Biology 9700/33 May/June 2025: question paper and mark scheme

Question

When plant tissue is placed into a solution of sodium chloride, water moves between the sodium chloride solution and the cells in the plant tissue. You will investigate the effect of surface area of plant tissue on the movement of water between a sodium chloride solution and the cells in a sample of plant tissue. You are provided with the materials shown in Table 1.1. Table 1.1 labelled contents hazard volume / cm3 P 5 cylinders of plant tissue in distilled water none – S 2.0 mol dm–3 sodium chloride solution none 200 It is recommended that you wear suitable eye protection. You will need to: • cut cylinders of plant tissue into different lengths • soak different lengths of plant tissue in sodium chloride solution for 20 minutes • measure the final length of the plant tissue. Carry out step 1 to step 12. step 1 Using the forceps, put the cylinders of plant tissue onto the white tile. step 2 Cut each cylinder of plant tissue to 40 mm length. The cylinders of plant tissue all have the same diameter, as shown in Fig. 1.1. The radius is calculated by dividing the diameter by 2. diameter Fig. 1.1 (a) (i) Measure the diameter of one cylinder of plant tissue and calculate the radius, r. diameter = …… r = …… [1] To investigate the effect of surface area, you will use one whole cylinder of plant tissue and cut the other cylinders into a different number of pieces. step 3 Label five beakers with the number of pieces of plant tissue (n) as shown in Table 1.2. Table 1.2 length (h) of each beaker labelled number of pieces of plant tissue (n) small piece / mm 1 1 1 40 1 1 1 2 2 2 2 20 2 2 4 4 4 4 4 10 4 8 8 8 8 8 8 5 16 16 16 16 16 16 2.5 step 4 Put one whole cylinder of plant tissue into the beaker labelled 1. step 5 Cut each of the other four cylinders of plant tissue into the number of pieces shown in Table 1.2 and put them into the appropriately labelled beaker. In step 6 you will use a syringe to measure the volume of sodium chloride solution, S, you will put into each beaker. (ii) State the volume of S that you will put into each beaker and give a reason for the volume that you have stated. volume of S …… cm3 reason …… [1] step 6 Put the volume of S you stated in (a)(ii) into each of the beakers. step 7 Start timing and wait for 20 minutes. Use this time to continue with other parts of Question 1. Fig. 1.2 shows an example of how to calculate the total surface area of plant tissue placed in each beaker. EXAMPLE: a cylinder with a length of 40 mm length, h = 40 mm diameter surface area of cylinder = 2πr 2 + 2πr h = (2 × 3.14 × r 2) + (2 × 3.14 × r × 40) where: π = 3.14 r = radius of cylinder = diameter ÷ 2 h = height or length of cylinder The total surface area depends on the number of pieces, n. Total surface area = surface area of one cylinder × number of pieces = (2πr 2 + 2πrh)n Fig. 1.2 (iii) Complete Table 1.3 by calculating the total surface area of the whole piece of plant tissue (1) and the total surface area for the plant tissue cut into 16 pieces. Use the formulae shown in Fig. 1.2. Show your working in Table 1.3. Table 1.3 n h / mm surface area of one piece / mm2 total surface area / mm2 1 40 16 2.5 [2] (iv) Describe what happens to the total surface area when one whole cylinder of plant tissue is cut into 16 smaller pieces. …… [1] step 8 After the 20 minutes (step 7), pour the sodium chloride solution from around the cylinder of plant tissue in beaker 1 into the container labelled For waste. Put the plant tissue onto the white tile. step 9 Measure the length of the cylinder of plant tissue. Record this length in (a)(v). step 10 Repeat step 8 for beaker 2. step 11 Place the cylinders of plant tissue end‑to‑end so that they are touching. Measure their total length, as shown in Fig. 1.3. Record this length in (a)(v). total length Fig. 1.3 step 12 Repeat step 10 and step 11 using the plant tissue in beaker 4, beaker 8 and beaker 16. (v) Record your results in an appropriate table. [5] (vi) With reference to the total surface area, describe the trend in your results. …… [1] (vii) Explain the trend you described in (a)(vi). …… [2] (viii) State one source of error in this investigation when measuring the dependent variable in step 11 and step 12. …… [1] (ix) Suggest how you could modify this procedure to investigate the effect of temperature on the movement of water between the sodium chloride solution and the cells in the plant tissue. …… [2] (b) A student investigated the effect of different concentrations of sodium chloride solution on red blood cells. The student: • counted the number of whole red blood cells in six samples of blood • put each sample into a different concentration of sodium chloride solution for 10 minutes • counted the number of whole red blood cells remaining in each concentration • calculated the number of red blood cells remaining as a percentage of the number of red blood cells in each sample at the start. The results are shown in Table 1.4. Table 1.4 percentage concentration percentage number of whole of sodium chloride red blood cells remaining 0.00 0.0 0.40 3.0 0.50 10.0 0.65 46.0 0.80 96.0 0.90 100.0 (i) Plot a graph of the data shown in Table 1.4 on the grid in Fig. 1.4. Use a sharp pencil. Fig. 1.4 [4] (ii) State the concentration of sodium chloride solution that has the same water potential as the red blood cells. sodium chloride concentration = ……% [1] (iii) With reference to water potential, explain the effect of 0.4% sodium chloride solution on red blood cells. …… [1] [Total: 22]

Question

L1 is a slide of a stained transverse section through a plant organ. (a) (i) Draw a large plan diagram of a region of the organ on L1 to include the epidermis and two vascular bundles. Use a sharp pencil. Use one ruled label line and label to identify the phloem. [5] (ii) Observe the xylem on the section of the plant organ on L1. Select a line of four adjacent xylem vessel elements. Each xylem vessel element must touch at least one of the other xylem vessel elements. • Make a large drawing of this line of four xylem vessel elements. • Use one ruled label line and label to identify the lumen. [5] (b) Fig. 2.1 is a diagram of a stage micrometer scale that is being used to calibrate an eyepiece graticule. One division, on either the stage micrometer scale or the eyepiece graticule, is the distance between two adjacent lines. The length of one division on this stage micrometer is 0.1 mm. stage micrometer eyepiece graticule 0 10 20 30 40 50 60 70 80 90 100 Fig. 2.1 (i) Use Fig. 2.1 to calculate the actual length of one eyepiece graticule unit. Show your working and give your answer in micrometres (µm). actual length = …… µm [2] Fig. 2.2 is a photomicrograph of a stained transverse section of the same plant organ as the section on L1 but from a different plant. This was taken using the same microscope and eyepiece graticule as in Fig. 2.1. The eyepiece graticule scale has been placed across one of the larger sections of vascular tissue, labelled T in Fig. 2.2. T 0 10 20 30 40 50 60 70 80 90 100 Fig. 2.2 (ii) Use the calibration of the eyepiece graticule unit from (b)(i) to calculate the actual length of the section of vascular tissue T in Fig. 2.2. Show your working and use appropriate units. actual length of the vascular tissue T = …… [2] (c) Fig. 2.3 is the same photomicrograph as that shown in Fig. 2.2. Fig. 2.3 (i) Identify three observable differences, other than colour, between the section on L1 and the section in Fig. 2.3. Record these three observable differences in Table 2.1. Table 2.1 feature L1 Fig. 2.3 [3] (ii) Identify the plant organ on L1 and in Fig. 2.3. State how one observable feature helped you to identify the plant organ. plant organ …… [1] [Total: 18]