Final answer:
Allopatric speciation is the process where differences accumulate between populations that were once joined, leading to the formation of new species. Geographic isolation prevents gene flow, causing divergent evolutionary paths through natural selection, mutation, and genetic drift. Examples include variations in warm-blooded animal sizes in different climates and distinct species of squirrels on either side of the Grand Canyon.
Step-by-step explanation:
The accumulation of differences between populations that once formed a single population is known as allopatric speciation. This phenomenon occurs when populations become geographically isolated, leading to the interruption of gene flow. Over time, each population evolves independently, with natural selection, mutation, and genetic drift resulting in divergent evolutionary paths. This can result in significant differences in allele frequencies between the populations, and often, the emergence of distinct species.
For instance, habitat isolation can be a trigger for allopatric speciation. An example is a cricket population that becomes divided due to a natural event such as a flood. The separated populations, now reproductively and genetically independent, may experience different evolutionary pressures. This can lead to variations in physical traits, such as size or reproductive timing, which is known as a cline. The latitudinal cline seen in warm-blooded animals, where individuals in cooler climates are larger to conserve heat, is one such example of phenotypic variation due to allopatric speciation.
A classic example of allopatric speciation is the distinct species of squirrels found on opposite sides of the Grand Canyon. Geographical barriers like the canyon prevent gene flow between the populations, leading to speciation over time.