Cambridge A Level Biology 9700 — 2013 Oct/Nov Paper 2 · Variant 2

This document consists of 14 printed pages and 2 blank pages. DC (LEG/SW) 63267/4 © UCLES 2013 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Subsidiary Level and Advanced Level * 1 3 2 3 7 5 8 6 7 8 * BIOLOGY 9700/22 Paper 2 Structured Questions AS October/November 2013 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 in the spaces provided at the top of this page. Write in dark blue or black ink. 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. Electronic calculators may be used. 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.

2 9700/22/O/N/13 © UCLES 2013 For Examiner’s Use Answer all the questions. 1 Fig. 1.1 is a diagram of a transverse section through a vein. Y X magnification × 35 Fig. 1.1 (a) Calculate the actual diameter of the vein marked by the line X–Y. Show your working and give your answer in millimetres (mm). answer … mm [2] (b) The presence of a valve would help to confirm that the blood vessel in Fig. 1.1 is a vein and not an artery. Describe three structural features of the blood vessel shown in Fig. 1.1 that would help to identify it as a vein and not as an artery. 1. … … … 2. … … … 3. … … …[3]

3 9700/22/O/N/13 © UCLES 2013 [Turn over For Examiner’s Use (c) Explain how the following structural features of a capillary are related to its function. (i) The capillary wall is composed of a single layer of squamous epithelial cells. … …[1] (ii) The diameter of the capillary lumen is approximately 8 μm. … …[1] (d) The inner lining of arteries and veins is composed of a layer of epithelial cells supported by a layer of elastic and connective tissue. The epithelial cells are capable of cell division by mitosis. (i) State the role of mitosis in cell division of epithelial cells. … … … …[2] (ii) Explain why the epithelial cells undergo mitosis and not meiosis. … … … …[2]

4 9700/22/O/N/13 © UCLES 2013 For Examiner’s Use (e) Fig. 1.2 is a diagram of a cell in late prophase of mitosis. Fig. 1.2 Complete Fig. 1.3 to show the same cell in the anaphase stage of mitosis. Fig. 1.3 [2] [Total: 13]

5 9700/22/O/N/13 © UCLES 2013 [Turn over For Examiner’s Use 2 Keratin and chitin are two important biological molecules. Keratin is found in hair, fur and skin. Chitin is a modified polysaccharide found in a number of different organisms, for example in fungal cell walls and the hard outer skeletons of insects. (a) Features of chitin and keratin are shown in the boxes in Fig. 2.1. example: Keratin and chitin are insoluble in water cellulose triglyceride amylopectin collagen Keratin and chitin have structural functions Keratin is a fibrous protein The monomers of chitin are β-1,4 linked Keratin and chitin contain nitrogen Fig. 2.1 Write, in each box, the biological molecules from the list below that have the same feature. Each box may contain one, or more than one, biological molecule. The first box has been completed as an example. amylopectin cellulose collagen haemoglobin mRNA triglyceride [5]

6 9700/22/O/N/13 © UCLES 2013 For Examiner’s Use (b) Chitin and the products of chitin hydrolysis have many useful medical and environmental applications. Chitinase enzymes can be used commercially to hydrolyse chitin. Enzyme stability and activity are important considerations in technological applications of chitinase. Fig. 2.2 is a graph showing the effects of temperature on chitinase extracted from a soil bacterium. The relative activity of the enzyme was measured at different temperatures, with 100% representing maximum enzyme activity. 30 20 10 0 0 20 40 relative activity / % 60 80 100 40 50 temperature / °C 60 70 Fig. 2.2 (i) With reference to Fig. 2.2, state the optimum temperature for the chitinase enzyme. …[1]

7 9700/22/O/N/13 © UCLES 2013 [Turn over For Examiner’s Use Fig. 2.3 is a graph showing how temperature affects the stability of chitinase. The activity of the enzyme was measured over a time period of 72 hours at each of five different temperatures. 0 0 20 40 relative activity / % 60 80 100 20 40 time / h 60 80 28 °C 37 °C 40 °C 50 °C 60 °C Fig. 2.3 (ii) With reference to Fig. 2.2 and Fig. 2.3, describe and discuss the effect of temperature on chitinase activity and stability. … … … … … … … … … … …[5] [Total: 11]

8 9700/22/O/N/13 © UCLES 2013 For Examiner’s Use 3 (a) Explain the need for transport systems in plants. … … … … … … …[3] (b) Fig. 3.1 is a drawing of a transverse section through part of the stem of a dicotyledonous plant. Cell A and cell B are involved in the transport of dissolved organic molecules. cell A cell B 1 +m Fig. 3.1 (i) Name cell A and cell B. cell A … cell B …[1]

9 9700/22/O/N/13 © UCLES 2013 [Turn over For Examiner’s Use (ii) With reference to Fig. 3.1, explain how the different structures of cell types A and B are related to their function. … … … … … … … … … …[5] (c) Complete Table 3.1 to state four differences between transport systems in mammals and in plants. Table 3.1 transport system in mammals transport system in plants [4] [Total: 13]

10 9700/22/O/N/13 © UCLES 2013 For Examiner’s Use 4 Staphylococcus aureus is a bacterium that is the cause of many different infectious diseases. (a) Fig. 4.1 is a diagram of S. aureus. 1 +m Fig. 4.1 (i) Cell structures, such as mitochondria, endoplasmic reticula (ER), Golgi apparatus, lysosomes and chloroplasts are found only in eukaryotic cells. These are not present in Fig. 4.1. With reference to Fig. 4.1, describe other features that support the fact that S. aureus is a prokaryote. … … … … … …[3] (ii) State the main difference in the composition of the plant cell wall compared to the bacterial cell wall. plant cell wall … bacterial cell wall …[2]

11 9700/22/O/N/13 © UCLES 2013 [Turn over For Examiner’s Use (b) Bacterial cells behave in a similar way to plant cells when immersed in solutions of different water potential. Suggest and explain what would happen to bacteria placed in a solution with a water potential more negative than their cell contents. … … … … … …[3] (c) Some strains of S. aureus have become resistant to one or more of the antibiotics used to treat infections. The mechanisms of antibiotic resistance involve proteins, for example: • enzymes to breakdown antibiotics • membrane proteins that inactivate antibiotics • membrane proteins that pump out antibiotics. Explain why antibiotic resistance arises as a result of mutation. … … … …[2] [Total: 10]

12 9700/22/O/N/13 © UCLES 2013 For Examiner’s Use 5 Read the following passage. The three-toed sloth, Bradypus variegatus, is a very slow-moving mammal found in Central and South America that spends most of its life living in trees. The thick, long grey fur of the sloth in Fig. 5.1 has a green appearance. Individual hairs of the sloth have grooves in them where water can collect. Fig. 5.1 Research has shown that the green colour is due to the presence of algae living on the sloth’s fur, the most common species being Trichophilus welckeri. Algae are eukaryotic, photosynthetic organisms. Many other species of non-photosynthetic eukaryotes, both unicellular and multicellular, have been found living on the sloth’s fur. These include different species of roundworms, insects and saprotrophic fungi.

13 9700/22/O/N/13 © UCLES 2013 [Turn over For Examiner’s Use (a) Explain the ecological terms population and community, using examples given in the passage. population … … … community … … …[4] (b) Suggest why the sloth and its fur can be described as a small ecosystem. … … … … … … … … …[3] [Total: 7]

14 9700/22/O/N/13 © UCLES 2013 For Examiner’s Use 6 (a) Nicotine, in cigarette smoke, is highly addictive. A nicotine vaccine has been developed to try and reduce the effects of addiction. The vaccine stimulates an immune response to produce antibodies that bind to the nicotine molecule. Fig. 6.1 is a diagram of an antibody molecule. On Fig. 6.1: • label three structural features that enable an antibody molecule to carry out its function. • next to each label, state the function of the feature. Fig. 6.1 [3] (b) Nicotine has an effect on the cardiovascular system, such as making platelets sticky, so causing blood to clot. This increases the risk of thrombosis and reduces blood flow. Outline other effects of nicotine on the cardiovascular system. … … … … … …[3] [Total: 6]

15 9700/22/O/N/13 © UCLES 2013 BLANK PAGE

16 9700/22/O/N/13 © UCLES 2013 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. BLANK PAGE

CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the October/November 2013 series 9700 BIOLOGY 9700/22 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 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 2013 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.

Page 2 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2013 9700 22 © Cambridge International Examinations 2013 Mark scheme abbreviations: ; separates marking points / alternative answers for the same point R reject A accept (for answers correctly cued by the question, or by extra guidance) AW alternative wording (where responses vary more than usual) underline actual word given must be used by candidate (grammatical variants excepted) max indicates the maximum number of marks that can be given ora or reverse argument mp marking point (with relevant number) ecf error carried forward I ignore AVP alternative valid point (examples given)

Page 3 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2013 9700 22 © Cambridge International Examinations 2013 1 (a) 1.4 mm ; ; two marks for the correct answer A 1.3 / 1.34 / 1.37 / 1.43 / 1.46 / 1.5 tolerance on measurement of 49 mm = ± 2 mm (i.e. 47 to 51 mm) if answer not given or incorrect allow one mark for correct measurement and correct use of formula (measurement divided by the magnification of 35 or showing the rearranged formula) [2] (b) 1 large / wide, lumen (relative to thickness of wall) ; A artery narrow lumen 2 irregular shape ; AW A flattened / oval / not round(ed) (shape) ; A artery, round(ed) / regular (shape) I ref. to (vein) not spherical / artery spherical 3 thin / AW, tunica media / middle layer / (smooth) muscle and elastic layer or (proportionately) less, elastic / (smooth) muscle, in, tunica media / middle layer ; 4 (relatively) thin, tunica externa / tunica adventicia / outer layer / fibrous coat / fibrous layer ; R small(er) 5 tunica intima / tunica interna / inner layer / endothelium, smooth / not ‘crinkly’ / not wavy / AW ; alt if mp 3 not awarded, award 1 mark only for thin (smooth) muscle layer / less (smooth) muscle thin elastic layer / less elastic tissue [max 3] (c) (i) short distance for diffusion (of molecules / ions / named) ; A reduced distance / thin / short pathway / AW increased rate / AW, of diffusion (of molecules / ions / named) ; A fast(er) / (more) efficient I easy / better [max 1] (ii) 1 small size allows contact with (many body) cells / AW ; A idea of extending into small spaces 2 red blood cell, close to, (body) cells / tissue for (efficient), diffusion / AW ; A in contact with / close to, capillary wall / endothelium, for diffusion 3 red blood cells / blood flow, slow(s) down / idea of more time, for (efficient) diffusion / cells to obtain sufficient nutrients / AW ; treat ref. to lower pressure as neutral 4 (plasma / blood, containing), glucose / nutrients / named nutrient / oxygen, close to / AW, body cells ; [max 1]

Page 4 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2013 9700 22 © Cambridge International Examinations 2013 (d) (i) (produce genetically identical daughter epithelial cells for) 1 (for tissue) repair ; R cell repair 2 idea of replacing, dead / destroyed / damaged / worn-out / AW, cells ; A replacement of cells, unqualified if mp 1 gained 3 ref. protection of, underlying tissue / muscle and elastic layer / tunica media / AW ; 4 meiosis produces, haploid cells / cells with n chromosomes / cells with one set of chromosomes ; A cells with half the number of chromosomes 5 meiosis for gamete formation ; A sex cells R meiosis in gametes [max 2] (ii) ignore ref. to 23/46 chromosomes (mitosis to), maintain genetic stability / produce genetically identical cells / produce clones ora or meiosis produces genetically different cells ; (mitosis), ensures cells retain function / cells function as tissue / AW ; (mitosis) maintains chromosome number ; A maintains, diploid number / 2n meiosis produces, haploid cells / cells with n chromosomes / cells with one A cells with half the number of chromosomes meiosis for gamete formation ; A sex cells R meiosis in gametes [max 2] (e) ignore labels max 1 if nuclear, membrane / envelope, shown no marks if chromosomes with two chromatids drawn 1 four separate, chromatids / daughter chromosomes, shown in each half ; 2 all centromeres leading A ‘V’ shapes if centromere not obvious (point of V towards pole) or all centromeres attached to spindle fibres ; [2] [Total: 13]

Page 5 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2013 9700 22 © Cambridge International Examinations 2013 2 (a) [max 5] (b) (i) 47.5 ˚C ; [1] (ii) accept activity for relative activity throughout accept manipulated data quotes and penalise once for, incorrect / no, units Fig. 2.2 (relative activity of enzyme at different temperatures) 1 as temperature increases, activity increases up to, optimum / 47.5 ˚C (allow ecf from (i), then decreases ; A peaks (for increase then decrease) 2 activity increases from 30 ˚C to 47.5 ˚C, then decreases to 70 ˚C ; also mp 1 or increase or decrease, described with comparative data (activity and temperature compared with another activity and temperature) 3 at higher temperatures (compared to most others) enzyme still active ; 4 high optimum temperature (compared to most other enzymes) ; Fig. 2.3 (stability over time for enzyme maintained at different temperatures) 5 enzyme becomes less stable over time ; A activity decreases over time A description if at least two temperatures described 6 data quote to support ; activity at two times for any one temperature if time 0 or ‘start’, then assume 100% relative activity if 100%, assume time 0 Keratin and chitin contain nitrogen collagen / haemoglobin ; 1st mark mRNA ; 2nd mark allow only one incorrect molecule to be listed for max 1 Keratin and chitin have structural functions cellulose ; collagen ; allow only one incorrect molecule to be listed for max 1 Keratin is a fibrous protein collagen ; no marks if other molecules given The monomers of chitin have β-1,4 linkages between them cellulose ; no marks if other molecules given

Page 6 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2013 9700 22 © Cambridge International Examinations 2013 7 (over the time period) the lower the temperature, the more stable the enzyme ; ora A enzyme has higher activity at the lower temperatures A stated temperatures (at least two) to illustrate the point e.g. 28 ˚C higher activity than 40 ˚C throughout A 28 ˚C, highest activity / enzyme most stable (throughout) 8 data quote to support ; temperatures and (relative) activity (with one time) discussion points 9 AVP ; ; 10 e.g. Fig 2.2 reason for increasing activity up to optimum / decrease after optimum e.g. ref. collisions, kinetic energy increase e.g. denaturation at 60–70 ˚C R denaturation at 50 ˚C (but A denaturation begins) suggested reason for higher optimum temperature e.g. more bonds Fig. 2.3 (suggests that) more molecules become, denatured / inactive, as time progresses greater stability / higher activity, at 40 ˚C than 37 ˚C between 40–50 hours Fig. 2.2 and 2.3 optimum temperature for activity not most stable temperature steep decrease in stability at 60 ˚C in a short time as (nearly complete) denaturation occurs allow once only commercial application e.g. if hydrolysis occurs over a longer time period, better to use a lower temperature than optimum [max 5] [Total: 11] 3 (a) 1 large (size / volume / organism) ; A multicellular / many cells A larger 2 (so) small(er) / low, surface area : volume ; as size increases, SA:V decreases = 2 marks 3 diffusion (alone), not enough / too slow (to supply needs) ; 4 explanation ; e.g. surface too far from, centre / AW, of plant distances too far to supply required, nutrients / substances requires, supplies in bulk / mass flow 5 (so require) xylem and phloem, qualified ; e.g. transport in different directions xylem transports water (and mineral ions) and phloem transports, assimilates / photosynthates / sugars / amino acids [max 3]

Page 7 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2013 9700 22 © Cambridge International Examinations 2013 (b) (i) cell A = companion cell A companion ; cell B = (phloem) sieve tube element A sieve tube, sieve tube cell [1] (ii) allow ecf from (i) for incorrect names of cells cell A / companion cell 1 mitochondria for, aerobic respiration / oxidative phosphorylation / ATP, production / AW ; R ATP energy A release / supply, ATP / energy (for the cell) treat as neutral cell B also has mitochondria 2 RER / many ribosomes, for, polypeptide / protein, production ; if mps 1 and 2 not given, one mark for mitochondria and, ribosomes / RER 3 ref. nucleus and, genes coding for (required) proteins / synthesis of ribosomes or nucleolus synthesises ribosomes ; cell B / sieve tube element 4 (at least) one main structural feature ; R hollow peripheral cytoplasm / AW e.g. pushed against walls no nucleus / no RER / no vacuole / no Golgi / few organelles / reduced ER / few mitochondria R no organelles 5 (to) minimise / reduce, resistance to (mass) flow ; AW e.g. uninterrupted flow / more efficient transport of sucrose 6 (so) maximum volume transported (/unit time) ; A idea of 7 sieve plates, qualified ; e.g. stop bulging allow mass flow / reduce barrier to flow become plugged with, P-protein / callose, to prevent losses / after damage 8 no plasmodesmata (as on Fig. 3.1) to maintain pressure or plasmodesmata (not shown) for diffusion of sucrose into sieve tube / AW ; [max 5]

Page 8 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2013 9700 22 © Cambridge International Examinations 2013 (c) transport system in mammals transport system in plants 1 arteries, veins, capillaries A delivery to cells by arteries and capillaries xylem and phloem ; A vascular bundle 2 heart / pump no heart / no pump / (xylem and phloem) have different mechanisms for (mass) flow ; A transpiration pull in xylem / pressure gradients in phloem 3 double circulation no double circulation / xylem unidirectional flow / phloem source to sink / AW ; R single circulation 4 closed circulation not closed circulation / pits / plasmodesmata ; A open 5 one (circulatory) system / water and organic molecules transported in same vessels / AW two (separate) systems / water transport in separate vessels to organic molecules ; 6 (all) living cells living and dead cells ; A dead cells in xylem 7 transports, (respiratory) gases / oxygen / carbon dioxide respiratory gases not transported ; 8 transports glucose accept within correct list (phloem) transports sucrose ; accept within correct list 9 faster rate of flow slower rate of flow ; 10 rate of flow controlled by, nervous system control of heart / action of heart / vasoconstriction and vasodilation / AW accept ref. endocrine system rate of flow, not controlled by nervous system / (in xylem) controlled by external factors / (in xylem) controlled by transpiration rate ; 11 components include blood cells cells not transported / AW ; 12 13 14 AVP ;;; homeostasis involved / concentration of dissolved substances controlled ref. to defence e.g. immune system e.g. blood clotting organ-based valves present no homeostasis / AW ; no equivalent to immune system callose formation ; tissue-based ; no valves ; [max 4] [Total: 13]

Page 9 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2013 9700 22 © Cambridge International Examinations 2013 4 (a) (i) penalise once if the term genetic material is used instead of DNA 1 no nuclear envelope / no (true) nucleus ; A no nuclear membrane A no nucleus envelope A DNA free in cytoplasm ora A DNA as nucleoid 2 DNA, loop / circular ; A DNA not linear 3 DNA, not in chromosomes / DNA not associated with, histones / proteins ; A naked DNA 4 no nucleolus ; 5 (presence of) plasmids ; 6 (only) have, 70S / small / 18–20 nm, ribosomes ; 7 presence of, capsule / slime layer ; 8 ref. small (cell) size / less than 5 µm / (only) 1 µm ; A ora for eukaryotes [max 3] (ii) plant cell cellulose ; treat as neutral ref. to microfibrils / fibres bacterial cell murein / peptidoglycan ; A peptoglycan / polysaccharide and amino acid [2] (b) 1 cell contents shrink / cytoplasm shrinks ; AW R cell shrinks unless clear that the cell wall remains, intact / same size 2 cell (surface) membrane / plasma membrane, peels away / AW, from cell wall ; A plasmolysis occurs / cell becomes flaccid 3 (movement of) water out by osmosis ; 4 down water potential gradient / from high to low water potential / to lower water potential /from less negative to more negative water potential ; A ψ for water potential [max 3] (c) 1 (mutation involves) change in sequence of, bases / nucleotides (of DNA); A (mutation leads to) altered, mRNA / codons A change leads to new alleles (genes code for, polypeptides / proteins, so) 2 different, protein structures / proteins, possible / synthesised ; A different, primary / tertiary / 3-D, structure 3 (so) range of / different, functions possible / AW ; [max 2] [Total: 10]

Page 10 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2013 9700 22 © Cambridge International Examinations 2013 5 (a) max 2 if no examples from passage given population 1 all individuals / all organisms / AW, of, Trichophilus welckeri three-toed sloths / Bradypus variegatus one / a, species of roundworm one / a, species of insect any one ; one / a, species of saprotrophic fungi one / a, species of algae A one (particular), species / kind / type I e.g. the roundworms etc. treat as neutral same organisms 2 idea of in, an (specified) area / AW ; e.g. place / habitat e.g. (sloths) in the, forest / trees (at one time)in central / south America in the sloth’s fur / on the sloth 3 at the same time ; allow once only 4 (named organisms) share same gene pool / ref. isolated from other populations (of the same species) ; community 5 all populations of all species / all organisms / AW, living in a (particular) area / AW ; 6 examples ; all the organisms living on the sloths fur or roundworms, insects, fungi, algae, on sloth’s fur/ in same area in second example do not need ref. to fur or area if mp 5 given 7 at, the same / one, time ; allow once only [max 4] (b) 1 has biotic and abiotic components / biological and physical components ; A living and non-living components 2 described by use of examples from text ; e.g. water and organisms A fur as an abiotic factor 3 ref. energy flow / nutrient cycling ; A described e.g. food web, algae as producers, fungi as decomposers A food chains look for at least one link 4 ref. interactions / functional entity ; AW e.g. self-contained / self-sustaining / inter-relationships [max 3] [Total: 7]

Page 11 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2013 9700 22 © Cambridge International Examinations 2013 6 (a) labels to correct areas, mark to max 3 AVP ; e.g. light and heavy polypeptide chain, ref. forming variable region / different primary structure(s) giving different shapes ; heavy / polypeptide, chain constant region gives antibody class ; AW [max 3] (b) 1 increases heart rate ; A heart, pumps / beats faster 2 increased blood pressure / hypertension ; 3 damage to, endothelial / arterial, lining ; A damage to, tunica intima / lining of veins 4 (so) contributes to plaque / atheroma ; A atherosclerosis 5 vasoconstriction or constricts / reduces diameter of, arterioles / blood vessels ; A more resistance to blood flow must be in context 6 reduced blood flow to extremities / AW ; [max 3] [Total: 6]