3 Main Questions:
-What is ribozymes?
An RNA molecule that functions as an enzyme, catalyzing reactions during RNA splicing.
- What is protobiont?
A collection of abiotically produced molecules surrounded by a membrane or membrane-like structure.
- What is half-life?
The amount of time it takes for 50% of a sample of a radioactive isotope to decay.
5 Main Facts:
- The earliest evidence of life on Earth comes from fossils of microorganisms that are about 3.5 billions years old.
- There is scientific evidence that Earth and the other planets of the solar system formed about 4.6 billion years ago, condensing from a vast cloud of dust and rocks that surrounded the young sun.
- As the bombardment of early Earth slowed, conditions on the planet were extremely different from those of today.
- It is unclear whether the atmosphere of young Earth contained enough methane and ammonia to be reducing.
- The presence of small organic molecules, such as amino acids, is not sufficient for the emergence of life as we know it.
Diagram:
The proposed ancestors of mitochondria were aerobic, heterotrophic prokaryotes (meaning they used oxygen to metabolize organic molecules obtained from other organisms). The proposed ancestors of plastids were photsynthetic prokaryotes.
Summary:
Conditions on early Earth made the origin of life possible. The earliest evidence of life on Earth comes from fossils of microorganisms that are about 3.5 billion years old. The hypothesize that chemical and physical processes on early Earth, aided by the emerging force of natural selection, could have produced very simple cells.
For the first few hundred million years, life probably could not have originated or survived on Earth because the planet was still being bombarded by huge chunks of rock and ice left over from the formation of the solar system.
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