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The molecular geometry of the left-most carbon atom in the molecule below is:
A) octahedral
B) tetrahedral
C) trigonal planar
D) T-shaped
E) trigonal bipyramidal
|
B
|
Chemistry/166
|
Chemistry
| null |
The bond angles marked a, b, and c in the molecule below are about __________, __________, and __________,
respectively.
A) 120, 120, 90
B) 90, 90, 90
C) 120, 120, 109.5
D) 109.5, 90, 120
E) 109.5, 120, 109.5
|
E
|
Chemistry/167
|
Chemistry
| null |
Based on molecular mass and dipole moment of the five compounds in the table below, which should have the
highest boiling point?
A) $CH_3OCH_3$
B) $CH_3CN$
C) $CH_3CHO$
D) $CH_3Cl$
E) $CH_3CH_2CH_3$
|
B
|
Chemistry/168
|
Chemistry
| null |
On the phase diagram above, segment __________ corresponds to the conditions of temperature and pressure under which the solid and the gas of the substance are in equilibrium.
A) CD
B) AB
C) AD
D) BC
E) AC
|
E
|
Chemistry/169
|
Chemistry
| null |
The phase diagram of a substance is given above. The region that corresponds to the solid phase is __________.
A) w
B) x
C) y
D) z
E) x and y
|
A
|
Chemistry/170
|
Chemistry
| null |
Based on the figure above, the boiling point of ethyl alcohol under an external pressure of 0.0724 atm is
________eC.
A) 60
B) 20
C) 70
D) 80
E) 40
|
B
|
Chemistry/171
|
Chemistry
| null |
The graph shown below depicts the relationship between concentration and time for the following chemical
reaction. The slope of this line is equal to __________.
A) -k
B) -1/k
C) k
D) ln[A]o
E) 1/k
|
A
|
Chemistry/172
|
Chemistry
| null |
Which energy difference in the energy profile below corresponds to the activation energy for the forward
reaction?
A) x
B) y
C) x + y
D) y - x
E) x - y
|
A
|
Chemistry/173
|
Chemistry
| null |
A 25.0-mL sample of a solution of a monoprotic acid is titrated with a 0.115 M NaOH solution. The titration
curve above was obtained. Which of the indicators in the table would be best for this titration?
A) bromocresol purple
B) bromthymol blue
C) thymol blue
D) phenolpthalein
E) methyl red
|
B
|
Chemistry/174
|
Chemistry
| null |
Consider the following table of $K_{sp}$ values. Which compound listed below has the greatest molar solubility in water?
A) $ZnCO_3$
B) $CdCO_3$
C) $CaF_2$
D) $AgI$
E) $Cd(OH)_2$
|
C
|
Chemistry/175
|
Chemistry
| null |
Consider the following table of $K_{sp}$ values. The solubility of manganese hydroxide ($Mn(OH)_2$) is 2.2e-5 M. What is the Ksp of $Mn(OH)_2$?
A) 2.1e-14
B) 4.3e-14
C) 1.1e-14
D) 2.2e-5
E) 4.8e-10
|
B
|
Chemistry/176
|
Chemistry
| null |
Consider the following table of $K_{sp}$ values. The molar solubility of __________ is not affected by the pH of the solution.
A) $AlCl_3 $
B) $Na_3PO_4$
C) $NaF$
D) $KNO_3$
E) $MnS$
|
D
|
Chemistry/177
|
Chemistry
| null |
Consider the following table of $K_{sp}$ values. In which of the following aqueous solutions would you expect AgCl to have the lowest solubility?
A) 0.020 $AgNO_3$
B) 0.020 M $BaCl_2$
C) pure water
D) 0.015 $NaCl$
E) 0.020 $KCl$
|
B
|
Chemistry/178
|
Chemistry
| null |
The equilibrium position corresponds to which letter on the graph of G vs f (course of reaction) below?
A) A
B) B
C) C
D) D
E) E
|
C
|
Chemistry/179
|
Chemistry
| null |
Dichlorophenolindophenol (DPIP), an electron acceptor that changes from blue to clear when reduced, can be used to visually determine the rate of photosynthesis. In an experiment, a solution of chloroplasts containing DPIP was divided among 4 tubes. The samples were then exposed to light (1500 lumens) and/or heat (85oC), and light transmittance was measured over time using a spectrophotometer. Higher transmittance is correlated to lighter color. The results of the experiment are provided. Which of the following can be reasonably concluded from the experimental results?
A. The onset of photosynthesis is visible when DPIP is oxidized and changes from clear to blue.
B. Chloroplasts exposed to heat had the highest rate of photosynthesis.
C. Photosynthesis is stimulated when chloroplasts are exposed to light only.
D. The solution in all four tubes was clear at time 0.
|
C:DPIP acts as a substitute for NADP+ in photosynthesis. During photosynthesis, DPIP is reduced and becomes colorless, which results in an increase in light transmittance. According to the data, an increase in light transmittance over time is found for the tube exposed to light only.
|
Biology/1
|
Biology
| null |
The figure above shows a model generated from a study of interactions in a Serengeti ecosystem. This figure describes hypothesized relationships between a parasite that causes disease in wildebeest, rinderpest, and other important components of the ecosystem. Thick arrows represent dominant effects, and “grass” is in a dotted circle because that variable was not directly measured in the study.1. Which of the following can most reasonably be predicted based on this figure?
A. Increasing the amount of rinderpest would decrease the amount of grass.
B.Increased fire would lead to higher tree and elephant populations.
C. Increasing the amount of rinderpest could indirectly lower tree numbers.
D. Increased human populations have a net positive effect on the elephant population.
|
C: Increased rinderpest prevalence would lower wildebeest populations, increasing the amount of grass (because wildebeests feed on the grass) and providing more material to start and spread fires, thereby decreasing the number of trees. Choice (C) is thus correct.
|
Biology/2
|
Biology
| null |
Question below refers to the diagram
Which of the following chambers or vessels carry deoxygenated blood in the human heart?
A. 4 only
B. 1 and 2 only
C. 5 only
D. 1, 2, and 4
|
D: Deoxygenated blood from the vena cava enters the right atrium (2), then the right ventricle (1), and then enters the pulmonary arteries (4). The left atrium (5), left ventricle (6), and aorta (3) all carry oxygenated blood.
|
Biology/3
|
Biology
| null |
Which of the following represents the correct pathway taken by a nerve impulse as it travels from the spinal cord to effector cells?
A. 1-2-3-4
B. 6-5-4-3
C. 2-3-4-5
D. 4-5-6-7
|
D: This question tests your ability to trace the neural pathway of a motor (effector) neuron. The nerve conduction will travel from the spinal cord (where interneurons are located) to the muscle
|
Biology/4
|
Biology
| null |
The brain of the frog is destroyed. A piece of acid-soaked paper is applied to the frog's skin. Every time the piece of paper is placed on its skin, one leg moves upward. Which of the following conclusions is best supported by the experiment?
A. Reflex actions are not automatic.
B. Some reflex actions can be inhibited or facilitated.
C. All behaviors in frogs are primarily reflex responses.
D. This reflex action bypasses the brain.
|
D: Because the brain is destroyed, it is not associated with the movement of the leg.
|
Biology/5
|
Biology
| null |
A nerve impulse requires the release of neurotransmitters at the axonal bulb of a presynaptic neuron. Which of the following best explains the purpose of neurotransmitters, such as acetylcholine?
A. They speed up the nerve conduction in a neuron.
B. They open the sodium channels in the axonal membrane.
C. They excite or inhibit the postsynaptic neuron.
D. They open the potassium channels in the axonal membrane.
|
C: Neurotransmitters are released from the axonal bulb of one neuron and diffuse across a synapse to activate a second neuron. The second neuron is called a postsynaptic neuron. A neurotransmitter can either excite or inhibit the postsynaptic neuron. The myelin sheath speeds up the conduction in a neuron, so (A) is wrong. Also eliminate (B) and (D), as both sodium and potassium channels open during an action potential. Neurotransmitters are not involved in actions related to the axon membrane. They do not force potassium ions to move against a concentration gradient
|
Biology/6
|
Biology
| null |
Which of the following DNA strands would serve as a template for the amino acid sequence shown above?
A. 3′-ATGCGACCAGCACGT-5′
B. 3′-AUGCCACUAGCACGU-5′
C. 3′-TACGGTGATCGTGCA-5′
D. 3′-UACGGUGAUCGUGCA-5′
|
C: The DNA template strand is complementary to the mRNA strand. Using the mRNA strand, work backward to establish the sequence of the DNA strand. Don't forget that DNA strands do not contain uracil, so eliminate (B) and (D).
|
Biology/7
|
Biology
| null |
If a mutation occurs in which uracil is deleted from the messenger RNA after methionine is translated, which of the following represents the resulting amino acid sequence?
A. Serine–histidine–serine–threonine
B. Methionine–proline–glutamine–histidine
C. Methionine–proline–leucine–alanine–arginine
D. Methionine–proline–alanine–arginine–arginine
|
B Use the amino acid chart to determine the sequence after uracil is deleted. The deletion of uracil creates a frameshift.
|
Biology/8
|
Biology
| null |
The mRNA above was found to be much smaller than the original mRNA synthesized in the nucleus. This is due to the
A. addition of a poly(A) tail to the mRNA molecule
B. addition of a cap to the mRNA molecule
C. excision of exons from the mRNA molecule
D. excision of introns from the mRNA molecule
|
D: The mRNA is modified before it leaves the nucleus. It becomes smaller when introns (intervening sequences) are removed. A poly(A) tail and a cap are added to the mRNA and would therefore increase the length of the mRNA, so you can eliminate (A) and (B). Choice (C) is also incorrect, as exons are the coding sequences that are kept by the mRNA.
|
Biology/9
|
Biology
| null |
A scientist studies the storage and distribution of oxygen in humans and Weddell seals to examine the physiological adaptations that permit seals to descend to great depths and stay submerged for extended periods. The figure below depicts the oxygen storage in both organisms
Compared with humans, approximately how many liters of oxygen does the Weddell seal store per kilogram of body weight?
A. The same amount of oxygen
B. Twice the amount of oxygen
C. Three times the amount of oxygen
D. Five times the amount of oxygen
|
B: The Weddell seal stores twice as much oxygen as humans. Calculate the liters per kilograms weight for both the seal and man using the information at the bottom of the chart. The Weddell seal stores 0.058 liters/kilograms (25.9 liters/450 kilograms) compared to 0.028 liters/kilograms (1.95 liters/70 kilograms) in humans.
|
Biology/10
|
Biology
| null |
A scientist studies the storage and distribution of oxygen in humans and Weddell seals to examine the physiological adaptations that permit seals to descend to great depths and stay submerged for extended periods. The figure below depicts the oxygen storage in both organisms
During a dive, a Weddell seal's blood flow to the abdominal organs is shut off and oxygen-rich blood is diverted to the eyes, brain, and spinal cord. Which of the following is the most likely reason for this adaptation?
A. To increase the number of red blood cells in the nervous system
B. To increase the amount of oxygen reaching the skeletomuscular system
C. To increase the amount of oxygen reaching the central nervous system
D. To increase the oxygen concentration in the lungs
|
C: The most plausible answer is that blood is redirected toward the central nervous system, which permits the seal to navigate for long durations. Choice (A) is incorrect; the seal does not need to increase the number of red blood cells in the nervous system. Choice (B) can also be eliminated, as the seal does not need to increase the amount of oxygen to the skeletal system. Eliminate (D) because the diversion of blood does not increase the concentration of oxygen in the lungs.
|
Biology/11
|
Biology
| null |
Consider the following enzyme pathway:
An increase in substance F leads to the inhibition of enzyme 3. All of the following are results of the process EXCEPT
A. an increase in substance X
B. increased activity of enzyme 6
C. decreased activity of enzyme 4
D. increased activity of enzyme 5
|
D: If substance F leads to the inhibition of enzyme 3, then substances D and E and enzymes 3, 4, and 5 will be affected. The activity of enzyme 5 will be decreased, not increased.
|
Biology/12
|
Biology
| null |
The graph above shows the oxygen dissociation curves of maternal hemoglobin and fetal hemoglobin. Based on the graph, it can be concluded that
A. fetal hemoglobin surrenders O2 more readily than maternal hemoglobin
B. the dissociation curve of fetal hemoglobin is to the right of maternal hemoglobin
C. fetal hemoglobin has a higher affinity for O2 than does maternal hemoglobin
D. fetal and maternal hemoglobin differ in structure.
|
C: Based on the graph, fetal hemoglobin has a higher affinity for oxygen than maternal hemoglobin. Fetal hemoglobin does not give up oxygen more readily than maternal hemoglobin, so eliminate (A). You can also get rid of (B), as the dissociation curve of fetal hemoglobin is to the left of the maternal hemoglobin. Finally, eliminate (D) because fetal hemoglobin and maternal hemoglobin are different structurally, but you can't tell this from the graph.
|
Biology/13
|
Biology
| null |
The graph below shows the growth curve of a bacterial culture.
Which of the following represents the carrying capacity of the environment?
A. 2
B. 3
C. 4
D. 5
|
D： The carrying capacity is the maximum number of organisms of a given species that can be maintained in a given environment. Once a population reaches its carrying capacity, the number of organisms will fluctuate around it.
|
Biology/14
|
Biology
| null |
The graph below shows the growth curve of a bacterial culture.
Which of the following shows the exponential growth curve of the population?
A. 1
B. 2
C. 3
D. 4
|
D：During the exponential growth phase of a population, the size doubles during each time interval. This part of the graph looks like a parabola.
|
Biology/15
|
Biology
| null |
The following bar graph shows the relative biomass of four different populations of a particular food pyramid.
The largest amount of energy is available to
A. population A
B. population B
C. population C
D. population D
|
B: The largest amount of energy is available to producers. Population B is most likely composed of producers because they have the largest biomass.
|
Biology/16
|
Biology
| null |
The following bar graph shows the relative biomass of four different populations of a particular food pyramid.
Which of the following would be the most likely result if there was an increase in the number of organisms in population C?
A. The biomass of population D will remain the same.
B. The biomass of population B will decrease.
C. The biomass of population C will steadily increase.
D. The food source available to population C would increase.
|
B An increase in the number of organisms in population C would most likely lead to a decrease in the biomass of B because population B is the food source for population C. Make a pyramid based on the biomasses given. If population C increases, population B will decrease. Eliminate (A) and (C), as we cannot necessarily predict what will happen to the biomass of populations that are above population C. Choice (D) can also be eliminated because the food source available to population C would most likely decrease, not increase.
|
Biology/17
|
Biology
| null |
The cell cycle is a series of events in the life of a dividing eukaryotic cell. It consists of four stages: G1, S, G2, and M. The duration of the cell cycle varies from one species to another and from one cell type to another. The G1 phase varies the most. For example, embryonic cells can pass through the G1 phase so quickly that it hardly exists, whereas neurons are arrested in the cell cycle and do not divide.
During which phase do chromosomes replicate?
A. G1
B. S
C. G2
D. M
|
B: Chromosomes replicate during interphase, the S phase. Choices (A) and (C) are incorrect because during G1 and G2, the cell makes protein and performs other metabolic duties.
|
Biology/18
|
Biology
| null |
The cell cycle is a series of events in the life of a dividing eukaryotic cell. It consists of four stages: G1, S, G2, and M. The duration of the cell cycle varies from one species to another and from one cell type to another. The G1 phase varies the most. For example, embryonic cells can pass through the G1 phase so quickly that it hardly exists, whereas neurons are arrested in the cell cycle and do not divide.
In mammalian cells, the first sign of prophase is the
A. appearance of chromosomes
B. separation of chromatids
C. disappearance of the nuclear membrane
D. replication of chromosomes
|
A: The first sign of prophase in mammalian cells is the appearance of chromosomes
|
Biology/19
|
Biology
| null |
The cell cycle is a series of events in the life of a dividing eukaryotic cell. It consists of four stages: G1, S, G2, and M. The duration of the cell cycle varies from one species to another and from one cell type to another. The G1 phase varies the most. For example, embryonic cells can pass through the G1 phase so quickly that it hardly exists, whereas neurons are arrested in the cell cycle and do not divide.
Mitosis occurs in all of the following types of cells EXCEPT
A. epidermal cells
B. hair cells
C. red blood cells
D. pancreatic cells
|
C: Mitosis occurs in all of the following type of cells except mature red blood cells. Mature red blood cells are short-lived and do not divide.
Source Url:https:// /ap/biology/question-114-answer-and-explanation.html
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Biology/20
|
Biology
| null |
The cell cycle is a series of events in the life of a dividing eukaryotic cell. It consists of four stages: G1, S, G2, and M. The duration of the cell cycle varies from one species to another and from one cell type to another. The G1 phase varies the most. For example, embryonic cells can pass through the G1 phase so quickly that it hardly exists, whereas neurons are arrested in the cell cycle and do not divide.
Since neurons are destined never to divide again, what conclusion can be made?
A. These cells will go through cell division.
B. These cells will be permanently arrested in the G1 phase.
C. These cells will be permanently arrested in the G2 phase.
D. These cells will quickly enter the S phase.
|
B Because neurons are not capable of dividing, it is reasonable to conclude that these cells will not complete the G1 phase. This is a reading comprehension question. The passage states that cells that do not divide are arrested at the G1 phase. Choice (A) is incorrect because these cells will not be committed to go through cell division. You can also eliminate (C) and (D), as the cells will not enter the G2 or S phase.
|
Biology/21
|
Biology
| null |
The following graphs show the permeability of ions during an action potential in a ventricular contractile cardiac fiber. The action potential of cardiac muscle fibers resembles that of skeletal muscles.
Based on the graph, the resting membrane potential of the muscle fibers is closest to
A. -90 mV
B. -70 mV
C. 0 mV
D. +70 mV
|
A: According to the graph, the resting membrane potential of the muscle fiber is close to -90mV.
|
Biology/22
|
Biology
| null |
The following graphs show the permeability of ions during an action potential in a ventricular contractile cardiac fiber. The action potential of cardiac muscle fibers resembles that of skeletal muscles.
Which of the following statements is true concerning the initial phase of depolarization?
A. Voltage-gated K+ channels open in the plasma membrane.
B. The concentration of Ca2+ ions within the plasma membrane becomes more negative.
C. The membrane potential stays close to -40 mV.
D. The permeability of the sarcolemma to Na+ ions increases.
|
D:Refer to the second graph about the membrane permeability of ions during a muscle contraction. During depolarization, the membrane is permeable to Na+. Choice (A) can be eliminated because the voltage-gated K+ channels do not open until after depolarization. Eliminate (B) because the concentration of Ca2+ does not become more negative. Choice (C) is also incorrect, as the membrane potential changes from -90 mV to +20 mV.
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Biology/23
|
Biology
| null |
The following graphs show the permeability of ions during an action potential in a ventricular contractile cardiac fiber. The action potential of cardiac muscle fibers resembles that of skeletal muscles.
In cardiac fibers, the duration of an action potential is approximately
A. 0.10 secs
B. 0.20 secs
C. 0.25 secs
D. 0.30 secs
|
D: Refer to both graphs in the passage. In cardiac fibers, the duration of an action potential—a neuronal impulse—is approximately 0.3 seconds.
|
Biology/24
|
Biology
| null |
The following graphs show the permeability of ions during an action potential in a ventricular contractile cardiac fiber. The action potential of cardiac muscle fibers resembles that of skeletal muscles.
One major difference between the action potential of cardiac muscle fibers and the action potential of skeletal muscle fibers is that in cardiac muscle fibers
A. the membrane is permeable to Na+, not K+
B. voltage-gated K+ channels open during depolarization, not repolarization
C. depolarization is prolonged compared to that in skeletal muscle fibers
D. the refractory period is shorter than that of skeletal muscle fibers
|
C: In cardiac muscle fibers, depolarization is prolonged compared to that in skeletal muscle fibers. Eliminate (A) because the membrane is permeable to both Na+ and K+. Choice (B) can also be eliminated; in cardiac muscle fibers, voltage-gated K+ channels open during repolarization. Finally, (D) is wrong because the refractory period is longer in cardiac muscle fibers compared to skeletal muscle fibers.
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Biology/25
|
Biology
| null |
The data below concerns the general animal body plan of five organisms
The two most closely related organisms are
A. sea anemone and hagfish
B. eel and salamander
C. hagfish and eel
D. sea anemone and salamande
|
B The two most closely related organisms are the two with the most shared derived characteristics.
|
Biology/26
|
Biology
| null |
The data below concerns the general animal body plan of five organisms
The correct order of evolution for the traits above is
A. jaws – vertebral column – walking legs
B. walking legs – jaws – vertebral column
C. jaws – walking legs – vertebral column
D. vertebral column – jaws – walking legs
|
D: Shared derived characteristics are newly evolved traits that are shared with every group on a phylogenic tree except for one. Vertebral columns are present in every group except for the sea anemone, so it must have evolved first. Walking legs are only found in the salamander, indicating that it most likely evolved most recently.
|
Biology/27
|
Biology
| null |
The data below concerns the general animal body plan of five organisms
Pre- and post-zygotic barriers exist that prevent two different species from producing viable offspring. All of the following are pre-zygotic barriers EXCEPT
A. anatomical differences preventing copulation
B. different temporality of mating
C. sterility of offspring
D. incompatible mating songs
|
C: Pre-zygotic barriers to reproduction are those that prevent fertilization, so you can eliminate (A), (B), and (D). Choice (C) is an example of a post-zygotic barrier to reproduction.
|
Biology/28
|
Biology
| null |
The data below concerns the general animal body plan of five organisms.
Birds and insects have both adapted wings to travel by flight. The wings of birds and insects are an example of
A. divergent evolution
B. convergent evolution
C. speciation
D. mutation
|
B: Convergent evolution occurs when two organisms that are not closely related independently evolve similar traits, such as the wings of insects and birds. Divergent evolution occurs when two closely related individuals become more different over time and can lead to speciation.
|
Biology/29
|
Biology
| null |
The following synthetic pathway of a pyrimidine, cytidine 5' triphosphate, CTP, begins with the condensation of two small molecules by the enzyme, aspartate transcarbamylase (ATCase).
Which of the following is true when the level of CTP is low in a cell?
A. CTP is converted to ATCase.
B. The metabolic traffic down the pathway increases.
C. ATCase is inhibited, which slows down CTP synthesis.
D. The final product of the pathway is reduced.
|
B: When the level of CTP is low in a cell, the metabolic traffic down the pathway increases. This pathway is controlled by feedback inhibition. The final product of the pathway inhibits the activity of the first enzyme. When the supply of CTP is low, the pathway will continue to produce CTP.
|
Biology/30
|
Biology
| null |
The following synthetic pathway of a pyrimidine, cytidine 5' triphosphate, CTP, begins with the condensation of two small molecules by the enzyme, aspartate transcarbamylase (ATCase).
This enzymatic phenomenon is an example of
A. transcription
B. feedback inhibition
C. dehydration synthesis
D. photosynthesi
|
B: This enzymatic phenomenon is an example of feedback inhibition. Feedback inhibition is the metabolic regulation in which high levels of an enzymatic pathway's final product inhibit the activity of its rate-limiting enzyme. Transcription, (A), is the production of RNA from DNA. Dehydration synthesis, (C), is the formation of a covalent bond by the removal of water. In photosynthesis, (D), radiant energy is converted to chemical energy.
|
Biology/31
|
Biology
| null |
The following synthetic pathway of a pyrimidine, cytidine 5' triphosphate, CTP, begins with the condensation of two small molecules by the enzyme, aspartate transcarbamylase (ATCase).
The biosynthesis of cytidine 5'-triphosphate requires
A. a ribose sugar, a phosphate group, and a nitrogen base
B. a deoxyribose sugar, a phosphate group, and a nitrogen base
C. a ribose sugar, phosphate groups, and a nitrogen base
D. a deoxyribose sugar, phosphate groups, and a nitrogen base
|
C: The biosynthesis of cytidine 5′-triphosphate requires a nitrogenous base, three phosphates, and the sugar ribose. Pyrimidines are a class of nitrogenous bases with a single ring structure. The sugar they contain is ribose, which is shown in the pathway diagram
|
Biology/32
|
Biology
| null |
Here is a sketch of a molecule of the sex hormone, testosterone, that is derived from cholesterol.
Which of the following statements best describes the action of this hormone on cells of the human gonads?
A. The hormone acts as the first messenger when it binds to and activates the G protein-coupled receptor on the surface of cells in the testes. This activates the mobile G protein located inside the cell.
B. The hormone enters cells in the testes by first binding with a membrane receptor, which causes a channel to open in the membrane, allowing the testosterone to flood into the cell.
C. The hormone readily passes through the cell membrane and binds to a receptor in the cytoplasm. The hormone and receptor then enter the nucleus and act as a transcription factor that turns on one or more genes.
D. The hormone binds with cAMP on the surface of the cell. Once attached to cAMP, the hormone enters the cell and initiates a signal transduction pathway.
|
C: The sex hormone testosterone is lipid soluble (hydrophobic) and dissolves directly through the cell membrane. Choices A and B correctly describe the action of a hydrophilic signal. Cyclic AMP is a secondary messenger found in the cytoplasm, not on the surface of a cell.
|
Biology/33
|
Biology
| null |
Which of the following statements accurately accounts for the shape of the graph?
A. The rate of photosynthesis stops increasing because chlorophyll molecules begin to decompose due to increased heat, not increased light.
B. The rate of photosynthesis slows as chlorophyll molecules, which are proteins, denature.
C. Photosynthesis ceases when protons are no longer released by the photolysis of water.
D. The rate of photosynthesis increases until the light-harvesting apparatus in the thylakoid membranes become saturated and cannot make use of additional light
|
D: The graph flattens out but doesn't decrease. Therefore, photosynthesis is still going on. That indicates that choices A, B, and C cannot be correct.
|
Biology/34
|
Biology
| null |
Here is a sketch of an animal cell.
Which of the following statements is correct?
A. Structure A detoxifies poisons in the cell.
B. Structure B packages proteins for export.
C. Structure C synthesizes RNA.
D. Structure D consists of cytoskeleton.
|
B: Structure B is the Golgi apparatus, which packages and secretes proteins made by the ribosomes in the E.R. The centrioles shown as structure A consist of microtubules. Structure C is a lysosome. Strucure D consists of ribosomes on the E.R.
|
Biology/35
|
Biology
| null |
Chronically high levels of glucocorticoids can result in obesity, muscle weakness, and depression. This looks like several diseases but actually is only one, Cushing syndrome. Excessive activity of either the pituitary or the adrenal gland can cause the disease. To determine which gland has abnormal activity in a particular patient, doctors use the drug dexamethasone, a synthetic glucocorticoid that blocks ACTH (adrenocorticotropic hormone) release.
Based on the graph, which gland is affected in the patient with Cushing syndrome and what is the reasoning behind your answer?
A. The pituitary, because although ACTH is blocked, the pituitary is still sending a signal to the adrenal glands.
B. The pituitary, because blocking ACTH has no effect on cortisol levels.
C. The adrenal gland, because the pituitary is prevented from stimulating the adrenal glands, and yet cortisol levels are still high.
D. The adrenal gland, because the pituitary is sending a signal to the adrenal gland and the adrenal glands have stopped producing cortisol.
|
C: The patient is still producing too much cortisol even though the pituitary is not sending a signal to the adrenal glands. ACTH, which would normally stimulate the adrenal to release cortisol, is blocked by the dexamethasone. If the adrenals were healthy, they should not be producing anything. Unfortunately, they are. Compare the patient with the normal person.
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Biology/36
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Biology
| null |
Here is the final reaction in the citric acid cycle. It shows the regeneration of oxaloacetate.
After studying the reaction, determine which of the following statements is correct.
A. The enzyme malate dehydrogenase is allosteric.
B. The reaction is exergonic; the released energy is absorbed by NAD+.
C. The reaction is a reduction reaction.
D. NAD+ is oxidized into NADH.
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B: Energy is released, and NAD+ binds to hydrogen released by malate.
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Biology/37
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Biology
| null |
Oxygen is carried in the blood by the respiratory pigment hemoglobin, which can combine loosely with four oxygen molecules, forming the molecule oxyhemoglobin. To function properly, hemoglobin must bind to oxygen in the lungs and drop it off at body cells. The more easily the hemoglobin binds to oxygen in the lungs, the more difficult the oxygen is to unload at the body cells. Here is a graph showing two different saturation-dissociation curves for one type of hemoglobin at two different pH levels.
Based on your knowledge of biology and the information in this graph, which statement about the hemoglobin curves is correct?
A. Hemoglobin B has a greater affinity for oxygen and therefore binds more easily to oxygen in the lungs.
B. Hemoglobin A is characteristic of a mammal that evolved at sea level where oxygen levels are high.
C. In an acidic environment, hemoglobin drops off oxygen more easily at body cells.
D. Hemoglobin A is found in mammals with a higher metabolism.
|
C: The line to the right shows a lower affinity for oxygen. CO2 dissolved in water produces carbonic acid. What this graph demonstrates is that the blood near respiring cells, which release carbon dioxide, make the surrounding area acidic. This acidic environment causes hemoglobin to release its oxygen to the cells where it is needed.
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Biology/38
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Biology
| null |
2. Animals maintain a minimum metabolic rate for basic functions such as breathing, heart rate, and maintaining body temperature. The minimum metabolic rate for an animal at rest is the basal metabolic rate (BMR). The BMR is affected by many factors, including whether an animal is an ectotherm or endotherm; its age and sex; and size and body mass. Here is a graph that shows the relationship of BMR per kilogram of body mass to body size for a group of mammals.
Which statement correctly describes the relationship between BMR and body mass?
A. The relationship between BMR and body mass is a direct one. The larger the body mass the higher the BMR is and the greater the breathing rate is.
B. The relationship between BMR and body mass is a direct one. The larger the body mass the higher the BMR is and the lower the breathing rate is.
C. The relationship between BMR and body mass is inversely proportional. The larger the body mass, the lower the BMR is and the lower the breathing rate is.
|
C: The energy to maintain each gram of body mass is inversely related to body size. This graph describes a relationship between X and Y that is inversely proportional. When the relationship is directly proportional the line goes diagonally from the lower left to upper right. Each gram of mouse requires 20 times as many calories as a gram of elephant even though the whole elephant uses more calories than a whole mouse. The higher the metabolic rate, the higher the oxygen and food requirement per unit of body mass.
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Biology/39
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Biology
| null |
Refer to the codon table for the following question.
Here is a small stretch of mRNA that would be translated at the ribosome:
. . . AUG CUG AAA UCAGGG . . .
Suppose a spontaneous mutation altered the boldface A and changed it to a U.
What effect, if any, would this have on the protein formed?
A. Because of redundancy in the code, there would be no change in the protein formed.
B. The amino acid sequence formed from this stretch of DNA would be
Met–Leu–Lys–Ser–Gly.
C. The polypeptide would not form because translation would stop at UAA.
D. Translation would continue and a polypeptide would form because AUG codes for start as well as for methionine.
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C: UAA codes for a stop sequence. Translation would cease at that point in the process.
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Biology/40
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Biology
| null |
Two ecologists, Peter and Rosemary Grant, spent thirty years observing, tagging, and measuring finches (a type of bird) in the Galápagos Islands. They made their observations on Daphne Major—one of the most desolate of the Galápagos Islands. It is an uninhabited volcanic cone where only low to the ground cacti and shrubs grow. During 1977, there was a severe drought and seeds of all kinds became scarce. The small, soft seeds were quickly eaten by the birds, leaving mainly large, tough seeds that the finches normally ignore. The year after the drought, the Grants discovered that the average width of the finches' beak had increased.
Which of the following statements best explains the increase in beak size?
A. Finches with bigger and stronger beaks were able to attack and kill the finches with smaller beaks.
B. Finches with bigger beaks were larger animals with stronger wings that could fly to other islands and gather a wide variety of seeds.
C. During the drought, the finches' beaks grew larger to accommodate the need to eat tougher seeds.
D. Finches with larger beaks were able to eat the tougher seeds and were healthier and reproduced more offspring that inherited the trait for wider beaks.
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D: This is classic Darwinian evolutionary theory—the survival of the best adapted.
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Biology/41
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Biology
| null |
Two ecologists, Peter and Rosemary Grant, spent thirty years observing, tagging, and measuring finches (a type of bird) in the Galápagos Islands. They made their observations on Daphne Major—one of the most desolate of the Galápagos Islands. It is an uninhabited volcanic cone where only low to the ground cacti and shrubs grow. During 1977, there was a severe drought and seeds of all kinds became scarce. The small, soft seeds were quickly eaten by the birds, leaving mainly large, tough seeds that the finches normally ignore. The year after the drought, the Grants discovered that the average width of the finches' beak had increased.
Which of the following statements best explains the mechanism behind the change in beak size?
A. A new allele appeared in the finch population as a result of a mutation.
B. A change in the frequency of a gene was due to selective pressure from the environment.
C. A new trait appeared in the population because of recombination of alleles.
D. A new trait appeared in the population because of genetic drift.
|
B: Choices A, C, and D all have the same problem. A new trait may have appeared by a single mutation, by recombination of alleles, or by genetic drift. However, that does not explain how the birds, on average, came to have longer beaks
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Biology/42
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Biology
| null |
Answer the following two questions based on this pedigree for the biochemical disorder known as alkaptonuria. Affected individuals are unable to break down a substance called alkapton, which colors the urine black and stains body tissues. Otherwise, the condition is of no consequence. Males are shown as squares, females as circles. Afflicted individuals are shown in black. If there is a carrier condition, it is not displayed.
Which of the following best states the pattern of inheritance shown in the pedigree?
A. The trait is sex-linked dominant.
B. The trait is sex-linked recessive.
C. The trait is autosomal dominant.
D. The trait is autosomal recessive.
|
D: Look at individuals 1 and 2. Neither has the condition, but they have a daughter with the condition. Sex-linked dominant and autosomal dominant are eliminated because neither parent has the condition. Sex-linked recessive is also eliminated because if the father passed the trait to his daughter, he would have to have the condition. For the daughter to have the condition, she would have had to inherit two affected X chromosomes—one from each parent.
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Biology/43
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Biology
| null |
Answer the following two questions based on this pedigree for the biochemical disorder known as alkaptonuria. Affected individuals are unable to break down a substance called alkapton, which colors the urine black and stains body tissues. Otherwise, the condition is of no consequence. Males are shown as squares, females as circles. Afflicted individuals are shown in black. If there is a carrier condition, it is not displayed.
Which of the following statement is supported by the information given in the pedigree?
A. The P generation mother is X-X.
B. The P generation father is X-Y.
C. If parents 1 and 2 in row II have another child, the chance that the child would be afflicted with alkaptonuria is 25%.
D. The genotype of woman 1 is X-X.
|
C: Since the trait is inherited as autosomal recessive, individuals 1 and 2 are each hybird. The chance that any child of theirs will have the condition is 25%.
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Biology/44
|
Biology
| null |
Four vials were set up to investigate bacterial transformation. Vials 1 and 2 each contained E. coli bacteria that had been made competent and had then been mixed with a plasmid containing the gene for ampicillin (pAMP) resistance. Vials 3 and 4 both contained E. coli that had also been made competent but had not been mixed with a plasmid. Each vial of bacteria was poured onto a nutrient agar plate. Vials 1 and 3 were poured onto plates that contained the antibiotic ampicillin. Vials 2 and 4 were poured onto plates that did not contain ampicillin.
This figure shows what the nutrient agar plates looked like. The shaded plates represent extensive growth, and the dots represent individual bacterial colonies.
Plates that have only ampicillin-resistant bacteria growing on them include which of the following?
A. Plate 1 only
B. Plate 2 only
C. Plate 3 only
D. Plates 1 and 3 only
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A: The few colonies growing on Plate 1 consist of bacteria that have taken up the plasmid and are resistant to ampicillin. Plate 2 consists of both antibiotic-resistant bacteria as well as nonresistant bacteria. There is no antibiotic in the agar on Plate 2 to distinguish the two bacteria.
Source Url:https:// /ap/biology/question-161-answer-and-explanation.html
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Biology/45
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Biology
| null |
Four vials were set up to investigate bacterial transformation. Vials 1 and 2 each contained E. coli bacteria that had been made competent and had then been mixed with a plasmid containing the gene for ampicillin (pAMP) resistance. Vials 3 and 4 both contained E. coli that had also been made competent but had not been mixed with a plasmid. Each vial of bacteria was poured onto a nutrient agar plate. Vials 1 and 3 were poured onto plates that contained the antibiotic ampicillin. Vials 2 and 4 were poured onto plates that did not contain ampicillin.
This figure shows what the nutrient agar plates looked like. The shaded plates represent extensive growth, and the dots represent individual bacterial colonies.
Which of the following statements explains why there was no growth on Plate 3?
A. The heat shock technique to make the E.coli competent killed the bacteria.
B. Those particular E.coli bacteria were inhibited from growing by the nutrient in the agar.
C. Those bacteria were not transformed.
D. The bacteria culture died because they have a short life span.
|
C: The bacteria on Plate 3 were not transformed. That means they did not uptake a plasmid and were not resistant to antibiotic. There is antibiotic in the agar on that plate, which killed the nontransformed bacteria
|
Biology/46
|
Biology
| null |
Four vials were set up to investigate bacterial transformation. Vials 1 and 2 each contained E. coli bacteria that had been made competent and had then been mixed with a plasmid containing the gene for ampicillin (pAMP) resistance. Vials 3 and 4 both contained E. coli that had also been made competent but had not been mixed with a plasmid. Each vial of bacteria was poured onto a nutrient agar plate. Vials 1 and 3 were poured onto plates that contained the antibiotic ampicillin. Vials 2 and 4 were poured onto plates that did not contain ampicillin.
This figure shows what the nutrient agar plates looked like. The shaded plates represent extensive growth, and the dots represent individual bacterial colonies.Which of the following statements best explains why there were fewer colonies on Plate 1 than on Plate 2?
A. The bacteria on Plate 2 did not transform.
B. There was no antibiotic in the agar in Plate 2 that would have restricted growth of bacteria.
C. The transformation of bacteria on Plate 2 was more successful.
D. The bacteria on Plates 1 and 2 were not taken from the same culture.
|
B: The few colonies growing on Plate 1 consist of bacteria that have taken up the plasmid and are resistant to ampicillin. Plate 2 consists of both antibiotic-resistant bacteria as well as nonresistant bacteria. There is no antibiotic in the agar on Plate 2 to distinguish the two bacteria.
|
Biology/47
|
Biology
| null |
Four vials were set up to investigate bacterial transformation. Vials 1 and 2 each contained E. coli bacteria that had been made competent and had then been mixed with a plasmid containing the gene for ampicillin (pAMP) resistance. Vials 3 and 4 both contained E. coli that had also been made competent but had not been mixed with a plasmid. Each vial of bacteria was poured onto a nutrient agar plate. Vials 1 and 3 were poured onto plates that contained the antibiotic ampicillin. Vials 2 and 4 were poured onto plates that did not contain ampicillin.
This figure shows what the nutrient agar plates looked like. The shaded plates represent extensive growth, and the dots represent individual bacterial colonies.
In a variant of this experiment, the plasmid contained GFP (green fluorescent protein) in addition to ampicillin resistance. Which of the following plates would have the highest percentage of bacteria that would fluoresce?
A. Plate 1 only
B. Plate 2 only
C. Plate 3 only
D. Plate 4 only
|
A: There would be fluorescent bacteria on both Plates 1 and 2. However, 100% of the bacteria on Plate 1 would fluoresce while only a percentage of the bacteria on Plate 2 would do so
|
Biology/48
|
Biology
| null |
Here is a sketch of a neuromuscular junction in a patient with an autoimmune disease. Acetylcholine (ACh) is the stimulatory neurotransmitter.
Which of the following predicts what will happen in the continued presence of the antibodies?
A. Ca++ ions will flood into the motor neuron ending, increasing the release of more ACh.
B. The amount of neurotransmitter being released will decrease.
C. The number of action potentials in the motor neuron will decrease.
D. Antibodies will destroy the postsynaptic receptors, and the muscle response will diminish.
|
D: In an autoimmune disease, the immune system mistakenly attacks its own body structures. The antibodies attack the postsynaptic muscle receptors, not the neuron function
|
Biology/49
|
Biology
| null |
The graph on the left (A) shows an absorption spectrum for chlorophyll a extracted from a plant. The graph on the right (B) shows an action spectrum from a living plant, with wave lengths of light plotted against the rate of photosynthesis as measured by release of oxygen.
Which statement best explains the difference between the two spectra?
A. Graph A plots the absorption spectrum of a red plant; graph B plots an absorption spectrum for a green plant.
B. The chlorophyll from Graph A cannot carry out the light-dependent reactions; but the chlorophyll in graph B can.
C. The data from Graph A characterize several photosynthetic pigments that reflect almost no light; the data from Graph B characterize chlorophyll a, which reflects only green light.
D. Graph A shows an absorption spectrum for an unusual type of chlorophyll a.
|
B: Graph A shows the absorption spectrum for chlorophyll that was extracted from a living plant. Once separated from the grana and stroma, chlorophyll by itself cannot carry out photosynthesis.
|
Biology/50
|
Biology
| null |
Cystic fibrosis is the most common inherited disease in the U.S. Among people of European descent, 4% are carriers of the recessive cystic fibrosis allele. The most common mutation in individuals with cystic fibrosis is a mutation in the CFTR protein that functions in the transport of chloride ions between certain cells and extracellular fluid. These chloride transport channels are defective or absent in the plasma membranes of people with the disorder. The result is abnormally high concentration of extracellular chloride that causes the mucus that coats certain cells to become thicker and stickier than normal. Mucus builds up in the pancreas, lungs, digestive tract, and other organs. This leads to multiple effects, including poor absorption of nutrients from the intestines, chronic bronchitis, and recurrent bacterial infections.Scientific work has been carried out to measure where the relative amounts of CFTR protein are localized in the affected cells
After studying the graph, which of the following statements about CFTR protein is correct?
A. Transcription is not occurring.
B. Translation is not occurring.
C. CFTR protein does not fold properly after it is synthesized.
D. CFTR protein is not being packaged in the cytoplasm.
|
D: Ribosomes produce protein for export. Once synthesized, the protein is packaged into vesicles in the Golgi for secretion. The graphs show that the amount of CFTR is high where synthesis occurs in the E.R. and low in the vesicles and Golgi. So the protein was synthesized in the ribosomes but not packaged.
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Biology/51
|
Biology
| null |
Based on the cladogram, which of the following is NOT true?
A. Only some tetrapods have amnions.
B. Mammals and amphibians are more closely related than mammals and birds.
C. Ancestor 2 lived before ancestor 3; and we do know when that was.
D. Lungfishes and amphibians share a common ancestor.
|
C: This cladogram does not have a time scale attached to it. All we can say about any clade or lineage is that one evolved earlier or later than another. A cladogram is constructed to show the development of different traits and the lineage of related organisms that evolved with that trait.
|
Biology/52
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Biology
| null |
From 1972 to 2004, researchers studying the greater prairie chicken observed that a population collapse mirrored a reduction in fertility as measured by the hatching rate of eggs. Comparison of DNA samples from the Jasper County, Illinois, population with DNA from feathers in a museum collection showed that genetic variation had declined in the studied population. The researchers translocated prairie chickens from Minnesota, Kansas, and Nebraska into the Illinois prairie chicken population in 1992 and found that the hatching rate in Illinois prairie chickens changed. Here is a graph of the data.
Which of the following statements most accurately explains what happened to the studied population of prairie chickens after translocation and why?
A. The hatching rate increased because genetic variation declined.
B. The hatching rate increased because genetic variation increased.
C. The hatching rate decreased because genetic variation decreased.
D. The hatching rate decreased because the translocated animals were invasive and grew to dominate the population.
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B: Prior to translocation, the chickens had become inbred, diversity had decreased, and fertility had declined.
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Biology/53
|
Biology
| null |
In a study of dusty salamanders, Desmognathus ochrophaeus, scientists brought individuals from different populations into the laboratory and tested their ability to mate and produce viable, fertile offspring. Here is the graph of the data.
The degree of reproductive isolation is represented by an index ranging from 0 (no isolation) to 2 (complete isolation).
Which of the following statements best describes the evolutionary history of dusty salamanders?
A. Mutation alone caused the two populations to diverge.
B. Both mutation and genetic drift cause the two populations to diverge.
C. Both mutation and genetic drift caused the two populations to become separate species after they were separated by great distance.
D. Reproductive isolation between the two populations increases as the distance between them increases
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D: The question does not reveal anything about mutation or genetic drift. The point here is that in this case, divergence is a function of geographic distance.
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Biology/54
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Biology
| null |
Scientists carried out a series of experiments to study innate immunity in fruit flies. They began with a mutant fly strain in which a pathogen is recognized but the signaling that would normally trigger an innate response is blocked. As a result, the flies did not make any antimicrobial peptides (AMP). The researchers then genetically engineered some of the mutant flies to express significant amounts of a single AMP, either defensin or drosomycin. They then infected the flies with a fungus, Neurospora crassa, by shaking anesthetized flies for 30 seconds in a Petri dish containing a sporulating fungal culture. The 6-day survival rate was monitored and recorded.
Here is a graph displaying some data from the experiment.
KEY:
A Wild type
B Mutant + drosomycin
C Mutant + defensin
D Mutant
Which of the following statements is supported by the data?
A. Each AMP provided minimal immunity against fungal infection.
B. Both AMPs provided better immunity than did either one alone.
C. Drosomycin provided immunity against the fungal infection.
D. There was no control in this experiment.
|
C: The survival of mutant flies + drosomycin was greater than mutant flies + defensin. Two controls, A and D, were included in this experiment.
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Biology/55
|
Biology
| null |
An experiment was carried out with guppies, which are brightly colored, popular, aquarium fish. Three hundred guppies were added to 12 large pools. Cichlids, a voracious predator, were added to 4 of the pools. Killifish that rarely eat guppies were added to 4 other pools. No other fish were added to the last 4 pools. After 16 months, a time period that represents 10 generations for guppies, all the guppies were analyzed for size and coloration. Here are the data.
Which of the following statements is supported by the data?
A. Cichlids were an agent of selection, eating the more visible, brightly colored guppies.
B. Killifish were an agent of selection, eating the more visible, brightly colored guppies.
C. Guppies, as a group, experienced change in coloration, from brightly colored to dull in order to survive.
D. Individual guppies experienced a mutation that caused a change in coloration and enabled them to avoid being eaten.
|
A: Killifish do not eat guppies, but cichlids do. So cichilds were the agent of selection. No organism or population changes in order to survive. If individuals are not adapted, they die. No individual changes during its lifetime. Rather, the frequency of a particular trait in a population may change.
|
Biology/56
|
Biology
| null |
An experiment was carried out with guppies, which are brightly colored, popular, aquarium fish. Three hundred guppies were added to 12 large pools. Cichlids, a voracious predator, were added to 4 of the pools. Killifish that rarely eat guppies were added to 4 other pools. No other fish were added to the last 4 pools. After 16 months, a time period that represents 10 generations for guppies, all the guppies were analyzed for size and coloration. Here are the data.
Which of the following statements best expresses the point of this experiment?
A. Mutations can be brought about by the environment.
B. Mutations occur randomly.
C. Agents of selection are not always readily apparent.
D. Evolution does not always require millions of years
|
D: The evolution in this population—the change in frequency of the trait for brightly colored spots—occurred rapidly, within 16 months. Evolution does not always require millions of years. The rate of change is a function of the pressure from the environment to change.
|
Biology/57
|
Biology
| null |
Here is a sketch of prokaryotic DNA undergoing replication and transcription simultaneously.
If 1 is thymine, what is a?
A. Adenine
B. Thymine
C. Cytosine
D. Uracil
|
B: First orient yourself in the drawing. The process at the top of the sketch is replication; the bottom is transcription. So if 1 is thymine, then its complement, I, is adenine. Therefore, if I is adenine, then its base pair is thymine.
|
Biology/58
|
Biology
| null |
Here is a sketch of prokaryotic DNA undergoing replication and transcription simultaneously.
If 4 is adenine, what is D?
A. Adenine
B. Thymine
C. Cytosine
D. Uracil
|
D: The bottom of the diagram represents transcription. Therefore, if 4 is adenine, then D is its complement in RNA, which is uracil.
|
Biology/59
|
Biology
| null |
Intact chloroplasts are isolated from dark-green leaves by low-speed centrifugation and are placed into six tubes containing cold buffer. A blue dye, DPIP, which turns clear when reduced, is also added to all the tubes. Then each tube is exposed to different wavelengths of light. A measurement of the amount of decolorization is made, and the data are plotted on a graph. Although the wavelengths of light vary, the light intensity is the same.
Which statement below best describes the results of the experiment?
A. The lower the wavelength of light, the greater the rate of photosynthesis.
B. The highest wavelengths of light provide the fastest rate of photosynthesis.
C. The highest rate of photosynthesis results from exposure to two different wavelengths of light.
D. The greatest reduction in DPIP occurs at 550 nm light intensity.
|
C: The greatest reduction (change in color of DPIP) occurs at 650 nm + 700 nm of light. The steeper the decline of the graph, the greater the reduction of DPIP.
|
Biology/60
|
Biology
| null |
A group of scientists wished to learn about the energy efficiency of different modes of locomotion. They studied the literature that was based on accurate measurements and produced this graph based on the data they analyzed.
Which of the following statement accurately describes what the scientists discovered?
A. An animal with a large body mass expends more energy per kilogram of body mass than a small animal, regardless of the type of locomotion.
B. Swimming has to overcome drag as well as gravity.
C. Running is the least energy-efficient means of locomotion.
D. The best parameter to measure in this type of experiment is CO2 consumption
|
C: According to the data, an animal with a small body mass expends more energy per kilogram of body mass regardless of the type of locomotion. Swimming is the most efficient means of locomotion. Swimming does not have to overcome gravity; the swimmer is supported by the water.
|
Biology/62
|
Biology
| null |
Oxygen is carried in the blood by the respiratory pigment hemoglobin, which can combine loosely with four oxygen molecules to form the molecule oxyhemoglobin. To function properly, hemoglobin must bind to oxygen in the lungs and drop it off at body cells. The more easily the hemoglobin bonds to oxygen in the lungs, the more difficult for the hemoglobin to unload the oxygen at the body cells. Here is a graph showing two different saturation-dissociation curves for one type of hemoglobin at two different pH levels.
Based on your knowledge of biology and the information in this graph, which statement about the hemoglobin curves is correct?
A. Hemoglobin B has a greater affinity for oxygen and will therefore bind more easily to oxygen in the lungs.
B. Hemoglobin B is characteristic of a mammal that evolved at a high elevation where oxygen is rare.
C. When CO2 levels in the blood are high, as shown in hemoglobin B, hemoglobin releases oxygen more readily.
D. Hemoglobin A is the type found in mammals with a higher metabolism. Hemoglobin B is characteristic of mammals.
|
C: This graph is focused on the strength of the bond between Hb and oxygen at pH 7.2 and pH 7.4. At a lower at pH, which is more acidic, the attachment is weaker. This makes sense because as cells carry out cellular respiration, they release CO2, which makes the blood more acidic. The blood pH changes from normal 7.4 to the more acidic 7.2. At pH 7.2, the Hb can release more of its oxygen where it is needed, at the cells
|
Biology/63
|
Biology
| null |
The following reaction occurs in the citric acid cycle. Study the reaction as it is shown here.
Which of the following statements is correct?
A. This is part of the reaction that produces pyruvate.
B. The reaction is an example of negative feedback.
C. The reaction is an oxidation reaction.
D. The reaction occurs in the cristae membrane.
|
C: Oxidation is the loss of electrons or of hydrogen. You can see that hydrogen has been lost by the succinate to form fumacate. If this is part of the citric acid cycle, then pyruvate is the starting point of this reaction, not the product. The citric acid cycle produces CO2 and ATP. Feedback mechanisms are complex. This is certainly not one. The stem of the question states that this is part of the citric acid cycle, which occurs in the inner matrix of the mitochondria, not the cristae membrane.
|
Biology/64
|
Biology
| null |
Identify the phase of meiosis when recombination occurs, and state the reason for your decision.
A. Picture 1, because sister chromosomes are lined up on the metaphase plate.
B. Picture 1, because homologous pairs are lined up on the metaphase plate.
C. Picture 2, because homologues are paired up in synapsis.
D. Picture 3, because homologous pairs are exchanging genetic material.
|
C: Recombination occurs when homologous pairs bind together during synapsis and crossing-over occurs. Picture 1 is in metaphase. Synapsis and crossing-over have already occurred. The homologous pairs are about to separate. Picture 2 shows prophase. Synapsis is occurring, and crossing-over can occur at this point. Picture 3 shows sister chromatids lined up on the metaphase plate. There can be no crossing-over because there is only one chromosome.
|
Biology/65
|
Biology
| null |
Which of the following statements best describes what this cell will accomplish as part of the immune system?
A. It will secrete a chemical that will form holes in the pathogen.
B. It will produce antibodies against the antigen it is engulfing.
C. It will circulate in the bloodstream for a lifetime and will be able to identify the antigen in the future.
D. It will present pieces of the antigen on its surface membrane.
|
D: A macrophage is an antigen-presenting cells (APC). It will alert the adaptive immune system about a particular invader.
|
Biology/66
|
Biology
| null |
You carry out an experiment to study transpiration in plants using a two-week-old bean plant. You set up a potometer by cutting the stem of a plant and securing it into clear flexible tubing that has been tightly connected to a calibrated pipette. Water fills the potometer from the plant stem to the tip of the pipette.
You measure water loss from your potometer at 10-minute intervals and plot your data on the graph as Line B.
You then explore what happens if you expose the plant to different conditions. Which of the following statements is correct based on proposed changes to the potometer?
A. Increasing the green wavelengths of light will increase the rate of transpiration and account for Line A on the graph.
B. Placing a plastic bag over the plant will increase the rate of transpiration and account for Line A.
C. Placing a fan near the plant will decrease the rate of transpiration and account for Line C.
D. Painting the upper leaf surface of most of the leaves with clear nail polish will decrease the rate of transpiration and account for Line C.
|
D: Green plants reflect green light; they do not absorb it and cannot use it as an energy source. Placing a plastic bag over the leaves will decrease transpiration, resulting in Line C. Placing a fan near the plant will increase transpiration, causing Line A.
|
Biology/67
|
Biology
| null |
You carry out an experiment to study transpiration in plants using a two-week-old bean plant. You set up a potometer by cutting the stem of a plant and securing it into clear flexible tubing that has been tightly connected to a calibrated pipette. Water fills the potometer from the plant stem to the tip of the pipette.
You measure water loss from your potometer at 10-minute intervals and plot your data on the graph as Line B.
Which of the following is NOT correct about transpiration in plants?
A. Water moves upward from the roots to the shoots in the xylem by active transport from an area of high osmotic potential to an area of low osmotic potential.
B. Plants lose water through stomates in their leaves.
C. The movement of water through a plant is facilitated by the physical and chemical properties of the water itself.
D. Placing a container of water between the light source and the plant is necessary to prevent the introduction of heat as a second variable in the experiment.
|
A: Notice the question states NOT. All the other answer choices are correct. Water moves up the plant through the xylem by passive transport because of the physical properties of water. Choice D refers to the use of a heat sink, which is necessary in this experiment to make sure that the temperature does not rise during the experiment. If the temperature did rise, it would constitute another variable in the experiment
|
Biology/68
|
Biology
| null |
Which of the following statements is supported by the information presented in the graph, which shows a comparison of two regions in Oregon, one deforested and the other undisturbed?
A. Roots of plants are efficient at absorbing nitrates from the soil.
B. Variation in the amount of nitrate in stream water is due to periods of intense rain.
C. Replanting trees after an area has been clear-cut can prevent nitrate runoff into rivers.
D. The presence of trees in an area causes an increase of nitrates in the soil.
|
A: After deforestation, the nitrate runoff onto the rivers increased. There is no evidence presented that trees were replanted. Choice D is clearly false
|
Biology/69
|
Biology
| null |
Here is a food web for a habitat that is threatened by developers who will remove three-fourths of the grasses in the area on which the mice and rabbits feed.
Which of the following statements describes what will most likely happen to the wildlife in the area?
A. The hawk will begin to eat frogs instead of snakes and mice.
B. Since three trophic levels are shown in the food web, 75% of the organisms in this food web will die.
C. Based on the number of trophic levels, about 25% of the mice and rabbits will die.
D. The hawk population will decrease
|
D: Even though numbers are mentioned in the question, they are not relevant. There is no way to determine if hawks will begin to eat frogs, which is niche displacement. You can deduce only the obvious.
|
Biology/70
|
Biology
| null |
Here is a sketch showing cyclic photophosphorylation in the grana of plant cells.
Which of the following statements about this process is correct, and what is the reason for it?
A. It is similar to oxidative phosphorylation in cellular respiration because its function is to generate ATP.
B. It is similar to glycolysis because it involves an electron transport chain.
C. It is the opposite of cellular respiration because it releases oxygen rather than utilizes it.
D. It is the opposite of the citric acid cycle because ATP is utilized, not produced.
|
A: The only thing this process produces is ATP. No NADPH or oxygen is released. The function of this process is to provide ATP for the Calvin cycle, which uses enormous quantities of ATP.
|
Biology/71
|
Biology
| null |
In the microscopic world of a pond, paramecia are ferocious predators that prey on smaller protists. In a classic experiment, two species of paramecia were grown separately in culture. The species in culture A was P. caudatum. The species in culture B was P. bursaria. Then the two species were combined in one culture dish (culture C).
Which of the following is the most likely explanation for the growth pattern of the two populations combined in culture C?
A. P. caudatum is driving P. bursaria to extinction because P. caudatum is the fitter species.
B. P. caudatum and P. bursaria share a niche.
C. P.caudatum and P. bursaria occupy different niches.
D. P. caudatum is feeding on P. bursaria but only to a limited degree
|
C: Almost by definition, the two species do not share a niche because both populations are surviving. However, the environment has limited resources. In fact, the S-shaped growth curve shown in all three of these graphs is called a logistic growth curve. It is characteristic of some microorganisms under conditions of limited resources.
|
Biology/72
|
Biology
| null |
Intact chloroplasts are isolated from dark-green leaves by low-speed centrifugation and placed into six tubes containing cold buffer. A blue dye, DPIP, which turns clear when reduced, is also added to all the tubes. The amount of decolorization is a function of how much reduction and, therefore, how much photosynthesis occurs. Each tube is exposed to different wavelengths of light. A measurement of the amount of decolorization is made, and the data are plotted on a graph. Although the wavelengths of light vary, the light intensity in each tube is the same.
Which statement below best explains the results of this experiment and the reason for it?
A. The rate of photosynthesis is highest when a tube is exposed to light in the 550 nm range because that wavelength of light contains the greatest amount of energy.
B. The rate of photosynthesis is highest when exposed to light in the 550 nm range because that wavelength of light contains the least amount of energy.
C. The rate of photosynthesis is highest when exposed to combined light in the 650 nm and 700 nm ranges because the combination of the two wavelengths of light contains the greatest amount of energy.
D. The rate of photosynthesis is highest when exposed to combined light in the 650 nm and 700 nm ranges because there are two photosystems in chloroplasts that absorb light in two different wavelengths.
|
D: The amount of energy in light is inversely proportional to its wavelength. The shorter the wavelength of light, the more energy it contains. The lines on the graph that are closest to the x-axis represent the greatest amount of reduction and, therefore, the greatest amount of photosynthesis. According to the graph, the most reduction or photosynthesis occurs with two wavelengths of light combined. The reason is that in chloroplasts, two photosystems, P700 and P680, absorb light of different wavelengths.
|
Biology/73
|
Biology
| null |
Today, two distinctly different beak sizes occur in a single population of finch in an isolated region of West Africa. This finch, the black-bellied seedcracker, is considered a delicacy. The oldest residents of the region remember that all black-bellied seedcrackers used to appear identical. The change in population is shown in the graph.
Which of the following statements best identifies the change in the population of finches and the most likely reason for it?
A. Convergent evolution; two distinct varieties evolved into one variety because only one type of seed now exists.
B. Diversifying selection; one population of finch divided into two populations because at least two types of seeds are now available.
C. Directional selection; one original variety was replaced by another because one food source was replaced by another.
D. Stabilizing selection; the original population died out, leaving only individuals with either long or short beak size.
|
B: There used to be one population of black-bellied seedcracker; now there are two. The single population diverged because of a change in food.
|
Biology/74
|
Biology
| null |
Here is a figure showing the change in one ancestral population of birds over time.
Which of the following statements best supports the evidence presented in the picture?
A. Evolution was gradual and regular with small changes over a long period of time.
B. The environment stayed the same for long periods of time.
C. These birds evolved from a single species that went extinct.
D. These birds evolved mainly as a result of genetic drift.
|
B: The y-axis shows time. The change you see in the birds is sudden. It is not gradual and slow. It occured suddenly. The environment directs evolution. So if a species remains the same for a long time, one can assume that the environment has not changed for all that time. The ancestral species is still alive; it did not go extinct. None of the information leads you to think that evolution occurred because of genetic drift.
|
Biology/75
|
Biology
| null |
Which of the following statements is correct about the plant cell structure shown?
A. A is the site of ATP synthase.
B. B is the site where ATP is produced.
C. C is the structure from which oxygen is released.
D. D is the site of PGAL formation.
|
C: This is a chloroplast. The light-dependent reactions, where ATP is synthesized and oxygen is released, occurs in the grana (C). The light-independent reactions, where PGAL is made, occur in the stroma (B). Nothing related to photosynthesis is occurring in A, which is the outer membrane of the chloroplast
|
Biology/76
|
Biology
| null |
β-thalassemia is a disease that strikes mainly people of Mediterranean and Asian descent. It involves a flaw in the gene that codes for β-globin, one of the protein chains that make up hemoglobin (Hb). A trial was conducted. The patient in this trial was typical of individuals with β-thalassemia. He needed monthly blood transfusions and daily treatments to lower blood iron levels. In 2007, when the patient was 19 years old, scientists removed some of his bone marrow cells and treated them with a modified virus that was engineered to carry a good copy of the β-globin gene. They infused the repaired cells into the patient. After several months, the scientists assessed the patient. Here is a graph of the results.
Which of the following statements is supported by the information provided?
A. The gene therapy trial failed.
B. The gene therapy trial was a success, but the patient still requires blood transfusions.
C. Researchers transplanted a gene directly into the patient's red blood cells.
D. Researchers inserted a gene into a virus vector that carried the normal hemoglobin gene into the patient's cells.
|
D: This was a very successful treatment. The patient's hemoglobin (Hb) levels are approaching normal levels. There are no sudden and severe drops in Hb levels, and the patient no longer requires transfusions.
|
Biology/77
|
Biology
| null |
This graph represents three idealized survivorship curves for different populations.
Which of the following statements correctly explains the information shown on this graph?
A. Line A describes a population that produces few offspring and requires much parental care.
B. Line B describes a population like sea stars that exhibit external fertilization.
C. Line C describes a population that exhibits high survival of the young with high death rates of older individuals in the population.
D. Line A describes survivorship patterns of insects.
|
A: Line A describes the survivorship curve for mammals like humans: few offspring, much parental care, and death at old age. Line C is characteristic of external fertilizers, like sea stars, where there is enormous predation of young. Line B is characteristic of a population that is vulnerable throughout its life but is not particularly vulnerable at any one stage more than at any others.
|
Biology/78
|
Biology
| null |
The agave, or century plant, generally grows in arid climates with unpredictable rainfall and poor soil. The plant exhibits what is commonly called big bang reproduction. An agave grows for years, accumulating nutrients in its tissues until there is an unusually wet year. Then it sends up a large flowering stalk, produces seeds, and dies.
Which of the following statements gives the most likely explanation for how the agave plant has evolved this unusual life strategy?
A. This strategy is determined by the plant's genes, which are inherited.
B. This particular life strategy was selected for by the harsh, desert environment.
C. This strategy is the result of a series of mutations that occurred because of the great heat in the desert.
D. This strategy is the result of a series of mutations that occurred because of the great heat in addition to the lack of rain in the desert.
|
B: Choices C and D have the theory backward. Mutations may provide variety in a population, but they do not occur to provide a variety or a solution to a problem. Mutations occur. If they are advantageous, that new characteristic may increase in frequency in a population. If they are deleterious, that trait may disappear.
|
Biology/79
|
Biology
| null |
Here are drawings of four amino acids.
Molecule A is serine and has polar side chains. Molecule B is lysine, which is basic and positively charged. Molecule C, glutamate, is acidic and negatively charged. Molecule D is glycine. It has nonpolar side chains.
Which of the following statements is correct about these amino acids?
A. Molecule A can readily dissolve through a plasma membrane.
B. Only Molecules B and C can readily dissolve through a plasma membrane.
C. Molecules A, B, and C can all readily dissolve through a plasma membrane.
D. Only Molecule D can readily dissolve through a plasma membrane.
|
D: In general, substances that are polar and/or charged cannot diffuse through a membrane; only nonpolar molecules can.
|
Biology/80
|
Biology
| null |
To which of the following labeled trophic levels would a herbivore most likely be assigned?
A. A
B. B
C. C
D. D
|
D: Herbivores tend to be the primary consumers of trophic pyramids, and thus would take up the first level up from the bottom.
|
Biology/81
|
Biology
| null |
A behavioral endocrinologist captures male individuals of a territorial bird species over the course of a year to measure testosterone (T) levels. In this population, males may play one of two roles: (1) they may stay in their natal group (the group they were born in) and help raise their younger siblings, or (2) they may leave the natal group to establish a new territory. Use this information and the two histograms that follow to answer the following questions.
Testosterone level in this population may be an example of
A. adaptive radiation.
B. an adaptation.
C. divergent selection.
D. development.
|
B: Testosterone level is an adaptive trait in this population, one that has been molded by natural selection (or possibly sexual selection; we cannot determine this from the question) to aid in reproduction. Adaptive radiation is a process by which many speciation events occur in a newly exploited environment and does not apply here. This is not an example of divergent selection because both breeding and nonbreeding males have low testosterone levels during at least one part of the year; if the two male types always differed in testosterone level, this population could eventually split into two populations. Development and sperm production may be related to testosterone but are not addressed in this experiment.
|
Biology/82
|
Biology
| null |
A behavioral endocrinologist captures male individuals of a territorial bird species over the course of a year to measure testosterone (T) levels. In this population, males may play one of two roles: (1) they may stay in their natal group (the group they were born in) and help raise their younger siblings, or (2) they may leave the natal group to establish a new territory. Use this information and the two histograms that follow to answer the following questions.
What can you infer about the role of testosterone in reproduction in this species?
A. It is detrimental to breeding.
B. It aids adult males only.
C. It ensures that all males reproduce equally.
D. It aids in breeding.
|
D: Since testosterone levels are increased only during the breeding season, we can infer that testosterone has some role in breeding. Since reproductive males express higher testosterone levels only during the breeding season, we hypothesize that testosterone is beneficial, as opposed to detrimental, to breeding.
|
Biology/83
|
Biology
| null |
Which of the following is the best explanation of the results presented in the preceding graph, collected from the same population in a different year?
A. The so-called helper males are actually breeding.
B. The population has stopped growing.
C. Females are equally attracted to adult and helper males.
D. Testosterone level is affected by many processes.
|
A: Since testosterone seems to be linked with reproduction, we infer from the new data that the "nonbreeding" males are actually breeding and therefore have elevated testosterone levels. Females, population growth, and number of offspring produced are not considered in this example. Finally, although testosterone does affect many physiological processes, none of these are discussed or illustrated in this example
|
Biology/84
|
Biology
| null |
The DNA placed in this electrophoresis gel separates as a result of what characteristic?
A. pH
B. Charge
C. Size
D. Polarity
|
C: Gel electrophoresis separates DNA on the basis of size. Smaller samples travel a greater distance down the gel compared to larger samples.
|
Biology/85
|
Biology
| null |
If this gel were used in a court case as DNA evidence taken from the crime scene, which of the following suspects appears to be guilty?
A. Suspect A
B. Suspect B
C. Suspect C
D. Suspect D
|
B: His DNA fingerprint seems to exactly match that of the evidence DNA sample.
|
Biology/86
|
Biology
| null |
Which two suspects, while not guilty, could possibly be identical twins?
A. A and B
B. A and C
C. B and C
D. B and D
|
B: A and C seem to share the exact same restriction fragment cut of their DNA. Perhaps they are messing with our heads and added the DNA from the same individual twice.
|
Biology/87
|
Biology
| null |
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