In our discussion of speciation, I came across the term, cladogenesis. There are two ways to describe what happens to species in their respective lineagee, and this term deals with the way evolution branches. A species with either split into different clades, or groups according to characteristics. Or, a species will continue on a single lineage.
Adaptations will cause a species to split into groups. This is where a lineage is split, and it is how we obtain an increase in the number of species.
This is the opposing idea from cladogenesis that explains a single lineage. Instead of a species branching into subspecies, this is the idea that gradual change can lead to replacement such as the change between early species of humans and homo sapiens.