Cambridge A Level Biology 9700 — 2013 May/June Paper 3 · Variant 2

This document consists of 13 printed pages and 3 blank pages. DC (NF/SW) 52076/6 © UCLES 2013 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Subsidiary Level and Advanced Level * 3 7 5 1 5 2 6 3 2 2 * BIOLOGY 9700/32 Advanced Practical Skills 2 May/June 2013 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 ink. Do not use red ink, staples, paperclips, highlighters, glue or correction fluid. You may use a pencil for any diagrams, graphs or rough working. 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 9700/32/M/J/13 © UCLES 2013 For Examiner’s Use You are reminded that you have only one hour for each question in the practical examination. You should: • read carefully through the whole of Question 1 and Question 2 • then plan your use of the 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. 1 Yeast cells use enzymes as part of their metabolic reactions. Some of these reactions release oxygen from hydrogen peroxide solution. You are required to investigate the effect of temperature (independent variable) on the release of oxygen from hydrogen peroxide solution. You are provided with: labelled contents hazard volume / cm3 Y yeast cell suspension none 20 H hydrogen peroxide solution irritant harmful 20 Proceed as follows: You are required to change the temperature of Y during the investigation. 1. Put the beaker containing Y into a large beaker (W) which will be the water-bath as shown in Fig. 1.1. beaker (W) for water-bath Y Fig. 1.1

3 9700/32/M/J/13 © UCLES 2013 [Turn over For Examiner’s Use (a) (i) Decide what level of water you will start with in W. Show on Fig. 1.1 the level of water in W. [1] 2. Put hot water from the beaker provided into W to below the level you decided. Add hot water and cold water as needed to obtain a water-bath of between 40 °C and 45 °C. Adjust the volume of water to the level you decided in (a)(i). The beaker may float but should not spill its contents. 3. Keep Y (in W) at a temperature between 40 °C to 45 °C. Fig. 1.2 shows the apparatus set up to measure the release of oxygen from hydrogen peroxide solution. The oxygen released into B can be measured (dependent variable) by counting the number of bubbles. 1 cm small test-tube (in a clear beaker or container) large test-tube (in a test-tube rack) cold water delivery tube A B Fig. 1.2 The end of the delivery tube should be 1 cm below the level of the water in test-tube B as shown in Fig. 1.2. (ii) Decide how you will standardise the position of the delivery tube in test-tube B as shown in Fig. 1.2. Describe how you standardised the position of the tube. … [1] 4. Put water from the beaker or container, labelled cold, into test-tube B as shown in Fig. 1.2. 5. Remove the small beaker or container containing Y from W. 6. Record the temperature of Y. …

4 9700/32/M/J/13 © UCLES 2013 For Examiner’s Use 7. Stir Y and put 1 cm3 into the large test-tube A. Put the beaker containing Y back into W. The reaction will start as soon as you add H (in step 8). You are required to count the number of bubbles released into B by making a small mark on Grid 1.1 for each bubble as it is released for the intervals shown below. If the number of bubbles is too many to record for any one time, record ‘too many’ for that interval. Example 1st 30 s l l l l l l l l l l l l l l l 15 Grid 1.1 – for recording higher temperature 1st 30 s 2nd 30 s 3rd 30 s 4th 30 s 5th 30 s 6th 30 s 7th 30 s 8th 30 s

5 9700/32/M/J/13 © UCLES 2013 [Turn over For Examiner’s Use 8. Put 4 cm3 of H into the large test-tube A, immediately put in the bung and start timing and recording. 9. After 4 minutes, remove the bung from test-tube A. You are provided with a container labelled ‘for waste’ and a container labelled ‘for washing’ so you can re-use the large test-tube A. 10. Decide on a lower temperature for your next investigation. Adjust the temperature of W and put the beaker containing Y into W for 5 minutes. After this 5 minutes, record the temperature of Y … 11. Repeat steps 7 to 9. Use Grid 1.2 to record your readings. Grid 1.2 – for recording lower temperature 1st 30 s 2nd 30 s 3rd 30 s 4th 30 s 5th 30 s 6th 30 s 7th 30 s 8th 30 s

6 9700/32/M/J/13 © UCLES 2013 For Examiner’s Use (iii) Prepare the space below and record your results. [6] (iv) Identify two significant sources of error in your investigation. … … … … [2]

7 9700/32/M/J/13 © UCLES 2013 [Turn over For Examiner’s Use (v) Describe three modifications to this investigation which would improve the confidence in your results. … … … … … … [3]

8 9700/32/M/J/13 © UCLES 2013 For Examiner’s Use In a similar investigation, some scientists investigated the effect of the concentration of hydrogen peroxide on the release of oxygen from hydrogen peroxide solution, using yeast as a source of enzymes. The breakdown of hydrogen peroxide solution was measured by the time taken to collect 20 cm3 of oxygen. The results are shown in Table 1.1. Table 1.1 percentage concentration of hydrogen peroxide time taken to collect 20 cm3 of oxygen / s trial 1 trial 2 trial 3 trial 4 trial 5 mean 4 46 48 48 47 45 47 6 28 28 20 27 26 27 8 21 17 18 17 21 19 12 12 13 14 9 14 16 11 9 10 9 11 10 20 8 9 9 8 10 9 (b) (i) Two of the values in Table 1.1 are anomalous. Draw a circle around each of these values. [1] (ii) Complete Table 1.1 by calculating the missing value. [1] (iii) Plot a graph of the data shown in Table 1.1. [4]

9 9700/32/M/J/13 © UCLES 2013 [Turn over For Examiner’s Use (iv) Using the data in Table 1.1 and your graph, explain the results for the investigation. … … … … [2] [Total: 21] Question 2 starts on page 10

10 9700/32/M/J/13 © UCLES 2013 For Examiner’s Use 2 M1 is a slide of a stained transverse section through a plant stem. This plant species is a native of the Mediterranean region. draw this sector Fig. 2.1 (a) (i) Draw a large plan diagram of the part of the stem indicated by the shaded sector in Fig. 2.1. On your diagram, use a ruled label line to show the pith. [5]

11 9700/32/M/J/13 © UCLES 2013 [Turn over For Examiner’s Use (ii) The cells in each corner of the stem are different from the cells in the centre of the stem. Make a large drawing of one group of three whole, adjacent (touching) cells • from the tissue in one corner, as observed on the specimen on M1. Make a large drawing of one group of three whole, adjacent (touching) cells • from the tissue in the centre of the stem, as observed on the specimen on M1. On your drawing, use a ruled label line and label to show one cell wall. cells from the tissue in one corner cells from the tissue in the centre of the stem [5]

12 9700/32/M/J/13 © UCLES 2013 For Examiner’s Use (iii) Use the eyepiece graticule scale to find the mean width of the: • cells in the centre of the stem • cells in a corner of the stem. State the ratio of the mean width of the cells in the centre of the stem to the mean width of the cells in a corner. Note: You are not required to calibrate the eyepiece graticule scale with a stage micrometer. You will lose marks if you do not show all the steps in finding the ratio. [3] (iv) The cells in the corner of the stem on M1 carry out the function of support. Suggest one observable feature which supports this conclusion. … … … [1]

13 9700/32/M/J/13 © UCLES 2013 For Examiner’s Use Fig. 2.2 is a photomicrograph of a stained transverse section through a stem of a different plant species. Fig. 2.2 (b) Prepare the space below so that it is suitable for you to record observable differences between the specimens on slide M1 and in Fig. 2.2 to include: • the vascular tissue • at least two other tissues. [5] [Total: 19]

14 9700/32/M/J/13 © UCLES 2013 BLANK PAGE

15 9700/32/M/J/13 © UCLES 2013 BLANK PAGE

16 9700/32/M/J/13 © UCLES 2013 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. University of 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.

CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the May/June 2013 series 9700 BIOLOGY 9700/32 Paper 32 (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 2013 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.

Page 2 Mark Scheme Syllabus Paper GCE AS/A LEVEL – May/June 2013 9700 32 © Cambridge International Examinations 2013 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 excepted) 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 ACE Analysis, Conclusions and Evaluation (skills) MMO Manipulations, Measurement and Observation (skills) PDO Presentation of Data and Observations (skills)

Page 3 Mark Scheme Syllabus Paper GCE AS/A LEVEL – May/June 2013 9700 32 © Cambridge International Examinations 2013 Expected Answers 1 (a) (i) [1] MMO decision 1 1 level of water in large beaker shown equal to or above level of yeast suspension in small beaker AND below level of top of small beaker; (ii) [1] MMO decision 1 1 mark (test-tube B or delivery tube); (iii) [6] If recorded as graph or bar chart, not table, only mp4 and mp6 can be scored. PDO recording 2 mp1 table with all cells drawn AND headings (top row or left of recorded data column) either temp(erature/)°C or time sec(onds) or s; Do not give mark if • any units (°C or sec(onds) or s) are in cells of headed row/column • two rows of data in one cell mp2 heading number (of) bubbles; MMO collection 2 mp3 exactly 8 readings per run for higher temperature AND exactly 8 readings per run for lower temperature AND whole numbers only; mp4 first reading higher than last reading for both temperatures; MMO decision 2 mp5 higher temperature recorded first; mp6 one temperature between 40 and 45(0C) AND second temperature at least 5(0C) lower;

Page 4 Mark Scheme Syllabus Paper GCE AS/A LEVEL – May/June 2013 9700 32 © Cambridge International Examinations 2013 (iv) [max 2] ACE Interpretation 2 max 2 cause of error AND idea of error mp1 (dependent variable) (counting) bubbles bubbles too fast/very fast/too many difficult rate varies miss(ed) some; mp2 size of bubbles varies; mp3 (independent variable) temperature or reaction mixture/yeast/A can change/difficult to keep constant loses heat; Do not give mark if • state that temperature of room or water-bath/W or Y when in beaker changes (v) [max 3] ACE improvements 3 max 3 mp1 (dependent variable) gas syringe or idea of downward displacement of water and measure volume of gas or less/lower concentration or volume (not amount) of hydrogen peroxide or enzyme; mp2 (standardised variables) put vaseline/grease around bung (in A) or replace with better-fitting bung pH (controlled using) buffer; mp3 (independent variable) maintained in thermostat(ically controlled water-bath) or describe use of heating and cooling or hot/cold water AND uses thermometer (to check temperature) or describe how to insulate A or more temps/bigger range of temps (not two temps further apart/larger change in temps); mp4 repeat more than once/replicates/more times/multiple tests;

Page 5 Mark Scheme Syllabus Paper GCE AS/A LEVEL – May/June 2013 9700 32 © Cambridge International Examinations 2013 (b) (i) [1] MMO decision 1 1 circles 6% trial 3: 20 AND circles 12% trial 4: 9; (b) (ii) [1] ACE interpretation 1 1 13 (entered in gap in table or by question); Do not give mark if • 13.0/13.00/13.25 • 12/12.4/12.40 (iii) [4] PDO layout 4 mp1 x-axis: percent(age) or % conc(entration) (of) hydrogen peroxide or H202 AND y-axis: (mean) time (taken) to collect (20 cm3 of) oxygen or O2 (/) sec(onds) or s ; Must have units for both axes mp2 scale on x-axis: 5 to 2 cm, labelled each 2 cm AND scale on y-axis 10 to 2 cm, labelled each 2 cm; mp3 • check there are six points • all six as small cross (does not go outside square on grid) or dot in circle or cross in circle • correct plotting of points, mp4 six plots with either ruled lines exactly point to point or hand-drawn smooth curve for whole graph • starts and ends exactly at end points • also passes through at least two other points exactly • within half a small square of any remaining points AND (quality) smooth line less than 1 mm thick (check with grid);

Page 6 Mark Scheme Syllabus Paper GCE AS/A LEVEL – May/June 2013 9700 32 © Cambridge International Examinations 2013 (iv) [2] ACE conclusion 2 mp1 at high/increasing concentrations: • more/many active sites used/occupied/bind/join/ used or • more/many enzyme- substrate complexes/E-S complexes OR at low concentrations: • less/fewer active sites occupied/bind/join/used or • less/fewer enzyme- substrate complexes/E-S complexes; mp2 idea of why reaches maximum rate (limiting factor) • not enough enzyme/active sites or • limiting factor is enzyme concentration or • all active sites occupied • active sites saturated; [Total: 21] 2 (a) (i) [5] PDO layout 1 mp1 Do not give mark if • any shading • drawn over the print of the question • any ruled lines Do not give mark if less than 40mm from outmost line to base of corner vascular bundle AND clear, sharp, unbroken lines Do not give mark if • less than two lines and less than four enclosed areas (ignore cells) or any lines with • any part of line 1mm or thicker (use grid) • any feathery or broken or dashed line or gap • any tail or overlap; MMO collection 3 mp2 no cells drawn AND top right sector drawn; mp3 draws at least seven lines across any point of width of section (outside to inside); mp4 corner vascular bundle: • wider than deep and • outer line not straight or concave AND divided into at least 3 regions (ignore cells and vertical rays); MMO decision 1 mp5 labels pith with label line either touching or further to the centre than the innermost line or ending further to the centre than the inside edge of the vascular bundle;

Page 7 Mark Scheme Syllabus Paper GCE AS/A LEVEL – May/June 2013 9700 32 © Cambridge International Examinations 2013 (ii) [5] PDO layout 1 mp1 Suitable drawing; Do not give mark if • any shading • drawn over the print of the question • any ruled lines in lines of corner cells Do not give mark if • less than 40 mm at widest distance across largest cell Do not give mark if • less than six outer enclosed areas or if any outer lines (of enclosures) • are thicker than 1 mm (use grid) • are feathery, broken/dashed or have gaps • have tails or overlaps; MMO collection 3 mp2 only 6 complete cells drawn AND as two groups of 3 touching cells; mp3 seven or fewer cells in total AND (cells from tissue in centre) widest dimension of the biggest cell is at least 2 times the narrowest dimension of the smallest cell (from cells in the corner); mp4 in either group of three cells: • all cells must be drawn with double lines all the way round and • where two pairs of cells touch there must be 3 lines (representing the middle lamella); MMO decision 1 mp5 one correct label “cell wall”, with one label line which must touch outermost line of a cell or finish between the two cell wall lines;

Page 8 Mark Scheme Syllabus Paper GCE AS/A LEVEL – May/June 2013 9700 32 © Cambridge International Examinations 2013 (iii) [3] MMO decision 1 mp1 shows measurements for both types of cell AND as whole numbers or x.5 only AND units as “eyepiece”, (e)gu or epu or “units” or “divisions” or “lines” or “marks” written anywhere; Can have • values recorded in any context, e.g. in addition • ½ instead of 0.5 • decimals in means Do not give mark if • no units • units in m, cm, mm, µm, nm • not clear which measurements correspond to which type of cell PDO display 2 mp2 shows division by number of cells (3 or more), for both cell types; mp3 for final answer only: larger whole number to smaller whole number (larger number first) OR as fraction, with larger whole number over smaller whole number AND to the lowest common denominator; (iv) [max 1] ACE conclusion 1 max 1 one from: thick walls large walls small cells/lumen closely packed cells no spaces between cells high ratio of wall to cell (much) staining;

Page 9 Mark Scheme Syllabus Paper GCE AS/A LEVEL – May/June 2013 9700 32 © Cambridge International Examinations 2013 (b) [5] PDO recording 2 mp1 organise as table with three columns or rows separated by lines (no cells needed) AND two columns headed M1/slide and Fig 2.2 in any order AND third column contains features; mp2 only observable differences (at least two) recorded; Do not give mark if describes “cell” rather than “section” or “stem” for incorrect tissues ACE interpretation 2 feature Slide M1 Fig. 2.2 max 1 mp1 vascular bundles/vascular tissue/xylem/phloem any comparative statement except size, or distance in from outside any comparative statement except size, or distance in from outside, or in corners; max 2 mp2 pith/centre not hollow/(has) cells/more cells/big(ger) (not “present”) hollow/no cells/less cells/small(er) (not “absent”); mp3 thickened cells/ collenchyma/ sclerenchyma/fibres/ described in corners/not (on) vascular bundles/idea of more (not present/absent) not in corners/(on) vascular bundles/idea of less (not present/absent); mp4 cortex/( layer) under epidermis no/less/small(er) air spaces yes/more/large(r) air spaces; mp5 outer layer/epidermis thick(er) or more/2 layer(s) of cells or no gaps/stomata/guard cells or trichomes/hairs (not root hairs) (not smaller) thin(ner) or less/1 layer of cells or gaps/stomata/ guard cells or no trichomes/hairs (not root hairs) (not bigger) [Total: 19]