AP BIOLOGY

Detailed explanation-1: -A new river separating a population can result in allopatric speciation. When geologic and climatic conditions are stable, punctuated equilibrium occurs. The hummingbird and the flower it pollinates have coevolved. When geologic and climatic conditions are changing, evolution may occur more quickly.

Detailed explanation-2: -In allopatric speciation, organisms of an ancestral species evolve into two or more descendant species after a period of physical separation caused by a geographic barrier, such as a mountain range, rockslide, or river. Sometimes barriers, such as a lava flow, split populations by changing the landscape.

Detailed explanation-3: -Allopatric speciation, also known as geographic speciation, is speciation that occurs when biological populations of the same species become isolated due to geographical changes such as mountain building or social changes such as emigration.

Detailed explanation-4: -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.