Cambridge A Level Biology 9700 — 2006 Oct/Nov Paper 4 · Variant 1

This document consists of 12 printed pages and 4 lined pages. SP (MML 10817 4/05) T11540/3 © UCLES 2006 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Level BIOLOGY 9700/04 Paper 4 Structured Questions A2 Core October/November 2006 1 hour 15 minutes Candidates answer on the Question Paper. Additional Materials: Answer Paper. 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 pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Section A Answer all questions. Section B Answer one question. 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 3 2 1 4 5 Section A 6 or 7 Total

Section A Answer all questions. Write your answers in the spaces provided. 1 Carbohydrates and lipids are important fuels in generating ATP in animal cells. (a) Explain the relative energy values of carbohydrate and lipid as respiratory substrates. … … … … … … [3] Aerobic respiration uses oxygen and produces carbon dioxide as a waste substance. Animal cell metabolism can be analysed using the respiratory quotient, RQ. The RQ is the volume of the carbon dioxide produced divided by the volume of the oxygen consumed. (b) State typical RQ values for carbohydrates and lipids. carbohydrate … lipid … [2] The Siberian hamster, a small rodent like a mouse, had its RQ measured at different air temperatures. Fig. 1.1 shows the results of this experiment. 2 9700/04/O/N/06 For Examiner’s Use © UCLES 2006 © UCLES 2006

Fig. 1.1 (c) Using the information in Fig. 1.1, describe and explain the relationship between RQ and air temperature. … … … … … … … … [4] (d) State a circumstance under which the RQ value would rise to over 1.0. … … [1] [Total: 10] 5 10 15 20 25 30 0.90 0.85 0.80 0.75 0.70 0 respiratory quotient (RQ) air temperature / °C x x x x x 3 9700/04/O/N/06 [Turn over For Examiner’s Use © UCLES 2006 © UCLES 2006

2 The colour of the tips of the hair in Australian Shepherd dogs is controlled by a gene at the A locus. There are three alleles at this locus which are: As Black hair tips Ay Red hair tips At Copper hair tips A cross between two dogs with copper hair tips will always produce offspring with copper hair tips. A cross between two dogs with black hair tips may produce some offspring with red hair tips and some with copper hair tips. (a) State the ratio of offspring phenotypes from the following crosses: (i) AsAt × AyAy offspring phenotypes … ratio … (ii) AsAt × AtAy offspring phenotypes … ratio … (iii) AyAt × AyAt offspring phenotypes … ratio … [6] 4 9700/04/O/N/06 For Examiner’s Use © UCLES 2006 © UCLES 2006

(b) A dog breeder wishes to know whether a dog with red hair tips is either homozygous or heterozygous for this characteristic. (i) State the cross needed to determine the dog’s genotype. … … [1] (ii) Explain why the offspring of this cross will reveal the genotype of the dog. … … … … … … [3] [Total: 10] 5 9700/04/O/N/06 [Turn over For Examiner’s Use © UCLES 2006 © UCLES 2006

3 In mammalian kidneys, the loop of Henle is closely associated with the process of osmoregulation. (a) Explain what is meant by osmoregulation. … … … … [2] Fig. 3.1 shows the water potential of renal fluid as it passes through the loop of Henle. Fig. 3.1 A – proximal convoluted tubule B – midway along descending loop C – apex of loop D – midway along ascending loop E – distal convoluted tubule water potential of renal fluid / kPa 0 –500 –1000 –1500 –2000 –2500 –3000 –3500 –4000 A B C D E region of nephron 6 9700/04/O/N/06 For Examiner’s Use © UCLES 2006 © UCLES 2006

(b) Using the information given in Fig. 3.1, describe and explain what happens to the renal fluid as it passes through the loop of Henle. … … … … … … … … [5] (c) Control systems often work by using negative feedback. These systems require a receptor and an effector. In the process of osmoregulation name the receptor and effector involved. Receptor … Effector … [2] [Total: 9] 7 9700/04/O/N/06 [Turn over For Examiner’s Use © UCLES 2006

4 In Central America the Isthmus of Panama closed about 3 million years ago creating a land bridge between North and South America. Snapping shrimps on the Caribbean side of the isthmus appear almost identical to those on the Pacific side, having once been members of the same population. When males and females from different sides of the isthmus were put together they snapped aggressively instead of courting. They had become separate species. An outline of the region is shown in Fig. 4.1. Fig. 4.1 (a) The term species is often used in the context of evolution of new species. Explain the meaning of the term species. … … … … [2] (b) State the likely isolating mechanism and type of speciation taking place. Isolating mechanism … Type of speciation … [2] Caribbean Sea North America South America North Pacific Ocean Isthmus of Panama 8 9700/04/O/N/06 For Examiner’s Use © UCLES 2006

(c) Explain how the process of speciation occurred in the snapping shrimp population. … … … … … … … … … … … [4] [Total: 8] 9 9700/04/O/N/06 [Turn over For Examiner’s Use © UCLES 2006

5 The lower epidermis of a dicotyledonous leaf is perforated with stomata. Each stoma is bounded by two guard cells which control the size of the pore. Fig. 5.1 shows a scanning electron microscope photograph of an open and a closed stoma. Fig. 5.1 X4000 (a) Calculate the length of the pore of the open stoma in Fig. 5.1. Show your working. Answer … [2] 10 9700/04/O/N/06 For Examiner’s Use © UCLES 2006

(b) Explain the importance of abscisic acid, ABA, in causing stomatal closure. … … … … … … … … [4] (c) Under conditions of low wind speed, the rate of transpiration decreases, even though the stomata of the leaves are open. Explain why this is so. … … … … [2] [Total: 8] 11 9700/04/O/N/06 [Turn over For Examiner’s Use © UCLES 2006

Section B Answer one question. 6 (a) Describe how the structure of neurones speeds up the transmission of action potentials. [6] (b) Explain, using a named example, how sensory receptors in mammals convert energy into action potentials. [9] [Total: 15] 7 (a) Describe the transfer of light energy to chemical energy in ATP during photosynthesis. [6] (b) Describe the process of oxidative phosphorylation. [9] [Total: 15] … … … … … … … … … … … … … … … … … 12 9700/04/O/N/06 For Examiner’s Use © UCLES 2006

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16 9700/04/O/N/06 For Examiner’s Use © UCLES 2006 … … … … … … … … … … … … … … … … … … … … … … … … Copyright Acknowledgements: Question 5 Fig. 5.1. © Biophoto Associates 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.

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the October/November 2006 question paper 9700 BIOLOGY 9700/04 Paper 4 (Theory 2), 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 instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began. 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 grade thresholds for various grades are published in the report on the examination for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses. • CIE will not enter into discussions or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the October/November 2006 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

Page 2 Mark Scheme Syllabus Paper GCE A/AS LEVEL - OCT/NOV 2006 9700 4 © UCLES 2006 Question Expected Answers Marks 1 (a) 1 2 3 4 5 (carbohydrates) less reduced / less hydrogen / less C-H bonds ; R H2 for, aerobic respiration / ETC / NAD / ATP ; less energy ; per, unit mass / mole ; accept figs for 3 and 4 carbohydrate has lower energy density ;; accept as alternative to 3 & 4 for 2 marks 3 max (b) carbohydrate = 1.0 ; lipid = 0.6 – 0.8 ; 2 (c) RQ remains stable between 3°C and 10°C / AW ; rise between 10°C and, 20°C / 25°C ; 0.74 to, 0.76 / 0.8 ; accept difference for figs marks sharp rise, between 25°C and 27°C / after 25°C ; 0.8 to 0.91 / peaks at 0.91 ; 3 max at low temperatures hamster uses lipids ; reason ; e.g. more heat generated from lipid respiration at higher temperatures more carbohydrates are used ; 4 max (d) anaerobic respiration / conversion of carbohydrate to fats as animal hibernates; 1 [Total: 10]

Page 3 Mark Scheme Syllabus Paper GCE A/AS LEVEL - OCT/NOV 2006 9700 4 © UCLES 2006 Question Expected Answers Marks 2 (a) (i) black red ; 1 : 1 ; 2 (ii) black copper red ; 2 : 1 : 1 ; 2 (iii) red copper ; 3 1 ; 2 (b) (i) test / back, cross ; with, copper / AtAt / homozygous recessive ; (ii) if all offspring red, homozygous ; if some offspring copper, heterozygous ; ref. equal proportions of offspring ; mark (i) and (ii) together 4 max [Total: 10]

Page 4 Mark Scheme Syllabus Paper GCE A/AS LEVEL - OCT/NOV 2006 9700 4 © UCLES 2006 Question Expected Answers Marks 3 (a) control / maintain, water / solute, concentration / potential ; of, body fluids / internal environment / cells ; 2 (b) 1 2 3 4 5 6 7 8 9 10 B / C, lower ψ than A ; accept C lower ψ than B accept ψ gets more negative as fluid moves down descending limb comparative figs ; water moves out by, diffusion / osmosis ; into, medulla tissue / tissue fluid ; D / E, higher ψ than C ; accept ψ gets less negative as fluid moves up ascending limb comparative figs ; Na+ / Cl-, move out ; into, medulla tissue / tissue fluid ; by active transport ; A and E same ψ / AW ; penalise once for no units allow either 4 or 8 5 max (c) receptor – hypothalamus ; effector – pituitary gland / cells or walls of collecting duct ; R anterior pituitary 2 [Total: 9]

Page 5 Mark Scheme Syllabus Paper GCE A/AS LEVEL - OCT/NOV 2006 9700 4 © UCLES 2006 Question Expected Answers Marks 4 (a) similar morphological, physiological, biochemical and behavioural features ; (minimum 3 for mark ) interbreed / reproduce ; produce fertile offspring ; occupy same niche ; reproductively isolated; 2 max (b) isolating mechanism – land barrier / AW ; accept geographical isolation type of speciation – allopatric ; 2 (c) 1 2 3 4 5 6 7 8 geographical barriers / description ; barrier to gene flow ; no interbreeding / separate breeding populations / reproductively isolated ; (gene) mutations occur / new alleles ; different selection pressures / e.g. of selection pressure ; ref. natural selection / description ; change in allele frequency / OWTTE ; develop different chromosome numbers / ref. polyploidy ; 4 max [Total: 8]

Page 6 Mark Scheme Syllabus Paper GCE A/AS LEVEL - OCT/NOV 2006 9700 4 © UCLES 2006 Question Expected Answers Marks 5 (a) 5.0 – 5.5 ; µm ; accept correct values for mm, cm or m 2 (b) 1 2 3 4 5 6 7 8 plant produces ABA ; (due to) high temperature ; (due to) reduced water supply / water loss / drought ; guard cells lose K+ ; ref. water potential gradient ; guard cells lose water ; loss of turgor causes stomatal closure ; AVP ; e.g. stress hormone / different thickness of cell wall / ABA binds to receptors on guard cells 4 max (c) (rate of transpiration due to) difference in relative humidity inside and outside, stomata / leaf ; in still air / low wind speed, external water vapour remains close to stomata / AW ; reduced, concentration gradient / water potential gradient ; 2 max [Total: 8]

Page 7 Mark Scheme Syllabus Paper GCE A/AS LEVEL - OCT/NOV 2006 9700 4 © UCLES 2006 6 (a) Describe how the structure of neurones speeds up the transmission of action potentials. [6] (b) Explain, using a named example, how sensory receptors in mammals convert energy into action potentials. [9] [Total: 15] (a) (b) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 myelin sheath / schwann cell ; insulates, axon / dendron ; impermeable to Na+ / K+ ; depolarisation only at nodes of Ranvier ; ref. local circuits ; action potentials ‘jump’ from node to node ; saltatory conduction ; speed increased by 50 times / 0.5 ms-1 to 100 ms-1 ; axons with large diameter / giant axon ; reduce resistance ; elongated, axon / dendron / neurone ; 6 max ref. specific example ; e.g. pacinian corpuscle / rod / cone / hair cell correct stimulus ; e.g. touch / pressure light / sound detail of receptor response ; e.g. deformation of pacinian corpuscle membrane stimulus causes Na+ channels to open ; Na+ enters cell ; K+ channels open ; K+ leaves cell ; depolarisation ; receptor / generator potential ; greater than threshold leads to, action potential / impulses ; less than threshold only localised depolarisation ; increased stimulus leads to increased frequency of action potentials ; AVP ; apply max 8 for points 15 - 24 9 max Total 15

Page 8 Mark Scheme Syllabus Paper GCE A/AS LEVEL - OCT/NOV 2006 9700 4 © UCLES 2006 7 (a) Describe the transfer of energy to ATP during photosynthesis. [6] (b) Describe the process of oxidative phosphorylation. [9] [Total: 15 ] (a) (b) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 light absorbed by chlorophyll / AW ; ref. photosystems ; ref. harvesting clusters / accessory pigments ; reaction centre / P680 / P700 ; excitation of electrons / AW ; ETC ; idea of different energy levels ; ADP + Pi → ATP ; cyclic / non-cyclic, photophosphorylation ; chemiosmosis / ATP synthase / description ; 6 max reduced NAD / FAD ; passed to ETC ; hydrogens removed ; R H2 split into H+ and e- ; e- passed to carriers ; H+ stays in mitochondrial matrix ; oxygen final e- carrier ; joins with H+ / reduced ; R H2 / hydrogen forms water ; ref. energy levels of carriers ; energy available to convert ADP and Pi to ATP ; occurs three times ( for each reduced NAD ) / ref. total yield ; chemiosmosis / ATP synthase / description ; 9 max [Total: 15]