Cambridge A Level Biology 9700 — 2014 May/June Paper 3 · Variant 1

This document consists of 15 printed pages and 1 blank page. DC (NF/SW) 65732/6 © UCLES 2014 [Turn over Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level * 7 7 2 3 5 0 8 4 5 9 * BIOLOGY 9700/31 Advanced Practical Skills 1 May/June 2014 2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions. 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 an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. Electronic calculators may be used. 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. For Examiner’s Use 1 2 Total

2 9700/31/M/J/14 © UCLES 2014 Before you proceed, read carefully through the whole of Question 1 and Question 2. Plan the use of the two hours to make sure that you finish all the work that you would like to do. If you have enough time, consider how you can improve the accuracy of your results, for example by obtaining and recording one or more additional measurements. You will gain marks for recording your results according to the instructions. 1 The Benedict’s test can be used to detect the presence of reducing sugars such as glucose. A solution to be tested is mixed with Benedict’s solution, heated and the time taken to the first appearance of a colour change recorded. A student suggested the hypothesis: “the time taken for the Benedict‛s solution to show the first appearance of a colour change will decrease as the temperature increases.” You are required to investigate the effect of different temperatures (the independent variable) when carrying out the Benedict’s test. You are provided with: labelled contents hazard volume / cm3 G 4% glucose solution none 60 Benedict’s solution Benedict’s solution harmful irritant 80 You must now read up to the end of step 4 before proceeding. You will need to standardise the Benedict’s test to compare the time taken to the first appearance of a colour change at four different temperatures, 70 °C, 80 °C, 90 °C and 100 °C. Use 4 cm3 of G for each temperature tested. (a) (i) Decide the volume of Benedict’s solution you will use for each test. Complete the table to show the volume of Benedict’s solution you will use. solution volume / cm3 Benedict’s G 4 [1]

3 9700/31/M/J/14 © UCLES 2014 [Turn over Proceed as follows; 1. Set up a water-bath and maintain it at the first temperature of 70 °C. 2. Test 4 cm3 of G with Benedict’s solution using the volume you decided in (a)(i). Start timing when the test-tube is placed into the water-bath and record the time taken for the first appearance of a colour change at the top of the mixture in the test-tube. If no colour change occurs after 4 minutes, stop the experiment and record ‘more than 240’. 3. Immediately pour the contents of the test-tube into the container labelled ‘for waste’. Fill the test-tube with water from the container labelled ‘for washing’. Empty the contents of the test-tube into the container labelled ‘for waste’. 4. Repeat steps 1 to 3 with the other temperatures of the water-bath, 80 °C, 90 °C and 100 °C. (ii) Prepare the space below and record your results. [2] The student’s hypothesis was: “the time taken for the Benedict‛s solution to show the first appearance of a colour change will decrease as the temperature increases.” (iii) State whether your results support this hypothesis. … Use your results to explain your answer. … … … … [2]

4 9700/31/M/J/14 © UCLES 2014 You are required to: • select one temperature from 70 °C, 80 °C, 90 °C or 100 °C to carry out the Benedict’s test • make different concentrations of glucose from the solution G • estimate the glucose concentrations of solutions S1 and S2 at the selected temperature. You are provided with: labelled contents hazard percentage concentration volume / cm3 S1 glucose solution none unknown 15 S2 glucose solution none unknown 15 W distilled water none – 100 To compare the concentrations of glucose you will need to standardise the temperature using your results from (a)(ii). (iv) State the temperature you will use. State a reason for the temperature you have chosen. temperature … reason … … [1]

5 9700/31/M/J/14 © UCLES 2014 [Turn over You are now required to carry out a serial dilution of glucose solution, G, to reduce the concentration of G by half between each successive dilution. You will need 15 cm3 of each glucose concentration. Fig. 1.1 shows how to make the first concentration of 2% glucose solution. 30 cm3 of 4% glucose solution, G 15 cm3 of 4% glucose solution, G 15 cm3 of distilled water, W 30 cm3 of 2% glucose solution, G … … … … Fig. 1.1 (v) Complete Fig. 1.1 to show how you will make two further concentrations of G. [2]

6 9700/31/M/J/14 © UCLES 2014 You will need to test the different concentrations of glucose, as well as S1 and S2, with Benedict’s solution. (vi) Decide the volumes of solutions you will use in your investigation. Complete the table. solution volume / cm3 Benedict’s glucose solutions S1 S2 [1] Proceed as follows: 5. Prepare all the concentrations of glucose solution as shown in Fig. 1.1 in the containers provided. 6. Set up a water-bath and maintain it at the temperature you decided in (a)(iv). 7. Test the four concentrations of glucose solution and S1 and S2 to compare the concentration of glucose. 8. Record your results in (vii) on page 7.

7 9700/31/M/J/14 © UCLES 2014 [Turn over (vii) Prepare the space below and record your results. [3] (viii) Complete Fig. 1.2 below to show: • each percentage concentration of glucose solution (the concentration of G is shown) • where the samples S1 and S2 fit in the series of concentrations. 0 4 G percentage concentration of glucose [2] Fig. 1.2

8 9700/31/M/J/14 © UCLES 2014 (ix) Describe three modifications to this investigation which would improve the confidence in your results. … … … … … … … … … [3] (x) A systematic error occurs when apparatus with scales are used, since the scales may be slightly different. For example, when measuring the same line, two rulers may give different lengths. However, as long as the same ruler is used for all the measurements, the trend is not affected because the error is consistent. State one piece of apparatus used in this investigation that may have a systematic error. Suggest whether this affected your results and give a reason for your answer. apparatus … reason … … [1] [Total: 18]

9 9700/31/M/J/14 © UCLES 2014 [Turn over Question 2 starts on page 10

10 9700/31/M/J/14 © UCLES 2014 2 (a) The eyepiece graticule scale in your microscope may be used to measure the actual length of the layers of tissues or cells, if the scale has been calibrated against a stage micrometer. However, to help draw the correct shape and proportions of tissues or cells, as in (a)(i) and (a)(ii), it is not necessary to calibrate the eyepiece graticule scale. J1 is a stained transverse section through a plant leaf. This plant species grows in sub-tropical and temperate regions. You are not expected to have studied this leaf. (i) Draw a large plan diagram of the mid-rib of the leaf on J1. The mid-rib is shown by the shaded area in Fig. 2.1. On your diagram, use a ruled label line and label to show the xylem. Fig. 2.1 [4]

11 9700/31/M/J/14 © UCLES 2014 [Turn over (ii) Within the vascular bundles the xylem is made up of chains of vessel elements (arranged in lines). Select two different chains of xylem vessel elements. Make a large drawing of three complete adjacent (touching) xylem vessel elements from each of these two selected chains. On your drawing use a ruled label line and label to one lumen. first chain second chain [5]

12 9700/31/M/J/14 © UCLES 2014 (b) Fig. 2.2 is a photomicrograph of the surface of a plant leaf showing stomata. This plant species grows throughout the world’s temperate regions. X magnification × 230 Fig. 2.2 (i) Use the magnification on Fig. 2.2 to calculate the actual length, in μm, of line X. You may lose marks if you do not show your working or if you do not use appropriate units. … μm [4] (ii) State one observable feature of the leaf surface, shown in Fig. 2.2, that supports the conclusion that water loss was being reduced in this leaf. Explain how this feature reduces water loss. feature … explanation … [1]

13 9700/31/M/J/14 © UCLES 2014 [Turn over Fig. 2.3 is a photomicrograph of a stained surface of another leaf showing stomata. This plant species is native to North Africa and South-west Asia. magnification × 230 Fig. 2.3 (c) Prepare the space below so that it is suitable for you to record the observable differences between the specimens shown in Fig. 2.2 and in Fig. 2.3. Record your observations in the space you have prepared. [4]

14 9700/31/M/J/14 © UCLES 2014 Rising concentrations of carbon dioxide in the atmosphere have been recorded by scientists for over one hundred years and can be used to predict future increases. Scientists have studied the effect of carbon dioxide on the number of stomata per mm2 on the upper and lower epidermis of leaves of one species of plant. A large sample of plants was grown in air containing one of each of the following concentrations of carbon dioxide: • 380 μmol mol−1 (the concentration measured in the atmosphere now) • 560 μmol mol−1 (the predicted concentration in the atmosphere 50 years in the future) • 800 μmol mol−1 (the predicted concentration in the atmosphere 100 years in the future). All other variables were standardised. After a set time the number of stomata per mm2 on the upper and lower epidermis of the leaves was found and the mean number of stomata per mm2 was calculated. The results are shown in Table 2.1. Table 2.1 concentration of CO2 / μmol mol−1 mean number of stomata / mm2 upper epidermis (U) lower epidermis (L) 380 2 104 560 3 121 800 8 142

15 9700/31/M/J/14 © UCLES 2014 (d) Plot a chart of the data shown in Table 2.1. [4] [Total: 22]

16 9700/31/M/J/14 © UCLES 2014 BLANK PAGE Copyright Acknowledgements: Fig. 2.2 © GARRY DELONG/SCIENCE PHOTO LIBRARY. Fig. 2.3 © GARRY DELONG/SCIENCE PHOTO LIBRARY. 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. 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.

CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the May/June 2014 series 9700 BIOLOGY 9700/31 Paper 3 (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 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 May/June 2014 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 – May/June 2014 9700 31 © Cambridge International Examinations 2014 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 accepted) 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

Page 3 Mark Scheme Syllabus Paper GCE AS/A LEVEL – May/June 2014 9700 31 © Cambridge International Examinations 2014 1 (a) (i) volume given the same or more than G (4–10 inclusive) ; [1] (ii) organised into table + all columns separated by a line + all headings underlined ; headings temp(erature) / °C + time / s or sec(onds) ; [2] (iii) answer according to candidates results + further qualification ; use of data (at least two temperatures AND two references to time) or idea of an increase in kinetic energy increases the rate of reaction ; [2] (iv) statement of temperature with units °C + valid reason ; [1] (v) shows transfer of 15 cm3 (of 2% to the next dilution) + adds 15 cm3 of (distilled) water / W ; 1(.0)% AND 0.5% ; [2] (vi) all four volumes correct ; solution volume/cm3 Benedict’s same volumes as stated in (a) (i) glucose 4 S1 4 S2 4 [1] (vii) records 6 times (for 4 concentrations of glucose + S1 + S2 ) ; records whole seconds only ; highest concentration of glucose is shortest time ; [3] (viii) shows position of 0.5, 1(.0) and 2(.0), scale – one space = 0.5 ; shows position of S1 + S2 correctly according to their results ; [2]

Page 4 Mark Scheme Syllabus Paper GCE AS/A LEVEL – May/June 2014 9700 31 © Cambridge International Examinations 2014 (ix) more / wider / narrower range of glucose concentrations ; do individually / each test-tube separately to prevent timing error or replicate / repeat ; idea of thermostatically-controlled water-bath ; use of white card / tile to observe colour change ; [max 3] (x) syringe or thermometer or stopwatch + no effect + if use same syringe or thermometer or stopwatch or idea of different syringe used + systematic error + not true value ; [1] [Total: 18] 2 (a) (i) at least 2 lines for upper epidermis + 2 lines for lower epidermis + vascular bundle + size at least 60mm across midrib + no shading ; no cells + one complete vascular bundle in the midrib + vascular bundle subdivided ; one concave surface and one convex surface + enclosed area beneath or above (or around) the vascular bundle ; uses label line + label to xylem ; [4] (ii) at least 6 cells + size at least 20 mm across largest cell at narrowest + sharp continuous lines ; only 2 groups of 3 cells drawn, each cell touching at least one other cell ; one cell has at least 3 corners ; cell walls drawn as double lines + middle lamella between ; use label line(s) + label to one lumen ; [5]

Page 5 Mark Scheme Syllabus Paper GCE AS/A LEVEL – May/June 2014 9700 31 © Cambridge International Examinations 2014 (b) (i) correct measurement of line X (18–20 mm or 1.8–2(.0) cm) ; uses mm and converts to µm by multiplying by 1000 ; shows division by 230 ; rounds answer to appropriate number of significant figures ; [4] (ii) idea of stomata / guard cell(s) + closed + reduces transpiration or evaporation or diffusion of water ; [1] (c) mp1 organise as table with 3 columns headed feature + Fig. 2.2 + Fig. 2.3 ; max 3 for differences mp feature Fig. 2.2 Fig 2.3 2 guard cells size (some) large(r) / thicker (some) small(er) / thinner ; 3 nucleus of the guard cells rounder or small(er) / short(er) more elongated or large(r) / long(er) ; 4 stomata shape or length narrow / elongated / slits or long(er) oval or short(er) ; 5 stomata / guard cell number few(er) more ; 6 (epidermal) cells shape or size narrow / elongated / rectangular / oblong or longer / narrower irregular / star- shaped / convoluted or shorter / wider ; 7 (epidermal) cells wall small indentations wavy large indentations smooth ; 8 number of types of cells more less ; 9 arrangement of any cells in rows / lines / linear / parallel scattered / random ; 10 line or strip present absent ; [max 4]

Page 6 Mark Scheme Syllabus Paper GCE AS/A LEVEL – May/June 2014 9700 31 © Cambridge International Examinations 2014 (d) (x-axis) concentration of CO2 µmol mol–1 + label on blocks upper epidermis / U, lower epidermis / L, 380 + 560+ 800 + (y-axis) mean number of stomata / mm2 ; (x-axis) even width of blocks and even distance between blocks +, + (y-axis) 20 to 2 cm labelled every 2 cm, except 0 ; correct plotting of each bar in the same order as the table + ruled sharp line ; all vertical lines drawn as ruled sharp lines + all lines meeting exactly + labels for upper and lower must either be directly below the correct bar or inside the bar or shaded with a key ; [4] [Total: 22]