Multiple Choice
Which organisms are most critical in the nitrogen cycle due to their ability to fix atmospheric nitrogen?
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35. Soil
Nitrogen Fixation
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How do plants obtain the nitrogen they need for growth?
A
By producing nitrogen through cellular respiration
B
By absorbing nitrate and ammonium ions from the soil
C
By directly absorbing nitrogen gas ($N_2$) from the atmosphere
D
By photosynthesizing nitrogen compounds from sunlight
Verified step by step guidance1
Understand that nitrogen is an essential nutrient for plants, as it is a key component of amino acids, proteins, and nucleic acids.
Recognize that plants cannot directly use nitrogen gas ($N_2$) from the atmosphere because it is highly stable and requires conversion into a usable form.
Learn that nitrogen fixation is a process carried out by certain bacteria in the soil or in symbiotic relationships with plants (e.g., legumes). These bacteria convert $N_2$ into ammonia ($NH_3$), which can then be transformed into ammonium ($NH_4^+$) or nitrate ($NO_3^-$).
Understand that plants absorb nitrogen primarily in the form of nitrate ($NO_3^-$) and ammonium ($NH_4^+$) ions through their roots from the soil.
Recognize that photosynthesis is unrelated to nitrogen acquisition, as it is a process for converting sunlight into chemical energy, not for synthesizing nitrogen compounds.
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