Origins of Life

1. Origins of Life • Early Idea: Spontaneous Generation • The idea that non-living material can produce life—Life magically appears! • Examples • Meat produces maggots • Mud produces fish (mudskippers) • Grain produces mice

2. Origins of Life • Francesco Redi disproved the theory of spontaneous generation in 1668 • Experiments with rotting meat

3. Origins of Life • Also during this time, scientists were just beginning to use microscopes… • They were able to see that microorganisms were EVERYWHERE! • Even though Redi was able to disprove the theory of spontaneous generation, many scientists thought that microorganisms arose spontaneously from a “vital force” in the air

4. Origins of Life • Louis Pasteur • Disproved the spontaneous generation of microorganisms • Experiments with broth

5. Origins of Life • Pasteur’s experiments showed that microorganisms do not arise from the broth alone even in the presence of air • Biogenesis became the accepted theory about the origin of life • Biogenesis is the idea that living organisms only come from other living organisms

6. How Did Life Begin On Earth? • Currently, there is no way to know for certain how life began on Earth. • Scientists have developed theories about the origins of life, using the scientific method to test hypotheses about conditions on early Earth. • Only about 1% of all known species exist today • 99% are extinct!

7. How Did Life Begin On Earth? • Early Earth • Very Hot • Meteorite Collisions • Volcanoes • Very little oxygen • Atmosphere made of H2O Vapor, CO2, Nitrogen gas, Methane & Ammonia

8. How Did Life Begin On Earth? • Ingredients for Life: Before life can occur, you need the molecules of life • 1st: Formation of simple organic molecules • 2nd: Organization into complex organic molecules • Proteins/Carbohydrates/Nucleic Acids/Lipids • So… How did this happen in such a harsh environment?

9. How Did Life Begin On Earth? • Alexander Oparin (1930’s) • Life began in the oceans • Sun, lightening & heat caused chemical reactions producing organic molecules • These molecules washed into the ocean forming primordial soup

10. How Did Life Begin On Earth? • Miller & Urey (1953) • Tested Oparin’s theory by simulating conditions on early Earth in a lab • Mixture of H2O vapor, ammonia, methane, and hydrogen gasses were zapped with electrodes • Cooled gasses condensed in flask • After a week, several kinds of amino acids, sugars, and other small organic molecules were present in the flask

11. How Did Life Begin On Earth? • The next steps in the origin of life were the formation of complex organic molecules and cells. • Sidney Fox – produced protocells by heating solutions of amino acids • Protocells – a large ordered structure, enclosed by a membrane, that carries outsome life activities, such as growth and division.

12. The First True Cells • First forms of life were prokaryotes that likely evolved from protocells • Anaerobic Heterotrophs • Later, early prokaryotes evolved to be able to make their own food • These were similar to archaebacteria and used chemosynthesis to produce their food

13. The First Photosynthetic Prokaryotes • Likely the next kind of organisms to have evolved were: • Able to use sun to make glucose • Produced OXYGEN, which changed Earth’s atmosphere • Lightening + Oxygen = Ozone Layer formation

14. The First Eukaryotes • The Endosymbionic Theory • Lynn Margulis – 1960’s • Eukaryotes evolved from prokaryotes • Evolved b/c of symbiotic relationships between early prokaryotic bacteria (mitochondria & chloroplasts)

15. The Record Of Life • Paleontologists – scientists who study ancient life, often using fossil evidence • Uses fossils to determine look and characteristics of the organism, as well as the climate and geography of the area. • Fossils – evidence of an organism that lived long ago • typically found in sedimentary rock • compressed clay/sand/mud

16. The Record Of Life • Different kinds of fossils: • Trace • Casts • Imprints • Petrified • Molds • Amber • Frozen Trace Fossil Cast Fossil Imprint Fossil Mold Fossil Amber Fossil Frozen Fossil

17. The Record Of Life • Fossil Aging • Relative Dating – The deeper the fossil, the older it is. • Radiometric Dating – Uses radioactive isotopes to determine specific ages of fossils. • Potassium-40: used for really old fossils • Carbon-14:used for fossils less than 50,000 years old

18. Geologic Time Scale • Chronology, or calendar, of the Earth’s history. • Based on evidence from rocks • Organized according to living organisms of the time period • 4 different eras

19. Time Line of Earth’s History • 4.6 billion ybp – Earth forms • hot/volcanoes/meteors/ancient atmosphere • 3.9 billion ybp – Earth cools • water vapor condenses. Millions of yrs of rainstorms create oceans • 3.9-3.5 billion ybp – Precambrian Era • First organisms appear, photosynthesizing organisms add OXYGEN to atmosphere • 3.5 billion ybp – unicellular prokaryotes • 1.8 billion ybp – eukaryotic organisms develop • 544 million ybp – multicellular eukaryotes (sponges & jellyfish)

20. Time Line of Earth’s History • 540 million ybp – Paleozoic Era • Animals & plants appeared • 500 million ybp – first vertebrates • 430 million ybp – first land plants • 390 million ybp – first amphibians • 300 million ybp – first reptiles • 250 million ybp – mass extinction

21. Time Line of Earth’s History • 245 million ybp – Mesozoic Era • Age of the Dinosaurs • 245 million ybp – Triassic Period • 225 million ybp: first dinosaurs • 210 million ybp: first mammals • 208 million ybp – Jurassic Period • 150 million ybp: first birds • 144 million ybp – Cretaceous Period • 135 million ybp: continents broke apart & began to drift • 66 million ybp: mass extinction of dinosaurs

22. Time Line of Earth’s History • 66 million ybp – Cenozoic Era • Era in which we now live • 30 million ybp – Primates appear • 200,000 ybp – Modern Humans Appear