BIO 265 Lecture 13

Microevolution

Evolutionary processes that occur within species

Macroevolution

Evolution above the species level, including rates of evolution, origin of novel features, evolutionary trends, and patterns of origination, extinction, and diversification of higher taxa

Gradualism

The hypothesis that evolution proceeds gradually; this is the pace that Charles Darwin believed predominated

Punctuated equilibrium

A pace of evolutionary change in which long periods of little change (stasis) is followed by short periods of rapid change

Habitat tracking

The shifting of the geographic distributions of species in concert with the distributions of their typical habitat

Saltation

Sudden evolutionary changes that happen in a single generation, rather than gradually

Living fossils

Organisms that have changed so little over millions of years that they closely resemble ancestors from millions of years ago

Phylogenetic niche conservatism

Tendency of species to retain their ancestral traits and maintain a long-continued dependence on much the same resources and environmental conditions

End Ordovician (440 mya)

May have been proportionally the second largest extinction

Late Devonian (365 mya)

May have been multiple extinction pulses of up to 15 my in duration

End Permian (250 mya)

Most severe mass extinction event

End Triassic (215 mya)

One of the least intense mass extinctions

Cretaceous-Tertiary or K-T (65 mya)

About 50% of all species became extinct; evidence for impact of a large meteor

Background extinction rate

The extinction rate occurring outside of mass extinction events; roughly estimated to be ~1 extinction per million species years; encompasses about 96% of known extinction events

Evolutionary trend

A persistent, directional change in the average value of a feature (character state)

Passive trend

Lineages in the clade evolve in both directions with equal probability

Active (or driven) trend

Changes in one direction are more likely than changes in the other

Predictability of evolutionary paths

The evolutionary history of life was inevitable; states that evolutionary parallelism and convergence are widespread and dictate evolutionary process at small and large scales

Contingency of evolutionary paths

The path of evolution has been directed by chance events, such that the outcome of history would be different if any of the antecedent events had been different