lec 28- radiation and extinction Flashcards
what was the biggest adaptive radiation event ever?
the Cambrian explosion, origin of many new body plans
the DNA of how many living phyla existed before the Cambrian explosion?
37
what influenced early diversification?
HOX and regulatory genes
who came up with the punctuated equilibrium theory?
Niles Eldredge and Stephen Jay Gould
what is the punctuated equilibrium theory?
history of species diversity is relatively stable (Stasis) but is interrupted (punctuated) by geologically brief periods of rapid change and speciation
what does the punctuated equilibrium model oppose?
Neo-Darwinian views that evolutionary change is slow (gradualism), as the model supported rapid evolution
relatively rapid speciation with no fossils is likely due to:
founder effects, drift, Evo-Devo changes and selection
what are the two ways lineages can split (speciation)?
Anagenesis: slow lineage splitting
Cladogenesis: faster with survival of ancestor
what is background extinction?
the normal expected rate of extinction for a particular taxonomic group, relatively slow for most organisms
what is mass extinction?
the loss of many whole clades or organisms in a relatively short time span
what are the 5 extinction events?
- End-Ordovician extinction
- Late-Devonian extinction
- End-Permian extinction
- Late-Triassic extinction
- End-Cretaceous extinction
what was the biggest extinction in the big 5 that killed the most life and when did it occur?
-End-Permian extinction, 90% of all species, 96% of marine species, 70% terrestrial vertebrates
-occured 250 Mya
what are some examples of species that went extinct during the End Permian extinction?
-all ammonites
-trilobites
-mammal-like reptiles
what are some potential causes for the End Permian extinction?
-major release of volcanic gases (CO2 and H2S) leading to ocean warming, acidification, Anoxia (O2 loss to cells)
-Siberian traps (Lava flows)
-formation of pangaea, which changed ocean circulation patterns
did the formation of Pangaea reduce shallow water habitats like the great barrier reef?
yes
when did the End Cretaceous extinction occur?
66 Mya
who came up with the hypothesis that a meteorite hit earth during the Cretaceous and how did they come to it?
-Alvarez brothers found iridium in the clay layer from the Cretaceous, indicating that iridium which is more common on asteroids most likely hit the earth for it to be so common across that layer
-crater at Yucatan Peninsula, Mexico
is boundary clay the sign of the cretaceous extinction event?
yes
how were the ecosystems disrupted from the asteroid hit?
-global fires first occurred, then nuclear winter which had dark cold conditions and disrupted vegetation resulting in extinction on land and in water
what is the 6th big mass extinction event?
occuring right now by the humans hunting, fishing, moving species around, and causing radical environmental changes
what is the new geological period of humans called?
Anthropocene
how have flightless birds come to be and how have some gone extinct?
-flightless birds came to be on islands with no predators
-when predators were introduced, some flightless birds went extinct like the Lyalls Wren from a cat
how much of a temperature increase is a tipping point for many models?
4 degrees celcius increase
