AP BIOLOGY

Detailed explanation-1: -When Arizona’s Grand Canyon formed, squirrels and other small mammals that had once been part of a single population could no longer contact and reproduce with each other across this new geographic barrier. They could no longer interbreed. The squirrel population underwent allopatric speciation.

Detailed explanation-2: -The canyon became a geographic barrier separating the forests and squirrels on each rim. One population of squirrels had become two separate populations that could no longer reproduce. According to National Geographic, this type of speciation is allopatric speciation.

Detailed explanation-3: -Allopatric speciation is caused by geographic isolation. Once the Grand Canyon was formed, squirrels could mate only with squirrels on the same side of the canyon. Each population adapted to its environment. Speciation doesn’t occur every time a population is split into two groups by a geographic barrier.

Detailed explanation-4: -When populations become reproductively isolated, they can evolve into two separate species. Reproductive isolation can develop in a variety of ways, including behavioral isolation, geographic isolation, and temporal isolation.

Detailed explanation-5: -Approximately 10, 000 years ago the Kaibab Squirrel (Sciurus kaibabesis) was geographically separated from a common ancestor of the Abert’s squirrel. This separation cut off the gene flow from the Abert’s squirrel and the Kaibab squirrel began to evolve on its own.