From Biol301

• Self quiz on BlackBoard
• Test ?'s are from class notes only; memorize and understand

Contents 1 Phylogenies and Systematics 1.1 Phylogeny 1.2 Systematics 1.2.1 Key Approaches to Systematics

Phylogenies and Systematics

Phylogeny

• evolutionary tree, shows relationships between organisms
• emphasizes recency of common ancestors

1. Cladograms

• Just show branching order.
• no trunk, no main species, no main line of descent
• branches are not to scale
• time procedes in one direction
• (leaf=node)->(edge=branch)->(ancestral node)->(edge=branch)->etc.->root

2. Phylogram

• branch lengths are to scale; there is information about time or genetic distance.

Systematics

• The science of naming and classifying organisms.
• Biodiversity science (systemitists)
• Taxonomy: very related to systematics but not quite the same

Key Approaches to Systematics

1. Only monophyletic groups are recognized;

• Monophyletic includes all descendants of a common ancestor.
• clade = monophyletic group
• cladistics = naming monophyletic groups

2. Emphasises discrete characteristics

• DNA can only be four discrete states: ATCG

3. Parsimony

• Used to find the shortest or "best" tree; has the fewest necessary mutations to account for all differences
  • Occams Razor: simplest explanation is most likely to be the correct explanation.
• Used to reconstruct ancestral characteristics
  • use tree to infer a suggested parsimony, use other observations to prove (like fossils)