Question

a population of birds lives on a small island. another population of the same species lives on the mainland. the distance between the island and the mainland is too great for birds to fly back and forth. recently, a series of sandbars and tiny islands have formed between the island and the mainland. what is the most likely effect of this?
○ an increase in mutations in both bird populations
○ an increase in gene flow between the bird populations
○ an increase in genetic drift between the bird populations
○ an increase in mutations in the island population

Explanation:

1. Analyze Option 1: Mutations are random and not directly caused by the formation of sandbars/islands, so no increase in mutations for both populations. Eliminate.
2. Analyze Option 2: The sandbars and tiny islands form a "bridge" that allows birds to move between the island and mainland (previously too far to fly). Gene flow is the transfer of genetic material between populations. With the new landforms, birds can migrate, increasing gene flow. This makes sense.
3. Analyze Option 3: Genetic drift is random change in allele frequencies, often in small populations. The new landforms allow gene flow, which reduces genetic drift between populations, not increase. Eliminate.
4. Analyze Option 4: Mutations are random and not caused by the new landforms, so no increase in mutations in the island population. Eliminate.

Answer:

B. an increase in gene flow between the bird populations