Cambridge A Level Biology 9700 — 2016 May/June Paper 5 · Variant 3

This document consists of 9 printed pages and 3 blank pages. DC (ST/SW) 126036 © UCLES 2016 [Turn over * 0 4 9 9 2 7 1 3 8 1 * BIOLOGY 9700/53 Paper 5 Planning, Analysis and Evaluation May/June 2016 1 hour 15 minutes Candidates answer on the Question Paper. No Additional Materials are required. 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. Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level

2 9700/53/M/J/16 © UCLES 2016 1 Fig. 1.1 shows some of the plants growing in a pond and on the land around the pond. Some students decided to investigate the changes in the distribution and abundance of species of land plants at different distances from the edge of the pond. They started their investigation at the plants growing next to the water, as shown in Fig. 1.1. start of investigation water plants land plants Fig. 1.1 (a) (i) State the independent and dependent variables in this investigation. independent variable …  dependent variable … …[2]

3 9700/53/M/J/16 © UCLES 2016 [Turn over (ii) Describe a systematic sampling method the students could use to find out how the distribution and abundance of the plant species changed as the distance from the edge of the pond increased. Your description of the sampling method should be detailed enough for another person to use. … … … … … … … … … … … … … … … … … … … … … … … …[8]

4 9700/53/M/J/16 © UCLES 2016 (b) The students also collected samples of soil at different distances from the pond edge and estimated the water content. The students wanted to find out if the water content of the soil at the different distances sampled was related to the number of different plant species found at the same distances. To do this, a Spearman’s rank correlation (rs ) was carried out using the data in Table 1.1. Table 1.1 sample water content / arbitrary units rank number of species rank rank difference (D) D2 1 28 1 3 10 –9 81.00 2 26 2 4 9 –7 49.00 3 21 3 5 8 –5 25.00 4 18 4 6 7 –3 9.00 5 15 5.5 8 6 –0.5 0.25 6 14 7.5 9 4.5 3 9.00 7 15 5.5 10 3 2.5 6.25 8 14 7.5 9 4.5 3 9.00 9 13 9.5 11 2 7.5 56.25 10 13 9.5 12 1 8.5 72.25 D2 / = The formula for Spearman’s rank correlation is: r n n D 1 6 s 3 2 # = - - e o / rs = Spearman’s rank correlation n = number of pairs of observations D = difference between each pair of ranked measurements / = sum of

5 9700/53/M/J/16 © UCLES 2016 [Turn over (i) Complete Table 1.1 to show D2 / . [1] (ii) Use the information in Table 1.1 to calculate the value for rs. Show the values for: • D 6 2 # / • n n 3 - rs = …[2] (iii) State what the value for rs shows about the relationship between soil water content and the number of species present. … …[1] (c) (i) The group of students then investigated the relationship between soil air content and the number of different plant species at the same sampling points. The students calculated the rs value as +0.86. Table 1.2 shows part of a Spearman’s rank probability table. Table 1.2 n (number of pairs) 8 9 10 11 12 significance level 5% 0.738 0.700 0.648 0.618 0.618 significance level 1% 0.881 0.883 0.794 0.755 0.727 The students concluded that their rs value of +0.86 for the relationship between soil air content and the number of species present was significant at both the 5% level and 1% level. Explain how the students reached this conclusion. … … … … …[2]

6 9700/53/M/J/16 © UCLES 2016 (ii) Based on the result of their Spearman’s rank test and the significance of the rs value, the students concluded that: Soil air content caused the difference in the number of plant species that could grow at different distances from the edge of the pond. Suggest why this conclusion may not be valid. … … … … … … …[2] [Total: 18]

7 9700/53/M/J/16 © UCLES 2016 [Turn over 2 There are chemicals in the brain which give feelings of pleasure and reward. Nicotine in cigarette smoke is believed to cause addiction by increasing the secretion of these chemicals in the brain. Research into the treatment of nicotine addiction was carried out using rats to test the effect of a drug, topiramate, which blocks the secretion of these chemicals. Topiramate was administered to the rats in a saline solution. Table 2.1 shows the treatment given to six groups of healthy laboratory rats. Table 2.1 group of rats treatment with topiramate treatment with a standard concentration of nicotine 1 none (saline solution only) given 2 low concentration given 3 high concentration given 4 high concentration not given (water given instead) Groups 5 and 6 were pre-treated with nicotine for 14 days to simulate nicotine addiction 5 none (saline solution only) given 6 high concentration given One of the chemicals in the brain associated with pleasure and reward is dopamine. The concentration of dopamine was measured in all six groups.

8 9700/53/M/J/16 © UCLES 2016 (a) (i) State three variables which should have been standardised in this investigation. 1 … … 2 … … 3 … …[3] (ii) Groups 1, 4 and 5 are all controls. Explain why these were included. control groups 1 and 5 … … control group 4 … …[2] Fig. 2.1 and Fig. 2.2 show the results of using topiramate on the dopamine secretion in the brain. 0 20 40 60 dopamine secretion / percentage change from normal concentration 80 100 group 1 group 2 group of rats group 3 0 100 200 300 dopamine secretion / percentage change from normal concentration 400 group 5 group 6 group of rats Fig. 2.1 Fig. 2.2

9 9700/53/M/J/16 © UCLES 2016 (b) Rats pre-treated with nicotine were used as a model for humans addicted to nicotine. In rats that have not been treated with topiramate (groups 1 and 5), the secretion of dopamine in response to nicotine is greater in rats that have been pre-treated with nicotine (group 5), than in rats that have not been pre-treated with nicotine (group 1). Calculate the ratio of the increase in dopamine secretion caused by pre-treatment with nicotine (group 5) compared to no pre-treatment with nicotine (group 1). …[2] (c) State three conclusions that can be drawn about the effect of topiramate on the secretion of dopamine by the brain in response to nicotine. 1 … … 2 … … 3 … …[3] (d) The researchers also studied the effect of topiramate on two other brain chemicals, noradrenaline and serotonin. They found that topiramate: • completely inhibits the release of noradrenaline, which is associated with pleasure and reward • stimulates the secretion of serotonin, which has been shown in human trials to reduce smoking and inhibit the secretion of dopamine. Suggest why the researchers concluded that topiramate could be successful in treating nicotine addiction. … … … … …[2] [Total: 12]

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® IGCSE is the registered trademark of Cambridge International Examinations. This document consists of 8 printed pages. © UCLES 2016 [Turn over Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level BIOLOGY 9700/53 Paper 5 Planning, Analysis and Evaluation May/June 2016 MARK SCHEME Maximum Mark: 30 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 May/June 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 – May/June 2016 9700 53 © Cambridge International Examinations 2016 Mark scheme abbreviations: ; separates marking points / alternatives answers for the same point R reject A accept (for answers correctly cued by the question, or extra guidance) AW alternative wording (where responses vary more than usual) underline actual word given must be used by candidate (grammatical variants accepted) max indicates the maximum number of marks that can be given ora or reverse argument ecf error carried forward I ignore mp marking point (with relevant number)

Page 3 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9700 53 © Cambridge International Examinations 2016 Question Expected answer Extra guidance Mark 1 (a) (i) distance from the pond ; distribution / abundance / numbers, of (different), species of plant / types of plant / sorts of plant / land plants ; A position from pond I ref. to distance from starting point A distribution / abundance / numbers, of the plants [2] (ii) any 8 from: 1 use a (named) transect ; 2 method of measuring, transect / line ; 3 ref. to distance / length, of transect ; 4 ref. to selecting where around pond to place the transect(s) ; 5 ref. to suitable sampling technique ; 6 ref. to sampling intervals (in context of transect / line) ; 7 use of, same / stated size, quadrat / frame / point frame / sample area ; A belt (interrupted or continuous) or line transect. A description in terms of a line / AW A idea of use of either one or two measuring tapes, e.g. string with measured marks A idea of until the plants no longer change A stated distance, 10 m minimum e.g. (frame) quadrat / point frame / point quadrat A description A diagram I quadrant / quadrent I a square / square shape, unqualified A look at / observe, what is touching the line for a line transect A continuous sampling A (stated) regular intervals for an interrupted transect I fixed intervals unless qualified R any random placing, e.g. throwing / use of random numbers A if size of quadrat / frame / sample area is stated as between 0.25 m2 – 1 m2 size I controlled size unqualified

Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9700 53 © Cambridge International Examinations 2016 8 ref. to method to identify (the different) species ; 9 ref. to method of estimating abundance / distribution ; 10 ref. to care taken not to miss, low growing / AW, species ; 11 replicate transect (at least once) ; 12 sample at different times of, year / seasons ; 13 safety any 1 from: • ref. to injury / getting lost and staying with a group ; • allergy to plants and wearing gloves / protective clothing ; • allergy to pollen / hay fever and wearing mask or taking medication ; • ref. to dangerous environment described / hazardous plants / hazardous animals and wearing suitable shoes / protective clothing / repellent ; e.g. photographs / (dichotomous) key / app / expert / nature guide / book / AW A species identified as A, B, C, etc. counting / density / percentage cover / frequency / abundance scale (ACFOR or equivalent) / cover-abundance scale (Braun- Blanquet) / presence or absence / AW I repeat in the same transect A repeat, steps / the transect / the experiment at a different (start) point (round the pond) need risk plus precaution I low / high risk [max 8]

Page 5 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9700 53 © Cambridge International Examinations 2016 (b) (i) ΣD2 = 317 ; A 317.0 / 317.00 [1] (ii) (6 × ΣD2 =) 1902 and (n3 – n =) 990 ; rs = (1 – 1.92 =) – 0.92 ; A one mark for the formula: rs = 1 – 1902 990 A –0.9 or – 0.921 R –.90 ecf from (b)(i) ecf to max 1 if one or both of calculations (6 × ΣD2 =) and (n3 – n =) are wrong [2] (iii) there is a negative correlation / as soil water increases the number of species decreases / ora ; ecf from (b)(i) A correct interpretation of rs value calculated A negative association / inverse relationship / inversely proportional, for correlation I significant / not significant I qualifications 'strong' or 'weak' [1] (c) (i) evidence that the students used the probability table for 10 pairs of data ; the rs value is greater than the critical values at 5% and at 1% / ora ; A if critical values 0.648 and 0.794 are used A rs value is greater than actual critical values 0.648 and 0.794 A ecf for wrong number of pairs A rs value is greater than actual values at p / probability = 0.05 and 0.01 I ref. to left / right [2] (ii) idea that Spearman’s rank correlation only shows there is a relationship not a cause / effect ; any 1 from: • sampling / transect(s), may be unrepresentative of the whole area ; • other (named) biotic / abiotic / environmental I ref. to 'not due to chance' (must have positive idea of correlation / relationship) I do more samples / not enough replicates were taken I other factors influence the data (factor must be qualified)

Page 6 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9700 53 © Cambridge International Examinations 2016 factors may be contributing to distribution of plants ; A other environmental / biotic / abiotic / factors influence the data named factors : soil pH, light / light intensity, slope, temperature, (soil) moisture / water, grazing, wind, minerals / ions / mineral salts / salts / humus, soil organisms, pathogens, effluent / herbicide I nutrients I any ref. to stats e.g. need to take account of standard error [max 2] Total: [18] 2 (a) (i) any 3 from: 1 body, mass / weight ; 2 age ; 3 number in each (test) group ; 4 ref. to sex (composition of the groups) ; 5 species / variety / type / genetic strain / breed /AW (of rat) ; 6 factor that might affect dopamine secretion ; 7 volume of nicotine used ; 8 concentration of saline ; 9 volume of saline ; 10 volume of topiramate ; 11 each high concentration of topiramate (should be the same concentration) ; 12 time between giving the, treatments / topiramate or I amount throughout I mass / weight unqualified A mass / weight of rats I biomass of rats / size of rats A all same sex or equal numbers of each sex A gender A stress / diet / food / water / environmental temperature I body temperature A each low concentration (Group 2) should be the same for each rat I concentration of topiramate unqualified A time treatments are given

Page 7 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9700 53 © Cambridge International Examinations 2016 saline, and nicotine ; 13 time between giving, treatments / nicotine / topiramate / saline, and measuring the concentration of dopamine ; 14 method of administration of, nicotine / topiramate / treatment ; [max 3] (ii) control groups 1 and 5 to see if / show that / test that, topiramate is, causing the effect / blocking secretion of dopamine / blocking secretion of (pleasure and reward) chemicals ; control group 4 to show any effect that topiramate has, on its own / without nicotine ; A to show that saline solution on its own does not have an effect on / block secretion of dopamine / (pleasure and reward) chemicals R increase in dopamine A to see if there is a relationship between topiramate and dopamine secretion A idea of in context of, rats never given nicotine / ‘normal’ rats [2] (b) group 5 pre-treatment = 280 (% increase) and group 1 no pre-treatment = 64 (% increase) ; 35:8 ; A figures in a formula A 8:35 if clear which is which A 4.375:1 / 4.38:1 / 4.4:1 / 4:1 A quotients 4.375 / 4.38 / 4.4 / 4 A fractions 35/8 / 4.375/1 / 4.38/1 / 4.4/1 / 4/1 R units or % in final ratio ecf if graph misread for one mark [2] (c) any 3 from: 1 (topiramate / it), reduces the release of dopamine (from the brain) ; 2 the higher the concentration of topiramate, the greater the reduction / the lower the secretion (of dopamine) ; A inhibits / blocks A reduces the (dopamine) response / AW A inhibits / blocks

Page 8 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9700 53 © Cambridge International Examinations 2016 3 (the, percentage) reduction / drop, in dopamine secretion, is lower in the rats pre-treated with nicotine (280% to 120% = 57%) (than in rats not pre- treated with nicotine) (64% to 16% = 75%) ora ; 4 any 1 from: • in pre-treated rats / group 6, (high concentration of) the topiramate reduces the response by 160% ; • in rats without pre-treatment / group 2, (low concentration of) the topiramate reduces the response by 40% ; • in rats without pre-treatment / group 3, (high concentration of) the topiramate reduces the response by 48% ; A references to addicted / non-addicted rats A by 57% / by approximately half A by 63% / by approximately two thirds A by 75% / by three quarters [max 3] (d) (topiramate / it) inhibits / reduces / blocks, pleasure / reward / AW, so smokers, gain less from smoking / less enjoyment / become less addicted / likely to smoke fewer cigarettes / AW ; idea that topiramate affects, more than one / all / three brain chemicals and so has a cumulative / additive effect (on suppressing the addiction) ; A because it has an effect on more than one chemical it has a, bigger / larger / further / AW, effect [2] Total: [12]