nitrogen/carbon/water cycles

Living things need organic nitrogen to __.

survive

Nitrogen is unusable in the atmosphere because it exists as __ (N2).

diatomic nitrogen

Plants prefer __ over nitrite but will take in both.

nitrate

Nitrogen fixation occurs when nitrogen-fixing bacteria combine nitrogen with __.

hydrogen

Nitrogen is converted from N2 to __ (ammonia) or NH4 (ammonium).

NH3

Most plants cannot use __ directly as a nutrient source.

ammonia

Nitrifying bacteria convert ammonia and ammonium into __ first, then into nitrate.

nitrite (NO2)

During assimilation, different forms of nitrogen compounds are absorbed by plants through __.

soil & roots

Ammonification is the process where nitrogen re-enters soil through __ or waste.

plant/animal deaths (decomposition)

In denitrification, nitrogen goes back into the atmosphere as __ and N2O.

N2

Evaporation is the process where the sun's energy turns water into __.

vapor

In condensation, water vapor cools to form __.

clouds

Precipitation occurs when water falls back to Earth as __, sleet, or hail.

rain

During collection, water runs off and gathers in oceans, lakes, and __.

rivers

Photosynthesis involves the absorption of carbon dioxide (CO2) from the __.

atmosphere

During cellular respiration, organic molecules like glucose are broken down for __.

energy

Decomposition releases carbon stored in dead organisms back into the atmosphere as __.

CO2

Combustion releases large amounts of __ into the atmosphere.

carbon dioxide