Selection and evolution

1(a) any two from: 2 1 predation / fishing ; 2 food qualified ; e.g. competition / limited amount 3 disease ; 4 AVP ; e.g. idea that birth rate and death rate are roughly equal 1(b) 1 organisms have changed over time ; 2 any one from: 2 ref. to natural selection / selective advantage for survival / survival of the fittest ; 3 ref. to long period of time ; 4 ref. to variation ; 1(c) any three from: 3 1 as the generation time increases, the rate of evolution decreases / relationship is inversely proportional / AW ; ora 2 not linear / exponential / decreasing gradient ; 3 (longer generation time) so less, reproduction / DNA replication ; ora 4 ref. to fewer mutations ; ora 5 idea of (so) less chance of evolution ; ora mp5 must be linked to mp3 or mp4 © UCLES 2021 Page 6 of 22 1(d) any three from: 3 1 well adapted to their environment ; 2 environment / selection pressures, stayed, constant / stable ; ora 3 mutations qualified ; e.g. fewer / not selected for / low rate 4 AVP ; e.g. no natural predators / cannot migrate / no separation of populations (for speciation to occur) Question Answer Marks

8(a)(i) artificial selection ; 1 8(a)(ii) any five from: 5 1 (humans) choose / cross / breed from, females / cows / cattle, with, good / high, milk yield ; 2 (humans) choose / cross / breed from, males / bulls, with, mother / sisters / daughters, with, good / high, milk yield ; 3 (humans) choose / cross / breed from, desirable offspring ; 4 continue / repeat, for (several) generations ; 5 allele(s) for, high milk yield / desired trait, passed on ; 6 increase in frequency of, good / best / high yield, allele(s) ; 7 artificial insemination / A.I. ; 8 AVP ; 8(b) any three from: 3 1 mean / mode / median / average / intermediate, selected against / not favoured / less fit / die ; 2 (both) extremes, selected for / favoured / more fit / survive / reproduce ; 3 bimodal distribution ; 4 diversifying selection ; 5 causes / maintains, polymorphism / genetic diversity ; © UCLES 2021 Page 13 of 16

10(a) any eight from: 8 1 named geographical barrier ; e.g. river / mountain / sea / lake 2 population, separated / divided (into two) ; 3 no, mating / breeding / gene flow, between, populations / groups ; 4 different (named), selection pressures / environments / conditions ; 5 different mutations ; 6 individuals with beneficial alleles, are selected for / survive / reproduce / have a selective advantage ; 7 genetic drift / founder effect ; 8 change in, allele frequency / gene pool ; 9 over a long time / many generations ; 10 can no longer (successfully), interbreed / reproduce / produce fertile offspring, with, old / original / other, population / species ; 11 allopatric (speciation) ; 10(b) any seven from: 7 1 environment changes ; 2 species cannot adapt (fast enough) ; 3 climate / temperature / sea level, change ; 4 extinct species / species at risk ; 5 competition / predation / disease, from, new / introduced / alien / invasive, species ; 6 extinct species / species at risk ; 7 (named) habitat, degradation / loss ; 8 extinct species / species at risk ; 9 hunting by humans / poaching / (over)fishing ; 10 extinct species / species at risk ; 11 AVP ; 12 extinct species / species at risk ; © UCLES 2021 Page 16 of 16

8(a) 1 different alleles at a single gene locus have small effects (on the phenotype) ; 3 2 different genes may have an, additive / combined, effect (on the phenotype) ; 3 ref. to multiple genes / polygenes / description ; 8(b) any two from: 2 1 quantity / availability, of, food / nutrients ; A competition for food 2 quality of food / malnutrition ; 3 disease ; 4 temperature ; © UCLES 2021 Page 17 of 22 8(c) any four from: 4 1 humans apply selection pressure ; 2 select parents that show desired characteristic ; R gene / allele 3 breed these parents together ; R IVF ignore AI 4 select offspring with desired characteristics ; 5 breed selected offspring ; 6 repeating over many generations ; 7 AVP ; e.g. some outbreeding required to avoid, inbreeding depression / combining harmful recessive alleles © UCLES 2021 Page 18 of 22

8(a) 1 individuals in a population with, intermediate phenotypes / AW, more likely to, survive / reproduce 3 or individuals in a population with, intermediate phenotypes / AW, are selected for ; 2 individuals in a population with extreme phenotypes, die or individuals in a population with extreme phenotypes are selected against ; 3 no change in environment ; 8(b)(i) poor camouflage / AW ; 2 predation ; 8(b)(ii) narrower curve ; 2 curve to right with apex at dark brown ; 8(c) 1 random / chance, change in allele frequency 2 or description of alleles not passed onto the next generation ; 2 larger influence in smaller population / AW ; © UCLES 2021 Page 18 of 22

8 any five from: 5 1 due to (Great Central) Valley / during migration, populations / they, are separated / geographically isolated ; 2 no, mating / breeding / gene flow, between, them / populations ; 3 different (named), selection pressures / environments / conditions / habitats ; 4 different mutations ; 5 natural selection ; 6 genetic drift / founder effect ; 7 change in allele frequency OR change in / different, gene pool ; 8 leads to different, morphological / behavioural / biochemical / physiological, features ; 9 allopatric speciation ; © UCLES 2021 Page 17 of 21

8 any five from: 5 1 geographical, isolation / separation or ref. to Panama / land, separating populations ; 2 no, gene flow / interbreeding, between both populations ; 3 different, environmental conditions / selection pressures ; 4 random / different, mutations ; 5 (different), alleles selected for / gene pool / changes in allele frequency ; 6 over time populations have different, morphological / physiological / behavioural, features ; 7 eventually reproductive isolation occurs ; 8 allopatric speciation ; © UCLES 2021 Page 20 of 24

8 any five from: 5 1 due to (Great Central) Valley / during migration, populations / they, are separated / geographically isolated ; 2 no, mating / breeding / gene flow, between, them / populations ; 3 different (named), selection pressures / environments / conditions / habitats ; 4 different mutations ; 5 natural selection ; 6 genetic drift / founder effect ; 7 change in allele frequency OR change in / different, gene pool ; 8 leads to different, morphological / behavioural / biochemical / physiological, features ; 9 allopatric speciation ; © UCLES 2021 Page 17 of 21

1(a)(i) any two from: 2 1 high birth rate / short generation time / AW ; 2 few / no, predators ; 3 little competition ; 4 plenty of food available / wide range of food types eaten / omnivore ; 5 no / fewer, diseases ; 6 well adapted / no selection pressures against them ; A description 1(a)(ii) any three from: 3 1 directional selection ; 2 blonde spines have a selective advantage / described / AW ; 3 allele frequency for blonde spines increases / increased homozygosity (for recessive or blonde allele) ; 4 inbreeding ; 5 small gene pool (at start) / little genetic variation ; 6 founder effect / genetic drift / bottleneck effect ; A description © UCLES 2022 Page 5 of 22 1(b) any four from: 4 accept local for native throughout because alien species: 1 compete with native species ; 2 for, food / same niche / light / resources or reduce food source of native species ; 3 feed on / predators of, native species ; 4 can cause extinction in native species ; 5 can breed more successfully than native species ; 6 often have no, natural predator / grazers ; 7 may disrupt, habitats / ecosystems / food webs / food chains ; ignore environment 8 cause reduction in biodiversity ; 9 may introduce disease ; © UCLES 2022 Page 6 of 22

8(a) 1 sympatric ; 3 any two from: 2 no geographical barrier / not geographically isolated ; 3 ref. to behavioural isolation / described ; 4 ref. to reproductive isolation / described ; © UCLES 2022 Page 18 of 22 8(b) any three from: 3 ora in terms of easier for crop yields 1 longer time to, grow / mature ; 2 fewer offspring (per cross / AW) ; 3 feature can only be measured in, about 50% of offspring / females ; 4 milk yield must be measured over period of time ; 5 ref. to ethical issues ; 6 ref. to difficulty in identifying suitable males for use in crosses ; 7 cattle require more, care / support or more expensive ; 8 AVP ; e.g. more dangerous to carry out breeding of large cattle 8(c) any two from: 2 1 mass / quantity / size ; 2 disease resistance ; 3 resistance to, insects / pests ; 4 rate of growth ; 5 drought resistance ; 6 resistance to herbicides ; 7 AVP ; e.g. resistance to, flooding / wind © UCLES 2022 Page 19 of 22

5(a) any four from: 4 1 geographical isolation / allopatric (sub)speciation ; 2 little / no, (inter)breeding / gene flow, between populations ; 3 different, selection / selective, pressures (on each population) ; 4 different mutations (in each population) ; 5 adaptation to, environment / habitat / climate / food / vegetation ; 6 gives, morphological / ecological / behavioural, differences ; 5(b)(i) any two from: 2 1 natural / selection ; 2 dark, colour / fur, selected for / adaptive / good, in woods / warm / shade ; 3 camouflage / right colour, protects against, (named) predators ; 5(b)(ii) any two from: 2 1 genetic drift / not natural selection ; 2 as small size in north not, adaptive / beneficial ; 3 (small) lose heat faster / harder to keep warm ; 4 smaller fat reserves not good with unstable food supply ; 5 less food in north reduces, growth / size ; 6 AVP ; 5(c) any three from: 3 1 (hybrid populations have) more, genetic variation / alleles ; 2 genes / mutations / alleles, from both (sub)species ; 3 more potential to adapt / can adapt better (in future) ; 4 genes / alleles, for migration may let some find new habitats ; 5 have, genes / alleles, for, warm and cold / different temperatures ; © UCLES 2022 Page 12 of 19 5(d) any three from: 3 1 obtain, blood / tissue / DNA ; 2 (test) both (sub)species / migratory and non-migratory ; 3 use PCR to amplify DNA ; 4 use, (gel) electrophoresis / DNA profiling / DNA fingerprinting, and EITHER compare results OR to see genetic, differences / changes ; 5 sequence DNA and, count / identify, differences / changes ; 6 check / test, for correlation between, DNA / genetic profiles / alleles / markers, and migratory behaviour ; 7 use, databases / bioinformatics, to find, name / role of, genes / sequences (that, differ / are associated with migration) ; 8 AVP ; Question Answer Marks

5(a) any four from: 4 1 geographical isolation / barrier qualified ; Ignore separation 2 no, interbreeding / gene flow (between European and American populations) ; Ignore reproductive isolation here (needs to be late on in process) 3 different, environmental (conditions) / selection pressures ; 4 random / different, mutations ; 5 different, alleles selected for / gene pool / changes in allele frequency ; 6 populations have different, morphological / physiological / behavioural, features ; 7 after, a long time / many generations, reproductive isolation occurs / cannot interbreed to produce fertile offspring ; 8 allopatric (speciation) ; © UCLES 2022 Page 12 of 22 5(b) any three from: 3 1 not possible / difficult, to come to a (reliable) conclusion ; A AW 2 small difference in height / heights are similar (so natural selection not more important than genetic drift) ; 3 taller / lighter, bison could be an advantage in reaching higher vegetation (so natural selection may be important) ; 4 difference in mass, may not be due to genetic factors / may be due to nutrient value of diet / may be due to quantity of food, (so natural selection may not be important) ; 5 genetic drift (in ancestral population) may have led to, European bison being, taller / lighter or American bison being, shorter / heavier ; 5(c) 1 European bison has a, close / recent / common, ancestor with that of, cattle / Bos 3 or European bison is more closely related to, cattle / Bos, (than to American bison) ; 2 European bison may have interbred with, cattle / Bos ; 3 mitochondria are inherited from, mother / female ; © UCLES 2022 Page 13 of 22 5(d) any four from: 4 1 obtain / use, blood / cells / tissue / DNA ; 2 from, both species / cattle and European bison ; 3 use PCR to, replicate / amplify, DNA ; 4 use, electrophoresis (described) / DNA profiling / DNA fingerprinting, to see genetic differences / compare the banding (patterns) ; 5 sequence DNA and, count / identify, (percentage) difference / similarity or sequence DNA and compare the, nucleotide / base, sequence ; 6 use, genome / DNA, microarray ; R for gene expression 7 ref. to bioinformatics / database / (computer) software ; 8 similarity indicates, close relationship / more recent split ; 9 if they can breed to produce (viable) offspring (they are closely related) ; © UCLES 2022 Page 14 of 22

5(a) any four from: 4 1 (partial) geographical, isolation / separation / barrier; 2 little / no, interbreeding / gene flow (between puma populations) ; 3 different, environmental (conditions) / selection pressures ; 4 e.g. climate / vegetation / habitat / available prey ; 5 random / different, mutations ; 6 different, alleles selected for / gene pool / changes in allele frequency ; 7 allopatric (sub speciation) ; 5(b) any three from: 3 1 obtain, blood / cells / tissue / DNA ; 2 from two (or more) individuals, at different locations / across range / from North and South America / from the different subspecies ; 3 use PCR to, replicate / amplify DNA ; 4 use, gel electrophoresis / DNA profiling / DNA fingerprinting ; 5 sequencing of DNA ; 6 use, genome / DNA, microarray ; R for gene expression 7 ref. to bioinformatics / database / (computer) software ; 8 compare similarity (of different sub species); © UCLES 2022 Page 13 of 23 5(c)(i) any two from: 2 discontinuous (no mark) because: 1 feature either present or absent ; 2 categoric ; 3 no range / no intermediates or qualitative data or does not show a normal distribution curve; 5(c)(ii) any three from: 3 1 these features are controlled by, genes / alleles ; 2 ref. to genetic drift ; 3 (population went through a) bottleneck ; 4 low / reduced, number of alleles / genetic diversity / genetic variation / genetic polymorphism (in population) ; A some alleles lost 5 inbreeding ; 6 low / reduced, heterozygosity or high / increased, homozygosity ; 7 rare / deleterious, recessive alleles show their effects (as homozygous) ; 8 AVP ; e.g. number of breeding males reduced even more as some have, non-functional / undescended, testes © UCLES 2022 Page 14 of 23 5(c)(iii) any two from: 2 1 Texas is closest to Florida ; ora A / B, distant / far away 2 (Texas and Florida pumas) are most closely-related / most genetically similar share most recent common ancestor ; ora A / B 3 Texas and Florida, climates / habitats / environment, are similar ; ora for A / B 4 AVP ; e.g. Texas has too many pumas

5(a) any five from: 5 1 evolution / speciation / natural selection ; 2 random / spontaneous ; 3 mutations (occurred) ; 4 adapting some plants to, alpine habitat / high altitude / mountains ; 5 (in this habitat) these plants, survived / were selected for ; 6 (selection pressure is / must resist) cold / strong winds / thin soil ; 7 alleles for alpine features passed to offspring ; 8 change in, allele frequency / gene pool (of population) ; 9 population become, morphologically / physiologically / biochemically, different ; 10 less, herbivores / competition, in new niche ; 11 AVP ; 5(b)(i) any three from: 3 1 time period = from 0.95 million years (to present) ; 2 mountains high enough to exceed treeline ; 3 this provides alpine, habitat / region / niches ; © UCLES 2022 Page 12 of 19 5(b)(ii) any two from: 2 1 compare / find similarities in / find differences in, DNA ; 2 of alpine species and related (lowland) species ; 3 find (time) when species, evolved / separated / diverged / speciated ; 4 many, DNA / base / nucleotide, differences / changes / mutations, means they, separated a long time ago / have a distant common ancestor ; 5 AVP ; © UCLES 2022 Page 13 of 19

6(a) any four from: 4 1 breed / cross, plants with desired (named) characteristics ; 2 breed, better / best, offspring, repeatedly / for many generations ; 3 (correct ref. to) inbreeding / line breeding ; 4 (correct ref. to) hybridisation / outbreeding / outcrossing ; 5 (gives) hybrid vigour / heterosis / outbreeding enhancement (in offspring) ; 6 F1 have, same genotype / uniform phenotype ; 7 AVP ; 6(b)(i) any one from: 1 1 (IR8) less likely to, fall over / lodge / collapse ; 2 (IR8) higher proportion / more, of plant is, edible / grain ; 6(b)(ii) check for, genes / alleles / DNA, for high yield and flood tolerance ; 1 6(b)(iii) any one from: 1 1 to, maintain high yield / increase yield / give higher yield ; 2 to avoid inbreeding depression or to maintain, hybrid vigour / heterosis ; © UCLES 2022 Page 14 of 19 6(c)(ii) any four from: 4 variety A: 1 gibberellin binds to, receptor / GID1 ; 2 DELLA protein breaks down ; 3 PIF / transcription factor (released) to, bind to DNA / transcribe genes ; 4 stem / internode / cell, elongation / growth, occurs ; 5 A, is lele / has no Le allele ; 6 A does not produce its own (active) gibberellin ; variety B: 7 does not respond to / no effect from, gibberellin ; 8 lacks / has non-functional, gibberellin receptor ; 6(c)(ii) any two from: 2 1 (BZR1) binds to promoter ; 2 to switch gene on / so gene is expressed / allow transcription ; 3 allows binding of RNA polymerase (to DNA / promoter) ; © UCLES 2022 Page 15 of 19

5(a) 1 at 95 °C, (DNA) denatures / (dsDNA) splits into single strands / H bonds break ; 3 2 at 50 °C, primers, anneal / bind, (to ssDNA) ; 3 at 72 °C, complementary / second, (DNA) strand is made ; A DNA replicated / (ssDNA) is made into dsDNA 5(b) any four from 1–7: 5 1 M. pygmaea (populations) geographically isolated / separated by sea or water ; 2 M. pulvinaris (populations) geographically isolated / mountain tops separated ; M. pygmea or M. pulvinaris / South Island or Stewart Island species: 3 no / little, interbreeding / gene flow, between populations ; 4 different, selection pressures / environment ; 5 different / random, mutations ; 6 different changes in allele frequencies / different gene pools ; 7 (so) allopatric speciation could be occurring (within either species) / AW ; M. pottsiana / North Island species: 8 no geographical isolation ; 9 (so) interbreeding / gene flow, occurs, within / between, population(s) ; 10 similar, selection pressures / environment ; © UCLES 2022 Page 12 of 19 5(c) any two from: 2 1 genetic drift / bottleneck / founder effect ; 2 migration ; 3 mutation ; 4 artificial selection / selective breeding ; © UCLES 2022 Page 13 of 19

5(a) any five from: 5 1 evolution / speciation / natural selection ; 2 random / spontaneous ; 3 mutations (occurred) ; 4 adapting some plants to, alpine habitat / high altitude / mountains ; 5 (in this habitat) these plants, survived / were selected for ; 6 (selection pressure is / must resist) cold / strong winds / thin soil ; 7 alleles for alpine features passed to offspring ; 8 change in, allele frequency / gene pool (of population) ; 9 population become, morphologically / physiologically / biochemically, different ; 10 less, herbivores / competition, in new niche ; 11 AVP ; 5(b)(i) any three from: 3 1 time period = from 0.95 million years (to present) ; 2 mountains high enough to exceed treeline ; 3 this provides alpine, habitat / region / niches ; © UCLES 2022 Page 12 of 19 5(b)(ii) any two from: 2 1 compare / find similarities in / find differences in, DNA ; 2 of alpine species and related (lowland) species ; 3 find (time) when species, evolved / separated / diverged / speciated ; 4 many, DNA / base / nucleotide, differences / changes / mutations, means they, separated a long time ago / have a distant common ancestor ; 5 AVP ; © UCLES 2022 Page 13 of 19

6(a) any four from: 4 1 breed / cross, plants with desired (named) characteristics ; 2 breed, better / best, offspring, repeatedly / for many generations ; 3 (correct ref. to) inbreeding / line breeding ; 4 (correct ref. to) hybridisation / outbreeding / outcrossing ; 5 (gives) hybrid vigour / heterosis / outbreeding enhancement (in offspring) ; 6 F1 have, same genotype / uniform phenotype ; 7 AVP ; 6(b)(i) any one from: 1 1 (IR8) less likely to, fall over / lodge / collapse ; 2 (IR8) higher proportion / more, of plant is, edible / grain ; 6(b)(ii) check for, genes / alleles / DNA, for high yield and flood tolerance ; 1 6(b)(iii) any one from: 1 1 to, maintain high yield / increase yield / give higher yield ; 2 to avoid inbreeding depression or to maintain, hybrid vigour / heterosis ; © UCLES 2022 Page 14 of 19 6(c)(ii) any four from: 4 variety A: 1 gibberellin binds to, receptor / GID1 ; 2 DELLA protein breaks down ; 3 PIF / transcription factor (released) to, bind to DNA / transcribe genes ; 4 stem / internode / cell, elongation / growth, occurs ; 5 A, is lele / has no Le allele ; 6 A does not produce its own (active) gibberellin ; variety B: 7 does not respond to / no effect from, gibberellin ; 8 lacks / has non-functional, gibberellin receptor ; 6(c)(ii) any two from: 2 1 (BZR1) binds to promoter ; 2 to switch gene on / so gene is expressed / allow transcription ; 3 allows binding of RNA polymerase (to DNA / promoter) ; © UCLES 2022 Page 15 of 19

3(a)(i) any two from: 2 1 oxygen / gas, supply / diffusion / transfer ; 2 to, submerged / underwater, cells / tissues / roots ; 3 for aerobic respiration ; 3(a)(ii) any one from: 1 1 anaerobic respiration / ethanol fermentation ; 2 high tolerance to, alcohol / ethanol OR high / more, alcohol / ethanol, dehydrogenase ; 3(a)(iii) any three from: 3 1 cross / breed, rice / plants / individuals, with fast-growing stems ; 2 select / choose, and breed offspring with fast-growing stems ; 3 repeat (crossing and selection) over generations ; 4 hybridise / outbreed / out-cross OR avoid / reduce, inbreeding depression / background selection ; 3(a)(iv) any three from: 3 1 auxin increases stem, growth / length / height ; 2 protons / hydrogen ions / H+, move / pumped, into cell wall(s) ; 3 (expansins) break, links / (H) bonds, between cellulose, molecules / microfibrils ; 4 water enters cell(s) by osmosis ; 5 cells, elongate / expand / increase in volume / swell ; 3(b) any three from: 3 1 O. nivara, adapted to / selected for, dry / drier, conditions / habitats ; 2 different habitats / ecological isolation ; 3 prevent interbreeding / no gene flow / reproductive isolation ; 4 polyploidy / auto(poly)ploidy ; 5 AVP ; © UCLES 2023 Page 10 of 17

3(a)(i) discontinuous ; 1 3(a)(ii) any two from: 2 1 mutation A description or (formation of a) new allele ; 2 change in, environment / selection pressure ; A description 3 cross pollination / cross breeding / hybridisation ; 4 new allele combination / codominant alleles together ; 3(a)(iii) any three from: 3 both types 1 (inter)breed to produce fertile offspring / not reproductively isolated ; 2 occupy the same niche ; 3 same / similar, morphology / physiology / biochemistry ; A description I fruit shape 4 have, similar / same, genes / DNA sequences / genomes ; 5 similar / same, proteins / amino acid sequences ; © UCLES 2023 Page 10 of 25 3(b) any five from: 5 1 (populations) can produce many offspring / AW ; 2 genetic variation occurs (in populations) / described ; 3 ref. mutations / sexual reproduction / gamete formation / random fertilisation ; 4 ref. competition qualified ; e.g. mates / food / resources 5 ref. selection pressure ; 6 some individuals have advantageous, adaptations / phenotype / traits / AW ; 7 (so) they, survive / reproduce / have a selective advantage ; 8 (so) pass on their advantageous allele(s) ; 9 (so) the (advantageous) allele frequency increases ; © UCLES 2023 Page 11 of 25

5(a)(i) q2 = 0.6 3 or q = √ 0.6 or q = 0.775 or p = 0.225 ; 2pq = 2  0.225  0.775 or 0.35 ; allow ecf from mp1 35 % ; allow ecf from mp2 5(a)(ii) any four from: 4 1 no migration or no flow of, alleles / genes, into / out of, the population ; 2 population is isolated / described ; e.g. separated by geographical barrier I ref to island alone 3 random mating is occurring ; 4 rats move around island / AW ; 5 large population ; 6 rats have high reproductive rate / no predators ; 7 rats are diploid ; 8 have two different alleles (for the gene) / heterozygous ; © UCLES 2023 Page 15 of 25 5(b) any three from: 3 1 new allele initially found in heterozygotes ; dominant advantageous allele 2 (new) dominant allele is, expressed in heterozygote / always expressed ; 3 selection can act on individuals with dominant allele straight away / AW ; recessive advantageous allele 4 (new) recessive allele is not expressed, in heterozygote / due to dominant allele or recessive allele only expressed in homozygous recessive (genotype) ; 5 selection can only act on individuals who are homozygous recessive ; 6 it takes time for homozygous recessive (genotype) to occur / AW ; © UCLES 2023 Page 16 of 25

2 any seven from: 7 1 (random) mutation ; 2 directional selection ; 3 antibiotic acts as selection pressure / AW ; 4 bacteria with, mutation / gene / allele, (that codes for antibiotic resistance), have selective advantage ; 5 (so) survive / reproduce ; 6 ref. binary fission / asexual reproduction / vertical transmission ; 7 ref. transduction / transformation / conjugation / horizontal transmission ; I sexual reproduction 8 (resistance) allele frequency increases / gives rise to a population of resistant bacteria ; 9 fast (evolution) due to short generation time ; 10 increased chance of resistance if people do not finish full course of antibiotics / overuse of antibiotics ; 11 AVP ; e.g. some antibiotics may act as mutagens e.g. enzymes that break down the antibiotic © UCLES 2023 Page 8 of 24

9(a)(i) any three from: 3 1 (random) mutation(s) allows detection of high frequency ; 2 selection pressure is bat (predation) ; 3 those that can detect, high frequencies / bats, survive / don’t get eaten / have selective advantage / are selected for ; 4 these, reproduce / pass on (beneficial) allele(s) ; 5 those that can detect high sounds / beneficial alleles, increase (in frequency / in population) ; 9(a)(ii) any four from: 4 1 ref. to receptor / generator, potential ; 2 vesicles of (named) neurotransmitter, move towards / fuse with, (presynaptic) membrane ; 3 (named) neurotransmitter, release / exocytosis ; 4 neurotransmitter binds to receptors on sensory neurone ; 5 Na+ / sodium, ions enter (sensory neurone) ; 6 depolarisation (of membrane of sensory neurone) ; 7 ref. to threshold potential / all-or-nothing response ; © UCLES 2023 Page 14 of 16 9(b) any three from: 3 S1 sympatric (speciation) ; S2 different mutations ; S3 gave, (named) phenotypic / behavioural, differences ; S4 which gave behavioural, isolation / separation ; S5 (leading to) inability to reproduce together / reproductive isolation / genetic isolation / no gene flow between them ; or any three from: A1 allopatric (speciation) ; A2 geographical, separation / barrier, in the past ; A3 different, mutations / selection pressures ; A4 gave, (named) phenotypic / behavioural, differences ; A5 inability to reproduce together / reproductive isolation / genetic isolation / no gene flow between them, after populations re-join ; © UCLES 2023 Page 15 of 16

3(a) any five from: 5 1 select plants (resistant to disease) / AW ; 2 by exposing plants to disease to show resistance ; 3 breed (selected plants with resistance) ; 4 plant seeds / grow offspring ; 5 select offspring with resistance and breed together ; 6 (repeat for) many generations ; 7 AVP ; e.g. named wheat disease / rust disease / mildew disease 3(b) any two from: 2 1 reduction in genetic variation / gene pool made smaller / decrease in heterozygosity / increase in homozygosity ; I loss of biodiversity 2 less hybrid vigour ; 3 inbreeding depression ; 4 harmful recessive alleles could, come together / be expressed ; 5 (population) susceptible to, environmental change / new disease ; 6 AVP ; e.g. disadvantageous traits occur / reduced fertility / susceptible to metabolic disorders Question Answer Marks

9(a)(i) any three from: 3 1 (random) mutation(s) allows detection of high frequency ; 2 selection pressure is bat (predation) ; 3 those that can detect, high frequencies / bats, survive / don’t get eaten / have selective advantage / are selected for ; 4 these, reproduce / pass on (beneficial) allele(s) ; 5 those that can detect high sounds / beneficial alleles, increase (in frequency / in population) ; 9(a)(ii) any four from: 4 1 ref. to receptor / generator, potential ; 2 vesicles of (named) neurotransmitter, move towards / fuse with, (presynaptic) membrane ; 3 (named) neurotransmitter, release / exocytosis ; 4 neurotransmitter binds to receptors on sensory neurone ; 5 Na+ / sodium, ions enter (sensory neurone) ; 6 depolarisation (of membrane of sensory neurone) ; 7 ref. to threshold potential / all-or-nothing response ; © UCLES 2023 Page 14 of 16 9(b) any three from: 3 S1 sympatric (speciation) ; S2 different mutations ; S3 gave, (named) phenotypic / behavioural, differences ; S4 which gave behavioural, isolation / separation ; S5 (leading to) inability to reproduce together / reproductive isolation / genetic isolation / no gene flow between them ; or any three from: A1 allopatric (speciation) ; A2 geographical, separation / barrier, in the past ; A3 different, mutations / selection pressures ; A4 gave, (named) phenotypic / behavioural, differences ; A5 inability to reproduce together / reproductive isolation / genetic isolation / no gene flow between them, after populations re-join ; © UCLES 2023 Page 15 of 16

5 (many) generations / (many) years / (a long) time / AW ; 6 mutations / similarities ; meiosis / crossing over / recombination ; databases ; amino acid ; microarray ; Question Answer Marks

7(a)(i) as mutation rate increases lifespan decreases ; 1 7(a)(ii) any three from: 3 1 high(er) mutation rate gives more, genetic diversity / genetic variation / alleles / chance of beneficial allele ; 2 short(er) lifespan gives more generations (per year / per unit time) ; 3 with, high(er) mutation rate / short(er) lifespan, they, adapt / evolve, better / more easily / faster ; 4 mouse (and ferret) may, adapt / evolve, faster ; 5 AVP ; © Cambridge University Press & Assessment 2024 Page 11 of 15 7(b)(i) comparison: 2 C1 genetic engineering faster / selective breeding slower ; any one reason from: R2 selective breeding occurs over (many) generations ; R3 all cows could be surrogate mothers for engineered embryos (giving large increase in allele frequency in one generation) ; R4 AVP ; 7(b)(ii) any two from: 2 1 (improve named) quality of, animal / milk ; 2 (improve) quantity / yield, of milk ; 3 AVP ; Question Answer Marks

2(a) 1 genetic / genotype / alleles 3 or example ; mutation / crossing over / independent assortment / random fertilisation / random mating 2 environmental or example ; climate / disease / food availability / soil pH / selection pressure 3 combination / interaction, of genes and environment or example ; gene (expression) is modified by environment 2(b)(i) any three from: 3 1 formation of new species from, pre-existing species / common ancestor ; 2 change in, characteristics / phenotypes ; 3 over, time / generations ; 4 natural selection ; 5 changes in, gene pools / allele frequencies or genetic drift ; © Cambridge University Press & Assessment 2024 Page 6 of 20 2(b)(ii) any three from: 3 1 compare sequences (of DNA) ; 2 the more similar the sequences the more, closely related the species / recent the common ancestor ; ora 3 over time mutations accumulate or less time fewer mutations occurred ; 4 ref. to bioinformatics / software / database ; 5 AVP ; e.g. molecular clock / constant rate of mutation e.g. mtDNA has no crossing over e.g. the percentage similarity can be used to build a phylogenetic tree © Cambridge University Press & Assessment 2024 Page 7 of 20

7(a)(i) any three from: 3 1 disruptive / diversifying (selection) ; 2 extremes / carnivores and detritus feeders, survive / are selected for and intermediates, die / are selected against ; 3 high / intense, competition ; 4 intermediates, outcompeted for / don’t get enough, detritus / algae, and, (fairy) shrimp / small animals ; 5 lack of / limited, food is selection pressure ; 6 AVP ; © Cambridge University Press & Assessment 2024 Page 11 of 15 7(a)(ii) any three from: 3 1 stabilising (selection) ; 2 extremes / carnivores and detritus feeders, die / are selected against / are not selected for, and intermediates, survive / are selected for ; 3 low / less / prevents, competition ; 4 intermediates can eat, both types / all / a wider range, of food ; 5 greater variety in the diet improves the growth and development of (intermediate) tadpoles ; 7(a)(iii) 1 normal distribution curve ; 7(a)(iv) any two from: 2 1 new species form due to reproductive isolation ; 2 caused by, ecological / behavioural, separation / isolation / differences ; 3 in same geographical region ; 4 AVP ; 7(b) any three from: 3 1 ref. to DNA sequence (for all / three species) ; 2 find / count, nucleotide / base, differences / similarities ; 3 fewer differences means, more closely related / less time since divergence / less time to common ancestor ; 4 bioinformatics / database / software / BLAST ; 5 S. hammondii and S. bombifrons, have the fewest genetic differences / are the most genetically similar ; © Cambridge University Press & Assessment 2024 Page 12 of 15

2(a) any six from: 6 1 mutation / described ; 2 genetic drift / described ; 3 founder effect / group separated from main population to found a new population ; 4 bottleneck effect / large fall in population ; 5 natural / directional / disruptive, selection ; Ignore artificial / stabilising selection 6 migration / gene flow / interbreeding between populations ; 7 genetic recombination / linkage groups broken / crossing over ; 8 AVP ; e.g. effect larger in small populations 2(b) any three from: 3 1 inbreeding / described ; 2 produces homozygous plants / increases homozygosity ; 3 outbreeding / described ; 4 hybridisation / producing a hybrid ; 5 hybrids / offspring / F1, are (all) heterozygotes / have increased heterozygosity ; © Cambridge University Press & Assessment 2024 Page 6 of 19

7(a)(i) any three from: 3 1 disruptive / diversifying (selection) ; 2 extremes / carnivores and detritus feeders, survive / are selected for and intermediates, die / are selected against ; 3 high / intense, competition ; 4 intermediates, outcompeted for / don’t get enough, detritus / algae, and, (fairy) shrimp / small animals ; 5 lack of / limited, food is selection pressure ; 6 AVP ; © Cambridge University Press & Assessment 2024 Page 11 of 15 7(a)(ii) any three from: 3 1 stabilising (selection) ; 2 extremes / carnivores and detritus feeders, die / are selected against / are not selected for, and intermediates, survive / are selected for ; 3 low / less / prevents, competition ; 4 intermediates can eat, both types / all / a wider range, of food ; 5 greater variety in the diet improves the growth and development of (intermediate) tadpoles ; 7(a)(iii) 1 normal distribution curve ; 7(a)(iv) any two from: 2 1 new species form due to reproductive isolation ; 2 caused by, ecological / behavioural, separation / isolation / differences ; 3 in same geographical region ; 4 AVP ; 7(b) any three from: 3 1 ref. to DNA sequence (for all / three species) ; 2 find / count, nucleotide / base, differences / similarities ; 3 fewer differences means, more closely related / less time since divergence / less time to common ancestor ; 4 bioinformatics / database / software / BLAST ; 5 S. hammondii and S. bombifrons, have the fewest genetic differences / are the most genetically similar ; © Cambridge University Press & Assessment 2024 Page 12 of 15

2(a)(i) no geographical separation / AW ; 1 2(a)(ii) any three from: 3 1 do not, interbreed / interact / recognise each other ; 2 due to differences in, courtship / mating ; e.g. mating calls / time of year 3 different group sizes ; A description (e.g. groups vs solitary) 4 different, hunting / feeding / diets ; © Cambridge University Press & Assessment 2025 Page 6 of 19 2(b)(i) any one from: 1 1 no black patch on, top of body / back ; 2 small eyepatch ; 3 grey patch just behind dorsal fin ; 4 taller dorsal fin ; 5 larger pale patch on underside near tail ; 6 bulbous / rounded / squarer, head ; 2(b)(ii) any three from: 3 1 population, isolated from other populations / migrated ; 2 small (starting) population ; 3 small gene pool / low genetic diversity ; 4 reference to, chance / founder effect ; 5 change in allele frequency / some alleles lost ; 6 AVP ; © Cambridge University Press & Assessment 2025 Page 7 of 19 2(c) any two from: 2 1 habitat, size / destruction / disturbance / pollution ; 2 hunting (by humans) ; 3 reference to food source ; 4 measure sea temperature ; 5 genetic diversity / inbreeding ; 6/7 AVP ; ; e.g. geographical range / migration patterns / movements / disease / breeding frequency / mortality rate © Cambridge University Press & Assessment 2025 Page 8 of 19

2 any six from: 6 for either 1 random / chance (event) ; 2 not (natural) selection / not caused by selection pressure ; 3 loss of (some) alleles ; I loss of gene 4 (so) increase in frequency of, one / small number of, allele(s) or increase in homozygosity / decrease in heterozygosity ; 5 small(er) gene pool / reduction in genetic variation ; genetic drift 6 (random), fusion of gametes / mating / death of individual / mutation ; 7 larger effect in small population ; founder effect 8 small number of individuals, isolated / start new population / migrate ; 9 not all alleles present from original population / alleles not representative of original population ; 10 AVP ; e.g. ref. to bottleneck effect genetic drift occurs gradually over time founder effect is a one-off event © Cambridge University Press & Assessment 2025 Page 10 of 25

2(a)(i) any four from: 4 1 antibiotic acts as selection pressure ; 2 bacteria with antibiotic resistance (gene / allele) have selective advantage / selected for ; ora 3 bacteria with antibiotic resistance (gene / allele), survive / reproduce ; ora 4 pass on, gene / allele, (for antibiotic resistance) or increase in allele frequency (for antibiotic resistance) ; 5 ref. to plasmids ; 6 (horizontal gene transfer) by, transduction / transformation / conjugation ; 7 (horizontal gene transfer) gives rapid increase of resistant bacteria ; 2(a)(ii) any two from: 2 1 drug prevents attachment of mRNA to ribosome or drug prevents attachment of tRNA to, amino acid / ribosome / mRNA or drug binds to ribosome ; 2 protein (coded for by antibiotic resistance gene) not made ; 3 so antibiotic able to work ; © Cambridge University Press & Assessment 2025 Page 9 of 20 2(b)(i) any three from: accept ora throughout 3 natural selection 1 environment as selection pressure ; ora human acts as selection pressure 2 random mating ; ora humans select organisms to breed 3 takes more generations for effects to be seen / slower process / AW ; 4 organisms not selected for desirable phenotypes ; ora humans select features 5 can result in speciation ; 6 does not decrease, genetic diversity / hybrid vigor ; 7 inbreeding less likely to occur ; 8 greater heterozygosity ; 2(b)(ii) 1 offspring (from F1) will not be genetically similar / AW ; 2 2 offspring (from F1) will produce variation in next crop / will not be true-breeding plants; © Cambridge University Press & Assessment 2025 Page 10 of 20

4(a) any four from: 4 1 geographical, isolation / barrier (caused by the, river / canyon walls) ; 2 no gene flow between (isolated ancestral) populations ; 3 different, selection pressures / environment ; 4 different / random / independent, mutations (in each population) ; 5 different changes in allele frequencies / different gene pools / different alleles selected for ; 6 populations have different, morphological / physiological / behavioral, features ; 7 leads to, reproductive isolation / inability to interbreed (to produce fertile offspring) ; 8 allopatric speciation ; 4(b) any three from: 3 DNA sequencing ora for fossils 1 provides more information (about the whole organism) ; 2 more precise / more accurate ; 3 only a small sample of DNA is needed ; 4 can give estimate of when species diverged/how closely related two organisms are / molecular clock can estimate time of divergence ; 5 quantitative ; 6 AVP ; e.g. idea of. avoids convergent evolution problems © Cambridge University Press & Assessment 2025 Page 12 of 20 4(c) any one from: 1 not enough fossils ; small sample sizes ; DNA degrades over time ; this depends on an estimated mutation rate ; Question Answer Marks

3(a)(i) any two from: 3 q2 = 0.068 ; q = 0.260768 ; p = 0.739232 ; 2pq = 0.385536 ; and 38.6 / 39 (%) ; 3(a)(ii) any two from: 2 1 migration / AW, occurs or population is not isolated or gene flow, in / out, of population ; 2 no random mating ; 3 ref. to mutations ; 4 ref. to selection ; © Cambridge University Press & Assessment 2025 Page 14 of 27 3(b) any three from: 3 1 inbreeding ; 2 low genetic diversity / small gene pool ; 3 founder effect / bottleneck ; 4 genetic drift ; 5 tailless (cat) has a selective advantage / is selected for ; ora 6 tailless allele is dominant ; 7 allele frequency for tailless (phenotype) increases ; 3(c) any three from: 3 1 mutation results in (black) spots (phenotype / allele) ; 2 selection pressure is, ability to catch prey / AW or individuals with spots, have a selective advantage / are selected for ; ora 3 spotted (cheetahs), survive / reproduce ; ora 4 spotted, allele / mutation, passed on (to offspring) ; 5 spotted, allele / mutation, frequency increased ; © Cambridge University Press & Assessment 2025 Page 15 of 27

6(a) any three from: 3 1 self-contained / functional / specific (unit) ; 2 community / all species / all populations ; 3 ref. to interactions ; 4 abiotic / physical / non-living, and, biotic / biological / living, factors / environment ; 5 idea that linked by, energy flow / mineral cycling / food webs / food chains / nutrient cycle ; 6(b) if individuals can breed to produce fertile offspring ; 1 6(c) any three from: 3 1 allopatric speciation ; 2 geographical, isolation / barrier / separation ; 3 (so) no gene flow (between populations) ; 4 (populations have) different, mutations / advantageous alleles / alleles increase in frequency ; 5 (populations have) different, selection pressures / environments ; © Cambridge University Press & Assessment 2025 Page 20 of 27

7(a)(i) oxygenated 3 1 percentage (of root tissue as aerenchyma), remains low ; any two from: deoxygenated 2 percentage (of root tissue as aerenchyma), increases gradually / small increase, initially / until 24 hours ; 3 percentage (of root tissue as aerenchyma), larger / steeper / more rapid, increase after 24 hours ; 4 percentage (of root tissue as aerenchyma), stays the same / is constant / plateaus / levels off / reaches maximum, at, the end / 48 hours ; 5 data quote ; two times and two percentages with units time / h percentage of root tissue as aerenchyma when deoxygenated 0 0.1 – 0.3 12 0.5 – 0.6 24 0.8 36 2.5 – 2.6 48 6.5 – 6.6 60 6.5 – 6.6 7(a)(ii) 1 (aerenchyma is a tissue) with many / more / large, air spaces ; 3 2 (so) oxygen, diffuses / moves, (from the aerial parts) to root (cells) / lower parts of the plant / AW ; 3 (for) aerobic respiration ; © Cambridge University Press & Assessment 2025 Page 21 of 27 7(b) any four from: 4 1 fast(er), stem / internode, growth ; 2 (so) leaves / flowers, above water level ; 3 (so) photosynthesis / gas exchange / reproduction, can occur ; 4 (root cells) tolerant to (increased concentration of) ethanol or (root cells) have more ethanol dehydrogenase ; 5 so, anaerobic respiration / ethanol fermentation, can occur ; 6 AVP ; e.g. leaves have ridges 7 AVP ; e.g. to trap air (so oxygen can be taken in by plant) © Cambridge University Press & Assessment 2025 Page 22 of 27

4(a) 1 diploid ; 3 2 allele ; 3 dominant (allele) ; 4(b) any four from: 4 1 CDV acts as a selection pressure ; 2 DNA / allele, for black (coat) gives resistance to CDV or DNA / allele, for black (coat), gives (selective) advantage / is selected for, if / when, CDV is common / dogs are common ; in the south (context must be established at least once): 3 more CDV (infection) in wolves ; 4 black wolves, more likely to survive / have selective advantage / are selected for ; ORA greys 5 black wolves more likely to, breed / reproduce ; ORA greys 6 pass on / increase the frequency of, allele for black coat ; ORA grey 4(c) 1 positive (linear) correlation / positive relationship / direct relationship / directly proportional 4 or as % with (anti-CDV) antibodies increases the % of black wolvesincreases ; plus any three from: 2 wolves that survive CDV will, later / as a result, have antibodies ; 3 high % of antibodies show population with high level of CDV ; 4 in population with high % antibodies, grey wolves have died / more black wolves are left ; 5 gene / DNA / allele / protein, that gives black coat, helps survival / gives resistance to CDV / defends against CDV ; 6 AVP ; © Cambridge University Press & Assessment 2025 Page 12 of 18

4(a) 1 mutation ; 2 2 horizontal transmission / conjugation / transformation / transduction ; 4(b) idea of tracking, mutations / resistance genes / resistance alleles 1 or identifies mechanisms of resistance or (informed) choice / production, of antibiotic ; 4(c) any three from: 3 1 streptomycin is selection pressure ; 2 bacteria with, mutation / resistance, survive / reproduce / have a selective advantage ; ora 3 allele / gene, for resistance passed on ; 4 directional selection ; © Cambridge University Press & Assessment 2025 Page 14 of 23

4(a) 1 diploid ; 3 2 allele ; 3 dominant (allele) ; 4(b) any four from: 4 1 CDV acts as a selection pressure ; 2 DNA / allele, for black (coat) gives resistance to CDV or DNA / allele, for black (coat), gives (selective) advantage / is selected for, if / when, CDV is common / dogs are common ; in the south (context must be established at least once): 3 more CDV (infection) in wolves ; 4 black wolves, more likely to survive / have selective advantage / are selected for ; ORA greys 5 black wolves more likely to, breed / reproduce ; ORA greys 6 pass on / increase the frequency of, allele for black coat ; ORA grey 4(c) 1 positive (linear) correlation / positive relationship / direct relationship / directly proportional 4 or as % with (anti-CDV) antibodies increases the % of black wolvesincreases ; plus any three from: 2 wolves that survive CDV will, later / as a result, have antibodies ; 3 high % of antibodies show population with high level of CDV ; 4 in population with high % antibodies, grey wolves have died / more black wolves are left ; 5 gene / DNA / allele / protein, that gives black coat, helps survival / gives resistance to CDV / defends against CDV ; 6 AVP ; © Cambridge University Press & Assessment 2025 Page 12 of 18

4(a)(i) 0.3 ; 1 4(a)(ii) any four from: 4 1 genetic drift ; 2 (drift as) frequency, fluctuates / decreases and increases / shows random changes / does not change markedly in just one direction ; 3 directional selection ; 4 from (generation) 2 to 7 / at first, T decreases as, T is selected against and from (generation) 7 to 13 / later, T increased as, T is selected for; 5 may be, stabilising selection / selection for heterozygotes ; 6 (stabilising selection) keeps relative allele frequencies roughly the same ; © Cambridge University Press & Assessment 2025 Page 10 of 17 4(b) any three from: 3 1 small(er) population ; 2 causes (genetic) bottleneck (effect) ; 3 chance events, have greater relative effect on / cause larger fluctuations in, allele frequency ; 4 more likely for one allele to, replace another / go extinct / become fixed ; 5 by chance T organisms, did not mate / pass on T allele or by chance offspring with T died ; 4(c) Hardy-Weinberg ; 1 Question Answer Marks

4(a) any three from: 3 1 formation of new species from, pre-existing species / (common) ancestor ; A description 2 over, time / generations ; 3 mutations / changes in gene pools / changes in allele frequencies ; 4 change in, characteristics / phenotypes ; 5 natural selection ; 6 AVP ; e.g. genetic drift / allopatric / sympatric 4(b)(i) A names for numbers throughout 3 any three from: max two for similarities in both figures: 1 diverged into two groups, at the same time / 67 million years ago 2 idea that group 1 is on a different (evolutionary) branch to group(s), 3 / 4 ; 3 idea that group 3 and group 4 diverge more recently / AW or group 3 and group 4 on the same (evolutionary) branch ; differences: 4 first divergence resulted in, group 1, in, Figure 4.2 but in, Figure 4.1, group 1, formed later ; 5 group 2 are closely related to group, 3 / 4, in Figure 4.2 or group 2 are closely related to group 1 in, Figure 4.1 ; © Cambridge University Press & Assessment 2026 Page 13 of 25 4(b)(ii) any two from: 2 1 compare, base / nucleotide, sequences (of DNA) or identify, similarities / differences, in, base / nucleotide, sequences (of DNA) ; 2 more similarities means species, are more closely related / have a more recent common ancestor ; 3 ref. to arrange in groups of shared mutations ; 4 ref. bioinformatics ; A description 4(b)(iii) data from more species ; 1 4(c) any three from: 3 1 less genetic, diversity / variation ; 2 alleles not exchanged between non-sister chromatids ; 3 allele combinations remain the same (as parents) ; ora 4 linkage groups not broken / AW ; ora © Cambridge University Press & Assessment 2026 Page 14 of 25

3(a)(i) any three from: 3 1 PCR to amplify DNA ; 2 (gel) electrophoresis, to compare / separate, DNA fragments ; 3 microarray to, compare / analyse, genomes ; A polymorphisms 4 database / bioinformatics, to, compare / analyse, sequences of, (DNA) bases / nucleotides ; © Cambridge University Press & Assessment 2026 Page 9 of 23 Trace ID: PC-913B5F5E92 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/4a2 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/42 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/ 3(a)(ii) any four from: 4 1 allopatric (speciation) ; 2 idea of no contact so, reproductive isolation / no gene flow (between populations) ; 3 different mutations occur (in each population) ; 4 different selection pressures (for each population) ; 5 ref. to (named) morphological / (named) behavioural / ecological / niche, differences (between populations) ; 6 so can no longer interbreed to produce fertile offspring ; 3(a)(iii) 1 they are now different species / speciation has taken place ; 3 2 (different mating calls shows) behavioural, isolation / separation ; 3 (when S female and N male mate) offspring not produced / (fertilised) eggs are not viable ; 3(b) 1 genes / genetic and environment(al) ; 3 2 polygenes / many genes involved ; 3 diet / food (availability) / competition for food / nutrients / temperature / disease ; © Cambridge University Press & Assessment 2026 Page 10 of 23 Trace ID: PC-913B5F5E92 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/4a2 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/42 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/

4(a) 1 q = √0.11 or q = 0.33166 3 and p = 1 – 0.33166 or p = 0.66834 ; 2 2pq = 2  0.66834  0.33166 or 2pq = 0.44332 and  100 ; 3 44 ; max 1 if no working is shown but have correct answer 4(b) apply ora throughout 3 1 (only) continuous, is polygenetic / involves more than two genes / involves many genes ; 2 in continuous different alleles have a small(er) effect (on the trait) ; 3 (only) continuous has, genes / alleles, showing an additive effect ; 4(c) any three from: 3 1 founder effect / genetic drift ; A description 2 geographical, isolation / separation / barrier (between populations) ; 3 no gene flow / no interbreeding / reproductive isolation (between populations) ; 4 different mutations occurred ; 5 different, selection pressures / environments ; 6 different changes in allele frequencies ; © Cambridge University Press & Assessment 2026 Page 11 of 20 Trace ID: PC-C51CA5D8F2 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/4a3 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/43 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/

4(a) any six from: 6 1 allopatric (speciation) ; 2 geographical, isolation / separation / barrier (between populations) or ref. to Panama / land / barrier, separating populations ; 3 (so) reproductive isolation / no gene flow / no interbreeding (between populations) ; 4 different mutations ; 5 different, selection pressures / environments ; 6 different, alleles selected for / changes in allele frequency / gene pools ; 7 ref. to (named) behavioural / ecological / niche, differences (between populations) ; 8 no longer interbreed to produce fertile offspring ; 4(b) ecosystem 3 1 interactions of, community / all species / all populations ; 2 ref. to abiotic / physical / non-living, and, biotic / biological / living, factors / environment ; niche 3 role / function, of a species (in its ecosystem) ; © Cambridge University Press & Assessment 2026 Page 13 of 22 Trace ID: PC-C13BFDE7F5 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/4a4 CMaarkm Scbhermide gJuene 2·0 2p6 a| Spoaurccea: mpapbarciadmgbreid.gceo.comm 9700/44 Mark Scheme June 2026 Downloaded from PapaCambridge - https://papacambridge.com/