Cambridge A Level Biology 9700 — 2012 Oct/Nov Paper 3 · Variant 3

This document consists of 12 printed pages. DC (NF/SW) 47055/6 © UCLES 2012 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Subsidiary Level and Advanced Level * 5 0 8 0 5 2 6 2 8 9 * BIOLOGY 9700/33 Advanced Practical Skills 1 October/November 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 9700/33/O/N/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 An enzyme catalyses the hydrolysis (breakdown) of sucrose to reducing sugars. This enzyme is essential in a seed to provide reducing sugars so that the seed can grow. A student suggested the hypothesis: “seeds soaked in a sucrose solution release the enzyme which will hydrolyse the sucrose solution into reducing sugars”. You are required to: • soak seeds in a sucrose solution to enable the enzyme to hydrolyse the sucrose to reducing sugars • show the release of the enzyme by testing for reducing sugars in the solution surrounding the seeds • make different concentrations from a solution of reducing sugars • carry out Benedict’s test on the reducing sugars and on the solution surrounding the seeds and use the results to estimate the concentration of reducing sugars in the solution surrounding the seeds. You are provided with: labelled contents hazard volume / cm3 S sucrose solution none 15 R 0.4% reducing sugars solution none 30 W distilled water none 100 Benedict’s solution Benedict’s solution harmful irritant 60 labelled hazard details seeds none dried

3 9700/33/O/N/12 © UCLES 2012 [Turn over For Examiner’s Use Proceed as follows: (a) (i) You will need to select 10 seeds to use in the investigation. State which variable you will need to standardise (keep the same) when selecting the seeds. … [1] 1. Select your 10 seeds and put them into a large test-tube. Put 3 cm3 of S into the same test-tube and leave for 20 minutes. 2. Set up a water-bath and heat the water to a suitable temperature to test for reducing sugars using the Benedict’s test. (ii) State the temperature you will need to maintain in the water-bath to carry out the Benedict’s test. temperature … [1] (iii) You will need to make dilutions of the 0.4% solution of R, so that the concentration of R is reduced by 0.1% between each successive dilution. You will need 10 cm3 of each concentration. Prepare the space below to show the • concentration of R • volume of R • volume of distilled water, W. [3]

4 9700/33/O/N/12 © UCLES 2012 For Examiner’s Use (iv) You will need to test the different concentrations of R and 2 cm3 of the solution surrounding the seeds. State the volume of Benedict’s solution and the volume of each of the concentrations of R. volume of Benedict’s solution … volume of each concentration of R … [1] 3. Make the dilutions of R you decided in (a) (iii). 4. Using the volumes you decided in (a) (iv) carry out the Benedict’s test on your concentrations of R. Record the time taken for the first appearance of a colour change. If there is no colour change after 180 seconds record ‘more than 180’. 5. After the seeds have been soaked for 20 minutes, carry out the Benedict’s test on the solution surrounding the seeds. (v) Prepare the space below and record your results. [4]

5 9700/33/O/N/12 © UCLES 2012 [Turn over For Examiner’s Use (vi) Estimate the concentration of reducing sugars in the solution that surrounded the seeds. … [1] The student’s hypothesis was: “seeds soaked in a sucrose solution release the enzyme, E, which will hydrolyse the sucrose solution into reducing sugars”. (vii) State whether your results support this hypothesis. … Use your results to explain your answer. … … … [2] (b) Describe how you could modify this procedure to investigate the effect of temperature on the release of the enzyme from the seeds. … … … … … … … [3]

6 9700/33/O/N/12 © UCLES 2012 For Examiner’s Use Scientists investigated the effect of pH on the activity of the same enzyme found in leaves and in the bark of rubber trees. A standard volume and concentration of sucrose solution was mixed with the same volume of extract from either leaves or bark. The activity of the enzyme was measured by finding out the concentration of reducing sugars produced in an hour. The scientist’s results are shown in Table 1.1. Table 1.1 pH activity of enzyme concentration of reducing sugars / mmol hour–1 in leaves in bark 4.0 8 10 5.3 53 19 6.4 33 30 7.2 18 32 7.8 7 18

7 9700/33/O/N/12 © UCLES 2012 [Turn over For Examiner’s Use (c) (i) Plot a graph of the data shown in Table 1.1. [4] (ii) Use the data to describe the trend for the activity of the enzyme in the leaves. … … … [1] (iii) Explain the change in the activity of the enzyme in the leaves between pH 5.3 and pH 6.4. … … … [1] [Total: 22]

8 9700/33/O/N/12 © UCLES 2012 For Examiner’s Use 2 K1 is a slide of a stained transverse section through a plant root. This plant species is a native of Bangladesh, India and Pakistan. (a) (i) Draw a large plan diagram of the whole specimen on K1. On your diagram use a label line and label to show the cortex. [5]

9 9700/33/O/N/12 © UCLES 2012 [Turn over For Examiner’s Use (ii) Make a drawing of one group of five complete cells from the centre of the root. [4]

10 9700/33/O/N/12 © UCLES 2012 For Examiner’s Use Fig. 2.1 shows a diagram of a stage micrometer scale that is being used to calibrate an eyepiece graticule. One division, on either the stage micrometer scale or the eyepiece graticule, is the distance between two adjacent lines. The length of one division on this stage micrometer is 0.01 mm. Fig. 2.1 (b) (i) Using this stage micrometer, where one division is 0.01 mm, calculate the actual length of one eyepiece graticule unit using Fig. 2.1 by completing Fig. 2.2. Step 1 1 eyepiece graticule unit = divided by = … mm Step 2 Convert the answer to a measurement with the unit most suitable for use in light microscopy. multiplied by = … Fig. 2.2 [3]

11 9700/33/O/N/12 © UCLES 2012 [Turn over For Examiner’s Use Fig. 2.3 is a photomicrograph showing part of an organ from a plant of a different species. X Y Z Fig. 2.3 (ii) Fig. 2.3 shows a photomicrograph taken using the same microscope with the same lenses as Fig. 2.1. Use the calibration of the eyepiece graticule unit from (b)(i) and Fig. 2.3 to calculate the actual total length of the cells labelled X, Y and Z. You will lose marks if you do not show all the steps in your calculation and do not use the appropriate units. [2] Question 2 continues on page 12

12 9700/33/O/N/12 © UCLES 2012 For Examiner’s Use Fig. 2.4 is a photomicrograph of a transverse section of an organ from a different plant species. Fig. 2.4 (c) Prepare the space below so that it is suitable for you to record observable differences between the specimen on slide K1 and in Fig. 2.4. to include: • the vascular tissue • at least two other tissues. [4] [Total: 18] Copyright Acknowledgements: Question 1 Fig. 2.3 © DR KEITH WHEELER / 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.

CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the October/November 2012 series 9700 BIOLOGY 9700/33 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 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 2012 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 – October/November 2012 9700 33 © 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 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 – October/November 2012 9700 33 © Cambridge International Examinations 2012 1 (a) (i) [1] size or diameter or length or width or surface area (bod) or volume (bod) or colour or whole or same shape; MMO decision 1 Do not give mark if • any other variable than seeds Ignore • number • mass same type or species or age (ii) [1] MMO decision 1 (any one temperature) o or degree(s) C AND any whole number 80 to and including 100 ; (iii) [3] (0).3 AND (0).2 AND (0).1; mp1 Not required are • units • zero Do not give mark if • incorrect units e.g. mol dm–3 cm3 or ml(s) shown at least once for R AND (0.3)7.5 and (0.2) 5 and (0.1)2.5; mp2 Do not give mark if • on on units e.g. cm or cm2 MMO decisions 3 mp3 values of (R and W) for ALL tubes must add up to 10 (minimum two tubes); (iv) [1] MMO decision 1 cm3 or ml(s) once AND(volume of R) 2 AND (one volume of Benedict’s) any one whole number 2 to 10 that is 2 or 3 or 4 or 5 or 6 or 7 or 8 or 9 or 10;

Page 4 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2012 9700 33 © Cambridge International Examinations 2012 (v) [4] table with all cells drawn AND heading (top row or column to left of recorded data) percent(age) or % conc(entration) (of )R or reducing sugars ; mp1 Do not give mark if • % in cells of headed column • other units e.g. mol dm–3 • more than one row in one cell for multiple trials (heading for any column/row including mean) only time (with) s or sec(onds); PDO recording 2 mp2 Do not give mark if • units in cells of this column/row • min(utes) • headings for volumes or method information or in cells e.g. volumes and concentrations in same cell (mark first column/row of recorded results) records at least three results with whole numbers only that is any whole number less than 180 or records ‘ > or more than 180’; mp3 Must have • whole numbers between 3 and 180 or ’ > or more than 180’ Do not give mark if • ‘< or less than 180’ • e.g. 0:45 or 50:45 (mark first column/row of recorded time for recording correct pattern) recorded time for 0.4% is the shorter/lower value than lowest concentration; MMO collection 2 mp4 Must have • units for time recorded somewhere e.g. seconds with tenths or min:sec • minimum two recorded times including ‘more than 180’ Do not give mark if • no units for time anywhere

Page 5 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2012 9700 33 © Cambridge International Examinations 2012 (vi) [1] Do not give mark if no results for R or results all more than 180 or S. correct estimate with their time results AND uses only one of following values • one value of 0.1, 0.2 , 0.3 ,0.4 • between 0.1 and 0.2 • between 0.2 and 0.3 • between 0.3 and 0.4 • less than 0.1 • more than 0.4 • or their own concentrations; ACE interpretation 1 Do not give mark if • calculate or estimate between two of their concentration values • description or colour only in results (vii) [2] Do not give mp 1 if no result for seeds ecf for mp 2 (should be) yes if result is positive for reducing sugar; mp1 Can have • no if their result for S is negative for reducing sugar ACE conclusion 2 mp2 positive result described for seed sample either time or colour change AND so reducing sugars OR sucrose broken down; OR negative result no colour change or stayed blue AND so no reducing sugars OR sucrose not broken down;

Page 6 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2012 9700 33 © Cambridge International Examinations 2012 (b) [3] MUST mention seeds (in solution/sucrose) in correct context to access marks. Do not give mark if • change more than one variable (independent) 5 or more temperatures or described OR gives examples of 5 or more (units NOT required); mp1 Do not give mark if • change more than one variable • in context of Benedict’s test (how to keep temperature standardised in context of different temperatures only) use thermostat(ically-controlled) water-bath; mp2 Do not give mark if • ref. to temperature controlled room e.g. air conditioned or thermostat controlled room (standardisation of variables only in context of changing temperature) same number or example of number or mass or example of mass of seeds Ignore amount OR same volume or example of volume with units of sucrose OR concentration or example of concentration of sucrose solution OR (seeds NOT Benedict’s) same time in water-bath; ACE improvements 3 mp3 Do not give mark if • not idea that changing temperature (c) (i) [4] If draw a chart then max 1 for O O x-axis pH(p.h. PH Ph) AND y-axis conc(entration of) reducing sugar(s) (/) mmol(e) hr–1; S scale on x-axis 1.0 to 2 cm with 4 at origin labelled each 2cm except 8 need not be labelled AND y-axis 10 to 2 cm labelled each 2 cm; except origin and 60 need not be labelled PDO layout 4 P correct plotting of • five points Check first four points for bark and last point for leaves;

Page 7 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2012 9700 33 © Cambridge International Examinations 2012 L plots joined with ruled lines exactly point to point or curve through set of 5 points AND (quality) smooth line for bark less than 1 mm thick use grid AND for each line a label leaves and bark or uses key; Additional guidance: O S Must have label of value of origin if zero not at origin P plots (crosses or centre of dot) must be nearer than halfway line – up or down or either side OR if meant to be within two lines then must not be on line above or below or either side Can have ecf if origin not zero but use scales as given ecf if scale correct but not labelled every 2 cm ecf if reverse axes and scale is x-axis 20 to 2 cm and y-axis to 1 to 2 cm ecf if scale of pH 2 to 2 cm on x-axis or y-axis Do not give mark if • any blobs or dots alone • any cross or dot too large L Do not give mark if • any feathery or gap in line or dashed line • any irregular thickness • any extrapolation (ii) [1] (activity/concentration of reducing sugars) increases/rises to (pH) 5.3 AND decreases to (pH) 7.8; or rises by 2.5 ACE interpretation 1 (iii) [1] ACE conclusion 1 In correct context idea of (enzyme) denatured or denaturation; [Total: 22]

Page 8 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2012 9700 33 © Cambridge International Examinations 2012 2 (a) (i) [5] PDO layout 1 mp1 Do not give mark if drawn over the print of question or any shading anywhere or any ruled or compass lines or break in outline which does not have a line to seal open ends AND Do not give mark if smaller than 60 mm across widest point AND (clear, sharp, unbroken lines); Do not give mark if • less than 3 enclosed area the outermost enclosed area has • any part of line 1mm or thicker (use grid) • any feathery or dashed or gap in line • any ’tails’ or overlaps mp2 no cells drawn AND whole section drawn; mp3 (epidermal layer and endodermis) both layers drawn as paired lines with a gap between the layers; Do not give mark if • regular enclosed areas e.g. ovals or circles between innermost paired lines MMO collection 3 mp4 line separating pith from endodermis layer is continuous and wavy OR for epidermis three lines (two layers) for most of layer; labels cortex with label line touching; MMO decision 1 mp5 Do not give mark if • any label which is biologically incorrect e.g. animal or cell structure • any label written within drawn area (ii) [4] Do not give mark if drawn over the print of question or any shading anywhere or any ruled or compass lines AND Do not give mark if smaller than 40 mm across widest cell; PDO layout 1 mp1 AND (clear, sharp, unbroken lines) outer boundary lines of any cells Do not give mark if • less than 5 cell outlines any of outermost lines have • any line 1 mm or thicker (use grid) • any feathery or dashed or gap in line • any ’tails’ or overlaps

Page 9 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2012 9700 33 © Cambridge International Examinations 2012 mp2 only five complete cells drawn AND each cell must touch another cell at least at one point to form one group ; Do not give mark if • any ruled or compass lines mp3 at least one intercellular space at least 3 mm across at widest point OR at least three cells with rounded shape with no straight sharp corners in correct context; MMO collection 2 Can have • drawn vacuoles/nucleus Do not give mark if or more cells raw EM organelles e.g. mitochondria raw incorrect cell structure e.g. sieve plates, ll cells drawn separate PDO recording 1 mp4 all cells with cell walls drawn as double lines all the way round (inner line can touch but not cross outer line-overlap) AND (between any two adjacent cells middle lamella drawn) so three lines less than 4 mm across at widest point; (b) (i) [3] MMO decision 1 mp1 Step 1 Ignore first box second box must be whole number 3 to 92 AND EITHER answer must be (0).00X(……) where X is a number 1 to 9 OR expressed in standard form e.g. x 10–3; Do not give mark if fraction (either box in Step 2) 1000 or 103 AND any answer from step 1 in other box; PDO display 1 mp2 ecf any answer to step 1 µm or mm AND answer from step 1 ×1000; ACE interpretation 1 mp3

Page 10 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2012 9700 33 © Cambridge International Examinations 2012 (ii) [2] measures correctly in eyepiece graticule units; measures total length 57 or 58 or 59 or 60 or 61 or 62 (epg units) MMO collection 1 mp1 Do not give mark if • m or mm or cm or m or stage micrometer units • hoice of measuring e.g. mm and epgu (shows multiplication by answer from (b)(i)) any one value (multiplied by) X by answer from (b)(i) step 2; PDO display 1 mp2 Can have • alternative signs or * or value (b)(i) Do not give mark if • division shown (c) [4] mp1 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 K1/slide and Fig 2.4 AND third column/row contains list of tissues; PDO recording 1 (features) K1/slide. Fig 2.4 (K1 or Fig 2.4 either way round and other column to left, right or in middle) ,

Page 11 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2012 9700 33 © Cambridge International Examinations 2012 max 1 ACE interpretations 3 max 2 feature K1 Fig. 2.4 (vascular bundles or tissue shape) absent or not visible/seen or cross shape or not in ring or irregular present or visible/distinct or ring or regular; (position) inner or inside or near endodermis/pericycle outer or towards outside or near epidermis; (quantity of vascular tissue bundles/xylem/ phloem) Idea of less or small(er) or few(er), narrow(er) Idea of more or large(r) or wide(r); mp2 cambium no(one) or absent or has not yes or present or has; mp3 pith or middle or centre any difference for central area either way round e.g. present vs absent or small(er) vs large(r) or not hollow vs hollow; mp4 endodermis or pericycle or stele yes or present or has no(one) or absent or has not; mp5 cortex large(r) or wider or more small(er) or narrower; mp6 epidermis thickened layer/ collenchyma/ sclerenchyma thin(ner) or narrow(er) or one cell no(one) or absent or has not thick(er) or wide(r) or large(r) or more than one cell has or present or yes; mp7 hairs (root) or (trichomes) yes or present or has or many hairs or rough no(one) or absent or has not or smooth; [Total: 18]