The majority of Earth's atmosphere (78%) is nitrogen gas, making it the largest source of nitrogen. However, atmospheric nitrogen has limited availability for biological use, leading to a scarcity of usable nitrogen in many types
of ecosystems. The nitrogen gas in the atmosphere is not in an useable form for the plants. Plants must have nitrogen
for several purposes. They need it for amino acids, proteins, and DNA. What is the BEST explanation of a natural
process on how nitrogen is turned into an useful form for plants?
A)
Nitrogen fixation; nitrogen-fixing bacteria change nitrogen gas into
nitrites and nitrates. It is then put back into the soil for plants to absorb
through their root system.
Nitrogen fixation; ammonia and nitrates are changed into nitrogen gas.
Plants can absorb the nitrogen gas directly out of the atmosphere into an
useful form
B)
Denitrification; nitrogen-fixing bacteria change nitrogen gas into ammonia
and nitrates.
D)
Denitrification; ammonia and nitrates are changed into nitrogen gas.