Which of the following is the best example of gene flow?

• A. A small group of individuals becomes isolated and forms a new population with different allele frequencies.
• B. A population of birds migrates to a new area and breeds with the local population, introducing new alleles.
• C. A mutation occurs in a single individual, creating a new allele in the population.
• D. Natural selection favors individuals with a certain trait, increasing its frequency in the population.

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the concept of gene flow. Gene flow refers to the transfer of genetic material (alleles) between populations, typically through migration and interbreeding. It increases genetic diversity within a population and can introduce new alleles.
2. Step 2: Analyze the options provided. The goal is to identify the scenario that best represents gene flow, which involves the movement of alleles between populations.
3. Step 3: Evaluate the first option: 'A small group of individuals becomes isolated and forms a new population with different allele frequencies.' This describes genetic drift, not gene flow, as it involves isolation rather than the exchange of alleles between populations.
4. Step 4: Evaluate the second option: 'A population of birds migrates to a new area and breeds with the local population, introducing new alleles.' This is a clear example of gene flow because it involves migration and interbreeding, leading to the introduction of new alleles into the local population.
5. Step 5: Evaluate the remaining options. 'A mutation occurs in a single individual, creating a new allele in the population' describes mutation, not gene flow. 'Natural selection favors individuals with a certain trait, increasing its frequency in the population' describes natural selection, not gene flow. Therefore, the second option is the best example of gene flow.