Cambridge A Level Biology 9700 — 2015 May/June Paper 3 · Variant 4

This document consists of 12 printed pages. DC (RW/SW) 87489/4 © UCLES 2015 [Turn over Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level * 5 5 3 8 4 0 3 6 9 8 * BIOLOGY 9700/34 Advanced Practical Skills 2 May/June 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, paperclips, 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 9700/34/M/J/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 Plant cells contain an enzyme, catalase, which catalyses the hydrolysis (breakdown) of hydrogen peroxide into oxygen and water. An extract of plant tissue contains catalase. You are required to investigate the effect of solution X on the activity of the catalase in a plant extract P by: • preparing different concentrations of solution X • investigating the effect of different concentrations of solution X by counting the number of bubbles of oxygen released in two minutes • finding the rate of activity of the catalase by measuring the time taken to collect 2 cm3 of the oxygen. You are provided with: labelled contents hazard volume / cm3 X 0.3% solution of X harmful 20 W distilled water none 100 P plant extract solution none 90 H hydrogen peroxide solution harmful irritant 90 T tap water none – When carrying out a practical procedure, the hazards of the use of all the apparatus and all of the reagents 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 apparatus and reagents in step 1 on page 4. State the level of risk of the procedure: low or medium or high. hazard … level of risk … [1]

3 9700/34/M/J/15 © UCLES 2015 [Turn over (b) (i) You are required to make a serial dilution of the 0.3% solution of X which reduces the concentration of X by a factor of 10 between each successive dilution. You will need to prepare 10 cm3 of each concentration of solution X. You should use the beakers shown in Fig. 1.1 to show how you will prepare the serial dilutions. You will need to use 9 cm3 of each different concentration of X in the investigation. For each beaker, complete Fig. 1.1 to show how you will dilute the solution by: • stating, under the beaker, the concentration and volume of the solution available for use in the investigation • using one arrow, with a label above the beaker, to show the concentration and volume of the solution X added to prepare the concentration • using another arrow, with a label above the beaker, to show the volume of W added to prepare the concentration. … … … 0.3 % solution 10 cm3 0.3 % solution of X 1 cm3 0.3 % solution of X 0 cm3 W of X 9 cm3 to use … … … … … … … … … Fig. 1.1 [3]

4 9700/34/M/J/15 © UCLES 2015 You are required to investigate the effect of different concentrations of X on the activity of catalase by finding the number of bubbles of oxygen released in two minutes. Proceed as follows: 1. Prepare the concentrations of X as shown in (b)(i). Note: syringe labelled X should be used for solution X only. 2. Put 10 cm3 of P into each of the concentrations of X, including 0.3% X. Shake gently to mix. 3. Put 20 cm3 of P and 18 cm3 of W into a separate beaker. 4. Leave for at least three minutes. Read step 5 to step 13 before proceeding. 5. Put 10 cm3 of H into each of five test-tubes. 6. Put 10 cm3 of the mixture of P and W into one of the test-tubes. 7. Put the bung (with the delivery tube attached) into this test-tube. 8. Put the end of the delivery tube into the large beaker containing water labelled T. 9. Start timing and count the number of bubbles of oxygen released in 2 minutes. 10. Record the result in (b)(ii). Note: if no bubbles are released then make sure the bung is securely fitted into the test-tube. You may ask for petroleum jelly if necessary. 11. Put 10 cm3 of the mixture of P with the lowest concentration of X into another test-tube containing H. 12. Repeat steps 7 to 10. 13. Repeat steps 11 and 12 with each of the other concentrations of X, including 0.3% X. Consider how you will obtain results which are as accurate as possible.

5 9700/34/M/J/15 © UCLES 2015 [Turn over (ii) Prepare the space below and record your results. [5]

6 9700/34/M/J/15 © UCLES 2015 You are required to find the rate of activity of the catalase by measuring the time taken to collect 2 cm3 of oxygen produced by the hydrolysis of H. You are going to collect the oxygen released by displacement of water as shown in Fig. 1.2. sealed syringe bubbles of oxygen push (displace) the water out of the syringe beaker labelled T containing tap water oxygen from test-tube Fig. 1.2 The sealed syringe is full of water and is upside down over the end of the delivery tube. You need to time how long it takes for the bubbles of oxygen to push (displace) 2 cm3 of the water out of the syringe. 14. Put 5 cm3 of H into a clean test-tube. 15. Put 10 cm3 of the mixture of P and W into this test-tube. 16. Put the bung (with the delivery tube attached) into this test-tube. 17. Fill the sealed syringe with water from the beaker and turn it upside down keeping the open end of the syringe under the water as shown in Fig. 1.2. 18. Immediately put the end of the delivery tube into the beaker of water so that the bubbles of oxygen pass into the syringe. 19. Start timing. (iii) Record the time for 2 cm3 of oxygen to be collected. time … Using your recorded time, calculate the rate of activity of the catalase in cm3 s–1. You may lose marks if you do not show your working and do not use the appropriate units. rate of activity …cm3 s–1 [2]

7 9700/34/M/J/15 © UCLES 2015 [Turn over (iv) Using your knowledge of enzymes, suggest how solution X may be changing the activity of the catalase. … … … … …[2] (v) Identify one significant source of error when using each of the two methods to measure the dependent variable. one significant error in counting the number of bubbles … … one significant error in measuring the displacement of water … … [2] (vi) This first procedure investigated the effect of the concentration of X on the activity of catalase in the plant extract. To modify this procedure for investigating another variable, the independent variable (concentration of X) would need to be standardised. Describe how the independent variable (concentration of X) will be standardised. … … Consider how you would modify this procedure to investigate the effect of temperature on the activity of the catalase in the plant extract. Describe how the independent variable, temperature, will be investigated. … … … … [3] [Total: 18]

8 9700/34/M/J/15 © UCLES 2015 2 In an investigation into the circulation of blood in giraffes, it has been found that as the length of the neck increases the thickness of the muscle wall of the left ventricle increases. The results for five giraffes are shown in Table 2.1. Table 2.1 length of neck / cm thickness of muscle wall in left ventricle / mm 53.0 22.00 73.5 28.75 82.5 31.75 92.0 35.00 106.5 39.75 You are required to use a sharp pencil for graphs. (a) (i) Plot a graph of the data in Table 2.1. [4]

9 9700/34/M/J/15 © UCLES 2015 [Turn over (ii) A giraffe was found to have a neck length of 95.0 cm. Using the graph, estimate the thickness of the muscle wall in the left ventricle. …mm [1] (iii) Suggest one reason for the relationship shown in the graph. … …[1]

10 9700/34/M/J/15 © UCLES 2015 (b) Fig. 2.1 shows four photomicrographs of stained transverse sections through blood vessels, Q, R, S and T. Q R S T Fig. 2.1 (i) Choose one of the blood vessels shown in Fig. 2.1 which carries blood away from the heart. State the blood vessel, Q, R, S or T, which you have chosen … Draw a large plan diagram of this blood vessel. [5]

11 9700/34/M/J/15 © UCLES 2015 [Turn over A student observed a blood vessel from a different specimen. The student determined the ratio of the widest diameter of the blood vessel to the thickness of the blood vessel wall, using the actual measurements shown below. widest diameter of the blood vessel = 1460 μm thickness of the blood vessel wall = 75 μm Ratio is 1460:75 However, a ratio may be simplified by dividing each side by the same number to give the smallest possible whole number on each side. In this example, both sides of the ratio 1460:75 are divisible by 5, so the simplest ratio is 292:15. (ii) Determine the simplest ratio of the mean diameter of the blood vessel S to the mean thickness of the wall of the blood vessel in Fig. 2.1. On Fig. 2.1 show where you take your measurements. You may lose marks if you do not show all the steps in your working. ratio …[4] (c) M1 is a slide of a stained transverse section through a plant stem. This plant species grows throughout the world. You are not expected to be familiar with this specimen.

12 9700/34/M/J/15 © UCLES 2015 (i) Observe one large vascular bundle. Select one group of four adjacent xylem vessel elements with at least two of the vessel elements touching. Make a large drawing of this group of four xylem vessel elements. Use one ruled label line and label to identify one lumen. [5] (ii) Describe one observable difference between the structure of the xylem vessel elements drawn in (c)(i) and the structure of the blood vessels in Fig. 2.1. … …[1] (iii) Suggest one observable feature, shown by both the specimen on M1 and Fig. 2.1, which supports the conclusion that these structures transport materials. Explain how this feature may help the transport of materials in the vessel elements in M1. feature … explanation … … [1] [Total: 22] 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.

® IGCSE is the registered trademark of Cambridge International Examinations. CAMBRIDGE INTERNATIONAL EXAMINATIONS Cambridge International Advanced Subsidiary and Advanced Level MARK SCHEME for the May/June 2015 series 9700 BIOLOGY 9700/34 Paper 3 (Advanced Practical Skills 2), 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 May/June 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 – May/June 2015 9700 34 © 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 – May/June 2015 9700 34 © Cambridge International Examinations 2015 1 (a) level of risk) medium or high ; [1] (b) (i) (labels under correct sequence of beakers) 0.03 + 0.003 + 0.0003 + % ; shows transfer of 1 cm3 of solution from previous beaker to 2 beakers ; adds 9 cm3water / W to three beakers ; [3] (ii) 1 table with heading + percentage concentration of X ; 2 table with heading + number or no. of bubbles ; 3 records results for W or 0% and 4 concentrations ; 4 records lowest concentration of X with a higher number of bubbles than highest concentration of X ; 5 repeats at least one concentration ; [5] (iii) whole seconds recorded and shows 2 divided by this value ; correct answer calculated to correct number of significant figures ; [2] (iv) idea of inhibits activity ; idea of preventing substrate binding to the enzyme / active site or fewer enzyme- substrate complexes formed ; [2] (v) (counting bubbles) different sizes or too fast or bubbles group together ; (displacement of water) gas escapes from delivery tube or not all bubbles go into syringe or parallax error ; [2] (vi) (independent variable) use the same concentration of X ; 5 or more temperatures ; use thermostatically-controlled water-bath ; [3] [Total: 18]

Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9700 34 © Cambridge International Examinations 2015 2 (a) (i) orientation (x-axis) length of neck / cm + (y-axis) thickness of muscle wall in left ventricle / mm ; scale (x-axis) 2 cm to 10 labelled each 2 cm + must have 50 at the origin + (y-axis) 2cm to 5 labelled each 2 cm, + must have 20 at origin ; plotting correct plotting of 5 points ; line 5 plots with ruled lines exactly point to point or line of best fit + quality smooth line less than 1 mm thick ; [4] (ii) correct estimate from candidate graph; [1] (iii) idea of thicker / stronger / wall or muscle to push blood up longer neck or to push the blood further; [1] (b) (i) 1 correct selection of vessel Q or T ; 2 size at least 100 mm + no shading ; 3 length of drawing is at least twice the size of the narrowest width ; 4 draws at least three lines across wall + inner line crinkled ; 5 proportions of vessel walls correct with one selected ; [5] (ii) 1 shows on Fig. 2.1 where measured S ; 2 shows at least 5 of measurements of the diameter + 5 measurements of the thickness of the wall ; 3 measures at least 3 for each in whole mm or to ±0.5 mm ; 4 answer shown as larger number to smaller number to lowest common denominator ; [4] (c) (i) 1 sharp continuous lines + size at least 40 mm for at least one cell ; 2 draws only 4 xylem vessels + at least 2 touching ; 3 for at least 2 cells, walls drawn as double lines, with middle lamella ; 4 straight line where 2 cells meet or at least one cell with at least one angle present ; 5 correct label with label line ending in the lumen ; [5] (ii) idea that Fig. 2.1 has thicker walls than the xylem or Fig. 2.1 has more than one layer xylem has only one ; [1] (iii) lumen + space / no (cell) contents or lumen + idea of less resistance ; [1] [Total: 22]