When a lineage splits into multiple line of descents, then, it leads to speciation. It is a process by which a single population evolves into different species. The process of speciation leads to the development of two or more species as the lineages are splitted. These two evolved species are genetically independent.
Hence, the blank can be filled with 'speciation'.
This would be mitosis. mitosis consist of four main parts interphase,prophase,metaphase, anaphase, and telophase which also included cytokinesis which you can also study this term by using this terminology ( I P M A T )
Im pretty certain it is volcanic eruption
