Cambridge A Level Biology 9700 — 2009 Oct/Nov Paper 5 · Variant 2

For Examiner’s Use 1 2 3 Total This document consists of 7 printed pages and 1 blank page. DC (CW/KN) 15839/4 © UCLES 2009 [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. * 4 9 8 8 2 4 5 0 5 7 * BIOLOGY 9700/52 Paper 5 Planning, Analysis and Evaluation October/November 2009 1 hour 15 minutes Candidates answer on the Question Paper. No Additional Materials are required.

2 9700/52/O/N/09 © UCLES 2009 For Examiner’s Use 1 A definition of probiotics is: ‘Live microorganisms which when administered in adequate amounts confer a health benefit to a person’. Lactic acid bacteria (LAB), which can be found in yoghurt, are commonly used as probiotics. The longer these bacteria survive in gastric juice (in the stomach) and intestinal juice (in the small intestine) the greater the benefit to the person. The effect of immobilisation and continuous culture on the probiotic characteristics of the LAB bacterium Bifidobacterium longum was studied. Two continuous culture system were used: C1: a control culture containing free bacteria, C2: a test culture containing bacteria immobilised in beads. The temperature of the fermenters was varied during the culture period. Day 1–6 37 °C Day 7–13 35 °C Day 14 onwards 32 °C Samples were collected from each culture system at different times. These cells were tested for their tolerance to a variety of environmental stresses. (a) Suggest two variables in the fermenter that should be controlled. For each variable, suggest a method by which it might be controlled. 1. variable … method of control … … 2. variable … method of control … …[4]

3 9700/52/O/N/09 © UCLES 2009 [Turn over For Examiner’s Use The ability of cells to survive in the stomach and intestines was tested by mixing the cultures with artificial gastric and intestinal juices and incubating for 1 hour at 37 °C. Cell survival was estimated by counting the number of live colonies growing on culture plates after 48 hours. Fig. 1.1 shows the effect of immobilisation and continuous culture on cell survival of B. longum. 0.01 0.1 1 10 100 cell survival / % gastric juice intestinal juice control day 3 continuous fermentation of immobilised cells day 3 day 6 day 9 day 12 day 15 C1: control C2: intestinal juice + immobilised cells C2: gastric juice + immobilised cells Fig. 1.1 (b) Describe what these results show about the percentage survival of B. longum in continuous culture. … … … … … …[3] (c) The standard deviation of the survival rates for control cells after 3 days was estimated at 2±1% in gastric juice and 21±9% in intestinal juice. State the data needed to calculate the standard deviation. … …[2] [Total: 9]

4 9700/52/O/N/09 © UCLES 2009 For Examiner’s Use 2 Fig. 2.1 shows a diagram of a pollen trap. collection funnel cover vacuum pump pulling in air at a rate of 10 dm3 min–1 microscope slide with an adhesive surface 10 mm × 42 mm 2 mm × 14 mm opening Fig. 2.1 This apparatus can be used to estimate the number of pollen grains present in the atmosphere. The apparatus is left for a period of time, the slide removed and a pollen stain added. The number of pollen grains are counted using a microscope. A student thought that there would be more pollen in the atmosphere during the day than during the night. The hypothesis was: As the light increases the number of pollen grains present in the atmosphere will increase and then decrease as the light decreases. (a) Outline a procedure, using this pollen trap, that the student could use to test this hypothesis. … … … … … … … … … … … … … … …

5 9700/52/O/N/09 © UCLES 2009 [Turn over For Examiner’s Use … … …[8] (b) In a further investigation, the student collected pollen between 06.00h and 12.00h on a dry, hot day and estimated the number of pollen grains in 1 m3 of air. The mean number of pollen grains visible in the field of view = 6 The area of the field of view = 0.25 mm2 The number of pollen grains in 1 m3 of air = 2800 Use the data collected by the student and the information in Fig. 2.1 to show how the student obtained this number. Show all the steps in your calculation. [3] (c) The student then collected pollen for the same time period on a wet, hot day. The mean number of pollen grains visible in the field of view = 2 The chi-squared test at 1 degree of freedom showed that the results were significant at 0.05 probability. (i) State a null hypothesis for the chi-squared test. … …[1] (ii) Explain why the student chose the chi-squared test. … …[1] (iii) Explain why the student used 1 degree of freedom. …[1] [Total: 14] www.OnlineExamHelp.com

6 9700/52/O/N/09 © UCLES 2009 For Examiner’s Use 3 Discs of a plant tissue with cells containing a red pigment were cut and washed in running water for 24 hours. These discs were used by a group of students in an investigation to test the hypothesis: Ethanol increases membrane permeability more than an increase in temperature. Fig. 3.1 shows the experimental set up used. 0% 20% 40% 60% 80% 100% 10°C 20°C 30°C 40°C 50°C 60°C experiment 1 experiment 2 discs of plant tissue water-bath at 30 °C test-tubes containing different concentrations of ethanol test-tubes containing water placed in water-baths at different temperatures for 30 mins Fig. 3.1 After 30 minutes the liquid around the discs of plant tissue was poured into a colorimeter tube. A colorimeter with a blue filter was used to measure the absorbance of light. Water was used to standardise the absorbance of the colorimeter to 0. The more red pigment in the liquid the higher the absorbance of light. (a) (i) Identify the two independent variables in the investigation. 1. … 2. …[2] (ii) Identify the dependent variable. …[1]

7 9700/52/O/N/09 © UCLES 2009 For Examiner’s Use Table 3.1 shows the results of experiment 1. Table 3.1 absorbance at each ethanol concentration 0% 20% 40% 60% 80% 100% student 1 0.00 0.12 0.21 0.35 0.65 0.70 student 2 0.10 0.10 0.22 0.32 0.60 0.75 student 3 0.00 0.18 0.20 0.38 0.59 0.72 student 4 0.00 0.18 0.35 0.35 0.65 0.76 student 5 0.15 0.10 0.18 0.34 0.62 0.75 Table 3.2 shows the results of experiment 2. Table 3.2 absorbance at each temperature 10 °C 20 °C 30 °C 40 °C 50 °C 60 °C student 1 0.00 0.00 0.00 0.09 0.65 0.79 student 2 0.15 0.20 0.05 0.15 0.70 0.85 student 3 0.10 0.05 0.00 0.18 0.62 0.81 student 4 0.00 0.00 0.04 0.30 0.75 0.88 student 5 0.10 0.00 0.02 0.25 0.60 0.85 (b) (i) On Table 3.1, indicate by placing a circle around the value, two results that may be anomalous. [2] (ii) Suggest why the design of this investigation does not provide reliable results to allow a conclusion to be made about the hypothesis. … … … … … …[2] [Total: 7]

8 9700/52/O/N/09 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. www.OnlineExamHelp.com

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the October/November 2009 question paper for the guidance of teachers 9700 BIOLOGY 9700/52 Paper 52 (Practical 2), 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 2009 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 2009 9700 52 © UCLES 2009 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 for examiners)
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

Page 3 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – October/November 2009 9700 52 © UCLES 2009 Question Expected answer Extra guidance Mark AO 1 (a) For each factor, allow both marks anywhere in the answer. If two factors given in one answer, mark the first unless nothing is written in no.2. For 1 and 2 – ignore amount for the variable, but not for the method of control 2 × 2 of: 1. ref. to nutrient / substrate; ref. to suitable context e.g. concentration / volume / flow rate / composition; 2. ref. to bacteria culture added; ref. to suitable context e.g. volume or mass of (immobilised) cells / volume of culture; 3. pH; use buffer / named buffer; 4. ref. to anaerobic conditions; ref. to a suitable method of providing condition in a fermenter; e.g. nitrogen / carbon dioxide, atmosphere; Ignore type of fermentation system unless qualifications apply only to batch culture. Reject food as variable, but allow method if reference to concentration or mass in solution. Ignore mass of nutrient unless in terms of making up solutions. Allow ref. to, oxygen / air supply / aerobic bubbling air/oxygen / use of sparger / air lift. [2] [2] P M (b) Assume that the answer is about immobilised cells unless the answers says otherwise. Allow marking points expressed as figures in the correct context. 3 of: 1. immobilised cells have lower survival rates than control cells on day 3; 2. immobilised cells have higher survival rates in gastric juice than in intestinal juice; 3. (immobilised cells) survival increases with time of fermentation; 4. decrease in temperature increases survival ; 5. not all cells survive / some die ; 6. allow: idea that survival in intestinal juice and gastric juice become almost the same by day 12 / 15 ; 1. Allow reverse argument. 2. Survival rate in gastric juice in control cells is lower than in intestinal juice; 3. Allow day 3 is the lowest / 15 days max. 4. Allow temperature has little effect on the increase in survival. [3] C

Page 4 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – October/November 2009 9700 52 © UCLES 2009 Question Expected answer Extra guidance Mark AO (c) idea of: number of samples (for each condition tested); mean value (for each condition tested); Allow any word that implies samples e.g. readings / values / repeats / sample size. Do not allow number of cells surviving. Allow marks on a labelled formula. Ignore any other ref. to figures / measurements / undefined symbols. [2] D Total: [9] P2 M2 D2 C3 www.OnlineExamHelp.com

Page 5 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – October/November 2009 9700 52 © UCLES 2009 Question Expected answer Extra guidance Mark AO 2 (a) If carried out in Glasshouse / room do not award. points 9,10 and 11 8 of: independent variable 1. ref. to exposing slide / apparatus for period of time in different light intensities to include dark (zero intensity) / to light and dark conditions; dependent variable 2. ref. to counting pollen in field of view; 3. ref. to counting at least 3 areas of the slide; 4. ref. measuring diameter of field of view using graticule; 5. ref. to calculating area of field of view (using formula πr2) ; control variables – max 4 6. ref. time of exposure constant; 7. ref. same location for all readings; 8. ref. to removing any pollen on opening between each slide ; 9. ref. to outside location; 10. detail of location; e.g. no walls/hedges/trees in the way / facing wind; 11. ref. to an attempt to control environmental factors / some environmental variable cannot be controlled ; reliability 12. ref. to repeating the whole investigation on 3 different days and taking mean; safety: max 1 13. low risk investigation ; pollen allergy and use of mask; electrical safety and ref. to water ; 1. Allow ref to range of times covering light and dark periods. 3. Allow using 3 traps (at the same time) and taking counts. 7. Room / Glasshouse – need precise ref. to same location. 10. Allow specified place – on roof, wall, field. 11. Ignore wind speed if related to pump. 12. Allow if take 3 repeats on the same day plus mean. Several = 3 or more. [8] M

Page 6 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – October/November 2009 9700 52 © UCLES 2009 Question Expected answer Extra guidance Mark AO (b) (i) If the total number of pollen grains is correct and the volume of air is correct from a calculation, give both marks. Allow any method of calculation that give the expected values. Calculations of values e.g. total pollen collected = number of pollen per mm2 × surface area collection strip (1/0.25 × 6 = 24) × 420 (10 × 42) = 10080; volume of air m3 in 6 hours = volume per min × min in 1hour × no. hours ÷ 1000 (10 dm3 × 60x 6 ÷ 1000 = 3.6 m3 ); Use of calculated values: pollen in 1 m3 = 2800 3.6 10080 = ; allow marks either for words or figures allow ‘back’ calculations allow other calculations e.g. 0.25 420 = 1680 × 6 = 10080 6 60 10080 × = 28 pollen per minute 28 × 100 or 10 28 × 1000 = 2800 in 1 m3 Allow ecf if either of the values calculated incorrectly, but used correctly in the formula. [3] D (c) (i) there is no difference in the number of pollen grains in (hot)dry air and (hot)wet air ; humidity / dryness / wetness does not affect the number of pollen grains; do not allow alternative hypothesis do not allow if differences in light given [1] D (ii) ref. to the data being categoric / discrete; Allow discontinuous, but NOT discontinuous variation. Allow expressed as ref. to significance between observed and expected data. [1] D (iii) there are two conditions counted, so 2-1= 1 Allow 2 sets of data or two conditions sampled. Reject 2 – 1 = 1 unqualified [1] D Total: [14] M8 D6

Page 7 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – October/November 2009 9700 52 © UCLES 2009 Question Expected answer Extra guidance Mark AO 3 (a) (i) ethanol concentration; temperature; Allow alcohol concentration. [2] P (ii) pigment released / light absorbance; Ignore membrane permeability. [1] P 2 of: absorbance at each ethanol concentration / % 0 20 40 60 80 100 student 1 0 0.12 0.21 0.35 0.65 0.70 student 2 0.10 0.10 0.22 0.32 0.60 0.75 student 3 0 0.18 0.20 0.38 0.59 0.72 student 4 0 0.18 0.35 0.35 0.65 0.76 student 5 0.15 0.10 0.18 0.34 0.62 0.75 (b) (i) If more than 2 given – allow marks if all correct, lose 1 for every incorrect. [2] E (ii) 2 of: ref. to insufficient data: ref. to idea that cannot make comparisons between ethanol and temperature; ref. to needing all the temperature and ethanol concentrations; allow if refers to comparing like with like allow if refers to only 0% ethanol and 30oC being comparable [2] E Total: [7] 3P 4E