Life on earth through time

1. Life on earth through time

2. Let’s start at the beginning... • How did the solar system (and earth) form from a rotating cloud of dust, particles and gases? 4.6 By

3. Half-a-billion years later... • Lava plains and moon craters date back to ~3.9 By • How did the moon form?

4. Life, maybe • Marine sediment by 3.8 By; evidence for liquid water on earth • Oldest fossil in 3.5 By old rocks in Western Australia • Debate continues… is this really evidence for life at 3.5 By? 3500 Ma

5. Cyanobacteria • Suggested to be an early form of cyanobacteria • Stromatolites- layers formed by webs of filimentous cyanobacteria

6. Prokaryotes to Eukaryotes • About a billion years of evolution gave us membrane-bound organelles • Endosymbiotic theory 2100 Ma

7. O2 rich atmosphere • Photoautotrophs: • 6 CO2 + 6 H2O-> C6H12O6 +6 O2 • Oxygenated atmosphere by 1.8 Ba • Aerobic organisms- use O2 to covert food to energy is favorable relative to fermentation

8. Complex multi-cellular life • See a surge in diversity of multi-cellular life ~600 My… • Improvement in fossil record • First chordates 600 Ma

9. Phanerozoic • Apparent life • Rich fossil record starts in middle age of the earth

10. Early fish 440 Ma • Appear in upper Cambrian (550 Ma) • Jawless, cartilagenous and eventually the bony fishes • Importance of the bony lineage

11. Land plants • A progression from marine algae to freshwater algae to green algae • Vascular land plants- have the ability to transport water and nutrients within plant 430 Ma

12. Trees • What are the benefits of a woody trunk? • With plants and trees well established, what is next? 370 Ma

13. Amphibians • Land dwellers • Return to water to lay eggs and for larvae to mature • Adaptations: 3-chambered heart, limbs and girdle bones, sturdy but flexible spinal column, ear structure 360 Ma

14. Insects • First insects were wingless • Wings appear in late Carboniferous • Extensive radiation before the Permian 300 Ma

15. Reptiles • Reproduce without returning to water • Enclosed eggs • Pass through larval stage • Born in essentially adult form 290 Ma

16. Dinosaurs • Dinosaurs: started off small with light build (225 Ma) • Large carnivores Jurassic and Cretaceous • Were they cold or warm-blooded? • Vascular development of bones • Relation to birds

17. 210 Ma

18. Early Mammals • Tiny shrew-like creatures • Reliable temperature control • Co-existing with Dinosaurs through Mesozoic 210 Ma

19. Birds • Poor fossil record • Archaeopteryx: the perfect evolutionary link between theropods and modern birds • Feathers on a reptile • Jaw bone with teeth • Wings retained claws 150 Ma

20. IMPACT! 65 Ma

21. K-T boundary • Bolide ~10 km in diameter crashed into Earth sending up dust, ejecta into the atmosphere • Cloud blocked sunlight and led to the demise of plants, base of food chain • Marine and terrestrial animals perished

22. Whales • From land to sea • Descendents of carnivorous land mammals, the earliest of whom could walk and swim • With increasing size, lost limbs • Adapted feeding strategy 50 Ma

23. Primates • Grasping, mobile hand • Overlapping field of vision • By 34 Ma- anthropoids (apes, monkeys, humans) 34 Ma

24. Genus Homo • 2.4 Ma: Homo habilis • 1.8 Ma: Homo erectus • Increased cranial capacity; sloped forehead, jutting jaw, robust teeth 2.4 Ma

25. Homo sapiens neaderthalensis • Heavy brow ridges, chinless jaws, large brain cavity, short limbs, bulky torso • Hunted, used fire for warmth, light, cooking, constructed shelters from the skins • 34,000 yrs-replaced by Homo sapiens sapiens 320 ky

26. Mass Extinctions K-T boundary Permo-Triassic boundary

27. “Mother of all extinctions” • Late Permian: 90% of all marine species lost or reduced; tropical marine invertebrates hardest hit • On land, spore bearing ferns gave way to conifers, ginkoes and gymnosperms • Amphibians, reptiles lost • Causes: Configuration of the continents, loss of epeiric seas, ice on poles, volcanic activity

28. Late Ordivician (440 My) and late Devonian ME’s triggered by global cooling with the growth of the ice caps- due to compressed biomes, lowered sea level • Impacted: marine invertebrates • Late Devonian: again cooling- reefs communities hit hardest

29. The influence of tectonics on climate • Position of continents dictates: • Ocean circulation and heat transport • Sea level (freeboard)- Pangaea • Ability to form ice caps

30. Example: Miocene grasslands and horse evolution • Closure of Tethys (~35 Ma) with collision of Africa and Eurasia • Cooling & drying with loss of forests, expansion of grasses

31. Horse adaptations • Horses in Eocene (50 Ma): small, 4 toed, fed on shrubs and foliage • Grasses expanded • Horses in Miocene • Higher crowned teeth • Fewer toes • Bigger, stronger, faster

32. Organisms effect on the environment? • Examples: • Photosynthesis • Spread of land plants • Nutrient cycling

33. The marine N cycle • Nitrogen is an essential nutrient the limiting nutrient • When there is more available nitrogen in a useful form, primary productivity is higher, CO2 removed from atmosphere “The biological pump”

34. Sedimentary d15N • Use stable isotopes of N to identify relative inputs/outputs in ocean in past • Sediment and microfossil samples

35. Peru-Chile Margin

36. Goals • Changes in productivity through time • Variability in denitrification (the removal of nitrate) in the Eastern Tropical North Pacific • Understanding the role of the N-cycle in glacial-interglacial CO2 cycles