Phylogeny and Systematics Order out of chaos…

Phylogeny Phylon = tribe Genesis = origin The evolutionary history of a species or a group of related species Part of the science of Systematics Systematics ecompasses phylogeny and taxonomy The evolutionary history of a species or group of species

Fossils Form in sedimentary rocks Hard parts such as shell, bone, or teeth Hardened by mineralization Soft parts replaced by mineralization becoming stone Molds or casts of decayed organisms Preservation in amber, ice, tar

Relative Dating Younger sediments are on top of older ones Index fossils are widespread and reliable ones Rock layers provide a “relative” age for fossils in the layers

Geological Time Scale Four eras: Precambrian, Paleozoic, Mesozoic, and Cenozoic Boundaries between eras correspond to mass extinctions Eras are subdivided into Periods Periods are subdivided into Epochs

Absolute Dating Ages given in year quantities Ratio of Carbon-12 to Carbon-14 Carbon-14 decays to Nitrogen-14 Half-life of C-14 is 5,730 years U-238 has a half-life of 4.5 billion years L-amino acids convert to D forms over time Racemization clock is temperature sensitive Click here to see a half life simulation

Types of Radioactive Decay Alpha decay – Helium nucleus ejected Beta decay – Electron or positron ejected Gamma decay – Gamma photon emitted Read more about radioactive decay

Continental Drift Major geographic factor in evolution Continents move about on the Earth’s surface Continents merged as Pangea 250 mya. Pangea begins to break up 180 mya.

How the dinosaurs died out…

Mass Extinctions Mass extinctions are followed by diversification of survivors Extinctions are inevitable in a changing world Permian extinction: 95% of marine animals became extinct in less than 5 million yrs. Cretaceous extinction separates Mesozoic and Cenozoic eras: 65 mya Impact hypothesis

SYSTEMATICS The study of biological diversity in an evolutionary context

Carolus Linnaeus, or Carl Linné, , Swedish botanist

Taxonomy The naming and classification of organisms Formalized by Carolus Linnaeus( ) Binomial nomenclature: Genus & species Leopard = Panthera pardus African Lion = Panthera leo Hierarchical classification system Taxon = a group at any level (plural,taxa)

Domains

Diversity of Systems

CLADISTICS A Taxonomic Approach To Classification

Cladistics Phylogenetic approach to classification Based on dichotomous (2-way) branching Branches show new species budding from a common ancestor Branching symbolizes historical chronology Each branch is called a clade Clades consist of an ancestral species and all of its descendants: Monophyletic

Examine groups for common ancestors. Branches should bifurcate (split in two). Taxon one consists of an ancestral species and all of its descendents Taxon 2 includes some, but not all of A’s descendents Taxon 3 lacks a common ancestor. Two ancestors for one group (D,E,G,H)

Cladistic Analysis Clades are defined by their shared-derived characters The outgoup (Lancelet) and ingroup share characters that were present in the common ancestor. The ingoup is defined by the presence of a vertebral column.

Phylogeny Inferred From Morphological data (comparative anatomy) Fossil data DNA Proteins Embryology (embryo & fetal development)

Molecular Clocks Rely on genomic regions that evolve at a fairly constant rate Must be referenced to fossil records to provide accuracy Difficult to relate to absolute time