Classification

Taxonomy Taxonomy – classification of organisms Binomial system of nomenclature (Linnaeus) –Genus and species –Ex: Homo sapiens Taxon (taxa) – formal grouping of organisms at any level Why classify?

Taxa The Linnaeus System works by placing each organism into a layered hierarchy of groups. The groupings (taxa) of taxonomy from most general to most specific are: Kingdom Phylum (animals) or Division (plants) Class Order Family Genus Species Several acronym mnemonics have been made for these, for instance King Phillip came over for good soup, or Kings Play Chess On Funny Green Squares.

Fig. 23-1, p. 485 DOMAIN Eukarya KINGDOM Animalia PHYLUM Chordata CLASS Mammalia ORDER Carnivora FAMILY Felidae GENUS Felis SPECIES Felis catus

Example

Phylogeny: the evolutionary history of a species

Phylogeny What do you think the term evolutionary classification is referring to? If you lived in the time of Linnaeus, how would you have classified dolphins? Barnacles and crabs? Phylogeny – study of evolutionary relationships –Species in a genus have a common ancestor –Genuses in a family have a common ancestor, etc. –Conclusion: the higher the taxon, the further back the common ancestor

Cladograms –Cladistic analysis identifies and considers only those characteristics that are evolutionary innovations –Derived characteristics – characteristics that appear in recent parts of a lineage, but not in older members –Derived characteristics are used to construct cladograms DNA and RNA Analysis to Classify Organisms (similarities and relationships) –African vulture and American Vulture (Turkey Vulture) once thought to be closely related; now we know the American vulture is more closely related to the stork. Molecular clock – uses DNA comparisons to estimate the length of time 2 species have been evolving independently. Complex because each genome has several “ticks” to follow.

Clade Consists of a common ancestor and all its descendants

A Cladogram

Fig. 23-8b, p. 494