AP BIOLOGY

Detailed explanation-1: -An atmosphere is made of the layers of gases surrounding a planet or other celestial body. Earth’s atmosphere is composed of about 78% nitrogen, 21% oxygen, and one percent other gases.

Detailed explanation-2: -The most abundant naturally occurring gas is nitrogen (N2), which makes up about 78% of air. Oxygen (O2) is the second most abundant gas at about 21%. The inert gas argon (Ar) is the third most abundant gas at 0.93%.

Detailed explanation-3: -’ Nitrogen makes up 78 per cent of the air we breathe, and it’s thought that most of it was initially trapped in the chunks of primordial rubble that formed the Earth. When they smashed together, they coalesced and their nitrogen content has been seeping out along the molten cracks in the planet’s crust ever since.

Detailed explanation-4: -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-5: -The other primary reason is that, unlike oxygen, nitrogen is very stable in the atmosphere and is not involved to a great extent in chemical reactions that occur there. Thus, over geological time, it has built up in the atmosphere to a much greater extent than oxygen.