Chapter 20: Phylogenesis and the History of Life

Phylogeny

evolutionary history and relationships of an organism

Discipline of systematics

classifies organisms and determines their evolutionary relationships

What does each branch point represent?

the divergence of two taxa from a common ancestor

Sister taxa

groups that share an immediate common ancestor

Limitations of phylogenic trees

Phylogenic trees show patterns of descent, not phenotypic similarity

The levels if classification

taxonomy is the ordered division and naming of organisms

Taxonomic Groups

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

Prokaryote

a single-celled organism that does not have a nucleus or membrane-bound organelles; examples are archaea and bacteria

Eukaryote

a single-celled organism with a nucleus and membrane bound organelles

Binomial

two part scientific name of a species

Genus

first part of scientific name.

Specific epithet

The second part is unique for each species within the genus

Taxonomic unit

any level of hierarchy is called a taxon

The more complex similar structures are

the more likely it is that they are homologous

Clade

group of species that includes an ancestral species and all its descendants

Clade (2)

monophytic signifying that consists of the ancestor species and all its descendants

Organism

has both shared and different characteristics

Shared ancestral character

a character that originated in an ancestor of the taxon

Shared derived character

evolutionary novelty unique to a particular clade

Maximum parsimony

assumes that the tree that requires the fewest evolutionary events (appearances of shared derived characters) is the most likely