Cambridge A Level Biology 9700 — 2009 May/June Paper 3 · Variant 1

This document consists of 11 printed pages and 1 blank page. SPA (SHW 00338 7/08) V00355/6 © UCLES 2009 [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. * 8 2 4 0 0 7 7 1 6 5 * BIOLOGY 9700/31 Paper 31 Advanced Practical Skills May/June 2009 2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions For Examiner’s Use 1 2 Total

9700/31/M/J/09 © UCLES 2009 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 the work that you would like to do. You must record all your results and will not be penalised if these results are not as expected. 1 Yeast cells contain enzymes, which catalyse the breakdown of glucose to produce ethanol and carbon dioxide. These products change the environment of the yeast cells and can affect their activity and survival. The carbon dioxide when dissolved forms a weak acid so the more carbon dioxide that is released the more acid will be formed. You are required to investigate the effect of different concentrations of ethanol on the activity of yeast cells by measuring the change in pH, using Universal Indicator paper. You are provided with: • five labelled tubes each containing 0.7 g of dried yeast • at least 50 cm3 ethanol, labelled E • at least 100 cm3 20% glucose solution, labelled G • at least 100 cm3 distilled water, labelled W Ethanol is harmful and highly flammable. If any comes into contact with your skin, wash immediately under cold water. It is recommended that you should wear eye protection. Keep the ethanol covered when you are not using it. It is important to find the pH of the glucose solution and the ethanol before starting the investigation. Place a small piece of the Universal Indicator paper on a white tile. Using a clean pipette, place a drop of glucose solution onto the paper. Use the colour chart to identify the pH. Repeat, after cleaning the pipette, to find the pH of ethanol. (a) (i) Record the colour of the Universal Indicator paper and the pH for the glucose solution and the ethanol below. [2] 2

3 9700/31/M/J/09 © UCLES 2009 [Turn over For Examiner’s Use Clean and dry the tile. You are going to change the independent variable, the concentration of ethanol. Table 1.1 shows how to make up two of the concentrations you should use. Table 1.1 volume of distilled water / cm3 volume of ethanol / cm3 percentage concentration of ethanol 10 0 0 6 4 40 (ii) Using the information in Table 1.1, decide which other concentrations to make and complete Table 1.2 including the concentrations from Table 1.1. Table 1.2 tube number volume of distilled water / cm3 volume of ethanol / cm3 percentage concentration of ethanol [3]

4 9700/31/M/J/09 © UCLES 2009 For Examiner’s Use Tubes 1 to 5 each contain the same mass (0.7 g) of dried yeast. 1. Adding the water before the ethanol, use the syringes provided to make up the ethanol concentrations in the correct tubes. 2. Use the beaker, or other container provided, to make a water bath with warm water between 45 °C and 50 °C. 3. Shake the tubes carefully to thoroughly mix the ethanol and water. 4. Place the tubes into the warm water and leave them for at least 5 minutes. 5. Use the marker pen provided to label the white tile as shown in Fig. 1.1. 6. Arrange two rows of small pieces of Universal Indicator paper on the white tile as shown in Fig. 1.2. tube 1 min 1 2 3 4 5 10 min tube 1 min 1 2 3 4 5 10 min Universal Indicator paper Fig. 1.1 Fig. 1.2 7. After the tubes have been in the water bath for at least five minutes start a stopwatch or stop clock or note the time on a clock. 8. Use a clean 10 cm3 syringe to put 10 cm3 of the glucose solution into each tube starting with tube 1. Each time shake the tube well and return it to the warm water bath. 9. When the clock shows one minute, use the glass rod to remove a drop from the contents of tube 1 and place the drop onto the correct piece of Universal Indicator paper. 10. Clean the glass rod and use it to remove a drop as described in step 9 from the other four tubes. 11. When the clock shows 10 minutes, use the glass rod to take further drops as described in step 9.

5 9700/31/M/J/09 © UCLES 2009 [Turn over For Examiner’s Use (iii) Prepare the space below, to record both the colour of each piece of Universal Indicator paper and the pH. [4] (b) (i) Identify a significant source of error in this investigation. … … [1] (ii) You used syringes to measure the volumes of ethanol and water. State the volume of the smallest division on the syringe ……………… State the degree of uncertainty ……………………………… [1]

6 9700/31/M/J/09 © UCLES 2009 For Examiner’s Use A student decided to investigate the effect of temperature on the activity of enzymes in yeast. The student measured the activity of the enzymes by counting the number of bubbles of carbon dioxide, which were released in three minutes. The results of the student’s investigation are shown in Table 1.3. Table 1.3 temperature / °C enzyme activity / mean number of carbon dioxide bubbles released per minute 15 5 20 7 30 11 35 15 40 18 (c) (i) Plot a graph of the data shown in Table 1.3. [4] (ii) From the graph, estimate the enzyme activity at 25 °C. … [1]

7 9700/31/M/J/09 © UCLES 2009 [Turn over For Examiner’s Use (iii) Suggest how the student should make sure that the results of this investigation are as accurate as possible, … … … … as reliable as possible. … … … … [3] In carrying out this investigation the student made the hypothesis that: The activity of the enzymes in yeast increases as temperature increases. (d) State whether you think that this hypothesis is supported by the student’s results. Explain your answer. … … … … [2] [Total: 21]

8 9700/31/M/J/09 © UCLES 2009 For Examiner’s Use 2 J1 is a slide of a stained transverse section of a plant organ. (a) Draw a large, low power, plan diagram of a quarter of the specimen as shown in Fig. 2.1. quarter Fig. 2.1 Label the phloem and xylem in a vascular bundle. [5]

9 9700/31/M/J/09 © UCLES 2009 [Turn over For Examiner’s Use (b) Fig. 2.2 is a photomicrograph showing some cells from a transverse section of a root viewed under high-power. magnification × 400 Fig. 2.2 (i) Calculate the mean width of the cells shown in Fig. 2.2 in micrometres (
m). Mark clearly on Fig. 2.2 the cells which you used in your calculation. Show your working. …
m [4]

10 9700/31/M/J/09 © UCLES 2009 For Examiner’s Use (ii) Fig. 2.3 is an outline of a longitudinal section of a root. Label with a label line and the letter X, the area on Fig. 2.3 from which the section shown in Fig. 2.2 may have been cut. central vascular tissue root cap Fig. 2.3 [1] Fig. 2.4 is a photomicrograph showing some cells from a transverse section from another part of the same root taken under high-power. magnification × 400 Fig. 2.4

11 9700/31/M/J/09 © UCLES 2009 For Examiner’s Use (c) From Fig. 2.4 make a large, labelled drawing of three complete cells which are touching and include at least one cell with a nucleus. Show clearly on Fig. 2.4 the three cells, which you have drawn. [5] (d) Prepare the space below so that it is suitable for you to show the differences between the cells shown in Fig. 2.2 and Fig. 2.4. Record your observations in the space which you have prepared. [4] [Total: 19] [Paper total: 40]

12 9700/31/M/J/09 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 2009 question paper for the guidance of teachers 9700 BIOLOGY 9700/31 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. • CIE will not enter into discussions or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the May/June 2009 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 A/AS LEVEL – May/June 2009 9700 31 © UCLES 2009 Question Expected Answers Additional Guidance Mark 1 (a) (i) Record colour of paper and pH for glucose and ethanol. MMO collection 2 with reference to glucose and ethanol record a colour for each; one colour matches one pH or between two pH values; pH 5.2 5.5 5.8 6.1 6.4 6.7 colours brown/ orange/yellow pink/ brown pink/ purple/violet/lilac/magenta/ red/burgundy/plum OR (if no colours given) with reference to glucose and ethanol two pH values from scale, same or different; Credit ONLY the given pH values Credit less than/<5.2 with yellow or more than/>6.7 with purple/AW [1] [1] (ii) Decide which other concentrations to make and complete the table. MMO decisions 3 (%) 0 and 40 plus any three which are evenly/serially spaced e.g. 0, 20, 30, 40, 50 or 0, 10, 20, 30, 40; correct volumes used to dilute up to 10 cm3 AND correct %; (tubes listed) either most dilute/lowest % to most concentrated/highest % or most concentrated to most dilute; Ignore where 0 is listed [1] [1] [1]

Page 3 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – May/June 2009 9700 31 © UCLES 2009 (iii) Prepare space to record colour of each piece of paper and pH. PDO recording 2 MMO collection 2 single table AND all cells drawn AND %/percent(age) (top or left of data heading only); (headings) colour AND pH; two different colours for two tubes recorded; (collected data/colours or pH) clearly for 1 min(ute)/start and 10 min(utes)/end; heading heading heading heading heading Do not credit if % in body of table Do not credit if pH/colour in body of table Collection of colour for two tubes. Credit colour differences such as light orange vs orange Credit colours only or pH values only – looking for clear collection of 1 minute and 10 minutes Credit for one tube of data for 1 min and 10 min as minimum [1] [1] [1] [1] (b) (i) Identify a significant error – read complete answer for any correct one. ACE interpretation 1 judging colour/matching exact colours/colours very close together/pH paper narrow scale/colours not on scale/between colours/identification of colours; idea of timing not the same/different/described; loss of CO2/gas/AW; Do not credit timing unqualified [max 1] (ii) State degree of uncertainty (of syringes). ACE interpretation 1 +/– AND half total division AND cm3; Error with one reading is +/– half the smallest division with correct units as use syringe to measure single volume and release al contents [1]

Page 4 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – May/June 2009 9700 31 © UCLES 2009 (c) (i) Plot a graph of the data shown. PDO layout 4 O x-axis temp(erature) (/)°C AND y-axis (number/no. of) bubbles/min or per min or min–1; S scale as 10°C to 2 cm and 5 to 2 cm; Credit origin other than 0 e.g. 5/10/15 if labelled Credit unlabelled origin only if should be 0 P plotting correct points using crosses/dots in circles only; Do not credit if an extra point plotted at 25°C. No cross larger than x or more than one blob larger than o. All plots must be on horizontal lines except for the 4 to 2 cm scale points within a square of the intersection/centre of dot must not touch horizontal lines. L line of best fit (no more than 2 points on one side)/points joined with straight line; Quality – line no thicker than 1 mm thick max Complete line should be smooth/not feathery. Do NOT credit bubbles min1 Do not credit S if awkward scale or if less than half grid on y or x axis Do not credit P plotting if awkward scale or if only blobs/dots/blobs in circles Do not credit dot with cross Credit x in circles Credit line of best fit – no extrapolation Joins point to point no extrapolation beyond first and last points [1] [1] [1] [1] (ii) Estimate enzyme activity at 25°C. ACE interpretation 1 correct reading using candidate’s graph at 25°C AND bubbles per minute or min–1; Credit whole number of bubbles only Credit 0.5 up or down [1]

Page 5 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – May/June 2009 9700 31 © UCLES 2009 (iii) Suggest how to make sure results are as accurate as possible and as reliable as possible. ACE improvements 1 control of any variable/use a water bath/same type of yeast/same volume of yeast/keep time the same/stagger the start/have separate experiments/(keep pH same) using buffer; Accuracy: collect volume using measuring cylinder/gas syringe/video to count bubbles/AW; Reliability 1: increase number or range of temperatures/2 extra named examples; Reliability 2: repeat more/several times/twice/obtain three readings/(at each temp); Reliability 3: calculate mean; Credit in either accuracy or reliability Do not credit ref to enzymes or amount of yeast Accuracy: (change method of measuring to obtain results as close as possible to the true value) Reliable: (to have results which are as repeatable as possible) Credit only two reliability marks [1] [1] [1] [1] [1] [max 3] (d) State whether you think the hypothesis is supported by the student’s results. Explain your answer. ACE conclusion 2 hypothesis true/yes/OR re-states the hypothesis OR partly true/true but only…; Either (true for) 15 to 40°C as increases from 5 to 18/ or any two correct temps within 15 and 40/41 with two correct numbers of bubbles/may have two temps and difference in number of bubbles/calculated rate of increase/gradient; OR ONLY TRUE: 15 to 40°C as increases from 5 to 18/ or any two correct temps with two correct numbers of bubbles/may have two temps and difference in number of bubbles; idea that (NOT TRUE) below 15°C and/or above 40°C as no data; Needs clear statement Do not credit idea that totally wrong Credit temp as long as units are present once [1] [max 1] [Total: 21]

Page 6 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – May/June 2009 9700 31 © UCLES 2009 Question Expected Answers Additional Guidance Mark 2 (a) Draw a large, low power, plan diagram of quarter. Label phloem and xylem in a vascular bundle. PDO layout 1 MMO collection 3 MMO decision 1 clear, sharp, unbroken lines AND no shading AND cannot fit totally within the 6 cm by 6 cm grid; no cells AND outline irregular; clear layer/layers below cortex AND cortex at widest is thicker than narrowest point of layer below; Ignore epidermis (2 lines) at least 3 complete vascular bundles AND length of largest vascular bundle twice length of smallest vascular bundle; Do not credit if whole section drawn phloem and xylem are labelled on the layer below cortex or a vascular bundle as shown by candidate; [1] [1] [1] [1] [1] (b) (ii) Calculate mean width of the cells in micrometres. Mark clearly the cells you used. Show your working. cell(s) marked on Fig 2.2 AND Credit separate or one line across cells selected selected cell(s) measured with mm or cm shown; Do not credit if line is not on the fig. Do not credit measurements in metres or micrometres. MMO collection 1 MMO decision 1 PDO display 2 5 or more complete cells measured; Credit even if not shown on Fig. 2.2. Do not credit if partial cells included. shows any number of measurements added up or line measurement and divided by number of measurements/cells; Check recorded cell measurements are at or between 0.5 to 5.5 cm or 5 mm to 55 mm Ignore more sig. figs. OR if single line is drawn check measurement of line is less than 170 mm/ 17 cm Ignore the answer [1] [1] [1]

Page 7 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – May/June 2009 9700 31 © UCLES 2009 divides by 400 and multiplies by (cm) 10 000/104 or (mm) 1000/103; E.g. cell 1 = 20 mm cell 2 = 21 mm cell 3 = 17 mm cell 4 = 16 mm cell 5 = 21 mm Mean = 5 21 16 17 21 20 + + + + = 19 mm 19 mm = 19 × 1000 µm = 19 000 Mag. = ×400 Actual = 400 19000 = 475 Must show division by 400 [1] (ii) Label with a line and the letter X, the area from which section may have been cut. ACE conclusion 1 Credit anywhere between bracket for central vascular tissue and end of label line for root cap Do not credit if longitudinal section shown [1]

Page 8 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – May/June 2009 9700 31 © UCLES 2009 (c) Make a large labelled drawing of 3 complete cells which are touching, include at least 1 cell with a nucleus. clear, sharp, AND unbroken lines Ignore cell walls crossing over as cells appear to overlap. no shading AND Ignore nucleus. Do not credit stippled cytoplasm or shaded cell walls. cannot fit totally into the 6 cm by 6 cm grid; 3 complete cells marked on Fig. 2.4 AND drawn 3 complete cells touching; Ignore additional incomplete cells. 2 nuclei each drawn near to one edge of cell; Nucleus not in centre of cell. Do not credit if additional detailed organelles or cell wall details e.g. plasmodesmata have been drawn which are not visible. PDO layout 1 MMO collection 1 PDO recording 1 MMO decisions 2 space between outer wall and cytoplasm shown in part of two cells; Ignore labelling. nucleus and cell wall correctly labelled; Do not credit nucleolus. [1] [1] [1] [1] [1]

Page 9 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – May/June 2009 9700 31 © UCLES 2009 (ii) Show the differences between the cells in Fig. 2.2 and Fig. 2.4. PDO recording 1 organise as a table/ Venn diagram/ ruled connected boxes headed comparative statements opposite each other; [1] ACE interpretation 3 feature Fig. 2.2 Fig. 2.4 nuclei Ignore ref. to nuclear membrane/size few/less distinct/less stained more/dense/obvious/ more stained; chromosomes/dividing cells/mitosis/anaphase interphase present fewer in interphase not visible all in interphase; cytoplasm/ plasma membrane more/fills cells not visible/pulled away less/does not fill cells/ visible/pulled away; size/ number of cells Credit more (tightly packed) smaller/calculated mean/ecf/more larger/calculated more than Fig 2.2/fewer; shape of cells have oval/corners/angular/h exagonal rounded/AW; (Intercellular) spaces/gaps fewer/more/larger; Credit either way [max 3] [Total: 19]