Cambridge A Level Biology 9700 — 2007 Oct/Nov Paper 3 · Variant 1

This document consists of 8 printed pages. SP (SLM/CGW) T30185/5 © UCLES 2007 [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 in the spaces provided on the Question Paper. 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 both questions. The number of marks is given in brackets [ ] at the end of each question or part question. You are advised to spend an hour on each question. At the end of the examination, fasten all your work securely together. * 4 5 6 5 2 1 0 5 3 9 * BIOLOGY 9700/31 Paper 31 Advanced Practical Skills October/November 2007 2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the confidential instructions For Examiner’s Use 1 2 Total

2 9700/31/O/N/07 For Examiner’s Use © UCLES 2007 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. 1 The enzyme catalase is found in a wide range of living organisms. It catalyses the breakdown of hydrogen peroxide which is a highly reactive by-product of respiration. 2H2O2 catalase 2H2O + O2 The rate of this reaction can be monitored by measuring the rate of bubble production of oxygen gas. You are required to investigate the effect of potato tissue extract on hydrogen peroxide. Take care. Hydrogen peroxide is corrosive when in contact with skin or eyes. Wear safety glasses while performing this experiment. You are provided with 40 cm3 of water, labelled beaker 1. You are provided with 20 cm3 of 20 vol H2O2, labelled beaker 2. You are also provided with 10 cm3 of potato tissue extract containing catalase, labelled C. You are going to make a serial dilution of the 20 vol H2O2. • Label two small beakers 3 and 4. • Into beaker 3 place 10 cm3 of 20 vol H2O2 from beaker 2. • Add an equal volume of water from beaker 1 to produce 10 vol H2O2. • Into beaker 4 place 10 cm3 of 10 vol H2O2 from beaker 3. • Add an equal volume of water from beaker 1 to produce 5 vol H2O2. You are provided with the apparatus as shown in Fig. 1.1. beaker or test-tube rack to support large test-tube use petroleum jelly to make airtight if no bubbles appear water test-tube large test-tube Fig. 1.1 • Place 4 cm3 of 20 vol H2O2 from beaker 2 into the large test-tube. Add 1 cm3 of potato extract solution C. Immediately place the bung of the delivery tube firmly into the large test-tube. Bubbles of gas should come from the end of the delivery tube. • If no bubbles appear then use petroleum jelly to make the delivery tube airtight.

3 9700/31/O/N/07 [Turn over For Examiner’s Use © UCLES 2007 (a) Determine the number of bubbles produced in an appropriate length of time. Repeat the process with solutions from beakers 1, 3 and 4. (i) Record your results in the space below. [2] (ii) Identify the most significant source of error in the collection of your data. … …[1] (iii) Describe how you could modify your experiment to make the results more reliable. … … … …[3] (b) A student carried out a similar experiment. The student used a constant concentration of hydrogen peroxide but used pieces of potato tissue of varying surface area. (i) Describe how you would prepare the potato pieces. … … … …[3]

4 9700/31/O/N/07 For Examiner’s Use © UCLES 2007 Table 1.1 shows the data the student recorded. Table 1.1 volume of potato tissue / cm3 surface area of potato tissue / cm2 time taken to produce 40 cm3 of gas / secs 1 1 180 1 2 110 1 4 62 1 8 27 (ii) Suggest a control for this experiment. Give a reason for this control. … … …[2] (iii) Plot a graph of the student’s data on the grid below to show the effect of surface area on gas production. [4]

5 9700/31/O/N/07 [Turn over For Examiner’s Use © UCLES 2007 (iv) Describe the pattern shown by the results. … …[1] (v) Using your knowledge of enzymes and the information provided, explain the pattern shown by the results. … … …[2] (vi) Use your graph to determine the time taken for a piece of potato of 5.5 cm2 to evolve 40 cm3 of gas. …[2] (vii) Calculate the rate of reaction in cm3 of gas per second for a piece of potato of 5.5 cm2. …[1] (c) Describe how you would set up and perform a similar experiment to determine the effect of temperature on the rate of the reaction. … … … … … … … … … …[4] [Total: 25]

6 9700/31/O/N/07 For Examiner’s Use © UCLES 2007 2 (a) You are provided with a stage micrometer scale on a microscope slide. The 1 cm stage scale is divided into 100 divisions. The length of each division is 0.1 mm. Calculate the length of each division in micrometres. Show your working. …µm [1] (b) (i) Your microscope has been fitted with an eyepiece graticule. J1 is a transverse section of a stem. Carefully examine the section under the high-power of your microscope. Put a ring around the number written on the objective lens. × 40 4 mm
 ˝ other … Identify a large, empty xylem vessel and adjust the slide so that the xylem vessel is in the centre of your field of vision. Count the number of divisions of the eyepiece graticule across the diameter of the xylem vessel. number of divisions … (ii) Remove the slide and replace it with the stage micrometer scale. Using the same magnification, adjust the focus until you can see the eyepiece graticule on top of the stage scale. Explain why the stage scale appears larger than the eyepiece graticule. … … …[1] (iii) Count the number of eyepiece graticule divisions that fit into one stage scale division. number of eyepiece graticule divisions … Use this information to calculate the actual width between each division on the eyepiece graticule. Show your working. …[2]

7 9700/31/O/N/07 [Turn over For Examiner’s Use © UCLES 2007 (iv) Calculate the actual diameter of the xylem vessel. …[2] (c) Make a large, low-power, labelled plan diagram of one quarter the section, J1. [5]

8 9700/31/O/N/07 For Examiner’s Use © UCLES 2007 (d) Make a large, high-power, labelled drawing to show the cells present in a vascular bundle including a phloem sieve tube and the cells immediately next to it. No more than eight cells should be drawn. [4] [Total: 15] 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 October/November 2007 question paper 9700 BIOLOGY 9700/31 Paper 31 (Advanced Practical 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. All Examiners are instructed that alternative correct answers and unexpected approaches in candidates’ scripts must be given marks that fairly reflect the relevant knowledge and skills demonstrated. 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 October/November 2007 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

Page 2 Mark Scheme Syllabus Paper GCE A/AS LEVEL – October/November 2007 9700 31 © UCLES 2007 Skill Total marks Breakdown of marks Question 1 Question 2 Successful collection of data and observations 8 marks 3 5 Manipulation, measurement and observation 16 marks Nature of measurements or observations 8 marks 6 2 Recording data and observations 4 marks 2 2 Display of calculation and reasoning 2 marks 0 2 Presentation of data and observations 12 marks Data layout 6 marks 4 2 Interpretation of data or observations and identifying sources of error 6 marks 5 1 Drawing conclusions 3 marks 2 1 Analysis, conclusions and evaluation 12 marks Suggesting improvements 3 marks 3 0 MMO = Manipulation, measurement and observation Collection = Successful collection of data and observations Decisions = Decisions relating to measurements or observations PDO = Presentation of data and observations Recording = Recording data and observations Display = Display of calculation and reasoning Layout = Data layout ACE = Analysis, conclusions and evaluation Interpretation = Interpretation of data or observations and identifying sources of error Conclusions = Drawing conclusions Improvements = Suggesting Improvements

Page 3 Mark Scheme Syllabus Paper GCE A/AS LEVEL – October/November 2007 9700 31 © UCLES 2007 Question no. Mark Scheme points Accept H2O2 for hydrogen peroxide Mark ‘what if’s/extra notes 1 (a) (i) PDO recording table, 4 concentrations recorded; (first/top) hydrogen peroxide , (other) number of bubbles and (unit of time); 1 1 Allow no outer boundary (does not need the bottom or top or edge lines) lines do not need to be ruled- see examination report all cell lines must be shown Ignore beaker 1 etc./and excess columns Ignore vol – as this is an unknown unit Reject other units %/cm3 /volume/ units in body of table Accept time taken with no. of bubbles/(time eg s, secs, mins.)/or rate of bubble production with units 1 (a) (ii) ACE Interpretation bubbles different sizes/no.of bubbles; loss of gas/not airtight/difficult to put bung in ; 1 max e.g. released too quickly/unevenly/miscounts bubbles Accept amount of bubbles Reject no bubbles see examination report. 1 (a) (iii) ACE Improvements method of measuring volume; use closed system/syringe to add substrate; use petroleum/Vaseline; use a waterbath; repeat/replicate; use a buffer; equilibration; mix using glass rod/shake extract and hydrogen peroxide; 3 max collect gas in measuring cylinder/burette/using (gas) syringe/manometer/slow speed video recording Reject biuret/inverted test tube Accept if graduated Reject air conditioning Reject larger volume of H2O2/increase measuring time/measure height of froth/have someone else help etc./cleaning apparatus/additional H2O2 concentrations ignore mistakes 1 (b) (i) MMO collection 1. idea of keeping the volume/mass/size of potato the same; 2. subdivides more than 1to give at two different surface areas; 3. method mark e.g. trim/remove/peel skin (from potato)/ using scalpel/cork borer; 3 Alternative wording 1 etc cm3 cube/gives three dimensions/cylinder with quoted length/diameter with quoted length/gives a mass. Reject crushing Must be clear that using 2 constant volumes/mass and then splitting these into different surface areas Credit on diagrams Max 1 if volume not kept the same e.g. could get 1 method mark

Page 4 Mark Scheme Syllabus Paper GCE A/AS LEVEL – October/November 2007 9700 31 © UCLES 2007 Question no. Mark Scheme points Accept H2O2 for hydrogen peroxide Mark ‘what if’s/extra notes 1 (b) (ii) MMO decisions boil/heat above 80oC/no potato/implies potato replaced; to show effect of enzyme/catalyst/enzyme will not work; 1 1 Ignore enzyme denatured ‘use boiled potato as this will have a denatured enzyme’ = point 1 only: need to add ‘so this will not work’ to get pt 2. Accept point 2 even if haven’t got point 1. e.g. replace hydrogen peroxide reject pt 1 but then write this is to show that ‘enzyme doesn’t work’ accept pt 2. 1 (b) (iii) PDO layout • select which variable(s) to plot and plot appropriately on clearly labelled x- and y-axes • plot all points or bars to an appropriate accuracy follow the IOB recommendations for putting lines on graphs O area/cm2 on x axis, and time/secs on y axis ; S scale, more than half grid(x and y) used for plotted area; P all points correctly plotted with crosses/dots (in circles); L points joined with ruled lines/curve through all points; 4 Wrong orientation/labels loses O mark but can gain S, P and L no awkward scales should be x axis 1cm to 1 vol and y axis 2cms to 50 secs./1 cm to 20 secs allow other simple scales Reject plotting if awkward scale used. Where a point eg 27 should clearly be above or below a line Reject if on the line. See examination report. no dips in curve allowed especially between last two points, extrapolation beyond first and last points by 2 squares only/reject if go over axis line thickness of line less than half a square has to be one continuous line 1 (b) (iv) ACE interpretation describe the patterns and trends shown by tables and graphs 1 (b) (v) ACE conclusion 1. as surface area increases time to release gas decreases/gets shorter/rate increases/AW; 2 (more area) more active sites (exposed); 3. so hydrogen peroxide/substrate binds/attaches, to active site/more ESC’s formed; 1 2 Ora as surface area decreases time to release gas increases/rate is slower/AW ignore Inversely proportional Mark iv and v together reject point 1 if answer to iv is contradictory in v. Accepts collides/links/occupies/slots into/filled Reject reacts with Read carefully for where the active sites are

Page 5 Mark Scheme Syllabus Paper GCE A/AS LEVEL – October/November 2007 9700 31 © UCLES 2007 Question no. Mark Scheme points Accept H2O2 for hydrogen peroxide Mark ‘what if’s/extra notes 1 (b) (vi) ACE interpretation find an unknown value by using co-ordinates check 5.5 cm2 from their graph/allow 1 either side of your reading; secs/s; 1 1 Units can be awarded if value incorrect. If scale awkward try to read as close as possible can’t do this if scale totally incorrect. Accept where 1 small square = 4 whole number only, where 1 small square = 5 accept to .5 only. 1 (b) (vii) ACE interpretation calculate other quantities 40/fig from b vi; 1 If no working then calculate and award mark if answer correct. See examination report on significant figures. 1 (c) MMO decisions 1. range of at least 5 regularly spaced different temperatures; 2. use of waterbath/described; 3. volume of hydrogen peroxide constant; 4. volume of potato/extract constant; 5. concentration of hydrogen peroxide constant/same beaker; 6. warm hydrogen peroxide and potato/extract separately first; 7. method of measurement to give rate; 8. repeat; 1 1 2 max Ignore 80+°C and below 5°C regular = 5 or multiples Allow room temperature plus 4 Points 1 and 2 then 2 from points 3 to 7 Reject amount/quantity Reject enzyme/substrate – see examination report. If quote a volume/mass needs to be clear kept constant may only get this when repeat expt. 2 (a) PDO display show their working in calculations, and the key steps in their reasoning 100; 1 2 (b) (i) credit given in 2 (b) (ii) –

Page 6 Mark Scheme Syllabus Paper GCE A/AS LEVEL – October/November 2007 9700 31 © UCLES 2007 Question no. Mark Scheme points Accept H2O2 for hydrogen peroxide Mark ‘what if’s/extra notes 2 (b) (ii) ACE conclusions stage scale is magnified is more/eyepiece graticule is not magnified as much/by (objective) lens; 1 Reject Just magnified/highly Accept higher X40 allowed if they have ringed x40 in b i 2 b (iii) MMO collection follow instructions given in the form of written instructions or diagrams PDO display show working in calculations and the key steps in the reasoning look at units given then if micrometres check answer is 100 or 2 a divided by their epg/if mm then 0.1 or 0.01/epg ; answer whole number; 1 1 epg is eyepiece graticule ecf is error carried forward NB assessing ‘key steps in reasoning to make calculation’ therefore method of calculation If answer incorrect/no units then look for correct working : With micrometers for 100 or ecf (2 a)/ no of epg or With mm 0.1/no. of epg or 0.01/no.of epg; max 1

Page 7 Mark Scheme Syllabus Paper GCE A/AS LEVEL – October/November 2007 9700 31 © UCLES 2007 Question no. Mark Scheme points Accept H2O2 for hydrogen peroxide Mark ‘what if’s/extra notes 2 (b) (iv) MMO Collection use their apparatus to collect an appropriate quantity of data or observations, including subtle differences in colour or other properties of materials ACE Interpretation use their apparatus to collect an appropriate quantity of data or observations, including subtle differences in colour or other properties of materials Check answer is b i; x b iii/x100/epg or x0.1/epg or 0.01/epg; 1 1 If answer incorrect but have written down their working as answer from b i ; x their answer from b iii then two marks; or b i ; x 100/epg OR 0.1/epg OR 0.01/epg; Ignore units Can still get 1 mark if they have neither of the above but have shown that used either b i or multiplied by b iii;

Page 8 Mark Scheme Syllabus Paper GCE A/AS LEVEL – October/November 2007 9700 31 © UCLES 2007 Question no. Mark Scheme points Accept H2O2 for hydrogen peroxide Mark ‘what if’s/extra notes 2 (c) PDO layout MMO collection use their apparatus to collect an appropriate quantity of data or observations, including subtle differences in colour or other properties of materials MMO decision sharp, clear, unbroken lines, no shading, quarter; no cells, larger than 3 1 rd width; epidermis to is less than distance from top edge of vascular bundle to space of pith; small and large vascular bundles; two correct labels of tissues; 1 1 1 1 1 Quarter shown by 5 to 7 vascular bundles Narrowest point to widest point Look for vascular bundle nearest to epidermis. Ignore cell names

Page 9 Mark Scheme Syllabus Paper GCE A/AS LEVEL – October/November 2007 9700 31 © UCLES 2007 Question no. Mark Scheme points Accept H2O2 for hydrogen peroxide Mark ‘what if’s/extra notes 2 (d) PDO layout MMO collection PDO Recording sharp, clear, unbroken lines; 3–8 , touching, larger than 6 cm; drawn phloem sieve tube, plus one other type of cell from xylem vessel/sclerenchyma/companion cell; any 2 from (phloem) sieve tube/cell, companion cell, xylem (vessel), sclerenchyma correctly labelled; 1 1 1 1 Max 1 for textbook see examination report. No touching cell wall lines/complete cell walls Reject if more than 8 cells. Reject if drawing not like slide e.g. too much detail drawn sieve plate and pores between cells or nuclei in cells. Phloem sieve cell (psc) should • not have right angle/sharp corners • have fairly thin or single line cell wall • bigger than companion cell Companion cell vs phloem sieve cell • smaller than psc or xylem vessel/sclerenchyma • thinner cell wall than xylem vessel/sclerenchyma Xylem vessel/sclerenchyma vs pst/companion cell • thicker cell wall • sclerenchyma smaller and thicker wall than xylem