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The amount of oxygen in Earth's atmosphere has fluctuated over geological time scales. Oxygen levels were much lower in the past, particularly in the early stages of Earth's history. Around 2.4 billion years ago, there was a significant increase in oxygen levels known as the Great Oxidation Event, leading to the current levels of approximately 21% oxygen in the atmosphere.

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1y ago

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Earths early atmosphere was changed dramatically by the evolution of?

photosynthetic organisms, like cyanobacteria, which produced oxygen as a byproduct of photosynthesis. This led to the increase in atmospheric oxygen levels, changing the composition of Earth's early atmosphere.


How did earths atmosphere change during precambrian time?

During the Precambrian time, the Earth's atmosphere underwent significant changes, transitioning from a reducing atmosphere dominated by gases like methane and ammonia to an oxidizing atmosphere with increasing levels of oxygen, due to the development of photosynthetic organisms. This increase in oxygen levels laid the foundation for the evolution of complex multicellular life forms.


Why did the amount of oxygen's in earths atmosphere increase dramatically?

The amount of oxygen in the atmosphere increased because the number of photosynthetic organisms, which release oxygen, on the earth dramatically increased. This lead to the Great Oxygenation Event, or the Oxygen Crisis, 2.4 billion years ago - when this free O2 entered the Earth's atmosphere.


How has the earths atmosphere changed over millions of years?

The earth's atmosphere has changed significantly over millions of years due to various factors such as volcanic activity, changes in the Earth's orbit, and the evolution of living organisms. For example, early Earth had a different composition with high levels of carbon dioxide and little oxygen. Over time, the atmosphere changed to its current composition with nitrogen as the dominant gas and oxygen supporting life.


What is the approximate percent of oxygen by volume present earths lower atmosphere?

Oxygen makes up about 21% of Earth's lower atmosphere by volume.