Question

In the one-island model, what will eventually happen to an allele's frequency on the island, in the absence of other microevolutionary forces?

Group of answer choices

-It will become fixed if it attains a frequency greater than 0.5

-It will become the same as that found on the continent

-It will be tend toward the average of the island allele frequency and the mainland frequency

-It will become fixed if it attains a frequency less than 0.5

Answer 1

In the absence of other microevolutionary forces, genetic drift can cause an allele's frequency on an island to change by chance, potentially leading to that allele becoming fixed or lost in the population, irrespective of its initial frequency.

Step-by-step explanation:

Genetic Drift and Allele Frequencies

In the one-island model, without the influence of other microevolutionary forces, an allele's frequency on the island may change due to genetic drift. Genetic drift is a mechanism of evolution in which allele frequencies of a population change over generations due to chance events. This stochastic process can result in an allele becoming fixed (i.e., the only allele present in the population) or lost, regardless of the allele's initial frequency. Importantly, if genetic drift is the only acting force, the allele's frequency has the potential to wander, or 'drift', towards fixation or loss simply as a byproduct of the randomness inherent in the reproductive process of the population.

The concept of genetic drift is particularly relevant in small, isolated populations, such as those found on islands, where it tends to have a stronger effect due to smaller population sizes. Over time, this could mean that an allele could either become fixed or lost purely by chance, and this fixation or loss could occur regardless of the allele's initial frequency. Therefore, none of the answer choices perfectly fits the scenario where only genetic drift is acting on a population. The island's allele frequencies might diverge from those of the mainland and could become unique to the island population.

To summarize, in the absence of other microevolutionary forces, the allele frequency on the island will either drift until it becomes fixed or lost within that isolated population. This phenomenon indicates the random nature of genetic drift, especially in small populations. Ultimately, the specific outcome is unpredictable and depends on chance events affecting which individuals survive and reproduce from generation to generation. Therefore, in the context of the options provided, the allele will become fixed if it attains a frequency greater than 0.5 is incorrect, as an allele can become fixed regardless of whether its frequency is greater or less than 0.5, provided there are no other forces at play.