domains and the new classification system

4.2.2 c ii

how has classification changed

used to be based on observable characteristics, members of different species could look similar if in same environment

comparing DNA base sequences

see how closely related species are, more similar means more related

how can species have differences in DNA

mutations accumulating over long periods of time from a common ancestor

comparing sequencing of amino acids

compare number of amino acids in a common protein, sequence of amino acids determined by DNA sequence

limitation of comparing amino acid sequences

the genetic code is degenerate so some amino acids may be coded for by different codons

who proposed a change to the classification system and what was it

woese 1977 added a new taxa above kingdom called domain

added 3 domains in 1990: archaea, bacteria and eukaryota

how were the 3 domains distinguished

type of rRNA / ribosomes found and cell membrane structure

how many kingdoms are in the new model

6 as prokaryote split into eubacteria and arcaeabacteria, the other 4 kingdoms are in the same domain of eukaryota

what is eubacteria

found everywhere, majority of bacteria in this kingdom

what is archaea bacteria

extremophiles, eg live in thermal hot springs and anaerobic conditions