Rucete ✏ AP Biology In a Nutshell
22. Labs — Practice Questions
This chapter introduces core AP Biology lab skills, including experimental design, data analysis, and biological interpretation of results.
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(Multiple Choice — Click to Reveal Answer)
1. A cube of sugar beet is placed in a beaker of distilled water open to the atmosphere. Which statement correctly describes the figure?
(A) The water potential of the distilled water is 0 bars, and the total water potential of the cube of sugar beet is also 0 bars.
(B) The water potential of the distilled water is 0 bars, and the total water potential of the cube of sugar beet is –0.32 bars.
(C) The water potential of the distilled water is +0.32 bars, and the total water potential of the cube of sugar beet is –0.32 bars.
(D) The water potential of the distilled water is –0.32 bars, and the total water potential of the cube of sugar beet is +0.32 bars.
Answer
(B) — Distilled water has 0 bars water potential, and the sugar beet cube has solute potential –0.32 bars, so total water potential is –0.32 bars.
2. Which light condition is expected to produce the highest ET50 value for photosynthesis using the floating leaf disk method?
(A) White light
(B) Green light because chlorophyll absorbs the most energy from green light
(C) Red light because chlorophyll reflects red light
(D) Green light because chlorophyll reflects green light
Answer
(D) — Chlorophyll reflects green light, which results in the least energy absorbed and therefore the slowest photosynthesis rate, increasing ET50.
3. Which experimental condition is appropriate as a control for testing NaCl effect on peroxidase activity?
(A) Using a different salt (KCl)
(B) No salt (no NaCl) added
(C) Temperature of 37°C
(D) Replacing enzyme with water
Answer
(B) — To isolate NaCl's effect, the control must keep all conditions constant except for having no NaCl.
4. What is the purpose of using potassium hydroxide (KOH) in a cellular respiration experiment with a respirometer?
(A) To provide oxygen to the organism
(B) To kill bacteria inside the respirometer
(C) To absorb the carbon dioxide produced during respiration
(D) To prevent contamination of the respirometer
Answer
(C) — KOH reacts with carbon dioxide to form a solid, allowing measurement of oxygen consumption only.
5. Which of the following best represents a null hypothesis in a fruit fly behavior experiment testing light preference?
(A) Fruit flies prefer light environments.
(B) Fruit flies show no preference for light or dark.
(C) Fruit flies always move toward light.
(D) Light harms fruit flies.
Answer
(B) — A null hypothesis predicts no difference or effect; in this case, no preference between conditions.
6. Which of the following is a correct interpretation if two data sets have overlapping 95% confidence intervals?
(A) The results are statistically significant.
(B) The mean of one data set is much higher.
(C) There is no clear statistical difference between them.
(D) The F1 generation has evolved significantly.
Answer
(C) — Overlapping 95% confidence intervals suggest the difference may not be statistically significant.
7. In the diffusion and osmosis lab, which molecule was too large to pass through dialysis tubing?
(A) Glucose
(B) Water
(C) Iodine
(D) Starch
Answer
(D) — Starch molecules are too large to pass through the pores of dialysis tubing, unlike water and glucose.
8. What condition will most likely increase transpiration rate in a plant?
(A) High humidity
(B) Low light
(C) High wind
(D) Closed stomata
Answer
(C) — Wind increases water loss by moving water vapor away from the leaf surface, increasing the gradient.
9. Which of the following is a model organism commonly used in studying artificial selection in the lab?
(A) Arabidopsis thaliana
(B) Brassica rapa (Fast Plants)
(C) Caenorhabditis elegans
(D) Homo sapiens
Answer
(B) — Fast Plants are ideal for artificial selection due to their rapid life cycle and controlled pollination.
10. In a Hardy-Weinberg simulation, which of the following must be true for the population to remain in equilibrium?
(A) Small population size
(B) High mutation rate
(C) No selection
(D) Gene flow from other populations
Answer
(C) — One of the conditions for Hardy-Weinberg equilibrium is no natural selection acting on the population.
11. What does the ET50 value represent in the floating leaf disk assay?
(A) The time it takes for all disks to float
(B) The concentration of CO₂ in the solution
(C) The time it takes for 50% of the disks to float
(D) The rate of light absorption by the disks
Answer
(C) — ET50 is the time required for 50% of leaf disks to float, which indirectly reflects the rate of photosynthesis.
12. Which variable would most directly affect the rate of enzyme activity?
(A) Light intensity
(B) pH level
(C) Wind speed
(D) Atmospheric pressure
Answer
(B) — Enzyme activity is highly sensitive to pH; changes can denature enzymes or alter their function.
13. In the bacterial transformation lab, what is the role of ampicillin in the agar plates?
(A) To feed the bacteria
(B) To kill all bacteria
(C) To select for transformed bacteria
(D) To stimulate growth of plasmids
Answer
(C) — Only bacteria that have absorbed the plasmid containing the resistance gene can grow on ampicillin plates.
14. In which lab is guaiacol used to detect oxygen production?
(A) Enzyme Activity
(B) BLAST
(C) Transpiration
(D) Fruit Fly Behavior
Answer
(A) — Guaiacol binds to oxygen and forms a brown compound, allowing the measurement of peroxidase activity.
15. What is the relationship between water potential and solute concentration?
(A) Higher solute concentration means higher water potential
(B) Solute concentration has no effect on water potential
(C) Higher solute concentration lowers water potential
(D) They are unrelated concepts
Answer
(C) — As solute concentration increases, water potential decreases because solutes bind water molecules.
16. What is the purpose of a chi-square test in a lab experiment?
(A) To prove a hypothesis is true
(B) To calculate standard error
(C) To evaluate statistical significance of results
(D) To analyze pH change
Answer
(C) — Chi-square tests determine whether observed data differ significantly from expected results.
17. What does a non-overlapping 95% confidence interval between two groups indicate?
(A) A large sample size
(B) A statistically significant difference
(C) Measurement error
(D) Constant variables
Answer
(B) — Non-overlapping confidence intervals suggest that the means differ significantly.
18. In a restriction enzyme lab, why do different individuals show different band patterns on the gel?
(A) They have different proteins
(B) They have different DNA sequences
(C) The gel is contaminated
(D) Their blood type differs
Answer
(B) — Restriction enzymes cut at specific DNA sequences, so DNA variation results in different fragment sizes.
19. In the Hardy-Weinberg formula, what does 2pq represent?
(A) Homozygous dominant genotype
(B) Homozygous recessive genotype
(C) Heterozygous genotype
(D) Frequency of alleles
Answer
(C) — 2pq represents the frequency of the heterozygous genotype in the population.
20. What structure in plant cells helps prevent bursting in hypotonic environments?
(A) Nucleus
(B) Cell wall
(C) Plasma membrane
(D) Mitochondria
Answer
(B) — The rigid cell wall provides structural support and prevents bursting when water enters the cell.
21. What characteristic makes Fast Plants (Brassica rapa) ideal for artificial selection experiments?
(A) They require no water
(B) They reproduce by cloning
(C) They have a short generation time and controlled pollination
(D) They are resistant to all environmental changes
Answer
(C) — Fast Plants grow quickly (about 40 days) and require cross-pollination, making them ideal for artificial selection studies.
22. In the BLAST lab, what does a high degree of homology between two species' DNA suggest?
(A) The species are distantly related
(B) The species have no evolutionary connection
(C) The species share a recent common ancestor
(D) One species is extinct
Answer
(C) — High homology in DNA sequences suggests evolutionary closeness and a recent common ancestor.
23. What does the slope of a line in a photosynthesis experiment represent when graphing floating leaf disks over time?
(A) Rate of chlorophyll degradation
(B) Time required for oxygen to dissolve
(C) Rate of photosynthesis
(D) Thickness of the leaf disks
Answer
(C) — As more disks float over time due to oxygen production, the slope reflects the rate of photosynthesis.
24. Which condition could increase the rate of cellular respiration in germinating seeds?
(A) Decreased oxygen
(B) Increased temperature
(C) High salinity
(D) Cold storage
Answer
(B) — Higher temperatures can increase enzyme activity and the rate of cellular respiration, up to a limit.
25. What is the role of the dialysis tubing in diffusion and osmosis labs?
(A) To simulate a cell wall
(B) To break down molecules
(C) To act as a selectively permeable membrane
(D) To filter starch only
Answer
(C) — Dialysis tubing mimics a selectively permeable membrane, allowing small molecules to pass while blocking larger ones.
26. In a mitosis experiment, students count 50 cells in interphase and 10 in mitosis. After treatment with a chemical, they count 30 in interphase and 30 in mitosis. What statistical method should be used to determine if the difference is significant?
(A) t-test
(B) Chi-square test
(C) ANOVA
(D) Regression analysis
Answer
(B) — The chi-square test is used to evaluate whether observed differences in categorical data are statistically significant.
27. What conclusion can be drawn if a potato cube shows a 0% change in mass after being soaked in a sucrose solution overnight?
(A) The potato absorbed a lot of water
(B) The potato lost all its water
(C) The solution was isotonic to the potato cells
(D) The solution had a higher water potential than the potato cells
Answer
(C) — A 0% mass change indicates that the internal and external water potentials are equal, meaning the solution is isotonic.
28. In the energy dynamics lab, what would a low energy transfer efficiency between trophic levels most likely indicate?
(A) Producers were highly efficient
(B) Consumers stored most of the energy
(C) Most energy was lost as heat or waste
(D) All energy was conserved and reused
Answer
(C) — Only a small percentage of energy is transferred between trophic levels; most is lost as heat or metabolic waste.
29. During gel electrophoresis, a DNA fragment travels a shorter distance than expected. What is the most likely reason?
(A) The fragment is very small
(B) The fragment is negatively charged
(C) The fragment is very large
(D) The agarose gel was too short
Answer
(C) — Larger DNA fragments move more slowly through the gel and thus travel shorter distances.
30. A student runs a BLAST search for a gene found in a fossil. The closest match is to a gene in a modern reptile. What does this suggest?
(A) The fossil is unrelated to reptiles
(B) The fossil likely shares ancestry with modern reptiles
(C) The fossil DNA is contaminated
(D) The fossil belonged to a mammal
Answer
(B) — BLAST results showing close genetic homology suggest evolutionary relatedness to modern reptiles.
31. Why is a logarithmic scale sometimes used in enzyme activity graphs?
(A) To smooth out irregular data
(B) To account for decreasing substrate concentration
(C) To better represent rapid rate changes
(D) To plot negative values
Answer
(C) — Enzyme activity can change rapidly under certain conditions; logarithmic scales can help visualize these rates more clearly.
32. In the bacterial transformation lab, what would it imply if colonies grew on the LB/ampicillin plate from the tube that had no plasmid?
(A) Successful transformation
(B) Failure of ampicillin
(C) Spontaneous mutation providing resistance
(D) All bacteria naturally resist ampicillin
Answer
(C) — Though rare, spontaneous mutation can confer resistance. This result indicates such a mutation or contamination.
33. In a Hardy-Weinberg simulation, what would happen to allele frequencies over time if gene flow is introduced?
(A) Frequencies would remain stable
(B) Mutation rate would drop
(C) Allele frequencies would likely shift
(D) The population would reach fixation
Answer
(C) — Gene flow introduces new alleles, disrupting Hardy-Weinberg equilibrium and causing shifts in allele frequencies.
34. A leaf disk sinks in sodium bicarbonate but fails to float under light. What could be the cause?
(A) The leaf disk is dead
(B) The syringe was not sealed
(C) The light intensity is insufficient
(D) The solution is too acidic
Answer
(C) — Without adequate light, photosynthesis cannot occur, so oxygen isn't produced to make the disks float.
35. During transpiration experiments, which variable must be controlled to isolate the effect of wind on water loss?
(A) Type of plant used
(B) Soil nutrients
(C) Humidity, light, and temperature
(D) Leaf shape
Answer
(C) — To test the effect of wind accurately, other factors like humidity, light, and temperature must be kept constant.
36. In the enzyme catalysis lab, how can you determine the optimal temperature for peroxidase activity?
Answer
Measure the reaction rate (e.g., color change using guaiacol) at various temperatures and identify the temperature with the highest rate. This is the optimal temperature.
37. In a transpiration experiment, how can you ensure that wind is the only variable affecting transpiration rate?
Answer
Control other variables such as light, humidity, temperature, and use the same species of plant across trials. Only change wind speed.
38. What does it mean if transformed bacteria glow under UV light but do not grow on ampicillin plates?
Answer
The plasmid likely included the GFP gene but not the ampicillin resistance gene, or transformation with the resistance portion failed.
39. Why is it important to replicate trials in an experimental design?
Answer
Replication increases reliability, reduces the impact of outliers, and allows for statistical analysis of data.
40. In the BLAST lab, what does a low E-value (e.g., 1e-50) indicate about a DNA sequence alignment?
Answer
A low E-value indicates a highly significant match, meaning the alignment is unlikely to have occurred by chance.
41. How does sucrose concentration outside a plant cell affect its water potential?
Answer
Higher external sucrose lowers the water potential outside the cell, causing water to move out of the cell by osmosis.
42. How would removing the enzyme from an enzyme-substrate reaction affect the results?
Answer
The reaction would not occur or proceed extremely slowly, showing that the enzyme is essential for catalysis.
43. In the photosynthesis lab, what would be the effect of using a green filter over the light source?
Answer
Photosynthesis rate would decrease because chlorophyll reflects green light, absorbing less energy for the reaction.
44. Why is pH important in enzyme activity experiments?
Answer
Each enzyme has an optimal pH. Deviations can denature the enzyme or change the shape of the active site, reducing function.
45. In population genetics, what does it mean if allele frequencies change significantly over generations?
Answer
It indicates that the population is evolving, likely due to selection, mutation, gene flow, or genetic drift.
46. How does heat affect protein structure in an enzyme lab?
Answer
Excessive heat can denature the protein, altering its shape and destroying enzyme activity.
47. What would you conclude if a control plate shows bacterial growth in a transformation experiment without plasmid?
Answer
This could indicate contamination or natural antibiotic resistance in the bacteria; the results would be unreliable.
48. How does increasing the surface area of leaf disks affect photosynthesis rate in the floating disk lab?
Answer
Increased surface area may increase the rate due to more chloroplasts being exposed to light, enhancing oxygen production.
49. Why is a standard curve useful in the enzyme lab?
Answer
It allows you to quantify unknown concentrations by comparing absorbance values to known standards.
50. In a DNA electrophoresis lab, how can you tell the size of a DNA fragment?
Answer
Compare the migration distance of the fragment to a DNA ladder of known sizes; smaller fragments travel farther.