18 phylogenics

systematics

study of organismal diversity and grouping

synapomorphy

shared derived characters

phylogeny

depictions of inferred relationships

sister taxon

the closest relatives of a given taxon on a phylogenetic tree. they have the most recent common ancestor

outgroup

one or more species known to be distantly related

node

represent a hypothetical common ancestor

clade

an ancestor and all its descendants

maximum parsimony

-relationships inferred by minimizing the # of evolutionary steps required to explain the data.

-all steps have equal weight

-typically used for morphological data sets

maximum likelihood

-relationships inferred with a substitution model

-accounts for nucleotide chemistry, codon redundancy, morphological complexity

-typically used for genomic data sets

homology

shared between organisms because of descent with a common ancestor

analogy

shared between organisms because of convergent evolution

most recent common ancestor

the most recent individual from which all the people in the group are directly descended

convergent evolution

organisms with similar ecology may develop similar adaptations

substitution model

describes the probability of one nucleotide (DNA) or amino acid (protein) being replaced by another during evolution

molecular clock

locus/loci with relatively constant rate of neutral substitution, useful for estimating divergence time

how do u know when a phylogeny is time calibrated?

the root of the tree corresponds to a known age, and the branches have lengths that reflect the estimated time since the divergence event