Cambridge A Level Biology 9700 — 2010 Oct/Nov Paper 2 · Variant 1

This document consists of 14 printed pages and 2 blank pages. DC (SM/CGW) 29418/2 © 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 in the spaces provided at the top of this page. Write in dark blue or black pen. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. 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. * 9 8 4 3 4 6 3 9 9 8 * BIOLOGY 9700/21 Paper 2 Structured Questions AS October/November 2010 1 hour 15 minutes Candidates answer on the Question Paper. No Additional Materials are required. For Examiner’s Use 1 2 3 4 5 Total

2 9700/21/O/N/10 © UCLES 2010 For Examiner’s Use 1 (a) Complete the passage with the most appropriate term. Within each ecosystem there is a … of organisms that interact with each other and with their environment. Each species fills a particular … within the ecosystem. Feeding relationships in food webs are an example of the interactions species have with each other. In old field ecosystems in North America, producers, such as blue grass, provide energy for grazing animals. These animals form the … … … in the food chain. [3] (b) Very little of the energy consumed by grazing animals is available to carnivores. State two reasons why this is so. 1. … … 2. … …[2] [Total: 5]

3 9700/21/O/N/10 © UCLES 2010 [Turn over For Examiner’s Use 2 (a) Table 2.1 shows some of the structures in different parts of the gas exchange system. Complete Table 2.1 by indicating with a tick (✓) if the structure is present in each part of the gas exchange system or a cross (✗) if it is not. Table 2.1 structure trachea bronchus bronchiole alveolus ciliated epithelium goblet cells cartilage smooth muscle [4] (b) An exercise physiologist investigated aspects of breathing in an athlete. The minute volume is the volume of air breathed in during one minute. The data recorded is in Table 2.2. Table 2.2 vital capacity / dm3 breathing rate at rest / breaths min–1 minute volume / dm3 5.8 11 5.5 (i) Explain how the physiologist would determine the vital capacity of the athlete. … … … … …[2] (ii) Calculate the athlete’s tidal volume. Answer = …[1]

4 9700/21/O/N/10 © UCLES 2010 For Examiner’s Use (c) Fig. 2.1 shows a cross section of a coronary artery partially blocked by plaque causing atherosclerosis. Fig. 2.1 Explain why atherosclerosis in coronary arteries may limit the ability of people to take vigorous exercise. … … … … … …[3]

5 9700/21/O/N/10 © UCLES 2010 [Turn over For Examiner’s Use (d) Describe the effects of nicotine and carbon monoxide in cigarette smoke on the cardiovascular system. nicotine … … … … … … carbon monoxide … … … … … …[3] [Total: 13]

6 9700/21/O/N/10 © UCLES 2010 For Examiner’s Use 3 Red blood cells are suspended in plasma which has a concentration equivalent to that of 0.9% sodium chloride (NaCl ) solution. A student investigated what happens to red blood cells when placed into sodium chloride solutions of different concentration. A small drop of blood was added to 10 cm3 of each sodium chloride solution. Samples were taken from each mixture and observed under the microscope. The number of red blood cells remaining in each sample was calculated as a percentage of the number in the 0.9% solution. The results are shown in Fig. 3.1. 0 10 0.0 20 30 40 50 60 70 80 90 100 0.5 1.0 concentration of NaCl / % percentage of cells remaining 1.5 Fig. 3.1 (a) With reference to Fig. 3.1, describe the student’s results. … … … … … … … …[3]

7 9700/21/O/N/10 © UCLES 2010 [Turn over For Examiner’s Use The student also measured the cell volumes of the red blood cells in three of the sodium chloride solutions. The results are shown in Table 3.1. Table 3.1 concentration of sodium chloride / % mean red cell volume / µm3 0.7 120 0.9 90 1.5 65 Fig. 3.2 shows the appearance of some red blood cells removed from the 1.5% sodium chloride solution. Fig. 3.2 (b) Explain the results shown in Fig. 3.1, Table 3.1 and Fig. 3.2, in terms of water potential. 0% NaCl solution … … … … … 0.7% NaCl solution … … … … … 1.5% NaCl solution … … … … …[6]

8 9700/21/O/N/10 © UCLES 2010 For Examiner’s Use Red blood cells each contain about 240 million molecules of haemoglobin that transport oxygen and carbon dioxide. (c) Describe the role of haemoglobin in the transport of oxygen and carbon dioxide. oxygen … … … … carbon dioxide … … … …[4] (d) The haematocrit is the proportion of the blood that is composed of red blood cells. Samples of blood were taken from an athlete who lived at sea level since birth and moved to live and train at an altitude of 5000 m for three weeks. The haematocrit and the number of red blood cells per mm3 were determined before moving to high altitude and after three weeks at that altitude. The results are shown in Table 3.2. Table 3.2 altitude haematocrit number of red blood cells × 106 per mm3 sea level 0.45 6.1 5000 m (after three weeks) 0.53 7.3 (i) Calculate the percentage increase in the number of red blood cells per mm3 after three weeks at 5000 m. Show your working. Answer = … % [2]

9 9700/21/O/N/10 © UCLES 2010 [Turn over For Examiner’s Use (ii) Explain why the haematocrit increases at altitude. … … … … … …[3] [Total: 18]

10 9700/21/O/N/10 © UCLES 2010 For Examiner’s Use 4 Cholera bacteria release the enzyme neuraminidase which alters some of the surface proteins on the membranes of epithelial cells in the small intestine. These surface molecules become receptors for the toxin, choleragen, released by cholera bacteria. The toxin stimulates the cells to secrete large quantities of chloride ions into the lumen of the small intestine. Sodium ions and water follow the loss of chloride ions. (a) (i) Name the pathogen that causes cholera. …[1] (ii) Suggest how chloride ions are moved from the epithelial cells into the lumen of the small intestine. … …[1] (iii) Explain how cholera bacteria are transmitted from one person to another. … … … … …[3] A potential vaccine for choleragen was trialled on volunteers. Fig. 4.1 shows the concentration of antibodies against choleragen in the blood of a volunteer who received a first injection at week 0, followed by a booster injection at week 15. 0 1 injection injection 2 3 4 5 16 time / weeks antibody concentration 17 18 19 20 21 22 23 15 Fig. 4.1

11 9700/21/O/N/10 © UCLES 2010 [Turn over For Examiner’s Use (b) Using the information in Fig. 4.1, explain the differences between the responses to the first injection and the booster injection. … … … … … … … … … …[4] (c) Discuss the problems involved in preventing the spread of cholera. … … … … … … … … … … … … … … …[4] [Total: 13]

12 9700/21/O/N/10 © UCLES 2010 For Examiner’s Use 5 (a) Cellulose is a polysaccharide. Fig. 5.1 shows three sub-units from a molecule of cellulose. CH2OH C C C O C C H OH H H H OH H CH2OH C C C O C C H OH H H H OH H CH2OH C C C O O C C H OH H H H OH H O O Fig. 5.1 (i) Name the sub-unit molecule of cellulose. …[1] (ii) Name the bonds that attach the sub-unit molecules together within cellulose. …[1] (b) Cellulose has high mechanical strength which makes it suitable for the cell walls of plants. Explain how cellulose has such a high mechanical strength making it suitable for the cell walls of plants. … … … …[2]

13 9700/21/O/N/10 © UCLES 2010 [Turn over For Examiner’s Use Plant cell walls consist of cellulose that is embedded in a matrix of compounds, such as pectins and proteins. Cell wall material is synthesised inside the cell and transported to the cell surface membrane as shown in the drawing made from an electron micrograph in Fig. 5.2. A L K J H G F E D C B Fig. 5.2 (c) Locate the parts of the cell labelled in Fig. 5.2 which apply to each of the following statements. You must only give one letter in each case. You may use each letter once, more than once or not at all. The first answer has been completed for you. statement letter from Fig. 5.2 organelle that contains DNA H transports cell wall material to the cell surface membrane site of transcription site of ribosome synthesis site of photosynthesis [4]

14 9700/21/O/N/10 © UCLES 2010 For Examiner’s Use (d) Enzymes known as expansins are found in the matrix of cell walls to help the growth of cells. Use the information in Fig. 5.2 to describe how proteins made by the ribosomes reach the matrix of the cell wall. … … … … … …[3] [Total: 11]

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16 9700/21/O/N/10 © UCLES 2010 BLANK PAGE Copyright Acknowledgements: Fig. 2.1 GJLF / Science Photo Library Fig. 3.2 Steve Gschmeissner / Science Photo Library 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 2010 question paper for the guidance of teachers 9700 BIOLOGY 9700/21 Paper 2 (AS Structured Questions), maximum raw mark 60 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/AS LEVEL – October/November 2010 9700 21 © UCLES 2010 Mark Scheme abbreviations: ; separates marking points / alternative answers for the same point R reject A accept (for answers correctly cued by the question or guidance on the mark scheme) AW alternative wording (where responses may vary more than usual) underline actual word given must be used by the candidate (grammatical variants excepted) max indicates the maximum number of marks that can be given ora or reverse argument

Page 3 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – October/November 2010 9700 21 © UCLES 2010 1 (a) community ; niche ; A role second trophic level / first level consumers / primary consumer level ; A other appropriate terms [3] (b) loss (of energy-containing food in producers or in grazers) in indigestible parts / not being absorbed / faeces / egestion ;; one mark for producer, one mark for grazer excretion (in, grazers / herbivores / primary consumers) ; respiration (in, grazers / herbivores / primary consumers) ; loss of energy in movement / AW (in, grazers / herbivores / primary consumers); AVP ; e.g. heat energy [max 2] [Total: 5] 2 (a) structure trachea bronchus bronchiole alveolus ciliated epithelium


 goblet cells


/   cartilage

  smooth muscle


 one mark each row [4] (b) (i) athlete takes a deep breath and then breathes out as much air as possible / AW ; suitable method to record this, e.g. spirometer / breathing out into a bell jar of water ; [2] (ii) 0.5 dm3 / 500 cm3 ; [1] (c) reduced supply of blood to, heart / cardiac, muscle ; reduced supply of glucose (to cardiac muscle) ; R no reduced supply of oxygen (to cardiac muscle) ; R no less aerobic respiration / (more) anaerobic respiration (of cardiac muscle) ; build up of, lactate / carbon dioxide ; ref. limited cardiac output ; AVP ; e.g. ref. to consequences to (muscles of) body with reduced blood supply, ref. to pain caused by angina R heart attack / AW [3]

Page 4 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – October/November 2010 9700 21 © UCLES 2010 (d) damages, lining of arteries / endothelium ; accept once speeds up (atheromatous / fibrous) plaque development ; accept once increases chance of blood clotting / promotes thrombosis ; accept once nicotine increases heart rate / AW ; increases blood pressure ; makes platelets ‘sticky’ ; decreases blood flow to, extremities / AW ; constriction of blood vessels ; (max 2) carbon monoxide combines with haemoglobin / forms carboxyhaemoglobin / higher affinity for haemoglobin (than oxygen) ; reduces oxygen-carrying capacity / AW (in context of, haemoglobin / blood) ; promotes release of damaging free radicals / peroxides / superoxides / oxidising agents ; causes, platelets and neutrophils to stick together / platelets to stick to endothelium ; ref. hypoxia damage to cardiovascular system ; (max 2) [max 3] [Total: 13] 3 (a) accept ora penalise once if refs. in context of rates e.g. faster no cells remaining, correct concentration value given (accept up to 0.26%) ; 100% / AW, cells remaining, ref. from 0.86%–0.9% / AW ; steep increase in percentage cells remaining between 0.5–0.8% ; A to 0.7% if next marking point included steepest increase between 0.7–0.8% ; comparative data quote to support ref. to increase ; [max 3] (b) max 5 if no mention of water potential anywhere in the answer correct use of term osmosis linked to water potential (in context of high to low) ; 0% and 0.7% (net) water in (to red cells) ; 0%, all cells burst / (haemo)lysis of all cells ; general ref. to bursting at 0.7%, some cells burst ; ora either concentration ; cell membrane cannot withstand pressure ; (0.7%) (remaining) cells swollen / cell volume increases ; 0.7% water potential gradient not as steep as in, water / 0% ; 1.5% (net) loss of water from cells ; cells, shrink / AW or cell volume decreases ; A descriptions relative to biconcave disc shape [max 6]

Page 5 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – October/November 2010 9700 21 © UCLES 2010 (c) 4, oxygen molecules / O2, per (molecule of) haemoglobin ; (forms) oxyhaemoglobin (in lungs) ; A marking points 1 and 2 as equation ref. oxygen remains bound until blood in area of low pO2 / high pCO2 / high(er) temperature ; A in area of respiring tissues (max 3) carbon dioxide combines with haemoglobin ; terminal, amine / amino, group of haemoglobin ; A –NH2 carbamino-haemoglobin ; R carboxyhaemoglobin ref. to hydrogen ions from carbonic acid ; ref. carbon dioxide remains bound until blood in area of low pCO2 / high pO2 ; [max 4] (d) (i) 19.7 / 20 (%) ;; allow 1 mark if incorrect answer but correct working shown 7.3 – 6.1 / 6.1 × 100 / 1.2 / 6.1 × 100 [2] (ii) partial pressure / AW, of oxygen is, low / lower than at sea level ; haemoglobin less well saturated ; more red blood cells / more haemoglobin ; compensates for, smaller volume of oxygen absorbed (per red blood cell) / lower saturation of haemoglobin ; A ref. to tissues receiving sufficient oxygen AVP ; e.g. ref to erythropoietin (EPO) [max 3] [Total: 18] 4 (a) (i) Vibrio cholerae ; [1] (ii) active transport / described as movement against concentration gradient ; A facilitated diffusion / described [1] (iii) (bacteria) leave infected person in faeces / AW ; (bacteria) enter water supply / AW ; A idea of contaminated, food / utensils (bacteria) ingested by uninfected person ; [3] (b) must be in context of B-lymphocytes / B-cells / plasma cells max 3 if T-cells secondary response A ora presence of memory cells / AW (giving larger numbers) ; ref. increased chance of, encountering antigen / antigen presentation / clonal selection ; ref. larger numbers cells following, clonal expansion / AW (cf primary response) ; (so) shorter duration for onset of antibody production ; (so) higher antibody concentration ; secondary response antibody production (by plasma cells) lasts longer ; AVP ; e.g. faster rate, plasma cell / antibody, production, ref. longer-life of cells involved in secondary response [max 4]

Page 6 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – October/November 2010 9700 21 © UCLES 2010 (c) 1 poor sanitation / no treatment of faecal waste / AW ; 2 contamination of (drinking) water supply ; 3 poverty, qualified / poor living conditions 4 poor hygiene ; 5 poor / lack of, (health) education about transmission ; 6 ref to natural disasters ; e.g. assistance / aid / medical help / AW, cannot arrive in time 7 ref. refugees / displaced people ; 8 lack of, water purification equipment / bottled water / AW ; 9 no rehydration therapy available (at time when needed) ; 10 no (effective) vaccine ; 11 further detail ; (bacteria live in gut, where immune system is not effective) 12 AVP ; e.g. contamination of vegetable plots with faecal waste, ref. to different strains [max 4] [Total: 13] 5 (a) (i) β glucose ; [1] (ii) glycosidic ; [1] (b) many hydrogen bonds within the molecule ; idea of parallel chains / AW ; hydrogen bonds between cellulose molecules ; to form microfibrils ; held together by more hydrogen bonds to form fibres ; [2 max] (c) function letter from Fig. 5.1 organelle that contains DNA H structure that transports cell wall material to the cell surface membrane A site of transcription H site of ribosome synthesis J site of photosynthesis D [4] (d) polypeptide / protein, in (cisternae of) RER ; to Golgi (apparatus / AW) ; modification / glycosylation / packaging ; vesicle(s) formed / transport in vesicle ; A vacuole membrane of vesicle fuses with cell surface membrane ; exocytosis / described ; [max 3] [Total: 11]