What effect does plate tectonics have on organic evolution?
Plate tectonics creates geographic isolation that allows divergent evolution within species separated and protects the isolated species from competition.
An example of geographic isolation can be seen in the squirrels of the Grand Canyon. The squirrels on north side of the canyon are larger have denser fur and darker, than squirrels on the south side of the canyon. The geographic isolation have allowed these changes in the species.
A classic example is the finches of the Galapogos islands. The finches on island are geographic isolated from the finches on the mainland. The isolation has provided the finches from competition so that finches on the islands occupy ecological niches that are occupied by other species on the mainland. It is consider that there are 13 species of finches on the Galapogas Islands due to geographic isolation caused by plate tectonics.
However the squirrels are still squirrels and could interbreed if not isolated. The 13 species of finches actually should be considered to be subspecies as the finches are observed to interbreed and form hybrids. The isolated species have not become new species.
Plate tectonics creates geographic isolation that can cause changes with species but does not create new species. Plate tectonics affect organic evolution changing species. but does not affect Darwinian evolution the creation of new species.