1. Earth’s Early History

2. Mystery of Life’s Origins
Using radiometric dating, scientists believe the Earth to be between 4.2 and 4.6 Billion Years Old.
Earth’s early atmosphere contained little or no oxygen.
Made up of mostly: CO2, water vapor, and nitrogen

3. How did Life Begin? 3 ideas of how life may have gotten on Earth
Divine Creation – a higher being put us here on Earth
Extraterrestrial Origin – life may have come to Earth via an asteroid or meteorite.
Spontaneous Origin – process through which life is thought to have developed when molecules of non-living matter reacted chemically during the 1st billion years.

4. Spontaneous Origin 1920’s A.I. Oparin – Primordial Soup Model
Oceans were a big soup bowl with large amounts of organic molecules
Chemical reactions spontaneously occurred in soup with energy from lightning/volcanoes
Proposed that Earth’s early atmosphere lacked oxygen, yet had plenty of nitrogen, hydrogen, water vapor (earth was hot), methane and ammonia.

5. Stanley Miller 1953, tested Oparin’s hypothesis
Placed gases in apparatus, zapped it, and found some basic chemicals could have formed spontaneously
2 problems
Too slow
Not sure methane and ammonia was available, and if it was, UV would destroy it

7. Louis Lerman 1986 – Bubble Model
Chemical reactions took place in the bubbles of the ocean
Reactions would take place faster in bubbles
Inside bubbles, methane and ammonia protected from UV rays
Leading hypothesis accepted to date

8. Origins of Eukaryotic Cells
Endosymbiotic Theory – proposes that a symbiotic relationship evolved over time, between primitive eukaryotic cells and the prokaryotic cells within them.
Ex. Mitochondria and Chloroplasts are thought to have been ancient prokaryotes
Both have their own DNA, ribosomes and both reproduce by binary fission like bacteria cells