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Biology CBSE Live product
Class 8 (2025-26)
Our Home: Earth, a Unique Life-Sustaining Planet
The uniqueness of Earth
3.
Earth a unique planet
Question:
3
m.
Choose the correct answer from the given options.
Why is the presence of oxygen a unique feature of Earth?
1.
Which organisms first produced oxygen on early Earth?
Aerobic respiration
Cyanobacteria
About 21%
2.
Which life process requires oxygen?
Cyanobacteria
About 21%
Aerobic respiration
3.
What percentage of Earth’s atmosphere is oxygen today?
About 21%
Cyanobacteria
Aerobic respiration
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