Which of the following statements best describes why

Transcript Which of the following statements best describes why

Please read Science 1

Which of the following statements best describes why Experiment 1 is important?

Experiment 1 demonstrates that insects can thrive under the given conditions.

Experiment 1 establishes that both Beetle A and Beetle B eat whole-wheat flour. Experiment 1 establishes the non competitive total population of each insect.

Experiment 1 demonstrates that the caterpillar has a much slower growth rate than the beetles.

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Explanation

Experiment 1 is a control experiment that establishes the population size of each insect when provided with an adequate food supply for any size population. This population size is used to compare what happens when there is less food and/or more species eating the same finite supply of food.

If Beetle A in Experiment 1 was left to grow indefinitely, one would initially observe an increase, followed by a brief plateau, and then a rapid decline in the population size. What would be the most likely cause of the final decline?

Other species of insects Limited supply of food Limited supply of minerals Long-term effects of confinement

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Explanation

 The most likely limiting resource that is discussed and applicable to the paragraph is food supply. Over an indefinitely long period of time, the food supply would run out and population size would cease to increase. The population size would eventually start declining due to starvation.

What would happen if, in Experiment 2, Beetle B and caterpillars were put in the same vial?

The caterpillars would die by Week 10 because of overpopulation by Beetle B.

The average population of Beetle B would reach 100 and the average population for caterpillars would reach 5 because of competition for food.

The average population of caterpillars would reach 50 while Beetle B would die because caterpillars are stronger competitors for food.

The average population of Beetle B would reach 500 while the average population of caterpillars would reach 20, as in Experiment 2.

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Explanation

 While Experiment 3 suggests that both species of beetles compete for food, Experiment 2 suggests that Beetle A does not compete with caterpillars for food. Therefore, Beetle B should not be expected to compete with the caterpillars for food either.

Which of the following statements is true of Experiment 3?

Beetle B is the more dominant of the two beetle species.

Beetle A and Beetle B compete for space, food, or both.

The population size of beetle B is smaller than Beetle A due to migration.

The population size of Beetle B is smaller than Beetle A due to the absence of the caterpillars.

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Explanation

 The decrease in both Beetle A and Beetle B population sizes indicate that there is interspecies competition for resources. All the other statements are not true.

Suppose that, instead of starting with six of each species in Experiment 3, only three of each species were placed in the vial. After ten weeks, what percentage of the total population would the Beetle B species constitute?

15% 25% 75% 85%

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Explanation

 The ratio of Beetle A to Beetle B should remain the same regardless of the initial number of beetles. Hence, Beetle A constitutes 75% while Beetle B constitutes 25%.

Suppose another species of beetle, Beetle C, replaces Beetle A in Experiment 3. After ten weeks, only the Beetle C species can be found in the vial. Which of the following hypotheses does NOT explain the result in terms of competition?

The adult and larval Beetle C species ate the eggs and pupae of the Beetle B species.

The Beetle C species hoarded the food supply and defended it from the Beetle B species.

The Beetle B species was unable to reproduce due to a genetic mutation.

The Beetle C species secretes an enzyme on the food supply that can only be broken down by its own digestion system

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Explanation

 The dearth of the Beetle B species in all the other choices is due to a result of direct influence of the Beetle C species. The failure to reproduce due to a genetic mutation is not a result of competition.

Please read Science 2

1 Which of the following scenarios definitively exemplifies drug resistance?

A specific antibiotic treats a broad spectrum of bacterial infections.

A specific antibiotic does not treat bacterial infections caused by

Staphylococcus

A specific antibiotic has become ineffective in treating bacterial infections from some strains of

Staphylococcus

A specific antibiotic treats bacterial infections from

Staphylococcus

but does not treat bacterial infections from the bacterium

Pseudomonas

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Explanation

 Drug resistance, defined in paragraph 1, is the ability to resist the effects of a once-potent antibiotic.

satisfies this definition.

Which statement is true of the given distribution curves?

The unshaded region in Curve 1 represents 5% drug non-resistance.

Curve 2 represents 100% drug resistance.

Curve 1 represents 95% drug resistance.

Curve 2 is not related to drug resistance.

Explanation

 The unshaded region in curve 1 corresponds to strains of bacteria that are resistant to antibiotics. Thus, curve 2 arises from the survival of these strains.

Which of the following conclusions is NOT consistent with the results of the experiment?

Doxycycline had no effect on

Staphylococcus

Kanamycin and ethambutol were about equally effective on

Staphylococcus

Streptomycin was effective at all concentrations on

Staphylococcus

Sulfamethoxazole was effective only at low concentrations on

Staphylococcus.

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Explanation

 From the table, sulfamethoxazole prevents growth at high concentrations. Its effectiveness diminishes as its concentration decreases, as seen by strong growth. Thus, sulfamethoxazole was most effective at high concentrations.

If the concentration of antibiotics used is to be kept at a minimum to prevent drug resistance, which of the antibiotics listed in the table would be the best choice for treatment of Staphylococcus ?

Kanamycin Ethambutol Streptomycin Sulfamethoxazole

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Explanation

 From the table, streptomycin still prevented bacterial growth at the lowest concentration whereas all the other antibiotics were ineffective.

Suppose that a strain of bacteria arose which was resistant to streptomycin. Which of the following scenarios would you expect to occur in the course of time?

The streptomycin-resistant strain would come to dominate the population of bacteria as the other strains died off after being exposed to antibiotics.

At least one of the other antibiotics would prove effective in treating the streptomycin-resistant bacteria.

The new strain of bacteria would become the source of a new family of antibiotics useful in treating previously intractable infections.

The distribution curves for bacteria treated with streptomycin would now include a substantial shaded region on the right-hand side.

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Explanation

 The distribution curves show that, over the course of time, the strains of bacteria which can be treated using any specific antibiotic die off, leaving a population of bacteria consisting solely of drug-resistant strains. If we start with a strain of bacteria which we know to be resistant to the most effective antibiotics, we can confidently expect that this strain will come to dominate the population of bacteria.

Please read Science 3

The characteristics common to the studies is that both:

measured periods of maximum glaciations utilized ancient and modern sedimentary rocks analyzed data from marine sediments measured the depth of the cycles

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Explanation

 Both studies state that they are analyzing marine sediment. Study 2 makes no mention of sedimentary rocks (ruling out

). Depth of the cores is irrelevant (ruling out

) and only study 2 states that it measured peak glaciation (ruling out

Which of the following characteristics of a sequence of marine sediments or sedimentary rocks would make it unsuitable for a study such as this?

I. an age of only 30,000 to 40,000 years II. depth of ocean water III. location away from the polar ice caps

I only II and III only I, II, and III I and III only

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Explanation

 The passage makes no mention of the relevance of ocean depth or proximity to polar ice caps, but it does mention that these sequences have a minimum age of 50,000 years.

Each of the following is true EXCEPT:

Both studies are compatible with the claim that major climate changes occur at intervals of 50,000 years or more.

Both studies provide support for the claim that cyclic climate changes caused changes in sediment patterns.

Sediment size was a central factor in the results of both studies.

Both studies concerned ancient marine sedimentary rocks.

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Explanation

 Sediment size was the crucial factor in Study 1 but not Study 2 (where the central factors were the abundance and shape of microfossils).

According to the theory discussed in the passage, as glacial melting increases, the sediments along coastlines and microfossils within oceans should respectively show:

more deposition and cooler global temperatures more erosion and cooler global temperatures 3.

more deposition and warmer global temperatures

more erosion and warmer global temperatures

Explanation

 As stated in the second paragraph, glacial melting results in deposition and warmer global temperatures.

Which of the following hypotheses was investigated in Study 1?

Changes in sea level cause sequences of sediments.

Cycles occur every 50,000, 100,000, 5 million and 12 million years.

The sea level is currently rising.

Cyclicity in sediment deposition is the result of changes in global ice volume.

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Explanation

 Study 1's hypothesis was that marine sediments record sequences of sediment that occur in cycles. #

is the conclusion of study 1, not a hypothesis.

and

are not discussed in Study 1.

Please read Science 4

Which one of the following statements best describes why Experiment 1 is important?

Experiment 1 shows that the hamsters need an average of 10 hours of sleep.

Experiment 1 is used as a basis of comparison by the other experiments.

Experiment 1 shows that hamsters exercise regularly.

Experiment 1 has no relation with the other experiments.

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Explanation

 Experiment 1 is a control experiment that establishes the behavior of hamsters under normal conditions. Conclusions drawn from all the other experiments are based on comparisons to Experiment 1.

Which of following statements is NOT consistent with hamster sleep patterns?

The greater the dark exposure in a 24-hour period, the less a hamster sleeps.

The length of light exposure affects a hamster’s sleep pattern.

Under normal conditions, a hamster will sleep an average of 10 hours.

The greater the light exposure in a 24-hour period, the less a hamster sleeps.

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Explanation

 From the “Hamster sleep pattern” graph, the greater the dark exposure (Experiment 3), the more a hamster sleeps.

What would one expect to observe at Day 3 if the hamsters were exposed to 15 hours of light?

The hamsters would sleep and exercise less.

The hamsters would sleep and exercise more.

The hamsters would sleep less and exercise more.

No change from the normal would be observed.

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Explanation

 From the graphs, it is clear that the hamsters need at least 5 days to respond to a 20-hour light exposure. Hence, no observable change would occur at Day 3 even at a 15-hour light exposure.

Which of the following statements is true regarding hamster exercise patterns?

Normal hamster sleep patterns lead to a steady decrease in the number of hours hamsters exercise a day.

Hamsters exercise more when more food is provided.

Hamsters deprived of light will eventually exercise very little or not at all.

Sleep deprivation and exercise are not related.

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Explanation

 According to the “Hamster exercise pattern” graph, the odometer for hamsters in Experiment 3 plateaus after the eighth day, indicating that all exercise has ceased or decreased to negligible levels.

In view of the experimental results on hamsters, which of the following statements is a sound hypothesis regarding the behavior of mice exposed to light for abnormally long periods during 24-hour days?

The mice will not react, either in sleep patterns or in exercise patterns, protracted exposure to light.

The mice will sleep more and exercise less than the hamsters when exposed to light for protracted periods.

The mice will exhibit a rapid increase in the number of exercise hours, reaching a cumulative distance of about 200 kilometers in 10 days.

The mice will react the same way as the hamsters to prolonged light exposure, but this reaction will not necessarily take place at the same rate.

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Explanation

 Given the gross similarities between mice and hamsters, it is reasonable to expect them to respond similarly to prolonged light exposure (and there is no evidence suggesting otherwise, ruling out 1 and

). The two are different species, however, and the hypothesis that predicts identical behavior (

) is too strong for that reason. Another set of similar experiments will have to be performed to definitively determine the time frames for mice.

If the hamsters in Experiment 3 were put under normal conditions again after Day 20, what would most likely be observed?

No observable changes will occur as the hamsters have grown accustomed to sleeping in and not exercising.

No observable changes will occur as the hamsters’ circadian rhythms were destroyed.

The hamsters will increasingly sleep less and exercise more to a point that matches Experiment 2.

The hamsters will increasingly sleep less and exercise more to a point that matches Experiment 1.

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Explanation

 Since the effects on the disruption of circadian rhythm is reversible, as mentioned in the passage, the hamsters’ sleep and exercise patterns will eventually reflect those of hamsters that experience normal light and darkness exposure.

Please read Science 5

Which statement characterizes the migration of SDS-associated proteins?

Diffusion moves the proteins from a region of higher concentration to one of lower concentration.

An electric field causes negatively charged objects to migrate toward the anode (positive end). The electrical resistance of negatively charged objects determines the speed of migration. Osmosis of water indirectly causes the migration of the proteins.

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Explanation

 SDS-associated proteins, which are negatively charged, will travel toward the positive end of an electric field. All the other options are true statements, but do not describe the SDS-PAGE context.

A protein of weight 45 000 Da would be expected to migrate to the region on the graph marked

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Explanation

 From the table, the weight 45 000 falls between the first 2 data points. This would correspond to region W on the graph.

A protein essential for metabolism has just been discovered. SDS PAGE reveals that this protein migrates a distance of 1.7 cm. Which statement best characterizes the new protein?

The weight of the protein is somewhere between 6 000 Da and 11 000 Da.

The weight of the protein is somewhere between 11 000 Da and 17 000 Da.

The weight of the protein is somewhere between 14 000 Da and 17 000 Da.

The weight of the protein is somewhere between 17 000 Da and 35 000 Da.

Explanation

 Since a protein weighing 17 000 Da travels 1.8 cm, and since the new protein traveled only 1.7 cm, we can confidently conclude that the new protein is heavier and thus rule out answers #1, #2, and #3. #4 is the only answer allowing for heavier weights.

Another essential protein in metabolism is made up of 2 units, each unit traveling a different distance from the other. The combined weight of the 2 units is approximately 50 000 Da. Referring to the regions W, X, Y and Z on the graph, which combination will NOT give the possible weight of each unit?

X + Z 2.

Y + Z 3.

X + Y W + Y

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Explanation

 All the other combinations can be manipulated to give a combined weight of approximately 50 000 Da. The highest weight that Y + Z can attain under 25 000 Da.

What would happen if an electric field were to be applied to SDS-PAGE for an indefinite length of time?

Larger proteins will reach the anode before the smaller proteins.

All proteins will eventually reach a limiting resistance in the matrix, at which point they cease to migrate further.

Proteins associated with more SDS will reach the anode while proteins associated with less SDS will stop migrating due to resistance.

All proteins will eventually reach the anode.

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Explanation

 It is consistent with the information provided that, given an indefinitely long period of time, all negatively charged proteins will reach the anode at the rates determined by their sizes. Smaller proteins will arrive at the anode before the larger proteins, ruling out #1.

Please read Science 6

The final three-dimensional structure of a protein, regardless of the folding pathway models, ultimately depends on:

how it is manufactured by the cell.

the flexibility of the peptide bonds.

the number of amino acids.

the sequence of the amino acids.

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Explanation

 The passage states (in the first sentence) that each protein is characterized by the sequence of amino acids and that this sequence is what makes the protein unique.

A mutation of an important amino acid affects the proper conformation of the protein. Which of the proposed models cannot account for this observation?

Diffusion-collision model.

Nucleation model.

Hydrophobic-collapse model.

None of the above.

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Explanation

 All the models are based on the fact that the amino acid sequence specifies the proper conformation. A loss of a vital amino acid in any of the models would lead to the wrong conformation.

A certain mutation of an amino acid, which is thought to play a major role in initiating protein folding, does not affect the general structure of the protein. Which of the proposed models cannot account for this observation?

Diffusion-collision model Nucleation model Hydrophobic-collapse model None of the above

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Explanation

 According to the nucleation model, the mutated amino acid will fail to produce a properly folded protein. However, the protein still acquires the proper fold, suggesting the shortfall of this model.

The nucleation model suggests that some amino acids are more important than others whereas the diffusion-collision model supposes that all amino acids are equally important. Which of the following statements is NOT true?

A mutation in an important amino acid in the nucleation model will have no effect according to the diffusion-collision model.

A mutation in an amino acid, which is important in the nucleation model, will result in a wrong conformation.

A mutation in an amino acid might affect proper protein conformation according to the diffusion collision model.

A mutation in a certain amino acid might have an effect according to both the nucleation model and the diffusion-collision model.

Explanation

 Even though the diffusion-collision model does not posit that there are any especially important amino acids, it is still the case, according to that model, that a mutation of any amino acid might affect the folding pathway

Implicit in the nucleation model is the assumption that:

temperature is an important factor for a protein to attain the proper conformation the presence of salt promotes a protein in attaining the proper conformation the addition of a strong base will destroy the peptide bonds and thus the protein the time required to attain the proper conformation is dependent on the length of the protein

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Explanation

 Since the nucleation method is akin to a domino effect, it follows that the longer a protein, the longer it will take to attain the proper conformation.

A molecular chaperonin is a protein that aids small proteins in establishing their structures. The chaperonin has a barrel-like cavity that provides an unfolded protein an opportunity to fold. If the hydrophobic-collapse model can be used to explain this particular folding process, what can be said about the amino acids of the molecular chaperonin that come in contact with the unfolded protein?

The amino acids in the molecular chaperonins are hydrophobic.

The amino acids in the molecular chaperonins are hydrophilic.

The amino acids in the molecular chaperonins are both hydrophobic and hydrophilic.

The amino acids in the molecular chaperonins are not involved in the folding process.

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Explanation

 According to the hydrophobic-collapse model, hydrophobic amino acids prefer to interact with themselves. Thus, the interacting molecular chaperonin amino acids must be hydrophilic to promote protein folding.

A fourth, all-inclusive view of protein folding is that similar proteins can fold via any of the three models. What cannot be said of proteins that conform to this all inclusive model?

The structure of a protein can be attained by any model.

The length of the protein does not influence the choice of a model.

The sequence of the protein determines the folding pathway.

A folding pathway that is hindered by a mutation can be compensated by another.

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Explanation

 Statements #1 and #4 demonstrate that a protein fold can be achieved by any of the three suggested pathways. While sequence is the only element important in the folding process, hence negating Statement #2, the fact that similar proteins can attain proper conformations via any of the proposed pathways, in this particular case, suggests that sequence does not determine the folding pathway.

Please read Science 7

Which of the following statements is supported by the data presented in the graph?

Amount of clay depends on time only Amount of clay depends on time and climate Climate depends upon amount of clay only The graph does not support a relationship between climate, amount of clay, or time

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Explanation

 The three variables described in the passage and shown on the graph indicate a relationship that can only be explained by climate, time, and amount of clay.

The graph indicates that after 100,000 years the greatest change in amount of clay (g/cm3) has occurred in which climate?

Climate XX Climate ZZ Climate TT Climate WW

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Explanation

 Climate XX, because the graph is logarithmic, climate XX has experienced a change from 0 g/cm3 to 30 g/cm3. Climate ZZ only changes from 0 to 15 g/cm3.

For any given climate, which of the following generalizations is supported by the graph?

As time increases, the amount of clay present increases.

As time increases, the change in amount of clay decreases.

As the amount of clay increases, the change in the amount of clay decreases.

As time increases, the amount of clay present changes.

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Explanation

 The other answers are not true.

because, whether the change is an is true increase or a decrease, there always is a change between two points in time for any given climate.

Based on the information in this graph, an extended graph including data up to 10,000,000 years would show the least change in amount of clay present in which climate?

Climate ZZ 2.

Climate WW Climate TT Climate QQ

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Explanation

 Climate QQ has a relatively stable slope, indicating small changes in amount of clay present. Slopes for all other graphs are steeper.

A ranking of these soils from most developed to least developed changes significantly between 1,000-10,000 years and 10,000-100,000 years. If we extended this graph back to include data to 0 years, which of the following could be predicted to occur?

Climate TT and YY would have equal ranking.

Climate YY would have the highest ranking.

All soils would have equal ranking.

Climate TT would have the highest ranking.

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Explanation

 As stated in the passage, all soils began with no clay present, and the graph also supports this assertion where soils in climates XX, ZZ, WW, and QQ develop clay much later than time 0 years.

Please read Science 8

Which statement explains some of the strategy employed in experiment 1?

Adding a radioactive label to the LDL particle ensured that the particle would be soluble in the blood.

Adding a radioactive label to the LDL particle allowed the rate of transport to be measured.

Adding a radioactive label to the LDL particle allowed the test animal to metabolize the LDL.

Adding a radioactive label to the LDL particle altered the protein component of the particle.

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

Explantion

The correct answer is 2. The addition of the radioactive label on the LDL particle allowed the researcher to measure radioactive levels in the blood against other tissues. This, in turn, allowed the researcher to follow the rate of transport of the LDL. As the hypothesis stated that the transport of the LDL is dependent on a protein component of the LDL interacting with a receptor on the cells, the strategy required that the movement of the particle be measured. Choices 1,

, and

are all incorrect because the addition of the radioactive label has no impact on the solubility or metabolism of the LDL particle nor does the addition of the label alter the protein component of the LDL particle.

A minor criticism of the scientist's strategy employed for experiment 1 is

the method used for measuring the rate of transport.

the use of an animal as a model for a human disease. the use of radioactivity, because it is dangerous.

the injection of the LDL particle instead of the ingestion through diet.

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Explanation

 The correct answer is 4. The relation between coronary heart disease and cholesterol is primarily due to high consumption of cholesterol through the diet. Analysis of cholesterol transport through the introduction of this lipid directly into the bloodstream versus through the digestive tract may not be the best experimental strategy for understanding this relationship. Choice

is incorrect, as it describes a valid method for measuring the amount of a molecule. Choice

is incorrect, as it describes the widely accepted use of animals as models for humans. Choice

is incorrect since, although radioactivity can be dangerous, it does not invalidate the strategy employed by the scientist.

A major criticism of the scientist's interpretation of the result of experiment 1 is that

measurement of radioactivity does not accurately reveal the relative amount and, therefore, the rate, of LDL in the blood.

variation in the rate of transport of the altered LDL is controlled by a receptor molecule.

variation in the rate of transport of the altered LDL is a result of the alteration of the protein component in the particle.

there must be a comparison to unaltered LDL transport rates.

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Explanation

 The correct answer is 2. The result reveals only that changing the LDL protein component has an effect on the rate of transport of the particle. It does not show directly the presence of a receptor molecule and its interaction with the protein. Choice

is incorrect, as the use of a radioactive label is an accurate way to measure the amount of LDL particle. Choice

is incorrect, as this is exactly what the experiment revealed. Choice 4 is incorrect because the passage states, "The results of the experiment revealed that when the LDL protein was altered, the LDL particles remained in the blood much longer

than particles with an unaltered protein

Based on the hypothesis, as the radioactivity decreases from the blood, it would increase

in the fur of the animal.

in the body cells of the animal.

nowhere; the radioactivity would be degraded.

in the lungs of the animal.

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Explanation

 The correct answer is 2. This is because cholesterol is used by cells in their membranes, in the production of lipid hormones, or in the dispersion of fat during digestion. Therefore, the cholesterol would leave the blood and enter the cells by the transport mechanism proposed in the hypothesis. Choices

and

are incorrect because cholesterol does not play a role in fur or lung tissue as described in the passage. Choice

is incorrect because cellular processes will not degrade the radioactivity: Radioactivity decays over a longer time period than was covered by the experiment.

In support of the scientist's interpretations of the result of experiment 1, one would predict that which of the following tissues would exhibit the greatest number of cholesterol receptors?

liver adrenal glands ovaries all of the above

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Explanation

 The correct answer is 4. The role of cholesterol involves fat digestion in the liver (choice 1) and lipid-like hormones, such as adrenaline and estrogen, produced in the adrenal glands (choice 2) and ovaries (choice 3), respectively. If the hypothesis is correct, then the receptors that mediate the transport of cholesterol of these cell types should be quite abundant in these tissues.

Graph 1 reveals that

total cholesterol levels are reduced approximately 15 fold more in individuals who were administered the drug Cissus versus individuals who did not receive the drug.

total cholesterol increased in subjects who did not receive the drug Cissus in the experiment.

total cholesterol decreased at a faster rate in individuals who received the drug Cissus versus those who did not receive the drug.

no change in cholesterol levels was observed in any test subjects.

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Explanation

 The correct answer is 1. The graph plots the percentage of total cholesterol measured after six weeks in individuals who received the drug Cissus versus those who received no drug (but did receive a placebo). As the

-axis exhibits negative percentage intervals the bar size corresponds to the extent of decrease in cholesterol levels. Those subjects who received Cissus exhibited a reduction in cholesterol by 11.6%. Those who received a placebo exhibited a decrease of 0.7% (15-fold difference). Choice

is incorrect because the graph does not reveal changes over time, which would indicate rate.

What does Graph 2 state about the source of blood cholesterol?

LDL particles are the only source of total blood cholesterol.

LDL particles are a major but not sole source of total blood cholesterol.

LDL particles do not contribute to total blood cholesterol levels.

The graph does not reveal any meaningful data about the source of blood cholesterol.

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Explanation

 The correct answer is 2. Graph 2 reveals that LDL levels are at 2% in those test subjects NOT given the drug Cissus. Graph 1 reveals that there was a reduction in total cholesterol levels in those subjects. There must be another component contributing to blood cholesterol levels to account for this variation in total versus LDL levels in test subjects. Choice 4 is incorrect because the graph clearly shows a reduction in blood LDL cholesterol levels of 9.3% in those subjects taking Cissus.

The scientist concluded the drug is effective in controlling total cholesterol levels. This means that

high HDL levels in the blood may contribute to a reduction in total blood cholesterol.

low HDL levels in the blood contribute to an increase in total blood cholesterol.

high LDL levels contribute to a reduction in total blood cholesterol.

HDL levels increase when LDL levels increase.

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Explanation

 The correct answer is 1. The HDL levels of test subjects receiving the drug Cissus increased approximately 17-fold over those subjects who did not receive the drug (Graph 3). This increase, coupled with the concomitant decrease of total and LDL associated cholesterol in Graphs 1 and 2, along with the scientist interpretation that the drug was effective, indicates that high HDL levels correlate with low blood cholesterol levels. Choice

is incorrect because Graphs 1 and 3 reveal a decrease in LDL and an increase in HDL in response to administration of the drug Cissus.

Please read Science 9

Which of the two hypotheses should be rejected based on the evidence described?

hypothesis 1 hypothesis 2 Neither hypothesis should be rejected.

Both hypotheses should be rejected.

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Explanation

 The correct answer is

. Because there is a single line of evidence, the iridium layer of sediment, which supports both statements, neither can be rejected at this point.

What type of evidence would allow for the acceptance of hypothesis 2?

identification of a large crater resulting from an asteroid impact occurring approximately 65 million years ago no evidence of a large crater resulting from an asteroid impact occurring approximately 65 million years ago the remains of extensive lava flows dating back to 65 million years ago no evidence for lava flows dating back to 65 million years ago

Explanation

 The correct answer is 3. Lava flow results from volcanic eruptions; an extensive lava flow dating to the time of the mass extinction would support volcanic eruptions (hypothesis 2) more than asteroid impacts (hypothesis 1). Choice

is not correct, as the lack of evidence for one hypothesis (asteroid impact) does not lend support to the competing hypothesis (volcanic eruption). Choice 2.

is incorrect, as it provides solid evidence in support of hypothesis 1 (asteroid impact). Choice

is incorrect, and it provides no evidence in support of hypothesis

The recently uncovered evidence discussed in passage 2 lends support to

hypothesis 1.

hypothesis 2.

neither hypothesis.

both hypotheses.

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Explanation

 The correct answer is 4. Both the quartz grains and the lava flows, along with the iridium layer, lend strong support to both an asteroid impact and volcanic activity. This evidence does not result in the rejection of either hypothesis, but it does lead to the acceptance of both hypotheses and the need for further testing.

The discovery of additional evidence supporting both hypotheses allows which of the following conclusions to be drawn?

Both events occurred approximately 65 million years ago, leading to global climate change and a mass extinction.

A massive asteroid impacted first, which led to extensive volcanic eruptions and the resulting mass extinction.

The iridium deposition was the result of both asteroid impact and volcanic eruptions occurring 65 million years ago.

all of the above

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Explanation

 The correct answer is 4. All three statements (1,

, and 3) can be conclusions drawn based on all the evidence assembled. Both events could have occurred simultaneously (choice 1) or one event could have spurred the second event (choice 2), which would result in the deposit of iridium (choice 3) among the other evidence identified.

Please read Science 10

Graph A demonstrates

the length of the light waves absorbed by chlorophyll.

the ultraviolet portion of the electromagnetic spectrum absorbed by chlorophyll.

the extent to which chlorophyll absorbs light of all wavelengths in the electromagnetic spectrum.

nothing conclusive about chlorophyll.

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Explanation

 The correct answer is 1. The graph plots the amount of light energy absorbed (

-axis) by chlorophyll against the wavelength of the light (

-axis). A portion of the electromagnetic spectrum is plotted on the

-axis. Choices 2 and 3 are incorrect because the graph shows only the visible portion of the electromagnetic spectrum. Choice 4 is incorrect because the graph clearly shows the specific wavelengths of visible light that chlorophyll absorbs.

Chlorophyll exhibits the greatest absorption of light of

high energy.

low energy.

equal energy.

You cannot determine the energy content of light from this graph.

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Explanation

 The correct answer is 1. Energy content of light is inversely proportional to its wavelength. The graph demonstrates that chlorophyll absorbs more light of the higher energy, shorter wavelength (400 –450 nm) versus the lower energy light of the longer wavelength (650 –700 nm). Choice

is incorrect because the wavelength of light reveals the relative energy the light possesses.

A scientist wants to measure the photosynthetic activity of the common aquatic plant Elodea under various growth conditions. A good indicator of photosynthetic activity would be

the amount of carbon dioxide produced.

the amount of oxygen produced.

the amount of water produced.

the rate of stem/leaf growth.

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Explanation

 The correct answer is 2. Photosynthesis is the process by which a cell uses light energy to convert water and carbon dioxide to oxygen and sugar. The amount of product should indicate the activity of the process of photosynthesis. Choices Choice activity.

4 1

and

are incorrect because these are the building blocks for the photosynthetic process, not the products. is incorrect because many factors contribute to the rate of stem/leaf growth. This is not a direct measure of photosynthetic

Please read Science 11

Which of the following conclusion(s) can be drawn from the data in Table A?

A.The lower the pH, the greater the photosynthetic activity.

The higher the pH, the more oxygen is generated.

Increased acidity leads to a reduction in photosynthetic activity.

Carbon dioxide uptake is not indicative of photosynthetic activity.

1 2 3 4 5

Explanation

 The correct answer is

. Photosynthesis is the process by which a cell uses light energy to convert water and carbon dioxide to oxygen and sugar. The amount of product should indicate the activity of the process of photosynthesis. At pH 5, the amount of oxygen generated is 5-fold greater than at pH 7. Choice with increasing pH. Choice

increased acidity means a decrease in pH; and

is incorrect because reflecting increased photosynthetic activity. Choice is incorrect because the oxygen production decreases decrease in pH facilitates oxygen generation, thereby

is incorrect because photosynthesis is the process by which a cell uses light energy to convert water and carbon dioxide to oxygen and sugar. This definition requires that carbon dioxide be used for the process; therefore, carbon dioxide uptake is indicative of photosynthetic activity, in this experiment.

Based on the results reported in Table A, the rate of photosynthesis is limited by

A.the amount of oxygen available.

the amount of hydrogen ion available.

the amount of carbon dioxide available.

an acidic environment.

1 2 3 4 5

Explanation

 The correct answer is

. The mols of oxygen generated during the photosynthetic event are directly proportional to the mols of carbon dioxide available, regardless of pH. Photosynthesis is the process by which a cell uses light energy to convert water and carbon dioxide to oxygen and sugar. Choice

is incorrect because oxygen is a product of photosynthesis. Choice Choice

4 2

is incorrect because although pH and, therefore, hydrogen ion concentration, has an affect on the overall rate of photosynthesis, the reaction is still limited to the amount of carbon dioxide available (see direct relationship between mols of carbon dioxide relative to mols of oxygen at each pH). is incorrect because an acidic environment is the direct result of hydrogen ion concentrations.

Please read Science 12

The results of this graph can be described in which of the following way(s)?

Oxygen levels are decreasing as the sugar levels decrease.

Carbon dioxide levels are decreasing as the sugar levels decrease.

The amount of sugar available has no impact on carbon dioxide production.

Carbon dioxide levels are increasing with increasing sugar levels.

1 2 3 4 5

Explanation

 The correct answer is 1. Sugar levels are decreasing with increasing time ( levels are increasing ( time,

generated (

with increasing time,

x y y-

-axis). As time progresses, oxygen levels are decreasing and carbon dioxide -axis). This also demonstrates that the amount of sugar available (less with increasing -axis) impacts the amount of carbon dioxide -axis). Choices axis).

and 4 are incorrect because carbon dioxide levels are increasing as sugar levels are decreasing over time. Choice 3 is incorrect because the graph clearly shows that the amount of sugar available (less with increasing time,

axis) impacts the amount of carbon dioxide generated (more

What conclusion(s) can be drawn from the interpretation of these results?

The reverse reaction of photosynthesis must be occurring.

A plant will use carbon dioxide instead of oxygen to make sugars.

Not enough time passed to draw a conclusion.

Under low oxygen conditions, sugar can still be generated by this plant.

1 2 3 4 5

Explanation

 The correct answer is 1. The graph illustrates the reverse reaction of photosynthesis. Photosynthesis is the process by which a cell uses light energy to convert water and carbon dioxide to oxygen and sugar. In this experiment, the products of photosynthesis (sugar and oxygen) were made available to Elodea. The resulting production of carbon dioxide and the depletion of oxygen as sugar levels decrease support this conclusion. Choice increasing. Choice

2 3

is incorrect, as there is no sugar being produced and carbon dioxide levels are is incorrect because the graphs generated are smooth and without outliers. An additional experiment conducted for a longer time period may generate new data; however, based on this graph, this statement that "not enough time passed to draw a conclusion" is invalid. Choice 4 is incorrect because there is no data demonstrating an increase in sugar over the course of the experiment.

The scientist repeated the previous experiment (question 18) in the absence of light. The results obtained were identical to those plotted in Graph B. These results

indicate that the reverse reaction of photosynthesis can occur in the absence of light.

are an anomaly.

refute the data obtained in the first experiment (Graph B).

do not provide any new data.

2 3 4 5

Explanation

 The correct answer is

. These data are in agreement with the data obtained under all of the same conditions except the presence of light (Graph B). Photosynthesis is the process by which a cell uses light energy to convert water and carbon dioxide to oxygen and sugar. In this experiment, the products of photosynthesis (sugar and oxygen) were made available to Elodea. The resulting production of carbon dioxide and the depletion of oxygen as sugar levels decrease support this conclusion. Choice

is incorrect as there is no basis to assume that these data are faulty. Choice

is incorrect because these data agree with the data represented in Graph B; therefore, the data is not refuted but supported. Choice generating new data).

is incorrect because the results do provide new data as the data were generated in the absence of light (a new variable,