BIOL 121 Lecture Notes - Lecture 32: Bear, Waimanu, Adaptive Radiation
Document Summary
No gene flow between the isolated populations, each allopatric (geographically-isolated) population may become genetically unique over time and its gene pool is changed by a number of process, one of which is natural selection. Geographic isolation can promote allopatric speciation eg: porkfish (plate tectonics) cannot be interbreed anymore because they were isolated from each other reproductive isolated. Example: antelope squirrels - grand canyon: birds & other organisms that easily disperse across canyon have not diverged into different species on opposite side of the canyon. Allopatric speciation can occur via a founder event: Establishment of a new population by a small number of individuals. South america: common ancestor 5 million years and 600,000 years ago adaptive radiation large no. of spp. Adaptive radiation on an island chain: ecological opportunities exist, may stimulate evolutionary changes. Water barriers restrict gene flow between populations, so populations on different islands may evolve adaptations to their local environments.
