Chapter 9 - Taxonomy

Taxonomy – the science of classifying organisms – has two purposes: To identify the organism To represent relationships among them

History of Taxonomy: Aristotle – believed in the “ladder of nature” – sponges were at the bottom and humans were at the top – he classified things as either plants or animals ( see fig.1 pg.326)

9.1 Taxonomic Systems Carl Linnaeus- 18 th century – he classified organisms based on structure The more features organisms have in common, the closer their relationship

He introduced binomial nomenclature: a 2 name system for naming organism using Latin or Greek ( Latin is a dead language) Ex. Castor canadensis – beaver Genus species - the Genus name is always a capital letter

The 2 names indicate similarities in anatomy, embryology & evolution ancestry Ex. – Ursus americanus (black bear) Ursus horribilis (grizzly bear) koala bear Genus: Phascolarctos Species: cinereus Panda bear Genus Ailuropoda Species: melanoleuca

Modern Taxonomy Today we use these major categories and evidence to support classification: Fossil records – they provide clues, but are rarely complete. Anatomy – a) homologous structures – similar in structure but may have different functions. b) vestigial structures – structures that once had a purpose but no longer serve a function. Comparative embryology – ex. – all vertebrates have a stage as an embryo where they look alike. Comparative biochemistry – comparing DNA, genes and proteins.

Fossil Records

Homologous Structures

Vestigial Structures Vestigial hind legs in a python. Evidence that snakes descended from lizzards.

Comparative Embryology

Comparative Biochemistry

Levels of Classification Organisms are classified based on 7 taxa (levels) Kingdom Phylum Class Order Family Genus Species

Until recently organisms were grouped into 5 kingdoms:

Now it is believed that Monera should be 2 separate kingdoms: Eubacteria

And Archaebacteria

Phylogeny – the history of the evolution of organisms – often shown in a diagram called a phylogenetic tree – see pg.329

A three Domain system of Classification