Classifying Organisms Taxonomy Hierarchical system of classification Different

Classifying Organisms

Taxonomy • Hierarchical system of classification – Different levels of specificity • Purpose – Scientific name – allows precise identification • Genus species • Example - Homo sapiens – Grouping according to evolutionary relationships

Species • Group of organisms that: – Share fairly consistent appearance and function – Can be distinguished from other organisms – Interbreed • Approximately 1. 4 million species identified • Estimated 10 million in existence

Variation Within a Species

Taxon • Named taxonomic unit at a particular hierarchical level – Domain – Kingdom – Phylum – Class – Order – Family – Genus – Species Most Inclusive Least Inclusive

Structural Relationships • Homologous – Similar structures – Shared ancestor – Often differ because of divergent evolution • Analogous – Similar structures – Different ancestors – Product of convergent evolution

Phenetics • Grouping according to sum of shared characteristics – Individual characteristic are equal in significance

Cladistics • Grouping according to evolutionary divergence – Cladogram – a graphical representation of evolutionary relationships • Each branch point is assigned a homology – Derived Character

Types of groupings • Monophyletic – Single ancestor • Polyphyletic – Multiple ancestors – Not an acceptable grouping • Paraphyletic – Excluded species share common ancestor

Bacteria • Prokaryotes • Most primitive organism – Many highly specialized forms • Most abundant on earth – Found everywhere • 12 -15 major groups • Evolved efficient methods to harness energy – Aerobic respiration – Photosynthesis

Archaea • Prokaryotes • Diverged from Bacteria • Three categories – Methanogens – Extremophiles – Nonextreme archaebacteria

Eukarya • Eukaryotes • Complex organelles • Most have energy organelles – Mitochondria – Chloroplasts • Includes organisms with the following: – Sexual reproduction – Diploid genomes – Multicellular

Origin of Eukaryotes