Cambridge A Level Biology 9700 — 2010 May/June Paper 3 · Variant 2

This document consists of 13 printed pages and 3 blank pages. DC (SHW 00478 5/09) 15991/6 © UCLES 2010 [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 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. You are advised to spend one hour on each question. * 1 4 8 3 5 7 3 7 3 1 * BIOLOGY 9700/32 Paper 32 Advanced Practical Skills May/June 2010 2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions For Examiner’s Use 1 2 Total

9700/32/M/J/10 © UCLES 2010 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 and then plan your use of the time to make sure that you finish all of the work that you would like to do. You will gain marks for recording your results according to the instructions. 1 Yeast cells contain enzymes which catalyse the breakdown of glucose to produce carbon dioxide and water. The carbon dioxide reacts with water and forms a weak acid. Bromothymol blue is a pH indicator and changes colour as shown in Table 1.1. Table 1.1 pH colour of bromothymol blue 8 blue 7 green 6 yellow You are required • to immobilise the yeast cells in sodium alginate beads • to follow a student’s procedure to investigate the independent variable, changing the surface area of the beads. You are provided with • 15 cm3 of yeast suspension, labelled Y • 15 cm3 of 2.0 % sodium alginate solution, labelled S • 50 cm3 of 1.5 % calcium chloride solution, labelled C • 40 cm3 of 2.0 % glucose solution, labelled G • 50 cm3 of bromothymol blue, labelled B • 20 cm3 of sodium hydroxide solution, labelled A 1. Put 20 cm3 of C into a large test-tube. 2. Put 5 cm3 of S into a small beaker or container. 3. Collect 5 cm3 of Y from below the froth and put it into the same container as S. Mix well. 4. Use a 5 cm3 syringe to collect 2 cm3 of the mixture S and Y. 2

3 9700/32/M/J/10 © UCLES 2010 [Turn over For Examiner’s Use 5. Suspend the 5 cm3 syringe over the large test-tube containing C as shown in Fig. 1.1. mixture S and Y gently press down with thumb 5 cm3 syringe barrel resting on top of large test-tube test-tube calcium chloride solution, C Fig. 1.1 6. Gently press down on the plunger of the syringe with your thumb to release a drop into solution C. The drop should form a bead. 7. Repeat step 6 to make the number of beads that you think you will need. 8. Tip the contents of the large test-tube into a Petri dish or shallow container.

4 9700/32/M/J/10 © UCLES 2010 For Examiner’s Use You will need to calculate the mean surface area of the beads. Use blunt forceps to pick up the beads. To do this • decide on the number of beads you will measure • use the 2 mm × 2 mm grid to measure each bead • calculate the surface area of each bead using the formula surface area = 4r2 where  = 3.14, r = radius of a bead • calculate the mean surface area of the beads. (a) (i) Prepare the space below to show your measurements and calculations. Show all the steps in your calculation of the mean. mean surface area of the beads …mm2 [5]

5 9700/32/M/J/10 © UCLES 2010 [Turn over For Examiner’s Use A student suggested that it was possible to investigate the independent variable, surface area, by changing the number of beads. The maximum number of beads used was 20. Decide the other numbers of beads to use and state the different number of beads you will use. … … Carry out the student’s procedure. 9. Label as many small test-tubes as you will need with the number of beads for each test-tube. 10. Put 10 cm3 of solution G into each test-tube. 11. Put 1 cm3 of B into each test-tube. Put the bung in each test-tube in turn and mix. 12. If the contents of the test-tube are not blue, add one drop at a time of A to the contents of each test-tube to turn them all the same blue colour. 13. Put the required number of beads into each test-tube. 14. Put the bung in each test-tube in turn and mix contents. Mix every 2 minutes for 6 minutes. 15. Record your observations after each 2 minutes, up to 6 minutes. (ii) Prepare the space below to record your observations. [7]

6 9700/32/M/J/10 © UCLES 2010 For Examiner’s Use (iii) The student realised that there were two independent variables in this procedure. State the two independent variables. … … [1] (iv) Suggest how you would make three improvements to the student’s procedure. … … … … … … … [3] A student set up the apparatus as shown in Fig. 1.2 as another way to measure the carbon dioxide produced by immobilised yeast cells over a period of 75 minutes. The student measured the distance the liquid moved in the capillary tubing. beads coloured drop of liquid scale Fig. 1.2

7 9700/32/M/J/10 © UCLES 2010 [Turn over For Examiner’s Use The student’s results are shown in Table 1.2. Table 1.2 time / min total distance moved by the liquid in the capillary tube / mm 0 0 15 3 30 10 45 18 60 19 75 19 (b) Describe and explain the results shown in Table 1.2. … … … … … … … [3] [Total: 19]

8 9700/32/M/J/10 © UCLES 2010 For Examiner’s Use 2 M1 is a slide of a stained transverse section through a plant organ. (a) (i) Draw a large plan diagram of a half of the specimen as shown in Fig. 2.1. draw this half Fig. 2.1 Label the xylem and the cortex. [5]

9 9700/32/M/J/10 © UCLES 2010 [Turn over For Examiner’s Use (ii) Make a high-power drawing of • a group of three complete touching xylem vessels and • a group of three complete touching cortex cells. Label a cell wall and a lumen. xylem vessels cortex cells [5]

10 9700/32/M/J/10 © UCLES 2010 For Examiner’s Use Fig. 2.2 is a photomicrograph showing part of an organ from a plant of a different species. X Fig. 2.2 The actual length of the line X is 1900 μm. (b) (i) Calculate the magnification of the specimen shown in Fig. 2.2. Show all the steps in your calculation. [3]

11 9700/32/M/J/10 © UCLES 2010 [Turn over For Examiner’s Use (ii) Prepare the space below so that it is suitable for you to record the observable differences between the specimens on slide M1 and in Fig. 2.2. Record your observations in the space you have prepared. [4]

12 9700/32/M/J/10 © UCLES 2010 For Examiner’s Use A student investigated water absorption by a plant. The apparatus was set up by the student as shown in Fig. 2.3. water level at start water added after each hour to top up to the water level at start water level at start water level after each hour Fig. 2.3

13 9700/32/M/J/10 © UCLES 2010 For Examiner’s Use The volume of water added to top up the water level was recorded each hour for a total of 5 hours. From this data the student calculated the volume of water absorbed by the plant. The student’s results are shown in Table 2.1. Table 2.1 time / hours volume of water absorbed / cm3 hr −1 1 0.9 2 1.5 3 2.1 4 2.3 5 1.6 (c) Plot a graph of the data shown in Table 2.1. [4] [Total: 21]

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16 9700/32/M/J/10 © UCLES 2010 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.

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the May/June 2010 question paper for the guidance of teachers 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 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 2010 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 2010 9700 32 © UCLES 2010 Question Expected Answers Additional Guidance Marks 1 (a) (i) Calculate the surface area of each bead and the mean surface area of beads. MMO decision 1 1. 5 or more (bead radii/diameters); [1] MMO collection 1 2. measures diameter or records radius AND units mm; Reject any measurements not whole number of mm Reject 6 mm or more for diameter or 3 mm or more for radius [1] ACE interpretation 1 3. one correct calculation for one bead surface area; [1] 4. shows addition of bead measurements divided by number measured or each surface area added together and divided by number; [1] PDO display 2 5. answer no more than 3 sig. figs.; [1]

Page 3 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2010 9700 32 © UCLES 2010 Question Expected Answers Additional Guidance Marks (ii) Prepare the space below to record your observations. 1. table with all cells drawn (heading top/left) AND surface area (/)mm2 or no. of beads; Reject if units in body of table [1] PDO recording 2 (heading) 2. colour/observation; [1] 3. only records at 2, 4 and 6 (minutes); [1] MMO collection 2 (highest no. of beads) 4. yellow/green; [1] 5. surface area recorded; [1] 6. use 20 beads in one tube and at least 3 different numbers of beads; [1] MMO decisions 3 7. even range; [1] (iii) The student realised that there were two independent variables in this procedure. State the two independent variables. ACE interpretation 1 surface area or number of beads AND enzyme or yeast concentration/quantity; Reject more than two variables [1]

Page 4 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2010 9700 32 © UCLES 2010 Question Expected Answers Additional Guidance Marks (iv) Suggest how you would make three improvements to the student’s procedure. idea of cubes with equal volume of yeast; Reject amount [1] idea of equal shaking; repeat measurements AND mean or average; colorimeter/white card or pH paper or meter; separate beads using Petri dish/larger container; use thermostatically-controlled water-bath; ACE improvements 3 idea keep time the same e.g. stagger start or have separate experiments; [max 2] use more beads or more surface areas;

Page 5 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2010 9700 32 © UCLES 2010 Question Expected Answers Additional Guidance Marks (b) Describe and explain the results shown in Table 1.2. 1. (in context of data) stops increasing or levels off or stops or stays constant or no more carbon dioxide or reaction stops; [1] (in any correct context use of) 2. enzyme or catalase or active sites or ESCs; ACE conclusions 3 3. glucose or substrate fits into active sites or forms ESCs or (slowing or stops) lack of glucose or substrate or glucose not high enough or build up of product or ethanol lack of oxygen build up of carbon dioxide change in pH carbon dioxide dissolves into glucose or substrate or solution or water; [max 2] Total [19]

Page 6 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2010 9700 32 © UCLES 2010 Question Expected Answers Additional Guidance Marks 2 (a) (i) Draw a large plan diagram of a half of the specimen as shown in Fig. 2.1. Label xylem and the cortex. PDO layout 1 clear, sharp, (not thicker than grid line for whole line) unbroken lines AND no shading AND large 5 cm or more from centre of stele to epidermis; [1] no cells AND drawn only half with detail (shown by epidermis line); Reject if overlaps the text of question [1] MMO collection 2 endodermis shown by two lines AND length between epidermis and endodermis is at least twice the diameter of stele; [1] draws region of xylem central; [1] MMO decision 2 Reject if any label is biologically incorrect. one correct label with label line from xylem or cortex; Reject if any writing on drawing [1]

Page 7 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2010 9700 32 © UCLES 2010 Question Expected Answers Additional Guidance Marks (ii) Make a high-power drawing of a group of three complete touching xylem vessels and a group of three complete touching cortex cells. Reject all marks if only two cells drawn except label mark? PDO layout 1 1. clear, sharp, (not thicker than grid line for whole line) unbroken lines AND no shading AND smallest group of complete touching cells will not fit inside 6 × 6 cm grid; [1] only 6 complete cells drawn AND two groups of 3 touching cells; [1] MMO collection 2 cell wall in at least one cell drawn angular in one group of three AND other group of cells rounded; [1] (xylem) thicker cell wall than (cortex) cell walls; Measure thickest on both. Allow only if cell walls drawn as double lines for both groups of cells [1] MMO decision 2 correct labels with label lines to lumen in xylem AND any cell wall; Reject if any writing on drawing [1]

Page 8 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2010 9700 32 © UCLES 2010 Question Expected Answers Additional Guidance Marks (b) (i) Calculate the magnification of the specimen shown in Fig. 2.2. Actual length of line X = 1900 µm. MMO collection 1 measures line X correctly with mm or cm; [1] show in last calculation before answer 52 or 52.5 or 53 or 53.5 or 54 with 1.9 OR 5.2 or 5.25 or 5.3 or 5.35 or 5.4 with 0.19 OR 52000 or 52500 or 53000 or 53500 or 54000 with 1900; [1] ACE interpretation 2 correct calculation of any figure divided by 1900 or 1.9 or 0.19; [1] (ii) Prepare the space below so that it is suitable for you to record the observable differences between the specimens on slide M1 and in Fig. 2.2. organise as a table/venn diagram/ruled connected boxes AND headed M1 and Fig 2.2 AND all comparative statements opposite each other; [1] PDO recording 2 only differences recorded; [1]

Page 9 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2010 9700 32 © UCLES 2010 feature M1 Fig. 2.2 1. xylem shape star-shape; 2. xylem position centre; 3. phloem clearer or can see or present not clear or cannot see or absent; 4. pith absent present; 5. thickened cells under epidermis absent thick ring/present; 6. epidermis layers one or thin(ner) two or thick(er); ACE interpretation 2 7. size cortex stele/xylem larger/wider/thicker or more smaller/narrower/ thinner or less smaller/narrower/ thinner or less larger/wider/thicker or more; Reject all ticks with crosses unless have key [max 2]

Page 10 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2010 9700 32 © UCLES 2010 Question Expected Answers Additional Guidance Marks (c) Plot a graph of the data shown in Table 2.1. O x-axis time /hr(s) or hour(s) y-axis AND vol(ume) /cm3 hr-1; [1] S scale as 1hr to 2 cm (allow no 0) Allow 1 at origin as long as 1hr to 2 cm must label origin. AND 0.5 cm3 to 2 cm; Allow 0. 5 at origin must label origin if not 0 [1] P correct plotting with crosses or dot in circle; Intersection of cross must be clear to show plot [1] PDO layout 4 L straight line between all points or smooth curve through all points; Quality – no thicker than on grid, not feathery for the complete line Joining plots • Ruled lines plot to plot • Curve through all plots Extrapolation • Not beyond x- or y-axis • If in context of data correct to go to 0,0 must be within 2 mm of 0 If not correct in context of data then no extrapolation at either end of data Must have units Reject S if awkward scale Reject P plotting if awkward scale Reject if only blobs or dots or blobs in circles Reject if not five plots [1] Total [21]