Extinction
Extinction of Dinosaurs and Other Species
Introduction to Extinction
Understanding extinction through the lens of modern animals.
Exploration of which extinct animals include:
A. Dimetrodon
B. Mammoth
C. Smilodon
D. Trilobite
Overview of Extinct Animals
Trilobites:
Dominant during the Paleozoic Era.
Did not survive the end of the Permian extinction.
Dimetrodon:
An early synapsid; closely related to mammals.
Went extinct in the Triassic period.
Smilodon (saber-toothed cat):
Extinct but has close relatives like lions.
Mammoth:
Extinct but related to modern elephants.
Conclusion on Extinct Animals
All options A, B, C, and D (Dimetrodon, Mammoth, Smilodon, Trilobite) are correct in being extinct.
Evolution of species includes both emergence and extinction.
Definition of Extinction
Extinction: The entire population of a species is gone.
Recent extinctions attributed largely to human activities:
Thylacine (Marsupial Wolf):
Extinct in 1936 due to hunting and disease.
Carolina Parakeet:
Extinct in 1918 due to deforestation and feather demand.
Passenger Pigeon:
Last individual died in 1914.
Overhunting despite population of 5 billion.
Current Status of Extant Species
Extant Species: Species that are currently alive.
Many extant species are at risk of extinction:
Javan Rhino: Less than 60 remain in the wild.
Spix Macaw: Extinct in the wild, survives only in captivity.
Efforts to Prevent Extinction
Intensive human efforts can bring species back from brink:
Example: California condors saved through captive breeding from only 22 individuals.
Natural Extinction process
Extinction is a natural, ongoing process in Earth's history.
Average lifespan of species before extinction is:
One million to ten million years.
With approx. 10,000,000 species on Earth, one extinction occurs annually.
Mass Extinctions
There are historical mass extinction events where numerous species went extinct simultaneously:
End of the Permian
End of the Triassic
End of the Ordovician
End of the Devonian
End of the Cretaceous (66 million years ago):
Major extinction event that eliminated non-avian dinosaurs.
Other Groups Extinct during the End Cretaceous
Extinct during the end Cretaceous:
A. Ammonites
C. Mosasaurs
Survived =
D. Multituberculate mammals
B. Champsosaurs
Paleontology at the University of Alberta
The museum showcases animals before and after the end Cretaceous mass extinction.
At that time, non-avian dinosaurs were still dominant in both numbers and size.
Evolving Groups Pre-Cretaceous Extinction
Birds were present and had diversified, represented by now-extinct groups such as Hesperinithiformes and Antornithiformes.
Pterosaurs (largest flying animals) did not survive the event.
Early mammals were small, like shrew or mouse-sized insectivores:
Example: Multituberculates (e.g., Campo Baatar).
Fossilized remains mainly consist of isolated teeth.
Post-Cretaceous Survivors
Surviving groups included:
Placental mammals (distant relative of modern deer).
Marsupial mammals (example: opossum jaw).
Extinction of multituberculates by approximately 35 million years ago.
Turtles and Crocodiles:
Common both pre and post-Cretaceous mass extinction.
Survived possibly due to inhabiting freshwater environments.
Recent studies suggest:
Freshwater habitats may have provided better survival rates during mass extinction events.
Vegetation Changes
Cretaceous landscape dominated by ferns, moss, conifers, and beginning to see flowering plants.
By the end of the Cretaceous, familiar marine life included:
Plankton, clams, snails, bony fish, sharks, and various extinct species such as:
Ammonites
Mosasaurs
Plesiosaurs
Champsosaurus
Survived the end Cretaceous extinction but became extinct by the end of the Eocene (about 33 million years ago).
Superficially crocodilian but has a distinct evolutionary history.