Age of earth and solar system ….4.5-4.6 bya (radioisotopic dating of meteorites)

1. Age of earth and solar system….4.5-4.6 bya (radioisotopic dating of meteorites)

2. Early impacts were colossal A Mars sized chunk hit earth and dislodged a chunk of earth that became the moon Some solid crust by about 4 bya (some rocks in Canada are 3.96 billion years old). Surface water by about 3.8 bya (sedimentary rocks of that age in Greenland)

3. How do we define life? What steps do you need to get evolution of life?

4. What steps do you need to get evolution of life? P459 Small organic molecules (like amino acids) Joining of these into longer macromolecules (like proteins, nucleic acids) A packaging of some sort Origin of self replication

5. Small Organic Molecules like amino acids? Miller and Urey Hydrogen methane and ammonia

6. 2. Assembly of these building blocks into polymers Now we need to get them together into proteins and nucleic acids Drip solutions onto hot rocks evaporation borders encourage polymerization (hooking together) or Ice!

7. Miller and Bada As an ice crystal forms, it stays pure: Only molecules of water join the growing crystal, while impurities like salt or cyanide are excluded. These impurities become crowded in microscopic pockets of liquid within the ice, and this crowding causes the molecules to collide more often. Chemically speaking, it transforms a tepid seventh-grade school dance into a raging molecular mosh pit.http://discovermagazine.com/2008/feb/

8. 3. Packaging-Acquire cellular form We know now that membranes often form spontaneously under certain circumstances-vesicles Hydrophobic molecules in a mixture organize into a bilayer at the surface of droplets like the lipid bilayer of a plasma membranes This will control entry and exit from the “cell”

9. 4. Origin of self replicating polymers RNA world Important in protein synthesis but also can take on enzyme like functions. DNA probably evolved later as a safe depository for genetic info-more stable

10. So what evidence do we see for early life?

11. Oldest fossils of Prokaryotes Stromatolites p440 Similar to Cyanobacteria (3.5bya) Relatives still exist in Western Australia

12. Chemical fingerprints-Carbon Isotope (Harrison, Manning and Mojzis) Remember those sedimentary rocks in Greenland (3.85).. Those rocks have been heated and squished so unlikely to see fossils but… Look at carbon isotope ratios and can detect presence of life..

13. “The carbon aggregates in the rocks have a ratio of about 100-to-one of 12C (the most common isotope form of carbon, containing six protons and six neutrons) to 13C (a rarer isotopic form of carbon, containing six protons and seven neutrons). The light carbon, 12C, is more than 3 percent more abundant than scientists would expect to find if life were not present, and 3 percent is very significant……..” http://www.sciencedaily.com/releases/2006/07/060721090947.htm

14. Where?? • Surface ponds-Primordial soup-Surface dangerous! Why? • Deep sea vents- Interesting amino acids form there • “The worst impacts would have been 10-100 million years apart and a handful of hardy bacterial souls could have survived at the bottom of the oceans….” • Science News December 2000

15. Other planets? Panspermia hypothesis… Europa (moon of JUPITER) water and active volcanoes -hydrothermal vents in liquid ocean capped by ice?? Mars-today is cold and dry but had liquid water and it may have had an atmosphere that warmed it…

16. What else do we know? We do find large spherical organic molecules called fullerenes at meteor impact sites. Bacteria can survive outer space!

17. Last fall…. (Time Magazine description of article in PLOS) • That adds up to about 20 billion Earths in our galaxy alone, says lead author Erik Petigura, of the University of California, Berkeley. That in turn means that an Earth-like world is likely to be just 12 light-years away, and that its parent star is visible to the naked eye. “It’s really amazing when you think about it,” Petigura says. • Read more: 20 Billion Earths in the Milky Way Alone? | TIME.comhttp://science.time.com/2013/11/04/so-much-for-earth-being-special-there-could-be-20-billion-just-like-it/#ixzz2mKVgqMRv

18. Figure 23.10 1,100 1,000 25 900 800 20 700 600 15 Total extinction rate (families per million years): Number of families: 500 400 10 300 200 5 100 0 0 Mesozoic Paleozoic Era Period Cenozoic Q E O S D C P Tr J C P N 542 488 444 416 359 299 251 200 145 65.5 0 Time (mya)

19. Precambrian before about 500mya • Prokaryotes • Eukaryotes-1.8bya is fossil date for evolution of multicellularity but is some evidence for much earlier • Cambrian explosion • Paleozoic • End Permian Extinction • Mesozoic • Cretaceous Extinction • Cenozoic

20. Cambrian explosion about 500mya (550mya) Nearly all major “styles” or body plans of animals appear! Major evidence is from Burgess Shale in B.C. CANADA (also from China and Greenland) Are earlier fossils of animals but are soft and squishy (see Fig 25.2 p483 bottom right Ediacaran)

22. Paleozoic Period about 500-250mya Climate-Moist Swampy Plants-ferns, mosses, horsetail Giant insects

23. Many diverse amphibians were large! 9ft And scary fish Science Daily Tiktaalik roseae, an early tetrapodomorph (late Devonian period, ~380 M. y. ago) (Credit: Arthur Weasley, GNU Free Documentation licence)

24. Many Diverse Synapsids (p 441 mentioned) A dicynodont Thrinaxodon-cynodont nationalgeographic.com

25. More Synapsids

26. Figure 23.4a Reptiles (including dinosaurs and birds) OTHER TETRAPODS †Dimetrodon Synapsids †Very late (non-mammalian)cynodonts Therapsids Cynodonts Mammals

27. Figure 23.10 1,100 1,000 25 900 800 20 700 600 15 Total extinction rate (families per million years): Number of families: 500 400 10 300 200 5 100 0 0 Mesozoic Paleozoic Era Period Cenozoic Q E O S D C P Tr J C P N 542 488 444 416 359 299 251 200 145 65.5 0 Time (mya)

28. End Permian-250mya Effect 90-96% of all species Who Extinct? Synapsids, many Amphibians! Giant insects-dragonflies, cockroaches Horsetail trees, Tree ferns (some) Why? Huge amounts of lava oozing out of the earth Siberia Formation of Pangaea Mixing of oceans slows-anoxic http://www.nationalgeographic.com/ngm/0009/feature4/

29. Mesozoic about 250-65mya • Since Pangaea had formed===DRY • Plants-conifers… • Dinos super diverse! Mammals around.. • Flying and pollinating insects begin to diversify with flowering plants

30. Pterosaurs Plesiosaurs Ichthyosaurs Dinosaurs

31. Cretaceous Extinction event (K/T)! Figure 23.10 1,100 1,000 25 900 800 20 700 600 15 Total extinction rate (families per million years): Number of families: 500 400 10 300 200 5 100 0 0 Mesozoic Paleozoic Era Period Cenozoic Q E O S D C P Tr J C P N 542 488 444 416 359 299 251 200 145 65.5 0 Time (mya)

32. 7 miles across…

33. Cretaceous (K/T) Effect 50% of all species Who? Dinosaurs, Pterosaurs, Plesiosaurs, many small marine species On land nothing bigger than 25 kgs survived-all survivors were small Why? Impact

34. There is debate about the precise role of the impact on Dinosaur Extinctions.. • Opinions range from…. • Impact was the cause • Impact was one of the causes • Impact was the straw that broke the camel’s back (dinos were in decline before the impact)

35. Cenozoic -65mya to present Spreading apart of continents.. Flowering plant diversity accelerates Insects continue dramatic diversification Mammals diversify

36. More Mass Extinction… • Catastrophism • So.. Although classic “Darwinian” slow adaptive evolution is important…. • we now appreciate the role of catastrophic events (chance events) in the evolution of the diverse forms of life on the planet!

37. Remember…there is a creative side.. Extinctions open up new space for “adaptive radiations” • Ex. Mammals after Cretaceous extinction event • Ex. Dinos diversified after End-permian extinction when Synapsids extinct

38. The species alive today are only a tiny fraction of all those that have ever lived. • The vast majority of all species in the history of the planet have gone extinct. • So extinction is normal • Average lifespan of a species from its origin to its extinction is between 1 and 5 million years

39. Species Average Lifespan years (MYA) All Invertebrates Raup (1978) 11 Marine Invertebrates Valentine (1970) 5–10 Marine Animals Raup (1991) 4 Marine Animals Sepkoski (1992) 5 All Fossil Groups Simpson (1952) .5–5 Mammals Martin (1993) 1 Cenozoic Mammals Raup and Stanley (1978) 1–2 Diatoms Van Valen 8 Dinoflagellates Van Valen (1973) 13 Planktonic Foraminifera Van Valen (1973) 7 Cenozoic Bivalves Raup and Stanley (1978) 10 Echinoderms Durham (1970) 6 Silurian Graptolites Rickards (1977) 2 Adapted from the book “extinction rates”, edited by Lawton, J, and May, R.[8] Wikipedia!!

40. How long did it take for diversity to recover after Permian extinction event? ESTIMATE!!! Figure 23.10 1,100 1,000 25 900 800 20 700 600 15 Total extinction rate (families per million years): Number of families: 500 400 10 300 200 5 100 0 0 Mesozoic Paleozoic Era Period Cenozoic Q E O S D C P Tr J C P N 542 488 444 416 359 299 251 200 145 65.5 0 Time (mya)

41. www.geol.umd.edu/.../lectures/natresources.html