes the phospholipid bilayer more permeable to water.
D) causing membranes to include more phospholipids that have unsaturated fatty acids.
E) stimulating the reabsorption of glucose through channel proteins.


Answer: A

Low selectivity of solute movement is a characteristic of

Low selectivity of solute movement is a characteristic of 

A) filtration from the glomerular capillaries.
B) H+ pumping to control pH.
C) secretion along the distal tubule.
D) salt pumping to control osmolarity.
E) reabsorption mechanisms along the proximal tubule.


Answer: A

A primary reason that the kidneys have one of the highest metabolic rates of all body organs is that

A primary reason that the kidneys have one of the highest metabolic rates of all body organs is that 

A) they are the body's only means of shedding excess nutrients.
B) they operate an extensive set of active-transport ion pumps.
C) they store the body's excess fats.
D) they have membranes of varying permeability to water.
E) they have an abundance of myogenic smooth muscle


Answer: B

The reason that the steroid hormone aldosterone affects only a small number of cells in the body is that

The reason that the steroid hormone aldosterone affects only a small number of cells in the body is that

A) it is unable to enter nontarget cells.
B) nontarget cells convert aldosterone to a hormone to which they do respond.
C) only its target cells contain aldosterone receptors.
D) nontarget cells destroy aldosterone before it can produce any effect.
E) only its target cells get exposed to aldosterone


Answer: C

Prolactin stimulates mammary gland growth and development in mammals and regulates salt and water balance in freshwater fish. Many scientists think that this wide range of functions indicates that prolactin

Prolactin stimulates mammary gland growth and development in mammals and regulates salt and water balance in freshwater fish. Many scientists think that this wide range of functions indicates that prolactin

A) is a nonspecific hormone.
B) interacts with many different receptor molecules.
C) is derived from two separate sources.
D) is an evolutionarily conserved hormone.
E) has a unique mechanism for eliciting its effects.


Answer: D

Ammonia

Ammonia 

A) has low toxicity relative to urea.
B) is the major nitrogenous waste excreted by insects.
C) is soluble in water.
D) can be stored in the body as a precipitate.
E) is metabolically more expensive to synthesize than urea.


Answer: C

Interstitial fluid is

Interstitial fluid is 

A) the route for the exchange of materials between blood and body cells.
B) identical to the composition of blood.
C) found only in the lumen of the small intestine.
D) the internal environment inside animal cells.
E) the fluid inside the gastrovascular cavity of Hydra.


Answer: A

Examine Figure 32.1. Near a goose's abdomen, the countercurrent arrangement of the arterial and venous blood vessels causes

Examine Figure 32.1. Near a goose's abdomen, the countercurrent arrangement of the arterial and venous blood vessels causes

A) the blood in the feet to be as warm as the blood in the abdomen.
B) the temperature at the abdomen to be less than the temperature at the feet.
C) the loss of the maximum possible amount of heat to the environment.
D) the venous blood to be as cold near the abdomen as it is near the feet.
E) the temperature difference between the contents of the two sets of vessels to be minimized.


Answer: E

Unlike most bony fishes, sharks maintain body fluids that are isoosmotic to seawater, so they are considered by many to be osmoconformers. Nonetheless, these sharks osmoregulate at least partially by

Unlike most bony fishes, sharks maintain body fluids that are isoosmotic to seawater, so they are considered by many to be osmoconformers. Nonetheless, these sharks osmoregulate at least partially by

A) monitoring dehydration at the cellular level with special gated aquaporins.
B) using their gills and kidneys to rid themselves of sea salts.
C) possessing a special adaptation that allows their cells to operate at an extraordinarily high salt concentration.
D) tolerating high urea concentrations that balance internal salt concentrations to seawater osmolarity.
E) synthesizing trimethylamine oxide, a chemical that binds and precipitates salts inside cells.


Answer: D

If a person loses a large amount of water in a short period of time, he or she may die from dehydration. ADH can help reduce water loss through its interaction with its target cells in the

If a person loses a large amount of water in a short period of time, he or she may die from dehydration. ADH can help reduce water loss through its interaction with its target cells in the

A) anterior pituitary.
B) kidney.
C) adrenal gland.
D) bladder.
E) posterior pituitary


Answer: B

Fight-or-flight reactions include activation of

Fight-or-flight reactions include activation of 

A) the thyroid gland, leading to an increase in the blood calcium concentration.
B) the anterior pituitary gland, leading to cessation of gonadal function.
C) the pancreas, leading to a reduction in the blood sugar concentration.
D) the adrenal medulla, leading to increased secretion of epinephrine.
E) the parathyroid glands, leading to increased metabolic rate.


Answer: B

During mammalian labor and delivery, the contraction of uterine muscles is enhanced by oxytocin. This is an example of

During mammalian labor and delivery, the contraction of uterine muscles is enhanced by oxytocin. This is an example of

A) a negative feedback system.
B) a hormone that is involved in a positive feedback loop.
C) signal transduction immediately changing gene expression in its target cells.
D) a hormone that acts in an antagonistic way with another hormone.
E) the key role of the anterior pituitary gland in regulating uterine contraction.


Answer: B

Compared to wetland mammals, water conservation in mammals of arid regions is enhanced by having more

Compared to wetland mammals, water conservation in mammals of arid regions is enhanced by having more

A) ureters.
B) juxtamedullary nephrons.
C) urinary bladders.
D) podocytes.
E) Bowman's capsules.


Answer: B

A human who has no access to fresh water but is forced to drink seawater instead

A human who has no access to fresh water but is forced to drink seawater instead 

A) will excrete more water molecules than taken in, because of the high load of ion ingestion.
B) will risk becoming overhydrated within 12 hours.
C) will thrive under such conditions, as long as he has lived at the ocean most of his life.
D) will find that drinking saltwater satiates his thirst.
E) will develop structural changes in the kidneys to accommodate the salt overload.


Answer: A

The thin horizontal arrows in Figure 32.1 show that

The thin horizontal arrows in Figure 32.1 show that 

A) the goose's legs get progressively warmer as the blood moves away from the abdomen to the feet.
B) the warmer arterial blood can bypass the legs as needed, when the legs are too cold to function well.
C) the warmer venous blood transfers heat to the cooler arterial blood.
D) the arterial blood is always cooler in the abdomen, compared to the temperature of the venous blood in the feet of the goose.
E) the warmer arterial blood transfers heat to the cooler venous blood.


Answer: E

Excretory structures known as protonephridia are present in

Excretory structures known as protonephridia are present in 

A) cnidarians.
B) earthworms.
C) vertebrates.
D) insects.
E) flatworms.


Answer: E

The nitrogenous waste that requires the most energy to produce is

The nitrogenous waste that requires the most energy to produce is 

A) urea.
B) uric acid.
C) ammonia.
D) ammonium.


Answer: B