biogeochemical cycles: the nitrogen cycle
decide if each statement is true or false - drag & drop your
verdict into the box. if you think it is false, write an explanation why.
statement verdict explanation
during storms, lightning adds
nitrogen to the earth’s
atmosphere.

denitrifying bacteria are able to
return nitrogen directly to the
atmosphere.

animals and plants can take in
and use nitrogen gas from the
atmosphere when they respire.

without bacteria, the nitrogen
cycle would still function but not
as efficiently.

nitrification turns ammonium ions
into nitrites and nitrates.

Question

biogeochemical cycles: the nitrogen cycle
decide if each statement is true or false - drag & drop your
verdict into the box. if you think it is false, write an explanation why.
statement verdict explanation
during storms, lightning adds
nitrogen to the earth’s
atmosphere.

denitrifying bacteria are able to
return nitrogen directly to the
atmosphere.

animals and plants can take in
and use nitrogen gas from the
atmosphere when they respire.

without bacteria, the nitrogen
cycle would still function but not
as efficiently.

nitrification turns ammonium ions
into nitrites and nitrates.

Accepted Answer

### Statement 1: During storms, lightning adds nitrogen to the Earth’s atmosphere.
# Brief Explanations:
Lightning actually fixes atmospheric nitrogen (converts $N_2$ to nitrogen compounds like nitrates) which enter the soil, not add nitrogen to the atmosphere. So the statement is false.
# Answer:
Verdict: FALSE
Explanation: Lightning fixes atmospheric nitrogen into compounds (e.g., nitrates) that enter the soil, not add nitrogen to the atmosphere.

### Statement 2: Denitrifying bacteria are able to return nitrogen directly to the atmosphere.
# Brief Explanations:
Denitrifying bacteria convert nitrates ($NO_3^-$) back into gaseous nitrogen ($N_2$), which is released into the atmosphere. This matches their role in the nitrogen cycle. So the statement is true.
# Answer:
Verdict: TRUE
Explanation: (No explanation needed as it is true.)

### Statement 3: Animals and plants can take in and use nitrogen gas from the atmosphere when they respire.
# Brief Explanations:
Plants and animals cannot directly use atmospheric $N_2$ gas. Plants rely on nitrogen - fixing bacteria or nitrogen - containing compounds in the soil, and animals get nitrogen from consuming plants or other animals. Respiration involves gas exchange of $O_2$ and $CO_2$, not nitrogen gas utilization. So the statement is false.
# Answer:
Verdict: FALSE
Explanation: Plants/animals cannot directly use $N_2$ from the atmosphere. Plants need fixed nitrogen (e.g., from soil), animals get nitrogen from food. Respiration does not utilize $N_2$.

### Statement 4: Without bacteria, the nitrogen cycle would still function but not as efficiently.
# Brief Explanations:
Bacteria (nitrogen - fixing, nitrifying, denitrifying) are essential for key steps of the nitrogen cycle (e.g., fixing $N_2$, converting ammonia to nitrates, returning $N_2$ to the atmosphere). Without bacteria, these processes would not occur, and the nitrogen cycle would not function at all. So the statement is false.
# Answer:
Verdict: FALSE
Explanation: Bacteria perform essential nitrogen - cycle steps (fixation, nitrification, denitrification). Without them, the nitrogen cycle would not function.

### Statement 5: Nitrification turns ammonium ions into nitrites and nitrates.
# Brief Explanations:
Nitrification is the process where nitrifying bacteria first convert ammonium ions ($NH_4^+$) to nitrites ($NO_2^-$) and then to nitrates ($NO_3^-$). This is the correct definition of nitrification. So the statement is true.
# Answer:
Verdict: TRUE
Explanation: (No explanation needed as it is true.)

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QUESTION IMAGE

Question

Explanation:

Statement 1: During storms, lightning adds nitrogen to the Earth’s atmosphere.

Statement 2: Denitrifying bacteria are able to return nitrogen directly to the atmosphere.

Answer: