Classification and cladistics

taxonomic levels

domain, king, phylum, class, order, family, genus, species, subspecies

difficulties with taxonomic levels

• disagreement about species, no common agreement about which trait are specific to each group, divergence is gradual, hard to tell when things are different enough to be part of a separate group

advantages of classification corresponding to evolutionary relationship

• every organism sharing the same common ancestor has to be in the same taxonomic group

• in each group, all of the species evolved from the same common ancestor

• e.g. new bat species will all have mammalian characteristics

clades

groups of organisms with common ancestry and shared characteristic - evidence to classify into clade come from base sequence of gene or amino acid sequences of proteins

molecular clock

give estimates as mutation rates are affected by length of generation time, size of population, intensity of selective pressure

principle of parsimony

simpliest answer is usually correct

taxonomy vs cladistifcs

taxo - based on characteristics

cladistics - based on evolutionary origin and gene sequeuncing

new system to classify!

eukaryotes, archaebacteria, eubacteria