Final answer:
Allopatric speciation occurs when physical barriers like new rivers or lakes, or navigational challenges like oceanic dispersal of seeds, geographically isolate populations leading to the formation of new species due to genetic divergence.
Step-by-step explanation:
Allopatric speciation is a form of speciation that occurs when a population is divided by physical barriers, leading to genetic divergence and the formation of new species. Geographic isolation can be caused by several events, such as:
- A river forming a new branch
- Erosion creating a new valley
- A group of organisms being transported to a new location and being unable to return
For example, the formation of a new lake might separate two rodent populations, preventing gene flow and leading to speciation. However, the effectiveness of these barriers depends on the organisms' biology and dispersal capabilities. While two separate insect populations in nearby valleys may continue to intermingle, non-flying species such as rodents would become isolated, promoting speciation.