7.2 Phylogenetic relationships

Phylogeny

The evolutionary history of relationships among organisms.

Phylogenetic Tree

"Diagram showing evolutionary history and relationships between species

Lineage

Series of ancestor–descendant populations through time.

Node

"Represents a splitting event: speciation (species tree)

Root

The common ancestor of all species/taxa in the tree.

Cladogenesis

Evolutionary process where one ancestral species splits into two or more distinct species (branching evolution).

Anagenesis

Gradual evolution of a single lineage without branching.

Taxon

"Any named group of species (e.g.

Clade

A taxon including a common ancestor and all its descendants.

Sister Species / Clades

Two species or clades that are each other’s closest relatives.

Characters

"Heritable traits used to reconstruct phylogenies (morphology

Shared Character

Trait two lineages have in common.

Derived Character

"A trait unique to a lineage

Synapomorphy

A shared derived trait that provides evidence of common ancestry.

Homologous Traits

"Traits inherited from a common ancestor (e.g.

Analogous Traits

Traits with similar function but evolved independently (convergent evolution). Example: bird vs bat wings as wings.

Evolutionary Reversal

"A trait reverts from a derived state back to an ancestral state (e.g.

Homoplasies

Similar traits due to convergent evolution or evolutionary reversals.

Ingroup

Group of organisms of primary interest in a phylogeny.

Outgroup

"Species closely related but outside the ingroup

Parsimony Principle

The simplest phylogenetic tree (fewest changes/homoplasies) is preferred.

Maximum Likelihood Modeling

Statistical method to identify the tree most likely to produce observed DNA sequence data.

Monophyletic Group

A clade containing a common ancestor and all its descendants.

Paraphyletic Group

Group with a common ancestor but missing some descendants.

Polyphyletic Group

Group that does not include the most recent common ancestor.

Molecular Clock

Uses mutation rates to estimate divergence times; calibrated with fossils or biogeographic data.

Radiometric Dating

Dating method using half-life decay of radioactive isotopes.

Stratigraphy

Dating method based on rock/sediment layering.

Applications of Phylogenetic Analysis

"Reconstruct past events

Binomial Nomenclature

"Two-part naming system by Carl Linnaeus: genus + species (e.g.

Linnaean Classification

"System grouping species into Families

Phylogenetic Classification

Modern system naming only monophyletic clades based on evolutionary history.