Final answer:
The predominant evolutionary force in a population of koalas with a selection coefficient of 0.02 is natural selection. Mutation introduces new genetic variation, which is essential for evolution, while genetic drift can heavily influence allele frequencies in small populations and is exemplified by the founder effect.
Step-by-step explanation:
Evolutionary Forces and Koalas
When analyzing the evolution of ear tuftedness in a population of diploid koalas and given a selection coefficient of 0.02, the predominant evolutionary force in this population is likely natural selection. This is because the selection coefficient represents the strength of selection against a phenotype, which implies that some koalas with certain ear tuft alleles are more fit and thus have a reproductive advantage over others.
Mutation is necessary for evolution as it introduces new genetic variations, while genetic drift describes random fluctuations in allele frequencies, which can have a pronounced impact in small populations. The founder effect is a form of genetic drift that occurs when a new population is established by a small number of individuals, leading to a reduced genetic diversity that reflects the founders' gene pool.
Migration (also known as gene flow) involves the movement of alleles between populations, which can alter allele frequencies. In the absence of emigration or immigration, as suggested for the koala population under study, we can exclude migration as the predominant factor. Thus, of the four forces—mutation, migration, genetic drift, and natural selection—natural selection is the primary force given the known selection pressure identified by the selection coefficient.