AP BIOLOGY

Detailed explanation-1: -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-2: -Earth’s atmosphere is composed of about 78 percent nitrogen, 21 percent oxygen, 0.9 percent argon, and 0.1 percent other gases.

Detailed explanation-3: -Oxygen is a major component of the solid earth, along with Si and elements such as Mg, Ca and Na. Nitrogen is not stable as a part of a crystal lattice, so it is not incorporated into the solid Earth. This is one reason why nitrogen is so enriched in the atmosphere relative to oxygen.

Detailed explanation-4: -Dinitrogen is the most common form. It makes up 78 percent of the atmosphere but cannot be used by plants. It is taken into the soil by bacteria, some algae, lightning, and other means.

Detailed explanation-5: -The abundance of gases in the atmosphere in the decreasing order is as follows: nitrogen, oxygen, argon, water vapour, carbon dioxide. Hence nitrogen constitutes 78% of the atmospheric air and is the most abundant gas in the atmosphere. Q. The second most abundant gas in the atmosphere is carbon dioxide.