Niche, allele frequency and conservation: exam questions

Answer: C – no migration (gene flow) in or out; must also be large, random mating, no mutation, no selection

• q² = 1 ÷ 2500 = 0.0004 (1)
• q = 0.02 (1)
• p = 1 − 0.02 = 0.98 (1)
• 2pq = 2 × 0.98 × 0.02 = 0.039 / 0.0392 (1)

• calculate the expected genotype frequencies (p², 2pq, q²) from the allele frequencies
• compare with observed genotype / allele frequencies in later generations
• a difference / change in frequency means allele frequency is changing (the population is evolving)

• mutation produced the resistance allele
• antibiotic is a selection pressure / kills non-resistant bacteria
• resistant bacteria survive and reproduce
• pass on the resistance allele to offspring, so the frequency of the allele increases in the population
• over many generations / bacteria divide rapidly, so the change happens quickly
• Max 4

• populations are separated / cannot interbreed (for example by a geographical barrier)
• no gene flow between the populations
• mutations occur independently, creating different alleles
• different environments give different selection pressures, so different alleles are selected
• allele frequencies / gene pools change and become increasingly different
• eventually the populations cannot interbreed to produce fertile offspring
• Max 5

• niche: the role of a species in its habitat / how it obtains resources and its interactions with other species
• behavioural: named behaviour (for example nocturnal activity, hibernation, migration) in a named organism
• anatomical: named structural feature (for example thick fur, rolled leaves with hairs) in a named organism
• link of one adaptation to survival (for example reducing heat loss or water loss)

• zoos: captive breeding programmes increase numbers of endangered animals
• zoos: managed breeding / exchanging animals between zoos maintains genetic diversity and avoids inbreeding
• zoos: reintroduction and research and education support wild conservation
• zoos: limitation: expensive, few individuals, small populations lose genetic diversity, animals may not adapt to the wild
• seed banks: cheap, small space, store many seeds from many species and alleles
• seed banks: limitation: some seeds cannot be stored, seeds lose viability, plants do not adapt to changing conditions
• reasoned conclusion: both are useful but habitat protection is also needed
• Max 6

• drying reduces water content so seeds do not germinate / metabolic reactions slow / fungi do not grow
• low water content prevents ice crystals forming that would damage cells
• low temperature slows respiration / metabolism / enzyme activity, so seeds remain viable for longer