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What killed the dinasours - Coggle Diagram
What killed the dinasours
İntroduction and background
(paragraphs1-6)
The 'great dying and other mass extinctions
64-66 million years ago, Mesozoic Era, fossils were found
more than %50 of all known species extinct
example of mass extinction
Permo-triassic extinction
%90 of all species living at that time were extinguished
cause is many changing global conditions
K-T extinction
extinction of dinosaurs at the boundary between Cretaceous period (K)- Tertiary peridod(T)
incorporates scientist from different fields
divide age of mamals and age of dinasours
Mamals and non-dinasaurian reptiles relatively unaffected
dramatic incease in diversity at the K-T boundary
Current arguments(paragraphs 21-35)
The intrinsic gradualists
volcanism
enough dust and soot to block the sunlight -> climate change
plate tectonics
The 'extrinsic catastropthists'
The Alvarez Hypothesis
large extraterrestrial object collided with earth and throw dust into air therefore climate change happened.
iridium layer says asteroid impact
Multiple asteroid impacts
climate change happened
Complications for scientists(paragraphs 7-12)
Time resolution
Determining the age of rocks or fossils, carbon dating with organic material usage
Reconstruction
Understanding the paleoecology around the K-T boundary
The fossil record
New fossils are hidden in the rocks , North America
Falsifiability
Hypotheses about dinosaures extinction. However, can not be proven by scientists
The nature of extinction
Cessation of the origination of new species that renders a group extinct, dinosaurs species ceased to originate around the K-T boundary
Invalid hypotheses (paragraphs 13-20)
Mammals outcompeted the Ds.:
not provable, cannot reconstruct the ecosystem and see if the mammals outcompeted ds.
Mammals ate all of the Ds.’ eggs:
we have no evidence,mamals changed their diet to eat eggs
Ds. got so big that they crushed themselves:
proved false , no general trend of increasing for dinosaurs in this era
Cosmic rays killed the Ds.:
non provable,K-T boundary can emmit dangerous radiation,
Disease killed the Ds.:
flowering plants arose (4 years before the extinction) -> allergic reaction
cross into new areas -> travelling dinosaurs spread diseases x the last dinosaurs were quite normal so it could not be like that
The Ds. just faded away into extinction:
decline in dinasour diverstiy in late Cretaceous period, runs into problems of time resolation,hypothesis states that dinosaurs slowly went extinct,
Conclusion(paragraphs 36-41)
The main problem with both the 'intrinsic' and 'extrinsic' hypotheses:
Issue of the selectivity of the mass extinction, some organisms were wiped out
Why it is important to understand the K-T extinction
Understanding mass extinctions in general and providing a glimpse of our own mortality