Cambridge A Level Biology 9700 — 2011 Oct/Nov Paper 3 · Variant 5

This document consists of 11 printed pages and 1 blank page. DC (NF/CGW) 34210/7 © UCLES 2011 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Subsidiary Level and Advanced Level * 7 6 2 5 2 0 9 0 0 5 * BIOLOGY 9700/35 Advanced Practical Skills 1 October/November 2011 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 9700/35/O/N/11 © UCLES 2011 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 of the work that you would like to do. You will gain marks for recording your results according to the instructions. 1 Enzyme E catalyses the hydrolysis of sucrose to the reducing sugars, glucose and fructose. Glucose and fructose can diffuse through a partially permeable (selectively-permeable) membrane. The wall of Visking (dialysis) tubing is partially permeable. A bag made of Visking tubing, containing enzyme E and sucrose solution, is placed into a large test-tube containing distilled water. The large test-tube is placed in a water-bath. You are required to follow the time course of this enzyme-catalysed reaction by testing the distilled water surrounding the bag. Samples of water around the bag are taken at intervals during 20 minutes and tested for reducing sugars using Benedict’s solution. You are provided with: labelled contents hazard volume / cm3 E invertase solution irritant 15 S sucrose solution none 15 Benedict’s solution Benedict’s solution harmful irritant 60 W distilled water none 200 You are also provided with: • V, one length of Visking (dialysis) tubing in distilled water.

3 9700/35/O/N/11 © UCLES 2011 [Turn over For Examiner’s Use You will need to run the time course for the enzyme-catalysed reaction for 20 minutes. Fig. 1.1 shows the procedure for investigating the time course of the enzyme-catalysed reaction. The times you will use are 5 minutes, 10 minutes, 15 minutes and 20 minutes. warm water-bath visking tubing containing S (step 7) 20 15 10 5 after 20 minutes remove bag and put into container for waste (step 14) step 12 step 11 add E (step10) steps 8 and 9 first large test-tube (steps 8 and 9) second large test-tube (step 11) 30 cm3 distilled water in each large test-tube Fig. 1.1 You are advised to read steps 1 to 19 before proceeding. Proceed as follows: 1. Label the large test-tubes with the times and put 30 cm3 of distilled water into each one. 2. While you are doing steps 3 to 16 you will need to heat up the beaker of water labelled for Benedict’s test so that it can be used later to carry out the Benedict’s test. Decide on the temperature you plan to use for this water-bath. (i) State the temperature you have chosen in the space below. … °C [1] 3. Prepare a water-bath between 35 °C and 40 °C using the beaker of water labelled for reaction. 4. Put all the labelled large test-tubes into the water-bath labelled for reaction. 5. Tie a knot in the Visking tubing as close as possible to one end so that it seals the end forming a bag. 6. To open the other end, wet the Visking tubing and rub the tubing gently between your fingers.

4 9700/35/O/N/11 © UCLES 2011 For Examiner’s Use 7. Put 4 cm3 of S into the open end of the bag. 8. Put the bag into the water in the first large unlabelled test-tube. 9. Allow 3 minutes for S in the bag to reach the same temperature as the distilled water surrounding the bag. 10. Put 4 cm3 of enzyme E into the bag. You need to mix the enzyme with the substrate. Remove the bag, close the open end between your fingers. Holding both ends tightly, turn the bag upside down several times and this will mix the contents. 11. Put the bag back into the second large test-tube, labelled 5. Start timing the time course. 12. After 5 minutes remove the bag and contents and place it into the next large test-tube. 13. Repeat step 12 as shown in Fig. 1.1. 14. After 20 minutes, put your bag with its contents into the container labelled for waste. 15. At the end of the 20 minutes put the contents of each large test-tube into separate labelled small containers. 16. Test the contents of the small containers for reducing sugars using Benedict’s solution. You will need to keep the volume of Benedict’s solution the same for each test. Decide on the volume of sampling solution and Benedict’s solution you plan to use for each test. (ii) State the volume of sampling solution and Benedict’s solution you have chosen. volume of sampling solution … volume of Benedict’s solution … [2] 17. In the small test-tubes, add the volumes of samples and Benedict’s given in (ii). 18. Put all the test-tubes into the water-bath for Benedict’s test and immediately start timing. 19. Record the time for the change from blue to the first colour you see (ignore any further colour changes). If there is no colour change at 10 minutes, record “more than 600”.

5 9700/35/O/N/11 © UCLES 2011 [Turn over For Examiner’s Use (iii) Prepare the space below and record your results. [4] (iv) Identify one significant source of error in this investigation. … … [1] (v) Describe a suitable control for this investigation. … … [1] (vi) Suggest how you would make two improvements to this investigation. … … … … … [2]

6 9700/35/O/N/11 © UCLES 2011 For Examiner’s Use A student investigated the effect of placing pieces of tissue from a potato in sucrose solutions of different concentrations. At the start, each sample of potato tissue was weighed and the initial mass was recorded. Then each sample of potato tissue was placed into a different concentration of sucrose solution. After a set time the potato tissue was removed and the final mass of the potato tissue was recorded. The change in mass and percentage change of mass for each sample of potato tissue was calculated. The results of the student’s investigation are shown in Table 1.1. Table 1.1 sucrose concentration / mol dm–3 initial mass / g final mass / g change in mass / g percentage change in mass 0.0 2.54 3.18 0.64 25.0 0.2 2.43 2.62 0.19 0.4 2.40 2.45 0.05 2.0 0.6 2.71 2.30 – 0.41 – 15.0 0.8 2.44 2.49 0.05 2.0 1.0 2.58 1.80 – 0.78 – 30.0 (b) (i) Complete Table 1.1. [1]

7 9700/35/O/N/11 © UCLES 2011 [Turn over For Examiner’s Use (ii) Plot a graph of the data shown in Table 1.1. [4] (iii) Draw a circle around the anomalous result on the graph. [1]

8 9700/35/O/N/11 © UCLES 2011 For Examiner’s Use (iv) Complete Table 1.2 below. Table 1.2 diagrams of potato cells with arrows showing the direction and quantity of water movement from your graph, state one example of a sucrose concentration where this water movement occurs and explain how you chose this example Cell A example … explanation … … … … … Cell B example … explanation … … … … … Cell C example … explanation … … … … … [3] (v) Explain, in terms of water potential, the movement of water in cell A. … … … … … … [2] [Total: 22]

9 9700/35/O/N/11 © UCLES 2011 [Turn over For Examiner’s Use 2 L1 is a slide of a stained transverse section through a plant leaf. The plant belongs to a genus which grows widely especially in Chile and Argentina. Fig. 2.1 (a) (i) Draw a large plan diagram of the part of the leaf indicated by the shaded area in Fig. 2.1. Label the palisade mesophyll and the epidermis. [6]

10 9700/35/O/N/11 © UCLES 2011 For Examiner’s Use (ii) Between the vascular bundles are openings (canals) surrounded by a wall of cells. Make a large drawing of six adjacent (touching) cells making up this wall of cells (the inner wall of the canal). Label with the letter F a stained feature inside one cell. [6] (iii) State one observable feature of the epidermis that supports the conclusion that this is a leaf from a plant growing in a dry habitat. Suggest how this feature helps the plant to survive in a dry habitat. … … … [1]

11 9700/35/O/N/11 © UCLES 2011 For Examiner’s Use Fig. 2.2 is a photomicrograph of a transverse section through a leaf of a different plant species. This plant is native to Europe, North Africa and Asia but grows widely throughout the world. Fig. 2.2 (b) Prepare the space below so that it is suitable for you to record three observable differences between the specimen on L1 and in Fig. 2.2. Record your observations in the space you have prepared. [5] [Total: 18]

12 9700/35/O/N/11 © UCLES 2011 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. BLANK PAGE

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the October/November 2011 question paper for the guidance of teachers 9700 BIOLOGY 9700/35 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 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 October/November 2011 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 – October/November 2011 9700 35 © University of Cambridge International Examinations 2011 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: Teachers’ version Syllabus Paper GCE AS/A LEVEL – October/November 2011 9700 35 © University of Cambridge International Examinations 2011 1 (a) (i) [1] one temperature + 80(.0); MMO decisions 1 [1] Additional guidance A any range 80 to 100 e.g. 80 to 85 (ii) [2] equal volume or excess of Benedict’s solution with respect to volume of sampling solution; [1] Additional guidance A not less than 2 cm3 A 15 cm3 or less A total volume 20 (not 21) cm3 R whole number only MMO decisions 2 [1] both must have units cm3 or ml(s);

Page 4 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – October/November 2011 9700 35 © University of Cambridge International Examinations 2011 (iii) [4] table with all cells drawn AND heading (top or left) with (reaction) time / min(utes); mp1 Additional guidance A no outer boundary A test-tube or S and E or sampling (solution) with mins R mins in body of table R test-tube number or test-tube alone R if convert to seconds Ignore test-tube / additional columns / rows (heading on any one time column or row including mean) time / seconds (s) (to first colour change); PDO recording 2 mp2 Additional guidance Ignore heading for test-tubes R headings for standardised variables e.g. volumes or temperature records results for at least four sample times ; mp3 Additional guidance A 0 minutes A times or colours(blue to green to yellow to orange to orange/brown to red) R ‘no change’ records as times in whole seconds (numbers) only ‘less than 601’ time; (mark first column or row of recorded time taken) MMO collection 2 mp4 Additional guidance A minimum of four recorded times including ‘more than 600’

Page 5 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – October/November 2011 9700 35 © University of Cambridge International Examinations 2011 (iv) [1] max 1 Cause of error WITH idea of error mp1 (dependent) (change of Benedict’s solution) judge or observe or identifying colour is difficult or varies or not same; mp2 timing as all test-tubes together or observing change in test-tube is difficult or varies or not same; ACE interpretation max 1 mp3 (standardised) glucose or sample solution from previous tube or contamination is transferred on outside of Visking tubing bag to next test-tube; (v) [1] ACE improvement 1 [1] boil enzyme (and sucrose) Or replace enzyme / E with water or use water / W instead of enzyme / E Or replace sucrose with water / W or use water instead of sucrose Or use sucrose and water / W Or use enzyme and water / W; (Ignore equal volume or 2 cm3 of each) Ignore denature enzyme (needs how) R 0% sucrose or 0% enzyme

Page 6 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – October/November 2011 9700 35 © University of Cambridge International Examinations 2011 (vi) [max 2] Mark first three ideas for any correct two [max 2] (independent variable) sample more often (e.g. every 2 minutes) or narrower (range); mp1 Additional guidance R idea of wider range (dependent variable) weigh mass of precipitate; mp2 Additional guidance R colorimeter (Benedict’s) thermostatically-controlled water-bath or water-bath at a named temperature (80 to 100 / boiling); mp3 Additional guidance A digital or electronic A description of use of heating and cooling with Bunsen or hot and cold water mp4 (Benedict’s) idea of heat or do each test-tube separately replicate / repeat; mp5 Additional guidance A more times/trials/readings or repeats or repeat Ignore mean mp6 (standardised variables) use separate Visking tubing bags / one Visking tubing bag for 5 minutes, one for 10 minutes, one for 15 minutes, one for 20 minutes or test the water before putting in Visking tubing; mp7 use a buffer; ACE improvements max 2 mp8 check temperature of solution has reached temperature of water-bath or equilibrate enzyme or allow longer time for solutions to reach surrounding temperature in boiling tube; (b) (i) [1] missing value 7.82 or 7.8 or 8.0; ACE interpretation 1 [1] Additional guidance R 8

Page 7 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – October/November 2011 9700 35 © University of Cambridge International Examinations 2011 (ii) [4] x-axis sucrose conc(entration) mol dm–3 AND y-axis change in mass/g or percentage (%) change in mass; A label anywhere on right side of grid O Additional guidance Must have units on x-axis AND y-axis R put both units g and % R mol/dm–3 A mol/dm3 scale as x-axis 0.2 to 2 cm AND y-axis 10 to 2 cm ; S Additional guidance A no 0 label at origin and no end labels R awkward scale correct plotting of each point to within half a square i.e. less than 1 mm from intersection i.e. plot has to be nearer than halfway from a line – up or down or either side OR if meant to be between two lines then must not be on line above or below or either side; P Additional guidance A small cross or dot in circle or cross in circle A ecf if x-axis not 0 if scale 20 to 2 cm. R awkward y-axis scale R blobs or dots alone R cross too large ruled lines point to point or ruled lines of best fit R extrapolated A extrapolation from line of best fit to vertical or horizontal lines of plotted point only AND quality clear sharp; R if • less than 5 plots • line 1 mm or thicker • any feathery line • irregular thickness PDO layout 4 L Additional guidance A ecf from incorrect P

Page 8 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – October/November 2011 9700 35 © University of Cambridge International Examinations 2011 (iii) [1] ACE interpretation 1 [1] circle around 0.8 plotted point; (iv) [3] R if any incorrect ref. to sucrose solution. (Cell A no change in mass) take value for cell A (Cell B losing mass) AND any value higher than value for cell A (Cell C gaining mass) AND any value lower than cell A; example 0.4 example any value more than 0.4 example any value less than 0.4 ACE interpretation 1 [1] Additional guidance Must have mol dm–3 once [1] (Cell A) no change in mass or 0% change in mass; (Cell B) losing mass or figures most negative change in mass Or idea of more water out / exosmosis Or less water in / endosmosis AND (Cell C) gaining mass or positive quote most positive change in mass Or less water out / exosmosis Or more water in / endosmosis; PDO display 2 [1] Additional guidance Ignore ref. to size (v) [2] [1] (cell A) no net move(ment) or diffusion or equal move(ment) or diffusion (of water) in and out; R ‘no osmosis’ ACE conclusion 2 [1] water potential is same inside and outside cell or no difference; [Total: 22]

Page 9 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – October/November 2011 9700 35 © University of Cambridge International Examinations 2011 2 (a) (i) [6] PDO layout 1 [1] no shading AND length across widest point (top to bottom) is more than 50 mm AND (clear, sharp, unbroken lines) Must have four or more hand-drawn lines and / or enclosed areas (not cells) R if • drawn over the print of question • any line 1 mm or thicker • any feathery or broken / dashed • 3 ‘tails’ or overlaps or gaps (ignoring gaps for stomata) • any ruled or dashed lines in drawing [1] no cells drawn AND drawn correct part of leaf AND one closed end; [1] region across closed end or at least two stomata gaps; MMO collection 3 [1] (outermost two lines) drawn with two lines closer than 4 mm at widest point AND at least three defined enclosed areas (not cells); [1] at least two of defined enclosed areas divided into two regions OR has three outside layers (four lines) (not including any line for palisade); correct label with one label line to each of palisade mesophyll layer and epidermis; label line to within a defined layer for the palisade mesophyll layer and label line to epidermis between any two lines outside this palisade layer or the outermost line. MMO decision 2 [1] Additional guidance R if • any label which is biologically incorrect e.g. from incorrect organ or animal or cell structures • any label within drawn area • any label to open space, epidermis must have two lines

Page 10 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – October/November 2011 9700 35 © University of Cambridge International Examinations 2011 (ii) [6] Ignore any inclusion inside canal. PDO layout 1 [1] no shading AND largest dimension of one cell larger than 30 mm in any direction AND (clear, sharp, unbroken lines for outer cell lines only) Must have five or more enclosed areas R if • drawn over the print of question • any line 1 mm or thicker or ruled • any feathery or broken/dashed line • any ’tails’ or overlaps or gaps if two lines for cell walls • any ruled lines; only (any) 6 cells touching AND form a single chain in an arc (semicircle or full circle); [1] Additional guidance R any ruled lines (for innermost cells) cells not uniform size AND no extra line (canal lining as a line); [1] Additional guidance R any ruled lines MMO collection 3 [1] any one cell showing an inclusion; R any three cells with small inclusions / chloroplasts PDO recording 1 [1] cell walls as double lines with middle lamella between three adjacent cells; one correct label (F) (with label line) to any one cell with enclosed area drawn inside; MMO decision 1 [1] Additional guidance R F not totally inside when no label line R label line within cell R any label other than F

Page 11 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – October/November 2011 9700 35 © University of Cambridge International Examinations 2011 (iii) [max 1] (thick) presence of cuticle / lignified / resin cells few air spaces / less spongy mesophyll few stomata or pores prevents / reduces ‘loss of water’ or transpiration or evaporation or ‘diffusion of water’ or trap water; ACE conclusion max 1 max 1 sunken stomata prevents / reduces diffusion or absorb or trap water or moisture or moist air increase humidity;

Page 12 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – October/November 2011 9700 35 © University of Cambridge International Examinations 2011 (b) (i) [5] PDO recording 1 [1] organise as a table / Venn diagram / ruled boxes AND headed L1 and Fig. 2.2 AND first difference opposite each other; MMO decision 1 [1] only three observable differences recorded; ACE interpretation max 3 max 3 mp feature L1 Fig. 2.2 1. vascular bundle arrangement in line / along centre / scattered scattered / within columns random; 2. vascular bundle number or closeness few(er) or more or close more or few(er) or further apart; 3. air spaces / number of air spaces packing / number of cells none many / more compact more cells / mesophyll present few/less loose fewer cell / less mesophyll; 4. canals or openings present none / absent; 5. number of stomata / guard cells many / more or few / less few / less or many / more; 6. distribution of stomata / guard cells all round or both sides or upper and / or lower one side or only upper epidermis or not lower epidermis; 7. cuticle present / thick / large absent / thin / small; 8. epidermal layers R cells more than one layer / thick large one layer / thin small; 9. collenchymas / sclerenchyma present absent; 10. palisade layer or cells present absent / not clear; 11. overall shape smooth wavy / irregular; [Total: 18]