Here's why:
* Extinction: Extinction events happen at various points along the branches of a phylogenetic tree, not necessarily at the base. A species can go extinct long after its lineage diverged from the ancestral population.
* Modern Populations: Modern populations are represented at the tips of the branches, not at the base. They are the descendants of the ancestral population.
Think of it like a family tree:
* Base: The oldest ancestor, the common ancestor for all members of the family.
* Branches: Different lineages within the family.
* Tips: The current generation of family members.
The root of the phylogenetic tree shows where all the life forms on the tree share a common ancestor. As you move up the branches, you see the diversification and evolution of different species over time.
