phylogenies Flashcards
taxonomy:
organizing species into hierarchy of groups
who invented taxonomy and binomial nomenclature?
Carolus Linnaeus
taxon:
unit at any level of hierarchy
binomial nomenclature
naming organisms using Genus and Species
order of taxonomy (most specific to broad)
species, genus, family, order, class, phylum, kingdom, domain
family for fox
canidae
order for fox
carnivora
class for fox
mammal
phylum for fox
chordata
kingdom for fox
Animalia
domain for fox
eukarya
phylogenetic trees connect
classification to evolutionary history
branch point:
common ancestor shared by branches
root:
common ancestor of tree
basal taxon:
oldest common ancestor
sister taxa:
share unique common ancestor
to create phylogenies, you look for ___ and ignore ____
look for homologies, ignore analogies
homologies:
shared traits due to similar ancestry
morphological homology
similar physical structure or traits
molecular homology
similar DNA, especially mutations
analogous structures are similar due to ______ not because of ____
similar due to shared lifestyle, not because of shared ancestry
analogies often arise due to ____
convergence
how to identify analogies:
-other traits are ___ _____
-complex structures are more likely to be ____, not ____
-similarities in _____ and ____are less likely to be analogies
- not similar
-homologies, not analogies
-cDNA and long sequences
cladistics
classifies organisms by common ancestry
cladistics may not match classification by …
physical traits
clade
common ancestor and all taxa that descent from it
shared ancestral characteristic
existed before common ancestor of clade
shared derived characteristic
new trait is unique to clade (only within clade)
arranging homologies: 2 options
maximum parsimony and maximum likelihood
maximum parsimony: focus on…
simplicity in connections
traits evolve as few times as possible
maximum parsimony
maximum likelihood focus on simplicity in
steps
genomes store evolutionary history: ___ evolve more slowly
critical genes (most mutations are BAD)
genomes store evolutionary history: ____ evolve faster
less critical genes
increased number of genes in genome provides…
more material for mutations and natural selection (evolution!)
why do duplicated genes mutate faster?
-less critical
-free of selective pressure
-original copy is still functional, so mutations are less dangerous
exadaptation: after mutation, duplicated genes…
serve new function
horizontal gene transfer
- part of genome is shared with unrelated species
- shared traits not from recent common ancestor
mechanics of horizontal gene transfer:
- transposable elements
- plasmids
- viruses
