Life On Earth

1. Life On Earth

3. Origins of Life on Earth • “Big Bang” • Earth formation • Cooling period • Early atmosphere • H, N, CO, CO2 • Life begins…..

4. Origins of Life on Earth • Spontaneous generation vs. Biogenesis?

5. Origins of Life on Earth • Conditions of early earth • Oxidizing vs. Reducing environments

6. Four-Stage Hypothesis • Chemical evolution: formation of simple organics • Monomers to polymers (complex organics) • Origin of enclosed cell membrane • Origin of an self replication What evidence do we have for these hypotheses?

7. Testing the four-stage hypothesis • Stage 1: Chemical evolution • Miller-Urey experiment

8. Testing the four-stage hypothesis • Stage 2: Formation of polymers • Evaporation of solutes • Colloidal properties of sand/clay

9. Testing the four-stage hypothesis • Stage 3: Enclosed membrane • Liposomes • Protobionts and natural selection

10. Testing the four-stage hypothesis • Stage 4: Self replicating molecules • RNA World

11. Dawning of the Cell • What were the first cells like? • Where did they live? • How did they get their energy?

12. Dawning of the Cell • Prokaryotic = “before” “nucleus” • First bacteria split • Archaebacteria • Eubacteria

14. Dawning of the Cell • Atmospheric changes • Diversity of metabolism Stromatolites

15. The Unseen Multitudes • Incredibly small • Rapid reproduction • Most are good, some are bad

16. Sizes and Shapes • Three basic shapes

17. Reproduction • Prokaryotic Conjugation • Transformation • Transduction

19. Photoautotrophic • Cyanobacteria • “Blue-green algae” • Heterocysts • 3 – 1.5 bya

20. Photoheterotrophic • Where did the DO of marine ecosystems go? • Flow cytometry • Most abundant bacteria on earth?

21. Chemoautotrophic • Deep-sea hydrothermal vents • Produce food using H2S • Cold seeps • CH4

22. Chemoheterotrophic • Pathogenic Bacteria • Endotoxins • Gram -, glycolipids, membrane breakdown • Exotoxins • Gram +, protein, secretion outside bacterium

23. Eukaryotic Origin?

24. Diversity of Protists • Free O2 led to an explosion of diversity • Single and multicelled forms • Early eukaryotes provided the building blocks for the fungi, plants and animals • Protistans represent a diverse group at the crossroads to all the other Kingdoms.

25. Diversity of Protists • Animal-like Protistans (Protozoans) • Single celled heterotrophs • Plant-like Protistans (algae and seaweeds) • Single and multicellular autotrophs • Some are both heterotrophic and autotrophic

26. Diversity of Protists • Protozoans • Amoebas • Flagellates • Ciliates

27. Diversity of Protists • Slime Molds • Analogous to fungi (absorption) • Convergent evolution • Plasmodial slime molds • Cellular slime molds

28. Diversity of Protists • Plasmodial slime molds • Amoeboid style of feeding • Decomposers • Found on forest floor

29. Diversity of Protists • Cellular slime molds • Unicellular feeding mode • Under stress conditions aggregate into slug colony • Move to new feeding location and disassemble

30. Diversity of Protists • Plant-like protists (unicellular algae) • Euglenas • Dinoflagellates • Diatoms • Green algae

31. Diversity of Protists • Plant-like protists (multicellular algae) • Green seaweed • Red seaweed • Brown seaweed

32. From Single-celled to multi-celled life