Notes 4 (missed lecture) Flashcards
What do synapomorphies define?
monopyletic clades
Criterion for maximum parsimony
- fewest evolutionary changes
2. fewest homoplasies
Outgroup is assumed to be..
ancestral
Ingroup is assumed to be…
Derived
Methods for determiining relationships
- UPGMA
2. Maximum parsimony
Bootstrapping
general technique to see how frequently relationships are supported
Single character change could be easily missed
Humans are most closely related to
Chimps
phylogenetic hypothesis testing
Multiple datat sets with the same info support relationships. Like molecular and morphological.
Challenges 4
- scoring characters can be hard
- determing homology is difficult
- How do we score continuous traits like height?
- How do we determine if characters are independent? since tRNAs match up is a change one or two?
Homoplasy examples 5
- Spines are leaves whereas thorns are branches
- fish and octapus eye look similar but are anataomically different
- Long beak shape evolved independently
- flowering plants evolved differently in cold tropics
- Cactus evolved multiple times in different parts of the world
Mutational saturation issues (2)
third codon position evolves more quickly (less functional constraint)
mutliple substitutsion at same site will wipe out signal
More rapidly evolving genes give ideas for…
relationships amoung younger taxa
MOre slowly evolving genes give relationships for..
relationships among more ancient taxa
Issue with rapid speciation
there’s little time for changes to occur or synapomorophies to form
shorter branches are worse than longer branches for determining relationships
Solutions to the issue
- More data allows us to identify more synapomorphies
