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 was first to disprove 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?
Early Earth
Very Hot
Meteorite Collisions
Volcanoes
Very little oxygen
Atmosphere made of H2O Vapor, CO2, N gas, CH4 & NH3

7. 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?

8. How Did Life Begin On Earth?
Miller & Urey (1953)
Tested theory by simulating conditions on early Earth in a lab
Mixture of H20 vapor, NH3, CH4, and H gasses was 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

9. How Did Life Begin On Earth?
The next steps in the origin of life were the formation of complex organic molecules and cells
Heat caused the amino acids to form proteins and also caused the production of ATP and nucleic acids
Doing this formed “protocells” – or large ordered structures, enclosed by a membrane that carries out life functions

10. 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

11. 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

12. The Endosymbiont Theory
Lynn Margulis, in 1960’s
Eukaryotes evolved from prokaryotes as a result of symbiotic relationship between prokaryotic bacteria