BIO A01 Lecture 8: Classification & Phylogeny I

Practice vocabulary flashcards covering the principles of phylogenetic trees, systematics, homologies, homoplasies, character traits, and tree topologies from Lecture 8 of BIO A01.

Systematics

The science of organizing and understanding the history of organismal evolution, which relies on phylogenies.

Phylogenetic Tree

A two-dimensional, bifurcating diagram that captures the evolution and diversification of a group of organisms through time, depicting branch order and branch lengths.

Node (Branch Point)

A point on a phylogenetic tree where an ancestral lineage divides into two descendant lineages, representing a common ancestor.

Sister Taxa

Lineages or taxa that share an immediate common ancestor with each other; their positions can be rotated around a node without changing the implied evolutionary relationships.

Polytomy

A branch point on a phylogenetic tree from which more than two descendant groups emerge, reflecting unresolved evolutionary relationships.

Phenotypic Plasticity

A change in the phenotype associated with a given genotype in response to different environmental conditions.

Pleiotropy

The expression of multiple, seemingly unrelated phenotypic traits controlled by a single gene, such as the frizzled feather trait in chickens.

Vicariance

The geographic separation and splitting of a lineage caused by geological events such as continental breakup, island formation, or mountain uplifting.

Homologous Traits

Features in different taxa that share a common evolutionary origin and embryonic structure as a product of divergent evolution.

Analogous Traits

Features that perform a similar function but evolved independently without a common ancestral origin, arising via convergent evolution.

Convergent Evolution

The process by which two or more distinct organisms independently evolve the ability to perform similar functions or develop similar traits, often through adaptive radiation in allopatry.

Homoplasy

Any similarity in traits across taxa that is not due to shared ancestry, including convergent analogous traits, parallelism, and evolutionary reversals.

Evolutionary Reversal

A form of homoplasy where a derived character state reverts back to an ancestral state, such as Gastrotheca guentheri regaining lower jaw teeth after frogs lacked them for 200 million years.

Halteres

Modified wings in insects, such as the hindwings of Diptera or forewings of Strepsiptera, that function gyroscopically to detect deviations from desired flight orientation.

Ancestral Trait

A character state that was present in the ancestor of a particular group or clade under consideration.

Derived Trait

A novel character state that differs from the ancestral trait and arose later within a lineage.

Synapomorphy

A derived trait shared among a group of descendants that serves as evidence of their common ancestry, such as vertebrae in vertebrates or milk production in mammals.

Outgroup

A lineage that falls outside the focal group being studied but is closely related to it, used to identify ancestral versus derived character states.

Monophyletic Group

A phylogenetic grouping consisting of a common ancestor and all of its descendants, uniquely providing an accurate reflection of evolutionary history.

Paraphyletic Group

A phylogenetic grouping that includes a common ancestor and some, but not all, of its descendants.

Polyphyletic Group

A grouping of organisms that does not include their most recent common ancestor.