AP Biology Term 4 Quiz 2
Multiple Choice Questions (2 points each)
1. A dog is following the scent of a jackrabbit. Which of the following accurately describes how the dog’s
brain integrates information for smell?
(A) Chemoreceptors in the brain send impulses for smell in the nasal cavity.
(B) Chemoreceptor cells in the nasal cavity send impulses to the appropriate area of the brain.
(C) Chemoreceptors on epithelial cells of the tongue send hormones to the appropriate area of the brain.
(D) Receptors originating in the nose send action potentials to the motor regions of the brain.
B
2. The diagram above depicts the response to a pinprick (stimulus) on the tip of a human finger. The
arrows show the direction of impulse transmission along the labeled axons. If axon II was damaged
before the pinprick, which of the following is most likely?
(A) The person will not feel the pinprick.
(B) The person can no longer feel pain.
(C) The person’s finger will not withdraw reflexively.
(D) The person cannot transmit nerve impulses to the brain.
C
3. The healthy human immune system responds to pathogens with both specific and nonspecific
processes. Which of the following models depicts a nonspecific response?
B
4. The diagram above illustrates feedback control as exerted by the hormone thyroxine. Following
surgical removal of the thyroid gland, the level of TSH in the blood will increase. Which of the
following best explains this increase?
(A) Residual blood thyroxine, from prior to thyroid gland removal, will bind to cells in
the anterior pituitary, signaling more TSH secretion.
(B) Thyroxine will remain bound to thyroxine receptors on various body cells, and these
body cells will secrete additional hormones that stimulate the anterior pituitary to secrete TSH.
(C) Thyroxine that was stored in the anterior pituitary prior to thyroid gland removal will signal more
TSH secretion.
(D) A decrease in thyroxine levels means a loss of inhibition to the hypothalamus and anterior pituitary,
leading to increased TSH secretion.
D
5. Antidiuretic hormone (ADH) is important in maintaining homeostasis in mammals. ADH is released
from the hypothalamus in response to high tissue osmolarity. In response to ADH, the collecting duct and
distal tubule in the kidney become more permeable to water, which increases water reabsorption into the
capillaries. The amount of hormone released is controlled by a negative feedback loop. Based on the
model presented, which of the following statements expresses the proper relationship between osmolarity,
ADH release, and urine production?
(A) As tissue osmolarity rises, more ADH is released, causing less water to be excreted as urine.
(B) As tissue osmolarity rises, less ADH is released, causing less water to be excreted as urine.
(C) As tissue osmolarity rises, more ADH is released, causing more water to be excreted as urine.
(D) As tissue osmolarity rises, less ADH is released, causing more water to be excreted as urine.
A
6. When a stimulus is applied to a receptor in the skin, an action potential is propagated along a neuron to
the brain, where another signal is sent back to the muscle for a response. Which of the following best
describes what occurs when the action potential reaches a chemical synapse at the end of an axon?
(A) The action potential jumps from one axon to the next connecting axon.
(B) The action potential travels through the synapse to the next connecting dendrite.
(C) The action potential jumps the synapse to the next connecting dendrite.
(D) The action potential causes a release of neurotransmitters that travel across the synapse.
D
7. Researchers conducted a controlled experiment to investigate the effect of diet on the health of beef
cattle. The initial hypothesis was that an abrupt change in diet will benefit beef cattle by reducing the
sizes of bacterial populations living in the digestive systems of the cattle. In the experiment, the
researchers determined the relative abundance of two bacterial species found in the rumen of cattle. The
rumen is a part of the stomach that acts as a fermentation chamber in cattle and other ruminants. Shown in
the table are the results from before and after an abrupt change in the cattle’s diet. Based on the results,
which of the following best explains why the initial hypothesis should be revised?
(A) The diets were too similar, since cellulose and starch are both carbohydrates obtained from eating
plants.
(B) The abundance of one of the bacterial species increased in response to the change in diet.
(C) The change in the diversity of microorganisms had no observable effect on cattle physiology.
(D) The ability of rumen fluid to resist changes in pH counteracted the changes in microorganism
diversity.
B
8. Precise regulation of specific hormone levels is required for optimal sperm production in mammals, as
summarized in the figure above. Anabolic-androgenic steroids (AAS) are synthetic variants of
testosterone that are sometimes abused by persons who desire to enhance their athletic performance or
alter their physique. Assuming that AAS function in the same way as naturally occurring testosterone, it
is most likely that long-term abuse of AAS would
(A) stimulate FSH secretion
(B) stimulate testosterone production
(C) stimulate LH secretion
(D) reduce sperm production
D
9. Information is transmitted through the nervous system when one neuron signals another neuron. The
structure of neurons enables transmission to proceed quickly and efficiently. Which of the following
diagrams correctly identifies both the structure of neurons and the direction of information flow
between neurons?
D
10. The graph above shows changes in glucagon and insulin secretions at different concentrations of
blood glucose. Which of the following feedback mechanisms is best supported by the data?
(A) A falling glucagon level causes a rise in the insulin level, which maintains equal amounts of both
hormones in the blood.
(B) A high glucagon level causes a rise in the insulin level, which maintains high levels of both hormones
in the blood.
(C) A low glucose level causes the release of glucagon, which stimulates the release of more glucose from
tissues, which in turn lowers the amount of glucagon being released.
(D) A low glucose level causes the release of insulin, which stimulates the release of more glucose from
tissues, which in turn increases the amount of insulin being released.
C
11. When the dorsal lip of the blastopore is removed from one developing embryo and successfully
implanted into a different location in a second embryo of the same species at the same developmental
stage, which of the following is the most likely result?
(A) Two neural tubes form in the second embryo.
(B) Both embryos continue to develop normally.
(C) The second embryo fails to develop a head.
(D) The second embryo splits into two almost immediately.
(E) The tissues derived from mesoderm fail to develop in the second embryo.
A
Questions 12-13 refer to the diagram below of nerve-impulse transmission.
12. Observation of the direction of the nerve impulse supports the conclusion that fiber X is
(A) an axon
(B) a dendrite
(C) an effector
(D) a ganglion
(E) a synapse
A
13. Which of the following statements is true about the neurotransmitter used to transmit the impulse
at the synapse?
(A) It is constantly released by fiber X.
(B) It is constantly released by fiber Z.
(C) It is released by fiber X when an impulse travels the length of fiber X.
(D) It is released by fiber Z after an impulse travels across Y.
(E) It is passed from fiber Z to fiber X by way of Y.
C
14. Negative feedback is used to maintain homeostasis of many essential molecules. When
insulin levels are too low, people tend to feel fatigued. Because insulin is involved in
fuel storage and oxidation, low levels of insulin can have devastating effects on organs
and tissues. Which is the most likely explanation for the trend seen in the above graph
from 30 minutes to 120 minutes?
A) Insulin levels are decreasing because the insulin is releasing energy to regulate
homeostasis.
B) Beta cells from the pancreas release insulin into the blood to convert glucose into
glycogen in the liver as a way to lower blood glucose levels.
C) The pancreas released low levels of glucagon, and thus, higher levels of insulin are
needed to substitute for glucagon and maintain hormonal homeostasis.
D) Insulin levels are decreasing in response to a decrease in blood glucose levels.
D
15. Neuronal signals are transmitted intracellularly by action potentials and intercellularly by
neurotransmitter release. Many psychoactive drugs alter neuron activity by acting on
neurotransmitters. Drugs like Prozac or Zoloft are selective serotonin reuptake inhibitors
(SSRIs) that block the neurotransmitters from being reabsorbed into the presynaptic
terminal. What are the biological system effects of this change at the synapse?
A) Signal duration would be extended at the postsynaptic neuron.
B) More action potentials are fired because the presynaptic neuron believes no serotonin
neurotransmitters are being released.
C) The presynaptic neuron would be inactivated because serotonin is not being reused.
D) There would be no synaptic transmission.
A
16. Dopaminergic neurons exist in tracts passing from the midbrain to the frontal cerebral
cortex. When these nuerons release the dopamine neurotransmitter, people feel pleasure
and have increased attention. Drugs like Abilify and Clozaril are dopamine and
norepinephrine antagonists. What effect will an antagonist like Abilify and Clozaril have
on a neural synapse?
A) Because dopamine has been released and no effect has occured, the neuron will continue
to release dopamine until an effect occurs.
B) Dopamine is not released from the pre-synaptic neuron, eliminating dopamine signaling.
C) The drugs will bind to the receptor sites, preventing post-synaptic signal reception.
D) The antagonists prolong the signaling of dopamine.
C
17. A sample of human blood was placed in a test tube containing a physiological saline solution (0.9%
sodium chloride). This type of solution is often used intravenously to quickly rehydrate patients. A drop
of the blood from the test tube was placed on a slide and red blood cells (RBCs) were observed under a
microscope. Three possible outcomes are diagrammed below.
Which of the following best predicts which diagrammed microscope view the laboratory worker would
see and best explains why?
(A) View 1 because RBC membranes are freely permeable to water
(B) View 2 because the RBCs use energy to allow sodium entry and to pump water out
(C) View 2 because the rate of water movement into the RBCs equals the rate of water movement out of
the cells
(D) View 3 because the sodium-potassium pumps in the RBC membranes use energy to keep the sodium
out but allow water to freely flow into the cells
C
18. The endocrine system incorporates feedback mechanisms that maintain homeostasis. Which of
the following demonstrates negative feedback by the endocrine system?
(A) During labor, the fetus exerts pressure on the uterine wall, inducing the production of
oxytocin, which stimulates uterine wall contraction. The contractions cause the fetus
to further push on the wall, increasing the production of oxytocin.
(B) After a meal, blood glucose levels become elevated, stimulating beta cells of the
pancreas to release insulin into the blood. Excess glucose is then converted to
glycogen in the liver, reducing blood glucose levels.
(C) At high elevation, atmospheric oxygen is more scarce. In response to signals that oxygen is low, the
brain decreases an individual’s rate of respiration to compensate for the difference.
(D) A transcription factor binds to the regulatory region of a gene, blocking the binding of
another transcription factor required for expression.
B
19. The mechanism of action of many common medications involves interfering with the normal
pathways that cells use to respond to hormone signals. Which of the following best describes a
drug interaction that directly interferes with a signal transduction pathway?
(A) A medication causes the cell to absorb more of a particular mineral, eventually poisoning the cell.
(B) A medication enters the target cell and inhibits an enzyme that normally
synthesizes a second messenger.
(C) A medication enters the target cell’s nucleus and acts as a mutagen.
(D) A medication interrupts the transcription of ribosomal RNA genes.
B
20. The last part of the metamorphosis of a tadpole to an adult frog results in the disappearance of
the tail. This stage of development most likely occurs by
(A) cells of the tail dying and the nutrients being absorbed and reused by the body
(B) shedding of the tail so energy is not spent on maintenance of an unneeded part
(C) bilateral division of the tail and fusion with the developing hind limbs
(D) individual cells of the tail migrating to the developing gonads
A
21. A human kidney filters about 200 liters of blood each day. Approximately two liters of liquid and
nutrient waste are excreted as urine. The remaining fluid and dissolved substances are reabsorbed and
continue to circulate throughout the body. Antidiuretic hormone (ADH) is secreted in response to reduced
plasma volume. ADH targets the collecting ducts in the kidney, stimulating the insertion of aquaporins
into their plasma membranes and an increased reabsorption of water. If ADH secretion is inhibited, which
of the following would initially result?
(A) The number of aquaporins would increase in response to the inhibition of ADH.
(B) The person would decrease oral water intake to compensate for the inhibition of ADH.
(C) Blood filtration would increase to compensate for the lack of aquaporins.
(D) The person would produce greater amounts of dilute urine.
D
22. The diagram above shows a developing worm embryo at the four-cell stage. Experiments have
shown that when cell 3 divides, the anterior daughter cell gives rise to muscle and gonads and the
posterior daughter cell gives rise to the intestine. However, if the cells of the embryo are separated from
one another early during the four-cell stage, no intestine will form. Other experiments have shown that if
cell 3 and cell 4 are recombined after the initial separation, the posterior daughter cell of cell 3 will once
again give rise to normal intestine. Which of the following is the most plausible explanation for these
findings?
(A) A cell surface protein on cell 4 signals cell 3 to induce formation of the worm’s intestine.
(B) The plasma membrane of cell 4 interacts with the plasma membrane of the posterior portion of cell 3,
causing invaginations that become microvilli.
(C) Cell 3 passes an electrical signal to cell 4, which induces differentiation in cell 4.
(D) Cell 4 transfers genetic material to cell 3, which directs the development of intestinal
cells.
A
Questions 23-25
Both myoglobin and hemoglobin are proteins that bind reversibly with molecular oxygen. The graph
below shows the oxygen-binding saturation of each protein at different concentrations of oxygen.
23. Which of the following statements is correct?
(A) At 10 mm Hg partial pressure, hemoglobin binds oxygen but myoglobin does not.
(B) At 20 mm Hg partial pressure, myoglobin and hemoglobin bind oxygen in equal amounts.
(C) At 40 mm Hg partial pressure, myoglobin has a greater affinity for oxygen than hemoglobin has.
(D) At 80 mm Hg partial pressure, myoglobin binds twice as much oxygen as hemoglobin
binds.
C
24. Strenuous exercise lowers the blood pH, causing the curves for both hemoglobin and myoglobin to
shift to the right. This shift results in
(A) an unloading of O2 at higher partial pressures
(B) an increase in the number of O2-binding sites
(C) the capture of more O2 by hemoglobin
(D) the capture of more O2 by myoglobin
A
25. Which of the following best describes the physiological significance of the different oxygen-binding
capabilities of hemoglobin and myoglobin?
(A) They prevent muscles from depleting oxygen levels in the blood.
(B) They cause muscles to become anaerobic.
(C) They prevent glycogen depletion in muscles.
(D) They enhance movement of oxygen from the blood into the muscles.
D
26. The illustration above depicts a neuromuscular junction of a patient with an autoimmune disorder.
Acetylcholine is a stimulatory neurotransmitter. Which of the following would be the most likely result of
the continued presence of the antibody?
(A) An increase in action potentials in the motor neuron and constant nerve pain
(B) A decrease in action potentials in the muscle, causing muscle weakness and fatigue
(C) A decrease in the opening of sodium-gated channels in the muscle, causing less sodium to be released
from the muscle
(D) An increase in the opening of sodium-gated channels in the motor neuron because of the
accumulation of acetylcholine in the junction
B
27. The Hedgehog protein (Hh) plays a critical role during a certain period of embryo development, but it
normally has no role in adults except for the maintenance of adult stem cells. However, the Hedgehog
protein has been detected in 70 percent of pancreatic cancer cell samples. As illustrated in the figures
below, the Hedgehog protein binds to an integral membrane protein receptor known as Patched (Ptc), thus
initiating a pathway of gene expression. When Hedgehog is absent, Ptc inhibits another protein known as
Smoothened (Smo), which, in turn, blocks the activation of a group of proteins collectively known as the
Hedgehog signaling complex (HSC). The inactivation is the result of proteolytic cleavage of one
component of the HSC complex, a transcription factor known as Cubitus interruptus (Ci). When
Hedgehog is present, it binds to Ptc, which prevents the inhibition of Smo by Ptc. The result is that Ci
remains intact and can enter the nucleus, where it binds to and activates certain Gene
One approach to treating patients with pancreatic cancer and other cancers in which the Hedgehog protein
is detected is to modify the Hedgehog signaling pathway. Which of the following is the most useful
approach?
(A) Treating patients with a molecule that is structurally similar to Hedgehog and that will bind to and
interact with Ptc in the same fashion as Hedgehog
(B) Injecting patients with embryonic cells so that Hedgehog will bind to those cells instead of the cancer
cells
(C) Treating patients with a membrane-soluble compound that can bind to Smo and block its activity
(D) Injecting patients with a preparation of purified membrane-soluble Ci that will enter the nuclei of the
cancer cells and induce gene transcription
C
28. Dopaminergic neurons exist in tracts passing from the midbrain to the frontal cerebral cortex.
When these nuerons release the dopamine neurotransmitter, people feel pleasure and have
increased attention. Drugs like Abilify and Clozaril are dopamine and norepinephrine
antagonists. What effect will an antagonist like Abilify and Clozaril have on a neural synapse?
A) Because dopamine has been released and no effect has occured, the neuron will continue to
release dopamine until an effect occurs.
B) Dopamine is not released from the pre-synaptic neuron, eliminating dopamine signaling.
C) The drugs will bind to the receptor sites, preventing post-synaptic signal reception.
D) The antagonists prolong the signaling of dopamine.
C
29
A
30
A
Free Response Questions
1. Tetrodotoxin (TTX) is a neurotoxin that blocks the N + channels of the neuronal membrane.
The puffer fish, which contains TTX in its liver, is considered a delicacy in Japan even though
eating incorrectly prepared puffer fish can be fatal to humans. (10 points)
(a) Describe TWO functions of neurotransmitters at the postsynaptic membrane.
neurotransmitters interact with receptor proteins on the membrane of the postsynaptic cell,
causing ionic channels on the membrane to either open or close. When these channels open,
depolarization occurs, resulting in the initiation of another action potential
(b) Based on the information provided above, explain how TTX most likely interferes with the
transmission of information across synapses.
When TTX binds to voltage gated sodium channels, it prevents them from opening as they
usually would when a graded potential passes threshold.
As a result, neurons and muscles cannot fire action potentials. TTX essentially blocks
communication, both from neuron to neuron, and from neuron to muscle. This causes paralysis
in the affected muscles. If a fatal dose has been ingested, death occurs by paralysis of the
respiratory muscles.
2. (a)Discuss Four steps in which the mother of an infant’s immune system would be activated
following an new infection from a pathogen. Predict how the mother’s immune respond will
differ for the second infection to the same pathogen. (5 points)
(b) Predict the consequence of a nursing infant who Is infected by a pathogen which has infected
her mother 3 months before. Justify your prediction (5 points)
3. In mammals, heart rate during periods of exercise is linked to the intensity of exercise.
Discuss, in detail, the interactions of the respiratory, circulatory, and nervous systems
during exercise. (10 points)
4. Discuss how excretion of hypertonic urine is dependent upon Loop of Henle and the
collecting Duct in the nephron? (10 points)
In the ascending limb of the loop of the nephron (loop of Henle), the thick portion actively
transports out sodium chloride into the tissue of the outer renal medulla. The concentration of
salt is greater in the direction of the medulla. The ascending limb is impermeable to water. Urea
leaks from the collecting duct and contributes to the high solute concentration. Water leaves the
descending limb of the loop of the nephron. Due to the osmotic gradient, water diffuses out of
the collecting duct into the renal medulla so that urine becomes hypotonic