(a) Both DNA fragments are negatively charged and move towards the positive electrode. The shorter 300 bp fragment passes through the gel matrix more readily and therefore migrates farther than the 420 bp fragment.

Both DNA fragments are negatively charged and move towards the positive electrode. The shorter 300 bp fragment passes through the gel matrix more readily and therefore migrates farther than the 420 bp fragment.

(b) Lane 2 is Ld, lane 3 is LL and lane 4 is dd. Lane 2 has both allele-sized bands, so the individual is heterozygous.

Lane 2 is Ld, lane 3 is LL and lane 4 is dd. Lane 2 has both allele-sized bands, so the individual is heterozygous.

(c) Expected numbers are 20 LL, 40 Ld and 20 dd. Observed values 19, 42 and 19 are close to that expectation, with deviations of -1, +2 and -1.

Expected numbers are 20 LL, 40 Ld and 20 dd. Observed values 19, 42 and 19 are close to that expectation, with deviations of -1, +2 and -1.

(d) Any two valid checks with explanations earn full credit. For example, use the same primers and PCR conditions so amplification differences do not mimic allele-frequency differences, and include a no-template control so contaminating DNA is detected. Equivalent checks include a positive control, equal-quality DNA or standardised gel conditions with a reference ladder.

Any two valid checks with explanations earn full credit. For example, use the same primers and PCR conditions so amplification differences do not mimic allele-frequency differences, and include a no-template control so contaminating DNA is detected. Equivalent checks include a positive control, equal-quality DNA or standardised gel conditions with a reference ladder.

(e) The distinguishable 420 bp and 300 bp bands let breeders identify carriers and choose parents that retain both marker alleles. One limitation is that this single DNA region samples only a small part of the genome, so retaining its two alleles does not establish high genome-wide diversity. Alternatively, explain that the marker has no demonstrated relationship to fitness, or that it cannot establish reproductive compatibility. Use the marker alongside broader genetic or breeding evidence appropriate to the chosen limitation; only one explained limitation is required.

The distinguishable 420 bp and 300 bp bands let breeders identify carriers and choose parents that retain both marker alleles. One limitation is that this single DNA region samples only a small part of the genome, so retaining its two alleles does not establish high genome-wide diversity. Alternatively, explain that the marker has no demonstrated relationship to fitness, or that it cannot establish reproductive compatibility. Use the marker alongside broader genetic or breeding evidence appropriate to the chosen limitation; only one explained limitation is required.

(a) A and B are closest relatives because they share the most recent common ancestor on the tree and have the highest sampled sequence identity. The conclusion applies to the sampled loci and taxa.

A and B are closest relatives because they share the most recent common ancestor on the tree and have the highest sampled sequence identity. The conclusion applies to the sampled loci and taxa.

(b) Restricted gene flow separates allele pools. New mutations introduce variants, and random sampling in small founder populations changes allele frequencies through drift. Independent changes accumulate, increasing genetic divergence.

Restricted gene flow separates allele pools. New mutations introduce variants, and random sampling in small founder populations changes allele frequencies through drift. Independent changes accumulate, increasing genetic divergence.

(c) Different breeding months prevent many matings between A and B even if they occupy the same island. This temporal pre-fertilisation isolation reduces allele transfer between the gene pools. Selection and drift can then increase divergence; separate species form only if effective reproductive isolation becomes sufficiently strong.

Different breeding months prevent many matings between A and B even if they occupy the same island. This temporal pre-fertilisation isolation reduces allele transfer between the gene pools. Selection and drift can then increase divergence; separate species form only if effective reproductive isolation becomes sufficiently strong.

(d) Measure natural mating, fertilisation and fertile-offspring production where contact is possible, and combine this with behavioural, genomic and ecological evidence. A controlled breeding study could test compatibility but may not represent mate choice in nature. Include within-population crosses under the same conditions as between-population crosses to check that the method permits successful breeding. One limitation is that geographically isolated populations cannot be observed interbreeding naturally, so separation alone does not establish reproductive incompatibility. Alternatively, explain why interbreeding cannot assess asexual reproduction or be tested in fossils; only one explained limitation is required. Reproductive isolation despite opportunities to mate would support separate species, whereas natural interbreeding with fertile offspring would support a shared biological species.

Measure natural mating, fertilisation and fertile-offspring production where contact is possible, and combine this with behavioural, genomic and ecological evidence. A controlled breeding study could test compatibility but may not represent mate choice in nature. Include within-population crosses under the same conditions as between-population crosses to check that the method permits successful breeding. One limitation is that geographically isolated populations cannot be observed interbreeding naturally, so separation alone does not establish reproductive incompatibility. Alternatively, explain why interbreeding cannot assess asexual reproduction or be tested in fossils; only one explained limitation is required. Reproductive isolation despite opportunities to mate would support separate species, whereas natural interbreeding with fertile offspring would support a shared biological species.

(a) The lizards warm by 12 degrees C in sun and by 5 degrees C in shade. The final temperature in sun is 7 degrees C higher than in shade. These results describe the treatments but do not alone prove that shade is the only cause of the difference.

The lizards warm by 12 degrees C in sun and by 5 degrees C in shade. The final temperature in sun is 7 degrees C higher than in shade. These results describe the treatments but do not alone prove that shade is the only cause of the difference.

(b) Moving into or remaining in shade is behavioural thermoregulation. Shade reduces radiant heat absorbed from direct sunlight, lowers net heat gain and limits the rise in body temperature. Moving back into sunlight when cooler could increase heat gain.

Moving into or remaining in shade is behavioural thermoregulation. Shade reduces radiant heat absorbed from direct sunlight, lowers net heat gain and limits the rise in body temperature. Moving back into sunlight when cooler could increase heat gain.

(c) The lower final temperature in shade, 24 rather than 31 degrees C after 24 minutes, supports a benefit of limiting overheating. Maintaining a viable temperature range supports enzyme and cellular function. One possible limitation is reduced feeding opportunity: if food occurs mainly in exposed areas, remaining in shade reduces access and can lower energy intake. Alternatively, explain inadequate protection when shaded sites are still too hot, or the inability to choose shade where it is absent. Only one limitation, its relevant condition and its consequence are required.

The lower final temperature in shade, 24 rather than 31 degrees C after 24 minutes, supports a benefit of limiting overheating. Maintaining a viable temperature range supports enzyme and cellular function. One possible limitation is reduced feeding opportunity: if food occurs mainly in exposed areas, remaining in shade reduces access and can lower energy intake. Alternatively, explain inadequate protection when shaded sites are still too hot, or the inability to choose shade where it is absent. Only one limitation, its relevant condition and its consequence are required.

(d) Randomly allocate similar lizards to replicated sun and shade enclosures, standardise starting temperature, surface, airflow and measurement time, and record body temperature repeatedly with calibrated equipment. Report variation among animals and restrict the conclusion to the tested species, temperatures and 24-minute period.

Randomly allocate similar lizards to replicated sun and shade enclosures, standardise starting temperature, surface, airflow and measurement time, and record body temperature repeatedly with calibrated equipment. Report variation among animals and restrict the conclusion to the tested species, temperatures and 24-minute period.

(a) The plotted series starts at 8 in day 1, reaches a maximum of 25 in day 4, and finishes at 7 in day 8. The final value is lower than the initial value.

The plotted series starts at 8 in day 1, reaches a maximum of 25 in day 4, and finishes at 7 in day 8. The final value is lower than the initial value.

(b) Testing identifies infected people sooner. Isolation reduces their effective contacts during the infectious period, decreasing opportunities for pathogen transfer and potentially lowering the effective reproduction number below one.

Testing identifies infected people sooner. Isolation reduces their effective contacts during the infectious period, decreasing opportunities for pathogen transfer and potentially lowering the effective reproduction number below one.

(c) Influenza virus reaches respiratory surfaces in virus-containing particles and enters susceptible respiratory epithelial cells. It uses host-cell machinery to produce new viral particles. Infection damages respiratory tissue and can impair respiratory function. New particles leave the infected person in respiratory particles and can reach another susceptible person's respiratory surfaces during close contact.

Influenza virus reaches respiratory surfaces in virus-containing particles and enters susceptible respiratory epithelial cells. It uses host-cell machinery to produce new viral particles. Infection damages respiratory tissue and can impair respiratory function. New particles leave the infected person in respiratory particles and can reach another susceptible person's respiratory surfaces during close contact.

(d) Predefine new confirmed cases per population and test positivity, use consistent case definitions, record testing volume and intervention timing, and compare matched communities or interrupted time series while adjusting for vaccination, mobility and earlier confirmed case counts. Protect privacy through de-identification and community governance. Replicate over sufficient time and report uncertainty.

Predefine new confirmed cases per population and test positivity, use consistent case definitions, record testing volume and intervention timing, and compare matched communities or interrupted time series while adjusting for vaccination, mobility and earlier confirmed case counts. Protect privacy through de-identification and community governance. Replicate over sufficient time and report uncertainty.

(a) Southern and northern populations differ in dry-year survival and genetic diversity, but the observations are population comparisons rather than reversible responses measured within individuals. An evolutionary-adaptation claim requires evidence that survival differences are inherited and cause different reproductive success across generations. Common-garden breeding evidence could test those requirements.

Southern and northern populations differ in dry-year survival and genetic diversity, but the observations are population comparisons rather than reversible responses measured within individuals. An evolutionary-adaptation claim requires evidence that survival differences are inherited and cause different reproductive success across generations. Common-garden breeding evidence could test those requirements.

(b) Pollen-mediated fertilisation can introduce southern alleles into northern offspring. Sexual reproduction and recombination place those alleles into new genetic combinations, increasing heritable drought-response variation. If the introduced variants improve reproductive success as conditions dry, natural selection can increase their frequency across generations.

Pollen-mediated fertilisation can introduce southern alleles into northern offspring. Sexual reproduction and recombination place those alleles into new genetic combinations, increasing heritable drought-response variation. If the introduced variants improve reproductive success as conditions dry, natural selection can increase their frequency across generations.

(c) Introduced alleles could disrupt locally adapted northern gene combinations, and crosses between divergent populations could reduce fertility or survival. Pollen transfer could also move pathogens, while drought-associated traits could reduce fitness under wetter conditions.

Introduced alleles could disrupt locally adapted northern gene combinations, and crosses between divergent populations could reduce fertility or survival. Pollen transfer could also move pathogens, while drought-associated traits could reduce fitness under wetter conditions.

(d) Use replicated northern controls, southern pollen sources and several crossing proportions in common gardens and reciprocal sites. Randomise blocks and standardise seed age and soil treatment. Measure germination, survival and lifetime seed production across dry and normal years, genotype offspring to confirm pollen-mediated gene flow, and apply biosecurity screening and stopping rules before broader release.

Use replicated northern controls, southern pollen sources and several crossing proportions in common gardens and reciprocal sites. Randomise blocks and standardise seed age and soil treatment. Measure germination, survival and lifetime seed production across dry and normal years, genotype offspring to confirm pollen-mediated gene flow, and apply biosecurity screening and stopping rules before broader release.

(a) The substituted DNA base changes the sequence transcribed into mRNA and hence a codon read by a ribosome. During translation, that codon specifies a different amino acid. The changed amino-acid sequence can alter the protein's three-dimensional structure and active-site shape or behaviour, affecting substrate binding or catalysis. Activity at 62% of the reference indicates partial function, not absence of the enzyme. A named R-group interaction is not needed to explain these links.

The substituted DNA base changes the sequence transcribed into mRNA and hence a codon read by a ribosome. During translation, that codon specifies a different amino acid. The changed amino-acid sequence can alter the protein's three-dimensional structure and active-site shape or behaviour, affecting substrate binding or catalysis. Activity at 62% of the reference indicates partial function, not absence of the enzyme. A named R-group interaction is not needed to explain these links.

(b) Replication strengthens the activity comparison but association alone does not establish causation for the organism. Linked variants, assay conditions and interactions between genotype and environment could contribute. Compare the sequence variants in a shared genetic background under matched conditions, including a reference form and procedural controls. Repeat the activity assays and measure the relevant whole-organism phenotype. Conclusions should remain limited to the tested genotypes and environments.

Replication strengthens the activity comparison but association alone does not establish causation for the organism. Linked variants, assay conditions and interactions between genotype and environment could contribute. Compare the sequence variants in a shared genetic background under matched conditions, including a reference form and procedural controls. Repeat the activity assays and measure the relevant whole-organism phenotype. Conclusions should remain limited to the tested genotypes and environments.

(a) Mutation can introduce heritable R1 or R2 variants, while recombination forms new allele combinations. These processes do not occur because insects need resistance. Pesticide exposure favours resistant survivors, whose reproduction increases resistance alleles in the gene pool. Migration transfers alleles between fields and chance sampling causes drift, particularly in small populations. These processes can operate together; the survival rise alone does not identify their separate contributions.

Mutation can introduce heritable R1 or R2 variants, while recombination forms new allele combinations. These processes do not occur because insects need resistance. Pesticide exposure favours resistant survivors, whose reproduction increases resistance alleles in the gene pool. Migration transfers alleles between fields and chance sampling causes drift, particularly in small populations. These processes can operate together; the survival rise alone does not identify their separate contributions.

(b) Refuges retain susceptible breeders that can interbreed with resistant insects, reducing the relative transmission of resistance alleles. Success depends on refuge size, connectivity and movement. Sample multiple fields and refuges repeatedly across generations, comparing resistance alleles and linked markers. Record pesticide dose and insect movement alongside survival. Shared resistance and surrounding marker patterns may support spread, whereas different genetic backgrounds may suggest separate origins, subject to sampling uncertainty.

Refuges retain susceptible breeders that can interbreed with resistant insects, reducing the relative transmission of resistance alleles. Success depends on refuge size, connectivity and movement. Sample multiple fields and refuges repeatedly across generations, comparing resistance alleles and linked markers. Record pesticide dose and insect movement alongside survival. Shared resistance and surrounding marker patterns may support spread, whereas different genetic backgrounds may suggest separate origins, subject to sampling uncertainty.

(a) Ectotherms obtain most heat externally, whereas endotherms generate substantial metabolic heat. Both function within tolerable body-temperature ranges. As air temperature rises by 12 degrees C, basking increases a lizard's radiant heat gain, while shade reduces that input. Moving between sites can keep body temperature within a functional range, but its effectiveness depends on access to cooler and warmer microhabitats and cannot guarantee a fixed temperature.

Ectotherms obtain most heat externally, whereas endotherms generate substantial metabolic heat. Both function within tolerable body-temperature ranges. As air temperature rises by 12 degrees C, basking increases a lizard's radiant heat gain, while shade reduces that input. Moving between sites can keep body temperature within a functional range, but its effectiveness depends on access to cooler and warmer microhabitats and cannot guarantee a fixed temperature.

(b) Greater skin blood flow can transfer internal heat to the surface, and evaporation removes heat while consuming water. Metabolic heat production also has an energy cost; hot or humid conditions can limit heat loss. Use replicated animals under safe standardised heat, airflow and hydration conditions for matched durations. Record body temperature and behaviour, water loss and metabolic activity, with welfare stopping rules. Report variation and restrict conclusions to the conditions and species tested.

Greater skin blood flow can transfer internal heat to the surface, and evaporation removes heat while consuming water. Metabolic heat production also has an energy cost; hot or humid conditions can limit heat loss. Use replicated animals under safe standardised heat, airflow and hydration conditions for matched durations. Record body temperature and behaviour, water loss and metabolic activity, with welfare stopping rules. Report variation and restrict conclusions to the conditions and species tested.

(a) Bacteria leave an infectious person's respiratory tract in airborne material and enter another person's respiratory tract. Infection can damage lung tissue and impair gas exchange despite host defences. Crowding increases contacts, poor ventilation allows infectious material to accumulate, delayed diagnosis prolongs opportunities for exposure and movement connects neighbourhoods. The rising counts are consistent with spread but cannot establish which factor caused it or separate transmission changes from changes in detection.

Bacteria leave an infectious person's respiratory tract in airborne material and enter another person's respiratory tract. Infection can damage lung tissue and impair gas exchange despite host defences. Crowding increases contacts, poor ventilation allows infectious material to accumulate, delayed diagnosis prolongs opportunities for exposure and movement connects neighbourhoods. The rising counts are consistent with spread but cannot establish which factor caused it or separate transmission changes from changes in detection.

(b) Early case detection enables treatment; effective antibiotics reduce viable bacteria, and ventilation reduces airborne exposure. Combining them addresses infectious sources and transmission, but access, treatment completion and resistance may limit success. Compare matched areas or a staged program using the same case definition and testing effort. Track ventilation, treatment completion and new cases alongside occupancy, movement and access. Protect privacy, involve the community and maintain care while reporting uncertainty.

Early case detection enables treatment; effective antibiotics reduce viable bacteria, and ventilation reduces airborne exposure. Combining them addresses infectious sources and transmission, but access, treatment completion and resistance may limit success. Compare matched areas or a staged program using the same case definition and testing effort. Track ventilation, treatment completion and new cases alongside occupancy, movement and access. Protect privacy, involve the community and maintain care while reporting uncertainty.