Nitrogen Cycle Practice Flashcard

Front

What is the nitrogen cycle?

Back

The nitrogen cycle is the process by which nitrogen is converted between its various chemical forms, including atmospheric nitrogen, ammonia, and nitrates, through biological and physical processes.

Front

Why can't plants and animals use atmospheric nitrogen directly?

Back

Plants and animals cannot use atmospheric nitrogen directly because it is in a gaseous form (N2) that is not reactive. They rely on nitrogen compounds like ammonia or nitrates, which are produced through the nitrogen cycle.

Front

What percentage of the Earth's atmosphere is nitrogen?

Back

Nitrogen constitutes about 78% of the Earth's atmosphere.

Front

Where does most of the nitrogen cycle occur?

Back

Most of the nitrogen cycle occurs in the soil.

Front

What role do bacteria play in the nitrogen cycle?

Back

Bacteria play a crucial role in the nitrogen cycle by converting atmospheric nitrogen into ammonia (nitrogen fixation) and then into nitrates (nitrification), which plants can absorb.

Front

What is nitrogen fixation?

Back

Nitrogen fixation is the process of converting atmospheric nitrogen (N2) into ammonia (NH3) or related compounds in soil, making it available for plants.

Front

What is nitrification?

Back

Nitrification is the process by which ammonia is converted into nitrites (NO2-) and then into nitrates (NO3-) by bacteria in the soil.

Front

What happens to dead plants and animals in the nitrogen cycle?

Back

Dead plants and animals decompose, releasing nitrogen back into the soil in the form of ammonia, which can then be converted into nitrates.

Front

What is denitrification?

Back

Denitrification is the process by which nitrates are converted back into nitrogen gas (N2) by bacteria, returning nitrogen to the atmosphere.

Front

What is the significance of legumes in the nitrogen cycle?

Back

Legumes have bacteria in their root nodules that can fix atmospheric nitrogen, enriching the soil with nitrogen compounds.