Massachusetts Comprehensive Assessment System (MCAS) Biology Practice Test

What is a probable reason for the less genetic variation in the collared lemming populations studied?

1. The populations are isolated from one another.

2. There was interbreeding between the two populations.

3. The populations were subjected to different environmental pressures.

4. There was a significant mutation within the populations.

The correct answer is: There was interbreeding between the two populations.

The phenomenon of reduced genetic variation within collared lemming populations can be attributed to interbreeding between those populations. When two populations that have distinct genetic profiles interbreed, the resulting offspring may exhibit similarities in genetic traits, which can lead to a homogenization of the gene pool. This reduces the overall genetic diversity because the variations that might have been present separately in each population begin to converge. In contrast, isolation of populations often leads to increased genetic divergence over time due to the lack of gene flow between them, while different environmental pressures can drive distinct adaptations and therefore can enhance variation within populations. Significant mutations, while capable of introducing new traits, would not be the primary driver of genetic variation reduction in this context. Therefore, interbreeding serves as a clear and probable reason for the less genetic variation observed in the studied populations.