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This is an HL topic in IB Bio HL (grade 11)
When was the Formation of Earth
4.5 billion years ago
What was proto-earth like?
During accretion, the proto-Earth was compressed by gravity, causing an increase in temperature. This rise in temperature, along with additional heat supplied by radioactive decay, caused the proto-Earth to become a hot molten mass. As the proto-Earth cooled, it stratified according to density leading to a layered composition.
What is the most favoured explanation of the origin of water on Earth?
That Earth acquired water from extraplanetary objects.
What is the most favoured explanation of the origin of water on Earth?
That Earth acquired water from extraplanetary objects.
What was the weather like in pre-biotic Earth?
Early Earth had frequent volcanic eruptions, meteorites, lighting and high temperatures. High energy UV radiation that would have penetrated the Earth’s surface.
What was pre-biotic atmosphere #1 like?
Earth’s first atmosphere likely began as a region of escaping hydrogen and helium, because these were the main gases in the dusty, gassy disk around the Sun from which the planets formed.
What was pre-biotic atmosphere #2 like?
Earth’s second atmosphere came from Earth itself. It is generally thought that ammonia (NH3), methane (CH4), carbon dioxide (CO2) and water vapour (H2O) were present sometime after the crust cooled due to volcanic outgassing. There was very little oxygen (O2) in the atmosphere because it quickly reacted with other elements.
What was the atmosphere like in early earth?
“Reducing atmosphere” with higher proportion of reactive gasses such as ammonia (NH3) and hydrogen (H2). Very little oxygen (O2).
What was the temperature like in early earth and why?
Significantly warmer than today due to heat from asteroid collisions and accretion (coming together, formation) of the planet.
What was the UV radiation like in early earth?
No ozone (O3) layer to block radiation from the sun so intense UV radiation reached the surface.
What was the volcanic activity like in early earth?
Volcanic eruptions released gasses (H2O and CO2) into the atmosphere.
What was the asteroids role in early earths conditions?
Constant bombardment by asteroids as the solar system was forming.
What 4 hypotheses did Oparin and Haldane propose as to how life could’ve originated on earth?
1:Formation of simple organic molecules from inorganic compounds
2:Assembly of carbon compounds into polymers
3:The formation of a polymer that can self replicate
4:Packaging of molecules into compartments with an internal chemistry different from the surroundings
State the properties of INORGANIC molecules.
Do not have both carbon and hydrogen within the same molecule
Usually have a small number of atoms
Often associated with non-living matter
State the properties of ORGANIC molecules.
Contain carbon and hydrogen
Can be large molecules with many atoms
Usually associated with living organism
State examples of biological monomers.
amino acids, nitrogenous bases, fatty acids and simple sugars
How were polymers formed?
Formed by monomers spontaneously in early earth via anabolic reactions —> creating proteins and RNA strands.
Define reducing atmosphere.
early Earth atmosphere were chemically reducing in nature, meaning they are reactive gasses that easily transfer electrons electrons when they react.
Note 
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