Tectonic plates have carried the organisms with them as they move around the world. Some organisms are isolated from others, evolving in their own paths, others are introduced to other populations forcing them to compete head on, with only the most successful surviving. And then, plates will carry the organisms that live on them to different climates forcing them to evolve in new ways, and then the moving plates also change global weather patterns, forcing organisms to evolve to suit those changing conditions
