1. The Evolution of Life

2. Geologic Time

3. The Precambrian – Age of Bacteria
4.6 billion – 545 million years ago

4. The Paleozoic – Age of Fishes
million years ago

5. The Mesozoic – Age of Dinosaurs
million years ago

6. The Cenozoic – Age of Mammals
65 million years ago to present day

7. The Precambrian – Age of Bacteria
4.6 billion – 545 million years ago

8. Early Microbial Evolution
The earliest organisms must have been very simple resembling early prokaryotic cells.
Lack nuclei
Anaerobic
Chemoautotrophs that obtained their carbon from carbon dioxide dissolved in the oceans.

9. Prokaryotes
Archaebacteria - Moderen bacteria that live in extremely hostile conditions.
Appear to be close to the root of the tree of life.
Obtain their energy through chemical reactions.
Methanogens
Anaerobic
Halophiles
Salty conditions
Thermophiles
Extreme heat

10. Rate of Evolution in Early Organisms
Early organisms experience a higher rate of evolution because…
Early organisms lacked the efficient enzymes for DNA replication.
There were many errors as DNA was copied from one generation to the next
More errors meant more mutations and a higher rate of evolution.

11. What is the evidence of rapid early diversification of Organisms?
Stromatolites
Photosynthesis begins 3.5 billion years ago

12. The Oxygen Revolution
2.35 billion years ago

13. Photosynthesis Most important new metabolic process evolved gradually
Organisms that lived close to ocean surface probably developed means of absorbing sunlight (UV in particular)
Once absorbed, developed method of turning it into energy
Modern organisms of purple sulfur bacteria and green sulfur bacteria much like early photosynthetic microbes, use H2S instead of H2O for photosynthesis

14. Photosynthesis
Using water for photosynthesis developed later, perhaps 3.5 billion years ago
First appearing in cyanobacteria (blue-green algae)
By product of O2, released into atmosphere
Changed the world!

15. Oxygen Crises The rise of oxygen created a crisis for life.
It attack the bonds of organic molecules.
Many species went extinct.
Species that survived had to evolve new metabolic mechanisms or live in environments where there was no Oxygen.
Oxygen could be used to generate a far superior metabolic pathway that would provide much more energy.

16. Early Eukaryotes Fossil evidence dates to 2.1 bill. Yr ago
Dates to when O2 rising in atmosphere
DNA evidence suggests that prokaryotes and eukaryotes separated from common ancestor much earlier
O2 played a key role in eukaryote evolution
Cells can produce energy more efficiently using aerobic metabolism than anaerobic metabolism
Adaptations of aerobic organisms could develop adaptations that required more energy than would be available for anaerobic organisms

17. What two adaptations lead to the rise of modern eukaryotes?
Some cells developed specialized infoldings of their membranes that compartmentalized certain cell functions.
Large host cells absorbed smaller prokaryotes with specialized functions. These cells developed a symbiotic relationship
Smaller cells developed into mitochondria

18. Mitochondria contain their own DNA.
What evidence suggest that modern eukaryotes developed mitochondria through edosymbiosis?
Mitochondria contain their own DNA.
A single circular chromosome
DNA is structured like prokaryote DNA
Mitochondria divide independently of the cell

19. The Ediacaran Fauna (575 mya)

20. Precambrian Continents
Precambrian continents were smaller, thinner, and moved more rapidly

21. The Paleozoic

22. The Paleozoic – Age of Fishes
million years ago

23. The Cambrian Explosion (525 mya)

24. The Cambrian Explosion
Animal branch of the tree of life
Different classifications based on body plan
All known body plans made appearance in fossil record in a time span of 40 million years
<1% of Earth’s age
Animal diversity began 545 mill. Yr ago

25. Why did the diversification of animals occur so suddenly?
Oxygen levels reached a high enough level for the survival of larger and more energy intensive life forms.
The evolution of genetic complexity
A milder climate away from a snow ball earth
Efficient preditors

26. Why haven’t we seen other explosions of diversification like the Cambian?
Once predators were efficient and widespread, it was more difficult for entirely new body forms to find an available environment.

27. The Cambrian World

28. Middle Paleozoic Seas

29. Dunkleosteus – Late Devonian

30. Colonization of Land Life flourished where liquid water exist
Life on land was more complicated
Had to develop means of collecting solar energy above ground and nutrients below
Protection from U.V. light
Life in shallow ponds or edges of lakes
Water evaporates
Natural selection favored that which could withstand periods of drought

31. Colonization of Land
DNA evidence suggests that plants evolved from an algae.
algae developed thick cell walls to help them survive dry periods.
It took only 75 mill. Yrs for animals to follow plants out of water

32. Appear in the Late Silurian, diversify in the Devonian
First Land Plants and Insects
Appear in the Late Silurian, diversify in the Devonian

33. First trees and forests
Late Devonian
Archaeopteris

34. Eusthenopteron and Ichthyostega
Animals move ashore
Eusthenopteron and Ichthyostega

35. The Formation of Pangaea

36. Geologic Time

37. The Mesozoic – Age of Dinosaurs
million years ago

38. Origination of Mammals

39. Origination of Birds
Archaeopteryx (Jurassic)

40. White Cliffs of Dover: Cretaceous Chalk

41. Cretaceous marine turtle, ~ 15’
Archelon
Cretaceous marine turtle, ~ 15’

42. First Flowers, Bees, and Grass
145 million years ago in the Cretaceous period

43. The End-Mesozoic Extinction

45. Did an impact kill the dinosaurs?
Iridium layer at the K-T boundary
High abundance of rare metals at the K-T boundary
Osmium, gold and platinum
Spherical Rocks called droplets found in the K-T boundary.
Soot found in the boundary.

46. Geologic Time

47. The Cenozoic – Age of Mammals
65 million years ago to present day

48. Radiation of mammals and large, predatory birds

49. The Paleogene of North America

50. Largest known land mammal – 18’ at the shoulder
Peraceratherium
Largest known land mammal – 18’ at the shoulder

51. Mass Extinctions

52. Mass Extinctions Possible Causes Impacts Active volcanism
Impact sites found for K-T boundary
Suspected for Permian extinction 245 mill yr ago
Active volcanism
Climate change
External influence for copying errors
Increase in solar particles or radiation hitting surface
Local supernova

53. Extinctions
Demise of Species