Early Atmosphere of Earth, Biology 

• Evidence suggests that active volcanoes covered early Earth. In addition, Earth was probably very hot and bombarded by comets and asteroids 4.2 billion years ago.
• Earth cooled enough to solidify, water vapour to condense, and fall as rain (this allowed permanent oceans)
• Atmosphere: theories suggest it’s atmosphere was similar to gasses from the volcanoes. This means there was little oxygen, and the atmosphere was mostly made of CO2, water vapour, and nitrogen.
• The 1st Organic Molecules: Carbon based molecules are called organic molecules. Some think the Earth had chemical reactions from the limited oxygen, as well as the large amounts of energy from UV rays and lightening, which allowed organic molecules to form.

—Theories suggest that the first organic molecules were amino acids and nucleotides.

Multiple Hypotheses:
1. Organic Molecules: these may have also come on Earth from comets or meteorites. When biochemists added the molecules to water, they formed vesicles,which may be the predecessor to cells.

2. Building Larger Organic Compounds: How did these form without enzymes?  Ocean water containing organic molecules came on a hot surface. After drying, they bonded together to form larger compounds. 

3. Early Genetic Material: Some scientists hypothesise that some of the 1st organic molecules to form & self replicate were RNA molecules. (Called RNA World Hypothesis.)

• RNA molecules: RNA is a catalyst in modern cells. Because of this, RNA self replicates. This is why all organisms share the same genetic code: Yet, no one has seen full RNA molecules self replicate.

Formation of Microspheres: 

• Microsphere: tiny bubbles filled w/ groups of large organic molecules, which form in specificconditions.
• May have preceded lining cells. 
• They combine together until they become unstable and split, precursor to cell division
• In theory, whenever microspheres split, the RNA would be in the new microsphere too. Predecessor to how cells pass on genetic information.

Life on Earth: 

• 2.2 Billion years ago, photosynthetic bacterial cells became common. These cells used sunlight to produce food and give oxygen. Slowly, the ozone layer began to form. The oxygen levels rose, until they because what they are today,