AP BIOLOGY

Detailed explanation-1: -Human activities, such as making fertilizers and burning fossil fuels, have significantly altered the amount of fixed nitrogen in the Earth’s ecosystems.

Detailed explanation-2: -Overview: The nitrogen cycle involves three major steps: nitrogen fixation, nitrification, and denitrification. It is a cycle within the biosphere which involves the atmosphere, hydrosphere, and lithosphere. Nitrogen is found in several locations, or reservoirs.

Detailed explanation-3: -Correct answer: Explanation: Condensation is not part of the nitrogen cycle. It is part of the water cycle, during which water molecules condense together in the atmosphere to form clouds.

Detailed explanation-4: -Four processes participate in the cycling of nitrogen through the biosphere: (1) nitrogen fixation, (2) decay, (3) nitrification, and (4) denitrification.