Final answer:
In the scenario where only yellow birds with genotype bb colonize a new island, the allele frequency would be b: 1 and B: 0. Genetic drift would happen more quickly on an island, and genetic diversity increases the chances of survival following environmental changes. Gene flow can alter allele frequencies when individuals migrate between populations.
Step-by-step explanation:
The question pertains to a scenario where a population of yellow birds with genotype bb has colonized a new island. The resulting population of birds would have an allele frequency of b: 1 and B: 0 since all the birds are yellow, carrying the bb genotype which indicates that only the b allele is present in the population. There is no presence of the B allele, as only yellow birds (bb) were part of the founding population.
When considering genetic drift, it would happen more quickly on an island compared to the mainland because of the smaller population size and reduced genetic variation. Genetic drift can lead to the elimination of alleles by chance when only a small number of individuals reproduce.
In a different scenario, amongst two genera on an island, Genus B, having a wider variety of genetic traits, would have a higher probability of surviving a volcanic explosion. This is because genetic diversity within a population can provide a greater chance for some individuals to possess traits that are advantageous in changing environmental conditions.
Gene flow between island populations, as seen with Galápagos medium ground finches, can alter allele frequencies when individuals move from one population to another. The example of finches illustrates how gene flow is one of the mechanisms by which allele frequencies can change in a population.