Rucete ✏ AP Biology In a Nutshell
22. Labs — Practice Questions 3
This chapter covers key experimental skills in AP Biology, including lab design, data interpretation, and core science practices.
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(Multiple Choice — Click to Reveal Answer)
1. Which factor would most directly increase the precision of experimental results in a controlled biology lab?
(A) Increasing the number of variables
(B) Decreasing sample size
(C) Including more replicates
(D) Using different measuring tools
Answer
(C) — More replicates increase the reliability and statistical power of the data.
2. In a Hardy-Weinberg simulation, what condition must be met to avoid evolution?
(A) Large population size
(B) Gene flow
(C) Selective mating
(D) High mutation rate
Answer
(A) — Large population size helps prevent genetic drift, which could cause evolution.
3. Which of the following would be the best hypothesis for a photosynthesis lab using leaf disks?
(A) Photosynthesis occurs faster in complete darkness.
(B) If the light intensity increases, then the rate of leaf disk flotation will increase.
(C) Oxygen bubbles always form on the underside of leaves.
(D) Leaf color does not affect gas exchange.
Answer
(B) — It clearly identifies a testable relationship between an independent and dependent variable.
4. Why is dialysis tubing often used to model cell membranes in osmosis labs?
(A) It is permeable to all molecules
(B) It replicates active transport
(C) It selectively allows certain molecules through
(D) It is impermeable like a cell wall
Answer
(C) — Dialysis tubing is semipermeable and mimics the selective permeability of biological membranes.
5. Which of the following setups would be best to measure transpiration rates under varying humidity levels?
(A) A potometer with identical plants in controlled chambers
(B) Measuring dry weight of soil
(C) Observing plant growth in sunlight
(D) Measuring chlorophyll concentration
Answer
(A) — A potometer allows precise measurement of water loss under different environmental conditions.
6. What is the function of a positive control in an experiment?
(A) To remove bias
(B) To provide a known response
(C) To reduce variability
(D) To test multiple variables
Answer
(B) — A positive control is expected to produce a known outcome, confirming the experimental system works correctly.
7. In a diffusion lab, why are small molecules like iodine able to pass through dialysis tubing?
(A) They are hydrophobic
(B) They are actively transported
(C) They are small enough to diffuse through pores
(D) They are neutral in charge
Answer
(C) — Small molecules diffuse through the semi-permeable membrane due to their size.
8. A student performs a fruit fly lab and finds equal numbers of flies on both sides. What is the best conclusion?
(A) The flies prefer both environments
(B) The test lacked replication
(C) There is no behavioral preference
(D) Flies always move randomly
Answer
(C) — Equal distribution indicates no significant preference between environmental conditions.
9. Which of the following best defines the independent variable in an experiment?
(A) The variable measured at the end
(B) The variable that changes as a result
(C) The variable controlled by the experimenter
(D) The variable that is averaged
Answer
(C) — The independent variable is deliberately manipulated to test its effect on the dependent variable.
10. In the bacterial transformation lab, why do some plates include arabinose?
(A) To kill untransformed cells
(B) To select for antibiotic resistance
(C) To activate the GFP gene
(D) To sterilize the medium
Answer
(C) — Arabinose induces expression of the GFP gene on the plasmid, allowing bacteria to glow under UV light.
11. Why are Fast Plants ideal for artificial selection experiments in a school lab setting?
(A) They require no light
(B) They grow slowly and predictably
(C) They reproduce quickly and have visible traits
(D) They contain human genes
Answer
(C) — Fast Plants complete their life cycle in about 40 days, making them suitable for classroom studies of selection.
12. What is the best reason for using a blank solution when calibrating a spectrophotometer?
(A) To prevent overheating
(B) To zero out background absorbance
(C) To add color contrast
(D) To speed up reactions
Answer
(B) — The blank sets the baseline absorbance, removing interference from solvents or reagents.
13. A plant in a closed terrarium is exposed to strong light. Which change is most likely?
(A) Increased transpiration
(B) Decreased stomatal opening
(C) Reduced photosynthesis
(D) Slower water uptake
Answer
(A) — Strong light increases photosynthesis and opens stomata, leading to more water loss through transpiration.
14. In an osmosis experiment, which result would confirm that water entered the cell?
(A) Decreased volume
(B) Decreased mass
(C) Increased mass
(D) Equal concentration inside and outside
Answer
(C) — A mass gain indicates that water moved into the cell, typical in hypotonic environments.
15. Why are 95% confidence intervals useful when comparing two sets of lab data?
(A) They show pH variation
(B) They determine causation
(C) They reflect the range of possible true means
(D) They eliminate error
Answer
(C) — A 95% confidence interval estimates the range in which the true population mean likely falls, helping assess data significance.
16. What does a high standard deviation in experimental results indicate?
(A) The data is very consistent
(B) The mean is incorrect
(C) There is a lot of variability
(D) The sample size is too small
Answer
(C) — A high standard deviation means the data points are spread out, indicating variability in results.
17. In gel electrophoresis, why do smaller DNA fragments move faster?
(A) They are more negatively charged
(B) They interact more with the gel
(C) They pass through the gel matrix more easily
(D) They dissolve into the buffer
Answer
(C) — Smaller DNA fragments navigate through the pores of the gel more easily, so they migrate farther.
18. What is the function of a negative control in an experiment?
(A) It ensures that the experimental setup can detect a response
(B) It removes background noise
(C) It demonstrates the expected response
(D) It shows the result in the absence of the experimental variable
Answer
(D) — A negative control confirms that no effect occurs when the independent variable is absent.
19. In the enzyme catalysis lab, what would be the most appropriate dependent variable?
(A) pH of the solution
(B) Type of enzyme used
(C) Rate of product formation
(D) Presence of buffer
Answer
(C) — The rate at which the product forms (e.g., O₂ or color change) is the variable being measured.
20. Why should experiments be repeated multiple times?
(A) To increase the mean value
(B) To show bias
(C) To reduce error and confirm reliability
(D) To change the variables
Answer
(C) — Repetition increases accuracy and helps detect anomalies or patterns in the data.
21. What conclusion can be drawn if the confidence intervals of two groups do not overlap?
(A) The groups are genetically identical
(B) The data sets are not statistically different
(C) The difference is likely statistically significant
(D) There was a measurement error
Answer
(C) — Non-overlapping confidence intervals suggest a statistically significant difference between the means.
22. In a lab using floating leaf disks, what is the reason for applying vacuum infiltration before starting the experiment?
(A) To fill the disks with CO₂
(B) To coat them in wax
(C) To remove air and allow disks to sink
(D) To kill off any bacteria
Answer
(C) — Vacuum infiltration removes air from the disks so they sink; as photosynthesis occurs, they rise again.
23. Which component of a lab report is used to summarize key findings and address the hypothesis?
(A) Introduction
(B) Methods
(C) Results
(D) Conclusion
Answer
(D) — The conclusion section interprets the results and discusses whether the hypothesis was supported.
24. If a student observes bubbles forming on underwater plant leaves exposed to light, what process is occurring?
(A) Transpiration
(B) Cellular respiration
(C) Photosynthesis
(D) Osmosis
Answer
(C) — Photosynthesis releases oxygen gas, which forms bubbles on submerged leaves.
25. Why is it important to control environmental variables like temperature and light during an experiment?
(A) To eliminate dependent variables
(B) To ensure reproducibility and isolate the effect of the independent variable
(C) To reduce the sample size
(D) To speed up the experiment
Answer
(B) — Controlling external factors allows clearer interpretation of how the independent variable affects the dependent variable.
26. A student records unusually high absorbance values in a spectrophotometry lab. What is the most likely cause?
(A) The enzyme was denatured
(B) The sample was too diluted
(C) The cuvette was dirty or misaligned
(D) The pH was too low
Answer
(C) — A dirty or misaligned cuvette can cause light to scatter, leading to artificially high absorbance readings.
27. In a transformation experiment, bacteria grow on an LB/amp plate but do not glow under UV light. What does this suggest?
(A) Transformation was unsuccessful
(B) Arabinose was missing, preventing GFP expression
(C) Ampicillin resistance was not conferred
(D) The bacteria are not E. coli
Answer
(B) — Arabinose is required to activate the promoter that triggers GFP gene expression.
28. During a Hardy-Weinberg simulation, a population undergoes a bottleneck event. What will most likely happen?
(A) Allele frequencies will remain constant
(B) Genetic drift will increase
(C) Mutations will decrease
(D) Gene flow will stabilize
Answer
(B) — Bottleneck events reduce genetic variation and increase the impact of random drift on allele frequencies.
29. A student uses a potometer but fails to seal the apparatus properly. What is the likely result?
(A) Increased transpiration rate
(B) Reduced stomatal opening
(C) Air leaks causing inaccurate water uptake measurements
(D) More water moving into the plant
Answer
(C) — Leaks will disrupt the pressure gradient, leading to incorrect readings of water movement.
30. In a gel electrophoresis lab, why might two different DNA samples show identical banding patterns?
(A) The samples were not stained
(B) The DNA was degraded
(C) The individuals are genetically similar at the tested loci
(D) The current was too low
Answer
(C) — Identical banding patterns suggest that the two DNA sources have matching sequences at the restriction sites used.
31. A student performs a BLAST search and finds a gene sequence with an E-value of 2.1. What does this imply?
(A) The match is highly significant
(B) The gene is from the same species
(C) The match is likely due to chance
(D) The gene is not expressed
Answer
(C) — Higher E-values (>1) imply the similarity may be random and not biologically meaningful.
32. In the osmosis lab, why is the internal solute concentration of a potato determined at the point of 0% mass change?
(A) The potato is hypertonic at that point
(B) No net water movement occurs
(C) The sucrose is fully absorbed
(D) All enzymes are active
Answer
(B) — At 0% mass change, the solution is isotonic to the potato, indicating equal water potential inside and out.
33. What does a p-value of 0.01 indicate about the results of an experiment?
(A) The results are not statistically significant
(B) There is a 1% chance the result is due to random variation
(C) The hypothesis is incorrect
(D) The experiment needs more trials
Answer
(B) — A p-value of 0.01 means there is only a 1% probability that the observed results occurred by chance, indicating strong statistical significance.
34. In an enzyme lab, why does the reaction rate plateau at high substrate concentrations?
(A) The temperature is too low
(B) The enzymes are saturated and working at maximum capacity
(C) The substrate is inactive
(D) The solution becomes too acidic
Answer
(B) — At high substrate levels, all enzyme active sites are occupied, so the rate levels off.
35. What is the most appropriate use of a chi-square test in AP Biology labs?
(A) To measure enzyme activity
(B) To determine differences in observed vs. expected data distributions
(C) To compare means
(D) To calculate percent error
Answer
(B) — Chi-square tests are used to evaluate whether observed distributions differ significantly from expected ones.
36. In the floating leaf disk lab, what does a lower ET50 value indicate about the rate of photosynthesis?
Answer
A lower ET50 means the disks floated faster, indicating a higher rate of photosynthesis due to more oxygen production.
37. Why is it necessary to use a buffer solution during an enzyme catalysis experiment?
Answer
Buffers maintain a stable pH, ensuring that enzyme structure and activity are not affected by pH fluctuations.
38. A student observes no growth on a control LB plate in a transformation experiment. What does this suggest?
Answer
It suggests that the cells were likely dead or not properly plated, indicating a procedural error in handling or incubation.
39. How can a spectrophotometer help measure enzyme activity in a lab?
Answer
It quantifies changes in absorbance over time, which correlates with the rate of product formation in the reaction.
40. In a Hardy-Weinberg simulation, what effect does non-random mating have on allele frequencies?
Answer
Non-random mating increases the frequency of certain genotypes, disrupting Hardy-Weinberg equilibrium and altering allele distribution.
41. Why is it important to randomize the starting side of fruit flies in a choice chamber behavior lab?
Answer
To reduce bias caused by directional preference or environmental inconsistencies, ensuring more reliable behavioral data.
42. What does it mean if two DNA samples yield different banding patterns after restriction digestion and electrophoresis?
Answer
It indicates genetic differences between the samples at the restriction sites, suggesting different DNA sequences.
43. Why should the light source be kept constant when measuring the rate of photosynthesis in leaf disk labs?
Answer
To ensure that variations in photosynthesis rate are due to the tested variable, not inconsistent light exposure.
44. How does surface area affect transpiration rate in a plant?
Answer
Larger surface areas (more leaves) lead to more stomata and greater water loss, increasing the transpiration rate.
45. What is one way to confirm that a specific plasmid has been taken up by transformed bacteria?
Answer
Plate the bacteria on antibiotic-containing media; growth indicates successful uptake of a plasmid with a resistance gene.
46. In enzyme experiments, why might boiling the enzyme before the test cause the reaction to fail?
Answer
Boiling denatures the enzyme, disrupting its active site and rendering it inactive, so the reaction does not proceed.
47. Why are statistical tests like chi-square important in biological research?
Answer
They help determine whether observed differences are due to chance or represent real, significant effects.
48. In a photosynthesis lab, what role does bicarbonate solution play?
Answer
It provides a source of carbon dioxide, which is required for photosynthesis in the leaf disk assay.
49. What is the significance of using a DNA ladder in gel electrophoresis?
Answer
The DNA ladder contains fragments of known sizes and is used to estimate the sizes of unknown DNA samples.
50. Why does increasing the number of trials improve the reliability of experimental results?
Answer
It reduces the influence of random error and increases confidence in the observed trend or outcome.