1
AQA A-LEVEL BIOLOGY PAPER 3 2026/2027 |
BIOLOGY | 100 VERIFIED Q&A | DETAILED
RATIONALES | PASS GUARANTEED – A+ GRADED
SECTION 1: PRACTICAL SKILLS & EXPERIMENTAL DESIGN - Questions 1-20
Q1: Independent Variable
The student is reviewing experimental design. In an investigation into the effect of light intensity on
photosynthesis, what is the independent variable?
A. Rate of oxygen production
B. Light intensity
C. Temperature
D. Carbon dioxide concentration
Correct Answer: B
Rationale: The independent variable is the factor deliberately changed by the investigator. Here,
light intensity is varied. The rate of oxygen production is the dependent variable. Temperature and
CO₂ concentration are controlled variables. [100% CORRECT]
Q2: Dependent Variable
The student is reviewing experimental design. In an experiment measuring the effect of pH on
enzyme activity, what is the dependent variable?
A. pH
B. Temperature
C. Time taken for substrate to be broken down
D. Enzyme concentration
Correct Answer: C
Rationale: The dependent variable is the factor measured. Here, the rate of enzyme activity (e.g.,
time for substrate breakdown) is measured. pH is the independent variable. Temperature and
enzyme concentration are controlled. [100% CORRECT]
Q3: Control Variables
The student is reviewing experimental design. Why are control variables kept constant?
A. To ensure the independent variable affects the dependent variable
B. To make the experiment easier
C. To reduce the number of repeats
D. To increase the sample size
,2
Correct Answer: A
Rationale: Control variables are kept constant so that any change in the dependent variable can be
attributed to the independent variable, ensuring a valid test. [100% CORRECT]
Q4: Control Group
The student is reviewing experimental design. What is the purpose of a control group?
A. To provide a baseline for comparison
B. To increase the sample size
C. To test the independent variable
D. To measure the dependent variable
Correct Answer: A
Rationale: A control group is not exposed to the independent variable, providing a baseline to
compare the experimental group against, helping to validate results. [100% CORRECT]
Q5: Accuracy vs. Precision
The student is reviewing measurement. What is the difference between accuracy and precision?
A. Accuracy is closeness to true value; precision is closeness of repeated measurements
B. Accuracy is closeness of repeats; precision is closeness to true value
C. They are the same
D. Accuracy is only for qualitative data
Correct Answer: A
Rationale: Accuracy refers to how close a measurement is to the true value. Precision refers to how
close repeated measurements are to each other. [100% CORRECT]
Q6: Reliability
The student is reviewing experimental design. How can reliability be improved?
A. By taking more repeats and calculating a mean
B. By using a larger sample
C. By controlling more variables
D. By changing the independent variable
Correct Answer: A
Rationale: Reliability is improved by repeating measurements and calculating a mean, reducing the
effect of random errors. A larger sample improves representativeness, not necessarily reliability.
[100% CORRECT]
Q7: Validity
, 3
The student is reviewing experimental design. What makes an experiment valid?
A. It tests what it is intended to test and controls all relevant variables
B. It has many repeats
C. It uses expensive equipment
D. It produces precise data
Correct Answer: A
Rationale: Validity means the experiment measures what it claims to measure. This requires
controlling all variables except the independent variable and using appropriate methods. [100%
CORRECT]
Q8: Random Error
The student is reviewing errors. What causes random error?
A. Unpredictable variation in measurements
B. Faulty equipment
C. Incorrect calibration
D. Systematic bias
Correct Answer: A
Rationale: Random errors are unpredictable fluctuations due to limitations of measurement or
biological variation. They can be reduced by repeats and averaging. [100% CORRECT]
Q9: Systematic Error
The student is reviewing errors. What causes systematic error?
A. Faulty calibration or biased equipment
B. Random fluctuations
C. Biological variation
D. Small sample size
Correct Answer: A
Rationale: Systematic errors are consistent, directional errors caused by faulty equipment, incorrect
calibration, or biased methods. They affect accuracy. [100% CORRECT]
Q10: Uncertainty
The student is reviewing measurement. How is uncertainty calculated for a measurement using a
ruler with 1 mm divisions?
A. ±0.5 mm
B. ±1 mm
C. ±2 mm
D. ±0.1 mm
AQA A-LEVEL BIOLOGY PAPER 3 2026/2027 |
BIOLOGY | 100 VERIFIED Q&A | DETAILED
RATIONALES | PASS GUARANTEED – A+ GRADED
SECTION 1: PRACTICAL SKILLS & EXPERIMENTAL DESIGN - Questions 1-20
Q1: Independent Variable
The student is reviewing experimental design. In an investigation into the effect of light intensity on
photosynthesis, what is the independent variable?
A. Rate of oxygen production
B. Light intensity
C. Temperature
D. Carbon dioxide concentration
Correct Answer: B
Rationale: The independent variable is the factor deliberately changed by the investigator. Here,
light intensity is varied. The rate of oxygen production is the dependent variable. Temperature and
CO₂ concentration are controlled variables. [100% CORRECT]
Q2: Dependent Variable
The student is reviewing experimental design. In an experiment measuring the effect of pH on
enzyme activity, what is the dependent variable?
A. pH
B. Temperature
C. Time taken for substrate to be broken down
D. Enzyme concentration
Correct Answer: C
Rationale: The dependent variable is the factor measured. Here, the rate of enzyme activity (e.g.,
time for substrate breakdown) is measured. pH is the independent variable. Temperature and
enzyme concentration are controlled. [100% CORRECT]
Q3: Control Variables
The student is reviewing experimental design. Why are control variables kept constant?
A. To ensure the independent variable affects the dependent variable
B. To make the experiment easier
C. To reduce the number of repeats
D. To increase the sample size
,2
Correct Answer: A
Rationale: Control variables are kept constant so that any change in the dependent variable can be
attributed to the independent variable, ensuring a valid test. [100% CORRECT]
Q4: Control Group
The student is reviewing experimental design. What is the purpose of a control group?
A. To provide a baseline for comparison
B. To increase the sample size
C. To test the independent variable
D. To measure the dependent variable
Correct Answer: A
Rationale: A control group is not exposed to the independent variable, providing a baseline to
compare the experimental group against, helping to validate results. [100% CORRECT]
Q5: Accuracy vs. Precision
The student is reviewing measurement. What is the difference between accuracy and precision?
A. Accuracy is closeness to true value; precision is closeness of repeated measurements
B. Accuracy is closeness of repeats; precision is closeness to true value
C. They are the same
D. Accuracy is only for qualitative data
Correct Answer: A
Rationale: Accuracy refers to how close a measurement is to the true value. Precision refers to how
close repeated measurements are to each other. [100% CORRECT]
Q6: Reliability
The student is reviewing experimental design. How can reliability be improved?
A. By taking more repeats and calculating a mean
B. By using a larger sample
C. By controlling more variables
D. By changing the independent variable
Correct Answer: A
Rationale: Reliability is improved by repeating measurements and calculating a mean, reducing the
effect of random errors. A larger sample improves representativeness, not necessarily reliability.
[100% CORRECT]
Q7: Validity
, 3
The student is reviewing experimental design. What makes an experiment valid?
A. It tests what it is intended to test and controls all relevant variables
B. It has many repeats
C. It uses expensive equipment
D. It produces precise data
Correct Answer: A
Rationale: Validity means the experiment measures what it claims to measure. This requires
controlling all variables except the independent variable and using appropriate methods. [100%
CORRECT]
Q8: Random Error
The student is reviewing errors. What causes random error?
A. Unpredictable variation in measurements
B. Faulty equipment
C. Incorrect calibration
D. Systematic bias
Correct Answer: A
Rationale: Random errors are unpredictable fluctuations due to limitations of measurement or
biological variation. They can be reduced by repeats and averaging. [100% CORRECT]
Q9: Systematic Error
The student is reviewing errors. What causes systematic error?
A. Faulty calibration or biased equipment
B. Random fluctuations
C. Biological variation
D. Small sample size
Correct Answer: A
Rationale: Systematic errors are consistent, directional errors caused by faulty equipment, incorrect
calibration, or biased methods. They affect accuracy. [100% CORRECT]
Q10: Uncertainty
The student is reviewing measurement. How is uncertainty calculated for a measurement using a
ruler with 1 mm divisions?
A. ±0.5 mm
B. ±1 mm
C. ±2 mm
D. ±0.1 mm
