SCIENCE
ENVIRONMENTAL SCIENCES
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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12
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21
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58
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78
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Detailed explanation-1: -The air in Earth’s atmosphere is made up of approximately 78 percent nitrogen and 21 percent oxygen.
Detailed explanation-2: -In fact, the troposphere contains three-quarters of the mass of the entire atmosphere. The air here is 78% nitrogen and 21% oxygen. The last 1% is made of argon, water vapor, and carbon dioxide.
Detailed explanation-3: -So how did Earth end up with an atmosphere made up of roughly 21 percent of the stuff? The answer is tiny organisms known as cyanobacteria, or blue-green algae. These microbes conduct photosynthesis: using sunshine, water and carbon dioxide to produce carbohydrates and, yes, oxygen.
Detailed explanation-4: -Oxygen makes up 21% of the atmosphere.
Detailed explanation-5: -By around 600 million years ago, concentrations of molecular oxygen in our atmosphere finally reached around 21 percent.