Rucete ✏ AP Biology In a Nutshell
22. Labs — Practice Questions 2
This chapter introduces common lab techniques and experimental analysis strategies used in AP Biology to strengthen scientific reasoning and data interpretation skills.
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(Multiple Choice — Click to Reveal Answer)
1. Which of the following best represents the purpose of including a control group in a lab investigation?
(A) To test multiple independent variables
(B) To generate a hypothesis
(C) To provide a basis for comparison
(D) To increase sample size
Answer
(C) — A control group serves as a baseline to compare with experimental outcomes and validate that observed effects are due to the independent variable.
2. A student sets up an experiment to measure the effect of salinity on plant growth. Which variable is the dependent variable in this experiment?
(A) Type of plant
(B) Amount of sunlight
(C) Salinity level
(D) Growth of the plant
Answer
(D) — The dependent variable is the one being measured or observed in response to changes in the independent variable (salinity level).
3. What feature makes dialysis tubing a suitable model for a cell membrane?
(A) It actively transports molecules
(B) It allows for DNA replication
(C) It has selective permeability
(D) It contains organelles
Answer
(C) — Dialysis tubing mimics a semipermeable membrane by allowing some molecules to pass while blocking others.
4. In the photosynthesis lab using leaf disks, what is the role of sodium bicarbonate?
(A) It lowers pH for enzyme activity
(B) It supplies carbon dioxide for photosynthesis
(C) It prevents leaf disks from floating
(D) It acts as a dye to monitor O₂ levels
Answer
(B) — Sodium bicarbonate provides a carbon source (CO₂) necessary for photosynthesis in the floating leaf disk experiment.
5. Which of the following would best help reduce bias in a fruit fly behavior lab?
(A) Counting flies manually once
(B) Conducting the experiment only once
(C) Using multiple trials and randomizing placement
(D) Placing flies on the preferred side initially
Answer
(C) — Multiple trials and randomization help ensure results are not due to chance or bias in placement.
6. Why is it important to use the same species and age of plants in a transpiration experiment?
(A) To test multiple species
(B) To increase variability
(C) To control biological variables
(D) To compare results across ecosystems
Answer
(C) — Keeping species and age constant controls biological variability, ensuring that observed differences result from the tested environmental factor.
7. In an osmosis lab, potato cores in a 0.6 M sucrose solution lost mass. What does this indicate about the solution relative to the potato cells?
(A) The solution is hypotonic
(B) The potato has a lower solute concentration
(C) The solution is hypertonic
(D) Water entered the potato
Answer
(C) — A loss of mass indicates water exited the potato, meaning the surrounding solution was hypertonic.
8. What is the main function of buffer solutions in enzyme activity experiments?
(A) To stop reactions immediately
(B) To maintain constant pH
(C) To increase temperature
(D) To break down enzymes
Answer
(B) — Buffers maintain a stable pH, which is crucial for preserving the structure and function of enzymes during experiments.
9. A student used 5 replicates in a peroxidase reaction. Which statistical value best represents the consistency of the results?
(A) Mean
(B) Mode
(C) Standard deviation
(D) Chi-square value
Answer
(C) — Standard deviation measures the spread of data and shows how consistent repeated measurements are.
10. A high standard error of the mean (SEM) suggests that:
(A) Data points are tightly clustered
(B) The mean is highly reliable
(C) There is high variability in the data
(D) The experiment had no controls
Answer
(C) — A high SEM means the sample mean varies widely, suggesting high variability in the sample data.
11. A plant cell is placed in a solution and becomes flaccid. What can be concluded?
(A) The solution is isotonic
(B) The solution is hypertonic
(C) The cell has gained water
(D) The cell burst due to osmosis
Answer
(B) — In a hypertonic solution, water leaves the cell, making it flaccid as the membrane pulls away from the wall.
12. In an experiment testing the effect of pH on enzyme activity, which pH should be tested?
(A) Only the known optimal pH
(B) pH 0–3 only
(C) A range of pH values across acidic, neutral, and basic
(D) A single pH known to denature enzymes
Answer
(C) — A valid experiment tests a wide pH range to identify the pH at which the enzyme works best.
13. In the floating leaf disk lab, what is the primary reason disks initially sink?
(A) They lack chloroplasts
(B) They are filled with oxygen
(C) Air spaces are replaced with water
(D) They are heavy due to starch content
Answer
(C) — When vacuum infiltrated, air spaces are replaced by water, causing the leaf disks to sink until photosynthesis produces gas.
14. In a transpiration lab, what measurement tool is commonly used to estimate water loss over time?
(A) Thermometer
(B) Ruler
(C) Potometer
(D) Microscope
Answer
(C) — A potometer is designed to measure the rate of water uptake by a plant, which reflects transpiration rate.
15. If a restriction enzyme cuts DNA at a specific site and a mutation alters that site, what is the result on a gel electrophoresis pattern?
(A) More bands appear
(B) DNA won’t stain
(C) Fewer or different-sized bands appear
(D) DNA migrates faster
Answer
(C) — A mutation in the restriction site prevents cutting, leading to altered band patterns on the gel.
16. A student uses a spectrophotometer to measure color change in an enzyme reaction. What is being measured?
(A) Change in pH
(B) Amount of DNA
(C) Light absorbance
(D) Temperature of the sample
Answer
(C) — A spectrophotometer measures how much light is absorbed by a solution, which is used to track concentration changes during a reaction.
17. In the bacterial transformation lab, why is heat shock used during the procedure?
(A) To sterilize the bacteria
(B) To kill untransformed cells
(C) To encourage plasmid uptake
(D) To synthesize GFP
Answer
(C) — Heat shock temporarily creates pores in the bacterial membrane, allowing plasmid DNA to enter the cell.
18. Why is it important to include a negative control in a DNA electrophoresis experiment?
(A) To ensure that restriction enzymes are working
(B) To compare protein levels
(C) To show results without added DNA
(D) To replicate gel staining steps
Answer
(C) — A negative control (no DNA) ensures the observed bands are truly due to added DNA and not contamination.
19. In a population genetics simulation, which factor is removed to test for genetic drift?
(A) Random mating
(B) Natural selection
(C) Large population size
(D) Mutation
Answer
(C) — Genetic drift is more significant in small populations. Removing large population size allows drift to become evident.
20. What is the main reason a researcher would calculate the standard error of the mean (SEM) in a lab report?
(A) To find the mode of a data set
(B) To determine enzyme activity
(C) To quantify precision of the mean
(D) To summarize qualitative results
Answer
(C) — SEM provides a measure of how accurately the sample mean estimates the population mean.
21. Which factor would most likely improve the reliability of experimental results?
(A) Using only one replicate
(B) Performing multiple trials
(C) Avoiding data recording
(D) Changing multiple variables at once
Answer
(B) — Multiple trials help identify consistent patterns and reduce the effect of outliers or random errors.
22. A student incorrectly uses a spectrophotometer without calibrating it first. What is the likely consequence?
(A) The light intensity will be too low
(B) All samples will yield identical values
(C) Absorbance readings will be inaccurate
(D) The DNA will degrade
Answer
(C) — Failing to calibrate introduces systemic error, making absorbance readings unreliable.
23. Which of the following would serve as an appropriate positive control in an enzyme activity experiment?
(A) A boiled enzyme solution
(B) A test tube with no substrate
(C) A known active enzyme with substrate
(D) A buffer solution with no enzyme
Answer
(C) — A positive control is expected to produce a reaction, confirming that the setup can detect a working enzyme.
24. What is the expected result if chloroplasts are placed in darkness during a photosynthesis lab?
(A) Light reactions will still occur
(B) Oxygen production will increase
(C) No photosynthesis will occur
(D) The disks will rise faster
Answer
(C) — Without light, the light-dependent reactions stop, halting photosynthesis and oxygen production.
25. Which type of graph would best show the change in enzyme activity across a range of pH levels?
(A) Bar graph
(B) Line graph
(C) Pie chart
(D) Scatter plot with no trend line
Answer
(B) — A line graph clearly shows trends in enzyme activity as pH increases or decreases.
26. In a fruit fly behavior lab, if flies consistently avoid one side of a chamber, which is most likely true?
(A) The flies are randomly distributed
(B) A repellent stimulus is present on that side
(C) There is no environmental influence
(D) The chamber is unbalanced
Answer
(B) — A consistent avoidance pattern indicates a stimulus (e.g., light, odor) acting as a repellent in that section.
27. Why is ampicillin added to some agar plates in a bacterial transformation lab?
(A) To stain the bacteria
(B) To promote plasmid uptake
(C) To kill non-transformed cells
(D) To grow only Gram-positive bacteria
Answer
(C) — Ampicillin kills cells that do not carry the resistance gene, allowing only successfully transformed cells to grow.
28. What is the primary reason scientists use model organisms in lab experiments?
(A) They are genetically identical to humans
(B) They live long enough to study aging
(C) They are easy to maintain and manipulate genetically
(D) They produce large proteins quickly
Answer
(C) — Model organisms like fruit flies or Fast Plants are convenient due to short lifecycles and genetic accessibility.
29. A student notices that all her photosynthesis data points are clustered at a very low ET50 value. What might this indicate?
(A) Light was too weak
(B) Disks were damaged
(C) Photosynthesis occurred very rapidly
(D) Water pressure was too high
Answer
(C) — A low ET50 means it took little time for half of the disks to rise, indicating rapid photosynthesis.
30. During gel electrophoresis, why might a DNA band appear smeared rather than crisp and defined?
(A) Too much enzyme was used
(B) DNA was too small
(C) Loading dye was omitted
(D) Too much DNA was loaded or it degraded
Answer
(D) — Overloading DNA or degradation causes smearing instead of clear, sharp bands.
31. In the osmosis/diffusion lab, what happens when a potato core gains mass in a sucrose solution?
(A) Water moved out of the cells
(B) The solution was hypertonic
(C) The solution was hypotonic to the potato
(D) The solute entered the cells
Answer
(C) — If the potato gains mass, water entered the cells, which happens when the external solution has a higher water potential (is hypotonic).
32. In the energy dynamics lab, trophic efficiency was calculated as 10%. What does this mean?
(A) 10% of the biomass was excreted
(B) Only 10% of energy transfers to the next level
(C) 90% of organisms were eaten
(D) 10% of sunlight was absorbed by plants
Answer
(B) — Trophic efficiency refers to the percentage of energy passed from one trophic level to the next; typically around 10%.
33. A chi-square value is calculated as 9.2. The critical value is 5.99. What should the student conclude at the 0.05 significance level?
(A) Accept the null hypothesis
(B) Reject the null hypothesis
(C) Repeat the experiment
(D) Increase sample size
Answer
(B) — If the chi-square value exceeds the critical value, the null hypothesis is rejected as the observed differences are statistically significant.
34. What can be concluded from a BLAST output showing an E-value of 1e-100?
(A) The sequence similarity is random
(B) The sequences are evolutionarily distant
(C) The alignment is highly significant
(D) The sequences do not match
Answer
(C) — A very low E-value indicates a highly significant sequence match, likely due to shared ancestry.
35. In a restriction enzyme lab, two siblings show different DNA banding patterns. What might this suggest?
(A) They are not related
(B) They are genetically identical
(C) They have inherited different alleles at restriction sites
(D) The gel was contaminated
Answer
(C) — Siblings can inherit different combinations of alleles; if restriction sites differ, they produce unique banding patterns.
36. In a transpiration lab, what would happen if the leaves of the plant were coated in petroleum jelly?
Answer
Transpiration would decrease significantly because the jelly blocks stomata, preventing water vapor from escaping.
37. Why is it important to rinse the cuvette with the solution to be measured before inserting it into the spectrophotometer?
Answer
Rinsing ensures that the cuvette contains only the test solution and no contamination from previous samples, improving accuracy.
38. What would it mean if leaf disks in a photosynthesis lab do not float under any light condition?
Answer
Photosynthesis is not occurring. Possible causes include lack of carbon dioxide, damaged leaf tissue, or ineffective light intensity.
39. In the bacterial transformation lab, what does growth on LB/ampicillin + arabinose plates indicate?
Answer
It indicates successful transformation with a plasmid carrying both ampicillin resistance and GFP genes, and expression triggered by arabinose.
40. Why must the heat shock step be precisely timed in bacterial transformation?
Answer
Too short or too long exposure can reduce transformation efficiency or kill the bacteria due to temperature stress.
41. What is the purpose of the buffer solution in gel electrophoresis?
Answer
The buffer conducts electricity and maintains pH, ensuring consistent movement of DNA through the gel.
42. In the osmosis lab, how could you determine the concentration of solutes inside a potato cell?
Answer
Soak potato cores in various sucrose solutions and identify the molarity where there is no net mass change; this equals internal solute concentration.
43. How does the addition of NaCl affect enzyme activity in a peroxidase lab?
Answer
High NaCl concentrations may disrupt enzyme shape or function by affecting ionic interactions, reducing activity.
44. Why is it useful to calculate the percent change in mass in osmosis experiments rather than absolute change?
Answer
Percent change accounts for differences in initial mass, allowing comparison across different samples.
45. In a fruit fly lab, what would be a valid way to quantify behavior preference?
Answer
Record the number of flies on each side of the chamber over time and calculate the proportion in each area.
46. A student finds that both control and experimental groups show bacterial growth on ampicillin plates. What should they check first?
Answer
Check if the ampicillin was properly added or stored, as degraded antibiotic would allow all bacteria to grow.
47. How would you determine whether light intensity affects photosynthesis rate using the floating disk method?
Answer
Expose disks to different light intensities and measure ET50 for each; faster rise times indicate higher rates of photosynthesis.
48. Why is standard deviation reported in lab graphs?
Answer
It shows variability within data and helps determine reliability and significance of the results.
49. In a Hardy-Weinberg simulation, what condition must be present for allele frequencies to remain stable?
Answer
No mutation, random mating, no migration, large population size, and no selection must all be present.
50. What conclusion can be drawn if a sample’s 95% confidence interval does not overlap with that of another sample?
Answer
The means are likely significantly different at the 0.05 level; the observed difference is unlikely due to chance.