Phylogeny and the Tree of Life

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Slide 1

Investigating the Tree of Life

Phylogeny is the evolutionary history of a species or group of related species.

The discipline of systematics classifies organisms and determines their evolutionary relationships.

Systematists use fossil, molecular, and genetic data to infer evolutionary relationships.

Taxonomy is the ordered division and naming of organisms.

Slide 2

Binomial Nomenclature

In the 18th century, Carolus Linnaeus published a system of taxonomy based on resemblances.

The two-part scientific name: Genus species.

The first letter of the genus is capitalized, and the entire species name is italicized

Both parts together name the species. This is the species specific epithet.

Slide 3

Hierarchical Classification

Linnaeus introduced a system for grouping species in increasingly broad categories.

The taxonomic groups from broad to narrow are domain, kingdom, phylum, class, order, family, genus, and species.

A taxonomic unit at any level of hierarchy is called a taxon.

Slide 4

Taxonomy: Hierarchical Organization: Domain Kingdom Phylum Class Order Family Genus species

Species:

Panthera

pardus

Genus: Panthera

Family: Felidae

Order: Carnivora

Class: Mammalia

Phylum: Chordata

Kingdom: Animalia

Archaea

Domain: Eukarya

Bacteria

Slide 5

Linking Classification and Phylogeny Evolutionary Relationships

Systematists depict evolutionary relationships in branching phylogenetic trees.

Their PhyloCode recognizes only groups that include a common ancestor and all its descendents.

A phylogenetic tree represents a hypothesis about evolutionary relationships.

Each branch point represents the divergence of two species.

Sister taxa are groups that share an immediate common ancestor.

Slide 6

Species

Canis

lupus

Pantherapardus

Taxidea

taxus

Lutra lutra

Canis

latrans

Order

Family

Genus

Carnivora

Felidae

Mustelidae

Canidae

Canis

Lutra

Taxidea

Panthera

Phylogenetic Trees

Evolutionary Relationships

Slide 7

A rooted tree includes a branch to represent the last common ancestor of all taxa in the tree:

Sister

taxa

ANCESTRAL

LINEAGE

Taxon A

Polytomy is a branch from which more than two groups emerge