How many living species?
5000 bacterial species per gram of soil (ា% DNA bp identity)
Millions of non-microbial species (& dropping)
Whole genomes: 45 done since 1995, 322 in the pipeline! (ref)
Sequence bits: 16234 (in 1995) to 79961 species (in 2000) NCBI
& Why study more than one species?
Comparisons allow discrimination of
subtle functional constraints.