Extinction - Paleo

Pseudoextinction

disappearance of species by its evolution into a species recognized as another species (gradualism)

cannot use biological species concept

Extirpation

death of population in one area but population remains in another location

Background extinction

ongoing extinction of individual species due to biological and geological factors

• loss of prey, predation, competition, parasitism/pathogens, habitat loss

Mass extinction

Geologically instantaneous elevation of global extinctions beyond background extinction rates

>10% families and >40% loss of species

Earthbound Mechanisms

• global temperatures

• marine regressions

• volcanism

• ocean effects

Extraterrestrial mechanisms

• radiation

• bollide impacts

End Ordovician

Two pulse extinction event

1 - growth of ice sheets modifies ocean chemistry, glacial maximum causes regression losing shelf environments, ice melting moved oxygen depleted water from deep sea to shallow waters

2 - return of warmer waters causes anoxia and euxhinia, major brachiopod loss

End Devonian

Strong effect on shallow water tropical reef

Greening of land from large forests leeches nutrients onto water causing massive algal bloom taking in O2 in water causing anoxia

Greening forests take lots of CO2 causing global cooling

(Volcanism and impacts in Sweden also considered)

End Permian

Great Dying

loss of 80-96% of species

end of trilobites, tabulates, and rugose, plants not severely affected

1. formation fo Pangaea

2. High levels of volcanism

3. Changes of Ocean chemistry (super ocean made from pangaea)

4. meteor impact? (Australia)

End Triassic

poorly known due to lack of rock record

maybe rifting of Pangaea increased volcanic activity causing global warming and anoxia

End Cretaceous

extraterestrial impact and tectonics big causes

Iridium layer between a change in fossils, shocked quartz, glassy spherules, evidence of wildfires