Constructing Phylogenies

A. Background Information B. General Info

Background Information

Determine relationships by comparing traits of different organisms

Ancestral trait

trait present outside of particular clade

Derived trait:

trait present in MRCA of particular clade not present outside of that clade

Generally more derived traits in common

-> more closely related

Homology (homologous)

• = derived from a common ancestor (arm of bat, human, and whale)

  • Homologies are good characteristics to build a tree ex. Bone structure in tetrapods

Analogy (analogous)

•  = convergent evolution (independently acquired) because of similar evolutionary presence ex. Flying squirrels in america and australia 

  • Not good for phylogenies ex. Flight in tetrapods (bat and rat are more close than bat and bird)

Clades based on derived traits

• Members of a clade share derived traits due to presence of those traits in mrca

• Clades can be defined by unique derived traits absent from CA’s of other clades

Document traits compare groups by similarity, make tree

More groups more complexity

Use computers and different methods to track viruses for example