Cambridge A Level Biology 9700 — 2016 May/June Paper 2 · Variant 1

This document consists of 13 printed pages and 3 blank pages. DC (ST/FD) 109211/4 © UCLES 2016 [Turn over Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level * 0 3 2 4 7 2 3 3 5 5 * BIOLOGY 9700/21 Paper 2 Structured Questions AS 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.

2 9700/21/M/J/16 © UCLES 2016 Answer all the questions. 1 Table 1.1 shows features of three infectious diseases: malaria, tuberculosis (TB) and cholera. Complete Table 1.1. Table 1.1 feature malaria tuberculosis cholera name of pathogen ……………………… falciparum Mycobacterium tuberculosis ……………………… ……………………… type of organism ……………………… bacterium ……………………… method of transmission ……………………… ……………………… ……………………… ……………………… ……………………… ……………………… drinking water and food contaminated with human faeces [6] [Total: 6] 2 Macrophages synthesise intracellular enzymes. Fig. 2.1 is a summary diagram of events that occur in a macrophage. bacteria $ % & ' ( ) * + - Fig. 2.1

3 9700/21/M/J/16 © UCLES 2016 [Turn over (a) (i) Name the process at A. …[1] (ii) Name the stages of protein synthesis that occur at E and at F. E … F …[2] (iii) Name organelles B, G, H and J. B … G … H … J …[4] (b) Describe what happens to the bacteria between C and D. … … … … … … … …[3]

4 9700/21/M/J/16 © UCLES 2016 (c) Macrophages are antigen presenting cells (APCs). Antigens from pathogens such as the bacteria shown in Fig. 2.1 are presented to helper T-lymphocytes as shown in Fig. 2.2. helper T-lymphocyte antigen T cell receptor APC Fig. 2.2 Very few helper T-lymphocytes respond to the presence of APCs by binding in the way shown in Fig. 2.2. Suggest why this is so. … … … … … …[2] [Total: 12]

5 9700/21/M/J/16 © UCLES 2016 [Turn over 3 A student studied a transverse section of the trachea of a small mammal. The student drew a plan diagram of the section as shown in Fig. 3.1. 0 Fig. 3.1 Fig. 3.2 is a photomicrograph of the area labelled M in Fig. 3.1. 1 3 2 VPRRWK PXVFOH Fig. 3.2 (a) Name: (i) the type of epithelium at N …[1] (ii) the structures at O …[1] (iii) the tissue at P. …[1]

6 9700/21/M/J/16 © UCLES 2016 (b) Smooth muscle in the trachea and in the bronchi relaxes during strenuous exercise. Suggest the advantages of relaxing this smooth muscle during periods of strenuous exercise. … … … … … …[2] (c) The walls of the trachea and bronchi contain elastic fibres. Elastic fibres are made of bundles of the fibrous protein elastin. • Each molecule of elastin is a single polypeptide. • The primary structure contains a large proportion of the amino acid glycine. • Glycine has a hydrophobic R group. • Glycine does not occur at regular intervals in the polypeptide. • The polypeptide forms random coils that change shape as the elastic fibres are stretched and recoil. • Elastin molecules are joined to each other by many covalent bonds to form a cross-linked network. Describe two ways in which the structure of a collagen molecule differs from the structure of an elastin molecule described above. 1 … … 2 … …[2] [Total: 7]

7 9700/21/M/J/16 © UCLES 2016 [Turn over 4 (a) Transpiration is often described as ‘an inevitable consequence of gas exchange in leaves’. Explain what is meant by this description. … … … … … …[3] (b) Explain how hydrogen bonding is involved in the movement of water in the xylem. … … … … … …[3] Southern beech trees of the genus Nothofagus grow in forests in the South Island of New Zealand. Fig. 4.1 shows a small part of a forest. Most of the trees in the forests form a thick canopy of leaves. These are known as canopy trees. The tallest trees are known as emergent trees. Some trees do not reach the canopy and are known as suppressed trees. emergent tree canopy trees suppressed tree Fig. 4.1

8 9700/21/M/J/16 © UCLES 2016 Researchers determined the rates of transpiration of emergent, canopy and suppressed trees in a forest over a 14 hour period from 06.00 until 20.00 on one day in the summer. The results are shown in Fig. 4.2A. They also recorded changes in light intensity above the canopy over the same time period as shown in Fig. 4.2B. 0 06.00 08.00 10.00 12.00 14.00 time of day 16.00 18.00 20.00 1 2 3 4 5 6 7 mean transpiration rate per tree / kg h–1 8 9 10 0.0 06.00 08.00 10.00 12.00 14.00 time of day 16.00 18.00 20.00 0.5 1.0 light intensity / arbitrary units 1.5 2.0 Key emergent trees canopy trees suppressed trees                           $ %   Fig. 4.2

9 9700/21/M/J/16 © UCLES 2016 [Turn over (c) Use Fig. 4.2A to compare the transpiration rates of the emergent, canopy and suppressed trees in the forest over 14 hours. … … … … … … … … … … … …[4] (d) The factors that affect transpiration rate vary considerably at different places inside forests. Use the information in Fig. 4.1 and Fig. 4.2 to suggest reasons for the difference in the transpiration rates of the emergent and suppressed trees. … … … … … … … … … … … …[4] [Total: 14]

10 9700/21/M/J/16 © UCLES 2016 5 (a) Fig. 5.1 is a diagram of part of an animal cell in a stage of mitosis. spindle fibres Fig. 5.1 (i) Draw a diagram in the space below to show the stage of mitosis that follows the stage in Fig. 5.1. [3] (ii) Describe the roles of the spindle fibres during mitosis. … … … … … …[2]

11 9700/21/M/J/16 © UCLES 2016 [Turn over Bone marrow contains many stem cells. Some of these stem cells are responsible for the replacement of red blood cells. During the production of red blood cells a series of changes occur to the cell structure. Fig. 5.2 shows the production of a red blood cell from one of these stem cells. stem cell many mitotic divisions many mitotic divisions final changes in cell structure mature red blood cell cell < cell ; Fig. 5.2 (b) (i) Outline the changes that occur as cell X becomes a mature red blood cell. … … … … … …[3] (ii) Suggest what may happen to cell Y. …[1]

12 9700/21/M/J/16 © UCLES 2016 (c) People who travel to high altitude become acclimatised to the conditions. Athletes often train at high altitude before competing at sea level. A group of male and female athletes who trained at sea level moved to high altitude for further training. Sports scientists analysed blood samples taken from the athletes to measure any changes in the concentration of haemoglobin in the blood and changes in the haematocrit. Haematocrit is the volume of red blood cells expressed as a percentage of the total volume of a sample of blood. The results are shown in Table 5.1. Table 5.1 feature of the blood at sea level after 19 days at high altitude percentage increase mean concentration of haemoglobin in the blood / g 100 cm–3 13.3 15.1 … mean haematocrit 41.0 42.5 3.7 (i) Complete Table 5.1 by calculating the percentage increase in haemoglobin concentration. [1] (ii) Explain why it is necessary for the athletes to increase the concentration of haemoglobin in their blood when acclimatising to high altitude. … … … … … … … … … …[4] [Total: 14]

13 9700/21/M/J/16 © UCLES 2016 6 Fig. 6.1 shows an incomplete diagram of the fluid mosaic model of membrane structure. The diagram shows the cell surface membrane of a eukaryotic cell. Fig. 6.1 (a) State what is meant by the term fluid mosaic. … … … …[2] (b) State the thickness of a cell surface membrane. …[1] (c) List four features of cell surface membranes of eukaryotic cells that are not visible in Fig. 6.1. 1 … … 2 … … 3 … … 4 … …[4] [Total: 7]

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® IGCSE is the registered trademark of Cambridge International Examinations. This document consists of 7 printed pages. © UCLES 2016 [Turn over Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level BIOLOGY 9700/21 Paper 2 AS Level Structured Questions May/June 2016 MARK SCHEME Maximum Mark: 60 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 21 © 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 21 © Cambridge International Examinations 2016 1 must have correct spellings of Plasmodium and Vibrio cholera feature malaria tuberculosis cholera name of pathogen Plasmodium ; Mycobacterium tuberculosis Vibrio cholerae ; type of organism protoctist / protoctistan ; A protist / protozoan / sporozoan bacterium bacterium ; A bacteria mode of transmission by, a vector or (feeding or biting by) Anopheles / mosquito ; via, (airborne) droplets / aerosol(s) (infection) ; drinking water and food contaminated with human faeces [6] [Total: 6] 2 (a) (i) phagocytosis / endocytosis ; R pinocytosis I engulfing [1] (ii) E transcription ; F translation ; A post translation(al) modification [2] (iii) B (phagocytic / endocytic) vacuole / phagosome ; A vesicle R incorrectly qualified vacuole or vesicle (e.g. permanent / large / secretory / Golgi / excretory) I food / pathogenic G (80S) ribosome ; A rough endoplasmic reticulum R RER / rough ER I 70S or any other type of incorrect S as a qualification H Golgi (body / apparatus / complex) ; J mitochondrion ; A mitochondria [4] (b) I fusion of lysosomes with phagosome and diffusion of products of digestion 1 bacteria are, killed / destroyed / broken down / digested ; A hydrolysed A cell wall broken down R bacteria are cut up 2 (by hydrolytic) enzymes ; 3 any example, e.g. carbohydrase / lysozyme / protease / nuclease ; 4 killed by, hydrogen peroxide / H2O2 / free radicals / AW ; 5 AVP ; e.g. correctly named substrate for enzyme murein / peptidoglycan, polysaccharide(s), polypeptides, nucleic acids, lipids e.g. correctly named bonds broken glycosidic, peptide, ester, phosphodiester [max 3]

Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9700 21 © Cambridge International Examinations 2016 (c) 1 idea that only, a few / some / small number / AW, with correct specificity ; 2 (different) T-lymphocytes are specific to different antigens ; 3 (T cell) receptor is, complementary (in shape to antigen) ; 4 AVP ; e.g. this may be during a primary immune response so no memory cells e.g. disease state (HIV / AIDS and leukaemia) or treatment where few T-lymphocytes in the body [max 2] [Total: 12] 3 (a) (i) N ciliated ; A pseudostratified I columnar / cuboidal R cilia [1] (ii) O mucous glands ; A mucus glands / serous glands [1] (iii) P cartilage ; [1] (b) I more air can enter unqualified 1 more air / oxygen, reaches the, alveoli / gas exchange surface ; 2 more gas exchange / greater absorption of oxygen / excretes more carbon dioxide ; AW A maximises oxygen obtained 3 satisfies increased demand for oxygen / AW ; 4 trachea / bronchi / airways, widen / AW ; e.g. dilate / expand / enlarge A diameter of lumen increases 5 reduces resistance to air flow ; R rate of air flow increases [max 2] (c) collagen has three polypeptides / a quaternary structure ; I more than one polypeptide unqualified glycine is every third amino acid ; I at regular intervals R roughly / approximately (triple) helix / helical (shape) ; I regular coils’ R alpha helix [max 2] [Total: 7] 4 (a) transpiration is an inevitable consequence because 1 stomata open ; 2 for diffusion in of carbon dioxide / carbon dioxide required for photosynthesis ; 3 water vapour, diffuses out / moves out down the water potential gradient ; A description of water potential gradient / high to low water potential A vapour pressure gradient / water vapour gradient allow water vapour if it is clear that evaporation has occurred A water evaporates and diffuses out R water evaporates out I water (vapour) concentration gradient [3]

Page 5 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9700 21 © Cambridge International Examinations 2016 (b) 1 adhesion of water to, cellulose / lining / walls (of xylem vessels) ; A adhesive force 2 ref to, hydrophilic / polar, property of cellulose (fibres) ; A hydrophilic / polar, parts of lignin 3 cohesion between water molecules ; cohesive force 4 maintains column of water / prevents water column breaking / AW ; 5 ref. to transpiration pull / AW ; I transpiration unqualified [max 3] (c) mp3 – units for rates of transpiration must appear once correctly in the whole answer to award this point 1 rate (of transpiration) of all trees is 0 at, 06.00 / start ; A no transpiration 2 rates (of transpiration) increase and decrease (in all three) ; A peaks 3 highest rates: emergent trees at 14.30 at 8.5 kg h–1 canopy trees at 14.30 at 3.5 kg h–1 suppressed trees at 13.00 at 1.6–1.7 kg h–1 ; must have units at least once accept kg / h or kg per hour 4 emergent trees (always) have highest rate or suppressed trees have lowest rate ; A emergent trees have higher rate than, canopy and suppressed, trees 5 rate of emergent trees is, much / AW, higher than rates for canopy and suppressed trees ; 6 emergent trees have, steeper / steepest, increase in (transpiration) rate ; A emergent trees have, steeper / steepest, decrease in (transpiration) rate [max 4] (d) following factors may be given in answers, any three of these factors = 1 mark light, intensity / wavelength I ‘more light’ humidity temperature wind speed / air movement size of tree / height / area of leaves water availability / depth or length of roots transpiration rate for emergent trees is higher because … accept ora for suppressed trees accept vapour pressure gradient / water vapour pressure gradient / water vapour diffusion gradient for water potential gradient 1 high(er) light intensity for emergent trees increase in stomatal aperture ; ora A more sunlight A stomata open more I more stomata open 2 lower humidity for emergent trees so steeper water potential gradient ; ora A description of water potential gradient 3 higher temperature / AW, for emergent trees so higher rate of, evaporation / diffusion ; ora 4 higher wind speed for emergent trees so, steeper water potential gradient / lower humidity ; ora A ref. to diffusion shells / descriptions of water potential gradient 5 emergent trees have longer roots so take up more water ; 6 emergent trees have more leaves so, greater surface area / more stomata per unit area (of leaf) ; [max 4] [Total: 14]

Page 6 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9700 21 © Cambridge International Examinations 2016 5 (a) (i) if draw other stages mark first one only – either left to right or top to bottom four chromatids / daughter chromosomes, drawn as single structures between equator and poles ; V shaped, chromatids / daughter chromosomes, in correct orientation ; spindle (fibres) attached to all four, centromeres / kinetochores / apex, and centrioles ; R if these extend between chromatids [max 3] (ii) 1 attach to the, centromeres (at prophase) ; A kinetochores I if attach at metaphase 2 attach to, centrioles ; A centrosome / MTOC 3 arrange the chromosomes on the, equator / metaphase plate ; 4 pull / move, (daughter) chromosomes, apart / to the poles ; A separates for moves apart A (sister / identical) chromatids I ends R homologous chromosomes [max 2] (b) (i) 1 produces / makes / synthesises, haemoglobin ; I fills up 2 produces / makes / synthesises, carbonic anhydrase ; I fills up 3 loss / AW, of the nucleus ; 4 loss / AW, of (named) organelles ; e.g. ribosomes / (R)ER / mitochondria 5 becomes biconcave / described ; 6 AVP ; e.g. cell surface / antigens / named antigens ref. to cytoskeleton [max 3] (ii) cell Y 1 remains / stays as a, stem cell ; 2 divides / undergoes mitosis ; I ref. to becoming a type of blood cell / platelet R if it becomes a cell other than a blood cell / platelet [max 1]

Page 7 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2016 9700 21 © Cambridge International Examinations 2016 (c) (i) 13.5 ; [max 1] (ii) 1 low(er) partial pressure of oxygen (at high altitude) ; A pO2 / ppO2 2 less oxygen in, inhaled air / lungs / alveoli ; 3 so haemoglobin, is not fully saturated / has lower saturation (with oxygen) (than at sea level) / lower affinity for oxygen ; 4 idea that more red blood cells so, higher concentration of / more haemoglobin ; 5 allows, same / similar / enough, volume of oxygen to be transported in the blood as at sea level ; 6 volume of oxygen transported in the blood is less ; 7 less oxygen for (aerobic) respiration / lack leads to anaerobic respiration ; 8 any consequence, e.g. fatigue, altitude sickness ; [max 4] [Total: 14] 6 (a) fluid phospholipids (and proteins), move / AW ; mosaic proteins / glycoproteins, scattered / AW (in the phospholipid bilayer) ; A different types of proteins I pattern unqualified [2] (b) 7 nm ; A any size or range within 6 nm and 10 nm A 7 nanometres [1] (c) cholesterol ; unsaturated fatty acids ; A phospholipid tails carbohydrate chains added to protein(s) / glycoproteins ; A oligosaccharides for carbohydrate chains carbohydrate chains added to lipids / glycolipids ; glycocalyx ; channel protein(s) / AW ; A aquaporin(s) ; carrier proteins / AW ; peripheral / extrinsic, proteins ; attachment to, cytoskeleton / microfilaments ; receptor(s) ; antigen(s) ; AVP ; [max 4] [Total: 7]