Cambridge A Level Biology 9700 — 2014 May/June Paper 3 · Variant 2

This document consists of 13 printed pages and 3 blank pages. DC (NF/SW) 65735/6 © UCLES 2014 [Turn over Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level * 5 1 9 6 1 8 6 5 6 6 * BIOLOGY 9700/32 Advanced Practical Skills 2 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. Do not use staples, paperclips, glue or correction fluid. You may use an HB pencil for any diagrams or graphs. 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 9700/32/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 one or more additional measurements. You will gain marks for recording your results according to the instructions. 1 You are provided with a solution labelled, E, containing an enzyme which coagulates (clots) milk. Calcium ions are required for this coagulation. You are required to investigate the concentration of calcium ions (the independent variable), on the progress of this enzyme-catalysed coagulation. When a mixture of milk, enzyme and calcium chloride is gently rotated the coagulation goes through the stages shown in Fig. 1.1. Stage 3 is the end-point of the enzyme-catalysed coagulation. stage 1 stage 2 stage 3 the end-point stage 4 past the end-point film of milk flows/drains back into milk quickly film of milk drains slowly and sticks to inside of test-tube small spots/ clots stick to inside of test-tube as film of milk drains back all the milk has coagulated Fig. 1.1 You are provided with: labelled contents hazard volume / cm3 C 20% calcium chloride solution harmful irritant 50 W distilled water none 100 M milk none 100 E 1% enzyme solution harmful irritant 20

3 9700/32/M/J/14 © UCLES 2014 [Turn over You are now required to carry out a serial dilution of calcium chloride solution, C, to reduce the concentration of C, by half between each successive dilution. You will need 10 cm3 of each calcium chloride solution. (a) (i) Complete Fig. 1.2 to show how you will make three further concentrations of calcium chloride solution by serial dilution. 20 cm3 of 20% calcium chloride solution, C 10 cm3 of 20% calcium chloride solution, C … … … … … … … … [3] Fig. 1.2 Proceed as follows: 1. Prepare all the concentrations of calcium chloride solution as shown in Fig. 1.2 in the containers provided. 2. You are provided with a water-bath. Adjust the temperature to between 35 °C and 40 °C. You will need to maintain this temperature during steps 3 to 10. 3. Put 1 cm3 of each of the four concentrations of calcium chloride solution into separate test-tubes. 4. Put 10 cm3 of M into each test-tube. 5. Gently shake each of the test-tubes to mix M and calcium chloride solution. 6. Put the test-tubes into the water-bath and leave for at least three minutes.

4 9700/32/M/J/14 © UCLES 2014 Read steps 7 to 11 before proceeding. 7. Remove the test-tube containing the mixture with the highest concentration of the calcium chloride solution from the water-bath. The process of coagulation will start when E is added to each test-tube. Put 1 cm3 of solution E, so that it runs down the side of the test-tube to form a layer on the surface of the mixture as shown in Fig. 1.3. syringe push gently E in syringe slanted test-tube E running down inside of test-tube layer of E forming on top of mixture mixture Fig. 1.3 8. Gently shake the test-tube to mix the solutions and start timing. 9. Gently rotate the test-tube, as shown in Fig. 1.1 on page 2, to form a film of milk on the inside of the test-tube. 10. Continue to rotate the test-tube whilst holding it over the black card on the table (see Fig. 1.4). film of milk black card table Fig. 1.4 Record the time to reach the end-point as shown in stage 3 in Fig. 1.1. Ignore any small bubbles on the inside of the test-tube. If the end-point has not been reached by 4 minutes, stop the experiment and record ‘more than 240’.

5 9700/32/M/J/14 © UCLES 2014 [Turn over 11. Repeat steps 7 to 10 using the other concentrations of calcium chloride solution. (ii) Prepare the space below and record your results. [5] (iii) Identify one significant source of error in measuring the dependent variable in this investigation. … … … [1]

6 9700/32/M/J/14 © UCLES 2014 (iv) 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] (v) Describe a suitable control for this investigation. … … … [1] In a similar investigation on the enzyme-catalysed coagulation of milk, a student studied the effect of heating solution E at 70 °C for different times. After heating, the time to reach the end-point was recorded as in your investigation. This was repeated for each of the different times. (b) (i) State two variables that need to be kept the same (standardised) in this investigation. Describe how you would standardise each of these variables. variable 1 … description … … variable 2 … description … … [2]

7 9700/32/M/J/14 © UCLES 2014 [Turn over The results of this investigation are shown in Table 1.1. Table 1.1 time of heating solution E / s time to reach the end-point / s 60 30 150 75 185 96 240 140 300 220 (ii) Plot a graph of the data shown in Table 1.1. [4]

8 9700/32/M/J/14 © UCLES 2014 (iii) Explain the trend shown in your graph. … … … … … … … [3] [Total: 20]

9 9700/32/M/J/14 © UCLES 2014 [Turn over Question 2 starts on page 10

10 9700/32/M/J/14 © UCLES 2014 2 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 proportion of tissues, as in (a), it is not necessary to calibrate the eyepiece graticule scale. L1 is a stained, longitudinal section showing the tissues of a young root tip. (a) Draw a large plan diagram of L1. Use a ruled label line and a label to show the position of the area in which you can see cells showing stages of mitosis. [5] Fig. 2.1 is a photomicrograph of root cells. P Q R S T Fig. 2.1

11 9700/32/M/J/14 © UCLES 2014 [Turn over (b) Make a large drawing of each of the five cells labelled P, Q, R, S and T on Fig. 2.1. On your drawing use ruled label lines and labels to identify two different stages of mitosis. Annotate one of the stages to describe one observable feature that supports your identification. [6]

12 9700/32/M/J/14 © UCLES 2014 Fig. 2.2 is a photomicrograph of root cells from a different region of the root. 31 +m Fig. 2.2 (c) Use the scale bar below Fig. 2.2 to calculate the magnification of Fig. 2.2. You may lose marks if you do not show your working or if you do not use appropriate units. [4]

13 9700/32/M/J/14 © UCLES 2014 Fig. 2.1 is shown again here to help you answer (d). P Q R S T Fig. 2.1 (d) Prepare the space below so that it is suitable for you to record the observable differences, other than colour, between the specimens in Fig. 2.1 and in Fig. 2.2. Record your observations in the space you have prepared. [5] [Total: 20]

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16 9700/32/M/J/14 © UCLES 2014 BLANK PAGE Copyright Acknowledgements: Fig. 2.1 © HERVE CONGE, ISM/SCIENCE PHOTO LIBRARY. Fig. 2.2 © DR JOHN RUNIONS/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 9700/32 Paper 32 (Advanced Practical Skills 2), 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 32 © 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 32 © Cambridge International Examinations 2014 1 (a) (i) (labels under correct sequence of beakers) + 10 + 5 + 2.5 + % ; adds previous concentration of C to each of the last two beakers + 10cm3 ; adds water / W + 10 cm3 to three beakers ; [3] (ii) organised into table + all columns separated by a line + all headings underlined ; headings (top or to left of data) percentage concentration + (any column/row headed) time (/)s or seconds ; whole seconds for at least three concentrations ; records highest concentration first ; highest concentration recorded in shorter time than next concentration ; [5] (iii) (dependent) stage 3 or end-point + idea of judging / determining ; [1] (iv) syringe or thermometer + no effect + if use same syringe or thermometer ; [max 1] or syringes + affect accuracy + not true value ; (v) replaces calcium chloride / C with water ; [1] (b) (i) calcium chloride + optimum % conc. of calcium chloride from investigation or stated figure % e.g. 20% ; type of milk or volume of milk + same milk or same volume or stated volume e.g. 2 cm3 ; temperature of water-bath + use 70 °C maintained by thermostatically controlled water-bath or temperature of milk (reaching desired temperature) + check temperature of milk has reached 70 °C or milk (has reached) 70 °C (before enzyme added) ; volume of enzyme + use same volume of E or stated volume e.g. 1 cm3 of E or concentration of enzyme / E + use same conc. of E or 1% E ; [max 2]

Page 4 Mark Scheme Syllabus Paper GCE AS/A LEVEL – May/June 2014 9700 32 © Cambridge International Examinations 2014 (ii) (x-axis) time of heating solution E / seconds + (y-axis) time to reach the end-point / seconds ; (x-axis) 2 cm to 50 seconds, labelled each 2 cm, except origin and 300 seconds + (y-axis) 2 cm to 50 seconds, labelled each 2 cm, except origin and 250 ; correct plotting of five points as small cross or dot in circle or cross ; five plots + ruled sharp lines exactly point to point or ruled line of best fit + sharp smooth line ; [4] (iii) structure of protein / substrate / enzyme / active site or bonds + changed / altered / destroyed / no longer complementary / broken ; fewer ESCs / Enzyme Substrate Complexes or less substrate can bind ; idea of enzyme denatured ; [3] [Total: 20] 2 (a) at least 3 lines + size at least 40 mm across greatest width of root tip + no shading ; no cells + one closed end with one open end ; root cap as separate area or two lines around margin ; chooses (correct) area to cells undergoing mitosis ; label (e.g. mitosis) to area with cells undergoing mitosis ; [5] (b) at least 5 cells + size at least 50 mm across largest cell at widest point + sharp continuous lines ; only 5 whole cells drawn + enclosure drawn in cells Q and S ; for cells P, R and T whole nuclei drawn as different shapes ; for Q chromosomes drawn as a mass ; 2 labels + 2 lines + 2 different stages of mitosis identified ; one correct annotation of one stage ; [6] (c) measures scale bar within range + mm + to 0.5 ; (range 13–15 mm) ; shows conversion of scale bar in mm to µm (× 1000) or shows conversion of 31 µm to mm (31 divided by 1000 = 0.031 mm) ; show measurement of scale bar in µm divided by 31 µm or shows measurement of scale bar in mm divided by 0.031 mm ; correct answer 451.61 / correct answer rounded to a whole number (452) ; ecf [4]

Page 5 Mark Scheme Syllabus Paper GCE AS/A LEVEL – May/June 2014 9700 32 © Cambridge International Examinations 2014 (d) organise as table with 3 columns headed feature + Fig. 2.1 + Fig. 2.2 ; [5] max 4 for differences point of comparison Fig 2.1 Fig 2.2 cells undergoing mitosis visibility of chromosomes more chromosome / chromatids visible few(er) chromosome / chromatids not visible ; metaphase or anaphase present / (one cell in) metaphase / anaphase absent / no metaphase / anaphase ; interphase or telophase less or no telophase more or (one / two cells in) telophase ; cell walls or cell shape or cell arrangement not visible / absent or rectangular / 4 sides or scattered / irregular / random prominent / present or 6 sides / 5 sides or aligned / regular / ordered ; cell packing or air spaces or cells touching loosely packed / more spaced out / separated or more air spaces or have spaces between cells or cells not touching closely packed / less spaced out; or none or few air spaces or have no spaces between cells or cells touching ; nucleus present or all cells show a nucleus not all cells show a nucleus or some cells have a nucleus ; [max 5] [Total: 20]