Cambridge A Level Biology 9700 — 2016 Oct/Nov Paper 3 · Variant 6

This document consists of 12 printed pages and 4 blank pages. DC (ST/SG) 116102/4 © UCLES 2016 [Turn over Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level * 2 2 2 5 4 4 2 4 7 8 * BIOLOGY 9700/36 Paper 3 Advanced Practical Skills 2 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

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3 9700/36/O/N/16 © UCLES 2016 [Turn over 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 Antibiotics are tested by observing how effective the antibiotics are at killing bacteria or preventing their growth. Agar blocks can be used to set up a model for antibiotic testing. In this model an acid represents the antibiotic solution and the blue stain in the agar block represents the bacteria. You will investigate the effect of the antibiotic solution (independent variable) on ‘killing the bacteria’, shown by the blue colour changing to yellow as the end-point. You are required to: • prepare different concentrations of the antibiotic solution, A, using serial dilution • record the time taken to reach the end-point (yellow) for each of the concentrations of A • record the time taken to reach the end-point for an unknown concentration of antibiotic solution, U • use the results to estimate the concentration of antibiotic in U. You are provided with: labelled contents hazard volume / cm3 A 1% acid (antibiotic solution) irritant 50 W distilled water none 100 U unknown concentration of acid (antibiotic solution) irritant 30 B agar block containing a blue stain none – You are advised to wear suitable eye protection, especially when using the antibiotic solution, A. If A comes into contact with your skin, wash off with cold water. (a) When carrying out a practical procedure the hazards of using the solutions need to be considered. Then the level of risk needs to be assessed as low or medium or high. State the hazard with the greatest level of risk when using the solutions then state the level of risk of the procedure: low or medium or high. hazard … level of risk …[1]

4 9700/36/O/N/16 © UCLES 2016 (b) You are required to make a serial dilution of the 1% antibiotic solution, A, which reduces the concentration by half between each successive dilution. You will need to prepare 20 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 antibiotic solution available for use in the investigation • use one arrow, with a label above the beaker, to show the volume and concentration of antibiotic 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.

5 9700/36/O/N/16 © UCLES 2016 [Turn over … … … 20 cm3 of 1% 40 cm3 of 1% antibiotic solution, A 0 cm3 of W antibiotic solution to use … … … Fig. 1.1 [3]

6 9700/36/O/N/16 © UCLES 2016 Proceed as follows: 1. Prepare the concentrations of antibiotic solution as decided in (b)(i) and as shown in Fig. 1.1. 2. Adjust the volumes so that there is 20 cm3 of antibiotic solution in each beaker. 3. Label a beaker as U and put 20 cm3 of U into this beaker. You will need to cut the agar block, B, into smaller pieces as shown in Fig. 1.2. To avoid staining your skin, try not to touch the agar. You may use the blunt forceps and paper towels to handle the agar. 4 cm 6 cm 5 mm 5 mm agar block, B not to scale Fig. 1.2 4. Place the agar block, B, onto a white tile and cut into identical pieces, each 5 mm # 5 mm as shown in Fig. 1.2. You do not need to adjust the depth. 5. Put one piece of agar into each beaker containing the concentrations prepared in step 1 and start timing. 6. Gently stir the contents of each beaker at intervals. 7. Record in (b)(ii) the time taken for the pieces of agar to reach the end-point. Note that the colour of the agar may change from blue to green and then to yellow. If any piece of agar has not changed to yellow after 240 s, stop timing and record as ‘more than 240’. Note that the same concentrations of antibiotic solution can be used again.

7 9700/36/O/N/16 © UCLES 2016 [Turn over (ii) Prepare the space below and record your results for the known concentrations of antibiotic solution. [5] 8. Put one piece of agar into the beaker labelled U and start timing. (iii) Record the time taken for the piece of agar in U to change to reach the end-point. time taken … [1] (iv) Use your results in (b)(ii) and (b)(iii) to estimate the concentration of antibiotic solution in U. …[1] (v) Identify one significant source of error in this investigation. … …[1]

8 9700/36/O/N/16 © UCLES 2016 (vi) This procedure investigated the effect of the concentration of the antibiotic solution (the independent variable) on its diffusion into stained agar blocks. To modify this procedure for investigating the effect of another independent variable, the concentration of antibiotic solution would need to be standardised. Describe how the concentration of antibiotic solution could be standardised. … … Describe how you would modify this procedure to investigate the effect of the independent variable, temperature, on diffusion into stained agar blocks. … … … … …[3] (c) In your investigation the antibiotic solution entered the agar blocks by diffusion. In animals, some substances cross cell surface membranes either by simple diffusion or by facilitated diffusion. A student investigated the rate of glucose uptake into animal cells. These animal cells were placed into different concentrations of glucose and the rate of glucose uptake into the cells was measured. All the other variables were standardised. The results are shown in Table 1.1. Table 1.1 external concentration of glucose / mmol dm–3 rate of glucose uptake by cells / mmol cm–3 h–1 0 0 1 205 3 320 5 395 10 450 20 455

9 9700/36/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] (ii) Use your graph to estimate the rate of glucose uptake by cells for an external concentration of glucose of 7 mmol dm–3. Show on your graph how you estimated the rate of glucose uptake. rate of glucose uptake … mmol cm–3 h–1 [1] (iii) Using the graph, explain how the results of the investigation support the idea that glucose enters cells by facilitated diffusion. … … … … …[2] [Total: 22]

10 9700/36/O/N/16 © UCLES 2016 2 M1 is a slide of a stained transverse section through a plant leaf. You are not expected to be familiar with this specimen. This leaf has several vascular bundles along its length. (a) Select the central vascular bundle which is larger than the others. You are required to use a sharp pencil for drawings. (i) Draw a large plan diagram of the quarter of the midrib shown by the shaded area in Fig. 2.1. Use one ruled label line and label to identify the phloem. midrib draw this quarter Fig. 2.1 You are expected to draw the correct shape and proportions of the different tissues. [4]

11 9700/36/O/N/16 © UCLES 2016 [Turn over (ii) Observe the xylem tissue in the vascular bundle of the midrib on M1. Select one group of four adjacent (touching) cells in a chain. Each cell of the chain must touch at least one of the other cells. Make a large drawing of this group of four cells. Use one ruled label line and label to identify the cell wall of one cell. [5]

12 9700/36/O/N/16 © UCLES 2016 (b) Fig. 2.2 is a photomicrograph of a stained transverse section through a different type of leaf, including the midrib. You are not expected to be familiar with this specimen. X Y Fig. 2.2 (i) Use the line X–Y to determine the simplest ratio of the depth of the midrib to the length of the vascular bundle. You may lose marks if you do not show your working. simplest ratio … [4]

13 9700/36/O/N/16 © UCLES 2016 (ii) Suggest one observable feature, shown in Fig. 2.2, which supports the conclusion that this plant may grow in an aquatic habitat. … …[1] (c) Prepare the space below so that it is suitable for you to record observable differences between the leaf midrib on M1 and the leaf midrib in Fig. 2.2. Record your observations in the space you have prepared. [4] [Total: 18]

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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 9700/36 Paper 3 Advanced Practical Skills 2 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 36 © UCLES 2016 Question Answer Mark 1(a) (risk assessment) irritant + medium risk ; 1 1(b)(i) (decisions on serial dilutions) 1 correct concentrations of 0.5, 0.25, 0.125, 0.0625 + % ; 2 shows transfer of 20 cm3 of 1% to next dilution + 20 cm3 transferred from 2nd to 3rd beaker and from 3rd to 4th and from 4th to 5th + cm3 ; 3 adds 20 cm3 of water to each beaker ; 3 1(b)(ii) (recording results) 1 table drawn + heading, percentage concentration of antibiotic ; 2 heading, time + seconds ; 3 records results for at least four concentrations ; 4 correct pattern of results, the highest concentration of antibiotic recorded as the shortest time for colour change ; 5 times recorded as whole seconds ; 5 1(b)(iii) (records time for U) appropriate number for time + seconds ; 1 1(b)(iv) (interpretation of estimate) correct estimate in accordance with recorded times ; 1

Page 3 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016 9700 36 © UCLES 2016 Question Answer Mark 1(b)(v) (source of error with reason) appropriate error with reason e.g. colour + difficult to judge ; 1 1(b)(vi) (modification to investigate another variable) 1 (to standardise concentration of antibiotic) uses stated concentration of antibiotic or uses same concentration of antibiotic ; 2 (changes independent variable – temperature) at least five temperatures ; 3 (method) uses thermostatically controlled water-bath ; 3 1(c)(i) (layout of data) 1 (x-axis) external concentration of glucose / mmol dm–3 + (y-axis) rate of glucose uptake by cells / mmol cm–3 hr–1 ; 2 (scale on x-axis) 5 to 2 cm, labelled at least each 2 cm + (scale on y-axis) 100 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 joined point to point, drawn as a thin line ; 4 1(c)(ii) (interpretation) correctly reads value for rate of glucose uptake from graph at 7 mmol dm–3 ; 1

Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016 9700 36 © UCLES 2016 Question Answer Mark 1(c)(iii) (conclusion) 1 reference to carrier proteins / channel proteins ; 2 (at low concentrations of external glucose) carrier proteins available or (at high concentrations of external glucose) limited availability of carrier proteins ; 2 Total: 22 Question Answer Mark 2(a)(i) (plan drawing) 1 large size + no shading ; 2 no cells + at least three lines or two lines and part of vascular tissue + correct section drawn ; 3 part of vascular tissue + epidermis drawn as two lines drawn closely together ; 4 uses one label line + one label to phloem ; 4

Page 5 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016 9700 36 © UCLES 2016 Question Answer Mark 2(a)(ii) (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 four cells drawn, each cell touching at least one other cell + no shading ; 3 cell walls drawn as two lines close together ; 4 at least one cell drawn with at least five sides ; 5 uses one label line + one label to cell wall ; 5 2(b)(i) (simplest ratio) 1 measures depth of the midrib + length of the vascular bundle ; 2 records whole numbers (mm) or to 0.5 (mm) for both measurements ; 3 displays, in final ratio, larger number to smaller number ; 4 final answer as simplest ratio ; 4 2(b)(ii) (conclusion) thick cuticle or air spaces or AVP ; 1

Page 6 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2016 9700 36 © UCLES 2016 Question Answer Mark 2(c) (observable differences) organises comparison into three columns with one column for features, one headed M1 and one headed Fig. 2.2 ; any three observable differences of comparison ; ; ; 4 Total: 18