1. Extinction

2. Frequency vs Size for impacts – 1 “killer” impact every one hundred million years  is this the random mechanisms to populate the galaxy?

3. Extraterrestrial influences and extinctions Is there a 26 million year periodicity in the extinction record? 4 possible explanations: 1.Galactic plane hypothesis 2.Companion star hypothesis 3.Planet X hypothesis 4.Artifact of the way the data are collected Vertical lines drawn every 26 million years

4. Extraterrestrial influences and extinctions Is there a 26 million year periodicity in the extinction record? 4 possible explanations: 1.Galactic plane hypothesis: our solar system moves up and down in a 26 million year cycle through the plane of the galaxy. When we pass through the center, we encounter more gas/dust, higher chance of disturbing the orbit of an asteroid or comet

5. Extraterrestrial influences and extinctions Is there a 26 million year periodicity in the extinction record? 4 possible explanations: 1. 2.Companion star hypothesis: our sun has a companion star (small brown dwarf, <.08 size of sun) in an orbit that passes through the Oort cloud every 26 million years

6. Extraterrestrial influences and extinctions Is there a 26 million year periodicity in the extinction record? 4 possible explanations: 1. 2. 3.Planet X hypothesis: there is a planet that we have never seen, located in an orbit beyond Pluto, that disturbs the Kuiper Belt

7. New Evolutionary Niches Open The Rats Become the Kings

8. Natural Selection Random pairings of traits Ecosystem survival rules Each pairing has a different survival probability If Ecosystem remains largely unchanged, end result is a distribution of most probable values Change takes time: statistical processes require a large number of generations to manifest In the short term, things may appear to be stable

9. Implications I External disruption changes the ecosystem survival rules and therefore changes evolutionary pathways Random large scale catastrophes can reset both the evolutionary clock and the evolutionary timescale This is been a very important component of species evolution on Earth

10. Implications II Evolutionary Clock gets reset Life recovers (relatively rapidly) to fill new ecological niches  this empowers species diversification This means that “survival of the fittest” doesn’t work on long timescales  random catastrophe important Strangely, nature confirms that a “new world will arrive out of the ashes of the old one” This will happen again (right after the final)