Massachusetts Comprehensive Assessment System (MCAS) Biology Practice Test

What is most likely to occur to two rodent populations that mate only within their respective soil color types?

1. They will interbreed.

2. They will become more similar.

3. They will become two different species.

4. They will migrate to new areas.

The correct answer is: They will become two different species.

When two rodent populations mate only within their respective soil color types, they are likely to experience reproductive isolation based on their environmental preferences. Over time, this isolation can lead to the populations accumulating genetic differences due to distinct selective pressures and adaptations to their specific environments. As each population becomes genetically distinct, they may develop varying traits, behaviors, or adaptations that further reinforce their separation. This process, driven by natural selection and genetic drift, can ultimately result in speciation, where the populations become two different species. Each group will have unique evolutionary pathways shaped by their specific habitats and the characteristics that help them survive and reproduce in those environments. Additionally, since mating occurs within homogenous soil color types, there will be limited gene flow between the populations, which further solidifies their separation and uniqueness over time.