Problem: The process of splitting one species into two or more new species resulting from changes in the original gene pool is called (Click to select) . (Click to select) hypothesized that speciation occurred gradually over time. The (Click to select) of evolution suggests that speciation occurs after populations become isolated and changes continue to occur slowly as each group follows its own evolutionary pathway. In this model, it is often difficult to determine when exactly speciation occurred due to many (Click to select) links between species over time. More often, however, the fossil record shows that species appear quite suddenly and remain unchanged (Click to select) over time. The (Click to select) says that a period of no change is interrupted by speciation. Need Assignment Help?