lec 13 Flashcards
Two extinction types
Actual Extinction
Functional Extinction
Actual Extinction
end of an organism/species
- when the last existing member of a species dies
Functional Extinction
Only a few individuals left
- population not viable
- odds of survival slim
- can be years or decades prior to actual extinction
Mass extinction event
Loss of a large number of species on earth in a short period of time
- does not include minor extinction events(pre-Cambrian, now maybe)
percent of animal species that are extinct
66%
natural extinction rate
1-10 species/five years, 9% of species per million years
Most species survive
1-10 million years(according to the fossil record)
human activity on birds
since 1800, 106 species have been lost, trend has reversed in past two decades, naturally 1-2 birds per hundred years
extinctions correlated with
major environnmental changes
- climate change
- atmostphere(O2)
- Land masses
- continental drift
- floods
- glaciation
- volcanic eruptions
- meteorite impacts
How many major extinction events have there been?
5.
End-Ordovician mass extinction resulted of
Massive glaciers formed over the land, sea levels dropped, ocean temps. dropped, 60% to 70% of all species went extinct.
-Ranked as the second largest of the five major extinctions
Late Devonian Mass Extinction resulted of
Uncertain, though two large meteorites collided with Earth at this time, Impact created massive fires, tsunami, major amounts of dust shoot up into atmosphere, 70% of all species west extinct
This extinction event lasted as long as 20 million years
End-Permian Mass Extinction result of
Enormous meteorite hits Australia, outpouring of lava into the oceans that reduces O2 content of oceans, oceans release toxic CO2 and H2S into atmosphere. These gases poison those that survived the meteorite impact resulting in a 96% decline in species on Earth
-enormous evolutionary significance: on land, it ended the rise of mammal-like reptiles
End-Triassic Mass Extinction result of
Uncertain as to exact cause; however, a large meteorite hit what is now Quebec at this time. About 70% to 75% of all species went extinct
-Most non-dinosaurs and large amphibians eliminated, leaving dinosaurs with little competition
End-Cretaceous Mass Extinction result of
Likely a meteor collision. In addition to a meteor the Indian continent saw significant volcanism that occurred continuously for ~500,000 years. Iridium layer could have resulted from this volcanism. There is no doubt about the significance of the meteor impact, what is in question is how much did the volcano add to the impact
