Phylogeny

Phylogeny

the evolutionary history of a species or a group of related species

Systematics

a scientific discipline focused on classifying organisms and determining evolutionary relationships

Taxonomy

a scientific discipline concerned with naming and classifying the diverse forms of life

Taxon

the named taxonomic unit at any level of the hierarchy 

Phylogenetic Tree

the evolutionary history of a group of organisms can be represented by a branching diagram

Basal Taxon

a lineage that diverges from all other members of its group early in the history of the group

Morphology

the study of size, shape, and structure of organisms (including animals, plants, and microorganisms)

Homologies

phenotypes and genetic similarities due to a shared ancestry

Analogy

similarity between two species that is due to convergent evolution rather than to descent from a common ancestor

Convergent Evolution

when similar environmental pressures and natural selection produce similar (analogous) adaptations in organisms from different evolutionary lineages

Species 

an evolutionary lineage (branch) on the tree of life, all descending from a common ancestor

Clade

a most recent common ancestor (MRCA) and all of its descendants

Synapomorphy

shared, derived trait present in ancestor and descendants

Homoplasy

shared character not inherited from a common ancestor

Cladogram

only the branching pattern is shown on tree (monophyletic group)

Sister Taxa

two species or clades that are each other’s closest relatives on a given tree

Vestigial Structure

structure that has lost its function