Cambridge A Level Biology 9700 — 2011 Oct/Nov Paper 3 · Variant 6

This document consists of 11 printed pages and 1 blank page. DC (NH/DJ) 34602/6 © UCLES 2011 [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. * 0 0 1 1 4 5 5 4 4 9 * BIOLOGY 9700/36 Advanced Practical Skills 2 October/November 2011 2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions. For Examiner’s Use 1 2 Total

© UCLES 2011 9700/36/O/N/11 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 Question 1 and Question 2. • Plan your use of the time to make sure that you finish all the work that you would like to do. You will gain marks for recording your results according to the instructions. 1 Enzyme E catalyses the hydrolysis of sucrose to glucose and fructose. By adding enzyme E to different concentrations of sucrose the reducing sugars, glucose and fructose, will be formed. After a set time, the presence of reducing sugars can be determined by using Benedict’s solution. The end-point of this investigation is the time taken for the reducing sugars to change the colour of Benedict’s solution from blue to the first colour you see (ignore any further colour changes). You are required to find the sucrose concentration of a sample, U, by using the results of Benedict’s tests on the reaction of enzyme E on different concentrations of sucrose. You are provided with: labelled contents hazard percentage concentration volume / cm3 E invertase solution irritant – 25 S sucrose solution for serial dilution none 10 25 U sucrose solution none unknown 10 Benedict’s solution Benedict’s solution harmful irritant – 60 W distilled water none – 150 2

3 [Turn over © UCLES 2011 9700/36/O/N/11 For Examiner’s Use You are required to carry out a serial dilution of sucrose solution, S, to reduce the concentration of the sucrose solution by half between each successive dilution. Fig. 1.1 shows how to make the first concentration of 5% sucrose solution. 20 cm3 of 10% sucrose solution, S 20 cm3 of 5% sucrose solution, S … … … … … … 10 cm3 of distilled water, W 10 cm3 of 10% sucrose solution, S Fig. 1.1 (a) (i) Complete Fig. 1.1 to show how you will make three further concentrations of sucrose solution, S. [3] As part of this investigation you are required to set up a suitable control. (ii) Describe how you will set up this control using the apparatus provided. … … …[1]

4 © UCLES 2011 9700/36/O/N/11 For Examiner’s Use You are advised to read steps 1 to 11 before proceeding. Proceed as follows: 1. Prepare the concentrations of sucrose solution as shown in Fig. 1.1, in the containers provided. 2. While you are doing steps 3 to 7 you will need to be heating up the water in the beaker labelled for Benedict’s test to a temperature of more than 80 °C. 3. Put 2 cm3 of the 10% sucrose solution, S into a labelled test-tube. 4. Put 2 cm3 of E into the same test-tube. 5. Repeat steps 3 and 4 with each of the concentrations of sucrose and U. 6. Set up your control. 7. Put all the test-tubes into the water-bath labelled for reaction, between 35 °C and 40 °C, for 8 minutes. 8. After the test-tubes have been in the water-bath for 8 minutes, remove the test-tubes. 9. Put 4 cm3 of Benedict’s solution into each test-tube. 10. Put all the test-tubes into the water-bath at more than 80 °C and immediately start timing. 11. Record the time for the change from blue to the first colour you see (ignore any further colour changes). If there is no colour change after 10 minutes, record ‘more than 600’.

5 [Turn over © UCLES 2011 9700/36/O/N/11 For Examiner’s Use (iii) Prepare the space below and record your results. [4] (iv) Using your results, complete the following statement. The concentration of the unknown sucrose sample, U, is between …% sucrose solution and …% sucrose solution. [1] (v) Suggest how you would modify this investigation to obtain a more accurate estimate of the sucrose concentration in sample U. … … … … …[2]

6 © UCLES 2011 9700/36/O/N/11 For Examiner’s Use Peas are preserved by storing them in a freezer at low temperatures. However, during storage peas lose some of their Vitamin C content. The effect of temperature, on Vitamin C content, was investigated in peas at two temperatures, –12 °C and –6 °C. The Vitamin C content of peas was measured before being placed in cold storage and then at 20 day intervals. The results are shown in Table 1.1. Table 1.1 storage / days percentage of Vitamin C content at –12 °C percentage of Vitamin C content at –6 °C 0 (before freezing) 100 100 20 95 64 40 89 43 60 86 13 (b) (i) Plot a graph of the data shown in Table 1.1. [4]

7 [Turn over © UCLES 2011 9700/36/O/N/11 For Examiner’s Use (ii) A hypothesis was suggested that: Peas stored for 60 days at 10 °C would contain no vitamin C. State whether you support this hypothesis and use the results to explain the reasons for your answer. … … … … … … … … …[2] (iii) Find the difference in Vitamin C content of peas at 26 days stored at the two different temperatures. Show on your graph where you obtained the data. …% [2] [Total: 19]

8 © UCLES 2011 9700/36/O/N/11 For Examiner’s Use 2 N1 is a slide of a stained transverse section through a plant stem. This plant genus is found in Africa, Asia, Australasia, Europe and North America. Fig. 2.1 (a) (i) Draw a large plan diagram of the part of the stem indicated by the shaded area in Fig. 2.1. Label the xylem. [6]

9 [Turn over © UCLES 2011 9700/36/O/N/11 For Examiner’s Use Hair-like structures called trichomes are attached to the epidermal cells. Choose a whole trichome and its attached epidermal cells which can be clearly observed. (ii) Make a large drawing of a whole trichome and five epidermal cells at the base of the trichome. Label the trichome and one epidermal cell. [6] (iii) Suggest a possible function for the trichome on this stem. …[1]

10 © UCLES 2011 9700/36/O/N/11 For Examiner’s Use Fig. 2.2 is a photomicrograph of a transverse section through a stem of a different plant species. This plant genus is found in Europe, Middle East and North Africa. 700 μm Fig. 2.2 (b) (i) Using the scale bar calculate the magnification of Fig. 2.2. You may lose marks if you do not show your working or if you do not use appropriate units. magnification x … [3]

11 © UCLES 2011 9700/36/O/N/11 For Examiner’s Use (ii) Prepare the space below so that it is suitable for you to record three observable differences between the specimens on N1 and in Fig. 2.2. Record the observations in the space you have prepared. [5] [Total: 21]

12 9700/36/O/N/11 © UCLES 2011 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 October/November 2011 question paper for the guidance of teachers 9700 BIOLOGY 9700/36 Paper 3 (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. • Cambridge will not enter into discussions or correspondence in connection with these mark schemes. Cambridge is publishing the mark schemes for the October/November 2011 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 – October/November 2011 9700 36 © University of Cambridge International Examinations 2011 Mark scheme abbreviations: ; separates marking points / alternative answers for the same point R reject A accept (for answers correctly cued by the question, or by extra guidance) AW alternative wording (where responses vary more than usual) underline actual word given must be used by candidate (grammatical variants excepted) max indicates the maximum number of marks that can be given ora or reverse argument mp marking point (with relevant number) ecf error carried forward I ignore ACE Analysis, Conclusions and Evaluation (skills) MMO Manipulations, Measurement and Observation (skills) PDO Presentation of Data and Observations (skills)

Page 3 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – October/November 2011 9700 36 © University of Cambridge International Examinations 2011 1 (a) (i) [3] (labels under correct sequence of beakers) 2.5 AND 1.2(5) AND 0.6(25); MMO decisions 1 [1] mp1 Additional guidance Must have • % once • concentrations to at least 1 decimal place EITHER (uses serial dilution) (adds previous concentration of S to each of three beakers and same volume) 10 cm3 of 5(%) or shown by arrow with 10 cm3 AND 10 cm3 transferred from third beaker to fourth and from fourth beaker to fifth beaker; [1] mp2 Additional guidance Must have cm3 once ecf if mp1 is incorrect (adds (distilled) water / W to each of three beakers BUT MUST add previous concentration to fourth and fifth beakers) water / W and 10 cm3; MMO decisions 2 [1] mp3 Additional guidance Must have cm3 once ecf if mp1 is incorrect and/or if mp2 is incorrect

Page 4 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – October/November 2011 9700 36 © University of Cambridge International Examinations 2011 (uses simple dilution) 10% (S) 2.5 and AND 1.25 and AND W 7.5 8.75 0.625 and 9.375 OR 10 % (S) 5 and AND 2.5 and AND 1.25 and W 15 17.5 18.75 OR max 1 for mp2 and mp3 Additional guidance Must have • cm3 once • 10(%) for each test-tube with % once or arrow from first beaker to each one ecf if mp1 is incorrect R rounded volumes up or down. R just S. (ii) [1] boil enzyme (and sucrose) Or replace enzyme / E with water or use water / W instead of enzyme / E Or replace sucrose with water / W or use water instead of sucrose Or use sucrose and water / W Or use enzyme and water / W ; (Ignore equal volume or 2 cm3 of each) ACE improvement 1 [1] Additional guidance A ref. to use of test-tube AND ref. to idea of only water e.g. in beaker or 20 cm3 BOTH correct R ref. to water only with Benedict’s R only 10% sucrose or sucrose AND enzyme AND Benedict’s in any combination R give more than one Ignore denature enzyme (needs how)

Page 5 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – October/November 2011 9700 36 © University of Cambridge International Examinations 2011 (iii) [4] table with all cells drawn AND heading percent(age)conc(entration); [1] Additional guidance A no outer boundary A % or percent(age) A test-tube / additional columns or rows or U separate R units in cells of this column or row R other units e.g. mol dm–3 (heading for any column or row including mean) time (/) s or sec(ond)s; PDO recording 2 [1] Additional guidance A columns / rows for test-tubes or observations A notes outside the area of table R units in cells of this column or row R min(utes) R additional method R t or T records whole seconds (numbers) ‘less than 601’ for ANY 5 concentrations and U and W / control (7) anywhere; (mark first column or row of recorded time taken) [1] Additional guidance Must have • whole numbers • values 600 or less • organised into concentration order or time order ignore U and control Ignore mean times or .0 results records correct pattern highest concentration recorded is shorter time than next concentration ; (mark first column or row of recorded time taken) MMO collection 2 [1] Additional guidance A any values e.g. seconds with tenths or min:sec A minimum two recorded times including ‘more than 600’ once

Page 6 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – October/November 2011 9700 36 © University of Cambridge International Examinations 2011 (iv) [1] correct two concentrations from their results as times; (should be 3% so between 5 and 2.5) ACE interpretation 1 [1] Additional guidance Must be • between two neighbouring concentrations • if same as one concentration then between lower or higher concentration and value given R calculate any value between concentrations (v) [max 2] max 2 mp1 (independent variable) Idea of use concentration(s) (more / repeat with more / narrower(ignore wider) AND have answer for (a)(iv) then either (using estimate) between ... and ... or between 10 and 0.625 / lower / higher in correct context); ecf from own results above / below if no answer to (a)(iv) A only between 10 and 0.625 examples given relevant to their estimate or smaller intervals or repeat U; mp2 Additional guidance Give mp1 and mp2 if list at least two more concentrations between correct values or examples of smaller intervals or implies all differences e.g. 0.5% ecf from own estimates for above or below range mp3 (dependent variable) heat each test-tube separately; Ignore ref. to colorimeter (tests / readings for each concentration) replicate; mp4 Additional guidance A more times or repeats or repeat or repeat U Ignore ‘take more readings’ (standardised variables) use thermostatically-controlled water-bath for Benedict’s test or at named temperature for test; ACE interpretation max 2 mp5 Additional guidance A digital or electronic A description of use of heating and cooling with Bunsen or hot and cold water

Page 7 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – October/November 2011 9700 36 © University of Cambridge International Examinations 2011 (b) (i) [4] x-axis labelled as storage (/) days AND y-axis labelled as percentage of vitamin (C content); O Additional guidance Must have units on x-axis and y-axis A % scale as x-axis 10 to 2 cm AND y-axis 20 to 2 cm ; S Additional guidance A no 0 label at origin and no end label R awkward scale correct plotting of each point (except 100) to within half a square i.e. less than1 mm from intersection; i.e. plot has to be nearer than halfway from a line – up or down or sideways OR if meant to be between two lines then must not be on line P Additional guidance A small cross or dot in circle or cross in circle ecf if x-axis not 0 if scale 20 to 2 cm. R awkward y-axis scale R extra plot for reading off (26) using the same symbol as graph plots R blobs or dots alone R cross too large (both lines on one set of axes) ruled lines point to point or ruled line of best fit (two plots on line and then one either side of line) AND quality clear sharp; R extrapolated when point to point A extrapolation from line of best fit to vertical or horizontal lines of plotted point only Must have key or line labelled with temp.; R if • less than 5 plots • line 1 mm or thicker • any feathery line • irregular thickness • line meets top more then 2 mm from 100 PDO layout 4 L Additional guidance A ecf from incorrect P

Page 8 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – October/November 2011 9700 36 © University of Cambridge International Examinations 2011 (ii) [2] Idea of comparison between –12 and –6 –12 / lower temp lose less vit C higher vit C at –12 OR –6 / higher temp lose more vit C or decreases more steeply or more significant decrease lower at –6 [1] OR as temp. increases / rises less vit C; no / partially / can’t predict results provide no evidence / only results for –12 and –6 / no results for 10 / still 13%/some vit C at –6; quote of data –12 (o C) (at 60 days) 86% AND –6 (o C) 13%; yes OR difference 73% ACE conclusion 2 [1] Additional guidance Must have percentage / % once (iii) [2] [1] Shows on graph two readings 26 days for –6 and –12; Readings to whole number only ACE interpretation 2 [1] (has used correct readings from graph) to obtain correct answer rounded to whole number; e.g. 94 – 62 = 32 [Total: 19]

Page 9 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – October/November 2011 9700 36 © University of Cambridge International Examinations 2011 2 (a) (i) [6] Ignore trichomes and ignore cells for mp1 only. PDO layout 1 [1] no shading AND larger than 60 mm across widest point AND (clear, sharp, unbroken lines) ; Must have four or more hand drawn lines and/or enclosed areas (not cells) R if drawn over the print of question R any line 1 mm or thicker R any feathery or three gaps or overlaps in line R any ruled or dashed lines in drawing [1] no cells drawn AND only half stem AND two corners; [1] bulge on at least one corner OR definite region epidermis to epidermis of collenchyma across corner; MMO collection 2 [1] (epidermis) drawn with two lines closer than 4 mm at widest point AND at least one continuous line to show boundary of pith drawn; (one vascular bundle drawn in both corners) at least three regions AND vascular bundle drawn within each corner; [1] Additional guidance Must have both outer and inner lines curved towards the epidermis correct label, with label line to enclosed area, xylem; (should be inner area within vascular bundle) MMO decision 2 [1] Additional guidance R if • any label which is biologically incorrect e.g. from incorrect organ or animal • any label within drawn area • any label to open space

Page 10 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – October/November 2011 9700 36 © University of Cambridge International Examinations 2011 (ii) [6] PDO layout 1 [1] no shading AND trichome larger than 30 mm at longest point AND (clear, sharp, unbroken lines for outer cell line only); Must have five or more enclosed areas R if • drawn over the print of question • any line 1mm or thicker • any feathery or broken/dashed line • 0 ‘tails’ or overlaps or gaps • any ruled lines one whole trichome drawn AND attached to at least one epidermal cell; [1] Additional guidance R if any gap between trichome and attached cell R any ruled lines five adjacent epidermal cells made of different shapes in a line; MMO collection 2 [1] Additional guidance R if internal structures inside cells e.g. vacuole / nuclei R any ruled lines PDO recording 1 [1] (any one trichome) rounded or pointed end AND along MOST of one cell or across more than one cell AND only one cell in each trichome; [1] cell walls drawn as double lines with middle lamella between at least three adjacent epidermal cells; correct label with label line to trichome and one epidermal cell ; MMO decision 2 [1] Additional guidance R if any label is biologically incorrect e.g. epithelium or from incorrect organ or animal or cell organelles R any label within drawn area

Page 11 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – October/November 2011 9700 36 © University of Cambridge International Examinations 2011 (iii) [1] Ignore surface area unless in incorrect context. ACE conclusion 1 [1] absorb or trap water / moisture / moist / air OR prevent predators eating stem OR protection / protects from (mechanical) damage OR prevents ‘loss of water’ / transpiration / evaporation / ‘diffusion of water’ OR increase humidity;

Page 12 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – October/November 2011 9700 36 © University of Cambridge International Examinations 2011 (b) (i) [3] measures scale bar correctly in mm; 11.5 or 12(.0) or 12.5 or 13(.0) or 13.5 or 14(.0); MMO collection 1 [1] Additional guidance Can have 1.15 or 1.2 or 1.25 or 1.3 or 1.35 or 1.4 cm Must have units somewhere that is clear EITHER shows conversion of scale bar measurement to µm (measurement mm) × 1000 OR (measurement cm) × 10 000 OR shows conversion of µm to mm or cm 700 ÷1000 OR 700 ÷10 000 [1] Additional guidance Can have alternative signs for multiplication and division PDO display 2 [1] shows Allow range in mm/cm/µm 11.5, 12, 12.5, 13, 13.5, 14 in mm e.g. 13 in cm e.g. 1.3 in µm e.g. 13 000 measurement of scale bar ÷ scale 0.07 0.7 700 AND rounds to whole number ; (11.5) × 16 (12) × 17 (12.5) × 18 (13) × 19 (13.5) × 19 (14) × 20 OR [1] shows length of Fig. 2.2 divided by length of scale bar AND multiplied by 700 OR multiplied by length of Fig 2.2; (700 divided by length of scale bar) Can have between 80 mm / 80.5 to 90 mm ÷ 11.5 to 14 (to 0.5 mm only) OR 8.0 / 8.05 cm to 9 cm ÷ 1.15 to 1.4 (to 0.05 cm only) PDO display 2 [1] same length of Fig 2.2 in µm divided by answer AND rounded to whole number; A × 16 to × 20 in correct context of length of scale bar

Page 13 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – October/November 2011 9700 36 © University of Cambridge International Examinations 2011 (ii) [5] Mark first three differences only. PDO recording 1 [1] organise as a table / Venn diagram / ruled boxes AND headed N1 and (Fig.) 2.2 AND first difference opposite each other; MMO decision 1 [1] only three observable differences recorded ;

Page 14 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – October/November 2011 9700 36 © University of Cambridge International Examinations 2011 ACE Interpretation max 3 max 3 mp feature N1 Fig. 2.2 mp1 (overall shape or ref. to lumen or pith centre) R ‘not circular’ or folded lobed or star-shape or has bulges or AW e.g. irregular, square / rectangular, folded oval or round or circular or AW; R regular mp2 (corners or collenchymas or sclerenchyma or thickened cells) present or yes or has absent or no(ne) or has not; mp3 (vascular bundle position or shape) in lobes or bulges or corners separate / scattered (at edge) if idea of ‘all over’ / curved in a ring or circle or around or surrounding mp4 (vascular bundle number) few(er) R xylem or phloem lots or more; mp5 (vascular bundle sizes vary) large and small or vary / different similar / same size; mp6 (trichome(s)) R smooth / rough yes or present or has no(ne) or absent or has no mp7 (centre or pith) R vacuole not hollow (lumen / air space absent or no(ne)) hollow (lumen air space present or yes or has) mp8 (stomata / pores / openings / lenticels) Ignore sunken absent or has not or no(ne) or few present or has or yes or more; [Total: 21]