lecture 7- phylogenies

Phylogeny

The evolutionary history of a group of organisms.

Systematics

The science of classifying organisms and determining their evolutionary relationships.

Taxonomy

The naming and classification of organisms.

Binomial nomenclature

A two-part scientific name: Genus and species (e.g., Homo sapiens).

Cladistics

A method of classification based on common ancestry and shared derived traits.

Principle of parsimony

The simplest explanation (least number of evolutionary changes) is preferred.

Root of phylogenetic tree

Represents the most recent common ancestor of all taxa in the tree.

Node

A branching point in a tree; represents a common ancestor and speciation event.

Sister taxa

Two taxa that are each other's closest relatives.

Monophyletic group (clade)

A group that includes a common ancestor and all of its descendants.

Shared derived character (synapomorphy)

A trait shared by a group of organisms due to a common ancestor, not found in more distant ancestors.

Ancestral character

A trait inherited from a common ancestor, present in both the group being studied and its outgroup.

Homologous traits

Structures with similar origin due to shared ancestry.

Analogous traits

Structures that appear similar due to convergent evolution, not common ancestry.

Convergent evolution

Independent evolution of similar traits in distantly related organisms.

Homoplasy

A trait that appears similar in two taxa but was not inherited from a common ancestor.

Evolutionary reversal

A return to an ancestral trait after it was previously lost.

Outgroup

A taxon outside the group of interest; helps determine ancestral vs. derived traits.

Phylogenetic character types

Morphological, molecular (DNA), developmental, and behavioral traits.

Linnaean classification

Traditional system of ranking organisms, which doesn’t always reflect evolutionary history.

LUCA

Last Universal Common Ancestor; had DNA, cell membranes, ribosomes, and other core features.

Parsimony in trees

Helps choose the tree with the fewest evolutionary changes.

Cutting the tree

One snip = monophyletic group (clade); multiple snips = not monophyletic.