Cambridge A Level Biology 9700 — 2010 Oct/Nov Paper 3 · Variant 3

This document consists of 10 printed pages and 2 blank pages. DC (LEO/SW) 24029/3 © 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 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 both 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. * 3 9 1 8 5 2 3 8 4 5 * BIOLOGY 9700/33 Advanced Practical Skills 1 October/November 2010 2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions. For Examiner’s Use 1 2 Total

2 © UCLES 2010 9700/33/O/N/10 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 When plant tissue is soaked in methylene blue the tissue takes up the stain and is coloured blue. Copper sulfate solution affects the selective permeability of cell membranes. You are provided with labelled contents hazard concentration / % volume / cm3 C copper sulfate solution harmful irritant 0.3 60 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 5 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, concentration of copper sulfate solution, on samples of plant tissue which have been soaked in methylene blue.

3 © UCLES 2010 [Turn over 9700/33/O/N/10 For Examiner’s Use (a) (i) Decide on the concentrations of copper sulfate solution you will use in your investigation. You will need 10 cm3 of each concentration of copper sulfate solution. Prepare the space below to show • the concentrations of copper sulfate solution • the volumes of copper sulfate solution • the volumes of distilled water. [3] Make up the copper sulfate solutions that you have chosen in the containers provided. Put 10 cm3 of the appropriate concentration of copper sulfate solution into a labelled test-tube.

4 © UCLES 2010 9700/33/O/N/10 For Examiner’s Use You are provided with five pieces of plant tissue with the same cross-sectional area in a container of water, labelled P. Proceed as follows: (Always use blunt forceps when handling the plant tissue to avoid contact with the methylene blue). 1. Remove the pieces of plant tissue from the container, labelled P, and place them onto a white tile. You will need to prepare one sample of plant tissue to put into each of the concentrations of copper sulfate solution. (ii) State which variable you will need to control when preparing the plant tissue samples. …[1] (iii) Describe how you will control this variable and prepare the samples of plant tissue. … …[2] 2. Prepare the samples of plant tissue as you described in (iii). 3. Empty the coloured water from the container, labelled P. 4. Place the samples back into the empty container, labelled P. 5. 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. 6. Remove the samples of plant tissue and add one sample of plant tissue to each test-tube of copper sulfate solution. 7. Immediately start timing. 8. Observe the test-tubes for 5 minutes and record your observations. 9. After five minutes, mix the contents of the test-tubes, by inserting a bung and inverting each test-tube.

5 © UCLES 2010 [Turn over 9700/33/O/N/10 For Examiner’s Use (iv) Prepare the space below and record your observations. [5] (v) Suggest how copper sulfate solution affects plant cell membranes. … …[1] (vi) Identify three significant sources of error in your investigation. … … … … … … …[3]

6 © UCLES 2010 9700/33/O/N/10 For Examiner’s Use (vii) Suggest how you would make three improvements to this investigation. … … … … … … … …[3] [Total: 18]

7 © UCLES 2010 [Turn over 9700/33/O/N/10 For Examiner’s Use 2 K1 is a slide of a stained transverse section through a plant organ. draw this quarter Fig. 2.1 (a) (i) Draw a large plan diagram of a quarter of the specimen as shown in Fig. 2.1. Label the endodermis and the cortex. [5] (ii) Make a high-power drawing of one large xylem vessel and the single layer of cells touching a quarter of the vessel’s circumference. Labels are not required. [5]

8 © UCLES 2010 9700/33/O/N/10 For Examiner’s Use Fig. 2.2 is a photomicrograph of a transverse section through a quarter of a different organ from the same plant species. Fig. 2.2 (b) Prepare the space below so that it is suitable for you to record the observable differences between the specimens on K1 and that in Fig. 2.2. Record your observations in the space you have prepared. [4]

9 © UCLES 2010 [Turn over 9700/33/O/N/10 For Examiner’s Use (c) (i) Table 2.1 shows the results of an investigation into the contents of phloem sieve tube elements. Table 2.1 contents concentration in phloem sieve tube elements / μg cm–3 sucrose 120 ammonium ions 45 calcium ions 85 magnesium ions 105 sodium ions 115 Plot a chart of the data shown in Table 2.1. [4]

10 © UCLES 2010 9700/33/O/N/10 For Examiner’s Use (ii) The contents of the xylem vessels were also investigated and the concentration of calcium ions was found to be 190 μg cm–3. Use the result for the xylem vessels and the data from Table 2.1 to calculate the percentage difference between the concentration of calcium ions in the xylem vessels and the concentration of calcium ions in the phloem sieve tube elements. You may lose marks if you do not show your working or if you do not use appropriate units. [2] (d) The investigation into xylem vessel contents also found that there was no sucrose present. Suggest why there is 120 μg cm–3 of sucrose in the phloem sieve tube elements. … … … … … … … …[2] [Total: 22]

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UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the October/November 2010 question paper for the guidance of teachers 9700 BIOLOGY 9700/33 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 October/November 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 A LEVEL – October/November 2010 9700 33 © UCLES 2010 Question Expected Answers Additional guidance 1 (a) (i) Decide on the concentrations of copper sulfate solution you will use in your investigation. [3] [1] any 4 or more (volumes/concentrations); [1] (highest concentration) 0.3 to 0.15; MMO decisions 3 [1] any three consecutive concentrations (including 0 if present) with two intervals • the same • or serial dilution by half • or serial dilution by ten; (ii) State which variable you will need to control when preparing the plant tissue samples. [1] MMO decision 1 [1] length or surface area or size or dimensions or volume; Allow methylene blue (iii) Describe how you will control this variable and prepare the samples of plant tissue. [2] [1] (control) measure cut (methylene) rinsing/washing the same any example of length 3 cm or less/size; excess MMO decisions 2 [1] (prepare samples) use of scalpel/knife or ruler; (methylene blue) water

Page 3 Mark Scheme: Teachers’ version Syllabus Paper GCE A LEVEL – October/November 2010 9700 33 © UCLES 2010 (iv) Prepare the space below and record your observations. [5] Reject • if units for % in body of table • other units e.g. mol dm–3 [1] table with all cells drawn AND heading (top or left) percentage conc(entration); Reject • if headings/columns for method/volumes/time 5 mins or size/lengths PDO recording 2 [1] (heading) colour or observations or description; [1] (records clear separate observations/colours) after/during 5 min/before mixing AND after mixing (after/at 5 min); MMO collection 2 [1] difference in the strength of colour between the first and last test-tube observations; Key e.g. + = colour MMO decision 1 [1] 5 or more concentrations or observation for water or replicate recorded; (v) Suggest how copper sulfate solution affects plant cell membranes. [1] ACE conclusion 1 [1] In correct context of increasing or just copper sulfate Idea of damages or destroys or makes more denatures (increases copper sulfate) increases (decreases copper sulfate) decreases (increases copper sulfate) decreases (decreases copper sulfate) increases it or ((cell) membrane(s)) phospholipid(s) fluid mosaic (model/structure) (fully) permeable protein fluidity permeability selective permeability;

Page 4 Mark Scheme: Teachers’ version Syllabus Paper GCE A LEVEL – October/November 2010 9700 33 © UCLES 2010 (vi) Identify three significant sources of error in your investigation. [3] Reject temperature pH evaporation any errors which affect all test-tubes equally Cause of error Error [1] (dependent) qualitative; [1] [1] [1] colour/colour change/observations mixing difficult judging seeing; qualitative; more difficult to judge colour/colours the same; ACE interpretation MAX 3 [1] [1] [1] [1] (standardised variables) potato or position in potato or age or storage lengths/size/surface areas/volumes Allow mass staining/washing/handling/forceps potato/samples (into test-tubes) not same different/variety old; not same; not same loses stain damages potatoes ends not stained or middle more stain; time not same/delayed time/not at same time; max 3

Page 5 Mark Scheme: Teachers’ version Syllabus Paper GCE A LEVEL – October/November 2010 9700 33 © UCLES 2010 (vii) Suggest how you would make three improvements to this investigation. [3] [1] same potato or position in same age or storage or fresh use micrometer/cork borer/vernier callipers/ruler with smaller divisions; [1] leave in methylene blue longer/stronger concentration/more than 5 minutes idea of wash more; [1] more/wider/narrower/different/examples range of concentrations or use burette or graduated pipette or smaller syringe or with smaller divisions; [1] stagger start or do individually or use more stop clocks or use help; [1] colorimeter or datalogger with light sensor; Reject calorimeter ACE improvements MAX 3 [1] repeat or replicate; max 3 [Total: 18]

Page 6 Mark Scheme: Teachers’ version Syllabus Paper GCE A LEVEL – October/November 2010 9700 33 © UCLES 2010 2 (a) (i) Draw a large plan diagram of a quarter of the specimen as shown in Fig. 2.1. Label the endodermis and cortex. [5] Reject • if drawn over the print of question Reject • thick lines-than grid • feathery lines • 3 ’tails’ or overlaps or gaps PDO layout 1 [1] clear, sharp, unbroken lines AND no shading AND uses most of space provided; [1] no additional cells drawn AND (epidermis shows) only the correct quarter; [1] epidermis drawn with two lines 3 mm or closer for most of length; MMO collection 3 [1] innermost line is wavy/undulating line; Reject • if any label is biologically incorrect e.g. regions belonging to other organs or animals. • label within drawn area MMO decision 1 [1] correct label with label lines to cortex and endodermis ;

Page 7 Mark Scheme: Teachers’ version Syllabus Paper GCE A LEVEL – October/November 2010 9700 33 © UCLES 2010 (ii) Make a high-power drawing of one large xylem vessel and the single layer of cells touching a quarter of the vessel’s circumference. Labels are not required. [5] Reject • if drawn over the print of question Reject • thick lines – than on grid • feathery lines • 4 ‘tails’ or overlaps or gaps if double lines for all cells • 1 if single line for any cell PDO layout 1 [1] clear, sharp, unbroken lines AND no shading AND uses most of space provided; [1] one xylem vessel drawn Ignore band inside AND only single layer of surrounding cells ; Reject if layer of cells all round xylem vessel If xylem vessel not circular/polygonal [1] (surrounding cells) (single layer) three to eight cells in a layer only; Allow not touching. Reject any spaces if single line for cell walls. any gaps between cell walls – floating cells MMO collection 3 [1] (all cells including xylem vessel) no enclosed spaces more than 1mm between adjacent double cell walls; PDO recording 1 [1] cell walls drawn as double lines with middle lamella between three adjacent cells from surrounding cells;

Page 8 Mark Scheme: Teachers’ version Syllabus Paper GCE A LEVEL – October/November 2010 9700 33 © UCLES 2010 (b) Prepare the space below so that it is suitable for you to record the observable differences between the specimens on K1 and that in Fig. 2.2. [4] PDO recording 1 [1] organise as a table/Venn diagram/ruled boxes AND headed K1 and Fig 2.2 AND first difference opposite each other; K1 Fig 2.2 feature K1 Fig.2.2 hairs/trichomes Ignore root no hairs/trichomes; 1 epidermis thick(er) or more/2 layers thin(ner) or few(er); 2 cortex yes/present/more no(one)absent/less; 3 endodermis yes/present no(one)/absent; 4 pericycle yes/present no(one)/absent; 5 vascular bundles xylem ring/centre/no(one)/absent/ fewer scattered/AW/towards edge/yes/present/more; either way round for present/absent/under epidermis; 6 thickened cells/ sclerenchyma Allow collenchymas bundle sheath/AW no(one)/absent yes/present; yes/present no(one)/absent; 7 pith pith/centre cells rounded angular/pentagonal/AW; ACE interpretation 3 [1] [1] [1] [1] [1] [1] [1] [1] [1] [1] [1] [1] 8 air spaces/lenticels stomata yes/present no(one)/absent no(one)/absent; yes/present; Ignore • tick and cross without a key • ref. to non-observable features • 3D shapes max 3

Page 9 Mark Scheme: Teachers’ version Syllabus Paper GCE A LEVEL – October/November 2010 9700 33 © UCLES 2010 (c) (i) Plot a chart of the data shown in Table 2.1. [4] MAX 2 for O and S if line graph drawn O [1] x-axis content(s) AND y-axis conc(entration in) phloem or sieve tube/element (/) µg cm–3; Must have units Reject scale on y-axis any other than 20 to 2 cm. S [1] scale as even widths to 2 cm AND y-axis 20 to 2 cm; Reject if y-axis scale is awkward if bars arranged differently from order of table if horizontal lines are too thick – 1mm/half square or not clear Allow bars if scale 20 to 2 cm. even if not 0 25 to 2 cm P [1] correct plotting of each bar; horizontal top line must be clear, sharp and ruled to show plot line must be on horizontal line for sucrose line must be between two lines for all other contents PDO layout 4 L [1] each bar separate if vertical lines only then must be at least 1 cm apart. AND quality – vertical lines no thicker than on grid, not feathery for the complete line; bars – • ruled lines Reject irregular thickness • labelled clearly with contents – any clear labels e.g. chemical formulae NH4, Ca, Mg, Na or mixture – underneath, must be directly below correct bar or inside bar or shaded with key. Reject solid shading If line shading outside a bar

Page 10 Mark Scheme: Teachers’ version Syllabus Paper GCE A LEVEL – October/November 2010 9700 33 © UCLES 2010 (ii) Calculate the percentage difference between the concentration of calcium ions in the xylem vessels and the concentration of calcium ions in the phloem sieve tube elements. [2] [1] shows subtraction (190 – 85) divided by 190 multiplied by 100; (190/190 – 85/190) × 100 or (1 – 85/190) × 100 PDO display 2 [1] Reject if no working Allow any answer less than 100 to no more than 3 significant figures 1 decimal place AND percentage/%; (d) Suggest why there is 120 µg cm–3 of sucrose in the phloem sieve tube elements. [2] [1] (phloem sieve tube elements) (sucrose) transported leaf(ves)/allow type of leaf cell/source to roots/other tissues/sink(s); ACE conclusions MAX 2 [1] (detail) load(ed) (in source) or (transported by) mass flow/bulk transport/translocation (sucrose) too large to move out of phloem or sieve tubes or xylem walls impermeable; [Total: 22]