Lecture 19: Extinction (Exam 3) Flashcards
The definition of extinction and two ways species can “go extinct”
- complete disappearance of a genetic lineage worldwide (and forever)
- two ways: species terminates, or species evolves from a previous form enough to be called a “new” species
The types of extinctions
- background extinction
- extinction events
- mass extinctions
background extinction
- sum of all normal species terminations during a defined time interval
extinction events
- species go extinct for a shared reason which may be regional in scale or may apply to only certain clades or certain ecological guilds
mass extinctions
dissappearance of “much of life” when many species of a broad ecological range died out worldwide and somewhat “rapidly”
the six mass extinctions, roughly when they occurred, and how much life lost
- ordovician-silurian extinction: 440 MYA; 86% loss
- late devonian extinction - 365 MYA; 75% loss
- Permian-Triassic extinction - 252 MYA; 96% loss
- Triassic-Jurassic Extinction - 201.3 MYA; 80% loss
- Cretaceous-Paleogene Extinction - 66 MYA; 60-76% loss
- Holocene Extinction - 11,700 years ago to present; loss continuing
causes +
victims of mass extinctions, generally
causes: meteors, volcanic eruptions, major changes in earth’s atmosphere
victims: random and suffer from “bad genes” (can’t adapt) or “bad luck” (chance events)
What recovery time is proportional to
scale of extinction; larger scale, larger recovery time
what macroevolution is and what processes it involves
- evolutionary patterns and process above the level of the individual
- differential speciation and extinction rates based on heritable traits
Biotic and abiotic drivers of macroevolution (and why its probably more complicated)
- biotic: intrinsic factors, like standing genetic variation
- abiotic: extrinsic factors, driven by changing environments
- complicated because it is a mix of both
