Periodic Extinctions Have Been the Rule for Life on Earth
description
Transcript of Periodic Extinctions Have Been the Rule for Life on Earth
Periodic Extinctions Have Been the Rule for Life on Earth
• Extinction has been wide spread.– Cambrian -
• 80% of families -• > 90% of species
– Permian - • 60% families• 90% species
– Cretaceous - • 20% families• > 50% species
Is it possible that life has not been a process of ever expanding
diversity?• Could speciation
and diversification be a process of periodic extinction and subsequent reradiation?
So How Old is the Earliest living Organism?
Gunflint Chert in Banded Iron formation -- Lake Superiorabout 1.9 b.y. old
Stromatolites - bacterial tuftsWestern Australia & elsewhere
Contain fossilbacteria (cyanbobacteria)3.5 - 4.0 b.y. old
For many years 5 kingdom system held
• New Techniques have discovered much more diversity, leading to revision of classification
Bio 103 home