Chapter 18 Phylogeny and the Tree of Life

Phylogeny u Phylon = tribe, geny = genesis or origin u The evolutionary history of a species or a group of related species.

Phylogeny u Found in the fossil record, molecules and genomes.

Systematics u The study of biological diversity and classification. u Uses evidence from the fossil record and other sources to reconstruct phylogeny.

Systematics fuses: 1. Phylogeny- tracing of evolutionary relationships. 2. Taxonomy- the identification and classification of species.

Taxonomy u Modern system developed by Linnaeus in the 18 th century.

Linnaeus Taxonomy 1. Binomial Nomenclature – two names for each organism. Ex - Homo sapiens 2. Hierarchical System – arranges life into groups. Ex - Kingdom  Species: List

7 hierarchical divisions u Kingdom  Phylum  Class  Order  Family  Genus  Species u King Phillip Came Over From Germany Sorry.

Scientific names u Composed of Genus and species. u Written in Latin and shown in italics or underlined.

Phylogenetic Tree u Branching diagram showing evolutionary relationships between organisms. u AKA Cladogram

Phylogenetic tree - Example

Trees show: u Ancestral lineage u Branch points u Length of branch point suggests “time” and degree of closeness.

Phylogenetic tree - Example Branch point Ancestral Lineage

DNA patterns u If similar DNA – more closely related, more recent common ancestor. u If different DNA – less closely related, less recent common ancestor.

Making a Tree u Maximum parsimony – requires fewest DNA base changes. (most simple explanation) u Branch lengths – suggest the closeness of the relationships

5 Kingdom System u R.H. Whittaker u System most widely used, but is changing.

Main Characteristics u Cell Type u Structure u Nutrition Mode

Current Views u Domains – a system of classification that is higher than kingdom.

3 Domains 1. Bacteria – prokaryotic. 2. Archaea – prokaryotic, but biochemically similar to eukaryotic cells. 3. Eukarya – the traditional eukaryotic cells.