Multiple Choice
Which event marks the end of the Mesozoic Era and is associated with the mass extinction of the dinosaurs?
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24. History of Life on Earth
History of Life on Earth
Multiple Choice
The early atmosphere on Earth is thought to have lacked which of the following gases?
A
Methane
B
Carbon dioxide
C
Water
D
Nitrogen
E
Oxygen
Verified step by step guidance1
Understand the context: The early atmosphere of Earth refers to the period shortly after the planet formed, approximately 4.5 billion years ago.
Identify the gases present: The early atmosphere was primarily composed of gases released from volcanic activity, such as methane (CH₄), carbon dioxide (CO₂), water vapor (H₂O), and nitrogen (N₂).
Recognize the absence of oxygen: Oxygen (O₂) was not a significant component of the early atmosphere. It became abundant only after the evolution of photosynthetic organisms, which released oxygen as a byproduct.
Consider the role of photosynthesis: Photosynthetic organisms, such as cyanobacteria, began producing oxygen through the process of photosynthesis, which gradually increased the oxygen levels in the atmosphere.
Conclude the analysis: Based on the historical development of Earth's atmosphere, oxygen was the gas that was initially absent in the early atmosphere.
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