Cambridge A Level Biology 9700 — 2016 Oct/Nov Paper 3 · Variant 1

This document consists of 13 printed pages and 3 blank pages. DC (LEG/CGW) 116080/3 © UCLES 2016 [Turn over Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level * 0 8 2 2 5 8 9 7 5 2 * BIOLOGY 9700/31 Paper 3 Advanced Practical Skills 1 October/November 2016 2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions. 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 an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. Electronic calculators may be used. 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. For Examiner’s Use 1 2 Total

2 9700/31/O/N/16 © UCLES 2016 Before you proceed, read carefully through the whole of Question 1 and Question 2. Plan the use of the two hours to make sure that you finish all the work that you would like to do. If you have enough time, think about how you can improve the accuracy of your results, for example by obtaining and recording one or more additional measurements. You will gain marks for recording your results according to the instructions. 1 Some people feel unwell after drinking animal milk. This is because they are unable to digest the reducing sugar lactose found in this milk. Other sources of milk, such as milk made from plant material, do not contain this reducing sugar and can be included in the diet instead. You are required to: • prepare different concentrations of reducing sugar solution, R, using serial dilution • determine the concentration of reducing sugar in two samples of milk • identify which milk would be the most suitable for a person who is unable to digest lactose. You are provided with: labelled contents hazard volume / cm3 R 1% reducing sugar solution none 50 W distilled water none 50 Benedict’s Benedict’s solution none 50 M1 milk none 40 M2 milk none 40 (a) You are required to make a serial dilution of the 1% reducing sugar solution, R, which reduces the concentration by half between each successive dilution. Decide how many different concentrations you will prepare for your serial dilution. You will need to prepare 10 cm3 of each concentration. Fig. 1.1 shows the first two beakers you will use to make your serial dilution. (i) Complete Fig. 1.1 by drawing as many extra beakers as you need for your serial dilution. For each beaker: • state, under the beaker, the volume and concentration of the reducing sugar solution available for use in the investigation • use one arrow, with a label above the beaker, to show the volume and concentration of reducing sugar solution added to prepare the concentration • use another arrow, with a label above the beaker, to show the volume of W added to prepare the concentration.

3 9700/31/O/N/16 © UCLES 2016 [Turn over … … … 10 cm3 of 1% 20 cm3 of 1% reducing sugar solution, R 0 cm3 of W reducing sugar solution to use … … … [3] Fig. 1.1

4 9700/31/O/N/16 © UCLES 2016 Proceed as follows: 1. Set up a water-bath and heat to boiling ready for step 6. 2. Prepare the concentrations of reducing sugar solution as decided in (a)(i) and in Fig. 1.1. (ii) You will be required to carry out the Benedict’s test on each of the reducing sugar solutions you have prepared. You will use 2 cm3 of reducing sugar solution for each test. State the volume of Benedict’s solution you will use for each reducing sugar test. Explain why you have selected this volume. volume of Benedict’s solution … cm3 explanation … … [1] 3. Put 2 cm3 of 1% reducing sugar solution into a test-tube. 4. Put the volume of Benedict’s solution you stated in (a)(ii) into the same test-tube. 5. Shake the test-tube gently to mix the contents. 6. Put this test-tube into the boiling water-bath (prepared in step 1) and record in (a)(iii) the time taken for the first appearance of a colour change. If there is no colour change after 90 s, stop timing and record as ‘more than 90’. 7. Repeat step 3 to step 6 for each of the other concentrations of reducing sugar that you prepared in step 2. (iii) Prepare the space below and record your results. [3]

5 9700/31/O/N/16 © UCLES 2016 [Turn over (iv) A student carried out step 1 to step 7 and recorded the result for one of the concentrations as 42 s. Calculate the rate of this reaction. You may lose marks if you do not show your working. … s–1 [2] You are required to find the concentration of reducing sugar in two samples of milk, M1 and M2, using Benedict’s solution. (v) State the variables that you will need to standardise so that you can compare the results of the Benedict’s test on M1 and M2 with those recorded in (a)(iii). … … … …[2] 8. Repeat step 3 to step 6 for each of M1 and M2 and record your results in (a)(vi). (vi) Record your results for M1 and M2. M1 … M2 … [1] (vii) Use your results in (a)(iii) to estimate the percentage concentration of reducing sugar in each of M1 and M2. M1 … M2 …[2] (viii) State which sample, M1 or M2, would be most suitable for a person who is unable to digest lactose. Give a reason for your answer. sample … reason …[1]

6 9700/31/O/N/16 © UCLES 2016 (b) In most people the reducing sugar lactose is hydrolysed by an enzyme during digestion to produce monosaccharides which are absorbed into the blood. Some people do not produce this enzyme. When they drink animal milk, the lactose is undigested. Certain bacteria use the undigested lactose for respiration and produce hydrogen gas. This enters the bloodstream, and is transported to the lungs where it is breathed out (exhaled). Scientists can measure the concentration of hydrogen in exhaled air. A scientist gave a person who does not produce this enzyme a drink of animal milk. The effect of drinking milk containing lactose was investigated by measuring the concentration of hydrogen in exhaled air every 20 minutes for 80 minutes. The results are shown in Table 1.1. Table 1.1 time after drinking milk containing lactose / minutes concentration of hydrogen in exhaled air / ppm 0 15 20 17 40 24 60 52 80 80

7 9700/31/O/N/16 © UCLES 2016 [Turn over You are required to use a sharp pencil for graphs. (i) Plot a graph of the data shown in Table 1.1. [4]

8 9700/31/O/N/16 © UCLES 2016 Fig. 1.2 is a photomicrograph of a stained transverse section through an animal organ. The bacteria that use lactose may be found in the lumen of this organ. You are not expected to be familiar with this specimen. Fig. 1.2

9 9700/31/O/N/16 © UCLES 2016 [Turn over You are required to use a sharp pencil for drawings. (ii) Draw a large plan diagram of the half of the organ shown by the shaded area in Fig 1.3 . draw this half Fig. 1.3 You are expected to draw the correct shape and proportions of the different tissues. [4] [Total: 23]

10 9700/31/O/N/16 © UCLES 2016 2 J1 is a slide of a stained transverse section through a plant leaf. You are not expected to be familiar with this specimen. You are required to use a sharp pencil for drawings. (a) (i) Observe the upper epidermis at the top of the leaf on J1. Select one group of three cells with: • two cells from the upper epidermis • one adjacent (touching) cell from the tissue below. Each cell of the group must touch at least one of the other cells. Make a large drawing of this group of three cells. Use one ruled label line and label to identify the cell wall of one cell. [4] (ii) State the function of the cell you have drawn from the tissue below the epidermis. Identify one observable feature of this cell that supports your answer. function of cell … observable feature …[2]

11 9700/31/O/N/16 © UCLES 2016 [Turn over Fig 2.1 is a photomicrograph of a stained transverse section through part of a leaf from a different type of plant. You are not expected to be familiar with this specimen. Fig. 2.1 (b) Prepare the space below so that it is suitable for you to record observable differences between the leaf on J1 and the leaf in Fig. 2.1. Record your observations in the space you have prepared. [4]

12 9700/31/O/N/16 © UCLES 2016 (c) You are required to measure the diameter of the field of view using the clear plastic ruler. Proceed as follows: 1. Put the clear plastic ruler on the stage of the microscope and view the scale lines using low power (×100). 2. Measure the diameter of the field of view and record this in (c)(i). (i) Diameter of the field of view … mm [1] Fig. 2.2 is the same photomicrograph as in Fig. 2.1 showing the field of view at the same magnification as the field of view you have just measured. X field of view Z Y Fig. 2.2 (ii) Using appropriate measurements, calculate the fraction of the diameter of the field of view occupied by the leaf in Fig. 2.2 along the line X–Z. fraction of diameter of field of view …[1] (iii) Using your answers to (c)(i) and (c)(ii) calculate the depth of the midrib, as shown by line Y–Z. Give your answer to the nearest μm. You may lose marks if you do not show your working. …μm [2]

13 9700/31/O/N/16 © UCLES 2016 (iv) A student used a clear plastic ruler to measure the field of view of a microscope. The student replaced the ruler with a slide of a leaf and estimated the diameter of the midrib. Using these results the student calculated the actual diameter of the midrib. State how this student could have modified their method to obtain a more accurate result. State the apparatus the student would use and describe the method. apparatus … … method … … … … …[3] [Total: 17]

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® IGCSE is the registered trademark of Cambridge International Examinations. This document consists of 6 printed pages. © UCLES 2016 [Turn over Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level BIOLOGY 9700/31 Paper 3 Advanced Practical Skills 1 October/November 2016 MARK SCHEME Maximum Mark: 40 Published 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 should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the October/November 2016 series for most Cambridge IGCSE®, Cambridge International A and AS Level components and some Cambridge O Level components.

Page 2 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016 9700 31 © UCLES 2016 Question Answer Mark 1(a)(i) (decisions on serial dilutions) 1 correct concentrations of 0.5, 0.25, 0.125, 0.0625 + % ; 2 shows transfer of 10 cm3 of 1% to next dilution + 10 cm3 transferred from 2nd to 3rd beaker and from 3rd to 4th and from 4th to 5th + cm3 ; 3 adds 10 cm3 of water to each beaker ; 3 1(a)(ii) (decision) volume of Benedict’s solution equal to or greater than 2 cm3 of reducing sugar ; 1 1(a)(iii) (recording results) 1 table drawn + heading, percentage concentration of reducing sugar ; 2 heading, time + seconds ; 3 times recorded as whole seconds ; 3 1(a)(iv) (calculation) 1 shows 1 divided by 42 ; 2 correct answer as 0.024 ; 2

Page 3 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016 9700 31 © UCLES 2016 Question Answer Mark 1(a)(v) (decisions) two from 1 states volume of Benedict’s solution ; 2 states volume of M1 + M2 ; 3 states temperature of water-bath ; 2 1(a)(vi) (recording results) records time in seconds for M1 + M2 ; 1 1(a)(vii) (interpretation) 1 states percentage concentration of reducing sugar for M1 (either known concentration or between known concentrations) ; 2 states percentage concentration of reducing sugar for M2 (either known concentration or between known concentrations) ; 2 1(a)(viii) (conclusion) M2 + no or very little reducing sugar ; 1

Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016 9700 31 © UCLES 2016 Question Answer Mark 1(b)(i) (layout of data) 1 (x-axis) time after drinking milk containing lactose / minutes + (y-axis) concentration of hydrogen in exhaled air / ppm ; 2 (scale on x-axis) 20 to 2 cm, labelled at least each 2 cm + (scale on y-axis) 20 to 2 cm, labelled at least each 2 cm ; 3 correct plotting of five points with a small cross or dot in circle ; 4 five plots either joined point to point or as a smooth curve, drawn as a thin line ; 4 1(b)(ii) (plan drawing) 1 large size + no shading ; 2 no cells + correct section drawn + appropriate detail of inner section ; 3 outermost layer drawn as two lines ; 4 draws gap between outer and inner layer ; 4 Total: 23

Page 5 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016 9700 31 © UCLES 2016 Question Answer Mark 2(a)(i) (layout of drawing) 1 quality of line for outer wall of cells thin and sharp + minimum size at least 40 mm across largest cell ; 2 only three cells drawn + each cell touching at least one of the other cells ; 3 draws contents in at least one cell ; 4 uses one label line + one label to cell wall ; 4 2(a)(ii) (conclusion) (function) photosynthesis ; (feature) chloroplasts ; 2 2(b) (observable differences) organises comparison into three columns with one column for features, one headed J1 and one headed Fig. 2.1 ; any three observable differences of comparison ; ; ; 4 2(c)(i) (diameter of field of view) records measurement within range ; 1 2(c)(ii) (fraction of the diameter of the field of view) estimates within range ; 1

Page 6 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016 9700 31 © UCLES 2016 Question Answer Mark 2(c)(iii) (depth of midrib) 1 shows answer to (c)(i) multiplied by answer to (c)(ii) ; 2 decision to multiply by 1000 (to convert to µm) ; 2 2(c)(iv) (improvements) 1 reference to eyepiece graticule + stage micrometer ; 2 measurement of midrib using eyepiece graticule ; 3 reference to calibration of eyepiece graticule ; 3 Total: 17