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GCSE · Biology

B-RP Biology Required Practicals and Data Analysis

AQA 8464 · Calculator allowed · about 90 minutes

Total Marks

Name: _______________________________ Date: ____ / ____ / ______

Answer ALL questions. Show all your working.

Deepa's group carried out the four standard food tests on a range of school-canteen food samples. Their method notes are shown below, with some gaps left to complete.

Test for reducing sugars: reagent = Benedict's solution; method = ____; positive result = blue solution turns green, then yellow, then a brick-red precipitate forms
Test for starch: reagent = ____; method = add a few drops directly to the food sample at room temperature; positive result = orange-brown solution turns blue-black
Test for protein: reagent = biuret reagent (sodium hydroxide solution, then dilute copper sulfate solution); method = add the reagents and mix at room temperature, do not heat; positive result = ____
Test for lipids (fats): reagent = ethanol, then water; method = shake the sample with ethanol, then pour the mixture into water; positive result = ____

(a)Complete the method for the reducing sugars test (the blank after 'method =').(1)

(b)Complete the reagent used for the starch test (the blank after 'reagent =').(1)

(c)Complete the positive result for the protein test (the blank after 'positive result =').(1)

(d)Complete the positive result for the lipids test (the blank after 'positive result =').(1)

(Total for Question 1 is 4 marks)

A student prepares a temporary mount of onion epidermis to view under a light microscope. The microscope has an eyepiece lens of x10 and an objective lens of x40.

(a)Name one piece of equipment, other than the microscope, needed to prepare the temporary mount, and state its purpose.(2)

(b)Explain why iodine solution is added to the onion epidermis before it is viewed.(1)

(c)Calculate the total magnification of the microscope.(1)

(d)Using a calibrated eyepiece graticule, the student measures the image of one epidermal cell as 2400 um long. Using the total magnification from part (c), calculate the actual length of the cell, in um.(2)

(Total for Question 2 is 6 marks)

On 03/03/2026, Priya's group began the required practical investigating osmosis in potato tissue. They planned to cut chips from the same potato using a cork borer, and place them into sucrose solutions of different concentrations for a fixed length of time, measuring the mass of each chip before and after.

(a)Identify the independent variable and the dependent variable in this investigation.(2)

(b)State two variables, other than concentration, that should be controlled to make this a fair test, and explain why one of them must be controlled.(3)

(c)Explain why each potato chip should be blotted dry with a paper towel before its mass is measured.(1)

(Total for Question 3 is 6 marks)

Before starting the required practical investigations, students must complete a risk assessment for the equipment and chemicals they will use.

(a)The enzyme investigation uses a water bath heated to around 35-40 degC. State one hazard this presents, and one control measure to reduce the risk.(2)

(b)The food tests use iodine solution. State one hazard this presents, and one control measure to reduce the risk.(2)

(Total for Question 4 is 4 marks)

Deepa's group tests a control tube of distilled water alongside each food sample when carrying out the food tests.

(a)Explain why a tube containing distilled water, instead of a food sample, should be tested alongside the food samples.(2)

(b)One of Deepa's food samples turns blue-black when iodine solution is added, but stays blue (no colour change) when biuret reagent is added. What does this tell you about the composition of the food sample?(2)

(Total for Question 5 is 4 marks)

Jack's group investigated the effect of pH on the rate of reaction of an enzyme that breaks down starch. They mixed the enzyme with starch solution at a fixed temperature, using buffer solutions of different pH values. Every 30 seconds, they removed a sample of the reaction mixture and tested it with iodine solution on a spotting tile.

(a)Identify the independent variable and the dependent variable in this investigation.(2)

(b)State two variables, other than pH, that should be controlled in this investigation, and explain why one of them must be controlled.(3)

(c)Describe how the group would know when the reaction had finished (the end-point).(2)

(Total for Question 6 is 7 marks)

A separate group investigated the effect of light intensity on the rate of photosynthesis of pondweed, using a lamp at different distances from a boiling tube of pondweed in sodium hydrogencarbonate solution. (Photosynthesis: 6CO2 + 6H2O -> C6H12O6 + 6O2, using light energy.)

(a)Identify the independent variable and the dependent variable in this investigation.(2)

(b)Name one variable, other than distance, that must be controlled in this investigation, and describe how it could be controlled.(2)

(c)State one hazard associated with using a lamp close to a water bath in this investigation, and a suitable control measure.(2)

(Total for Question 7 is 6 marks)

Priya's group placed potato chips, each with an initial mass of 1.40 g, into sucrose solutions of different concentrations for 30 minutes, then blotted them dry and re-weighed them. Their results are shown below.

Concentration of sucrose solution (mol/dm³): 0.0, 0.2, 0.4, 0.6, 0.8, 1.0
Initial mass (g): 1.40, 1.40, 1.40, 1.40, 1.40, 1.40
Final mass (g): 1.61, 1.53, 1.42, 1.47, 1.19, 1.05
Percentage change in mass (%): 15.0, ?, 1.4, 5.0, -15.0, -25.0

(a)Calculate the percentage change in mass for the 0.2 mol/dm³ solution. Give your answer to 1 decimal place.(2)

(b)One result in the table is anomalous. Identify it, and explain why it is anomalous.(2)

(c)Suggest one reason why the result at 0.6 mol/dm³ might have occurred.(1)

(d)Describe how the group could check whether the result at 0.6 mol/dm³ is a genuine anomaly.(1)

(Total for Question 8 is 6 marks)

Jack's group (from Question 6) recorded the following times for the iodine test to stop giving a blue-black colour at each pH.

pH: 5, 6, 7, 8, 9
Time taken for starch to be fully broken down (s): 220, 130, 70, 145, 260

(a)Calculate the rate of reaction at pH 7, in s^-1. Give your answer to 3 significant figures.(2)

(b)Calculate the rate of reaction at pH 9, in s^-1. Give your answer to 3 significant figures.(2)

(c)Describe the relationship shown between pH and rate of reaction.(2)

(Total for Question 9 is 6 marks)

Amara used the ruler-drop method to measure her own reaction time five times. Her partner released a 30 cm ruler without warning and Amara caught it as quickly as she could; the results were converted into a reaction time in milliseconds (ms) each time.

Amara's reaction times (ms): 210, 195, 202, 340, 198

(a)Identify the anomalous result.(1)

(b)Calculate the mean reaction time, excluding the anomalous result. Give your answer in seconds.(3)

(c)Calculate the range of the four valid results, in ms.(1)

(d)Suggest one improvement that would increase the reliability of this investigation.(1)

(Total for Question 10 is 6 marks)

Chidi's group used a 0.25 m² quadrat to sample daisies growing in a rectangular school field measuring 100 m by 40 m. They placed the quadrat at 5 randomly chosen points and counted the daisies in each.

Number of daisies per quadrat: 12, 8, 15, 9, 11

(a)Calculate the mean number of daisies per quadrat.(1)

(b)Calculate the total area of the field, in m^2.(1)

(c)Estimate the total daisy population in the field. Show your working.(3)

(Total for Question 11 is 5 marks)

Priya's group plotted a graph of percentage change in mass (y-axis) against concentration of sucrose solution (x-axis), using their results from Question 8 (treating the 0.6 mol/dm³ point as anomalous and excluding it from the line of best fit).

(a)Describe the shape/trend of the graph the group would expect to plot.(2)

(b)Use the graph to estimate the concentration of sucrose solution that is isotonic to the potato cells (where percentage change in mass = 0). Show your reasoning.(2)

(c)Explain, in terms of water potential, why the potato chips gained mass in the 0.0 mol/dm³ solution (distilled water).(3)

(Total for Question 12 is 7 marks)

Chidi's group used random sampling to estimate the total daisy population in Question 11. They then planned a second investigation: to find out whether the number of daisies changes with distance from a hedge that casts shade over part of the same field.

(a)Explain why random sampling was appropriate for estimating the total daisy population in Question 11.(2)

(b)Explain why systematic sampling along a transect line would be more appropriate than random sampling for the second investigation (daisy number against distance from the hedge).(2)

(Total for Question 13 is 4 marks)

Jack's group reflected on their pH investigation from Questions 6 and 9.

(a)Explain, in terms of enzyme structure, why the rate of reaction decreases at pH values above and below the optimum of pH 7.(3)

(b)The end-point in this method is judged by eye using a spotting tile, which is subjective. Suggest one improvement to make the results more reliable, and explain how it would improve the investigation.(2)

(c)Suggest one other factor, besides pH, that this required practical could be adapted to investigate.(1)

(Total for Question 14 is 6 marks)

Data analysis across the required practicals raises some general questions about the quality of evidence.

(a)Define the terms 'repeatable' and 'reproducible' in the context of a scientific investigation.(2)

(b)A second group repeats the enzyme investigation from Question 9, using a different water bath and their own set of spotting tiles, and obtains very similar rate values to the original group. Does this make the original data more repeatable, more reproducible, or both? Explain your answer.(2)

(c)A student notices that school fields with more daisies also tend to have more clover. Suggest why this correlation does not necessarily mean that daisies cause clover to grow (or vice versa).(2)

(Total for Question 15 is 6 marks)

Using the actual cell length of 6 um found in Question 2, and a further micrograph measurement, extend the microscopy calculations using standard form.

(a)Convert the actual cell length of 6 um (from Question 2) into metres. Give your answer in standard form.(2)

(b)A different specialised cell has an actual length of 1.2 x 10^-5 m and is viewed at a total magnification of x800. Calculate the image length you would expect to measure, in mm.(3)

(Total for Question 16 is 5 marks)

A group investigated the rate of bubble production from pondweed at a range of distances from a lamp.

Distance from lamp (cm): 10, 20, 30, 40, 50
Bubbles of oxygen produced per minute: 55, 32, 18, 10, 6

(a)The relative light intensity reaching the pondweed is estimated using the equation: relative light intensity = 1 / distance^2. Calculate 1 / distance² for d = 30 cm and for d = 50 cm. Give your answers in standard form (units cm^-2).(3)

(b)Describe the relationship between 1/distance² and the rate of bubble production shown by the data between 30 cm and 50 cm.(2)

(c)Explain why the rate does not continue to increase in the same proportion at the smallest distance tested (10 cm).(2)

(Total for Question 17 is 7 marks)

Olivia and Ben want to investigate the effect of caffeine drink concentration on human reaction time, using a method based on the ruler-drop test from Question 10.

Plan an investigation they could carry out. Your answer should include:
- how you will vary the caffeine concentration and measure reaction time
- which variables must be controlled and how
- how you will make your results reliable
- any safety or ethical considerations.

(Total for Question 18 is 6 marks)

Mark scheme · B-RP Biology Required Practicals and Data Analysis

Question 1

(a) B1 add the reagent to the sample and heat in a water bath (e.g. at about 75 degC) for a few minutes, oe
(a) Answer: Add Benedict's solution to the sample and heat in a water bath for a few minutes.
(b) B1 iodine solution (iodine dissolved in potassium iodide solution), oe
(b) Answer: Iodine solution.
(c) B1 blue solution turns purple / lilac, oe
(c) Answer: The blue solution turns purple (lilac).
(d) B1 a cloudy / milky white emulsion forms, oe
(d) Answer: A cloudy, milky-white emulsion forms.

Question 2

(a) B1 equipment named, e.g. mounted needle / cover slip / scalpel / pipette
(a) B1 correct purpose, e.g. mounted needle to lower the cover slip and avoid air bubbles; cover slip to protect/flatten the sample; scalpel to cut a thin section; pipette to add a drop of water or stain
(a) Answer: Mounted needle, used to lower the cover slip slowly onto the sample so that air bubbles are not trapped underneath.
(b) B1 it stains the cells/nuclei so that the cell structures show up more clearly under the microscope, oe
(b) Answer: It stains the cell structures (e.g. the nucleus), making them easier to see under the microscope.
(c) B1 400 (from 10 x 40), cao
(c) Answer: x400
(d) M1 actual size = image size / magnification = 2400 / 400, oe
(d) A1 6 um cao
(d) Answer: 6 um

Question 3

(a) B1 independent variable: concentration of the sucrose solution, oe
(a) B1 dependent variable: change in mass of the potato chip (e.g. percentage change in mass), oe
(a) Answer: Independent variable: concentration of sucrose solution. Dependent variable: change in mass of the potato chip.
(b) B1 temperature of the solutions, oe
(b) B1 size/dimensions (length and diameter) of each potato chip, oe; allow volume of solution, time left in the solution, or using chips from the same potato
(b) B1 explanation, e.g. if temperature were not controlled, any difference in mass change could be caused by temperature affecting the rate of osmosis rather than by concentration, making the test unfair/invalid, oe
(b) Answer: Temperature of the solutions and the size (length/diameter) of each potato chip (also accept volume of solution or time in solution); if temperature were not controlled, differences in results could be due to temperature rather than concentration.
(c) B1 to remove excess surface solution/water, which would otherwise be included in the mass and make the measurement inaccurate, oe
(c) Answer: Blotting removes surface liquid clinging to the chip, so only the mass of the chip itself is measured, giving a more accurate result.

Question 4

(a) B1 hazard: scalds/burns from the hot water (or steam), oe
(a) B1 control measure: use a test-tube holder/tongs to remove tubes, and keep the water bath away from the edge of the bench, oe
(a) Answer: Hazard: scalds from the hot water. Control measure: use tongs or a test-tube holder to handle the tubes, and position the water bath away from the edge of the bench.
(b) B1 hazard: iodine solution irritates/stains skin and eyes, oe
(b) B1 control measure: wear eye protection (safety goggles) and avoid skin contact, washing hands if contact occurs, oe
(b) Answer: Hazard: iodine solution can irritate the skin and eyes. Control measure: wear eye protection and avoid skin contact.

Question 5

(a) B1 it acts as a control, allowing comparison with the food samples, oe
(a) B1 it checks that the reagents themselves do not produce a colour change/false positive, so any colour change seen in the food samples can be confidently attributed to the food, oe
(a) Answer: It is a control: it shows that any colour change in the food samples is caused by the food itself, not by the reagents alone.
(b) B1 the sample contains starch (positive iodine test), oe
(b) B1 the sample does not contain protein (negative biuret test, as the solution stayed blue rather than turning purple), oe
(b) Answer: The sample contains starch (positive iodine test) but does not contain protein (biuret test stayed blue, so it was negative).

Question 6

(a) B1 independent variable: pH of the buffer solution, oe
(a) B1 dependent variable: time taken for the starch to be fully broken down (or the rate of the reaction), oe
(a) Answer: Independent variable: pH of the buffer solution. Dependent variable: time taken for all the starch to be broken down.
(b) B1 temperature (e.g. using a water bath at a fixed temperature), oe
(b) B1 volume/concentration of enzyme solution and volume/concentration of starch solution used each time, oe
(b) B1 explanation, e.g. if temperature were not controlled, a faster or slower reaction could be caused by a change in temperature rather than pH, making the comparison unfair, oe
(b) Answer: Temperature (kept constant with a water bath) and the volume/concentration of enzyme and starch solutions; if temperature were not controlled, differences in rate could be due to temperature rather than pH.
(c) B1 a sample of the mixture is added to a drop of iodine solution on the spotting tile at regular intervals, oe
(c) B1 the end-point is reached when the iodine solution no longer turns blue-black (it remains orange-brown), showing all the starch has been broken down, oe
(c) Answer: A sample is tested with iodine solution at regular intervals; the reaction has finished when the iodine no longer turns blue-black (it stays orange-brown).

Question 7

(a) B1 independent variable: distance of the lamp from the pondweed (light intensity), oe
(a) B1 dependent variable: rate of oxygen bubble production (bubbles produced per minute), oe
(a) Answer: Independent variable: distance of lamp from pondweed. Dependent variable: rate of bubble (oxygen) production.
(b) B1 concentration of carbon dioxide, oe
(b) B1 by using the same concentration of sodium hydrogencarbonate solution in every test, oe; allow temperature controlled by keeping the tube in a water bath, or using the same length/species of pondweed
(b) Answer: Carbon dioxide concentration, controlled by using the same concentration of sodium hydrogencarbonate solution each time.
(c) B1 hazard: electric shock from mains equipment near water, or burns from the hot lamp bulb, oe
(c) B1 control measure: keep electrical connections away from water/spillages, or allow the lamp to cool before handling / do not touch the bulb, oe
(c) Answer: Hazard: electric shock from the lamp near water. Control measure: keep the lamp's electrical connections away from any water and spillages.

Question 8

(a) M1 (1.53 - 1.40) / 1.40 x 100, oe
(a) A1 9.3% cao (accept 9.2857...% rounding to 9.3%)
(a) Answer: 9.3%
(b) B1 the result at 0.6 mol/dm³ (+5.0%) is identified as anomalous
(b) B1 explanation: it does not fit the otherwise steadily decreasing trend shown by the other results (it should be lower than the +1.4% recorded at 0.4 mol/dm³, and likely negative), oe
(b) Answer: The result at 0.6 mol/dm³ (+5.0%) is anomalous, as it breaks the otherwise steadily decreasing trend shown by the rest of the data.
(c) B1 e.g. the chip was not blotted dry as thoroughly as the others (extra surface water added to the mass); or the chip was accidentally swapped/mislabelled with a different concentration; or a measurement/recording error, oe (any one sensible suggestion)
(c) Answer: For example, the chip may not have been blotted dry as thoroughly as the others, adding extra surface water to its measured mass.
(d) B1 repeat the test at 0.6 mol/dm³ (ideally several times, with a fresh chip) and compare the new result(s) with the original trend, oe
(d) Answer: Repeat the test at 0.6 mol/dm³ with a fresh chip and see whether the new result fits the trend shown by the other concentrations.

Question 9

(a) M1 rate = 1 / time = 1 / 70, oe
(a) A1 0.0143 s^-1 cao (awrt 0.0143)
(a) Answer: 0.0143 s^-1
(b) M1 rate = 1 / time = 1 / 260, oe
(b) A1 0.00385 s^-1 cao (awrt 0.00385)
(b) Answer: 0.00385 s^-1
(c) B1 the rate increases as pH rises from 5 to 7, oe
(c) B1 the rate then decreases as pH rises further from 7 to 9, so pH 7 gives the fastest reaction (an optimum pH), oe
(c) Answer: The rate increases from pH 5 to a maximum at pH 7, then decreases from pH 7 to pH 9; pH 7 is the optimum pH for this enzyme.

Question 10

(a) B1 340 ms
(a) Answer: 340 ms
(b) M1 excludes 340 ms and sums the remaining four values: 210 + 195 + 202 + 198 = 805, oe (ecf: if a different value was excluded following an incorrect part (a), accept the consistent recalculated mean)
(b) M1 805 / 4 = 201.25 (ms), oe
(b) A1 0.201 s cao (awrt 0.201; accept 201 ms if converted correctly with working shown)
(b) Answer: 0.201 s
(c) B1 15 ms cao (210 - 195)
(c) Answer: 15 ms
(d) B1 take more repeat readings (e.g. at least 10) and calculate a mean, oe; or use a computer/software-based reaction timer instead of the ruler-drop method to remove human timing and catching error
(d) Answer: Take more repeat readings (e.g. at least 10) so that a more reliable mean can be calculated.

Question 11

(a) B1 11 cao (from (12+8+15+9+11)/5 = 55/5)
(a) Answer: 11 daisies per quadrat
(b) B1 4000 m² cao (from 100 x 40)
(b) Answer: 4000 m²
(c) M1 number of quadrats that would fit in the field = total area / quadrat area = 4000 / 0.25, oe
(c) dM1 = 16000 (quadrats); estimated population = mean per quadrat x number of quadrats = 11 x 16000, oe (ecf: allow an incorrect mean carried through from part (a), provided the method here is correct)
(c) A1 176000 (daisies) cao (accept 176,000)
(c) Answer: 176 000 daisies

Question 12

(a) B1 a downward (negative) trend: percentage change in mass decreases as concentration increases, oe
(a) B1 the line crosses the x-axis (percentage change = 0) at one particular concentration, oe
(a) Answer: The graph shows a downward, roughly straight-line trend: percentage change in mass decreases as concentration increases, crossing the x-axis at one point.
(b) M1 reads/interpolates between the 0.4 mol/dm³ point (+1.4%) and the 0.8 mol/dm³ point (-15.0%), ignoring the anomalous 0.6 mol/dm³ point, oe
(b) A1 answer in the range 0.40 - 0.50 mol/dm³ (awrt 0.43 mol/dm³)
(b) Answer: Approximately 0.43 mol/dm³ (accept any value in the range 0.40-0.50 mol/dm³).
(c) B1 distilled water has a higher (less negative) water potential than the solution inside the potato cells, oe
(c) B1 water moves from a region of higher water potential to a region of lower water potential (down a water potential gradient), oe
(c) B1 water moves into the potato cells by osmosis, across the partially permeable cell membrane, causing the cells (and the chip) to gain mass, oe
(c) Answer: Distilled water has a higher water potential than the potato cells, so water moves into the cells by osmosis, across the partially permeable membrane, down the water potential gradient, causing the chip to gain mass.

Question 13

(a) B1 it avoids bias, e.g. the student unconsciously choosing quadrat positions with more or fewer daisies, oe
(a) B1 it gives a sample that is representative of the whole field, so the population estimate is valid, oe
(a) Answer: Random sampling avoids bias in where the quadrats are placed, giving a representative sample of the whole field so the estimate is valid.
(b) B1 this investigation is looking for a pattern/gradient in daisy number linked to distance from the hedge, oe
(b) B1 systematic sampling along a transect at set distance intervals directly links each result to its distance from the hedge, which random sampling would not reliably show, oe
(b) Answer: The investigation is testing for a trend with distance from the hedge, so systematic sampling along a transect (at set intervals from the hedge) links each result directly to distance, unlike random sampling.

Question 14

(a) B1 a pH away from the optimum changes the shape of the enzyme's active site, oe
(a) B1 at more extreme pH values the enzyme becomes denatured, so the active site shape is permanently changed, oe
(a) B1 the substrate (starch) can no longer bind to (fit) the active site, so fewer successful enzyme-substrate collisions occur and the rate of reaction is lower, oe
(a) Answer: Away from the optimum pH, the enzyme's active site changes shape (and becomes denatured at more extreme pH), so starch molecules can no longer fit the active site, reducing the rate of reaction.
(b) B1 use a colorimeter to measure the colour change of the iodine/starch mixture objectively, instead of judging by eye, oe
(b) B1 this removes the subjectivity/human error in judging the end-point, giving more precise and reliable/repeatable data, oe
(b) Answer: Use a colorimeter to measure the colour change objectively instead of judging it by eye; this removes human error/subjectivity from deciding the end-point, making the results more reliable.
(c) B1 temperature, oe; or concentration of amylase (enzyme), or concentration of starch
(c) Answer: Temperature (also accept enzyme concentration or starch concentration).

Question 15

(a) B1 repeatable: the original experimenter, using the same method and equipment, obtains the same/similar results on repeating the investigation, oe
(a) B1 reproducible: the investigation is repeated by a different person, or using different equipment/methods, and similar results are still obtained, oe
(a) Answer: Repeatable: the same person, method and equipment give similar results on repeating the test. Reproducible: a different person, or different equipment/method, still gives similar results.
(b) B1 reproducible (not simply repeatable), oe
(b) B1 because a different group, using different equipment, obtained similar results, showing the finding holds beyond the original group's specific method/equipment, oe
(b) Answer: Reproducible - a different group using different equipment obtained similar results, showing the finding does not just depend on the original group's own set-up.
(c) B1 a third (confounding) factor, e.g. light availability, soil quality/nutrients, or moisture, could independently affect the growth of both daisies and clover, oe
(c) B1 without a controlled experiment changing only one variable, a correlation alone cannot show that one directly causes the other, oe
(c) Answer: A third factor, such as soil quality or light availability, could independently affect both daisies and clover; a correlation alone, without a controlled experiment, cannot prove that one causes the other.

Question 16

(a) M1 converts um to m by dividing by 10⁶ (1 um = 1 x 10^-6 m), oe
(a) A1 6 x 10^-6 m cao
(a) Answer: 6 x 10^-6 m
(b) M1 rearranges magnification = image size / actual size to give image size = actual size x magnification, oe
(b) M1 1.2 x 10^-5 x 800, oe
(b) A1 9.6 mm cao (from 9.6 x 10^-3 m)
(b) Answer: 9.6 mm

Question 17

(a) M1 method: squares the distance then takes the reciprocal (1 / d²), for either value
(a) A1 d = 30 cm: 1.11 x 10^-3 cm^-2 (awrt), cao
(a) A1 d = 50 cm: 4.00 x 10^-4 cm^-2, cao
(a) Answer: d = 30 cm: 1.11 x 10^-3 cm^-2; d = 50 cm: 4.00 x 10^-4 cm^-2.
(b) B1 as 1/distance² increases, the rate of bubble production increases, oe
(b) B1 the increase is roughly directly proportional (a straight-line relationship) over this range, oe
(b) Answer: Over this range, the rate of bubble production increases roughly in direct proportion to 1/distance² (a straight-line relationship).
(c) B1 at this high light intensity (short distance), light is no longer the limiting factor, oe
(c) B1 another factor, such as carbon dioxide concentration or temperature, becomes limiting instead, so the rate increase levels off rather than continuing at the same rate, oe
(c) Answer: At the shortest distance, light is no longer limiting the rate; another factor (e.g. CO2 concentration or temperature) becomes limiting instead, so the rate rises by proportionally less than expected.

Question 18

Level 1 (1-2): Basic, isolated relevant points are made, e.g. reaction time will be measured with a ruler, or different caffeine amounts will be tested, with little or no logical structure and most control/reliability/ethical detail missing.
Level 2 (3-4): Some relevant detail is given in a reasonably logical order: the independent and dependent variables are identified, one or two control variables are named, and repeats are mentioned, but the plan lacks depth in either reliability or safety/ethical considerations.
Level 3 (5-6): A detailed, logically sequenced plan that clearly identifies the independent, dependent and control variables, describes a fair-test method (including a baseline/placebo comparison), explains how repeats and means will improve reliability, and includes appropriate safety and ethical considerations.
Indicative content:
- Independent variable: concentration/dose of caffeine in the drink given to participants (e.g. 0 mg, 40 mg, 80 mg, 120 mg caffeine per drink)
- Dependent variable: reaction time, measured using the ruler-drop test (distance the ruler falls before being caught, converted to a time)
- Control variables: same participant(s) tested each time, same time of day, same volume of drink, same person dropping the ruler, a quiet/consistent testing environment, and no other stimulants (e.g. no other caffeinated drinks) before testing
- Method: measure a baseline reaction time before caffeine; give the caffeine drink; wait a fixed, suitable time (e.g. 20-30 minutes) for the caffeine to be absorbed; repeat the reaction time test
- Reliability: repeat each reaction time measurement several times (e.g. at least 5) at each caffeine dose and calculate a mean, excluding any anomalous results; test multiple participants and average across them
- Use of a control/placebo drink that looks and tastes the same but contains no caffeine, to account for any placebo effect
- Safety and ethical considerations: keep caffeine doses within safe limits for the age group, exclude participants with relevant health conditions (e.g. heart conditions) or high caffeine sensitivity, obtain informed consent (and parental consent for minors), and allow participants to withdraw at any time
- Present results in a table and/or graph and describe the conclusion linking caffeine dose to the trend in reaction time

Biology Required Practicals and Data Analysis - Worksheets, Questions and Revision

B-RP Biology Required Practicals and Data Analysis

Question 1

Question 2

Question 3

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question 10

Question 11

Question 12

Question 13

Question 14

Question 15

Question 16

Question 17

Question 18