Cambridge A Level Biology 9700 — 2008 Oct/Nov Paper 3 · Variant 2

This document consists of 11 printed pages and 1 blank page. SP (FF/DT) T66298/3 © UCLES 2008 [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. * 1 6 1 4 2 2 3 4 4 7 * BIOLOGY 9700/32 Paper 32 Advanced Practical Skills October/November 2008 2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the confidential instructions For Examiner’s Use 1 2 Total

2 9700/32/O/N/08 © UCLES 2008 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. 1 You are required to investigate the effects of two solutions, T1 and T2, on the cells of onion epidermal tissue. • Solution T1 is a 1.0 mol dm–3 solution of potassium nitrate. • Solution T2 is a 1.0 mol dm–3 solution of lead nitrate (toxic). • Beaker W contains distilled water. • Beaker O contains distilled water and two pieces of onion. It is very important to stop the onion from drying out. Place a few drops of distilled water on a microscope slide. Remove a piece of onion and using forceps or fingers peel off the inner concave epidermis as shown in Fig. 1.1. Pull the epidermis from the top of the piece towards the tip. Immediately place the epidermis of the onion in the distilled water on the microscope slide. inner concave epidermis piece of onion onion epidermis distilled water Fig. 1.1 Pour enough distilled water into the Petri dish to cover the base. Using a scalpel carefully cut one piece of the epidermis approximately 5 mm by 5 mm and place it into the water in the Petri dish. Repeat until you have at least 3 small square pieces of epidermis floating in the Petri dish. Mount one of the squares of epidermis on a microscope slide in distilled water. Cover with a cover slip and label the slide. Repeat with two more squares of epidermis, mounting one in solution T1 and another in solution T2.

3 9700/32/O/N/08 © UCLES 2008 [Turn over For Examiner’s Use (a) (i) Using low and high power, carefully examine the onion cells in the distilled water and draw and label one cell which shows the most details of its structure. [2] You may need to reduce the amount of light entering the microscope by closing the iris diaphragm or reducing the light intensity. Then look at the onion cells in T1 and T2 and observe as many cells as possible. Record your observations carefully. (ii) Prepare and use the space below to present your observations from the slides made with distilled water, T1 and T2. [4]

4 9700/32/O/N/08 © UCLES 2008 For Examiner’s Use (iii) Explain your observations from the slides made with distilled water, T1 and T2. … … … … … … … [3] (iv) Identify two significant sources of error in the experiment. 1. … … 2. … … [2] (b) Suggest how you could modify this experiment to investigate more fully the effect of lead nitrate. … … … … … [3]

5 9700/32/O/N/08 © UCLES 2008 [Turn over For Examiner’s Use (c) In a similar investigation involving a range of sodium chloride concentrations, a student obtained the results shown in Table 1.1. Table 1.1 percentage plasmolysis of cells sodium chloride concentration / mol dm–3 batch 1 batch 2 batch 3 batch 4 mean 0 0 0 0 0 0 0.2 2 4 1 1 2 0.4 5 77 7 5 0.6 27 25 30 28 27 0.8 76 82 84 35 1.0 99 100 98 100 99 (i) Complete Table 1.1 by calculating the missing values taking into account any anomalous values. [1] (ii) Plot a graph of concentration of the sodium chloride solution against the percentage plasmolysis of the cells. [3]

6 9700/32/O/N/08 © UCLES 2008 For Examiner’s Use (iii) State the concentration at which there is 50% plasmolysis of the cells represented in Table 1.1 and your graph on Page 5. … [1] (d) The student’s hypothesis was: The more concentrated the solution the more plasmolysed the cells become. Draw an appropriate conclusion to the student’s experiment. You should include in your conclusion whether the experimental data support the hypothesis and produce a revised hypothesis if necessary. … … … … … [2] [Total : 21]

7 9700/32/O/N/08 © UCLES 2008 [Turn over For Examiner’s Use 2 Fig. 2.1 is a photomicrograph of a transverse section of a tubular structure from an animal. Fig. 2.1 (a) (i) Draw a large low-power plan diagram of the specimen in photomicrograph Fig. 2.1. [4]

8 9700/32/O/N/08 © UCLES 2008 For Examiner’s Use (ii) Fig. 2.2 shows the same specimen as Fig. 2.1 but it is a longitudinal section. It includes the image of an eyepiece graticule. Fig. 2.3 shows a photomicrograph of a stage micrometer scale using the same lenses as Fig. 2.2 and includes an image of the same eye piece graticule. 0 2 4 6 8 10 2 3 0 2 4 6 8 10 Fig. 2.2 Fig. 2.3 Each division on the stage scale is 0.1 mm Count the number of eyepiece graticule units across the lumen of the structure on Fig. 2.2. number of eyepiece graticule units … Count the number of eyepiece graticule units that match an exact number of stage micrometer scale divisions. number of eyepiece graticule units … number of stage micrometer scale divisions …

9 9700/32/O/N/08 © UCLES 2008 [Turn over For Examiner’s Use Use this information to calculate the actual width of the lumen in Fig. 2.2. Show your working. actual width of the lumen on Fig. 2.2 … [4] (iii) Suggest how an error in measuring the width of the lumen could occur. … … [1]

10 9700/32/O/N/08 © UCLES 2008 For Examiner’s Use (b) The whole specimen in Fig. 2.2 is repeated below without the graticule scale as Fig. 2.4. Fig. 2.5 shows a longitudinal section of a specimen from a different type of organism. Fig. 2.4 and Fig. 2.5 are not reproduced at the same scale. 50µm Fig. 2.4 Fig. 2.5 (i) Prepare the space below so that it is suitable for you to compare and contrast the specimens in Fig. 2.4 and Fig. 2.5 and then record your observations. [5]

11 9700/32/O/N/08 © UCLES 2008 For Examiner’s Use (ii) Suggest one feature which indicates that the specimen in Fig. 2.5 is a plant. … … … [1] (iii) Draw five representative cells from Fig. 2.5 that show the diversity of cell shape and size. Please mark on Fig. 2.5 the cells that you have drawn. [4] [Total : 19]

12 9700/32/O/N/08 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. BLANK PAGE

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the October/November 2008 question paper 9700 BIOLOGY 9700/32 Paper 32 (Advanced Practical 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. 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 2008 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 2008 9700 32 © UCLES 2008 Question Expected Answers Additional Guidance Marks Draw and label ONE cell in distilled water 2 MMO collection 1 (a) (i) one cell drawn (at high power), two lines for cell wall; correct cell structure and cell wall and nucleus labelled correctly; Ignore low power. Reject two or more cells together. Rej. if have additional organelles mitochondria, chloroplasts, Golgi. [2] Present your observations from the slides made from distilled water, T1 and T2 2 MMO decisions, 2 PDO recording 1 (a) (ii) Either single table, all cells drawn, column headings: solution/slide/(distilled) water/W and T1 and T2; to left/across top, observations/feature/e.g. to right/ underneath/clear what is recorded in the boxes; T1 cell membranes/cytoplasm pulled away from cell wall/plasmolysed; T2 granules/particles in cell/more plasmolysed/destroyed/stained/coloured e.g. brown/black/AW; Or when only drawings given three drawings, labelled (distilled) water/W, T1 and T2; clear that cell walls and cell membranes are all different (for water, T1 and T2); T1 cell membranes/cytoplasm pulled away from cell wall/plasmolysed; T2 granules/particles in cell/more plasmolysed/destroyed/stained/coloured e.g. brown/black/AW; No outer boundary needed for table. Reject cells shrink or become smaller. Accept vacuole shrinking or drawn. Allow any description that cells have been destroyed/cell membranes ruptured/disorganised/ leakage of cell. Reject cell walls broken down. [4]

Page 3 Mark Scheme Syllabus Paper GCE A/AS LEVEL – October/November 2008 9700 32 © UCLES 2008 Explain observations from water, T1 and T2. 1 (a) (iii) Idea of 1. high/less negative water potential to lower/more negative water potential/down water potential gradient Any two of: 2. (in water)idea of water has moved in/no net movement; 3. (in T1/T2) idea of water has moved out; 4. (in T2/lead nitrate) killed/destroyed cells/toxic/effect described/AW; AND by osmosis at any point; In correct context. Accept ψ. Solute/osmotic potential is ignored but must be the same as water potential i.e. from high to low, so reject pt1 if wrong way. Ignore hypotonic and hypertonic but must be in correct context if used. Must be correct with the candidate’s own results. Reject cell wall destroyed. [1] [2 max] Identify two sources of error in this experiment 2 ACE interpretation 1 (a) (iv) Two from evaporation from solutions/concentration of solution changes; cells left different lengths of time/too short a time/not long enough; AVP; volume/no. of drops used; or different or different onions/parts of onion/not fresh/have been frozen/stored; Reject not immersed. Reject should be same time –not an error. Reject amount. Mark for any correct. Reject improvements. [2 max]

Page 4 Mark Scheme Syllabus Paper GCE A/AS LEVEL – October/November 2008 9700 32 © UCLES 2008 Suggest how you could modify the experiment to investigate the effect of lead nitrate. 3 ACE improvements 1 (b) more/serial dilution concentrations of lead nitrate; Then any TWO from at least 3 specified lead nitrate concentrations; repeat each concentration/more than one strip (per concentration); keep the time the same/give an example of a time/longer time; keep the volume AND method /use graduated pipette/no.of drops the same/AW; same onion/same part/fresh; detailed measurement method/use of eyepiece graticule to measure plasmoylsed cells/count number of plasmolysed cells in a sample of 20 or more; Reject shorter time. [1] [2 max]

Page 5 Mark Scheme Syllabus Paper GCE A/AS LEVEL – October/November 2008 9700 32 © UCLES 2008 Complete the Table 1.2 by calculating the missing values PDO display 1 (c) (i) 6,81; A whole numbers only and both correct [1] Plot a graph of concentration of sodium chloride against the percentage plasmolysis of the cells PDO layout 1 (c) (ii) [3] O x-axis conc, mol dm–3/M or molar/mole(s)/l or per litre AND y-axis percentage/% plasmolysis; Rej. mol/dm–3 and mol dm3. [1] S/P scale as shown/y axis 25 to 2cms, allow no 0 marked AND plotting crosses or dot in circle ONLY AND 0.0, 0.2 and 0.6 and1.0 plotted correctly; no larger then X or O plots 0.2 must be on horizontal line, 0.2 and 0.6 and 1.0 between the horizontal lines. Ignore incorrect calculated mean plots i.e. 0.4 and 0.8. Rej. blobs in or out of circle. [1] L either ruled lines joining each point or smooth curve through 0; no thicker than no feathery line, line must go to 0 Rej. any extrapolation beyond either axis. [1]

Page 6 Mark Scheme Syllabus Paper GCE A/AS LEVEL – October/November 2008 9700 32 © UCLES 2008 Question Expected Answers Additional Guidance Marks State concentration at which 50% plasmolysis occurred 1 ACE interpretation 1 (c) (iii) take reading from candidates own graph, AND must have units; Allow two decimal places. Ecf units from graph. [1] ‘The more concentrated the solution the more plasmolysed the cells become’ draw conclusion include whether the data support the hypothesis and produce a revised hypothesis if necessary 2 ACE conclusion 1 (d) General statement : Either support or no support or partial support for the hypothesis or writes a conclusion which states the hypothesis; quotes 2 sets of figs. with both axes; OR idea that up to 0.4 /low concentration only small % plasmolysed/or % plasmolysis does not increase evenly with increasing concentration/or levels off at high concentration; Needs clear statement. Reject supports conclusion. Idea of correct relationship may quote figures to get same idea. Reject all/100% plasmolysed. [2]

Page 7 Mark Scheme Syllabus Paper GCE A/AS LEVEL – October/November 2008 9700 32 © UCLES 2008 Question Expected Answers Additional Guidance Marks Draw a LARGE, LOW-POWER plan diagram of photomicrograph fig 2.1. (artery) 1 MMO collection, 3 PDO layout 2 (a) (i) sharp, clear unbroken lines, height no more than two thirds the length ; no cells, no shading, larger than 6 cm in any direction; at least three lines (plus very thin inner layer if shown); uneven all the way round and one solid inner line; Outer two lines only No more than 2 errors. Actual = 5.5 cm to 9 cm. [4]

Page 8 Mark Scheme Syllabus Paper GCE A/AS LEVEL – October/November 2008 9700 32 © UCLES 2008 Use this information to calculate the actual width of the lumen. 2 MMO collection, 1 PDO recording, 1 PDO display 2 (a) (ii) Each division on stage scale is 0.1 mm = V First mark Reject any measurements given for mark points 1 and 2. Accept units or divisions. First Mark No. of eyepiece grat. W 7 14 28 29 Second Mark No. of eyepiece grat. Y 4.5 9.0 9 18 7 18 25 36 7 18 25 36 No on stage micrometer Z 5 10 5 10 2 5 7 10 2 5 7 10 Third Mark Show logical reasoning EITHER Z divided by Y first, then proceed and allow multiplication by either V and then W, or W and then V, even though not strictly the correct reasoning. Ignore answer and units. Rej. if additional figs. even if x1. OR Z x V AND divided by Y. followed by x W Ignore answer and units. Rej. if additional figs. even if x1. Fourth Mark Need NOT be the correct answer Either between 100 and 999 with µm Allow standard form if correct. Reject metres. OR answer between 0.1 and 0.99 with mm; Allow standard form if correct. Reject metres. First two marks are for – collecting the correct data. The third mark is for display – showing clear reasoning in the calculation. Fourth mark is for recording – use of the correct units. [4] Suggest how an error in measuring the lumen could occur 1 ACE interpretation 2 (a) (iii) not knowing where edge is/lumen irregular shape/preparation squashed/only 1 measurement/thicknesses of lines(stage micrometer)/between divisions on eyepiece graticule/one scale line is not at edge of lumen/focussing of both scales/lining up the scales; Ignore parallax error [1]

Page 9 Mark Scheme Syllabus Paper GCE A/AS LEVEL – October/November 2008 9700 32 © UCLES 2008 Compare and contrast specimens Fig. 2.4 and 2.5. 2 MMO collection 1 PDO recording 2 ACE interpretation 2 (b) (i) organised as a table/Venn diagram/ruled boxes connected, correctly headed; comparative statements opposite each other; Fig. 2.4 Fig. 2.5 both have lumen/central space; lumens larger, smaller; number (lumen/tubes) single/one, more/lots; cells /cell walls/end walls none/absent, present; bands absent/none present; Ref. pits/circles/spots none, present; Must have at least one similarity. Accept tubes/vessels as alternative to lumen. Reject ref. to Fig. 2.4 having cells – not visible. Reject uses Rej. ref. lignin/cellulose with walls or bands. [5]

Page 10 Mark Scheme Syllabus Paper GCE A/AS LEVEL – October/November 2008 9700 32 © UCLES 2008 Suggest one feature which indicates the Fig 2.5 is a plant ACE conclusion 2 (b) (ii) have cell walls/xylem/phloem/sieve tube (element)/companion cell/pits/rings; Ignore cellulose, lignin, vessel on own. Reject sieve plates. [1] Make a labelled drawing of 5 representative cells. 1 MMO collection, 3 MMO decisions 2 (b) (iii) 5 shown on Fig.; drawn 3 diverse cells; 3 different sizes; at least 1 cell drawn with bands/parts of bands/pits; AND longer than wide; Reject point 1 if more than 5 marked or drawn. Entire cells or open tubes. Ignore labels. Reject points 2, 3 and 4 if more than 2 TS or textbook. Max 1 point, 1 only [1] [3]