Cambridge A Level Biology 9700 — 2006 May/June Paper 4 · Variant 1

This document consists of 10 printed pages and 2 lined pages. SP (CW/CGW) T10865/2 © UCLES 2006 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Level BIOLOGY 9700/04 Paper 4 Structured Questions A2 Core May/June 2006 1 hour 15 minutes Candidates answer on the Question Paper. Additional Materials: Answer Paper (should be available on request.) 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 a pencil for any diagrams, graphs, or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer all questions in Section A and one question from Section B. Circle the number of the Section B question you have answered in the grid below. 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. Centre Number Candidate Number Name For Examiner’s Use 1 2 3 4 5 Section A 6 or 7 TOTAL

2 9700/04/M/J/06 For Examiner’s Use © UCLES 2006 Section A Answer all the questions. 1 The metabolic pathway in which a hexose sugar, such as glucose, is broken down in respiration by cells starts with glycolysis. Fig. 1.1 outlines the key stages of glycolysis. hexose triose phosphate 2ATP 2ADP 2ATP reduced NAD NAD pyruvate A Fig. 1.1 (a) State where in the cell glycolysis takes place. …[1] (b) Name substance A. …[1] (c) Explain why the hexose is converted to substance A. … … … …[2]

3 9700/04/M/J/06 [Turn over For Examiner’s Use © UCLES 2006 (d) Briefly describe what happens to pyruvate if yeast is deprived of oxygen. … … … … … … … …[4] [Total: 8]

4 9700/04/M/J/06 For Examiner’s Use © UCLES 2006 2 Fig. 2.1 shows the results of experiments investigating the effect of different light intensities on the rate of photosynthesis of cucumber plants measured as mm3 CO2 uptake per cm2 leaf area per hour. The experiments were carried out at two different temperatures and two different carbon dioxide concentrations. 0 0 50 100 150 200 250 1 2 3 light intensity / arbitrary units rate of photosynthesis /mm3 cm-2 h-1 4 5 6 A B C 7 key A 0.04% C02 20°C B 0.04% C02 30°C C 0.13% C02 30°C Fig. 2.1 (a) With reference to Fig. 2.1, (i) describe the shape of curve A, … … … … … …[3]

5 9700/04/M/J/06 [Turn over For Examiner’s Use © UCLES 2006 (ii) explain the reasons for the difference between curves B and C. … … … … … … …[4] (b) Suggest two ways in which a commercial grower of cucumbers may increase the yield of the growing crop. 1 … … 2 … …[2] [Total: 9]

6 9700/04/M/J/06 For Examiner’s Use © UCLES 2006 3 During the process of the excretion of nitrogenous waste in mammals, blood passes from the renal artery into networks of capillaries called glomeruli. Fig. 3.1 is an electronmicrograph showing the relationship between the capillaries and the renal capsule cells, called podocytes. Fig. 3.1 (a) Name structures A and B. A … B … [2] (b) Draw an arrow, on Fig. 3.1, to show the passage of fluid out of the capillary. [2] (c) (i) Name the fluid that collects in the capsular space. … …[1] (ii) Describe how the composition of this fluid differs from blood plasma. … … … …[2]

7 9700/04/M/J/06 [Turn over For Examiner’s Use © UCLES 2006 (d) Ultrafiltration involves the removal of small molecules, including urea, from the blood into the renal capsule. Explain what is required for ultrafiltration to occur. … … … … … …[3] [Total: 10] 4 (a) Name the transmitter which is responsible for the transmission of nerve impulses across a cholinergic synapse. …[1] (b) Outline the role of calcium ions in synaptic transmission. … … … … … … … …[4] (c) Explain how a synapse ensures one-way transmission of nerve impulses. … … … …[2] [Total: 7]

8 9700/04/M/J/06 For Examiner’s Use © UCLES 2006 5 (a) The summer squash plant produces fruit that are either white or yellow in colour and are either shaped like a disc or a sphere. The dominant phenotypes are white and disc- shaped fruit. Using the symbols A for white and a for yellow and B for disc and b for sphere, draw a genetic diagram to show what proportion of offspring will have yellow and sphere-shaped fruit if a white and disc-shaped fruit plant, heterozygous for both genes, is self-fertilised. [6]

9 9700/04/M/J/06 [Turn over For Examiner’s Use © UCLES 2006 Sickle cell anaemia is a blood disease that is frequently fatal when homozygous. It is caused by an autosomal recessive allele. Heterozygotes have sickle cell trait and appear normal. Malaria is a potentially fatal infectious disease of the blood caused by the protoctist, Plasmodium. In parts of the world where malaria is endemic the frequency of the sickle cell allele is high. (b) Explain the possible health consequences, in such areas, for a person who is homozygous dominant and for a person who is homozygous recessive for the sickle cell allele. (i) homozygous dominant for the sickle cell allele … …[1] (ii) homozygous recessive for the sickle cell allele. … …[1] (c) Explain why heterozygotes have a strong selective advantage in areas where malaria occurs. … … … … … …[3] [Total: 11]

10 9700/04/M/J/06 For Examiner’s Use © UCLES 2006 Section B Answer one question. 6 (a) Explain the meaning of the term homeostasis with specific reference to the control of raised blood glucose concentration in mammals. [8] (b) Describe the role played by ADH in osmoregulation in mammals. [7] [Total: 15] 7 (a) Describe the role of natural selection in evolution. [8] (b) Explain, using named examples, how mutation can affect phenotype. [7] [Total: 15] … … … … … … … … … … … … … … … … … …

11 9700/04/M/J/06 [Turn over For Examiner’s Use … … … … … … … … … … … … … … … … … … … … … … … … … … … …

12 9700/04/M/J/06 … … … … … … … … … … … … … … … … … … … … … … … … 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 University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge. For Examiner’s Use

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Level and GCE Advanced Subsidiary Level MARK SCHEME for the May/June 2006 question paper 9700 BIOLOGY 9700/04 Paper 4 Maximum raw mark 60 This mark scheme is published as an aid to teachers and students, to indicate the requirements of the examination. It shows the basis on which Examiners were initially instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began. Any substantial changes to the mark scheme that arose from these discussions will be recorded in the published Report on the Examination. All Examiners are instructed that alternative correct answers and unexpected approaches in candidates’ scripts must be given marks that fairly reflect the relevant knowledge and skills demonstrated. Mark schemes must be read in conjunction with the question papers and the Report on the Examination. The minimum marks in these components needed for various grades were previously published with these mark schemes, but are now instead included in the Report on the Examination for this session. • CIE will not enter into discussion or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the May/June 2006 question papers for most IGCSE and GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

Page 1 Mark Scheme Syllabus Paper GCE A/AS Level – May/June 2006 9700 04 © University of Cambridge International Examinations 2006 Question Expected Answers Marks 1 (a) cytoplasm ; [1] (b) hexose bisphosphate / phosphorylated 6C sugar / fructose bisphosphate ; [1] (c) hexose energy rich ; does not react easily / AW ; phosphorylation activates hexose ; maintains concentration gradient of glucose inside and outside cell ; [2 max] (d) does not enter Krebs cycle ; decarboxylated / CO2 released ; forms ethanal ; reduced / ref: reduced NAD ; to ethanol ; reduced NAD does not enter ETC ; ref: alcohol dehydrogenase ; irreversible ; [4 max] [Total: 8] 2 (a) (i) at low light intensities ; rate of photosynthesis is proportional to light intensity / light intensity is limiting ; after 1 units of light ; rate levels off / reaches plateau ; relevant fig plus units ; [3 max] (ii) (B) after 3 units light intensity not limiting ; CO2 now limiting ; (C) curve continues to increase until 5 units of light ; light intensity limiting ; correct description of law of limiting factors ; detail. collisions of CO2 and enzymes ; AVP ; e.g., further detail of enzymes [4 max] (b) optimum temperature ; method e.g. heaters / ventilation ; optimum CO2 concentration ; burners / combustion / add dry ice / pump in CO2 up to 1% ; high light intensity / longer duration of light / artificial lighting ; ref. irrigation ; ref. fertilisers ; ref. pest / disease control ; ref. artificial pollination ; [2 max] [Total: 9]

Page 2 Mark Scheme Syllabus Paper GCE A/AS Level – May/June 2006 9700 04 © University of Cambridge International Examinations 2006 Question Expected Answers Marks 3 (a) A – basement membrane ; B – minor process / foot ; [2] (b) arrow going from capillary (through pore in capillary wall) and through gaps in podocyte processes ; arrow continues into renal capsule ; [2] (c) (i) glomerular filtrate ; [1] (ii) less protein ; no large protein ; ref. less than MM 68 000 to 69 000 ; no blood cells ; AVP ; [2 max] (d) sufficient hydrostatic (blood) pressure ; comparison between afferent and efferent vessels ; to force fluid through ; basement membrane ; selective barrier / AW ; [3 max] [Total: 10] 4 (a) acetylcholine / Ach ; [1] (b) wave of depolarisation / action potential, in pre-synaptic axon / membrane ; Ca2+ channels open ; Ca2+ enter pre-synaptic neurone / synaptic knob ; causes synaptic vesicles to move towards presynaptic membrane ; ref. exocytosis of Ach / neurotransmitter ; [4 max] (c) vesicles found only in, pre-synaptic knob / neurone ; receptors found only in post-synaptic membrane ; [2] [Total: 7] 5 (a) parental genotypes ; e.g. AaBb x AaBb gametes ; correct use of punnett square ; F1 genotypes ; F1 phenotypes ; (must link to genotypes) yellow and sphere 1/16 ; [6] (b) (i) contract / die from, malaria ; [1] (ii) contract / die from, sickle-cell anaemia ; [1] (c) resistant to malaria ; detail ; more likely to survive ; and reproduce ; pass on sickle-cell allele ; [3 max] [Total: 11]

Page 3 Mark Scheme Syllabus Paper GCE A/AS Level – May/June 2006 9700 04 © University of Cambridge International Examinations 2006 Question Expected Answers Marks 6 (a) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 maintenance of constant / stable, internal environment ; despite changes in external environment ; negative feedback ; receptor and effector ; beta cells ; in islets of langerhans / pancreas ; release insulin (into blood) ; alpha cells stop releasing glucagon ; affects liver / muscle cells ; increased permeability to glucose / absorption from blood ; increased use of glucose in respiration ; increase in conversion of glucose to glycogen ; stored in liver and muscles ; fall in blood glucose concentration / return to normal ; [8 max] (b) 15 16 17 18 19 20 21 22 23 24 25 26 27 low blood water content / water potential ; detected by osmoreceptors ; in hypothalamus ; ADH produced / released ; from posterior pituitary gland ; target kidney ; cells of collecting duct ; binds to receptors ; vesicles with water permeable channels ; fuse with cell membrane ; cells more permeable to water / water passes into cells ; urine lower volume ; higher concentration ; [7 max] [Total: 15]

Page 4 Mark Scheme Syllabus Paper GCE A/AS Level – May/June 2006 9700 04 © University of Cambridge International Examinations 2006 Question Expected Answers Marks 7 (a) 1 2 3 4 5 6 7 8 9 10 11 12 individuals in population have great reproductive potential / AW ; numbers in population remain roughly constant ; many fail to survive / die ; do not reproduce ; due to environmental factors / named factor ; variation in members of population ; those best adapted survive ; reproduce / pass on alleles ; R genes genetic variation leads to change in phenotype ; ref: changes in gene pool ; over time produces evolutionary change ; new species arise from existing ones [8 max] (b) 13 14 15 16 17 18 19 20 21 22 23 24 gene) example ; (sickle cell / PKU ) change in gene / DNA / base change ; different amino acid ; different polypeptide / different protein / non-functional protein ; AVP ; details AVP ; details (chromosome) example ; (Down’s, Turner’s syndromes) structural changes in chromosomes ; change in number of chromosomes ; change in sets of chromosomes / ref. polyploidy ; AVP ; details AVP ; details [7 max] [Total: 15]