Lecture 18 - Extinctions & Adaptive Radiations Flashcards
What does the history of life reveal?
the rise and fall of major groups of organisms
What are the 3 factors that major changes can be attributed to?
- plate tectonics/continental drift
- mass extinctions
- adaptive radiations
What was the formation of countries originally called?
Pangea
How many times has Pangea formed?
come together and shifted apart 3 times
How many mass extinction events occurred?
5
How many of earth’s species became extinct during these mass extinctions?
More than 50%
What was the Permian extinction?
- loss of 95% of marine species
- largest extinction ever
- caused by volcanoes
What was the Cretaceous extinction?
- loss of mammals
- probably caused by meteor (65 mya)
- loss of dinosaurs
What is evidence of a meteorite?
The Chicxulub crater off the coast of Mexico
Why could we be in the midst of the 6th mass extinction?
- more species than ever
- extinction rates are extremely high
What are 3 taxonomic issues why current species estimates are bad?
- lumpers vs. splitters
- different species definitions
- hard to distinguish hybrids from distinct species
What are 5 types of reasons that explain why current species estimates are bad?
- taxonomic issues
- geographic biases
- taxonomic biases
- taxonomists are going extinct
- difficulty of documenting extinction
What are 3 reasons why past species estimates are bad?
- fossilization is rare
- fossils are nearly impossible to ID to species
- fossil record is biased
What is the fossil record bias toward?
- large, widespread organisms
- higher taxa
- North America/Europe
- economic importance
When can adaptive radiations occur? (3)
- when organisms colonize a new habitat
- when groups go extinct
- when key innovations evolve
