Phylogenetics, Transitional Fossils, and Evolutionary Trait Dynamics

Vocabulary flashcards reviewing core evolutionary biology concepts including phylogenetic tree construction, transitional fossils like Tiktaalik, and trait dynamics such as exaptation and reversals based on the lecture.

Principle of parsimony

The evolutionary principle stating that the phylogenetic tree arrangement requiring the least number of evolutionary steps is the preferred hypothesis, because evolving traits is considered rare.

Evolutionary reversal

An evolutionary process where a trait changes from state 0 to state 1, and then turns back to state 0 in a lineage, which counts as two evolutionary steps on a phylogenetic tree.

Polytomy

An unresolved node in a phylogenetic tree where multiple branches emerge simultaneously because available data or equal character step counts cannot separate which lineages branched off first.

Coelacanth

A deep-ocean fish once known only from fossils until a live specimen was caught off Madagascar in the 1950s, notable for having an articulated piece of skeleton extending off its pelvic girdle.

Tiktaalik

A transitional fossil discovered in mid-Devonian sedimentary rocks in northern regions like Baffin Island, serving as an intermediate missing link between lobe-finned fish and early tetrapods.

Neil Shubin

The paleontologist who predicted the existence and location of Tiktaalik in mid-Devonian strata, discovered the fossil near Greenland/Baffin Island, and authored the book Your Inner Fish.

Exaptation

A trait that originally evolved for one function (such as feathers for insulation or species recognition display) and was later co-opted by natural selection for a different function (such as flight).

Ray-finned fish

A group of bony fish, exemplified by the perch, characterized by fin rays powered by a shoulder girdle rather than an articulated limb structure.