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The Origin of Life (The Atmosphere of Early Earth (Life on Early Earth…
The Origin of Life
The Atmosphere of Early Earth
Intro
There was little oxygen in the air. There was nitrogen, water vapor, carbon dioxide, and methane, which were the major gases at that time.
Life on Early Earth
Most likely the earliest forms of life appeared on Earth some time between 3.5 and 4.0 billion years ago.
Early lifeforms most likely did not need oxygen to survive and they were probably unicellular organisms and lived in the ocean
The first organisms probably were like present day archaea
Modeling Conditions on Early Earth
Scientists reason that early living things
did
actually rise from living things
In 1953, A young student and his adviser provided the first clues as to how organisms might have arisen on Earth by recreating the conditions of early Earth in a Lab. They placed water as an ocean and a mixture of gases into a flask. They kept all organisms out. Then sent lightning through. Within a week, they found samll chemical units that when joined together could form proteins which were one of the building blocks of life
The first cells
Intro
Scientists hypothesize that the small chemical units of life formed gradually over millions of years and joined to form the large chemical building blocks found in cells. Eventually, some of these large chemicals joined together and became the forerunners of the first cells.
Support From Fossil Evidence
Scientists have discovered fossil of what appear to have been e.4 to 3.5 billion year old archaea-like organisms. These fossils support the idea that cells could have lived back then.
The first cells were probably heterotrophs that used the chemicals in their surroundings for energy.
At some point much later, some of the cells may have developed the ability to be autotrophs which had an effect on the atmosphere. As they made their own food, they produced oxygen. As autotrophs thrived, oxygen accumulated in Earth's atmosphere.
Unanswered Questions
Laboratory experiments can still never prove how life first appeared on Earth. They can only test hypotheses about how life forms could have arisen.
Scientists are still looking for how life arose through experiments, evidence, and questions.