PTYS 214 – Spring 2011 Next week is Spring Break – NO CLASSES Class website: http://www.lpl.arizona.edu/undergrad/classes/spring2011/ Pierazzo_214/ Useful Reading: class website “Reading Material” http://www.pnas.org/content/96/20/10955.full http://en.wikipedia.org/wiki/Mass-independent_fractionation http://en.wikipedia.org/wiki/Fossil_record_of_fire http://en.wikipedia.org/wiki/Great_Oxygenation_Event Announcements
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PTYS 214 – Spring 2011
Next week is Spring Break – NO CLASSES
Class website: http://www.lpl.arizona.edu/undergrad/classes/spring2011/Pierazzo_214/
Useful Reading: class website “Reading Material” http://www.pnas.org/content/96/20/10955.full http://en.wikipedia.org/wiki/Mass-independent_fractionation http://en.wikipedia.org/wiki/Fossil_record_of_fire http://en.wikipedia.org/wiki/Great_Oxygenation_Event
Announcements
Midterm
Total Students: 30
Class Average: 72.6
Low: 35
High: 103
Midterm is worth 20% of the grade
5 0 6 0 7 0 8 0 9 0
0
5
10
# S
tude
nts
GradeE D C B A
Early Life Summary
Evidence of the earliest life on Earth is difficult to prove:
– Isotopic evidence seems to date it back to about 3.5 Gyr (Pilbara craton, Australia)
– Oldest stromatolites are about 3.46 Gryr old
– Earliest microfossils (accepted) date back to about 2.55 Gyr (Transvaal Supergroup, South Africa)
– Earliest molecular biomarkers date back to about 2.5-2.7 Gyr old rocks (Pilbara, Australia)
Atmospheric Oxygen
All terrestrial life requires energy, carbon and nutrients, and liquid water
Why is atmospheric oxygen important for life?
1. All terrestrial multicellular life requires high O2 CH2O + O2 → H2O + CO2 + energy
2. Almost all terrestrial life requires some protection from UV
Earth-like complex life requires not only energy, water, nutrients and carbon but also oxygen and ozone (UV
protection)
Suppose the environment has everything indicated above (Phanerozoic eon)
Does it mean that the animal life will evolve smoothly?
No!
Mass ExtinctionSharp decrease in the number of species in a relatively
short period of time
1) It must be a rapid event (from less than 10,000 to 100,000 years)
2) A significant part of all life on Earth became extinct (use of families is more reliable than species; for example extinction of 18% of all families corresponds to about 40% of all genera and 70% of all species)
3) Extinct life forms must have came from different phyla, lived in different habitats, spread out over the whole world