Cambridge A Level Biology 9700 — 2010 Oct/Nov Paper 5 · Variant 2

This document consists of 7 printed pages and 1 blank page. DC (AC/CGW) 32692/1 © UCLES 2010 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education 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 pen. You may use a pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. 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. * 0 9 4 8 4 0 6 2 0 0 * BIOLOGY 9700/52 Paper 5 Planning, Analysis and Evaluation October/November 2010 1 hour 15 minutes Candidates answer on the Question Paper. No Additional Materials are required. For Examiner’s Use 1 2 Total

2 9700/52/O/N/10 For Examiner’s Use © UCLES 2010 1 A student noticed that the leaves on a plant growing close to a wall had two sorts of leaves. The leaves next to the wall were in the shade and looked different from the leaves on the side away from the wall that were exposed to the sun. The length of the internodes on the stem also looked different. The student decided to investigate the differences by measuring some features of 30 leaves and internodes from each side of the plant. Fig. 1.1 shows the leaf shape Fig. 1.2 shows an internode internode Fig. 1.1 Fig. 1.2 Table 1.1 shows the student’s results. Table 1.1 shaded leaves exposed leaves mean internode length / mm 23 ± 4 15 ± 3 mean surface area of leaves / mm2 2750 ± 12 1800 ±15 mean mass of leaves / mg 50 ± 8 60 ± 10 mean leaf surface area : leaf mass ratio 55 ± 9 30 ± 6 rate of water loss / mg mm–2 h–1 50 ± 11 65 ± 12 (a) (i) State the independent variable being investigated. …[1]

3 9700/52/O/N/10 [Turn over For Examiner’s Use © UCLES 2010 (ii) Outline the procedures the student could use to obtain these results. … … … … … … … … … … … … … … … … … … … …[8]

4 9700/52/O/N/10 For Examiner’s Use © UCLES 2010 The student carried out t-tests for leaf surface area : leaf mass ratio and for internode length. The leaf surface area : leaf mass ratio gave the value t = 12.6 The formula for t-test is t = ⏐x1 – x2⏐  s1 2 n1 + s2 2 n2 (b) (i) Complete the calculation to find the value of t for the internode length. Show your working. t = – 42 30 + = 0.9 t = …[3] Table 1.2 shows the critical values at p < 0.05 for the t-test. Table 1.2 degrees of freedom 18 20 21 22 23 24 25 26 27 28 29 30 40 60  critical value 2.10 2.09 2.08 2.07 2.06 2.06 2.06 2.06 2.05 2.05 2.04 2.04 2.02 2.00 1.96 The number of degrees of freedom is 58. (ii) State how the number of degrees of freedom was calculated. … …[1] (iii) State and explain the meaning of these results. … … … …[2]

5 9700/52/O/N/10 [Turn over For Examiner’s Use © UCLES 2010 In a further investigation, the student cut sections of the leaves from the shaded side and from the exposed side of the plant. The following procedures were carried out: Transverse sections were made of each leaf and high-power drawings were made from these sections. The relative thickness of both the leaf and the cuticle were measured using an eyepiece graticule and the difference in the distribution of chloroplasts was observed. Fig. 1.3 shows drawings made from transverse sections of these leaves. leaf from shaded side of plant leaf from exposed side of plant Fig. 1.3 (c) (i) Explain how the actual thickness of the leaf could be measured. … … …[2] (ii) With reference to the student’s results, state what conclusions can be drawn about the differences in adaptations shown by shaded leaves and exposed leaves of the plant. … … … … … …[3] [Total: 20]

6 9700/52/O/N/10 For Examiner’s Use © UCLES 2010 2 Fig. 2.1 shows a freshwater crustacean. This animal has a two-chambered heart that can be seen through the exoskeleton. heart Fig. 2.1 An investigation into the effect of temperature on heart rate was carried out using this organism to test the hypothesis: Heart rate doubles for every 10 °C increase in temperature. Five crustaceans, each measuring 5 mm in length, were placed in water of different temperatures and left for five minutes. The heart beat was counted for 20 seconds using a tally counter and stop watch. Table 2.1 shows the results of the investigation. Table 2.1 heart rate / beats per minute temperature / °C 5 10 15 20 25 30 35 specimen 1 30 45 63 96 132 165 84 specimen 2 33 51 69 105 150 171 87 specimen 3 33 48 66 93 130 174 69 specimen 4 45 57 87 111 168 183 78 specimen 5 24 36 51 78 120 135 75 (a) (i) Identify two variables that have been controlled during this investigation. 1. … 2. …[2] (ii) Suggest one other variable that should be controlled. … …[1]

7 9700/52/O/N/10 For Examiner’s Use © UCLES 2010 (iii) Suggest one feature of the procedure which may cause the results to be inaccurate. … …[1] (iv) Suggest a reason why the student used five specimens at each temperature. … …[1] The student calculated the percentage change in heart rate for each specimen. Table 2.2 shows these results. Table 2.2 percentage change in heart rate temperature / °C 5 –10 10 –15 15 –20 20 –25 25 –30 30 –35 specimen 1 50 40 52 38 25 -49 specimen 2 55 35 52 42 14 -49 specimen 3 45 38 40 39 34 -60 specimen 4 27 52 28 51 9 -57 specimen 5 50 41 53 54 12 -44 (b) (i) Suggest why the student converted the raw data to percentage change. … …[1] (ii) Describe how the percentage change between 25 °C and 30 °C was calculated. … …[1] (iii) Predict the effect on the heart rate of an increase in temperature to 40 °C. … …[1] (c) Assess how far the results of the investigation support the hypothesis. … …[2] [Total: 10]

8 9700/52/O/N/10 © UCLES 2010 BLANK PAGE 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 October/November 2010 question paper for the guidance of teachers 9700 BIOLOGY 9700/52 Paper 5 (Planning, Analysis and Evaluation), maximum raw mark 30 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/AS LEVEL – October/November 2010 9700 52 © UCLES 2010 Mark schemes abbreviations: ; separates marking points / alternative answers for the same point R reject A accept (for answers correctly cued by the question, or guidance on the mark scheme) AW alternative wording (where responses vary more than usual) underline actual word given must be used by the candidate (grammatical variants excepted) max indicates the maximum number of marks that can be given

Page 3 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – October/November 2010 9700 52 © UCLES 2010 Question Expected answer Extra guidance Mark 1 (a) (i) light + intensity / exposure; do not allow light unqualified or position in shade / sun [1] (ii) 8 of: independent variable: 1. ref. to a systematic way of obtaining leaves; dependent variables: 2. ref. to a method of measuring surface area; 3. ref. to how surface area is calculated; 4. ref. to idea of both sides needed to get total surface area; 5. ref. to a method of measuring mass; 6. ref. to finding dry mass; 7. ref. to a method of measuring internode length either on the plant or a cut section from a plant; 8. ref. to a method of measuring water loss; 9. ref. method of using the transpiration apparatus; 10. ref. to keeping constant environment when measuring water loss; (max. 6) safety: 11. ref. to low risk investigation; reliability 12. ref. to mean values of the whole sample; 13. ref. to method of working out SA : mass ratio; 14. ref. to calculating standard deviation; ignore any reference to planting seeds / potted plants 1. e.g. 3rd leaf from the apex / different heights / all from the same height / equal light exposure 2. e.g. draw round each leaf on grid or use transparent grid over leaf / measure diameter(s) of leaf 3. count squares / use formula πr2 5. e.g. digital balance / scales 6. e.g. sample leaves dried in oven until mass constant 7. by holding against a ruler / use string or cotton to mark distance measure with ruler 8. e.g. use a potometer / weigh leaf / place leaf inside a plastic bag (to collect water) 9. measure distance moved by water / weigh at hourly intervals / weigh bag or leaf after a stated time 11. e.g. ref. heat and suitable precaution if use dry mass / leaf allergy 12. do not allow ‘mean of three idea’ 14. ignore formula [8]

Page 4 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – October/November 2010 9700 52 © UCLES 2010 (b) (i) t = 23 – 15 ; 30 42 + 30 32 ; ) 9 . 0 ( ) 8 ( = 8.9; ignore any working in the answer allow 9 / 8.89 and 8.88 • 8 allow ecf for incorrect figure from subtraction [3] (ii) total number of measurements –1 for each set of measurement / (30 – 1) + (30 – 1) = 58; allow 2n – 2 / (n – 1) + (n – 1) 60 – 2 = 58 [1] (iii) ref. (both) calculated / t values are greater than the critical value / 0.2; both results are significant / not due to chance / caused by another factor / light exposure; if the calculation is omitted from (b)(i) both marks are still available allow ecf from (b)(i) ignore null hypothesis unless explained [2] (c) (i) ref. to counting the number of eye piece graticule units; ref. to idea of finding the value of an eyepiece unit with a stage micrometer allow descriptions / ref. to a standard graticule unit value [2]

Page 5 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – October/November 2010 9700 52 © UCLES 2010 (ii) Marks are for conclusions about the adaptations shown by the plants. Do not allow marks for answers that restate the data in table 1.1 3 of: EITHER for shade leaves: 1. thinner cuticle increases light penetration; 2. thinner leaf / shorter palisade cells increases light penetration (to inner parts of leaf); 3. spongy mesophyll has more chloroplasts to increase light absorption; 4. cells less densely packed / larger air spaces for better gas diffusion; 5. larger surface area to absorb limited light / enables more photosynthesis with less light availability; OR for sun / exposed leaves: 1. thicker cuticle limits water loss; 2. (large / long palisade cells) contain more chloroplasts to absorb maximum light; 3. fewer chloroplasts in spongy mesophyll as little light penetrates / palisade is light saturated; 4. densely packed cells / smaller air spaces reduce water loss; 5. smaller surface area reduces water loss; Look for the understanding that shade leaves have adaptations that maximise photosynthesis and sun leaves have adaptations to minimise water loss. allow mix and match for sun and shade leaves but take care not to give the same mark twice. candidates should make it clear which type of leaf they are referring to. ignore anything related to growth ignore any references to internodes ignore any references to stomata [3] [Total: 20]

Page 6 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – October/November 2010 9700 52 © UCLES 2010 2 (a) (i) 2 of: length of organism; time for adjustment (to temperature); time of measurement; do not allow size [2] (ii) 1 of: activity / age / sex / mass of organism; source / type / pH / volume of water; oxygen supply; do not allow microscope lamp / light [1] (iii) 1 of: counting high rates is error prone; changes in temperature; activity / stress affect heart rate; allow oxygen content if not in (ii) e.g. light from microscope / cooling [1] (iv) idea of sufficient measurements for reliability / to remove anomalous results; do not allow accurate ignore reduce error / fair test [1] (b) (i) allows for different starting points between individuals / can see the changes more clearly; looking for the idea that ‘it is easier to see what is happening / make comparisons’ [1] (ii) C 25 at rate C 25 and C 30 at rate in difference / C 25 at rate C 30 at rate ° ° ° ° − ° × 100; allow correct use of any figures from the table e.g. 132 132 165 − × 100 [1] (iii) decrease (by at least 50%) / falls to a very low value / may stop; [1] (c) support: 5 °C – 15 °C / 15 °C – 25 °C / 10 °C – 20 °C (as rate approx. doubles with10 °C increase); does not support: 20 °C – 30 °C increases but does not double / 25 °C – 35 °C decreases / above 30 °C rapidly decreases with temperature increase; allow ‘below 30 °C’ / ‘up to 25 °C’ allow above 30 °C – 35 °C rapidly decreases with temperature increase; [2] [Total: 10]