AP BIOLOGY

Detailed explanation-1: -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-2: -Two species of antelope ground squirrels are separated by the Grand Canyon. They are hypothesized to descend from a common ancestor, populations of which were separated as the canyon formed. If this hypothesis is correct, it would be an example of:-sympatric speciation by dispersal.

Detailed explanation-3: -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-4: -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.

Detailed explanation-5: -When individuals with intermediate phenotypes are favoured and extreme phenotypes are selected against, the selection is said to be stabilizing.