aivnodsuvisudbvisudn

C. Mitochondria and chloroplasts do not function independently from the eukaryotic host cell. Some of the ancestral mitochondria and chloroplast genes are now located in the genome of the host cell. Thus, respiration and photosynthesis cannot occur without the manufacture of necessary enzymes by the host genome.

All of the following support the endosymbiotic theory that ancestors of mitochondria and chloroplasts were once independent, free-living prokaryotes EXCEPT: A. Mitochondria and chloroplasts divide independently of the eukaryotic host cell by a process similar to binary fission. B. Mitochondria and chloroplasts have ribosomes that more closely resemble those of bacteria than of eukaryotic cells. C. Mitochondria and chloroplasts function independently from the eukaryotic host cell. D. Mitochondria, chloroplasts, and bacteria have a single, circular chromosome without histones or proteins.

A. The AP exam does not expect you to recognize the exact structure of each amino acid. Instead, this question evaluates your understanding of how amino acids bond together. In particular, two amino acids form a peptide bond as a result of hydrolysis. That is, a water molecule is formed and released as a covalent bond is created between two adjacent amino acid molecules. More specifically, the OH in the carboxyl group (COOH) of one amino acid and the H of the amino group (NH2) of an adjacent amino acid combine to form a water molecule, as shown below:

Amino acids are joined together by peptide bonds to form proteins. Which of the following groups of amino acid molecules is arranged so that the circled atoms will properly form a peptide bond?

B

An animal that is harmless copies the appearance of an animal that is dangerous as a defense mechanism to make predators think twice about attacking. A. Aposomatic coloration B. Batesian mimicry C. Deceptive markings D. Cryptic coloration

B. Because the solution in the beaker turned blue, you know that the IKI diffused through the bag, into the solution in the beaker, and reacted with the starch. Since the contents of the bag did not turn blue, you know that the starch did not diffuse from the beaker into the bag. Thus, you know the bag is permeable to IKI and not permeable to starch. Since no test for glucose was reported, no conclusion can be drawn for the bag's permeability to glucose.

An iodine solution (IKI or Lugol's solution) turns from yellow-brown to blue when it reacts with starch, but not when it reacts with glucose. A bag made from a selectively permeable material and containing iodine solution is placed into a beaker containing a solution of glucose and starch. Using only this information, which of the following can be correctly concluded if the solution in the beaker turns blue but the contents of the bag remain unchanged in color? A. Glucose moved from the beaker into the bag. B. The bag is permeable to IKI, but not to starch. C. The bag is permeable to IKI and glucose, but not to starch. D. The bag is permeable to IKI, but not to starch and glucose.

B-Endotherms are organisms whose metabolic rates do not respond to shifts in environmental temperature.

An organism exposed to wild temperature fluctuations shows very little, if any, change in its metabolic rate. This organism is most probably a A. ectotherm. B. endotherm. C. thermophyle. D. ascospore.

(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.

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. D. The larger the animal, the faster the heart rate and breathing rate both are.

Apoptosis is anything but random. It is controlled by both internal and external signals that lead a class of enzymes called caspases to assist in the digesting of a cell marked for apoptosis.

Apoptosis, which is programmed cell death, is a necessary process in living organisms. Which of the following is NOT correct about apoptosis? A. It occurs randomly. B. A particular cell dies when it is no longer needed by the organism. C. A cell carries out apoptosis when too many mutations have accumulated. D. Plant cells carry out apoptosis as a defense measure in cells that have been infected by parasites.

C. This question evaluates your ability to read and understand data in graphical form. Answer choices A, B, and D are not supported by the data presented in the figure. Answer choice A is not supported by the data in the figure because the data compare shade and sun leaves exposed to the same amount of light at various intensities (800, 900, and 1000 μmol photons/m2/sec, for example). Answer choice B is not supported by the data in the figure because the data compare equal surface areas of plant leaves (light intensity is per m2). Answer choice D implies that shade leaves have a higher maximal photosynthetic rate than sun leaves, but the data for light intensities above 200 μmol photons/m2/sec indicate the opposite. Because the hypothesis presented in answer choice C cannot be refuted by the data in the graph, it is the best of the hypotheses presented among the four answer choices.

As demonstrated by light intensities above 800 μmol photons/m2/sec, leaves from the plant grown in the sun reached a higher maximal photosynthetic rate. Which of the following is the best hypothesis that can explain why plants grown in full sunlight reach a higher maximal photosynthetic rate than plants grown in shade? A. The sun leaves were exposed to more light than shade leaves. B. The sun leaves had a greater surface area than shade leaves. C. Leaves grown in the sun were thicker than shade leaves, with additional layers of photosynthetic cells. D. The photosynthetic apparatus of leaves grown in the shade were more efficient than those leaves grown in the sun.

B. At light intensities below 50 μmol photons/m2/sec, the rate of photosynthesis is so low that cells require additional energy from respiration. When respiration increases, the production of CO2 from respiration exceeds assimilation of CO2 by photosynthesis. Although other answer choices may explain why CO2 assimilation is low, only answer choice B answers why CO2 assimilation is negative below 50 μmol photons/m2/sec.

At light intensities below 50 μmol photons/m2/sec, which of the following best explains why values of CO2 assimilation are negative? A. Leaf stomata close in response to low light intensities, limiting access to CO2. B. Rates of respiration exceed those of photosynthesis at light intensities below 50 μmol photons/m2/sec. C. The Calvin cycle reverses and releases CO2 at light intensities below 50 μmol photons/m2/sec. D. At light intensities below 50 μmol photons/m2/sec, only cyclic photophosphorylation occurs and thus no CO2 is assimilated

A-The total solute potential for side A is 1.0 MPa (remember that for NaCl, i = 2), and the total solute potential for side B is 0.8 MPa. Therefore, side A has a higher concentration of solute (hypertonic).

At the beginning of the experiment, A. Side A is hypertonic to side B. B. Side A is hypotonic to side B. C. Side A is isotonic to side B. D. Side A is hypotonic to side B with respect to sucrose.

A. The action spectrum is a plot of photosynthetic rate against light wavelengths absorbed. The highest rate of photosynthetic activity occurs at about 450 nm.

At what wavelength of light is the rate of photosynthesis greatest? A. 450 nm B. 500 nm C. 550 nm D. 650 nm

A

B

(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.

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.

A-As RNA polymerase adds new nucleotides to the 3'end of the new strand, it is moving toward the 5'end of the (antiparallel) template strand.

Based on the preceding picture, which direction would RNA polymerase move? A. 3′ → 5′ along the template strand B. 3′ → 5′ along the complementary strand C. 5′ → 3′ along the template strand D. 5′ → 3′ along the complementary strand

A. Caffeine is an adenosine signaling antagonist, blocking the effect of adenosine. When caffeine binds to the adenosine receptor, it blocks the G protein-coupled receptor from initiating the adenosine signaling pathway. As a result, PKA is not activated and drowsiness does not occur.

Because caffeine has a structure very similar to adenosine, it can bind to the adenosine receptor but cannot activate it. Which of the following best describes the effect of caffeine when it binds to the adenosine receptor? A. Caffeine blocks the effect of adenosine by preventing the binding of adenosine to the adenosine receptor. B. Caffeine enhances the effect of adenosine, overstimulating the adenosine signal transduction pathway and ultimately causing it to fail. C. Caffeine restores the effect of adenosine by substituting for it as a signaling molecule. D. Caffeine has no effect on the activity of adenosine.

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.

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 Speciation occurred in the Galapagos finches as a result of the different environments on the islands. This is an example of divergent evolution. The finches were geographically isolated. Choice (A), convergent evolution, is the evolution of similar structures in distantly related organisms. Choice (C), disruptive selection, is selection that favors both extremes at the expense of the intermediates in a population. Choice (D), stabilizing selection, is selection that favors the intermediates at the expense of the extreme phenotypes in a population.

Certain populations of finches have long been isolated on the Galapagos Islands off the western coast of South America. Compared with the larger stock population of mainland finches, these separate populations exhibit far greater variation over a wider range of species. The variation among these numerous finch species is the result of A. convergent evolution B. divergent evolution C. disruptive selection D. stabilizing selection

C Pheromones act as sex attractants, alarm signals, or territorial markers. Auxins are plant hormones that promote growth, so eliminate (A). Hormones are chemical messengers that produce a specific effect on target cells within the same organism, so eliminate (B). Enzymes are catalysts that speed up reactions, so eliminate (D).

Chemical substances released by organisms that elicit a physiological or behavioral response in other members of the same species are known as A. auxins B. hormones C. pheromones D. enzymes

D

Chemiosmosis occurs in I.Mitochondria II. Nuclei III. Chloroplasts A. I only B. II only C. III only D. I and III

(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.

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.

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.

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

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.

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 Beta cells secrete insulin. Destruction of beta cells in the pancreas will halt the production of insulin. Therefore, eliminate (A), (B), and (C). This will lead to an increase in blood glucose levels.

Destruction of all beta cells in the pancreas will cause which of the following to occur? A. Glucagon secretion will stop and blood glucose levels will increase. B. Glucagon secretion will stop and blood glucose levels will decrease. C. Glucagon secretion will stop and digestive enzymes will be secreted. D. Insulin secretion will stop and blood glucose levels will increase.

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.

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

(D) Protons flowing down a gradient through ATP synthase provide energy to phosphorylate ADP into ATP. Energy from the exergonic flow of electrons to oxygen provides the energy to pump protons across the cristae membrane and form a gradient.

During oxidative phosphorylation, the energy needed to drive ATP synthesis comes from one source. Which of the following statements states the immediate source of that energy? A. Electrons flow down an electron transport chain as they are attracted to oxygen. B. The transfer of a phosphate group to ADP is exergonic. C. The bonding of electrons to oxygen at the end of the chain releases energy. D. The proton gradient across the membrane where the ATP synthase is embedded represents potential energy.

A The primitive atmosphere lacked oxygen (O2). It contained methane (CH4), ammonia (NH3), and hydrogen (H2).

During the period when life is believed to have begun, the atmosphere on primitive Earth contained abundant amounts of all the following gases EXCEPT A. oxygen B. hydrogen C. ammonia D. methane

(C) Although it is true that during the Krebs cycle pyruvate is completely broken down to CO2, the most energy from cellular respiration is released during oxidative phosphorylation, when all the energy stored in NADH and FADH2 from previous stages of cellular respiration is released.

Energy is harvested during cellular respiration in stages. Which of the following correctly states which phase of cellular respiration harvests the most energy and the correct explanation why? A. The most energy is released during the Krebs cycle because it is here that pyruvate is completely broken down into CO2. B. The most energy is released during the Krebs cycle because in addition to the production of ATP, both FADH2 and NADH are produced. Each of those molecules will release 2 ATPs and 3 ATPs, respectively. C. The most energy is released during oxidative phosphorylation because in addition to the phosphorylation of ADP into ATP, all the potential energy held in NADH and FADH is transferred to ATP. D. The most energy is released during oxidative phosphorylation because H2O is completely broken down into H+ and O2.

(B) The extra nitrate does not contribute any more to the algae growth than the initial increase. Phosphate is the main contributing factor to algae growth.

Figure 1 shows the growth of the filamentous green algae Spirogyra in a flask of sterilized pond water that contains nitrate. If phosphate is added to the flask as shown, the growth curve changes to that shown in Figure 2. Which of the following graphs is the best prediction of the algae growth if more nitrate (NO3) is added along with the phosphate?

B. This molecule, an α-glucose polysaccharide, is starch or glycogen, both energy storage molecules. Starch is found in plant cells, while glycogen is found in animal cells. In contrast, cellulose (not shown), a β-glucose polysaccharide, functions as a structural element in the cell walls of plants.

For which molecule is energy storage a major function?

(B) Prior to translocation, the chickens had become inbred, diversity had decreased, and fertility had declined.

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. 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.

(C) Cystic fibrosis is solely an inherited disease. No environmental component causes the disease. It is an autosomal recessive disease. In order to have the disease, a person must have inherited two mutated genes, one from each parent. Polygenic inheritance involves the inheritance of several genes. An example is height, skin, or hair color—any trait where a tremendous variety occurs in a population.

From the description of cystic fibrosis above, which of the following statements is correct? A. The disease is similar to cancer in that it has both an environmental and a genetic cause. B. Cystic fibrosis is an example of a genetic disease caused by polygenic inheritance because several genes must be mutated in order for the disease to occur. C. Cystic fibrosis is an example of pleiotropy because one mutated gene causes multiple effects. D. A person who has one cystic fibrosis allele will have the disease.

C Choice (A) and (B) are incorrect: These organisms exhibit the same behavior because they were subjected to the same environmental conditions and similar habitats. This is an example of convergent evolution. However, they are not genetically similar, so (C) is the answer. (One is an insect and the other a bird.) They are analogous, so (D) is also incorrect. They exhibit the same function but are structurally different.

Hawkmoths are insects that are similar in appearance and behavior to hummingbirds. Which of the following is LEAST valid? A. These organisms are examples of convergent evolution. B. These organisms were subjected to similar environmental conditions. C. These organisms are genetically related to each other. D. These organisms have analogous structures.

A Choices (B) and (D) are incorrect: Hemoglobin's affinity for O2 decreases as the concentration of H+ increases (or the pH decreases) and as the concentration of CO2 increases (or the concentration of HCO3- increases). Also eliminate (C), as hemoglobin's affinity for oxygen in tissue muscles does not increase during exercise.

Hemoglobin is a molecule that binds to both O2 and CO2. There is an allosteric relationship between the concentrations of O2 and CO2. Hemoglobin's affinity for O2 A. decreases as blood pH decreases B. increases as H+ concentration increases C. increases in exercising muscle tissue D. decreases as CO2 concentration decreases

(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.

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.

(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.

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.

(B) This may seem tricky, but Choice B is correct. Immune responses are specific. Each challenge with a new antigen results only in a primary immune response for that antigen.

Here is a graph that depicts a first exposure to antigen A on Day 1 with a subsequent, primary immune response. A second exposure to antigen A on Day 30 results in a secondary immune response due to the presence of circulating memory cells that release antibodies against antigen A. There is also a first exposure to antigen B on Day 30. Which of the following graphs accurately depicts the immune response to antigen B and the reason for it? A. Graph A. The primary response to antigen B is almost as fast and large as the secondary immune response to antigen A because the entire immune system was activated by the first exposure to antigen A. B. Graph B. Immune responses are specific. The fact that there was an earlier exposure to antigen A has no bearing on the response to antigen B on Day 30. C. The response to antigen B on Day 30 is larger than the secondary immune response to antigen A because the immune system has already been activated and all new responses are heightened. D. There is almost no immune response to antigen B because the immune system is fully engaged in a secondary response to antigen A.

(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.

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.

(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.

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.

(B) Energy is released, and NAD+ binds to hydrogen released by malate.

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.

(B) The process of hydrolysis releases oxygen from water into the air.

Here is the simplified equation for photosynthesis: 6CO2 + 12 H2O → C6H12O6 + 6H2O + 6O2 Which of the following choices correctly traces the atom identified with an arrow?

C. High fructose corn syrup, as the name implies, is fructose made from corn starch. Since starch is a polymer of glucose, starch must be broken down into glucose monomers and each glucose monosaccharide must be converted into a fructose monosaccharide. This turns out to be a cheaper way of making a sweetener than by extracting sucrose, a disaccharide of glucose and fructose, from sugar cane or sugar beets. (For the final HFCS product, the manufactured fructose is back blended with glucose to produce a sweetener that is about 55% fructose and 45% glucose. Apparently, this HFCS fructose/glucose mixture better simulates the taste of sucrose than pure fructose alone.)

High fructose corn syrup (HFCS) is a sweetener containing fructose that is derived from corn starch and often added to soft drinks. Which of the following reactions would most likely be involved in the production of HFCS? (The letter "n" indicates multiple copies of a molecule in a polymer.) A. (glucose)n → polysaccharide B. sucrose → fructose + glucose C. glucose → fructose D. starch → (fructose)n

D Homologous structures are organisms with the same structure but different functions. The forelegs of an insect and the forelimbs of a dog are not structurally similar. (One is an invertebrate and the other a vertebrate.) They do not share a common ancestor. However, both structures are used for movement. All of the other examples are vertebrates that are structurally similar.

Homologous structures are often cited as evidence for the process of natural selection. All of the following are examples of homologous structures EXCEPT A. the wings of a bird and the wings of a bat B. the flippers of a whale and the arms of a man C. the pectoral fins of a porpoise and the flippers of a seal D. the forelegs of an insect and the forelimbs of a dog

C-The average enamel thickness started at 10, increased to 12, and then increased to 15. It is therefore increasing overall.

How is average enamel thickness changing in this population? A. There is no real change. B. The color and size are changing. C. It is increasing. D. It is decreasing.

B When a forest of trees is devastated by fire, secondary succession is most likely to occur. Secondary succession refers to ecological succession in a disturbed community. Choice (A) is incorrect because plants and animals will continue to inhabit the region once the community is reestablished. You can also eliminate (C), as tough grasses are not pioneers. Finally, (D) is incorrect because it cannot be determined if the number of species will be stabilized.

If a forest of fir, birch, and white spruce trees was devastated by fire, which of the following would most likely happen? A. Only animal life would continue to inhabit the region. B. Secondary succession would begin to occur. C. Only tough grasses would appear. D. The number of species would stabilize as the ecosystem matures.

A The oxygen released during the light reaction comes from the splitting of water. (Review the reaction for photosynthesis.) Therefore, water must have originally contained the radioactive oxygen. Carbon dioxide is involved in the dark reaction and produces glucose, so eliminate (B). Glucose is the final product and would not be radioactive unless carbon dioxide was the radioactive material, so (C) is incorrect. Finally, eliminate (D), because nitrogen is not part of photosynthesis.

If a photosynthesizing plant began to release 18O2 instead of normal oxygen, one could most reasonably conclude that the plant had been supplied with A. H2O containing radioactive oxygen B. CO2 containing radioactive oxygen C. C6H12O6 containing radioactive oxygen D. NO2 containing radioactive oxygen

B-In competitive inhibition, an inhibitor molecule resembling the substrate binds to the active site and physically blocks the substrate from attaching.

If inhibitor 1 is able to bind to the active site and block the attachment of the substrate to the enzyme, this is an example of A. noncompetitive inhibition. B. competitive inhibition. C. a cofactor. D. a coenzyme.

A. Adaptive radiation can occur when a single species is introduced into an unoccupied area with many available niches. Rapid evolution of many species occurs as the available niches are exploited. Once all the niches are filled, evolutionary rates decline.

If the diagram describes the pattern of evolution after a single species is introduced to a remote, newly formed island, the pattern in the diagram best suggests A. adaptive radiation B. allopatric speciation C. coevolution D. multiple occurrences of gene flow

C. A single tree can support large numbers of insects (represented by the second tier of the pyramid), which can, in turn, support many birds (or other insects) that eat the insects. One or two large predators, such as hawks, may occupy the fourth tier.

If the figure illustrates a pyramid of numbers, which of the following would best explain the relative sizes of the trophic levels? A. The lowest trophic level represents decomposers. B. The lowest trophic level represents carnivorous plants. C. The lowest trophic level represents a single tree in a forest. D. The pyramid represents the ecological state of an early successional stage.

C If the herring population decreases, this will lead to an increase in the number of crustaceans and a decrease in the phytoplankton population. Reorder the organisms according to their trophic levels and determine which populations will increase and decrease accordingly.

If the herring population is reduced by predation, which of the following is most likely to occur in this aquatic ecosystem? A. The mackerels will be the largest predator in the ecosystem. B. The small crustacean population will be greatly reduced. C. The phytoplankton population will be reduced over the next year. D. The small crustaceans will become extinct.

B-Water would now flow into the bag because the solute gradient has been reversed. Now the beaker is hypotonic compared to the dialysis bag. Water thus moves into the bag.

If this bag were instead placed into a beaker of distilled water, what would be the expected result? A. There will be a net flow of water out of the bag, causing it to decrease in size. B. There will be a net flow of water into the bag, causing it to swell in size. C. The bag will remain the exact same size because no water will move at all. D. The solute will flow out of the dialysis bag into the beaker.

D-Water will move from a hypotonic solution (side B) toward a hypertonic solution (side A). Sodium will diffuse from a region of more sodium (side B) to a region of less sodium (side A).

If you examine side A after a couple of days, you will see A. an increase in the concentration of NaCl and sucrose and an increase in water level. B. a decrease in the concentration of NaCl, an increase in water level, and no change in the concentration of sucrose. C. no net change. D. an increase in the concentration of NaCl and an increase in the water leve

(C) Some scientists believe that some complex molecules necessary for life on Earth might have come from outer space. That might be true. However, the purpose of Miller's experiment was to demonstrate that the molecules necessary for life to develop could have formed under the conditions of the early Earth. He did not succeed in demonstrating that the first molecules were self-replicating.

In 1953, Stanley Miller, while working under the guidance of Harold Urey at the University of Chicago, carried out a series of experiments with substances that mimicked those of early Earth. His experimental setup yielded a variety of amino acids that are found in organisms alive on Earth today. The purpose of these experiments best supports which of the following hypotheses? A. The basic building blocks of life originated in outer space and came to Earth carried by comets or meteorites. B. The molecules necessary for life to develop were located in deep-sea vents. C. The molecules necessary for life to develop could have formed under the conditions of the early Earth. D. The molecules necessary for life on Earth were self-replicating proteins, just like the ones produced in Miller's experiments.

C. When Elodea is exposed to light, electrons are energized and noncyclic and cyclic photophosphorylation begins, generating ATP, NADPH, and O2. In the Calvin cycle phase of photosynthesis, the CO2 in the BTB solution that the ATP and NADPH generated in photophosphorylation is used to generate glucose. When the CO2 is consumed, the solution becomes basic (as H+ is converted to H2CO3) and the yellow BTB turns blue. The reverse reaction is observed in Reaction I, where the addition of CO2 causes the blue BTB to become more acidic and turns the blue BTB to yellow.

In Reaction IV, the BTB solution with Elodea changes from yellow to blue when exposed to light. Which of the following is the most likely cause of this change? A. Light is causing the BTB to become more acidic. B. Elodea is releasing CO2 in response to the exposure to light. C. Photosynthesis is occurring in Elodea. D. The Elodea plant is dying.

C-If 9 percent of the population is homozygous recessive, this means that q2 = 0.09, and that the square root of q2 = 0.30 = q. This means that p = 0.70 since p + q = 1. Thus, the percentage of the population that is homozygous dominant: p2 = (0.7)2 = 0.49 or 49 percent.

In a certain population of squirrels that is in Hardy-Weinberg equilibrium, black color is a recessive phenotype present in 9 percent of the squirrels, and 91 percent are gray. What percentage of the population is homozygous dominant for this trait? A. 21 percent B. 30 percent C. 49 percent D. 70 percent

D. Cells at the surface of a leaf secrete a waxy coating to reduce transpiration. Because wax is a hydrophobic substance, leaves do not easily submerge in water. Soap molecules contain both hydrophobic and hydrophilic regions. When soap is added to water, the hydrophobic regions of the soap molecules cluster over the hydrophobic waxy coating of the leaf, while the hydrophilic regions of the soap molecules face away from the leaf surface. In this way, the waxy leaf surface is covered by soap molecules with their hydrophilic regions facing the surrounding water molecules. As a result, the leaves more easily fall through the water.

In a laboratory exercise, a student cuts disks of plant leaves and puts them in a beaker of water. To help submerge the leaves, a drop of soap is added to the water. How does the soap help submerge the leaf disks? A. The soap molecules enter through the stomata of the leaf and bond to oxygen molecules. B. The soap molecules bond to air bubbles on the surface of the leaf and remove them. C. The soap molecules decrease the pH of the water, allowing excess H+ to bond to the leaf surface. D. The hydrophobic regions of the soap molecules attach to the waxy leaf surface, while the hydrophilic regions form hydrogen bonds with the water molecules.

A-Directional selection occurs when members of a population at one end of a spectrum are selected against, while those at the other end are selected for. Taller giraffes are being selected for; shorter giraffes are being selected against.

In a population of giraffes, an environmental change occurs that favors individuals that are tallest. As a result, more of the taller individuals are able to obtain nutrients and survive to pass along their genetic information. This is an example of A. directional selection. B. stabilizing selection. C. sexual selection. D. disruptive selection.

D Ribosomes are the site of protein synthesis. Therefore, the correct answer should start with ribosome. So eliminate (A) and (C). The polypeptide then moves through the rough ER to the Golgi apparatus, where it is modified and packaged into a vesicle. The vesicle then floats to the plasma membrane and is secreted. Choice (D) is your answer.

In animal cells, which of the following represents the most likely pathway that a secretory protein takes as it is synthesized in a cell?

A Peroxisomes catalyze reactions that produce hydrogen peroxide, ribosomes are involved in protein synthesis, and mitochondria contain enzymes involved in cellular respiration. Eliminate (B) and (D) because lysosomes are the sites of degradation; they contain hydrolytic enzymes but do not produce hydrogen peroxide. Choice (C) is incorrect, as the Golgi apparatus sorts and packages substances that are destined to be secreted out of the cell. Interestingly, O2 concentration generally doesn't play an important role in regulating respiration.

In cells, which of the following can catalyze reactions involving hydrogen peroxide, provide cellular energy, and make proteins, in that order? A. Peroxisomes, mitochondria, and ribosomes B. Peroxisomes, mitochondria, and lysosomes C. Peroxisomes, mitochondria, and Golgi apparatus D. Lysosomes, chloroplasts, and ribosomes

D. The function of the CFTR protein is to generate an electrochemical gradient that allows the passive flow of Cl- across the plasma membrane. In response, water follows, moving across the membrane in response to the gradient. When water does not flow, the surface liquid on the cells is deficient and thick mucus develops.

In epithelial cells expressing the cystic fibrosis mutation, the CFTR protein is not functional. How does this contribute to the symptoms of the disorder? A. Stimulated by a buildup of epinephrine, muscle cells contract and produce coughing. B. Airways are constricted as a result of the buildup of water in epithelial cells. C. Cells unable to move Cl- across the plasma membrane die, and cellular debris produces thick mucus. D. Thick mucus develops in the lungs because water is not induced to cross the plasma membrane by an electrochemical gradient.

D Animal cells have centrioles. Both animal and plant cells have an endoplasmic reticulum, membrane-bound organelles, and lysosomes. Only plants have a cell wall made of cellulose and large vacuoles.

In general, animal cells differ from plant cells in that animal cells have A. a cell wall made of cellulose B. lysosomes C. large vacuoles that store water D. centrioles within centrosomes

A. It is important to understand that a single signaling molecule, initiating the same signal transduction pathway, can have different effects in different cell types. Also, there are only three types of membrane receptors (G protein-coupled receptors, ligand-gated ion receptors, and protein kinase receptors), but there are more than 700 known signaling molecules for G protein-coupled receptors alone. Each signaling molecule binds to a specific receptor, initiating a signal transduction pathway that is specific to the signaling molecule and cell type. The PKA produced by the epinephrine signal transduction pathway, then, is going to be different than that of the PKA produced by the adenosine pathway. Since epinephrine is associated with promoting the fight-or-flight response, PKA triggers the release of glucose from glycogen. The release of glucose provides a source of energy for fight-or-flight activities. Muscle fatigue, drowsiness, and reducing blood flow to the heart (as a result of vasoconstriction) do not promote the fight-or-fight response.

In general, the hormone epinephrine (adrenaline) causes increases in blood pressure, breathing rate, and the rate of cell metabolism—all activities associated with the fight-or-flight response. Like adenosine, epinephrine is also a ligand for a G protein-coupled receptor. Though different from adenosine in other respects, the epinephrine signal transduction pathway, like that of adenosine, produces cAMP and activates PKA. Which of the following is most likely the mechanism that describes how epinephrine works? A. In muscle cells, PKA triggers the release of glucose from glycogen. B. In muscle cells, PKA produces muscle fatigue. C. In brain cells, PKA causes drowsiness. D. In heart muscle, PKA causes vasoconstriction, or narrowing of the blood vessels.

B In humans, fertilization normally occurs in the fallopian tube. The ovary is the female gonad that contains eggs, so eliminate (A). The uterus is the organ that houses the developing embryo, so eliminate (C). Finally, (D) can also be eliminated because the placenta is the structure that nourishes the embryo.

In humans, fertilization normally occurs in the A. ovary B. fallopian tube C. uterus D. placenta

D The net primary productivity is what the energy producers have left for storage after their own energy needs have been met. Energy stored = (Total energy produced) - (energy used in cellular respiration). Choice (A) is incorrect; it is not the energy available to producers. You can also eliminate (B) because it is not the total chemical energy in producers—it's the gross primary productivity. Get rid of (C) as well because it is not the biomass (total living material) among producers.

In most ecosystems, net primary productivity is important because it represents the A. energy available to producers B. total solar energy converted to chemical energy by producers C. biomass of all producers D. energy available to heterotrophs

A The tendency of climbing vines to twine their tendrils around a trellis is called thigmotropism. Thigmotropism refers to growth stimulated by contact with an object. Choice (B), hydrotropism, refers to growth of a plant toward water. Choice (C), phototropism, refers to growth toward light. Choice (D), geotropism, refers to growth toward or against gravity.

In plants, the tendency of climbing vines to twine their tendrils around a trellis is called A. thigmotropism B. hydrotropism C. phototropism D. geotropism

(C) The question does not give you enough background to determine anything more than to say that some traits are favored more than others in a particular environment.

In the Tularosa Basin of New Mexico are black lava formations surrounded by light-colored sandy desert. Pocket mice inhabit both areas. Dark-colored ones inhabit the lava formations, while light-colored mice inhabit the desert. Which of the following statements is correct about this scenario? A. The two varieties of mice descended from a recent common ancestor. B. The mouse population was originally one population that diverged into two species because of mutations. C. Selection favors some phenotypes over others. D. Originally the mice were all dark colored. As the lava decomposed into sand, the color of some mice changed because that color was favored in that environment.

B. Activation of this receptor protein (a receptor tyrosine kinase, or RTK) induces autophosphorylation which, in turn, phosphorylates relay proteins. The relay protein then exchanges a GTP for the GDP on a nearby G protein, which, in this case, is the Ras protein.

In the figure, the activated receptor proteins allow the binding of a relay protein (shown at II). In turn, the relay protein triggers the activation of the G protein called Ras. How is the Ras protein activated? A. The relay molecule binds to Ras. B. A GDP molecule on Ras is replaced with a GTP molecule. C. Ras is enzymatically split to form two active proteins. D. Ras binds to a second relay protein, forming the active form of the protein.

B. A phospholipid consists of two fatty acids and a phosphate group attached to a glycerol molecule. The phosphate group "head," represented in the figure with a circle, is polar and hydrophilic. The fatty acid "tails," shown as wavy lines, are hydrophobic. When immersed in water, the hydrophilic head of a phospholipid orients toward the water molecules and the hydrophobic tails face away from the water. The orientation that satisfies these constraints is a bilayer (or "sandwich") with the hydrophilic heads facing the water and the fatty acid tails facing the center of the bilayer. The optimal orientation occurs when a flat bilayer (in which the fatty acid tails at the ends of the bilayer are in contact with water) closes to form a circle (or sphere in three dimensions) as observed in the plasma membranes of cells.

In the following figures, a phospholipid is represented by two lines attached to a circle. The circle represents the phosphate group, and the two wavy lines represent the fatty acids. When immersed in water, which of the following shows the expected orientation of the phospholipids?

A. Because lysosomes are sites of chemical breakdown (catabolic processes), the abnormal accumulation of substances within them results from the absence or malfunction of a lysosomal enzyme. These are generally called lysosomal storage diseases and include diseases where various undigested materials, including carbohydrates and lipids, accumulate due to the absence of a correctly functioning lysosomal enzyme. Since cytosol glycogen and blood glucose levels are normal, plasma membrane transport is not the source of the problems associated with the disease.

In the inherited disorder called Pompe disease, glycogen breakdown in the cytosol occurs normally and blood glucose levels are normal, yet glycogen accumulates in lysosomes. This suggests a malfunction with A. enzymes in the lysosomes B. enzymes in the mitochondria C. membrane transport during exocytosis D. membrane transport during endocytosis

(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.

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.

A. There are two reasons why you would expect the proton pumps in bacteria to be similar to those found in mitochondria and chloroplasts and not in animal, plant, or fungal cells. First, generating ATP with proton pumps in eukaryotic cells occurs only in these organelles. The other mechanism for generating ATP (substrate-level phosphorylation) occurs in the cytosol by water-soluble enzymes (during glycolysis). Bacteria, which do not have mitochondria or chloroplasts, must use their plasma membrane for ATP generation by proton pumps. Second, as described by endosymbiosis theory, mitochondria, chloroplasts and bacteria have a common evolutionary origin. The theory explains the origins of eukaryotic cells as the result of a coming together of prokaryotes in a mutualistic, symbiotic relationship: A non-photosynthetic bacterium became a mitochondrion as it merged with a second bacterium that became a eukaryotic animal cell. Similarly, a photosynthetic bacterium became a chloroplast and a non-photosynthetic bacterium became a mitochondrion as both merged with a third bacterium to become a eukaryotic plant cell. These symbiotic assemblages became the ancestors of eukaryotes. Evidence for this theory includes the similarities of their ribosomes, their DNA, and their membranes.

In the process of generating ATP, hydrogen ions (H+, or protons) are transported across the inner mitochondrial membrane and the thylakoid membrane by a proton pump (an ATPase). You would expect to find similar proton pumps in the plasma membranes of A. bacteria B. mammalian muscle cells C. mammalian nerve cells D. plants and fungi

(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.

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.

B This relationship is an example of parasitism. Parasitism is a form of symbiosis in which one organism benefits and the other is harmed. Choice (A), commensalism, is a form of symbiosis in which one organism benefits and the other is unaffected. Choice (C), mutualism, is a form of symbiosis in which both organisms benefit. Choice (D), gravitropism, is the growth of a plant toward or away from gravity.

Lampreys attach to the skin of lake trout and absorb nutrients from its body. This relationship is an example of A. commensalism B. parasitism C. mutualism D. gravitropism

(B) Glycolysis would cease if there were not a constant supply of NAD+ to bind to hydrogen. Glycolysis produces pyruvate, which is the raw material for the citric acid cycle, not oxidative phosphorylation. Glyocolysis does occur in the cytoplasm, but that is not important.

Many different fermentation pathways occur in different organisms in nature. For example, skeletal muscle cells convert pyruvate into lactic acid when no oxygen is present. Yeast cells can produce alcohol and carbon dioxide under the same circumstances. However, regardless of the specific reactions, the purpose of glycolysis is an important one. Which statement best describes the importance of glycolysis? A. It produces large amounts of ATP by substrate level phosphorylation. B. It reoxidizes NADH so that glycolysis can continue. C. It produces pyruvate, which is the raw material for oxidative phosphorylation. D. It occurs in the cytoplasm.

(B) The body temperature of an ectotherm increases with the ambient temperature. A homeotherm or an endotherm can raise and lower its body temperature to maintain a steady body temperature.

Mice are mammals. As such, they are endotherms. They maintain internal heat metabolically. A lizard is an ectotherm and gains its body heat from the environment. Which of the following graphs most accurately depicts this situation?

A. Microtubules are the components of the spindle apparatus used in mitosis (and meiosis). The microtubules organize the chromosomes, separate the chromosomes into chromatids, and tow the chromatids to opposite poles that eventually become nuclei of the daughter cells. Because colchicine prevents microtubule assembly, mitosis cannot advance beyond prophase.

Microtubules are protein filaments assembled from tubulin protein subunits. The chemical colchicine prevents the assembly of microtubules by binding to tubulin protein subunits. Which of the following cellular processes would be most impaired by the application of colchicine? A. the alignment and separation of chromosomes during mitosis B. the coordination of ribosomes and mRNA during protein synthesis C. the movement of substances across the plasma membrane D. the accumulation of protons inside the thylakoids of chloroplasts during chemiosmosis

D. The more polar the molecule, the greater its attraction to the hydrophilic, polar molecules of cellulose. The greater the attraction, the shorter the distance between the origin and the pigment band relative to other pigments. Therefore, chlorophyll b molecules are the most polar.

Molecules of which of the following pigments are the most polar or contain the most polar groups? A. carotene B. xanthophyll C. chlorophyll a D. chlorophyll b

D. All available niches on the mainland were long ago filled by species that, over millions of years, became highly specialized for their niches. Whereas the woodpecker finch is well adapted for seeking insects on the Galápagos Islands, various species of woodpeckers are even more specialized for the same purpose on the mainland. Had an actual woodpecker found its way to the Galápagos Islands before the adaptive radiation of finches, evolution of the woodpecker finch would have been unlikely.

More than a dozen species of Darwin's finches with various specialized adaptations inhabit the Galápagos Islands. Each species possesses a specialized adaptation for obtaining food. Why is it that similar adaptations do not exist among the finches of the South American mainland, the presumed origin of the Galápagos finch ancestor? A. The various foods available on the mainland are different than those on the Galápagos Islands. B. South American predators limited evolution of the mainland finch. C. Reproductive isolation is not possible on the mainland. D. The available niches that the Darwin's finches exploited on the Galápagos Islands were already occupied by other species of birds on the mainland.

(B) Resistance to a certain chemical arises because exposure to the chemical kills all the insects except the ones that are already resistant to it. The resistant population is selected for in this way and reproduces a new population in which all the individuals are resistant.

Mosquitoes resistant to the pesticide DDT first appeared in India in 1959 within 15 years of widespread spraying of the insecticide. Which of the following statement best explains how the resistant mosquitoes arose? A. Some mosquitoes experienced a mutation after being exposed to DDT that made them resistant to the insecticide. Then their population expanded because these moquitoes had no competition. B. Some mosquitoes were already resistant to DDT when DDT was first sprayed. Then their population expanded because all the susceptible mosquitoes had been exterminated. C. DDT is generally a very effective insecticide. One can only conclude that it was manufactured improperly. D. Although DDT is effective against a wide range of insects, it is not effective against mosquitoes.

C. It is important that cells have a large surface area relative to their volume in order to maximize the ability of cells to import necessary nutrients and export wastes. The greater the surface area is, the greater the area for carrying out these processes. A large cell may not have enough surface area to accommodate the transport needs of the cell. Another limitation to cell size is the genome-to-volume ratio. The genome of a cell (the cell's genetic material or chromosomes) remains fixed in size and fixed in its ability to control the activity of the cell (by producing RNA, which in turn produces proteins). The genome may not be able to accommodate the protein (and enzyme) needs of a large cell.

Most animal cells, regardless of species, are relatively small and about the same size. Relative to larger cells, why is this? A. Smaller cells avoid excessive osmosis and subsequent lysis. B. Smaller cells have a smaller surface-to-volume ratio. C. Smaller cells have a larger surface-to-volume ratio. D. Smaller cells fit together more tightly.

B. If the proton channels associated with ATP synthase are blocked, H+ cannot move from the intermembrane space (the compartment between the inner and outer membranes) across the cristae membranes into the matrix. The expectation, then, is that H+ concentration increases in the intermembrane space.

Oligomycin is an antibiotic that blocks proton channels in the cristae of mitochondria by binding to ATP synthase. Which of the following would be the first expected response after the application of oligomycin to cells? A. Water production would increase. B. H+ would increase inside the intermembrane space (the compartment between inner and outer membranes). C. H+ would increase in the matrix (inside mitochondrial inner membrane). D. H+ would increase outside mitochondria.

(C) Allopatric isolation refers to isolation due to geographic separation. Sympatric isolation refers to isolation caused by something other than geography, such as polyploidy. These fish clearly exhibited allopatric isolation because the two populations lived in different ponds with different selective factors. The pressure for selection came from the predatory fish. After years of being separated, the two fish populations could no longer mate. Therefore, allopatric isolation brought about reproductive isolation.

On Andros Islands in the Bahamas, populations of mosquito fish, Gambusia hubbsi, colonized a series of ponds. These ponds are no longer connected. However, the environments are very similar except that some ponds contain predatory fish, while others do not. In high predation ponds, selection has favored the evolution of a body shape that enables rapid bursts of speed. In low predation ponds, another body type is favored—one that is well-suited to swim for long periods of time. When scientists brought together sample mosquito fish from the two types of ponds, they found that the females mated only with males that had the same body type as their own. Which of the following statements best describes what happened to the mosquito fish as evidenced by the mating choice in the female fish? A. Reproductive isolation caused geographic isolation. B. Reproductive isolation was not complete. C. Allopatric isolation brought about reproductive isolation. D. Sympatric isolation brought about reproductive isolation.

B

On the basis of what happens at the end of this chart, what is the most likely explanation for the population decline after point E? A. The population became too dense and it had to decline. B. There was a major environmental shift that made survival impossible for many. C. Food became scarce, leading to a major famine. D. The population had become too large.

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.

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) 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.

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 with a lower 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.

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.

B Photosynthesis requires light, carbon dioxide, and water and produces oxygen and glucose.

Photosynthesis requires A. glucose, light, CO2 B. light, CO2, water C. water, soil, O2 D. O2, water, light

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.

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

b

Protein that prevents the binding of RNA polymerase to the promoter site. A. Enhancer B. Repressor C. Operator D. Promoter

D. The shaded amino acids have nonpolar side chains. Nonpolar side chains are hydrophobic; when these amino acids occur together, they cluster so that the side chains are facing away from the surrounding aqueous solution.

Question below refers to the following diagram of a fragment of a protein. Each amino acid is shown with its R group (side chain) indicated by an R. Amino acids with polar, acidic, or basic side chains are white, while amino acids with nonpolar side chains are shaded. The arrangement of the shaded amino acids illustrates how A. hydrogen bonding between amino acid side groups contributes to the secondary structure of the protein B. ionic bonding between amino acid side groups contributes to the secondary structure of the protein C. amino acids with nonpolar side chains contribute to the formation of a helix D. the hydrophobic response of amino acid side chains contributes to the tertiary structure of the protein

D. The circles show the primary amino acid sequence (amino acid names and their sequential order) and the α-helices (as the protein passes through the membrane) illustrate the protein's secondary structure (hydrogen bonding between amino acids). Tertiary structure describes interactions of the hydrophobic and hydrophilic side groups of the amino acids (as shown by the aggregation of hydrophobic side groups with adjacent membrane phospholipids and the folding of the protein inside and outside of the membrane), hydrogen bonding or ionic bonding between side groups (as shown by protein folding), and disulfide bonds of cysteine (none occur in this protein). Because glycophorin is a protein that consists of two separate polypeptide strands, it is a protein with quaternary structure.

. The protein shown in the figure illustrates characteristics of which levels of protein structure? A. only primary structure B. only primary and secondary structures C. only primary, secondary, and tertiary structures D. primary, secondary, tertiary, and quaternary structures

D-Habituation is the loss of responsiveness to unimportant stimuli or stimuli that do not provide appropriate feedback. This is a prime example of habituation

A baby duck runs for cover when a large object is tossed over its head. After this object is repeatedly passed overhead, the duck learns there is no danger and stops running for cover when the same object appears again. This is an example of A. imprinting. B. fixed-action pattern. C. agonistic behavior. D. habituation.

D If the contents of the cell separated from the cell wall, then water was moving out of the cell. This would cause the space between the cell wall and the cell membrane to expand, so eliminate (B). This also means that the concentration of solutes in the extracellular environment would be hypotonic with respect to the cell's interior, which is why (D) is the correct answer. You can eliminate (C) because the vacuole is within the cell; it contains a solution with a much lower osmotic pressure than that of the sugar solution. Lastly, eliminate (A): Because the fluid in the cell was hypertonic to the sugar solution, fluid was moving out of the vacuole and caused it to become smaller.

A cell from the leaf of the aquatic plant Elodea was soaked in a 15 percent sugar solution, and its contents soon separated from the cell wall and formed a mass in the center of the cell. All of the following statements are true about this event EXCEPT A. the vacuole lost water and became smaller B. the space between the cell wall and the cell membrane expanded C. the large vacuole contained a solution with much lower osmotic pressure than that of the sugar solution D. the concentration of solutes in the extracellular environment is hypertonic with respect to the cell's interior

D-The experiments are very well represented on the AP Biology exam, and you should read this chapter carefully and learn how to design and interpret experiments.

A cell is placed into a hypertonic environment and its cytoplasm shrivels up. This demonstrates the principle of A. diffusion. B. active transport. C. facilitated diffusion. D. plasmolysis.

D This question tests your ability to associate what happens when enzymes are denatured and what would happen in the synaptic cleft. Acetylcholinesterase is an enzyme that degrades acetylcholine in the synaptic cleft. If acetylcholinesterase is denatured, acetylcholine will still be released from the presynaptic membrane and continue to diffuse across the synaptic cleft and bind to the postsynaptic membrane because acetylcholine is not degraded.

A chemical agent is found to denature all enzymes in the synaptic cleft. What effect will this agent have on acetylcholine? A. Acetylcholine will not be released from the presynaptic membrane. B. Acetylcholine will not bind to receptor proteins on the postsynaptic membrane. C. Acetylcholine will not diffuse across the cleft to the postsynaptic membrane. D. Acetylcholine will not be degraded in the synaptic cleft.

D-It is important to try to measure only one variable at once. The 18 slugs may have moved to the higher-temperature, higher-salinity conditions because they need high temperatures to survive, even if they dislike high salinity, and vice versa. The original experiment circumvents this problem by giving a choice for all the possible combinations of variables. Answer E is an interesting issue, but two individuals is probably too small a number to warrant throwing away the study results.

A classmate has set up a similar experiment in the following manner: Of the 20 slugs that she puts in her tray, 18 move to the high-salinity, high-temperature section within one hour, while the other 2 move to the low-salinity, low-temperature section. She concludes that slugs prefer conditions of high salinity and temperature. What is wrong with this conclusion? A. She didn't specify what the two temperatures or salinities were. B. The slugs may not have been able to move where they wanted. C. Crowding may have affected the behavior of the slugs, causing the 2 others to move to the other section. D. She is measuring two variables at once with no control, and therefore can't conclude anything about slug tastes.

C Amino acids are organic molecules that contain carbon, hydrogen, oxygen, and nitrogen, so eliminate (A), (B), and (D). Don't forget to associate amino acids with nitrogen because of the amino group (NH2).

A feature of amino acids NOT found in carbohydrates is the presence of A. carbon atoms B. oxygen atoms C. nitrogen atoms D. hydrogen atoms

C-The example to know is the cattle egrets that feast on insects aroused into flight by cattle grazing in the insects' habitat. The birds benefit because they get food, but the cattle do not appear to benefit at all.

A form of species interaction in which one of the species benefits while the other is unaffected is called A. parasitism. B. mutualism. C. commensalism. D. symbiosis.

(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.

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.

B A heterotroph obtains its energy from organic molecules. An autotroph obtains energy from sunlight utilizing pigments such as chlorophyll, and uses CO2 and water to make organic molecules. Therefore, (A) and (C) can be eliminated. Heterotrophs can obtain their energy from ingesting autotrophs, but they can also consume other heterotrophs.

A heterotroph A. obtains its energy from sunlight, harnessed by pigments B. obtains its energy by oxidizing organic molecules C. makes organic molecules from CO2 D. obtains its energy by consuming exclusively autotrophs

D The mean weight of the offspring in the next generation will be heavier than the mean weight of the original population because all the lighter horses in the original population died off. The normal distribution for weight will therefore shift to the heavier end (to the right of the graph).

A large island is devastated by a volcanic eruption. Most of the horses die except for the heaviest males and heaviest females of the group. They survive, reproduce, and perpetuate the population. Since weight is highly heritable and the distribution of weights approximates a binomial distribution, the offspring of the next generation would be expected to have A. a higher mean weight compared with their parents B. a lower mean weight compared with their parents C. the same mean weight as members of the original population D. a higher mean weight compared with members of the original population

C-This is a classic example of Batesian mimicry.

A lizard lacking a chemical defense mechanism that is colored in the same way as a lizard that has a defense mechanism is displaying A. aposometric coloration. B. cryptic coloration. C. Batesian mimicry. D. Müllerian mimicry.

C-Even though an amino acid doesn't have direct contact with the substrate, it still plays a role in the overall shape of the enzyme.

A mutation in a bacterial enzyme changed a previously polar amino acid into a nonpolar amino acid. This amino acid was located at a site distant from the enzyme's active site. How might this mutation alter the enzyme's substrate specificity? A. By changing the enzyme's pH optimum B. By changing the enzyme's location in the cell C. By changing the shape of the protein D. An amino acid change away from the active site cannot alter the enzyme's substrate specificity.

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.

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.

D-Low numbers of stomata help to reduce water loss, helpful in hot and dry regions.

A new plant was discovered and determined to have an unusually low number of stomata on the undersides of its leaves. For what environment would this plant most likely be best adapted? A. Cold and rainy B. Humid and sunny C. Hot and humid D. Hot and dry

D Tropism describes the reaction of plants to a stimulus. Gravitropism specifies a reaction to gravity, and negative specifies that the reaction is away from the stimulus.

A plant grows in the opposite direction of the gravitational force. This is an example of A. positive thignotropism B. negative phototropism C. positive phototropism D. negative gravitropism

C-Exergonic reactions give off energy, and hydrolysis reactions are reactions that use water to break apart a compound. Redox reactions are reactions that involve the movement of electrons. Dehydration reactions are reactions that bring two molecules together, releasing water as a product.

A reaction that includes energy as one of its reactants is called a(n) A. exergonic reaction. B. hydrolysis reaction. C. endergonic reaction. D. redox reaction.

C

A researcher conducts a survey of a biome and finds 35 percent more species than she has found in any other biome. Which biome is she most likely to be in? A. Tundra B. Tiaga C. Tropical rainforest D. Temperate deciduous forest

(D) The action potential is an all-or-nothing response. It either happens or it does not. It doesn't change strength. With a stronger stimulus, only the frequencies of the response increases. The axon does not become hyperpolarized; it depolarizes. If the axon at rest is at -90 mV, the hyperpolarization will measure at -100 mV, for example, not at 50 mV.

A researcher is experimenting with nerve transmission using neurons from a giant squid. At the beginning of the experiment, the axon is at rest and has a threshold measured at -70 mV at 37oC. The axon receives one stimulus that triggers one action potential in the axon. Subsequent stimuli are much stronger. Which of the following statements explains what happens when several strong stimuli are experienced by the axon? A. The axon becomes hyperpolarized to -90 mV. B. The axon becomes hyperpolarized to -50 mV. C. The strength of the action potential becomes greater. D. The frequency of the action potential increases.

B. The signaling molecule, or ligand, is epinephrine. It initiates the signal transduction pathway when it binds to the G protein-coupled receptor. At the end of the pathway, a protein kinase (PKA) is activated which, in turn, activates the binding of an ATP to the CFTR protein, opening its gated Cl- channel.

A signal molecule for this signal transduction pathway is A. CFTR B. epinephrine C. GTP D. adenylyl cyclase

B. In a signaling cascade, the first activated protein kinase is able to activate multiple copies of the second protein kinase. Then, each copy of the second protein kinase is able to activate multiple copies of the third. Because each protein kinase functions repeatedly until it is dephosphorylated, each step of the cascade magnifies the response.

A signaling cascade is illustrated by protein kinase 1, protein kinase 2, protein kinase 3, and MAP. What purpose does this cascade serve? A. The cascade makes the target of the signal more specific. B. The cascade amplifies the signal. C. The cascade reduces the necessary activation energy for the overall reaction. D. The cascade generates the necessary energy for activating transcription.

D-The volume of the container is not a major factor that affects enzyme efficiency.

A student conducts an experiment to test the efficiency of a certain enzyme. Which of the following protocols would probably not result in a change in the enzyme's efficiency? A. Bringing the temperature of the experimental setup from 20°C to 50°C B. Adding an acidic solution to the setup C. Adding substrate but not enzyme D. Placing the substrate and enzyme in a container with double the capacity

B-When the body has too little water, ADH works to increase the amount of water available. This drive to maintain a stable condition is an example of homeostasis.

ADH is a hormone secreted by the kidneys that reduces the amount of water excreted in the urine. ADH is released in times of dehydration. This is an example of A. innate behavior. B. maintaining homeostasis. C. failure to respond to the environment. D. positive feedback.

D. The plot representing a higher than normal acid environment (which is a lower than normal pH, or in this graph, pH = 7.2), is below the plot representing a normal pH (pH = 7.4). The lower curve corresponds with lower hemoglobin saturation. Be extra careful with questions that have pH or acid/base information. Make notes on the test indicating which pH is acid and which is basic.

According to the graph, which of the following correctly describes the activity of hemoglobin in a higher than normal acid environment? A. Hemoglobin is unable to release oxygen. B. Hemoglobin releases less oxygen to the tissues. C. Oxygen saturation of hemoglobin is higher. D. Oxygen saturation of hemoglobin is lower.

A. As PO2 increases (moves to the right on the graph), hemoglobin saturation also increases (moves up on the graph). Note that the graph does not tell you anything about cause and effect—which quantity causes an effect in the other quantity. It's possible that they both increase together for unrelated reasons.

According to the graph, which of the following is correct? A. Hemoglobin saturation increases as increases. B. Blood pH decreases as increases. C. Hemoglobin saturation increases as blood pH decreases. D. Blood pH has no effect on oxygen saturation of hemoglobin.

B The event that had to occur before oxygen filled the atmosphere was that autotrophs, which make their own food and give off oxygen, had to evolve.

According to the heterotroph hypothesis, which event had to occur before oxygen filled the atmosphere? A. Heterotrophs had to remove carbon dioxide from the air. B. Autotrophs, which make their own food, had to evolve. C. Heterotrophs had to evolve. D. Autotrophs had to convert atmospheric nitrogen to nitrate.

(B) Whenever a pump is involved, the mechanism is active transport. Glucose is always transported by either simple diffusion or facilitated diffusion. However, neither process requires the expenditure of energy. Choices C and D refer to passive transport.

Active transport involves the movement of a substance across a membrane against its concentration or electrochemical gradient. Active transport is mediated by specific transport proteins and requires the expenditure of energy. Which of the following statements describes an example of active transport? A. Glucose is transported across some membranes by carrier proteins down a concentration gradient. B. Freshwater protists such as amoeba and paramecia have contractile vacuoles that pump out excess water. C. Countercurrent exchange in the capillaries of fish gills enables fish to absorb large amounts of oxygen from the surrounding water where oxygen levels are low. D. A red blood cell will lyse (burst) if placed into a hypotonic solution because large amounts of water flood into the cell.

(B) Uric acid is the nonsoluble nitrogen waste, not urea. Ammonia is the most toxic nitrogen waste, not urea.

African lungfish often live in small, stagnant, freshwater pools. With reduced gills, they differ from other fish in that they breathe air. They also differ in that they release the nitrogen waste urea instead of ammonia. Which of the following statements correctly explains how this is an advantage for lungfish? A. Urea is insoluble in water and sinks to the bottom of the small pools. Thus the poisonous substance is isolated from the fish. B. Ammonia, which is highly toxic, would endanger lungfish that inhabit the small pools. C. Other fish in the small pools can use urea as an energy source. D. The highly toxic urea makes the pool uninhabitable to competitors.

A-Water will flow out of the bag because the solute concentration of the beaker is hypertonic compared to the dialysis bag. Osmosis passively drives water from a hypotonic region to a hypertonic region.

After the bag has been sitting in the beaker for a while, what would you expect to have happened to the bag? A. There will have been a net flow of water out of the bag, causing it to decrease in size. B. There will be have been a net flow of water into the bag, causing it to swell in size. C. The bag will be the exact same size because no water will have moved at all. D. The solute will have moved out of the dialysis bag into the beaker

A Both prokaryotes and eukaryotes possess double-stranded DNA. Choices (B), (C), and (D) are correct differences between prokaryotes and eukaryotes.

All of the following are differences between prokaryotes and eukaryotes EXCEPT A. eukaryotes have linear chromosomes, while prokaryotes have circular chromosomes B. eukaryotes possess double stranded DNA, while prokaryotes possess single stranded DNA C. eukaryotes process their mRNA, while in prokaryotes, transcription and translation occur simultaneously D. eukaryotes contain membrane-bound organelles, while prokaryotes do not

D If potential mates have similar breeding seasons they will most likely mate. Use common sense to eliminate the other answer choices. If the organisms don't meet, they won't reproduce; eliminate (A). Also eliminate (B) and (C): If potential mates do not share the same behaviors (such as courtship rituals), they may not mate.

All of the following are examples of events that can prevent interspecific breeding EXCEPT A. the potential mates experience geographic isolation B. the potential mates experience behavioral isolation C. the potential mates have different courtship rituals D. the potential mates have similar breeding seasons

D All of the choices are examples of hydrolysis except the conversion of pyruvic acid to glucose. Hydrolysis is the breaking of a covalent bond by adding water. In all of the correct examples, complex compounds are broken down to simpler compounds. The conversion of pyruvic acid to acetyl CoA is an example of decarboxylation—a carboxyl group is removed as carbon dioxide and the 2-carbon fragment is oxidized.

All of the following are examples of hydrolysis EXCEPT A. conversion of fats to fatty acids and glycerol B. conversion of proteins to amino acids C. conversion of starch to simple sugars D. conversion of pyruvic acid to acetyl CoA

D The sympathetic division is active during emergency situations. This leads to a decrease in peristalsis in your gastrointestinal tract. (Your stomach shuts down.) Stimulation of the sympathetic nervous system leads to (A), pupils dilating, (B), peripheral blood vessels constricting, and (C), sweating.

All of the following are stimulated by the sympathetic nervous system EXCEPT A. dilation of the pupil of the eye B. constriction of blood vessels C. increased secretion of the sweat glands D. increased peristalsis in the gastrointestinal tract

D. In this experiment, time is an independent variable and respiratory rate is the dependent variable. Temperature is also an independent variable, but this variable was assigned two values (10°C and 25°C) for the purpose of examining how temperature affects respiratory rate over time. But within each chamber, the temperature must be constant (either 10°C or 25°C). Only time and respiratory rate are allowed to vary. Since respiratory rate is indirectly measured by changes in the quantity of oxygen consumed, the amount of oxygen in each chamber is allowed to change. Note that KOH was added to the animal chambers to absorb any CO2 produced, thus maintaining a constant amount of CO2 in the chambers.

All of the following must remain unchanged during data collection EXCEPT: A. atmospheric pressure B. the volume of the animal chamber C. the amount of CO2 in the animal chamber D. the amount of oxygen in the animal chamber

C All of the listed organs secrete digestive enzymes except the gall bladder. The gall bladder stores and secretes bile produced by the liver, which is an emulsifier, not an enzyme. The mouth, (A), secretes salivary amylase. The stomach, (B), secretes pepsin. The small intestine, (D), secretes protease.

All of the following organs in the digestive system secrete digestive enzymes EXCEPT the A. mouth B. stomach C. gall bladder D. small intestine

B The respiratory rate in humans will be affected by an increase in the amount of CO2 and a drop in pH levels, which is the same as an increase in hydrogen ion levels. Strenuous exercising will also modify the respiratory rate. O2 concentration generally does not play an important role in regulating respiration

All of the following play an important role in regulating respiration in humans EXCEPT A. an increase in the amount of CO2 in the blood B. a decrease in the amount of O2 in the blood C. a decrease in the plasma pH level D. strenuous exercise

B Insulin decreases the level of blood glucose by increasing the storage of glycogen in muscles. The other hormones are correctly paired with their respective function.

All of the following statements are true EXCEPT A. thyroxine increases the rate of metabolism B. insulin decreases storage of glycogen C. vasopressin stimulates water reabsorption in the kidney D. epinephrine increases blood sugar levels and heart rate

D Hydrophobic means "water fearing," so water cannot be a hydrophobic solvent. Water is a polar solvent; it contains both negatively and positively charged ends that can form hydrogen bonds with other polar substances. Water can break up into H+ and OH- ions.

All of the following statements describe the unique characteristics of water EXCEPT A. it is a polar solvent B. it forms hydrogen bonds with disaccharides C. it can dissociate into hydrogen ions and hydroxide ions D. it is a hydrophobic solvent

A. In cellular respiration, glucose is broken down and energy is extracted and stored in NADH, FADH2, and ATP. During the oxidative phosphorylation stage of respiration, electrons from NADH (and FADH2) enter the electron transport chain (ETC) in the mitochondrion inner membrane. As this occurs, protons (H+) move across the membrane from the matrix into the intermembrane space, generating a proton gradient. At the end of the ETC, the electrons combine with a proton and oxygen to form H2O. In contrast, the electrons in photosynthesis originate in H2O from inside the thylakoids of chloroplasts and enter an ETC chain in the thylakoid membrane. As the electrons pass along the ETC, protons move into the thylakoids from the stroma, generating a proton gradient. At the end of the ETC, the electrons combine with NADP+ and a proton (H+) to form NADPH. Ultimately, the NADPH is used to generate glucose. For both respiration and photosynthesis, electrons pass through an ETC and generate a proton gradient. But for the origins and endpoints of the electrons involved, the two processes are the reverse of one another.

Question below refers to the following figure that shows portions of a mitochondrion and a chloroplast. A chemiosmotic gradient is generated in both cellular respiration and photosynthesis. The gradient is generated as electrons pass along an electron transport chain in membranes of mitochondria and chloroplasts. Which of the following correctly describes the origin of these electrons as they enter the electron transport chain and the endpoint when they leave the electron transport chain? A. For respiration, electrons originate from NADH and end in H2O; for photosynthesis, electrons originate from H2O and end in NADPH. B. For respiration, electrons originate from H2O and end in NADH; for photosynthesis, electrons originate from NADPH and end in H2O. C. For both respiration and photosynthesis, electrons originate from NADH or NADPH and end in H2O. D. For respiration, the electrons originate from glucose, and for photosynthesis, the electrons originate from CO2; for both photosynthesis and respiration, the electrons end in ATP.

(B) This equation shows cellular respiration. The definition of reduction is the gain of electrons or hydrogen. Free oxygen on the left side of the equation exists by itself, but on the right side it has combined with hydrogen. Also, remember that during cellular respiration, oxygen combines with protons and electrons during oxidative phosphorylation.

Referring to the simplified reaction of cellular respiration shown here, which of the following statements is correct? C6H12O6 + 6O2 → 6CO2 + 6H2O + energy A. C6H12O6 is reduced. B. O2 is reduced. C. CO2 is reduced. D. H2O is reduced.

B In meiosis, the sister chromatids separate during the second metaphase of meiosis (Meiosis II), whereas the sister chromatids separate during metaphase of mitosis.

Regarding meiosis and mitosis, one difference between the two forms of cellular reproduction is that in meiosis A. there is one round of cell division, whereas in mitosis there are two rounds of cell division B. separation of sister chromatids occurs during the second division, whereas in mitosis separation of sister chromatids occurs during the first division C. chromosomes are replicated during interphase, whereas in mitosis chromosomes are replicated during prophase D. spindle fibers form during prophase, whereas in mitosis the spindle fibers form during metaphase

(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.

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.

(B) When orcas moved into the area, the population of sea otters declined. This caused the population of sea urchins to increase and, ultimately, the kelp population to decline.

Sea otters in the North Pacific are a keystone species. That means they are not abundant in a community. However, they do exert major control over other species in the community. Here is a food chain in which the sea otter is a keystone species. Kelp → Sea urchin → Sea otter → Orca Here are two graphs showing the populations of sea otters and sea urchins from 1970 to 2000. In the late 1990s, orcas, which are active hunters of sea otter, moved into the area. Which of the following graphs correctly shows the kelp population from 1970 to 2000?

c

Short sequence by promoter that assists transcription by interacting with regulatory proteins. A. Enhancer B. Repressor C. Operator D. Promoter

c

Similar evolutionary changes occurring in two species that can be related or unrelated. A. Divergent evolution B. Convergent evolution C. Parallel evolution D. Coevolution

C

Some animals have patterns that can cause a predator to think twice before attacking. A. Aposomatic coloration B. Batesian mimicry C. Deceptive markings D. Cryptic coloration

A. When the stomata are open, water diffuses out of the leaf. At the same time, CO2, required for photosynthesis, diffuses into the leaf. CO2 diffuses into a leaf much slower than H2O exits because H2O concentration is usually much higher inside the leaf than outside; there is a steep H2O concentration gradient, promoting relatively rapid diffusion of water out of the leaf. In contrast, the low CO2 concentration in the atmosphere generates a small concentration gradient and a slow diffusion rate for CO2 into the leaf. In addition, a CO2 molecule is larger than H2O and, as a result, diffuses more slowly.

Stomata allow gases, such as H2O and CO2, to exchange between the inside of a plant leaf and the surrounding environment. Which of the following occurs under normal daytime environmental conditions? A. H2O diffuses out of the leaf faster than CO2 enters. B. H2O diffuses out of the leaf slower than CO2 enters. C. CO2 diffuses out of the leaf faster than H2O enters. D. H2O exchanges with CO2 at equal rates.

(B) Rain forests are responsible for the cycle of rain, absorption of water by roots, transpiration from leaves, cloud formation, and rain again. Without trees to absorb and evaporate water, the region will dry up and perhaps become a desert under a hot sun.

Stretching out from the equator is a wide belt of tropical rain forests that are being cut down to provide exotic woods for export to the U.S. and to make land available to graze beef cattle. Which of the following statements is a negative consequence of clear-cutting the tropical rain forests? A. Indigenous populations will have access to modern conveniences. B. There will be less precipitation in those clear-cut areas. C. U.S. markets will have access to less expensive beef. D. Deforestation will allow more sunlight to penetrate areas that were kept dark by dense vegetation.

B. The sweat of individuals with cystic fibrosis is salty because it contains high amounts of Cl- and Na+. In the sweat-producing cells of normal individuals, Cl- is reabsorbed by CFTR. So in sweat-producing cells with a mutated form of the CFTR protein, the movement of Cl- by the CFTR protein must be in the opposite direction as to its movement in epithelial cells of the lungs. As a result, in sweat glands that express a mutated form of the CFTR protein, Cl- does not return to cells and remains in the sweat. Answer choices A and C are incorrect because both would result in decreasing the amount of Cl- or Na+ in sweat—opposite to that occurring in individuals with cystic fibrosis. Answer choice D is incorrect because cystic fibrosis is caused by mutations of the gene that code for CFTR, not the G protein-coupled receptor.

Sweat is produced by cells of the sweat glands and transported to the skin surface through ducts. The sweat of individuals with cystic fibrosis is very high in salt (NaCl), so much so that sweat is analyzed for its Cl- content as a test for cystic fibrosis. This can best be explain by A. a failure of the CFTR protein to allow the flow of Cl- into ducts of the sweat glands B. a failure of the CFTR protein to reabsorb Cl- from sweat after the sweat is secreted into the ducts C. a failure of the Na+/K+ pump to allow Na+ to pass through ducts D. a failure of the G protein-coupled receptor to respond to the signaling molecule

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.

Testosterone level in this population may be an example of A. adaptive radiation. B. an adaptation. C. divergent selection. D. development.

A The Krebs cycle occurs in the mitochondrial matrix. Don't forget to review the site of each stage of aerobic respiration. Glycolysis, the first step in aerobic respiration, occurs in the cytoplasm. The electron transport chain occurs along the inner mitochondrial membrane. Oxidative phosphorylation occurs as protons (H+ ions) move from the intermembrane space to the mitochondrial matrix.

The Krebs cycle in humans occurs in the A. mitochondrial matrix B. inner mitochondrial membrane C. outer mitochondrial membrane D. intermembrane space

A. The Rf value is the ratio of the distance traveled by a pigment to the distance traveled by the solvent.

The Rf value of a pigment is the ratio of the distance traveled by a pigment to the distance traveled by the solvent. Which pigment has the greatest Rf value? A. carotene B. xanthophyll C. chlorophyll a D. chlorophyll b

B. Carbon dioxide combines with water, forming HCO3- and H+. The increase in concentration of H+ makes the BTB solution acidic, causing a blue solution of BTB to turn yellow.

The addition of carbon dioxide (CO2) to BTB has which of the following effects? A. It causes the BTB solution to become basic. B. It increases the concentration of hydrogen ions (H+) in the BTB solution. C. It turns BTB green. D. It has no effect on the BTB solution.

(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.

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.

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.

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

B

The bold line that point C intersects is known as the A. biotic potential. B. carrying capacity. C. limiting factor. D. maximum attainable population.

D Because the brain is destroyed, it is not associated with the movement of the leg. Choice (A) is incorrect, as reflex actions are automatic. Choices (B) and (C) can also be eliminated; both of these statements are true but are not supported by the experiment.

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.

C This is an example of mutualism. Both organisms benefit. Choice (A), parasitism, is an example of a symbiotic relationship in which one organism benefits and the other is harmed. Choice (B), commensalism, is when one organism benefits and the other is unaffected. Choice (D), endosymbiosis, is the idea that some organelles originated as symbiotic prokaryotes that live inside larger cells.

The calypso orchid, Calypso bulbosa, grows in close association with mycorrhizae fungi. The fungi penetrate the roots of the flower and take advantage of the plant's food resources. The fungi concentrate rare minerals, such as phosphates, in the roots and make them readily accessible to the orchid. This situation is an example of A. parasitism B. commensalism C. mutualism D. endosymbiosis

B. Each plot shows the accumulation of oxygen consumption as time passes. The slopes of the plots represent the rates of oxygen consumption (changes in O2 with time, expressed as ml ⋅ g-1 ⋅ min-1, or ml/g • min). Because the slopes are constant (nearly straight lines), the respiratory rates are constant, but differ for the two temperatures. Oxygen production is recorded in ml/g, which means the amount of oxygen produced, in milliliters, is divided by the weight, in grams, of the hamster. As a result, oxygen production by hamsters with different sizes is averaged over their weights. Although these hamsters may indeed have different respiratory rates (due to size or even physiological differences), these differences are not detectable in the reported data.

The data in the graph above are consistent with which of the following conclusions? A. As time progresses, respiration rate increases in hamsters. B. The rate of respiration for hamsters increases with increases in environmental temperature. C. Temperature increases with increases in the weights of hamsters. D. The larger the hamster, the greater its rate of respiration.

(C) In order for transcription of a gene or genes to occur, RNA polymerase must bind to a promoter. In Choices A and B, the repressor is bound to the operator, which excludes RNA polymerase from binding to the promoter and prevents transcription. Choice D does not make any sense because RNA polymerase does not bind to the operator. It's a matter of specificity, like a lock and key.

The disaccharide lactose is available to E. coli in the human colon if the host drinks milk. Digestion of lactose into glucose and galactose begins with the hydrolysis of lactose by the enzyme β-galactosidase, which is encoded by gene Z in the lac operon. Which of these diagrams correctly depicts the lac operon when lactose is being utilized?

D. Because there is a finite amount of NAD+ in the cytoplasm, glycolysis would stop once all of the NAD+ is converted to NADH. In the presence of oxygen, there would always be enough NAD+ because NADH is converted back to NAD+ during oxidative phosphorylation, when electrons from NADH are used to generate ATP from ADP. But when oxygen is absent, as it is during fermentation, oxidative phosphorylation (and cellular respiration) cannot occur because oxygen is not available as the final acceptor of the electrons in the electron transport chain. Under conditions where oxygen is absent, then, fermentation serves to replenish the NAD+, allowing glycolysis to continue and to generate 2 ATP. Note that yeasts are fungi and do not do photosynthesis.

The end product of the alcohol fermentation pathway is the alcohol ethanol. A considerable amount of energy still remains in ethanol, yet ethanol is a waste product for the yeast cells that produce it. What, then, is the purpose of fermentation? A. Fermentation provides CO2 for photosynthesis. B. Fermentation provides CO2 for cellular respiration. C. Yeast cells excrete ethanol in order to provide a defense against invading bacteria. D. Fermentation replenishes the NAD+ necessary for glycolysis to continue.

A Positive feedback occurs when a stimulus causes an increased response. Choices (B), (C), and (D) are examples of negative feedback.

The endocrine system maintains homeostasis using many feedback mechanisms. Which of the following is an example of positive feedback? A. Infant suckling causes a mother's brain to release oxytocin, which in turn stimulates milk production. B. An enzyme is allosterically inhibited by the product of the reaction it catalyzes. C. When ATP is abundant the rate of glycolysis decreases. D. When blood sugar levels decrease to normal after a meal, insulin is no longer secreted.

C Electrons passed down along the electron transport chain from one carrier to another lose energy and provide energy for making ATP. Glucose is decomposed during glycolysis, but this process is not associated with energy given up by electrons; eliminate (A). Glucose is made during photosynthesis, so eliminate (B). NADH is are energy-rich molecule, which accepts electrons during the Krebs cycle. Therefore, (D) is incorrect as well.

The energy given up by electrons as they move through the electron transport chain is used to A. break down glucose B. make glucose C. produce ATP D. make NADH

C. Signaling molecules are small molecules that bind to larger receptor proteins embedded in the plasma membrane. In general, the binding of the signaling molecule to the receptor protein induces a change in the shape of the receptor protein. Although you do not need to know this to answer this question, the receptor protein here is a receptor tyrosine kinase (RTK) that, when activated by the signaling molecule, causes two RTKs to form a pair (dimer). Autophosphorylation follows, allowing the subsequent phosphorylation of relay proteins.

The figure shows two signaling molecules binding to a transmembrane receptor protein (shown at I). What do these signaling molecules do? A. They provide energy to the receptor molecules that will be used to activate relay proteins and cascade proteins. B. They disable a signal transduction pathway by causing two adjacent receptor proteins to lock together. C. They activate the receptor proteins, causing them to initiate a signal transduction pathway. D. They activate the receptor proteins, causing them to open a gated ion channel, allowing the passage of specific molecules across the membrane.

A-Prokaryotic and eukaryotic cells do have similar structures, the organelles in eukaryotic cells took care of having a smaller surface area-to-volume ratio, and eukaryotic cells are not able to multiply faster.

The first simple cells evolved approximately 3.5 billion years ago, followed by the more complex eukaryotic cells 2.1 billion years ago. Which of the following statements is correct? A. Eukaryotic organelles helped create separate environments for metabolic reactions, thus increasing their metabolic efficiency. B. Prokaryotic and eukaryotic cells have no structural similarities. C. The organelles in larger eukaryotic cells took care of the problems of having a larger surface area-to-volume ratio. D. Eukaryotic cells are able to multiply faster based on their more complex structure.

B. A phospholipid with an unsaturated fatty acid tail (one with one or more double covalent bonds) creates a kink in the tail that spreads adjacent phospholipids apart, making the membrane more fluid. In contrast, phospholipids with saturated fatty acids pack more closely together and make the membrane more viscous. Answer choice A is incorrect because an increase in cytosol solute concentration will help the cytosol tolerate chilling, but it will not keep the plasma membrane fluid. Answer choice C is incorrect because glucose and other sugar molecules do not occur in the plasma membrane except as attached to phospholipids (glycolipids) or to proteins (glycoproteins). Furthermore, replacing phospholipids entirely with glucose molecules would destroy the integrity of the plasma membrane. Answer choice D is incorrect because the two phospholipid layers of the plasma membrane are asymmetric, each side specific to the direction it faces. Exchanging the phospholipids from one side to the other would damage that integrity.

The fluidity of the plasma membrane can vary in response to temperature changes. For bacteria and yeast cells, which of the following would be a viable strategy to maintain homeostasis of the plasma membrane in a temperature-varying environment? A. Increase the concentration of solutes in the cytosol. B. Change the ratio of phospholipids with double covalent bonds in their tails to those without double covalent bonds in their tails. C. Replace phospholipids with glucose molecules. D. Exchange phospholipids from one side of the plasma membrane to the other.

B. The graph shows that the stomata are open during the day and closed during the night. This makes sense because stomata must be open to allow for the diffusion of CO2 into the leaf for photosynthesis. But in addition, the graph shows that the stomata are open even larger and for a longer period of time when CO2 concentrations are low. Since photosynthesis does not occur at night, CO2 is not needed, and stomata close to reduce transpiration.

The following graph plots the size of the stomatal aperture as a function of time of day for a typical plant under various environmental conditions. Three environments are investigated: normal conditions, very dry soil, and an experimentally induced low CO2 environment. Which of the following is best supported by the data presented in the graph? A. Under normal conditions, stomata are closed during the daytime and open during the nighttime. B. Stomata open in response to low CO2 concentrations in the environment. C. Stomata open in response to low H2O concentrations in the soil. D. Stomata close in response to high temperatures.

(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.

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) The definition of Hardy-Weinberg equilibrium is that the allelic frequencies will not change. If one trait becomes advantageous and the allelic frequency changes, then the population is no longer in Hardy-Weinberg equilibrium.

The frequency of a particular allele in a population of 1,000 birds in Hardy-Weinberg equilibrium is 0.3. If the population remains in equilibrium, what would be the expected frequency of that allele after 500 years? A. It will increase if the allele is favorable or will decrease if it is unfavorable for individuals in that population. B. Not enough information is provided to determine if the frequency of the allele will remain the same or change. C. The frequency of the allele will remain at 0.3 because the population is at Hardy-Weinberg equilibrium. D. The frequency of the allele will remain the same; this is an example of the bottleneck effect.

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.

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

(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.

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.

(A) Remember that operons are found in prokaryotes, not higher organisms. However, higher animals may utilize a similar mechanism. For the same reason, you must eliminate Choice B. Operons are a means of controlling transcription of genes, whereas Choice C focuses on what happens after transcription. Operons have nothing to do with the cell cycle.

The lac operon is found only in prokaryotes and consists of structural genes and a promoter and operator. Which of the following statements explains why we study the lac operon? A. It represents a principal means by which gene transcription can be regulated. B. It explains how baby mammals utilize lactose from their mothers as they nurse. C. It illustrates how RNA is processed after it is transcribed. D. It illustrates possible control of the cell cycle and may lead to an understanding of cancer.

B The largest amount of energy is available to producers. Population B is most likely composed of producers because they have the largest biomass.

The largest amount of energy is available to A. population A B. population B C. population C D. population D

(B) Oxygen is needed to attract electrons down an electron transport chain in the light-dependent reactions. Water entering the plant through the roots ultimately provides hydrogen for the Calvin cycle, but first it is needed in the light-dependent reactions. CO2 enters the plant through the stomates; it is not released by the light-dependent reactions.

The light reactions of photosynthesis supply the Calvin cycle with which of the following? A. The light reactions provide oxygen for the light-independent reactions. B. ATP and NADPH provide the power and raw materials for the Calvin cycle. C. Water entering the plant through the roots provides hydrogen directly to the Calvin cycle. D. CO2 released by the light-dependent reactions provides the raw material for the Calvin cycle.

D The liver does not break down peptides into amino acids. It performs all of the following functions: stores amino acids absorbed in the capillaries, as in (A); detoxifies harmful substances, as in (B); and makes bile, as in (C).

The liver is a vital organ that performs all of the following functions EXCEPT A. storing amino acids that were absorbed in the capillaries of the small intestine B. detoxifying harmful substances such as alcohol or certain drugs C. synthesizing bile salts that emulsify lipids D. breaking down peptides into amino acids

A. The activity of protein II is an example of facilitated transport. Since no ATP is required (as is for protein I), the transport must be passive and down a concentration gradient. In contrast, the transport of Na+ and K+ is carried out by a single cotransporter protein (the Na+/K+ pump) and transports both Na+ and K+, each against a concentration gradient, and requires ATP. In addition, the Na+/K+ pump moves Na+ out of the cell and K+ into the cell, not the other way around. Steroids traverse the plasma membrane without the assistance of protein carriers because steroids are nonpolar, and the nonpolar characteristic of the plasma membrane does not present a barrier.

The membrane protein II is most likely doing which of the following? A. transporting glucose down a concentration gradient (from a region of higher concentration to one of lower concentration) B. transporting a small hydrophilic molecule against a concentration gradient (from a region of lower concentration to one of higher concentration) C. transporting Na+ out of the cell in coordination with the transportation of K+ into the cell by membrane protein I D. transporting a steroid hormone out of the cell by active transport

B Respiration is the transport of oxygen into an organism and carbon dioxide out of an organism.

The moist skin of earthworms, spiracles of grasshoppers, and the mucus membranes lining alveoli are all associated with the process of A. excretion B. respiration C. circulation D. digestion

D. The enzymes in the lysosome are enzymatically active because the pH inside the lysosome is 5. The pH is maintained by pumping H+ ions (protons) into the lysosome by active transport proton pumps into the lysosome membrane.

The normal pH of the cytosol is about 7.2. Most enzymes in the lysosome, however, are only active at a pH of 5. This suggests that A. only acidic substances can undergo enzymatic processing in lysosomes B. most enzymes in the lysosome are incapable of catalyzing substrates inside the lysosome C. enzymes in the lysosome are released to the cytosol D. protons are actively pumped into the lysosome

B. The amino acids represented by shaded circles are inside the plasma membrane among the hydrophobic fatty acid chains of the phospholipids. As a result, that part of the protein is made up of hydrophobic amino acids, that is, amino acids with hydrophobic side groups (R groups or side chains). These side groups project outward into the fatty acids so that hydrophobic-hydrophilic incompatibilities are averted. In contrast, the amino acids that penetrate the aqueous environments of the cytosol and extracellular fluid (white circles) are dominated by amino acids with hydrophilic side groups (polar or charged side groups).

The parts of the protein represented by the shaded circles (numbers 73-95) are most likely dominated by amino acids with A. hydrophilic side groups facing the outside of the protein B. hydrophobic side groups facing the outside of the protein C. polar side groups facing the outside of the protein D. charged side groups facing the outside of the protein

(C) Carbon dioxide is a balanced and nonpolar molecule that can readily diffuse through the membrane. Starch is too large to diffuse through a membrane. Only protons pass through mitochondrial membranes.

The plasma membrane is selectively permeable and regulates what enters and leaves a cell. It consists of a phospholipid bilayer embedded with proteins. Which of the following statements about the membrane is correct? A. Carbon dioxide is a polar molecule and readily diffuses through the hydrophilic layers of the membrane. B. Starch readily diffuses across the membrane into the liver, where it is stored as glycogen. C. Aquaporins are special water channels in the plasma membrane that facilitate the uptake of large amounts of water without the expenditure of energy. D. Oxygen passes through the cristae of mitochondria mainly through ATP synthase channels.

B The primary site of glucose reabsorption is the proximal convoluted tubule. The glomerulus, (A), is a tuft of capillaries that filters fluid into the Bowman's capsule. Choice (C), the loop of Henle, is the site of salt reabsorption. Choice (D), the collecting duct, is the site in which urine is concentrated.

The primary site of glucose reabsorption is the A. glomerulus B. proximal convoluted tubule C. loop of Henle D. collecting duct

C The principle inorganic compound found in living things is water. Water is a necessary component for life.

The principle inorganic compound found in living things is A. carbon B. oxygen C. water D. glucose

B. The reaction is in equilibrium because the concentrations of reactants and product are such that the rate of the forward reaction (formation of product C) equals that of the reverse reaction (formation of A and B from C), and the net production of C (or A and B) is zero. By decreasing C, the forward reaction will again exceed that of the reverse reaction, producing more C, until equilibrium is reached again. Adding more enzyme would only help if there were a considerable excess of reactants (essentially, not enough enzyme to go around). Increasing the temperature could increase the rate of reactions (in both directions), but if the reaction is in equilibrium, the net production of product will still be zero.

The reaction A + B → C is catalyzed by enzyme K. If the reaction is in equilibrium, which of the following would allow more product C to be produced? A. removing some of reactant A B. removing some of reactant C C. adding more enzyme K D. increasing the temperature of the system

C. Once all of the available enzyme molecules are engaged with the reactants, no additional reactants can be catalyzed. As a result, the reaction rate remains constant during the interval between 6 and 9 minutes. Note that the reaction rate, the amount of product formed per unit of time, is the slope of the plotted curve (a straight line between 6 and 9 minutes).

The reaction maintains its maximum rate during the interval from 6 to 9 minutes. Which of the following best explains why the reaction is limited to the observed rate? A. The cleft formed by the active site of the enzyme is at its maximal aperture. B. The concentration of reactant J is at its maximum. C. All of the available enzyme molecules are bound to substrate molecules. D. The temperature of the reaction is at its maximum value.

A-When interbreeding ceases because some sort of barrier separates a single population into two (an area with no food, a mountain, etc.), the two populations evolve independently, and if they change enough, then, even if the barrier is removed, they cannot interbreed. This is allopatric speciation.

The relatives of a group of pelicans from the same species that separated from each other because of an unsuccessful migration are reunited 150 years later and find that they are unable to produce offspring. This is an example of A. allopatric speciation. B. sympatric speciation. C. genetic drift. D. gene flow.

D The resting potential depends on active transport (the Na+K+-ATPase pump) and the selective permeability of the axon membrane to K+ than to Na+, which leads to a differential distribution of ions across the axonal membrane.

The resting membrane potential depends on which of the following? I. Active transport II. Selective permeability III. Differential distribution of ions across the axonal membrane A. III only B. I and II only C. II and III only D. I, II, and III

A. The graph shows that the cuvette with the higher concentration of substrate (succinate) has a higher rate of respiration.

The results of the experiment indicate that the respiratory rate increases as A. the concentration of substrate increases B. the concentration of DPIP increases C. the concentration of enzyme increases D. the time increases

B The similarity suggests that humans and chimpanzees are more closely related than humans and dogs. Because these two organisms share similar amino acid sequences, humans must share more recent common ancestors with chimpanzees than with dogs.

The sequence of amino acids in hemoglobin molecules of humans is more similar to the hemoglobin of chimpanzees than it is to the hemoglobin of dogs. This similarity suggests that A. humans and dogs are more closely related than humans and chimpanzees B. humans and chimpanzees are more closely related than humans and dogs C. humans are related to chimpanzees but not to dogs D. humans and chimpanzees are closely analogous

D Muscle contractions require calcium ions, so (I) is required. You need energy order to have a muscle contraction, so (II) is required. And actin is one of the proteins involved in muscle contractions, so (III) is required. The answer is (D).

The sliding action in the myofibril of skeletal muscle contraction requires which of the following? I. Ca2+ II. ATP III. Actin A. I only B. II only C. II and III D. I, II, and III

B. The sole function of mitochondria is to carry out the same energy-generating metabolic pathway that occurs in aerobic bacteria. Similarly, the sole function of chloroplasts is to carry out the energy generating metabolic pathway that occurs in photosynthetic bacteria. In addition, all use the same molecular machinery (ATP synthase) to accomplish these processes. These observations best support the hypothesis that mitochondria and chloroplasts are derived from bacteria. The remaining answer choices do not support the observed similarities as well: eukaryotic and prokaryotic cells may share a common ancestor, but there are no observations that establish that such an ancestor used ATP synthase; convergent evolution would result in similar functions (as observed), but through different mechanisms; and there are no observations that suggest that mitochondria or chloroplasts can survive independently outside a eukaryotic cell.

The structure of ATP synthase in the plasma membranes of bacteria is nearly identical to that in the mitochondria and chloroplasts of eukaryotic cells. This similarity best supports which of the following hypotheses? A. Eukaryotic and prokaryotic cells share a common ancestor. B. Mitochondria are derived from ancient aerobic bacteria, and chloroplasts are derived from ancient photosynthetic bacteria. C. The similarity of ATP synthase in bacteria, mitochondria, and chloroplasts is an example of convergent evolution. D. Mitochondria and chloroplasts escaped from eukaryotic cells and formed aerobic and photosynthetic prokaryotes.

B This question tests your understanding of what stage is responsible for the synthesis of new proteins for lactose utilization. The region of bacterial DNA that controls gene expression is the lac operon. Structural genes will be transcribed to produce enzymes, which produce an mRNA involved in digesting lactose.

The synthesis of new proteins necessary for lactose utilization by the bacterium E. coli using the lac operon is regulated A. by the synthesis of additional ribosomes B. at the transcription stage C. at the translation stage D. by differential replication of the DNA that codes for lactose-utilizing mechanisms

d

The tandem back-and-forth evolution of closely related species, which is exemplified by predator-prey relationships. A. Divergent evolution B. Convergent evolution C. Parallel evolution D. Coevolution

C. A protein that transports a substance across the plasma membrane, either actively (like protein I) or passively (like protein II), is specific to the substance to be transported. In that way, the plasma membrane controls which substances to be transported. Furthermore, different kinds of cells have specific proteins that serve the needs of that kind of cell. Only protein I requires ATP and only protein II requires a downhill gradient. Proteins are necessary for the transport of ions and large, uncharged polar substances. But small, nonpolar (hydrophobic) substances (such as O2 and CO2) can diffuse across the membrane without the assistance of a transport protein.

The transport of a substance through both protein I and protein II A. requires ATP B. requires a gradient from higher concentration to lower concentration in the direction of transport C. requires that the membrane protein (protein I or protein II) is specific to the substance to be transported D. requires that the substance to be transported is hydrophobic

(A) If malonate is a competitive inhibitor, it competes with the enzyme (succinate dehydrogenase) for succinate. If malonate is a noncompetitive inhibitor, increasing succinate will not increase the rate of reaction because the enzyme is being inhibited by malonate.

There are two types of enzyme inhibition: competitive and noncompetitive. Competitive inhibitors compete with the substrate for one active site, while noncompetitive inhibitors bind to another part of the enzyme and alter its shape. Malonate is an inhibitor of the respiratory enzyme succinate dehydrogenase in the following reaction. Which of the following choices best describes the best way to determine whether malonate is a competitive or a noncompetitive inhibitor of succinate dehydrogenase? A. In the presence of malonate, increase the concentration of succinate, the substrate. If the rate of reaction increases, then malonate is a competitive inhibitor. B. In the presence of malonate, increase the concentration of succinate, the substrate. If the rate of reaction increases, then malonate is a noncompetitive inhibitor. C. Malonate can alternate between a competitive and noncompetitive inhibitor depending on what is required. D. A coenzyme must be affecting the rate of the reaction.

C

This biome contains plants whose roots cannot go deep due to the presence of a permafrost. A. Desert B. Tundra C. Taiga D. Deciduous forests

D

This biome contains trees that drop their leaves during the winter months. A. Desert B. Tundra C. Taiga D. Deciduous forests

D

This biome has cold winters and is known for its pine forests. A. Desert B. Tundra C. Taiga D. Deciduous forests

A

This biome is the driest of the land biomes and experiences the greatest daily temperature fluctuations. A. Desert B. Tundra C. Taiga D. Deciduous forests

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.

This enzymatic phenomenon is an example of A. transcription B. feedback inhibition C. dehydration synthesis D. photosynthesis

(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.

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.

B

This process couples the production of ATP with the movement of electrons down the electron transport chain by harnessing the driving force created by a proton gradient. A. Glycolysis B. Chemiosmosis C. Fermentation D. Calvin cycle

D

This process has as its products NADP+, ADP, and sugar. A. Glycolysis B. Chemiosmosis C. Fermentation D. Calvin cycle

A

This process leads to the net production of two pyruvate, two ATP, and two NADH. A. Glycolysis B. Chemiosmosis C. Fermentation D. Calvin cycle

A-Cholesterol is one of the lipids that serves as the starting point for the synthesis of sex hormones.

This represents the backbone of a structure that is vital to the construction of many cells and is used to produce steroid hormones.

C, p atom surrounded by o D-Purines have a double-ring structure; pyrimidines, a single-ring one. B-The ribosome is the site of protein synthesis. (OH at the end)

This structure plays a vital role in energy reactions. This structure is a purine found in DNA. This structure was synthesized in the ribosome.

D

Those being hunted adopt a coloring scheme that allows them to blend in to the colors of the environment. A. Aposomatic coloration B. Batesian mimicry C. Deceptive markings D. Cryptic coloration

B The most likely explanation for this phenomenon is that these birds have different ecological niches. An ecological niche is the position or function of an organism or population in its environment. Eliminate (A) because we do not know if there is a short supply of resources. Choice (C) can also be eliminated because we do not know how long the bird species live together. The breeding patterns of the bird species does not explain the lack of competition, which eliminates (D) as well.

Three distinct bird species, flicker, woodpecker, and elf owl, all inhabit a large cactus, Cereus giganteus, in the desert of Arizona. Since competition among these birds rarely occurs, the most likely explanation for this phenomenon is that these birds A. have a short supply of resources B. have different ecological niches C. do not live together long D. are unable to breed

D-Herbivores tend to be the primary consumers of trophic pyramids, and thus would take up the first level up from the bottom.

To which of the following labeled trophic levels would a herbivore most likely be assigned? A. A B. B C. C D. D

(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.

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.

D Cohesion, adhesion, and capillary action are special properties of water that are necessary for transpiration to occur. Water is a hydrophilic, polar molecule.

Transpiration is a result of special properties of water. The special properties of water include all of the following EXCEPT A. cohesion B. adhesion C. capillary action D. hydrophobicity

a

Two related species evolve in a way that makes them less similar. A. Divergent evolution B. Convergent evolution C. Parallel evolution D. Coevolution

b

Two unrelated species evolve in a way that makes them more similar. A. Divergent evolution B. Convergent evolution C. Parallel evolution D. Coevolution

(A) All the other choices promote outbreeding, the introduction of new genes into a population.

Unlike large populations, small populations are vulnerable to various processes that draw populations down an extinction vortex toward smaller and smaller populations until no individuals survive. Which of the following statements correctly identifies the factors that endanger a population? A. Inbreeding and loss of genetic variation threaten a population. B. Migration of new individuals into the population threatens a population. C. Mutation reduces the health of a population. D. Breeding with individuals from a different population may cause the extinction of the first population due to a decrease in diversity.

A Villi and microvilli are fingerlike projections present in the small intestine that dramatically increase the surface area available for nutrient absorption.

Villi and microvilli are present in the small intestine and aid in reabsorption by A. increasing the surface area of the small intestine B. decreasing the surface area of the small intestine C. making the small intestine more hydrophilic D. making the small intestine more hydrophobic

A

Warning coloration adopted by animals that possess a chemical defense mechanism. A. Aposomatic coloration B. Batesian mimicry C. Deceptive markings D. Cryptic coloration

(D) This region has the most consistently warm temperature and the highest precipitation.

Water climate diagrams summarize the climate for a region. Average temperature is shown on the left axis, precipitation on the right axis, and months of the year on the x-axis. Assuming that a major limiting factor for plant growth is availability of water, choose the graph below that depicts the region with the best conditions for plant growth.

D. When adenosine binds to the G protein-coupled receptor, it causes a GTP to replace the GDP attached to the inactive G protein. This exchange, a GTP for a GDP, activates the G protein. Activation causes a subunit of the G protein (Gα), together with the GTP, to bind to and activate the membrane-bound effector protein, adenylyl cyclase (AC).

What activates adenylyl cyclase (AC)? A. ATP only B. ATP and GTP C. a subunit of the G protein D. GTP bound to a subunit of the G protein

D. At some point as the temperature rises, the bonds that hold the enzyme together and maintain its three-dimensional shape break down. When the three-dimensional shape is lost, the enzyme can no longer function and is said to be denatured.

What best explains the change in the rate of reaction beyond 45°C (106°F)? A. At high temperatures, the rapid reaction rate quickly consumes all of the reactants and the reaction is completed. B. At high temperatures, the substrate becomes locked into the active site of the enzyme, preventing the binding of additional reactants. C. At high temperatures, the reactants are moving so fast that they cannot stabilize long enough to settle into the active site of the enzyme. D. At high temperatures, the secondary and tertiary structures of the enzyme are disrupted.

A. Temperature is a measure of the average kinetic energy of the molecules in a system—the higher the temperature, the greater the average kinetic energy. Kinetic energy is a measure of how fast an object is moving—the faster a molecule is moving, the greater its kinetic energy. When the temperature increases, molecules move faster, colliding more frequently with the necessary activation energy (the energy necessary for a reaction to progress to completion).

What best explains the change in the rate of reaction from 10° to 40°C (50° to 104°F)? A. With increasing temperature, more substrate molecules collide with sufficient activation energy to react. B. Because molecules expand as their kinetic energy rises, they become larger targets, increasing their chances of collisions. C. At higher temperatures, there are more enzyme molecules available to carry out the reactions. D. As the temperature rises, fewer inhibitory molecules are available to block the active site of the enzyme.

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.

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.

C. From years 3 to 8, the numbers of reported spiders on both islands with and without lizards appear to be increasing and decreasing in parallel. This suggests that some other factor (rain, drought, or temperature, for example) is affecting the number of surviving spiders from year to year. None of these factors in particular, however, can be identified with the data provided in the figure. Thus, answer choice D cannot be accepted.

What does the pattern of variation in the numbers of spiders from year 3 to year 8 on islands both with and without lizards suggest? A. Numbers of spiders have stabilized. B. Survival for spiders on islands with and without lizards is increasing. C. A factor other than lizards is contributing to the numbers of spiders reported. D. A drought is limiting the amount of food available to spiders.

B-Because thicker enamel in this species indicates foods that are more difficult to process, the answer is B. Answer E is incorrect because our model has no predictive power; if the food resources change, the enamel thickness may as well, to either a thicker or thinner average (enamel thickness could also stay the same).

What inference can you make about this species' diet? A. Its food resources are getting softer and easier to process. B. Its food resources are getting harder and more difficult to process. C. The population is growing. D. The population is shrinking.

(D) Once again, the environment provides the direction for evolutionary change. Tuna and sharks are fish; dolphins are mammals. Fish and mammals do not share a recent common ancestor.

What is the best explanation for the fact that tuna, sharks, and dolphins all have a similar streamlined appearance? A. They all share a recent common ancestor. B. They all sustained the same set of mutations. C. They acquire a streamlined body type to survive in their particular environment. D. The streamlined body has a selective advantage in that environment.

(D) The shorter the wavelength of light, the greater the penetrating power. Therefore, light with a wavelength of 550 nm has the greatest penetrating power. Light that is reflected is not absorbed.

What is the best explanation for the results in Question 61? A. 650 nm and 700 nm of light have the greatest penetrating power. B. The photosynthetic pigments in the experiment do not absorb light in the 650 nm and 700 nm range. C. Only wavelengths of 650 nm and 700 nm are reflected by the chlorophyll. D. The chloroplasts have two photosystems that absorb light in different wavelengths.

B-No physical barrier separated the two populations; this is therefore an example of sympatric, not allopatric speciation. The other answer choices are not types of speciation.

What kind of speciation does this example illustrate? A. Allopatric B. Sympatric C. Isolated D. Polyploidy

B. When light is not available to carry out photosynthesis, cellular respiration becomes the dominant metabolic process. Cellular respiration breaks down glucose to generate ATP and CO2. The blue BTB turns yellow as the solution becomes more acidic from the addition of CO2 (as observed in Reaction I in the figure). If, as in answer choice C, the Elodea plant were decaying, organisms responsible for the decay would be releasing CO2 (from respiration), not O2.

What metabolic process is responsible for the change observed in Reaction VI? A. When light exposure ends, CO2 stored in the chlorophyll of the Elodea plant is released. B. The Elodea plant is carrying out cellular respiration. C. The absence of light is causing the Elodea plant to die and to release O2 into the BTB solution. D. In the absence of light, the Calvin cycle reverses and releases CO2.

C. Light that is not absorbed is reflected. The wavelengths of light that are not absorbed in photosynthesis occur mostly in the 525 to 575 nm region. This can be seen most clearly by examining the plot for photosynthetic rate. Not coincidentally, the color of light in the 525 to 575 nm region is green, the color we see when we look at a leaf.

What wavelengths would most contribute to the composition of light reflected from a chloroplast? A. 400-450 nm B. 450-500 nm C. 525-575 nm D. 650-700 nm

(C) Oxygen and sunlight do not vary when driving from forest to grasslands. The limiting factor for plant growth is water. Less precipitation occurs in the grasslands than in the forests.

When driving from east to west in the U.S. from a forest ecosystem to grasslands, trees gradually give way to grasses. Which of the following is the critical factor responsible for this shift? A. Amount of sunlight B. Availability of oxygen C. Availability of water D. Length of growing season

C

When oxygen becomes unavailable, this process regenerates NAD+, allowing respiration to continue. A. Glycolysis B. Chemiosmosis C. Fermentation D. Calvin cycle

(C) The importance of internal organelles is that they compartmentalize the cell so that widely different reactions can all occur at the same time, each in their own space.

When the first tiny prokaryotic cell took up residence inside a larger prokaryotic cell, it heralded the advent of the eukaryotic cell and led to an explosion of new life on Earth. Since then, most cells on Earth have internal organelles. Which of the following best summarizes an advantage of having internal membranes and organelles? A. DNA can reproduce more efficiently. B. Even though prokaryotes do not have mitochondria, they contain structures that carry out the same function. C. Organelles separate specific reactions in the cell and increase metabolic efficiency. D. Compartmentalization enables prokaryotes to reproduce more quickly.

D. Although it is clear that the dissected island lizards were not eating spiders (answer choice A), that explanation does not explain why the spider populations were smaller on the islands with the introduced lizards. Instead, the lizards and spiders were competing for the same resources—food in particular. When the lizards were introduced to the islands, the amount of food available for the spiders decreased, reducing the sizes of their populations. Answer choice C suggests that the size of the spider populations declined as a result of an introduced parasite. Although that is a possible explanation, no data to specifically support this conclusion is provided. In contrast, the introductory paragraph makes it clear that spiders and lizards eat the same food.

When the researchers dissected some of the lizards, they found evidence of flies, moths, and crickets in their digestive tracts, but no spiders. How then can the data be explained? A. The lizards on these islands do not eat spiders. B. Spiders were capturing and eating lizards. C. The introduced lizards carried a parasite that infected spiders. D. Both lizards and spiders compete for the same resources.

A. Called evaporative cooling, the water left behind cools because of the energy used (heat of vaporization) to convert the evaporating water molecules from the liquid to the gaseous state.

When water evaporates from the surface of a pond, what happens to the remaining liquid water? A. The surface water cools. B. The surface water warms. C. The surface water temperature remains unchanged. D. The pH of the remaining water decreases.

(A) Prokaryotes do not have internal membranes. They do not have a defined nucleus. Instead, they have DNA in a nucleoid region. All cells carry out cellular respiration, but they do not necessarily do it in mitochondria. The surface-to-volume ratio of cells varies with the cell's size. Smaller cells have a greater surface-to-volume ratio.

Which aspects of cell structure best reveals the unity of all life? A. All cells are surrounded by a plasma membrane. B. All cells have at least one nucleus. C. All cells carry out cellular respiration in mitochondria. D. The surface-to-volume ratio of all cells is the same.

B-Line B still shows an increase in weight at 50 minutes, whereas line A has leveled out and is isotonic at 50 minutes.

Which line or lines represent bags that contain a solution that is hypertonic at 50 minutes? A. A and B B. B C. C D. D and E

A-The most water would diffuse into the most hypertonic solution; line A shows the biggest increase in weight.

Which line represents that bag with the highest initial concentration of glucose? A. A B. B C. C D. D

C-Line C showed no net change in weight, indicating the concentration of the solution inside the bag was the same (isotonic) as the solution in the beaker.

Which line represents the bag that contained a solution isotonic to the 0.5 M solution? A. A B. B C. C D. D

C. This is a drawing of a phospholipid. The phosphate group on the left forms a hydrophilic head. The two long hydrocarbon chains extending to the right are hydrophobic tails. Hydrophilic ("water loving") means that a molecule (or group of atoms) has a strong affinity for or is capable of mixing with or dissolving in water. Hydrophobic ("water fearing") means the molecule resists mixing with water.

Which molecule forms a hydrophilic head and a hydrophobic tail?

D. This polypeptide is drawn to show only its primary structure, that is, a linear display of its amino acids. The secondary, tertiary, and quaternary structures of polypeptides (proteins) illustrate the complex three-dimensional shapes that are essential for their proper functioning.

Which molecule is drawn to show only its primary structure?

B. When substances K and L are removed by subsequent reactions, the reaction J → K + L is no longer in equilibrium. As a result, more of K and L will be produced by the forward reaction (J → K + L) than that of J in the reverse reaction (K + L → J).

Which of the following actions is most likely to cause the reaction to generate additional amounts of product K and L? A. Add more of enzyme E. B. Add enzymes that will convert K and L to other substances. C. Add an enzyme that will convert J to a different molecule, M. D. Add energy to the reaction by raising the temperature of the solutions.

D The main challenge for organisms residing in hot arid environments is water loss. Long loops of Henle and storage of water in fatty tissues conserve water resources and large ears help disperse heat. Secretion is the elimination of water in the kidneys, which would not be advantageous for an organism in a dry environment.

Which of the following adaptive features would least likely be found in an animal living in a hot arid environment? A. Long loops of Henle to maximize water reabsorption B. Storage of water in fatty tissues C. Large ears to aid in heat dispersion D. Short loops of Henle to maximize water secretion

B Legume plants are able to live in nitrogen-poor soil because they obtain nitrogen from nitrogen-fixing bacteria. These plants cannot make their own proteins without nitrogen from nitrogen-fixing bacteria, so eliminate (A), (C), and (D).

Which of the following best accounts for the ability of legumes to grow well in nitrogen-poor soils? A. These plants make their own proteins. B. These plants have a mutualistic relationship with nitrogen-fixing bacteria. C. These plants are capable of directly converting nitrogen gas into nitrates. D. These plants do not require nitrogen to make plant proteins.

A. During the stages labeled W and Y, the horizontal lines indicate that energy is being absorbed but the temperature is not changing. Instead, the absorbed energy is used to break the hydrogen bonds that hold the water molecules together, changing the physical state of the water—from solid to liquid and from liquid to gas. The energy absorbed during these periods is called the heat of fusion (for line labeled W) or the heat of vaporization (for line labeled Y).

Which of the following best describes the water during the periods indicated by W and Y as the graph progresses from left to right? A. More hydrogen bonds are breaking than forming. B. The water is not absorbing any heat energy. C. The temperature of the water is rapidly changing. D. The water is losing energy as fast as it is absorbed

D. Enzymes catalyze both forward and backward reactions. The concentrations of reactants and products determine which direction is dominant. When the reaction reaches equilibrium, each reaction in the forward direction (J → K + L) is matched by one in the reverse direction (K + L → J) and the net activity is zero.

Which of the following best explains the progress of the reaction after 15 minutes? A. The enzyme is depleted. B. All of reactant J is converted to products K and L. C. The reaction is completed and all chemical activity has ended. D. For every additional molecule of K and L generated, a molecule of K and a molecule of L combine to form a molecule of J.

D Populations can be described as the evolutionary unit because changes in the genetic makeup of populations can be measured over time. Eliminate (A), as genetic changes occur only at the individual level. Only under Hardy-Weinberg equilibrium does the gene pool remain fixed over time in a population. However, this statement does not explain why the population is the evolving unit, so (B) is incorrect. Choice (C) is true but does not address the question.

Which of the following best explains why a population is described as the evolutionary unit? A. Genetic changes can only occur at the population level. B. The gene pool in a population remains fixed over time. C. Natural selection affects individuals, not populations. D. Individuals cannot evolve, but populations can.

D. Although disease, competition, and carrying capacity each could be responsible for the decline between 18 and 30 months, no data to support these hypotheses are provided. The only answer that is supported by the provided data is that the rate of growth is zero at 18 months and 30 months.

Which of the following best supports the data presented in the graph above? A. Disease was responsible for the change in population size between 18 and 30 months. B. Competition was responsible for the change in population size between 18 and 30 months. C. The carrying capacity of the environment for this population is 1,200 individuals. D. The rate of growth is zero at 18 months and 30 months.

D. To demonstrate that there is no substance in Elodea that causes the change observed in Reaction VI, a dead plant, unable to carry out cellular respiration, can be put in a solution of BTB and kept in the dark.

Which of the following can be used to demonstrate that a metabolic activity rather than a substance stored in the Elodea plant is responsible for the change observed in Reaction VI? A. Reaction IV B. Reaction V C. Reaction VII D. a dead plant in a solution of blue BTB

A-Neutrophils are phagocytic cells of the immune system. They roam the body looking for rubbish to clear.

Which of the following cells is most closely associated with phagocytosis? A. Neutrophils B. Plasma cells C. B cells D. Memory cells

D-Cell walls are present in prokaryotes but not eukaryotic animal cells. Ribosomes and cell membranes are present in both of them. Chloroplasts and large central vacuoles are not seen in either of them. Animal cells have small vacuoles.

Which of the following characteristics would allow you to distinguish a prokaryotic cell from an animal cell? A. Ribosomes B. Cell membrane C. Chloroplasts D. Cell wall

C. Because the graph shows a decline in the sizes of spider populations only on islands where lizards were introduced, one can conclude that the introduction of lizards was responsible for that decline. Of the choices given, answer choice C provides a simple, straightforward explanation consistent with the data—that lizards were eating the spiders. Answer choice A cannot be justified because no data were presented for spider populations on habitats other than islands. Answer choices B and D suggest that spiders pursue concealment to avoid getting eaten when lizards are present, but no observations are presented to support that conclusion and the data indicate that they were being eaten in spite of any elusive behaviors.

Which of the following conclusions is best supported by the data? A. Spiders cannot escape from predators when they are confined to an island habitat. B. In the presence of predators, spiders are less likely to emerge from hiding during daylight hours. C. Where spiders and lizards coexist, sizes of spider populations are reduced by spider predation. D. Spiders avoid areas where lizards are present.

C A symbiotic relationship is a relationship among two organisms in which both benefit. Choice (A) describes parasitism, and (B) describes commensalism. Choice (D) is an example of altruistic behavior.

Which of the following describes a symbiotic relationship? A. A tapeworm feeds off of its host's nutrients causing the host to lose large amounts of weight. B. Certain plants grow on trees in order to gain access to sunlight, not affecting the tree. C. Remora fish eat parasites off of sharks; the sharks stay free of parasites, and the remora fish are protected from predators. D. Meerkats sound alarm calls to warn other meerkats of predators.

B. Water moves across a selectively permeable membrane from a region of higher water potential to a region of lower water potential. Because pure water has a water potential of zero and the potato has a water potential of less than zero, water moves into the potato across the plasma membrane. Plasmolysis would only occur if water moved in the opposite direction, out of the potato cells. When plasmolysis occurs, water leaves the vacuoles, the vacuoles collapse, cell turgor drops, and the plasma membrane shrinks and pulls away from the cell wall.

Which of the following describes the activity after the potato is immersed into the water? A. Water moves from the potato into the surrounding water. B. Water moves from the surrounding water into the potato. C. Potato cells plasmolyze. D. Solutes in the water move into the potato.

D. Pure water, with no solutes, has a water potential of zero. The presence of solutes in water or in the water of the potato cells decreases the water potential (makes it more negative). The potato, with central vacuoles filled with water containing solutes, has a negative water potential.

Which of the following describes the initial condition when the potato enters the water? A. The water potential of the pure water is negative. B. The water potential of the pure water is positive. C. The water potential of the potato is positive. D. The water potential of the potato is negative.

B Pepsin works in the stomach (not the small intestine) to break down proteins to peptides. Complete digestion occurs in the small intestine. Pancreatic lipase breaks down fats into three fatty acids and glycerol, so eliminate (A). Pancreatic amylase breaks down carbohydrates into simple sugars, so (C) can also be eliminated. Bile emulsifies lipids and makes them more accessible to lipase, so get rid of (D).

Which of the following does NOT take place in the small intestine? A. Pancreatic lipase breaks down fats to fatty acids and glycerol. B. Pepsin breaks down proteins to amino acids. C. Pancreatic amylase breaks down carbohydrates into simple sugars. D. Bile emulsifies fats into smaller fat particles.

A. When respiration is high, more CO2 is produced. As CO2 enters the blood, it diffuses into red blood cells, where the enzyme carbonic anhydrase combines the CO2 with H2O to form H+ and HCO3-. These ions return to the blood, where the increase in H+ lowers the pH (makes it more acidic). Thus, the lower plot, representing a more acidic (than normal) blood, corresponds with tissues where respiration is higher. The lower plot indicates a lower hemoglobin saturation. So this graph supports the hypothesis that more oxygen is released in tissues where respiration is high.

Which of the following hypotheses is best supported by the data presented in the graph? A. More oxygen is released by hemoglobin in tissues where respiration is high. B. Less oxygen is released by hemoglobin in tissues where respiration is high. C. Respiration is higher in tissues where pH is higher than normal. D. Respiration is lower in tissues where pH is lower than normal.

B Unlike eukaryotes, prokaryotes (which include bacteria) do not contain membrane-bound organelles. Bacteria contain circular double-stranded DNA, ribosomes, and a cell wall, so (A) and (D) are incorrect. Also eliminate (C) because bacterial cell membranes are made up of a bilipid layer with proteins interspersed.

Which of the following is NOT a characteristic of bacteria? A. Circular double-stranded DNA B. Membrane-bound cellular organelles C. Plasma membrane consisting of lipids and proteins D. Ribosomes that synthesize polypeptides

(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.

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.

C

Which of the following is a biotic factor that could affect the growth rate of a population? A. Volcanic eruption B. Glacier melting C. Destruction of the ozone layer D. Sudden reduction in the animal food resource

(C) This question focuses on the order of activity at the synapse. An electrical impulse travels down the axon, causing voltage-gated calcium channels in the presynaptic membrane to open. Calcium ions flood into the terminal branch. This causes presynaptic vesicles to fuse with the membrane and release their contents, neurotransmitter, into the synapse.

Which of the following is a direct result of depolarizing the presynaptic membrane of an axon? A. The postsynaptic cell produces an action potential. B. Synaptic vesicles fuse with the presynaptic membrane. C. Voltage-gated calcium channels in the membrane open. D. Neurotransmitter is released into the synapse.

(D) The coupling of exergonic and endergonic reactions is an important biochemical strategy. The exergonic flow of electrons in the cristae membrane of mitochondria provides the energy to pump protons across the cristae membrane and maintain a gradient.

Which of the following is an example of a coupling of an exergonic reaction with an endergonic one? A. Unicellular organisms that live in freshwater, such as amoeba, must pump out excess water using their contractile vacuoles. B. The enzyme lactase binds with lactose to produce molecules of glucose and galactose. C. Electrons escaping from chlorophyll a are replaced by those released by the hydrolysis of water. D. The flow of electrons down an electron transport chain in mitochondria powers the pumping of protons against a gradient into the outer compartment.

(C) Pioneer organisms colonize an area that is not habitable by other organisms and alter it over time in a way that makes the area habitable for other organisms. Pioneer organisms are producers, such as lichens that are symbionts—an intertwined relationship of a fungus and an algae.

Which of the following is correct about organisms that are the first to colonize a habitat undergoing ecological succession? A. They are the fiercest competitors in the area. B. They maintain the habitat as it is for their own kind. C. They change the habitat in a way that makes it more habitable for other organisms. D. They are small invertebrates.

A. The reason why one pigment moves farther than another is because it has a lower affinity for the hydrophilic, polar molecules of the chromatography paper. Conversely, the stronger the affinity between pigment and paper, the shorter the distance between the origin and the pigment band relative to other pigments. The remaining answer choices are not so much responsible for the primary separation of pigments as they are for increasing (or decreasing) the separation between bands of pigments. There are also some interactions between the pigments and the solvent, but none of the answer choices addresses this.

Which of the following is most responsible for the separation of pigments on the chromatography paper? A. the attraction of the pigment to the chromatography paper B. the speed at which the solvent moves up the chromatography paper C. the time allowed for the solvent to move up the chromatography paper D. the length of the chromatography paper

C-The other four are the four main factors that can affect enzyme efficiency.

Which of the following is not a change that would affect the efficiency of the enzyme shown above? A. Change in temperature B. Change in pH C. Change in salinity D. Increase in the concentration of the enzyme

B-Succession is an ecological process in which landforms evolve over time in response to the environmental conditions. Commensalism is when one organism benefits while the other is unaffected. Mutualism is when both organisms reap benefits from the interaction. Parasitism is when one organism benefits at the other's expense. Competition is the situation in which organisms fight for some limited resource.

Which of the following is not a form of interspecies interaction? A. Commensalism B. Succession C. Mutualism D. Parasitism

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.

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.

C. Like question 27, this question evaluates your ability to read and understand data in graphical form. According to the figure, at light intensities between 100 and 150 μmol photons/m2/sec, CO2 assimilation in shade leaves is greater than that in sun leaves. Two hypotheses are plausible: shade leaves are assimilatingmore CO2 than sun leaves because they are doing more photosynthesis than sun leaves or shade leaves are releasing less CO2 because they are doing less cellular respiration than sun leaves. This latter hypothesis occurs because under low light conditions, some cells may be doing photosynthesis while other cells may be doing cellular respiration. The hypothesis in answer choice C describes this scenario where the shade leaves are releasing less CO2 because more cells are photosynthesizing than respiring compared to sun leaves. For these leaves, apparently, shade leaves are more efficient than sun leaves under low light conditions. Answer choice A is not supported by the data because the CO2 assimilation data in the figure is independent of leaf surface area (CO2 assimilation is per m2). Answer choice B is incorrect because respiration releases CO2, the opposite of CO2 assimilation. Answer choice D contradicts the data presented in the figure, as shade leaves are more efficient than sun leaves for light intensities between 100 and 150 μmol photons/m2/sec. Therefore, only answer choice C supports one of the two plausible hypotheses that could explain the data in the figure.

Which of the following is the best hypothesis that can explain the observed differences in CO2 assimilation for leaves grown in shade and sun at light intensities between 100 and 150 μmol photons/m2/sec? A. Shade leaves have a greater surface area than sun leaves. B. At these low light intensities, high rates of respiration in leaves grown in the shade result in higher rates of CO2 assimilation than leaves grown in the sun. C. At these low light intensities, leaves grown in the shade have lower rates of respiration than leaves grown in the sun. D. At these low light intensities, the photosynthetic apparatus of leaves grown in the sun is more efficient than those grown in the shade.

A-The oxygen released by plants is produced during the light reactions of photosynthesis. The main inputs to the light reactions are water and light. Water is the source of the oxygen.

Which of the following is the source of oxygen produced during photosynthesis? A. H2O B. H2O2 C. CO2 D. CO

C-Water potential = pressure potential + solute potential. Water passively moves from regions with high water potential toward those with lower water potential.

Which of the following is true about water potential? A. It drives the movement of water from a region of lower water potential to a region of higher water potential. B. Solute potential is the only factor that determines the water potential. C. Pressure potential combines with solute potential to determine the water potential. D. Water potential always drives water from an area of lower pressure potential to an area of higher pressure potential.

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.

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. Pyruvate, the product of glycolysis, is the initial substrate for the Krebs cycle. All of the steps of the Krebs cycle that normally reduce NAD+ to NADH can also reduce DPIP if NAD+ and pyruvate are continuously provided. However, only succinate is provided, so only succinate can contribute electrons (normally for the reduction of FAD to FADH2).

Which of the following is true with respect to the availability of electrons from other steps of the Krebs cycle? A. No other steps of the Krebs cycle are involved in the reduction of electron acceptors. B. Electrons from other steps could also reduce DPIP, but the substrates for these steps are consumed before succinate is added. C. FAD is the only electron acceptor for the Krebs cycle. D. NAD+ is the only electron acceptor for the Krebs cycle.

A The biomass is the total bulk of a particular living organism. The phytoplankton population has both the largest biomass and the most energy.

Which of the following organisms has the largest biomass in this food chain? A. Phytoplanktons B. Mackerels C. Herrings D. Sharks

C Secondary consumers feed on primary consumers. If you set up a pyramid of numbers, you'll see that the herrings belong to the third trophic level.

Which of the following organisms in this population are secondary consumers? A. Sharks B. Mackerels C. Herrings D. Small crustaceans

B-The activation energy of a reaction is the amount of energy needed for the reaction to occur. Notice that the activation energy for the enzymatic reaction is much lower than the nonenzymatic reaction.

Which of the following points on the preceding energy chart represents the activation energy of the reaction involving the enzyme? A. A B. B C. C D. D

B Translation, the synthesis of proteins from mRNA, occurs in the cytoplasm. DNA replication (I) occurs in the nucleus. Transcription (II), the synthesis of RNA from DNA, occurs in the nucleus.

Which of the following processes occur in the cytoplasm of an eukaryotic cell? I. DNA replication II. Transcription III. Translation A. I only B. III only C. II and III only D. I, II, and III

B. Cohesion is the attraction between like substances. Because of the hydrogen bonding between them, water molecules stick to other water molecules, holding them together to form a vertical column in plant xylem vessels. The water molecules in the column also demonstrate adhesion, the attraction between unlike substances, when they form weak hydrogen bonds with the cellulose and other molecules in the walls of the plant vessels. This mechanism, however, helps the water column oppose the downward pull of gravity.

Which of the following properties is responsible for holding together the water molecules in a vertical column of water in xylem vessels of a plant? A. the strong adhesion property of water B. the strong cohesion of property of water C. the high heat capacity of water D. the strong cohesion property of cellulose in the xylem cell wall

A. Reaction II is a control that demonstrates that darkness does not cause a blue BTB solution to yellow. Thus, the plant, in some way, is responsible for the change.

Which of the following reactions is a control for Reaction VI? A. Reaction II B. Reaction III C. Reaction IV D. Reaction V

C. The reaction NAD+ + H+ + 2e- → NADH occurs in glycolysis as energy from pyruvate is used to attach the electrons and protons to NAD+. The result is NADH, a molecule to be used in oxidative phosphorylation (where the reverse of this reaction occurs), if oxygen is present, to generate 3 ATPs. The reverse of this reaction also occurs during anaerobic reactions. In the absence of oxygen, the Krebs cycle and oxidative phosphorylation cannot occur, and no NAD+ is released from NADH. In order to at least continue with glycolysis, where a net of 2 ATPs is generated, the NADH is converted back to NAD+ during alcohol or lactic acid fermentation, allowing glycolysis to continue.

Which of the following reactions occurs in the forward direction during glycolysis but in the reverse direction during fermentation? A. pyruvate → lactate B. pyruvate → ethanol C. NAD+ + H+ + 2e- → NADH D. ADP + P → ATP

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.

Which of the following represents the carrying capacity of the environment? A. 2 B. 3 C. 4 D. 5

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.

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 During the exponential growth phase of a population, the size doubles during each time interval. This part of the graph looks like a parabola.

Which of the following shows the exponential growth curve of the population? A. 1 B. 2 C. 3 D. 4

(D) The exergonic flow of electrons in the electron transport chain of mitochondria provides the energy to establish a proton gradient. Most CO2 released from cellular respiration comes from the citric acid cycle. Protons flow through the ATP synthase down a gradient, not by active transport.

Which of the following statements about cellular respiration is correct? A. Most CO2 produced during cellular respiration is released from glycolysis. B. Protons are pumped through ATP synthase by active transport. C. The final electron acceptor of the electron transport chain is NAD+. D. ATP is formed because an endergonic reaction is coupled with an exergonic reaction.

(C) Saturated fatty acids are linked to heart disease. Proteins make up most cell surface receptors. Steroids are lipids but are not made of glycerol and fatty acids like typical lipids.

Which of the following statements about lipids is correct? A. Unsaturated fatty acids are linked to heart disease. B. Lipids make up most cell surface receptors. C. Phospholipids are water soluble. D. Steroids are lipids that consist of glycerol and fatty acids.

C-Only photosystem I is involved in the cyclic reactions. Photosystem II is not.

Which of the following statements about photosynthesis is incorrect? A. H2O is an input to the light-dependent reactions. B. CO2 is an input to the Calvin cycle. C. Photosystems I and II both play a role in the cyclic light reactions. D. O2 is a product of the light-dependent reactions.C-Only photosystem I is involved in the cyclic reactions. Photosystem II is not.

(C) All the other choices refer to the light-independent reactions.

Which of the following statements about the light-dependent reactions of photosynthesis is correct? A. They provide the carbon that becomes incorporated into sugar. B. They produce PGA, which is converted to glucose by carbon fixation in the light-independent reactions. C. Water is split apart, providing hydrogen ions and electrons to NADP for temporary storage. D. They occur in the stroma of chloroplasts.

C Trypsin is an enzyme, which are proteins and organic catalysts that speed up reactions without altering them. They are not consumed in the process. Therefore, you can eliminate (A) and (B). The rate of reaction can be affected by the concentration of the substrate up to a point, so (D) can be eliminated.

Which of the following statements about trypsin is NOT true? A. It is an organic compound made of proteins. B. It is a catalyst that alters the rate of a reaction. C. It is operative over a wide pH range. D. The rate of catalysis is affected by the concentration of substrate.

(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.

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.

(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.

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.

(D) A macrophage is an antigen-presenting cells (APC). It will alert the adaptive immune system about a particular invader.

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.

This is classic Darwinian evolutionary theory—the survival of the best adapted.

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.

(A) Hydrogen bonding determines secondary and tertiary structure but not primary.

Which of the following statements describes the structural level of a protein that is least affected by hydrogen bonding? A. Primary structure depends on the sequence of amino acids. B. Tertiary structure has a shape dependent on the interactions of side chains of amino acids. C. Quaternary structure results from the aggregation of more than one polypeptide unit. D. An α-helix is an example of a secondary structure of a polypeptide.

(A) The question states NOT. Every choice is correct about apoptosis except Choice A. Apoptosis is programmed cell death, not a form of cell division.

Which of the following statements is NOT correct about apoptosis? A. Apoptosis, a special type of cell division, requires multiple cell signaling. B. The fact that apoptosis is widespread across several kingdoms is evidence that it evolved early in the evolution of eukaryotes. C. Apoptosis plays a crucial role in the development of fingers in embryonic development. D. Apoptosis prevents an aging and dying cell from damaging neighboring cells.

(B) Without the signal from the gonads to develop into a male, the rabbit remains a female.

Which of the following statements is a correct conclusion to draw from this experiment? A. In rabbits, female development requires a hormonal signal from the female gonad. B. In rabbits, male development requires a hormonal signal from the male gonad. C. In mammals, gonad development is triggered by sex hormones. D. In mammals, all embryos develop male gonads without signals to do otherwise.

(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.

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.

(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.

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.

(D) The head of a phospholipid is hydrophilic, and the tails are hydrophobic. The phosphate head is charged and therefore polar.

Which of the following statements is not correct about lipids? A. Lipids consist of fatty acids and glycerol. B. Steroids are examples of lipids. C. The molecules of a saturated fatty acid are packed so close together that they form a solid at room temperature. D. The head of a phospholipid is hydrophobic, and the tails are hydrophilic.

(A) After deforestation, the nitrate runoff onto the rivers increased. There is no evidence presented that trees were replanted. Choice D is clearly false.

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.

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.

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.

C-Secondary carnivores > primary carnivores > primary consumers = herbivores > primary producers.

Which of the following tends to be highest on the trophic pyramid? A. Primary consumers B. Herbivores C. Primary carnivores D. Primary producers

B-The endosymbiotic theory proposes that mitochondria and chloroplasts evolved through the symbiotic relationship between prokaryotic organisms.

Which of the following theories is based on the notion that mitochondria and chloroplasts evolved from prokaryotic cells? A. Fluid mosaic model B. Endosymbiotic model C. Taxonomic model D. Respiration feedback model

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.

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. Vesicles that form by phagocytosis usually merge with a lysosome, and their contents are digested by the hydrolytic enzymes inside the lysosome.

Which of the following would most likely describe the fate of a vesicle formed as a result of phagocytosis? A. The vesicle merges with a mitochondrion. B. The vesicle merges with a lysosome. C. The vesicle is shuttled to the nucleus, and its contents become part of the nucleolus. D. The vesicle releases its contents to the cytoplasm to be digested.

C. Chlorophylls a and b have absorption peaks in the long wavelength area (between 650 and 750 nm). Of the two, chlorophyll a has the greatest absorption at the longest wavelength of light.

Which of the pigments absorbs the most light energy at the longest wavelength? A. β carotene B. lutein C. chlorophyll a D. chlorophyll b

C. Sweating cools bodies because the energy used to change the liquid state of the sweat to the gas state comes from our bodies. When we lose body energy to this process, we feel cooled. The stage on the graph that represents the change from liquid to gas is labeled Y.

Which part of the graph represents the cooling effect of sweating? A. W B. X C. Y D. Z

D. Reaction VII, occurring in the dark, shows that Elodea does not cause the yellow BTB solution to turn blue. Thus, light must be present for the observed color change (from yellow to blue) to occur in Reaction IV. In addition, Reaction III shows that light alone does not cause the color change observed in Reaction IV.

Which reaction supports a conclusion that the change in the color observed in Reaction IV is caused by the influence of light on Elodea and not by some acidic or basic substance in the Elodea plant? A. Reaction II B. Reaction III C. Reaction V D. Reaction VII

B. The line labeled X represents liquid water as it changes temperature from 0°C to 100°C.

Which state of matter does the line labeled X represent? A. gas B. liquid C. solid D. a mixture of liquid and solid

(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.

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.

D. Hardwood trees are in greatest abundance in the climax stages of succession for a temperate forest community typical of the eastern United States.

Which successional stage would contain the greatest abundance of hardwood trees? A. A B. B C. C D. D

A. Plants with an r-selected life history are opportunistic, pioneer species that reproduce and mature quickly and produce many offspring. These species are usually the first species to invade a habitat when succession begins, when a previously uninhabited region becomes available, or after a climax community has been destroyed.

Which successional stage would contain the greatest abundance of plants with an r-selected life history? A. A B. B C. C D. D

(B) Anaerobic respiration is much less efficient at making ATP than is aerobic respiration. Glycolysis produces only 2 net ATPs from each molecule of glucose. The yeast can survive on glucose alone.

Yeast cells carry out both aerobic and anaerobic respiration. A yeast cell that is fed on glucose is moved from an aerobic to an anaerobic environment. Which of the following statements is correct and gives the correct reason for it? A. The cell dies because it cannot make ATP. B. The cell would need to consume glucose at a much greater rate because aerobic respiration is much more efficient as compared with anaerobic respiration. C. The cell would need to consume another food source other than glucose because it will not be able to make adequate ATP with only glucose. D. The cell will begin to divide rapidly because larger cells require more oxygen and glucose than smaller ones.

C-The original question describes an organism that can be classified as a K-selected population. Individuals of this class tend to have fairly constant size, low reproductive rates, and offspring that require extensive care.

You observe a species that gives birth to only one offspring at a time and has a relatively long life-span for its body size. Which of the following is probably also true of this organism? A. It lives in a newly colonized habitat. B. It is an aquatic organism. C. It requires relatively high parental care of offspring. D. The age at which the offspring themselves can give birth is relatively young.

(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.

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.