2025 DHS H2 Biology Prelims Paper 4 QP

© DHS 2025 9744/04 [Turn over Name: Centre/Index Number: Class: DUNMAN HIGH SCHOOL Preliminary Examination Year 6 H2 BIOLOGY Paper 4 Practical Candidates answer on the Question Paper. 9744/04 2 September 2025 2 hours 30 minutes READ THESE INSTRUCTIONS FIRST Write your centre number, index number, name and class at the top of this page. Give details of the practical shift and laboratory, where appropriate, in the boxes provided. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Answer all questions in the spaces provided on the question paper. The use of an approved scientific calculator is expected, where appropriate. You may lose marks if you do not show your working or if you do not use appropriate units. The number of marks is given in brackets [ ] at the end of each question or part question. Shift Laboratory For Examiner’s Use 1 20 2 23 3 12 Total 55 This document consists of 20 printed pages.

2 © DHS 2025 9744/04 1 During this question you will require access to a microscope and slide Y. Slide Y is a slide of a transverse section of a leaf from a yew tree. You are not expected to be familiar with this specimen. (a) Draw a large plan diagram of the whole transverse section of the leaf on slide Y. A plan diagram shows the arrangement of different tissues. Your drawing should show the correct shapes and proportions of the different tissues. No cells should be drawn. Labels are not required. [4]

3 © DHS 2025 9744/04 [Turn over (b) Observe the outer layer of cells on the upper surface of the leaf on slide Y. This outer layer is called the upper epidermis and is one cell thick. The upper surface of the leaf can be identified using Fig. 1.1. Fig. 1.1 Select a group of four cells comprising two cells from the upper epidermis and two cells from the layer below the upper epidermis. Each cell must touch at least two other cells in the group. Make a large drawing of this group of four cells. [5]

4 © DHS 2025 9744/04 (c) Fig. 1.2 is a photomicrograph of a stained transverse section of a different leaf. Fig. 1.2 (i) Identify two observable differences, other than colour, between the leaf section in Fig. 1.2 and the leaf section on slide Y. Record these differences in Table 1.1. Table 1.1 Feature Fig. 1.2 Y [2]

5 © DHS 2025 9744/04 [Turn over (ii) The leaf section shown in Fig. 1.2 is from a xerophytic plant which grows in sand dunes where there is very little water. State two observable features of the leaf section shown in Fig. 1.2 which help the plant to survive in dry conditions. Explain how each feature allows the plant to survive in dry conditions. Feature 1: ............................................................................................................................ Explanation: …......................................................................................................................... …......................................................................................................................... Feature 2: ............................................................................................................................ Explanation: …......................................................................................................................... …………………………………………………………………………………… [2]

6 © DHS 2025 9744/04 (d) Fig. 1.3 is the same photomicrograph as that shown in Fig. 1.2. Fig. 1.3 You will need to use the grid to find the area of vascular bundles and the total area of the leaf section in Fig. 1.3. Each square of the grid is 1 cm2. In some squares, the leaf section or vascular bundle does not fill the whole square. You are to count the squares that are half full as ½, and count the squares that are more than half full and full as 1. (i) State the area of the vascular bundles and the total area of the leaf section in Fig. 1.3. area of vascular bundles = .......................................... cm2 total area of leaf section = .......................................... cm2 [2]

7 © DHS 2025 9744/04 [Turn over (ii) Calculate the area of the vascular bundles as a percentage of the total area of the leaf section. Show your working. percentage = .......................................... [2]

8 © DHS 2025 9744/04 (e) Fig. 1.4 shows a photomicrograph of a stage micrometer scale that is being used to calibrate an eyepiece graticule. Fig. 1.4 One division, on either the stage micrometer scale or the eyepiece graticule, is the distance between the two adjacent lines. (i) Calculate the actual length of one eyepiece graticule unit shown in Fig. 1.4. Give your answer in micrometers. Show your working. actual length of one eyepiece graticule unit = .......................................... [3] [Total: 20]

9 © DHS 2025 9744/04 [Turn over 2 Yeast cells contain the enzyme catalase which catalyses the breakdown of hydrogen peroxide, releasing oxygen. You will investigate the effect of pH on the activity of catalase in an extract from yeast cells. You will need to immobilise the yeast cells in sodium alginate beads. When a bead containing yeast cells is dropped into hydrogen peroxide solution the bead will sink. As oxygen is released the bead will rise. The more oxygen released, the faster the bead will rise. You are provided with the materials shown in Table 2.1. Table 2.1 labelled contents hazard volume/cm 3 Y yeast cell suspension none 15 H 3.0% hydrogen peroxide solution harmful irritant 30 S sodium alginate solution none 30 C calcium chloride solution none 30 B3 buffer pH 3 none 10 B4 buffer pH 4 none 10 B6 buffer pH 6 none 10 B7 buffer pH 7 none 10 B8 buffer pH 8 none 10 If any solution comes into contact with your skin, wash off immediately under cold water. It is recommended that you wear suitable eye protection.

10 © DHS 2025 9744/04 Carry out step 1 to step 20. step 1 Put 10 cm3 of C into a boiling tube. step 2 Put 5 cm3 of S into a small beaker. step 3 Stir Y and put 3 cm3 of Y into the beaker used in step 2. Mix well. step 4 Use a 5 cm3 syringe to collect 2 cm3 of the mixture of S and Y (prepared in step 3). step 5 Position the 5 cm3 syringe over the boiling tube containing C as shown in Fig. 2.1. Fig. 2.1 step 6 Gently press down on the plunger of the 5 cm3 syringe with your thumb to release one drop into solution C. The drop should form a bead. step 7 Repeat step 6 until you have used all 2 cm3 of the mixture. Leave the beads in the solution C for 1 minute. step 8 Tip the contents of the boiling tube from step 7 into a Petri dish. step 9 Add 2 cm3 of each pH buffers B3, B4, B6, B7 and B8 into the five empty vials. step 10 Put two beads into each of the vials containing pH buffers B3, B4, B6, B7 and B8. step 11 Label a test-tube B3. step 12 Put 3 cm3 of the pH buffer B3 into the test-tube labelled B3.