Planning, analysis and evaluation

1(a)(i) number of (different) species (of plant) / species richness ; 2 abundance / number / frequency / population / density, of each species (of plant) ; 1(a)(ii) ref. to trampling / trampled versus non-trampled ; 1 1(b) any eight from: 8 1 use, quadrat(s) / a (named type of) transect ; 2 idea of sampling in the trampled and untrampled area ; 3 ref. to, method of, random placement of quadrats / systematic sampling along the transect ; 4 ref. to use of, same / stated, size (frame / point), quadrat ; 5 method of identifying species ; 6 ref. to a method of estimating abundance ; 7 idea of taking care to note low growing / small / easy to miss, species ; 8 idea of sampling at least 3 separate points in the open land and on the shortcut path / 3 different line transects ; 9 repeat (whole investigation) at different times of, year / seasons ; 10 calculate / use, Simpson’s index (of diversity) ; 11 plants causing irritation / allergy and wearing, gloves / protective clothing or pollen causing, hay fever / allergy, and wearing mask or taking medication or ref. to environmental hazard related to its risk and wearing, suitable shoes / protective clothing or suitable mitigation ; © UCLES 2021 Page 6 of 9 1(c)(i) support: 2 (all) the times, for path / trampled area, are, longer / higher / slower (than untrampled) / ora ; do not support: idea of no information about soil air spaces ; 1(c)(ii) S = 2.8 ; 2 M 95% confidence interval = 68.1 / 68.2, to 79.5 / 79.4 ; 1(c)(iii) any two from: 2 1 95%, probability / confidence that / chance that, the, true / population / parametric / actual, mean, lies within these limits ; 2 the difference between means is (likely to be) significant (at p<0.05 because there is no overlap between 95% CI for untrampled and trampled) ; 3 idea that the narrower CI (in the untrampled area), the closer the calculated mean is to the true mean / ora ; 1(d)(i) any two from: 2 1 idea of using a grid and tracing outline / using transparent grid over leaf ; 2 idea of systematic counting of squares fully and more than half covered ; 3+4 AVP ; ; 1(d)(ii) there is a negative correlation 1 or as time taken for (10 cm3) of water to drain through decreases, leaf surface area increases / ora ; 1(d)(iii) 1 working at, p = 0.05 / p<0.05 ; 2 2 correlation / relationship, is, significant / not due to chance, as calculated r (0.455) is greater than (critical value of) s 0.447 ; © UCLES 2021 Page 7 of 9

2(a)(i) time taken for, indigo carmine / solution / indicator, to, turn blue / change colour ; 1 2(a)(ii) any one from: 1 number / mass, of beads (of immobilised cells) ; size / surface area, of beads ; concentration of alginate ; density / number, of cells / protoctists ; ambient / background / AW, light (intensity) ; pH ; concentration of indicator ; species / type, of protoctist / unicell / AW ; 2(b)(i) 2.55 ; 1 2(b)(ii) any three from: 3 1 idea that increasing, hydrogencarbonate / carbon dioxide, (concentration) increases, the rate of photosynthesis / the rate / photosynthesis / the rate of reaction / ora ; 2 idea that increasing, light intensity, increases, the rate of photosynthesis / the rate / photosynthesis / the rate of reaction / ora ; 3 ref. to when carbon dioxide / hydrogencarbonate, is a limiting factor using information from Table 2.1 ; 4 ref. to when light is a limiting factor using information from Table 2.1 ; © UCLES 2021 Page 8 of 9 2(b)(iii) any two from: 2 1 idea of, (small) range / number / AW, of different concentrations of, (sodium hydrogencarbonate / carbon dioxide) solution ; 2 idea of, (small) range / number / AW, of different light intensities ; 3 idea of outside air has not been excluded so change in colour may not be due only to oxygen produced ; 4 idea that colour change is, subjective / difficult to see ; 5 idea that only, one species / a protoctist / a unicell, is tested (so may not be valid for all species / types, of photosynthetic organisms ; © UCLES 2021 Page 9 of 9

1(a) 0.5 cm3 of the stock solution ; 2 idea of adding 9.5 cm3 of buffer / water / filling to the 10 cm3 mark with buffer / water (in a volumetric flask) ; 1(b)(i) idea that (result / it, is) quantitative / AW ; ora 1 1(b)(ii) independent variable: 2 concentration of ONPG / substrate ; dependent variable: absorbance (on colorimeter) ; 1(c)(i) any eight from: 8 1 ref. to preparing / using at least five concentrations of ONPG 2 stated range of five dilutions, from 1%v down, with % units 3 method of keeping β-galactosidase / enzyme, cold (prior to use) ; 4 idea of bringing enzyme and substrate to temperature / equilibrating, before mixing ; 5 method of keeping reactants / reaction mixture, at, constant / controlled / stated / standardised, temperature ; 6 same / constant / stated / standardised / known, volume / concentration / mass of, X / inhibitor ; 7 same / constant / stated / standardised / known, volume of, ONPG / substrate ; 8 same / constant / stated / standardised / known, volume / concentration, of β-galactosidase / enzyme ; 9 ref. to measuring absorbance / intensity of colour (on colorimeter) after one set time ; 10 additional detail of use of colorimeter ; 11 repeat at least twice / three replicates, and calculate mean ; 12 idea of repeating, whole experiment / range of concentrations, without X / inhibitor ; 13 named hazard and risk and precaution ; 1(c)(ii) 1 curve, to the right of / below, original curve ; 2 2 curve / line, must meet the plateau of original curve on the graph ; 1(c)(iii) 1 correct placement of V ; 2 max 2 correct placement of K ; m 1(c)(iv) (reaction with competitive inhibitor / X) has higher / has increased / increases, K value (compared to no inhibitor) ; 1 m © UCLES 2021 Page 7 of 10 1(d) assume ref. to PPI unless specific treatment stated 3 any three from: 1 idea that PPI overall is more effective / is immediately effective, on improvement / removal (of symptoms) ; 2 either at 12 and 16 weeks / later, overlap of error bars means difference (in effect between PPI and H RA) is not significant ; 2 or at 4 and 8 weeks / earlier, no overlap of error bars – suggesting difference (in effect, between PPI and H RA) may be, 2 significant ; 3 no statistical test to compare groups / t test, done (to test for significance) ; 4 idea that H RA is catching up / may be better in the long term ; 2 5 AVP ; ; any two from: • less than 50% patients reported no symptoms • no information on severity of symptoms pre-trial • no data on side effects • size of the two test groups not given • no data on long term effects (where H RA may be better) 2 Question Answer Marks

2(a)(i) idea of compare / AW, observed and expected (data / results / ratios / phenotypes) 1 or data is categoric / discrete / discontinuous / nominal ; 2(a)(ii) idea of no (significant) difference between the observed and the expected (results) 1 or idea of difference between observed and expected (results) is due to chance ; © UCLES 2021 Page 8 of 10 2(a)(iii) 3 ( O−E )2 offspring phenotype O E E purple axial flowers 1756 1882 (A 1881) 8.44 (1881.56250) (8.379175) purple, terminal flowers 653 627 1.08 (627.18750) (1.062338) white, axial flowers 702 627 8.97 (627.18750) (8.923823) white, terminal flowers 234 209 ; 2.99 ; (209.06250) (2.974608) χ2 = 21.48 ; (21.339944) χ2= 21.33 / 21.34 / 21.48 for mp3 (to allow for using calculator values or rounded values) 2(a)(iv) 7.82 ; 1 © UCLES 2021 Page 9 of 10 2(a)(v) apply ecf as needed 3 1 reject (null hypothesis) and state that, the calculated value / χ2, is higher than, 7.82 / the critical value / the critical value they give in (iv) from the table ; 2 If null hypothesis rejected: (between O and E): there is a significant difference / the difference is not due to chance idea that there is a less than 5% probability that the difference is due to chance / there is a more than 95% probability that the difference is not due to chance ; 3 From mp1 If null hypothesis rejected or mp2 If there is a significant difference / AW stated idea that: genes are on the same chromosome / are not on different chromosomes / are linked / show autosomal linkage / do not assort independently ; A idea of, ‘may be / can be’, throughout © UCLES 2021 Page 10 of 10

1(a) independent variable: 2 concentration of, copper (II) sulfate ; dependent variable: volume of, oxygen ; 1(b)(i) 1 minimum of five stated dilutions and correct units ; 2 2 method of serial dilution for a minimum of 2 intermediate (concentrations) ; © UCLES 2021 Page 7 of 11 1(b)(ii) any six from: 6 1 maintaining a constant temperature and a suitable method ; 2 maintaining a constant pH and use a buffer ; mp 3 and 4 and 5: if ‘amount’ rather than ‘volume’, penalise only once and ecf the following ones 3 same / stated, volume of catalase / enzyme or same / stated, concentration of catalase / enzyme ; 4 same / stated, volume of each copper sulfate / inhibitor solution ; 5 measure / record, volume of oxygen / gas collected, in set time / set intervals or time taken to reach a set volume ; 6 state a suitable control ; 7 use new / fresh (named) solutions for each replicate / experiment ; 8 repeat at least twice / three replicates, and finding mean for at least one concentration ; 9 named hazard and risk and precaution ; e.g. hazard risk precaution irritant / allergy catalase / enzyme moderate / medium, hazard irritant / allergy hydrogen peroxide moderate / medium, hazard wear gloves / goggles / mask PPA oxidising agent copper(II) sulfate irritant / allergy moderate / medium, hazard corrosive toxic do not pour down sink 10 AVP ; © UCLES 2021 Page 8 of 11 1(b)(iii) 1 axes correctly orientated with labels ; 3 2 axes labels have correct units ; 3 line shows downward trend as concentration of copper(II) sulfate increases ; e.g. volume of oxygen / mm3or cm3 concentration of copper sulfate / mol dm–3 1(c)(i) All three lines correctly drawn / indicated ; 3 1 V or V correctly labelled for lines drawn ; max max 2 K correctly labelled (on correct line) ; m 1(c)(ii) plateaus below V / does not reach V / V is lower (than without inhibitor) ; 2 max max max same / almost same / similar, K ; m Question Answer Marks

2(a)(i) remove / cover, anthers (from plant B) ; 1 2(a)(ii) method of transferring pollen (from anther) to stigma ; 1 or shake anthers, on / over, stigmas ; © UCLES 2021 Page 9 of 11 2(b) any three from: 3 light, intensity / duration / amount / strength / wavelength / colour ; temperature ; frequency of watering / amount of water ; humidity ; CO / O concentration ; 2 2 growing medium / soil composition ; planting density ; 2(c)(i) 2 ( O−E )2 offspring phenotype O E E purple petals 102 62 25.81 long pollen grains red petals 112 62 40.32 round pollen grains purple petals 14 62 37.16 round pollen grains red petals 20 62 28.45 ; long pollen grains χ2 = 131.74 ; © UCLES 2021 Page 10 of 11 2(c)(ii) 1 reject and state that their calculated value / χ2,is higher than 7.82 / critical value ; 3 any two from: 2 (if the null hypothesis is rejected) There is a significant difference between the expected and observed values or there is a less than 5% / 0.05 probability that the difference has occurred due to chance ; 3 genes, are on the same chromosome / are not on different chromosomes / are linked / do not assort independently or autosomal linkage or alleles (likely to be) inherited together ; 4 the two genes are close together (on the same chromosome) or small number of recombinants ; 2(d) 1 yes in copper sensitive plants and no in copper tolerant plants / only in copper sensitive plants ; 2 2 decrease, in percentage / %, viability, in sensitive plants / ora or slight increase, in percentage / %, viability, in tolerant plants ; 3 in sensitive plants, there is no overlap of (error) bars, which means the difference may be significant or in tolerant plants, there is an overlap of (error) bars, which means difference is not significant ; 4 no statistical test was carried out (in copper-sensitive plants) ; 5 growth of pollen tube does not indicate pollen grain is viable ; 6 no reference to concentration of copper ions used in the investigation ; © UCLES 2021 Page 11 of 11

1(a) idea of: 2 grinding with sand to break open the cells / release enzyme ; filtering through cloth to remove, sand / debris / AW ; 1(b)(i) (idea that result / it, is) quantitative / AW ; 1 1(b)(ii) independent variable: 2 concentration of catechol / substrate ; dependent variable : absorbance (on colorimeter) ; © UCLES 2021 Page 7 of 11 1(c)(i) any eight from: 8 1 ref. to preparing / using, at least five dilutions concentrations of catechol ; 2 stated range of at least five concentrations from 1% downwards with % units ; 3 method of keeping catechol oxidase / enzyme solution / banana extract cold ; 4 idea of bringing enzyme and substrate to temperature / equilibrating, before mixing ; 5 method of keeping reactants / reaction mixture, at, constant / controlled / stated / standardised, temperature ; 6 same / constant / stated / standardised / known, volume / concentration / mass of, Y / inhibitor ; 7 same / constant / stated / standardised / known, volume of, catechol / substrate ; 8 same / constant / stated / standardised / known, volume / concentration, of catechol oxidase / enzyme / banana extract ; 9 ref. to measuring absorbance / intensity of colour (on colorimeter) after one set time ; 10 additional detail of use of colorimeter ; 11 repeat at least twice / three replicates, and calculate mean ; 12 idea of repeating, whole experiment / range of concentrations, without, Y / inhibitor ; 13 named hazard and risk and precaution ; 1(c)(ii) curve should be to the right of the original curve ; 2 curve should plateau below the original curve ; 1(c)(iii) correct placement of V and K ; 2 max m 1(c)(iv) (reaction with non-competitive inhibitor) has same K value than with no inhibitor ; 1 m © UCLES 2021 Page 8 of 11 1(d) any three from: 3 1 combination of drugs gives a larger reduction in blood pressure ; 2 no error bars ; 3 no, statistical test / t-test, done to compare groups ; 4 no data on long term results ; 5 AVP ; ; any two from: • no information on blood pressure prior to trial • no information on type of blood pressure • no information on number of patients in each group • no data on side effects • ref. to reduction in blood pressure brought about by the placebo alone • no data on, age / gender © UCLES 2021 Page 9 of 11

2(a)(i) any one from: 1 idea of compare / AW, observed and expected (data / results / ratios / phenotypes) ; or data is, categoric / discrete / discontinuous / nominal ; 2(a)(ii) idea of no (significant) difference between the observed and the expected (results) ; 1 or idea of difference between observed and expected (results) is due to chance ; 2(a)(iii) 3 ( O−E )2 offspring phenotype O E E wrinkled wings 44 36 1.78 rosy eyes (36.000) (1.77778) wrinkled wings 2 12 8.33 red eyes (12.000) (8.33333) normal wings 2 12 8.33 rosy eyes (12.000) (8.33333) normal wings 16 4 ; 36.00 ; red eyes (4.000) (36.00000) χ2 = 54.44 ; (54.44444) apply ecf as needed 2(a)(iv) n–1 and probability of 0.05 / one less degree of freedom than number of categories and probability of 0.05 ; 1 © UCLES 2021 Page 10 of 11 2(a)(v) apply ecf as needed 3 1 reject (null hypothesis) and state that, the calculated value / χ2, is higher than, 7.82 / the critical value ; 2 If null hypothesis rejected: (between O and E): there is a significant difference / the difference is not due to chance idea that there is a less than 5 % probability that the difference is due to chance / there is a more than 95% probability that the difference is not due to chance ; 3 From mp1 If null hypothesis rejected or mp2 If there is a significant difference / AW, stated idea that: genes, are on the same chromosome / are not on different chromosomes / are linked / show autosomal linkage / do not assort independently ; A idea of, ‘may be / can be’, throughout mp3 © UCLES 2021 Page 11 of 11

1(a)(i) independent variable temperature ; 2 dependent variable volume of carbon dioxide / time to collect stated or fixed volume of CO ; 2 1(a)(ii) idea that: 1 ensures glucose and yeast are, uniformly distributed / homogeneously mixed / evenly mixed / completely mixed / AW ; 1(a)(iii) any seven from: 7 1 use a minimum of five different temperatures ; 2 state a suitable range of identified temperatures ; 3 idea of same / constant / stated / standardised / known, volume of, yeast-glucose / mixture (in the test-tube) ; 4 method of maintaining a, constant / stated, temperature ; 5 leave mixture to equilibrate to (each) temperature ; 6 leave for, set time / stated time, and measure volume (of carbon dioxide) or time how long to collect same volume (of carbon dioxide) from (each) sample ; 7 use a control using, killed yeast / water replacing yeast ; 8 ref. to a minimum of, two repeats / three replicates (for each temperature), and calculating means ; 9 idea of repeat investigation with narrower range of temperatures (around that which seems the one giving maximum rate) ; 10 low risk ; ‘medium risk’ needs hazard and risk and precaution. A yeast + allergy/irritant + gloves / mask / goggles /PPE 11 AVP e.g. maintaining a constant pH and using a buffer ; © UCLES 2021 Page 7 of 11 1(a)(iv) 1 horizontal axis labelled temperature / oC 2 and vertical axis labelled volume of carbon dioxide / cm3 / mm3 ; 2 curve starts low, reaches a maximum and then decreases ; 1(b) 1 flask 2 (provides the evidence) as in C. tropicalis there is lower CO (production / volume / AW) ; 3 2 2 (for flask 2, C. tropicalis compared to S. cerevisiae) 65% v 93% (after 30 minutes) CO as % of maximum or 2 manipulated figure i.e. 28% different ; 3 idea that: when transferred from conditions with oxygen to conditions with no oxygen yeasts have to use fermentation / anaerobic respiration but C. tropicalis does so at a much slower rate (as no Crabtree effect) thus less CO produced 2 ora ; © UCLES 2021 Page 8 of 11

2(a) idea of no (clear), relationship / trend ; 1 or as latitude increases, (bird) species diversity / numbers of (bird) species, (slightly) decreases / (might) show a downward trend ; 2(b)(i) any three from: 3 1 data (for latitude and number of species) is, paired / linked ; 2 number of bird species and latitude / (i.e. the data points) within samples are independent of each other ; 3 the data, is ordinal / is interval / is discrete / can be ranked ; 4 (scatter) graph / Fig. 2.2, suggests a, (decreasing) relationship / correlation ; 5 there are, 17 (paired) observations / more than 5 (paired) observations ; 6 idea that bird species selected randomly / AW ; 2(b)(ii) idea that 1 there is no, correlation / relationship, between latitude and the number of (bird) species ; 2(b)(iii) any four from: 4 1 critical value (for p = 0.05%) = 0.485 or critical value for p = 0.01% = 0.615 ; 2 value for r / calculated value, is < than critical value ; s 3 null hypothesis is accepted ; 4 there is no significant correlation (between latitude and number of bird species) ; 5 there is a (weak) negative correlation (between latitude and number of bird species as shown by the negative value for r ) ; s © UCLES 2021 Page 9 of 11 2(c) any three from 3 all marking points are ideas that: limitations of the data 1 only used counts of bird species (may not apply to all species) ; 2 do not know the, number of individuals of each species / relative abundance of each species / species evenness ; limitations of sampling birds 3 hard to identify some (bird) species / miss some (bird) species / some (bird) species look similar / miss birds that fly away / birds migrate / only resident birds or species counted / qualified ref to volunteers / AW ; latitudes sampled 4 nothing above 40N / nothing before 37N / need wider range of latitudes / AW ; 5 no data on latitudes south of the equator ; sampling sites 6 not random / only sampled in certain locations / sample locations do not cover the whole of the peninsula / many near the coast / locations may not be representative of the peninsula / only 17 sites / sampling sites do not extend beyond the peninsular / AW ; habitats 7 no information on habitats (at locations) / not all location may be equally suited for birds / different habitats have different conditions / AW ; timings 8 only sampled, on one day / in one year / sampled in, winter / one season ; ora © UCLES 2021 Page 10 of 11 2(d) any three from: 3 1 catch birds within area and count total captured and mark and release them ; 2 detail e.g. idea of: marking technique not, harmful / too obvious e.g. idea of: giving time for populations to mix before second sample taken – days or weeks not more ; 3 catch second sample and count total number of birds and number of marked birds ; 4 ref. to Lincoln / Petersen, index ; © UCLES 2021 Page 11 of 11

1(a)(i) independent variable 2 type of sugar or glucose / monosaccharide and maltose / disaccharide ; dependent variable height / length, of gas ; 1(a)(ii) to allow yeast / cells, to be evenly distributed ; 1 1(a)(iii) any seven from: 7 1 same / stated, concentration of glucose and maltose solutions ; 2 same / stated, volume of each sugar solution ; 3 same / stated, volume of yeast suspension (for each tube) / equally divide yeast suspension between (each tube) ; 4 same / stated, volume of water in each (large) tube ; 5 method of maintaining a constant temperature ; 6 maintaining a constant pH and use a buffer ; 7 measure / record, height of gas / liquid, in set time or measure / record, time taken, to reach a set height of gas / liquid ; 8 use of a ruler / AW for measuring gas / liquid ; 9 control, using killed yeast / replace yeast with water ; 10 repeat at least twice / three replicates, and finding mean (for at least one sugar) ; 11 low risk ; © UCLES 2021 Page 8 of 11 1(b)(i) any one from: 1 divide the volume of gas collected in a stated time, by the (same) time ; 1÷ time to reach a stated volume of gas ; use a tangent to the line and divide volume by time / calculate gradient ; 1(b)(ii) any three from: 3 1 rate of respiration is higher for glucose (than maltose) / ora ; 2 initial rate of reaction / respiration faster ; 3 gas / CO ,production is higher with glucose / ora ; 2 4 maltose is broken down before it can be respired / glucose can be respired immediately ; 5 maltase / enzyme, needed to break down maltose ; 1(c) any three from: 3 1 not subjective / ora ; 2 more accurate / ora ; 3 more precise / ora ; 4 can continuously record data (with data logger / computer) ; 5 meter can be used if colour blind / ora ; 6 meter does not pose a risk or hazard / ora ; © UCLES 2021 Page 9 of 11

2(a) any one from: 1 frog, age / size / mass / stage of maturity / from same population ; light intensity ; humidity ; time of day ; time of year ; duration of recording ; background noise ; 2(b) as (body) temperature increases the interval between calls decreases ; 1 2(c)(i) any three from: 3 1 data (for temperature and calls) is, paired / linked ; 2 data is continuous ; 3 data shows normal distribution ; 4 scatter diagram, suggests a linear, relationship / correlation ; 5 there are at least five (paired) observations ; 2(c)(ii) there is no, correlation / relationship, between the intervals between calls and temperature ; 1 2(c)(iii) any two from: 2 significant because 1 (critical value for p = 0.05 / 5% is) 0.279 or (critical value for p = 0.01 / 1% is) 0.361 ; 2 value for r / 0.717, is > than critical value (so null hypothesis is rejected / accept the alternative hypothesis) / ora ; © UCLES 2021 Page 10 of 11 2(d) any two from: 2 1 duration of each call ; 2 number of calls in a set time ; 3 number / frequency, of pulses, within each call ; 4 length of time between pulses within each call ; 5 sound frequency (kHz) / pitch ; 6 duration of each pulse ; 2(e) any three from: 3 1 capture frogs and count / find number / record number and mark and release them ; 2 suitable marking so not harmful / too obvious / not removed or appropriate time between first and second capture so frogs time to mix ; 3 capture second sample and count / find number / record number of frogs and count / find number / record number, of marked frogs ; 4 use Lincoln / Petersen, index ; © UCLES 2021 Page 11 of 11

1(a)(i) independent variable temperature ; 2 dependent variable volume of carbon dioxide / time to collect stated or fixed volume of CO ; 2 1(a)(ii) idea that: 1 ensures glucose and yeast are, uniformly distributed / homogeneously mixed / evenly mixed / completely mixed / AW ; 1(a)(iii) any seven from: 7 1 use a minimum of five different temperatures ; 2 state a suitable range of identified temperatures ; 3 idea of same / constant / stated / standardised / known, volume of, yeast-glucose / mixture (in the test-tube) ; 4 method of maintaining a, constant / stated, temperature ; 5 leave mixture to equilibrate to (each) temperature ; 6 leave for, set time / stated time, and measure volume (of carbon dioxide) or time how long to collect same volume (of carbon dioxide) from (each) sample ; 7 use a control using, killed yeast / water replacing yeast ; 8 ref. to a minimum of, two repeats / three replicates (for each temperature), and calculating means ; 9 idea of repeat investigation with narrower range of temperatures (around that which seems the one giving maximum rate) ; 10 low risk ; ‘medium risk’ needs hazard and risk and precaution. A yeast + allergy/irritant + gloves / mask / goggles /PPE 11 AVP e.g. maintaining a constant pH and using a buffer ; © UCLES 2021 Page 7 of 11 1(a)(iv) 1 horizontal axis labelled temperature / oC 2 and vertical axis labelled volume of carbon dioxide / cm3 / mm3 ; 2 curve starts low, reaches a maximum and then decreases ; 1(b) 1 flask 2 (provides the evidence) as in C. tropicalis there is lower CO (production / volume / AW) ; 3 2 2 (for flask 2, C. tropicalis compared to S. cerevisiae) 65% v 93% (after 30 minutes) CO as % of maximum or 2 manipulated figure i.e. 28% different ; 3 idea that: when transferred from conditions with oxygen to conditions with no oxygen yeasts have to use fermentation / anaerobic respiration but C. tropicalis does so at a much slower rate (as no Crabtree effect) thus less CO produced 2 ora ; © UCLES 2021 Page 8 of 11

2(a) idea of no (clear), relationship / trend ; 1 or as latitude increases, (bird) species diversity / numbers of (bird) species, (slightly) decreases / (might) show a downward trend ; 2(b)(i) any three from: 3 1 data (for latitude and number of species) is, paired / linked ; 2 number of bird species and latitude / (i.e. the data points) within samples are independent of each other ; 3 the data, is ordinal / is interval / is discrete / can be ranked ; 4 (scatter) graph / Fig. 2.2, suggests a, (decreasing) relationship / correlation ; 5 there are, 17 (paired) observations / more than 5 (paired) observations ; 6 idea that bird species selected randomly / AW ; 2(b)(ii) idea that 1 there is no, correlation / relationship, between latitude and the number of (bird) species ; 2(b)(iii) any four from: 4 1 critical value (for p = 0.05%) = 0.485 or critical value for p = 0.01% = 0.615 ; 2 value for r / calculated value, is < than critical value ; s 3 null hypothesis is accepted ; 4 there is no significant correlation (between latitude and number of bird species) ; 5 there is a (weak) negative correlation (between latitude and number of bird species as shown by the negative value for r ) ; s © UCLES 2021 Page 9 of 11 2(c) any three from 3 all marking points are ideas that: limitations of the data 1 only used counts of bird species (may not apply to all species) ; 2 do not know the, number of individuals of each species / relative abundance of each species / species evenness ; limitations of sampling birds 3 hard to identify some (bird) species / miss some (bird) species / some (bird) species look similar / miss birds that fly away / birds migrate / only resident birds or species counted / qualified ref to volunteers / AW ; latitudes sampled 4 nothing above 40N / nothing before 37N / need wider range of latitudes / AW ; 5 no data on latitudes south of the equator ; sampling sites 6 not random / only sampled in certain locations / sample locations do not cover the whole of the peninsula / many near the coast / locations may not be representative of the peninsula / only 17 sites / sampling sites do not extend beyond the peninsular / AW ; habitats 7 no information on habitats (at locations) / not all location may be equally suited for birds / different habitats have different conditions / AW ; timings 8 only sampled, on one day / in one year / sampled in, winter / one season ; ora © UCLES 2021 Page 10 of 11 2(d) any three from: 3 1 catch birds within area and count total captured and mark and release them ; 2 detail e.g. idea of: marking technique not, harmful / too obvious e.g. idea of: giving time for populations to mix before second sample taken – days or weeks not more ; 3 catch second sample and count total number of birds and number of marked birds ; 4 ref. to Lincoln / Petersen, index ; © UCLES 2021 Page 11 of 11

1(a) idea of replace (live) water plant / Egeria densa with: 1 dead / AW, water plant (of the same volume) or sterile / inert / glass beads / AW, material (of same volume) or pond water with sodium hydrogencarbonate (no water plant) ; 1(b)(i) any seven from: 7 1 use, lamp / AW, at different distances from plant or use, lamp / AW, with different power ratings / wattages (at same distances) ; 2 use a minimum of five, different / stated, light intensities / AW ; 3 use, a light meter / an app, to measure light intensity ; 4 carry out investigation, in a darkened room / with no other light source / AW ; 5 measure / note / record, the distance the, meniscus / AW, moves along the capillary tube / scale, in a fixed time or measure / note / record, the time the, meniscus / AW, takes to travel, a fixed distance on the capillary tube / scale ; 6 use, same / stated, length of water plant / Egeria densa ; 7 use, same / stated, mass / concentration, of sodium hydrogencarbonate ; 8 use a method to reduce heating effect of lamp ; 9 idea of equilibration / acclimatisation, of, water plant / Egeria densa / whole apparatus (to each light intensity) ; 10 use at least three measurements (at each light intensity / AW,) and calculate a mean ; 11 safety comment with hazard, risk and precaution ; © UCLES 2022 Page 5 of 9 1(b)(ii) horizontal axis labelled: 3 distance from light bulb / light intensity / power rating of light bulb / AW and vertical axis labelled: rate of photosynthesis / rate of movement of meniscus / distance meniscus moved (in set time) / time taken for meniscus to move (a set distance) ; correct units: (distance from light bulb) cm / mm (light intensity) lux / cd (candela) / alternative units (power rating of bulb) W and (rate of photosynthesis) cm min–1 / mm min–1 / cm s–1 / mm s–1 (rate of movement of meniscus) cm min–1 / mm min–1 / cm s–1 / mm s–1 (distance meniscus moved) cm / mm (time for meniscus to move) min / s ; appropriately shaped line ; positive gradient (may level off at higher light intensities) for, light intensity / power rating of light bulb, against, rate of photosynthesis / rate of movement / distance moved negative gradient (may level off at higher light intensities) for, light intensity / power rating of light bulb against time to move set distance negative gradient (may level off at shorter distances) for distance from light bulb against, rate of photosynthesis / rate of movement / distance moved positive gradient (may level off at shorter distances) for distance from light bulb against time to move set distance 1(c)(i) 0.88 ; 1 © UCLES 2022 Page 6 of 9 1(c)(ii) idea of: 1 1 difficulty in achieving, concentrated / not spread out / AW, spot of extract ; 2 each pigment, spreads out during migration / gives long streak / runs into each other / overlaps / AW (so difficult to measure accurately) ; 3 pigment may, fade / be too pale to see clearly / AW, (so difficult to measure accurately) ; 4 uniformity / quality / grade, of (chromatography) paper ; 5 type of solvent ; 6 different, laboratory / ambient / AW, conditions ; Question Answer Marks

2(a) type of woodland / 1 presence or absence of native tree species / AW ; 2(b)(i) three standardised variables ; 1 from: 25 traps / same number, of traps in each area 25 traps / same number, of traps in each trapping session mass / 10 g, food (for rodents) / bait time interval / 24 hours, before checking trap four / same number of, days / sessions (for each area) month / April / season / time of year 2(b)(ii) any suitable method of generating, random numbers / coordinates / positions ; 2 use the numbers generated, as coordinates / grid reference, to locate each trap site ; © UCLES 2022 Page 7 of 9 2(c)(i) 0.716 / 0.717 / 0.718 ; ; 2 if answer is incorrect, ALLOW 1 mark max for: correct answer to, two significant figures / more than three significant figures 1 – calculated Σ(n/N)2 2(c)(ii) any three from: 3 conclusions: 1 the biodiversity / (species) diversity, in the area with a mixture of native tree species and saltcedar trees is, greater / higher / AW, than the, biodiversity / (species) diversity, in the area of only saltcedar trees ; 2 the area with a mixture of native tree species and saltcedar trees, has more, (rodent) species / types (than the area with only saltcedar trees) / AW ; explanations (max two): 3 idea of (diversity is lower in the area with only saltcedar trees because) fewer food sources (for rodents) ; ora 4 saltcedar trees provide less, protection / shelter / nesting sites / niches / AW ; ora 5 AVP ; 2(d)(i) both error bars correctly plotted ; 1 2(d)(ii) any two from: 2 1 how close, the calculated / sample, mean is (likely to be) to, the true / actual / real / AW, mean ; 2 there is overlap in the, SE / error, bars (of the two means) ; 3 (this indicates that) there is no (statistically) significant difference (between the two means) ; 2(d)(iii) idea that: 1 there is no difference between the abundance of the deer mouse in, areas with only saltcedar trees and in areas with a mixture of native tree species and saltcedar trees / the two types of woodland ; © UCLES 2022 Page 8 of 9

3 any four from: 4 1 brine soak / treatment 4, kills, 100% / all, slipper limpets ; 2 brine soak / treatment 4 and, chilled conditions / 4 °C to 5 °C, kills fewer mussels (than brine soak at 12 °C to 13 °C) ; 3 repeat brine rinse / treatment 3, and at 12 °C to 13 °C kills all slipper limpets and very few mussels (so could be best) ; or repeat brine rinse / treatment 3, and at 4 °C to 5 °C kills nearly all slipper limpets and no mussels (so could be best) ; 4 appropriate paired data quote ; 5, 6 ref. to reason for uncertainty ; ; e.g. only tested 30 individuals / not enough replicates no data on long-term impact no results for, small / <30 mm / young, mussels did not test with mixture of slipper limpets and mussels idea that conclusion not tested statistically idea that there is a cost implication (for the different treatments) © UCLES 2022 Page 9 of 9

1(a)(i) independent variable: 2 (type of) habitat / described ; dependent variable: density / number / AW, of stomata ; 1(a)(ii) Radius / diameter (of field of view / image / circle / Fig 1.2) ; 2 number of stomata ; 1(a)(iii) 2 marks for density range: 2 0.014–0.019 ; ; if outside this range one mark for: stomatal number: 61 (full) – 69 (all) ; area: 4069 – 4301 ; © UCLES 2022 Page 6 of 10 1(a)(iv) any six from: 6 1 ref. to method of, random / systematic sampling of plants ; 2 (take leaves) from same species, that is present in both habitats ; 3 collect a minimum of 5 leaf samples (in both habitats) ; 4 same position / age, of leaf (on plant) ; 5 impressions to be taken from, lower / upper / both / same, surface(s) (of leaves) ; 6 (impressions viewed using) same, magnification / lens / size of field of view ; 7 count stomata (in field of view) ; 8 details of systematic counting / count only whole stomata / take a photograph and mark ; 9 repeat, (same) experiment (both habitats) minimum of twice, and calculate a mean ; 10 safety: hazard and risk and mitigation ; 1(b)(i) 73 (%) ; 1 © UCLES 2022 Page 7 of 10 1(b)(ii) support – max 2 marks: 3 1 stomatal density on upper surface is higher in plants grown in high light intensity ora ; 2 difference in (mean) stomatal density on upper surface (between the two light intensities) is greater than the difference between the lower surfaces ora ; 3 stomatal density on lower surface is similar / very close ; 4 leaf 1 stomatal density on lower surface is less than in plants grown in low light intensity ora ; 5 calculate pair of stomatal densities (for 1 to 4) ; doesn’t support – max 2 marks: 6 mean stomatal density, on lower / both, surface(s) is higher in plants grown in high light intensity ora ; 7 for 2 out of 3 leaves / leaf 2 and 3, stomatal density is not higher only on the upper surface / is higher on lower / both, surface(s) ; 8 calculate pair of stomatal densities (for 6 / 7) ; ecf 9 no statistical analysis done ; 10 data only, for one species / L. esculentum ; © UCLES 2022 Page 8 of 10

2(a)(i) any one from: 1 (faecal samples) can be, collected remotely / AW, without harming the chimpanzees / investigators ; (faecal samples) are, non-invasive / less stressful for chimpanzees / limits human interaction / no risk of infection / no need to anesthetise chimpanzees ; 2(a)(ii) any two from: 2 make into a, suspension / solution / liquify faeces ; filtered / centrifuged (to remove solids) ; 2(a)(iii) idea of: 1 genetic profiling / DNA fingerprinting / DNA profiling / DNA sequencing / genetic analysis / (DNA) electrophoresis ; 2(b) any three from: 3 1 (some) SIV antibodies will bind to HIV antigens ; 2 details of, which / number of lines / bands, match / don’t match / AW ; 3 (some) SIV and HIV antibodies have similar (protein), structures / shape ; 4 HIV– people do not contain (HIV) antibodies / SIV– chimpanzees do not contain (SIV) antibodies ; 5 the tests are valid as there is a line in each of the control regions ; 2(c)(i) 1 allows for, valid / meaningful, comparison (between SIV+ and SIV– chimpanzees) ; 2 2 the groups have different, initial / original numbers ; 2(c)(ii) no difference between the, life expectancy / AW, of chimpanzees that are SIV+ and SIV– ; 1 © UCLES 2022 Page 9 of 10 2(c)(iii) mp1: 2 probability / it, is where null hypothesis is rejected ora ; or probability / it, is where critical values are chosen ; mp2: less than, 0.05 / 5% / 5 in 100, probability that the, result / it, is not significant / is due to chance ; or more than, 0.95 / 95% / 95 in 100, probability that the, result / it, is significant / is not due to chance ; 2(c)(iv) any two from: 2 idea that: 1 results, may not be due to death from SIV / may be due to disappearance ; 2 death could be due to, hunting / accident / fighting / predators / lack of food / disease (infectious or other) / AW ; 3 ages of chimps were estimated ; 4 uninfected chimpanzees may catch SIV during the investigation ; 5 no data on, male/female chimps (as life expectancy may differ) ; © UCLES 2022 Page 10 of 10

1(a)(i) width of red area after soaking 1 or width of red area remaining ; 1(a)(ii) axes correctly labelled for independent and dependent variable ; 2 line / smooth curve, showing inverse correlation ; 1(b)(i) any seven from: 7 1 use, same / same age, beetroot ; 2 minimum 5 cubes with different, size / dimensions ; 3 widths evenly spaced / if stated must be within range 0.5–5 cm ; 4 equipment for cutting / measurement of cubes ; 5 calculate / AW, the SA:V ratio ; 6 cubes are fully, covered / submerged, (by calcium hypochlorite) ; 7 remove after, same / stated, time (minutes) ; 8 method of maintaining the same temperature (once cubes are immersed) ; 9 method of drying cubes (after soaking) ; 10 cut in half and measure the width of the red tissue after soaking ; 11 repeat experiment a minimum of twice and calculate a mean ; 12 named hazard and risk and precaution ; hazard risk precaution calcium Irritant / harmful / gloves / goggles hypochlorite toxic / corrosive PPE / tweezers scalpel cuts / injury, to cut away from skin fingers / cut on a tile beetroot allergen gloves © UCLES 2022 Page 7 of 10 1(b)(ii) Initialvolumeofredcubevolumefinalredcube 2 1 ; Initialvolumeofredcube 2 100 ; 1(c)(i) 17% (student 4 at 65°C) ; 2 mean given of 89.3 at 25°C ; 1(c)(ii) any two from: 2 1 all (cubes of) same, size / volume / dimension / number / SA:V ; 2 use, same / same age of, beetroot ; 3 sufficient water to cover the cubes completely ; 4 same volume of water in each beaker ; 5 same colorimeter ; 6 stir / AW, before taking sample for colorimeter reading ; 7 check / AW, temperature of water in beakers have equilibrated ; 8 zero colorimeter / calibrate, before each readings ; 9 use thermostatically controlled water-bath ; 1(c)(iii) 1 more (betalain) released as temperature increased 2 or as temperature increases more betalain released ; max 1 from: 2 membrane, fluidity / permeability / AW, increases as temperature increases ; 3 membrane proteins denature, at high(er) temperatures ; © UCLES 2022 Page 8 of 10

2(a) any three from: 3 1 capture a large sample (from one area / more than one area) ; 2 count / record, the number caught ; 3 test and, count / record, the number infected ; 4 number / population, of infected divided by, population / total number,  100 ; 5 mark-release-recapture method and Lincoln Index ; 2(b)(i) numbers (of infected badgers / cows) per unit area ; 2 allow (valid) comparison (between infected cows and infected badgers) ; 2(b)(ii) any three from: 3 1 method of testing (for bTB in badgers and cows) ; 2 year of data collection ; 3 type / breed / of, cattle ; 4 cattle kept, outdoors / indoors ; 5 number of areas counted each year ; 6 season / time of year, (data collected) ; 2(c)(i) no, correlation / relationship, between the number of infected badgers and the number of affected cows. 1 or no, correlation / relationship, in the occurrence of infection between badgers and cows ; © UCLES 2022 Page 9 of 10 2(c)(ii) max 2 3 support 1 combined data / A–J / graph / Fig 2.2, shows a positive, correlation / relationship / correct correlation described ; 2 combined data / A–J / graph / Fig 2.2, shows a significant, correlation / relationship ; 3 (so) culling (infected) badgers lowers infection in cattle ; max 2 does not support – graph 4 separated data / A–H and D–J are clustered ; or no data between 0.4 and 0.6 per km2 ; 5 data taken from different years ; does not support – table 6 separated data / A–H and D–J, shows a negative, correlation / relationship ; 7 separated data / A–H and D–J, does not show a significant, correlation / relationship ; 8 correlation does not mean causation ; 9 only data sets from 10 areas / only 10 out of 30 study areas sampled ; 10 data only from England / one country ; © UCLES 2022 Page 10 of 10

1(a)(i) concentration / water potential, of sucrose (solution) ; 1 1(a)(ii) (the coloured sucrose drop / it) would sink / AW ; 1 1(a)(iii) 1 water, leaves potato (by osmosis) ; 2 2 (sucrose) solution, becomes less dense ; 1(b)(i) (add) 8 cm3 of stock solution with 12 cm3 of (distilled) water ; 1 1(b)(ii) ref. to hazard and risk ; 1 1(b)(iii) Any six from: 6 1 use minimum of 5 different concentrations of sucrose solution ; 2 method of maintaining the same temperature (once potato pieces are immersed) ; 3 use same, type / age, of potato ; 4 all pieces of potato are, the same / stated, dimensions ; 5 method to create potato of a certain dimensions ; 6 potato pieces are fully covered / submerged (by sucrose solution) ; 7 remove after same / stated time ; 8 ref. to measuring mass of potato before and after ; 9 method of drying potato pieces (before measuring final mass) ; 10 repeat experiment a minimum of twice and calculate a mean ; 11 idea of repeat with new concentrations of sucrose to get closer to the equivalent sucrose concentration ; 1(c) –1.15 ; 1 © UCLES 2022 Page 7 of 10 1(d)(i) any one from: 1 1 data is continuous ; 2 data is normally distributed ; 3 comparing (two) means ; 4 standard deviations are approximately the same ; 5 fewer than 30 values / samples (for each potato) ; 1(d)(ii) no difference between, the water potential of, the two types of potato / Record and Kerr’s Pink (potato) ; 1 1(d)(iii) 38 ; 1 1(d)(iv) any three from: 3 1 critical value (at df = 38 and p = 0.05%) = 2.024 ; 2 calculated (t–) value / 1.890 is < than critical (t–) value / 2.024 ; ora 3 null hypothesis is accepted ; 4 there is no significant difference (between the means of the water potentials of the two varieties of potato) ; Question Answer Marks

2(a) to, absorb / remove / take up, the carbon dioxide produced (during respiration of blowfly larvae) ; 1 2(b) direction 1 the coloured fluid will, move upwards and explanation (oxygen is, taken in / used in respiration) so, decreases the, volume / pressure of gas (in test-tube) ; © UCLES 2022 Page 8 of 10 2(c) 1 remove substance X ; 2 2 replace X with an inert material / glass beads / AW ; 2(d) any one from: 1 temperature ; number of, (blowfly) larvae ; mass of, (blowfly) larvae ; age of, (blowfly) larvae ; food source for, (blowfly) larvae ; mass / number of, substance X / inert material / beads ; time to, equilibrate ; time, for measurement (of meniscus movement) ; 2(e) any two from: 2 1 the larvae were not fully adjusted / equilibrated ; 2 the larvae were at a lower temperature (than the apparatus) ; 3 the larvae were less active ; 2(f) 5.34 ;; 2 incorrect answer max one for working: (  0.52  68) ÷10 ; © UCLES 2022 Page 9 of 10 2(g) 0.56 ;; 2 incorrect answer max one for working: 3.00 / 5.34 ; © UCLES 2022 Page 10 of 10

1(a)(i) to allow, oxygen / air, to enter for respiration 1 or because, bacterium / B. subtilis, respires aerobically / AW ; 1(a)(ii) as, population growth of bacteria / bacterial growth, increases / AW, the, cloudier / more turbid, the culture broth 1 or measuring the, turbidity / cloudiness, by eye against a cross in background / with a colorimeter / turbidity meter / colour chart ; 1(b) replace antibiotic with, (distilled) water / nutrient solution ; 1 1(c) can improve: 2 add, catalase / peroxidase / manganese(IV) oxide ; explain why: results / effect / killing, B. subtilis / bacteria , is only due to, honey / MGO or results / effect / killing, B. subtilis / bacteria, is not due to hydrogen peroxide ; 1(d) description or table or diagram for 10%: 2 1 Correct method to dilute stock (honey) solution to 10% ; table 2 At least five dilutions including 10% all with correct volumes of stock and nutrient solution including units ; 1(e) independent variable 2 MGO / Manuka / honey, concentration ; dependent variable turbidity ; © UCLES 2022 Page 5 of 11 1(f) predict: 2 lower concentration, tubes / AW, will be, turbid / cloudy or higher concentration, tubes / AW, will be, clear / not cloudy or the lower the concentration the more, turbid / cloudy, the tubes / AW ; ora explain: MGO / (Manuka) honey, inhibits the growth of / kills, B. subtilis / bacteria or lower concentrations have less, ability / MGO, to, inhibit the growth of / kill, B. subtilis / bacteria ; ora © UCLES 2022 Page 6 of 11 1(g) any five from: 5 1 same / stated, volume of, culture / broth used ; 2 same / stated, volume of Manuka honey ; 3 mix / stir, honey (concentrations) and, culture / broth (prior to starting) ; 4 method to measure turbidity ; 5 idea that: write down / note / record, which concentration(s) the broth, is clear / is clearest ; any two from 6–8 ;; 6 method of maintaining temperature (10°C – 50°C if stated) 7 same / stated, time (left in incubator) (12–48 hours if stated) 8 use a buffer to maintain pH (pH 4–10 if stated) 9 repeat at least twice / 3 replicates and finding mean ; 10 named hazard and risk and precaution ; Hazard Risk Precaution Live cultures / bacterium / B. subtilis Allergy / Infection / irritation / toxic Wear gloves / goggles / mask / PPE Honey Allergy Wear gloves / goggles / mask / PPE Broth Irritant / allergy Wear gloves / goggles / mask / PPE 1(h)(i) there is no difference in the effect / effectiveness, of Manuka (honey) and Germania (honey) ; 1 © UCLES 2022 Page 7 of 11 1(h)(ii) yes 1 yes ; no 1(h)(iii) results: 2 Manuka honey, kills more bacteria / is more effective (than Germania) ; ora statistical analysis: first three / 1, 2 and 3, are significantly different or last two / 4 and 5, not significantly different against MRSA or 1 is only significant at p = 0.05 or 2 / 3, are significant at the, p = 0.01 / p = 0.001 ; © UCLES 2022 Page 8 of 11

2(a) any one from: 1 To ensure no gossypol in any of the cows / to remove gossypol from cows or idea of: feeding on same diet standardises cows (for start of experiment) ; 2(b)(i) any three from: 3 1 the (mean) milk yields are, very close / similar, between groups ; 2 no statistical test or should carry out a, statistical test / t-test ; 3 overlap of SE (then no significant difference) ; 4 detail of which groups, are not / may be, significantly different ; not significantly may be significantly different different A and B A and E A and C B and E A and D C and E B and C D and E B and D C and D © UCLES 2022 Page 9 of 11 2(b)(ii) any two from: 2 enough evidence because: 1 trend that as gossypol (in diet) increases, milk yield increases ; ora 2 paired data quote (to support) ; not enough evidence because: 3 idea that: no information that differences in milk yield are caused by (differences in) gossypol ; 4 idea that: no information on, nutritional content / AW, of , no gossypol diet / GM cottonseed ; 5 idea that: there is no cottonseed in A so cannot compare with (diets) B to E or There is only soybean in A so cannot compare with (diets) B to E ; 6 no statistical test or should carry out a, statistical test / t-test ; 2(c)(i) there is a relationship because: 1 as free (gossypol) intake increases, plasma (gossypol) concentration increases or shows a positive correlation ; © UCLES 2022 Page 10 of 11 2(c)(ii) allow description of diet instead of group B, etc. 3 any three from: 1 (Group) E has the highest risk (of toxicity) or (Group) C has the lowest risk (of toxicity) ; 2 sequence of risk, highest to lowest, is E →B →D →C ; 3 ref. to higher free gossypol and (–) isomer values for highest risks or ref. to lower free gossypol and (–) isomer values for lower risks ; 4 paired data quote from Table 2.2 to support mp 2 or 3 ; 5 free gossypol will be easily absorbed and more toxic (than bound gossypol) or Bound gossypol is less easily absorbed and less toxic / not toxic ; 6 idea that: uncertain how much free gossypol turns into bound gossypol when eaten ; 7 AVP ; © UCLES 2022 Page 11 of 11

1(a) any two from: 2 1 use coloured filter / set wavelength ; 2 calibrate colorimeter / set colorimeter (absorbance) to zero ; 3 water (used to calibrate colorimeter) ; 1(b)(i) From description or table: 2 1 Correct method to dilute stock solution with water to 0.1% ; Table: 2 At least five stated concentrations including 0.1%, all with correct volumes of stock and water including volume units and concentration unit ; 1(b)(ii) independent variable 1 protein concentration and dependent variable absorbance ; 1(b)(iii) 1 x-axis protein concentration and % 2 and y-axis absorbance and au or no units added ; 2 line drawn showing positive correlation ; 1(b)(iv) copper(II) ions, binding with the nitrogen atoms, that form peptide bonds ; 2 will have same number of peptide bonds ; © UCLES 2022 Page 5 of 10 1(c) any six from: 6 1 same / stated, volume of protein concentrations and egg ; 2 same / stated, volume of biuret solution ; 3 add / mix / stir, protein (concentrations) / egg and, biuret ; 4 measure / record, absorbance / colorimeter reading, for (known) protein (concentrations) / egg ; 5 use calibration curve to find protein conc. in egg ; 6 dilute egg (suspension) by factor of 10 ; 7 same / stated, concentration of biuret solution ; 8 same / stated, time (for colour development) before taking reading ; 9 3 replicates and finding mean ; © UCLES 2022 Page 6 of 10 1(c) 10 named hazard and risk and precaution ; Hazard Risk Precaution Corrosive Biuret solution Irritant Moderate / medium, hazard / risk Corrosive Sodium hydroxide Wear gloves / goggles / mask / PPE Irritant Corrosive Irritant Copper sulphate Moderate / medium, hazard / risk Hazardous to the aquatic environment Do not pour down sink Egg / Albumin / Protein Allergen Wear gloves / goggles / mask / PPE / do not consume 11 multiply protein concentration in egg, by dilution factor (to obtain actual concentration of protein) ; © UCLES 2022 Page 7 of 10

2(a) any two from: 1 1 same number of each sex ; 2 same / similar, age or five years old ; 3 same, breed / type / AW (of sheep) ; 4 same / similar, mass / size ; 5 do not have, mutation / mutant allele / Huntington’s (disease / allele) / neurological disease ; 2(b) any two from: 2 1 DNA (sequencing), only identifies presence of genes ; 2 RNA (sequencing) identifies, active / switched on / expressed, genes or DNA (sequencing) does not identify, active / switched on / expressed, genes ; 3 more copies of (m)RNA (compared to DNA) ; 4 quantity of RNA indicates level of gene expression ; 2(c)(i) t-test ; 2 comparing means / continuous data / data has a normal distribution / comparing two samples with fewer than 30 values ; 2(c)(ii) there is no difference in the mean counts between the OVT73 and control ; 1 © UCLES 2022 Page 8 of 10 2(c)(iii) any two from: 2 1 to make a comparison ; 2 to identify if OVT73 (mean) counts was higher / lower (than control) ; 3 use of data from Table 2.1 to support mp2 ; 2(d) max one from contribute 2 1 two different testing kit used ; 2 commercial kits used, so (presumably) accurate ; 3 statistical tests / analysis were carried out ; max one from improves 4 (test) more sheep ; 5 reanalyse the 10 genes using kit 1, to confirm there was significant difference ; 6 (test) more tissue samples / test the same (tissue) samples again ; 2(e)(i) 1.33 ; 1 2(e)(ii) For anterior striatum, SE (ranges) do not overlap, suggesting there is a significant difference 1 or For cerebellum / motor cortex, SE (ranges) do overlap, so there is not a significant difference ; 2(e)(iii) more urea (in cell), so more transport proteins, more removal of urea ; 1 © UCLES 2022 Page 9 of 10 2(f) any two from: 2 1 none of the genes coded for enzymes in the urea cycle ; 2 no loss of (striatal) neurones (in OVT73 / transgenic sheep) ; 3 more, urea produced / transport proteins made / gene expression so cells require more energy ; © UCLES 2022 Page 10 of 10

1(a)(i) to allow, oxygen / air, to enter for respiration 1 or because, bacterium / B. subtilis, respires aerobically / AW ; 1(a)(ii) as, population growth of bacteria / bacterial growth, increases / AW, the, cloudier / more turbid, the culture broth 1 or measuring the, turbidity / cloudiness, by eye against a cross in background / with a colorimeter / turbidity meter / colour chart ; 1(b) replace antibiotic with, (distilled) water / nutrient solution ; 1 1(c) can improve: 2 add, catalase / peroxidase / manganese(IV) oxide ; explain why: results / effect / killing, B. subtilis / bacteria , is only due to, honey / MGO or results / effect / killing, B. subtilis / bacteria, is not due to hydrogen peroxide ; 1(d) description or table or diagram for 10%: 2 1 Correct method to dilute stock (honey) solution to 10% ; table 2 At least five dilutions including 10% all with correct volumes of stock and nutrient solution including units ; 1(e) independent variable 2 MGO / Manuka / honey, concentration ; dependent variable turbidity ; © UCLES 2022 Page 5 of 11 1(f) predict: 2 lower concentration, tubes / AW, will be, turbid / cloudy or higher concentration, tubes / AW, will be, clear / not cloudy or the lower the concentration the more, turbid / cloudy, the tubes / AW ; ora explain: MGO / (Manuka) honey, inhibits the growth of / kills, B. subtilis / bacteria or lower concentrations have less, ability / MGO, to, inhibit the growth of / kill, B. subtilis / bacteria ; ora © UCLES 2022 Page 6 of 11 1(g) any five from: 5 1 same / stated, volume of, culture / broth used ; 2 same / stated, volume of Manuka honey ; 3 mix / stir, honey (concentrations) and, culture / broth (prior to starting) ; 4 method to measure turbidity ; 5 idea that: write down / note / record, which concentration(s) the broth, is clear / is clearest ; any two from 6–8 ;; 6 method of maintaining temperature (10°C – 50°C if stated) 7 same / stated, time (left in incubator) (12–48 hours if stated) 8 use a buffer to maintain pH (pH 4–10 if stated) 9 repeat at least twice / 3 replicates and finding mean ; 10 named hazard and risk and precaution ; Hazard Risk Precaution Live cultures / bacterium / B. subtilis Allergy / Infection / irritation / toxic Wear gloves / goggles / mask / PPE Honey Allergy Wear gloves / goggles / mask / PPE Broth Irritant / allergy Wear gloves / goggles / mask / PPE 1(h)(i) there is no difference in the effect / effectiveness, of Manuka (honey) and Germania (honey) ; 1 © UCLES 2022 Page 7 of 11 1(h)(ii) yes 1 yes ; no 1(h)(iii) results: 2 Manuka honey, kills more bacteria / is more effective (than Germania) ; ora statistical analysis: first three / 1, 2 and 3, are significantly different or last two / 4 and 5, not significantly different against MRSA or 1 is only significant at p = 0.05 or 2 / 3, are significant at the, p = 0.01 / p = 0.001 ; © UCLES 2022 Page 8 of 11

2(a) any one from: 1 To ensure no gossypol in any of the cows / to remove gossypol from cows or idea of: feeding on same diet standardises cows (for start of experiment) ; 2(b)(i) any three from: 3 1 the (mean) milk yields are, very close / similar, between groups ; 2 no statistical test or should carry out a, statistical test / t-test ; 3 overlap of SE (then no significant difference) ; 4 detail of which groups, are not / may be, significantly different ; not significantly may be significantly different different A and B A and E A and C B and E A and D C and E B and C D and E B and D C and D © UCLES 2022 Page 9 of 11 2(b)(ii) any two from: 2 enough evidence because: 1 trend that as gossypol (in diet) increases, milk yield increases ; ora 2 paired data quote (to support) ; not enough evidence because: 3 idea that: no information that differences in milk yield are caused by (differences in) gossypol ; 4 idea that: no information on, nutritional content / AW, of , no gossypol diet / GM cottonseed ; 5 idea that: there is no cottonseed in A so cannot compare with (diets) B to E or There is only soybean in A so cannot compare with (diets) B to E ; 6 no statistical test or should carry out a, statistical test / t-test ; 2(c)(i) there is a relationship because: 1 as free (gossypol) intake increases, plasma (gossypol) concentration increases or shows a positive correlation ; © UCLES 2022 Page 10 of 11 2(c)(ii) allow description of diet instead of group B, etc. 3 any three from: 1 (Group) E has the highest risk (of toxicity) or (Group) C has the lowest risk (of toxicity) ; 2 sequence of risk, highest to lowest, is E →B →D →C ; 3 ref. to higher free gossypol and (–) isomer values for highest risks or ref. to lower free gossypol and (–) isomer values for lower risks ; 4 paired data quote from Table 2.2 to support mp 2 or 3 ; 5 free gossypol will be easily absorbed and more toxic (than bound gossypol) or Bound gossypol is less easily absorbed and less toxic / not toxic ; 6 idea that: uncertain how much free gossypol turns into bound gossypol when eaten ; 7 AVP ; © UCLES 2022 Page 11 of 11

1(a)(i) any one from: 1 use coloured filter / set wavelength (of light) ; calibrate colorimeter / set colorimeter (absorbance) to zero ; use distilled water (to, calibrate colorimeter / set to zero) ; 1(a)(ii) 1 5 stated concentrations and units ; 3 2 (reasonably) evenly spaced ; 3 method for dilution shown for at least 2 concentrations other than 2.0% and 0% ; 1(a)(iii) correct axis labels and orientation ; 2 x-axis label: percentage glucose concentration y-axis label: absorbance (no units or absorbance units or arbitrary units) appropriately shaped line ; line with negative gradient 1(b)(i) glucose concentration (of potato) ; 1 © UCLES 2023 Page 5 of 10 1(b)(ii) any six from: 6 1 ref. to, same / stated, potatoes (used for investigation) ; 2 ref. to, same / stated, storage conditions (of potatoes) ; e.g. (low) temperature in dark carbon dioxide concentration 3 additional stated storage condition (of potatoes) ; 4 use minimum of 5 different storage times (of potatoes) ; 5 ref. to stated storage times (of potatoes) ; 6 ref. to, same / stated, volume of potato juice (for glucose assay) ; 7 at each storage time, measure / note / record, absorbance (of potato juice used in glucose assay) or at each storage time carry out glucose assay ; 8 repeat at least twice / 3 replicates for each storage time, and find a mean ; 9 named hazard and risk and precaution ; e.g. hazard risk precaution Benedict’s reagent irritant gloves / eye protection / PPE toxic (to aquatic environment) don’t pour down sink hot water (bath) burns / scalds use tongs / gloves / eye A water-bath protection potato allergy gloves / eye protection / PPE knife / scalpel injury cut away from hand © UCLES 2023 Page 6 of 10 1(c) any two from: 2 1 as gamma radiation dose increases, (percentage) volatile nitrogen compounds (in raw potatoes) decrease ; 2 (percentage) volatile nitrogen compounds (in raw potatoes), are significantly different, at different doses of gamma radiation ; 3 idea that no change in percentage glucose (in raw potatoes), therefore decrease in acrylamide in cooked potato chips, is not due to glucose / must be due to asparagine ; 4 idea that decrease in volatile nitrogen compounds at increased gamma radiation doses indicates decrease of asparagine (so less acrylamide is made in the Maillard reaction) ; 1(d)(i) (–)61 (%) ; 2 correct working ; © UCLES 2023 Page 7 of 10 1(d)(ii) any three from: 3 supports: 1 idea that, gamma radiation and hot water treatment / treatment 2, decreases the (acrylamide) concentration (of potato chips) more than, gamma radiation only / treatment 1 ; 2 idea that, 95% confidence intervals / 95% CI / error bars (for treatment 1 and treatment 2), do not overlap (at all gamma radiation doses), therefore treatment with radiation and hot water is significantly different from treatment with radiation alone ; 3 paired data quote (to support) ; does not support: 4 idea that hot water treatment alone decreases acrylamide concentration (of potato chips) ; 5 idea that, 95% confidence intervals / 95% CI / error bars (for treatment 2), overlap (at all gamma radiation doses), therefore decrease in acrylamide due to hot water treatment and gamma radiation is not significantly different from hot water treatment alone) ; 6 ref. to only one variety of potato investigated ; 7 no statistical test or should carry out a, statistical test ; © UCLES 2023 Page 8 of 10

2(a)(i) distance from GM rice plants 1 and direction from GM rice plants ; 2(a)(ii) apply herbicide to young plants ; 2 count the number of young plants that survive ; 2(a)(iii) any two from: 2 1 as distance from GM rice plants increases, (percentage) gene flow decreases / pollen dispersal decreases ; ora 2 (percentage) gene flow / distance of pollen dispersal, is higher in direction of (normal) wind / NW direction (than other directions) ; ora 3 pollen cannot disperse further than 10 m / no gene flow at 10m (or further) ; 2(b)(i) 0.036 ; 1 2(b)(ii) any three from: 3 1 critical value (for p = 0.05) = 2.145 or critical value (for p = 0.01) = 2.977 ; 2 value for t / 9.043 / calculated value, is greater than critical value ; 3 null hypothesis is rejected ; 4 there is a significant difference between percentage gene flow from GM rice plants to weedy rice plants and percentage gene flow from weedy rice plants to GM rice plants ; © UCLES 2023 Page 9 of 10 2(b)(iii) any one from: 1 1 investigation only, carried out once / not repeated ; 2 investigation only on, wind-pollinated crop / one crop species / (GM and weedy) rice / one non-crop species ; 3 investigation only investigated, one / two, gene(s) ; 4 investigation only, in one geographical area ; 5 investigation only in, experimental trials / without herbicide use ; 6 no long-term data / no data over several generations ; 7 gene flow (from GM plants to wild plants), was shown to occur ; 8 idea that wild plants with herbicide-resistant gene, difficult to remove / have selective advantage ; © UCLES 2023 Page 10 of 10

1(a) any one from: 1 volume of (pH7) buffer ; speed of centrifuge ; time in centrifuge ; 1(b) idea that time for disc rising decreases as catalase activity increases ; ora 1 1(c)(i) distance from base of shoot ; 1 1(c)(ii) any six from: 6 1 method to cut, tissue from carrot (root) ; 2 minimum of 5 distances chosen (or stated distances) ; 3 same / stated, mass / volume, of cut carrot (used to make the extract) ; 4 mix / stir, liquid carrot extract (before dipping filter paper discs) ; 5 method of maintaining temperature (10°C – 40°C if stated) ; 6 same / stated, height / depth / (stated) volume, of hydrogen peroxide (solution) ; 7 measure / note / record, the time the filter paper disc takes to rise to the surface (of hydrogen peroxide solution) ; 8 use at least three measurements for each distance and calculate a mean ; 9 safety: hazard and risk and mitigation ; 10 carrying out a control with disc, dipped / AW, in water / buffer (to show rise of the discs is due to the carrot extract) ; 1(d)(i) volume of gas collected (after 1 minute) ; 1 © UCLES 2023 Page 8 of 12 1(d)(ii) distilled water / deionised water / water, in table heading ; 2 correct volumes of stock solution and water (in Table 1.1) ; 1(d)(iii) supports conclusions: 3 1 paired data quotes / manipulated data (from Fig. 1.7), to show increase in hydrogen peroxide concentration increases the volume of gas collected ; doesn’t support – max 2 marks: 2 idea that range (of hydrogen peroxide concentrations) is limited ; 3 idea that graph has not, plateaued / reached a maximum / AW, so we do not know the value of V ; max 4 idea that gas collected might not be only oxygen ; 5 no replicates / no repeats of investigation / no mean calculated ; Question Answer Marks

2(a) 1 idea of: 3 add lice to container and counting lice (on trout) at death or add lice to trout (in a container) and counting lice (on trout) at death or capture trout with lice attached and count lice (on trout) at death or trout(s) with (known) different number of lice attached (in separate containers) and see which die ; 2 idea of repeat with container (of trout) / trout (in a container) with no lice present ; 3 named environmental condition in container maintained as constant (for, experimental / control / both, conditions) or named feature of trout / lice maintained as constant (for, experimental / control / both, conditions) ; © UCLES 2023 Page 9 of 12 2(b)(i) any one from: 1 location of, boat / sampling site ; (electric) current ; time of year ; 2(b)(ii) any one from: 1 idea that young / small, trout will not be caught / AW ; ora idea that there will be more lice on the fish, caught / AW (as they are older / larger) ; ora 2(c)(i) allows for valid comparison; 2 (because) number (of sea trout), sampled / AW, varies ; 2(c)(ii) paired data quote / manipulated data (to show year 1 to 2 increase) ; 1 Data quotes: mean % with  year 13 attached lice 1 2.6 2 14.9 more / higher 12.3 times increased x5.7 © UCLES 2023 Page 10 of 12 2(c)(iii) any two from: 2 1 no difference between year 1 and year 2 of production cycle in 2004–2005 ; 2 number of sea trout sampled was small ; 3 (data from) only, 5 production cycles / 10 years ; 4 no statistical test carried out ; 2(d)(i) there is no, relationship / correlation, between the number of lice (on trout) and the distance from the (nearest) fish farm ; 1 2(d)(ii) (Ireland) significant / yes /  / AW 1 and (Scotland) not significant / no /  / AW ; 2(d)(iii) there is a negative correlation 1 or as distance from (nearest) fish farm increases, (mean) number of lice (per trout) decreases ; ora © UCLES 2023 Page 11 of 12 2(d)(iv) Max one from MP1–3 reasons for 95% CI: 2 1 95%, probability / confidence that / chance that, the, true / actual / population / parametric, mean lies within, this range / these limits or 2 to test whether the means (for number lice per trout at different distances from fish farms) are (significantly) different or to see / test, whether the, error bars / 95% CI / they, overlap or 3 to get a measure of how close the, calculated / AW, mean is likely to be to the, true / AW, mean or shorter, error bars / 95% CI, show true mean is likely to be closer to the calculated mean or longer, error bars / 95% CI, show true mean is likely to be further from the calculated mean ; One mark for exemplification: Exemplification of MP 2 or 3 from Fig. 2.3: MP2 Exemplification: idea that no / less overlap of (95% CI) error bars for Ireland, so (difference), is / may be, significant or idea that overlap of (95% CI) error bars for, Scotland / Ireland, so (difference), is not / may not be, significant ; I direct comparison between Ireland with Scotland MP3 Exemplification: idea that the, shorter / narrower, error bars for Ireland the closer the calculated mean is (likely to be) to the true mean or idea that the, larger / longer, error bars for Scotland, the further the calculated mean is (likely to be) from the true mean or shorter / narrower, error bars / confidence limits, with increasing distance (to nearest fish farm) in, Ireland / Scotland, shows the calculated mean is, getting / AW, closer to the true mean ; I direct comparison between Ireland with Scotland © UCLES 2023 Page 12 of 12

1(a) 1 part enzyme extract/polyphenol oxidase with 9 parts of water / buffer ; 1 1(b)(i) pH ; 1 1(b)(ii) any one from: 1 1 temperature of, solutions / tubes ; 2 wavelength of, light / (light) filter (of 470 nm) ; 3 concentration of enzyme / polyphenol oxidase ; 4 total length of time /time reading interval ; 1(c)(i) 1 figures from printed line at or below 0.26 au and 30 s 2 or figures from correct tangent ; 2 correct calculation / 0.0083 to 0.0089 / 8.3  10–3 to 8.9  10–3 ; 1(c)(ii) sketched line below printed line starting at origin and constantly increasing to 180 s ; 1 © UCLES 2023 Page 8 of 13 1(d) 1 state at least 5 dilutions (0.0–0.2%) of dopamine hydrochloride solution / substrate ; 7 2 describe a correct method to making at least 2 dilutions ; 3 add tubes to a water bath / incubator, at a, set / constant temperature (10–40 °C) ; 4 enzyme and substrate / (all) solutions equilibrated separately ; 5 state 2 different variables that are kept constant (volumes of enzyme and substrate or mixture / pH / filter or wavelength) ; 6 set to zero / calibrate, colorimeter using a, blank / water, at the start / between each reading ; 7 mix substrate and (buffered) enzyme and immediately add (colorimeter tube) to colorimeter ; or mix substrate and (buffered) enzyme and immediately start timing ; 8 measure absorbance at set time intervals (for set time) ; or record time at which red colour (first) appears ; 9 3 replicates / 2 repeats for same / one concentration and calculate a mean or 2 repeats, of experiment / each concentration, and calculate the means ; 10 calculate / find / work out rate (of reaction) ; © UCLES 2023 Page 9 of 13 1(d) 11 named hazard and risk and precaution ; Hazard Risk Precaution dopamine Toxic don’t drink hydrochloride don’t pour down the sink wear gloves Irritant / allergy wear gloves / goggles / mask/ PPE polyphenol Irritant / allergy oxidase / enzyme buffer Irritant / allergy 12 use water/boiled enzyme instead of enzyme as the control ; © UCLES 2023 Page 10 of 13 1(e) 1 enzyme: from different (plant) sources / only from plants / enzyme not used from bananas ; 2 2 sources of information: maybe out of date / maybe unreliable / not comparable ; 3 variables: 2 variables not controlled / not standardised / no information (temperatures, pH, timings, volumes, concentrations) ; 4 stats: no statistical test / analysis ; 5 substrate: no information, on what substrate was used / whether tested on bananas or other fruits ; 6 inhibitor: do not know type of inhibition (competitive v. non-competitive) ; 7 anti-browning agents: idea that other anti-browning agents maybe more or less effective / may impact differently ; 8 anti-browning agents should be tested on all sources of enzyme / each only tested on one source of enzyme / may act differently on other sources of enzyme ; 9 validity: 2 independent variables ; 1(f) sketched line (starts at origin) levels out showing lower Vmax ; 1P Question Answer Marks

2(a)(i) any two from: 2 type /species of tree / type of bark ; height (of grid) above ground ; side / aspect of tree ; age / size of tree ; AVP grid placed horizontally / orientated as diamond shape ; © UCLES 2023 Page 11 of 13 2(a)(ii) 2 Hazard and risk – 1 mark ; Precaution – 1 mark ; Trees / plants scratches / allergy / irritation suitable / leaves / bark toxins PPE / medication / pollen don’t ingest Animals dangerous / allergy / bites / to medication / work in a /Animal waste xoplasmosis group / travel with an expert /suitable PPE Fungi / Lichen irritation / allergic reaction suitable PPE toxic / poisonous do not ingest Inhaling (lung) infection wear a mask fungal spores Traffic collision / fumes / air pollution cone off the road / hi vis vest / look + listen / suitable PPE Woods / holes Injury from look where you’re /trip hazards trips / falling / falling stepping / hard hat / don’t branches / getting climb trees / GPS / map lost / hypodermic needles 2(b) 1 39 / 90 (100) ; 2 2 43 / 43.3 (%) ; 2(c)(i) D = 2 and D2 = 4 ; 1 © UCLES 2023 Page 12 of 13 2(c)(ii) 0.760 / 0.759 ; ; 2 If answer is incorrect allow 1 mark for evidence of correct calculation 238.5 / 990 or 0.241 2(c)(iii) strong (correlation) ; 3 positive (correlation) ; (showing that) as distance from road increases, cover / abundance of lichen increases / ora ; 2(c)(iv) use critical values (of r ), at p= 0.05 or less ; 2 s if calculated r is greater than critical r value (correlation) is not due to chance s s or if calculated value of r is less than the critical r value (correlation) is due to chance ; s s © UCLES 2023 Page 13 of 13

1(a) (red to magenta shows) increase in, pH / decrease in, concentration of, carbon dioxide ; 2 (in the light C. vulgaris) uses up / AW, carbon dioxide for photosynthesis ; 1(b)(i) light intensity ; 1 1(b)(ii) any eight from: 8 1 use, lamp / AW, at minimum of 5 different distances from plant or use, lamp / AW, with minimum 5 different power ratings / wattages (at same distances) ; 2 use, a light meter / an app, to measure light intensity ; 3 idea that carry out investigation, in a darkened room / with no other light source ; 4 same / stated, mass / number / size, of alginate beads ; 5 same / stated, volume / concentration, of hydrogencarbonate indicator or same starting, colour / pH, hydrogencarbonate indicator ; 6 use a method to reduce heating effect of lamp ; 7 method to measure, colour / pH, of hydrogencarbonate indicator ; 8 measure / note / record, the colour/pH (of the indicator) after a, set / stated, time or measure / note / record, the time taken (for the indicator) to be a, set / stated, colour / pH ; 9 use at least three measurements for each light intensity and calculate a mean ; 10 safety: hazard and risk and mitigation ; © UCLES 2023 Page 8 of 13 1(b)(ii) hazard risk mitigation hydrogencarbonate irritant / allergy gloves / goggles / mask / indicator PPE / medication alginate beads / C. irritant / allergy gloves / goggles / mask / vulgaris PPE / medication heat (from bulb) burns / injury gloves / do not touch 11 use of a suitable control ; 1(c) will turn orange / yellow or pH decreases ; 2 respiration, produces carbon dioxide ; 1(d)(i) correct working ; 2 229 000 ; 1(d)(ii) 1 correct number of cells counted / 24 ; 3 2 correct working ; 3 correct calculation of number of cells per cm3 / 240 000 ; © UCLES 2023 Page 9 of 13 1(d)(iii) any two from: 2 Secchi stick is less accurate: 1 subjective / difficult to determine when circle is no longer visible ; 2 error of  0.5 mm in the ruler ; 3 Secchi stick, not held vertical ; 4 no replicates / no repeats of investigation / no mean calculated ; 5 idea that Secchi stick used is, different / AW, from Secchi stick used for calibration curve ; 6 idea that inserting Secchi stick, mixes / disturbs / AW, suspension ; © UCLES 2023 Page 10 of 13

2(a)(i) any two from: 2 height (of grids) above ground ; side / aspect, of tree ; age / size of tree ; type / species, of tree ; grid placed horizontally / orientated as diamond shape ; © UCLES 2023 Page 11 of 13 2(a)(ii) named hazard and risk ; 2 matching precaution ; hazard and risk – 1 mark precaution – 1 mark plants – leaves, bark, toxic / scratches / irritant / suitable pollen allergy PPE / medication / don’t ingest animals, animal waste dangerous / allergy / bites medication / work in a / toxoplasmosis group / travel with an expert / suitable PPE fungi, lichen toxic / irritant / allergy suitable PPE / medication inhaling fungal spores (lung) infection wear a mask woods, falling injury / getting lost look where you’re branches / trees, holes, stepping / boots / hard trip hazards hat / don’t climb trees / GPS / map / travel with an expert climbing trees (upper injury (from use a ladder / use height grid) trips / falls / falling ropes / hard branches) hat / training / use an expert 2(b) 63.3( / 100)  90 / 0.633  90 ; 2 57 (circles) ; 2(c)(i) there is no, difference, in the abundance of (salted shield) lichen between, exclosures and grazed areas ; 1 © UCLES 2023 Page 12 of 13 2(c)(ii) any one from: 1 1 no, significant difference, between exclosures and grazed areas, for base of tree ; or there is a, significant difference, between exclosures and grazed areas, for middle and upper parts of tree ; 2 the, percentage cover / abundance, of (salted shield) lichen is greater, as height of grid increases ; ora 3 percentage cover / abundance, of (salted shied) lichen is greater, in grazed areas (than in exclosures) ; ora 2(c)(iii) any two from: 2 1 check named abiotic factor is similar (in exclosures and grazed areas) ; 2 check named biotic factor is similar (in exclosures and grazed areas) ; 3 repeat the investigation, in other years (after 2013) ; © UCLES 2023 Page 13 of 13

1(a)(i) any one from: 1 1 idea that size (of apple) may not be, related / proportional, to ripeness ; 2 idea that (individual) apples may, ripen at different rates / AW ; 3 idea that other factors may affect, ripeness of apples / diameter of apples ; 1(a)(ii) any one from: 1 1 (pick apples with the) same / similar / AW, sugar content / colour / softness / age ; 2 test / measure / AW, sugar content / colour / softness / age (of apples) ; 1(b) 1 correct axis labels ; 2 2 correct shaped line ; 1(c)(i) 1 90 ; 2 2 50 ; © UCLES 2023 Page 7 of 10 1(c)(ii) any nine from: 9 1 idea of test on at least 5 days ; 2 use apples from same, tree / variety / type ; 3 use, same / stated, storage conditions (of apples) ; prepare apple extract solutions: 4 remove the, skin / seeds, of the apple ; 5 use, set / stated, mass of apple ; 6 method to, grind / AW, apple ; 7 centrifuge / filter ; measure ascorbic acid concentration using DCPIP: 8 place, set / stated, volume of (apple extract) solution in, conical flask / AW ; 9 idea of adding DCPIP dropwise to (apple extract) solution until blue colour remains ; 10 shake / mix / AW (after each drop of DCPIP) ; 11 measure / record, volume of DCPIP used (to reach end point) ; 12 read volume from bottom of meniscus (in burette) ; 13 use at least three replicates for each day and calculate a mean (DCPIP volume) ; 14 safety comment with hazard and risk and precaution ; hazard risk precaution DCPIP irritant / toxin / allergy gloves / goggles / mask / PPE apples allergy gloves / goggles / mask / PPE / medication / do not eat knife / scalpel injury cut away from hand 1(d) any two from: 2 1 data is continuous ; 2 scatter diagram, suggests a linear, relationship ; 3 data is normally distributed ; © UCLES 2023 Page 8 of 10 1(e) any three from: 3 for the conclusion: 1 apples have the second lowest –carotene concentration (of the fruits shown) ; 2 quoted data from Fig. 1.3 to support ; 3 idea that spread of data for apple is lower (than most fruits that were tested, as SD is smaller) against the conclusion: 4 idea that need to calculate, SE / 95% CI (to make a conclusion) ; 5 no statistical test carried out ; 6 idea that only 5 fruits were tested ; Question Answer Marks

2(a)(i) independent variable: type / AW , of trypsin ; 2 dependent variable: time (taken to break down gelatine) ; 2(a)(ii) any one from: 1 1 pH (of solution) ; 2 surface area / mass / volume, of cube ; 3 concentration of, gelatine / collagen, in cube ; 2(b)(i) mean = 131.1 ; 1 2(b)(ii) s = 3.2 ; 1 2(b)(iii) any three from: 3 1 critical value (at degrees of freedom = 22 and p = 0.05) = 2.074 ; 2 calculated (t–) value / 2.663 is, greater than, critical (t–) value / 2.074 ; ora 3 null hypothesis is rejected ; 4 there is a significant difference (at p = 0.05) ; © UCLES 2023 Page 9 of 10 2(b)(iv) any two from: 2 1 idea that salmon trypsin is adapted to colder temperatures ; ora 2 (at 20 °C) salmon trypsin forms enzyme–substrate complexes at a faster rate (than pig trypsin) ; ora 3 AVP ; © UCLES 2023 Page 10 of 10

1(a) any two from 2 1 low tide ; 2 day / date / month / season ; 3 (same) rocky shore / (same) location ; 4 (mid-shore) zone ; 5 random selection of rock pools ; 6 deepest part of rock pool measured ; 1(b)(i) there is no correlation between, species diversity / number of (different) species and depth ; 1 1(b)(ii) any three from 3 1 critical value for (p = 0.05) = 0.350 ; 2 value for, r / calculated value, is > than critical value ; s 3 null hypothesis is rejected ; 4 there is a significant correlation (between depth of rock pool and species diversity) ; 5 there is a positive correlation (between rock pool depth and species diversity) ; 1(b)(iii) 1. scatter diagram, does not indicate, a linear, relationship ; 1 2. (data is) not normally distributed ; 3. species diversity / number of species, is not continuous ; 1(c) any two from 2 1 location of the rocky shore is unknown ; 2 position of the mid-shore zone is unknown ; 3 size of rock pools is unknown ; 4 location of rock pool is unknown ; 5 height, of tide / tides, unknown ; © UCLES 2023 Page 9 of 12 1(d) any seven from 7 sampling process 1 belt transect ; 2 place a, rope / AW, from LWM to HWM ; 3 sample at regular intervals along the transect ; 4 use a quadrat ; 5 same / same size of, quadrat ; measuring process 6 method of identifying species (of algae) ; 7 take care not to miss small species ; 8 (count / record) number of (different) species (of algae) (in each quadrat) ; 9 method for determining abundance of each species (in each quadrat) ; 10 repeat belt transect at two other positions along the shore and calculate means ; 11 named suitable hazard and risk and precaution ; 12 AVP ; © UCLES 2023 Page 10 of 12

2(a) any one from: 1 suitable method for measuring a curve ; straighten shoot (before measuring) ; 2(b)(i) 38.7 and 45.3 ; 1 2(b)(ii) difference is significant ; 1 2(c) any two from: 3 1 ABA reduces (shoot) growth ; 2 SA increases (shoot) growth (by day 5) ; 3 ABA prevents, cell elongation / cell division or SA stimulates, cell elongation / cell division ; 4 description of the effect on growth by treatment C (ABA + SA) ; 5 ABA (partly) counteracts the effect (on growth) of SA or SA (partly) counteracts the effect (on growth) of ABA ; 2(d) 1 appropriate method of applying the solutions / hormones, to the roots only ; 3 max. two from: 2 same volume of solutions ; 3 measuring shoot lengths on day 1 and day 5 ; 4 named example of condition which is same as shoot spraying experiment ; 5 method to identify presence of hormone in shoot ; © UCLES 2023 Page 11 of 12 2(e)(i) one mark per row 3 gene effect on gene expression ABA alone SA alone CDKB2 large decrease no change / small increase ; KRP4 large increase no change / small increase ; CycD6 large decrease no change / small decrease ; 2(e)(ii) conclusion 1 2 fully supports and mRNA (ABA + SA / batch C) lower than with ABA (batch B) / ora ; conclusion 2 partially supports and mRNA (ABA + SA / batch C) higher than with ABA (batch B) but not as high as with water (batch A) / SA (batch D) or no statistical test carried out ; © UCLES 2023 Page 12 of 12

1(a)(i) any one from: 1 1 idea that size (of apple) may not be, related / proportional, to ripeness ; 2 idea that (individual) apples may, ripen at different rates / AW ; 3 idea that other factors may affect, ripeness of apples / diameter of apples ; 1(a)(ii) any one from: 1 1 (pick apples with the) same / similar / AW, sugar content / colour / softness / age ; 2 test / measure / AW, sugar content / colour / softness / age (of apples) ; 1(b) 1 correct axis labels ; 2 2 correct shaped line ; 1(c)(i) 1 90 ; 2 2 50 ; © UCLES 2023 Page 7 of 10 1(c)(ii) any nine from: 9 1 idea of test on at least 5 days ; 2 use apples from same, tree / variety / type ; 3 use, same / stated, storage conditions (of apples) ; prepare apple extract solutions: 4 remove the, skin / seeds, of the apple ; 5 use, set / stated, mass of apple ; 6 method to, grind / AW, apple ; 7 centrifuge / filter ; measure ascorbic acid concentration using DCPIP: 8 place, set / stated, volume of (apple extract) solution in, conical flask / AW ; 9 idea of adding DCPIP dropwise to (apple extract) solution until blue colour remains ; 10 shake / mix / AW (after each drop of DCPIP) ; 11 measure / record, volume of DCPIP used (to reach end point) ; 12 read volume from bottom of meniscus (in burette) ; 13 use at least three replicates for each day and calculate a mean (DCPIP volume) ; 14 safety comment with hazard and risk and precaution ; hazard risk precaution DCPIP irritant / toxin / allergy gloves / goggles / mask / PPE apples allergy gloves / goggles / mask / PPE / medication / do not eat knife / scalpel injury cut away from hand 1(d) any two from: 2 1 data is continuous ; 2 scatter diagram, suggests a linear, relationship ; 3 data is normally distributed ; © UCLES 2023 Page 8 of 10 1(e) any three from: 3 for the conclusion: 1 apples have the second lowest –carotene concentration (of the fruits shown) ; 2 quoted data from Fig. 1.3 to support ; 3 idea that spread of data for apple is lower (than most fruits that were tested, as SD is smaller) against the conclusion: 4 idea that need to calculate, SE / 95% CI (to make a conclusion) ; 5 no statistical test carried out ; 6 idea that only 5 fruits were tested ; Question Answer Marks

2(a)(i) independent variable: type / AW , of trypsin ; 2 dependent variable: time (taken to break down gelatine) ; 2(a)(ii) any one from: 1 1 pH (of solution) ; 2 surface area / mass / volume, of cube ; 3 concentration of, gelatine / collagen, in cube ; 2(b)(i) mean = 131.1 ; 1 2(b)(ii) s = 3.2 ; 1 2(b)(iii) any three from: 3 1 critical value (at degrees of freedom = 22 and p = 0.05) = 2.074 ; 2 calculated (t–) value / 2.663 is, greater than, critical (t–) value / 2.074 ; ora 3 null hypothesis is rejected ; 4 there is a significant difference (at p = 0.05) ; © UCLES 2023 Page 9 of 10 2(b)(iv) any two from: 2 1 idea that salmon trypsin is adapted to colder temperatures ; ora 2 (at 20 °C) salmon trypsin forms enzyme–substrate complexes at a faster rate (than pig trypsin) ; ora 3 AVP ; © UCLES 2023 Page 10 of 10

1(a)(i) concentration of, sodium chloride (solution) ; 1 1(a)(ii) distilled water / deionised water / pure water (as diluent) ; 2 correct volumes of stock solution and water (in Table 1.1) ; 1(b)(i) any one from: 1 1 allows valid comparison (between onions in different sodium chloride concentrations) ; 2 allows comparison as, initial / starting, mass (of onions) is, not constant / AW ; 1(b)(ii) any four from: 4 1 idea that the conclusion is only supported for onions left for hours ; ora 2 (ref. to intercept of x-axis / 0% change in mass / water potential of onions when left for) 48 hours is 3.1% sodium chloride ; 3 ref. to qualified experimental error ; 4 ref. to anomalous result(s) on graph ; 5 idea that line of best fit may give different value ; 6 ref. to intermediate concentrations (of sodium chloride) not tested (between 1% and 5% sodium chloride) ; 7 ref. to no, statistical analysis / standard error / 95% CI ; 8 idea that not all onion cells have the same water potential ; © Cambridge University Press & Assessment 2024 Page 5 of 9 1(c)(i) any six from: 6 1 use a minimum of five stated temperatures ; 2 suitable method to, maintain a constant temperature (for each replicate / experiment) ; 3 same / stated, variety / age / AW, of turnips ; 4 same / stated, dimensions / AW, of turnip block ; 5 ref. to apparatus for obtaining same size of turnip blocks ; 6 for each temperature, place turnip blocks in, a beaker / AW, of (fresh / new) distilled water ; 7 at each temperature, measure the initial mass and the final mass after a, set / stated, time ; 8 for each temperature, use at least three different blocks and calculate a mean ; 9 method to remove excess water from turnip block (before measuring final mass) ; 1(c)(ii) 1 horizontal axis label: 2 temperature, C and vertical axis label: rate of osmosis ; 2 appropriately shaped line ; © Cambridge University Press & Assessment 2024 Page 6 of 9 1(c)(iii) ref. to hazard and risk and precaution ; 1 hazard Risk Precaution knife / blade / AW injury cut away from the hand / cut down on to a, board / tile / AW turnip allergy irritant wear gloves / PPE hot water / water-bath / method scald / burn / injury wear, (heat resistant) of heating gloves / PPE use, tongs / AW Question Answer Marks

2(a) to prevent the parent (fruit flies), reproducing / mating / AW, with the, first generation / offspring / AW ; 1 2(b) to separate male and female fruit flies: 1 use hand lens / (binocular) microscope / AW or ref. to difference between male and female (fruit flies) and to place fruit flies: use a, paint brush / pooter / forceps / AW ; 2(c)(i) there is no difference between, the observed and expected, results ; 1 © Cambridge University Press & Assessment 2024 Page 7 of 9 2(c)(ii) 1 correct values of E ; 3 2 correct values of (O–E)2 / E ; offspring O E (O–E)2 / E phenotype dark red eyes 691 702 0.172 121 / 702 brown eyes 260 234 2.889 676 / 234 = 26 / 9 bright red 225 234 0.346 eyes 121 / 234 white eyes 72 78 0.462 36 / 78 = 6 / 13 total 1248 (1248) 3.869 3 (2 =) 3.869 ; 2(c)(iii) 1 ref. to correct critical value = 7.815 (p = 0.05 and df = 3) ; 2 2 calculated value of,  2 / 3.869, is less than 7.815 and null hypothesis is accepted ; 2(d)(i) 0.73 ; 1 © Cambridge University Press & Assessment 2024 Page 8 of 9 2(d)(ii) any four from: 4 breeding experiment (MAX 3): 1 ref. to the two genes (B / b and R / r), are not linked ; 2 idea that dominant alleles code for (functional) carrier, proteins / polypeptides ; 3 idea that in fruit flies with dark-red eyes entry of guanine and tryptophan (into organelle) allows pigments to be produced ; 4 fruit flies with white eyes, (have the genotype) bbrr / homozygous recessive (for both genes) or fruit flies with dark-red eyes are, B_R ; chromatogram (MAX 3): 5 fruit flies with dark-red eyes, have 4 pigments (in their eyes) ; 6 fruit flies with white eyes, have no pigments (in their eyes) ; 7 pigment 4 is drosopterin ; 8 idea that, ommochrome / brown pigment, is insoluble (in the chromatography solvent) or idea that none of the pigments in the chomatogram are, ommochrome / brown pigment ; © Cambridge University Press & Assessment 2024 Page 9 of 9

1(a)(i) wind speed ; 1 1(a)(ii) any six from: 6 1 method to use fan(s), to obtain a minimum of five different wind speeds ; 2 ref. to standardised variable for using the fan ; 3 use a method to maintain, same / stated, temperature ; 4 use a method to maintain, same / stated, light intensity ; 5 at each wind speed, measure / note / record / AW, the initial mass and final mass, in a fixed time ; 6 idea of equilibration / acclimatisation, of, plant / Japanese spiraea / apparatus ; 7 use at least three measurements for each wind speed and calculate a mean ; 8 safety comment with hazard and precaution ; hazard risk precaution Japanese spiraea / plant irritant / allergy gloves / mask / PPE soil biohazard / pathogens / allergy gloves / mask / PPE I irritant fan hair / clothing / AW, trapped in fan method to, control loose, hair / clothing / AW 9 method for measuring wind speed ; 10 idea of replacing water lost from plant (before each new measurement) ; © Cambridge University Press & Assessment 2024 Page 5 of 11 1(a)(iii) as wind speed, increases: 1 rate of transpiration - increases or decrease in mass, in fixed / stated time - increases or rate of decrease in mass - increases or time taken, for a fixed decrease in mass - decreases ; ora 1(b)(i) 26.3 ; 1 1(b)(ii) any one from: 1 1 use, same / stated, size of (blue) cobalt chloride paper ; 2 idea of use a (pink) colour standard (to determine end point) ; 3 idea of measure different positions on (lower) surface of leaf ; 4 idea of unbiased selection of, leaves / leaf position ; © Cambridge University Press & Assessment 2024 Page 6 of 11

2(a) any three from: 3 1 light intensity ; 2 duration / hours / AW, of light ; 3 volume, of water (added to soil) ; 4 type / pH, of soil ; 5 mineral (ion), concentration (in soil) ; 6 humidity ; 7 carbon dioxide concentration ; 2(b) (high mean temperature leads to) lower / AW (mean stomatal conductance), in both isohydric and anisohydric (species) ; 1 ora © Cambridge University Press & Assessment 2024 Page 7 of 11 2(c) any four from: 4 conclusion: 1 (water stress leads to) lower / AW, (mean stomatal) conductance in isohydric and anisohydric (species) ; ora explanation: 2 idea that (lower stomatal conductance when exposed to water stress indicates that) water loss (by transpiration) is reduced ; conclusion: 3 isohydric (species exposed to water stress and a high temperature) increase (mean stomatal) conductance or increased (mean stomatal) conductance for isohydric (species exposed to water stress and a high temperature) is (statistically) significant ; explanation: 4 idea that (increased mean stomatal conductance in isohydric species exposed to water stress and a high temperature) has a cooling effect ; conclusion: 5 anisohydric (species exposed to water stress and a high temperature) do not change (mean stomatal) conductance or change / difference / decrease / AW, in (mean stomatal) conductance for anisohydric (species exposed to water stress and a high temperature) is not (statistically) significant ; explanation: 6 idea that (unchanged mean stomatal conductance in anisohydric species when exposed to water stress and a high temperature) to allow carbon dioxide uptake (for photosynthesis) ; conclusion: 7 paired data quote to support conclusion ; © Cambridge University Press & Assessment 2024 Page 8 of 11 2(d)(i) idea that there is no difference between the (mean) percentage of leaves that were dead on (young trees from) isohydric 1 species and (young trees from) anisohydric species ; 2(d)(ii) 1883 ; 2 t = (190 – 35) / 8231 ; 2(d)(iii) 1 calculated value of, t /1883, is less than, 2011 / critical value (at p = 0.05) 3 or calculated value of, t /1883, is less than, 2682 / critical value (at p = 0.01) ; ora 2 null hypothesis is accepted (at p = 0.05 / p = 0.01) ; 3 there is no significant difference (at p = 0.05 / p = 0.01) ; Question Answer Marks

3(a)(i) (human volunteer / person and) no (mosquito) repellent / spray 1 or (human volunteer / person and) water (spray) ; or (human volunteer / person and) solvent (from repellent / spray) ; © Cambridge University Press & Assessment 2024 Page 9 of 11 3(a)(ii) named risk and matching precaution ; 1 risk precaution mosquitoes take blood meal (from scientist) protective clothing / gloves / masks / PPE or mosquitoes bite (scientist) mosquitoes transmit, disease / pathogen / yellow protective clothing / gloves / masks / PPE fever / AW use, disease / pathogen, free mosquitoes vaccine (against yellow fever) (mosquito) repellent / spray / solvent, protective clothing / gloves / masks / PPE allergy / irritant / toxic © Cambridge University Press & Assessment 2024 Page 10 of 11 3(b) any four from: 4 1 98% DEET is effective (at repelling mosquitoes) ; 2 idea that standard error / SE, overlap for 98% DEET and lemon eucalyptus oil, so these mosquito repellents are equally effective / no significant difference between these mosquito repellents ; 3 idea that lemon eucalyptus oil is, (slightly) more effective / equally effective (as 98% DEET), but, has a low concentration (of chemical) / might be safer or idea that lemon eucalyptus oil is, (slightly) more effective / equally effective, (as 98% DEET) but DEET is, toxic / irritant / harmful ; 4 idea that not true for all concentrations of DEET / 40% (concentration) DEET is much less effective ; ora 5 no statistical test carried out ; 6 only one human volunteer tested ; 7 idea that some mosquitoes are still attracted to the human volunteer (when using 98% DEET) ; 8 idea that mosquitoes used / Aedes aegypti, do not transmit malaria ; 9 idea that mosquitoes were not able to, take a blood meal from / bite, the human volunteer / investigation only measured attraction of mosquitoes (to the human volunteer) ; © Cambridge University Press & Assessment 2024 Page 11 of 11

1(a)(i) species of tree 1 or type of tree ; 1(a)(ii) any two from: 2 1 (same) number of / 3, plantations for each tree species ; 2 (same) size/area of, plot/(sampling)area / 36 m x 36 m / 1296m2 ; 3 (same / used a) belt transect (same method in all plots/plantations) ; 4 (same) months / seasons (of the year) or sampling at the same times ; © Cambridge University Press & Assessment 2024 Page 6 of 12 1(b) any five from: 5 using a belt transect: 1 use of tape / line / string, and quadrat (to create belt transect) ; 2 selecting a start point for the, transect / placement of tape / line / string or all transects same length, in plots / plantations / repeats ; 3 same (size) quadrat ; 4 sample at / use quadrat at, regular intervals / stated distances along the, tape / line / string / transect or continuous belt transect ; collecting data: 5 method to identify each of the plant (species in the quadrat) ; 6 count / record / note the number of (individuals), each plant species (n) (in each quadrat / at each sampling point) or estimate percentage (%) cover of each plant species (in each quadrat) ; 7 use at least 3 different transects (in each plot) ; 8 named hazard and risk and precaution ; e.g. (see table below) © Cambridge University Press & Assessment 2024 Page 7 of 12 1(b) hazard risk preca ution plants / fungi falling trees / branches hard hat thorns gloves / goggles / mask / long trousers / PPE irritant / allergy antihistamines / cover skin / first aid equipment i nfection (spores) (named) bites / infection / attack antivenom / antihistamine / trained, professionals / animal(s) / stings / allergy medics, available / insect parasite repellent / gloves / goggles / mask / PPE / cover skin plantation trip hazard correct footwear / watch where you are walking / use terrain walking sticks getting lost work in group / maps / use GPS / guide poachers being attacked / shot trained, professionals/ medics, available 1(c) any one from: 1 (does not support) 1. acacia and mango have the same means or acacia and mango have similar, D values / index or mango and invasive species have overlapping, D values / index / means +/- SD ; (does support / partially support) 2. sal tree has the highest, D value / index / mean or sal tree has greater, D values / Index / mean, than both alien species ; © Cambridge University Press & Assessment 2024 Page 8 of 12 1(d)(i) 2 concentration volume of stock volume of (distilled) / mg cm-3 solution / cm3 water / cm3 7.5 37.5 12.5 ; 2.5 12.5 37.5 ; 1(d)(ii) 1 correct processes and correct figures ; 3 2 (correct) answer to 3 significant figures ; ecf if mp1 is incorrect 3 decrease / minus (number) ; © Cambridge University Press & Assessment 2024 Page 9 of 12 1(e) any three from: 3 improvement impact 1 More, intermediate / smaller values / intervals better idea of the, trend / pattern / effect ; appropriate examples accepted 2 exclude anomalous results improve reliability ; 3 repeat reading for 2.5 / 5.0 / 7.5 mg cm-3 (any of check the anomaly / improve reliability ; these 3 might be anomalous) 4 repeat investigation at least twice better idea of trend / improve reliability / or reduce effect of anomalies ; repeat with more marigolds 5 (calculate) standard error / standard check for significance (difference between the deviation / confidence intervals / means) / checking accuracy ; statistical analysis 6 use marigold clones exclude genetic effects / improve validity ; 7 use Vernier calliper more precise measurements ; 8 measure the mass of all the roots improve reliability ; 1(f) any two from: 2 1 (same) mass of soil ; 2 sample from same depth ; 3 sampled at the same time ; 4 sample from same, distance from roots / position in the pot ; © Cambridge University Press & Assessment 2024 Page 10 of 12

2(a) 1 correct counting / correct number of divisions / 28 ± 2 ; 3 2 for correct conversion(s) to micrometres ; 3 correct answer / 8.96 / 8.32–9.6 ; 2(b)(i) measure the, widest / narrowest / longest, part of the each nucleus ; 1 2(b)(ii) any one from: 1 1 (same) magnification /  400 ; 2 (same) number of / 100 nuclei (measuring) per, person ; 3 (sample from / same) thyroid / gland ; 4 same / one, scientist (measuring the diameter) ; 5 idea that: type of tumour cell is unknown ; 2(b)(iii) there is no difference, in / between the (mean) nuclear diameters of, the Pap-stained cells and H&E- stained cells ; 1 2(b)(iv) accept null hypothesis 1 or there is no significant difference ; 2(b)(v) state 2 1 idea that this technique can be used to distinguish between benign and malignant cells or the mean nuclear diameter of benign cells is smaller than in malignant cells / ora ; explain 2 mean  2 SE, do not overlap or there is a significant difference in the mean nuclear diameters of benign cells and malignant cells ; © Cambridge University Press & Assessment 2024 Page 11 of 12 2(b)(vi) disadvantages 2  time consuming (prepping / counting / measuring)  labour intensive  shortage of skilled scientists  invasive  only thyroid / one tissue, used  human error – due to, small values / very close values / large numbers counted impact:  infection / bleeding  pain  tissue damage  metastasis  anxiety  delayed treatment  unnecessary treatment  idea of misdiagnosis  possibly not feasible on large scale  may not be true of other tumours © Cambridge University Press & Assessment 2024 Page 12 of 12

1(a)(i) independent variable 1 type of blood vessel / artery and vein and dependent variable mass required to break (the blood vessel) ; © Cambridge University Press & Assessment 2024 Page 6 of 11 1(a)(ii) any six from: 6 1 method to cut the blood vessel ; 2 method to measure blood vessel of, same / stated, length / AW ; 3 idea of discard samples that are damaged ; 4 idea of waiting (to see if the blood vessel breaks) before adding the next (10 g) mass ; 5 use, artery and vein / blood vessels, from the same source ; 6 add (10 g) masses, to the mass hanger, until the blood vessel breaks ; 7 idea of measuring mass of mass hanger / including mass of mass hanger ; 8 for each type of blood vessel, measure / note / record / AW, (total) mass when the blood vessel broke ; 9 use at least three measurements for each type of blood vessel and calculate a mean ; 10 safety comment with hazard and precaution ; hazard risk precaution knife / scalpel injury cut away from hand blood vessels biohazard / pathogens / allergy gloves / mask / PPE / use disinfectant / wash hands mass hanger falling injury suitable precaution to prevent injury 11 idea of repeat procedure with smaller mass intervals near to breaking mass ; © Cambridge University Press & Assessment 2024 Page 7 of 11 1(b)(i) 2 mass added / g length of vein / mm percentage increase in length of ring of vein 0 21 0 10 36 71 20 38 81 30 40 90 40 41 95 50 41 95 three values correct ;; one or two correct max 1 1(b)(ii) 1 to make a valid comparison (with other blood vessels / veins) ; 1 2 allows comparison as, initial / starting, length (of veins) is, not constant / AW ; 1(b)(iii) 1 correct orientation for axes and linear scale ; 3 2 axes labelled and units; 3 all points plotted correctly and line drawn accurately ; 1(b)(iv) 1 curve for artery starts at same point as the vein ; 2 2 curve for artery below curve for vein and does not intersect ; © Cambridge University Press & Assessment 2024 Page 8 of 11 1(b)(v) any two from: 2 1 starts at, same point / origin, as using percentage increase ; 2 (muscular) arteries have a thicker, wall / tunica media / muscle layer (than the vein) or 3 (muscular) arteries have more (smooth) muscle (than the vein) ; 4 idea of (muscular artery) withstands more (blood) pressure so stretches less (than the vein) ; 1(b)(vi) any two from: 2 1 use smaller mass intervals ; 2 extend the range of the masses added ; 3 use a, force meter / Newton meter / data logger / AW, (to apply force) ; 4 attach a, pointer / fiducial mark, to the ring of blood vessel (to improve length measurement / removing parallax) ; 5 use, same / stated, width of blood vessel ; © Cambridge University Press & Assessment 2024 Page 9 of 11

2(a) 1 cm3 of stock solution to 149 cm3 of distilled water ; 2 (dilution factor is) 150 ; 2(b) any one from: 1 1 measure from, top of the soil / bottom of stem / AW, to top of the stem / AW ; 2 straighten the stem (while measuring length) ; 3 place string along stem, and measure length of string ; 2(c)(i) 1.9 ; 1 2(c)(ii) any one from: 1 1 (mean stem) length was measured, in / to the nearest, cm ; 2 many anomalies in the results / identified anomaly ; 3 no statistical test carried out ; 2(c)(iii) any one from: 1 1 measure lengths in mm ; 2 idea of repeat high concentration GA experiment (to check anomaly) ; 3 3 measure, at same time every day / for more days ; 4 measure more seedlings / increase sample size ; 2(d) (SE =) 0.067 ; 2 (95% CI =) 1.38  0.13 ; © Cambridge University Press & Assessment 2024 Page 10 of 11 2(e) any three from: 3 1 highest (concentration of) GA with,red light / 680 nm 8 or lowest (concentration of) GA with, blue light / 470 nm 1 or highest (concentration of) GA in the dark / with no light ; 1, 2 lower (concentration of) GA for all wavelengths of light (compared to dark) 1 or higher (concentration of) GA for all wavelengths of light (compared to dark) ; 8 3 95% CI, does not overlap (for the lower concentration of GA for all wavelengths of light), so there is a significant 1 difference or 95% CI, does not overlap, (higher concentration of GA for all of the wavelengths of light), so there is a significant 8 difference ; © Cambridge University Press & Assessment 2024 Page 11 of 11

1(a)(i) 0.40 ; 1 1(a)(ii) fucoxanthin ; 2 diadinoxanthin ; 1(b) blue light: 3 1 S. costatum (will have), greater / faster / AW , (rate of photosynthesis than R. salina) ; ora green light: 2 S. costatum (will have), slightly / AW, greater / faster / AW , (rate of photosynthesis than R. salina) ; ora red light: 3 S. costatum (will have), the same / similar / AW, (rate of photosynthesis as R. salina) ; 1(c)(i) any one from: 1 1 idea that absorbance measured (with colorimeter) / colour of indicator solution, is not affected by algae ; 2 indicator solution can be separated from algal balls ; 3 (more accurate) standardisation of, mass / volume / AW, of algae ; 1(c)(ii) independent variables: 3 species / type, (of algal beads) ; wavelength / colour, of light ; dependent variable: absorbance / pH (of solution) ; © Cambridge University Press & Assessment 2024 Page 6 of 10 1(c)(iii) any eight from: 8 1 method for use of filters (to give blue, green, red coloured light) ; 2 use, same / stated, number / mass / volume, of algal beads (in each bottle) ; 3 place light source the, same / stated, distance (from algal beads) ; 4 carry out experiment in a darkened room ; 5 use, same / stated, volume / concentration, of indicator (in each bottle) ; 6 (use of a control bottle) replace the algal beads with, glass / plastic / AW, beads ; 7 use, red / pH 8.4, hydrogencarbonate indicator solution (at start) ; 8 detail of method to take sample (of indicator solution) from bottle ; 9 use a, same / stated, coloured, filter / light, in the colorimeter ; 10 method to calibrate colorimeter ; 11 ref. to, suitable time to leave algal beads and indicator solution (before measuring absorbance) ; 12 for each colour (filter) and species, measure / record / AW, absorbance, at same / stated, time(s) ; 13 use at least three measurements for each colour (filter) and species, and calculate a mean ; © Cambridge University Press & Assessment 2024 Page 7 of 10 1(c)(iv) hazard and risk and precaution ; 1 hazard risk precaution algae / beads irritant / allergy gloves / mask / goggles / PPE hydrogencarbonate irritant / allergy gloves / mask / goggles / PPE indicator (solution) heat from light source burns do not touch bulb / turn off lamp before handling 1(d)(i) any one from: 1 1 comparing the means of two (sets of data) ; 2 continuous data (collected) ; 3 (data are from populations that are) normally distributed ; 4 standard deviations are approximately the same ; 1(d)(ii) there is no difference, in the pH of samples (taken from the small bottles / of indicator solution), between R. salina and S. 1 costatum ; © Cambridge University Press & Assessment 2024 Page 8 of 10

2(a) 1 peat bog A has a higher number of species and a higher Shannon index (than peat bog B) ; ora 2 examples of suitable wording for mp1: number of species Shannon index peat bog A has a higher number of species ora peat bog A has a higher Shannon index ora peat bog A has 12 species, peat bog B has only 8 idea that number of species / species richness, is species more important for Shannon index no (individuals of) species T, U, W, V in peat bog B 2 peat bog B has a smaller range of species abundance and a higher Simpson’s index (than peat bog A) ; ora examples of suitable wording for mp2: relative species abundance Simpson’s index peat bog B has a smaller range of species peat bog B has a higher Simpson’s index ora abundance ora idea that (range of) species abundance / species peat bog B has a higher (total) number of individuals evenness / total number of individuals, is more ora important for Simpson’s index peat bog B has 135 (total) number of individuals, peat bog A has only 99 if mp1 and mp2 not awarded, then award 1 mark for: peat bog A has a higher number of species and peat bog B has a smaller range of species abundance ; ora © Cambridge University Press & Assessment 2024 Page 9 of 10 2(a) examples of suitable wording: number of species relative species abundance peat bog A has a higher number of species ora peat bog B has a smaller range of species abundance ora peat bog A has 12 species, peat bog B has only 8 species peat bog B has a higher (total) number of individuals ora no (individuals of) species T, U, W, V in peat bog B peat bog B has 135 (total) number of individuals, peat bog A has only 99 2(b)(i) any three from: 3 1 sample at different times of the year (not only over one month) ; 2 sample at, night / different times of day (not only between 13:00 and 16:00) ; 3 sample at sites other than along the path ; 4 use of (another) named technique to sample invertebrates ; 5 use an expert / (identification) app / guidebook (instead of an identification key) ; 2(b)(ii) 1 (for Tipula limbata) n / N = 0.083 and (n / N)2 = 0.007 ; 3 2  = 0.270 ; 3 D = 0.730 ; 2(b)(iii) peat bog A has (slightly) higher (biodiversity than peat bog B) ; ora 1 © Cambridge University Press & Assessment 2024 Page 10 of 10

1(a) any two from: 2 1 replace chloroplast (suspension) with, water / boiled chloroplast (suspension) ; 2 replace DCPIP with, water ; 3 keep (chloroplast suspension with DCPIP) in the dark ; 1(b)(i) 2 percentage time taken for rate of light-dependent concentration of DCPIP to stage of photosynthesis chloroplast decolourise / s / s–1 suspension 10 351 2.8 20 59 16.9 30 21 47.6 40 10 100.0 50 5 200.0 rates calculated correctly ; (correct) rates correctly rounded to one decimal place ; 1(b)(ii) 1 axes correctly orientated with labels and rate unit and appropriate scales ; 3 2 points plotted accurately (± ½ small square) ; 3 suitable line drawn ; © Cambridge University Press & Assessment 2024 Page 6 of 10 1(c) any two from: 2 (Did work in 10% sucrose solution because) 1 (sucrose solution) has, same / similar, water potential as in the chloroplast ; 2 water will not enter (chloroplast), by osmosis / as there is no water potential gradient / ora ; 3 chloroplasts will not burst / ora ; 1(d) 1 one, stated, concentration of chloroplast suspension ; 6 any five from: 2 minimum of five, stated, temperatures within the range 10 to 60 °C ; 3 method of maintaining a constant temperature ; 4 allowing chloroplast suspensions to reach set temperatures (before exposing to light) ; 5 swirl chloroplast suspension (before exposing to light) ; 6 method for ensuring same light intensity ; 7 carry out experiment in dark room ; 8 colour of sample to match chloroplast suspension (alone) / green colour standard ; 9 correct ref. to repeats and mean ; © Cambridge University Press & Assessment 2024 Page 7 of 10

2(a)(i) 3 1 description of random / systematic, sampling ; 2 use of, quadrats / (sweep) nets / (light) trap / pooter ; 3 Count the number of each phenotypes ; OR max. 2 marks if Mark-Release-Recapture method 4 capture ladybirds and count / find number / record, number of each phenotypes and mark and release them ; 5 suitable marking so not harmful / too obvious / not removed 6 capture second sample and count / find number / record, number of each phenotypes and count / find number / record number, of marked each phenotypes ; 2(a)(ii) 2 any two from: 1 ref. to data for spring 1929 and spring 1932 ; 2 sample size(s) ; 3 multiple sampling sites (in same area of Germany) ; 4 carry out statistical analysis ; Sampling took place with: 5 the same location(s) / habitat(s) / sampling site(s) / AW ; 6 the same time of day ; 7 the same duration (of sampling) ; 2(b)(i) Line for melanic phenotype is steeper (than non-melanic phenotype) ; 1 © Cambridge University Press & Assessment 2024 Page 8 of 10 2(b)(ii) 1 award if both graphs have been used ; 3 any two from: 2 all ladybirds have the same starting temperature ; 3 all ladybirds warm up when lamp is on ; 4 all ladybirds return to, original / starting, temperature ; 5 melanic reaches higher temperature / ora ; 6 melanic cool down faster / ora ; 7 females warm up quicker / ora ; 8 females reach higher temperature / ora ; 9 females take longer to cool down / ora ; 10 heavier warm up quicker / ora ; 11 heavier ladybirds reach higher temperature / ora ; 12 heavier ladybirds take longer to cool down / ora ; 13 the temperature plateaus for all except non-melanic females ; 2(c) 1 Pearson’s (linear correlation) / Spearman’s (rank correlation) ; 3 any two from: Pearson’s 2 data (for temperature and mass) is, paired / linked ; 3 data is continuous ; 4 scatter diagram, suggests a linear, relationship / correlation / association ; 5 there are at least 5 (paired) observations ; OR Spearman’s 6 data (for temperature and mass) is, paired / linked ; 7 the data is ordinal / interval ; 8 scatter diagram, suggests an increasing, relationship / correlation / association ; 9 there are more than 5 (paired) observations ; © Cambridge University Press & Assessment 2024 Page 9 of 10 2(d) 1 cross melanic with non-melanic ; 3 2 homozygous (dominant) melanic parent(s) will only have melanic offspring and heterozygous (melanic) parent(s) will have both phenotypes in offspring ; Details about breeding experiment – max 1 3 many breeding pairs ; 4 each breeding pair kept separate from other pairs or separate offspring from parents ; 5 count, the different phenotypes of offspring ; © Cambridge University Press & Assessment 2024 Page 10 of 10

1(a)(i) 0.40 ; 1 1(a)(ii) fucoxanthin ; 2 diadinoxanthin ; 1(b) blue light: 3 1 S. costatum (will have), greater / faster / AW , (rate of photosynthesis than R. salina) ; ora green light: 2 S. costatum (will have), slightly / AW, greater / faster / AW , (rate of photosynthesis than R. salina) ; ora red light: 3 S. costatum (will have), the same / similar / AW, (rate of photosynthesis as R. salina) ; 1(c)(i) any one from: 1 1 idea that absorbance measured (with colorimeter) / colour of indicator solution, is not affected by algae ; 2 indicator solution can be separated from algal balls ; 3 (more accurate) standardisation of, mass / volume / AW, of algae ; 1(c)(ii) independent variables: 3 species / type, (of algal beads) ; wavelength / colour, of light ; dependent variable: absorbance / pH (of solution) ; © Cambridge University Press & Assessment 2024 Page 6 of 10 1(c)(iii) any eight from: 8 1 method for use of filters (to give blue, green, red coloured light) ; 2 use, same / stated, number / mass / volume, of algal beads (in each bottle) ; 3 place light source the, same / stated, distance (from algal beads) ; 4 carry out experiment in a darkened room ; 5 use, same / stated, volume / concentration, of indicator (in each bottle) ; 6 (use of a control bottle) replace the algal beads with, glass / plastic / AW, beads ; 7 use, red / pH 8.4, hydrogencarbonate indicator solution (at start) ; 8 detail of method to take sample (of indicator solution) from bottle ; 9 use a, same / stated, coloured, filter / light, in the colorimeter ; 10 method to calibrate colorimeter ; 11 ref. to, suitable time to leave algal beads and indicator solution (before measuring absorbance) ; 12 for each colour (filter) and species, measure / record / AW, absorbance, at same / stated, time(s) ; 13 use at least three measurements for each colour (filter) and species, and calculate a mean ; © Cambridge University Press & Assessment 2024 Page 7 of 10 1(c)(iv) hazard and risk and precaution ; 1 hazard risk precaution algae / beads irritant / allergy gloves / mask / goggles / PPE hydrogencarbonate irritant / allergy gloves / mask / goggles / PPE indicator (solution) heat from light source burns do not touch bulb / turn off lamp before handling 1(d)(i) any one from: 1 1 comparing the means of two (sets of data) ; 2 continuous data (collected) ; 3 (data are from populations that are) normally distributed ; 4 standard deviations are approximately the same ; 1(d)(ii) there is no difference, in the pH of samples (taken from the small bottles / of indicator solution), between R. salina and S. 1 costatum ; © Cambridge University Press & Assessment 2024 Page 8 of 10

2(a) 1 peat bog A has a higher number of species and a higher Shannon index (than peat bog B) ; ora 2 examples of suitable wording for mp1: number of species Shannon index peat bog A has a higher number of species ora peat bog A has a higher Shannon index ora peat bog A has 12 species, peat bog B has only 8 idea that number of species / species richness, is species more important for Shannon index no (individuals of) species T, U, W, V in peat bog B 2 peat bog B has a smaller range of species abundance and a higher Simpson’s index (than peat bog A) ; ora examples of suitable wording for mp2: relative species abundance Simpson’s index peat bog B has a smaller range of species peat bog B has a higher Simpson’s index ora abundance ora idea that (range of) species abundance / species peat bog B has a higher (total) number of individuals evenness / total number of individuals, is more ora important for Simpson’s index peat bog B has 135 (total) number of individuals, peat bog A has only 99 if mp1 and mp2 not awarded, then award 1 mark for: peat bog A has a higher number of species and peat bog B has a smaller range of species abundance ; ora © Cambridge University Press & Assessment 2024 Page 9 of 10 2(a) examples of suitable wording: number of species relative species abundance peat bog A has a higher number of species ora peat bog B has a smaller range of species abundance ora peat bog A has 12 species, peat bog B has only 8 species peat bog B has a higher (total) number of individuals ora no (individuals of) species T, U, W, V in peat bog B peat bog B has 135 (total) number of individuals, peat bog A has only 99 2(b)(i) any three from: 3 1 sample at different times of the year (not only over one month) ; 2 sample at, night / different times of day (not only between 13:00 and 16:00) ; 3 sample at sites other than along the path ; 4 use of (another) named technique to sample invertebrates ; 5 use an expert / (identification) app / guidebook (instead of an identification key) ; 2(b)(ii) 1 (for Tipula limbata) n / N = 0.083 and (n / N)2 = 0.007 ; 3 2  = 0.270 ; 3 D = 0.730 ; 2(b)(iii) peat bog A has (slightly) higher (biodiversity than peat bog B) ; ora 1 © Cambridge University Press & Assessment 2024 Page 10 of 10

1(a) any three from: 3 1 catch (a sample of grey bush) crickets (within habitat) and count total captured and mark and release them ; 2 detail ; e.g. idea of suitable marking so not harmful / too obvious / not removed e.g. idea of leaving for a few days (to give time for populations to mix before second sample taken) 3 catch second sample and count total number of crickets and number of marked crickets ; 4 reference to Lincoln index ; 1(b) Table 1.1 completed correctly and (n / N)2 = 0.21 / 0.22 when answer rounded to 2 significant figures ; 3 D = 0.78 / 0.79 when rounded to 2 significant figures ; D = 0.783 ; must be to 3 significant figures ; © Cambridge University Press & Assessment 2025 Page 5 of 10 1(c)(i) any two from: 2 1 wind, speed / direction ; 2 (atmospheric) humidity ; 3 rainfall / soil water content ; 4 soil type ; 5 soil pH ; 6 salinity (of soil) ; 7 mineral / ion, concentration (of soil) ; 8 (atmospheric) carbon dioxide concentration ; © Cambridge University Press & Assessment 2025 Page 6 of 10 1(c)(ii) any seven from: 7 1 use quadrats ; 2 method of, random / systematic, placement of quadrats ; 3 use, same / stated, size (frame / point), quadrat ; 4 method of identifying (plant) species ; 5 count the number of individuals of each (plant) species ; 6 idea of taking care to note, low growing / small / easy to miss, species ; 7 idea of sampling, 10 or more / AW, separate points / quadrats (in the grey dune habitat) ; 8 (measure biodiversity of plant species) at regular intervals (over the 10-year period) and at the same time of the year ; 9 repeat (whole investigation over 10 years) at different, times of year / seasons ; 10 named hazard and risk and precaution ; hazard risk precaution plants / pollen allergy / irritation / injury gloves / eye protection / mask / PPE / protective clothing animals allergy / irritation / injury gloves / eye protection / mask / PPE / protective clothing grey dunes / ecosystem getting lost / trip hazard / wear suitable shoes / clothes / gloves / injury PPE stay, in a group / with expert / ranger © Cambridge University Press & Assessment 2025 Page 7 of 10

2(a) any two from: 2 1 data, are ordinal / can be ranked ; 2 data points within samples are independent of each other ; 3 there are 20 paired observations ; 4 coffee farms / sampling points, were selected at random ; 5 AVP ; 2(b) (there is) no correlation between the water availability and the number of months that elephants entered each (coffee) farm 1 per year ; 2(c)(i) all correct ; 1 r value significance s 0.63 yes –0.30 no 0.02 no 0.38 no © Cambridge University Press & Assessment 2025 Page 8 of 10 2(c)(ii) any one from: 1 negative correlation / the greater the density of December trees, the fewer the number of months that elephants entered each (coffee) farm / ora and (correlation) is weak / is not significant ; there is no correlation (between the density of December trees and the number of months that elephants entered each farm) ; 2(d) any three from: 3 support: 1 idea that reducing water availability is (significantly) correlated with a reduced number of times that elephants enter the (coffee) farm ; 2 idea that water availability was the only variable found to be significant (so reducing the number of water bodies might be the most effective action) ; ora does not support (max 2): 3 water bodies only counted, once / in March / in 2008 ; 4 investigation only, in one geographical area (of India) / at Nagarahole National Park ; 5 idea that size of, ponds / lakes / water holes, might also be important ; 6 idea that (questionnaire) does not record actual, number of times elephants entered the farms / number of elephants (per month) ; 7 idea that correlation does not indicate causation (so reducing the availability of water may not affect the number of elephant visits) ; © Cambridge University Press & Assessment 2025 Page 9 of 10

3(a) independent variable: 2 vaccinated or not vaccinated (against Rotavirus) ; dependent variable: number of children with (type 1) diabetes (per 100 000 population in Australia) ; 3(b)(i) 1 number of children (aged from 0 to 4 years) with (type 1) diabetes decreased, after the introduction of the vaccine 2 (against rotavirus) ; 2 number of children (aged from 0 to 4 years) with (type 1) diabetes increased (slowly) from, 2000 to 2007 / 2008 to 2015 ; 3(b)(ii) any three from: 3 1 idea that (mean) number of children aged from 0 to 4 years with (type 1) diabetes (per 100 000 population) is lower after introduction of vaccine ; 2 idea that, (95%) confidence intervals / (95%) CI / error bars (for before and after introduction of vaccine), in children aged from 0 to 4 years (before and after introduction of vaccine) do not overlap therefore number of children with (type 1) diabetes is significantly different (before and after introduction of vaccine) ; 3 10 to 14 year olds act as a control group (because they are not vaccinated against Rotavirus) or 10 to 14 year olds are unvaccinated (before and after introduction of vaccine) ; 4 idea that, (95%) confidence intervals / (95%) CI / error bars (for before and after introduction of vaccine), in children aged from 10 to 14 years (before and after introduction of vaccine) overlap, therefore number of (unvaccinated) children with (type 1) diabetes is not significantly different (before and after introduction of vaccine) ; © Cambridge University Press & Assessment 2025 Page 10 of 10

1(a)(i) any one from: 1 1 calibrate colorimeter ; 2 use, a blank / AW, to set (colorimeter absorbance) to zero ; 1(a)(ii) 1 rate of change in absorbance at pH 2.0 = 3 0.0036 / 3.6  10–3 ; 2 working: (0.52–0.23) / (120–40) or 0.29 / 80 ; 3 units: au s-1 ; © Cambridge University Press & Assessment 2025 Page 8 of 14 1(b)(i) any seven from: 7 1 prepare (at least) five solutions with stated pH values between pH 0 and 6.5 ; 2 same / stated, volume / concentration, of pepsin (solution) used ; 3 method to maintain a, constant / stated, temperature ; 4 equilibrate / AW, all (pepsin, pH / buffer / albumen) solutions separately (before mixing) ; 5 method to mix, pepsin and pH (buffer) albumen (solutions, before adding to colorimeter) ; 6 at each pH, measure / note / record / AW, absorbance at, set / stated, time intervals ; 7 use at least three replicates for each pH and calculate a mean rate (of change in absorbance / of protein hydrolysis, for each pH) ; 8 method to identify the optimum pH ; 9 idea that repeat experiment with smaller pH intervals around the optimum pH ; 10 safety comment with named hazard and risk and precaution ; hazard risk precaution albumen / eggs allergy / irritant gloves / goggles / mask / PPE pH buffer irritant / corrosive (at pH 0, 1, 2) gloves / goggles / mask / PPE pepsin allergy / irritant gloves / goggles / mask / PPE © Cambridge University Press & Assessment 2025 Page 9 of 14 1(b)(ii) 1 correct y-axis label ; e.g. rate of protein hydrolysis / aus-1 2 2 appropriately shaped line ; © Cambridge University Press & Assessment 2025 Page 10 of 14 1(c)(i) any two from: 2 1 test condition 2, decreases / hydrolyses / AW, CA3 and Sep70 ; 2 idea that acid / pH 4.0, with no active pepsin, does not change CA3 and Sep70 ; 3 (mass / size / AW of) CA3 is smaller than Sep70 ; ora 1(c)(ii) any two from: 2 1 idea that pepsin only causes damage (to the laryngeal epithelium) if (hydrochloric) acid / pH 4.0, is also present ; 2 investigation, only carried out once / was not repeated ; 3 idea that no information on species of mammal used (in investigation) or idea that investigation, not carried out in a person / carried out in a laboratory ; 4 idea that a reduction in quantity of Sep70 and CA3 may not cause damage to the laryngeal epithelium ; © Cambridge University Press & Assessment 2025 Page 11 of 14

2(a)(i) number of insect attraction events (in 6 hours) ; 1 2(a)(ii) any two from: 2 1 size / length / AW (of model / body / legs) ; 2 shape / AW (of model) ; 3 material / AW (of models) ; 4 thickness / weight / mass / density / AW (of models) ; 5 yellow, colour / shade / tone / pigment / AW (of models) ; 6 light, absorption / reflection / AW (of models) 7 size of spots (on model A and B) ; 8 (models are) odourless / AW ; 2(a)(iii) (measure insect attraction rate of) web with no model ; 1 © Cambridge University Press & Assessment 2025 Page 12 of 14 2(b)(i) any four from: 4 effect of colour and pattern: 1 idea that yellow colour (models A, C and D), have high insect attraction rates ; 2 idea that pattern (of spots) is less important than colour (for attracting insects) ; ora using information from Fig. 2.2: 3 idea that, (standard) error bars for yellow (colour, models A, C, D) and not yellow (colour, models B, E), do not overlap, (therefore insect attraction rate may be) significantly different ; 4 idea that, (standard) error bars for models A, C, and D overlap, (therefore insect attraction rate) is not significantly different (for yellow models with different patterns) ; or idea that, (standard) error bars for models B, and E overlap, therefore insect attraction rate is not significantly different (for black models with no yellow colour) ; 5 data quote, with units, to support ; 2(b)(ii) there is no difference between, the (mean) insect attraction rates, of the models ; 1 2(b)(iii) any two from: 2 1 data is continuous ; 2 comparing (two) means ; 3 fewer than 30 values ; 4 data is (from populations that are) normally distributed ; © Cambridge University Press & Assessment 2025 Page 13 of 14 2(c) any two from: 2 1 do investigation in, more than one, forest / geographical area / AW ; 2 idea of do investigation, at different times of the day / AW ; 3 do investigation in, more than one, month / season / year ; 4 idea that only count insects that touch the, model / web ; 5 use (more) models with different, colours / patterns or use 3–dimensional model (instead of, flat / 2–dimensional, model) ; 6 idea of (video) living spider on web ; © Cambridge University Press & Assessment 2025 Page 14 of 14

1(a) any two from: 2 1 mass of (mung bean) seedlings ; 2 age / variety / type / cultivar (of mung bean) seedlings ; 3 grinding time (using pestle and mortar) ; 4 speed of centrifuge / time in centrifuge ; 1(b)(i) explanation 2 idea of the temperature (of, solutions / reactants) will not have reached 30 ºC / AW or the rate of (enzyme)reaction, will change / not be constant / AW or reaction will start before reaching 30 ºC / AW ; modification equilibrate / AW, phosphatase/enzyme/extract and PPP/substrate, separately or equilibrate / AW , phosphatase / enzyme / extract and PPP / substrate before mixing ; 1(b)(ii) (sodium carbonate solution) denatures, the enzyme / phosphatase ; 1 © Cambridge University Press & Assessment 2025 Page 8 of 13 1(c) 1 five stated concentrations between 2 % and 0 % and units, % / percentage ; 2 2 correct method for dilution shown for two intermediates ; concentrations % 2 % stock / distilled water / cm3 phenolphthalein / cm3 2.0 50 0 1.6 40 10 1.5 37.5 12.5 1.2 30 20 1.0 25 25 0.8 20 30 0.5 12.5 37.5 0.4 10 40 0.25 6.25 43.75 0.0 0 50 1(d) 1 absorbance / AW, for the dilutions and extract / reaction mixture ; 2 2 use the calibration, curve / graph (to determine phenolphthalein / extract concentration) ; © Cambridge University Press & Assessment 2025 Page 9 of 13 1(e) any six from: 6 1 prepare five solutions with stated pH values up to pH 7 ; 2 equilibrate / AW, PPP / substrate, and, phosphatase / enzyme / extract, and buffer solutions, separately / before mixing ; 3 mix buffered, PPP / substrate, with, extract / enzyme solution ; 4 calibrate colorimeter or use a blank / AW, to, set colorimeter (absorbance) to zero / reset colorimeter ; 5 at each pH, stop the reaction / AW after a set time and, measure / note / record, absorbance ; 6 suitable method to identify the optimum pH ; 7 repeat experiment with smaller pH intervals around, the optimum pH / values with the highest absorbance / concentration (of phenolphthalein) ; 8 repeat experiment at least twice and calculate the mean (absorbance), for each pH / their means ; 9 named hazard and risk and precaution ; © Cambridge University Press & Assessment 2025 Page 10 of 13 1(e) hazard risk precaution phosphatase enzyme / mung allergy / irritant gloves / eye protection / PPE bean / extract phenolphthalein phosphate (PPP) sodium carbonate pH buffer irritant pH 3–7 gloves / eye protection / PPE or corrosive below pH 4 phenolphthalein toxic / irritant / allergy gloves / eye protection / PPE flammable keep away from naked flame 1(f)(i) point 6 on top line is circled ; 2 higher than, the V / 0.018 (mmoldm–3s–1) / the plateau ; max 1(f)(ii) (K withno inhibitor) 0.075 1 m and (K with inhibitor) 0.43 / 0.425 m and mmoldm–3 ; 1(f)(iii) 1 working 2 difference divided by K with no inhibitor (100) m (0.425 – 0.075) / 0.075 (100) ; 2 correct answer from working in mp1 ; © Cambridge University Press & Assessment 2025 Page 11 of 13

2(a) any two from: 2 1 (same) time of the year or (same) seasons or (same) months ; 2 (same) depth of, water / sea / sponge / (sea)bed / water pressure ; 3 (same) orientation of transect ; 2(b) 23 or 24 ; 2 correct working ; 2(c)(i) 1 any use of correct data to qualify a statement ; 3 supporting the conclusion ‘human activity equals lower diversity’ 2 station A has highest, index / diversity or station G / thermal power station, has lowest index or natural habitat / A, B, L, have a higher, index / diversity ; not supporting the conclusion ‘human activity does not equal lower diversity’ 3 housing / D and A, have a similar index or D / housing, has a higher index / (diversity) value than, B / L or J and K which have the same human activity have different, beta diversity indices / diversity or idea that the measure of diversity used just counts number of species and not number of individuals or did not, use / calculate, Simpson’s diversity index ; © Cambridge University Press & Assessment 2025 Page 12 of 13 2(c)(ii) answer must be in terms of the diversity of the sponges not diversity index (data) or beta diversity 3 A ‘it’ for ‘species diversity’ I biodiversity 1 correct index data quoted to support conclusion about species diversity ; any two from mp2–6: diversity in different locations in the bay: 2 idea that (stations A, B, L) closest to open ocean / at the edges of the bay, have higher diversity or idea that (stations E, F, G, H, I, J) furthest from open ocean / within the bay, have lower diversity or in the (Algeciras) Bay the diversity is lower than the marine habitat / ora ; diversity in industrial areas: (E,G, H, I) 3 idea that overall industries / industrial activity, results in lower diversity ; diversity in tourist areas (C, F, J, K) 4 idea that tourism results in varied impact (on diversity) and qualified with suitable examples ; 5 other (stated) factor affects diversity illustrated with a suitable station ; 6 impact of, housing / D, on diversity is, similar to natural habitats / less than other stations with human activity ; © Cambridge University Press & Assessment 2025 Page 13 of 13

1(a)(i) hazard and risk and precaution ; 1 hazard risk precaution chemical / anaesthetic toxic / allergy / irritant use, gloves / goggles / mask / PPE / use fume cupboard Drosophila / fruit flies allergy / use gloves / goggles / mask / PPE (spread of) pathogens / biohazard agar jelly / specimen tube, allergy / biohazard / pathogens use gloves / goggles / mask / PPE / containing food aseptic technique 1(a)(ii) any seven from: 7 1 (to produce heterozygotes) (breed) brown-eyed /AAdd, females with, scarlet-eyed / aaDD, males or (breed) scarlet-eyed / aaDD, females with, brown-eyed / AAdd, males ; 2 method to maintain a, constant / stated, temperature ; 3 idea of remove parent (fruit flies) from their offspring, before they are adults / before day 10 / before eggs hatch ; 4 put (anaesthetised), double heterozygotes / offspring from first cross, into (new specimen) tube ; 5 (cross double heterozygotes to give) a large number of offspring ; 6 use, stated / same / recommended / correct, dose / volume / concentration, (of chemical / anaesthetic) ; 7 identify, phenotype / eye colour, using, microscope / magnifying glass / hand lens ; 8 count / record, the number of flies of each, phenotype / eye colour ; 9 idea of method to prevent double counting (of flies) ; © Cambridge University Press & Assessment 2025 Page 8 of 10 1(a)(iii) 9 : 3 : 3 : 1 ; 2 red : brown : scarlet : white ; 1(b) any three from: 3 1 critical value (at degrees of freedom = 3 and p = 0.05) is 7.815 ; 2 calculated (χ2) value / 4.798, is less than, critical value / 7.815 ; 3 null hypothesis is accepted (at p = 0.05) ; 4 there is no significant difference (at p = 0.05) ;

2(a) type of treatment (solution) ; 1 2(b) any two from: 2 1 volume of, treatment / EchAMP / bacitracin, solution ; 2 concentration of, EchAMP / bacitracin, solution ; 3 concentration / volume , of fluorescence (chemical) ; 2(c)(i) (to) compare (the effect of EchAMP and) no EchAMP on, bacterial / E. coli (population), growth ; 1 2(c)(ii) (to) compare (the effect of EchAMP to) bacitracin / antibiotic (on bacterial / E. coli (population), growth) ; 1 2(d)(i) 1 axis labels with units on correct axes and completed key ; 2 2 three correct data points plotted at 7 hours, with data points joined to the correct values at 6 hours ; © Cambridge University Press & Assessment 2025 Page 9 of 10 2(d)(ii) any two from: 2 1 bacitracin reduces (population growth of E. coli) more than EchAMP (after 6 hours / at 7 hours) ; ora 2 no difference (in effect on E. coli) between 0 and 6 hours ; 3 bacitracin and EchAMP reduce (population growth of E. coli) more than the negative control, after 3 hours / at 6 hours / at 7 hours ; 2(e)(i) there is no difference between the (mean) fluorescence (emitted by E. coli after seven hours when exposed to), the 1 negative control and EchAMP ; 2(e)(ii) 1 correct working ; 3 2 (t =) 9.37 when rounded to 3 significant figures ; 3 (t =) 9.370 ; must be 4 significant figures 2(e)(iii) any four from: 4 1 idea that experiment is, not carried out in a person / carried out in a laboratory ; 2 idea that experiment, only used E. coli / did not use other bacteria ; 3 EchAMP may kill beneficial bacteria (in the digestive system) ; 4 EchAMP might not be as effective as other, treatments / antibiotics ; 5 EchAMP could, cause side effects / be toxic / AW, in humans or experiment only carried out for 7 hours / no information about longer term effects ; 6 EchAMP is a protein and would be digested (by enzymes in the digestive system) ; 7 idea that the EchAMP did not kill all of the E. coli ; © Cambridge University Press & Assessment 2025 Page 10 of 10

1(a)(i) 1 distilled / deionised / pure / AW, water (as diluent) ; 2 2 (use) 0.264g ABA and (dissolve in) 1 dm3 water ; 1(a)(ii) 1 add, 10 cm3 of, stock solution / 1  10–3 (mol dm–3 ABA), to 90 cm3 (distilled) water (to make 1  10-4 mol dm–3 ABA) ; 2 2 description, of one correct subsequent step of the serial dilution ; 1(b)(i) independent variable: 2 concentration of ABA ; dependent variable: number of grains germinated or length of shoot ; © Cambridge University Press & Assessment 2025 Page 9 of 14 1(b)(ii) any five from: 5 1 (use of a control for one group of 50 grains) replace the ABA solution with, distilled / deionised / pure / AW, water ; 2 ref. to (placing wheat grains in a container with) soil / paper / AW ; 3 carry out experiment in the dark ; 4 method to maintain a, constant / stated, temperature (for germination) ; 5 ref. to adding the, same / stated, volume / mass, of water (to container of wheat grains) ; 6 for each ABA concentration, count / record / AW, the number of (wheat) grains that have germinated, after a, same / stated, time or for each ABA concentration, measure / record / AW, the length of the shoot, after a, same / stated, time ; 7 safety comment with hazard and risk and precaution ; hazard risk precaution wheat grains irritant / allergy gloves / mask / PPE ABA / GA irritant / allergy / toxic gloves / mask / PPE soil biohazard / pathogens / gloves / mask / PPE allergy / irritant 1(c)(i) number of germinated grains, divided by the, total number of grains, x 100 ; 1 © Cambridge University Press & Assessment 2025 Page 10 of 14 1(c)(ii) 1 axes correctly orientated with labels and units ; 3 2 correct values on x-axis ; 3 line shows percentage germination decreases as ABA concentration increases ; 1(d)(i) any two from: 2 1 idea of smaller standard error (SE) shows that (the mean is) more reliable ; ora 2 idea of smaller SE shows that (calculated / sample) mean is closer to the, true / actual, mean ; ora 3 suitable example from Table 1.1 ; 4 correct ref. to overlap of SE from Table 1.1 ; for example: idea of, SE for 1  10–7 ABA concentration and 1  10–6 ABA concentration do not overlap, (therefore mean shoot length may be) significantly different or idea of, SE for 1  10–6 ABA concentration and 1  10–4 ABA concentration overlap, (therefore mean shoot length) is not significantly different 1(d)(ii) there is no difference, in the (mean) shoot length (of the seedlings grown from wheat grains with), no GA (treatment) and (1 1  10-5 mol dm–3) GA (treatment) ; © Cambridge University Press & Assessment 2025 Page 11 of 14 1(d)(iii) 1 use 38 degrees of freedom ; 3 2 compare (calculated) t-value with, critical (t-) value at, (p) = 0.05 / 5% ; 3 (if calculated) t-value is higher (than the critical t-value then) and reject null hypothesis / there is a significant difference ; ora Question Answer Marks

2(a) any one from: 1 1 idea that (cold buffer) prevents, (mitochondrial) enzymes / proteins , denaturing ; 2 idea that (cold temperature) prevents damage to mitochondria, by enzymes ; 3 idea that (buffer) prevents (osmotic) lysis of mitochondria ; 2(b)(i) 49.50 ; 1 © Cambridge University Press & Assessment 2025 Page 12 of 14 2(b)(ii) correct identification of anomalous results ;; 2 rate of oxygen consumption trial 1 trial 2 trail 3 trial 4 mean mitochondria alone 0.03 0.02 0.03 0.01 0.02 succinate added 50.22 49.10 48.53 50.15 49.50 ADP and succinate 139.23 170.10 142.67 138.10 147.53 added ADP, succinate and 0.00 0.10 0.00 0.01 0.03 cyanide added 2(b)(iii) 1 do not include, anomalies and calculate (a more accurate) mean ; 2 2 calculate, standard deviation / standard error / 95% confidence limits (for each trial) ; © Cambridge University Press & Assessment 2025 Page 13 of 14 2(c) any three from: 3 1 in mitochondria (alone): oxygen concentration does not change or do not use oxygen or rate of oxygen consumption is very low ; 2 adding succinate (and no ADP) increases the rate of, aerobic respiration / Krebs cycle / oxidative phosphorylation ; 3 adding succinate and ADP, gives a larger increase in the rate of, aerobic respiration / Krebs cycle / oxidative phosphorylation ; 4 oxygen acts as the final electron acceptor (in aerobic respiration / oxidative phosphorylation) ; 5 adding cyanide stops, (aerobic) respiration / oxidative phosphorylation ; © Cambridge University Press & Assessment 2025 Page 14 of 14

1(a) any one from: 1 (presence of) juglone (with a concentration of 1.0  10-3 moldm-3) and control (treatment) / absence of juglone ; concentration, of juglone ; 1(b)(i) 5 cm3 of (original / 0.1 mol dm-3) juglone (solution) ; 2 495 cm3 of the (mixture of) solvents ; 1(b)(ii) any one from: 1 use, syringe / graduated pipette / micropipette / burette ; use, volumetric flask ; use larger (stated) volumes (of both juglone and mixture of solvents) ; 1(c)(i) 1 (mixture of) solvents / solution, with no juglone ; 2 2 idea that to show that any effects observed (on the, germination / growth, of seeds) are a result of juglone ; © Cambridge University Press & Assessment 2025 Page 8 of 12 1(c)(ii) any seven from: 7 1 method for standardising the exposure of the seeds to juglone ; 2 ref. to use, same / stated, (cucumber) seeds ; 3 method to maintain a, constant / stated, temperature ; 4 method to maintain a, constant / stated, light intensity ; 5 ref. to standardise another key variable ; 6 idea of reapply juglone (to seedlings) after germination ; 7 count / note / record / AW, number of seeds planted and count number of seeds that germinate, after a, set / stated, time ; 8 method for measuring growth at 10 days (after the appearance of the seedling above the soil) ; 9 for juglone solution and control treatment, use a large number of seeds and calculate the mean (growth) for each group ; 10 safety comment with hazard and risk and precaution ; hazard risk precaution juglone irritant / toxin / allergy gloves / mask / PPE solvents irritant / toxin / allergy gloves / mask / PPE cucumber irritant / allergy gloves / mask / PPE seeds / plants soil biohazard / pathogens / gloves / mask / PPE allergy / irritant © Cambridge University Press & Assessment 2025 Page 9 of 12 1(d)(i) any two from: 2 1 data is continuous ; 2 comparing means (from the two groups) ; 3 data is (from populations that are) normally distributed ; 4 standard deviations (approximately) the same (between the two groups) ; 1(d)(ii) any three from: 3 1 (the critical value at 18 d.f. and p = 0.05 is) 2.101 ; 2 calculated value of t / 2.090, is less than, critical value / 2.101 (at p = 0.05) ; ora 3 null hypothesis is accepted (at p = 0.05) ; 4 there is no significant difference (at p = 0.05) ; © Cambridge University Press & Assessment 2025 Page 10 of 12

2(a) any two from: 2 1 (initial) volume / population / number, of bacteria (in bacterial suspensions) or volume of (bacterial) suspension or (original) optical density of (bacterial) suspensions ; 2 volume of nitrite (ion solution) ; 3 concentration / volume, of nutrient broth ; 2(b)(i) (species of bacterium:) nominal ; 2 (lowest nitrite concentration:) continuous ; 2(b)(ii) 1 correct reading of values from Figure 2.1 3 (Salmonella enteritidis =) 0.7 and (Salmonella typhimurium =) 5 ; 2 correct working ; 3 correct value for percentage difference ; 614 (%) / 86 (%) 2(b)(iii) (most affected =) Yersinia enterocolitica 1 (least affected =) Salmonella typhimurium ; © Cambridge University Press & Assessment 2025 Page 11 of 12 2(c) any four from: 4 1 idea that investigation, not carried out in a person / carried out in a laboratory ; 2 idea that investigation only carried out for 24 hours / no information about longer term effects ; 3 idea that experiment, only used 5 species of (pathogenic) bacteria / did not use other bacteria ; 4 pH in the, digestive system / stomach / intestines / AW, is not 4.8 / is different ; 5 idea that nitrites may, kill / reduce growth / AW, of / beneficial / AW, bacteria (in the digestive system) ; 6 nitrites could, cause side effects / be toxic / AW (in humans) ; 7 no evidence of control experiment ; 8 no statistical, test / analysis ; 9 idea that (bacterial) population sizes may not have decreased (as only measured when no bacterial population growth occurred) ; © Cambridge University Press & Assessment 2025 Page 12 of 12

1(a)(i) independent: sucrose concentration ; 2 dependent: width of stomata ; 1(a)(ii) 2.5 and 17.5 (to produce a 2.5% sucrose solution) ; 2 5 and 15 (to produce a 5.0% sucrose solution) ; 1(a)(iii) 1 use all sucrose concentrations ; 5 any four from: 2 leave the epidermis in sucrose solution for the same time ; 3 calibrate, the eyepiece graticule ; 4 measure the width of the stomata ; 5 measure stomata at their widest point ; 6 idea of (measuring) 3 or more (different) stomata (for any single concentration) ; 7 calculate the mean (width of the stomata) for any single concentration ; 8 named hazard and risk and precaution ; hazard risk Precaution plant material allergy / irritant gloves / eye protection / PPE slides / cover slip cuts ensure it is not placed near edge of bench or use glass bin / dustpan and brush / AW, for disposal. scalpel / knife cuts cut away from hand / cut onto board / tile / AW © Cambridge University Press & Assessment 2025 Page 8 of 12 1(a)(iv) predict: 2 (as sucrose concentration increases width of stomata) decreases ; Explain (must match the prediction): (as the sucrose concentration increases) water leaves the guard cells, by, osmosis / down a water potential gradient / from high to low water potential ; or (as the sucrose concentration increases) less water enters the guard cells, by osmosis / down a water potential gradient from high to low water potential ; 1(b)(i) 1 stomatal density = 367 (mm-2) ; 4 Any three of: 2 (number of stomata) = 13 ; 3 diameter of picture = 8.5 cm / 85 mm or radius of picture = 4.25 cm / 42.5 mm or length of scale bar / 40 µm = 1.6 cm / 16 mm ; 4 show stomatal density calculation ; 5 show magnification (calculation) ; 1(b)(ii) use more than one, field of view / slide / epidermis / (plantain lily) leaf ; 1 © Cambridge University Press & Assessment 2025 Page 9 of 12 1(b)(iii) 2 1 Environmental condition ; 2 Explanation ; dry / arid / less water So less water lost / less transpiration low humidity high temperature / warm / hot windy / high wind speed Question Answer Marks

2(a) (0 µmoldm-3 ABA = ) 1.85 and (400 µmoldm-3 ABA = ) 1.35 ; 2 27 ; 2(b) any two from: 2 1 as ABA concentration increases, transpiration rate decreases, except at (ABA concentration of) 50 ; 2 error bars for (ABA concs) 10 or 50 overlap with (ABA conc) 0 so, there is no significant difference (in transpiration rates) or error bars for (ABA concs) 100 overlap with (ABA conc) 10 so, there is no significant difference (in transpiration rates) or error bars for (ABA concs) 100 overlap with (ABA conc) 400 so, there is no significant difference (in transpiration rates) ; 3 error bars for (ABA concs) 100 or 400 do not overlap with (ABA conc) 0 so, there maybe, a significant difference (in transpiration rates) ; © Cambridge University Press & Assessment 2025 Page 10 of 12 2(c) any three from: 3 1 data for the non-mutant variety ; 2 need to carry out a statistical test ; 3 & 4 ref. to a named standardised variable ; ; 5 ref. to knowing that water is lost from a named part of plant (somewhere other than the stomata) ; Question Answer Marks

3(a) any two from: 2 1 age of seeds ; 2 all awns are straight / all awns are twisted at the start ; 3 temperature ; 4 light intensity / carry out in a dark room ; 5 time seeds left in the different humidities (before measuring them) ; 6 type / thickness / absorbency / size / dimensions / area, of filter paper ; © Cambridge University Press & Assessment 2025 Page 11 of 12 3(b) any three from: 3 1 add different volumes of water (to the filter paper) ; 2 leave one (filter paper) with no water ; 3 ref. to measuring appearance of awn ; 4 idea of repeat, for each humidity ; © Cambridge University Press & Assessment 2025 Page 12 of 12

1(a) any one from: 1 (presence of) juglone (with a concentration of 1.0  10-3 moldm-3) and control (treatment) / absence of juglone ; concentration, of juglone ; 1(b)(i) 5 cm3 of (original / 0.1 mol dm-3) juglone (solution) ; 2 495 cm3 of the (mixture of) solvents ; 1(b)(ii) any one from: 1 use, syringe / graduated pipette / micropipette / burette ; use, volumetric flask ; use larger (stated) volumes (of both juglone and mixture of solvents) ; 1(c)(i) 1 (mixture of) solvents / solution, with no juglone ; 2 2 idea that to show that any effects observed (on the, germination / growth, of seeds) are a result of juglone ; © Cambridge University Press & Assessment 2025 Page 8 of 12 1(c)(ii) any seven from: 7 1 method for standardising the exposure of the seeds to juglone ; 2 ref. to use, same / stated, (cucumber) seeds ; 3 method to maintain a, constant / stated, temperature ; 4 method to maintain a, constant / stated, light intensity ; 5 ref. to standardise another key variable ; 6 idea of reapply juglone (to seedlings) after germination ; 7 count / note / record / AW, number of seeds planted and count number of seeds that germinate, after a, set / stated, time ; 8 method for measuring growth at 10 days (after the appearance of the seedling above the soil) ; 9 for juglone solution and control treatment, use a large number of seeds and calculate the mean (growth) for each group ; 10 safety comment with hazard and risk and precaution ; hazard risk precaution juglone irritant / toxin / allergy gloves / mask / PPE solvents irritant / toxin / allergy gloves / mask / PPE cucumber irritant / allergy gloves / mask / PPE seeds / plants soil biohazard / pathogens / gloves / mask / PPE allergy / irritant © Cambridge University Press & Assessment 2025 Page 9 of 12 1(d)(i) any two from: 2 1 data is continuous ; 2 comparing means (from the two groups) ; 3 data is (from populations that are) normally distributed ; 4 standard deviations (approximately) the same (between the two groups) ; 1(d)(ii) any three from: 3 1 (the critical value at 18 d.f. and p = 0.05 is) 2.101 ; 2 calculated value of t / 2.090, is less than, critical value / 2.101 (at p = 0.05) ; ora 3 null hypothesis is accepted (at p = 0.05) ; 4 there is no significant difference (at p = 0.05) ; © Cambridge University Press & Assessment 2025 Page 10 of 12

2(a) any two from: 2 1 (initial) volume / population / number, of bacteria (in bacterial suspensions) or volume of (bacterial) suspension or (original) optical density of (bacterial) suspensions ; 2 volume of nitrite (ion solution) ; 3 concentration / volume, of nutrient broth ; 2(b)(i) (species of bacterium:) nominal ; 2 (lowest nitrite concentration:) continuous ; 2(b)(ii) 1 correct reading of values from Figure 2.1 3 (Salmonella enteritidis =) 0.7 and (Salmonella typhimurium =) 5 ; 2 correct working ; 3 correct value for percentage difference ; 614 (%) / 86 (%) 2(b)(iii) (most affected =) Yersinia enterocolitica 1 (least affected =) Salmonella typhimurium ; © Cambridge University Press & Assessment 2025 Page 11 of 12 2(c) any four from: 4 1 idea that investigation, not carried out in a person / carried out in a laboratory ; 2 idea that investigation only carried out for 24 hours / no information about longer term effects ; 3 idea that experiment, only used 5 species of (pathogenic) bacteria / did not use other bacteria ; 4 pH in the, digestive system / stomach / intestines / AW, is not 4.8 / is different ; 5 idea that nitrites may, kill / reduce growth / AW, of / beneficial / AW, bacteria (in the digestive system) ; 6 nitrites could, cause side effects / be toxic / AW (in humans) ; 7 no evidence of control experiment ; 8 no statistical, test / analysis ; 9 idea that (bacterial) population sizes may not have decreased (as only measured when no bacterial population growth occurred) ; © Cambridge University Press & Assessment 2025 Page 12 of 12

1(a) any sensible concentrations ; 2 corresponding volumes of distilled water and sucrose; 1(b) any seven from: 7 1 same / stated, variety / age / AW, of beetroots ; 2 remove the outer skin (of the beetroot) / AW ; 3 same / stated, dimensions / AW, of (beetroot) block / AW ; 4 ref. to apparatus for obtaining same size of (beetroot) blocks ; 5 for each sucrose concentration, place (beetroot) block in a suitable container and submerge / AW (in sucrose solution); 6 (for each sucrose concentration) measure the initial mass and the final mass ; 7 (measure final mass) after a (suitable) stated time ; 8 method to remove excess liquid from beetroot (before measuring final mass) ; 9 use at least three different (beetroot) blocks and calculate a mean, for each sucrose concentration ; 10 safety comment with named hazard and risk and precaution ; hazard risk precaution beetroot allergy / irritant gloves / mask / PPE knife / scalpel / cork borer / AW cut cut away from the hand / cut onto a, board / tile / AW 1(c)(i) 1 appropriate axis labels and units ; 2 2 sketch shows decreasing line crossing x-axis ; © Cambridge University Press & Assessment 2025 Page 8 of 12 1(c)(ii) (identify the) x-axis intercept point 1 or (identify the point on the x-axis where the mean) percentage change in mass is zero ; 1(c)(iii) rinse (beetroot) blocks (after cutting / before adding to sucrose solution) ; 1 Question Answer Marks

2(a) method for measuring a curved claw (on the image) ; 1 2(b)(i) any one from: 1 colour of disc ; material of disc ; type of particle ; 2(b)(ii) (level of) roughness 1 or (mean) particle diameter (on disc) ; 2(b)(iii) 24 or 25 (feeding visits) ; 1 2(b)(iv) any two from: 2 1 as the particle diameter increases, (percentage of feeding visits when buff-tailed bumblebees) gripped (on to the disc) increases ; ora 2 at 30 µm and 53 µm / over 30 µm, there is no, difference / change / increase / AW (in percentage of feeding visits when buff-tailed bumblebees gripped on to the disc) ; 3 3. at 5 µm, (buff-tailed bumblebees) only hover ; © Cambridge University Press & Assessment 2025 Page 9 of 12 2(c)(i) Table 2.2 completed 2 mean particle rank of mean percentage of feeding rank of percentage of Difference in D2 diameter on the particle diameter visits when the buff- feeding visits when the rank, D disc / μm on the disc tailed bumblebees buff-tailed bumblebees gripped on to the disc gripped on to the disc 5 1 0 1 0 0 9 2 4 2 0 0 12 3 16 3 0 0 16 4 79 4 0 0 30 5 99 5.5 0.5 0.25 53 6 99 5.5 ; 0.5 0.25 D2 = 0.5 ; 2(c)(ii) (r =) 0.99 / 0.986 ; 1 s 2(c)(iii) 0.99 / calculated value for r , is greater than 0.83 ; 1 s © Cambridge University Press & Assessment 2025 Page 10 of 12

3(a)(i) Table 3.1 completed correctly ; 1 type of fruit mean of samples apple 17 / 16.7 orange 33 / 33.3 pineapple 43 / 43.3 grapes 14 / 14.3 3(a)(ii) Table 3.2 completed correctly ; 2 type of variable type of data type of fruit categoric / qualitative nominal volume of juice extracted quantitative continuous © Cambridge University Press & Assessment 2025 Page 11 of 12 3(a)(iii) any two from: 2 1 standardise, (total) mass / volume, of fruit used or standardise number of pieces of fruit used or standardise, dimensions / mass / volume / size / surface area / AW, of (each fruit) piece ; 2 use same, age / ripeness of each fruit ; 3 use a more accurate method to measuring the volume (of pectinase) or use a more accurate method to measure the volume (of juice) ; 4 replace pectinase with, (distilled) water / denatured pectinase / boiled pectinase / AW ; 3(b) any two from: 2 1 idea that the volume of juice may not be correlated with the quantity of pectin ; 2 age / ripeness, of fruit affects quantity of juice ; 3 idea of cell walls of different fruits have different compositions ; © Cambridge University Press & Assessment 2025 Page 12 of 12

1(a) any two from: 2 1 time of day ; 2 (which) days (of week for exercise) ; 3 speed / distance, of walking / running ; 4 location / gradient / AW of, walking / running ; 5 temperature ; 1(b)(i) exercise (programme) ; 1 1(b)(ii) any three from: 3 1 (mean) difference in systolic blood pressure, increases / AW, after (the 12-week) exercise (programme) ; ora 2 (mean) difference in diastolic blood pressure, was, negative / a decrease, before (the 12-week) exercise (programme) and is, positive / an increase, after (the 12-week exercise programme) ; 3 systolic, blood pressure, increases / AW, after the walking test (before and after the 12-week exercise programme) ; ora 4 diastolic blood pressure, decreases / AW, after the walking test, before (the 12-week) exercise (programme) or diastolic blood pressure, increases / AW, after the walking test, after (the 12-week) exercise (programme) ; 5 paired data quote ; 1(c)(i) 0.31 ; 1 © Cambridge University Press & Assessment 2026 Page 8 of 13 1(c)(ii) any two from: 2 1 to calculate (95%) confidence intervals / CI or to plot error bars ; 2 to test, whether the means (for the resting systolic blood pressures) are (significantly) different or to test, whether the, SE values / error bars / (95%) CI, overlap ; 3 to get a measure of how close the, calculated / sample / AW, mean is likely to be to the, true / actual / AW, mean ; © Cambridge University Press & Assessment 2026 Page 9 of 13

2(a) 0.26 (s) ; 1 2(b)(i) 1 use of water as diluent ; 2 2 12 cm3 of, 0.5% / stock, caffeine solution and 8 cm3 of water ; 2(b)(ii) any seven from: 7 1 use of a minimum of five stated caffeine concentrations ; 2 use a stated volume of (each) caffeine solution ; 3 use, a (light) microscope (to observe D. magna) ; 4 use a method to maintain, same / stated, temperature or method to avoid overheating ; 5 ref. to standardised variable relating to D. magna ; 6 use a method to standardise, pH / oxygen concentration, of caffeine solutions ; 7 method for, equilibration / acclimatisation, of D. magna ; 8 at each (caffeine) concentration, count the number of cardiac cycles, in a, set / stated, time ; 9 use of a method to ensure accurate counting ; 10 at each (caffeine) concentration take at least three measurements ; 11 idea of use, new / fresh / different, D. magna ; © Cambridge University Press & Assessment 2026 Page 10 of 13

3(a) 1 correct axis labels: 2 percentage / %, cover of, (water) hyacinth and percentage / %, cover of, malancha ; 2 appropriately shaped line ; straight line with upward trend 3(b)(i) any suitable method of generating random numbers and matching to the (69) sampling locations ; 1 3(b)(ii) 48 (%) ; ; 2 award one mark for correct working if final answer incorrect or missing 3(b)(iii) t-test 1 and any one from: idea of comparing (the difference between two) means ; continuous data ; standard deviations (for each treatment) are approximately the same ; data (from populations that are) normally distributed ; fewer than 30 values (in each treatment) ; © Cambridge University Press & Assessment 2026 Page 11 of 13 3(b)(iv) ref. to hazard and risk and precaution ; 1 hazard risk precaution animals allergy / bites / injury / medication / work in a group / travel infection / disease with an expert / suitable PPE / first aid kit (plants) pollen allergy medication / mask environment woodland / falling injury / getting lost boots / hard hat / suitable branches or trees / thorns / trip clothing / PPE / GPS / map / stay in a hazards / holes / mud group / use an expert / water / river / Armand bayou injury / drowning / hypothermia / swept boots / lifejacket / wetsuit / use an away (by current) expert / do not enter water / use a boat / use a rope (water-borne) pathogens / infection / disease / irritation (from PPE / wash hands parasites / pollution pollutants) tools / knife (to cut plants) injury cut away from, hand / body / other people © Cambridge University Press & Assessment 2026 Page 12 of 13 3(b)(v) any four from: 4 in context of supports: 1 (removal of malancha) reduces, (mean) area / abundance (of water hyacinth) in treatment 1 and 2 (compared to, control / treatment 3) or (mean) area / abundance (of water hyacinth) is, lower / lowest / AW, in treatment 2, compared to, control / treatment 3 ; 2 (95%) confidence intervals / CI / error bars, for treatment 2 and 3, do not overlap and (mean area / abundance of water hyacinth) is significantly different ; in context of limits support: 3 (95%) confidence intervals / CI / error bars, for treatment 1 and 3, overlap and (mean area / abundance of water hyacinth) may not be significantly different ; 4 investigation only carried out, once / at one time of year / over period of 8 weeks ; 5 investigation only carried out at 12 locations ; 6 no statistical test / should carry out a statistical test ; © Cambridge University Press & Assessment 2026 Page 13 of 13

1(a)(i) direction 1 mark as prose (drop of coloured liquid will move) left / AW allow (move) towards, O. asellus / test-tube / AW ignore move towards respirometer and if nothing on answer line, check diagram and allow correct arrow / annotations on Figure 1.2 explanation (oxygen used in respiration) decreases / AW, volume / pressure (of ignore ref. to capillary action gas in respirometer) ; ignore volume / pressure is low (needs to be lower) A ‘a negative pressure is created’ 1(a)(ii) idea of replace (live) O. asellus with: 1 allow woodlouse / woodlice / asellus / invertebrate / animal / organism as AW for O. asellus (shown in sterile / inert / glass / plastic / AW, beads ; Figure 1.2) or dead / AW, O. asellus ignore respirometer with no O. asellus R if change another factor in addition to O. asellus © Cambridge University Press & Assessment 2026 Page 8 of 19 Trace ID: PC-B925341256 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. 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P97a00p/5a1 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/51 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 1(a)(iii) any six from: 6 ignore ref. to control experiment allow woodlouse / woodlice / asellus / invertebrate / animal / organism as AW for O. asellus 1 use a minimum of five stated temperatures ; 1 temperatures must include 5°C and 35°C, but do not need to be evenly spaced must see units at least once ignore temperatures outside the range 2 suitable method to maintain a constant temperature ; 2 A water-bath / incubator ignore temperature-controlled room / air conditioning / heater / fridge A ref. to use thermometer and ice / warm water (in a beaker) R Bunsen burner mp3, 4 & 6 allow standardised / controlled / fixed / constant as AW for same ignore known 3 use, same / stated, mass of, sodium hydroxide / NaOH (pellets) ; 3 ignore amount / number, of NaOH pellets ignore volume / concentration allow any value for mass if stated 4 use, same / stated, number / amount / mass, of O. asellus 4 ignore size / length / volume / concentration, of or O. asellus use, same / stated, age of O. asellus ; ignore same species / type / sex (of O. asellus) allow any value for number / mass if stated ignore O. asellus (collected / bought) from same, environment / population / supplier ignore same, food source of O. asellus (before investigation) © Cambridge University Press & Assessment 2026 Page 9 of 19 Trace ID: PC-B925341256 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/5a1 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/51 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 1(a)(iii) 5 method to, equilibrate / acclimatise, O. asellus ; 5 A leave O. asellus (in respirometer), in water- bath / at a set temperature, for, set / stated, time if stated, minimum time 5 minutes 6 at each temperature, measure the distance (moved by the drop 6 allow note / record as AW for measure of coloured liquid), in a, set / stated, time ignore calculate as AW for measure or allow length / mm / cm as AW for distance at each temperature, measure the time (for the drop of coloured ignore known time (in question stem) liquid), to travel a, set / stated, distance ; allow ‘how far’ as AW for distance allow ‘how long’ as AW for time ignore ref. to measuring without sodium hydroxide allow measuring the initial and final distance allow any value for distance / time if stated do not allow measuring distance and time if neither is set / stated 7 for each temperature, take at least three measurements ; 7 ignore calculate a mean A three replicates / repeat 2 times, at each temperature 8 safety comment with hazard and risk and precaution ; 8 ignore low / medium / high, risk R no risk hazard risk precaution ignore heat / temperature / hot water as hazard ignore irritant / toxic / burns as risk for sodium sodium hydroxide corrosive / caustic / (wear) gloves / goggles hydroxide (pellets) damage to eyes / safety glasses / PPE ignore irritant / toxic as risk for O. asellus O. asellus allergy / biohazard (wear) gloves / PPE / woodlouse / pathogens / infection © Cambridge University Press & Assessment 2026 Page 10 of 19 Trace ID: PC-B925341256 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. 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P97a00p/5a1 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/51 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 1(a)(iv) distance (in mm) 1 allow d / h / l for distance and allow t for time multiplied by,  r2 / area (of glass tube cross-section) allow over time / multiply by 1/t, as AW for divide by and time divided by time (in minutes) ; ignore per as AW for divided (in question stem) ignore units if stated A d  r2 / t r = radius of glass tube allow  d2 / 4 =  r2 (where d = diameter) 1(b)(i) (different / type of) respiratory substrate (solutions) ; 1 A (20%) glucose and (20%) maltose (solutions) A (different / type of) sugar (solutions) R concentration of, glucose / maltose / sugar (solutions) 1(b)(ii) add 4 cm3, (50%) stock (solution of glucose) to, 6 cm3, distilled 1 allow ml as AW for cm3 water ; allow (50%) glucose (solution) as AW for stock solution allow deionised / pure, water as AW for distilled water ignore water unqualified ignore C V = C V 1 1 2 2 A use 4 cm3 stock solution and top up to 10 cm3, with distilled water © Cambridge University Press & Assessment 2026 Page 11 of 19 Trace ID: PC-B925341256 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. 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P97a00p/5a1 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/51 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 1(b)(iii) any two from: 2 ignore volume of yeast suspension ignore volume / concentration, of, respiratory substrate / glucose / maltose / sugar, solution ignore time ignore light intensity ignore carbon dioxide / oxygen, concentration 1 concentration of yeast / mass of yeast (in suspension) ; R type of respiratory substrate 2 species / variety / type / age / AW, of yeast ; R volume of gas 3 temperature ; 3 R temperature that (solutions / AW) were boiled at 4 pH ; 5 size of (small) test-tube ; 1(c)(i) type of data: 1 ignore categoric / qualitative / independent (as these nominal / discontinuous ; are types of variable) R quantitative / continuous / interval / ordinal / discrete / dependent © Cambridge University Press & Assessment 2026 Page 12 of 19 Trace ID: PC-B925341256 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/5a1 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/51 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 1(c)(ii) (mean) volume (of gas collected after 30 minutes), is, greater / AW, 1 allow rate of, fermentation / (anaerobic) respiration, with, glucose (than with maltose) / ora as AW for volume (of gas) and ignore (glucose is) better / AW data quote (from Figure 1.5) ; data quotes: candidates should give data quotes for glucose and maltose or the calculated difference. need units at least once allow ml as AW for cm3 respiratory substrate volume of gas / cm3 glucose 1.85 to 1.90 (e.g. 1.875) maltose 1.45 calculated difference 0.40 to 0.45 (e.g. 0.425) © Cambridge University Press & Assessment 2026 Page 13 of 19 Trace ID: PC-B925341256 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/5a1 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/51 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 1(c)(iii) any two from: 2 ignore easier / more efficient ignore harder / more difficult ignore spelling of underlined words if it is clear what is meant 1 maltose, is a disaccharide / is not a monosaccharide, and needs 1 allow broken down / digested / converted (to to be hydrolysed (into glucose) glucose), as AW for hydrolysed or ignore glucose is, broken down / AW glucose, is a monosaccharide / is not a disaccharide, and does ignore glucose is, easier / AW, to break down not need to be hydrolysed ; ignore maltose is, harder / AW, to break down 2 idea that only glucose enters, glycolysis ; ora 2 A maltose cannot enter glycolysis (unless it has been broken down) ignore respiration unqualified 3 idea that entry of glucose into yeast cells is faster ; 3 A more glucose transporters available in yeast cells (than maltose transporters) A idea that gene expression for maltose, transporter / enzyme / maltase / AW, takes time © Cambridge University Press & Assessment 2026 Page 14 of 19 Trace ID: PC-B925341256 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. 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2(a)(i) any two from: 2 ignore comparing / difference, between (two) means (in question stem) 1 ignore quantitative data 1 (data is) continuous ; R discrete / discontinuous / categoric / nominal / qualitative, data 2 (data is) normally distributed ; 3 standard deviations are (approximately) the same ; 4 A 11 birds of song type A and 13 birds of song 4 fewer than 30, values / birds / AW (for each song type) ; type B 2(a)(ii) there is no, difference, in the (mean) bill length, between, (male) 1 allow birds / finches / males, as AW for G. conirostris (with song) type A, and (male G. conirostris with song) G. conirostris type B ; allow beaks as AW for bills ignore significant ignore (mean) mass ignore (mean) bill, depth / width R no, correlation / relationship / association R female (G. conirostris) 2(a)(iii) 22 ; 1 11 + 13 – 2 = 22 © Cambridge University Press & Assessment 2026 Page 15 of 19 Trace ID: PC-B925341256 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/5a1 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/51 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 2(a)(iv) 3 check Table 2.2 and answer for 2aiii ecf all mp for incorrect df / NR in 2aiii 1 ignore t-value unqualified (could be the 1 calculated (t-) value / 3.768, is greater than, 2.074 (critical value calculated or critical values) at df = 22 and p = 0.05) ; ora need to state correct critical value (for their df) allow correct critical value from table (circled / underlined etc) mp 2 & 3 ecf incorrect critical value to max 2 2 R null hypothesis is accepted 2 null hypothesis / H , is rejected ; 0 3 R correlation / relationship / association 3 A greater than 95% probability that the 3 there is a significant difference ; difference (between the means) is not due to chance / is significant or less than 5% probability that the difference (between the means) is due to chance / is not significant © Cambridge University Press & Assessment 2026 Page 16 of 19 Trace ID: PC-B925341256 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. 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P97a00p/5a1 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/51 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 2(b) 2 allow bird / finch as AW for G. conirostris ignore repeats / do a statistical test each food source = prickly pear and palo santo tree (or several different sources) 1 measure / AW, time spent, feeding / eating / AW, on each food 1 allow note / record / calculate as AW for source ; measure allow ‘how long’ as AW for time ignore observe time for mp1 ignore time at location (needs to be time spent eating) ignore calculate, percentage / proportion (of time) any one from: INTERNAL MAX 2 idea of method to identify, individual / song type, (male) 2 allow use of, rings / paint / markings to identify, G. conirostris ; individual / song type ignore listen unqualified 3 idea of method to observe (feeding of male) G. conirostris on 3 allow lab-based or field-based methods each food source ; do not accept ref. to birds with only one food source (birds must have a choice of food sources) A natural habitat (with both food sources) and observe A feeding stations with both food sources and observe A cage / AW, containing both food sources and observe A camera / AW (to observe), birds (feeding) on both food sources © Cambridge University Press & Assessment 2026 Page 17 of 19 Trace ID: PC-B925341256 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. 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Licensed for hosting on papacambridge.com only. P97a00p/5a1 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/51 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 2(c) 5 idea of studying (G. conirostris) for several generations ; 5 ignore longer time unqualified allow many / multiple as AW for several allow several years if stated, allow 3 or more years as AW for several years 6 use DNA analysis / AW ; 6 allow DNA sequencing / DNA profiling / genetic fingerprinting / genetic screening © Cambridge University Press & Assessment 2026 Page 19 of 19 Trace ID: PC-B925341256 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/5a1 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/51 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/

1(a) ref. to hazard and risk and precaution ; 1 mark as prose ignore any other hazard ignore low / medium / high, risk hazard risk precaution R no risk allow cut away from body knife / blade / scalpel cuts / injury cut away from the hand ignore cuts clothing / AW ; / AW (skin / hand or ignore gloves as precaution for knife / AW) cut onto a, board / tile / AW ignore glasses / goggles ignore biohazard avocado / catalase allergy (wear) gloves / PPE ignore hydrogen peroxide harmful / enzyme / mesocarp / irritant ignore damage / (chemical) burns hydrogen peroxide irritant / toxic (wear) gloves / goggles / safety / H O / corrosive glasses / PPE 2 2 / caustic / damage to eyes 1(b)(i) time / days, after picking / after harvesting / to ripen 1 ignore ripeness / time, unqualified or level / degree / stages / AW, of ripeness ; allow different as AW for level ignore age ; A colour of skin A softness of avocado / mesocarp ignore softness of skin © Cambridge University Press & Assessment 2026 Page 8 of 17 Trace ID: PC-8AD397FDC6 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/5a2 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/52 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 1(b)(ii) 7 ignore ref. to control experiment ignore ‘known’ for ‘same’ then ecf if repeated throughout allow standardised / controlled / fixed / constant A mesocarp as AW for avocado 1 use of five different (stages)/AW of ripeness ; 1 A method to obtain 5 stages of ripeness allow if 5 different levels of ripeness stated even if less than 5 descriptions given – allow the mark ignore age any six from: 2 same / stated / fixed, dimensions of avocado pieces ; 2 ignore removal of skin ignore size / mass / volume / SA for dimensions A cube with same / stated, dimensions / linear measurement(s) ignore length and width being the same unless ‘cube’ is mentioned cube 2 cm  2 cm – BOD ignore any stated dimensions larger than 10 cm A cylinders same length and diameter (if numbers stated need to see units at least once) 3 use knife / blade / scalpel / AW and ruler / AW (to cut the avocado pieces) 3 allow cutter as AW for knife or allow vernier calipers as AW for ruler use knife / blade / AW and cork-borer and ruler (to cut cylinders) ; © Cambridge University Press & Assessment 2026 Page 9 of 17 Trace ID: PC-8AD397FDC6 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/5a2 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/52 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 1(b)(ii) 4 use same, species / type / variety, of avocado 4 A Persea americana as same species or A same tree use same number / amount of pieces (in each beaker) ; A all pieces cut from same avocado A one/ a / the piece 5 use a suitable method to maintain a constant temperature of hydrogen 5 suitable methods: peroxide ; water-bath temperature-controlled room A air conditioning / heater, set at one temperature ignore incubator / air conditioning unqualified if stated, temperature between 10 °C to 40 °C 6 use same / stated, volume / concentration of hydrogen peroxide / H O ; ignore concentration or volume values 2 2 7 avocado added / AW to hydrogen peroxide and immediately start timer ; allow ‘and then’ as AW for immediately 8 suitable method / apparatus for measuring the quantity of oxygen 8 A gas as AW for oxygen produced / released ; ignore count bubbles unqualified allow: counting bubbles using camera add washing up liquid and measure height of foam produced collect oxygen over water / H O and 2 2 measure volume in inverted measuring cylinder © Cambridge University Press & Assessment 2026 Page 10 of 17 Trace ID: PC-8AD397FDC6 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/5a2 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/52 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 1(b)(ii) collect oxygen and measure volume in a gas syringe ignore syringe allow measuring loss of oxygen by loss in mass, using an electric balance and mass change calculated 9 at each stage / AW of ripeness, set / measure / record / fixed period of, time allow idea of recording time to sink (linked to release of oxygen) ; 10 at each stage of ripeness take at least three measurements ; 10 ignore calculate a mean A three replicates / repeat 2 times, at each stage / AW of ripeness 11 fresh / new / change / AW, hydrogen peroxide used in each experiment / different stages/AW of ripeness ; 1(c)(i) any suitable method of generating random numbers and matching to the 1 e.g. number all the trees and use a trees ; random number generator (to select the trees) ignore quadrats / co-ordinates 1(c)(ii) idea of to reduce the water loss from the avocados (while in storage) / AW ; 1 A reduces transpiration A reducing water evaporation allow no / stop / prevent AW for reduces allow losing moisture ignore ‘keep moist’ ignore vapour ignore prevent drying out ignore ref. to osmosis 1(c)(iii) 822  412 and 736  358 ; 1 © Cambridge University Press & Assessment 2026 Page 11 of 17 Trace ID: PC-8AD397FDC6 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/5a2 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/52 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 1(c)(iv) correct plotting of both bars (within ½ square) ;; 2 ecf for incorrect calculations from 1(c)(iii) 1 mark per bar if lines are thick or slanted take reading from top edge of bar group expected range 20dR 410–1234 30dR 378–1094 © Cambridge University Press & Assessment 2026 Page 12 of 17 Trace ID: PC-8AD397FDC6 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/5a2 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/52 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 1(c)(v) any four from: 4 ignore units if seen mp2 only valid if mp1 has been awarded mp4 only valid if mp3 has been awarded ignore ref. to dR 1 conclusion 0d compared with 10 –30d or between 10 –30d effect of (cold storage only on catalase activity) is, variable / increases and 0d 571 10d and 20d decreases / fluctuates / no pattern / trend ; 615 and 455 2 data comparison with 0d and 10 / 20 / 30d 0d 571 10d and 30d data from 3 to show fluctuations, 0d / 571 or 10d / 615 or 20d / 455 or 615 and 550 30d / 550 ; 0d 571 20d and 30d 3 conclusion 0d / all d with all dR 455 and 550 increased (mean) activity when allowed to ripen / dR (bigger than d) or conclusion all dR compared to 0d allow dR as AW for ‘time to ripening’ all, dR data / storage times, with ripening have greater (mean) activity than, allow stored at 7 degrees / AW for d 0d / ora ; allow stored at (7 and) 20 degrees / AW for dR 4 data comparison d with dR data to compare 10d with 10dR or 20d with 20dR or 30d with 30dR 4 ignore means of all d and all dR ; e.g. 20d 455 v 20dR 822 or A calculated difference between means data to compare 0d / 571 with 10dR / 642 and 20dR / 822 and 30dR / 736 5 error bars overlap (so may be) no significant difference (in catalase allow (95%) confidence activity) between, all / both, groups / in Figure 1.4 / AW ; intervals / CI / SE / standard error as AW both = all d data and dR for error bars ignore the size of error bars / SE / CI ignore optimum and highest mean activity A both groups for all groups R results ignore values © Cambridge University Press & Assessment 2026 Page 13 of 17 Trace ID: PC-8AD397FDC6 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/5a2 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/52 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 1(c)(vi) any two from: 2 R data is, not continuous / discrete / discontinuous / categoric / qualitative (data) not normally distributed ; ignore data is, continuous / quantitative standard deviations are different ; A comparing 7 means more than two means (to compare) ; ignore fewer than 30 values © Cambridge University Press & Assessment 2026 Page 14 of 17 Trace ID: PC-8AD397FDC6 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/5a2 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/52 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/

2(a)(i) (use an) identification key / app / expert ; 1 ignore photographs unqualified A (guide) book / AI / database ignore features – spots / colouring / patterns 2(a)(ii) any two from: 2 accept any stated length of transect 1 length of (belt) transect ; ignore width / size / orientation of belt transect 2 same / one, person counting (the butterflies on one transect) ; 3 time of the day ; ignore weather 4 time of the year / season / month ; ignore time unqualified 5 (period of) time spent counting ; © Cambridge University Press & Assessment 2026 Page 15 of 17 Trace ID: PC-8AD397FDC6 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/5a2 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/52 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 2(a)(iii) any three from: 3 ignore human error miscounting: AW for miscounting – inaccurate 1 butterflies can fly so difficult to count / move from place to place therefore numbers / incorrect numbers / counting or may counted more than once / could miss some ; recording, higher / lower, numbers / counting more than once / missing some 2 butterflies maybe, small / camouflaged, so difficult to see so, inaccurate (BOD – without ref. to counting or count /miss some ; numbers) allow inaccurate results for inaccurate 3 difficult to judge 2.5 m distance leading to inaccurate numbers ; numbers 4 person sampling maybe walking too fast so could miss some ; misidentifying: 5 butterflies, can fly / maybe (very) small, therefore unable to see, AW for misidentification – features / patterns, so inaccurate identification / difficult to identify ; inaccurate / incorrect identification / hard to identify, wrong identification 6 some butterflies have similar, colours / patterns, so could misidentify ; 7 person sampling may, lack the knowledge / AW, so could misidentify ; 8 person sampling may not be able to, see clearly / AW, so could misidentify; 9 person sampling may be walking too fast so could misidentify ; © Cambridge University Press & Assessment 2026 Page 16 of 17 Trace ID: PC-8AD397FDC6 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/5a2 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/52 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 2(b) 2 ignore predators / pollution prediction ignore light ignore selection pressures rural / farmland urban / towns and and woodland cities 1 ignore greenery 1 food / plants / flowers more… less… vegetation variety of.. less variety of .. 2 habitats / niche / trees more less 3 gardens / parks less more 4 active conservation of less/more more / less butterflies qualified 5 pesticides qualified less/more less / more 6 habitat fragmentation less more 7 temperature colder warmer 2(c) max 1 (mp2 only) if correct answer with no working shown 2 no ecf for incorrect working allow alternative method: 1 correct working: % calculated –100 (13 500 – 2300) ÷ 2300 (100) or ecf 11 200 ÷ 2300 (100) ; incorrect values taken from the graph and all three figures shown correct formula and correct answer from their figures 2 correct answer / 487 (%) ; R if not 3 significant figures © Cambridge University Press & Assessment 2026 Page 17 of 17 Trace ID: PC-8AD397FDC6 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/5a2 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/52 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/

1(a)(i) 1 correct axis labels ; 3 e.g. x-axis = temperature y-axis = rate of respiration 2 line rises and then falls ; ignore anaerobic / aerobic 3 line rising at an increasing rate to the optimum ; 3 ignore absence of fall accept any curve with an increasing e.g. three marks for: gradient mp2 and mp3 ignore starting point of curve ecf for incorrect mp1 with correct axes labels © Cambridge University Press & Assessment 2026 Page 8 of 14 Trace ID: PC-6F815CCF34 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/5a3 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/53 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 1(a)(ii) any eight from: 8 any eight from: 1 use a minimum of five stated temperatures ; 1 temperatures must include 10 ºC and 50 ºC must see units at least once 2 suitable method to maintain a constant temperature ; ignore temperatures outside the range 2 A water-bath / incubator ignore temperature-controlled 3 use, same / stated, number / amount / mass, of seeds ; room / air conditioning / heater / fridge A ref. to use thermometer and ice / warm water 4 use, same / stated, species / type / variety, of seeds ; 4 Ignore age (of seeds) 5 use, same / stated, volume / concentration, of sodium hydroxide / NaOH ; 5 Ignore mass / amount mp3, mp4 and mp5 allow standardised / fixed / controlled / constant as AW for same ignore known 6 method to, equilibrate / acclimatise, seeds to new temperature ; 6 A leave seeds in respirometer at new temperature / in water-bath / AW, for, set / stated time if stated, minimum time 5 minutes 7 at each temperature, measure the distance (moved by the coloured liquid), in 7 allow note / record as AW for a, set / stated, time measure or ignore calculate as AW for measure at each temperature, measure the time, (for the coloured liquid), to travel a, allow length / mm as AW for distance set / stated, distance ; ignore ref. to measuring without sodium hydroxide © Cambridge University Press & Assessment 2026 Page 9 of 14 Trace ID: PC-6F815CCF34 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/5a3 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/53 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 1(a)(ii) allow how far as AW for distance allow how long as AW for time ignore collecting gas in the syringe ignore ref. to open / close, tap 8 (replace seeds / repeat, with) sterile/ inert / glass / plastic / AW, beads 8 ignore respirometer with no seeds or R if another variable is changed as dead / AW, seeds ; well as the seeds 9 at each temperature, take at least three measurements ; 9 ignore calculate a mean A three replicates / repeat 2 times / multiple times, at each temperature 10 safety comment with hazard and risk and precaution ; 10 ignore burns ignore biohazard ignore hot water as a risk hazard risk precaution NaOH / sodium irritant / corrosive / caustic (wear) gloves / safety hydroxide / damage to eyes glasses / goggles / PPE seeds irritant / allergy (wear) gloves / PPE 11 Idea of: open the tap and use the syringe to reset the coloured liquid ; © Cambridge University Press & Assessment 2026 Page 10 of 14 Trace ID: PC-6F815CCF34 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/5a3 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/53 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 1(a)(iii) any four from: 4 1 divide diameter by 2 (to give radius) or radius = 0.5 mm ; 2 calculate (cross sectional) area (of the capillary tubing) 2 A r2 or d2 / 4 or Use calculation guidance area = 0.79 mm2 ; 3 distance multiplied by (cross sectional) area (to calculate volume of gas) ; r2  distance moved gets mp2 and mp3 4 divide by time ; 5 calculate a mean distance / rate ; 6 divide by mass of seeds used ; 1(b)(i) 0.846 ; 1 use calculation guidance A 0.85 1(b)(ii) (species =) B ; 2 No ecf from 1(b)(i) (evidence =) carbon dioxide (volume) is greater than oxygen (volume) ; ora A RQ is greater than 1 No ecf for wrong species 1(b)(iii) any one from: 1 ecf for species C only in 1(b)(ii) reason why oxygen measurements are too low ignore human error unqualified 1 (water bath) temperature was too low ; A temperature was high and enzymes 2 duration of the test, was too short / less than one minute ; denatured 3 idea of gas escaping from, respirometer / apparatus / AW ; R gas coming into apparatus © Cambridge University Press & Assessment 2026 Page 11 of 14 Trace ID: PC-6F815CCF34 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. 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2(a) independent variable: 2 number / amount of (daily) garlic capsules ; dependent variable: (resting systolic) blood pressure ; 2(b) capsule with no garlic ; 1 ignore ‘placebo’ unqualified A placebo capsule allow tablet / pill, as AW for capsule A capsule with, sugar / starch / cellulose / AW, (and no garlic) 2(c)(i) continuous ; 1 ignore quantitative / ordinal / ordered / dependent / interval / normally distributed R qualitative / categoric / discrete / discontinuous / nominal © Cambridge University Press & Assessment 2026 Page 12 of 14 Trace ID: PC-6F815CCF34 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/5a3 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/53 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 2(c)(ii) any three from: 3 ignore improved blood pressure as AW for blood pressure decreases comparing start to end of the investigation 1 (resting systolic) blood pressure decreased in all groups (over the 12 weeks) ; 2 SE for, start / 0 weeks and end / 12 weeks, do not overlap, therefore (mean resting systolic blood pressure may be) significantly different (in all groups) ; 2 allow if only one group is stated ignore standard deviation / 95%CI / comparing groups error bars 3 results / decrease in blood pressure, for 1 garlic capsule were not different to allow significant, decrease / AW the control ; (implies a difference) 4 SE for one garlic capsule and control, overlap (at all times) therefore (mean allow is significantly different resting systolic blood pressure) is not significantly different ; ignore ‘results are significant’ 4 ignore standard 5 results / decrease in blood pressure, for 2 and 4 garlic capsules were different deviation / 95%CI / error bars to the control allow is not significantly different or ignore no significant decrease (taking) 2 garlic capsules gives, greatest / AW, decrease in blood pressure ; ignore insignificant 6 SE for, 2 garlic capsules and control, do not overlap (at 8 weeks and 12 weeks) therefore (mean resting systolic blood pressure may be) significantly 6 ignore standard different deviation / 95%CI / error bars or allow significant, decrease / AW SE for, 4 garlic capsules and control, do not overlap (at 8 weeks) therefore (implies a difference) (mean resting systolic blood pressure may be) significantly different ; allow is significantly different ignore ‘results are significant’ 2(c)(iii) any two from: 2 ignore ref. to standard deviations 1 (data) not normally distributed ; (because the SDs are approximately the same) R standard deviations are 2 four / more than two, means to compare ; different / data is not continuous 3 more than one mean per group / means change over time ; ignore fewer than 30 values © Cambridge University Press & Assessment 2026 Page 13 of 14 Trace ID: PC-6F815CCF34 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/5a3 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/53 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 2(d) any two from: 2 ignore repeat unqualified 1 larger sample size / study more than 84 people ; 2 longer investigation / study for more than 12 weeks ; 3 standardise, age / sex / diet / smoking status / alcohol consumption / other 3 A exclude those already taking medication taken / time of day capsule taken / AW ; meds for blood pressure ignore ref. to take 3 garlic capsules 4 measurements of diastolic blood pressure ; 5 ref. to standardise measurement of blood pressure ; 5 A measure blood pressure, at same time of day / at same location / same body position © Cambridge University Press & Assessment 2026 Page 14 of 14 Trace ID: PC-6F815CCF34 Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/5a3 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/53 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/

1(a) pigment 1: carotene ; 2 pigment 2: chlorophyll a ; 1(b)(i) any eight from: 8 allow standardised / controlled / fixed / constant as AW for same ignore known allow: direct sunlight = high light intensity shade = low light intensity collect leaves from stinging nettles growing in direct sunlight and in the shade: ignore no light / dark as AW for shade 1 method to select plants growing in direct sunlight and in the shade, using, random / systematic, sampling 1 should be 2 or more different plants or allow sample plants at, method to grow plants in direct sunlight and in the shade ; coordinates / grid / quadrats, chosen using a random number generator allow sample plants at a fixed / set distance along a, line / transect R throwing quadrats ignore quadrants allow lab-based method to grow plants in different light intensities (e.g. lamp at different distances) ignore ref to controlled variables ignore ref to time (for growth) but R if less than 24 hours 2 collect / cut / AW, leaves (from plants growing) in direct sunlight and in the 2 allow if leaves are from (different parts) shade ; of same plant (in different light intensities) © Cambridge University Press & Assessment 2026 Page 8 of 18 Trace ID: PC-694F6C5F2D Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. 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Licensed for hosting on papacambridge.com only. P97a00p/5a4 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/54 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 1(b)(i) 9 remove, chromatogram / AW, from beaker / solvent, 9 allow paper / (TLC) plate as AW for when solvent front is close to top (of paper / TLC plate) chromatogram or allow solvent / front as AW for solvent front after, set / stated, time ; ignore time if stated 10 (use pencil to) mark position of solvent front (before the solvent evaporates) ; 10 A take photo of chromatogram collect the data needed to identify each chloroplast pigment: 11 use a, ruler / AW, to, measure / note / record / AW, distance (from origin) to solvent front and distance (from origin) to, (each) spot / pigment / AW ; 11 ignore calculate R / R formula f f 12 idea of measure to the, centre / AW, of (each) spot of pigment ; unqualified ignore ref. to repeats 13 note / record / AW, colour of each spot of pigment; © Cambridge University Press & Assessment 2026 Page 10 of 18 Trace ID: PC-694F6C5F2D Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/5a4 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/54 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 1(b)(ii) hazard and risk and precaution ; 1 ignore low / medium / high, risk R no risk ignore harmful unqualified hazard risk preca ution ignore plants / stinging nettles / trichomes environment / getting lost / trip (wear protective) as hazard woodland hazard shoes / clothes / PPE ignore wearing gloves as a precaution / gardens / injury / farmland stay, in a group / with allow check yourself / immunise (as / AW expert / ranger precaution against ticks) use GPS allow epipen as precaution for allergies animals allergy / irritation / injur (wear protective) NOTE: allow away from body y shoes / clothing / PPE ignore cuts clothing / AW ignore cutting leaves / plant unqualified for stay, with expert / ranger hazard pollen / spores allergy / irritation mask / goggles / PPE ignore water as hazard take, anti-histamines ignore allergy / corrosive as risk for solvent / hayfever medication knife / scalpel cuts / injury cut away from the hand / AW (skin / hand / AW) or cut onto a, board / tile / AW (named) flammable no naked flames solvent fumes / vapour: use fume cupboard / use irritant / toxic well-ventilated room / keep damage to, containers covered / safety lungs / AW glasses / goggles / mask / PPE © Cambridge University Press & Assessment 2026 Page 11 of 18 Trace ID: PC-694F6C5F2D Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. 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2(a) first experiment: 2 ignore rate of photosynthesis rate of oxygen production ; allow volume / number of moles / AW, of second experiment: oxygen produced, in a set time time taken to change colour (from blue-green to green) / rate of DCPIP reduction ; ignore rate of NADP reduction 2(b) any one from: 1 ignore light intensity / temperature ignore volume (of solutions) ignore ref to colour ignore pH ignore carbon dioxide ignore stirring R concentration of sodium chloride 1 mass / concentration, of A. doliolum (cells in suspension) ; 1 allow A. doliolum / cells / Anabaena / prokaryote 2 concentration of enzyme ; as AW for A. doliolum cells ignore size 3 time, in enzyme solution / for hydrolysis of cell walls ; 3 ignore time unqualified R time taken to change colour 4 concentration of DCPIP ; 2(c) idea that (enzyme partially hydrolysed the bacterial cell walls so): 1 ignore ref. to sodium chloride / NaCl ignore ref. to NADP / H+ (more) DCPIP can, diffuse / enter, cells ignore enter chloroplast or diffusion / AW, of DCPIP (into cells) is, faster / AW or ignore easier permeability of cell wall increases ; © Cambridge University Press & Assessment 2026 Page 12 of 18 Trace ID: PC-694F6C5F2D Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/5a4 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/54 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 2(d) Table 2.1 completed with correct volumes ; 2 ignore decimals concentration of volume of stock (volume) water ; ignore working / C V = C V sodium chloride solution of sodium (/ cm3) 1 1 2 2 solution chloride / moldm-3 / cm3 0.25 10 10 0.20 8 12 0.15 6 14 0.10 4 16 0.05 2 18 0.00 0 20 © Cambridge University Press & Assessment 2026 Page 13 of 18 Trace ID: PC-694F6C5F2D Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/5a4 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/54 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 2(e) 2 ignore rate of photosynthesis unqualified ignore first / second experiment allow NaCl as AW for sodium chloride allow peak / optimum / greatest / maximum as AW for highest 1 highest / AW, (mean rate of) oxygen production is at a lower sodium ignore any comparison between y-axis chloride concentration than the highest AW, (mean rate of) DCPIP reduction ; values ora ignore y-axis data quotes ignore ref. to lines crossing ignore comparisons between gradients of lines (e.g. fast decrease / slight decrease) 2 highest / AW, (mean rate of) oxygen production is at 0.10 moldm–3 2 need units for concentration at least (sodium chloride) once and highest / optimum / AW, (mean rate of) DCPIP reduction is at 0.20 moldm–3 (sodium chloride) ; © Cambridge University Press & Assessment 2026 Page 14 of 18 Trace ID: PC-694F6C5F2D Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/5a4 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/54 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/

3(a) any two from: 2 allow fungus as AW for M. pingshaense allow A. coluzzii / Anopheles as AW for mosquitoes allow uninfected A. coluzzii as AW for control 1 (infection / treatment with) GM M. pingshaense, reduces / AW, the 1 ignore ref. to non-GM M. pingshaense (percentage of mosquitoes that) produce eggs ; ignore kills mosquitoes 2 error bars for control and GM (M. pingshaense) do not overlap, 2 allow (95%) confidence therefore (mean percentage of mosquitoes that produce eggs) is significantly intervals / CI / standard error bars as different ; AW for error bars ignore standard deviation / SE / standard error unqualified allow significant, decrease / AW (implies a difference) allow may be significantly different ignore ‘results are significant’ 3 conclusion for non-GM M. pingshaense: 3 allow (95%) confidence intervals / CI / standard error bars as AW for error bars error bars for non-GM (M. pingshaense) and control overlap, therefore (mean percentage of mosquitoes that produce eggs) (may be) not significantly ignore standard deviation / SE / standard different error unqualified or error bars for non-GM (M. pingshaense) and GM (M. pingshaense) overlap, allow is not significantly different therefore (mean percentage of mosquitoes that produce eggs) (may be) not ignore no significant decrease significantly different ignore insignificant or large / AW, error bar for non-GM (M. pingshaense) shows that (calculated / sample) mean is (likely to be) further from the, true / actual, mean or ignore data / results / values as AW for idea that error bar, for non-GM (M. pingshaense) are, large / AW, and the mean mean is less reliable ; ignore accurate / valid / precise © Cambridge University Press & Assessment 2026 Page 15 of 18 Trace ID: PC-694F6C5F2D Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/5a4 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/54 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 3(b)(i) idea of placing a, net / glasshouse / AW, over the experimental area ; 1 allow web / mesh ignore (use) black fabric / curtain ignore close doors / windows of hut ignore insect repellent R insecticide 3(b)(ii) 1. Table 3.2 completed and correct values of (O–E)2 / E ; 2. (2 =) 2390 when rounded to 3 significant figures ; 3. (2 =) 2390 ; must be to 3 significant figures repeat O E O - E (O – E) 2 © Cambridge University Press & Assessment 2026 Page 16 of 18 ( O − E E ) 2 3 1. A as fractions / any decimal places 2. correct value of 2 to 3 or more sig figs use calculation guidance – give mp2 if their value of 2 rounds to 2390 (e.g. 2389.5, 2389.4, 2389) 2. and 3. allow ecf to max 2 from incorrect 1 13 1396 –1383 1912689 1370.1 (O–E)2/E 2 61 731 –670 448900 614.1 3 12 429 –417 173889 405.3 total: 2390 Trace ID: PC-694F6C5F2D Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. Licensed for hosting on papacambridge.com only. P97a00p/5a4 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/54 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 3(b)(iii) critical value: 1 allow critical value from table (e.g. 5.991 (p = 0.05 and df = 2) underlined / circled) allow 9.210 (p = 0.01 and df = 2) and explanation: yes / student was correct / reject null hypothesis / difference is significant allow ecf if incorrect 2 and calculated value / 2 / 2390, is greater than, critical value / 5.991 ; ora must give correct statistics for ecf: e.g. calculated value, is less than 5.991 and null hypothesis is accepted / student is incorrect 3(c) 4 allow fungus as AW for (GM) M. supports the conclusion: pingshaense allow A. coluzzii / Anopheles as AW for using Table 3.1: mosquitoes 1 (total) number of, A. coluzzii / mosquitoes is, lower / AW, with (GM) M. pingshaense ; ora 1 ignore ref. to egg production / reproduction 2 ignore reject null hypothesis using calculated value of 2: A significant decrease 2 there is a significant difference ; R correlation / relationship A less than, 5% / 0.05 / 1% / 0.01, probability that, difference is due to chance A ora greater than, 95% / 0.95 / 99% / 0.99, probability that difference is not due to chance ecf from incorrect 2 A ecf there is no significant difference (if calculated value of 2, is less than 5.991) © Cambridge University Press & Assessment 2026 Page 17 of 18 Trace ID: PC-694F6C5F2D Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. 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P97a00p/5a4 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/54 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 3(c) further information needed (max 3): ignore repeat investigation unqualified ignore larger sample size ignore do a control ignore ref. to statistical test ignore do investigation in other areas / countries ignore ref. to cost 3 ignore longer time unqualified 3 carry out investigation in other years ; ignore carry out investigation in other seasons 4 carry out investigation with other species of (Anopheles) mosquito ; 4 allow other types / varieties / AW, of (Anopheles) mosquito 5 idea of checking if, (GM) M. pingshaense could be, harmful / toxic / AW, to 5 and 6 ignore (GM) M. pingshaense humans ; could be harmful unqualified 6 idea of checking if (GM) M. pingshaense could be harmful / toxic / AW, to, livestock / ecosystems / biodiversity / (native) species / AW ; 7 idea of checking if, A. coluzzii / mosquitoes, become resistant to GM M. pingshaense ; 8 idea of checking how long (GM) M. pingshaense survives (on the black 8 A checking how often (GM) M. cotton fabric) ; pingshaense should be applied (to the black cotton fabric) © Cambridge University Press & Assessment 2026 Page 18 of 18 Trace ID: PC-694F6C5F2D Re-uploading, mirroring or re-hosting this file on any other website or domain is unauthorised and traceable. 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