Cambridge A Level Biology 9700 — 2012 May/June Paper 3 · Variant 4

This document consists of 9 printed pages and 3 blank pages. DC (NF/CGW) 37132/6 © UCLES 2012 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Subsidiary Level and Advanced Level * 2 2 3 5 2 0 6 8 9 1 * BIOLOGY 9700/34 Advanced Practical Skills 2 May/June 2012 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. You may use a pencil for any diagrams, graphs or rough working. Do not use red ink, staples, paper clips, highlighters, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. 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/12 © UCLES 2012 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. • 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 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: • make different concentrations of plant extract containing catalase • investigate the effect of different concentrations of plant extract by finding the time taken for a square of filter paper, soaked in the plant extract, to rise in hydrogen peroxide solution. You are provided with: labelled contents hazard volume / cm3 H hydrogen peroxide solution harmful irritant 100 W distilled water none 80 P 100% plant extract solution none 50 (a) (i) Decide on the concentrations of plant extract solution you will use in your investigation. You will need to make up 10 cm3 of each concentration of plant extract solution. Prepare the space on page 3 to show: ▪ the concentration of P ▪ the volumes of P ▪ the volumes of W. [3]

3 9700/34/M/J/12 © UCLES 2012 [Turn over For Examiner’s Use Use this space: You are advised to read steps 1 to 10 before proceeding. Proceed as follows: 1. Prepare the concentrations of plant extract solution as stated in (a)(i). 2. Put H into the test-tube, filling to within 2 cm from the top. 3. Cut squares of filter paper, 1 cm × 1 cm. 4. Use forceps to pick up one square of filter paper and dip the whole square into one of the concentrations of plant extract solution in its container. 5. Wipe the square against the inside of the container to remove excess plant extract solution from both sides of the square. 6. Hold the square so that the top of the square is level with the surface of H as shown in Fig. 1.1. surface of H Fig. 1.1 7. Release the square (you may need to shake the forceps) and start timing. 8. Record the time taken for the square to return to the surface. If the time is more than three minutes, stop timing and record ‘more than 180’. 9. Remove the square from the test-tube. 10. Repeat steps 4 to 9 with the other concentrations of plant extract.

4 9700/34/M/J/12 © UCLES 2012 For Examiner’s Use (ii) Prepare the space below and record your results. [6] (iii) Identify three significant sources of error in your investigation. … … … … … … … [3] (iv) Suggest how you would make three improvements to this investigation. … … … … … … … [3]

5 9700/34/M/J/12 © UCLES 2012 [Turn over For Examiner’s Use Catalase catalyses the hydrolysis of hydrogen peroxide into oxygen and water. A student investigated the effect of changing the concentration of hydrogen peroxide solution on this hydrolysis. For each concentration of hydrogen peroxide solution the time to collect 25 cm3 of oxygen was recorded. Table 1.1 shows the results of the student’s investigation. Table 1.1 percentage concentration of hydrogen peroxide time to collect 25 cm3 of oxygen / s 4 47 8 18 12 15 16 13 25 11 (b) (i) Plot a graph of the data shown in Table 1.1. [4]

6 9700/34/M/J/12 © UCLES 2012 For Examiner’s Use (ii) Explain the effect of changing the concentration of hydrogen peroxide. … … … … … … … [3] [Total: 22] 2 K1 is a slide showing transverse sections through blood vessels. Select one large artery and one large vein. (a) (i) Draw a large plan diagram of two different types of blood vessel on slide K1. Label the muscle layer in the artery. [5]

7 9700/34/M/J/12 © UCLES 2012 [Turn over For Examiner’s Use Fig. 2.1 is a photomicrograph of a transverse section through lung tissue. Fig. 2.1 (ii) Make a large drawing to show the walls of two whole alveoli that are touching each other. Label the gas exchange membrane. [5]

8 9700/34/M/J/12 © UCLES 2012 For Examiner’s Use Fig. 2.2 is a photomicrograph of a transverse section through healthy lung tissue. Fig. 2.3 is a photomicrograph of a transverse section through unhealthy lung tissue. G F E D C magnification × 95 magnification × 95 Fig. 2.2 Fig. 2.3 To find the mean diameter of an alveolus in the healthy lung, a student measured five alveoli, as shown by the lines C, D, E, F and G in Fig. 2.2. (iii) Use the magnification to calculate the mean actual diameter, in μm, of an alveolus using the lines C, D, E, F and G. You may lose marks if you do not show your working or if you do not use appropriate units. … μm [3]

9 9700/34/M/J/12 © UCLES 2012 For Examiner’s Use (iv) Prepare the space below so that it is suitable for you to show the observable differences between the specimens in Fig. 2.2 and Fig. 2.3. Record your observations in the space you have prepared. [5] [Total: 18]

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12 9700/34/M/J/12 © UCLES 2012 BLANK PAGE Copyright Acknowledgements: Question 2, Fig. 2.1 ED RESCHKE/PETER ARNOLD INC./SCIENCE PHOTO LIBRARY Question 2, Fig. 2.2 BIOPHOTO ASSOCIATES/SCIENCE PHOTO LIBRARY Question 2, Fig. 2.3 BIOPHOTO ASSOCIATES/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. 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.

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the May/June 2012 question paper for the guidance of teachers 9700 BIOLOGY 9700/34 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 must be read in conjunction with the question papers and the report on the examination. • Cambridge will not enter into discussions or correspondence in connection with these mark schemes. Cambridge is publishing the mark schemes for the May/June 2012 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

Page 2 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2012 9700 34 © University of Cambridge International Examinations 2012 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 AVP Alternative valid point (examples given as guidance)

Page 3 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2012 9700 34 © University of Cambridge International Examinations 2012 Question 1 Expected Answers (a) (i) [3] 100 AND • (simple dilution) next four concentrations (five concentrations in total) with four even intervals; e.g. 100, 80, 60, 40, 20 e.g. 100, 90, 80, 70, 60 e.g. 100, 75, 50, 25, 0 • (serial dilution) e.g. 100,50, 25,12.5, 6.25 e.g. 100,10,1,0.1 and 0.01 mp 1 Do not give mark if • rounds up or down e.g.12 or 13 or 6.3 • if no concentrations mp 2 for first four concentrations shows the use of 100% or plant extract / correctly • plant extract / P / 100 into all simple dilution • plant extract / P / 100 only for first one in a serial dilution AND (P) cm3 ; Do not give mark if • if no concentrations MMO decisions 3 mp 3 for first four concentrations total final volume 10 ;

Page 4 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2012 9700 34 © University of Cambridge International Examinations 2012 (a) (ii) [6] table with all cells drawn AND heading (top or left of recorded data column) percentage concentration (of) plant extract or P; mp 1 Do not give mark if • % in cells of headed column • other units mol dm-3 • no units (heading – column or row including mean) time (/)s or sec(onds); PDO recording 2 mp 2 Do not give mark if • units in cells of this column / row • min(utes) • additional method information either headings for columns / rows variables or in cells e.g. volumes and concentration in same cells (mark first column / row of recorded time taken) for at least four concentrations records whole seconds numbers less than 180 or ‘> or more than 180’; mp 3 Must have • whole numbers • numbers 180 or less MMO collection 2 mp 4 (mark first column / row of recorded time taken) (records correct pattern) highest concentration recorded is shorter time than lowest concentration ; mp 5 at least two readings per concentration or six or more concentrations; MMO decision 2 mp 6 mean / average recorded or rate recorded for two or more concentrations;

Page 5 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2012 9700 34 © University of Cambridge International Examinations 2012 (a) (iii) [max 3] Mark as incorrect idea that any errors which affect all tubes equally. cause of error WITH idea of error mp 1 (independent variable – different concentrations of plant extract, catalase) plant extract (on paper) not even or bubbles / foam on side; (do not give if gas bubbles/oxygen) mp 2 volume or amount or concentrations of extract time of dipping or soaking extract left on paper thickness of paper idea of different (different pieces of paper) not the same not removed varies; mp 3 (dependent variable – different times for paper to rise in hydrogen peroxide solution) timing paper sinking to bottom variable time for paper to reach bottom paper rises flat or paper on edge or foam on paper; mp 4 hydrogen peroxide not the same (concentration) for each square of paper or lost has P (from previous concentration) idea of used up or not new / fresh; ACE interpretation MAX 3 mp 5 paper idea of sticking to sides; mp 6 temperature of hydrogen peroxide rises;

Page 6 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2012 9700 34 © University of Cambridge International Examinations 2012 (a) (iv) [max 3] mp 1 (concentration of extract) idea of using more concentrations or serial dilution or repeat; Ignore mean or average mp 2 (standardised variables) use same piece / source of paper same time for soaking or dipping into plant extract; mp 3 pH use buffers to keep constant; mp 4 hydrogen peroxide use fresh hydrogen peroxide / renew for each square (so ‘not used up’); ACE improvements MAX 3 mp 5 container or squares use deeper / wider container so squares do not touch sides smaller or as circles; (b) (i) [4] mp 1 x-axis percentage concentration hydrogen peroxide or H2O2 AND y-axis time (/) s or sec(onds) to collect oxygen or O2; mp 2 scale as x-axis 5 to 2 cm labelled each 2cm AND y-axis 10 to 2 cm labelled each 2cm ; mp 3 correct plotting of • five points only • as small cross (does not go outside square on grid) or dot (in circle) or cross in circle to within half a square; five plots with ruled lines exactly point to point or curve through five points AND (quality) smooth line less than line thickness on grid; PDO layout 4 mp 4 Do not give mark if • any extrapolation

Page 7 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2012 9700 34 © University of Cambridge International Examinations 2012 (b) (ii) [3] mp 1 either ref. to increase or more hydrogen peroxide or substrate reacts with or binds to enzyme or catalase; or low hydrogen peroxide or substrate so does not react with or bind to enzyme or catalase; mp 2 correct ref. to use of active site(s) or ESC(s) or enzyme-substrate complexes; ACE conclusion 3 mp 3 (at high hydrogen peroxide) Idea of • limiting factor (or hydrogen peroxide not limiting factor) • too few active sites / ESCs or active sites full / allow ’enzyme saturated’ • temperature or pH; Do not give mark if • ref. to idea of reaction slows or slowing down or decreases [Total: 22]

Page 8 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2012 9700 34 © University of Cambridge International Examinations 2012 Question 2 Expected Answers (a) (i) [5] PDO layout 1 mp 1 not drawn over the print of question AND no shading AND largest blood vessel larger than 50 mm AND clear, sharp, unbroken lines for all outermost enclosed areas ; Do not give mark if • less than two outermost enclosed areas or if any outermost line has • any ruled or compass lines • any line more than1 mm • feathery or broken or dashed or gap • any ‘tail’ or overlap mp 2 no cells AND drawn at least two complete vessels; mp 3 drawn different vessels must be only two complete vessels AND different shapes; MMO collection 3 mp 4 (at least one complete vessel drawn with at least two layers (minimum three lines) AND in this vessel inner lining crinkled or corrugated all round; correct label muscle or tunica media with label line to layer touching endothelium (inner line) of complete vessel with thickest wall; Must have minimum of three enclosed areas, line must touch middle line or be between the middle and inner line MMO decision 1 mp 5 If label both vessels with muscle or tunica media then both must be correct Do not give mark if • any label which is biologically incorrect e.g. from incorrect organ or plant e.g. epidermis • any label within drawn area

Page 9 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2012 9700 34 © University of Cambridge International Examinations 2012 (a) (ii) [5] PDO layout 1 mp 1 not drawn over the print of question AND no shading AND larger than 50 mm across widest point of inner enclosed area on any alveolus AND clear, sharp, unbroken lines for all inner enclosed areas; Do not give mark if • less than two hand drawn inner enclosed areas any of the inner enclosed areas has • any ruled lines • any line more than 1mm • any feathery line or broken or dashed or gap in line • any ‘tails’ or overlaps or gaps mp 2 only two inner enclosed areas Ignore double lines AND with shared adjacent wall AND with outer line partly drawn to show each end of the shared wall; MMO collection 2 mp 3 at least 2 complete alveoli of different shapes; mp 4 drawn all shared walls with all other alveoli (all round both alveoli) AND (walls with) at least three nuclei drawn enclosed in the alveolar wall; Do not give mark if draw cells only correct label gas exchange membrane with label line(s) which • touches the line or between two lines; MMO decision 2 mp 5 Do not give mark if • any label is biologically incorrect e.g. from incorrect organ or plant e.g. epidermis or non-observable structures e.g. cilia • label within drawn area

Page 10 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2012 9700 34 © University of Cambridge International Examinations 2012 (a) (iii) [3] MMO collection 1 mp 1 shows at least one value for each of C, D, E, F, and G AND correct unit mm anywhere which match values; Ignore use of metres or mm shows addition of five values AND shows division by 5; mp 2 Do not give mark for • Sx/n unless x and n have key shows at least one conversion of mm to mm by showing • multiplication by ×1000 or 103; or conversion from cm to mm • ×10 000 or 104 AND shows figure divided by / or ÷ 95 or 95 PDO display 2 mp 3 Do not give mark if • metres anywhere • no mm or cm anywhere

Page 11 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2012 9700 34 © University of Cambridge International Examinations 2012 (b) [max 5] PDO recording 1 mp 1 organise as a table with only three columns or rows separated by lines (no cells needed) Ignore number column AND headings in any order only Fig. 2.2 / healthy and Fig. 2.3 / unhealthy AND third column or row contains features; only observable differences (at least two) recorded; MMO decision 1 mp 2 Do not give mark if • any similarities recorded • any function e.g. ‘for gas exchange’ or not observable tar • surface area to volume ratio • healthy and unhealthy / bursting / damaged ACE interpretation MAX 3 feature Fig. 2.2 healthy lung Fig. 2.3 unhealthy lung mp 1 size (of air space / lumen / diameter) surface area / gas exchange membrane alveolar wall Small / small(er) larg(er) more Large / larg(er); small(er) few(er) or less mp 2 number many few(er); mp 3 shape of alveolus or wall wavy / irregular / more folded smooth / even / less folded; mp 4 thickness thin(ner) thick(er); mp 5 number of nuclei many / more few(er) / less; mp 6 black particles ignore tar absent or no(one) or has not or some present or yes or has or more; Ignore • functions • ref. to colour • shape of cell or nucleus • 3-D descriptions such as spherical, biconcave, ball, disc • tick and cross without a key • diagrams Do not give ACE marks if • for each feature the difference is not opposite each other unless comparative statement e.g. more or -er Fig. 2.2 difference i difference ii Fig. 2.3 difference i difference ii [Total: 18]