Feedback on Gentic Variation 2016

Hi there
I was wondering if I could get some feedback on my answer to 2016 Q, and also what grade my answer would be

My answer: Genetic diversity describes the range of alleles present in a gene pool. Genetic drift is the random change in the allele frequency of a population, generally resulting in a loss of alleles. The effect of genetic drift would be more significant on small populations such as the flightless birds. The random death of an induvial may result in the loss of an allele in a small population where there are limited carriers of an allele. The loss of an allele would reduce the allele frequency, therefore reducing genetic diversity. In a large population such as the mainland, the death of an induvial is less likely to result in the complete loss of an allele due to the buffer in numbers, so there is a greater chance there are multiple carriers of an allele. If an induvial is lost, it is easier for the mainland to breed and return to stable allele frequency. Therefore the effect of genetic drift is more significant on the small population than on the mainland.

Migration is the movement of all in and out of a population. Emigration is when individuals leave, reducing all frequency and therefore reducing genetic diversity. Immigrating is when individuals enter the population introducing new alleles, therefore, increasing genetic variation. Migration has a larger effect in small populations as the population already has a smaller range of alleles, so the introduction or removal of alleles will have a proportionally larger effect.

As the birds are flightless, this means migration cant take the place of either the main or small population. Not having geneflow will have a more significant effect on the small population as inbreeding is more likely to take place. If inbreeding takes place, it increases the chance harmful recessive alleles will come together, which can produce a harmful genetic condition resulting in the death of an individual. Death of individuals in small populations may result in alleles being completely lost, reducing genetic diversity. Inbreeding also increases the homozygosity of offspring, as many offsprings of the same phenotype are produced, it reduces the population’s ability to successfully respond to changing environments and when new selection pressures come into play. There is a reduced chance that the individuals will carry alleles that provides a survival advantage in response to the new selection pressure. As a result, there is a chance small population may become extinct.

In larger pop, not having migration will have a less significant effect. In larger populations, such as the mainland, random mating can take place, reducing the chance of inbreeding. So even without migration, new alleles are being introduced through random mating, thus increasing the genetic diversity of the population.


How does the marking for bio work? If I get the E section right and the A/M wrong can I get E7?