Cambridge A Level Biology 9700 — 2010 Oct/Nov Paper 3 · Variant 1

This document consists of 9 printed pages and 3 blank page. DC (LEO/SW) 23620/4 © UCLES 2010 [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. * 5 9 4 4 0 3 0 5 7 2 * BIOLOGY 9700/31 Advanced Practical Skills 1 October/November 2010 2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions. For Examiner’s Use 1 2 Total

2 9700/31/O/N/10 © UCLES 2010 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 each question and then 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 Plant cells contain an enzyme, catalase, which catalyses the breakdown of hydrogen peroxide into oxygen and water. When a piece of potato is dropped into hydrogen peroxide it will sink and then the production of oxygen causes the potato to rise. The more oxygen produced the less time it takes for the potato to rise. You are required to investigate the independent variable, the surface area to volume ratio of pieces of potato, on the breakdown of hydrogen peroxide. The relationship of pieces of potato of different sizes to their surface area to volume ratio is shown in Fig. 1.1. (length Z) (divide length Z by half) (divide length by half again) increasing surface area to volume ratio (divide length by half) Fig. 1.1 You are provided with labelled contents hazard volume / cm3 H hydrogen peroxide irritant oxidising substance 200 cm3 labelled contents details quantity P potato pieces same cross- sectional area 4

3 9700/31/O/N/10 © UCLES 2010 [Turn over For Examiner’s Use Proceed as follows: 1. Prepare the pieces of potato as shown in Fig. 1.2. piece A piece B piece C piece D test-tube A test-tube B test-tube C test-tube D halve halve halve not needed Fig. 1.2 2. Label four test-tubes A, B, C and D. 3. Put 25 cm3 of H into test-tube A. 4. Put piece A onto a paper towel and gently remove any excess water. 5. Put piece A into test-tube A. Immediately start timing. 6. Record the time taken for piece A to rise to the surface. Do not touch the test-tube after you have started timing. If the piece of potato does not rise after 2 minutes stop timing and record ‘more than 2 minutes’. Proceed to the next test. 7. Repeat steps 3 to 6 for one piece of B, one piece of C and one piece of D.

4 9700/31/O/N/10 © UCLES 2010 For Examiner’s Use (a) (i) Prepare the space below and record your results. [6] (ii) Identify two significant sources of error in your investigation. … … … … … … … [2]

5 9700/31/O/N/10 © UCLES 2010 [Turn over For Examiner’s Use (iii) Suggest how you would make three improvements to this investigation. … … … … … … … …[3] A student investigated the effect of pH on the enzyme in potato tissue. The breakdown of hydrogen peroxide was measured by the release of oxygen. Fig. 1.3 shows the apparatus used. The student recorded the time for the oxygen released to displace 10 cm3 of water at five different pH values. graduated test-tube gas displaces water water delivery tube air tight bung potato tissue hydrogen peroxide Fig. 1.3

6 9700/31/O/N/10 © UCLES 2010 For Examiner’s Use The student’s results are shown in Table 1.1. Table 1.1 pH time to displace 10 cm3 of water / s trial 1 trial 2 trial 3 trial 4 trial 5 mean 5 17 14 16 14 15 15 6 8 5 15 6 5 6 7 2 10 3 3 4 3 8 8 6 6 17 7 9 20 16 17 16 16 17 (b) (i) Three 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] (iv) Explain the relationship between pH and the enzyme catalase shown in the data. … … … … … … [3] [Total: 20]

7 9700/31/O/N/10 © UCLES 2010 [Turn over For Examiner’s Use 2 J1 is a slide of a stained transverse section showing part of a lung of a mammal. (a) Make a large, high-power drawing to show details of five of the structures specialised for gas exchange (alveoli). The walls of one alveolus must be touching the walls of at least two other alveoli. Label where gas exchange takes place. [5]

8 9700/31/O/N/10 © UCLES 2010 For Examiner’s Use Fig. 2.1 is a photomicrograph of a transverse section through a lung from a mammal. The outer layer of the bronchiole and the wall of the blood vessel are labelled. outer layer of bronchiole wall of blood vessel Fig. 2.1 (b) (i) Draw a large plan diagram of the bronchiole shown in Fig. 2.1. Label the lumen. [5]

9 9700/31/O/N/10 © UCLES 2010 For Examiner’s Use (ii) Calculate the ratio of the mean thickness of the outer layer of the bronchiole compared to the mean thickness of the wall of the blood vessel shown in Fig. 2.1. Show clearly on Fig. 2.1 where you measured the thicknesses. You may lose marks if you do not show your working or if you do not use the appropriate units. [4] (iii) Prepare the space below so that it is suitable for you to compare the observable features of the bronchiole and blood vessel in the photomicrograph Fig. 2.1. [6] [Total: 20]

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UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the October/November 2010 question paper for the guidance of teachers 9700 BIOLOGY 9700/31 Paper 31 (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. • CIE will not enter into discussions or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the October/November 2010 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 A LEVEL – October/November 2010 9700 31 © UCLES 2010 Question Expected Answers Marks Additional Guidance 1 (a) (i) Prepare the space below and record your results. [6] 1. table with all cells drawn AND heading (top or left) surface area/cm2 or length/mm; [1] Reject • if units in body of table • t or T • additional columns details of method PDO recording 2 2. (heading) time with units; [1] 3. collects data as times for all four pieces of potato; [1] MMO collection 2 4. (A) recorded time different from other pieces; [1] Reject units must be clear so 1.2 or 1:2 must have min and s or secs 5. records all times correctly as whole seconds or minutes with seconds; UNITS must be clear somewhere [1] MMO decisions 2 6. replicate recorded; [1]

Page 3 Mark Scheme: Teachers’ version Syllabus Paper GCE A LEVEL – October/November 2010 9700 31 © UCLES 2010 (ii) Identify two significant sources of error in your investigation. [2] Reject temperature Cause of error Error 1. 2. 3. (dependent) timing /dropping/distance long pieces of potato ora shorter pieces (pieces of) potato not accurate/delayed/different; different height to top there is shorter distance to surface longer distance to surface; stick to sides/bottom of tube don’t sink to bottom; [max 1] 4. 5. 6. 7. (standardised variables) potato or position in potato or age or storage water left on potato (test)-tubes hydrogen peroxide not same different/variety old; not same/different; not same size/height; concentration changes/decreases evaporates/degenerates/breaksdown; [max 1] ACE interpretation MAX 2 8. (independent variable) lengths/size/surface areas/volumes not same different vary; [max 1] max 2 overall

Page 4 Mark Scheme: Teachers’ version Syllabus Paper GCE A LEVEL – October/November 2010 9700 31 © UCLES 2010 (iii) Suggest how you would make three improvements to this investigation. [3] 1. same potato or position in same age or storage or fresh use micrometer/cork borer/vernier callipers; [1] 2. use same volume/mass/volume ratio more surface areas/sizes; [1] 3. use a wider container or smaller potato use deeper container use tubes of same size clamp tubes in vertical position; [1] 4. method to dry the potato lid to cover hydrogen peroxide; [1] 5. (collect oxygen) use a gas syringe or water displacement/oxygen sensor; [1] ACE improvements Max 3 6. replicate/repeat; [1] max 3 (b) (i) Three of the values in table 1.1 are anomalous. Draw a circle around each of these values. [1] MMO decision 1 all three figures circled; [1]

Page 5 Mark Scheme: Teachers’ version Syllabus Paper GCE A LEVEL – October/November 2010 9700 31 © UCLES 2010 (ii) Complete table 1.1. by calculating the missing value. [1] ACE interpretation 1 7; Allow 9. [1] (iii) Plot a graph of the data shown in Table 1.1. [4] x-axis pH Reject t O AND y-axis time/s or seconds; [1] Must have units Reject awkward scale S scale as each pH to 2 cm AND 5 seconds to 2 cm; [1] Must use more than half grid in x and y. Reject plotting if scale is awkward if only dots/blobs or blobs in circles Allow cross in circle P correct plotting using crosses/dots in circle only; intersection of cross must be clear to show plot. NO cross must touch the line for the next square. [1] PDO layout 4 L straight line through points; error carried forward if scale or plotting incorrect quality – no thicker than on grid, not feathery for the complete line. joining plots – • ruled lines plot to plot • curve through all plots extrapolation • not beyond x- or y-axis [1] Reject if any extrapolation

Page 6 Mark Scheme: Teachers’ version Syllabus Paper GCE A LEVEL – October/November 2010 9700 31 © UCLES 2010 (iv) Explain the relationship between pH and the enzyme catalase shown in the data. [3] (in correct context of pH and activity (below 7/acid or above 7/ alkali) effect on) structure of protein/enzyme/active site or bonds changed/altered/destroyed/no longer complementary broken; [1] (below 7 or above 7) do not accept collision(s)/react fewer ECSs (enzyme substrate complexes) or less/no substrate can bind/combine/attach fit into enzyme/active site; [1] ACE conclusion 3 (below 7/above 7) (enzymes) denatured; [1] [Total: 20]

Page 7 Mark Scheme: Teachers’ version Syllabus Paper GCE A LEVEL – October/November 2010 9700 31 © UCLES 2010 2 Make a large, high-power drawing to show the details of five of the structures specialised for gas exchange (alveoli). The walls of one alveolus must be touching the walls of at least two other alveoli. Label where gas exchange takes place. [5] Reject if drawn over the print of question Reject • thick lines • feathery lines • 2 ‘tails’ or overlaps or gaps PDO layout 1 1. clear, sharp, unbroken continuous lines AND no shading AND use most of the space provided; [1] 2. five structures drawn AND at least 3 structures touching; [1] MMO collection 2 3. at least three alveoli different shapes/sizes AND thickness of one wall irregular; [1] 4. (walls with) at least 2 cells drawn AND at least one nucleus drawn; [1] MMO decisions 2 5. Reject • if any label is biologically incorrect e.g. cell wall. • label within drawn area • into centre of alveolus correct label with label line to wall of alveolus; [1]

Page 8 Mark Scheme: Teachers’ version Syllabus Paper GCE A LEVEL – October/November 2010 9700 31 © UCLES 2010 (b) (i) Draw a large plan diagram of the bronchiole shown in Fig. 2.1. Label the lumen. [5] Reject if drawn over the print of question Reject • thick lines – than grid • feathery lines • 3 ’tails’ or overlaps or gaps PDO layout 1 1. clear, sharp, unbroken lines AND no shading AND use most of space provided; [1] 2. no cells drawn AND width of base of fold greater than width of tip of fold; [1] MMO collection 2 3. 13 to 15 folds in lumen; [1] 4. shows indentation; [1] MMO decisions 2 5. Reject • if any label is biologically incorrect e.g. cell wall. • label within drawn area correct label with label line to lumen; [1]

Page 9 Mark Scheme: Teachers’ version Syllabus Paper GCE A LEVEL – October/November 2010 9700 31 © UCLES 2010 (ii) Calculate the ratio of the mean thickness of the outer layer of the bronchiole compared to the mean thickness of the wall of the blood vessel shown in Fig. 2.1. [4] Reject If lines not shown on both bronchiole and blood vessel shows one measurement on each of bronchiole and blood vessel; [1] Reject If no units If not both same units If metres or converted to metres or micrometres or standard form MMO collection 2 (one bronchiole measured) to nearest 0.5 mm AND mm; [1] shows mean adds measurements AND shows division by number of measurements; [1] MMO decisions 2 Reject • If given as decimal :1 • If smaller to larger number • If include units answer is larger whole number to smaller whole number or leaves as fraction; [1] Either must be to lowest common denominator

Page 10 Mark Scheme: Teachers’ version Syllabus Paper GCE A LEVEL – October/November 2010 9700 31 © UCLES 2010 (iii) Prepare the space below so that it is suitable for you to compare the observable features of the bronchiole and blood vessel in the photomicrograph Fig. 2.1. [6] organise as a table/ Venn diagram/ ruled boxes AND headed bronchiole and blood vessel AND differences opposite each other; [1] bronchiole blood vessel PDO recording 2 heading for similarities/similarity/compare (with contrast)/same; [1] MMO decision 1 attempted one similarity ; [1] Do not accept • tick and cross without a key • diagrams • 3-D description • incorrect biological terms e.g. endodermis bronchiole blood vessel similarity S max 1 lumen smooth muscle epithelium feature D1 lumen shape irregular/lobed/folded smooth/oval/not folded; D2 lumen size small(er) larg(er); D3 folds many/present none/absent; D4 no. of layers more/2 less/1; D5 outer/muscle layer/wall thick(er)/wid(er) thinn(er)/narrow(er); ACE interpretation 3 D6 overall shape circular/round oval/squashed circle; [max 3] If no organisation if in same sentence or following sentences. [Total: 20]