Cambridge A Level Biology 9700 — 2014 Oct/Nov Paper 3 · Variant 3

This document consists of 13 printed pages and 3 blank pages. DC (SJF/CGW) 70248/3 © UCLES 2014 [Turn over * 9 8 0 9 5 6 0 7 7 2 * BIOLOGY 9700/33 Advanced Practical Skills 1 October/November 2014 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, graphs or rough working. 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 Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level

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3 9700/33/O/N/14 © UCLES 2014 [Turn over Before you proceed, read carefully through the whole of Question 1 and Question 2. Plan the use of your time to make sure that you finish all the work that you would like to do. You will gain marks for recording your results according to the instructions. 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. 1 Plants translocate sap through phloem sieve tubes. Scientists discovered that aphids feed by pushing their stylet into a single phloem sieve tube as shown in Fig. 1.1. By using stylets it is possible for scientists to collect the sap from a single phloem sieve tube. phloem sieve tube aphid feeding stylet Fig. 1.1 You are required to estimate, as accurately as possible, the concentration of sucrose in a sample of sap, P, by: • carrying out a trial using the concentrations of sucrose solutions S1 and S2 • using the results of the trial to prepare further concentrations of sucrose solution • obtaining more readings, so that you can estimate more accurately the concentration of sucrose in P.

4 9700/33/O/N/14 © UCLES 2014 A drop or small volume of P is placed into a known concentration of sucrose solution. Fig 1.2 shows how the drop or small volume of P is released. marker line where drop is released P solution 5 cm3 syringe resting on top of large test-tube drop or small volume of P gently press plunger to release a drop or small volume of P sucrose solution Fig. 1.2 Immediately the drop or small volume of P is released, the syringe is removed.

5 9700/33/O/N/14 © UCLES 2014 [Turn over The drop of P may move up, move down or remain at the same level depending on the difference in the concentration between P and the sucrose solution. (a) (i) Show clearly on the diagrams below, using the key, how you would expect to see the drop or small volume of P move if: P is less concentrated than the sucrose solution ° ° ° a drop or small volume of P moves up Key: a drop or small volume of P moves down a drop or small volume of P remains at same level P is the same concentration the sucrose solution P is more concentrated than the sucrose solution [1] You are provided with: labelled contents hazard volume / cm3 S1 0.10 mol dm–3 sucrose solution none 200 S2 1.00 mol dm–3 sucrose solution none 200 P coloured sample of sap none 20 W distilled water none 200

6 9700/33/O/N/14 © UCLES 2014 Read step 1 to step 8 before proceeding. Proceed as follows: You are required to estimate the concentration of P using S1 and S2. 1. Place the 5 cm3 syringe on top of the large test-tube and use the marker pen to draw a line on the test-tube at the same height as the end of the syringe nozzle as shown in Fig. 1.2 (page 4). 2. Use the same syringe to suck up 4.0 cm3 of P. 3. Put 35 cm3 of S1 into the test-tube. 4. As shown in Fig. 1.2, release one drop or a small volume of P and remove the syringe from the sucrose solution. Note: P may come out without pushing the plunger, observe and record the direction of movement. 5. Immediately observe the movement of the drop or small volume of P. 6. Record your observations. 7. Wash out this test-tube. 8. Repeat steps 3 to 7 using S2. (ii) Prepare the space below to record your observations. [3]

7 9700/33/O/N/14 © UCLES 2014 [Turn over (iii) Complete the following by using one of the words ‘more’ or ‘less’. You may use each word once or more than once. P is … concentrated than 0.1 mol dm–3 (S1). P is … concentrated than 1.0 mol dm–3 (S2). Use your results to estimate the concentration of sucrose in P. estimate of concentration of sucrose in P …[1] (iv) State which solution, S1 or S2, you will dilute to prepare further concentrations. Use your results to explain the reason for your decision. … …[2] You are required to prepare further concentrations of sucrose solution by simple dilution, using the solution stated in (a)(iv). Decide on the further concentrations of sucrose solution you will use in your investigation. You will need 40 cm3 of each sucrose solution. (v) Prepare the space below to show: • the concentration of each sucrose solution • the volumes of sucrose solution • the volumes of W. [3]

8 9700/33/O/N/14 © UCLES 2014 9. Prepare all the concentrations of sucrose solution you have listed in (a)(v) in the containers provided. 10. Repeat steps 3 to 7 with each of the solutions. (vi) Prepare the space below to record your observations. [3] (vii) Using these additional results from (vi) state a more accurate estimate of the concentration of sucrose in P than in (iii). …[1]

9 9700/33/O/N/14 © UCLES 2014 [Turn over (viii) Describe how you would modify this procedure to investigate the concentration of sucrose in P, using Benedict’s solution. … … … … … … …[3] [Total: 17]

10 9700/33/O/N/14 © UCLES 2014 You are required to use a sharp pencil for drawings and graphs. 2 Plants translocate sap through phloem sieve tubes. Scientists discovered that aphids feed by pushing their stylet into a single phloem sieve tube as shown in Fig. 2.1. By using stylets it is possible for scientists to collect the sap from a single phloem sieve tube. phloem sieve tube aphid feeding stem stylet Fig. 2.1 Scientists have investigated the different rates of flow of sap in the stylets of aphids of different ages from hatching, H, up to the adult, M. The results are shown in Table 2.1. Table 2.1 different ages of aphid rate of flow of sap /μl h–1 trial 1 trial 2 trial 3 mean H 0.452 0.448 0.451 0.450 J 0.726 0.722 0.726 0.725 K 0.977 1.232 0.973 L 1.401 1.601 1.399 1.400 M 1.978 1.975 1.972 1.975 (a) (i) Circle the two anomalous results in Table 2.1. [1] (ii) Complete the table by calculating the missing mean value. [1]

11 9700/33/O/N/14 © UCLES 2014 [Turn over (iii) Plot a chart of the data in Table 2.1. [4] (iv) Describe the relationship between the age of the aphid and the rate of flow of sap. … … …[1] (v) Suggest two reasons which might explain the relationship described in (iv). … … … … …[2]

12 9700/33/O/N/14 © UCLES 2014 (b) K1 is a slide of a stained transverse section through a plant stem. This plant species grows widely including Europe, Asia and North America. You are not expected to be familiar with this specimen. To help draw a plan diagram with the correct shape and proportions of the tissues, an eyepiece graticule can be used to measure the layers of tissues, without the need to calibrate the eyepiece graticule scale. (i) Draw a large plan diagram of the part of the specimen on K1 indicated by the shaded sector in Fig. 2.2. draw this sector Fig. 2.2 Use one ruled label line and label to show the pith. [5]

13 9700/33/O/N/14 © UCLES 2014 [Turn over (ii) Observe the tissue between the xylem and the hollow centre of the specimen. Select one group of three cells with: • one cell containing cell structures • two cells which touch each other and also touch the cell which contains cell structures. Make a large drawing of this group of three cells. Use one ruled label line and label D to show one of the cell structures. [5]

14 9700/33/O/N/14 © UCLES 2014 Fig. 2.3 is a photomicrograph of an aphid feeding on a plant. R T magnification ×120 Fig. 2.3 (c) Calculate the actual length of the structure R to T, using the magnification, giving your answer in μm. You may lose marks if you do not show your working or if you do not use appropriate units. actual length … μm [4] [Total: 23]

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16 9700/33/O/N/14 © UCLES 2014 Copyright Acknowledgements: Question 2 Fig 2.3 © VOLKER STEGER/SCIENCE PHOTO LIBRARY. 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. 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. BLANK PAGE

® 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 2014 series 9700 BIOLOGY 9700/33 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 2014 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 2014 9700 33 © Cambridge International Examinations 2014 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 2014 9700 33 © Cambridge International Examinations 2014 1 (a) (i) 3 directions / arrows correct ; [1] (ii) organised into table + all columns separated by a line + all headings underlined ; headings solution + direction of movement ; results for S1 ‘down’ or downward arrow + S2 ‘up’ or upward arrow ; [3] (iii) P is …‘more’ concentrated than 0.10 mol dm-3 (S1) + P is ‘less’ concentrated than 1.00 mol dm-3 (S2) + estimate of P is less than 1/S1 or more than 0.1/S2 ; [1] (iv) S2 or 1.0 mol dm-3 ; (concentration of) P, was less concentrated than S2/1.0 mol dm-3 ; [2] (v) records at least 4 concentrations of sucrose solutions + mol dm-3 ; for at least 3 concentrations of sucrose records volumes of sucrose solutions + cm3 ; for 3 concentrations final volume makes 40 + cm3 ; [3] (vi) records directions for at least 3 concentrations of sucrose ; records correct trend + directions in continuous order ; shows results for repeated drops ; [3] (vii) correct estimate of P with their results ; [1] (viii) 1 hydrolysis of sucrose solutions or described ; 2 heat Benedict’s solution to stated temperature (e.g. 70°, 75°, 80°, 85°, 90°, 95°) or to 100 °C or boiling water ; 3 comparing colours of sucrose solutions + P ; 4 same or stated volume of sucrose solutions (e.g. 2 cm3) + same or stated volume of P (e.g. 2 cm3) ; [max 3] [Total: 17]

Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2014 9700 33 © Cambridge International Examinations 2014 2 (a) (i) 1.232 + 1.601 ; [1] (ii) 0.975 ; [1] (iii) label on x-axis (different) ages of aphid + label on y-axis rate of flow of sap / µl h–1 ; (x-axis) bars of equal width and equal distance apart, using more than 4 cm + scale on y-axis is 0.5 to 2 cm + labelled each 2 cm (except origin and 2.0) ; correct plotting of each bar in the order of the table (H, J, K, L, M) ; sharp vertical lines and horizontal lines (less than line thickness on grid) + labels for H, J, K, L, M directly below bar ; [4] (iv) as the age of the aphid increases the rate of flow of sap increases ; [1] (v) as aphids become older the stylets become larger ; as aphids become older access to larger phloem sieve tubes ; [2] (b) (i) 1 at least 4 lines + size at least 60 mm across radius + no shading ; 2 no cells drawn + correct quarter drawn ; 3 at least 5 layers (6 lines drawn) ; 4 epidermis drawn as two lines ; 5 label + label line to pith ; [5] (ii) 1 at least 3 cells + size at least 40 mm across largest cell at widest point + (quality of outer lines) sharp continuous line for each cell ; 2 only 3 cells drawn + as one group of touching cells ; 3 cell walls drawn as double lines (for at least 2 cells) with middle lamella between ; 4 drawn an air space between cells ; 5 label D + label line to cell structure ; [5] (c) measures line R to T within range + units mm / cm ; converts to µm by multiplying by 1000 (if R/T in mm) or 10 000 (if R/T in cm) ; shows division by 120 ; correct significant figures for answer ; [4] [Total: 23]