phylogenetics Flashcards
universality of cell biology
- argues for one common ancestor
- genetic code based on DNA
- genetic code expressed via RNAs
- 20 AAs
- ATP use
etc. ..
Why is Classification important?
What tool do we use for classification?
- we use tree of life to help
- important because it insures biologists use the same terminology and nomenclature
- all organisms are placed in hierarchical system
systematics
science of classification
-uses info to develop phylogenies
phylogenies
- geneologies extended over evolutionary time
- view evolution as a descent from a common ancestor
phylogenetic methods
- fossils
- organisms
- genes
- assesses similarities and differences
- all groups must be monophyletic clades
uses of phylogenies
- find ancestor of a pathogen
- history of species
cladogram
shows branching patterns and divergences from CA
-branch lengths are the same
phylogram
conveys time and rate of evolutionary events with branch length
characters
morphologic, anatomic, chemical, and genetic information
homologous
derived from the same common ancestor
analogous
similar, but not homologous
homoplastic characters (homoplasies)
- shared by 2 groups but not possessed by all intervening ancestors
- from parallel or convergent evolution
parallel evolution
- evolves independently in separate, but related groups
- e.g. winglessness in moths
- differs from convergent evolution because ancestors are more similar
convergent evolution
- appears to show relatedness, but doesn’t
- e.g. eyes of vertebrates and cephalopods
synapomorphies
-shared, derived characters
symplesiomorphies
- shared, NOT derived characters
- trait is shown in common ancestor and throughout lineage
apomorphic
derived
plesiomorphic
same as ancestor
autapomorphic
-UNSHARED, derived character
How to separate plesiomorphic from apomorphic
- fossil evidence
- embryology
- USE AN OUTGROUP
sister taxa
-share a common ancestor and diverged at the same time
polytomy
-an area of a phylogeny where a node branches into more than 2 branches
monophyletic
all descendants of a single common ancestor
paraphyletic
-one common ancestor, but not all descendants are included
polyphyletic
group of organisms without a common ancestor
molecular clock hypothesis
Emile Zuckerkandl and Linus Pauling hypothesized that rates of molecular change were constant enough to predict divergence times
Phylogenies –> Classification
- both are hierarchical, so its easy to go between the two
- DKPCOFGS
- names are binomial, italicized, need to be published
Molecular Systematics
- using genes instead of morphology for classification
- entire genomes are regularly sequenced
- rRNA is common sequencing site
- compare sequences of similar species to each other on public sites, like Genbank
