Cambridge A Level Biology 9700 — 2019 May/June Paper 4 · Variant 2

This document consists of 24 printed pages. DC (LK/TP) 164857/2 © UCLES 2019 [Turn over Cambridge Assessment International Education Cambridge International Advanced Subsidiary and Advanced Level * 8 3 6 6 6 1 5 2 7 3 * BIOLOGY 9700/42 Paper 4 A Level Structured Questions May/June 2019 2 hours 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. Section A Answer all questions. Section B Answer one question. 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 9700/42/M/J/19 © UCLES 2019 Section A Answer all questions. 1 (a) Fig. 1.1 is an electron micrograph showing a cross-section of a myelinated neurone. A B Fig. 1.1 Name A and B. A … B … [2] (b) Explain what is meant by saltatory conduction and describe its effect on the transmission of a nerve impulse. … … … … … … [3]

3 9700/42/M/J/19 © UCLES 2019 [Turn over (c) A type of sea snail, Conus purpurascens, produces a toxin that blocks calcium ion channels in the presynaptic knob of a cholinergic synapse. The presence of this toxin results in no action potentials in the postsynaptic neurone. Explain why the presence of this toxin results in no action potentials in the postsynaptic neurone. … … … … … … … … … … [5] [Total: 10]

4 9700/42/M/J/19 © UCLES 2019 2 Steelhead trout, Oncorhynchus mykiss, are fish that live in streams in North America. To increase the number of steelhead trout, captive breeding has occurred since 1992. Fish eggs and sperm are mixed and the young fish grow in large tanks of aerated water for the first year of their lives. Most are then released into the wild, however a few male and female fish are kept to become the parents of the next generation of captive-bred fish. Each tank may hold up to 50 000 fish. The young captive fish are fed processed food. Some young fish are unable to survive these conditions and a proportion die. Death is usually the result of poor wound-healing after accidents due to overcrowding and due to the spread of diseases. (a) (i) Name the expected pattern of variation in wound-healing ability in a population of fish. … [1] (ii) Name the process that results in improved survival of captive fish in second, third and subsequent generations of captive-bred fish. … [1] (b) Suggest and explain three ways in which the tank environment may make the phenotype of a captive fish different from a wild fish. … … … … … … … [3]

5 9700/42/M/J/19 © UCLES 2019 [Turn over Two groups of fish were bred and grown in the same environment and were then compared to see if they showed differences in gene expression. The two groups of fish came from: • eggs and sperm from parent fish that had always lived in the wild • eggs and sperm from parent fish that had been bred in captivity. Results from microarray analysis showed that the offspring of the wild and captive-bred fish differed in the expression of over 700 genes. (c) (i) Describe how microarray analysis can detect differences in the expression of many genes when comparing two samples, such as the offspring of wild and captive-bred fish. … … … … … … … … … … … … [5]

6 9700/42/M/J/19 © UCLES 2019 (ii) Explain how gene expression is controlled in eukaryotes such as fish. … … … … … … … … … … [4] (d) Many of the differences in gene expression between the offspring of the wild and captive-bred fish were in genes coding for proteins involved in the immune response and in genes coding for proteins involved in wound healing. The fish from captive-bred parents expressed these genes to a greater degree. The researchers concluded that the differences were inherited and adaptive. Explain why the researchers concluded that the differences in gene expression between the two groups of fish were: (i) inherited … … [1] (ii) adaptive. … … [1] [Total: 16]

7 9700/42/M/J/19 © UCLES 2019 [Turn over 3 Soybean, Glycine max, is an important food crop for human consumption and for feeding to animals. Two varieties of soybean are Vinton 81 and GTS 40-3-2. Vinton 81 has been developed in the traditional way by selective breeding (artificial selection) and GTS 40-3-2 is an example of a genetically modified (GM) organism. (a) GTS 40-3-2 is described as herbicide-resistant, as it can withstand the application of glyphosate herbicide. Glyphosate is sprayed on the crop to kill weeds. Outline how genetic engineering gave GTS 40-3-2 the trait of herbicide resistance. … … … … … … … … … … … [4]

8 9700/42/M/J/19 © UCLES 2019 (b) Countries vary in the extent to which they grow GM varieties, such as GTS 40-3-2, instead of traditional varieties such as Vinton 81. • In the USA, 94% of soybeans grown are GM. • In Europe, 0% of soybeans grown are GM. Scientists used computer models to predict the effect of two different changes in agricultural practice on soybean crop yields: • a global ban that reduces the cultivation of GM soybeans to 0% everywhere • all countries increasing the cultivation of GM soybeans to the 94% level of the USA. Table 3.1 shows the results of this modelling for four countries. Table 3.1 country percentage change in yield of soybeans decrease GM soybean cultivation to 0% of total increase GM soybean cultivation to 94% of total Argentina 0.00 +6.23 Bolivia –10.82 0.00 Brazil 0.00 +6.23 USA –5.87 0.00 Explain what the data in Table 3.1 suggests about the social and ethical implications of growing GM soybeans. … … … … … … … … … … … [5] [Total: 9]

9 9700/42/M/J/19 © UCLES 2019 [Turn over 4 Oculocutaneous albinism (OCA) is a type of albinism. There are many different forms of OCA. OCA1A is one form of OCA, caused by a recessive mutation in the autosomal gene, TYR, coding for the enzyme tyrosinase. This enzyme is involved in the biosynthetic pathway that results in the production of melanin, the pigment responsible for the colour of hair, skin and eyes. A person with OCA1A has white hair, very pale skin and pink eye colour. (a) Draw a genetic diagram to show the probability of a child having OCA1A, if both parents are carriers. Use the symbols A and a for the alleles. parental genotypes gametes offspring genotypes offspring phenotypes probability [4]

10 9700/42/M/J/19 © UCLES 2019 (b) Fig. 4.1 shows the biosynthetic pathway involving tyrosinase. tyrosinase tyrosinase tyrosine DOPA dopaquinone melanin Fig. 4.1 There are a number of different mutations of the TYR gene that can result in an absence of melanin and cause OCA1A. These include: • a missense mutation, caused by a base substitution, is most common • a nonsense mutation, caused by a base substitution, is less common • an insertion mutation, which is extremely rare. (i) A missense mutation results in a complete polypeptide chain that does not fold properly to form the functioning enzyme. A nonsense mutation results in a shortened polypeptide. Explain why a missense mutation results in a different product from a nonsense mutation. … … … … [2] (ii) Explain how an insertion mutation in TYR can lead to a lack of melanin in a person with OCA1A. … … … … … … … … [4]

11 9700/42/M/J/19 © UCLES 2019 [Turn over (c) Worldwide, 1 in 17 000 people are born with OCA. This compares with 1 in 165 people among the Guna people of Panama. The Guna people of Panama have a small population and mostly live on many small islands off the coast of Panama. Suggest reasons why the Guna population of Panama has a relatively high number of cases of OCA. … … … … [2] [Total: 12] 5 (a) Fig. 5.1 is a photomicrograph of part of the cortex of a kidney. Fig. 5.1 (i) On Fig. 5.1, use label lines and letters to label: G – the glomerulus L – the lumen of the Bowman’s (renal) capsule. [2] (ii) During ultrafiltration, components of blood in the glomerulus with a relative molecular mass greater than 68 000 are prevented from passing into the Bowman’s capsule. Name the structure that acts as this filtration barrier. … [1]

12 9700/42/M/J/19 © UCLES 2019 (b) The glomerular filtration rate (GFR) is the rate of flow of filtered fluid through the kidneys per unit time. The afferent arterioles supply blood to the glomerulus of each nephron within the kidney and the efferent arterioles take blood away from each glomerulus. The lumen diameters of the afferent and efferent arterioles have a large effect on the GFR. Normally the lumen diameters of the afferent and efferent arterioles are different, but they can change to increase or decrease the normal GFR in response to changing conditions. Complete Table 5.1 to indicate whether the GFR is normal, increased, or decreased for each combination of arteriole diameters shown. The first row has been completed for you. Table 5.1 afferent arteriole lumen diameter efferent arteriole lumen diameter GFR normal normal normal decreased normal … normal increased … [2] (c) After leaving the Bowman’s capsule, the glomerular filtrate passes through the proximal convoluted tubule, where selective reabsorption occurs. Describe and explain how all of the glucose in the glomerular filtrate is reabsorbed back into the blood. … … … … … … … … … … [5]

13 9700/42/M/J/19 © UCLES 2019 [Turn over (d) State and explain three features of a proximal convoluted tubule cell that adapt it to its function. … … … … … … [3] [Total: 13]

14 9700/42/M/J/19 © UCLES 2019 6 (a) State the general theory of evolution. … … … [1] (b) Different types of organism have evolved different structures containing light receptors. Eyes are organs containing light receptors. Fig. 6.1 describes the light receptors of several types of organism. Euglena (a single-celled eukaryote) has a simple eyespot that can only detect the intensity and direction of light. Turbellarian flatworms have cup-shaped eyes, each with a layer of light receptor cells. They can detect the intensity and direction of light better than Euglena. They also detect movement. The mollusc Nautilus has eyes with deeper cups and narrower openings for light to enter. They can form a rough image, see shapes and detect the direction of light better than turbellarian flatworms. The mollusc Nucella has eyes with lenses made of jelly. They can form a more detailed image than the eyes of Nautilus and can focus light to a small degree. Mammals have eyes that are more complex than Nucella. They have a fixed lens (the cornea) that bends light and a lens that can change shape to focus on objects at different distances. The lenses focus light onto a deeply cup-shaped layer of light receptor cells. The eyes form a very detailed image. Fig. 6.1

15 9700/42/M/J/19 © UCLES 2019 [Turn over Using the information in Fig. 6.1, suggest how a complex eye such as that of mammals could have evolved in successive stages. … … … … … … … … [4] (c) Octopuses are molluscs that have eyes very similar to those of mammals. Octopuses and mammals are not closely related. Octopuses and mammals have lenses that can change shape to focus on objects at different distances. Suggest reasons why octopuses and mammals have evolved similar eye structures. … … … … … … … … [2]

16 9700/42/M/J/19 © UCLES 2019 (d) Molecular evidence is used to investigate evolution. One study involved a marine worm, Platynereis dumerilii, that still has characteristics similar to its ancestors from 600 million years ago. Researchers sequenced all the proteins in light receptor cells of P. dumerilii and humans. The results showed that there are many similarities between the protein sequences of P. dumerilii and humans, particularly in the light-detecting protein opsin. (i) State what this molecular evidence indicates about the evolutionary origins of P. dumerilii and humans. … … [1] (ii) Explain how amino acid sequences indicate how close the relationship is between two species. … … … … … [2] [Total: 10]

17 9700/42/M/J/19 © UCLES 2019 [Turn over 7 (a) Define the term ecosystem. … … … … … … [3] (b) State the term used to describe: the functional role of a species within an ecosystem … a reproductively isolated group of organisms that interbreed to produce fertile offspring … physical factors in the environment such as temperature and soil pH. … [3] [Total: 6]

18 9700/42/M/J/19 © UCLES 2019 8 (a) Oxidative phosphorylation takes place in the mitochondrion. Table 8.1 shows the different stages of oxidative phosphorylation. The stages are not listed in the correct order. Table 8.1 stage description of stage Q protons diffuse through the membrane proteins into the matrix R a proton gradient is set up across the crista membrane S hydrogen atoms split into protons and electrons T protons combine with electrons and oxygen atoms to form water U electrons are passed from carrier to carrier V reduced NAD releases hydrogen atoms to cytochrome carriers W energy from electron transfer is used to pump protons into the intermembrane space X ATP synthase produces ATP Complete Table 8.2 to show the correct order of the stages. Two of the stages have been completed for you. Table 8.2 correct order letter of stage 1 V 2 … 3 … 4 … 5 R 6 … 7 … 8 … [4]

19 9700/42/M/J/19 © UCLES 2019 [Turn over (b) State the precise location in a mitochondrion of each of the following. ATP synthase … Krebs cycle … electron transport chain … coenzyme A … pyruvate … [5] [Total: 9]

20 9700/42/M/J/19 © UCLES 2019 Section B Answer one question. 9 (a) Describe how you would carry out an investigation into the effect of temperature on the rate of photosynthesis of an aquatic plant. [8] (b) Outline how degraded habitats may be restored, with reference to named examples. [7] [Total: 15] 10 (a) Outline the biological basis of contraceptive pills containing oestrogen and progesterone. [8] (b) Explain how speciation may occur as a result of geographical separation. [7] [Total: 15] … … … … … … … … … … … … … … … … … …

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24 9700/42/M/J/19 © UCLES 2019 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. To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge Assessment International Education Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cambridgeinternational.org after the live examination series. Cambridge Assessment International Education is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of the University of Cambridge Local Examinations Syndicate (UCLES), which itself is a department of the University of Cambridge. … … … … … … … … … … … … … … … … … … … … … … … …

This document consists of 21 printed pages. © UCLES 2019 [Turn over Cambridge Assessment International Education Cambridge International Advanced Subsidiary and Advanced Level BIOLOGY 9700/42 Paper 4 A Level Structured Questions May/June 2019 MARK SCHEME Maximum Mark: 100 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 International will not enter into discussions about these mark schemes. Cambridge International is publishing the mark schemes for the May/June 2019 series for most Cambridge IGCSE™, Cambridge International A and AS Level and Cambridge Pre-U components, and some Cambridge O Level components.

9700/42 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 2 of 21 Generic Marking Principles These general marking principles must be applied by all examiners when marking candidate answers. They should be applied alongside the specific content of the mark scheme or generic level descriptors for a question. Each question paper and mark scheme will also comply with these marking principles. GENERIC MARKING PRINCIPLE 1: Marks must be awarded in line with: • the specific content of the mark scheme or the generic level descriptors for the question • the specific skills defined in the mark scheme or in the generic level descriptors for the question • the standard of response required by a candidate as exemplified by the standardisation scripts. GENERIC MARKING PRINCIPLE 2: Marks awarded are always whole marks (not half marks, or other fractions). GENERIC MARKING PRINCIPLE 3: Marks must be awarded positively: • marks are awarded for correct/valid answers, as defined in the mark scheme. However, credit is given for valid answers which go beyond the scope of the syllabus and mark scheme, referring to your Team Leader as appropriate • marks are awarded when candidates clearly demonstrate what they know and can do • marks are not deducted for errors • marks are not deducted for omissions • answers should only be judged on the quality of spelling, punctuation and grammar when these features are specifically assessed by the question as indicated by the mark scheme. The meaning, however, should be unambiguous. GENERIC MARKING PRINCIPLE 4: Rules must be applied consistently e.g. in situations where candidates have not followed instructions or in the application of generic level descriptors.

9700/42 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 3 of 21 GENERIC MARKING PRINCIPLE 5: Marks should be awarded using the full range of marks defined in the mark scheme for the question (however; the use of the full mark range may be limited according to the quality of the candidate responses seen). GENERIC MARKING PRINCIPLE 6: Marks awarded are based solely on the requirements as defined in the mark scheme. Marks should not be awarded with grade thresholds or grade descriptors in mind.

9700/42 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 4 of 21 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 accepted) 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

9700/42 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 5 of 21 Question Answer Marks 1(a) A – Schwann cell / myelin sheath ; B – axon / axoplasm / cytoplasm ; 2 1(b) 1 action potential / impulse, ‘jumps’ from node to node ; 2 local circuits, set up between nodes / longer ; A local currents 3 fast / increases speed (of transmission of impulse) ; 3 1(c) any five from: 1 no calcium ions enter (the presynaptic knob) ; 2 (so) vesicles do not, move towards / fuse with, presynaptic membrane ; 3 no, exocytosis / release, of ACh ; R exocytosis of vesicles 4 ACh does not diffuse across (synaptic) cleft ; 5 no binding with receptor (protein) on postsynaptic membrane ; 6 sodium (ion) channels do not open ; 7 sodium ions do not enter (postsynaptic) neurone ; 8 no depolarisation (of postsynaptic membrane) ; 5

9700/42 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 6 of 21 Question Answer Marks 2(a)(i) continuous ; A normal distribution 1 2(a)(ii) evolution / natural selection / artificial selection / directional selection / adaptation / selective breeding ; 1 2(b) any three from: captive fish: 1 controlled conditions so phenotype less varied ; 2 more oxygen so larger ; 3 less space / overcrowding, so smaller ; 4 less space / overcrowding, so (signs of) disease / wounds ; 5 food qualified linked to, size / muscle / fat ; 6 AVP ; e.g. named tank condition linked to skin colour / no predators linked to increase in size / temperature linked to size 3

9700/42 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 7 of 21 Question Answer Marks 2(c)(i) any five from: 1 obtain mRNA from wild and captive bred fish / AW ; 2 reverse transcription of mRNA to produce cDNA ; 3 add fluorescent label to (c)DNA ; I colour A dyes / markers / tags 4 (microarray has) ssDNA probes ; 5 each from a, different / known, gene ; 6 (c)DNA hybridises / AW, to, probes / ssDNA (on microarray) ; 7 fluorescence shows the expressed genes ; 8 intensity of fluorescence (shows level of gene expression) ; 9 compare, fluorescence / gene expression (between fish groups) ; 10 AVP ; e.g. ref. to washing off excess (c)DNA (only), after hybridisation UV light / laser scanning (to record fluorescence pattern) 5

9700/42 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 8 of 21 Question Answer Marks 2(c)(ii) 1 ref. to transcription factors ; any three from: 2 TF / gene product / protein, bind to DNA ; 3 (TF binds to) promoter ; 4 switches genes, on / off ; AW I genes, expressed / not expressed 5 ref. to binding of RNA polymerase ; R if operator mentioned 6 mRNA is made / transcription occurs ; ora 7 AVP ; e.g.(so that genes are expressed) at the correct time / in the correct context / in the correct cell type / in the correct order ; 4 2(d)(i) any one from: 1 differences caused by selection in captive-bred population ; 2 (not environmental because) all, offspring / fish, were kept in same environment ; 1 2d(ii) idea that captive fish have better, wound healing / immune response ; 1

9700/42 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 9 of 21 Question Answer Marks 3(a) any four from: 1 gene (for herbicide resistance) from, another species / variety / (soil) bacterium ; A allele 2 ref. to restriction enzyme ; 3 ref. to (Ti) plasmid / vector / Agrobacterium / gene gun ; 4 (DNA) ligase ; 5 ref. to recombinant, DNA / plasmid ; 6 introduced into soybean, cells / genome / DNA ; I embryos 7 (new) gene, expressed / transcribed ; 8 (to produce) protein / enzyme, resistant to, glyphosate / herbicide ; 9 AVP ; e.g. ref. to tissue culture / produce callus / detail such as grow cells on growth medium / marker genes / insert promoter 4

9700/42 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 10 of 21 Question Answer Marks 3(b) 1 decrease / ban / 0%, GM soybean (cultivation), decreases yield ; 2 use GM soybean, more / 94%, increases yield ; use GM crops – accept ora throughout if GM crops banned 3 increase food supply / decrease food cost ; 4 relieve, hunger / starvation ; 5 less / more, herbicides used ; correct context needed 6 less / more, money spent on herbicides ; correct context needed 7 increase profits / improve economy ; 8 unknown health consequences ; (can be positive or negative) 9 high cost of GM seed ; 10 idea of decrease in, genetic variation / biodiversity ; 5

9700/42 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 11 of 21 Question Answer Marks 4(a) parental genotypes Aa × Aa and gametes A a and A a ; offspring genotypes AA Aa (Aa) aa ; offspring phenotypes (correctly linked to genotypes) normal normal / carrier (normal / carrier) OCA1A / albino / described ; probability 25% ; A 1 in 4 / 0.25 / ¼ I ratio 4 4(b)(i) missense results in a different amino acid ; nonsense ref. to STOP codon ; 2 4(b)(ii) any four from: 1 frameshift / described ; 2 change in, primary structure / amino acid sequence ; 3 protein / enzyme / tyrosinase, folds incorrectly / changes tertiary structure / changes 3D shape ; 4 may introduce STOP codon ; 5 shortened polypeptide / no tyrosinase produced ; 6 tyrosinase, non-functional / lacks active site / active site changed shape / cannot form ESCs ; 7 tyrosine not converted to DOPA / DOPA not converted to dopaquinone ; 8 (so) dopaquinone not formed to produce melanin ; 4

9700/42 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 12 of 21 Question Answer Marks 4(c) any two from: 1 small gene pool / low genetic variation / low genetic diversity / low heterozygosity / high homozygosity ; 2 isolated (population) / described ; 3 inbreeding (within their population) ; 4 albinism has a selective advantage ; 5 founder effect / genetic bottleneck ; 6 genetic drift ; 2

9700/42 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 13 of 21 Question Answer Marks 5(a)(i) correct lines ;; 2 5(a)(ii) basement membrane ; 1 5(b) afferent arteriole lumen diameter efferent arteriole lumen diameter GFR normal normal normal decreased normal decrease ; normal increased decrease ; 2 5(c) any five from: 1 active transport / pumping, of Na+ (out of cells) into, blood / tissue fluid ; 2 sodium (potassium) pumps in basal membrane ; 3 Na+ concentration decreases inside cells / Na+ concentration gradient set up ; 4 (so) Na+ enters (epithelial / tubule) cells from, lumen / filtrate ; 5 by facilitated diffusion ; 6 Na+ co-transports glucose into cell ; 7 this is, secondary / indirect, active transport ; 8 (facilitated) diffusion of glucose (out of cells) into blood ; 9 GLUT proteins ; 5

9700/42 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 14 of 21 Question Answer Marks 5(d) any three from: 1 microvilli, has large surface area / for increased (re)absorption ; I increase surface to volume ratio 2 many mitochondria provide ATP for, sodium (potassium) pumps / active transport ; 3 tight junctions / closely packed cells, hold adjacent cells together / prevents leakage / fluid cannot pass between cells / substances must pass through cells ; 4 many transport proteins for movement of named substance ; 3 Question Answer Marks 6(a) idea that organisms have changed over time ; 1 6(b) any four from: 1 ref. to mutation ; 2 (mutation) results in a change in eye structure ; 3 ref. to natural selection / selective advantage ; 4 light receptor (cells) develop ; 5 light receptor layer becomes cup-shaped ; 6 idea that entry for light becomes narrower ; 7 lens forms ; 8 fixed lens / cornea, (forms) ; 4

9700/42 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 15 of 21 Question Answer Marks 6(c) any two from: must refer to both octopus and mammal 1 had similar, selection pressures / light conditions ; 2 allows organisms to escape predators ; 3 allows organisms to find food ; 4 convergent evolution / described ; 2 6(d)(i) shared origin / common ancestor / same ancestor ; 1 6(d)(ii) any two from: 1 compare (amino acid sequences of two species) ; 2 more similar (amino acid sequence) more closely related the species are ; ora 3 more similar (amino acid sequence) more recent common ancestor / less time has elapsed (since a common ancestor); ora 4 ref. to molecular clock ; 2

9700/42 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 16 of 21 Question Answer Marks 7(a) any three from: 1 functional / self-contained / specific, entity / unit / area ; 2 community (of organisms) / all living organisms of all species / all populations of organisms ; 3 ref. to interactions ; 4 abiotic / physical, and, biotic / biological, factors ; A living and non-living 5 idea that linked by, energy flow / mineral cycling / food webs / food chains / nutrient cycle ; 3 7(b) niche ; species ; abiotic ; 3

9700/42 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 17 of 21 Question Answer Marks 8(a) correct order letter of stage 1 V 2 S 3 U 4 W 5 R 6 Q 7 X 8 T 6 correct = 4 marks 4/5 correct = 3 marks 2/3 correct = 2 marks 1 correct = 1 mark ;;;; 4 8(b) ATP synthase - cristae / inner membrane ; Krebs cycle - matrix ; electron transport chain - cristae / inner membrane ; coenzyme A - matrix ; pyruvate - matrix ; 5

9700/42 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 18 of 21 Question Answer Marks 9(a) any eight from: 1 microburette / (gas) syringe / photosynthometer ; 2 cut shoot (of aquatic plant) ; 3 place shoot in tube of hydrogen carbonate solution ; 4 to provide carbon dioxide ; 5 water bath / maintain temperature ; 6 choose 4 different temperatures ; 7 acclimatisation ; 8 lamp placed fixed distance away ; 9 measure length of bubble of, gas / oxygen, in set time or count number of bubbles produced in set time ; 10 repeat experiment twice more ; 11 calculate mean values ; 12 method to calculate rate of photosynthesis ; 13 AVP ; e.g. dark room / heat shield / LED bulbs 8

9700/42 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 19 of 21 Question Answer Marks 9(b) any seven from: restoration techniques 1 reforesting / replanting ; 2 reintroduction of, named / native, animal (species) ; 3 bioremediation / described ; 4 bubbling oxygen through / oxygenation of, water ; 5 ref. to normalising pH of, water bodies / soil ; 6 dredging / clearing / purifying, rivers / lakes / water bodies ; 7 litter / waste, removal ; 8 removal of toxic layer of soil / soil cleaned and put back ; 9 idea of improving soil fertility ; 10 removal of alien (plant / animal) species ; 11 protection against grazing ; 12 named example ; 13 named example ; 7

9700/42 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 20 of 21 Question Answer Marks 10(a) any eight from: 1 synthetic hormones used ; 2 as they do not get broken down quickly / act for longer ; 3 oestrogen / progesterone, (blood) concentrations remain high ; 4 (act on) anterior pituitary (gland) ; 5 FSH not, produced / secreted ; 6 Graafian / dominant, follicle does not develop ; 7 LH not, produced / secreted ; 8 ovulation prevented / described ; 9 cervical mucus thickens (to stop sperm) ; 10 prevents implantation / endometrium less well developed ; 11 ref. to negative feedback ; 12 AVP ; e.g. taken daily for 21 days then stops (for 7 days) to allow menstruation / taken daily throughout month 8

9700/42 Cambridge International AS/A Level – Mark Scheme PUBLISHED May/June 2019 © UCLES 2019 Page 21 of 21 Question Answer Marks 10(b) any seven from: 1 named geographical barrier ; e.g. river / mountain / sea 2 two populations (of same species) separated ; 3 no, breeding / allele flow / gene flow, between populations or reproductively isolated ; 4 different, selection pressures / (environmental) conditions ; 5 mutations occur ; 6 individuals with beneficial alleles, are selected for / survive / reproduce / have a selective advantage ; 7 beneficial alleles passed on ; 8 change in, allele frequency / gene pool ; 9 genetic drift ; 10 ref. to over a long time / many generations ; 11 (eventually) unable to interbreed to produce fertile offspring / reproductively isolated ; 12 allopatric (speciation) ; 7