Phylogenetics
- Systematics: study of diversity/evolutionary relationships
- Taxonomy (describing/naming/classifying)
- Nested hierarchy (domain -> species)
- Taxon (taxa pl.): general name for group @ any level
- Domain, kingdom, phylum, class, order, family, genus, species (King Phillip came over for great spaghetti)
- binomial nomenclature: two-name naming system where species = basic unit
- Linking taxonomy and phylogeny
- Linnaean classification/phylogeny can differ from each other
- Phylogeny (includes evolutionary history): groups with common ancestor and all descendants
- Phylogenetic species concept: smallest set of organisms that can be distinguished into phylogenetic tree (how much ancestry shared/how much evolution occurred)
- Basics of phylogenetics (Intro)
- Phylogenetic tree: branching diagram; pattern of descent; hypothesis about evolutionary relationships
- Dichotomies: 2-way branch points
- Extant species: alive, tips of branches
- How to read a phylogeny
- Rooted tree: represents most recent common ancestor of all taxa on tree
- Basal taxon: diverges early/originates near common ancestor (Ex: ancestor more like leopard, fewest changes) -> note that ancestors don’t have all char. Of descendants
- Branch point: divergence of 2 species from common ancestor
- Sister taxa: 2 taxa share immediate common ancestor (most recently related)
- Polytomy: >2 groups emerge from 1 branch
- Monophyletic: includes ancestor/all descendants
- All members of group share common ancestor, trace evolutionary relationships
- Paraphyletic grouping (missing descendants, common ancestor included): common ancestry and some but not all descendants, not a natural evolutionary grouping
- Polyphyletic grouping (wrong descendants, common ancestor is missing): doesn’t include most recent common ancestor and misrepresents evolutionary relationships
- Making phylogenetics: inferred from molecular/morphological traits
- Cladistics: groups organisms by common descent/ancestry
- Clade: group including ancestral species/all descendants
- General methods
- Homology (homologous): derived from common ancestor
- Analogies (analogous characteristics): not good for phylogenies
- Convergent evolution (independently acquired) bc of similar evolutionary pressure; not from same ancestor
- Homologies are good characteristics to build tree; all characters in phylogeny must result from homology (bat/bird wings are homologous as forelimbs, analogous as functional wings) -> divergent
- Shared ancestral characters: char. Of group present in ancestors that remain present in descendants
- Shared derived characters: char. Unique to particular clade; originates in recent CA and present in all descendants
- Outgroup: taxa diverged before lineage being studied
- Ingroup: taxa being studied
- Recent development use programs/math to analyze relationships (primary structure of proteins--DNA, mRNA sequence/molecular similarities: same pattern to distinguish homology from analogy)
| Homologous | Analogous |
|---|---|
| Common ancestry | Common selection pressures |
| Divergent evolution | Convergent evolution (wings in birds vs bats) |