IGCSE Biology 0610/63 May/June 2025 Past Paper with Answers

Question 1

In an investigation into the effect of temperature on the enzyme catalase, three test-tubes were set up: test-tube C kept cold, test-tube R kept at room temperature, and test-tube H kept hot. The catalase produced a foam of oxygen, and the maximum height of the foam was measured as 8 mm for C, 15 mm for R and 27 mm for H. Which is the best way to record these results?

1. a table with one column for the test-tube and one column headed "height of foam / mm", showing C = 8, R = 15 and H = 27
2. a table with a single column listing the numbers 8, 15 and 27, with no headings and no units given
3. a table with a column headed "height of foam / mm" but showing C = 27, R = 15 and H = 8 instead
4. a sentence saying only that the hot test-tube made the most foam, with none of the measured values recorded

Question 2

In the catalase investigation the maximum height of the oxygen foam was 8 mm in the cold test-tube C, 15 mm at room temperature in test-tube R, and 27 mm in the hot test-tube H. What is the correct conclusion from these results?

1. increasing the temperature increases the activity of the catalase
2. increasing the temperature decreases the activity of the catalase
3. changing the temperature has no effect on the activity of the catalase
4. the catalase is most active at the lowest temperature tested

Question 3

In the catalase investigation the student changed the temperature of the test-tubes and then measured the maximum height of the oxygen foam produced. Which option correctly identifies the independent variable and the dependent variable?

1. the independent variable is the temperature and the dependent variable is the height of the foam
2. the independent variable is the height of the foam and the dependent variable is the temperature
3. the independent variable is the volume of hydrogen peroxide and the dependent variable is the temperature
4. the independent variable is the temperature and the dependent variable is the volume of potato extract

Question 4 · Answer A

Step 1: The hydrogen peroxide needs to be at the test temperature before the enzyme is added. Step 2: Standing in the water-bath for five minutes lets the contents warm up or cool down to match the water-bath. Step 3: So the reaction is then carried out at the intended temperature, making the comparison fair.

Question 5 · Answer A

Step 1: Carrying out repeats produces several values for each temperature. Step 2: Any odd value that does not fit the pattern can then be identified as anomalous and left out. Step 3: A mean of the remaining values is more reliable, giving more confidence in the results.

Question 6 · Answer A

Step 1: The main hazard is cutting yourself with the knife. Step 2: Cutting on a firm surface with the blade moving away from the body keeps fingers out of the path of the knife. Step 3: So this is a sensible safety precaution for preparing the extract.

Question 7 · Answer A

Step 1: The radius is half the diameter, so 25 / 2 = 12.5 mm. Step 2: Volume = 3.14 x 12.5 x 12.5 x 29 = 14228.125 mm3. Step 3: There are 1000 mm3 in 1 cm3, so 14228.125 / 1000 = 14.228... which rounds to 14.2 cm3.

Question 8 · Answer A

Step 1: Oxygen is a gas, so its volume is best measured by collecting the gas itself. Step 2: A gas syringe collects the oxygen and gives a direct reading of its volume on a scale. Step 3: This is far more accurate than estimating from the height of a foam.

Question 9 · Answer A

Step 1: Iodine solution is orange-brown to start with. Step 2: When starch is present, the iodine turns a blue-black colour. Step 3: So a blue-black colour is the positive result for starch.

Question 10 · Answer A

Step 1: Vitamin C is detected using the blue dye DCPIP. Step 2: Vitamin C decolourises blue DCPIP, turning it colourless. Step 3: So DCPIP is the reagent used to test for vitamin C.

Question 11 · Answer A

Step 1: The independent variable must be the light intensity, set at several different values. Step 2: The rate of photosynthesis is measured as the volume of oxygen produced in a fixed time, while temperature, carbon dioxide supply and the plant are kept constant so the test is fair. Step 3: Repeating at each light intensity makes the results more reliable, so the first plan is the correct one.

Question 12 · Answer A

Step 1: A biological drawing should use single, clear, continuous lines with no shading. Step 2: It should be large, here larger than the photograph, and show the important features such as the textured tip and the shape of the cupule. Step 3: So the first option describes the best biological drawing.

Question 13 · Answer A

Step 1: Rearrange the formula: actual length = length of line PQ divided by the magnification. Step 2: actual length = 84 / 3.4 = 24.7 mm. Step 3: To two significant figures this is 25 mm.

Question 14 · Answer A

Step 1: Comparing the two acorns, the Turkey oak cupule is covered in short spines while the Caucasian oak cupule is smooth. Step 2: Less of the Turkey oak nut shows above its cupule than for the Caucasian oak. Step 3: So the spiny cupule and the smaller amount of nut showing are two valid differences.

Question 15 · Answer A

Step 1: Controlled variables are the conditions kept the same for every group. Step 2: The soil type and the room temperature were the same for all the pots. Step 3: The species and mass are being compared (the independent variable), and the proportion germinated is the measured outcome (the dependent variable), so they are not controlled.

Question 16 · Answer A

Step 1: A bar chart needs axes that are labelled with units and have a suitable scale for both the mean mass and the proportion germinated. Step 2: All six bars (two per species) should be plotted accurately, with gaps between the different species. Step 3: A key is needed so the reader can tell the two datasets apart, so the first option is correct.

Question 17 · Answer A

Step 1: Individual acorns vary, so a few of them may not be typical. Step 2: Measuring a large number gives a representative sample and reduces the effect of this natural variation. Step 3: This makes the results more reliable and helps avoid bias.

Question 18 · Answer A

Step 1: The mass of water lost is the initial mass minus the dried mass: 1.96 - 0.74 = 1.22 g. Step 2: Percentage water content = (mass of water / initial mass) x 100 = (1.22 / 1.96) x 100. Step 3: This gives 62.2%.

Question 19 · Answer A

Step 1: Protein is detected using biuret solution. Step 2: When protein is present, biuret solution changes from blue to purple. Step 3: So biuret solution is the reagent used to test for protein.