Cambridge A Level Biology 9700 — 2014 Oct/Nov Paper 3 · Variant 6

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. * 2 3 9 5 5 4 3 1 1 2 * BIOLOGY 9700/36 Advanced Practical Skills 2 October/November 2014 2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions. For Examiner’s Use 1 2 Total This document consists of 11 printed pages and 1 blank page. DC (NH/CGW) 70259/4 © UCLES 2014 [Turn over Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level

2 9700/36/O/N/14 © UCLES 2014 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 An enzyme, E, catalyses the hydrolysis (breakdown) of triglycerides into fatty acids and glycerol. The substrate for E will be the triglycerides present in milk, labelled M. The end-point of this hydrolysis can be determined by using an indicator, B, which changes colour to yellow when the fatty acids are produced. You are required to: • prepare different concentrations of the enzyme solution, E • investigate the effect of different concentrations of E (independent variable) on the hydrolysis of triglycerides in milk. You are provided with: labelled contents hazard volume / cm3 E 5% enzyme solution irritant 40 W distilled water none 60 B indicator solution stains 20 M milk none 40 A solution of alkali irritant 40

3 9700/36/O/N/14 © UCLES 2014 [Turn over You are required to dilute the 5% enzyme solution, E, to provide a range of known concentrations using simple dilution. Decide on the further concentrations of enzyme solution you will use in your investigation in addition to the 5% solution, E. You will need to use 20 cm3 of each enzyme solution. (a) (i) Prepare the space below to show: • the concentration of each enzyme solution • the volumes of E • the volumes of W. [3] Read step 1 to step 13 before proceeding. Proceed as follows: 1. Prepare all the concentrations of enzyme solutions you have listed in (a)(i) in the containers provided. You are required to investigate the effect of different concentrations of enzyme solutions on the hydrolysis of triglycerides in milk. The appearance of fatty acids can be detected using the indicator solution B. Every 30 seconds, for a total of 180 seconds, a sample of milk will be removed from the test-tube and placed on a tile. You will need to have prepared this tile before you add the enzyme solutions.

4 9700/36/O/N/14 © UCLES 2014 2. Wipe the tile clean with a damp paper towel and then dry the tile. Label the tile as shown in Fig. 1.1. The numbers indicate the sampling times in seconds. Put two drops of indicator solution, B, on the tile above each sampling time, as shown in Fig. 1.1. 30 indicator solution, B 60 90 120 150 180 Fig. 1.1 3. Prepare a water-bath between 35 °C and 40 °C. You will need to add hot water/cold water to maintain the temperature of the water-bath between 35 °C and 40 °C for steps 7 to 12. 4. Put 2.5 cm3 of M into a test-tube. 5. Put 2.5 cm3 of A into the same test-tube. 6. Repeat steps 4 and 5 for each of the concentrations of enzyme solution you are going to investigate, including the 5% concentration, E. 7. Put all the test-tubes into the water-bath. Allow 2 minutes for the contents of the test-tubes to reach the same temperature as the water-bath. The reaction will start as soon as you add the enzyme solutions so read steps 8 to 13 before proceeding. 8. Put 2.5 cm3 of the 5% concentration, E, into one of the test-tubes, leaving the test-tube in the water-bath. Stir the contents of the test-tube and start timing. 9. After 30 seconds use the pipette to transfer two drops of the contents of the test-tube to the drop of B, labelled 30. 10. Repeat step 9, at 30 second intervals, until a drop changes to yellow (end-point). 11. Record the time taken to reach the end-point.

5 9700/36/O/N/14 © UCLES 2014 [Turn over If the drop at 180 seconds does not reach the end-point, record ‘more than 180’ as your result. Once you have recorded a time for the end-point remove this test-tube from the water-bath and proceed to step 12. 12. Wipe the tile clean with a damp paper towel and then dry the tile. Label the tile again as shown in Fig. 1.1. 13. Repeat steps 8 to 12 with the remaining concentrations of enzyme solutions. (ii) Prepare the space below to record your results. [5] (iii) Identify one significant source of error in measuring the dependent variable in this investigation. … … …[1] (iv) Describe one improvement to this investigation which would increase the confidence in your results. … … …[1]

6 9700/36/O/N/14 © UCLES 2014 You are required to use a sharp pencil for graphs. (b) A student investigated an enzyme which hydrolyses starch to glucose over a period of 20 minutes. The student measured the mass of glucose present at four minute intervals. The volumes and concentrations of starch and enzyme were kept the same (standardised). (i) State two other variables that need to be standardised in this investigation. Describe how you would standardise each of these variables. … … … … … … …[3] The results are shown in Table 1.1. Table 1.1 time / min mass of glucose / mg 4 1.90 8 3.15 12 3.90 16 4.00 20 4.05 (ii) Using the results in Table 1.1, calculate the rate of production of glucose between: • 4 and 12 minutes …mg min–1 • 12 and 20 minutes. …mg min–1 [2]

7 9700/36/O/N/14 © UCLES 2014 [Turn over (iii) Plot a graph of the data in Table 1.1. [4] (iv) Explain the reasons for the change in mass of glucose between: • 0 and 12 minutes • 12 and 20 minutes. … … … … …[2] [Total: 21]

8 9700/36/O/N/14 © UCLES 2014 You are required to use a sharp pencil for drawings. M1 is a slide of a stained transverse section through a plant root. This plant species grows worldwide. You are not expected to be familiar with this specimen. 2 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. (a) (i) Explain how one observable feature on M1 identifies this specimen as a root. … … …[1] (ii) Draw a large plan diagram of the part of the specimen on M1 indicated by the shaded sector in Fig. 2.1. draw this half Fig. 2.1 Use one ruled label line and label to show the xylem. [5]

9 9700/36/O/N/14 © UCLES 2014 [Turn over (iii) Observe the xylem and the cortex of the specimen on M1. Select: • one group of three whole touching xylem vessels • one group of three whole touching cortex cells. Make a large drawing of each of these two groups of three cells. Use one ruled label line and label to show one lumen on one of your drawings. xylem vessels cortex cells [5]

10 9700/36/O/N/14 © UCLES 2014 Fig. 2.2 is a photomicrograph of part of a stained transverse section through a root of a different plant species. This plant species is found globally. Y Z Fig. 2.2 (b) Use the lines Y and Z shown on Fig. 2.2 to calculate the ratio of Y to Z. You may lose marks if you do not show your working or if you do not use appropriate units. ratio …[3]

11 9700/36/O/N/14 © UCLES 2014 (c) Prepare the space below so that it is suitable for you to record observable differences between the specimen on M1 and Fig. 2.2. Record your observations in the space you have prepared. [5] [Total: 19]

12 9700/36/O/N/14 © UCLES 2014 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. 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 2014 series 9700 BIOLOGY 9700/36 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 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 36 © 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 36 © Cambridge International Examinations 2014 1 (a) (i) at least 4 further concentrations of E + % ; at least 3 correct volumes for E + cm3 ; for at least three concentrations of E final volumes add up to 20 + cm3 ; [3] (ii) 1 organised into table all columns separated by a line + all headings underlined ; 2 headings (top or to left of data) percentage concentration of E + (any column / row headed) time (/)s or seconds ; 3 whole seconds for at least three concentrations of E ; 4 highest concentration of E recorded in shorter time than next concentration ; 5 records in multiples of 30 seconds ; [5] (iii) (dependent variable) colour or end-point + idea of judging / determining ; [1] (iv) replicates or put E / M in water-bath (to reach temperature) ; [1] (b) (i) 1 selects temperature + pH ; 2 temperature + use thermostatically controlled water-bath ; 3 pH + use buffers ; [3] (ii) 0.250 ; 0.019 ; [2] (iii) 1 (x-axis time / min(utes) + (y-axis) mass of glucose / mg ; 2 (x-axis) 2 cm to 5 minutes labelled each 2 cm except origin and 20 minutes + (y-axis) 2 cm to 1 mg each 2 cm except origin and 5 ; 3 correct plotting of five points as small cross or dot in circle or cross ; 4 five plots + ruled sharp lines exactly point to point or ruled line of best fit + sharp smooth line ; [4] (iv) (between 0 and 12 minutes) many enzyme substrate complexes / ESCs / binding / fitting of substrate / enzyme ; (between 12 and 20 minutes) fewer ESCs or less substrate can bind ; [2] [Total: 21]

Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2014 9700 36 © Cambridge International Examinations 2014 2 (a) (i) central stele / vascular tissue ; [1] (ii) 1 at least 2 lines + size at least 100 mm across diameter + no shading ; 2 no cells + half drawn ; 3 endodermis shown by 2 lines ; 4 correct proportion stele compared to cortex ; 5 label + line to xylem ; [5] (ii) 1 at least 6 cells + size at least 40mm across largest cell at widest point + sharp continuous lines ; 2 only 6 whole cells drawn + as two groups of touching cells ; 3 cell wall of xylem cells drawn correctly (angular) ; 4 cell walls as double lines with middle lamella between ; 5 label + line to lumen ; [5] (b) measures line Y within range + mm + to 0.5 ; (range 86–88 mm) measures line Z within range + mm + to 0.5 ; (range 14–16 mm) answer as larger whole number to smaller whole number to simplest ratio ; [3] (c) 1 organise as table with 3 columns headed feature + M1 + Fig. 2.2 ; 2 only observable differences recorded ; max 3 for differences – see table below: mp point of comparison Fig 2.1 Fig 2.2 3 stele shape vascular bundle / vascular tissue / xylem / phloem cross (do not accept irregular / central) round / circular / scattered ; 4 stele layers around stele endodermis 1 or 2 layers / fewer layers / thin 2 or 3 layers / more layers / thick ; 5 stele size in relation to diameter of root / size of specimen small(er) larg(er) ;

Page 5 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2014 9700 36 © Cambridge International Examinations 2014 mp point of comparison Fig 2.1 Fig 2.2 6 cortex air spaces shape of cells length of cells air spaces absent round / circular / oval small / short(er) air spaces present elongated / long / rectangular large / long(er) ; 7 cortex number of cells in cortex (must refer to cortex) packing filled with cells / more / many cells more packed not filled with cells / less / few(er) less packed ; 8 epidermal layer red stained cells (near epidermis) one layer / thin(ner) absent several layers / thick(er) present ; 9 total number of layers less / few(er) layers or expressed as a number of layers, e.g. 5 more layers or expressed as a number of layers, e.g. 8 ; [max 5] [Total: 19]