Beginnings of life | Life on earth and in the universe | Cosmology & Astronomy | Khan Academy
Khan Academy・2 minutes read
The Hadean Eon was inhospitable to life with lava flows and intense space impacts, followed by the Late Heavy Bombardment period that eradicated any early life forms on Earth. Prokaryotes, the first life forms, emerged 3.824 billion years ago, utilizing photosynthesis to produce oxygen and shaping Earth's atmosphere.
Insights
- The Hadean Eon was a harsh period with lava flows and space impacts, unsuitable for life to thrive due to its extreme conditions.
- Prokaryotes, the first life forms, emerged around 3.824 billion years ago, evolving from anaerobic organisms to photosynthetic prokaryotes that transformed Earth's atmosphere through oxygen production.
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Recent questions
What characterized the Hadean Eon?
Harsh environment with lava flows and space impacts.
What is the Late Heavy Bombardment?
Period of intense space impacts on Earth.
When did prokaryotes first emerge?
3.824 billion years ago.
What is the tree of life?
Suggests a common ancestor for prokaryotes and eukaryotes.
What marked the Archean Eon?
Emergence of prokaryotes utilizing photosynthesis.
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Summary
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Origins of Life and Oxygen Production
- The Hadean Eon, named after the Greek underworld, was characterized by a hellish environment with lava flows and space impacts, making it inhospitable to life.
- The Late Heavy Bombardment, following the formation of the moon, was a period of intense space impacts on Earth, believed to have eradicated any primitive life forms.
- The movement of Uranus and Neptune caused asteroids to collide with inner planets, including Earth and the moon, during the Late Heavy Bombardment.
- Life on Earth is thought to have originated after this period, with the first life forms, prokaryotes, emerging 3.824 billion years ago.
- Prokaryotes are unicellular organisms lacking a nucleus and membrane-bound organelles, contrasting with eukaryotes that possess these structures.
- The tree of life suggests a common ancestor for prokaryotes and eukaryotes, with bacteria and archaea being examples of prokaryotes.
- The earliest life forms were likely anaerobes that did not require oxygen and did not perform photosynthesis, obtaining energy from the environment.
- The Archean Eon, starting around 3.8 billion years ago, saw the emergence of prokaryotes utilizing photosynthesis to produce oxygen, eventually leading to significant changes in Earth's atmosphere.
