TJC 2023 JC1 H2 EOY P2 QP

1 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN [TURN OVER DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN READ THESE INSTRUCTIONS FIRST Write your name on all the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, highlighters, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. 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 any 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. For Examiner’s Use Section A / 20 Section B 1 / 11 2 / 12 3 / 14 4 / 23 Section C Essay / 25 Total / 105 TEMASEK JUNIOR COLLEGE PROMOTIONAL EXAMS 2023 Higher 2 CANDIDATE NAME CIVICS GROUP / 2 3 BIOLOGY 9744 SECTION B [PART I] STRUCTURED QUESTIONS FRIDAY, 22 SEPTEMBER 2023 2 hours 40 minutes Candidates answer on the Question Paper. No Additional Materials are required. This document consists of 7 printed pages and 1 blank page.

2 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN Answer all questions 1 (a) Fig. 1.1 shows the behaviour of eight chromosomes in one stage of meiosis of a diploid plant cell. Fig. 1.1 (i) Name the stage of the nuclear division. …………….………………………………………………….…..…………………………….…. [1] (ii) Based on the observation of the chromosomes in Fig. 1.1, explain why it cannot be a stage in mitosis. …………………………………………………………….………………………………………….. …………….………………………………………………….…..…………………………….…. [1] (iii) The diploid number of the flowering plant is 8. Complete Table 1.1 to show the number of chromosomes found in the cell at the end of each stage of the meiotic cell cycle. Table 1.1 [2] (iv) With reference to Table 1.1, explain the change in the number of chromosomes per cell by the end of cytokinesis I. …………………………………………………………….…………………………………………. …………………………………………………………….………………………………………….. …………….………………………………………………….…..…………………………….…. [1] stage no. of chromosomes per cell G1 8 S phase Anaphase I Telophase I Cytokinesis I 4 Cytokinesis II

3 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN [TURN OVER DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN Fig. 2.1 shows the change in the amount of DNA per nucleus during a meiotic cell cycle. Fig. 1.2 (b) With reference to Fig. 1.2, account for the changes in amount of DNA per nucleus from the start of the cell cycle to the end of meiosis I. ….…………………………………………………………………………………………………………… …….………………………………………………………………………………………………………… .…………….….…………………………………………………………………………………………….. …………………….………………………………………………………………………………………… .……………….…..……………………………………………………………………………………… [2] (c) Describe one difference between a pair of homologous chromosomes and sister chromatids of a chromosome. …………….….…………………………………………………………………………………………….. …………………….………………………………………………………………………………………… .……………….…..……………………………………………………………………………………… [1] T2 Time Amount of DNA per nucleus / au G2 T1 S 4 2 1 Interphase Legend T1: Telophase I T2: Telophase II G1

4 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN (d) State the challenges of using embryonic stem (ES) cells for research or medical treatment and explain how induced pluripotent stem cells (iPSCs) may overcome each of these challenges. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ….…………………………………………………………………………………………………………… …….………………………………………………………………………………………………………… .…………….….…………………………………………………………………………………………….. …………………….………………………………………………………………………………………… .……………….…..……………………………………………………………………………………… [3] [Total: 11]

5 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN [TURN OVER DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN 2 (a) Fig. 2.1 shows the relationship between CO 2 assimilation rate and increasing light intensity in a plant, when carbon dioxide concentration is not a limiting factor. Fig. 2.1 (i) Explain why the CO2 assimilation rate levels off at high intensity. ……….……………………………………….….…………………………………………………… …………………………………………………………….………………………………………….. ……….……………………………………….….…………………………………………………… …………………………………………………………….………………………………………….. …………….………………………………………………….…..…………………………….…. [2] (ii) Explain why the CO2 assimilation rate is negative at the lowest light intensity. ……….……………………………………….….…………………………………………………… …………………………………………………………….………………………………………….. ……….……………………………………….….…………………………………………………… …………………………………………………………….………………………………………….. …………….………………………………………………….…..…………………………….…. [2] (iii) Describe the significance of point A to the growth of the plant. ……….……………………………………….….…………………………………………………… …………………………………………………………….………………………………………….. ……….……………………………………….….…………………………………………………… …………………………………………………………….………………………………………….. …………….………………………………………………….…..…………………………….…. [2]

6 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN (b) The conditions in which young plants are grown affects their ability to photosynthesise at high and low temperatures when they are mature. Young maize and wheat plants were grown to maturity at high and low temperatures. When they were mature, their rate of photosynthesis was measured at different temperatures. The results are shown in Fig. 2.2. Fig. 2.2 (i) With reference to Fig. 2.2, compare one effect of temperature on the rate of photosynthesis of maize plants and wheat plants that were grown at high temperature. ……….……………………………………….….…………………………………………………… …………………………………………………………….………………………………………….. ……….……………………………………….….…………………………………………………… …………………………………………………………….………………………………………….. …………….………………………………………………….…..…………………………….…. [2] CO2 used per dm2 of leaf per hour / mg Temperature / oC Maize grown at high temperature Wheat grown at low temperature Maize grown at low temperature Wheat grown at high temperature

7 DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN [TURN OVER DO NOT WRITE IN THIS MARGIN DO NOT WRITE IN THIS MARGIN (ii) It was observed that low temperatures reduced the formation of the thylakoid membranes inside the chloroplasts of maize leaves, but not in wheat leaves. Using this information and the results in Fig. 2.2, suggest a possible reason for the different results for maize and wheat grown at low temperatures. ……….……………………………………….….…………………………………………………… …………………………………………………………….………………………………………….. ……….……………………………………….….…………………………………………………… …………………………………………………………….………………………………………….. …………….………………………………………………….…..…………………………….…. [2] (c) Describe two differences between Calvin cycle and Krebs cycle. ………………………………………………………………………………………………………………. ………………………………………………………………………………………………………………. ….…………………………………………………………………………………………………………… …….………………………………………………………………………………………………………… .…………….….…………………………………………………………………………………………….. …………………….………………………………………………………………………………………… .……………….…..……………………………………………………………………………………… [2] [Total: 12]  End of Section B Part I 

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