Classifying the Diversity of Life – Systematics Is the study of the diversity and relationships of organisms, both past and present. – Taxonomy Is the identification, naming, and classification of species.

Systems of Classification Classifying is a way of organizing information Classify = to put objects or ideas into groups on the basis of similarity Taxonomist – scientists who study classification Phylogony – evolutionary history of an organism. Why have a system of naming? – Local or common names of species can be different – Different languages name species differently

Aristotle first system of classification Two groups: All organisms as plants or animals Each animal according to where it lived – Land – Water – Air Each plant according to – Size – Structure

Carolus von Linneaus mid-1700’s Determined levels of classification – He used similarities in structure to determine relationships among organisms. Binomial Nomenclature Two-word naming system LATIN! – Genus Noun, Capitalized, Underlined – species Descriptive, Lower Case, Underlined

Hierarchical Classification – The taxonomic hierarchy: – Write them down from largest (Domain) to smallest

Classification and Phylogeny – The goal of classification is to reflect phylogeny, the evolutionary history of a species.

Sorting Homology from Analogy – Homologous structures What are they? Are one of the best sources of information about phylogenetic relationships. – Convergent evolution Involves superficially similar structures in unrelated organisms based on natural selection. – Analogy Is similarity due to convergence.

Molecular Biology as a Tool in Systematics – Molecular systematics Compares DNA and amino acid sequences between organisms. Can reveal evolutionary relationships.

The Cladistic Revolution – Cladistics Is the scientific search for clades, Clades are distinctive branches in the history of life.

Arranging Life into Kingdoms: A Work in Progress – Linnaeus designed a two-kingdom system of classification, Which was replaced by a five-kingdom system in the mid- 20th century. Now we use a six-kingdom system, which may change again! Copyright © 2007 Pearson Education Inc., publishing as Pearson Benjamin Cummings

– In the late 20th century, Molecular studies and cladistics led to the development of a three-domain system. Classification Schemes

Tools! Dichotomous Key: Allows people to identify organisms in the real world based on a series of two choices at each step.