Cambridge A Level Biology 9700 — 2015 Oct/Nov Paper 3 · Variant 5

This document consists of 11 printed pages and 1 blank page. DC (RW/SW) 118922/4 R © UCLES 2015 [Turn over Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level * 5 1 2 3 9 1 4 6 8 9 * BIOLOGY 9700/35 Advanced Practical Skills 1 October/November 2015 2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions. READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and 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, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. Electronic calculators may be used. You may lose marks if you do not show your working or if you do not use appropriate units. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 2 Total

2 9700/35/O/N/15 © UCLES 2015 Before you proceed, read carefully through the whole of Question 1 and Question 2. Plan the use of the two hours to make sure that you finish all the work that you would like to do. If you have enough time, consider how you can improve the accuracy of your results, for example by obtaining and recording one or more additional measurements. You will gain marks for recording your results according to the instructions. 1 A number of plant tissues are coloured because the cells contain chemicals called anthocyanins. These anthocyanins change colour according to the pH and the colour changes are reversible. You are provided with red cabbage which contains anthocyanins and can be used to make a pH indicator solution. You are required to: • prepare a pH indicator solution from red cabbage • investigate the effect of pH (the independent variable) on the colour of the indicator solution • identify the pH of the solutions, S1 and S2. You are provided with: Table 1.1 labelled contents hazard volume / cm3 pH 3 solution of pH 3 irritant 30 pH 4 solution of pH 4 irritant 30 pH 6 solution of pH 6 irritant 30 S1 solution of unknown pH irritant 30 S2 solution of unknown pH irritant 30 W distilled water none 30 labelled contents hazard quantity P red cabbage – pieces of leaves It is recommended that you wear safety glasses/goggles.

3 9700/35/O/N/15 © UCLES 2015 [Turn over When carrying out a practical procedure, the hazards of the use of all the apparatus and solutions need to be considered. Then the level of risk needs to be assessed as low or medium or high. (a) State the hazard with the greatest level of risk when using the solutions in Table 1.1. State the level of risk of using the solutions: low or medium or high. hazard … level of risk … [1] Proceed as follows: 1. Cut the red cabbage leaves into small pieces and place into the water in beaker A. 2. Heat the water in beaker A and boil for 5 minutes. 3. Turn off the Bunsen burner and leave the water in beaker A to cool for 5 minutes to produce a coloured liquid. This is your pH indicator solution. While you are waiting continue with Question 1. 4. After 5 minutes, pour approximately 100 cm3 of this pH indicator solution into a container. Most of the cabbage leaves should remain in beaker A. You are now going to investigate the effect of pH on the colour of the pH indicator solution. You will need to decide how to standardise the volume of pH indicator solution required to observe the colour change. So that you can observe the colour change clearly, you need to decide the volume of pH indicator solution to add. 5. Put 4 cm3 of the pH 6 solution into a test-tube. 6. Put 1 cm3 of pH indicator solution into the same test-tube and mix the contents. 7. Add further 1 cm3 volumes, up to 5 cm3, in order to decide which volume to use to observe the colour change clearly. 8. Record in (b)(ii) the final colour of the pH indicator solution at pH 6.

4 9700/35/O/N/15 © UCLES 2015 (b) (i) State the volume of pH indicator solution you will use to observe the colour change clearly and describe how you will standardise the volume of the pH indicator solutions to carry out step 9. volume …cm3 description … …[1] 9. Using the information in step 5 and (b)(i), find the colour of the pH indicator solution with pH 3, pH 4, W, S1 and S2. Record all your observations in (b)(ii). (ii) Prepare the space below and record all your observations. [5]

5 9700/35/O/N/15 © UCLES 2015 [Turn over (iii) Fig. 1.1 shows the position of pH 7 on a scale. Using your results in (b)(ii) complete Fig. 1.1 to show: • the positions of pH 3, pH 4 and pH 6 on the scale • the positions of W, S1 and S2 on the scale. pH 7 Fig. 1.1 [2] (c) Like red cabbage, beetroot cells also contain anthocyanins. A student investigated the effect of temperature on the cell surface membranes of beetroot. • Beetroot was cut into 1 cm3 cubes. • One cube of beetroot was put into each of five test-tubes containing water which had been heated to 25°C or 30°C or 35°C or 45°C or 50°C. • All other variables were standardised. • The cubes were removed after 15 minutes. • The absorbance of light by the coloured liquid left in the test-tubes was measured using a colorimeter. The absorbance of light by pure water is 0.000 arbitrary units.

6 9700/35/O/N/15 © UCLES 2015 The results of the student’s investigation are shown in Table 1.2. Table 1.2 temperature / °C absorbance of light by the coloured liquid / arbitrary units 25 0.080 30 0.155 35 0.225 45 0.395 50 0.580 You are required to use a sharp pencil for graphs. (i) Plot a graph of the data shown in Table 1.2. [4]

7 9700/35/O/N/15 © UCLES 2015 [Turn over (ii) Use your graph to estimate the absorbance of light at 40°C. Show on your graph how you estimated the absorbance of light. absorbance …[2] (iii) Explain the effect of temperature on the permeability of cell surface membranes in beetroot. … … … … …[3] The student decided to investigate the effect of alcohol on the cell surface membranes of beetroot cubes at 20°C. (iv) Describe how the temperature will be standardised in this investigation. … …[1] (v) Describe how the independent variable will be investigated. … … …[2] [Total: 21] Check that you have finished the whole of Question 1.

8 9700/35/O/N/15 © UCLES 2015 2 L1 is a slide of a stained transverse section through a plant stem. You are not expected to be familiar with this specimen. You are required to use a sharp pencil for drawings. (a) (i) Draw a large plan diagram of half of the stem to show the observable features. Use one ruled label line and label to identify the xylem. [5] (ii) Annotate your diagram to describe one difference between the cells in the centre (pith) and the cells in the outer layer (epidermis). [1]

9 9700/35/O/N/15 © UCLES 2015 [Turn over (iii) Select one group of four cells from the pith. Each cell of the group must touch two of the other cells. Make a large drawing of this group of four cells. Use one ruled label line and label to identify a cell wall. [5]

10 9700/35/O/N/15 © UCLES 2015 (b) Fig. 2.1 and Fig. 2.2 are photomicrographs of transverse sections (TS) of leaves from the same plant. TS of leaf grown in sunlight Y magnification ×100 Fig. 2.1 TS of leaf grown in shade magnification ×100 Fig. 2.2 (i) Calculate the actual thickness of the leaf grown in sunlight as shown by line Y on Fig. 2.1. You may lose marks if you do not show your working or if you do not use appropriate units. actual length …μm [3]

11 9700/35/O/N/15 © UCLES 2015 (ii) Prepare the space below so that it is suitable for you to record observable differences between Fig. 2.1 and Fig. 2.2. Do not include difference in thickness of the leaves. Record your observations in the space you have prepared. [4] (iii) A student observed a different plant of the same species shown in Fig. 2.1. The student determined the ratio of the thickness of a leaf grown in sunlight to the thickness of a leaf grown in shade as 120:60. However, a ratio may be simplified to the smallest possible whole number on each side. In this example, both sides of the ratio 120:60 are divisible by 60, so the simplest ratio for the thickness of leaves measured by the student is 2:1. The actual thickness of the leaf grown in shade in Fig. 2.2 is 70 μm. Determine the simplest ratio of the thickness of the leaf grown in sunlight in Fig. 2.1 compared to the thickness of the leaf grown in shade in Fig. 2.2. ratio … [1] [Total: 19]

12 9700/35/O/N/15 © UCLES 2015 BLANK PAGE Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge International Examinations Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cie.org.uk after the live examination series. Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge.

® IGCSE is the registered trademark of Cambridge International Examinations. CAMBRIDGE INTERNATIONAL EXAMINATIONS Cambridge International Advanced Subsidiary and Advanced Level MARK SCHEME for the October/November 2015 series 9700 BIOLOGY 9700/35 Paper 3 (Advanced Practical Skills 1), maximum raw mark 40 This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began, which would have considered the acceptability of alternative answers. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October/November 2015 series for most Cambridge IGCSE®, Cambridge International A and AS Level components and some Cambridge O Level components.

Page 2 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2015 9700 35 © Cambridge International Examinations 2015 Mark scheme abbreviations: ; separates marking points / alternative answers for the same point R reject A accept (for answers correctly cued by the question, or by extra guidance) AW alternative wording (where responses vary more than usual) underline actual word given must be used by candidate (grammatical variants accepted) max indicates the maximum number of marks that can be given ora or reverse argument mp marking point (with relevant number) ecf error carried forward I ignore

Page 3 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2015 9700 35 © Cambridge International Examinations 2015 1 (a) medium or high ; [1] (b) (i) stated volume (2 or 3 or 4 or 5 cm3) + use a syringe + same volume for each pH solution ; [1] (ii) mp1 table drawn + heading for solution(s) ; mp2 heading for colour ; mp3 records a colour for all 6 solutions (pH3, pH4, pH6, W, S1 and S2) ; mp4 records pH6 as a paler colour (pink, red or purple) than pH3 ; mp5 records a darker or brighter colour (pink, red or purple) for S2 than for pH3 or red for S2 if pH3 is pink ; [5] (iii) correct position of pH3, pH4 and pH6 on the scale ; W, S1 and S2 in correct positions on scale ; [2] (c) (i) mp1 (x-axis) temperature (/) °C + (y-axis) absorbance (of) light (by) coloured liquid (/) arbitrary units or au ; mp2 (x-axis) 5 to 2 cm labelled each 2 cm origin labelled 20 or 25 + (scale for y-axis) 0.1 to 2 cm labelled each 2 cm ; mp3 correct plotting of 5 points as a small cross or dot in circle ; mp4 5 plots + ruled sharp lines exactly point to point ; [4] (ii) shows on graph where reading taken off at 40 °C ; correct reading from graph + arbitrary units or au ; [2] (iii) as the temperature increases the permeability of the cell surface membranes increases ; cell membrane contains) protein ; high temperature denatures protein ; [3] (iv) thermostatically controlled water-bath ; [1] (iv) 5 or more concentrations of alcohol or examples of 5 concentrations ; serial dilution or simple dilution or described ; [2] [Total: 21]

Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2015 9700 35 © Cambridge International Examinations 2015 2 (a) (i) mp1 size at least 90 mm + no shading ; mp2 no cells + at least 3 lines + at least 3 enclosed areas drawn (denoting vascular bundles) + only half drawn ; mp3 draws outline with either 1 bulge or 2 half bulges ; mp4 at least 2 lines for epidermis (small space between these lines) ; mp5 uses label line + label to xylem ; [5] (iii) pith cells larger or pith cells have intercellular spaces or pith cells more loosely packed or pith cell wall thinner or pith cells rounder ora ; [1] (iii) mp1 at least 4 cells + size at least 40 mm across largest cell + sharp continuous lines ; mp2 only 4 cells drawn + each cell must touch at least one point on 2 other cells + no shading ; mp3 minimum of one intercellular space between cells ; mp4 cell walls drawn as double lines + middle lamella between ; mp5 uses label line + label to cell wall ; [5] (b) (i) correct measurement of line A (19–21 mm) ; shows division by 100 ; shows multiplication by 1000 or 103 ; [3] (ii) organised as table with 3 columns or rows headed for feature + K1 + Fig. 2.1 ; 3 observable differences between Fig.2.1 and Fig. 2. 2 ;;; [4] (iii) correct ratio as a larger whole number to a smaller whole number to the lowest common denominator ; [1] [Total: 18]