What is phylogeny?
The evolutionary history of relationships among organisms.
What is a phylogenetic tree?
A diagrammatic reconstruction of evolutionary history showing divergence of lineages.
What is a lineage?
A series of ancestor and descendant populations.
What is represented at the root of a phylogenetic tree?
The common ancestor of all species depicted in the tree.
What do nodes on a phylogenetic tree represent?
Splitting events such as speciation, gene duplication, or transmission events.
What do branch tips represent in a phylogenetic tree?
Modern species, populations, or lineages being studied.
What do red dots on some phylogenetic trees indicate?
Traits that evolved independently, distinguishing a lineage from its ancestor or sister lineage.
What is cladogenesis?
One species splitting into two or more distinct species, leading to branching.
What is anagenesis?
Gradual evolution of a species without splitting into multiple lineages.
What processes can cause divergence?
Natural selection, genetic drift, mutation, and lack of gene flow.
What happens if there is no gene flow between populations?
Populations diverge and speciation becomes very likely.
How is time represented on a phylogenetic tree?
As you move from the root to the tips, you are moving forward in time.
What do phylogenies trace?
Patterns of shared ancestry between lineages, including unique and shared ancestors.
What is a taxon?
Any group of species given a name.
What is a clade?
Any taxon that includes an ancestor and all its evolutionary descendants.
What are sister species or sister clades?
Two species or clades that are each other’s closest relatives.
What is the most inclusive clade?
All of life.
How do clades nest?
Clades are subsets of larger clades, forming a nested hierarchy.
Why must we be careful not to treat trees as ladders?
All lineages have had equal time to evolve; no organism is “higher” or “more advanced.”
Example: Humans and chimps
Humans did not evolve from chimps; both share a common ancestor. Each lineage has evolved traits unique to itself.
