1. ORIGINS OF LIFE

2. HISTORY OF THE SEARCH FOR A BEGINNING Spontaneous Generation: Idea that life comes from non-living things. Lazzaro Spallanzani (1729)* Francesco Redi* John Needham* *Were all contemporaries Louis Pasteur (1864)

3. REDI’S EXPERIMENT Proof that spontaneous generation did not work as Needham and others thought.

4. What did Spallanzani do? Was skeptical of spontaneous generation. Was influenced by the work of Redi. Redi said that animals didn’t just appear, that eggs were laid that were too small to see. Noted that covering the flask prevented growth of bacteria in the gravy.

5. Why was Needham Wrong? What do you see is the problem with Needham’s set up? Why did he think that his work supported SG?

6. PASTEUR’S EXPERIMENT Experiment proved SG was wrong, led to a deeper understanding “germs”

7. PASTEUR’S FLASK

9. ANCIENT EARTH-4.6BYA

10. ANCIENT EARTH IN UPPER MICHIGAN? -Greenstone, a rock that contains microfossils can be found in the UP -The fossils are prokaryotes (no nucleus)

11. EVIDENCE FOR ANCIENT LIFE WORLDWIDE

12. WORLD OF THE PRECAMBRIAN

13. EARTH’S ANCIENT ATMOSPHERE WATER VAPOR (H20) CARBON MONOXIDE (CO) CARBON DIOXIDE (CO2) HYDROGEN (H2) NITROGEN(N2) AMMONIA(NH3) METHANE (CH4)

14. MILLER AND UREY EXPERIMENT -Tried to imitate Earth’s early atmosphere by mixing gases -Simulated sun and lightning by electrical spark. -Produced organic molecules, including some components of DNA, RNA

15. ORGANIC MOLECULES IN SPACE AND FROM BELOW

16. HOW DO COMPLEX MOLECULES FORM? Organic molecules collect together in the absence of oxygen to form short protein chains. The molecules tend to form into “droplets”, these are coacervates, they are life-like but not alive. RNA has chemical properties that lead us to believe it was formed first.

17. FIRST CELLS Prokaryotes that are similar to bacteria. Anaerobes, can live without oxygen.

18. Photosynthesis-the Early Years Organisms would need to learn how to get food. Heterotrophs would need to get their own food (they can’t make their own). Autotrophs, organisms that can carry out photosynthesis, would have been successful. Early autotrophs would have used hydrogen sulfide instead of water. Formed stromatolites

19. BANDED IRON FORMATION

20. Evolution of Aerobic Metabolism Started as Earth’s atmosphere developed more Oxygen because of photosynthesis. Metabolism that uses oxygen. Gives more energy per sugar molecule than aerobic methods.

21. Eukaryotic Revolution! 1.4 to 1.6 BYA Cells that contain a nucleus. Have other organelles Reproduce sexually Sexual reproduction is an advantage because it mixes the genes around in a better way. Would lead the way to multi-cellular organisms.

22. What is an microbial mat? Very thin layer of microbes and cyanobacteria Provide clues to very early life on earth. Early example of photosynthesis. Grow in such a variety of places that scientists use them as a guide for the search for extraterrestrial life.

23. We study the past by using the present as a model! Principle of uniformitarianism Extremophiles Microbial Mats

25. Microbial Mats Continued

26. What are extremophiles? Organisms that live in extreme conditions. Severe cold, heat High acid or Low acid (pH scale) Extreme pressures Used as clues to possible life forms in space.

27. Let’s look at Yellowstone National Park for an Example

28. Other Examples

29. Halophiles, Methanogens

30. Where can we look to study life similar to our ancient origins? EXTREME LOCATIONS ON EARTH USE THIS INFORMATION TO SEEK OUT LIFE IN OTHER LOCATIONS IN OUR SOLAR SYSTEM OTHER SOLAR SYSTEMS TOO. CALLED ASTROBIOLOGY