Cambridge A Level Biology 9700 — 2012 Oct/Nov Paper 3 · Variant 4

This document consists of 11 printed pages and 1 blank page. DC (SJF/SW) 47058/5 © UCLES 2012 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Subsidiary Level and Advanced Level 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. * 6 5 3 9 8 8 2 7 3 8 * BIOLOGY 9700/34 Advanced Practical Skills 2 October/November 2012 2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions. For Examiner’s Use 1 2 Total

2 9700/34/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 The enzyme, E, hydrolyses (breaks down) the protein in milk. After the enzyme and milk are mixed, the protein is hydrolysed and the mixture will change from cloudy to clear. The end-point is reached when the mixture is clear. You are required to: • make different concentrations of the enzyme solution, E • investigate the effect of different concentrations of E, by finding the time taken to reach the end-point. You are provided with: labelled contents hazard volume / cm3 E 1.0 % enzyme solution irritant 20 W distilled water none 50 S milk none 50

3 [Turn over 9700/34/O/N/12 © UCLES 2012 For Examiner’s Use (a) (i) You will need to make dilutions of the 1.0 % solution of E, so that the concentration of E is reduced by 0.2 % between each successive dilution. You will need 5 cm3 of each concentration. Prepare the space below to show the: • concentrations of E • volumes of E • volumes of distilled water, W. [3] (ii) Decide on a control you will use. Describe how you will set up a control using the apparatus provided. … …[1]

4 9700/34/O/N/12 © UCLES 2012 For Examiner’s Use Proceed as follows: 1. Prepare the concentrations of E and the control as decided in (a) (i) and (ii). 2. Set up a water-bath and adjust the temperature to between 35 °C and 40 °C. Maintain the temperature of the water-bath. 3. Put 1 cm3 of the lowest concentration of E into a test-tube and put the test-tube into the water-bath. 4. Repeat step 3 for all the concentrations of E and the control prepared in step 1. 5. Leave the test-tubes for 2 minutes. 6. Remove the test-tubes containing the three highest concentrations of E. 7. Put 3 cm3 of S into each test-tube and mix well. 8. Record the time taken for each test-tube to reach the end-point. If the end-point is not reached by 240 seconds, record ‘more than 240’. 9. Repeat steps 6 to 8 with the remaining test-tubes in the water-bath. (iii) Prepare the space below and record your results. [5]

5 [Turn over 9700/34/O/N/12 © UCLES 2012 For Examiner’s Use (iv) Identify a significant source of error in your investigation. … …[1] (v) Suggest how you would modify this investigation to find the effect of pH on the rate of hydrolysis of the protein in milk. … … … … … … …[3]

6 9700/34/O/N/12 © UCLES 2012 For Examiner’s Use Gelatine is made up of protein which is hydrolysed by the enzyme protease. A student investigated the effect of pH 4.0 and pH 6.4 on the activity of protease. One piece of gelatine, with an area of 200 mm2, was placed in a Petri dish and covered with a solution of protease maintained at pH 4.0. The area of gelatine was recorded at intervals for 90 minutes. The investigation was repeated with another piece of gelatine and a solution of protease maintained at pH 6.4. The results of the student’s investigation are shown in Table 1.1. Table 1.1 time / minutes area of gelatine / mm2 pH 4.0 pH 6.4 0 200 200 30 165 190 45 105 185 60 50 145 90 0 100 (b) (i) Plot a graph of the data shown in Table 1.1. [4]

7 [Turn over 9700/34/O/N/12 © UCLES 2012 For Examiner’s Use (ii) Describe the trends shown by the data. … … … … …[2] (iii) Explain the difference in the effect of pH 4.0 and pH 6.4 on the activity of protease. … … … … … … …[3] [Total: 22]

8 9700/34/O/N/12 © UCLES 2012 For Examiner’s Use 2 M1 is a slide of a transverse section of a leaf. The plant is native to the Himalayas. (a) (i) Draw a large plan diagram of the whole section of the leaf on M1. On your diagram, use a label line and label to show the xylem. [5]

9 [Turn over 9700/34/O/N/12 © UCLES 2012 For Examiner’s Use (ii) Choose one group of three touching palisade cells which have different shapes and make a large drawing of the group. On your drawing, use a label line and label to show a chloroplast. [5]

10 9700/34/O/N/12 © UCLES 2012 For Examiner’s Use Fig. 2.1 is a photomicrograph of a transverse section of a different type of leaf from the same plant. Y Z Fig. 2.1 (b) Use the lines Y and Z shown on Fig. 2.1, 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. [3]

11 [Turn over 9700/34/O/N/12 © UCLES 2012 For Examiner’s Use (c) (i) Fig. 2.2 shows the outline of a plan diagram of the specimen shown in Fig. 2.1. Within this outline, complete the plan diagram of the specimen. [2] (ii) You are required to annotate Fig. 2.2 to describe three observable differences between Fig. 2.1 and M1. Draw label lines to three different features and use only the labels, P, Q and R. Next to each letter, describe how each feature on Fig. 2.1 differs from M1. [3] Fig. 2.2 [Total: 18]

12 9700/34/O/N/12 © UCLES 2012 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

CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the October/November 2012 series 9700 BIOLOGY 9700/34 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 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 34 © 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 34 © Cambridge International Examinations 2012 1 (a) (i) [3] mp 1 (0).8 AND (0).6 AND (0).4 AND (0).2; mp 2 (for correct concentration) Ignore 1 % cm3 or mls shown at least once AND at least three correct volumes of E with 0.2 % difference between concentrations; No ecf if incorrect concentrations. MMO decisions 3 mp 3 values for at least three E and W add up to 5; (ii) [max 1] Idea of • replace enzyme with water • W/water either as beaker or added to test-tube • W/water and S/milk; MMO decisions max 1 Do not give mark for more than one idea (iii) [5] table with all cells drawn AND heading (top row or column to left of recorded data) percent(age) or % conc(entration) of E or enzyme; mp 1 Can have • no outer boundary Ignore • test-tube/additional columns • notes outside area Do not give mark if • % in cells of headed column • other units e.g. mol dm–3 • no percentage or % • two rows in one cell for multiple trials (heading for any column/row including mean) only time (with) s or sec(onds); PDO recording 2 mp 2 • if have columns/rows for test-tubes or observations e.g. colour • any notes outside area Ignore • heading for test-tubes • t or T Do not give mark if • units in cells of this column/row • e.g. 45’ (units) • min(utes) • headings for volumes or method information or in cells • e.g. volumes and concentrations in same cells MMO colle mp 3 (mark first column/row of recorded time) records whole numbers only for ANY four (concentrations including control/0) that is any whole number between 3 and 240 or records > or more than 240;

Page 4 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2012 9700 34 © Cambridge International Examinations 2012 Do not give mark if • < or less than 240 • e.g. 0:45 or 50:45 (mark first column/row of recorded time for recording correct pattern) recorded time for 1% is shorter time/lower value than lowest concentration; Ignore control/0 mp 4 Must have • units for time recorded somewhere e.g. seconds with tenths or min:sec MMO decision 1 mp 5 records control or 0 ‘> or more than 240’ (seconds/s) (iv) [1] cause of error WITH idea of error ACE interpretation 1 end-point or when goes clear OR time in water-bath OR temp judging or observing seeing or figuring out or varies or subjective different or varies or not the same or drops or changes; (v) [3] (independent) at least 3 pHs or at least 3 examples or low pH and high pH and neutral/pH7; OR Idea of keep enzyme conc same/use E AND range of/different pHs; mp 1 Do not give mark if • change more than one variable mp 2 (method to change pH) (for all pHs) use buffers; ACE improvements 3 mp 3 (dependent) rate from data divide 1 by time or divide 1000 by time or plot graph of pH against time;

Page 5 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2012 9700 34 © Cambridge International Examinations 2012 (b) (i) [4] O x-axis time (/) min(utes) AND y-axis area of gelatine(/) mm2; S scale on x-axis 20 to 2 cm labelled each 2 cm except origin and 100 AND y-axis 50 to 2 cm labelled each 2 cm except origin and 200; P correct plotting of • points Ignore plots at 200 • as small cross (use square on grid) or dot (in circle use grid) or cross in circle to within half a square; PDO layout 4 L plots joined with ruled lines exactly point to point AND (quality) smooth line less than 1 mm thick AND (for each line) a label with correct pH or key; Additional guidance: O Ignore abbreviations e.g. t/T or A/a S ecf if no labels for O or if reverse O then scale must use more than half grid for both x and y axes Must have • label of value of origin if zero not at origin Do not give mark if • awkward scale e.g. to each 2 cm Time /mins Area/mm2 15 40 18 80 25 30 40 P Can have ecf if x-axis not 0 if scale 20 to 2 cm even Do not give mark if • awkward scale • any blobs or dots alone • any cross too large L Can have • ecf from incorrect P Do not give mark if • any feathery line • any irregular thickness • any extrapolation either end

Page 6 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2012 9700 34 © Cambridge International Examinations 2012 (ii) Ignore ref to enzyme activity [2] Do not give mark if wrong context mp 1 Idea of as/with increasing/longer time area/gelatine /protein decreases more in pH4 than pH6.4 OR pH 4.0 more area/gelatine /protein hydrolysed/broken down in same time/faster OR area/gelatine /protein decreases quicker/more ora pH 6.4 less area/gelatine /protein hydrolysed/broken down in same time/slower/it OR area/gelatine /protein decreases slower/less; ACE interpretation 2 mp 2 (pH 4) goes to zero or all area/gelatine/protein hydrolysed/broken down or no area/gelatine/protein left OR (pH 6.4) area/gelatine/protein goes to half or 100 (mm2); OR Ref to other quoted figures so pH 4 with time and area AND pH 6.4 with ref to same time and area Ignore units (iii) [3] mp 1 (pH 4) nearer/almost or at optimum; mp 2 (pH 4/acidic/lower pH) enzyme/it is more active or the activity higher/faster or works best/digests more or more (ESCs) or more (substrate binds to enzyme/active sites) ora (pH 6.4 or alkali or higher pH) enzyme/ it is less active or the activity lower/slower or few (ESCs) or few (er) (substrate molecules bind to active sites) OR pH 4.0 is fast and pH 6 is slow; ACE conclusions 3 mp 3 correct ref. to for either pH enzyme substrate complexes or ESCs idea that substrate (molecules) bind go into active sites; Ignore collision(s)/effective collisions OR (pH 6.4) idea of enzyme denatured Idea of enzyme shape/structure/molecule altered or bonds disturbed [Total: 22]

Page 7 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2012 9700 34 © Cambridge International Examinations 2012 2 (a) (i) Ignore additional lines/circle round drawing of specimen [5] PDO layout 1 mp 1 quality of plan diagram; Do not give mark if • drawn over the print of question or any shading or any ruled lines • smaller than 50 mm across widest point of midrib – 5 squares on grid AND (clear, sharp, unbroken lines) • stomata/breaks open-ended • less than four enclosed areas any of the line of enclosed area under outermost enclosed outline has • any line 1 mm or thicker • any feathery or broken/dashed line or gaps • any ’tails’ or overlaps mp 2 no cells drawn AND complete leaf drawn; mp 3 at least five lines counted across leaf as line through middle of central region across (upper to lower epidermis); Ignore lines for vascular bundle MMO collection 3 mp 4 central region drawn with at least 3 enclosed areas in shape which is not a symmetrical oval top to bottom; labels xylem with line touching line around enclosed area or ending inside enclosed area in vascular bundle with at least two regions; MMO decision 1 mp 5 Ignore • any labels identifying tissues associated with plant Do not give mark if • any label which is biologically incorrect e.g. from animal • any label written within drawn area

Page 8 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2012 9700 34 © Cambridge International Examinations 2012 (ii) [5] PDO layout 1 mp 1 quality of drawing; Do not give mark if • drawn over the print of question or any shading or any ruled lines • smaller than 50 mm across widest cell AND (clear, sharp, unbroken lines) • less than 3 cell outlines any of outermost lines have (even if more than 3) • any line 1mm or thicker • any feathery or broken/dashed line or gaps • any ’tails’ or overlaps mp 2 only three complete cells drawn AND cells must touch another cell at least at one point to form one group; mp 3 at least one cell has at least four internal enclosed areas drawn; MMO collection 2 Do not give mark if • additional organelles e.g. mitochondria, etc • lines/dots drawn within chloroplast enclosed areas PDO recording 1 mp 4 cell walls drawn as double lines with middle lamella between two complete adjacent cells; at least two cells must contain at least five small randomly scattered enclosed areas and labels only one chloroplast in any one cell with label line touching outermost line of chloroplast or into middle of chloroplast; MMO decision 1 mp 5 Do not give mark if • small enclosed areas form single line around most of boundary of any two cell • any label other than chloroplast • any label within drawn lines

Page 9 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2012 9700 34 © Cambridge International Examinations 2012 (b) [3] MMO collection 1 mp 1 shows unit as mm on measurements for both (Y and Z) or larger and smaller values AND measures Y and Z lines correctly; Y allow one of: 120(.00) or 120.5(0) or 121(.00) or 121.5(0) or 122(.00) or 122.5(0) or 123.(00) Z allow one of: 75(.00) or 75.5(0) or 76(.00) or 76.5(0) or 77(.00) shows any value of Y divided by any value of Z OR shows multiplication of both Y and Z by same number to give whole numbers; mp 2 Do not give mark if • use different units for Y and Z • conversions to metres • conversions to µm as larger whole number : or to smaller whole number to lowest common denominator; PDO display 2 mp 3 Do not give mark if • no measurements or working • if units

Page 10 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2012 9700 34 © Cambridge International Examinations 2012 (c) (i) [2] (ii) [3] PDO recording 1 mp 1 (plan no cells) has at least one line following outline in at least one ‘wing’ AND central region contains at least three enclosed areas; MMO decision 1 mp 2 label lines and labels P, Q and R to three different features;

Page 11 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2012 9700 34 © Cambridge International Examinations 2012 ACE interpretation max 3 Award marks from only one column for each mark point. [max 3] Labelled region Fig 2.1 M1 mp 1 [2 marks] overall shape number of tissues/regions has ‘wings’ or divided into two or irregular/ symmetrical/oval/AW; more; oval or more round or straight or regular/asymmetrical/triangular; few; mp 2 [1 mark] Do not give mark if membrane thin(ner) layer or one cell thick or less/fewer cells or loosely packed cells or no thickened layer/cells or cells not as round/AW or rough or hair(s) or trichomes; thick(er) layer or more cells or more compact/closely-packed or cells rounder shape or smooth or no hairs/trichomes; mp 3 + 4 [max 2 marks] Ignore general shape of cells Idea of thick layer; darker stained /contain more staining; OR longer /thinner/oval or more/closely packed cells OR (palisade cells/layer) missing/absent at 5; Idea of thin layer; less stained; round(er) cells or few/loosely packed cells; mp 5 [1 mark] Do not give mark if vacuole/s more (air/intercellular) spaces or fewer cells more (spongy mesophyll) cells or larger area; less spaces or more cells few (spongy mesophyll) cells/small area; mp 6 + 7 [max 2 marks] Do not give mark if vessel two/divided/four/more areas more xylem/cells (vessels) more xylem to phloem ; OR xylem inside phloem/xylem in centre phloem outside; OR cross-shape /butterfly shape; OR labels cells around it as present; one/single/ less; phloem one side only or not around xylem; round or oval shape; no /few cells ; mp 7 + 8 [max 2 marks] cross shape/butterfly shape; bundle sheath present or absent or layer or cells present/absent; round or oval or absent; bundle sheath present/absent or layer/cells present/absent; mp 9 [1 mark] indent or gap or curled or sunken stoma(ta) or present; straight or no indent or no gap or not curled or absent; mp 10 [1 mark] fold or ridge or lobe or present; no fold or no wings or absent; [Total: 18]