Phylogeny & Systematics Understanding the Tree of Life

An Introduction to Nomenclature and Classification Classification Systems: Assign a name to each organism Place into groups with similar traits & evolutionary histories The Linnean Classification System: Developed binomial nomenclature Gave organisms a 2-part name

Canis familiaris (dog) GENUS SPECIES NAME (group belongs to) (Latin description of a characteristic) Canis = canines familiaris = common Ursus arctos (Grizzly bear) Ursus = bear, arctos = Northern Acer rubrum (red maple) Acer = maple, rubrum = red

Process of Taxonomy Linneaus’ System Groups organisms to assigned TAXA (singular TAXON) Process called TAXONOMY Domain Kingdom Phylum Class Order Family Genus Species

A Taxonomic Example Canis Familiaris Domain = Eukarya (eukaryotes) Kingdom = Animalia (animals) Phylum = Chordata (spinal cord) Class = Mammalia (mammals) Order = Carnivora (carnivores) Family = Canidae Genus = Canis Species = familiaris

A simple phylogenetic tree

Phylogeny & Systematics Defined Phylogeny: Evolutionary history of a species or group of species often use the fossil record to “map out” connections Systematics: Analysis of diversity & relationships between organisms. May include: - morphology (how organisms look) - biochemical similarities - similarities in DNA

How do we use the Fossil Record? Use placement of organisms within the various layers of sediments Limitations… an incomplete record of true organism diversity

Layers in Time… Sediments settle at bottom of oceans, rivers, etc Fossils are formed in each layer Sea floor is pushed upward to form mountain ranges & eroded material exposes strata/fossils

Homologies & Analogies Homologous structures Analagous structures In difference species that serve different functions but came from the SAME ancestral parts Similar in appearance & function but came from DIFFERENT ancestors Examples: - bird vs insect - fish vs whale * Also called convergent evolution

Homologous Structures Analagous Structures Homologous Structures

Cladogram Clade: A group of species that includes an ancestral species plus all its descendants The analysis of how species are grouped in clades is called CLADISTICS Cladogram shows evolutionary history of specific traits & shared characteristics without a focus on the rate of evolutionary change

Phylogenetic Tree Phylogenetic Trees represent relative patterns of evolutionary branching An Ultrametric Tree will include data corresponding to the actual time of evolutionary events

Molecular Clocks Based on the principle that some genes/genomes evolve or mutate at a constant rate Can estimate the date of evolutionary events that can’t be determined accurately in the fossil record For example… DNA: more closely related organisms are, the closer their genetic code will be Cytochrome C: protein found in most organisms (differences in this protein due to mutation… close ancestry = few differences)