Cambridge A Level Biology 9700 — 2011 May/June Paper 3 · Variant 5

This document consists of 11 printed pages and 1 blank page. DC (CW/DJ) 31767/5 © UCLES 2011 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Subsidiary Level and 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 ink. You may use a pencil for any diagrams, graphs or rough working. Do not use red ink, staples, paper clips, highlighters, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. 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. * 5 2 7 5 1 9 7 1 2 0 * BIOLOGY 9700/35 Advanced Practical Skills 1 May/June 2011 2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions. For Examiner’s Use 1 2 Total

2 9700/35/M/J/11 © UCLES 2011 For Examiner’s Use You are reminded that you have only one hour for each question in the practical examination. You should: • Read carefully through the whole of each question. • Plan your use of the time to make sure that you finish all the work that you would like to do. You will gain marks for recording your results according to the instructions. 1 When plant tissue is soaked in methylene blue the tissue is coloured blue. Ethanol affects the selective permeability of cell membranes. You are provided with: labelled contents hazard concentration / % volume / cm3 E ethanol flammable 10 40 W distilled water none – 100 labelled contents hazard details quantity P stained plant tissue methylene blue will stain your skin same cross- sectional area, stained with methylene blue and washed 3 pieces If any methylene blue comes into contact with your skin wash off immediately with water. It is recommended that you wear safety goggles/glasses. You are required to investigate the effect of the independent variable, ethanol concentration, on samples of plant tissue which have been soaked in methylene blue. You are required to carry out a serial dilution of ethanol, E, to reduce the concentration of the ethanol by half between each successive dilution.

3 9700/35/M/J/11 © UCLES 2011 [Turn over For Examiner’s Use Fig. 1.1 shows how to make the first concentration of 5% ethanol. 20 cm3 of 10% ethanol, E 5% ethanol … … … 10 cm3 of distilled water, W 10 cm3 of 10% ethanol, E Fig. 1.1 (a) (i) Complete Fig. 1.1 to show how you will make three further concentrations of ethanol, E. [3] As part of this investigation you are required to set up a suitable control. (ii) Describe how you will set up this control using the apparatus provided. … …[1] Proceed as follows (Always use blunt forceps when handling the plant tissue to avoid contact with the methylene blue.) 1. Prepare the concentrations of E as shown in Fig. 1.1 in the containers provided. 2. Label test-tubes with the concentrations of E and the control. 3. Put 5 cm3 of each dilution of E and the control into the labelled test-tubes.

4 9700/35/M/J/11 © UCLES 2011 For Examiner’s Use 4. Remove the pieces of plant tissue from the container, labelled P, and place them onto a white tile. 5. Cut the ends off each piece of plant tissue. 6. Cut the plant tissue into equal lengths. These should be between 0.75 and 1 cm in length. The pieces should not get stuck to the side of the test-tube. 7. Empty the coloured water from the container, labelled P. 8. Place the samples back into the empty container, labelled P. 9. To remove excess methylene blue change the water five times, either using a syringe or by pouring off the water. Do not touch the plant tissue. 10. Remove the pieces of plant tissue from the beaker of water and place them on a paper towel to blot off excess water. 11. Add one piece of plant tissue to each test-tube and immediately start timing. 12. Observe the test-tubes after 10 minutes. You may find it helpful to mix the contents. 13. Record your observations. (iii) Prepare the space below and record your observations. [4]

5 9700/35/M/J/11 © UCLES 2011 [Turn over For Examiner’s Use (iv) You used syringes to measure the volumes of the ethanol used. State the volume of the smallest division on the syringe … State the degree of uncertainty in using the syringe to measure the volumes. …[1] (v) Explain the effect of the ethanol on the plant tissue. … … … … … … …[3] (vi) In step 5, the ends of the pieces of plant tissue were cut off. If the ends had not been cut off how would the results have been affected? … …[1]

6 9700/35/M/J/11 © UCLES 2011 For Examiner’s Use A student carried out a similar investigation into the effect of pH on samples of coloured plant tissue. The samples were placed in different buffer solutions. After 10 minutes, the samples were removed. The buffer solutions were placed in a colorimeter to measure the percentage absorbances. The results of this investigation are shown in Table 1.1. Table 1.1 pH of buffer solutions absorbance / % 4.0 83 6.0 39 7.3 10 7.8 38 8.5 78 (b) (i) Plot a graph of the data shown in Table 1.1. [4] (ii) Another sample of plant tissue was placed in a buffer solution and the absorbance was 46%. Use your graph to estimate the pH of the buffer solution at this absorbance. … …[2]

7 9700/35/M/J/11 © UCLES 2011 [Turn over For Examiner’s Use (iii) State two variables that need to be kept the same in this investigation. Describe how to keep each of these variables the same. … … … … … …[3] [Total: 22]

8 9700/35/M/J/11 © UCLES 2011 For Examiner’s Use 2 Fig. 2.1 is a photomicrograph of a transverse section through a root. draw this quarter magnification × 40 Fig. 2.1 (a) Draw a large plan diagram of the quarter shown in Fig. 2.1. Label the xylem. [5]

9 9700/35/M/J/11 © UCLES 2011 [Turn over For Examiner’s Use Fig. 2.2 is a photomicrograph of a transverse section through a root of a different plant species. 620 µm Fig. 2.2 (b) (i) Prepare the space below so that it is suitable for you to record the observable differences between the specimens in Fig. 2.1 and in Fig. 2.2. Record your observations in the space you have prepared. [4]

10 9700/35/M/J/11 © UCLES 2011 For Examiner’s Use (ii) Use the scale bar 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. magnification × … [4]

11 9700/35/M/J/11 © UCLES 2011 For Examiner’s Use (c) You are provided with a sample of banana, labelled B. Proceed as follows 1. Rub the cut end of the banana slice onto the centre of the microscope slide. Repeat until you can see an observable smear of banana tissue. 2. Add two drops of iodine onto the smear and carefully lower the cover slip onto the banana tissue in the smear. 3. Put the paper towel over the cover slip and gently press to separate the cells. 4. Look carefully under high power to find three cells with different shapes. Make a large drawing of these three cells. Label the cell wall and any observable internal structures of these cells. [5] [Total: 18]

12 9700/35/M/J/11 © UCLES 2011 BLANK PAGE Copyright Acknowledgements: Fig. 2.1 Claude Nuridsany and Marie Perennou/Science Photo Library Fig. 2.2 J.C. Revy, ISM/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. 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 May/June 2011 question paper for the guidance of teachers 9700 BIOLOGY 9700/35 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 must be read in conjunction with the question papers and the report on the examination. • Cambridge will not enter into discussions or correspondence in connection with these mark schemes. Cambridge is publishing the mark schemes for the May/June 2011 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 AS/A LEVEL – May/June 2011 9700 35 © University of Cambridge International Examinations 2011 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 excepted) 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 ACE Analysis, Conclusions and Evaluation (skills) PDO Presentation of Data and Observations (skills) MMO Manipulations, Measurement and Observation (skills)

Page 3 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2011 9700 35 © University of Cambridge International Examinations 2011 1 (a) (i) Complete Fig. 1.1 to show how you will make three further concentrations of ethanol, E solution. [3] (labels under correct sequence of beakers) 2.5 AND 1.25 AND 0.6(25); MMO decisions 3 [1] Additional guidance Must have • % once • Concentrations at least 1 decimal place (uses serial dilution to complete three unlabelled beakers) (adds previous concentration of E to each of three beakers) 5 (%) with volume Or shown by arrow from 5(%) with volume AND the same volume transferred from first beaker to second and from second beaker to third; [1] Additional guidance Must have • cm3 once ecf • if mp 1 incorrect (adds (distilled) water / W to each of three beakers) 10 cm3 (W/water); MMO decision 2 [1] Additional guidance Must have • cm3 once ecf • if mp1 incorrect • if mp2 incorrect BUT MUST add previous concentration to second and third beakers (ii) Describe how you will set up this control using the apparatus provided. [1] (test-tube) replace E / ethanol with equal or same or 10 cm3 volume of water OR (beaker) 20 cm3 or only water; ACE improvement 1 [1] Additional guidance Do not give mark if • 10% ethanol / E Ignore • 0% must have what this is i.e. water

Page 4 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2011 9700 35 © University of Cambridge International Examinations 2011 (iii) Prepare the space below and record your observations. [4] table with all cells drawn AND heading (top or left) percent(age) conc(entration) ; [1] Additional guidance Can have • % Do not give mark if • % in cells of the headed column / row • other units e.g. mol dm–3 (heading) colour or observations or description or result(s) AW; PDO recording 2 [1] Additional guidance Do not give mark if • additional columns/rows for method/volumes of E / lengths [1] records colour / no change for 5 concentrations AND control / 0 (6); records highest concentration with deeper blue than next concentration; MMO collection 2 [1] Additional guidance Can have • minimum two recorded colours (iv) State the volume of the smallest division on syringe. State degree of uncertainty. [1] +/– AND half smallest division AND cm3/ ml; ACE interpretation 1 [1] Additional guidance Can have • rounding up or down • percentage error if shows calculation as half division / 10 or any volume X 100 Must have percentage or %

Page 5 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2011 9700 35 © University of Cambridge International Examinations 2011 (v) Explain the effect of the ethanol on the plant tissue. [3] max 3 1. (ethanol) Idea of breaks down / destroys/damages cell or cell surface / plasma membrane; 2. Idea of decreases selective permeability or increases permeability; 3. Idea of effect on protein (in cell membrane) denatures or opens channels; ACE conclusion max 3 4. Idea of effect on phospholipid(s); (vi) If the ends had not been cut off how would the results have been affected? [1] max 1 1. lengths not same; 2. more colour from ends; ACE interpretation max 1 3. colour not same;

Page 6 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2011 9700 35 © University of Cambridge International Examinations 2011 (b) (i) Plot a graph of the data shown in Table 1.1. [4] x-axis pH of buffer solutions AND y-axis absorbance / %; [1] Additional guidance Must have • units Do not give mark if • any units for pH e.g. arbitrary units (scale on x-axis) 4.0 at 0 AND one pH to 2 cm must label each 2 cm AND (scale on y-axis ) 20 to 2 cm must label each 2 cm; [1] Additional guidance ecf if no labels for O If reverse O scale must have still have 20 to 2 cm Do not give mark if • awkward scale e.g. 25 to 2 cm, 40 to 2 cm correct plotting of each point; [1] Additional guidance 4.0 83 6.0 39 7.3 10 7.8 38 8.5 78 Can have • small cross or dot in circle Do not give mark if • awkward y-axis scale • blobs or dots alone • cross too large with any part of line touching 4 mm by 4 mm square – lines point to point AND • ruled, clear sharp and • quality ruled lines, thinner than half square; PDO layout 4 [1] Additional guidance Do not give mark if • any feathery line • irregular thickness • extrapolation at either end

Page 7 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2011 9700 35 © University of Cambridge International Examinations 2011 (ii) ... the absorbance was 46%. Use your graph to estimate the pH of the buffer solution at this absorbance. [2] ACE interpretation 1 [1] one correct reading from graph; MMO decision 1 [1] readings of any TWO values from graph; (iii) State two variables that need to be kept the same in this investigation. Describe how to keep each of these variables the same. [3] MMO decision 1 [1] (selects TWO variables for one mark) 1. Idea of size of plant material 2. type or part of plant or condition (Suitable method to keep the same ) using ruler / use cork borer / Vernier callipers; use same type or same part or fresh; 1. volume of buffer use syringe / measuring cylinder / graduated pipette burette; 2. temperature; use thermostatically-controlled water-bath; ACE improvements max 2 max 2 3. time staggered start or separate experiments; [Total: 22]

Page 8 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2011 9700 35 © University of Cambridge International Examinations 2011 2 (a) Draw a large plan diagram of the quarter shown in Fig. 2.1. Label the xylem. [5] clear, sharp, unbroken lines AND no shading AND larger than 60 mm by 60 mm; PDO layout 1 [1] Additional guidance Must have • four or more lines Do not give mark if • drawn over the print of question • any line thicker – than 1mm • any feathery line • 1 ‘tail’ or overlap or gap [1] no cells drawn AND correct quarter drawn; [1] (outer layer(s)outside stele) drawn as two / three lines wider than 5mm for most of layer; MMO collection 3 [1] (central vascular tissue) drawn with two lines for endodermis AND triangular regions / extra layer adjacent; correct label with label line to xylem; MMO decision 1 [1] Additional guidance Do not give mark if • any label which is biologically incorrect e.g. from incorrect organ or animal • label within drawn area

Page 9 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2011 9700 35 © University of Cambridge International Examinations 2011 (b) (i) Prepare the space below so that it is suitable for you to record the observable differences between the specimens on Fig. 2.1 and that in Fig. 2.2. [4] organise as a table/ruled boxes AND headed Fig. 2.1 and Fig. 2.2 AND first difference opposite each other; PDO recording 1 [1] Additional guidance Fig. 2.1 Fig. 2.2 OR Fig. 2.2 Fig. 2.1 ACE interpretation max 3 [max 3] feature Fig. 2.1 Fig. 2.2 1 small(er) / only one; large(r) or seven or more; 2 vascular tissue / xylem round / circular or middle / in centre star-shape / (seven) different area / not circular or more spread; 3 endodermis present / around stele absent / none; 4 cortex or parenchyma cells large(r) / wid-er circular / round / more even sizes small(er) / narrow(er) irregular / different sizes; 5 thickened / layer under or epidermis thick(er) / wide(r) / large(r) curled / bent; 6 epidermis or hairs / trichomes present / has hairs / trichomes / many absent / no / few hairs / trichomes or rough; 7 radius / size 1.25mm / smaller 1.7 mm / larger; 8 AVP;

Page 10 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2011 9700 35 © University of Cambridge International Examinations 2011 (ii) Use the scale bar to calculate the magnification of Fig. 2.2. [4] measures scale bar in mm; 14 or 14.5 or 15 or 15.5 or 16 mm MMO collection 1 [1] Additional guidance Do not give mark if • metres (converts to same units) (mm to µm) X 1000 14 000 or 14 500 or 15 000 or 15 500 or 16 000 ecf if mp1 incorrect MMO decision 1 [1] OR (converts µm to mm) 620/1000 shows division of converted scale bar measurement by 620; OR scale bar measurement in mm / 0.620; [1] Additional guidance ecf if no units or incorrect measurement or no or incorrect conversion PDO display 2 [1] whole number only; 22 or 23 or 24 or 25 or 26

Page 11 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2011 9700 35 © University of Cambridge International Examinations 2011 (c) ... find three cells with different shapes. Make a large drawing of these cells. Label the cell wall and any observable internal structures of these cells. [5] clear, sharp, unbroken lines AND no shading AND largest cell 50 mm at widest point; PDO layout 1 [1] Additional guidance Must have • three or more enclosed areas Do not give mark if • drawn over the print of question • any line thicker – than 1 mm • any feathery line • 0 ‘tails’ or overlaps or gaps if one line for cell walls check cell walls only. [1] only three cells drawn AND all different shapes; MMO collection 2 [1] three cells with cell walls drawn as double lines; PDO recording 1 [1] at least one cell contains three or more substantial inclusions drawn; correct label with label lines to cell wall AND starch (grain) or nucleus; MMO decision 1 [1] Additional guidance Do not give mark if • any label which is biologically incorrect e.g. from incorrect organ or animal • label within drawn area [Total: 18]