Cambridge A Level Biology 9700 — 2008 May/June Paper 5 · Variant 1

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Level This document consists of 10 printed pages and 2 blank pages. SP (FF/CG) T52787/2 © UCLES 2008 [Turn over 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 soft 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. * 8 6 0 1 3 0 1 4 0 1 * BIOLOGY 9700/05 Paper 5 Planning, Analysis and Evaluation May/June 2008 1 hour 15 minutes Candidates answer on the Question Paper. For Examiner’s Use 1 2 3 Total

2 © UCLES 2008 For Examiner’s Use 9700/05/M/J/08 1 (a) A type of mollusc Littorina littorea is a consumer of a seaweed Fucus spiralis. This seaweed has leaf-like branches and grows attached to rocks on the seashore. Percentage cover is a simple, non-destructive method of estimating biomass. A student thought that there would be a relationship between the percentage cover of seaweed and the numbers of the mollusc. The student carried out an investigation on a public beach to test the hypothesis: The number of Littorina littorea is proportional to the percentage cover of Fucus spiralis. Fig. 1.1 shows a quadrat used to measure percentage cover of the seaweed and the mollusc. Fig. 1.2 shows how these quadrats were placed on the beach along a transect line. 25 cm 25 cm part of transect line beach quadrats 2 m sea Fig. 1.1 Fig. 1.2 The percentage cover of seaweed was measured by counting the number of squares in which it occurred and the number converted to a percentage. The molluscs were measured by counting the total number in the quadrat, both on the seaweed and on the surrounding rocks. The student made 20 measurements at one metre intervals along a transect line parallel to the sea. A further two transect lines were laid in the same area, the measurements repeated and the mean calculated. (i) Identify the independent and the dependent variable in this investigation. independent variable … dependent variable … [1] (ii) Identify two ways in which the student has attempted to standardise this investigation. 1. … … 2. … … [2]

3 © UCLES 2008 [Turn over For Examiner’s Use 9700/05/M/J/08 (b) The summarised results of the student’s investigation are shown in Table 1.1. Table 1.1 sample number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 mean number of Littorina littorea 3 2 4 3 4 2 3 1 3 2 2 2 0 2 2 3 1 3 3 3 mean percentage cover of Fucus spiralis 42 40 79 31 72 21 24 39 56 15 11 35 24 43 27 0 15 16 13 40 (i) Suggest why the student identified the values of sample 13 as anomalous. … … [1]

4 © UCLES 2008 For Examiner’s Use 9700/05/M/J/08 Fig. 1.3 shows the graph that the student plotted. Graph to show the relationship between Littorina littorea and Fucus spiralis 0 0 20 40 60 80 10 30 50 70 90 1 2 3 axis 2 axis 1 4 5 Fig. 1.3 (ii) State suitable labels for the graph axes. axis 1 … axis 2 … [1] (iii) State what the graph shows about the relationship between Littorina littorea and Fucus spiralis. … … [1] (iv) State the extent to which the result of the investigation support the hypothesis. … … [1]

5 © UCLES 2008 [Turn over For Examiner’s Use 9700/05/M/J/08 (v) Suggest one factor, other than the amount of Fucus spiralis, which may have influenced the number of Littorina littorea. … … [1] [Total: 8]

6 © UCLES 2008 For Examiner’s Use 9700/05/M/J/08 2 Fig. 2.1 shows a simple apparatus used to measure the rate of photosynthesis. sealant gas collected from the plant water beaker pond weed 1 cm3 syringe barrel carbon dioxide sensor Fig. 2.1 (a) (i) Using this apparatus, plan an investigation to show the effect of carbon dioxide concentration on the rate of photosynthesis. … … … … … … … … … … … … … … … …

7 © UCLES 2008 [Turn over For Examiner’s Use 9700/05/M/J/08 … … … … … … [8] (ii) Sketch a graph in the space below to show the expected result of the investigation. Explain your expected result … … … [3] (b) The student measured the amount of oxygen in the gas collected by using an oxygen absorbent. These results were used to calculate the rate of photosynthesis. (i) State how the rate of photosynthesis is calculated from the student’s results. … … … [2] (ii) Suggest why the gas collected is not pure oxygen. … … [1] [Total: 14]

8 © UCLES 2008 For Examiner’s Use 9700/05/M/J/08 3 Fig. 3.1 is a section of a human kidney. Fig. 3.1 (a) A student investigated the proximal convoluted tubule and distal convoluted tubule of the human kidney using a microscope and slide showing similar detail to the one shown in Fig. 3.1. The mean diameter and the mean lumen diameter of twenty cross sections of each type of tubule was measured as shown in Fig. 3.2 using an eyepiece graticule. diameter lumen diameter Fig. 3.2

9 © UCLES 2008 [Turn over For Examiner’s Use 9700/05/M/J/08 Table 3.1 shows the results of this investigation. Table 3.1 tubule diameter lumen diameter proximal tubule distal tubule proximal tubule distal tubule mean diameter / µm 65 35 22 20 standard deviation 0.89 0.99 2.26 2.27 (i) Explain how the student measured and calculated the actual diameters of the tubules. … … … [2] (ii) State how the standard deviation indicates the reliability of the results for the diameter of the proximal and distal tubules. … … [1] (iii) A t -test was carried out and gave the value t = 2.09. Table 3.2 shows the critical values at p < 0.05 for the t -test. Table 3.2 degrees of freedom 18 19 20 21 22 23 24 25 26 27 28 29 30 40 60 ∞ critical value 2.10 2.09 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 38. State and explain the meaning of these results. … … … … [2]

10 © UCLES 2008 For Examiner’s Use 9700/05/M/J/08 (b) Based on the findings of the t -test the student concluded that the difference in lumen diameter was due to the thickness of the brush border of the columnar cells in the proximal tubule. Evaluate the extent to which the information provided enables a valid and reliable conclusion to be drawn. … … … … [2] Suggest one reason why the student’s conclusion may not be valid. … … [1] [Total: 8]

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UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the May/June 2008 question paper 9700 BIOLOGY 9700/05 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. All Examiners are instructed that alternative correct answers and unexpected approaches in candidates’ scripts must be given marks that fairly reflect the relevant knowledge and skills demonstrated. 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 May/June 2008 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

Page 2 Mark Scheme Syllabus Paper GCE A/AS LEVEL – May/June 2008 9700 05 © UCLES 2008 1 (a) (i) independent variable – amount/percentage/cover/of Fucus spiralis/seaweed/algae; reject number dependent variable – numbers of Littorina littorea/mollusc; [1] ignore mean (ii) two of: ignore in all cases reference to means/climate/same beach/weather mark the first answer on each line ref. to size/use of same quadrat; ref. to line/transect parallel to sea; ref. to repeat lines/transects at same distance from the sea; ignore ref. to experiment/it measurement/repeated ref. to 20 sets/lots of data (per transect); ref. to regular systematic placement (of quadrats); allow description/every metre intervals [2] (b) (i) answers must relate to specific data in the table one of: samples at 6 and 7/around the same value, have (3) molluscs; sample at 16/0 cover, has molluscs; percentage cover too high, should have molluscs; does not fit a general correlation/does not follow trend, expect some molluscs/ this has 0 molluscs; allow ref. to mean values rounded down to zero; [1] (ii) x-axis – mean percentage/amount of Fucus spiralis/%; allow seaweed/algae y-axis – mean number of Littorina littorea; allow mollusc [1] Mark (iii) and (iv) together. Read the whole answer and look for two ideas. One idea that relates to the pattern of data and one idea that relates to the support/no support of hypothesis. (iii) (iv) Route 1 there may be no relationship/data is scattered; does not support the hypothesis as there is no proportion/not a straight line relationship between the two species; Route 2 there is a slight (positive)/partial correlation; limited support for hypothesis as there a correlation/proportion at higher percentage cover/data quoted; allow: Route 3 described pattern e.g. as steps/increases unevenly; not supporting hypothesis as increase in cover is not necessarily followed by increase in Littorina; [2]

Page 3 Mark Scheme Syllabus Paper GCE A/AS LEVEL – May/June 2008 9700 05 © UCLES 2008 (v) one of: a suitable abiotic/position on beach factor; (e.g. temperature/heat, exposure, desiccation/light/rocks/rock pools/ distance from sea/wave action/pollution) a suitable biotic factor; (e.g. predation/competition other species for food source/human activities AW) [1] [Total: 8] 2 (a) (i) Look for what the candidate is going to do, not just that the variables are listed. reference to eight of: ref. to varying the independent variable: 1. suitable method of providing different concentrations of carbon dioxide; (e.g.(sodium) hydrogen carbonate/calcium carbonate/baking powder/ gas cylinder/bubbler) allow HO3 – 2. at least 5 concentrations of carbon dioxide; 3. ref. to measuring/maintaining each carbon dioxide concentration with the probe; ref. to measuring dependent variable: 4. amount of gas produced in known time/time to collect a known amount of gas; ref. to controlling any 2 of the key variables: 5. method of standardising pond weed; (e.g. mass/length/same piece/same number of leaves/same species) 6. method of maintaining constant light intensity; (e.g. light fixed distance from plant) – no fixed time limit on light exposure 7. method of maintaining temperature; (e.g. water bath/insulator) allow – air conditioned room 8. method of standardising water; (e.g. same volume/removing gases by boiling) ref. to any 2 procedures of using apparatus: 9. use of pond weed and syringe; (e.g. cutting pond weed and inserting into syringe under water/solution) 10. time for equilibration of pond weed in different carbon dioxide concentrations; 11. working in a dark room/green illumination/enclosing apparatus in a box to eliminate any other light sources; 12. ref. to 3 sets of measurements and a mean/average ref. to any 1 safety issue and precaution: 13. idea of a low risk experiment; 14. ref. to potential risks; (e.g. electric shocks faulty equipment/wet wiring/handling chemicals/cutting pond weed and sensible precautions) [8]

Page 4 Mark Scheme Syllabus Paper GCE A/AS LEVEL – May/June 2008 9700 05 © UCLES 2008 (ii) graph axes correct orientation and labelled and shape of curve correct; (photosynthesis) rate is proportional to carbon dioxide concentration/carbon dioxide is limiting at low concentration; until another factor becomes limiting (at high concentration.); [3] (b) (i) volume of oxygen obtained by subtracting reading after adding oxygen absorbent from initial reading of syringe; rate of photosynthesis = ( ) ( ) mins time cm oxygen of e mass/volum 3 ; reject amount allow fixed volume oxygen, rate is 1 divided by time [2] (ii) any one of: water used to make solutions contains air; allow nitrogen unused carbon dioxide gas from the solution; plant contains air which may be given off with oxygen; allow nitrogen air may remain in syringe when setting up the apparatus; allow respiration of microorganisms produces carbon dioxide; reject plants respire [1] [Total: 14] 3 (a) (i) ref. to measuring (tubules/lumens/sections) with eyepiece graticules; ref. to using stage micrometer and eyepiece graticule; e.g.; calculating the number of eyepiece graticule units per stage micrometer unit allow formula: division micrometer 1 of value units graticule eyepiece of number divisions micrometer stage of number × [2] (ii) the spread of data around the mean/(data with) a narrow spread is more reliable than that with a wide spread; allow with reference to data in table, e.g. tubule diameter is more reliable as spread of data/standard deviation is less [1] (iii) significant difference/not due to chance AW; because t > critical value (at 40 degrees of freedom/between 30 and 40 degrees of freedom); [2] Rate of photosynthesis Concentration of carbon dioxide Rate of photosynthesis Concentration of carbon dioxide

Page 5 Mark Scheme Syllabus Paper GCE A/AS LEVEL – May/June 2008 9700 05 © UCLES 2008 (b) mark together – for maximum marks, • look for one statement that supports validity or reliability • one other statement that either supports or does not support validity or reliability These can be awarded in the first part of the question. • one statement that does not support either validity or reliability This can only be awarded in the last part of the answer. support for reliability: 1. sufficient measurements made; 2. two dimensions measured/reference to standard deviation; 3. all available types of tubule measured; allow reverse arguments for 1 and 2 as marks for against reliability/validity support for validity: 4. ref. to t-test; allow ecf from (b)(iii) reject if linked to reliability against either reliability or validity: 5. size of the columnar cells was not measured; 6. the brush border was not measured /not visible; 7. ref. idea of difficulties in measuring diameter accurately from sections; 8. ref. to difficulty in recognising types of tubules; 9. (student) assumes that the difference in diameter of the total wall is entirely due to columnar cells; [3] [Total: 8]