evo lecture 2/3

Front

Darwins other big idea

Back

- phylogenetic tree

- branched out from a common ancestor

-tree of life not just evo can be symbol/ used for other things

Front

LUCA

Back

-last universal common ancestor/ descent

Front

evo trees

Back

-hypothesis could change based on data evo roots could change relationships

Front

evo trees structure

Back

- can be rooted or unrooted

-MRCA (most recent common ancestor)

- internal nodes

-terminal nodes

-can show decesent based on time/ over time

Front

rooted vs unrooted trees

Back

- unrooted: no representation abt which branch diverged first (no when?) biochem

-rooted: represent order of branching/ divergence events, time and order shown

Front

clade

Back

a group of taxa descended from defined common ancestor

Front

outgroup

Back

root the tree, you need a taxon that you are certain is outside the defined clade= an outgroup

Front

Trees from DNA seq

Back

-dna is dif bc of mutations

transitions purine-purine

transversions purine-pryidine

snp

Front

Occam’s Razor

Back

william of occam

most simple explanation likely the best

principle of parsimony

tree beuilding by parsimony= simplist tree is best

Front

tree building by parsimony

Back

Parsimony runs into problems with:
1)Large numbers of taxa (more opportunities for confounding changes!)

2)High mutation rates (parsimony works best when mutations are rare)

3)Evolutionarily divergent taxa (sheep and trout)